CLINICAL AND HISTOLOGICAL OBSERVATIONS OF HUMAN TEETH WITH CERVICALLY EXPOSED DENTINE

We have now attempted to correlate sensitivity with light- and scanning electron-microscopical observations on 65 caries-free human teeth with varying degrees of cervicafly exposed dentine. Teeth were grouped according to patient age ( 49 years) and sensitivity status. Teeth were then carefully extracted and randomly assigned, 31 for light and 34 for scanning electron microscopy. Observations by light microscopy were: depth of dentine loss ( 3 mm), open tubules at surface, material inside tubules, and thickness of reaction dentine ( 430 pm). Sections prepared for scanning electron microscopy were observed for open tubular orifices and material in tubules beneath the surface. Relations between observations were assessed by the Fisher-Irwin exact test. Because of limited sample sizes, none of the associations tested was statistically significant; therefore the results will be discussed in terms of general trends (with 0.05

teeth, which is higher than the 7-30% reported by Addy (1992), but we expected more sensitivity because the sample contained only teeth with cervically exposed dentine. The observed incidence of sensitive teeth may be age related as more than 50% of the teeth came from older subjects, who tend to have iess sensitivity (Seltzer and Bender, 1984). In agreement with other studies, sensitive teeth were found predominantly in younger subjects. Most sensitive teeth (1 l/14) exhibited open tubules at the surface and this is consistent with previous in vivo reports (Absi, Addy and Adams, 1989) and with the hydrodynamic hypothesis of pain induction through open tubules (Hirvonen and Narhi, 1984). However, surface openings were also observed sensitivity, histopathology.