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Class ii division 2 Class ii division 2 Document Transcript

  • IntroductionClass II division 2 can be defined according to Angle classification: whenthe buccal groove of the first mandibular permanent molar occludes distalor posterior to mesiobuccal cusp of upper first permanent molar, withretroclination of upper permanent central incisor.Three types of class II division 2 malocclusion can be distinguished,based on differences in the spatial conditions in the maxillary dental arch(Daskalogiannakis, 2000)Type A: the four maxillary permanentincisors are tipped palatally, without theoccurrence of crowding.Type B: the maxillary central incisors aretipped palatally and the maxillary lateralsare tipped labially.Type C: the four maxillary permanentincisors are tipped palatally with thecanine labial positioned.A Class II incisor relationship is defined by the British standardsclassification as being present when the lower incisor edge occludeposterior to the cingulum plateau of the upper incisors. Class II division 2includes those malocclusions where the upper central incisors areretroclined. The overjet is usually minimal, but may be increased. 2
  • Features of Class II division 2The Class 2 relationship of the dental arches, combined withretroclination of the upper incisors and excessive incisal overbite, are theessential features of this type of occlusion. The skeletal relationship anddental arch crowding are just as variable as in Class 2 Division 1occlusion, but the muscle factors show less variation.There is usually a low gonial angle, giving a rather square facial profile.In most cases, the lips have sufficient vertical dimension to be able tomeet in the rest position, and, in spite of any horizontal skeletalClass 2 discrepancy, the lips meet in front of the upper central incisors.The greater the skeletal discrepancy, therefore, the more retroclined theupper central incisors are likely to be. The level at which the upper andlower lips meet is usually high on the labial surface of the upper incisors.If there is crowding of the upper dental arch, the upper lateral incisors orcanines may be proclined in front of the lower lip function. There iscommonly a pronounced labio-mental groove beneath the lower lip.Fig. 17.11, illustrates these facial and dental characteristics of Class 2Division 2 occlusion.Aetiology of Class II division 2The majority of Class II division 2 malocclusions arise as a result of anumber of interrelated skeletal and soft tissue factors. 1- Skeletal pattern Classa II division 2 malocclusion is commenly associated with a mild Class II Skeletal pattern, but may also occur in association with Class I or even a Class III dental base relationship. Where the skeletal pattern is maore markedly Class II the upper incisors usually lie outside the control of the lower lip, resulting in a Class II, division 1 relasionship, but where the lower lip line is high relative to the upper incisors a Class II division 2 makocclusion can result. The vertical dimension is also important in the aetiology of Class II division 2 malocclusions and typically is reduced. A reduced lower face height occurring in conjunction with a Class II jaw relationship often results in the absence of an increased overbite. A cross-sectional view through the study models of a patient with a very severe Class II division 2 incisor relationship. Lack of an occlusal stop 3
  • allowed the incisors to continue erupting, leading to a significantlyincreased overbiteA reduced lower facial height is associated with a forward rotationalpattern of growth. This usually means that the mandible becomes moreprognathic with growth Fig. 5. While this pattern of growth is helpful inreducing the severity of a class II skeletal pattern, it also has the effect ofincreasing overbite unless an occlusal stop is created by treatment to limitfurther eruption of the lower incisors and to shift the axis of growthrotation to the lower incisal edges. 2- soft tissues The influence of the soft tissues in class II division 2 malocclusions is usually mediated by the skeletal pattern. If the lower facial height is reduced, the lower lip line will effectively be higher relative to the crown of the upper incisors (more than the normal 4
  • one-third coverage). A high lower lip line will tend to retrocline theupper incisors (fig, 10.6).In some cases the upper lateral incisors, which have a shortercrown length, will escape the action of the lower lip and thereforelie at an average inclination, whereas the central incisors areretroclined (fig 10.7).Class II division 2 incisor relationships may also result frombimaxillary retroclination caused by active muscular lips (fig.10.8), irrespective of the skeletal pattern. 5
  • 3- Dental factors As with other malocclusions, crowding is commonly seen in conjunctions with a class II division 2 incisor relationship. In addition, any pre-existing crowding is exacerbated because retroclination of the upper central incisors results in their being positioned in an arc of smaller circumference. In the upper labial segment this usually manifests in a lack of space for the upper lateral incisors which are crowded and typically are rotated mesiolabially out of the arch. In the same manner lower arch crowding is often exacerbated by retroclination of the lower labial segment. This can occur because the lower labial segment becomes trapped lingually to the upper segment by an increased overbite (fig 9). Lack of an effective occlusal stop to eruption of the lower incisors may result in their continued development, giving rise to an increased overbite. This may be due to a Class II skeletal pattern or retroclination of the incisors as a result of the action of the lips, leading to an increased inter-incisal angle. In addition, it has been found that in some Class II division 2 cases the upper central incisors exhibit a more acute crown and root angulations. However, rather than being the cause, this crown root angulations could itself be due to the action of the tooth relative to the root on eruption. 6
  • Occlusal featuresClassically, the upper central incisors are retroclined and the lateralincisors are at an average angulations or are proclined, depending upontheir position relative to the lower lip (see fig 7). Where the lower lip lineis very high the lateral incisors may be retroclined (see fig 6). The moresevere malocclusions occur either where the underlying skeletal pattern ismore Class II or where the lip musculature is active, causing abimaxillary retroclination.In mild cases the lower incisors occlude with the upper incisors, but inpatients with a more severe Class II skeletal pattern the overbite may becomplete onto the palatal mucosa. In a small proportion of cases thelower incisors may cause ulceration of the palatal tissues (fig 10), and insome patients retroclination of the upper incisors leads to stripping of thelabial gingivae of the lower incisors (fig 11). In these cases the overbite isdescribed as traumatic, but fortunately both are comparatively rare. 7
  • Another feature associated with a more severe underlying Class IIskeletal pattern is lingual crossbite of the first and occasionally thesecond premolars (fig 12) owing to the relative positions and widths ofthe arches, and possibly to trapping of the lower labial segment within aretroclined upper labial segment. 8
  • ManagementThere are two possible approaches to the management of a Class IIdivision 2 malocclusion – either accepting the incisor relationship, orcorrecting it. The incisor relationship can be accepted in those caseswhere the problem is mild, the overbite is complete onto tooth tissue, andfixed appliances are not indicated for another aspect of the malocclusion.Stable correction of a Class II division 2 incisor relationship is difficult asit requires not only reduction of the increased overbite, but also reductionof the inter-incisal angle which classically is increased (fig 13).If re-eruption of the incisors and therefore an increase in overbite is to beresisted, the inter-incisal angle needs to be reduced, preferably to between125o and 135 o, so that an effective occlusal stop is created (fig 14).The inter-incisal angle in a Class II division 2malocclusion can be reduced in a number ofways. • Torquing the incisor roots palatally lingually with a fixed appliance (fig 15). 9
  • • Proclination of the lower labial segment (fig 16). This approach should only be employed by the experienced as, although it provides additional space for alignment of the lower incisor teeth, proclination of the lower labial segment will only be stable if it has been trapped lingually by the upper labial segment.• Proclination of the upper labial segment followed by use of a functional appliance to reduce the resultant overjet and achieve intermaxillary correction (fig 17).• A combination of the above approaches. 10
  • The treatment approach chosen for a particular patient will depend uponthe aetiology of the malocclusion, the presence and degree of crowding,the patients profile, and their probable compliance.Once the decision has been made to accept or correct the incisorrelationship, consideration should be given as to whether extractions arerequired to relieve crowding and to provide space for incisor alignment.Some practioners have argued that closure of excess extraction space in aClass II division 2 malocclusion will result in further retroclination of thelabial segments and a dished-in profile. This claim is usually made inassociation with the presentation of isolated case reports. However,research using groups of carefully matched patients has shown that thereis little difference in the amount of retroclination of the lips betweenextraction and non-extraction treatment approaches. Nevertheless, itwould seem advisable in the management of Class II division 2malocclusions to minimize lingual movement of the lower incisors inorder to avoid any possibility of worsening the patients overbite; indeed,it ,may be preferable to accept a degree of lower arch crowding ratherthan run this risk. Certainly, extraction of permanent teeth in the lowerarch in Class II division 2 malocclusions should be approached withcaution, and if any doubt exists specialist advice should be sought. Inaddition, clinical experience suggests that space closure occurs lessreadily in patients with reduced vertical skeletal proportions, which arecommonly associated with Class II division 2 malocclusions, than inthose with increased lower face heights.In general, proclination of the lower labial segment should be consideredunstable, but it has been argued that in Class II division 2 malocclusionsthe lower labial segment is trapped behind the upper labial segment,resulting in retroclination of the lower incisors and constriction of thelower inter-canine width. This means that a limited increase in inter-canine width and a degree of proclination of the lower labial segment canbe stable, although it is important to assess the lower labial supportingtissues to ovoid iatrogenic gingival recession. This approach has theadvantage that proclination of the lower incisors will help to reduce bothoverbite and the inter-incisal angle.In view of the above comments, it is not surprising that Class II division 2malocclusions are managed more frequently on a non-extraction basis,particularly in the lower arch, than are other types of malocclusion.This discussion has highlighted some of the difficulties inherent inplanning treatment of Class II division 2 incisor relationships. Except forthe mild case, where management is to be limited to alignment of theupper arch, correction of Class II division 2 incisor relationships is bestleft to the specialist. 11
  • Approaches to the reduction of overbiteIntrusion of the incisorsActual intrusion of the incisors is difficult to achieve. Fixed appliancesare necessary and the mechanics employed pit intrusion of the incisorsagainst extrusion of the buccal segment teeth; as it is easier to move themolars occlusally than to intrude the incisors into bone, the former tendsto predominate. In practice, the effects achieved are relative intrusion,where the incisors are held still while vertical growth of the face occursaround them, plus extrusion of the molars. High-pull headgear can behooked onto the anterior segment of the arch-wire of an upper fixedappliance to try and achieve intrusion of the upper labial segment;however this approach has become less popular as concern over headgearsafety has increased.Increasing the anchorage unit posteriorly by including second permanentmolars (or even third molars in adults) will aid intrusion of the incisorsand help to limit extrusion of the molars. Arches which bypass thecanines and premolars to pit the incisors against the molars, for examplethe utility arch (fig 18), are employed with some success to reduceoverbite by intrusion of the incisors, although some molar extrusion doesoccur. 12
  • Eruption of the molarsUse of a flat anterior bite-plane on an upper removable appliance to freethe occlusion of the buccal segment teeth will. If worn conscientiously,limit further occlusal movement of the incisors and allow the lowermolars to erupt, thus reducing the overbite. This method requires agrowing patient to accommodate the increase in vertical dimension thatresults, otherwise the molars will re-intrude under the forces of occlusiononce the appliance is withdrawn. However, this tendency can be resistedto a degree if the treatment creates a stable incisor relationship.Extrusion of the molarsAs mentioned above, the major effect of attempting intrusion of theincisors is often extrusion of the molars. This may be advantageous inClass II division 2 cases as this type of malocclusion is usually associatedwith reduced vertical proportions. Again, vertical growth is required if theoverbite reduction achieved in this way is to be stable.Proclination of the lower incisorsAdvancement of the lower labial segment anteriorly will result in areduction of overbite as the incisors tip labially. This approach shouldonly be carried out by the experienced orthodontist. However, in a fewcases where the lower incisors have been trapped behind the upper labialsegment by an increased overbite, fitting of an upper bite-plane appliancemay allow the lower labial segment to procline spontaneously (fig 19). 13
  • SurgeryIn adults with a markedly increased overbite and those patients where theunderlying skeletal pattern id severe Class II, a combination oforthodontics and surgery is required.Practical managementThe incisor relationship is to be acceptedIn milder cases where the lower incisors occlude onto tooth tissue it maybe possible to accept the increased overbite, limiting treatment toalignment, particularly of the upper lateral incisors.As discussed above, it may be preferable to accept mild to moderatelower arch crowding rather than run the risk of extractions leading tolingual movement of the lower labial segment and a worsening of theoverbite. If the crowding is marked, extraction of lower first premolarsmay be required. However, if lower arch extractions run the risk that thelower incisors may tilt lingually and come to occlude with the palatalgingivae behind the upper incisors it may be preferable to use fixedappliance and correct the incisor relationship instead.Space for alignment of the upper can be created by extraction or by distalmovement of the upper buccal segment teeth. Extraction of the upper firstpremolars is usually indicated if the first premolars have been lost in thelower arch or the buccal segment relationship is greater than half unitClass II. Extraction of second premolars will give less space anteriorlyand can be considered if upper arch crowding is mild and or distalmovement of the molars id not indicated or the patient is unwilling towear headgear.Distal movement of the upper buccal segments can be considered wherethe lower arch alignment is to be accepted and the molar relationship isnot greater than half a unit Class II. Extraction of the upper second molarsmay be required to facilitate distal movement, provided that upper thirdmolars of a good size are present and in a favorable position. In somecases removable appliances can be used to achieve upper arch alignment.Although a removable appliance cannot be used to de-rotate rotated upperlateral incisors, relief of crowding and retraction of these teeth into theline of the arch may provide sufficient improvement (fig 10.17). Theappliance should incorporate a flat anterior bite-plane to free theocclusion of the lower labial segment and achieve some overbite 14
  • When planning treatment in these cases it is important to bear in mind that, if the upper incisors are retroclined, the upper canines should only be retracted sufficiently to provide space for alignment of the incisors. This is because retroclined upper incisors occupy less arch length than upright incisors; therefore if the maxillary canines are retracted to Class I, excess space will be created in the upper labial segment. This may leave the upper canines buccally positioned relative to the arch in a half-unit Class II relationship with the lower canines, in which case consideration should be given to correcting the incisor relationship instead.15
  • The incisor relationship is to be correctedCorrection of the incisor relationship is indicated where the overbite iscomplete to the palatal soft tissues, or is liable to become so followingextractions in the lower arch to relieve crowding. In some cases reductionof overbite is necessary in order to be able to treat other features of amalocclusion. Certainly, correction of the incisor relationship should begiven priority if the overbite is traumatic.Fixed appliancesWhen fixed appliances are used the inter-incisal angle can be reduced bypalatal/lingual root torque or by Proclination of the lower incisors. Therelative role of these two approaches in the management of a particularmalocclusion is a matter of fine judgment.Torquing of incisor apices is depending upon the presence of sufficientcortical bone palatally/lingually and places a considerable strain onanchorage. This type of movement is also more likely to result inresorption of root apices than other types of tooth movement.Mild crowding in the lower arch may be eliminated by forwardmovement of the lower labial segment. If crowding is marked, extractionswill be required and a lower fixed appliance used to ensure that spaceclosure occurs without movement of the lower incisor edges lingually (fig21). 16
  • Space for correction of the incisor relationship can be gained by upperarch extractions or by distal movement of the upper buccal segments. Ifheadgear is used for anchorage or distal movement, a direction of pullbelow the occlusal plane (cervical pull) is usually indicated in Class IIdivision 2 malocclusion as the vertical facial proportions are reduced. Alingual crossbite, if present usually affects the first premolars only. Ifextraction of the upper first premolars is not indicated or if the secondpremolars are involved, elimination of the crossbite will involve acombination of contraction across the affected upper teeth and expansionof the lower premolar width. Following treatment, the prognosis for thecorrected position is good as cuspal interlock will help to prevent relapse.On completion of treatment it is prudent to retain with a upper removableappliance incorporating a bite-plane. Ideally, retention should becontinued until growth is complete to try and prevent a return of theoverbite. Whilst this is not always practicable, one approach is to retainfor about six months full time, followed by six months nights only. IfProclination of the lower labial segment is decided upon, an assessmentof the stability of this movement needs to be made at the planning stageand permanent retention institute where indicated.Functional applianceFunctional appliances can be utilized in the correction of Class II division2 malocclusions in growing patients with a mold to moderate Class IIskeletal pattern and a relatively well-aligned lower arch (fig 22). 17
  • Reduction of the inter-incisal angle is achieved mainly by Proclination ofupper incisors, although some Proclination of the lower labial segmentmay occur as a result of the functional appliance. A prefunctional phaseto procline any retroclined incisors and expand the upper arch (to ensurethe correct buccolingual arch relationship at the end of treatment) isusually required, using a removable appliance (fig. 23).The upper incisors should be overproclined during the prefunctionalphase to allow for some retroclination during overjet reduction. Finally,fixed appliances may be required to detail the occlusion. If the lowerincisors have been proclined, the stability of their position should beassessed and, if doubtful, permanent retention (or at least retention untilgrowth is complete) should be instituted.SurgeryA stable aesthetic orthodontic correction may not be possible in patientswith an unfavorable skeletal pattern anteroposteriorly and/or vertically,particularly if growth is complete (Fig. 24). In these cases surgery may benecessary. A phase of presurgical orthodontics is required to align theteeth. However, arch leveling is usually not completed as extrusion of themolars is much more easily accomplished after surgery. Where theoverbite is particularly marked, the lower labial segment may have to beset down surgically, in which case space will have to be created distal tothe lower canines for the surgical cuts to be made. 18
  • ConclusionThe aetiology of Class II division 2 areSkeletal relationshipsThe skeletal pattern in division 2 malocclusion is usually mildly class II,although it may be class I or mildly class III. A reduced or average lowerfacial height is common, associated with an anterior mandibular growthrotation, which tends to increase the overbite. A relatively wide maxillarybase may lead to a lingual crossbite of the first premolars.Soft tissuesThe lips are usually competent and the lower lip line high (covering morethan one third of the incisor crown), the most significant factor in theaetiology. The lower lip level depends largely on the lower anterior facialheight. In general, the more reduced the lower anterior facial height, thehigher the lower lip line is likely to be. Where the lower lip is alsohyperactive, bimaxillary retroclination will result.Dental factorsThe cingulum on the upper incisors is often reduced or absent, which mayexacerbate the overbite. In addition, the likelihood of the teeth beingsmaller than normal is increased, as is the chance of a more acutecrown/root angulation. Retroclination of the upper and possibly of thelower incisors also makes existing crowding worse.Treatment planningThe following factors in particular must be considered in relation totreatment planning.The underlying skeletal discrepancy, both anteroposteriorly andvertically In general the more class II the skeletal pattern and the lowerthe FMPA, the more difficult treatment is likely to be to achieve a normalincisor relationship.The growth potential and pattern of facial growth In a growing patient,correction of both a class II skeletal pattern and deep overbite isfacilitated by favourable facial growth. Although a forward mandibulargrowth rotation aids correction of a class II skeletal discrepancy, it tendsto increase the overbite unless the centre of rotation becomes the lowerincisor edges by altering the interincisal angle with treatment and creatingan occlusal stop. 19
  • Profile considerations Occasionally a non-extraction approach may beadopted, usually in those with bimaxillary retroclination, to prevent theproposed risk of adverse profile change that may result from anextraction-based plan. There is, however, little difference in lip fullnesswith either approach. When the profile is particularly unfavorable in anadult, usually with a marked class II pattern and very reduced FMPA, acombined orthodontic/surgical approach will be required.The presence and degree of crowding Lower arch extractions should onlybe considered where the crowding is marked. There is a risk of a deepoverbite becoming traumatic as the lower incisors are allowed to droplingually if extractions are undertaken in the presence of mild-to-moderate crowding. In addition, as the lower labial segment is constrictedby the upper labial segment, some stable expansion of the lowerintercanine width and proclination of the lower incisors may be feasible,thereby providing space for relief of mild-to moderate crowding. Whereextractions are necessary, a lower fixed appliance should be used to closeresidual spacing and prevent retroclination of the lower labial segment. Inthese cases, consideration should be given also to upper arch extractionsand corrections of the incisor relationship.The lower lip level Where the lower lip level is at the gingival third of theupper incisor crowns or higher, correction of the incisor relationshipwithout recourse to indefinite retention is unlikely.The depth of overbite and inclination of the upper incisors The depth ofoverbite and the inclination of the upper incisors determine the twoapproaches to treatment: either accepting or altering the incisorrelationship.Overbite reduction may be achieved by various means, including• Molar eruption/extrusion• Upper and/or lower incisor intrusion• Lower incisor proclination• Through a combination of these methods• By surgery.In addition, proclination of the upper incisors, followed by a functionalappliance to correct the overjet created, will reduce the overbite.In a growing patient, use of a flat anterior bite plane on an upperremovable appliance will retard lower incisor eruption while allowing thelower posterior teeth to erupt, thereby reducing the overbite. Facialgrowth then accommodates the increase in lower facial height. As this is 20
  • not possible in the adult, overbite reduction must be by incisor intrusionrather than by molar extrusion. Extrusion of the upper molars by cervicalheadgear, or of both upper and lower molars using intra-oral elasticsattached to a fixed appliance, is only advisable in a growing patient as ameans of overbite reduction. Attempts to intrude the incisors by, forexample, utility arches produce effects that are more apparent than real,as the incisors are generally held at their original occlusal level while themolars are encouraged to erupt. This, together with the continuingvertical facial growth, leads to overbite reduction.Intrusion of the upper labial segment may be attempted also by attachinghigh-pull headgear to the anterior part of the arch wire incorporated in anupper fixed appliance.Lower incisor proclination is not usually stable unless the lower incisorshave been held in a retroclined position behind the cingulum of the upperincisors.Fitting an upper removable appliance with a flat anterior bite plane willallow spontaneous labial movement of the lower incisors to adopt aposition of labiolingual balance. Careful planning by a specialist isrequired if active proclination of the lower incisors is considered.A combined orthodontic/surgical approach is best in adults where theoverbite is deep and the skeletal pattern is markedly class II. 21
  • References:Burstone, C. R. (1977) Deep overbite correction by intrusion. AmericanJournal of Orthodontics, 72, 1–22.Leighton, B. C. and Adams, C. P. (1986). Incisor inclination in Class IIdivision 2 malocclusions. European Journal of Orthodontics, 8, 98–105Rutter, R. R. and Witt, E. (1990). Correction of Class II division 2malocclusions through the use of the Bionator appliance. Report of twocases. American Journal of Orthodontics and Dentofacial Orthopedics,97, 106–12.Selwyn-Barnett, B. J. (1991). Rationale of treatment for Class II division2 malocclusion. British Journal of Orthodontics, 18, 173–81. This paper contains a carefully constructed argument for managementof Class II division 2 malocclusion by proclination of the lower labialsegment rather than extractions, in order to avoid detrimental effects uponthe profile.Selwyn-Barnett, B. J. (1996). Class II division 2 malocclusion: a methodof planning and treatment. British Journal of Orthodontics, 23, 29–36.Lee, R. T. (1999). Arch width and form: a review. American Journal ofOrthodontics and Dentofacial Orthopedics, 115, 305–13..Kim, T. W. and Little, R. M. (1999). Post retention assessment of deepoverbite correction in Class II division 2 malocclusion. AngleOrthodontist. 69, 175–86.Mitchell, Laura (2000), An Introduction to Orthodontics , 2nd Edition104-114Peter Heasman (2003), Master Dentistry VOl.2 269 – 273 .Ausama A. Al-mulla (2008), orthodontics …. The challenge 203 – 211. 22