Effect of deproteinization on adhesion on the caries affected dentin

The aim of this in-vitro study was to evaluate the effect of NaOCl deproteinization of the caries affected dentine on the gap formation at the adhesive interface treated with different adhesive systems with the use of micro-ct. In this study, 96 human molars with carious lesions were collected and stored in saline solution at room temperature. Teeth were placed into molds with cold acrylic made of 10mm x 10mm x 10mm silicone impression material up to cemento-enamel junction. Enamel portion of the teeth was trimmed to reach the carious dentine. The carious dentine was removed with the excavator and steel rond burs. Caries affected dentin was determined as hard, bright and dark colored as a result of visual inspection, color and dentin resistance to excavation. In the microhardness tester (HMV-2, Microhardness Tester Shimadzu, Japan), the hardness of the caries affected dentin surface was checked by applying 1 Newton force from 3 different points for 15 seconds at a minimum distance of 40 μm for each sample. Prepared samples were randomly divided into two main groups: samples that were not deproteinized (Group A; n = 48; control group) and samples that were deproteinized (Group B; n = 48; experimental group). These main groups are divided into 4 subgroups (n=12) according to the adhesive systems tested: Two-step etch and rinse system was applied to the Group ASB and BSB samples; Two-step self etching system was applied to the Group ASE and BSE samples; Universal adhesive sysem was applied in etch and rinse mode to the Group AQER and BQER samples; Universal adhesive system (was used in self etching mode to the Group AQSE and BQSE samples. Adhesive systems were applied to the Group ASB, ASE, AQER and AQSE samples according to the manufacturers' instructions. Group BSB samples were etched with 37% phosphoric acid for 15 s and washed by water, then deproteinized by application of 6% sodium hypochlorite (NaOCl) for 15 s with microbrush, rinsed with water and light cured for 10 s. Group BSE samples were deproteinized by application of 6% sodium hypochlorite (NaOCl) for 15 s with microbrush, rinsed with water, then adhesive system was applied and light cured for 10 s. Group BQER samples were etched with K-etchant for 10 s and washed by water, then deproteinized by application of 6% sodium hypochlorite (NaOCl) for 15 s with microbrush, rinsed with water and light cured for 5 s. Group BQSE samples were deproteinized by application of 6% sodium hypochlorite (NaOCl) for 15 s with microbrush, rinsed with water, then adhesive system was applied and light cured for 5s. The teeth were restored with bulk-fill composite resin with the help of molds of 4 mm diameter and 4 mm height according the manufacturer's direction and light cured with LED for 20 s. All restored samples were stored in distilled water at 37°C prior to micro-CT analysis. The evaluation of microgap formation was done with the microtomography Skyscan 1174® device. Microgap formations are evaluated in mm3 and scans are recorded in TIFF format. Statistical analysis were done according to Kruskal Wallis and Mann Whitney U tests. In terms of micro-gap formation, the only statistically significant difference was found between Group A Control 1(ASB) and Group B Experimental 1(BSB) samples (p=0,043). There was no statistically difference about micro-gap formation between tested adhesive systems.