Open Collections

Amhmed, Mohamed

University of British Columbia

Effective biofilm elimination is crucial for successful endodontic treatment, yet studies indicate that 30-60% of root canals retain bacteria post-treatment, hindering long-term healing. Environmental factors, such as nutrient scarcity and antimicrobial exposure, influence biofilm recovery, metabolic activity, microbial composition, and diversity, potentially promoting the regrowth of resistant bacterial communities, which may impact the outcome of endodontic retreatment. This study hypothesizes that biofilm recovery, metabolic activity, and microbial composition are influenced by the type of primary irrigant and nutrient availability, which in turn affect biofilm susceptibility to re-exposure during retreatment. To investigate this hypothesis, two complementary biofilm models were utilized to assess biofilm behavior during primary irrigant exposure and subsequent re-exposure of the recovered biofilm. The open biofilm model, using HA discs, provided insight into fundamental biofilm mechanisms. This model was used to examine how primary antimicrobial agents (DJK-5 peptide and chlorhexidine) and nutrient availability affect biofilm recovery, metabolic activity, diversity, and composition. Findings showed that nutrient-poor environments slowed recovery and altered metabolic activity and microbial composition, yet DJK-5 maintained strong antimicrobial efficacy upon re-exposure, regardless of these metabolic and compositional changes. To extend these findings to clinically relevant conditions, the dentin block model, using natural teeth, was employed to account for the presence of a smear layer. This model enabled the evaluation of biofilm recovery following primary irrigation protocols under different nutrient conditions and the effectiveness of re-exposure protocols on recovered biofilms. Protocols incorporating DJK-5 peptide demonstrated high initial killing rates and extended biofilm recovery times of up to 16 weeks. The presence of a smear layer significantly influenced antimicrobial performance, with DJK-5-based protocols achieving superior efficacy compared to conventional protocols, particularly in smear-layer-retaining samples. Together, these findings enhance our understanding of biofilm behaviour under environmental stressors and highlight the role of antimicrobial selection and nutrient conditions in shaping biofilm resilience. The results underscore DJK-5’s potential as a promising antimicrobial strategy for endodontic applications, providing both mechanistic insights and clinically relevant efficacy.

Text

2025-03-07

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90472

Craniofacial Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/