Occlusal Morphology of the Mandibular First and Second Premolars in Iranian Adolescents

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Ramin Mosharraf
Fatemeh Hajian


In dental textbooks, the mandibular premolar occlusal morphology has been described as having a predominantly “U-shaped” central groove on the first premolar and a “Y-shaped” central groove on the second premolar. In this study, we examined students (n = 400) of Isfahan high schools (Iran) and first and second premolars were examined bilaterally. Morphological features of the crown, number, height and position of cusps, central grooves shape and sex of the teethwere recorded. For the mandibular first premolars, 21.5% of students exhibited H-shape grooves bilaterally; 70.0% had bilateral U-shape grooves; and 8.5% were mixed. For the mandibular second premolars, 73.0% exhibited 2-cusp forms bilaterally; 15.8% had 3-cusp forms bilaterally; and 11.3% were mixed. In the 2-cusp forms, the predominant occlusal pattern was U-shaped (44.0%). In this Iranian sample, the predominant occlusal pattern was U-shaped in both the first premolar and second premolar, which contrasts with conventional textbook descriptions.