Topography and Hydrophilicity Affect Oral Biofilm-Formation on Microstructured Titanium Surfaces

Objective: Biofilms on dental implants can cause implant failure. Patients with failed implants present a microbiota similar to that of periodontal disease; however, it remains unclear if biofilms formed on titanium (Ti) implants are similar to biofilms on teeth and how they are affected by implant surface properties like microtopography and hydrophilicity. Methods: To test this, in-vitro biofilms were formed on Ti-disk surfaces: pure-titanium (PT [Ra<0.2µm]), acid-etched (A [Ra<0.8µm]), A modified to be hydrophilic (modA), sand-blasted/acid-etched (SLA [Ra=4µm]), and hydrophilic SLA (modSLA). Disks were incubated for 24h in anaerobic conditions using human saliva (HS) or Mycoplasma-media (MM) with normal oral microbiota, including: Actinobacillus actinomycetemcomitans serotype b, Actinomyces israelii, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum ss nucleatum, Peptostreptococcus micros, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis. Colony forming units (CFUs) were counted and the proportion of each bacterial species analyzed using checkerboard DNA-DNA hybridization. Data were analyzed by ANOVA and significant differences determined using Bonferroni's modification of Student's t-test. Results: CFU numbers were sensitive to surface hydrophilicity and the media used. CFUs increased on modA and modSLA surfaces in MM, whereas only modSLA increased CFUs in HS. MM supported higher CFU's than HS on all surfaces. Biofilm composition also depended on microtopography: SLA and modSLA increased A. israelii, A. actinomycetemcomitans b, C. rectus, E. corrodens and S. sanguinis in MM. The proportion of A. actinomycetemcomitans b, C. rectus, and S. sanguinis increased on modSLA in HS. PT had the highest proportion of P. gingivalis in both media. Conclusions: Hydrophilic surfaces supported the greatest number of bacteria in both media, but this effect was reduced in HS; biofilm composition was sensitive to microtopography; and HS altered biofilm composition on all surfaces, suggesting that salivary components may alter the bacterial adhesion and biofilm formation on Ti implants in-vivo. (NIH-AR052102, ITI Foundation, Institut Straumann)