Effect of Oral Bacteria on the Mechanical Behavior of Titanium Dental Implants

Purpose: This study sought to determine whether the mechanical properties of titanium dental implants changed after exposure to bacteria. Materials and Methods: Two strains of bacteria (Streptococcus sanguinis and Lactobacillus salivarius) were used in the study. The adhesive properties of the two strains were investigated as follows. Titanium implants were placed in bacteria broth, seeded with the two bacteria strains, and left in the broth for 1 or 3 months. Another group of titanium implants was immersed in artificial saliva at 37°C for 3 months. Ten implants in each group were tested in 37°C artificial saliva to evaluate their mechanical flexural strength and fatigue life. Results: The bacterial cultures grew quickly on titanium surfaces. After 1 month of bacteria culture in vitro, the bacteria had produced corrosion pits on the titanium surfaces. After 3 months of bacterial culture, a 7% decrease in the flexural strength of the implant samples and a decrease of 15% in the number of cycles to failure by fatigue were seen versus implants not exposed to bacteria. Conclusions: These results demonstrate that, in physiologic conditions in vitro, bacteria have the capacity to produce a pitting corrosion phenomenon on exposed titanium surfaces, leading to a significant deterioration in the mechanical properties of the implant. It is therefore logical to conclude that bacteria may produce corrosion that reduces the useful life of dental implants. Keywords: corrosion, dental implants, mechanical properties, titanium