Enzymatic Activity Evaluation of Restored Teeth Prepared With Er:YAG-Laser or Rotatory Instruments.

Objectives: Dentinal endogenous enzymes degrade the collagen fibrils exposed after bonding to dentin, impairing the longevity of the hybrid layer. The application of high-power lasers for cavity preparations could be a factor that influences the activity of dentinal enzymes. The aim of this study was to evaluate the effects of different cavity preparation protocols on dentinal enzymatic activity.
Methods: Crowns of non-carious molars were sectioned to expose the dentin surfaces and assigned to one of the following groups, according to the type of preparation / adhesive technique to which they were submitted (n=5): G1- Burs/etch-and-rinse; G2- Burs/self-etching; G3- Er:YAG laser (150mJ/20Hz/3.0W) /etch-and-rinse; G4- Er:YAG laser (150mJ/20Hz/3.0W) /self-etching. After curing the adhesives, resin composite restorations were performed and specimens were cut into slabs of 1 mm each, glued to glass slides and polished. In situ zymography was performed on the specimens immediately after the treatment in accordance with Mazzoni et al., 2014. Self-quenched fluorescein-conjugated gelatin mixture was placed on top of each specimen, protected with a cover slip and incubated in a dark humidified chamber at 37°C overnight. Detection of endogenous enzymatic activity within the dentin was assessed with a multi-photon confocal laser scanning microscope and the integrated density of the fluorescent signal was quantified using ImageJ software. The intensity of fluorescence corresponds to the level of enzymatic activity. Statistical analysis was performed with one-way ANOVA and Tukey tests.
Results: In situ zymographic assay presented less pronounced enzymatic activity in the Laser-treated groups. Statistically significant differences were observed in the integrated density of the signal of the tested groups (p>0.05): G1 (30563) A; G2 (31187) A; G3 (22040) B; G4 (19954) B.
Conclusions: The use of Er:YAG Laser can modify the endogenous enzymatic activity of dentin regardless of the adhesive protocol performed. Further studies are needed to validate this investigation and define effective preparation protocols able to preserve dentinal integrity.