title: Effect of Er:YAG Laser on Shear Bond Strength of Composite to Enamel and Dentin of Primary Teeth.
abstract: OBJECTIVE
  Bond strength of composite resin to enamel and dentin of primary teeth is lower than that to permanent teeth; therefore, it may compromise the adhesive bonding. New methods, such as laser application have been recently introduced for tooth preparation. The purpose of this study was to evaluate the effect of tooth preparation with bur and Er:YAG laser on shear bond strength of composite to enamel and dentin of primary teeth.
  
  
  METHODS
  Seventy-five primary molar teeth were collected and 150 specimens were obtained by mesiodistal sectioning of each tooth. In each of the enamel and dentin groups, the teeth were randomly assigned to 3 subgroups with the following preparations: bur preparation + etching (37% H3PO4), laser preparation + etching, and laser preparation without etching. Single Bond adhesive and Z250 composite were applied to all samples. After thermocycling, the shear bond strength testing was preformed using the Instron Testing Machine. Data were analysed using SPSS-17 and two-way ANOVA.
  
  
  RESULTS
  The bond strength of enamel specimens was significantly higher than that of dentin specimens, except for the laser-non-etched groups. The enamel and dentin laser-non-etched groups had no significant difference in bond strength. In both enamel and dentin groups, bur preparation + etching yielded the highest bond strength, followed by laser preparation + etching, and the laser preparation without etching yielded the lowest bond strength (P < 0.001).
  
  
  CONCLUSIONS
  In both enamel and dentin groups, laser preparation caused lower shear bond strength compared to bur preparation.
authors.affiliation: Associate Professor, Department of Pedodontics, Member of social Determinants of Oral Health Research Center, Faculty of Dentistry, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Bahrololoomi
authors.affiliation: Pedodontist.
authors.forename: Mona
authors.initials: M
authors.lastname: Kabudan
authors.affiliation: Assistant Professor, Department of Periodontics, Faculty of Dentistry, Zahedan University of Medical Sciences, Zahedan, Iran.
authors.forename: Leila
authors.initials: L
authors.lastname: Gholami
keywords: Composite; Er:YAG laser; Primary teeth; Shear strength