The contribution of ceramic thickness and adhesive type on the de-bonding strength of dental ceramic veneers using Er,Cr:YSGG laser

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.