Project title comparative research of different antioxidants effectiveness on bond strength of NaOCL treated dentine after aging

The aim of this in vitro thesis study was to investigate the effect two antioxidants [(sodium ascorbate (SA) and proanthocyanidin (PA)] applied at different application times to the dentin surface after sodium hypochlorite (NaOCl) application on the short and long term SBS of between dentin and a two-step self-etch adhesive (Clearfil SE Bond). In this study, 160 permanent human molar teeth were cut with a low-speed diamond disc, exposing the coronal dentin surface. Dentin samples were embedded in acrylic cylinders with a diameter of 30 mm and a height of 10 mm. The samples were randomly divided into 8 main groups (n=20). Two control groups were prepared, one group with and one without application of NaOCl (CSE, NaOCl). Six antioxidant experimental groups [(SA1, SA5, SA10, PA1, PA5, PA10)] were prepared by applying 5.25% NaOCl for 10 minutes, then 10% SA and 15% PA antioxidant solutions to the remaining experimental samples at different application times (1 min, 5 min, 10 min). Samples in all groups were light cured by applying a two-step self-etch adhesive (Clearfil SE Bond, Kuraray Inc.) and composite (Filtek P60, 3M ESPE) according to the manufacturers' instructions. All groups were divided into two subgroups as immediate and long term groups (n=10). SBS tests were performed right after restoration on the immediate term groups, and after thermal aging procedures (5000 cycles) for the long term groups. As a result of this study; the SBS values of NaOCl group of immediate and long term groups were lower than the SBS values of both antioxidants groups of immediate and long term groups at all application times (p<0.05). At the immediate term SA groups; the SA group applied for 1 min showed a significantly lower SBS value than the groups applied SA for 5 and 10 min (p<0.05). At the immediate term PA groups, the SBS values of the PA group applied for 1 min was found to be significantly lower than the PA group applied for 5 minutes (p:0.019; p<0.05). In the long term, there was no statistically significant difference between the SBS values of both antioxidants groups at different application times (p>0,05). According to the findings of this in vitro study, it was observed that SBS values increased as the application time of both antioxidants increased after NaOCl application, for the immediate and long term groups. Within the limitations of this study, it could be recommended the application of 10% SA and 15% PA antioxidant agents for at least 1 minute in order to increase and protect the resin-dentin SBS values after application of NaOCl for the long term durability of the restorations. Keywords: Sodium hypochlorite, Shear bond strength, Sodium Ascorbate, Proanthocyanidin