Nonmetric tooth crown traits in a Sri Lankan aboriginal Vedda population.

This study was conducted to determine the frequencies of non-metric tooth crown traits of Vedda of Sri Lanka and to investigate the affinities of these morphological variations with those of other world populations. Fifty dental plaster casts were observed. The Arizona State University dental anthropology system was adopted for classification of the 16 traits observed. We used 13 traits to compare the Vedda and other world populations. Using the frequencies of 13 traits, Smith Mean Measure of Divergence was calculated to determine inter-population distances. Affinities among the Vedda and other world populations were expressed in two dimensions of the principal coordinate analysis. Cusp number in mandibular second molar and hypocone absence in maxillary second molar had the highest frequency at 95.9% and 93.8%, respectively. Shovelling, double shovelling in the maxillary central incisor and deflecting wrinkle in the mandibular first molar had the lowest frequency at 0%. The principal coordinate analysis showed that Sino American and Western Eurasian populations were separated in negative and positive directions in the first principal coordinate axis. Vedda located with the Western Eurasian population groups. Sahul and Sunda Pacific populations located in the intermediate position between Sino American and Western Eurasian populations. The dental phenotype of Vedda has close affinities with those of early south Asian populations. They are far different from Sino American and Sunda pacific populations. Vedda shows closer affinities to Sahul Pacific and South African (Bantu) populations.

Root canal morphology of mandibular permanent molars at different ages.

AIM: To investigate differences in the root canal morphology of permanent mandibular molar teeth at various ages. METHODOLOGY: Four hundred and eighty permanent mandibular first and second molars were examined. First and second molars were divided into six and five groups, respectively, according to the age of the patient at the time of extraction. Root canal morphology was studied using a clearing technique. The canal morphology of the mesial root was classified into three stages depending on its developmental pattern. When the root canal system was completely differentiated, the canal classification and the number of lateral canals and inter-canal communications were recorded. Vertucci's classification was taken as the main reference. Canal morphology was compared amongst age groups. RESULTS: In both first and second molars, developmental stages of canal morphology amongst age groups were significantly different (P < 0.0001). The prevalence of inter-canal communications was highly significantly different in the first (P < 0.0001) and less significant in the second molar (P < 0.05). After completion of the canal differentiation, the mesial roots of first molars had type IV and II canal forms. The majority of the mesial roots of second molars had type I and III canals. C-shaped canals were found in 3% of second molars. CONCLUSIONS: Mesial roots of first and second molars mostly had one large canal until 11 and 15 years of age, respectively. In both molars, the canal system was completely defined at 30-40 years. The prevalence of inter-canal communications was low at young and old ages but high at intermediate ages.