Objectives:
To evaluate the SBS of orthodontic brackets to composite restorative materials using various orthodontic bonding systems.
Methods:
60 metallic orthodontic brackets Elite Opti-Mim (Ortho Organizers) were used. 20 brackets were bonded to tooth-shaped samples of Filtek A 110(3M-ESPE) composite ( Group A ).20 brackets to similar samples with Filtek Z 250(3M-ESPE) composite (Group B) and 20 to human premolars ( Group C) as controls. The brackets were bonded to 10 teeth in each group by composite [ Illuminate -Ortho Organizers] adhesiveX or resin modified glass- ionomer [Fuji Ortho LC –GC International] adhesiveY. Samples were stored in water at 37oC for 24h then tested for SBS using a Hounsfield tensometer. Failure mode was evaluated
microscopically. The results were analysed with Multifactor ANOVA and the Newman-Keuls post hoc test.
Results:
Shear bond strengths
| Samples | Bonding system | Strength (MPa) | SD (MPa) |
| Group A
| X Y | 5.06 10.17 | 1.66 2.19 |
| Group B
| X Y | 5.87 9.16 | 1.99 3.56 |
| Group C | X Y | 5.70 10.38 | 2.65 3.84 |
Failure for B with X was mainly adhesive between bracket and bonding system. Failure for A with X and Y and for B with Y was mainly cohesive. In group C failures of X were cohesive/adhesive and of Y, mainly cohesive.
Conclusion:
RMGIC adhesive gave a higher SBS in both experimental groups and the control group, compared to that with composite (p<0.05). These values are satisfactory for clinical situations. Failure mode tended to be cohesive failures in most cases.