RESUMEN
AIM: To evaluate in vivo the bone tissue response of rats to varying amounts of infected and noninfected dentine debris. METHODOLOGY: Bone tissue reactions were evaluated histologically in 42 Wistar rats after 7, 30 and 60 days. For each animal, three surgical cavities were prepared on the femur and filled with varying amounts (5, 10 or 20 mg) of infected or noninfected dentine debris pellets. In the negative control group, the surgical cavities were not filled. At the end of each experimental period, the animals were euthanized. The samples were processed histologically and analysed using a light microscope. The presence and the severity of inflammatory reaction, as well as hard tissue deposition were evaluated. Data were subjected to statistical analysis and the effects of the dependent variables calculated using nonparametric tests Kruskal-Wallis and Mann-Whitney U with due Bonferroni corrections at P = 0.05. RESULTS: At 7 days, the presence of infected debris significantly increased the histopathological scores for neutrophils (P < 0.05), and abscess formation (P < 0.05). Noninfected debris scored significantly higher for lymphocyte infiltrate compared with the control group and infected debris (P < 0.05). Both infected and noninfected debris equally triggered eosinophil cells compared with no-dentine (P < 0.05). As for giant cells and macrophages, no difference was detected amongst the dentine groups (P > 0.05). Hard tissue deposition was similar regardless of the presence or the bacteriological status of the dentine (P = 1.00). None of the above histopathological parameters was significantly influenced by the amount of debris (P > 0.05). For all parameters evaluated, at 7 days of analysis, the inflammatory response was significantly more intense compared with 30 and 60 days (P < 0.05). Inflammatory parameters were scored similarly for the evaluated groups after 30 and 60 days (P > 0.05). However, hard tissue deposition has significantly increased after 30 days (P < 0.05). No difference was seen between 30 and 60 days of analysis (P = 1.00) for all histological parameters evaluated. CONCLUSION: The assumption that the amount of extruded debris may negatively affect the inflammatory response of bone tissue was not validated in the present in vivo animal study. Infected dentine may trigger acute inflammatory parameters especially during the first 7 days of contact with the tissue; however, in the long term, these negative effects are mitigated.