Evaluation of shear bond strength of metal and ceramic brackets on different surface roughenings on hybrid ceramic CAD-CAMmaterial

In view of the increase in the number of adult patients seeking orthodontic treatment, orthodontists have to stick their braces to prosthetic materials such as amalgam, composite, and porcelain in their patients while performing fixed orthodontic treatment. With the developing technology new materials are added every day to the dentistry. Hybrid ceramic CAD-CAM blocks are a new generation of prosthetic treatment materials. The aim of our work is to apply 6 different roughening techniques such as Hydrofluoric acid, Orthophosphoric acid, Cojet, Er-YAG Laser, Nd-YAG Laser and Femtosecond Laser to CAD-CAM blocks to see the bonding strength in metal and ceramic brackets. We will apply a shear test to see the bond strength on the brackets and compare the results with a scanning electron microscope and an optical profilometer. MATERIAL AND METHODS Sections of approximately 2 mm thickness were cut from 50 hybrid ceramic CAD-CAM blocs and 216 hybrid ceramic samples were obtained. The samples were abraded with 600,800,1000 grit silicon carbide abrasive (3MTM WetordryTM, 3M, St. Paul, MN, U.S.A). Surface smoothing with carbide abrasive was applied. The samples were divided into two main groups as metal and ceramic groups after ultrasonic water bath. These groups were then divided into 6 different subgroups (HFA, OFA, CJ, Er-YAG, Nd-YAG, FSL). Thus, the number of subgroups was fixed at 18. Following the roughening process, the upper right incisor brackets were bonded to the specimens. Samples were stored in distilled water at room temperature and then 1000 cycles were completed in the thermal cycling device. The samples were subjected to a shear test. Two samples from each group with roughening but without brackets were evaluated in terms of surface roughness with a scanning electron microscope and an optical profilometer. The breakage of the brackets from the material surface and the shape of the porcelain fracture were examined. One-way analysis of variance, Tukey's HSD test and chi square test and Kruskal-Wallis test were used for statistical evaluation (p<0.05). RESULTS AND CONCLUSIONS The roughness values of the groups measured in the profilometer were statistically different from each other (p<0.05). The most roughness values are listed as Er-YAG, FSL, CJ, Nd-YAG, HFA, OFA and untreated surface respectively. Bond strength value (SBS) test results are the clinically acceptable bond strength value (SBS) or more for all groups. In metal brackets, the Nd-YAG group statistically showed higher SBS values than CJ, Er-YAG and HFA. Metal brackets gave higher SBS values than porcelain brackets. These values are statistically significant in the Nd-YAG group.