Shear bond strength of two porcelain repairing systems using different surface preparation techniques

Statement of the problem: Fracture or chipping of veneering porcelain in PFM restorations is considered to be a very common failure in clinical practice. Many clinicians are using different intra- oral surface preparation techniques and repairing systems. However, the success rate is still of concern to be verified as an acceptable treatment modality.  Materials and methods: A total of 40 circular porcelain fused to metal specimens with 1 cm in diameter and 4   mm thickness were fabricated using feldspathic porcelain (VITA VMK Master, VITA, Germany) and nickel chromium base metal alloy (Wiron Light, BEGO, Germany). All 40 samples were subjected to 3000 cycles of thermo-cycling before the repair was performed. The specimens were divided into two equal groups of 20 samples each according to the repairing system used. (V; one step self-adhesive flowable composite resin, Vertise Flow, Kerr) and (F; two steps, Embrace First Coat, Pulpdent) followed by the application of self-adhesive composite resin (Vertise Flow). Each group of the two main groups was divided into two equal subgroups of 10 samples each according to the surface treatment applied before repair. (D; diamond stone surface roughening) and (H; hydrofluoric acid etching). Half of the specimens were subjected to accelerated photo-thermal aging before testing the shear bond strength. Shear bond strength was determined using NEXYGEN from Lloyd Instruments at a crosshead speed of 0.5mm/min. Statistical analysis was carried out using Kolmogorov-Smirnov and Shapiro-Wilk tests.  Results: No statistically significant differences were found between the two repairing systems or between the two surface treatments either before or after accelerated photo-thermal aging. The only significant difference was recorded between the two subdivisions where the two steps system was used on etched surfaces before and after photo-thermal aging.  Conclusion: The one step direct application of the self adhesive flowable composite resin (Vertise Flow) can be used without the incorporation of the additional primer (Embrace First Coat) step as they showed comparable results. Diamond stone roughening can be a good alternative to hydrofluoric acid. Clinical recommendations: The one step direct application of the self adhesive flowable composite resin (Vertise Flow) can be used effectively without the incorporation of the additional primer (Embrace First coat) step. When attempting to use the two steps system of First Coat plus Vertise Flow, it should not be used with hydrofluoric acid etching.