Three-dimensional inclination of the dental axes in healthy permanent dentitions - A cross-sectional study in a normal population

The 3-dimensional (3-D) inclination of the facial axis of the clinical crow n (FACC) and the size of the clinical crowns were measured in 100 white nor thern Italians. The subjects consisted of 22 Girls and 21 boys, ages 13-15 years (adolescents), and 31 women and 26 men, ages 16-26 years (adults), al l with a complete permanent dentition and Class I dental relationships. The 3-D coordinates of dental landmarks were obtained with a computerized elec tromagnetic digitizer. Clinical crowns heights and FACC inclinations in the anatomical frontal and sagittal planes relative to 2 reference planes, max illary and mandibular (between the incisive papilla and the intersection of the palatal/lingual sulci of the first permanent molars with the gingival margin), were calculated. Ages and sexes were compared by ANOVA. On average , the frontal plane FACCs of most teeth converged toward the midline plane of symmetry. In contrast, the incisors diverged from the midline plane or w ere nearly vertical. Within each quadrant, the inclinations of the postinci sor teeth progressively increased. In the sagittal plane, most teeth had a nearly vertical FACC. FACC inclinations showed sex- and age-related differe nces (P<.05). In the frontal plane, the canines, premolars, and molars were more inclined in adolescents than in adults. In the sagittal plane, a larg e within-group variability was observed. Clinical crown height was signific antly larger in males than in females in all maxillary and mandibular canin es, premolars, second molars, maxillary central incisors, and first molars. With age, some degree of dental eruption was found in maxillary and mandib ular canines, maxillary second premolars, and molars. The age-related decre ase in FACC inclination may be the effect of a progressive buccal and mesia l drift.