ORTHODONTIC MANAGEMENT OF A CROWDED CLASS III MALOCCLUSION...

ORTHODONTIC MANAGEMENT OF A CROWDED CLASS IIIMALOCCLUSION ON A CLASS III SKELETAL BASE: A CASE REPORT

Case ReportW.N. Wan Hassan. Orthodontic management of acrowded Class III malocclusion on a Class III skeletalbase: A case report. Annal Dent Univ Malaya 2010;17: 40–49.

W.N. Wan Hassan

Lecturer

Department of Children’s Dentistry andOrthodontics, Faculty of Dentistry,University of Malaya,50603 Kuala Lumpur.Tel: 03-79674802Email: [email protected]

Corresponding author: Dr Wan NurazreenaWan Hassan

ABSTRACT

A late adolescent patient presented with a Class IIImalocclusion on a skeletal Class III base, complicatedby severe upper arch and moderate lower archcrowding, reverse overjet, anterior and bilateralposterior crossbites with displacement, proclinedupper incisors, retroclined lower incisors, distallytipped lower canines and non-coincident centrelines.Treatment was undertaken on an extraction basis byemploying the use of an upper removable appliancewith Z-springs and posterior bite blocks to correct theanterior crossbite, quad helix and jockey arch for archexpansion, and pre-adjusted edgewise fixed applianceto level and align, space closure and achieve amutually protective functional occlusion. This paperdiscussed the rational and evidences behind thetreatment employed.

Key words: Class III, orthodontic camouflage

INTRODUCTION

In Class III malocclusion, the lower incisor edge liesanterior to the cingulum plateau of the palatal surfaceof the upper incisors (1). Class III malocclusion oftenpresents with a Class III skeletal base relationship. TheClass III relationship is thought to be due to polygenicmultifactorial inheritance with variable mode oftransmissions although there has been suggestions thatenvironmental factors such as enlarged tonsils andnasal blockages may contribute to mandibularprognatism (2). Generally the soft tissues are regardedto be of lesser importance in the aetiology of themalocclusion. The lip and tongue pressures are thoughtto influence the dental inclinations to compensate forthe underlying skeletal discrepancy.

Early treatment of the skeletal and dental Class IIIrelationships could be addressed orthopaedically suchas by the use of facemask with rapid palatal expansion(3,4) which has been shown to demonstrate long termfavourable improvement in the skeletal relationship(5). In older patients with moderate to severe skeletalClass III pattern, cases usually do not camouflage wellto conceal the skeletal problem and may needcombined orthodontic-orthognathic treatment.

When making a decision to treat by orthodonticsalone, Proffit and colleagues (2007) suggested that the

good characteristics for camouflage treatment weremild or mild to moderate skeletal Class III patients whohave passed their peak pubertal growth spurt with goodvertical proportions and reasonably good alignment ofthe teeth. It was also outlined that camouflagetreatment should be avoided in cases with severe ormoderate to severe skeletal Class III, vertical skeletaldiscrepancies, severe crowding or protrusion of theincisors, in adolescents with potential growth and innon-growing adults with more than mild discrepancieswhere surgery may offer better long-term results (6).Cephalometrically, the suggested thresholds belowwhich surgery was decided include ANB value of -4º,lower incisor angulation of 83º, maxillary tomandibular ratio of 0.84 and Holdaway angle of 3.5º(7).

These were good guidelines for treatment planningbut the decision should be made on individual basis.This paper will present a case of a late adolescentpatient who presented with Class III malocclusion ona skeletal Class III pattern, complicated by crowdingand existing dentoalveolar compensation that wasborderline for orthodontic-orthognathic treatment butwas treated by orthodontic camouflage.

CASE REPORT

A 16 years and 3 months old male attended theorthodontic clinic and complained that his front teethwere not straight. On clinical examination he presentedwith a Class III malocclusion on a mild skeletal ClassIII base with average lower face height and Frankfortmandibular plane angle. There was no signif icanttransverse discrepancy. The lips were competent at restwith a low smile line and the nasiolabial angle wasobtuse.

Orthodontic Management of Crowded Class III case 41

The oral hygiene was fair with BPE scores of 0 inall sextants apart from the lower labial segment whichscored as 2 due to the presence of calculus. Allpermanent teeth were present apart from the thirdmolars in all quadrants (Figure 1). The lower arch wasmoderately crowded with retroclined lower incisors anddistally inclined lower canines. The upper arch wasseverely crowded with a palatally erupted \2 andproclined upper incisors. In occlusion, the reverseoverjet was 2mm and the overbite was average. Themolar relationships were ¼ units Class III on the leftside and Class I on the right side. The caninerelationships were Class I on the left side and ¼ unitsClass II on the right side. The centreline was notcoincident with the upper centreline shifted to the leftby 2mm relative to the facial midline. Teeth incrossbites were:

On centric relation, there was an initial contact betweenthe upper left lateral and lower left central incisor. Themandible then displaced anteriorly by 2mm intomaximum intercuspation.

The dental panoramic tomogram showed normaldental development and presence of all thirdpermanent molars (Figure 2). The lateral cephalometricanalysis (Table 1) confirmed the Class III skeletalrelationship. Cervical spine maturation stage was atcervical stage 5 (CS 5). This was evident by theconcavity at the lower borders of the C2, C3 and C4,and both C3 and C4 being squared in shape (8) (Figure3). This suggested that the peak mandibular growth hasended at least 1 year before this stage.

Family history indicated that his father had a mildClass III skeletal pattern. However, none of hisimmediate family had undergone orthodontic ororthognathic treatment before.

Treatment aims included to ensure optimum oralhygiene and dental health and to monitor his growth

Figure 1. Pre-treatment intra-oral views in centric occlusion (From the top clockwise: anterior view,left buccal view, mandibular occlusal view, maxillary occlusal view and right buccal view).

42 Annals of Dentistry, University of Malaya, Vol. 17 2010

Table 1. Pre-treatment cephalometric values

VARIABLE PRE-TREATMENT NORMAL

SNA 81.2° 82° ± 3SNB 86.2° 79° ± 3ANB -5.0° 3° ± 1Wits appraisal -7.5mm -1 mmUpper incisor to maxillary plane angle 119.5° 108° ± 5Lower incisor to mandibular plane angle 82.4° 92° ± 5Interincisal angle 137.6° 133° ± 10Maxillary mandibular planes angle 20.5° 27° ± 5Upper anterior face height 47mm 55 mm ± 3Lower anterior face height 60mm 70.5 mm ± 4.5Face height ratio 56% 55%Lower incisor to APo line 3.4mm 0-2 mmLower lip to Ricketts E Plane -5.3mm 0 mm ± 3a

Sources of normal values: Jacobson (1975) Am J Orthod. 67:125-133.Houston WJB, Stephens CD & Tulley WJ (1992) A textbook of orthodontics. Wright, Oxford

throughout treatment. Treatment aimed to address thetooth arch length discrepancy, level and align botharches, correct the inter arch relationships achieving amutually protective functional occlusion and toprovide appropriate retention after fixed appliances.

Treatment by orthodontic camouflage was decidedand the treatment plan included:

1. Oral hygiene instruction2. Growth monitoring by the use of height and

weight charts.3. Upper removable appliance (URA) with

posterior blocks to disclude the occlusion andZ-springs to procline the 21/1

4. Quad helix5. Reassessment

After 4 months of treatment with the URA, positiveoverjet of the 21/1 and overbite were achieved. Thiswas followed by the use of quad helix to expand theupper arch. Nine months into treatment, his height hadnot changed suggesting no further growth hasoccurred. Lateral cephalometric assessment showedthat the upper incisors had further proclined to 128.2º(Table 2). In view of the severity of the crowding andthe incisor inclination, stage 2 treatment plan included:

Figure 2. Dental panoramic tomogram showing normal dental development andpresence of all third permanent molars.

Figure 3. Lateral cephalometric radiograph showingthe cervical spine maturation stage at CS5.


1. Extractions of all first permanent premolars2. Upper and lower pre-adjusted edgewise fixed

appliance (MBTTM prescription, 0.022” x0.028” slot)

3. Retention with removable Hawley retainers anda lower bonded retainer.

MBTTM Versatile+ (3M Unitek) brackets and bandswere fitted in the upper and lower arches followingextraction. The 7\27 were initially excluded. The0.012” nickel titanium archwire was f itted withlacebacks on all quadrants during the initial levellingand alignment stages (Figure 4). A progression of lightnickel titanium archwires were used to reach 0.017” x0.025” stainless steel archwire in the upper arch and0.020” stainless steel archwire with loops in the lower

arch. Nickel titanium push coil spring was used toopen the space for the \2. Once there was sufficientspace, the \2 bracket was inverted and bonded. Lightnickel titanium archwires (0.012”) were used to aprogression of up to 0.019” x 0.025” posted stainlesssteel archwire. Glass ionomer cement was placed onthe lower f irst permanent molars to disclude theocclusion during alignment of the \2, which was laterremoved once the tooth was in a positive overjet andoverbite relationship.

At 16 months into treatment, the quad helix wasremoved and space closure commenced usingelastomeric power chains. When the spaces had closed,there was still displacement due to the crossbites onthe second permanent molars. The 7\7 brackets werebonded. A jockey arch (0.8 mm stainless steel) was

Table 2. Mid-treatment cephalometric values

VARIABLE MID-TREATMENT CHANGE

SNA 80.5º -0.7ºSNB 85.0º -1.2ºANB -4.6º +0.4ºWits appraisal -5.3mm +2.2mmUpper incisor to maxillary plane angle 128.2º +8.7ºLower incisor to mandibular plane angle 81.1º -1.3ºInterincisal angle 131.2º -6.4ºMaxillary mandibular plane angle 19.5º -1ºUpper anterior face height 47.3mm +0.3mmLower anterior face height 60.2mm +0.2mmFace height ratio 56% 0%Lower incisor to APo line 1.9mm -1.5mmLower lip to Ricketts E Plane -2.4mm +2.9mm

Figure 4. Intraoral views showing upper and lower pre-adjusted edgewise appliance with 0.012”nickel titanium archwires for initial alignment. Quad helix was previously fitted for arch expansion(From the top clockwise: anterior viewmandibular occlusal view and maxillary occlusal view).


inserted into the extra-oral traction tubes and securedwith separators to support and aid further expansionof the upper arch (Figure 5). The teeth were alignedusing 0.012” nickel titanium archwire followed byupper 0.016” stainless steel archwire with passiveintrusion bends to prevent extrusion of the 7\7.Centre-line and buccal segment corrections were doneby judicious use of intermaxillary Classs III elastics.

Near end of treatment lateral cephalometricradiograph was taken to assess the incisor inclinations(Table 3). Cervical spine maturation assessment

indicated cervical stage 6 (CS 6), which was evidentby the concavity at the lower borders of the C2, C3and C4, and both C3 and C4 being rectangular verticalin shape (Figure 6) and suggested that the peakmandibular growth has ended at least 2 year before thisstage (8). After 25 months of treatment, the f ixedappliances were removed (Figure 7). The patient wasprovided with bonded lower retainer. Upper and lowerHawley retainers were also f itted to be worn for 6months full time and a further 6 months of night timewear.

Figure 5. Jockey arch used to support and facilitate concurrent expansion of the upper arch duringalignment of the 7\7 (From the top clockwise: anterior view, left buccal view and right buccal view).

Table 3. Near end of treatment cephalometric values

VARIABLE NEAR END OF CHANGETREATMENT

SNA 81.9° +0.7°

SNB 85.6° -0.6°

ANB -3.7° +1.3°

Wits appraisal -3.6mm +3.9mm

Upper incisor to maxillary 119.2° -0.3°plane angle

Lower incisor to mandibular 75.2° -7.2°plane angle

Interincisal angle 144.3° +6.7°

Maxillary mandibular 21.4° +0.9°plane angle

Upper anterior face height 46.2mm -0.8mm

Lower anterior face height 64.7mm +4.7mm

Face height ratio 58.4% +2.4%

Lower incisor to APo line -0.6mm -4mm

Lower lip to Ricketts E Plane -3.4mm +1.9mm

Figure 5. Overall superimposition of the pre-treatmentand near end of treatment lateral cephalometricsregistered at on the Sella-Nasion line at Sella.(Pre-treatment ——— ; Near end of treatment ——— )


Figure 6. Lateral cephalometric radiograph showing thecervical spine maturation stage at CS6.

Figure 7. Post treatment intraoral views (From the top clockwise: anterior view, left buccal view,mandibular occlusal view, maxillary occlusal view and right buccal view).

Figure 6. Cephalometric superimposition of the maxillaregistered at the maxillary key ridge.(Pre-treatment ——— ; Near end of treatment ——— )


DISCUSSION

The patient presented in the late adolescent age of 16years and 3 months with a cervical spine maturationassessment at stage CS5, which suggested that hispubertal growth spurt has passed by at least 1 year.The severity of the malocclusion and existingdentoalveolar compensation to camouflage theunderlying skeletal discrepancy suggested borderlineorthodontic camouflage or orthognathic treatmentapproach. This was supported by the cephalometricf inding of an ANB value of -5º and lower incisorinclination of 82º which were just below the suggestedthreshold for treatment by surgical approach (7). Theextra-oral clinical examination was mild skeletal ClassIII pattern with an aesthetically acceptable facialprof ile and was much more favourable than thatimplied from the cephalometric assessment.

When making a decision for treatment, it isimportant to obtain informed consent. For consent tobe valid, the patient should be explained of theproposed treatment, the risks involved and thealternative treatments (9). The parent and/or legalguardian should be included if the patient is below theappropriate legal age. Class III cases, particularly thosewith moderate or severe skeletal dysplasia, usually donot camouflage well (6). On the other hand,orthognathic treatment has the risks of increasedmorbidity associated with surgical treatments such asloss of sensation (temporary or permanent parasthesiaor anaesthesia) of the nerves where the surgical cut wasmade and risks associated with the general anaesthesiain general. Stability of treatment was also dependenton the type of surgical movement involved. Surgery

to move the maxilla forward was found to be stablef irst year post surgery while concurrent forwardmovement of the maxilla and backward movement ofthe mandible was found to be stable only with rigidf ixation, and single jaw movement to bring themandible back was found to be less stable (10). Thetreatments options and risks were discussed with thepatient, who then declined to undergo orthognathicsurgery and opted treatment to be done by orthodonticsalone.

Quite often a dilemma may arise in deciding themost suitable time to treat adolescents with skeletalClass III pattern who has passed their peak pubertalgrowth. Unlike patients with skeletal Class II pattern,any late mandibular growth may be unfavourable tothe treatment. Baccetti and colleagues (2007) foundthat the total mandibular length increased 3 times inboys compared with those with normal occlusionbetween CS4 to CS6. However, the significance of thisgrowth to affect the anterio-posterior relationship (e.g.ANB) was not discussed. On hindsight, perhaps it mayhave been prudent to wait for a couple more years tomonitor for any potential late mandibular growth.Nevertheless, the patient’s near end of treatmentcephalogram showed little change in the ANB value.The Wits appraisal was increased by 3.9 mm, whichsuggested a reduced skeletal Class III relationship. Thechanges were probably due to elimination of theanterior displacement which has resulted in themandible to be recorded in a more retruded positionrelative to the initial lateral cephalogram and/orchanges due to dentoalveolar remodelling of the Bpoint following lower incisor retroclination. Theoverall superimposition (Figure 5) showed littlesignificant antero-posterior change, suggesting thatpostponing the treatment to monitor for the latemandibular growth would have been of little differencein this case. Vertically, there was a small change in thelower anterior face height. This may have been areflection of vertical growth and/or the effect of theinter-arch mechanics used which had extruded thelower molars and incisors, thus displacing themandible downwards. Growth monitoring by the useof height chart showed that there was no change in thepatient’s height throughout treatment until the mostrecent record at debond. The lack of continued somaticgrowth in the past 2 years and sagittal mandibulargrowth, supported by the cervical spine maturationstage 6 of the near end of treatment cephalogramsuggested that his growth has slowed down. Therefore,the prognosis for stability was deemed to befavourable.

It was important to reinforce strict oral hygienemeasures prior to and during treatment as orthodontictreatment could increase the risk of enameldemineralisation and white spot lesions andsometimes remain after treatment (11). Prior totreatment, the patient already had white spot lesionsat the cervical margins of the lower right f irst

Figure 7. Mandibular superimposition registered at Bjork’sstructures of the mandible on the inferior dental canal and innercortical outline of the mandibular symphysis.(Pre-treatment ——— ; Near end of treatment ——— )


permanent molar, second and first premolars and thelower left second permanent premolar, suggesting thathe had a history of poor oral hygiene care. The oralhygiene instruction included the use of fluoridatedtoothpaste supplemented with daily rinse of 0.05%sodium fluoride mouthrinse. A systematic reviewfound that there was some evidence that the use ofdaily topical fluoride would reduce occurrence andseverity of white spot lesion (12). The paper alsorecommended the daily rinse of 0.05% sodium fluoridemouthrinse by patients with f ixed appliances.Fortunately the patient had maintained a good oralhygiene status throughout treatment. At debond, newsigns of decalcification were not detected.

Treatment was done on an extraction basis tocontrol the antero-posterior displacement (6) andrelieve the crowding. Initial treatment involvedproclination of the labial segment and expansion ofthe arch to improve the transverse relationship. Theamount of space gained was limited with an estimationof 0.5 mm to 0.6 mm of space gained for eachmillimetre of posterior arch width change and anaverage of 0.5 mm to 1 mm of space gained for a 5ºchange of two to four maxillary incisors (13,14) whichwere not sufficient to relieve the severe upper archcrowding. Furthermore, excessive proclination of theincisors would also have reduced the overbite, thusreducing the stability of the crossbite correction. Itmay also have further reduced the smile line, therebyaffecting the smile aesthetics. As the mid-treatmentcephalogram showed that the upper incisors hadproclined by 8.7º to an inclination of 128.2º, anyfurther proclination for space creation may have alsobeen detrimental to the periodontal health of theincisors. A long term follow-up study of Class IIIpatients treated orthodontically, whereby the labialsegment was greatly compensated compared withrandomly selected Class I and Class II cases, foundincreased morbidity measured by labial gingivalrecession and tooth mobility in functional occlusion(15). Although Burns and colleagues (2010) found thatcamouflage treatment could be done with varioustooth movement without deleterious effect on theperiodontium, they suggested that the upper and lowerincisal limits for dental compensation in Class III casesto be 120º to the sella-nasion line and 80º to themandibular plane, respectively (16).

It has been advocated that the use of labial roottorque could advance the ‘A’ point (17). On hindsight,this could have been done with the use of prescriptionswith less torque such as the Andrews (7º) or Roth (12º)or by inverting the brackets to increase the labial roottorque i.e. Andrews (-7º), Roth (-12o) and MBT (-17º)(18). Nevertheless, uprighting the upper labial segmentin cases with skeletal Class III dysplasia needed to bedone judiciously particularly when they would beretracted during space closure, as this may have beenat the expense of excessive retroclination of the lower

labial segment which may not be favourable for thehealth of the periodontium. The MBTTM was theprescription of choice for the pre-adjusted edgewiseappliance in this case to balance and prevent excessivecompensation in either labial segment. Theprescription also offered higher torque value for theupper left lateral incisor bracket (10º) compared withthe Andrews (3º) and Roth (8º) when inverted tofacilitate more labial root torque movement of thepalatally erupted tooth.

In order to camouflage Class III cases, it has beenadvocated to transpose the lower canine bracketswhich would effectively facilitate the dentoalveolarmovements and reduce the anchorage requirements(18). In this case, the lower canine brackets were nottransposed to prevent over compensation of thedentoalveolar relationship. Instead lower caninelacebacks were tied to facilitate antero-posteriorcontrol of the dentoalveolar movements duringlevelling and aligning. In a clinical control trial,canine lacebacks were found to prevent lower labialsegment proclination in the order of 2.5 mm (19).However, it should be noted that the use of lacebackshave been questioned with a randomised control trialfinding no difference of canine lacebacks to preventlower incisor proclination but found a statisticallysignificant difference of more mesial movement of themolars (20). Thus, in order to reduce the amount ofmesial movement of the molars, the lower secondmolars were also included in the canine lacebacks toincrease the posterior anchorage. The mechanics ofcanine lacebacks in this case also had another addedadvantage of facilitating distal root tipping of thelower canines to bring the roots closer to the lowersecond premolar roots, thus preventing space fromreopening post-treatment.

The working archwire used was upper 0.019” x0.025” stainless steel archwire. However, in the lowerarch, the archwire used was 0.020” stainless steel. A0.019” x 0.025” stainless steel may risk to proclinethe lower incisors despite the MBT labial root torque(-6º) prescription when the archwire is inserted in the0.022” x 0.028” slot of an existing retroclined lowerlabial segment, which would not have been favourablefor the overjet correction. The upper centreline wascorrected by the effect of the reciprocal anchorage viathe use of nickel titanium push coil spring on a rigidstainless steel archwire which was used to facilitatespace opening for the upper left lateral incisor. Spaceswere closed using elastomeric powerchains.Powerchains were not only cheaper than nickeltitanium coil spring but were as effective for spaceclosure. Although the rate of space closure have beenfound to be slightly faster with nickel titanium coilspring (0.81 mm per month or 0.26 mm per week)compared with powerchains (0.58 mm per month or0.21 mm per week), the differences were notstatistically significant (p > 0.05) (21,22).


Upper arch expansion was initially done with aquad helix, which was removed prior to space closureto reduce the posterior anchorage and encouragemesial movement of the upper buccal segment.Although the upper second permanent molars were incrossbite, they were not initially bonded to monitorthe overbite control. Expansion of the upper buccalsegment increased the risk for the palatal cusps to drop,thereby reducing the overbite and stability of thecrossbite correction. The more posterior the tooth, themore signif icant this effect would have been inreducing the overbite. Although it may have beenprudent to leave the upper second permanent molarsin crossbite, it was decided to correct the crossbite dueto the presence of a displacement, which preventedproper interdigitation of the occlusion. When theupper second permanent molars were bonded, a lightnickel titanium archwire was placed to align the teeth.The jockey arch was inserted into the extra-oraltraction tubes of the upper f irst molar bands tosimultaneously support the upper arch and facilitatethe crossbite correction during the later part of thetreatment. Both the quad helix and the jockey arch wereas effective for crossbite correction (23). McNally andcolleagues (2005) also reported that patients foundboth appliances as uncomfortable with the quad heliximpinging on the tongue while the jockey arch on thecheeks but more patients disliked the appearance ofthe jockey arch compared with the quad helix. Asanticipated, crossbite correction of the posteriorsegment had reduced the overbite resulting in lateralopen bites, which was addressed by the use of inter-arch box elastics. On hindsight, this could have alsobeen improved by application of buccal root torqueon the molars to lift the palatal cusps and increase theoverbite.

Stability of the crossbite correction was favourableprovided that there was positive overbite and goodposterior intercuspation (24,25). The posterior teethwere still not fully interdigitated at debond. However,this was expected to improve with occlusal settlingduring the retention period. There was some evidenceto show that occlusal settling with Hawley retainers wasbetter than clear overlay retainers after 3 months of fulltime wear (26), although the study have been criticisedto be weak and unrealiable (27). The lower incisorshad further retroclined beyond the normal limits tocompensate for the underlying skeletal discrepancy. Ithas been advocated that for stability of treatment thelower incisor position should remained unchanged(28). In view of the significant change in the lowerincisor position, fixed bonded retainer was placed asa long term retention strategy (6,24). The retentionregime for the Hawley retainers was 6 months full timefollowed by 6 months night time wear. Recentrandomised control trial found that the regimen to wearHawley retainers full time for 1 year were just aseffective with the regimen of 6 months full time and 6months night time wear (29). Therefore the choice of

regimen was based on the clinician’s preference. Thegingival level was monitored throughout treatment.Fortunately, there was no gingival recession despite thesignificant change in the lower incisor inclination. Thismay be due to thickness of the gingival biotype thathad favourably not caused any recession.Nevertheless, long term follow up is required tomonitor the health of the periodontium for any signsof deterioration (15).

CONCLUSION

The outcome of the treatment was good and the patientwas pleased with the overall aesthetics. The prognosisfor stability was expected to be favourable althoughthe periodontal health of the lower labial segmentneeded long term monitoring. It is important forclinicians to recognise the limitations of treatment andinform the patients of the risks involved and treatmentalternatives prior to commencing treatment. Treatmentmechanics should be properly employed based onscientif ic principles and evidences for successfulresults.

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