Effect of green tea and sodium ascorbate on the shear bond strength of orthodontic brackets bonded on bleached...

The primary objective was to assess and compare the shear bond strength of orthodontic brackets bonded on bleached enamel with and without using an anti-oxidizing agent.The secondary objective was to compare the shear bond strength of brackets between the groups with anti-oxidant application along with immediate bonding and that of delayed bonding without any anti-oxidant treatment, on bleached teeth.

75 premolars were collected and thereafter randomly distributed into the 5 groups. Group 1 to 4 had undergone bleaching with 10% carbamide peroxide and group 5 was control. Group 1 was bonded immediately after bleaching while bonding was delayed in group 4 for a period of 1 week. Groups 2 and 3 received the anti-oxidant treatment with 10% sodium ascorbate gel and 10% green tea gel respectively. Hounsfield universal testing machine was used for testing the shear bond strength.

For group 1, the shear bond strength was significantly lower (mean 4.9 MPa) than group 5 (mean 12.5 MPa). The significant differences were observed on comparing the shear bond strength of antioxidant-treated and delayed bonding groups with control (p < 0.05). Mean shear bond strength in groups 2, 3 and 4 were 7.5 MPa, 9.6 MPa and 5.8 MPa respectively.

The bond strength of brackets reduces immediately after the bleaching procedure. The bond strength can be reversed either by delaying the bonding for a period of 1 week or by using the anti-oxidizing agents but it is not up to the level of unbleached enamel.