Effect of benzalkonium chloride on dentin bond strength and endogenous enzymatic activity

Abstract

This in vitro study evaluated at baseline (T0) and over time (T12 months), the effect of a multi-mode universal adhesive compared with two experimental formulations blended with different concentrations of benzalkonium chloride (BAC), on bond strength and endogenous enzymatic activity. Methods and materials: Specimens were assigned to the following groups according to the adhesive protocol: G1) All-Bond Universal (ABU) self-etch (SE); G2) ABU + 0.5% BAC SE; G3) ABU + 1% methacrylate BAC SE; G4) ABU etch-and-rinse (E&R); G5) ABU + 0.5% BAC E&R; G6) ABU + 1% methacrylate BAC E&R. Gelatin zymography was performed on dentin powder obtained from eight human third molars. Endogenous enzymatic activity within the hybrid layer was examined using in situ zymography after 24 h (T0) or 1-year storage in artificial saliva (T12). Forty intact molars were prepared for microtensile bond strength test at T0 and T12. Results were statistically analyzed with three-way ANOVA (α = 0.05). Results: Gelatin zymography assay and in situ zymography quantification analyses indicated that all the BACcontaining formulations decreased matrix metalloproteinase expression. However, in situ zymography showed a general trend of enzymatic activity increase after aging. Microtensile bond-strength testing showed decrease in bond strength over time in all the tested groups; performances of the 1% methacrylate BAC experimental groups were worse than the control. Conclusions: BAC-containing adhesives reduce endogenous enzymatic activity both immediately and over time. However, independently from the adhesive employed, increase in the gelatinolytic activity over time and decrease in bond strength was found (especially in the BAC + 1% methacrylate groups), probably due to impaired polymerization properties. Clinical significance: Adhesives containing protease inhibitors are practical and efficient tools in clinical practice for enhancement of the longevity of dental restorations. However, extensive investigation of the mechanical and adhesive properties of the material is necessary prior to their clinical use.

Mitochondrial Dysfunctions May Be One of the Major Causative Factors Underlying Detrimental Effects of Benzalkonium Chloride

“…In our approach, we applied as a model tightly coupled (high-quality) rat liver mitochondria that are a proper biosensor for assessment of drugs and specific directed agents. A comprehensive analysis of BAC effects on mitochondria showed that BAC did not exhibit an uncoupling activity ( Figure 2), resembling in this respect the behaviour of other hydrophobic lipophilic quaternary ammonium compounds such as C 10 TEA and C 16 TMA investigated by us previously [66]. In the cited paper, these compounds, as exemplified by C 16 TMA, were found to possess high affinity to the membrane surface (the binding energy for C 16 TMA was equal to 48 kJ/mol), which apparently originated from its long hydrocarbon "tail," and enhanced activation energy (for C 16 TMA, 71 kJ/mol), and hence lowered permeability through lipid bilayer, possibly due to the small size of their charged "head."…”

“…In the cited paper, these compounds, as exemplified by C 16 TMA, were found to possess high affinity to the membrane surface (the binding energy for C 16 TMA was equal to 48 kJ/mol), which apparently originated from its long hydrocarbon "tail," and enhanced activation energy (for C 16 TMA, 71 kJ/mol), and hence lowered permeability through lipid bilayer, possibly due to the small size of their charged "head." Importantly, C 10 TEA and C 16 TMA were inactive in the BLM test (no diffusion electric potential was generated). Assuming that C 10 TEA, C 16 TMA, and BAC share similar properties (they are hydrophobic lipophilic quaternary ammonium compounds with screening of positive charge of lipophilic cations by bulky residues), this might explain the lack of uncoupling activity exerted by BAC (Figure 2), as well as the development of its inhibitory effect with time (Figures 2 and 3).…”

“…Importantly, C 10 TEA and C 16 TMA were inactive in the BLM test (no diffusion electric potential was generated). Assuming that C 10 TEA, C 16 TMA, and BAC share similar properties (they are hydrophobic lipophilic quaternary ammonium compounds with screening of positive charge of lipophilic cations by bulky residues), this might explain the lack of uncoupling activity exerted by BAC (Figure 2), as well as the development of its inhibitory effect with time (Figures 2 and 3). Most probably, depolarizing activity (Δψ decrease) of BAC was due to its inhibitory effect on the respiratory chain ( Figure 4).…”

“…The precise mechanism of inhibitory action of BAC on the translocase is unknown; this issue in the literature has been totally ignored. Keeping in mind, by analogy to C 16 TMA, a lowered permeability of BAC through lipid bilayer, we would like to speculate that the mitochondrial ADP/ATP in the state "c conformation" (with the active center opened on the cytoplasmic side of the inner membrane) might be one of the major targets of BAC in mitochondria, most accessible for direct interaction with BAC. We are inclined to think that BAC inhibitory effect on the ADP/ATP translocase might be similar to its antimicrobial action, being associated with insertion of BAC alkyl group into the hydrophobic core of the inner mitochondrial membrane, thus disturbing the membrane and the translocase dominating in the membrane.…”

“…BAC, a membrane-active cationic surfactant, is remarkable by its stability, high water solubility, low cost, and superior biocidal activity against most bacteria, fungi, algae, and some viruses [3][4][5][6]. It is extensively employed as an antimicrobial in hospitals, agriculture, and the food industry [4], in ophthalmic preparations [7], nasal sprays [8], multidose albuterol nebulizer solutions [9,10], as a skin disinfectant and hand sanitizer [11], in cosmetics, numerous toothpastes and mouth rinses, lozenges, and dental restoratives [12][13][14][15][16].…”