Comparison of the micro-tensile bond strengths of different bonding systems and microleakages of class v cavities prepared by conventional methods or lasers and restored with different composite materials and evaluation of the cavity-restoration surfaces by sem

The aim of this in vitro study is to compare the micro-tensile bond strengths of different bonding systems and microleakages of Class V cavities prepared by conventional methods or lasers and restored with different composite materials and to evaluate the cavity-restoration surfaces by SEM.96 premolars without caries and restorations extracted for orthodontic purposes were used.32 premolar was selected randomly and divided into 2 groups. Class V cavities were prepared in each teeth with Er:YAG laser on the buccal surfaces and the lingual/palatal surfaces were prepared with conventional method in first group. In the second group, buccal surfaces were prepared with conventional method and lingual/palatinal surfaces were prepared with Er:YAG laser. As a result, there were 32 cavities prepared with Er:YAG laser and 32 cavities prepared with conventional method. Cavity dimensions were 3 mm width and 3 mm heigth. The depth of the cavities were 2 mm.All 32 teeth in each group were divided into four subgroups consisted 8 cavities (4 buccal + 4 lingual) in these subgroups.4 different composite materials (Clearfil Majesty Posterior, Silorane, Amaris ve Filtek Z250) were applied on both subgroups with its adhesive system according to the manufacturer?s instructions.The specimens were stored in distilled water at 37 º C for 24 hours. Then they were termocycled for 1000 cycles between 5º C and 55 º C. After being cycled, all specimen were immersed in a %0.5 basic fuchsin for 24 hours.All teeth were sectioned in a mesio-distal direction to seperate the cavities prepared with different tecniques. Eventually, 8 new subgroups prepared with same techniques and materials were obtained.Then the cavities were sectioned in a bucco-lingual direction thruogh the centre of both cavities and were examined with steromicroscope.Class V cavities were prepared to the rest of the 64 teeth. 32 of those cavities will be prepared by Er:YAG laser and the other 32 were prepared by conventional methods on buccal surface. All teeth were grouped in 4 subgroups which consist of 8 cavities in each group and 4 different composite materials (Clearfil Majesty Posterior, Silorane, Amaris ve Filtek Z250) were applied with its adhesive system according to the manufacturer?s instructions.One tooth in each group was selected for SEM evaluation.The specimens were stored in distilled water at 37 º C for 24 hours. Then they were termocycled for 1000 cycles between 5º C and 55 º C. The micro-tensile test was performed in a universal testing machine.Bond strength was analysed statistically by `One Way ANOVA? and post hoc `Tukey? tests. The microleakage result was analysed with ki-square tests.In conclusion, statistically, the cavities prepared with laser and restored with Silorane or Amaris showed significantly lower bond strengths than the cavities prepared with laser and restored with Z250; the cavities prepared with conventional methods and restored with Silorane or Amaris has also showed significantly lower bond strengths than the cavities prepared with conventional methods and restored with Z250 as well as Clearfil Majesty Posterior.In the cavities that were prepared with laser or conventional methods it was observed that there were more leakage in the cavities that were restored with Silorane, on the other hand there were less leakage in the cavities that were restored with Z250 and Clearfil Majesty Posterior than it had been expected. While, at the cavities prepared with laser, there was no statistical difference between the occlusal and gingival margine, at the cavities prepared with conventional methods, gingival margins showed more leakage which was statistically significant.In SEM evaluation, it was observed that while the cavities prepared with laser showed thicker adhesive layer; cavities prepared with conventioanl methods showed thin adhesive layer except the groups restored with Clerafil Majesty Posterior or Z250.SEM examination indicated that while the cavities prepared with laser has frequent and long resin tags, the cavities prepared with conventional methods has sparse and short resin tags except the groups restored with Clerafil Majesty Posterior.Key words: Laser, Class V cavities, Microleakage, Microtensile Bond Strengths