Shear Bond Strength and Mode of Failure of Ceramic Brackets to Glazed Feldspathic Porcelain Using Different Bonding Protocols (In Vitro Study)

Abstract

OBJECTIVE:To evaluate the shear bond strength (SBS) of ceramic brackets bonded to feldspathic porcelain using different bonding protocols. MATERIAL AND METHODS: 30 porcelain fused to metal (PFM) disks were fabricated and randomly divided into three equal groups of 10 each. Each group had a different surface treatment as follows:-Group A: air abrasion, etching with hydrofluoric acid (HF), silane and Reliance Assure Plus (RA plus). Group B: air abrasion, silane and RA Plus (manufacturer's recommendation). Group C: air abrasion and RA Plus. Ceramic brackets were bonded to PFM discs using light cure-composite resin. Following thermocycling, SBS was measured using a universal testing machine. After bracket debonding, Failure mode was measured under stereomicroscope. RESULTS: Group A and group B showed the highest SBS value with a mean of 8.86 ± 1.99 and 10.32 ± 4.39 MPa respectively with no statistically significant difference among them. However, group C showed statistically significant lower SBS with a mean value of 1.84 ± 0.74 Mpa. Failure modes of groups A and B were predominantly at the adhesive / bracket interface. Meanwhile, group C showed mixed adhesive / porcelain interface and cohesive resin failure. CONCLUSION: Air abrasion and silane resulted in clinically acceptable bond strength among the groups regardless the use of HF. Silane appears to be integral in achieving adequate bond strength. The universal primer used in the current study can not be used as a substitute to silane.