Differences between Biofilm Growth Before and After Periodontal Therapy

Objective: The purpose of this study was to evaluate in vitro subgingival biofilm growth from plaque samples collected before and after scaling and root planing (SRP). Methods: Subgingival samples were collected before and after SRP from a 5mm pocket or greater with bleeding, along with 5ml of saliva from 9 patients diagnosed with chronic periodontitis. Calcium hydroxyapatite discs were coated with 10% filtered sterilized saliva for 2hrs, placed in 5ml of Trypticase Soy Broth (TSB) and innoculated with 100ul of dispersed subgingival plaque. Biofilms were grown anerobically at 37ºC for up to 10 days with transfer to fresh medium at 48 hour intervals. Biofilms were then processed at specific intervals for total viable counts and the species present were evaluated and semi-quantified by DNA-DNA hybridization. Biofilm composition was also analysed by Scanning Electron Microscopy (SEM). Results: Samples taken before SRP harbored more bacteria than after SRP (10⁷ versus 10⁶, p=0.004). However, both sets of biofilms grew at a similar rate, reaching a peak CFU of ~10⁸ cells as early as day 3 (p>0.05). Samples taken after SRP presented the same species as those samples taken previous to the procedure, but in less quantity (p<0.001). Greater amounts of red complex bacteria and A.actinomycetencomitans (~10⁴) were found both before and after SRP when compared to other species (~10²). SEM analysis showed growth of a complex structure comprised of rods, cocci,fusiforms and filaments in both sets of mature biofilms. Conclusion: Subgingival biofilms before and after SRP treatment present the same composition of bacterial flora and are able to grow similarly if given proper conditions. Therefore, subgingival bacteria that remains after SRP therapy has the potential to recolonize to pretreatment levels if not properly maintained.

This research was supported by a UFCD Student Summer Research Fellowship.