الفهرس 
Review of LiteratureOnly 14 pages are availabe for public view
 |  | from | 129 |  |  |
| | | from | 129 | | |
Abstract
All ceramic restorations have become more popular as a result of increase patients demands for esthetic restorations for more pleasant appearance. Recent advances in optical and mechanical properties, techniques of fabrication of all ceramic material in addition to new adhesive systems aid in increasing the use of ceramic materials. All ceramic restorations are frequently used not only for anterior teeth, but also for posterior teeth. Using all ceramic restorations for posterior teeth requires high mechanical properties for longevity under functional loading. Therefore, production of ceramic material made from lithium disilicate which has high flexural strength that can be used as an alternative for metal ceramic restorations. Lithium disilicate is commonly used to produce monolithic restorations through pressing or milling through computer-aided design/computer-aided manufacturing (CAD/CAM).
This study was performed to evaluate the effect of Er,Cr:YSGG on the flexural strength of lithium disilicate using two different surface treatments hydrofluoric acid etching and Laser irradiation.
The most common technique for removal of all ceramic restorations is cutting through the restorations which are a time consuming process due to high bond strength between the tooth structure and the restoration. Also, the difficulty in differentiation between the bonded restoration and the tooth structure during cutting will be difficult because the restoration, resin cement and tooth will almost have the same color.
Therefore, dentists should stop cutting for evaluation continuously in order to not unnecessarily cut in a sound tooth structure. This will prolong the duration of cutting to prevent damage of the underlying tooth structure and this prolonged time may cause discomfort for the patients.
Conventional cutting leads to destruction of the restoration into pieces and further re-bonding will be impossible. This will results in remaking a new resin bonded restoration which will carry additional time, effort and cost. In addition to patient dissatisfaction.
Little research has been done for an alternative technique for removal of all ceramic restorations to protect the remaining tooth structure, avoid re-manufacturing of the restoration and achieve patient satisfaction.
Forty specimens were prepared into discs of 10mm diameter divided into 2 groups according to thickness (1mm – 0.5mm) . Each group was divided into four subgroups (Control- Laser De-bonding only- Laser De-bonding & hydrofluoric acid etching- laser De-bonding & Laser etching). All groups were tested for biaxial flexural strength using universal testing machine on three ball test.
The results revealed that there were lower values of mean biaxial flexural strengths of the two thicknesses compared to the control group after different surface treatments. The control group showed the highest mean biaxial flexural strength. There was no difference between Laser de-bonding only and Laser de-bonding followed by Laser surface treatment groups; both showed lower mean values than the control group. Laser de-bonding followed by hydrofluoric acid surface treatment group showed the lowest mean biaxial flexural strength.