Purpose: The aim of this study was to assess the efficiency (time necessary for carious tissue removal) and effectiveness (caries removal capacity) of the Er:YAG laser using different pulse repetition rates. Materials and Methods: Fifty-two slabs of carious human dentin were selected, fixed, and a 3-mm2 circular area was delimited. According to a randomized complete block design, specimens were assigned to 4 groups (n = 13): Er:YAG laser at three pulse repetition rates (2, 3, and 4 Hz) and carbide bur at low speed (control). Time to remove carious tissue was recorded, and 5 calibrated examiners checked the cavities through tactile and visual analysis. Results: Concerning the efficiency, Kaplan-Meier analysis demonstrated that the bur was faster than Er:YAG laser, regardless of the frequency. The Kruskal-Wallis test showed a significant difference among groups (p = 0.0001). The Wilcoxon test verified that all frequencies were significantly different from the mechanical bur (p < 0.0001) and that 2 Hz differed significantly from 4 Hz (p = 0.0042). In the analysis of efficacy, medians from five examiners judgments were used. Interexaminer agreement (Kappa) varied from 0.24 (fair) to 0.75 (substantial). The Students t-test did not demonstrate a significant difference between 4 Hz and carbide bur (p = 1.0000), but both presented greater effectiveness in carious tissue removal than 2 and 3 Hz. Conclusion: Mechanical drilling was more efficient than Er:YAG laser, regardless of the pulse repetition rate used. Er:YAG laser irradiation with 4 Hz presented similar effectiveness to the carbide bur in a low-speed handpiece.
Keywords: Er:YAG laser, carious dentin, caries removal, pulse repetition rate, efficiency, effectiveness