Assessment of multispecies biofilm growth on root canal dentin under different radiation therapy regimens

Objectives To assess the growth of a multispecies biofilm on root canal dentin under different radiotherapy regimens. Materials and methods Sixty-three human root dentin cylinders were distributed into six groups. In three groups, no biofilm was formed ( n = 3): NoRT) non-irradiated dentin; RT55) 55 Gy; and RT70) 70 Gy. In the other three groups ( n = 18), a 21-day multispecies biofilm ( Enterococcus faecalis , Streptococcus mutans , and Candida albicans ) was formed in the canal: NoRT + Bio) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. The biofilm was quantified (CFUs/mL). Biofilm microstructure was assessed under SEM. Microbial penetration into dentinal tubules was assessed under CLSM. For the biofilm biomass and dentin microhardness pre- and after biofilm growth assessments, 45 bovine dentin specimens were distributed into three groups ( n = 15): NoRT) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. Results Irradiated specimens (70 Gy) had higher quantity of microorganisms than non-irradiated ( p = .010). There was gradual increase in biofilm biomass from non-irradiated to 55 Gy and 70 Gy ( p