1 Di - Silicate Dental Ceramic Surface Preparation by 2 1070 nm Fiber Laser : Thermal and Ultrastructural 3 Analysis 4

12 Background 13 Lithium di-silicate dental ceramics bonding, realized by using different resins, is strictly dependent 14 on micro-mechanical retention and chemical adhesion. The aim of this in vitro study was to 15 investigate the capability of a 1070 nm fiber laser for their surface treatment. 16 Methods 17 Samples were irradiated by a pulsed fiber laser at 1070 nm with different parameters (Peak Power 18 from 5 kW to 5 kW, RR 20 kHz, speed from 10 to 50 mm/s, total Energy Density from 1.3 to 27 19 kW/cm2) and the thermal elevation during the experiment was recorded by a Fiber Bragg Grating 20 (FBG) temperature sensor. Subsequently, the surface modifications were analysed by optical 21 microscope, Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). 22 Results 23 With a Peak Power of 5 kW, RR of 20 kHz and speed of 50 mm/s, the microscopic observation of the 24 irradiated surface showed increased roughness with small areas of melting and carbonization. EDS 25 analysis revealed that, with these parameters, there are no evident differences between laser26 processed samples and controls. Thermal elevation during laser irradiation ranged between 5 °C 27 and 9 °C. 28 Conclusions 29 1070 nm fiber laser can be considered as a good device to increase the adhesion of Lithium di-silicate 30 ceramics. 31