الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 130 |  |  |
| | | from | 130 | | |
Abstract
Summary
New technologies have been introduced as an alternative to the conventional mechanical removal technique of carious tissue, in which dental laser is one of them and have been widely tested, used and approved by literatures and studies.
A number of high-intensity lasers are introduced into dentistry and able to remove carious tissue with minimal intervention and lot of advantages such as lower noise and vibration, lower local anesthetic requirement, lower tissue contact, and lower trauma. These advantages can make the treatment more comfortable for children by facilitating the control of child’s behavior and attitude and increasing the satisfaction and cooperation.
One of those introduced lasers are Er:YAG laser and when used for cavity preparation it results in a surface with significantly different properties to that achieved by conventional mechanical methods.
That’s why many studies had been lately focusing on the impact of Er:YAG laser and whether the surface alterations created by it will result in more or less microleakage and bond strength compared to that achieved by conventional procedures.
The aim of this study was to compare the microleakage and shear bond strength of RMGI restorations in samples prepared by Er:YAG laser and conventional method in primary teeth. Also, to was to detect any possible correlation between the resultant scores of microleakage and shear bond strength.
In microleakage test, a total of 30 primary teeth were selected and divided into 2 groups; each group had 15 primary teeth. In the 1st group, class V cavities were prepared by diamond bur which had iso number of 109/010 with a cooling Spray and in the 2nd group, class V cavities were prepared by Er:YAG Laser with the following parameters; power 4 W, pulse repetition rate (frequency) 50 Hz, a non-contact position with 5-12 mm distance with a water Spray.
The cavity dimensions in all teeth were 3 mm mesio-distally and 2 mm occluso-gingivally with 1 mm depth.
After cavity preparation, cavities were rinsed with water and then received an application of Polyacrylic Acid as dentin conditioner for 20 seconds then rinsed again with water. Afterwards Samples were restored with RMGI restorations and light cured for 40 seconds and then were protected by using light cure adhesive coat and also light cured for 40 seconds.
Samples were kept in distilled water for 24 Hours and then thermocycled for 1000 cycles between 5°C and 55°C with 30 seconds of immersion in each bath, and 5 seconds of transfer time between baths. The specimens were placed afterwards in 2% methylene blue dye for 24h and then were sectioned into 2 sections in Bucco-Lingual plane direction through the center of the restoration under water spray coolant using Sectioning saw device.
The degree of microleakage indicated by dye penetration along cavity walls was examined and scored by using Stereomicroscope magnification at x30 for picture capturing and the extent of microleakage using dye penetration was determined.
In shear bond strength test, another 30 primary teeth were also selected and divided also into 2 groups and each group had 15 primary teeth; group 1 where teeth were prepared until a flat dentin surface was exposed by Diamond bur with cooling spray and group 2 in which teeth were prepared until a flat dentin surface was exposed by Er:YAG laser with the same parameters used in the previous test.
After exposing a flat dentin surface, Polyacrylic Acid as dentin conditioner was applied for 20 seconds then rinsed with water. The RMGI restorations were clamped on the prepared surface by using polyethylene tube with a diameter of 2.5 mm as a mold and then light cured for 40 seconds.
Afterwards the polyethylene tube was removed, the restorations were also protected by using light cure adhesive coat, light cured for 40 seconds, kept in distilled water for 24 Hours and then thermocycled for the same number of cycles as done in the previous test.
After performing microleakage comparison test with Mann-Whitney U test and analyzing the data, no significant difference between both groups was found (p=0.555).
For results of shear bond strength test, the T-test results showed that there was also no significant difference between the both groups (p=0.071).
Regarding to whether there is any correlation between micro-leakage scores and shear bond strength scores, no significant correlation between scores of both tests was detected or found (p=0.856).
Within the limitation of the present study it was concluded that there are no significant differences in results of any group, in microleakage test or shear bond strength test, when Resin Modified Glass Ionomer restoration used to restore samples prepared with ER:YAG laser or conventional bur. Er:YAG laser could be therefore used as an alternative technique for teeth preparation in restorative dentistry for primary teeth due to its advantages and for having an excellent acceptance among young children, giving that the required and needed knowledge of its use are present among the operating dentist and dental staff
Based on the findings of this study we can recommend that there should be more implementation of hard-tissue laser usage in dental praxis since it has an overall more appeal and excellent acceptance among young children with lesser perception of the pain triggers, given that, the dental staff and team, whom work in a laser-operated clinic, should be equipped with both knowledge and training in the laser field. Also more researches and studies, preferably clinical split mouth study design, with a larger sample size should be performed with different used parameters in Er:YAG laser to compare the effect of the heat generated with different parameters and the correspondingly created bond-strength between the tooth surface and RMGI on the same patient under the same occlusal stresses