American Journal of ORTHODONTICS and DENTOFACIAL ORTHOPEDICS Founded in 1915--Seventy.five years of continuous publication

Vo/ume 97 Number 3

March 1990

Copyright © 1990 by The C.V. Mosby Company

CASE REPORT

An American Board of Orthodontics case report Thomas S. Dietrich, DDS Alliance, Ohio

A case report is presented of a Class III, right subdivision malocclusion in the permanent dentition. There were significant arch form asymmetries, crossbite, crowding, and a midiine discrepancy. The case was treated to the standards of the American Board of Orthodontics. [This case was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.] (AM J OnTHOD DENTOFACORTHOP 1990;97:181-7.)

CASE REPORT HISTORY AND GENERAL CLINICAL PICTURE The patient was a normally developed girl aged 13 years 8 months at the time of initial records. She was past the circumpuberal growth spurt and had begun menstruation. She had a Class III, fight subdivision malocclusion in the permanent dentition, with significant arch form asymmetries, crossbite, crowding, and midline discrepancies. Her chief concern centered on the midline diastema and maxillary crowding.

DIAGNOSIS The teeth in habitual occlusion demonstrated a Class III, fight subdivision malocclusion. The crossbite of the upper fight premolars with the lower right second premolar and first molar was due to arch form asymmetries. There also was a mild anterior open bite and minimal overjet (see Fig. 1). The maxillary model exhibited a Brader coronal arch form in which only the left half was well related to its broad, Brader-shaped apical base. The midpalatal suture was in line with the mesial of the left central incisor. The right half of the dental arch was separated from the well-oriented left half by a 2 mm diastema. It appeared that the right side was more distal and the dental midline was to the right of the midpalatal suture. That is, the entire right half was asymmetric to the left side by being more posterior. The upper canines were blocked labially out of the arch form because of a 4.5 mm arch length deficiency (see Fig. 1).

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The lower model also exhibited an asymmetric coronal arch form. The left half (like the maxillary) had a Brader: shaped arch form that correlated with its Brader-shaped apical base. The lower midline was 2.5 mm to the left of the upper dental midline and, therefore, 1 mm to the left of the midpalatal midline. The lower fight coronal half was ovoid and "buckled out" off its apical base. The entire fight half was more anterior than the left hall The apex of the lower left canine was severely inclined mesially and the apex was actually in the anterior aspect of the arch instead of in the posterior. Vertically, the lower arch exhibited almost a reverse curve of Spee (see Fig. 1). The cephalometfic analysis of the lateral headplate revealed a mesiognathie mandible with average morphology. The maxilla was slightly protrusive and the profile was mildly convex. The denture bases were well related to each other anteropostefiorly and the anterior-vertical proportions of the maxilla and mandible were normal as well. The upper and lower incisors were almost ideally positioned within their respective apical bases and in relation to the skeletal profile. Vertically, however, the upper incisors were infraerupted and were the reason for the mild anterior open bite. The molars appeared adequately erupted (see Fig. 2). The evaluation of the frontal headplate revealed a mildly asymmetric mandible that was deviated 2 mm to the left of the frontal midline. This deviation may have been due to the actual asymmetry of the mandible or to a mandibular shift. The nasal floor had descended nearly parallel to the cranial base. Therefore, the tipped occlusal plane (right side more inferior) had resulted from dental compensations for an asymmetric or shifted mandible. The left half of the maxilla was

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Fig. 1. A through C, Pretreatment facial photographs. D through F, Pretreatment intraoral photographs. G and H, Pretreatment models at age 13 years 8 months.

L Fig. 2. Tracing of pretreatment lateral head film at age 13 years 8 months.

Fig. 3. Tracing of pretreatment frontal head film at age 13 years 8 rnonths.

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Fig. 4. A through C, Posttreatment facial photographs. D through F, Posttreatment intraoral photographs. G and H, Posttreatment models at age 16 years 7 months.

in line with the frontal midline, whereas the right half was 2 mm to the right. The axial inclinationsof the lower posterior teeth were excessively upright while the maxillary right posterior teeth were excessively tipped buccally (see Fig. 3).

INTRAORAL AND FUNCTIONAL ANALYSIS Clinically, the anterior frenum was broad based, thick, pendulant, and connected to the incisive papilla. When pulled, it depressed into the interdental suture. Even though the frehum was thick, there was a lack of tissue interdentally. During the clinical examination, it could not be determined whether there were prematurities and resultant shift. However, the location of occlusal wear facets suggested that a mandibular shift occurred with the right side moving anteriorly and the left side moving posteriorly. The dentition lacked incisal and cuspid guidance. There were numerous balancing and protrusive contacts. The patient also reported occasional clicking. However, the temporomandibular joints

appeared healthy and the mandible was capable of a full range of border movements without deviation or pain.

TREATMENT OBJECTIVES There were several treatment objectives as follows: 1. Achieve symmetric dental arch forms for ideal tooth positioning and closure of the diastema. This would require the extraction of four premolars to allow for lower arch constriction and for the additional space needed to align the upper canines. 2. Achieve a functional Class I occlusion. This would also require extractions to allow for the Class III correction and alignment of canines. The overbite could be increased by erupting the infraerupted maxillary incisors, and the overjet would improve as the Class III relations decreased. 3. Maintain the present facial balance,, which necessitated minimal incisor retraction during space closure.

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.f..... Fig. 5. Cephalometrictracings at pretreatment, age 13 years 8 months (solid lines), and posttreatment, age 16 years 7 months (dashed lines).

All these objectives were dependent on the proper selection of extractions, lower anchorage control, and mechanics.

TREATMENT PLAN The upper and lower second premolars were selected to be extracted for several reasons. The primary reason was that only a moderate amount of space was needed for each arch and no incisor retraction was desired. More specifically, the removal of the upper right second premolar would facilitate the advancement of the upper right first molar into Class I occlusion. The removal of the lower right second premolar would create the space where it was needed most for lower arch constriction. However, that would create a situation requiting additional anchorage to retract the lower right canine. The removal of the lower left second premolar would maintain a mechanical advantage in uprighting the lower left canine. It would be'extremely difficult to distalize the canine root without the levering advantage of the first premolar adjacent to it. Last, removal of the upper left second premolar was necessary to allow the upper first molar to advance along with the lower first molar and to maintain symmetry. Anchorage in the lower arch would be a 0.040-inch soldered lingual arch on the first molars. (I would have preferred the second molars; however, they were only partially erupted.) This would help maintain the position of the lower right first molar during lower canine retraction. To help ease the anchorage requirement here, the first premolar would be completely retracted first and then the canine. The lingual arch would also provide transverse stability while width changes were initiated. Later, after canine retraction, the lingual arch would be removed so that the lower right molar could be constricted. Class III elastic wear would be used to assist maxillary molar advancement. The increase in anterior

overbite would be achieved by anterior vertical box elastics on the canines and incisors. Since the upper anterior teeth were particularly infraerupted, this would provide a stable means for closing the anterior open bite. This would also allow more incisor crown length to be visible during smiling. The closure of the maxillary diastema would be accomplished with the upper left central incisor remaining exactly in place while the upper right central incisor was moved mesially to meet the upper left central incisor. If this procedure were not used, the dental midline would be off center to the right. It was also necessary that the lower midline be moved to the right 1 ram. The constriction of the arch forms would be corrected and symmetric dental arches would be achieved by arch wire mechanics. The lower arch, in particular, needed a significant increase in lingual crown torque. The prognosis was good, since most of the asymmetry involved the dentoalveolar process and not the skeletal framework.

TREATMENT PROGRESS Initially, the four second premolars were extracted. A soldered lingual arch was placed on the lower first molars with the anterior aspect several millimeters away from the lower incisors. The teeth were then fully banded and bonded (except for all second molars and the upper right canine) with a 0.018 × 0.025-inch edgewise appliance. All arch wires were flat with no anchorage bends or curve of Spee. The dental arches were leveled after 5 months and upper and lower 0.016 × 0.022-inch arch wires were placed. A reciprocal push coil was placed between the upper right lateral incisor and first premolar to begin midline correction and retraction of the first premolar. After 5 months, the midline was closed over and enough space was available for aligning the upper fight canine.

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Fig. 6. A through C, Postretention facial photographs. D through F, Postretention intraoral photographs. G and H, Postretention models at age 19 years.

Meanwhile, in the lower arch, open coils, tied back, retracted the first premolars and later the canines, separately. The right side, of course, was retracted much farther. After 1 year of treatment the canines were in Class I position. At this time there was a mild anterior open bite and a significant amount of maxillary extraction space to close. Class III elastics (3.5 ounce) were used intermittently because intraarch space closure had caused the canines to move slightly into Class II[ position. A face mask (reverse pull headgear) was also used for 6 weeks to advance the maxillary arch; however, it was discontinued because the patient experienced temporomandibularjoint clicking and pain. The lower lingual arch was removed to allow for constriction of the lower arch form. Anterior vertical box elastics were worn from canine to canine to extrude the anterior teeth for overbite correction. The final 6 months of treatment were spent aligning the upper second molars, which had finally erupted. The patient received active treatment for 35.5 months. The lower lingual arch was in place for 18 months. Class III

elastics were worn for a total of 4 months and anterior vertical elastics were worn for 4.5 months. The face mask was only worn for 6 weeks.

TREATMENT RESULTS INTRAORAL MODEL ANALYSIS The teeth in habitual occlusion demonstrated a Class l canine and molar relationship with both the upper and lower midlines in line with each other and the midpalatal suture. There was good posterior intercuspation with a 3 mm overjet and 20% overbite. The slightly excessive overjet was due to a previous maxillary tooth size discrepancy of 1 mm. The extraction of the smaller upper second premolars and the larger lower second premolars further increased the discrepancy (see Fig. 4). An analysis of the models showed good arch form and symmetry relative to the apical bases. In the maxillary arch, the anterior teeth were well aligned with the diastema closed, and the dental midline was now in line with the midpalatal

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f Fig. 7. Cephalometric tracings at posttreatment, age 16 years 7 months (solid lines), and postretention, age 19 years (dashed lines).

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Fig. 8. Cephalometric tracings at pretreatment, age 13 years 8 months (solid lines), and postretention, age 19 years (dashed lines).

suture. The canines had been constricted 3.5 mm as they were brought into the arch form. The first premolars were expanded 1.0 mm as they were retracted into a wider part of the arch, and the first molars were narrowed 6 ram. In the mandibular arch, the lower intercanine width decreased 2 mm as the arch form became constricted. The first premolar interarch width increased 1 mm because of the significant distalization of the right premolar into a wider part of the arch. The lower first and second molars were considerably constricted, that is, 6.5

mm and 5 mm, respectively. All the extraction sites in both arches were closed (see Fig. 4).

CEPHALOMETRIC ANALYSIS The lateral headplate and superimpositions revealed that both the maxilla and mandible rotated in a clockwise direction a similar amount during growth and treatment. The skeletal proportions of convexity and anterior vertical facial height therefore remained nearly the same. Assuming no tracing or

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positioning errors, the fight condyle (the side traced for the superimpositions) appeared to have been repositioned inferiorly and posteriorly. This might have been a result of the elimination of the suspected anterior shift on the right side (which now allowed the condyle to move posteriorly). Additionally, the anterior vertical elastics created a fulcrum in the molar area that distracted the condyle inferiorly. The nose continued to grow forward, while the lips remained well positioned to the nose and chin (see Fig. 5). Dentally, the upper and lower incisors became mildly more proclined and protrusive to the apical base and to the skeletal profile. Both the upper and lower incisors were mildly extruded, that is, 1.0 mm and 2.5 mm, respectively. This had permitted the overbite correction. Overall, both the upper and lower incisors remained well related. The maxillary molars advanced almost bodily for 5 mm and there was no extrusion. The lower molars erupted 3 mm and advanced bodily for 1.5 ram.

FUNCTIONAL ANALYSIS It was determined clinically that there were no prematurities or mandibular shifts. There was bilateral canine and incisor guidance with no balancing or protrusive contacts. The temporomandibularjoints were now healthy and the mandible was capable of all border movements.

SECONDARY TREATMENT The areas of major concern for relapse were maintenance of arch form and closure of the diastema and the extraction sites. The maxillary and mandibular arches were retained with removable, wraparound Rathbone retainers. The 3 mm band of clear acrylic on the labial bows, along with the lingual acrylic against the teeth would ensure close contact with the teeth for arch form alignment. The patient wore the retainers full time for only 12 months. However, she has continued to wear them nightly for an additional 16.5 + months. Retention will continue in this manner until she decides to discontinue it, at which time a bonded, lingual retainer will be placed on the upper central incisors indefinitely.

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FINAL EVALUATION Evaluation of the postretention records and cephalometric superimpositions, as compared with the posttreatment records, revealed minimal change. The most significant change during this time was apparent repositioning of the right condyle anteriorly and slightly superiorly. The condyles have probably assumed their normal positions within the glenoid fossae, since the elastics have been discontinued for some time. This condylar position was still more inferior and posterior than the pretreatment position. This supported the contention that the posttreatment condylar position was due to both the effect of repositioning the condyles with elastics and the elimination of a mesial mandibular shift (at least on the fight side). The dental changes were nonsignificant. The softtissue profile remained unchanged except for the lips, which relaxed and dropped back slightly. Functionally, there were no prematurities or mandibular shifts. There was bilateral canine and incisor guidance. The temporomandibular joints remained healthy (see Figs. 6 and 7). The primary goal of a symmetric, functional Class I occlusion was achieved. The overall evaluation comparing the pretreatment records with the postretention records was quite similar to the comparison with the posttreatment records. The overbite was corrected by lower and upper incisor extrusion. The Class III correction and arch form improvement resulted from selectively moving groups of teeth. The initial wellbalanced profile remained the same (see Fig. 8). It is important to accurately assess asymmetry. It is necessary to determine to what extent the nature of the asymmetry is skeletal or dentoalveolar, since the basis of the treatment plan depends on that evaluation. Reprint requests to:

Dr. Thomas S. Dietrich 32 E. Broadway Alliance, OH 44601

An American Board of Orthodontics case report.

A case report is presented of a Class III, right subdivision malocclusion in the permanent dentition. There were significant arch form asymmetries, cr...
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