In Vivo Antimicrobial Efficacy of Stannous Fluoride

Plaque Glycolysis and Regrowth Method (PGRM) is an ex vivo assay for the bioavailability, retention and proportional efficacy of dentifrices and rinses containing antimicrobial ingredients (J Clin Dent 6: 59, 1995; FDA 21 CFR Part 356 Vol 68: 103, May 30 2003).  High bioavailable stannous fluoride provides significant clinical efficacy for plaque and gingivitis (Archilla et al. J-Perio 75: 1592-5196, 2004).  Objective: This randomized double-blind triple-exposure cross-over study compared the in vivo antimicrobial effectiveness of stannous fluoride dentifrice and gel to NaF dentifrice by comparing plaque acidogenic virulence and plaque regrowth ex vivo. Methods: Formulations included 0.454 % SnF2 hexametaphosphate (Crest Clinical Gum Protection CGP), 0.454 % SnF2 hexametaphosphate (Crest® Pro Health CPH), 0.40% SnF2 gel (Colgate® GelKam GK) and 0.243 % NaF (Crest® Regular CR – Negative control).  Subjects collected baseline plaque samples from the upper dentition then brushed lingually for 30 seconds and swished 30 seconds with formulations.  Subjects took additional plaque samples from a mandibular quadrant 15 minutes and 45 minutes post treatment.  Swabs were vortexed in 0.03 % trypticase soy broth and plaque dispersions were normalized to an OD of 0.20 (600nm) and sucrose was added to initiate glycolysis at 37ºC for 2 hours.  Regrowth inhibition was measured by OD after incubating samples 4hrs in TSB.  Change in pH and OD at baseline, 15 and 45min was used to calculate. pH response (AUC pH) and regrowth (AUC RG) were compared across subjects adjusting for baseline.  Results: 22 subjects completed all visits.  AUC pH: CR 10.29a CPH14.60b CGP 17.91c GK 17.65c; AUC RG: CR 3.97a CPH9.4b CGP 10.95c GK 11.42c;  (a≠b≠c Students t p <0.05). Conclusion: SnF2 dentifrices and gel provided significant in vivo antimicrobial activity, suppressing glycolysis and regrowth of plaque.  PGRM is a useful screen in assessing proportional bioavailability of antimicrobial dentifrices.