Biofilm Formation on the Surface of Dentine Bonding Resins

Objectives: Root caries is a significant problem in the ageing population.  Exposed root surfaces can be sealed with dentine bonding agents (DBAs).  Biofilm formation must not be increased by resin sealants and may be reduced by an antibacterial DBA, Clearfil Protect Bond (PB) containing an antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) in its primer and fluoride in the bonding resin.  The aim of this study was to monitor biofilm formation on the surface of proprietary DBAs, including PB.

Methods: Biofilms were grown on the surface of root dentine specimens coated with DBAs: PB; Kuraray, Xeno III (X); Dentsply, Clearfil SE Bond (SE); Kuraray in a Constant Depth Film Fermenter.  3 specimens were tested per substrate.  These were inoculated with pooled mixed saliva and maintained with artificial saliva for 7 days.  Live:Dead Baclight fluorescent staining with confocal microscopy imaging, allowed analysis of image intensity across 5 cross-sections of each biofilm stack using image analysis software.

Results: The mean (SD) image intensity of 5 cross-sections for each surface was calculated.

	PB	PB Primer	Root surface (control)	X	SE
Live	101.9 (26.1)a	125.0 (55.8)a	165.8 (94.8)ab	206.0 (87.1)b	197.5 (47.2)b
Dead	108.2 (47.2)c	149.1 (47.4)c	140.5 (63.5)c	200.7 (90.5)c	295.7 (76.3)

Similar letters indicate no significant difference (ANOVA, Tukeys, p>0.05).  

PB and PB Primer accumulated significantly less live bacteria than X and SE.  SE accumulated more dead bacteria than all other surfaces.  Qualitative evaluation of images revealed biofilms on PB and PB Primer were markedly thinner and denser than those from other surfaces.

Conclusions: Application of PB or PB Primer to exposed root surfaces appears to reduce biofilm formation and change colonisation patterns.  Incorporation of MDPB and fluoride into DBAs appears to influence biofilm deposition.  Combined with sealing properties, these resins may have a role in the prevention of root surface caries.