A light microscopic and ultrastructural examination of calcified dental tissues on horses: 4. Cement and the amelocemental junction.

The research article is a microscopic and ultrastructural investigation on dental tissue, specifically cement and the amelocemental junction, in horses’ teeth.

Overview

The study used both light microscopic and ultrastructural examination methods to study the calcified dental tissues in horses. This specific piece of research focused on the cement and the amelocemental junction within a horse’s teeth.

Observations

• The researchers found differences in the diameter of cement lacunae depending upon the location within the tooth. The lacunae were larger in the infundibular cement than in the peripheral cement of the upper cheek teeth. However, they were even smaller in the peripheral cement of the lower cheek teeth. Despite this difference, the number of lacunae per unit area remained consistent across these three regions.
• Two types of cemental hypoplasia were identified in equine cheek teeth. The first, termed central infundibular cemental hypoplasia, was found in the central region of the infundibular cement. The cement surrounding these defects was quite porous and filled with large vascular channels. These central regions were found to be filled with connective tissue in recently erupted cheek teeth. The researchers thought these defects might play a role in the development of cemental caries given factors such as the size of the cemental irregularities, their relations to the occlusal surface, and the levels of surrounding cement porosity.
• The second type of cemental hypoplasia, junctional cemental hypoplasia, was identified in the amelodentinal junction of both peripheral and infundibular cement. This was visually characterized by varying spaces that looked like scenic, extended defects along the junction.

Further Observations and Assessment

• Research found two methods by which peripheral cement was deposited: directly (on unresorbed or resorbed enamel surfaces) and indirectly (where cement was separated from the enamel by a thin calcified layer).
• The surface of unresorbed enamel was found to have a pitted appearance with the bases of the pits formed by enamel prisms and the pit walls by interprismatic enamel.
• The cemental surface of resorbed enamel had depressions of varying shapes and sizes. This was considered to be the result of enamel resorption by odontoclasts, and the effect was more pronounced on the cemental surface of infundibular enamel than on peripheral enamel.

This research provides comprehensive microscopic and ultrastructural observations that further our understanding of calcified dental tissue in equine species.