Antibacterial, chemical and physical properties of sealants with polyhexamethylene guanidine hydrochloride

The aim of this study was to evaluate the influence of polyhexamethylene guanidine hydrochloride (PHMGH) in the physico-chemical properties and antibacterial activity of an experimental resin sealant. An experimental resin sealant was formulated with 60 wt.% of bisphenol A glycol dimethacrylate and 40 wt.% of triethylene glycol dimethacrylate with a photoinitiator/co-initiator system. PHMGH was added at 0.5 (G0.5%), 1 (G1%), and 2 (G2%) wt.% and one group remained without PHMGH, used as control (GCTRL). The resin sealants were analyzed for degree of conversion (DC), Knoop hardness (KHN), and softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle (θ) with water or α-bromonaphthalene, surface free energy (SFE), and antibacterial activity against Streptococcus mutans for biofilm formation and planktonic bacteria. There was no significant difference for DC (p > 0.05). The initial Knoop hardness ranged from 17.30 (±0.50) to 19.50 (± 0.45), with lower value for GCTRL (p < 0.05). All groups presented lower KHN after immersion in solvent (p < 0.05). The ΔKHN ranged from 47.22 (± 4.30) to 57.22 (± 5.42)%, without significant difference (p > 0.05). The UTS ranged from 54.72 (± 11.05) MPa to 60.46 (± 6.50) MPa, with lower value for G2% (p < 0.05). PHMGH groups presented no significant difference compared to GCTRL in θ (p > 0.05). G2% showed no difference in SFE compared to GCTRL (p > 0.05). The groups with PHMGH presented antibacterial activity against biofilm and planktonic bacteria, with higher antibacterial activity for higher PHMGH incorporation (p < 0.05). PHMGH provided antibacterial activity for all resin sealant groups and the addition up to 1 wt.% showed reliable physico-chemical properties, maintaining the caries-protective effect of the resin sealant over time.