الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
With advances in technology, other options besides the traditional cavity preparation with carbide burs and diamond points have emerged; among them are the laser and sonoabrasive system. The purpose of this in vitro study was to evaluate and compare the effect of different dentin preparation methods on surface roughness of dentin and shear bond strength of composite using self-etching adhesive system.
A total of 60 sound extracted permanent molar teeth were used in this study. The root portion of all teeth was cut off, and the crown part was inserted into self-curing acrylic resin using a custom made mold of 14mm diameter and 20 mm Length, exposing the buccal surface upwards. The 60 specimens were randomly divided according to tooth surface preparations into five groups of 12 specimens each; group I: the dentin surfaces were prepared with carbide bur, group II: the dentin surfaces were prepared with diamond stone, group III: the dentin surfaces were prepared with sono-abrasive tips, group IV: the specimens were irradiated with an Er: YAG laser (λ = 2940 nm) equipped with a contact hand-piece H14 and group V: the specimens were irradiated with an Er: YAG laser (λ = 2940 nm) equipped with a non-contact hand-piece HO2. The surface roughness of all samples was characterized using surface profilometer (Ra) and scanning electron microscope for visualizing the surface morphology of the roughened surfaces
The prepared dentine surfaces of all samples were treated with Adper Scotchbond SE one step self-etch universal adhesive and then restored with micro-hybrid resin composite. After water storage, thermocycling (500 cycles, 5ºC/55ºC) with a 15 second dwell time and a transfer time of 10 seconds corresponding to 6 months of clinical service, then all the
specimens were subjected to shear force until failure. Modes of failure were assessed using a stereomicroscope and the results in various groups were compared and statistically analyzed.
The results regarding surface roughness test were as follow: group I (Carbide bur 0.40 ± 0.04 μm), group II (Diamond bur 0.61 ± 0.04 μm), group III (Sono-abrasion 0.59 ± 0.05 μm), group IV (Contact Er: YAG laser 2.35 ± 0.16 μm) and group V (Non-contact Er: YAG laser 2.55 ± 0.08 μm).
The analysis of dentin SEM micrograph revealed that, in general laser irradiated dentin surfaces (group IV and group V) showed lack of smear layer and a rough, irregular, scaly structure with opened dentinal tubules, different from the ones prepared by rotary instruments and sono-abrasive system that showed presence of smear layer that partially or totally occluded the dentinal tubules.
The results of shear bond strength test were as follow: group I (Carbide bur 10.0 ± 2.63 MPa), group II (Diamond bur 11.58 ± 7.05 MPa), group III (Sono-abrasion10.19± 4.06 MPa), group IV (Contact Er: YAG laser 6.64 ± 5.24 MPa) and group V (Non-contact Er: YAG laser 6.29 ± 2.08 MPa). Kruskal Wallis test demonstrated significant differences between groups prepared with Er: YAG laser with both application modes (Contact and Non-contact) (group IV and V) and other groups. Stereomicroscope revealed that mixed and adhesive failure were the most dominant mode of failure.