A comparison of flexural strength of peek restorations with varying core and composite resin thickness

It is common to use indirect light- curing composite resins. In particular, indirect composite resins are used on many framework materials due to their advantages such as wearing with dental tissues, being easy to repair with laboratory procedures and aesthetic expectations. Today, in dentistry, polyether ether ketone (PEEK) material is used with indirect composite resins on PEEK framework to increase aesthetics, but there are some difficulties due to PEEK's internal structure to provide a durable and long term bonded. For this reason, there are chemical methods such as sandblasting, acid etching, silica coating and adhesive processes to create macro or micromechanical retention. There are many studies that have very high bond strength with mechanical and chemical adhesives, but the framework thickness and veneering thickness are very important in terms of the durability of the restoration and the fracture resistance. Therefore, the purpose of our study is; It is the comparison of the fracture strength of PEEK restorations with varying core and composite resin thickness. In our study, 2 different brands were used, namely GC Gradia and Ivoclar Nexco Paste, 180 sample PEEK samples were prepared. The first 9 groups of PEEK, which is divided into 18 groups, were applied with GC Gradia opeker and GC gradia indirect composite, and the last 9 groups with PEEK, Ivoclar Nexco Paste opaker and indirect composite. After all sample preparation for the experiment is completed; 1 mm / min with cutting device. Cutting speed was made. The data were analyzed on the computer using SPSS 25.0 (Statistical Packages of Social Sciences) program. Explanatory statistics are shown as mean ± standard deviation for continuous variables. The suitability of the data for normal distribution was evaluated with the Kolmogorov-Smirnov test. The homogeneity test of variances was evaluated by Levene test. Welch ANOVA was used for comparison of continuous variables that conform to normal distribution between groups but did not meet the assumption of homogeneity of variances, and Dunnett T3 test for binary comparison of variables that were statistically significant. Test results were interpreted by making Bonferroni correction. If p <0.05, the difference was considered significant. In our study, it shows that the thickness of the superstructure composite resin is significantly more effective in bending strength than the thickness of the substructure. Composite thickness is more effective and PEEK showed that its thickness did not affect. It was understood that the PEEK substrate thickness did not support the composite sufficiently in bending strength.