We experienced an infrequent case of unilateral buccoversion of the mandibular first molar after eruption of the sceond molar.
The case was a 20 year old woman. She had been examined and dental casts were taken longitudinally at two-month intervals since she was 3 years old. She had normal occlusion in the deciduous dentition and had not suffer from any premature loss of deciduous or permanent teeth. Both sides of the mandibular second premolar were congenitally absent and both sides of the mandibular second deciduous molar still remained. The maxillary dentition was nearly normal. The mandibular arch showed infraversions of both sides of the second deciduous molar and slight crowding on the anterior teeth. The mandibular right and left first molars were also in a nearly normal position before eruption of the second molars. However, the mandibular right first molar subsequently changed to the buccal side.
The following measurements were made on the longitudinal mandibular casts:
1. Distances from midline to the cervical midpoint of the lingual surface of the first molars.
2. Distances between the mesial contact point with the second deciduous molar and the distal contact point with the second molar of the first molar.
3. Vertical differences between the distal marginal ridge of the second deciduous molar and the mesial marginal ridge of the first molar.
4. Distances from the contact point of the right and left permanent central incisors to the cervical midpoint of the lingual surface of the first premolars, second deciduous molars, first molars and second molars. From the results of the measurements and examination of dental casts and
X-ray photographs, two differences between the right and left side in the dentition or occlusion were recognized. These was the difference of the connections between the most distal point of the second deciduous molar and the most mesial point of the first molar. Occlusal contacts on the right side were previously lost on lateral segments, while the occlusal contacts on the left side were kept.
We considered that these differences were the reason that buccoversion of only the right mandibular first molar occurred after eruption of the second molars.
This case report indicates a possibility of local malocclusion which occurs after eruption of the second molars.