ANALYSIS OF THE CUSP ANATOMY OF THE THIRD MOLAR.

Objective: The aim of this work was to characterize the cusp anatomy of third molars and to establish their differential features in relation to the dental arch. Materials and Methods: Two calibrated operators (k = 0.91) determined the number of cusps (C), cusp height (CH) and cusp angulation (CAg) of 961 cadaveric third molars, both upper (n = 462) and lower (n = 499), by means of image capture (800x RGB) and digital analysis (Meazure 2.0). The mean and standard deviation were calculated for each variable and compared using Student's t-test (p<0.05); the distribution of molars was analyzed according to the categories tri-, tetra- and pentacuspid (Chi2). MANOVA was used to determine the functional relationship of the measured variables in relation to the dental arch. Results: The distribution of molars according to the number of cusps was significantly different (p<0.0001). Lower molars were predominantly pentacuspid (62%), whereas upper molars were found to be mainly tricuspid (78%). The average CH (mm) was higher in the lower teeth (6.91±1.1 vs. 6.2±0.5, p<0.0001), where mesial cusps (7.08±1.2) were higher than distal cusps (6.81±1.1), and lingual cusps (7.14±1.3) were higher than vestibular cusps (6.8±1.1). As for the upper teeth, mesial cusps (6.4±1.2) were higher than distal cusps (6.1±0.9), being mesiopalatal (6.5± 1.3) and distal vestibular (6.2±1.0) the highest CH. The average cusp angulation was higher (p<0.001) in the lower teeth (46o±2) vs. the upper teeth (42o±2). The highest angulation among the lower molars and the upper molars was observed in the mesiolingual (48o±1) and the palatal (44o±2) cusps, respectively. C, CH and CAg values were significant as predictive factors associated with the arch (?2 = 0.19, 0.17, 0.12). Conclusion: In spite of the morphometric heterogeneity of the third molar, there are differential cusp anatomic features that have a predictive value in relation to the dental arch and contribute to a better characterization of the occlusal anatomy of the tooth.