Morphological differences between the first and second maxillary premolar crowns: A three-dimensional surface...

The current study used a three-dimensional (3D) surface homologous modeling to analyze the structure of maxillary first premolar (P¹) and second premolar (P²) crowns, to identify any morphological differences between them, particularly in their cuspal structures.

The study sample comprised 27 male elementary and junior high school students from Chiba Prefecture, Japan. Plaster casts were collected and the 3D coordinates were used to measure the crown structures. Thereafter, principal component (PC) analysis was carried out using the 3D coordinates of the homologous models, containing 4498 anatomical data points, including 9 landmarks.

The findings indicated that P¹ was significantly larger than P², despite both teeth exhibiting similar intercuspal distances. The homologous model analysis revealed that 61.5 % of the total variance could be explained up to the fourth PC. Overall size and shape in the mesiodistal and buccolingual directions were estimated using PC1 and PC2, respectively. Both components highlighted a shape factor, indicating that the buccal cusp was more well-developed than the lingual cusp in P¹ compared to P².

The variations in the size of the mesial and distal premolar teeth and the relationships between the cusps in the completed tooth crowns can be explained using molecular biology developmental models.