Alveolar index as a means of skull classification: a radiological study

Abstract

Alveolar index is an important parameter in intra and inter-ethnic classification of skull and in defining the positional relation of the maxilla to the mandible. The objective of the study was to evaluate the alveolar index of Nigerians using radiographs. 130 (90 males and 40 females) normal lateral view skull radiographs of adult Nigerians were used for this study. To determine the Alveolar Index, the Basion-Nasion (Ba-Na) and Basion to Prothion (Ba-Pr) distances were measured to nearest 0.01mm using a micrometer rule and the ratio between them was calculated in percentage. The mean Ba-Pr length was 88.84mm for males and 78mm for females, the mean Ba-Na length was 82.99mm for males and 73mm for females. The mean alveolar index for males was 107.28% and 106.94% for females. There were no significant differences (p>0.05) in the Alveolar Index and distribution of skull type between males and females as indicated by a t-test and Chi-square test. However, the Na-Pr length and Ba-Pr length differ significantly between males and females. Our findings show that most Nigerians have an alveolar index of greater than 103, an indication of prevalence of prognathism in the population. In addition, the extent of prognathism is similar in both males and females. We therefore recommend the consideration of Ba-Pr and Ba-Na lengths for sex determination in forensic examination.

Key Words: Alveolar index, Nigerians, Radiographs, Prognathism, Basion