Coronal morphology of the mandibular second premolar in the Singaporean Chinese.

Five hundred and sixty-four patients of Singaporean Chinese origin with bilateral second premolars present were screened. Morphological features of the crown, number and position of cusps and the sex of the patient were recorded. The mesio-distal dimensions of the crowns were measured. Three hundred and seventy-four (66.3 per cent) exhibited bilateral 2-cusp forms; 143 (25.4 per cent) were 3-cusp forms; and 47 (8.3 per cent) were mixed. There was no sex predilection in the three groups. In the 2-cusp forms, the predominant occlusal pattern was H-shaped (75.9 per cent). The 3-cusp type with a Y-shaped pattern and a squarish outline is a significant morphological and racial characteristic in the local population. The presence of 2-cusp and 3-cusp forms in an individual is an unusual developmental phenomenon.