The features of enamel histoarchitectonics in human permanent molar teeth at the occlusal surface of the crown and at the sites of transition of its approximal surfaces to vestibular and lingual ones

Abstract

Objective. The aim of this study is to characterize the dimensional orientation of enamel rods in human permanent molar tooth at the sites of transition from its aproximal surfaces to the vestibular and oral ones, and also at the occlusal surface. Materials and methods. Twenty permanent human molar teeth with intact enamel were used for the study. The teeth were sectioned in diagonal plane and the ground sections were prepared. Using polarizing microscope, the tilt angles between enamel rods and DEJ were measured in deep, medial and surficial layers of enamel. For the measurements the crown was divided into lower, middle, and upper thirds. The tilt angles were also measured at the occlusal surfaces of the crowns. Results. In the lower third of the crown the measures of the tilt angles between enamel rods and DEJ in medial and surficial layers of enamel were 84.8o ± 1,3 and 75.6o ± 2.0 respectively. In the middle third of the crown – 71.8o ± 2.2 and 80.1o ± 2.9 respectively. In the upper third of the crown – 55.4o ± 2.2 and 57.6o ± 2.5 respectively. In the occlusal surface of the molar teeth – 50.0 ± 3.0 and 53.8 ± 3.4 respectively. Conclusions. The following differences in the enamel histoarchitectonics were revealed at the sites of transition from the aproximal surfaces of molar crown to the lingual and vestibular ones: - in the lower third of the crown the rods follow an arch-like course (the top of the arch is directed towards the root); - in the middle third – the rods follow an arch-like course, but the top of the arch is directed towards the occlusal surface; - in the upper third – the rods follow a straight-line course. At the occlusal surface the enamel rods exhibit relatively straight-line course, but only at the sites corresponding to the middle point of the cusp slope.