الفهرس 
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Abstract
In this study we evaluated the SBS of monocrystalline ceramic brackets to feldspathic porcelain disks using three different surface preparations. 30 glazed feldspathic PFMdisks were fabricated and embedded in self cure acrylic resin. The samples were randomly allocated into 3 groups of 10 samples each according to the surface preparation as follows group A: air abrasion with 50 μm aluminum oxide particles + etching with 4% HF + silane + RA plus. group B : air abrasion + silane + RA plus. group C: air abrasion+ RA plus. Following surface preparation, ceramic brackets (Perfect Clear II Sapphire) were bonded to the conditioned surfaces using Transbond XT adhesive and light-cured.
After bonding, all the samples were stored in 37 oC distilled water for 24 hours. Afterwards, the samples were thermocycled for 2500 cycles in water between 5o C and 55o C with a dwell time of 10 seconds between the two baths. Shear bond testing was then performed with a Universal testing machine at a speed of 1 mm/min until bracket debonding. Failure mode and ARI of debonded specimen surfaces was analyzed under a stereomicroscope at 10x magnification.
The mean SBS in group A (SB + HF + Silane + Assure Plus) was 8.86 ± 1.99MPa, with a maximum of 12.44 MPa and a minimum of 5.65 MPa. Furthermore, In group B (SB + silane + Assure Plus), the mean was 10.32 ± 4.39 MPa with a maximum of 16.18 MPa and a minimum 6.25 MPa. On the other hand, group C (SB + Assure Plus) showed a mean bond strength of 1.84 ± 0.74MPa with a maximum of 3.02 MPa and a minimum of 0.93 MPa. One-way ANOVA showed statistically significant difference in the SBS between the groups (F=37.025, P<0.0001). Groups A and B had no statistically significant difference in SBS (P =0.364). On the contrary, group C showed statistically significantly lower SBS when compared to the other groups (P= <0.0001).
Groups A and B showed failure mode that was predominantly AB with one sample in group A showing cohesive porcelain failure, most the samples had ARI score3. Meanwhile, group C showed failure that was mostly APwith the majority of the samples shoeing ARI score 0. Monte Carlo modification of Chi Square test showed a statistically significant difference between the groups (X2=16.696, P=0.001). When group A and B were compared to group C there was a statistically significant difference in the failure mode and ARI score (P=0.027 and P=0.009 respectively).