الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 80 |  |  |
| | | from | 80 | | |
Abstract
This in vitro study was conducted to evaluate the bond strength of ceramic brackets bonded to glazed lithium disilcate discs using three different bonding protocols. 45 glazed lithium disilicate discs were fabricated and embedded in self-cure acrylic resin. The specimens were then randomly allocated into 3 groups of 15 samples according to bonding protocol. group A: Air Abrasion with 50 μm aluminum oxide particles + Assure Plus. group B: Air Abrasion with 50 μm aluminum oxide particles + Silane + Assure Plus. group C: Sandblasting with 50 μm aluminum oxide particles + hydrofluoric acid etching + silane + Transbond XT primer.Ceramic Brackets (Perfect Clear II Sapphire) were bonded to lithium disilicate surfaces similarly in all 3 groups using Transbond XT adhesive and light-cured.
After the bonding procedure all specimens were stored at 37o C in distilled water for 24 h. Specimens were then thermocycled for 500 cycles at 5° - 55°C with 30 s dwell time. Shear bond testing was then performed with a Universal testing machine at a speed of 1.00 mm/min and cell load of 500 N, until bracket debonding. Failure mode and ARI of debonded specimen surfaces was analyzed under a stereomicroscope at 18x magnification.
The mean SBS in group A (SB + Assure Plus) was 10.35 ± 1.35 MPa, with a maximun of 13.5 MPa and a minimum of 8.42 MPa. In group B (SB + silane + Assure Plus), the mean SBS was 11.63 ± 1.79 MPa, group C (SB + HF + silane + Transbond XT) showed a mean SBS of 11.49 ± 2.46 MPa, with a maximun of 16.07 MPa and a minimum of 8.48 MPa. One-way ANOVA showed no statistically significant difference (P=0.112, P< 0.0001) among the study groups with regards to SBS.
In group A failure mode was predominantly adhesive failure at the bracket-adhesive interface and complex cohesive-adhesive failures, whereas in group B failure mode was predominantly presented by failure at bracket-adhesive interface, and group C mainly adhesive failure mode at the adhesive-bracket interface.Monte Carlo modification of Chi Square test showed a statistically significant difference between the groups (P< 0.0001).