ABSTRACT
Statement of Problem: Laser irradiation makes structural and chemical changes on the dental hard tissues. These changes alter the level of solubility and permeability of dentin
Purpose: The aim of this study was to compare the microhardness and the structural changes in the dentin cavity floor prepared with Er: YAG laser and bur
Material and Methods: In this experimental study, fifteen intact human molars were selected. Two square cavities were prepared on the buccal and lingual surfaces of each tooth. One side was randomly prepared by Er:YAG laser and the other side by bur
The specimens were divided into two halves. Consequently, there were 30 samples in every group. One half was assigned for the Vickers's hardness test and the other one, for determination of Ca and P percentage and atomic elements analysis. The data were analyzed by Paired T-tests through SPSS16 [ alpha
Results: The means and the standard deviation of the microhardness were 69.77+/-25.62 and 51.33+/-9.31 Kg/mm2 in the laser and bur groups, respectively. Statistical analysis showed significant differences between the two groups [p=0.017]. Weight percentage of calcium in the laser cavity [65.5] was less than the bur cavities [68.21] and the difference was significant [p= 0.037]
Conclusion: The hardness of dentin in laser group was higher than the bur group because of the higher mineral content of the dentin. The hardness and the mineral content of dentin are important factors in the bonding effectiveness of the dental materials so with laser cavity preparation, good mineral substrate are available for a better bonding
ABSTRACT
Two important disadvantages of amalgam restorations are lack of adhesion to tooth structure and marginal leakage. In recent studies, the use of dentin adhesive on cavity walls before the insertion of amalgam proved to be the best method to reduce microleakage and increase chemical adhesion. Fourty premolar and molar teeth were collected and divided into two groups. The class V cavities were made at the buccal surfaces of the teeth [Depth 1. 5 mm, Length 3 mm and Width 2 mm]. All the angles of cavo-surfaces were Buttjoint. The teeth were then washed, cleaned, dried and randomly divided into 2 groups, the first group was coated with 2 layers of varnish. The second group was coated with adhesive resin system and then restored with amalgam. The teeth were kept in distilled water for 24 hours. The prepared surfaces were then polished and thermocycling was performed. All prepared surfaces were coated with nail varnish up to 0.5 mm around the restorative material. Further more each group was randomly divided into 2 subgroups, one group was kept in distilled water for 24 hours and the other group for 5 months. All groups were afterwards kept in 0.5% basic fuchsin solution for 24 hours. The teeth were then mounted in Acrylic resin, were cut into two halves from the centre of preparation with a diamond saw and checked by a stereomicroscope for determining the microleakage rate. Comparison between two groups showed degree of dye penetration into margins of restorations with Rely X ARC was lower than that of varnish. However no significant differences were observed among the groups except for occlusal margins after 24 hours and 5 months