Joint-design and welding effect on flexural strength of Ti-6Al-4V bars

Abstract

Purpose: The aim of this study was to microbiologically compare the surface of class V restorations performed with microhybrid composite resin or flowable composite resin, over 48 months, in order to determine an increased risk of secondary caries. Methods & Materials: 36 class V restorations were performed according to a standardized method, in order to asses if the different composite materials had changed the microbiological pattern on the restoration’s surface. Samples were collected over 48 months from the execution of the restoration, to evaluate the incidence of time on the growth of S. mutans, in correspondence of four different composite resins (two microhybrid and two flowable composite resins). Samples were managed with sterile paper points, withdrawing localized plaque on the margin of the restoration, then kept frozen in saline solution. For each tooth with class V restoration a control sample was taken from an healthy element, to analyze the relationship between presence of S. mutans and restoration. Samples were processed according to the method of PCR-Realtime, to find and quantify S. mutans. For restorations were used 2microhybrid composite resins, Venus Diamond (Heraeus Kulzer) and Ceram-x (Dentsply) and 2 flowable resins,Tetric Evoflow (Ivoclar Vivadent) and Venus Diamond flow (Heraeus Kulzer). Results: Flowable composite resins show an increased capability of creating a suitable substrate to bacterial growth, probably because of the surface porosity that this resin develops in time, caused by imbibitions of the organic matrix. The highest quantity of bacterial flora was found on restorations performed with flowable resin; also the highest relative quantity of S. mutans was found on the same kind of restoration. Conclusion: Flowable composite resins seem to offer a better substrate to bacterial growth in general; data obtained can state that there’s an increased growth of S. mutans in correspondence of restorations performedwith flowable composite resin.