The equine periodontium as a continuously remodeling system: morphometrical analysis of cell proliferation.

This research article explores the equine (horses, in common language) tooth behavior, focusing particularly on how equine teeth continuously remodel themselves through cell proliferation in the periodontium (the tissues surrounding and supporting the teeth). This behavior is linked to the unique characteristic of horse teeth, which keep erupting throughout the animal’s life.

Methods

• The study took tooth specimens from nine warm-blooded horses. Specifically, the extracted periodontal ligament (PDL), an essential part of the periodontium, was situated between the cementum (outer hard layer of the tooth root) and the alveolar bone (the bone in which the tooth socket is embedded).
• The specimens were classified into three levels — subgingival (beneath the gum), middle, and apical (at the tooth root).
• The PDL in each specimen was segmented further into three zones, one adjacent to the cementum, a central zone, and one adjacent to the alveolar bone. This categorization resulted in nine distinct regions of interest for the researchers.
• The study employed an immunohistochemical approach, using anti-Ki-67, a recognized marker for cell proliferation, along with an intricate morphometric procedure using an image analysis program to detect and measure cell proliferation.

Results

• The study’s results indicate that the proliferation index (a measure of cell division and growth) was high at the apical level and in the zone adjacent to the alveolar bone.
• Contrarily, the cell density (number of cells per unit of volume) was high at the subgingival level and in the zone next to the dental cementum.

Conclusions

• Detailed evaluation and statistical analysis of the parameters proliferation index and cell density in distinct areas of the equine PDL suggest dynamic processes such as cell migration. These processes involve cells moving from areas near the alveolar bone towards the dental cementum, and in a direction from root to crown of the tooth (apico-occlusal).
• Furthermore, the study reaffirms the close relationship between cell proliferation, cell migration, and tooth eruption, which is essential for understanding equine tooth growth and related dental health risks.