Myristyltrimethylammonium Bromide (MYTAB) as a Cationic Surface Agent to Inhibit Streptococcus mutans Grown over Dental Resins: An In Vitro Study

Abstract

This in vitro study evaluated the effect of myristyltrimethylammonium bromide (MYTAB) on the physical, chemical, and biological properties of an experimental dental resin. The resin was formulated with dental dimetacrylate monomers and a photoinitiator/co-initiator system. MYTAB was added at 0.5 (G_0.5%), 1 (G_1%), and 2 (G_2%) wt %, and one group remained without MYTAB and was used as the control (G_Ctrl). The resins were analyzed for the polymerization kinetics, degree of conversion, ultimate tensile strength (UTS), antibacterial activity against Streptococcus mutans, and cytotoxicity against human keratinocytes. Changes in the polymerization kinetics profiling were observed, and the degree of conversion ranged from 57.36% (±2.50%) for G_2% to 61.88% (±1.91%) for G_0.5%, without a statistically significant difference among groups (p > 0.05). The UTS values ranged from 32.85 (±6.08) MPa for G_0.5% to 35.12 (±5.74) MPa for G_Ctrl (p > 0.05). MYTAB groups showed antibacterial activity against biofilm formation from 0.5 wt % (p < 0.05) and against planktonic bacteria from 1 wt % (p < 0.05). The higher the MYTAB concentration, the higher the cytotoxic effect, without differences between G_Ctrl e G_0.5% (p > 0.05). In conclusion, the addition of 0.5 wt % of MYTAB did not alter the physical and chemical properties of the dental resin and provided antibacterial activity without cytotoxic effect.

Keywords: anti-bacterial agents; biocompatible materials; biofilms; dental caries; dental materials; dentistry; quaternary ammonium compounds.

Figure 1

Comprehensive results of polymerization kinetics (a–c), degree of conversion after 40 s of photoactivation (d), and ultimate tensile strength (UTS) (e). Same capital letters indicate no statistical difference among groups (p > 0.05). The groups had different polymerization kinetics without statistical difference for the degree of conversion and UTS.

Figure 2

Bacterial colony forming unit counting: (a) Streptococcus mutans biofilms and (b) planktonic S. mutans that were in contact with the polymerized samples. Values indicated by different letters indicate statistical differences among the groups (p < 0.05).

Figure 3

Cytotoxicity evaluation of the experimental dental resins expressed by percentage of cell viability: (a) structure of myristyltrimethylammonium bromide (MYTAB) and schematic drawing of sulforhodamine B (SRB) assay; and (b) MYTAB cytotoxicity assessed in normal human keratinocytes (HaCaT) line. Different capital letters indicate statistical differences among groups (p < 0.05).

Figure 4

Flowchart of the study design. Experimental dental resins were formulated with different concentrations of a quaternary ammonium compound (MYTAB). Bisphenol A glycol dimethacrylates (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) were used for the monomeric blend. The four experimental groups were evaluated for chemical, physical, and antibacterial properties, alongside their effect against human keratinocytes.