الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 74 |  |  |
| | | from | 74 | | |
Abstract
Our study aimed to evaluate the effect of the cavity configuration (c-factor) and the remaining dentin thickness (RDT) on resin bond strength of one-step self-etch universal adhesive using the micro-tensile bond strength test and evaluating the ultra-morphological structure of the resin/dentin interface using SEM.
Thirty non-carious extracted human permanent third molars were used. The occlusal surfaces of the molars were reduced in order to expose a superficial flat dentin surface (group A), cavities 4×3×2mm were prepared below the flat ground superficial dentin surface creating a deep cavity floor (group B), a diamond saw was used to remove the vertical walls of class I to create a deep flat dentin surface (group C). The one-step self-etch universal adhesive was applied to dentin surfaces according to the manufacture instructions. Teflon split mold was used for composite build-ups. After being stored in distilled water at 37°C for 24 hours, the resin-teeth bonded specimens were sectioned in two directions perpendicular to the adhesive/tooth interface using a water-cooled diamond saw to obtain beams (1 mm2). A tensile force was applied to each beam at a crosshead speed of 0.5 mm/minute until failure occurred.
The (μTBS) values were collected and statistically analyzed showing that, the superficial flat dentin (group A) has higher mean of micro-tensile bond strength (26.0 ± 3.9 MPa), then group C (deep flat dentin) (12.5±2.2 MPa), while group B (deep cavity floor) showed lowest micro-tensile bond strength (9.7±1.1 MPa).
There was a statistical significance difference in the relation between the remaining dentin thickness (2.9±0.22mm) and micro-tensile bond strength (26.0±3.9 MPa) in superficial flat dentin (group A) with p value p <0.05, but there was a no statistical significance difference in the relation between the remaining dentin thickness (1.3±0.13 mm) and micro-tensile bond strength (9.7±1.1 MPa) in deep cavity floor (group B), or remaining dentin thickness (1.2±0.16 mm) and micro-tensile bond strength (12.5±2.2 MPa) in deep flat dentin (group C). as the results of this study showed that, there was a direct proportional between the remaining dentin thickness (RDT) and micro-tensile
Summary
56
bond strength, where increasing the remaining dentin thickness (RDT), with a significance difference between group A and group B &C. while no a significance difference between group B&C.
SEM evaluation showed that, (universal bond) was able to penetrate into dentin forming numerous, deep and well-defined resin tags in superficial dentin, but in deep dentin showed less resin tags infiltration with narrow inter-tubular space , leading to thin hybrid layer. The most common fracture mode at superficial flat de