1ボトル1ステップシステムのEr:YAGレーザー照射歯質に対する接着

Abstract

Various studies have revealed that the Er:YAG laser is effective in endodontic, periodontal and surgical treatments, and it is used in actual clinical practice. In particular, the Er:YAG laser shows excellent clinical effects when cutting hard tooth tissue, and there have been many studies on adhesive restoration involving teeth irradiated with Er:YAG laser. In this study, focusing on the one-bottle one-step bonding system, we performed tensile bond and marginal leakage tests to evaluate its adhesive properties to enamel and dentin irradiated with Er:YAG laser.Experiment 1Flat bovine enamel or dentin surfaces were prepared using a model trimmer and water-resistant polishing paper (#600), and were irradiated with Er:YAG laser (100mJ, 10pps). Non-irradiated specimens were used as a control. After bonding procedures were performed on these adherent surfaces of 3mm in diameter, the specimens were stored in 37°C distilled water for 24 hours, and were divided into two experimental groups: the 24-hour storage group and the thermal stress group. In the thermal stress group, the specimens were subjected to 2,000 or 5,000 thermocycling in water from 5°C to 55°C with a dwell time of 30s at each temperature. Thereafter, a tensile bond test was performed in each group (n = 10).Experiment 2Saucer cavities (3mm in length, 2mm in width, and 1.5mm in depth) in extracted human molars were prepared setting the anatomical cervical line as the center, using a high-speed cutting diamond point. The marginal line was placed in the enamel on the coronal side and in the dentin on the gingival side. After cavity preparation, the internal cavity walls were uniformly irradiated with Er:YAG laser (100mJ, 10pps). Non-irradiated specimens were used as a control (n = 10). After bonding and filling procedures, these specimens were stored in 37°C distilled water for 24 hours, and thermo-stressed after finishing and polishing. Then, the dye-penetration test was performed according to the following procedures. The root apex was sealed using glass-ionomer cement, and the tooth surface was fully coated with nail varnish except for the area approximately 1mm off the cavity margin. After immersion in 0.5% basic fuchsin at 37°C for 24 hours, each specimen was cut longitudinally at the center of the cavity using a low-speed diamond saw. The degree of dye penetration into the coronal (enamel) or cervical (dentin) wall was evaluated by optical microscopy.From these experiments, the following conclusions were obtained:1. In the tensile bond test, the lased dentin exhibited lower bond strength than the non-irradiated dentin, while enamel showed almost the same bond strength regardless of the laser irradiation.2. In the dye penetration test, marginal microleakage was observed in the dentin cavity wall, whereas good marginal integrity was demonstrated at the enamel margin.