In-vitro effect of different instrumentations on adhesion of a multispecies bacterial mixture to root surfaces and the subsequent response of pulpal cells.

objectivesTo investigate in vitro the influence of instrumentation methods on the bacterial colonization of root dentine and pulpal cell behaviour seeded into the pulp cavum. MATERIALS AND

methodsExtracted teeth underwent root canal treatment with sealing of apices. The teeth were subjected to periodontal instrumentation using manual, ultrasonic scalers, air polishing, or left untreated. The root surfaces were then incubated with a mixture of six bacterial species for 2 h, 24 h and 10 weeks, before dentine samples were taken and analyzed for bacterial colony forming units (cfu) counts. In an additional series, pulpal cells were seeded into the reopened pulp chambers after 10 weeks of incubation with the bacterial mixture and analysed for interleukin (IL)-8 and matrix metalloprotease (MMP)-3 expression.

resultsAfter 2 and 24 h of incubation, instrumented dentine samples contained fewer bacteria than the controls (median (log10 cfu): 5.73 vs. 5.92; 7.71 vs. 8.01 (p = 0.007; p = 0.017)). At 24 h, among the instrumentation groups the highest cfu counts were observed in the ultrasonic group (p = 0.012 vs. manual scaler group; p = 0.002 vs. air polishing group). After 10 weeks, the number of viable bacteria (cfu) decreased in all groups with no difference between any group. Pulpal cells seeded in teeth, with or without prior instrumentation, but exposed to the bacterial mixture for 10 weeks, released higher levels of IL-8 and MMP-3 compared to those in uncontaminated and untreated controls.

conclusionsInstrumentation initially inhibits bacterial colonisation. Prolonged exposure of the outer root surface to bacteria may increase the inflammatory response of pulpal cells. CLINICAL RELEVANCE: Regular removal of bacteria from the root surface is supported by these in vitro data.