Evaluation of tissue reaction to some denture-base materials: an animal study

Controversy continues regarding the biocompatibility of denture base materials. One method to evaluate the biocompatibility of materials is in an animal study. Using dogs as subjects, the purpose of this study was to evaluate the vestibular tissue reaction to cobalt chromium (Co-Cr), heat cure acrylic resin, and acrylic resin mixed with aluminum oxide (Al2O3) compared with a control group using the histopathologic method.

Twelve disk shape samples (2 mm x 8 mm) in four groups of Co-Cr, acrylic resin, acrylic resin mixed with a 20% weight ratio of Al2O3, and a control group (Teflon) were fabricated. In one stage surgery two samples of each material (8 samples) was implanted in the buccal vestibule of each dog (n=6), subcutaneously. At 45 and 90-day intervals, half of the samples were excised along with peripheral tissue to assess the presence of inflammation by grading on a scale from 0 to 3 and the presence of a fibrotic capsule using histological observations. Data were analyzed using the Kruskal-Wallis, Mann-Whitney, and Tau b Kendal tests.

Tissue reaction between Co-Cr and the control group was significant (P=0.02), but it was not significant between other groups. There was no significant difference between the 45 and 90-day post-insertion samples. The formation of fibrotic capsule groups was significant (P=0.01). It was significant between the Co-Cr and acrylic resin groups (P=0.01) and the acrylic resin and control groups (P=0.01).

The Co-Cr group was more toxic than the other groups. The inflammation increased during time. The inflammation in two acrylic groups was greater than the control and less than the Co-Cr group. The formation of fibrotic capsule, except in the acrylic resin with Al2O3 group, increased over time.

Co-Cr alloys are toxic and can produce damage to living tissue. Heat cure acrylic resin materials have less toxicity, and their use is safer than Co-Cr alloys.