Pathological Study of Pulp Treated with Chemicals after Er:YAG Laser Preparation

Objective: The aim of this study was to clarify pulp reaction following cavity preparation with an Er:YAG laser and subsequent treatment with topically applied chemicals to achieve a high resin bond strength. Background Data: The application of chemicals has been found to effectively remove or reform the denatured layer produced by Er:YAG laser irradiation and has been proposed as a new strategy for improving resin bond strength. However, very little is known about pulp reaction to chemical procedures. Methods: Class 5 dentin cavities were prepared with an Er:YAG laser in 128 teeth in nine adult dogs. The teeth were then coated with glutaraldehyde (GA group), or phosphoric acid and sodium hypochlorite (PA group) to reform or remove the denatured layer. All the cavities were then restored with composite resin. In the control group, no chemical application was carried out prior to restoration. The animals were sacrificed immediately after, and at 7 and 90 days following treatment. The treated teeth were then extracted for histopathological examination of the pulp. Results: Pathological evaluation of the pulp indicated a good condition in each group at each of the three observation time points. No bacterial growth was observed on the cavity walls or bacterial invasion into the dentinal tubules or pulp chambers in any of the groups at any of the observation periods. Conclusion: Our findings suggest that the application of chemicals to remove or reform denatured layers is effective in obtaining better composite resin restoration with no pulp damage.