Chhattisgarh Dental College & Research InstituteRAJNANDGAON, CHHATTISGARH

Ayush And Health Sciences University of Chhattisgarh L i b r a r y D i s s e r t a t i o n

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Contents

1 INTRODUCTION.................................................................................................8

2 HISTORY OF MINI IMPLANTS.......................................................................12

3 THE DESIGN OF ORTHODONTIC MINI-IMPLANTS...................................22

3.1 Classifications of miniscrew Implants..........................................................22

3.2 Elements of Implant Design:.........................................................................26

4 ANATOMICAL CONSIDERATIONS................................................................37

5 BIOMECHANICAL CONSIDERATIONS.........................................................44

5.1 Maxillary anterior en masse retraction mechanics in extraction cases.........44

5.2 Mandibular anterior en masse retraction mechanics in extraction cases......46

5.3 Anterior Intrusion Mechanics in the Maxillary Arch....................................47

5.4 Anterior Intrusion Mechanics in the Mandibular Arch.................................47

5.5 Anterior en masse Retraction with Anterior Intrusion..................................48

5.6 Molar Intrusion Mechanics for Open bite Cases...........................................48

5.7 Maxillary Anterior Lingual Root Torque Mechanics....................................48

5.8 Molar Distalization Mechanics for Non-Extraction Cases...........................49

5.9 Protraction Mechanics in Extraction Cases...................................................50

5.10 Minor Tooth Movements Using Mini Implant Anchorage........................51

5.11 Buccal Cross bite (Scissors Bite) Correction.............................................52

6 INDICATIONS & CONTRAINDICATIONS.....................................................54

6.1 Indications.....................................................................................................54

6.2 Contraindications..........................................................................................55

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6.3 Relative Contraindications............................................................................56

7 CLINICAL APPLICATIONS..............................................................................58

8 BIOLOGY OF ORTHODONTIC IMPLANTS...................................................63

9 COMPLICATIONS WITH MINI IMPLANTS & THEIR MANAGEMENT....69

9.1 Complications During Insertion....................................................................70

9.2 Complications Under Orthodontic Loading..................................................75

9.3 Soft-Tissue Complications............................................................................78

9.4 Complications During Removal....................................................................80

10 ADVANTAGES OF MINI IMPLANTS..........................................................83

11 BIBLIOGRAPHY............................................................................................84

12 APPENDIX I.......................................................................................................86

13 APPENDIX II.....................................................................................................88

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INTRODUCTION“Truth is neither objectivity nor the balanced view; truth is a selfless subjectivity.”

-Knut Hamsun

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1 INTRODUCTION

The goal of Orthodontic practice is to achieve the desired results with minimum

undesired consequences, which is largely dependent on the availability of anchorage.

One such effect is the loss of anchorage. Anchorage, the degree of resistance to

displacement, is a critical component to successful orthodontic treatment. Anchorage

control is a fundamental problem in the treatment of malocclusions1.

In orthodontics, malpositioned teeth are corrected and proper alignment is achieved

by inducing strategically planned tooth movements through application of force. This

force originates from wires, elastics and other appliances attached to the teeth. To make

this force work in the planned direction, with the planned magnitude and for the

planned time, it is necessary to reduce or completely eliminate unwanted reciprocal

effects by using a reliable anchorage and to respect the principles of orthodontic

biomechanics at the same time.

Often, teeth that are in proper alignment are used to provide the force to move those

that are not, and are referred to as anchorage teeth. In accordance with Newton’s Third

Law of motion, outlined in 1687, which states that an applied force comprises of an

‘Action’ component & an equal & opposite ‘Reaction’ component; There is a reactive

or “equal and opposite force” for every applied force. Unfortunately, these reactive

orthodontic forces often result in undesirable movements of the teeth serving as

anchorage. As a result, orthodontists have historically used a variety of appliances and

strategies to enhance anchorage; particularly when minimal movement of the teeth

providing the anchorage is desired. This allows the movement of malaligned teeth

while leaving teeth that do not need to be moved relatively undisturbed.

However, with dental anchorage dependant on the number and quality of the teeth, if

anchorage is lost during the planned correction of the malocclusion anomaly will not

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be achieved. Anchorage enhancing appliances, such as headgear, are highly dependent

upon patient compliance for success. All manner of anchorage control concepts have

come and gone in the ensuing years, including Baker anchorage, headgear, lip

bumpers, Nance holding arches, Tip-back bends, lingual arches, uprighting springs,

sectional mechanics, dual arch mechanics and elaborate methods to set anchorage. But

in reality, absolute anchorage did not practically exist.

In an effort to establish anchorage without significant reliance on patient

cooperation, other forms of anchorage have been investigated2.

Restorative dental implants, despite their stability in bone, have limited use in

orthodontics due to cost, an extensive healing period after surgical placement, and

anatomic placement limitations. Still, the use of these titanium dental implants as a

form of anchorage has provided the potential for absolute, compliance independent,

orthodontic anchorage. The use of prosthetic implants as orthodontic anchorage made a

great advance. In osseointegrated implants, the relationship between the implant and

bone can be defined as a functional ankylosis.

Orthodontic miniscrew implants (read mini-implants) have been designed to

circumvent the limitations posed by restorative dental implants. These smaller bone

screws are significantly less expensive, are easily placed and removed, and can be

placed in almost any intra-oral region, including between the roots of the teeth.

Starting with the use of vitalium screwGainsforth, 1945 #7s3 and progressing to

conventional osseointegrated implants which have been used as orthodontic anchorage,

orthodontic therapy seems to be essentially facilitated.

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1.1 List of common terms used for mini-screw implants :

• Microimplants

• Micro-implant anchors

• Mini implants

• Mini implants for orthodontic anchorage

• Mini screws

• Ortho implants

• Ortho TAD

• TAD – Temporary Anchorage Devices

• Titanium screw Anchorage

As described by Ludwig 4

In 2005 by Carano and Melsen5 , it was agreed that the word Mini-Implant should

be applied to all these terms. In 2005 Mah and Bergstrand agreed to this aspect and

they pointed out that mini-implant is more appropriate than micro-implant or screw6,

because the word “micro” is defined as a magnitude of 10-6.

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History of Mini Implants“I am the owner of the sphere, the seven stars and of the solar year of Caeser’s

hand, and Plato’s brain, of Lord Christ’s heart, and Shakespeare’s strain, I am

History.”

- Ralph Waldo Emmerson

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2 HISTORY OF MINI IMPLANTS

In the 19th century, concepts were designed to anchor teeth to structures other than

teeth. This led to the development of Extra-oral anchorage systems. These appliances,

although mechanically efficient, imposed enough discomfort to the patients to deter

them from continuing their use and created practical compliance issues, affecting the

overall therapy negatively.

The era of skeletal anchorage began later, in 1945, with the failed experiments of

Gainsforth and Higley3 to anchor screws in the jaws of mongrel dogs. Using a 2.4-mm

pilot hole, a 3.4-mm-diameter X 13-mm-long Vitallium screw was placed in the

ascending ramus of 6 dogs. A rubber band delivering between 140 and 200 g of force

was attached from the screw head to a 0.040-inch wire that slid through a tube on the

upper molar band and was soldered to the upper canine band. The system was designed

to distally tip/retract the canine by immediately loading the screws with the rubber

bands. However, all the screws were lost in 16-31 days. The experiment, although

unsuccessful, the authors concluded that “anchorage may be obtained for orthodontic

movements in the future.”

There were no more published reports of attempts to use endosseous implants to

move teeth until the clinical case reports of Leonard Linkow in 19697. He used

mandibular blade-vent implants in a patient to apply Class ll elastics for retraction of

maxillary incisors.

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Figure 1 A- Spiral-shaft

implants (Chercheve). B- Various

sizes of early designed vent-plant

implants. C - a tripod implant,

assembled. D- Various early

designed blade implants. 8

In the 1970s, after Branemark and co-workers reported the successful

osseointegration of implants in bone 9, many orthodontists began taking

an interest in using implants for

orthodontic anchorage. Sherman

placed six vitreous carbon dental

implants into the extraction sites of

mandibular third premolars of dogs

and applied orthodontic forces in

1978. Two of the implants were firm

and were considered to be successful 10.

1979, Smith won the Milo Hellman Research Award of the American Association of

Orthodontists by studying the effects of loading bioglass-coated aluminum oxide

implants in monkeys and reported no significant movement of the implants during

force application. He described the interface between the bioglass implants and the

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surrounding tissue as fusion or ankylosis, despite the observation that intervening areas

of connective tissue were present 11.

After other similar efforts did not show much success, it was revisited by Creekmore

and Eklund in 1983. They inserted vitallium surgical bone screws below spina nasalis

to anchor upper incisor intrusion 12; the result was 6 mm of intrusion. Later, in similar

experiments, by Turley et al13 , the in-depth clinical and animal experimental

investigations established the base for today’s use of skeletal anchorage techniques.

The most important studies published between 1970 and 2000 were systematically

reviewed and, related to implants for orthodontic anchorage by Favero and Bressan in

their published article Orthodontic anchorage with specific fixtures: related study

analysis. The literature analysis was divided in specifics topics as materials, size and

screws shape, biomechanics, loading and healing time, used strength, surgery and

reasons to evaluate the success. One of very important aspects is that biocompatible

material had to be used.

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In Favero et al’s literature review there are different studies by different authors,

done with different materials 14.

EXPERIMENTS WITH TITANIUM

Experiments on animals Experiments on humans

Roberts 1984

Garetto 1985

Turley 1988

Roberts 1989

Linder-Aronson 1990

Wehrbein 1993

Block 1995

Southard 1995

Miotti 1996

Wehrbein 1997

Parr 1997

Akin -Nergiz 1998

Van Roekel 1989

Roberts 1990

Haanaes 1991

Higuchi 1991

Odman 1994

Roberts 1994

Wehrbein 1996

Kanomi 1997

Wehrbein 1998

Umemori 1999

Wehrbein 1999

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Experiments With Other Materials

Ceramics Biodegradable

materials

(Polyactide)

Vitallium Ticonium

Sherman 1978

Smith JR 1979

Mendez C 1980

Paige S 1980

Turley PK 1980

Gray 1983

Glatzmaier 1995

Glatzmaier 1996

Turley PK 1983

Gray JB 1983

Creekmore TD 1983

Douglass 1987

It took 60 years to progress from vitallium to the current standard, titanium.

Although, it ranks ninth among the earth’s most abundant elements, titanium was not

discovered until 1791 and was not mass produced before 1948 15. Three times stronger

than stainless steel, it exhibits little response to heat, electricity or magnetic forces. It is

highly biocompatible; and is inert. Type v titanium has the highest tensile strength,

hence most suitable for bone screws.

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In 1988, Shapiro and Kokich described the possibility of using dental implants for

anchorage during orthodontic treatment prior to being used for prosthodontic purposes 16. They emphasized the importance of the position of the implants as well as the proper

case selection and implant requirements during diagnosis and treatment planning.

1994, Roberts and co-workers reported on the clinical application of 3.75 mm x 7.0

mm standard Branemark fixture as anchorage in the retromolar area for closing a

mandibular first molar extraction site17. An anchorage wire attached to the implant was

extended to the vertical tube of the premolar bracket. Stabilizing the premolar anterior

to the extraction site allowed mesial movement of the molars without distal movement

of the more anterior teeth.

The osseointegration is analogous to the situation in which ankylosed tooth that can

be orthodontically loaded without moving, working as a stable anchorage unit, keeping

in mind that the absence of the periodontal membrane does not allow the cell

alterations which result in movements18. Nevertheless conventional dental implants can

be placed only in limited areas such as in the retromolar region or in edentulous areas. 19, 20. Another limitation has been the direction of force application such as when a

dental implant is placed on the alveolar ridge and is too large for horizontal orthodontic

traction. Furthermore, dental implants are troublesome for patients because of the

severity of surgery, the discomfort of the initial healing, and the difficulty of oral

hygiene.

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In 1997, Kanomi described a mini-implant

specifically made for orthodontic use21. He

reported that 1.2 mm diameter titanium mini-

implants provided sufficient anchorage for

intruding the lower anterior teeth. After four

months, the mandibular incisors were intruded

6 mm. Neither root resorption nor periodontal

pathology was evident. Kanomi applied an orthodontic force on the mini-implant

Figure 3 several months after implantation, anticipating osseointegration between the

mini-implant and the bone.

Figure 3 Intrusion achieved by mini implants in studies by Kanomi 21

He also mentioned the possibility of mini-implants being used for horizontal

traction, for molar intrusion, and as an anchor for molar distalization and distraction

osteogenesis.

1998 Costa et al presented a screw with a bracket-like head, using 2mm titanium

miniscrews for orthodontic anchorage22. The screws were inserted manually with a

screw driver directly through the mucosa without making a flap and were loaded

immediately. Of the 16 miniscrews used during the clinical trial, two became loose and

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Figure 2 Placement of mini-implant

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subsequently were lost before treatment was finished. They suggested that miniscrews

could be placed into

Inferior surface of the anterior nasal spine,

Midpalatal suture,

Infrazygomatic crest,

Retromolar area,

Mandibular symphysis area, and

Between the premolar and molar regions.

Majzoub and colleagues, in 1999, investigated the bone response of endosseous

implants to orthodontic loading23. Twenty-four short-threaded titanium implants were

inserted into the calvarial midpalattal suture of 10 rabbits. Two weeks following

insertion, a continuous distalizing force of 150 gm was applied for a period of eight

weeks. All but one test implant remained stable, exhibiting no mobility or displacement

throughout the experimental loading period.

The clinical applications with different micro-implants shapes and the micro-

implants with bracket head advantages were described in a research24. The micro-

implants with bracket head have two fins and a slot as a bracket making it easy for the

wire and ligature placement. There are two different threads for micro-implants:

clockwise and anticlockwise (must be anticlockwise clamped). This new technique

allows a simplified treatment, letting many possibilities of confection without the

necessity of complete appliances. This way, the treatment is faster, without the patient’s

cooperation. Different head types and shapes available in the market were presented.

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The self-puncturing titanium orthodontic micro-screws have changed the concepts

as in regard to surgical orthodontic treatments which use the skeletal anchorage

through a simplified and safe surgical approach. The installation of this new device

requires specific knowledge on surgical techniques, clinical application and judgment

for selecting the micro-screws, as well as the orthodontic activation

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The design of Orthodontic

mini-implants.“Simple is good”

-Jim Henson

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3 THE DESIGN OF ORTHODONTIC MINI-IMPLANTS.

3.1 Classifications of miniscrew Implants.

Labanauskaite et al in 2005 classified Orthodontic implants. 25

I. According to the shape and size

II. According to the implant bone contact.

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Osseointegrated.Nonosseointegrated.

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III. According to the application

- Used only for orthodontic purposes (orthodontic implants)

- Used for prosthodontic and orthodontic purposes

(prosthodontic implants).

Cope 26 classified Temporary anchorage devices as –

Biocompatible TADs.

Biologic TADs.

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Biocompatible TADs are further classified as follows-

Figure 4. Classification of Biocompatible TADs.

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Biocompatible TADsOsseointegrationDental Implant Palatal ImplantRetromolar ImplantPalatal Onplant Mechanical RetentionFixation Screws Fixation Screws with PlatesMini ImplantsFixation Wires

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Biologic Temporary Anchorage devices are classsified as -

Figure 5 Classification of Biologic TAD.

Currently, there are a number of commercially available miniscrew

implant systems for orthodontic use (Table I);

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Biological TADsOsseointegrationAnkylosed teethMechanicalDilacerated teeth

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3.2 Elements of Implant Design:

The main differences between the currently available miniscrew implants relate to

their composition, size, and design and include:

1. The alloy or metal used for their fabrication

2. Biocompatibilty

3. The design of the head portion

4. The design and diameter of threaded portion,

5. The length of the implant

3.2.1 Implant alloy or metal used -

The material must be nontoxic and biocompatible, possess excellent mechanical

properties, and provide resistance to stress, strain, and corrosion.

The materials commonly used for implants can be divided into 3 categories 14:

1. Biotolerant (stainless steel, chromium-cobalt alloy),

2. Bioinert (titanium, carbon), and

3. Bioactive (vetroceramic apatite hydroxide, ceramic oxidized

aluminum).

Commercially pure titanium is the material most often used in implantology. It

consists of 99.5% titanium, and the remaining 0.5% is other elements, such as carbon,

oxygen, nitrogen, and hydrogen. Most studies in the literature report on the use of

traditional titanium for prostheses, sometimes modified in the abutments to adapt to

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orthodontic requirements. However, pure titanium has less fatigue strength than

titanium alloys. A titanium alloy—titanium + aluminum+ vanadium (Ti6Al4Va)—is

used to overcome this disadvantage. Its mechanical characteristics, moreover, are well

suited to implant requirements: it is very lightweight, and it has excellent resistance to

traction and breaking, enabling it to withstand both masticatory loads and the stresses

of orthodontic forces.

The Orthodontic Mini Implant (OMI) [Leone, Italy] is made from implant steel

1.4441, which is still used in traumatology.

3.2.2 Biocompatibility:

With the exception of the Orthodontic Mini Implant, which is fabricated from

stainless steel, all other aforementioned systems are made of medical type IV or type V

titanium alloy. Because of its particular characteristics, titanium is considered an

excellent material: no correlation has been shown between titanium and the

development of neoplasm, and no allergic or

immunological reactions have been noted that

could be traced to the use of pure titanium.

Bone grows along the titanium oxide surface,

which is formed after contact with air or tissue

fluid. 27

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Figure 6

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3.2.3 Head design:

Most miniscrew implant systems are available in different designs to accommodate

both direct and indirect anchorage and avoid tissue irritation. The most frequent is the

button-like design with a sphere or a double sphere-like shape or a hexagonal shape.

Figure 7 Various miniscrew implants. A, The Aarhus Anchorage System. B, The AbsoAnchor. C, The

Spider Screw Anchorage System . D, The IMTEC Mini Ortho Implant

Miniscrew implants available with this design include the Aarhus Anchorage

System, the AbsoAnchor System, the Dual-Top Anchor System, the IMTEC Mini

Ortho Implant, the Lin/Liou Orthodontic Mini Anchorage Screw, the Miniscrew

Anchorage System, the Orthoanchor Kl System, and the Spider Screw Anchorage

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System. 28With a hole through the head or the neck of the screw, usually 0.8 mm in

diameter, this design is mostly used for direct anchorage.

A bracket like design is also available, which can be used for either direct or indirect

anchorage as provided by the Aarhus Anchorage System, the AbsoAnchor System, the

Dual-Top Anchor System, the Spider Screw Anchorage System, and the Temporary

Mini Orthodontic Anchorage System. 29.

Finally, a further hook design

is used by the LOMAS miniscrew

implant.

Dalstra 28 found that as Bone

density increases, the resistance

created by the stress surrounding

the screw becomes more

important in removal than in

insertion of the screw. At

removal, the stress is con-

centrated in the neck of the screw.

If an Allen wrench is used for

insertion and removal, the hole in

the center of the screw will weaken

the neck, which may lead to fracture. A hollow neck facilitates the insertion of a

ligature, but also weakens the neck. The strength of the screw is optimized by using a

slightly tapered cortical shape and a solid head with a screwdriver slot.

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Figure 8 From left to right: 1.5 mm cylindrical mini-implant

with a slot at the screw head; 1.6 mm tapered mini-implant with

a slot at the screw head; and 2.0 mm cylindrical mini-implant

with threads at the screw head

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3.2.4 Thread design:

3.2.4.1 Self-drilling versus self-tapping –

The miniscrew implant can have self tapping or self drilling thread design. A

prerequisite for self tapping placement is pilot drilling to prepare a hole for the implant.

Particularly for interradicular microimplants, pilot drilling has potential dangers, such

as damage to tooth roots, drill-bit breakage, overdrilling, and thermal necrosis of bone.

While self drilling screws doesn’t need pilot drilling for placement and can be placed

conveniently in narrow interdental areas.

Yan Chen 30 in 2008, compared the influences of Self-drilling versus self-tapping

orthodontic microimplants on the surrounding tissues biomechanically and

histologically in dogs. Fifty-six titanium alloy microimplants were placed on the buccal

side of the maxillae and the mandibles in 2 dogs were divided into 2 groups of 28; one

group of microimplants was self-drilling, and the other was self-tapping.

Approximately 200 g of continuous and constant forces were applied immediately

between 2 microimplants by stretching closed nickel-titanium coil springs for 9 weeks.

Peak insertion torque and removal torque were recorded immediately after the implants

were placed and when the dogs were killed, respectively.

They found that success rates were higher in the self-drilling group (93%) than in

self-tapping group (86%). Higher peak insertion torque and peak removal torque values

were seen in the self-drilling group in both the maxilla and the mandible. The mean

Peak Insertion Torque (PIT) values of the Self Drilling Implants (SDIs) in the maxilla

and the mandible were 5.6 and 8.7 Ncm, respectively. In the Self Tapping Implants

(STI) group, PIT values were 3.5 Ncm for the maxilla and 7.4 Ncm for the mandible.

A tendency to fracture was found in self-drilling group. The percentage of bone-to-

implant contact values was greater in the self-drilling group. They further found that

microimplants with high PIT might have closer initial contact with bone and might be

good for bone remodeling. SDIs cause less damage to bone during placement;

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therefore, osseointegration might happen earlier and be better than with STIs. From an

anchorage perspective, the greater the contact between the surface of the microimplant

threads and the cortical bone, the higher the initial grip of microimplants would be.

They concluded that Self-drilling microimplants can provide better anchorage and

can be recommended for use in the maxilla and in thin cortical bone areas of the

mandible.

It should be noted that even though SDIs have many advantages, if the bone is

dense, they should not to be chosen. STIs should be considered instead. In the maxilla

and areas with thin cortical bone in the mandible, microimplants would penetrate

easily. Failure due to stripping of bone was infrequent, so pilot drilling was not

necessary.

3.2.4.2 Conical Versus Cylindrical Designs –

Wilmes et al in 2008 found that conical mini-implants achieved higher primary

stabilities than cylindrical designs 31. Shinya Yano in 2006 suggested that tapered

orthodontic miniscrews induce bone-screw cohesion following immediate loading

hence advocated use of tapered rather than cylindrical designs. 32

Many other authors advocated the use of conical, rather than cylindrical designs, of

the implant body.

Another concern of using conical design is a

significant increase of MIT was observed mainly

in the taper type miniscrew which leads to higher

bone to implant contact surface along with higher

initial stability of the implants.

Although the conical group required high

removal torque, which means good initial

stability, it also showed high insertion torque

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which could affect adjacent tissue healing. The success rates and histomorphometric

analysis showed no significant difference between the cylindrical and conical groups.

The conical shape may need modification of the thread structure and insertion

technique to reduce the excessive insertion torque while maintaining the high

resistance to removal.

3.2.5 Length and diameter of the miniscrew implant -

Miniscrew implants are available in different lengths and diameters to accommodate

placement at different sites in both jaws. Most miniscrew implants have a thread

diameter ranging from 1.2 to 2.0 mm and a length from 4.0 to 12.0 mm, although some

of them are also available at lengths of 14.17 or even 21 mm. The advantage of thin

screw is the ease of insertion between the roots without the risk of root contact.

Seong-A Lim in 2008 suggested that that the maximum insertion torque increased

with increasing diameter and length of the orthodontic miniscrews as well as increasing

cortical bone thickness 33. An increase in screw diameter can efficiently reinforce the

initial stability of miniscrews, but the proximity of the root at the implanted site should

be considered. Miyawaki et al in 2003 reported that a diameter of 1.0 mm or less were

associated with mobility and failure of the screw 34. While Lin et al in 2003 and

Dalstra in 2004 showed that there increased chances of fracture with miniscrews of

diameters less than 1.2 mm 35.

Miyawaki in 2003 34 suggested use of miniscrew implant longer than 5 mm and

diameter more than 1mm. Costa et al in 2005 reported that miniscrew implants of 4 to

6 mm in length and diameter more than 1.2 mm are safe. Deguchi et al 36 after

evaluating the cortical bone thickness with the help of three-dimensional computed

tomographic suggested use of miniscrew implant of length 6 - 8 mm and 1.2- to 1.5-mm

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maximum diameter. In addition, for lingual orthodontics, the recommended location is

mesial to the first molar at 30°, and 8 to 10 mm in length.

Overall recent studies unanimously agree using miniscrew implant of length 6 - 8

mm and 1.2- to 1.5-mm in diameter is safe.

3.2.6 Osseointegration:

Because complete osseointegration of screws used in orthodontic applications is a

disadvantage that complicates the removal process, most of these devices are

manufactured with a smooth surface, thereby minimizing the development of bone in

growth and promoting soft tissue attachment at ordinary conditions and in the

absence of special surface treatment regimens. Till now only one study has been done

by Chaddad 37 in 2008 who have tried to modify miniscrew-implant surface

sandblasted, large grit, acid-etched (SLA).

Chaddad evaluated the clinical performance and the survival rate of machined

titanium versus sandblasted, large grit, acid-etched (SLA) mini-implants under

immediate orthodontic loading. Seventeen machined titanium (MT) mini-implants and

15 sandblasted, large grit, acid-etched (SLA) mini-implants were placed in 10 patients.

The mini-implants were immediately loaded and the patients seen at 7, 14, 30, 60, and

150 days. Clinical parameters such as anatomical location, character of the soft tissue

at the screw head emergence, type of mini-implant system, diameter, and length were

analyzed. In addition, the insertion torque recorded at the time of insertion was also

assessed.

Although the survival rate of the SLA mini-implants in this investigation was higher

compared with the MT group (93.5% to 82.5%), the correlation between the implant

surface characteristics and the rate of success was not statistically significant 37. These

findings suggest that altering an implant surface to create more surface area and

increase bone contact may not be the primary consideration when using mini-implants

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as orthodontic anchors. The SLA mini-implants presented a higher level of

osseointegration at the time of removal. This clinical observation was based on the

higher torque necessary for removal of SLA mini-implants when compared with

smooth machined titanium implants. Authors clinical experience indicates that surface

treated (SLA) implants could be advantageous in areas of poor bone quality, and

loading should be delayed for 6 to 8 weeks when initial osseointegration has occurred.

In the failure group, all the fixtures had their screw emergence at the oral mucosa

and recorded a torque range of less than 15 Ncm. The insertion torque statistically

influenced the survival rate of the mini-implants (P <.05). Surface treatment,

anatomical location, as well as soft tissue emergence were not statistically significant.

Authors concluded that surface characteristics did not appear to influence survival

rates of immediately loaded mini-implant. A torque value of more than 15 Ncm

recorded at the time of insertion appears to be one of the critical variables for mini-

implant survival under immediate loading.

3.2.7 Insertion torque -

The initial stability of a miniscrew is important because most incidences of

orthodontic miniscrew failure occur at the early stage. Miyawaki in 2003 reported that

the insertion torque is commonly used to evaluate the mechanical stability of implants

including miniscrews.

Studies have shown that a certain level of insertion torque is necessary in order to

achieve the initial anchorage at the screw and the bone interface, and that the insertion

torque of mini screws is an important factor in determining the appropriate initial

stability of a screw. Furthermore, it was suggested that excessive insertion torque, heat

at the border between the screw and bone, and mechanical injury can cause

degeneration of the bone at the implant-tissue interface.

Motoyoshi determined an adequate implant placement torque (IPT) for obtaining a

better success rate of 124 miniscrew-implants that were screwed into the buccal

Mini Implants

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alveolar bone of the posterior region in 41 orthodontic subjects 38. The peak value of

IPT was measured using a torque screwdriver. The success rate of the mini-implant

anchor for 124 implants was 85.5%. The mean IPT ranged from 7.2 to 13.5Ncm,

depending on the location of the implants. There was a significant difference in the IPT

between maxilla and mandible. The IPT in the mandible was, unexpectedly,

significantly higher in the failure group than in the success group. Therefore, a large

IPT should not be used always. According to author’s calculations of the risk ratio for

failure, to raise the success rate of 1.6-mm diameter miniimplants, the recommended

IPT is within the range from 5 to 10Ncm.

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Anatomical Considerations

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4 Anatomical Considerations

Miniscrews, mini implants, and miniplates are relatively easy clinical alternatives.

Orthodontic fixation screws can be placed either with or without flap raising. When

screws are placed without a flap, either drilling with a slow-speed handpiece or self-

tapping with a screwdriver (or a combination of them) can be used. Screws pass

through the soft tissue, and therefore the thickness of the soft tissue and cortical bone at

the surgical site are critical factors for success. Therefore, the use of endosseous

implants for absolute orthodontic anchorage has been the focus of many studies and

clinical trials. When the intraoral anchorage is stable, biocompatible, and free from site

specificity, it can be used effectively without patient compliance . Systems that can

satisfy these criteria include miniplates, and mini implants. These implants can be

placed in the inferior ridge of the pyriform aperture, maxillary alveolar bone, the

infrazygomatic crest, palatal alveolar bone, a maxillary tuberosity, the hard palate, and

the midpalatal suture area. To obtain sufficient screw fixation, understandings of the

bone density, screw shape and length as well as soft tissue and cortical bone thickness

are essential. This is probably responsible for the high prevalence of complications

such as hypersensitivity of the root, root fracture, and alveolar bone fracture resulting

from miniscrew insertion.

Here, the anatomical aspect on the maxilla and mandible, with the special reference

on the alveolar bone of the jaws will be introduced and described.

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4.1 Possible sites for placement of Miniscrew Implants in Maxilla –

Figure 9 Maxillary mini-implant locations. A. Below nasal spine. B. In the palate. C. Infrazygomatic

crest 39

Maxilla is the largest among the facial bones and forms the main part of the mid-

face region. Anatomically, the maxillary sinus is occupying as an air-filled space within

the maxilla. In this reason, the cortical plate surrounding the maxillary sinus is very

thin compared with the mandibular cortical plate. Furthermore, the facial aspect of the

maxilla above the level of the root apices is mainly composed of the cortical plate with

little spongy bone. The principal advantage of the miniscrewing on the buccal

interdental alveolar region is the ease in access. Even though the cortical plate is very

thin in this region, the initial anchorage can be provided in the adult patients. However,

care should be taken not to injure the dental roots and maxillary sinus when performing

the miniscrewing.

i. Area below the nasal spine the palate median or the paramedian area,

ii. Infrazygomatic crest,

iii. Maxillary tuberosities, and

iv. Alveolar process (both buccally and palatally) between the roots of the teeth.

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4.2 Possible sites for placement of Miniscrew Implants in Mandible –

The mandible is the largest, strongest and lowest bone in

the face. It has a horizontally curved body that is convex

forwards, and two broad rami, that ascend posteriorly. The

body of the mandible supports the mandibular teeth within

the alveolar process. The rami bear the coronoid and

condylar processes, and the condyle articulates with the

temporal bones at the temporomandibular

joints.

i. Symphysis or Parasymphysis,

ii. Alveolar process (between the roots of the teeth), and

iii. Retromolar area.

Deguchi et al quantitatively evaluated cortical bone thickness in various locations in

the maxilla and the mandible with the help of three-dimensional computed

tomographic images reconstructed for 10 patients 36. The distances from intercortical

bone surface to root surface, and distances between the roots of premolars and molars

were measured to determine the acceptable length and diameter of the miniscrew for

anchorage during orthodontic treatment.

They found that significantly less cortical bone thickness at the buccal region distal

to the second molar compared with other areas in the maxilla. Significantly more

cortical bone was observed on the lingual side of the second molar compared with the

buccal side. In the mandible, mesial and distal to the second molar, significantly more

cortical bone was observed compared with the maxilla. Furthermore, significantly

more cortical bone was observed at the anterior nasal spine level than at Point A in the

premaxillary region. Cortical bone thickness resulted in approximately 1.5 times as

Mini Implants

Figure 10 Mandibular mini-implant locations. A.

Retromolar area and molar region. B. Alveolar

process. C. Symphysis

P a g e | 36

much at 30° compared with 90°. Significantly more distance from the intercortical

bone surface to the root surface was observed at the lingual region than at the buccal

region mesial to the first molar. At the distal of the

first mandibular molar, significantly more distance

was observed compared to that in the mesial, and also

compared with both distal and mesial in the maxillary

first molar. There was significantly more distance in

root proximity in the mesial area than in distal area at

the first molar, and significantly more distance was

observed at the occlusal level than at the apical level.

They suggested that suggests that the best available location for a miniscrew is

mesial or distal to the first molar, and the best angulation is 30° from the long axis of

the tooth. From findings of the distance from the intercortical bone surface to the root

surface and the root proximity, the safest length is 6 mm with a diameter of 1.3 mm. In

addition, for lingual orthodontics, the recommended location is mesial to the first molar

at 30°, and 8 to 10 mm in length.

Maria Poggio40 provided an anatomical map to assist the clinician in miniscrew

placement in a safe location between dental roots using volumetric tomographic images

of 25 maxillae and 25 mandibles.

They suggest the order of the safer sites available in the interradicular spaces of the

posterior maxilla is as follows:

a. On the palatal side, the interradicular space between the maxillary first

molar and second premolar, from 2-8 mm from the alveolar crest.

b. On the palatal side, the interradicular space between the maxillary second

and first molars, from 2-5 mm from the alveolar crest.

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c. Both on buccal or palatal side between the second and first premolar,

between five and 11 mm from the alveolar crest.

d. Both on buccal or palatal side between the first premolar and canine,

between five and 11 mm from the alveolar crest.

e. On the buccal side, in the interradicular space between the first molar and

second premolar, from five to eight mm from the alveolar crest.

f. In the maxilla, the more anterior and the more apical, the safer the location

becomes.

g. The least amount of bone was in the tuberosity

The following is the order of the safer sites available in the interradicular spaces of

the posterior mandible:

a. Interradicular spaces between the second and first molar.

b. Interradicular spaces between the second and first premolar.

c. Interradicular spaces between the first molar and second premolar at 11

mm from alveolar crest.

d. Interradicular spaces between the first premolar and canine at 11 mm from

the alveolar crest.

e. The least amount of bone was between the first premolar and the canine.

They suggested that the features of the ideal titanium miniscrew for orthodontic

skeletal anchorage in the interradicular spaces should be 1.2- to 1.5-mm maximum

diameter, with 6–8 mm cutting thread and a conic shape.

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4.3 Safety Distance -

Huang suggested a method to evaluate the possibility of damaging the periodontal

ligament (PDL) is to calculate the safety distance41.

Safety distance: Diameter of the implant + PDL space (normal range 0.25 mm ±

50%) minimal distance between implant and tooth (1.5 mm) Example: Safety distance

(mm) of mini-implants when inserted between roots 1.2+(0.25 + 50%)+(1.5 +1.5) =

4.575. Therefore, the distance between roots needs to be at least 4.6 mm to reduce the

risk.

4.4 Safety Distance Modified

Gautam P and Valiathan A in 2006 42.

Safety distance = Diameter of the implant + 2 × [PDL space (normal range 0.25 mm

± 50%)] minimal distance between implant and tooth (1.5 mm)

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Biomechanical Considerations

in Mini Implant Use

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5 BIOMECHANICAL CONSIDERATIONS

The type of tooth movement that can be produced with Mini Implant anchorage is

determined by the same biomechanical principles and considerations that operate

during conventional orthodontic treatment, e.g. force, moment, center of resistance,

center of rotation. A Mini Implant can be placed in many different areas of the mouth

and at different heights on the gingiva relative to the occlusal plane, creating several

biomechanical orientations, e.g., low, medium and high. Thus, various types of tooth

movement can be produced depending on the position of the Mini Implant, the height

of the elastomer attachment, and the magnitude of the force applied. The following are

various clinical protocols that can be used routinely for effective tooth movement using

Mini Implant anchorage.

5.1 Maxillary anterior en masse retraction mechanics in extraction cases

For maxillary anterior en masse retraction, the line of action and the moment created

will vary depending on the location of the Mini Implant relative to the occlusal plane.

En masse retraction mechanics in extraction cases can be classified into three

categories much like the descriptors used traditionally for headgear traction: low,

medium, and high-pull mechanics.

Figure 11

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5.1.1 Medium—Pull Mechanics for the Maxillary Arch

Maxillary Mini Implants usually can be placed buccally between the second

premolar and first molar roots for anterior en masse retraction. When a maxillary Mini

Implant is placed about 8 to 10 mm above the main archwire, the term medium-pull en

masse retraction mechanics is used. If force is applied from a medium-pull Mini

Implant to a hook located between the lateral incisor and canine that extends 6 to 7 mm

vertically, the maxillary occlusal plane ordinarily can be maintained. Thus, medium-

pull mechanics are useful in treating patients who have normal overbite relationships.

5.1.2 Low-Pull Mechanics for the Maxillary Arch

When a Mini Implant is placed buccally between the roots of the maxillary second

premolar and first molar and is less than 8 mm away from the main archwire, the term

low-pull en masse retraction mechanics is used. If force is applied from a low-pull

Mini Implant to an anterior hook extending 6 to 7mm above the main archwire, the

maxillary Occlusal plane usually can be rotated in a clockwise direction. Therefore,

low-pull mechanics are useful in treating patients who have an open bite or an open-

bite tendency.

5.1.3 High-Pull Mechanics for the Maxillary Arch

When a Mini Implant is placed buccally between the maxillary second premolar and

the first molar roots, and is more than l0 mm away from the main archwire, the term

high-pull en masse retraction mechanics is used. If force is applied from a high-pull

Mini Implant to an anterior hook extending 6 to 7 mm above the main archwire, the

maxillary occlusal plane usually will rotate in a counterclockwise direction. Thus,

high-pull mechanics are useful in treating patients who have a deep bite or deep bite

tendency.

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5.2 Mandibular anterior en masse retraction mechanics in extraction cases

5.2.1 Medium-Pull Mechanics for the Mandibular Arch

Mandibular Mini Implants usually are placed buccally between the second premolar

and first molar roots for anterior en masse retraction. When a mandibular Mini Implant

is placed 6 to 8 mm away from the main archwire, the term medium-pull en masse

retraction mechanics is used. If force is directed from a medium-pull Mini Implant to a

hook located between the lateral incisor and canine that extends 4 to 6 mm below the

main archwire, the mandibular occlusal plane usually can be maintained. Therefore,

medium-pull mechanics are useful in treating patients who have normal overbite

relationships.

5.2.2 Low-Pull Mechanics for the Mandibular Arch

When a Mini Implant is placed buccally between the roots of the mandibular second

premolar and first molar and is less than 6 mm away from the main archwire, the term

low-pull en masse retraction mechanics is used. If force is applied from a mini implant

in a low-pull location to an anterior hook extending 4 to 6 mm below the main

archwire, a counterclockwise rotation of the mandibular occlusal plane typically can be

achieved. Low-pull mechanics are useful in treating patients who have an open bite or

open bite tendency.

5.2.3 High-Pull Mechanics for the Mandibular Arch

High-pull en masse retraction mechanics result when a Mini Implant is placed

buccally between the mandibular second premolar and first molar roots and more than

8 mm away from the main archwire. If force is applied from a high-pull Mini Implant

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to an anterior hook extending 4 to 6 mm below the main archwire, the mandibular

occlusal plane usually can be rotated in a clockwise direction. Therefore, high-pull

mechanics are useful in treating patients with a deep bite or deep bite tendency.

5.3 Anterior Intrusion Mechanics in the Maxillary Arch

For intrusion of the maxillary anterior teeth, Mini Implants can be placed between

the roots of the upper incisors. Force can be applied from the mini implant directly to

the main archwire. Usually a force originating from a single Mini Implant placed

between the maxillary central incisor roots is adequate to intrude the anterior dentition.

However, if there is a transverse cant to the occlusal plane. Two mini implants can be

placed bilaterally between the central and lateral incisor roots. Forces of differing

magnitudes then can be applied on each side for improvement of the canted occlusal

plane during intrusion.

5.4 Anterior Intrusion Mechanics in the Mandibular Arch

For intrusion of the mandibular anterior teeth, Mini Implants can be placed between

the roots of the lower incisors. Again, force can be applied from the Mini Implant

directly to the main archwire. One mini implant placed between the lower central

incisor roots usually is sufficient to allow for intrusion of the entire mandibular anterior

segment. However, if the occlusal plane is canted transversely, two mini implants can

be inserted between the central and lateral incisor roots bilaterally. Differential forces

then can be applied for improvement of the canted occlusal plane during intrusion.

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5.5 Anterior en masse Retraction with Anterior Intrusion

In deep bite extraction cases, high-pull mechanics are recommended in the maxillary

arch for intrusion of the anterior teeth during en masse retraction. In reality, it is

difficult to place Mini Implants higher in the buccal vestibule. In addition, high-pull

mechanics do not produce much of a horizontal force compared to low-pull or

medium-pull mechanics. Thus, we recommend using two posterior Mini-Implants in

low or medium-pull orientation combined with one or two anterior Mini Implants.

Posterior Mini Implants usually will be more effective in retracting the anterior teeth,

whereas anterior Mini Implants will be more effective in their intrusion. Furthermore,

anterior intrusion Mini Implants will counteract the tendency for incisors to tip

lingually during their retraction

5.6 Molar Intrusion Mechanics for Open bite Cases

‘In that it is possible to intrude molar teeth using Mini Implants, open bites can be

corrected relatively easily, especially skeletal open bites. If 1mm of absolute molar

intrusion is achieved posteriorly, an anterior open bite of 2 to 3 mm will be closed

anteriorly. A Mini Implant can be placed between the roots of the maxillary second

premolar and first molar and/or the first molar and second molar buccally and/or

palatally, for the intrusion of maxillary molar teeth. A transpalatal arch (TPA) is used

for palatal support in the absence of palatally-placed Mini Implants. In the mandibular

arch, however, it is not advisable to insert mini implants lingual to the molar roots: a

lingual holding arch can be used for support instead.

5.7 Maxillary Anterior Lingual Root Torque Mechanics

After anterior en masse retraction in an extraction case, severe lingual tipping of the

maxillary anterior teeth sometimes is observed. Whenever lingual root torque then is

applied, labial crown tipping usually is observed instead. To prevent this kind of labial

crown tipping, Class II elastics are required. Moreover, to prevent the side effects of

Class II elastics, up-and-down vertical elastics and high-pull headgear are used. Mini

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Implants in the maxillary buccal area, however, also can prevent labial crown tipping

during lingual root torque application; ligature wires are connected from the Mini

Implants to the anterior portion of the main archwire.

5.8 Molar Distalization Mechanics for Non-Extraction Cases

To correct Class II or Class III molar relationships, sometimes it is necessary to

distalize molar.

Mini Implants can be placed between the roots of the second premolar and first

molar, and nickel titanium coil springs can be used. After molar distalization, the

anterior teeth will need to be retracted. The first Mini Implant can be removed if it

interferes with this

retraction, & a second mini

implant is placed just distal

to the first one or between

the first molar & second molar roots

5.8.1 Retraction of the Entire Maxillary or Mandibular Dentition

Two buccally placed mini implants can provide

sufficient anchorage to move the entire maxillary or

mandibular dentition posteriorly. Usually mini implants

are inserted between the roots of second premolar and

first molar.

Retraction of the entire dentition is more positive in

patients who have mesially tipped posterior teeth. Thus, Mini Implants function nicely

in combination with the multiloop edgewise archwire (MEAW) technique of Kim

(Kim, 1999a,b, 141_.; Chang and Moon, 1999) for retraction of the entire dentition.

Mini Implants

Figure 12

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5.8.2 Midpalatal Mini Implant Placement For Molar Distalization

The midpalatal area also is a good site for mini implant placement because the

palate is covered with relatively thin keratinized mucosa and has adequate bone

volume. Additionally, there is no concern about a Mini Implant touching the roots of

adjacent teeth during implantation. However, if the patient has a broad unossified

suture, sufficient mechanical stability is not possible. In this situation it is better to

place the Mini Implants parasagittally. For molar distalization, orthodontic forces can

be applied from a Mini Implant to the center point of a transpalatal arch. Furthermore,

a mid-palatal mini implant can be used to anchor orthodontic force, which is applied

from a level high above the center of rotation of the molars. Thus, distalization traction

or distal tipping of roots can be achieved rather easily with midpalatal implants than

with buccally placed Mini implants.

If a bracket head type of Mini Implant is placed in the midpalatal area, a transpalatal

arch can be inserted directly into the bracket slots. Force can be applied directly to the

teeth from the transpalatal arch, much in the same manner as with a pendulum

appliance (Hilgem 1992;)_ The incorporation of a midpalatal mini implant into a

transpalatal arch can be technically challenging, however, because of the level of

precision required. In addition the application of elastomers for tooth movement can be

difficult especially in patients who have high and narrow palates

5.9 Protraction Mechanics in Extraction Cases

Sometimes molar protraction is needed in minimum or moderate anchorage cases or

unusual extraction cases. However, molar protraction is one of the most difficult tooth

movement to accomplish, especially in patients with a low mandibular plane, Class 2 &

a deep bite. If mini implants are incorporated into the treatment protocol, molars can be

moved forward more effectively and without disturbing the anterior teeth. Mini

implants, for this purpose can be placed between the roots of the mandibular canine

and first premolar or first premolar and 2nd premolar.

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5.10 Minor Tooth Movements Using Mini Implant Anchorage

5.10.1 Retromolar Mini Implants for Single Molar Uprighting -

A single retromolar Mini Implant is useful in uprighting a

mesially tipped molar. Elastic chain or ligature wire can be

connected from a retromolar Mini Implant to an attachment on

the tipped molar (Fig.5-31). These mechanics produce an

intrusive force during molar uprighting and prevent the

occlusal trauma that normally would occur with

conventional uprighting techniques. However, this type of

simple retromolar Mini Implant mechanics cannot control

the movement of a tooth precisely.

5.10.2 Molar Distalizatien Using a Single Mini Implant in an Edentulous Area

For distalization of a molar tooth (or teeth) that is (are)

adjacent to an edentulous area, an open coil spring can be

used on the main archwire in the edentulous region. To

prevent tipping, the anterior teeth labially, a Mini Implant

can be placed in the edentulous area and connected by a

ligature wire to a sliding hook on the main archwire as

shown in Figure 14. The open coil NiTi spring is

compressed by tying the ligature to the sliding hook and

moving the hook posteriorly along the archwire.

5.10.3 Molar Uprighting and/or Protraction or

Distalization Mechanics Using Two Mini Implants in an Edentulous Area

Mini Implants

Figure 14

Figure 13

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A single Mini implant cannot resist rotational or torquing forces. To resist rotational

and torquing forces, two Mini Implants can be placed

side-by-side in an edentulous area and then joined

together using light-cured resin. Subsequently, a

bracket can be bonded to the resin of the Mini Implant-

supported structure. A rectangular wire inserted into

this bracket will facilitate three-dimensional

movement of the involved tooth (Figure 12)

5.11 Buccal Cross bite (Scissors Bite) Correction

Correcting a scissors bite with conventional orthodontic mechanics requires the use

of through-the bite elastics (Graber, I972; Moyers, 1988;) However, if these elastics are

used, undesirable extrusion of the posterior teeth may occur. To correct a scissors bite

without causing molar extrusion, intra-arch mechanics, rather than interarch

mechanics, must be used. Transpalatal and lingual arches can be used to reinforce

anchorage in conventional intra-arch methods. If mini implants are used, the same type

of uprighting and intrusion is observed during buccal

cross bite correction. With only one Mini Implant,

however, it is difficult to apply orthodontic force in

the proper direction; if a bracket head type of Mini

Implant is selected, a wire can be extended from the

slot of the bracket to allow the force to be applied

more effectively. Different handed screws, i.e., right and left-handed, are inserted

depending upon the moment and force to be applied

Mini Implants

Figure 15

Figure 16

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Indications & Contraindications

“That, which does not kill us, makes us stronger.”

– Freidrich Nietzsche

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6 Indications & Contraindications

Indications, Contraindication & Relative Contraindications

Absolute anchorage represents new orthodontic paradigm and it is maybe the most

important advancement in recent times, because it offers the orthodontics of " action

without reaction", practically eliminating the third principle of Newton. Indications for

miniimplants can be for achieving the absolute anchorage or forces directions which

would be very difficult to achieve using the traditional mechanics.

There are two basic forms of absolute anchorage: -

Direct anchorage:

When active segment is pulled directly from min implant

.

Indirect anchorage:

When active segment is pulled from the reactive segment and this segment is

fixed to miniimplant to increase anchorage.

6.1 INDICATIONS

The most frequent indications are:

1. Molar intrusion.

2. Molar uprighting by crown distalizing or by root mesializing.

3. Anterior open bite treatment with molar intrusion (with or without

extractions).

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4. Anterior deep bite treatment with incisal intrusion (with or without

extractions) .

5. Leveling of transverse tipping of occlusal plane.

6. Extraction cases.

7. Distalizing or anchorage after distal movement with other kinds of

appliances, such as Pendulum.

8. Forced eruption of included or non-included teeth.

9. Asymmetric expansion.

10. Bodily movement of teeth or a group of teeth.

11. As surgical fixation with lingual brackets.

12. Absolute anchorage in lingual orthodontics.

13. They can be used in a growing patient.

14. Edentulous spaces closure.

6.2 CONTRAINDICATIONS

1. Systemic diseases such as diabetes, osteoporosis, osteomyelitis, blood

dyscrasias, metabolism disorders,etc.

2. Patient undergoing the radiotherapy in arches.

3. Psychological disorders.

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4. Presence of active oral infections.

5. Uncontrolled periodontal disease.

6. Presence of pathological formations in the zone, such as tumors or cysts.

7. Insufficient space for insertion of miniimplant.

8. Thin cortical bone and insufficient retention.

9. Deficient quality of the bone.

10. Soft tissue lesions, such as lichen planus, leucoplakia, etc.

11. Patient who does not accept miniimplant treatment.

6.3 RELATIVE CONTRAINDICATIONS

1. Tobacco, alcohol and drugs abuse.

2. Mouth breather.

3. Absence of 'ability to maintain the correct oral hygiene’.

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Clinical Applications

“That, which does not kill us, makes us stronger.”

– Freidrich Nietzsche

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7 CLINICAL APPLICATIONS

Guire reported potential uses of TADs for Orthodontic Purposes 43:

Three Dimensions and Three Tissue Considerations (3D/3T).

3D/3T Anterior-Posterior Vertical Transverse

Skeletal Possibly as anchors to

prevent unwanted dental

movement during

conventional orthopedic

corrections such as Herbst.

Possibly eliminate

compensatory

eruption of teeth occurring as

a result of natural growth to

yield a more anterior rather

than vertical growth.

Intrusion of upper

and/or lower facial

height in cases of excess

vertical growth through

counterclockwise

rotation of the mandible.

Possibly intrusion of

entire upper and/or

lower dental arch to

eliminate excess alveolar

display ("gummy

smile")

in cases of maxillary

alveolar hyperplasia.

Possibly true

orthopedic

maxillary

expansion, without

the undesirable

tipping of posterior

teeth that occurs in

traditional

expansion.

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Soft tissue Close spaces completely

from the posterior to maintain

the incisor position for

optimal lip support.

Close spaces completely

from the anterior to reduce

excessive lip protrusion.

In selected cases,

eliminate lip

incompetency through

decreasing lower-face

height.

Dental Close spaces completely

from anterior or posterior

congenitally missing teeth,

thus eliminating the need for

bridge or implant.

Close spaces in cases of

previously extracted or lost

teeth, thus possibly

eliminating a bridge or

implant.

Retract maxillary and/or

mandibular anterior segments

completely without unwanted

anterior molar movement,

i.e., loss of posterior

anchorage.

Uprighting tipped molars

without extruding.

Intrusion of over-

erupted Upper and/or

lower Anterior teeth in

cases of Deep bite.

Intrusion of

overerupted single or

multiple posterior teeth.

Extrusion of impacted

teeth without unwanted

reciprocal effects on

anchor teeth

True unilateral

movement of

buccal segments to

eliminate true

unilateral cross-

bites

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Maintain torque control of

incisors during retraction by

directing forces through the

center of resistance.

En masse movement of

arches mesially or distally to

correct Class II or III molar

and canine relations.

Asymmetric correction of

Class II or III dental relation.

Correction of a canted

occlusal plane.

3D/3T Anterior-Posterior Vertical Transverse

Other factors:

1. Oral health May decrease orthodontic treatment time, thereby

minimizing deleterious effect of orthodontic appliances

on oral hygiene procedures.

2. Perimeter In cases requiring the extraction of permanent teeth,

the orthodontist has the ability to choose a malformed,

previously restored, or otherwise compromised tooth

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rather than a virgin tooth that might normally be needed

in planning for anchorage requirements.

In Class I cases having a non-extraction lower arch

and congenitally missing one or two maxillary lateral

incisors, there is the possibility of unilateral or bilateral

space closure from the posterior, thus giving patient the

option of substituting a canine for the lateral incisor

instead of a bridge or implant.

Ability to distalize molars through translation (i.e.,

bodily movement) rather than tipping

3. Interactions Eliminate the need for patient compliance in headgear

or elastic wear thus reducing treatment time.

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Biological aspects of

Orthodontic Mini-implants

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8 Biology of orthodontic implants

Biologic aspects of orthodontic implantation, the healing process, and the formation

of the tissue-implant interface.

8.1 Bone-to-Implant interface:

Anabolic modeling on bone surfaces is the first osseous healing reaction following

implantation of a biocompatible device into cortical bone. Similar to fracture healing, a

bridging callus forms at the periosteal and endosteal surfaces. Under optimal

conditions (minimal trauma and vascular compromise) the callus originates within a

few millimeters from the margin of the implantation site. In rabbits, the lattice of

woven bone reaches the implant surface in about 2 weeks and is sufficiently compacted

and remodeled by 6 weeks to provide adequate resistance to loading. There is no

quantitative data for the early healing process in humans. Extrapolating from relative

durations of the remodeling cycles (6 weeks vs. 4 months), timing for the primary

callus (woven bone) may be similar to rabbits but the remodeling-dependent

maturation process probably requires 3 times longer (up to 18 weeks).

If periosteum is stripped, the callus must originate in the nearest untraumatized

osteogenic tissue. Since healing reactions are self limiting, extensive loss of the

osteogenic (inner) layer may preclude periosteal bridging altogether. Reapproximating

retracted periosteum when the wound is closed positions the nonosteogenic fibrous

(outer) layer near the implant. A compromised osteogenic reaction, associated with a

defect in the periosteal margin of bone, may favor invasion of fibrous connective

tissue. Extensive stripping of periosteum substantially inhibits the initial healing re-

sponse. Even though stimulating cytokines and growth factors are released from the

blood clot at the surgical site, essentially no competent osteoprogenitor cells survive

periosteal stripping. These cells must be reintroduced by ingrowth of new vascular

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tissue. Therefore the surgeon should minimize periosteal trauma consistent with

adequate access and appropriate soft tissue management.

Efficient reduction of an osseous defect by a bridging callus requires relative

stability of the approximating segments. An unloaded healing phase (two-stage implan-

tation procedure) is widely used to prevent extensive functional movement during

healing. However, there are other important biomechanical considerations:

Mechanical retention of the implant within the wound

Approximation of the periosteal margin of the cortex to the implant surface and

Functional flexure of the implanted bone.

Healing implants in functioning bones are never really "unloaded." The initial callus

reaction near the implant is primarily driven by local cytokines and growth factors;

however, the overall size and extent of the periosteal callus is mechanically dependent.

A surgical defect weakens the bone and, as a result, may increase peak strains at a

distance from the surgical site. Focal areas of new bone formation (additional regions

of woven or lamellar bone) are often noted around the bone. Remodeling of the callus

begins early in the healing period. According to the principle of adequate strength with

minimal mass, the callus reduces in size and reorients as internal maturation and

strength are attained. 18

Interface remodeling is essential in establishing a viable interface between the

implant and original bone. About a millimeter of compacta adjacent to the osseous

wound dies postoperatively despite optimal surgical technique. This is probably

because of inflammation and the relatively poor collateral circulation within cortical

bone. Dead bone is not useless tissue; it provides important structural support during

the initial healing phase. However, it must be replaced with vital bone (via remodeling)

to strengthen the interface and provide adaptable tissue for long-term maintenance.

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Remodeling of the nonvital interface is achieved by cutting/filling cones emanating

from the endosteal surface. The mechanism is similar to typical cortical remodeling

except that many of the cutting/filling cones are oriented perpendicular to the usual

pathway (long axis of the bone). In longitudinal sections, cutting/filling cones

occasionally deviate from the plane of the interface, turn 90 degrees, and form a

secondary osteon perpendicular to the interface. At the/same time the interface is

remodeled, the adjacent nonvital cortex (viewed in cross-section) is penetrated by

typical cutting/filling cones.

Maturation of the interface and supporting bone has been suggested to require an

elapsed time after implant placement of about 3 sigma (12 months) 44. The first 4

months (1 sigma) is the initial "unloaded" healing process. During maturation the

callus volume is decreased and interface remodeling continues. The bone maturation

phase requires an additional 2 sigma (8 months).

It was previously believed that maturation involved two physiologic transients:

The regional acceleratory phenomenon (RAP) and

Secondary mineralization of newly formed bone.

Extensive remodeling (RAP) in cortical bone is a well-known healing reaction to

surgical wounds and is certainly evident in bone surrounding implants. In general, the

remodeling sites decrease with increasing distance from the wound 27. It is also well

accepted that stiffness and strength of lamellar bone are directly related to mineral

content. Because of this, it was previously suggested that full strength of bone

supporting an implant would not be achieved until about 12 months (54 weeks) after

the bone is formed, that is, after completion of the secondary mineralization process.

However, recent evidence has shown that elevated remodeling is an ongoing response

of bone adjacent (<1 mm) to an implant 45. Because of rapid remodeling at the

interface, it is likely that the secondary mineralization process is not completed and the

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mineral content of bone supporting an implant remains lower than that of the

surrounding bone.

Long-term maintenance of the rigid osseous fixation involves continuous

remodeling of the interface and supporting bone. Bone, like other relatively rigid

materials, is subject to fatigue. Repetitive loading results in microscopic cracks

(microdamage). If allowed to accumulate, these small defects can lead to structural

failure. Because osteoclasts preferentially resorb more highly mineralized tissue,

cutting cones tend to remodel the oldest and presumably most weakened bone. This

physiologic mechanism helps to maintain structural integrity indefinitely. Human

cortical bone from long-bone midshaft diaphysis and rib remodels at a rate of about 2%

to 10% per year 27. No human data is available for mandibular cortical bone. However,

based on recent studies in dogs (which have diaphyseal and rib remodeling rates

similar to humans), cortical bone supporting the teeth may have a substantially higher

remodeling rate (30% to 40% per year). The interaction of mechanical and metabolic

factors in controlling adult bone remodeling is not well understood. Cortical bone

around an endosseous implant continues to remodel. Long-term maintenance of rigid

osseous fixation involves a remodeling rate of as much as approximately 500% per

year in bone immediately adjacent (within 1 mm) to an implant 27. Although the precise

reason for the sustained remodeling response is unclear, its physiologic control appears

strongly related to the mechanical stress distribution concentrated in bone adjacent to

the interface. Data from four animal species (including humans) indicate that the

elevated remodeling response is a universal mechanism necessary for the long-term

retention of rigidly integrated implants.

8.2 Support and load transfer /mechanisms:

The three basic means of retention of an endosteal dental implant in function are

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i. Fibroosseous retention,

ii. Biointegration and

iii. Osseointegration.

According to the American Academy of Implant Dentistry (AAID) Glossary of

Terms (1986) 46

Fibrosseous retention is defined as tissue-to-implant contact; interposition of

healthy, dense collagenous tissue between the implant and bone.

Osseointegration is defined as contact established between normal and remolded

bone and an implant surface without the interposition of non-bone or connective tissue.

Bioactive retention is achieved with bioactive materials such as hydroxyapatite

(HA), which bond directly to bone, similar to ankylosis of natural teeth. Bone matrix is

deposited on the HA layer as a result of some type of physiochemical interaction

between the collagen of bone and HA crystals of implant.

To a certain extent, it appears to be within the hands of the clinician to control which

method of load bearing will he established by the host. Relative movement during

healing has been shown to be the determining factor 47. If the implant is loaded so that

the implant moves relative to its surrounding bone during the healing phase, then a

tendon or ligament will occur around a plate or subperiosteal implant. If the implant is

allowed to heal without relative movement, then ankylosis can be expected to occur.

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Complications with Mini

Implants & their

management

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9 Complications with use of Mini Implants & their management

Risks, Complications of Orthodontic miniscrews and Measures to prevent it.

Complications can arise during miniscrew placement and after orthodontic loading

that affect stability and patient safety 48 .

COMPLICATIONS DURING INSERTION

i. Trauma to the periodontal ligament or the dental root.

ii. Miniscrew slippage.

iii. Nerve involvement.

iv. Air subcutaneous emphysema.

v. Nasal and maxillary sinus perforation.

vi. Miniscrew bending, fracture, and torsional stress.

COMPLICATIONS UNDER ORTHODONTIC LOADING

i. Stationary anchorage failure.

ii. Miniscrew migration.

SOFT-TISSUE COMPLICATIONS

i. Aphthous ulceration.

ii. Soft-tissue coverage of the miniscrew head and auxiliary.

iii. Soft tissue inflammation, infection, and peri-implantitis.

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COMPLICATIONS DURING REMOVAL

i. Miniscrew fracture.

ii. Partial osseointegration.

9.1 COMPLICATIONS DURING INSERTION

9.1.1 Trauma to the periodontal ligament or the dental root.

Interradicular placement of orthodontic miniscrews risks trauma to the periodontal

ligament or the dental root. Potential complications of root injury include loss of tooth

vitality, osteosclerosis, and dentoalveolar ankylosis. Trauma to the outer dental root

without pulpal involvement will most likely not influence the tooth's prognosis 49.

Dental roots damaged by orthodontic miniscrews have demonstrated complete repair of

tooth and periodontium in 12 to 18 weeks after removal of the miniscrew. 50

Interradicular placement requires proper radiographic planning, including surgical

guide with panoramic and periapical radiographs to determine the safest site for

miniscrew placement.

During inter-radicular placement in the posterior region, there is a tendency for the

clinician to change the angle of insertion by inadvertently pulling the hand-driver

toward their body, increasing the risk of root contact. 48 To avoid this, the clinician may

consider using a finger-wrench or work the hand-driver slightly away from their body

with each turn. If the miniscrew begins to approximate the periodontal ligament, the

patient will experience increased sensation under topical anesthesia. If root contact

occurs, the miniscrew may either stop or begin to require greater insertion strength 51. If

trauma is suspected, the clinician should unscrew the miniscrew 2 or 3 turns and

evaluate it radiographically.

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9.1.2 Miniscrew slippage

The clinician might fail to fully engage cortical bone during placement and

inadvertently slide the miniscrew under the mucosal tissue along the periosteum. High-

risk regions for miniscrew slippage include sloped bony planes in alveolar mucosa

such as the zygomatic buttress, the retromolar pad, the buccal cortical shelf, and the

maxillary buccal exostosis if present. Slippage in the retromolar pad can lead to the

greatest risk of iatrogenic harm if the miniscrew moves lingually in the submandibular

or lateral pharyngeal space near the lingual and inferior alveolar branch nerves. In the

retromolar region, serious consideration should be given to flap exposure for direct

visualization and a predrilled pilot hole, even for self-drilling miniscrews. If the al-

veolar tissue is thin and taut, some clinicians advocate placing the pilot hole with a

transmucosal method, using a slow-speed bur to perforate both tissue and cortical bone

without making a flap 52.

Miniscrew slippage can occur in dentoalveolar regions of attached gingiva if the

angle of insertion is too steep. Placement of miniscrews less than 30° from the occlusal

plane, typically to avoid root contact in the maxilla or to gain cortical anchorage in the

mandible, can increase the risk of slippage. To avoid this, the clinician can initially

engage bone with the miniscrew at a more obtuse angle before reducing the angle of

insertion after the second or third turn. Miniscrews should engage cortical bone after 1

or 2 turns with the hand-driver. Only minimal force should be used with the hand-

driver, regardless of bone density. Greater forces increase the risk of miniscrew

slippage.

9.1.3 Nerve involvement:

Nerve injury can occur during placement of miniscrews in the maxillary palatal

slope, the mandibular buccal dentoalveolus, and the retromolar region. Most minor

nerve injuries not involving complete tears are transient, with full correction in 6

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months. Long-standing sensory aberrations might require pharmacotherapy

(corticosteroids), microneurosurgery, grafting, or laser therapy 48.

Placement of miniscrews in the maxillary palatal slope risks injury to the greater

palatine nerve exiting the greater palatine foramen. The greater palatine foramen is

located laterally to the third molar or between the second and third molars. Location,

size, and shape of the foramen can vary with ethnicity. 53 The greater palatine nerve

exits the foramen and runs anteriorly, 5 to 15 mm from the gingival border, to the

incisive foramen. Miniscrews inserted in the palatal slope should be placed medial to

the nerve and mesial to the second molar. Placement of the miniscrew above the nerve

could increase the risk of palatal root contact and reduce biomechanical control.

Placement of the miniscrews in the mandibular buccal dentoalveolus risks injury to

the inferior alveolar nerve in the mandibular canal. The mandibular canal travels

forward in an S-shaped curve moving from buccal to lingual to buccal. The inferior

alveolar nerve occupies its most buccal position within the body of the mandible at the

distal root of the second molar and the apex of the second premolar, before exiting

from the mental foramen. Miniscrews inserted near the mandibular second molar and

the second premolars are at greatest risk for accidental damage to the inferior alveolar

nerve. 54 The soft-tissue appearance of the dentoalveolus can be deceptive, and a

panoramic radiograph should be taken to determine the vertical position of mandibular

canal and the location of the mental foramina. Greater caution is needed in adult

patients who might have a more occlusal position of the mandibular canal due to

resorption of the alveolar ridge.

Placement of miniscrews in the retromolar pad risks injury to the long buccal nerve

and the lingual nerve. The long buccal nerve branches off the mandibular nerve trunk

and crosses high on the retromolar pad supplying the mucosa of the cheek. The lingual

nerve runs immediately under the floor of the mouth and supplies general sensory

innervation to the anterior two thirds of the tongue. To avoid nerve involvement and

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slippage, the retromolar miniscrews should be no longer than 8 mm and placed in the

buccal retromolar region below the anterior ramus is been recommended.

9.1.4 Air subcutaneous emphysema:

Air subcutaneous emphysema is the condition in which air penetrates the skin or

submucosa, resulting in soft-tissue distention. Subcutaneous emphysema can occur

during routine operative dental procedures if air from the high-speed or air-water

syringe travels under the gingival tissues. The main symptom of air subcutaneous

emphysema is immediate mucosal swelling with or without crepitus (crackling).

Additional sequelae include cervicofacial swelling, orbital swelling, otalgia, hearing

loss, mild discomfort, airway obstruction, and possibly interseptal and interproximal

alveolar necrosis. Clinically visible swelling of the skin and mucosa occurs within

seconds to minutes after air has penetrated the submucosal space and typically spreads

to the neck (in 95% of cases) or the orbital area (in 45% of cases).

The clinician should be alert for subcutaneous emphysema during miniscrew

placement through the loose alveolar tissue of the retromolar, mandibular posterior

buccal, and the maxillary zygomatic regions. If a purchase point or pilot hole is to be

drilled through the mucosa, the clinician should use slow speed under low rotary

pressure. If either a pilot hole or a mucosal punch is placed, an air-water syringe should

never be used. Air from the syringe can enter the submucosal space through the small

tissue opening, even in attached tissue. Bleeding and saliva should be controlled with

suction, cotton, and gauze, rather than an air-water syringe. 48 In case of subcutaneous

emphysema, the clinician should immediately discontinue the procedure and take

periapical and panoramic radiographs to determine the extent of the condition. The

patient should not be dismissed until the swelling begins to regress and an infection can

be ruled out. Upon dismissal, the patient should be instructed to apply light pressure

with an ice pack for the first 24 hours. The clinician could prescribe a mild analgesic,

an antibacterial rinse, such as chlorhexidine, and an antibiotic prophylaxis for a week.

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In most cases of subcutaneous emphysema, careful observation for further problems or

infection is adequate, and swelling and symptoms generally subside in 3 to 10 days.

9.1.5 Nasal and maxillary sinus perforation:

Perforation of the nasal sinus and the maxillary sinuses can occur during miniscrew

placement in the maxillary incisal, maxillary posterior dentoalveolar, and zygomatic

regions. A posterior atrophic maxilla is a major risk factor for sinus perforation. The

sinus floor is deepest in the first molar region and can extend to fill a large part of the

alveolar process in posterior edentulous spaces. Penetration of the Schneiderian

membrane is a well-documented phenomenon that often occurs when the thin, lateral

wall of the sinus is infractured from the buccal side. Small (<2 mm) perforations of the

maxillary sinus heal by themselves without complications. 55 Ardekian et al and

Branemark et al 56 reported that immediately loaded dental implants that perforated the

nasal and maxillary sinuses showed no differences in implant stability.

If the maxillary sinus has been perforated, the small diameter of the miniscrew does

not warrant its immediate removal. Orthodontic therapy should continue, and the

patient should be monitored for potential development of sinusitis and mucocele. For

miniscrews placed in pneumatized, edentulous regions of the maxilla, or placed higher

in the posterior maxilla when intrusive forces are desired, the clinician should consider

angulating the miniscrew perpendicular to the alveolar ridge to avoid damage to the

sinus.

9.1.6 Miniscrew bending, fracture, and torsional stress:

Increased torsional stress during placement can lead to implant bending or fracture,

or produce small cracks in the peri-implant bone, that affect miniscrew stability. 39 Self-

drilling miniscrews should be inserted slowly, with minimal pressure, to assure

maximum miniscrew-bone contact. A purchase point or a pilot hole is recommended in

regions of dense cortical bone, even for self-drilling miniscrews. During miniscrew

placement in dense cortical bone, the clinician should consider periodically derotating

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the miniscrew 1 or 2 turns to reduce the stresses on the miniscrew and the bone. The

clinician should stop inserting the miniscrew as soon as the smooth neck of its shaft has

reached the periosteum. Over insertion can add torsional stress to the miniscrew neck,

leading to screw loosening and soft-tissue overgrowth. Once the miniscrew has been

inserted, torsional stress from wiggling the hand-driver off the miniscrew head can

weaken stability. When removing the hand-driver from the miniscrew head, the

clinician should gently separate the hand-driver handle from its shaft and then gently

remove the shaft from the miniscrew head.

9.2 COMPLICATIONS UNDER ORTHODONTIC LOADING

9.2.1 Stationary anchorage failure:

According to the literature, the rates of stationary anchorage failure of miniscrews

under orthodontic loading vary between 11% and 30%. If a miniscrew loosens, it will

not regain stability and will probably need to be removed and replaced. 57 Stability of

the orthodontic miniscrew throughout treatment depends on bone density, peri-implant

soft tissues, miniscrew design, surgical technique, and force load. 58

The key determinant for stationary anchorage is bone density. 59 Stationary

anchorage failure is often a result of low bone density due to inadequate cortical

thickness 49. Bone density is classified into 4 groups (Dl, D2, D3, and D4) based on

Hounsfield units (HU)—an x-ray attenuation unit used in computed tomography scan

interpretation to characterize the density of a substance.132

a) D1 (>1250 HU) is dense cortical bone primarily found in the anterior mandible

and the maxillary midpalatal area.

b) D2 (850-1250 HU) is thick (2 mm), porous cortical bone with coarse trabeculae

primarily found in the anterior maxilla and the posterior mandible.

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c) D3 (350-850 HU) is thin (1 mm), porous cortical bone with fine trabeculae

primarily found in the posterior maxilla with some in the posterior mandible.

d) D4 (150-350 HU) is fine trabecular bone primarily found in the posterior

maxilla and the tuberosity region.

Figure 17 Areas according to Bone density

Sevimay et al 60 reported that osseointegrated dental implants placed in Dl and D2

bone showed lower stresses at the implant-bone interface. D1-D3 bone is optimal for

self-drilling miniscrews. Placement of miniscrews in Dl and D2 bone might provide

greater stationary anchorage under orthodontic loading. Placement of miniscrews in D4

bone is not recommended due to the reported high failure rate. In general, stationary

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anchorage failure is greater in the maxilla, with the exception of the midpalatal region,

due to the greater trabeculae and lower bone density. 61 Loss of mid-palatal miniscrews

is likely a result of tongue pressure.

Peri-implant soft-tissue type, health, and thickness can affect stationary anchorage of

the miniscrew. Miniscrews placed in nonkeratinized alveolar tissues have greater

failure rates than those in attached tissues. 62 The movable, nonkeratinized alveolar

mucosa is easily irritated; soft-tissue inflammation around the miniscrew is directly

associated with increased mobility 34. Additionally, miniscrews placed in regions of

thick keratinized tissue, such as the palatal slope, are less likely to obtain adequate

bony stability. Thin, keratinized tissue, seen in the dentoalveolar or midpalatal region,

is ideal for miniscrew placement.

Miniscrew geometry and surgical technique directly influence the stress distribution

of peri-implant bone. Most miniscrew losses occur as a result of excessive stress at the

screw-bone interface. Self-drilling miniscrews can have greater screw-bone contacts

(mechanical grip) and holding strengths compared with self-tapping screws. 33

Heidemann et al 63 reported greater residual bone between screw threads of self-drilling

miniscrews compared with self-tapping miniscrews. Self-tapping miniscrews, like self-

drilling screws, can be placed without a predrilled pilot hole in the dentoalveolar region

if the cortical bone is thin. If a pilot hole is to be used, for either self-drill ing or self-

tapping miniscrews, the pilot hole size should be no greater than 85% of the diameter

of the miniscrew shaft for optimal stability.

It is still not clear the maximum force-load a miniscrew can withstand in regard to

stationary anchorage. Dalstra et al 35reported that miniscrews inserted into thin cortical

bone and fine trabeculae should be limited to 50 g of immediate loaded force. Buchter

et al 58 reported that miniscrews placed in dense mandibular bone remained clinically

stable with up to 900 g of force. Many articles reported miniscrew stability with

loading forces of 300 g or less. In regions of poor bone density, simply placing a longer

miniscrew under smaller orthodontic force does not ensure stationary anchorage. 64

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9.2.2 Miniscrew migration:

Orthodontic miniscrews can remain clinically stable but not absolutely stationary

under orthodontic loading.64 Unlike an endosseous dental implant, that osseointegrates,

orthodontic miniscrews achieve stability primarily through mechanical retention, and

can be displaced within the bone. Liou et al reported that orthodontic miniscrews

loaded with 400 g of force for 9 months extruded and tipped -1.0 to 1.5 mm in 7 of 16

patients. To account for potential migration, the clinician should allow a 2-mm safety

clearance between the miniscrew and any anatomical structures.

9.3 SOFT-TISSUE COMPLICATIONS

9.3.1 Aphthous ulceration:

Minor aphthous ulcerations, or canker sores, can develop around the miniscrew shaft

or on the adjacent buccal mucosa in contact with the miniscrew head. Aphthi are

characterized as mildly painful ulcers affecting nonkeratinized mucosa. Minor

aphthous ulcerations are typically caused by soft-tissue trauma but might occur as a

result of genetic predisposition, bacterial infection, allergy, hormonal imbalance,

vitamin imbalance, and immunologic and psychologic factors. Minor aphthous

ulcerations are self-limiting and resolve within 7 to 10 days without scarring. 65

Placement of a healing abutment, a wax pellet, or a large elastic separator over the

miniscrew head, with daily use of chlorhexidine (0.12%, 10 mL), typically prevents

ulceration and improves patient comfort. The occurrence of aphthous ulceration does

not appear to be a direct risk factor for miniscrew stability, but its presence might

forewarn of greater soft-tissue inflammation.

9.3.2 Soft-tissue coverage of the miniscrew head and auxiliary:

Miniscrews placed in alveolar mucosa, particularly in the mandible, might become

covered by soft tissue. The bunching and rubbing of loose alveolar tissue can lead to

coverage of both the miniscrew head and its attachments (ie, coil spring, elastic chain)

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within a day after placement. Soft-tissue coverage might be a risk factor for miniscrew

stability, as well as a clinical concern for the patient, who might think that the

miniscrew has fallen out. Miniscrew attachments (elastic chain, coil spring) that rest on

tissues will likely become covered by tissue. The soft-tissue overlaying the miniscrew

is relatively thin and can be exposed with light finger pressure, typically without an

incision or local anesthetic. Soft-tissue overgrowth can be minimized by placement of a

healing abutment cap, a wax pellet, or an elastic separator. In addition to its

antibacterial properties that minimize tissue inflammation, chlorhexidine slows down

epithelialization and might reduce the likelihood of soft-tissue overgrowth. The authors

suggest partial insertion with a longer miniscrew (10 mm) in regions of loose alveolar

mucosa, leaving 2 or 3 threads of the shaft exposed to minimize the possibility of soft-

tissue coverage.

9.3.3 Soft tissue inflammation, infection, and peri-implantitis:

Healthy peri-implant tissue plays an important role as a biologic barrier to bacteria.

Tissue inflammation, minor infection, and peri-implantitis can occur after miniscrew

placement. 66 Inflammation of the peri-implant soft tissue has been associated with a

30% increase in failure rate. Peri-implantitis is inflammation of the surrounding

implant mucosa with clinically and radiographically evident loss of bony support,

bleeding on probing, suppuration, epithelia infiltrations, and progressive mobility. The

clinician should be forewarned of soft-tissue irritation if the soft tissues begin twisting

around the miniscrew shaft during placement. Some clinicians advocate a 2-week soft-

tissue healing period for miniscrews placed in the alveolar mucosa before orthodontic

loading.135

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9.4 COMPLICATIONS DURING REMOVAL

9.4.1 Miniscrew fracture:

The miniscrew head could fracture from the neck of the shaft during removal. The

authors recommend a minimum diameter of 1.6 mm for self-drilling miniscrews that

are 8 mm or longer placed in dense cortical bone. The proper placement technique can

minimize the risk of miniscrew fracture during its removal. If the miniscrew fractures

flush with the bone, the shaft might need to be removed with a trephine. 49

9.4.2 Partial osseointegration:

Although orthodontic miniscrews achieve stationary anchorage primarily through

mechanical retention, they can achieve partial osseointegration after 3 weeks,

increasing the difficulty of their removal 19. The miniscrew typically can be removed

without complications a few days after the first attempt of removal.111

9.4.3 Ingestion of the mini-implant :

Byung-Ho Choi et al evaluated 10 dogs that each ingested 1 screw and 1 reamer. All

screws were passed spontaneously within 1 day, suggesting that spontaneous

evacuation usually occurs for orthodontic anchorage screw ingestion. Patients who

swallow these screws should be carefully observed before resorting to early surgical

removal of the screws 67. Eight of the 10 reamers ingested passed by the fourth day, but

2 became lodged.

Patients who swallow reamers should be carefully observed to determine whether

surgical removal is necessary. 68

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Advantages of Mini-implant

use

“That, which does not kill us, makes us stronger.”

– Freidrich Nietzsche

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10 Advantages of Mini Implants

• Absolute anchorage.

• New directions of forces.

• Major effectiveness of "en masse" dental movements.

• Reduction of treatment time.

• Less necessity for patient cooperation, especially if we compare microimplants

with intermaxillary elastics or headgear.

• Even though the failure index of microimplants is still high, it shouldn't be the

reason for worries if we take into account the following:

- Headgear and intermaxillary elastics also have a high percentage of failure due to

the absence of patient cooperation.

- Anchorage with auxiliary appliances such as Nance appliance also have a high

index of failure: Anchorage loss of approximately 2mm, lesions due to pressure

against palatine mucosa, infections (for example, candida albicans), debondings

and fractures of appliances, etc.

- Consequences of failures of a microimplant are nothing else but mobility or loss of

microimplant, which can be reinserted in the same site (another microimplant

with the larger diameter if the space permits it and if there is no inflammation in

the zone), or in different zone.

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APPENDIX - IProduct Company Postal address Web site

Aarhus Anchorage System

MEDICON eG Gänsäcker 15, D-78532, Tuttlingen, Germany

www.medicon.de

ScanOrto A/S Hans Edvard Teglers Vej 2, 2920-Charlottenlund, Denmark

www.aarhus-mini-implant.com

AbsoAnchor System Dentos 258 BunJi, Dong-In Dong, Jung-Gu, Taegu, Korea

www.dentos.co.kr

C-Implant Dentium Inc. 6F Dahn World B/D, 154-11 Samsung-dong, Kangnum-gu,

135-897 Seoul, Korea

www.implantium.com

Cizeta Titanium Miniscrew

Cizeta Surgical San Lazzaro di Savena, Bologna,

Italy

www.cizetasurgical.it

Dual-Top Anchor System

Jeil Medical Corporation

775-3 Daesung B/D, Daelim 3

Dong Youngdeungpoku, Seoul, Korea

www.jeilmed.co.kr

Distributed by RMO Inc.

P.O. Box 17085, Denver, CO

80217

www.rmortho.com

IMTEC Mini Ortho Implant

IMTEC Corporation

2401 N. Commerce, Ardmore, OK 73401

www.imtec.com

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Lin/Liou Orthodontic Mini

Anchorage Screw (LOMAS)

Mondeal Medical Systems GmbH

Moltkestrasse 39, D-78532 Tuttlingen, Germany.

www.mondeal.de

Distributed by Mondeal North

America, Inc.

6895 Lake Bluff Drive, Comstock Park, MI 49321

Miniscrew Anchorage System (MAS)

Micerium S.p.a. Via Marconi

Via Marconi 83, 16030 vegno, Italy

www.micerium.it

Product Company Postal address Web site Orthoanchor K1 System

Dentsply Sankin Corporation

Tokyo, Japan www.dentsply-sankin.com

Orthodontic Mini Implant (OMI)

Leone S.p.A. Via P. a Quaracchi 50, 50019

Sesto Fiorentino, Firenze, Italy

www.leone.it

Distributed by Leone America

501 W. Van Buren, Suite S, Avondale, AZ 85323

Spider Screw Anchorage System

HDC Via dell’Industria 19, 36030 Sarcedo, Italy

www.hdc-italy.com

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APPENDIX – II

FIGURE 1 A- SPIRAL-SHAFT IMPLANTS (CHERCHEVE). B- VARIOUS SIZES OF EARLY DESIGNED VENT-PLANT IMPLANTS. C - A

TRIPOD IMPLANT, ASSEMBLED. D- VARIOUS EARLY DESIGNED BLADE IMPLANTS. 8.................................13

FIGURE 3 INTRUSION ACHIEVED BY MINI IMPLANTS IN STUDIES BY KANOMI 21..................................................18

FIGURE 2 PLACEMENT OF MINI-IMPLANT..................................................................................................18

FIGURE 4. CLASSIFICATION OF BIOCOMPATIBLE TADS..................................................................................24

FIGURE 5 CLASSIFICATION OF BIOLOGIC TAD............................................................................................25

FIGURE 6............................................................................................................................................27

FIGURE 7 VARIOUS MINISCREW IMPLANTS. A, THE AARHUS ANCHORAGE SYSTEM. B, THE ABSOANCHOR. C, THE SPIDER

SCREW ANCHORAGE SYSTEM . D, THE IMTEC MINI ORTHO IMPLANT..............................................28

FIGURE 8 FROM LEFT TO RIGHT: 1.5 MM CYLINDRICAL MINI-IMPLANT WITH A SLOT AT THE SCREW HEAD; 1.6 MM

TAPERED MINI-IMPLANT WITH A SLOT AT THE SCREW HEAD; AND 2.0 MM CYLINDRICAL MINI-IMPLANT WITH

THREADS AT THE SCREW HEAD....................................................................................................29

FIGURE 9 MAXILLARY MINI-IMPLANT LOCATIONS. A. BELOW NASAL SPINE. B. IN THE PALATE. C. INFRAZYGOMATIC CREST 39.........................................................................................................................................38

FIGURE 10 MANDIBULAR MINI-IMPLANT LOCATIONS. A. RETROMOLAR AREA AND MOLAR REGION. B. ALVEOLAR

PROCESS. C. SYMPHYSIS............................................................................................................39

FIGURE 11..........................................................................................................................................44

FIGURE 12..........................................................................................................................................49

FIGURE 13..........................................................................................................................................51

FIGURE 14..........................................................................................................................................51

FIGURE 15..........................................................................................................................................52

FIGURE 16..........................................................................................................................................52

FIGURE 17 AREAS ACCORDING TO BONE DENSITY.....................................................................................76

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