الفهرس 
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Abstract
This study was carried out to investigate the compressive strength and shear bond strength of TCS with resin composite and GIC at different intervals of thermocycling ( after 0 cycles, 500 cycles and 1000 cycles).
For compressive strength test; Ninety (90) Cylindrical specimens with dimensions 6mm height and 3mm diameter were prepared (according to ISO9917-1; 2003) Teflon molds were used to fabricate these specimens. They were divided into three major groups on the basis of material type.
TCS, RMGIC were mixed and packed according to the manufacturer’s instructions; also composite resin were packed and cured according to the manufacturer’s instructions. The specimens were stored in distilled water at 37 oC for 24 hours before testing Group1:(n=30) cylindrical specimens of TCS only were fabricated, after setting they were divided into 3 subgroups; each ( n= 10) G- C1: samples were subjected directly to compressive loading using universal testing machine at crosshead speed of 1mm/min (ISO9917-1:2007), G - C2: samples were subjected to thermocycling (500 cycles) before application of compressive loading and the third subgroup G – C3: samples were subjected to thermocycling (1000 cycles) before application of compressive loading.
group 2 (n= 30) cylindrical assembly of TCS bonded to resin composite were fabricated, composed of 2mm height TCS and 4 mm resin composite, after setting they were divided into 3 subgroups (n= 10), G – C4: samples were subjected directly to compressive strength test, G – C5: samples were subjected to thermocycling (500 cycles) before application of compressive loading, G – C6: samples were subjected to thermocycling (1000 cycles) before application of compressive loading.
group 3: (n= 30) cylindrical assembly of TCS bonded to glass ionomer cement were fabricated, composed of 2mm height TCS and 4 mm GIC, after setting samples were divided into 3 subgroups (n= 10), G-C7: samples were subjected directly to compressive strength test, G-C8: samples were subjected to thermocycling (500 cycles) before, application of compressive loading, G-C9: samples were subjected to thermocycling (1000 cycles) before application of compressive loading.
For shear bond strength test, the TCS was examined for shear bond strength with human dentine, resin composite and GIC.
Premolar teeth were selected; occlusal dentine surface was flattened using diamond discs. Buttons of TCS (3mm width-2mm height) was obtained on the dentine surface by holding Teflon mold 3mm width - 2mm height on the flat surface, stored at 37 oc in 100 % humidity for 15 minutes until setting.
They were divided into three subgroups, each group 10 samples (n=10), subgroup1 (G-S1) were subjected directly to shear bond strength test using universal testing machine, subgroup2 (G-S2) and subgroup 3 (G-S3) were subjected to thermocycling for 500 and 1000 cycles respectively, after that they were subjected to shear bond strength test using universal testing machine using chisel head at interface between TCS and dentine with load 0.5 mm/m.
For shear bond strength with restorative materials ( RC and GIC) Teflon molds 2 mm high and 5 mm diameter central holes were used the holes were fully filled with TCS, samples were stored at 37 oc and 100 % humidity for 15 minutes until setting. Buttons of resin composite or GIC were fabricated on the surface of TCS, with dimensions of 2mm height, 3mm width.
GIC was mixed and packed according to the manufacturer’s instructions; also resin composite was packed and cured according to the manufacturer’s instructions, the specimens were stored in distilled water at 37 oC for 24 hours before testing.
Thirty ( 30) assembles of RC and TCS, which further divided into 3sub groups (n = 10),G-S4: samples were subjected directly to shear bond strength test, group 2(G-S5) and group 3 (G-S6) were subjected to thermocycling for 500 and 1000 cycles respectively then subjected to shear bond strength test using universal testing machine. Another 30 assembles of GIC cement and TCS, which further divided into 3sub groups (n=10), (G-S7) samples were subjected directly to shear bond strength test, subgroup 2(G-S8 ) and subgroup 3 (G-S9) were subjected to thermocycling for 500 and 1000 cycles respectively , after that subjected to shear bond strength test using universal testing machine.