Objectives: To evaluate the effect of ageing on shear bond strength (SBS) to enamel of orthodontic adhesives.
Methods: One hundred and eighty freshly extracted human molars stored initially in 0.5% Chloramine T, were randomly divided into twelve groups of 15.Brackets were bonded to teeth using: Right-On: (paste-liquid contact adhesive, TP Orthodontics, USA); Concise: (paste-paste, 3M Unitek, USA); Transbond: (light activated paste, 3M Unitek, USA); GC Fuji Ortho: (self-cured resin modified glass ionomer, liquid-powder, GC Japan); Ideal: (light activated compomer paste, GAC International, Inc. Islandia); and Super-Bond: (liquid-powder acrylic resin, Sun Medical Co. Japan) according to the manufacturers¢ instructions
Specimens were stored in distilled water at 37oC for 24 h or 30 days, and SBS for each adhesive was determined using an Instron machine.
Results: The table below shows the values (mean±sd) of SBS after 24 h and 30 days. Super-Bond was significantly the strongest material for both 24 h and 30 d SBS (p<0.05, ANOVA and Tukey test). Concise was significantly stronger than Right-On in 24 h SBS. Right-On SBS increased significantly after ageing for 30 days (p< 0.05, Paired T-Test), whilst Ideal and Super-Bond exhibited a decrease in SBS.
| SBS(MPa) | Concise | Transbond | Right-On | Fuji Ortho | Ideal | Super-Bond |
| 24 h | 8.02±5.76 b | 5.66±1.88 bc | 4.45±1.31 c | 6.79±3.04 bc | 6.33±2.4 bc | 20.64±3.7 a |
| 30 d | 8.84± 3.54 bd | 6.05 ± 2.85 cd | 10.33± 4.98 b | 7.65± 2.84 bd | 5.65±2.74 cd | 19.12±3.67 a |
| Similar superscripts in each row indicate means which are not significantly different.(p>0.05) | ||||||
Conclusions: SBS of Fuji Ortho and Ideal were comparable to those of chemically-cured and light-cured composites. SBS of Super-Bond was higher than that which is required for clinical use. The no mix adhesive was significantly stronger after ageing which suggests that it needs time to cure completely.