causesofcrestalboneloss-AlSheri

8/6/2019 causesofcrestalboneloss-AlSheri

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Dr. Mohammed Alshehri

Saudi Fellowship in Dental Implant

The early causes of crestal bone lossaround dental implant


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The longevity of dental implants is highly dependent on

integration between implant components and oral

tissues, including hard and soft tissues.

Introduction


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Studies have shown that submerged titanium implants

had 0.9 mm to 1.6 mm marginal bone loss from the rstthread by the end of rst year in function, while only 0.05

mm to 0.13 mm bone loss occurred after the rst year.

Adell et al. Int J OralSurg 1981

Jemt et al. Int J Perio Resto Dent 1990Cox et al. Int J Oral Maxillofac Implants1987

Introduction


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The rst report in the literature to quantify the earlycrestal bone loss was a 15-year retrospective study

evaluating implants placed in edentulous jaws.

In this study, Adell et al. reported an average of 1.2 mmmarginal bone loss from the rst thread during healingand the rst year after loading.

In contrast to the bone loss during the rst year, therewas an average of only 0.1 mm bone lost annuallythereafter.


Introduction


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Based on the ndings in sub-merged implants,

Albrektsson et al. andSmith and Zarb proposed criteriafor implant success, including a vertical bone loss less

than 0.2 mm annually following the implants first year of

function.

Albreksson et al. Int J Oral Maxillofac Implants 1986Smith D and Zarb G. J Prosthet Dent 1989

Introduction


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Non-submerged implants also have demonstrated early

crestal bone loss, with greater bone loss in the maxillathan in the mandible, ranging 0.6 mm to 1.1 mm, at the

rst year of function.

Buser et al. Clin Oral Implant Res 1990

Weber et al. Clin Oral Implant Res 1992Brgger et al. Clin Oral Implants Res1998

Introduction


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Heat generated at the time of drilling, elevation of the

periosteal ap, and excessive pressure at the crestal

region during implant placement may contribute to

implant bone loss during the healing period.

Surgical trauma


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Heat generation and excessive pressure

Eriksson and Albrektsson reported that the criticaltemperature for implant site preparation was 47C for 1minute or40C for 7 minutes.

Matthews and Hirsch demonstrated that temperature

elevation was inuencedmore by the force applied thandrill speed.

Eriksson RA, Albrektsson T. J Oral MaxillofacSurg 1984Matthews L, Hirsch C. JBone JointSurg 1972

Surgical trauma


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Heat generation and excessive pressure (Cont)

it was found that when both drill speed and applied force

were increased, no signicant increase in temperature

was observed due to efficient cutting.

Matthews L,H

irsch C. JB

one JointS

urg 1972Brisman DL. Int J Oral Masillofac Implant 1996

Surgical trauma


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Sharawy M. et al. compare the heat generated by thedrills of 4 different implant systems run at speeds of

1225,1667 and 2500rpm. All of the drill systems able to

prepare an 8mm site without the temperature rising more

than 4C (to 41C).

Surgical trauma


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For all drill systems the 1225 rpm drill speed produced

30 to 40% longer drilling times when compared to2500rpm and a 20% to 40% reduction in the timerequired forbone temperature to normalise. With greaterdepth of preparation and insufficient time between drillchanges, detrimental temperatures rise of47C+ may be

reached. The authors recommend that surgeons interruptthe drilling cycle every 5 to 10 seconds to allow irriganttime to cool the osteotomy.

Sharawy M. et al. Journal of Oral and MaxillofacialSurgery 2002

Surgical trauma


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Periosteal flap

The periosteal elevation has been speculated as one of

the possible contributing factors for crestal implant boneloss.

Wilderman et al. reported that the mean horizontal boneloss after osseous surgery with periosteal elevation is

approximately 0.8 mm, and the reparative potential ishighly dependent upon the amount of cancellous bone(not cortical bone) existing underneath the cortical bone.

Wilderman et al. J Periodontol 1970

Surgical trauma


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Periosteal flap (Cont)

The bone loss atstage IIimplant surgery in successfullyosseointegrated implants is generally vertical and noted

only around the implant characterized bysaucerization,

not the surrounding bone even though during the surgery

all the bone was exposed, Therefore, this hypothesis is

not generally supported.

Surgical trauma


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Research has indicated that occlusal overload often

resulted in marginal bone loss or de-osseointegration of

successfully osseointegrated implants.


Cox et al. Int J Oral Maxillofac Implants1987

Lindquist et al. J Prosthet Dent 1988

Block MS, Kent JN. J Oral MaxillofacSurg 1990

Sanz M et al. Clin Oral Implant Res 1991

Quirynen et al. Clin Oral Implant Res 1992

Tonetti MS, Schmid J. Periodontol 2000 1994

IsidorF

. et al. Clin Oral Implant Res 1996IsidorFet al. Clin Oral Implant Res 1997

Occlusal overload


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The crestal bone around dental implants could be a

fulcrum point for lever action when a bending moment is

applied, suggesting that implants could be more

susceptible to crestal bone loss by mechanical force.

Occlusal overload


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Factors associated with increased bending overload indental implants

1. Prostheses supported by 1 or 2 implants in theposterior region.

2. Straight alignment of implants.

3. Signicant deviation of the implant axis from the line

of action.

4. High crown/implant ratio.

5. Excessive cantilever length.

Occlusal overload


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Factors associated with increased bending overload indental implants (Cont)

6. Discrepancy in dimensions between the occlusal table

and implant head.

7. Parafunctional habits.

Rangert et al. Int J Oral Maxillofac Implants 1995

Occlusal overload


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Occlusal overload

Tooth Implant

Connection PDL Osseointgration,

functional ankylosisProprioception Periodontal mechanoreceptor Osseoperception

Tactile sensitivity High Low

Axial mobility 25-100 Q 3-5 Q

Fulcrum to lateral force Apical 3rd of root Crestal bone

Signs of overloading PDL thicking, mobiliy, Screw loosening or fractur wear facets, fremitus, pain abutment fx., bone loss


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The cortical bone is known to be least resisant to shear

force which is signicantly increased by bending

overload

Reilly DT, Burstein AH. JBiomech 1975

Occlusal overload


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According to VonRecum, when 2 materials of different

modules of elasticity are placed together without

intervening material and one is loaded, a stress contour

increase is observed where the two materials first comeinto contact.

VonRecum A, editor. Handbook ofBiomaterialEvaluation.New York: Macmillan Publishing Co.; 1986.

Occlusal overload


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Photo-elastic and 3-dimensional nite element analysis

(FE A) studies demonstrated V- or U-shaped stress

patterns with greater magnitude near the point of the rst

contact between implant and photo-elastic block, whichis similar to the early crestal bone loss phenomenon.

Bidez M, McLoughlin S, Lemons JE. FEA investiga-

tions in plate-form dental implant design. In: Lemon JE,

ed. Proceedings of the First World Congress ofBiome-

chanics.San Diego: Society ofBiomechanics; 1990

Occlusal overload


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Misch claimed that the stresses at the crestal bone may

cause micro-fracture or overload, resulting in early

crestal bone loss during the rst year of function, and the

change in bone strength from loading and mineralization

after 1 year alters the stress-strain relationship and

reduces the risk of micro-fracture during the following

years.

Misch CE. Contemporary Implant Dentistry,2nded. St. Louis: Mosby; 1999

Occlusal overload


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Wiskott andBelser described a lack of osseointegration

attributed to

1. An increased pressure on the osseous bed during

implant placement.

2. Establishment of a physiologic biologic width.

3. Stress shielding.

4. Lack of adequate biomechanical coupling between

the load-bearing implant surface and thesurrounding bone.

They focused on the signicance of the relationship

between stress and bone homeostasis.

WiskottHW, Belser UC. Clin Oral Im lants Res1999

Occlusal overload


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Based on the previous study byFrost, 5 types of strain

levels interrelated with different load levels in the bone

were described:

1) Disuse, bone resorption.

2) Physiologic load, bone homeostasis.

3) Mild overload, bone mass increase.

4) Pathologic overload, irreversible bone damage.5) fracture.

FrostHM. Angle Orthod1994;64:175-188.

Occlusal overload


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The concept of "microfracture proposed by Roberts et

al. and concluded that crestal regions around dental

implants are high stress bearingareas.

He also explained that if the crestal region is over-loaded

during bone remodeling, cervical cratering is created

around dental implants. The study also suggests that

axially directedocclusion as well as progressive loading

are recommended to prevent "microfracture" during thebone remodeling periods.

Roberts et al. J Indiana Dent Assoc. 1989

Occlusal overload


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Progressive loading on dental implants during healing

stages was rst described by Misch in the 1980s to

decrease early implant bone loss and early implant

failure. Based on the concept, progressive loading needs

to be employed to allow the bone to form, remodel, and

mature to resist stress with out detrimental bone loss by

staging application of diet, occlusal contacts, prosthesis

design, and occlusal materials.

Misch CE. Progressive bone loading. In: Misch CE, ed.

Contemporary Implant Dentistry,2nd ed. St. Louis:

Mosb ; 1999

Occlusal overload


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Appleton et al. reported a decrease in crestal bone loss

was observed in progressively loaded implants,

compared to implants without progressive loading, within

a similar healing and loading period; in addition, digital

radiographs indicated an increase in bone densityin the

crestal 40% of the implant in the progressive loaded

crowns.

Appleton et al. J Dent Res1997

Occlusal overload


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Greater crestal bone loss observed at the rst year of

function compared to following years can be explained

by a reduced occlusal overloador increased resistance

to occlusal overload after the rst year of function

includes a functional adaptation of the oral musculature,wear of the prosthesis material, and/or an increase in

bone densityafter a certain time period

Occlusal overload


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peri-implantitis is one of the two main causative factors

for implant failure in later stages. A correlation between

plaque accumulation and progressive bone loss around

implants has been reported in experimental studies and

clinical studies

Peri-Implantitis


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Tonetti andSchmid reported that peri-implant mucositis

is a reversible inammatory lesion conned to peri-

implant mucosal tissues without bone loss; on the other

hand, peri-implantitis begins with bone loss arounddental implants.

Peri-Implantitis


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Clinical features of peri-implantitis were described by

Mombellias including:

1) Radiographic evidence of vertical destruction of the

crestal bone.

2) Formation of a peri-implantpocketin association with

radiographic bone loss.

3) bleeding after gentle probing, possibly with

suppuration.

4) Mucosalswellingandredness.

5) No pain typically.

Peri-Implantitis


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In an experimental study evaluating the pattern of

ligature-induced breakdown of peri-implant and

periodontal tissues in beagle dogs, signicantly greater

tissue destruction was demonstrated clinically,radiographically, and histomorphometrically at implant

areas than at tooth sites.

It was also found that signicantly fewer vascularstructures existed at implant sites compared to

periodontal tissues.

Peri-Implantitis


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The difference in collagen ber direction (parallel to the

implant surface and perpendicular to tooth surface) and

amount of vascular structure may explain the faster

pattern of tissue destruction in peri-implant tissues thanperiodontal tissues.

Peri-Implantitis


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Literature has shown that peri-implantitis is similar in

nature to periodontitis in that the microbiota of peri-

implantitis resemble the microbiota of periodontitis;

however, there has been no evidence that peri-implantitisinduces crestal bone loss during healing and the rst

year of function at a faster rate than following years.

Peri-Implantitis


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Early crestal bone loss may result in an environment that

is favorable for anaerobic bacterialgrowth, thus possibly

contributing to more bone destruction in following years.

Nonetheless, in the majority of implants the bone loss isdramatically reduced after the rst year of prosthesis

loading. Therefore, it may not be justied that peri-

implantitis is the main causative factor for early implant

bone loss.

Peri-Implantitis


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Many implant systems have an abutments used with

conventional implant types which are flush with the

implant shoulder in the contact zone. This results in the

formation of microcracks between the implant and theabutment.

Microgap and The platform-switching concept


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Numerous studies have shown that bacterial

contamination of the gap between the implant and the

abutment adverselyaffects the stability of the periimplant

tissue. If above-average axial forces are exerted on the

implant, a pumpingeffect may ensue (depending on the

positive internal / external connection at the interface)

that may then result in a flow of bacteria from the gap,

provoking the formation of inflammatory connective

tissue in the region of the implant neck.

Hermann et al. J Periodontol. 2001

Todescan et al. Int J Oral Maxillofac Implants. 2002

Dibart et al. J Oral MaxillofacSurgery. 2005



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Berglundh et al. and Lindhe et al. also evaluated the

microgap of the Brnemark 2-stage implant and found

inamed connective tissue existed 0.5 mm above andbelow the abutment-implant connection, which resulted

in 0.5 mm bone loss within 2 weeks after the abutment

was connected to the implant.

Lindhe et al. Clin Oral Implant Res1992;3:9-16.



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Ericsson et al. coined the term distance-sleeve-associated infiltrated connective tissue to describe this

phenomenon. They interpreted this to be a biologicalprotective mechanism against the bacteria residing in themicrocrack, explaining the plaque independent bone lossof approximately 1 mm during the first year. This boneloss may result in a reduction of the marginal bone levelin both the vertical and the horizontaldimensions.

Ericsson et al. J Clin Periodontol. 1995



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If the microcrack is located close to the bone, thecreation of the biologic width will occur at the expense ofthe bone.

The platform switching effect was first observed in themid-1980s. At the time, larger-diameter implants wereoften restored with narrower abutments (AnkylosDensply, Friadent, Germany; Astra-Zeneca, Sweden;Bicon, Boston), as congruent abutments were often still

unavailable. As it later turned out, this was a remarkablecoincidence.

Lazzara RJ, PorterSS. Int J Periodontics Restorative Dent. 2006



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platform-switching concept requires that this microcrack

be placed away from the implant shoulder and closer

toward the axis in order to increase the distance of this

microcrack from the bone as a protective measure.



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The clinical term biologic width denotes the dimensions

of periodontal and periimplant soft-tissue structures such

as the gingival sulcus, the junctional epithelium, and the

supracrestal connective tissues.

Biologic width


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According to measurements conducted byGargiulo et al,

the average biologic width (from the base of the sulcus to

the alveolar bone margin) is 2.04 mm, of which 0.97 mmis epithelial attachment and1.07 mm is connective tissue

attachment. These dimensions, however, are in no way

static but subject to interindividual variation (from tooth to

tooth and from patient to patient) and will also vary

according to gingival type and implant concepts.

Gargiulo et al. J Periodontol.1961Cohen DW. Biologic width. Washington,DC. Presented at Walter ReedArmy Medical Center; 1962.

Biologic width


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Biologic width


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Numerous studies have shown that bone resorption

around the implant neckdoes not startuntil the implant is

uncovered and exposed to the oral cavity. This invariablyleads to bacterial contamination of the gap between the

implant and the superstructure. Bone remodeling will

progress until the biologic width has been created and

stabilized.

Quirynen M, Van Steenberghe D. Clin Oral Implants Res. 1994

Quirynen et al. Clin Oral Implants Res. 1994

Ericsson et al. J Clin Periodontol. 1995Persson et al. Clin Oral Im lants Res. 1996.

Biologic width


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This width progress not only apically, along the vertical

axis, but according to studies conducted by Tarnow et al,

there is also a horizontal componentamounting to 11.5mm. This is the reason to maintain a minimum distance

of 3 mm between 2 implants and platform switching in

the esthetic reconstruction zone in order to obtain intact

papillae and stable inter-implant bone.

Tarnow et al. J Periodontol. 2000

Tarnow et al.. J Periodontol. 1992Tarnow et al. J Periodontol. 2003

Biologic width


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Biologic width


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This width progress not only apically, along the vertical

axis, but according to studies conducted by Tarnow et al,

there is also a horizontal componentamounting to 11.5mm. This is the reason to maintain a minimum distance

of 3 mm between 2 implants and platform switching in

the esthetic reconstruction zone in order to obtain intact

papillae and stable inter-implant bone.

Biologic width


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bone volume/bone qualityMisch CE. Contemporary Implant

Dentistry. 2nd ed. Mosby; 1999

Summary and additional parameters on the

functional and esthetic long-term results


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Mucosal quality: type/thicknessKois JC. Compend Contin Educ Dent. 2001

Kois JC. JEsthet Dent. 1994;6:3-9.




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Condition of the adjacent teethPalacci P. Esthetic Implant Dentistry.

Quintessence; 2001.




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Distances to the adjacent teethTarnow et al. J Periodontol. 2000

Tarnow et al.. J Periodontol. 1992

Tarnow et al. J Periodontol. 2003




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Biologic width and the platform switchingconcept

Nentwig J Oral Implantol. 2004

Nentwig ckenversorgungen mit dem NMSystem. 1992

Blake A. WhatEveryEngineerShould Know about ThreadedFasteners Materials and Design.

New York, NY: Lawrence Livermore Laboratories, Marcel Dekker, Inc; 1986.

Driskell DriskellBioengineering; 1985.




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Implant design: macro-/micro-/nanoleveldesign and implant dimensions

Davies JE. Int J Prosthodont. 1998




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Abutment design: macro-/micro-/nanolevelDaftaryF. Int J DentSymp. 1995




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Augmentation procedures: type/materials/membranes

Buser et al. Int J Oral Maxillofac Implants 1995




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Surgical procedure: soft-tissue

management/ton of insertionBranemark et al. Scand J Plast ReconstrSurg. 1969

Adell R et al. Int J Oral MaxillofacSurgery. 1986

Cochran et al. J Periodontol. 1997




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implant insertion depth

time of loading/time of restoration




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Prosthetic procedure: frequency of

secondary-component replacementAbrahamsson J Clin Periodontol.1997




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Suturing techniques: materials




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Provisional restorations: abutmentmaterials/abutment shapes; crown

materials/crown shapes




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Definitive restorations: abutment

materials/abutment shapes; crown

materials/crown shapes




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Patient compliance: oral hygiene/

smoking/nutrition/recall intervals




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causesofcrestalboneloss-AlSheri