The Effect of Diamond Bur Preparation, Air Abrasion and Phosphoric Acid Etching on Micro-Roughness of Tooth Enamel

Background: Conventional diamond bur preparation, air abrasion, and acid etching of hard dental tissues have become an integral part of modern restorative dentistry. However, their influence on the surface microstructure of anisotropic enamel is poorly elucidated. This study investigated the effect of acid etching on the micro-roughness of buccal and occlusal enamel surfaces after traditional treatment with a diamond bur and a subsequent air-abrasion with mixtures based on Al₂O₃ or erythritol powders (AFP). Materials and Results: Eighteen unerupted wisdom teeth extracted for orthodontic reasons were included in the study. Only the coronal parts of the teeth were used. They were cleaned of pulp tissue fragments, sequentially treated in an ultrasonic bath with an 80% alcohol solution and distilled water, and then randomly divided into 2 groups of 9 samples each. In samples of Group 1, the ground surfaces were formed on the buccal sides, and in the samples of Group 2, they were made on the occlusal sides. The samples of each group were divided into subgroups of 3 depending on the type of tooth surface treatment: (1) grinding hard tissues with a diamond bur only; (2) grinding and an air abrasion using Al₂O₃ powder; (3) grinding and an air abrasion using erythritol-based powder (AFP). Areas for acid etching were allocated on the surface of each sample. The etching step was performed using a 37% phosphoric acid gel. Qualitative and quantitative alterations to the enamel surface were registered using SEM and applied software. Traditional enamel processing with a diamond bur contributed to the formation of the highest roughness value profiles: 9.9±0.7 µm (buccal enamel side) and 9.6±0.8 µm (occlusal enamel side). Acid etching of enamel after diamond bur preparation resulted in a decrease in roughness values of buccal and occlusal enamel sides down to 5.4±0.4 and 5.5±0.4 µm, respectively ( P =0.000). The use of AFP and Al₂O₃, followed by acid etching, reduced the roughness values to 5±0.4 and 5±0.3 µm ( P =0.000), respectively, and to 4.4±0.7 and 5.4±0.3 µm ( P =0.000), respectively. Conclusion: Air abrasion, followed by acid etching of the enamel, contributed to a significant reduction in the micro-roughness of surfaces formed by the diamond bur. It was also noted that there was no significant difference in roughness values between buccal and occlusal enamel after diamond bur preparation, air abrasion with erythritol, and acid etching. The lowest surface roughness of enamel was observed on buccal sections of tooth slabs after consecutive air abrasion with Al₂O₃ and acid etching.