Indiana University-Purdue University Indianapolis (IUPUI) / Eighteen adult human skulls with "normal occlusion" were examined with oriented lateral, 15, 25, 45, 75, and 90 degree cephalograms from which the mesio-distal axial inclinations of the teeth were measured. This study indicates that a large variation of the mesio-distal axial inclinations of the teeth may occur and still have a "normal occlusion". The standard deviations varied from a maximum of 11.0 degrees for the maxillary third molar to a minimum of 3.4 degrees for the maxillary cuspid. Rotation of the midsagittal plane of the head with the film effected the measurements of the maxillary first molars and cuspids, and the mandibular bicuspids by producing divergence of their roots on the film image. No relationship was found between measurements of this sample and measurements of mandibular plane, A-B plane, Y-axis, facial angle, angle of convexity, Down's occlusal plane, lower incisor - A-Pg, and interincisal angle. A positive relationship was found between the measurements of this sample and the posterior one-half of nasal floor, posterior occlusal plane, and the labiolingual axial inclination of the lower incisor.

Indiana University-Purdue University Indianapolis (IUPUI) / Tooth mass discrepancies have been studied extensively in Caucasian populations, but little has been done to compare differences between Caucasian and African-American populations. The objective of this study was to determine whether the incidence of tooth mass discrepancies between the maxillary and mandibular arches was greater in African-American populations than Caucasian populations. Pretreatment plaster orthodontic models of 100 African-American and 100 Caucasian patients from the Indiana University Orthodontic Clinic and from one private practitioner were measured with a Mitutoyo Digimatic® caliper accurate to 0.01 mm. Mesiodistal widths of all teeth from first molar to first molar were measured with the mesio-buccal and disto-buccal contact areas normally being the widest area. The investigator was blinded to the gender and ethnicity of the subject by assigning each model a random number which was matched to the patient profile only following statistical analysis. Anterior ratios and total (posterior+ anterior) ratios were calculated according to the methods described by Bolton and were compared to the Bolton means and standard deviations. Incidence of tooth mass discrepancy was also investigated according to gender and dental malocclusion classification of the individuals. Tooth mass discrepancies present a hurdle to the clinician in achieving an ideal occlusion. Reports of the incidence of significant discrepancies in defined populations alerts the practitioner to problems in finishing their patients' occlusions. Results of the study show nearly double the incidence of overall Bolton tooth mass discrepancy in the African-American sample than in the Caucasian. The overall tooth mass discrepancy was more severe in the African-American sample, while anterior tooth mass discrepancies were nearly identical in both populations.