الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 168 |  |  |
| | | from | 168 | | |
Abstract
air entrapment within the material during mixing.
This study was conducted to evaluate the shear bond strength and flexural strength of composite resin bonded to resin modified glass ionomer cement utilizing different bonding protocols. A total of 320 resin modified glass ionomer specimens were prepared in this study; 160 specimens for shear bond strength and 160 specimens for flexure strength. Each was divided into 16 groups (n=10) according to the three levels of the study; Level 1: type of glass ionomer (Fuji II LC or N100), Level 2: type of bonding protocol. group 1: No adhesive was used (control group), group 2: self-etch adhesive only, group 3: self-etch adhesive and flowable composite, group 4: Flowable composite only). And Level 3: type of composite (Grandio composite resin, Grandio flow composite resin).
For the shear bond strength test, specimens were prepared in a split teflon mold (6mm diameter x 2mm thickness). The surface of the filled mold was pressed with Polyester strip (Stripmat, Polydentia, Mezzovico, Switzerland) applied on the top of the specimen and then light cured for 20 seconds using LED curing unit. Prior to light curing of the adhesive, polyethylene tube (1.7mm diameter×2mm height) was placed over the uncured adhesive and each adhesive was cured for 10 seconds Composite was inserted inside the tube, Polyester strip (Stripmat, Polydentia, Mezzovico, Switzerland) was applied on the top of the tube and gently pressed to extrude the excess material. Light curing tip was placed directly over the polyester strip. The resin composite was cured for 20 seconds according to manufacturer’s instructions.
After curing the composite, the tubes were removed using bard parker blade # 11. Specimens with their composite cylinders were stored in distilled water for 24-hours prior to shear bond strength testing. All the specimens were mounted on acrylic resin blocks with cyano- acrylate glue and then placed in 100 % humidity at room temperature for 24 hours. After 24 hours, shear bond strength was tested using universal testing machine at a crosshead speed of 0.5mm/min (8) the maximum load required to de-bond the two materials was recorded for each specimen. Shear bond strength in Mega Pascal was calculated by dividing the load at failure (Newton) over the bonded surface area (mm2).
For the Flexural strength test, Specimens were prepared as described by Yap and Teoh (122). Specially-constructed split copper mold with a rectangular central opening measuring 12 mm in length, 2mm in width and 2mm in thickness was used to prepare glass ionomer specimens and then cured for 20 seconds. And the grouping was similar to the shear bond strength testing. After 24 hours, each of the prepared specimens was blotted dry and subjected to three-point loading in a universal testing machine (LR5K series, Lloyd Instruments, Ltd, UK), operated using Nexygen software version 4.6. Each specimen was supported by two rods 2mm in diameter). The test was run at a cross head speed of 0.5mm/min (15). The flexural strength was calculated according to the equation (100):
Flexural strength=3FL/2BH2
where F is the maximum load in newton (N), L is the distance between supports in mm; B and H are the specimen width and height respectively in mm8. Values were expressed in Mega Pascal (MPa).
Results of the shear bond strength showed a significant effect for the type of glass ionomer. In groups of control/grandio, flowable/ grandio, control/ grandio flow and flowable /grandio flow, N100 showed statistically significant higher shear bond strength than Fuji II LC (p=0.0001,p=0.005, p=0.05,p=0.0001 respectively). (p=0.0001, p=0.005, p=0.0001). In groups of Fuji II LC/ adhesive, Fuji II LC/ adhesive+flowable and N100/ adhesive+flowable, the grandio composite resin showed statistically significant higher shear bond strength than Grandio flow (p=0.004,p=0.001,p=0.012 respectively). In groups Fuji II LC/ Grandio, Fuji II LC/ Grandio Flow, adhesive and adhesive+ flowable groups showed statistically significant higher shear bond strength than the control and flowable groups
Results of the flexural strength showed that in groups Control/ Grandio, Control/ Grandio Flow, adhesive/Grandio, adhesive/Grandio Flow, Flowable/ Grandio Flow and adhesive+ Flowable /Grandio Flow, Fuji II LC showed statistically significant higher flexural strength than N100 (p=0.0001 for all these groups). In groups of Fuji II LC/ adhesive, Fuji II LC/ flowable N100/ adhesive, N100/flowable and N100/ adhesive+flowable, the grandio composite resin showed statistically significant higher flexural strength than Grandio flow(p=0.009,p=0.024,p=0.017, p=0.0001, p=0.0001 respectively). In groups Fuji II LC/ Grandio, adhesive group showed the highest flexural strength which is significant with control group and not significant with flowable and adhesive+ flowable groups. In Fuji II LC/ Grandio Flow, adhesive and adhesive+ flowable groups showed statistically significant higher flexural strength than the control and flowable groups