Effect of a modified methyl methacrylate-p-styrene sulfonic acid copolymer-based gel desensitizer on dentin permeability and tubule occlusion in human dentin in vitro

Abstract

Background/purpose: Tubular occlusion is an effective method to treat dentin hypersensitivity. This study aimed to determine the effect of a modified methyl methacrylate-p-styrene sulfonic acid copolymer-based gel desensitizer on dentin permeability and tubule occlusion in extracted human premolars.

Materials and methods: Hydraulic conductance (HC) measurement (n = 50) and scanning electron microscopy (SEM; n = 64) were performed. Tooth specimens were divided into 6 groups and treated with: G1, distilled water for 30 s; G2, distilled water for 5 min; G3, gel desensitizer for 30 s; G4, gel desensitizer for 5 min; G5, 3% potassium oxalate for 30 s; G6, 3% potassium oxalate for 5 min. HC of dentin were measured before and after 30 s-etching with 35% phosphoric acid, at 0, 30, 60 min after group treatment and after 5-min acid challenge with 6% citric acid. The degree of tubule occlusion and the penetration depth of each agent were also determined. ANOVA and multiple comparison tests were used for data analysis.

Results: G3, G4, G5 and G6 significantly decreased in HC after group treatment every observation period, compared to after acid-etching (P < 0.001), and had 100% degree of tubule occlusion with penetration depth about 7.62, 7.94, 8.59 and 8.66 μm, respectively. However, G6 showed the greatest reduction in HC (P < 0.05).

Conclusion: Gel desensitizer treatment, for only 30 s, could reduce dentin permeability and completely occlude the dentinal tubules, even though after acid challenge. However, 5-min treatment with potassium oxalate showed the greatest decrease in dentin permeability.

Keywords: Dentin hypersensitivity; Dentin permeability; Dentinal tubule occlusion; Gel desensitizer; Human dentin.

Figure 1

Mean (±1 SD) hydraulic conductance values of dentin before and after etching, after treatment with distilled water for 30 s (G1), distilled water for 5 min (G2), gel desensitizer for 30 s (G3), gel desensitizer for 5 min (G4), 3% potassium oxalate for 30 s (G5) and 3% potassium oxalate for 5 min (G6) at time 0, 30 and 60 min, and after acid challenge. The same lowercase letter represents no significant difference between observation periods in each group (P > 0.05, repeated measure, 1-way ANOVA).

Figure 2

(A–L) Scanning electron micrographs of cross sectional views of human dentin (original magnification X3000, scale bar = 5 μm). (A, B) treated with distilled water for 30 s; (C, D) treated with distilled water for 5 min; (E, F) treated with gel desensitizer for 30 s; (G, H) treated with gel desensitizer for 5 min; (I, J) treated with 3% potassium oxalate for 30 s; (K, L) treated with 3% potassium oxalate for 5 min; (A, C, E, G, I, K) before acid challenge; (B, D, F, H, J, L) after acid challenge.

Figure 3

(A–L) Scanning electron micrographs of longitudinal views of human dentin (original magnification X3000, scale bar = 5 μm). (A, B) treated with distilled water for 30 s; (C, D) treated with distilled water for 5 min; (E, F) treated with gel desensitizer for 30 s; (G, H) treated with gel desensitizer for 5 min; (I, J) treated with 3% potassium oxalate for 30 s; (K, L) treated with 3% potassium oxalate for 5 min; (A, C, E, G, I, K) before acid challenge; (B, D, F, H, J, L) after acid challenge. Arrows showing precipitates formed within dentinal tubules.

Figure 4

Mean (±1 SD) penetration depths of dentinal tubule occlusion after treatment with gel desensitizer (gray column) for 30 s (G3) and for 5 min (G4), and after treatment with 3% potassium oxalate (black column) for 30 s (G5) and for 5 min (G6). The same lowercase letter represents no significant difference between treatment times, and the same uppercase letter represents no significant difference between desensitizing agents (P > 0.05, 2-way ANOVA and Tukey test).