The Effect Of Er, Cr: YSGG Laser On The Shear Bond Strength And Seal Capability Between Tooth Surface And Fillings

ObjectiveTo evaluate the effect of Er, Cr: YSGG laser on the shear bond strength and seal capability between teeth surface and fillings and the possibility that laser can take the place of bur preparation in combination with etching.Methods20 recently extracted human molars were selected. I prepared enamel surfaces on buccal, lingual and mesial by traditional bur. The surfaces were treated by following methods ; A: control group, the surfaces were etched by total - etch system for 30 seconds. B; enamel surfaces were cut off with Er, Cr: YSGG laser. C: enamel surfaces were cut off with Er,Cr; YSGG laser and etched by total - etch system for 30 seconds. I prepared dental surfaces the same as enamel and the surfaces were treated by following methods : A: control group, the surfaces were etched by total - etch system for 15 seconds. B: dentalsurfaces were cut off with Er, Cr; YSGG laser. C: dental surfaces were cut off with Er,Cr: YSGG laser and etched by total - etch system for 15 seconds. A transparent plastic tube was filled with Tetric Ceram composite and placed on the treated tooth surfaces. After the tube molds were carefully removed, the roots of teeth were buried in epoxy resin. Then all the samples were stored in artificial saliva for 24 hours. Shear bond strength was measured with 1KN hydropuls Test System. Enamel and dental slices which were treated the same as described for the bond strength test were made into samples of SEM and topographical characteristics were examined with scanning electron mi-croscftpe. 18 human premolars devoid of caries and restorations were selected and divided 36 buccal, lingual surfaces into three groups. They were treated as following A-control group, the rfiavi ty V were pre-pared with bur and etched by total - etch system for 20 seconds. B: the cavity V were prepared with Er,Cr:YSGG laser. C: the cavity V were prepared with Er,Cr:YSGG laser and etched by total -etch system for 20 seconds. After Tetric Ceram composite were filled in the treated cavities, specimens were subjected to thermal cycling . The teeth were coated with two layers of nail varnish. Finally specimens were placed in 0. 5% basic fuchsin solution. The dye penetration of occlusal and gingival margins was examined with stereomicroscope.ResultsMean bond strength of etched bur - cut enamel , laser - cut enamel and etched laser - cut were 13. 04 2. 97MPa, 11. 42 3. 35Mpa and 10. 51 2. 31MPa.. Mean bond strength of etched bur -cut dental, laser - cut dental and etched laser - cut dental were 7.00 3.43Mpa, 7.13 2.68MPa, and 5.76 0.90MPa. The data were analyzed with a analysis of variance (ANOVA) , there were no statistically difference in enamel and dentine. ( P > 0. 05 ). SEM revealed: unconditioned enamel: there was a smear layer on the surface, with no evidence of prism structure. Laser - cut enamel; the surfaces were not flat and devoid of a smear layer, with some evidence of prism structure , like fish scale. Etched bur - cut enamel : there were no smear layer on the surface, with some evidence of prism structure. Etched laser - cut enamel: the surfaces were not flat and devoid of a smear layer, with some evidence of prism structure, like fish scale, the features were similar with laser - cut enamel. Unconditioned dentine: there was a smear layer on the surface, with no evidence of tubules. Laser - cut dentine: the surfaces were not flat and devoid of a smear layer, with open tubules. Etched bur-cut dentine; the surfaces were clean and absent of smear layer, with open tubules and diameter of tubules enlarging. Etched laser - cut dentine: the surfaces were not flat and devoid of a smear layer, with open tubules, the features were similar with laser - cut dentine. The data of dye penetration were analyzed with a analysis of Wilcox Mann - Whitney test, it was believed as following: On the occlusal walls, there were no significant differences in microleakage among bur - prepared group, laser - prepared group, laser - prepared in combination with etching ( P > 0. 05 ). On the gi...