Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2016-04-05, 13:01:42 | version 1.38.0
research | 13 1 2016 laser Fig. 1: Mean and standard deviation of the Shear Bond Strength (MPa) in the three groups. clear,butitisknownthatlaserirradiationcandevelop microstructural alterations and micro rupture of col- lagen fibres.9 The reported bond strengths of com- posite resin to dentine substrate prepared by erbium lasers have often been confusing and contradictory.10 TheEr,Cr:YSGGlaserhasawavelengthof2.79 μm. The ablation threshold in human dentin is 2.69 to 3.66 J/cm2 .11 The laser frequency is the number of laser pulses per second.12 Theoretically, an increase of the laser frequency would result in a smoother surface, which could reduce the gaps between the composite and the dental surface. The main objective of this study was to evaluate the bond strength of self-adhesive flowable com- posite Vertise™ Flow in dentin surfaces prepared with Er,Cr:YSGG laser with two different settings. The null hypotheses to test were: (a) the micro- shear bond strength of the restorations with Vertise™ Flow self-adhesive flowable composite is the same, in dentin surfaces prepared with bur and Er,Cr:YSGG laser; (b) micro-shear bond strength of the restorations with Vertise™ Flow self-adhesive flowable composite is the same, in dentin surfaces prepared with Er,Cr:YSGG laser with the settings 4.5 W, 50 Hz, 50 μs, 70 % air, 90 % water and with the settings 4.5 W, 75 Hz, 50 μs, 70 % air, 90 % water. Materials and methods The sample consisted of 15 non carious molars extracted by periodontal or orthodontic reasons. After extraction, the teeth were cleaned and stored in 0.5 % chloramine T at a temperature of about 4 °C to carry out the disinfection and preventing bacte- rial growth for no longer than three months until used in the experiment. Afterwards, the teeth were numbered by a person assigned, and distributed to the three groups (n=5) by another person assigned. To obtain the samples for the electron micros- copy, two from each group, the coronal occlusal third of the teeth and the roots were removed by bisecting the tooth transversely with a low speed diamond saw and copious supply of water. It re- sulted in approximately 2 mm thick dentin discs. To obtain the samples to the Tensile Bond Strength (TBS) test, three teeth from each group were longi tudinallysectionedintotwopartswheretheproximal enamel was removed by a disk to expose the dentin. Groups The laser samples were submitted to an Er,Cr:YSGG laser (Waterlase iPlus—Biolase Tech- nology Inc., Irvine, CA, USA), with two different settings , with the MZ8 tip, using the beam with an angle of 45° to the surface, with smooth move- ments in the horizontal and vertical, during twelve seconds in the dentin discs, and eight seconds in the teeth’s proximal surface, where the area was smaller than the discs. The dentin samples from the control group were not submitted to any laser treatment: Group 1: Control Group (n=10) Material: Ver- tise™ Flow (Kerr, Orange, CA, USA) (without laser surface treatment). Group 2: Settings 4.5 W, 50 Hz, 50 μs, 70 % air, 90 % water (n=10) (Fig. 7) Material: Vertise™ Flow (Kerr, Orange, CA, USA). Group 3: Settings 4.5 W, 75 Hz, 50 μs, 70 % air, 90 % water (n=10) (Fig. 8) Material: Vertise™ Flow (Kerr, Orange, CA, USA). The Vertise™ Flow self-adhesive flowable com- posite was applied in the dentin surface from each sample, about 3 mm delimited by a tape of poly ester (Mylar) and a silicone mold with 3 mm of diameter and 4 mm of high to the samples to the SBS test, directly to dentin in the discs used in the SEM, and lighted cured for 20 seconds with a LED curing light Bluephase C8 (Ivoclar Vivadent) 800 mW/cm2 . Subsequently, the samples were placed in an in- cubator at 37 °C with 100 % humidity for 24 hours. Next, they were thermocycled 500 times in baths of 5 °C and 55 °C for 20 seconds at each tempera- ture, to simulate the in vivo conditions in the oral cavity. At the end of thermocycling, the samples returned to the incubator for more than 24 hours. Control 10,000 7,500 5,000 2,500 ,000 Group 2 Surface Treatment Mean Shear Bond Strength Error bars: ± 1 SD Group 3 Fig. 1 12016