Cephalometrics

Crowding,Extraction,SlingShot,and Torque

Pletcher's spring

Prepared by: Ahmed S. BaattiahSupervisor: Prof. Maher Fouda

Male 16 years old, has severe crowding, midline deviation (dashed lines)Crowding,Extraction,SlingShot,and Torque

After several years, resorption results in a decrease in the vertical height of the bone, but more importantly, remodeling produces a buccolingual narrowing of the alveolar process as well.

Orthodontictreatmentstartswithextractionoffourofthe1stbicuspids(.014 Niti).UL2complete blockout

Force gauge

UL2complete blockout

Orthodontictreatmentstartswithextractionoffourofthe1stbicuspids(.014 Niti).

Fiveweekslater,.018 sswiresareinstalledwithopen coil springbetweenUL1and3andpowerchainbetweenUL3and7Correction of crowding for the lower anterior region is much easier. A rotation wedge is placed about 1 month post bracketing.

Rotation wedgesIt acts as a fulcrum between wire and bracket to correct the rotation. It is ligated to the tie wing of the bracket.

Three months post bracketing, space is being created for UL 2

Four monthspost bracketing,alingualbuttonisplacedonUL2withpowerchainx7(slingshot); Pletcher's springbetweenUL3and7.

(slingshot)

Provides continuous force for space closuresize: .012X.03050 per pack

Pletcher's spring

Pletcher's spring

Pletcher's spring

Four months post bracketing, a lingual button is placed on UL2 with power chain x7 (sling shot) Pletcher's spring between UL 3 and 7 .

(sling shot)

The moment to force ratio is at its lowest at the initial placement of modules or power chains as the force level is highest.This leads to distal crown tipping of the canine. As the tooth is retracted, the moment to force ratio increases due to dissipation of elastic force and binding of the archwire in the bracket produces a moment tending o upright the canine root. To optimize tooth movement sufficient time should be allowed for the distal root movement to occur.

Maxillary 0.016-inch stainless steel archwire with power chains to retract canines.

A common mistake is to change the elastic chain or module too often, thus maintaining high force levels and a moment to force ratio that produces distal crown tipping only .This also causes excessive mesial out rotation of the canines. Constantly high force levels can cause excessive hyalinization of the periodontal ligament and inhibit direct resorption around the canine.

Uncontrolled tipping with force bypassing the CRes. Note that the CRot is apically displaced.

Disadvantages of elastic modules

If the posterior segment undergoes direct bone resorption at the same time, loss of anchorage may result. It is therefore recommended that elastic modules or chain should be changed at an interval of 4-6 weeks optimize sliding retraction of the canine.

Bone resorption of the posterior segment

Most of the elastomeric chains generally lose 50-70% of their initial force during the first day of load application and at the end of 3 weeks retain only 30-40% of their original force.To overcome the problem of rapid force decay rate and provide for a more constant and consistent force delivery, prestretching of E chain has been suggested. But with this the increase in residual force at 3 weeks is only 5% coupled with a 50-75% reduction in the initial force after prestretching.

Lose of power chain

(4,5monthspostbracketing).

(4,5monthspostbracketing).

Fivemonthsintotreatment,crossbiteofUL2iscorrected;thereisnospacebetweenUL3and5,butthereisspacebetweenUR3and5.

NoticetherotationofUR3duetoretractionoftheclosedcoilspringOne month of closed coil spring (150 gms-9mm) results in the closure of the space between UR3 and 5 .

Atthesameappointment,thereisenoughspaceforUL2

Itisimmediatelycorrected whenarotationwedgeisplacedonthemesialofUR3However,thereisaninstantseparationofUR3and5.Theclosedcoilspringhastobeused.

Sevenmonthsoftreatment,thedentalmidlinescoincide(dashedlines).Extractionspaceshavebeen closedorbeingclosedUL2hasbeenmovedintothearch Butthealignmentneedstobeimprovedwitharchwiresequenceforasecondtimestartingwith.0175twistedwire.

ExtractionspaceshavebeenclosedorbeingclosedButthealignmentneedstobeimprovedwitharchwiresequenceforasecondtimestartingwith.0175twistedwire.

UL2hasbeenmovedintothearchButthealignmentneedstobeimprovedwitharchwiresequenceforasecondtimestartingwith.0175twistedwire.

UL2hasbeenmovedintothearchButthealignmentneedstobeimprovedwitharchwiresequenceforasecondtimestartingwith.0175twistedwire.

ThealignmentofUL2improvesonemonthofusing.016x.022sswirewithintroductionoftorque.(total14 monthsoftreatment )