الفهرس 
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Abstract
Objective : To evaluate bond strength of orthodontic brackets bonded to porcelain surface etched with Er laser versus hydrofluoric acid using different bonding systems. Material and methods : 120 feldspar porcelain disks. It divided equally into glazed (group I) and deglazed (group II). Each group was divided into two subgroups (A, B). In subgroup (A) etched with hydrofluoric acid. In subgroup (B) etched with Er, Cr: YSGG laser. Every subgroup was divided into three divisions (1, 2, 3) Silane+ Transbond XT primer, Monobond plus and Single bond universal were used respectively.Metal brackets were bonded to the porcelain surfaces using Transbond XT adhesive. CSBS, surface roughness and remnant index (ARI) were assessed. The data were statistically analyzed using ANOVA, post hoc LSD, t and Chi square tests. Results : Regarding to surface roughness values (nm) deglazed porcelain disks etched with HFA were significantly higher than the other 3 groups (p<.05). Glazed Er laser etched disks has the lowest surface roughness value. No significant differences in the surface roughness between glazed HFA and deglazed Er laser etched one (p>.05). Regarding CSBS the highest values were with using of Monobond plus or Single bond universal on glazed or deglazed Er laser porcelain, while the Silane+ Transbond XT primer provided the lowest CSBS value with glazed or deglazed HFA etched disks. Also using of Er laser etching on glazed or deglazed porcelain disks significantly increase CSBS values with using of the 3 bonding materials (p<.05). There were significant difference between Monobond plus or Single bond universal with Silane+ Transbond XT primer on glazed or deglazed porcelain disks etched either with Er laser or HFA (p<.05). No significant difference in CSBS value between Monobond plus and Single bond universal (p>.05). Conclusion : Surface roughness were more pronounced with utilization of HFA than Er laser. The 3 studied bonding materials provide significantly higher CSBS values with Er laser than in HFA.