Dental Tribune Middle East & Africa

Dental Tribune Middle East & Africa Edition | May - June 2013 T he patient presented as a healthy almost 13-year-old female of mixed Tunisian & German heritage with a history of no significant medical problems. Her oral hygiene was good and her dental health excellent. Her chief concerns were for the irregularity of the maxillary incisors and the deep bite. Diagnostic summary Extraoral evaluation revealed a well- balanced face with competent lips, prominent nose and chin, and slightly increased mento-labial fold. The lips were retrusive relative to Ricketts’ E-line, but nicely curved and well-related to each other (Fig. 1,B). A slight gingival display was evident on the maxillary right central incisor on full smile (Fig. 1,C) due to uneven gingival margins on the central incisors (Fig. 1,I) with upper midline coinciding with the facial midline (Fig. 1,A). Model analysis showed almost full Class II molar and canine relationships on the right side (Fig. 1,E) and almost perfect Class I relationships on the left side (Fig. 1,G), with the lower midline deviated 2.0 mm to the right of the upper midline (Fig. 1,I). The overbite was 8.0 mm without signs of palatal impingement, while overjet was only 3.0 mm due to the retroclined maxillary central incisors (Fig. 1,E&G). No space deficiency was observed in either arch (Fig. 1,H&J). Cephalometric evaluation indicated a slightly increased ANB angle, a low mandibular planer angle, retroclined maxillary incisors (relative to SN), and retruded (relative to the A-Pg line) but normally inclined (relative to MP) mandibular incisors and increased interincisal angle (Fig. 1,D). Radiographic examination revealed normal morphology without signs of pathology and presence of all 3rd molar buds (Fig. 1,F). Occlusal classification Edward H. Angle played a major role in developing a concept of occlusion in the natural dentition. His postulate was that the mesiobuccal cusps of the maxillary molars should occlude in the buccal groove of the mandibular molars. Given that molar relationship, and that the teeth in each arch are arranged on a smoothly curving line – defined by Angle as the “line of occlusion”1 – the occlusion would be normal. That brilliant simplification made more than a 100 years ago has been proven as correct, provided no aberrations in size and shape of the teeth, and his definitions of Class I, II and III malocclusions1 established the basis for orthodontic terminology. He further delineated his classifications by dividing them into divisions (according to maxillary incisor inclination) and subdivisions (according to specific types of asymmetric molar relationships).1 It has since the turn of the 20th century been customary for orthodontists to follow Angle’s teaching when classifying malocclusions. He states on page 40 of his original publication1 that “In the subdivision of the First Division one of the lateral halves only is in distal occlusion, the relation of the other lateral half of the lower arch being normal”. Although he clearly states that a subdivision is the occurrence of a unilateral malocclusion, with one normal and one abnormal side, he neglects to specify whether the subdivision is the normal or the abnormal side. Despite this, 34 surveys returned from a total of 54 submitted to orthodontic department chairs in the US showed that 22 taught their residents that subdivision refers to the Class II side while eight taught that it refers to the Class I side, and that three taught neither meaning.2 One chair responded that despite supporting the Class II side definition, several faculty members in the department disagreed.2 Before this controversy is resolved, Angle’s original definition should be followed, classifying the present malocclusion as Angle Class II, Division 2 subdivision,1 not as Class II, Division 2 subdivision right, and not as Class II, Division 2 subdivision left. Treatment objectives Our objectives were to level and align the dental arches, to establish bilateral Class I canine relationships with ideal intercuspation and normal overjet and overbite, and to place the dentition in positions conducive to optimal esthetics and minimal need for long-term retention. Treatment alternatives In Class I and Class II malocclusions the extraction decision is typically based on the mandibular dentition, and made according to a combined evaluation of arch length deficiency and incisor position. One reason is that the option of perimeter gain through distal molar movement is very limited in the mandible. Another is that lateral expansion in the absence of transverse discrepancies is likely to represent a significant relapse liability, as clearly demonstrated already in 1944 by Tweed when conducting a follow-up examination of non-extraction patients treated according to the expansion philosophy of the time.3 The relatively recent introduction of self-ligating brackets, incorrectly referred to by some as friction free despite the fact that they generate the same friction as any conventional bracket,4 combined with super-elastic arch wires with broad arch forms, has had the unfortunate effect of revitalizing the un-biologic concept of bimaxillary expansion for correction of arch length deficiency. Subdivision cases with midline discrepancy expressed as a deviation of the mandibular midline relative to the facial midline is typically treated with extraction of one mandibular premolar on the Class I side, allowing midline correction concomitant with canine retraction to a Class II relationship. Extraction of two maxillary premolars will allow finishing to bilateral Class I canine relationships with coinciding facial and dental midlines. In this patient the relative midline discrepancy was considerably smaller (Fig. 1,I) than the molar and canine asymmetry (Fig. 1,E&G) due to the expression of the malalignment in the maxillary anterior segment (Fig. 1,H). Since the need for mandibular midline correction was considered minimal, we decided not to perform any premolar extractions in the mandibular arch. As opposed to in the mandible, several mechanical alternatives are available for distalization of the posterior segments in the maxilla. We therefore agreed on a non-extraction approach also in the maxillary arch. Treatment progress Treatment was initiated with unilateral cervical headgear, adjusted with a long outer bow on the Class II side.5 The patient was compliant and used the appliance for 12 hours/day. Class I molar relationship was established on the right side after about four months (Fig. 2,C), with a super Class I relationship on the left side. Two months later bands were placed on the lower first molars and multi-bonded appliances with MBT prescription and 0.022” bracket slots were bonded to all premolars, incisors and canines (Fig. 2,E&F; Fig. 3,C&D). An anterior bite plate was delivered to prevent shearing off the mandibular incisor brackets (Fig. 2,E&F; Fig. 3,D). This approach was preferred over bite raisers on the occlusal surfaces of the molars to facilitate evaluation of the leveling progress and to take advantage of any molar extrusion and incisor intrusion. After four months of leveling, initially with 0.016” nitinol wires until rotations were corrected, followed by 0.016” and 0.020” SS wires with customized arch forms to insure minimal expansion of the lateral segments, 0.019” x 0.025” SS wires were placed. Elastic chains were used to close any interdental spaces, while Class II elastics were used on the right side to establish perfect intercuspation and co- inciding midlines. Minitubes were bonded to the mesiobuccal cusps of the mandibular second molars after 18 months (Fig. 2,G; Class II, Division 2 Subdivision Malocclusion: Diagnosis, Treatment and Retention By Authors Jon Årtun, DDS, Dr.Odont* | Erum Aurangzeb, DDS, MSD** *Professor & Orthodontic Program Director European University College | **Resident Orthodontist European University College _______________________________________________________________________________________________________ 22 CaSe Study

Dental Tribune Middle East & Africa

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