Abstract
The cusp of Carabelli trait was first described by Carabelli in 1842. If present, it is seen on the mesial aspect of the mesiopalatal cusp of the deciduous maxillary second molar or permanent maxillary first, second and third molar. The level of expression varies from a mere pit or groove to a well developed cusp. The objective of this study was to assess the prevalence of this trait in Abha Secondary School boys in the age range of 15-20 years. 917 subjects without caries or fillings (or missing) in permanent upper first (16/26) and second molars (17/27) were selected out of the 3408 students examined. The trait was recorded as present or absent in 16/26 and 17/27 only as most of the students had erupted premolars and unerupted third molars. The trait was present in 41.7% of the population out of which 82.2% were seen on 16/26 bilaterally. It showed more predilection to permanent maxillary right first molar 39.4% than permanent maxillary left first molar 35.8%. Only 3.1% of the population had the trait on 17/27. These results are in contrast with the prevalence studies carried out in Riyadh - 57.6% and Jeddah - 58.7%. Nevertheless, it places the Saudi population in moderate CT prevalence group.