Bilateral impactions of mandibular first, second, and third molars.

PATIEN'l' J. Z., a white boy 13 years 9 months of age, had a Class II, Division 1 malocclusion. This diagnosis could be determined only in the canine area, since no mandibular molars were present on either the right or the left side. The maxillary arch was normal in width and in protraction. The maxillary right second premolar was blocked out lingually and rotated mesially, and the maxillary left second premolar was absent. The left permanent first molar was rotated distally and slightly elongated, and the left permanent second molar was just erupting. The third molars were not present on either side of the arch. The mandible was normal in both width and protraction. On the left side the second premolar and the first, second, and third molars were missing. On the right side the first and second premolars were present but had drifted somewhat distally, and there was a space of approximately 3 mm. between these teeth; the permanent first, second, and third molars were absent (Fig. 1). Full-face and left-profile photographs disclosed a bimaxillary protrusion with hypotonicity of both the upper and lower lips (Fig. 2). A cephalometric head film revealed a bimaxillary protrusion and a large Frankfort-mandibular plane angle. There was also a large mandibular incisal angle (Fig. 3). Intraoral and extraoral roentgenograms revealed that the left second premolar and both third molars were present in the maxillary arch. In the mandibular arch the right second premolar was missing and the first, second, and third molars on both sides were impacted in a horizontal position, with the second molars lying over the first molars and the third molars lying over the second molars. It must be noted that the bone level appeared to dip down distally to the first premolars. This was most marked on the left side, where the second premolar was absent. This dipping-down of the bone is not attributed to alveolar bone resorption but, rather, to lack of development of the alveolar bone in this area (Figs. 4 and 5).