Aim of the work: The aim of this study was to evaluate the effect of antioxidant agents and delayed bonding on the shear bond strength (SBS) of glass ceramic veneers bonded to the bleached enamel.
Materials & Methods: A total number of sixty extracted maxillary central incisors with intact labial enamel were collected and randomly divided to six groups of ten teeth each. Ten teeth were remain without bleaching and the remaining fifty teeth were bleached using 35% hydrogen peroxide, (SDI Polaoffice tooth whitening system ). Sixty lithium disilicate glass ceramic discs of 4mm diameter and 5mm height were fabricated from IPS e.max Press and divided to six groups of ten discs each. Group I glass ceramic discs bonded to the unbleached enamel surface. Group II glass ceramic discs immediately bonded the bleached enamel after bleaching procedure without antioxidant. Group III glass ceramic discs immediately bonded to the bleached enamel after 10% ascorbic acid antioxidant application to the bleached enamel. Group IV glass ceramic discs immediately bonded to the bleached enamel after 20% ascorbic acid antioxidant application to the bleached enamel. Group V glass ceramic discs immediately bonded to the bleached enamel after 2% green tea antioxidant application to the bleached enamel. Group VI glass ceramic discs bonded to the bleached enamel after 2 weeks waiting period. The tested specimens, were tested for shear bond strength using a universal testing machine at a crosshead speed of 0.5mm/min until failure. The failure load was then recorded and statistically analyzed.
Results: Analysis of the mean SBS between all groups it was found that the highest mean SBS for the control group CG of 30.22 ±0.92 MPa followed by group VI, with a mean of 26.90 ±1.27 MPa and group V with a mean of 26.0 ±1.80 MPa then group III, with a mean of 25.0 ±1.60 MPa and group IV with a mean of18.99±1.69 MPa the lowest mean fracture loads of 13.25± 0.36 MPa was for group II.
Conclusions : Within the limitations of this study, it was concluded that antioxidant agents neutralize the effect of bleaching agents and considered a viable alternative to delayed waiting period.