The purpose of this study was to evaluate the priming effect of 2-hydroxyethylmetaclirate (HEMA) following acid treatment on resin bonding to prototype Er:YAG laser-irradiated dentine. Extracted bovine dentine following laser irradiation was acid treated by aqueous solution of 10% citric acid (10-0) or 10% citric acid/3% ferric chloride (10-3), and additionally treated with 35% HEMA. Pre-treated dentines were bonded to the polymethyl-methacrylate (PMMA) rod with 4-META/MMA-TBB resin (Super Bond C & B) and miniaturized dumbbell-shaped bonded specimens were prepared. These specimens profiled for tensile bond testing and fractured surfaces were observed by scanning electron microscopy (SEM). Cross-sections of resin-dentine interface were also examined. The HEMA treatment following acid conditioned by 10-3 or 10-0 for both laser-irradiated and non-irradiated dentines was significantly higher than that without HEMA treatment. SEM view of a fractured specimen showed some cohesive failure in cured resin, but almost all of the fractured surface shows boundary failure between the penetrated resin and underlying dentine. A cross-sectional view of the interface showed a very thick hybrid layer between the hybridized dentine and underlying dentine. It was concluded that HEMA treatment following acid conditioning provided a slightly higher bond strength for both the Er:YAG laser-irradiated and non-irradiated dentines. However, the bond strength of Er:YAG laser irradiated dentine was significantly lower than that of the non-irradiated dentine.

Objective: This study evaluated the influence of laser irradiation with a high pulse repetition rate on dentin bonding. Background Data: Although resin bonding to erbium:yttrium-aluminium-garnet (Er:YAG) laserirradiated dentin has frequently been investigated, the effects of a high pulse repetition rate have not yet been sufficiently investigated. Methods: Four groups treated under different laser conditions were evaluated in this study: 100 mJ/pulse-10 pulses per second [pps], 50 mJ/pulse-20 pps, 33 mJ/pulse-30 pps, and the unlased condition as a control. The total energy used to irradiate each group was adjusted to 1.0 W. After bovine dentin specimens were irradiated by an Er:YAG laser, acid conditioners (10% citric acid/3% ferric chloride) were applied to the lased surface. Thereafter, a PMMA rod was bonded to the lased dentin using 4-META/MMA-TBB resin, and mini-dumbbell-shaped specimens were prepared. These specimens were then tested under tensile mode and fractured surfaces were observed under scanning electron microscopy (SEM). Results: The bond strength of the unlased control was significantly higher than those of the three lased groups. Among the three lased groups, irradiation with higher output energy and lower pulse repetition rate tended to affect the higher bond strength. Upon SEM observation of the fractured surface, the lased groups showed the mixture of failure in the hybrid layer in almost part. There was no significant difference among the three lased groups. Conclusion: It can be concluded from the results of this study that a higher pulse repetition rate is not effective for resin bonding to laser-irradiated dentin.

Objective: The aim of this study was to investigate the correlation between the demineralization depth measured by dental computed tomography (CT) and the measured value from a non-destructive dental caries diagnosis with a laser. Methods: Optimal cut-off points were obtained for enamel and dentin caries, from the measured levels from a dental caries diagnosis with a laser, to investigate the clinical usefulness of a diagnosis using a laser. Using human teeth, the demineralization depth was measured and the caries were diagnosed by a dental caries diagnosis with a laser. Results: The optimal cut-off point was investigated for accuracy, sensibility, and specificity, which were calculated from the results. These results demonstrated the correlation between the measured values and demineralization depth in both the pit and fissure caries and smooth surface caries. The optimal cut-off points were found to be 16-21 in the fissure caries and 9-11 in the smooth surface caries. 50

The purpose of this study was to evaluate the tensile bond strength to peroxide-exposed dentin. Furthermore, the effect of ascorbic acid on the bond strength of peroxide-exposed dentin was investigated. Extracted bovine dentin was exposed to 10% carbamide peroxide, 30% hydrogen peroxide or distilled water for 30 min, then treated with 10% ascorbic acid (0,30, 90, 180 min), and conditioned with 10% citric acid/3% ferric chloride. The PMMA rod was bonded to the treated bovine dentin with 4-META/MMA-TBB resin. A mini-dumbbell-shaped bonded specimen was prepared from these bonded assemblies and the tensile bond strength was tested. The fractured surfaces were also observed with SEM. Exposure to peroxide before bonding significantly reduced bond strength. The application of ascorbic acid to the peroxide-exposed dentin increased bond strength. On the other hand, an adverse effect of ascorbic acid was found in distilled water-affected dentin.Extended resin fibers were partially seen in the peroxide-exposed dentin. In conclusion, peroxide reduced the bond strength, and the stronger the oxidation, the weaker the obtained bond. Anti-oxidation with ascorbic acid recovered the bond strength, and the effect increased the longer the ascorbic acid was applied.

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