A study of the thickness of cheek teeth subocclusal secondary dentine in horses of different ages.

The research studied the thickness of a particular kind of dentine in horse teeth called subocclusal secondary dentine. The study found that the thickness varied greatly among horses and even among different pulp horns in individual teeth. Contrary to expectations, the thickness did not increase with age.

Objective

The primary goal of this study was to determine whether subocclusal secondary dentine (a type of dentine located just below the occlusal, or biting, surface of a tooth) has a consistent thickness above different pulp horns (the part of the tooth where the blood vessels and nerves enter the tooth) in individual horses and whether its thickness increases with age.

Methods

• An analysis was conducted on 408 permanent cheek teeth (CT) extracted post mortem from 17 horses between the ages of 4 and 30 years old, with no history of dental disease.
• The teeth were dissected longitudinally through each pulp horn and the thickness of the subocclusal secondary dentine overlying each pulp horn was measured directly.

Results

• The thickness of subocclusal secondary dentine above the pulp horns of the tooth varied greatly. The range was from a mean thickness of 12.8 mm in a 4-year-old horse to 7.5 mm in a 16-year-old horse.
• Unexpectedly, the thickness of this dentine did not increase with age, contradicting the researchers’ initial hypothesis.
• There were no significant differences in the thickness of the dentine between the front (rostral) and back (caudal), or medial (middle) and lateral (side) areas of the cheek teeth, or between teeth on the opposite sides of the mouth (contralateral CT).
• Lower jaw CT had significantly thicker subocclusal secondary dentine than upper jaw CT.

Conclusion

• There is large variability in the thickness of subocclusal secondary dentine between horses and even between pulp horns in individual teeth, sometimes reaching as low as 2mm.
• This variation entails a risk of exposure or thermal damage to the pulp and thus of tooth root (apical) infection, even with modest reductions of CT occlusal overgrowths (an overgrowth is an area where tooth material exceeds the normal tooth surface).
• As a result of these findings, the researchers suggest that special care should be taken when reducing equine CT overgrowths, and larger dental overgrowths should be reduced in stages to minimize potential damage to the pulp.