inferred that occlusal interference is a possible etiology of Class II division 2 malocclusion. He suggested that the treatment should begin with correcting the centric relation position of the patients. This can accomplish by instruct the patients to open the mouth widely for an extended period of time and then slowly close the mouth until the first premature dental contact is detected. Some cases of Class I molar relation may not have a true Class II division 2 malocclusion. If the posterior bite reveals a cusp-to-cusp relationship, the standard procedure for correcting a typical Class II division 1 malocclusion can be performed. However, if the posterior bite reveals a full Class II relationship, and if a Class I molar relationship could not be expected after using the inter-maxillary elastics for a period of time, extraction of the maxillary bicuspids can be considered. Extraction in the mandibular arch is not suggested because correction of overbite has a high risk of relapse. Heide9
has also suggested that satisfactory results may be obtained by interdental stripping and tooth contouring, i.e., grinding of the erratic incisal edges and contact areas. Uribe and Nanda10
recommended that the treatment objectives should include the chief complaint of the patient and that the mechanics of correction should be individualized for each patient and based on specific treatment goals. Orthodontists generally have difficulty to decide whether the maxillary bicuspids should be extracted. Although tooth extraction may help to relieve anterior crowding, which is common in Class II division 2 malocclusion, it may also complicate the correction of anterior teeth retroclination during space closure of the tooth extraction. On the other hand, non-extraction therapy for correcting the Class II molar relationship, protusive lip profile and the created overjet after crowding relief. The treatment goal and the range of tooth movement in different mechanics of treatment should be clearly evaluted before treatment.
Preformed CIA nickel titanium intrusion wires are used in Class II division 2 malocclusion. A short wire is used in cases requiring extraction, and a long wire is used in non-extraction cases. These wires can deliver a force of 35-40 gm in patients with an average arch length and a full complement of teeth. An intrusion arch produces a labial tipping movement and intrusive forces while applying extrusive force on the molars. To achieve an ideal angulation in the anterior teeth, the intrusion arch wire should not be cinched back in distal end of the molar tubes initially. Thus, the incisors can be flared prior to their intrusion. The wire then could be cinched 2-3 mm distal to the molar tubes for intrusion as well as flaring of the incisors. The intrusion arch wire should first be ligated to the anterior segment between the two central incisors. This enables attachment of the wire at the most anterior point is related to the center of resistance of the incisors. Once the incisor root inclinations have been corrected, the intrusion arch wire can be ligated to the anterior segment at two lateral incisors and between the central incisors. During insertion, the wire should be bent 3-5 mm mesial to the first molar auxiliary tube (Figure 1)
. Since one of the treatment goals is to correct deep overbite in Class II division 2 malocclusion, vertical control could be important in some of the cases. Even though molar extrusion could help for overbite reduction, large amount of molar extrusion would result in mandible clockwise rotation, increase lower facial height and make chin backward in position. In these cases, anchorage should be well designed and prepared. TADs and other devices could provide anchorage in these cases to prevent further mandible clockwise rotation.
Intrusive arch could perform a extrusive force on molars and intrusive force on incisors that would help improve deep overbite in Class II division 2 malocclusion. The effect of intrusion also provides the labial crown torque on the upper anterior teeth. View Hi-Res Image
Some authors have demonstrated combined orthodontic and surgical methods to correct Class II division 2 malocclusion in adults. Stoelinga and Leenen11
had presented orthodontic treatments that included maxillary anterior subapical osteotomy and/or sagittal split ramus osteotomies. Anterior subapical osteotomy may help to improve deep bite and correct anterior teeth inclination. Sagittal split ramus osteotomy could provide forward mandibular movement to correct the sagittal dental or jaw bone relation.
Another widely discussed issue is whether extraction of tooth is required. Different patterns of extraction therapy have been suggested, including extraction of the first four premolars, extraction of maxillary first premolars and mandibular second premolars, extraction of maxillary second molars for maxillary arch distalization, extraction of maxillary premolars with mandibular incisors, or even extraction of a single mandibular incisor. In Class II division 2 cases, considerations such as crowding, molar relationships, overbite depth, retroclination of maxillary incisors, and hypodivergent facial pattern contribute to the dilemma of whether and at which sites extraction therapy should be performed. In Litt and Nielson,13
comparisons of identical twins revealed that, if one of the twins had undergone extraction of four premolars, the twin that had undergone extraction may have more mandibular forward growth rotation and more vertical molar extrusion as compared to the other twin. In adults, Tsou et al.14
suggested that an initial non-extraction treatment plan could be revised to extraction therapy after reevlalute the lip profile when anterior tooth inclination is corrected. Therefore, constant evaluation of changes in the features on the patients is necessary; the only disadvantage is prolonged treatment duration.
Class II division 2 malocclusion is characterized with retroclined incisors and deep overbite, some authors believed Class II division 2 malocclusion and deep incisal overbite would resulting in disk displacement and caused posterior condylar positioning. Pullinger15
found the association between nonconcentric condyle-fossa relationships and abnormal temporomandibular joint function. Stamm16
has found the measurement approximately 7o
higher angle of the condylar path inclination (CPI) in asymptomatic Class II division 2 malocclusion cases with Computer-Aided Axiography. The Class II division 2 malocclusion group rotated to a significantly higher angle in protrusive and mediotrusive movements and showed longer condylar path lengths than the control group. Anders17
also found increased mobility in mandibular protrusion and a somewhat steeper condylar path in young patients and concluded that the results collaborate the concept of functional TMJ adaptation to incisor inclination and speak for early uprighting of maxillary incisors.