SPACE CLOSURE

Prepared By: Dr.Maeen Saleh Al-Bahloly 2nd year orthodontic residentSupervised By: Dr.Ahmad Altarawenah Dr.Raed Alrbta

Outlines1) Introduction.2) Methods of space closure: Sliding mechanics. Loop mechanics.3) Closure of extraction spaces: Moderate anchorage treatment with 18 & 22-slot edgewise. Maximum anchorage treatment with 18 & 22-slot edgewise. Minimum anchorage treatment.4) Retraction methods.5) References.

Introduction

Space closure is an important step on orthodontic mechanotherapy ,solely dictated by clinical treatment objectives and irrespective of method employed.

Space closure should be individually tailored based on the diagnosis and treatment plan.

Selection of any method should be based on desired tooth movement.

Goals for any space closure method

• Differential space closure capability.• Axial inclination control.• Control of rotation and arch width.• Optimum biological response.• Minimum patient cooperation.• Operator convenience.

closure Determinants of space

• Amount of crowding.• Anchorage .• Axial inclination of canine and incisors.• Midline discrepancy and R/L symmetry.• Vertical dimensions.

When you start space closure??After alignment and leveling when you reach the working arch wire.

18-slot 16x22 SS.

22-slot 19x25 SS.

Methods of space closure

Sliding mechanics (frictional system):The bracket slides along the arch wire by using elastics, Niti coil spring or others.

Loop mechanics (frictionless system): The teeth are moved without the bracket sliding along the arch wire by a numerous design of springs and loops.

Sliding mechanics

• Teeth slide along the arch wire by energy stored in elastic or wire coil spring.

• Usual use 19x25 SS arch wire and place coil spring from a hook on the arch wire to the hook on molar band.

• Pre-adjusted appliances facilitate sliding mechanics because the level-slot line-up means that torque can stay passive during sliding.

Sliding mechanicsAdvantages:• Minimal wire bending time.• Initial wire placement is less time consuming.• Enhances patient comfort.• More efficient sliding of arch wire through posterior bracket slots.

Disadvantages:• Confusion concerning the ideal force levels.• Tendency to over activate the elastic and spring forced which cause

initial tipping and need time for tooth uprightening.• Variable forces.• Degradation of force.• Slower than loop mechanics due to friction.• Staining of E-chain.

Types of sliding mechanics:1) Movement of brackets along an arch wire.2) Movement of arch wire through brackets.

Methods of canine retraction in sliding mechanics:Elastic module with ligature.Elastomeric chains.Coil springs.

Elastic modules with ligature• A single elastic module used to secure arch wire

to brackets is attached to canine by ligature wires extending from the molar.

• These tiebacks are activated 2-3 mm or twice their original size to produce 100-150 gm of force.

Elastomeric Chain• Introduced to orthodontic at 1960.• Used for canine retraction,diastema closure,

rotation correction, arch constriction.

Advantages:• Inexpensive.• Relatively hygienic.• Easily applied.• No need for patient cooperation. Disadvantages:• Decreased and loss of effectiveness.• Chance of breakage.• Staining.• Difficult to clean.

Clinical consideration when using elastic• To optimize tooth movement, sufficient time should

be allowed for distal root movement to occur.• A common mistake is to change the elastic chain or

module too often that lead to high force level and M/F which cause distal crown tipping only.

• Also cause excessive mesial out rotation of canines.• Excessive force can inhibit direct resorption around

the canine, bone resorption in posterior segment with loss of anchorage.

• Elastic modules or chain should be changed every4-6 weeks.

Closed coil springs• Introduced to orthodontic world at 1931.Types :1. S.S coil spring:• Efficient for canine retraction.• It has a higher load deflection rate compared to Niti springs.2. Niti coil spring.3. Elgiloy coil spring.

• Samuels et al (1993), compared the space closing effectiveness of elastic modules and “150gm” Niti coil spring on 19x25 arch wire and found:

1. Niti springs produce more rapid and consistent movement.

2. Elastic modules produce approx. 33% less movement per unit time.

• 150gm coil spring is recommended. (Samuels et al 1998)

• Niti coil spring (9mm) coils, (3mm of actual coil spring) should not stretched by more than 9mm.

(Seidenbusch et al 1996)• Force degradation in Niti spring ranged from 8 -17% over 28 days. (Angolkar et al 1992) • Force degradation in elastomeric chain ranged

from 50-70% in the 1st day and 30-40% for the remaining 3weeks. (Baty 1994)

Causes of failure of spaces to close with sliding mechanics

1. Excessive friction: (1st suspected cause) Situations in which friction excessive:• Active forces between bracket & wire (especially torque force) • The ends of arch wire inside the molar tube.• Bracket or tube may be distorted with distal-end cutter.• Ceramic bracket produce more friction. (Kusy et al 1990)• Excessive space closing force plus severe curve of spee cause

bowing of the wire.• Multiple bracket distal to the space to be closed.• Conventional ligation with elastomeric modules as figure of 8.

2. Occlusal interference:• Lower canine brackets can impede upper canine tip when

correcting Cl II relationship.• Ricketts type utility & T-loop arches.• Higher occlusal forces in adult & Cl II /2 cases.3. Intra alveolar causes: (rare)• Retained deciduous teeth fragments.• Apices of extracted permanent teeth.• Root too close: Especially in the upper arch where canine angulation is greater.• Waisting of the bone: Atrophy of the alveolus due to old tooth loss.4. Idiopathic.

Sequence for dealing with a failure of space closure with sliding mechanics

• Check for causes as listed previously.• If no cause can be found and wire hard to swivel,

so the friction is too high.• Steps to lower friction:o Use thinner wire.o Remove curve of spee with overbite situations.o “ O ” configuration in one tie-wing only.

• Propping the bite with GIC on lower molars.• Increase the force for one visit.• Leaving the 2nd molar out of space closure for

1 or 2 visits.• If the space still not closed, increase in force is

not advisable. Check again for friction & occlusal interference, and consider switching to closing loop mechanics.

Other methods for reduction of friction • Wonder wire: It is a dual diameter wire has a rectangular anterior segment to maintain torque control & round in cross section in posterior segment.

• Self - ligating brackets: Use the elastic chain under the arch wire.

• Sectional mechanics: Using TMA cantilever spring in the buccal sulcus.

Problems during sliding mechanic of canine retraction

Occlusal interference -solution: bite plane.Poor canine control-solution: using a heavier arch wire.Rotation of canine mesiobuccally and molars

mesiopalatally-solution:palatal traction using lingual cleats or buttons.

Loop mechanicsAdvantages:• No friction except for the bracket between the loop

and the space.

Disadvantages:• fabrication; loop must not impinge on mucosa and

placed accurately between bracket.• Need good oral hygiene.• Increase flexibility at a stage when rigid wire is needed.• Small single loops give a short range of action.• Difficult activation.

Closing loopsDesign considerations:• Fabricated from rectangular wire to prevent

rolling of wire in the bracket slot.• The performance of the loop is determined by: 1.Spring properties: Determined by wire material (SS, beta -Ti), size of wire, distance between points of attachment.

2.Moment: It generates to bring the root apices together.o Placing some of the wire of the loop in a horizontal

direction improves it is ability to deliver the moments needed to prevent tipping.

o Additional moments must be generated by Gabel bends.

3. Location: there are 3 locationo Equal distance.o Closure to anterior .o Closure to posterior.• If it is in the center of the span, it produce equal

force and equal couples on the adjacent teeth.• If it is in one 1/3 of the distance between adjacent

brackets, the tooth closer to the loop extruded with moment and the tooth far away intruded .

4. Fail safe: Tooth movement should stop if patient not come for scheduled appointment.

5. Design: Should be simple, and loop more effective when closed rather than opened.

Biomechanics of closing loopsBends are placed on the mesial & distal legs of

loop, called Alpha& Beta bends.These bends produce Alpha and Beta moments

when wire is placed into bracket.Moment is determined by loop design.Force is produced by loop activation.

Neutral Activated

If Beta moment > Alpha moment

Anchorage enhanced by mesial root movement of posterior teeth with posterior extrusion& anterior intrusion. If Alpha moment > Beta moment

Anchorage of anterior segment increased by distal root movement.

Anterior extrusion & posterior intrusion.

If both equal no vertical force.

Activation of loop:• Pulling the distal end of wire through molar tube

and cinching back.• Soldering a tie back mesial to molar tube on

arch wire.

• Moment to force ratio (M/F) determined the type of tooth movement.

• Moment to force ratio for various tooth movement:

( M/F Ratio) ( Tooth movement) 5 : 1 Uncontrolled tipping.

8 : 1 Controlled tipping.

10 : 1 Translation.

> 10: 1 Root movement.

M/F could be increased by: (Brustone& Koenig)• Increase vertical dimension of loop.• Increase horizontal dimension in the apical part of

loop.• Increase the apical length of the wire.• Helix incorporation.• Angulation of loop legs.• Decrease interbracket distance.• Position of loop close to tooth to be retracted

bodily.

• The most way to increase M/F ratio by placing Preactivation bends or Gable bends (20 degree in each side).

Vertical loops• There are 2 types:1. Open vertical loop. loop legs should be separated.2. Close vertical loop. loop legs should be closed together and parallel.• Modified vertical loop like Omega loop.

Omega loop

Disadvantages of vertical loop:• Very high force.• Force & M/F extremely sensitive to small changes

in activation.• Discomfort to the patient.• Loss of anchorage and root control.• Dumping of teeth.• Small activation leads to rapid force decay &

intermittent force delivery.

Horizontal loops1) Opus closing loop:• Designed by Siatkowaski.• Fabricated from 16x22 or 18x25 SS or 17x25 TMA .• Close space under good control.• Activated by tightening it distally behind the molar

tube to produce maximal, moderate or minimal incisor retraction.

2) T-loop:• Segmented T-loop made from 17x25 TMA.

• Continuous arch wire with T-loop: Made from 16x22 SS or 19x25 SS.

Space closure problems during using continuous arch wire T-loop

Tipping of anterior &posterior segments to the extraction site-solution: increase alpha &beta moment.

Flaring of anterior teeth-solution: reduce alpha moments or increase distal activation.

Excessive lingual tipping of anterior teeth- solution: increase alpha moment.

3)Composite retraction spring:• Designed by Brustone.• Used with segmented arch technique for en

masse retraction of incisors or canine retraction.• Made of 18mil beta-Ti wire(the loop) welded to

17x25 beta-Ti.

Closure of extraction spaces• To obtain the desired result of closing spaces

within the arch, it is essential to control the amount of incisor retraction versus molar and premolar protraction.

• It depends on the amount anchorage needed.

• Most patients fall into the moderate anchorage category, it is desired to close the reminder of premolar extraction space with 50:50 or 60:40 ratio of anterior retraction to posterior protraction.

• The difference wire size in 18- and 22-slot edgewise appliances require a different approach to mechanotherapy.

Moderate anchorage treatment with 18-slot edgewise

• Most commonly used wire 16x22 SS.• Beta-Ti wire produce smaller force than SS.• Either loop or sliding mechanics can be used.• Single or narrow twin brackets on canine and

premolar is ideally for use of closing loops in continuous arch wire.

• Closing loop in a horizontal direction rather than vertical to prevent tipping.

• Greater retraction if 2nd molar is part of anchorage &less if incisor torque is required.

• Delta-,L- or T- shaped loop is preferred.• 17x 25 Beta-Ti wire used for finishing phase of

treatment.

Delta- loop T- loop

Moderate anchorage treatment with 22-slot edgewise

• Most commonly used wire 19x25 SS.• 18x25 SS wire can be used.• As a general rule,(60:40) it can be done in two

steps:1st Retracting the canines usually with sliding mechanics using Niti coil spring.2nd Retracting the four incisors usually with closing loop mechanics. • En masse retraction as one step using opus or T-loop.

Maximum anchorage treatment with 18-slot edgewise

• Most commonly used wire 16x22 SS.• Friction from sliding mechanics should be

avoided and using closing loop mechanics is better.

• To augment anchorage and reduce its strain by doing the following:

1. Adding stabilizing lingual arch.

2. Reinforce maxillary posterior anchorage with extra oral force and if needed use Cl III elastics from high pull headgear to supplement retraction force in the lower arch.

3. Retraction of canines independently preferably using a segmented closing loop and then retract the incisors with a second closing loop arch wire.

4. Use bone screws to stabilize the posterior segment which used to avoid two steps space closure.

Maximum anchorage treatment with 22-slot edgewise

• Most commonly used wire 19x25 SS.• The same basic approaches are used with 18-

slot appliance.• In sliding mechanics, a bone screw between

2nd molar and 1st molar is effective and easier with a Niti coil spring.

• The recommended procedure in two-step space closure, is en masse distal tipping of anterior teeth followed by uprightening.

Minimum anchorage treatment

• Requires anchor control to reduce the incisal retraction by the following:1) Involving many teeth in the anterior anchor unit as

possible.2) Extraction the most posterior teeth.3) Reinforce the incisor anchorage by placing active

lingual root torque in the incisor section of arch wire.4) Break down the posterior anchorage by moving the

posterior teeth forward one tooth at a time.

5)Use skeletal anchorage (bone screw) in either arch in canine region to bring posterior teeth forward.

Retraction methodsA) Methods of canine retraction: Sliding mechanics:• Closed coil spring ( SS, Niti, Co-Cr-Ni)• Elastomeric chains.• Elastic module activated with ligature wire. Loop mechanics: • Gjessing retraction spring.• Brustone T – loop.• Delta loop.• Omega loop.• L – loop. Extra oral: headgear.

Gjessing retraction spring

B) Methods of en masse retraction of four incisors: Sliding mechanics:• Closed coil spring ( SS, Niti, Co-Cr-Ni)• Elastomeric chains.• Elastic module with ligature wire. Loop mechanics: • Brustone T – loop.• Retraction utility arch.• Delta loop.• Omega loop.• L – loop.• Closing loop arch wire. Extra oral: headgear.

C) Methods of en masse retraction of six incisors: Sliding mechanics:• Closed coil spring ( SS, Niti, Co-Cr-Ni)• Elastomeric chains.• Elastic module activated with ligature wire. Loop mechanics: • Closing loops.• Brustone T – loop continuous arch wire.• Opus loop (siatkowaski).

Niti closed coil spring

Closing space with power chain

References • Contemporary Orthodontic 5th edition – William R.

Proffit.• Excellence in orthodontic 2010 – David Birnie,

Nigel Harradine.• Biomechanics in clinical orthodontic – Ravindra

Nanda.• Modern Edgewise mechanics and the segmented

arch technique – Dr.Charles J. Brustone.

Thank you