The comparison of the micro-tensile bond strengths and dentin surface roughness of class v cavities prepared by conventional methods or different parameters of Er:YAG laser and restored with composite material

The aim of this in vitro study is to compare the micro-tensile bond strengths of Class V cavities prepared by conventional methods or different parameters of Er:YAG laser and restored with composite material after applied 2000 times of thermocyclus. Dentin surface roughness performed by the same parameters and the conventional method was also compared.113 human permanent premolars with apexifications completed with no caries and restorations and extracted for orthodontic purposes were used.45 premolars were selected randomly and sectioned in a mesio-distal direction to obtain buccal and lingual/palatinal surfaces. Buccal or lingual/palatinal surfaces were ground with 100, 600 and 1200 grit silicon carbid paper under water respectively, to reach 2 mm under the enamel. All teeth were randomly divided into 9 groups consisted of 10 samples each and 5 surface roughness values of every sample were measured before conventional method and laser irradiation.After embedding all samples in acrylic resin blocks, different Er:YAG parameters and conventional method were applied to dentin surfaces and 5 surface roughness values were then determined again of every sample.68 remaining permanent premolars were sectioned in a mesio-distal direction to obtain buccal and lingual/palatinal surfaces. All teeth were randomly divided into 9 groups consisted of 15 samples each.Class V cavities were prepared by Er:YAG laser and convemtional method 1 mm above the enamel-cementum junction, cavity dimensions were 4 mm width and 4 mm heigth. The depth of the cavities were 2 mm.A bonding agent (Clearfil SE Bond, Kuraray Dental) and a composite material (Filtek Z250, 3M ESPE) were applied to the prepared cavities according to the manufacturer?s instructions.The specimens were thermocycled for 2000 times between 5º C and 55º C. The teeth were cutted mesio-distally first, then bucco-lingually perpendicularly to the bonded areas. 1mm x 1mm resin-dentin sticks were obtained.Statistical analysis was performed by using the `One Way ANOVA? and `Tukey HSD? tests. The comparison of parameters within groups was analysed with paired t test.In conclusion, statistically, laser irradiated dentin surfaces showed significantly more surface roughness values. At the cavities prepared with laser, there was no statistical difference between lower pulse durations with higher power and higher pulse durations with lower power. At laser groups, as the surface roughness increased, microtensile bond strength were decreased. Control group showed the highest bond strength.Keywords: Er:YAG Laser, Class V Cavities, Thermocyclus, Surface Roughness, Microtensile Bond Strength