The efficacy of techniques for the disinfection of artificial sub-surface dentinal caries lesions and their effect on demineralization and remineralization in vitro

Objectives The efficacy of three techniques for the disinfection of artificial sub-surface root caries lesions and their response to subsequent episodes of de- and remineralization was investigated quantitatively in vitro. Methods Sub-surface dentinal lesions (n = 20), cut into four experimental blocks and deliberately contaminated with Streptococcus mutans, were subject to either steam autoclaving (121 °C, 5 min), gamma irradiation (4100 Gy), immersion in 0.1% (w/v) thymol-distilled water solution (24 h) or reserved as a control. Next, the lesions were incubated aerobically in sterile nutrient broth for 24 h at 37 °C and resultant cultures plated onto blood agar and neutralisation agar. Ten blocks from each experimental group were then immersed in an acidic buffer solution or exposed to artificial saliva for 5 days. Baseline changes in the mineral content and distribution of the lesions were assessed by transverse microradiography (TMR). Results Micro-organisms were recovered from each control block and one block treated by gamma irradiation. Steam autoclaving and immersion in a thymol solution significantly decreased (p < 0.05) the amount of mineral lost from the body of lesions subject to a further acid challenge. Mineral ion uptake by lesions exposed to artificial saliva was significantly increased (p < 0.05) through disinfection by steam autoclaving. Conclusions Gamma irradiation proved the most acceptable method for the disinfection of sub-surface root dentine lesions having the least adverse effect on demineralization and remineralization.