Optimization of Er: YAG pulse duration and repetition rate for efficient, dentin‑preserving caries removal

PURPOSE: To evaluate the effects of pulse duration and repetition rate on Er: YAG laser ablation efficiency and sound dentin preservation in artificial and natural carious models. METHODS: Fifty-six artificially decalcified dentin specimens were allocated to six Er: YAG laser groups (L1-L6; pulse durations 50-300 µs, repetition rates 20-40 Hz, energies 60-70 mJ) and one rotary bur control (n = 8 each). Twenty-four natural carious molars were assigned to medium-short pulse (MSP: 100 µs, 40 Hz) versus bur or super-short pulse (SSP: 50 µs, 40 Hz) versus bur comparisons (n = 12 pairs each). Sound dentin loss (mm²) and treatment duration (s/mm²) were quantified using standardized radiography or three-dimensional surface scanning, and ablation threshold changes (ΔE = E₁ - E₂) were assessed in natural carious model. RESULTS: In the artificial model, L1 (70 mJ, 300 µs, 20 Hz) yielded the lowest sound dentin loss (median 0.040 mm², IQR 0.037-0.043), significantly less than bur (p < 0.001) and short-pulse groups L4 and L6 (p < 0.05 to p < 0.0001). L4 (70 mJ, 50 µs, 40 Hz) achieved the shortest laser treatment duration (mean 190.64 s/mm², SD 36.90; p < 0.05 vs. L1-L3). In natural caries, both MSP and SSP protocols preserved sound dentin comparably to bur (p > 0.05) but required 3.3- and 2.6-fold longer treatment times, respectively (p < 0.0001). Overall, 70% of specimens exhibited ΔE reductions of 5-10 mJ (maximum 20 mJ). CONCLUSION: Within a conservative energy range, short-pulse, high-repetition-rate Er: YAG settings enhance caries removal efficiency and lower ablation thresholds while preserving sound dentin similarly to rotary burs, supporting their application in minimally invasive deep-caries management.