Investigation of the effects of different surface treatments and metal framework manufacturing techniques in bonding the repair material to the porcelain fracture

Objective: Porcelain fused to metal restorations are still used in prosthetic treatments up to date. It is not always possible to remove the porcelain fused to metal restorations from the mouth without a new damage to repair the porcelain fractures. As a result of the advances in material technology recently, it was claimed that intraoral repair of porcelain fractures covering a small area is an effective and safe treatment option. Thus, the aim of the present study was determination of the most effective surface treatment option on the bond strength between the intraoral repair materials and metal substructures produced with different techniques. Method: In the present study, the same dental porcelain was applied on substructures ( n= 160) produced by three different production techniques ( laser sintering, casting and CAD/CAM). 2 mm diameter part of the porcelain surfaces from the samples were removed. Four different surface treatments to the metal surfaces were applied: hydrofluoric acid, laser, sandblasting and silica coating. After the repairment of all fractured surfaces, bond strengths between repair materials and porcelain fused to metal specimens were evaluated. A sample from each group was selected and the scanning electron microscope evaluations were performed. Statistical analysis were performed by using Two Way ANOVA and One Way ANOVA tests. Results: Comparison between the bond strengths of differently produced metal substructures and repair material showed that there was no statistically significant difference between bond strengths of metals produced with EOS, CAD-CAM and Consept Laser (p>0,05). It was observed that the substructures produced by casting were statistically different from the other substructures produced by EOS, CAD-CAM, and Consept Laser (p<0,05). The highest bond strength value was observed in the silica coating group (34.31 ± 3.31 MPa) on the cast substructure whereas the lowest bond strength value was observed in the laser applied group (18.55 ± 2.86 MPa) on the Consept Laser substructure. Results: Within the limitations of the present study, silica coating could be recommended as a surface treatment for the repair of porcelain fractures where the metal surface is exposed. Key words: Co-Cr, porcelain repair, silica coating, laser sintering, CAD/CAM, bond strength