[The comparison of shear bond strength of orthodontic brackets to bovine enamel pretreated by different conditions of Nd-YAG laser].
Laser beams can cause the enamel surface roughly which is similar to the effect of the traditional acid-etching technique. We wanted to study the possibility of the application of the laser on enamel etching. In this study we treated the enamel with different energy levels for orthodontic bracket placement and measuring the shear bond strength. 104 bovine teeth were polished by 600 # grit sandpaper, then cut, embedded, set and divided into 13 groups. The control group was not treated. 12 different energy levels (10pps 50, 70, 85, 100mJ; 15pps 83.3mJ; 20pps 50, 87.5, 100, 150mJ; 30pps 50, 86.7, 100mJ) were treated on the enamel. The orthodontic brackets were placed on 8 specimens of each group with orthodontic resin (Ormco). Then, the specimens were put in 37 degrees C water bath for 24 hours. 7 specimens of the control group of brackets fell off after water bath. The shear forces of the other 97 specimens were measured by the Instron at a crosshead speed of 0.5 mm/min. The shear strength of the only one specimen of the control group was 0.1MPa. The results for the range of shear strength of the laser group were 2.66-5.53MPa. The shear strength increased proportionately to the energy density. Because the mean shear strength of the laser group were significantly high, we can refer the practical application in orthodontic clinic. The laser beam only affected the area coated with Chinese ink, so the treated area is controllable. The fracture surface of the laser-etched was smooth.(ABSTRACT TRUNCATED AT 250 WORDS)
Lin
I H
IH
Department of Pediatric Dentistry, School of Dentistry, Kaohsiung Medical College, Taiwan, Republic of China.
Huang
S T
ST
D000818:Animals; D002417:Cattle; D003743:Dental Enamel / Q000528:radiation effects*; D053685:Laser Therapy; D016910:Orthodontic Brackets; D013718:Tensile Strength