The dentinal structure of equine incisors: a light and scanning electron-microscopic study.

This research investigates the microscopic structure of dentinal tubules in horse incisor teeth, providing detailed information about their three-dimensional organization and size variation. The study uses both scanning electron and light microscopy to visualize and measure these aspects.

Methodology

• Researchers employed scanning electron microscopy and light microscopy techniques to explore the dentinal makeup of equines’ incisor teeth from various perspectives. Teeth samples were examined both on the occlusal surfaces and longitudinally fractured teeth.
• Two types of processing techniques for the teeth were employed: decalcification (chemical process to remove calcium from the tooth making it softer for sectioning) and grinding (mechanical procedure to produce thin sections for imaging).

Findings

• The study highlighted that the dentinal tubules (microscopic channels in the dentine of a tooth), found in the periphery of the tooth, were directly continuous with those located in the circumpulpal secondary dentine, located around the tooth’s pulp.
• The tubules were found to have many side branches along their course, further branching near the intersection with enamel, the dentino-enamel junction.
• The research showed a distinction in the tubules found in the tertiary dentine – situated in the centre of the dental star, a visible feature on a horse’s tooth – having fewer and not being continuous with those of the surrounding secondary dentine.
• The study revealed the presence of a smear layer, an amorphous layer that covered the occlusal or cutting surface of teeth, which filled the tubular orifices on non-etched incisors.

Density and Dimensions of the Dentinal Tubules

• Further analysis was performed on etched incisors, which involved using an acid to expose and calculate the numerical density of the tubules in different areas of the tooth.
• The part of the tooth with the highest number of tubules per unit area was the secondary dentine, which forms the darker periphery of the dental star, compared to the pale centre or the tertiary dentine which had the smallest count.
• The widths of the tubules were also analysed, and the findings showed that they were widest near the pulp or centre of the tooth and gradually became narrower as they approached the dentino-enamel junction.
• Lastly, it was found that tubule widths measured on etched occlusal surfaces were significantly larger than the ones measured on non-decalcified, or natural, incisors because the etching process removes the intratubular dentine, exposing a larger diameter.