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Mechanical properties and antibacterial efficacy against Streptococcus mutans biofilms of novel bioactive tooth root
Nader Almutairi1, Mohammad Alenizy2, Ibrahim Ba-Armah3
1Dental Biomedical Sciences PhD Program, Graduate School, University of Maryland, Baltimore, MD 21201, USA; Department of Conservative Dental Sciences, College of Dentistry, Prince Sattam bin Abdulaziz University, Alkharj 11942, Saudi Arabia; Department of Biomaterials and Regenerative Dental Medicine, University of Maryland School of Dentistry, Baltimore, MD 21201, USA.
Objectives:
The aging population is retaining more natural teeth, increasing the prevalence of exposed root surfaces. These surfaces are prone to abrasion, erosion, and biofilm accumulation, leading to tissue loss, hypersensitivity, and root caries. The objectives of this study were to: (1) evaluate the surface and mechanical properties of experimental resin coatings containing dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) following simulated toothbrushing, and (2) assess their antibacterial efficacy and protective effects compared with commercial controls.
Methods:
Experimental groups with urethane dimethacrylate (UDMA)/ triethylene glycol divinylbenzyl ether (TEGDVBE)+ 5% DMAHDM+ 10% (EX1) or 20% NACP (EX2), along with commercial controls (Seal&Protect and Vanish XT), were tested. Sound and artificially-demineralized dentin served as controls. Hardness, surface roughness, surface loss, and water contact angle were assessed before and after 10,000 brushing cycles. Additionally, Streptococcus mutans (S. mutans) biofilm colony-forming units (CFU) was measured, and surface morphology was evaluated using SEM.
Results:
EX2 and Seal&Protect had similar hardness (0.12 ± 0.01)GPa (n = 5, p > 0.05), while the hardness values of EX1 and demineralized dentin were lower (0.09 ± 0.01)GPa and (0.07 ± 0.01)GPa (p < 0.05). After 10,000 cycles of brushing, EX1, EX2, and Seal&Protect maintained smooth surfaces (Ra=0.4-0.5 µm; n = 6, p > 0.05), whereas Vanish and uncoated dentin became rougher (Ra=2.0 ± 0.5 µm; p < 0.05). Surface loss after 10,000 cycles was minimal for experimental coatings (0.39-0.55 µm) and comparable to Seal&Protect (2.63 µm), while Vanish (8.42 µm) and dentin controls (19-27 µm) showed significantly greater loss (p < 0.05). Both experimental coatings reduced S. mutans biofilm CFU counts by 7 log, compared to all other groups (p < 0.05), while retaining hydrophobicity. SEM showed intact coatings in the experimental groups and in Seal&Protect, but Vanish and uncoated samples exhibited cracking and dentin exposure.
Significance:
The DMAHDM-NACP UDMA/TEGDVBE resin coating demonstrated surface and mechanical properties comparable to Seal&Protect and superior surface stability compared to Vanish XT, while achieving potent antibacterial activity not observed in either commercial control. These findings indicate strong potential for this multifunctional resin coating to protect tooth root dentin via physical shielding and sustained antibacterial performance.
