Effect of Dentin Hardness on Ablation Rate with Er:YAG Laser

Keigo Osuka, Tetsuya Amagai, Nobuyuki Kukidome, Yasuaki Takase, Shigeo Aida, Yoshito Hirai
2008 Photomedicine and Laser Surgery  
Objective: This study used artificially demineralized bovine dentin to ascertain the effect of hardness of demineralized dentin on ablation rate with the Er:YAG laser. Background Data: Before restoration of carious teeth, it is necessary to ablate any infected dentin that cannot be remineralized due to softening by the invading caries. A correlation has been suggested between the ablation efficiency of the Er:YAG laser and the progression of caries in dentin. To the best of our knowledge, no
more » ... dies have investigated the relationship between degree of demineralization by dentinal caries and ablation rate with the Er:YAG laser. Materials and Methods: Bovine mandibular anterior tooth roots were used as dentin samples. Each sample was soaked in a demineralizing solution (2 M lactic acid, pH 4.0) for 3 d to obtain demineralized dentin (DD) samples. Another group of samples were prepared without demineralization as a sound dentin (SD) group for comparison. After determining the Knoop hardness number (KHN) of each sample, the dentin surface was ablated with an Er:YAG laser. Tip output and pulse rate were set at 50 mJ and 20 pulses per second (pps), respectively, and the water spray was set at 3.5 mL/min. Ablation width, depth, and volume were measured following irradiation. Results: In the DD group, dentin hardness was 10.4 Ϯ 1.6 KHN at 100 m from the surface. In the sound dentin group, Knoop hardness was 51.0 Ϯ 1.6 KHN cross-sectionally throughout. No differences were observed from the surface to a depth of 2000 m. In the DD group, dentin ablation volume at the superficial demineralized layer was 2888 Ϯ 272 ϫ 10 4 m. In the SD group, dentin ablation volume was 1298 Ϯ 219 m 3 . The relationship between ablation volume and Knoop hardness was defined as Yϭ -40.699x ϩ 3350, revealing a marked negative correlation. Conclusion: The results demonstrate that the ablation volume for demineralized dentin was greater than that for sound dentin. The results suggest that the Er:YAG laser is capable of ablating infected dentin without damaging sound dentin by adjustment of tip output and pulse rate.
doi:10.1089/pho.2008.2163 pmid:19025406 fatcat:p43qdt6yargezkpn5vgy7muiyi