Purpose: De-bonding strength of ceramic veneers by laser use needs to be evaluated in detail. The aim of this study, is to determine the contribution of ceramic thickness and cementing agents to the de-bonding strength of ceramic veneers using Er,Cr:YSGG laser.

Methods: A total of 120 maxillary central incisors specimens were randomly divided into twelve groups on the basis of disc thickness, cementing agent, and  Er,Cr:YSGG  laser  use.  Under  laboratory  conditions,  120  IPS  Empress  II  system  discs  0.5mm,  1mm,  and  2mm  in  thickness  were  applied  to  the  tooth  surfaces,  for  laser  use.  An  Er,Cr:YSGG  laser  system  was  applied  to  the  central  surface  of  the  IPS  Empress II discs on specimens in all laser groups (Groups 1,3,5,7,9,11). Then the shear bond  strength  (SBS)  for  all  specimens  were  tested  with  a  testing  machine  at  a  speed  of 0.5mm/min. The SBS values were considered as the de-bonding strength.

Results: The  mean  de-bonding  strength  values  for  Groups  9  and  11  (0,5  mm  disc  thickness  +  laser  application)    have    the  lowest  median  load  (0.000  N),  while  Group  4  (2mm  disc thickness + no laser) has the highest median load (573.885 N). The de-bonding strengths of all the groups without laser application were higher than those of all groups with  laser  use.  When  laser  is  applied,  the  mean  de-bonding  strength  decreases  with  decreasing disc thickness, and it reaches zero at 0.5mm thickness of discs cemented by self- or total-etch adhesives.

Conclusions: The de-bonding strength decreases with laser use, and decreasing disc thickness. In the absence of laser, the mean de-bonding values of discs cemented by a total etch adhesive system are always higher than those of discs cemented  with  a  self-etch  adhesive  system.  Without  any  extra  load,  all  0.5mm  thick  discs were dislodged from teeth while applying or testing the laser.