Effect of preparation burs on the adhesion of resin-based composite and glass-ionomer to enamel, superficial and deep dentin - Diamond, carbide or Arkansas bur?

Abstract

Objective

This study aimed to determine whether the bur type affects the adhesion of resin-based composite and glass-ionomer restorative materials to enamel and dentin at different depths.

Methods

Wisdom molar teeth (N = 216) were prepared using three different types of burs: a) extra-fine diamond-coated bur, b) carbide bur (16–20 blade) and c) Arkansas bur at three occlusal depth levels: enamel, superficial dentin, and deep dentin. Specimens were then randomly assigned to receive either resin composite (RC) or glass-ionomer (GI). Half of the specimens were tested 24 h after bonding (dry) while the other half after thermocycling (500 cycles, 5–55 °C) for shear bond strength in a universal testing machine. Data were analyzed using Kruskal-Wallis, Wilcoxon rank-sum test with Bonferroni adjustment (α = 0.05). Additionally, Weibull modulus for each group was calculated to assess adhesion reliability using the various bur types on different substrates.

Results

The bur, restorative material type and aging affected the bond strength results (p<0.05) and the interaction terms were significant (p<0.05). In dry conditions, bur type did not affect the bond strength results (MPa) significantly on enamel and superficial dentin for both RC (5.73 ± 4.4–11.99 ± 7.62) and GI (4.93 ± 2.8–2.73 ± 0.75) (p>0.05). On deep dentin, carbide bur performed significantly better for RC (10.44 ± 4.08) than other bur types (6.06 ± 2.36–6.56 ± 3.58) (p<0.05). After thermocycling, bur type did not affect the bond strength results (MPa) significantly on enamel for both RC (13.19 ± 4.9–13.06 ± 5.57) and GI (4.50 ± 3.76–4.90 ± 3.11) (p>0.05). While on superficial dentin, bur type did not affect the bond strength results for RC (10.17 ± 5.98–7.07 ± 3.58), for GI diamond bur resulted in significantly lower bond strength (1.65 + 1.01) (p<0.05). On deep dentin, bur type did not affect the results for GI (3.24 ± 2.32–4.48 ± 2.26) but diamond bur resulted in higher bond strength (12.62 ± 6.47) than those of other burs (6.62 ± 3.05–7.14 ± 5.12) (p<0.05). Weibull modulus after thermocycling was the highest for Arkansas in RC (3.23) compared to other bur-material combinations (m = 1.6–2.9). After thermocycling, adhesion to enamel was not affected but independent from bur-material combinations in superficial and deep dentin increased significantly (p<0.05).

Significance

Tooth preparation on enamel does not benefit from the use of different bur types for increased adhesion both with resin composite and glass-ionomer. While a diamond bur cannot be recommended for glass-ionomer on superficial dentin, the same bur type enhances adhesion on deep dentin.