Antibacterial effects of surface pre-reacted glass-ionomer (S-PRG) filler eluate on polymicrobial biofilms

Abstract

Purpose: To analyze the effects of surface pre-reacted glass-ionomer (S-PRG) filler eluate on polymicrobial biofilm metabolism and live bacterial count.

Methods: Biofilm was formed using glass disks 12 mm in diameter and 150 µm in thickness. Stimulated saliva was diluted 50-fold with buffered McBain 2005 and cultured in anaerobic conditions at 37°C for 24 hours in anaerobic conditions (10% CO₂, 10% H₂, 80% N₂) to form the biofilm on the glass disks. Following this, biofilms were treated with (1) sterilized deionized water (control), (2) 0.2% chlorhexidine digluconate (0.2CX), (3) S-PRG eluate diluted to 10% (10% S-PRG)，(4) 20% S-PRG，(5) 40% S-PRG，(6) 80% S-PRG，and (7) S-PRG for 15 minutes (n= 10 per group), and samples were subdivided into two groups for measuring live bacterial count immediately after treatment and after 48 hours of culturing after treatment. The pH of the spent medium collected at the time of culture medium exchange was tested.

Results: Immediately after treatment, the live bacterial count of samples treated with drug solutions was significantly lower than the control (8.2 × 10⁸), and the counts of samples treated with 0.2CX (1.3 × 10⁷) and S-PRG (1.4 × 10⁷) were significantly lower than those treated with diluted S-PRG (4.4 × 10⁷-1.4 x 10⁸). When the medium was measured again after culturing for 48 hours, growth was continually inhibited in all treatment groups and the bacterial count of samples treated with S-PRG (9.2 x 10⁷) was significantly lower than that of samples treated with 0.2CX (1.8 × 10⁸). The pH of spent medium immediately after treatment was significantly higher in groups treated with drug solutions (5.5-6.8) than the controls (4.2), and it was highest in the S-PRG-treated group (6.8). Thereafter, when culturing was continued for 48 hours, the pH of all treated groups decreased; however, the pH of the S-PRG-treated group was significantly higher than groups treated with other drug solutions.

Clinical significance: Surface pre-reacted glass-ionomer (S-PRG) filler eluate not only reduced the live bacterial count of polymicrobial biofilm, but also continuously inhibited the lowering of pH.