Removal of infected dentin by an enzymatic caries removal system

Methods: Freshly extracted human teeth with carious cavitation into dentin were treated with SFC-V in combination with a dedicated plastic instrument and polymer brush (n=12), or round bur as a control (n=11). Biopsies were taken with a sterile round bur (#10) before and after treatment to quantify bacterial reduction. The sampled dentin was suspended in nutrient broth, aliquots were spread on blood agar plates and incubated anaerobically. Bacterial concentrations were determined as colony forming units/biopsy sample (CFU/B) Log10-reductions of total anaerobes were calculated for both treatments and analyzed statistically by t-tests. Wilcoxon Signed Rank Tests were used for infection levels after treatment (95% confidence level). The treated dentin surfaces were characterized by field-emission scanning electron microscopy (FE-SEM) and by hardness on probing.

Results: Infection levels before treatment were log10 4.83 (SD=0.85). SFC-V and bur treatment effectively reduced infection by 4.25 (1.21) and 4.21 (1.31) log units respectively, which were not significantly different (p=0.93). Both treatments highly significantly reduced bacteria by 3 log units (p=0.003 and p=0.001 respectively) resulting in <100 CFU/B after treatment (p=0.023 and 0.004 respectively). FE-SEM analysis revealed an organized dentin collagen structure with mostly open tubules after SFC-V treatment, while a smear layer was generated by bur treatment. Probing revealed a ratio of medium/hard surfaces (%) of 50/50 for SFC-V, and 0/100 for bur treatment.

Conclusion: Enzymatic caries removal with SFC-V in combination with dedicated instruments reduced bacteria to clinically insignificant levels; similar in effectiveness to bur treatment. FE-SEM evaluation and probing indicated that SFC-V has the potential to specifically remove infected dentin while retaining softened affected dentin, suggesting that SFC-V treatment is considerably less invasive than bur treatment.