Effect of selected sterilizing solutions on the microbial growth and mechanical properties of extracted human teeth

Abstract

Extracted human teeth (EHT) are used in dental teaching and research. The sterilization process should be performed under strict guidelines to avoid occupational hazards. The U.S. Center for Disease Control and Prevention (CDC) suggests autoclaving (121°C for 40 minutes) or immersion in 10% formalin for two weeks. However, formalin is considered cytotoxic and carcinogenic. The sterilization process should preserve the tooth structure to ensure the validity of the experimental results. Currently, no sterilization method can meet these criteria. This study compares the effects of Gigasept® FF New and Durr® ID 213 on microbial growth and tooth properties after 7 and 30 days of storage against 10% formalin and distilled water as control. For microbial testing, 40 samples were randomly divided into four primary groups (n=10) and immersed in the solutions before being added to Brain Heart Infusion (BHI) broth to check for turbidity, followed by the confirmation of bacterial growth on BHI agar. Microhardness tests (n=5) were performed using indentations on enamel (50g load) and dentin (25g load) for 10s for each group. Measurements were made at baseline, 7 and 30 days post-immersion. One sample from each group was derived for FESEM-EDX analysis to observe the structural and chemical changes. One-way ANOVA demonstrated a significant difference in the level of turbidity between the 7 and 30 days groups (p<0.001; p<0.001). Additionally, an independent sample t-test indicated a significant difference between the two means in the Gigasept® FF New sample (p=0.011). A one-way ANOVA microhardness test showed no significant difference between all solutions at 7 and 30 days (p=.256, p=.162, respectively). The paired t-test also showed no significant difference between baseline and 7 and 30 days (p>0.05). Durr® ID 213 did not cause any defect in enamel 7 days post-immersion, as the structure was similar to the control sample. In contrast, 10% formalin and Gigasept® FF New caused enamel surface roughness and defects. At 30 days post immersion, all groups showed more extensive enamel defects. 2% Durr® ID 213 is a potential sterilizing solution for EHT, as it inhibited microbial growth, had no significant effect on tooth hardness, and did not cause enamel breakdown up to 7 days.