Changes in the buccolingual inclination of first molars with growth in untreated subjects: A longitudinal study

OBJECTIVES: To assess longitudinal changes in the buccolingual inclination of the maxillary and mandibular first molars in untreated male and female subjects. MATERIALS AND METHODS: Forty-seven male and 48 female subjects whose longitudinal dental casts were available at ages 6-16 years, with normal maxillary and mandibular arch forms were included. The original casts at ages 6, 7, 8, 9, 10, 12, 14, and 16 years were digitized and standardized. Measurements were recorded as the differences in cusp heights in the vertical dimension for the mandibular and maxillary first molars using OrthoInsight software. RESULTS: On average, for boys from age 6 to 16 years, both maxillary and mandibular first molars uprighted with age. Maxillary molars uprighted 0.403 mm on the left and 0.418 mm on the right; mandibular molars uprighted 0.441 mm on the left and 0.589 mm on the right. Similarly, for girls from age 6 to 16, both maxillary and mandibular molars uprighted with age. Maxillary molars uprighted 0.67 mm on the left and 0.574 mm on the right; mandibular molars uprighted 0.358 mm on the left and 0.329 mm on the right. CONCLUSIONS: Maxillary molars erupted with buccal crown inclination at age 6 in both boys and girls and uprighted lingually with growth. At age 16, maxillary molars were not completely upright but rather maintained some buccal crown inclination. Mandibular molars erupted with lingual crown inclination at age 6 and uprighted buccally with age. At age 16, mandibular molars were not completely upright but rather maintained some lingual inclination.