Objective: The aim of this study was to assess effects of different pulse frequencies of Er,Cr:YSGG laser on resin-enamel bonding by two different test methods.
Methods: One-hundred twenty five bovine incisor teeth were used. Enamel surfaces were finished using 320-600-grit SiC abrasive papers. Enamel bond surfaces were prepared with three different methods; SiC, diamond bur (125-150μm), and laser. The Er,Cr:YSGG laser was used on prepared enamel surface area (8x8mm) with three different pulse frequencies (20,35 and 50hz). Resin composite (Valux, 3M ESPE, MN) was bonded to enamel surfaces with a self-etch adhesive (Clearfil SE Bond, Kuraray, Osaka). Resin-enamel bond strength was assessed with two different test methods; tensile bond strength (TBS; n=20) and micro-tensile bond strength (µTBS; n=5). TBS samples were prepared by using cylinder hole (3mm diameter, 5mm height). For µTBS samples, resin-enamel sticks were prepared at size of ~0.8 mm2. TBS and µTBS tests were carried out using universal testing machine (Instron 3382A, Norwood, MA) and micro-tensile tester (Bisco, IL), respectively. The samples prepared with SiC papers and burs used as control groups. One-way ANOVA and LSD test were used at statistical analysis.
Results:
Groups Test methods
| Control (SiC paper)
| Control (Bur)
| Laser 3 W – 20 Hz
| Laser 3 W – 35 Hz
| Laser 3 W – 50 Hz
|
µTBS Test
| 16.06 ±3.57 a
| 16.81±2.84 a
| 14.64±2.11 a
| 19.47±3.71 b
| 24±32±3.19 c
|
TBS Test
| 2.38 ± 1.89 a
| 2.84 ± 1.64 a
| 2.99 ± 3.63 a
| 2.82 ± 2.03 a
| 2.74 ± 2.43 a
|
Different superscripts indicate statistically differences in the same row (p<0.05).
Conclusion: µTBS results showed that increasing pulse frequency when laser deployed for conditioning, may increase immediate bond strength, whereas, TBS results shown that bond strength values were not increased. Therefore, laser frequency as well as test method should be considered in assessment of resin-enamel bond strength.