Multifaceted Roles of Environmental Factors toward Dental Implant Performance: Observations from Clinical Retrievals and In Vitro Testing

Objective: Oral bacteria and periodontal pathogen have been predominantly linked with early- and late- stage failures of titanium (Ti) dental implants (DI) respectively. This study is based on the hypothesis that bacterial colonization can damage the surface oxide (TiO₂) layer. Early-failed DI were compared with DI post-in vitro immersion in early colonizing oral bacteria; late failed DI were weighed against DI immersed in late colonizing anaerobic pathogens. Methods: Retrieval analysis: Seven early- stage failed implants with five of them connected to healing abutments (HAs), and ten late- stage failed retrievals were subjected to surface analysis. Bacteria immersion test: Three dental implants each were immersed in polycultures containing (i) early colonizers (Streptococcus mutans, S. salivarius, S. sanguinis) (ii) late colonizers (Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans). The implants were immersed for 30 days to simulate the healing period and bacterial biofilm adhesion. Optical microscope, x-ray photoelectron spectroscopy (XPS), and electrochemical test were performed to analyze the surface- morphology, chemistry, and potential respectively. Results: Early colonizers inflicted surface morphological damage (discoloration and pitting). Even though, XPS detected thinner oxide layer in 2/3 early retrievals, XPS and electrochemical tests illustrated that the TiO₂ layer was intact in HAs, and in DI post- immersion. Late colonizers also caused similar morphological damage (discoloration and pitting), while mechanical wear was evident with scratches, cracks, and mechanical fracture observed in late-stage retrievals. XPS indicated thinner oxide layer in late-stage retrievals (3/4), and in DI post-immersion in late colonizers. This was reflected in electrochemical test results post-immersion but not in the late-stage retrievals, which suggested an intact surface with corrosion resistance. Significance: This study concluded that bacteria could negatively affect implant surface with late colonizers demonstrating more pronounced damage on the surface morphology and chemistry. ©2018 The Academy of Dental Materials