The Effect of Fractional Co2 Laser & Sandblasting Surface Treatment on Shear Bond Strength of Cubic Zirconia (in Vitro Study)

Abstract

This study was performed to evaluate the effect of different surface treatment techniques which were: fractional CO2 laser with two different parameters and sandblasting wit 50 micron of AL2O3 on shear bond strength between ultra-translucent zirconia and MDP containing resin cement. Ultra-translucent zirconia samples (10 mm width×10mm length ×2 mm thickness) were prepared by cutting Bruxzir anterior block using a diamond disk mounted on Isomet 4000 microsaw. After that, samples were sintered according to the manufacturer's instructions. Then finished using sandpaper 400 and 1200 grit and ultrasonically cleaned in distilled water for 10 minutes. The specimens were air abraded with 50 µm Al2O3 particles for 15 seconds at a distance of 10 mm with a pressure of 2.5 bar. In order to standardize the distance between the surface of the plate and the nozzle, the nozzle was stabilized on a customized holder at 10 mm length measured by a ruler to hold the nozzle to be perpendicular on the plate during air abrasion. After air abrasion the specimen will be rinsed thoroughly under tap water to remove AL203 particles and air dried. The specimens were subjected to Co2 laser at two different parameters which are 10W/14 mJ with pulse duration 1.75 msec and the energy will be 28 J and 20W /10 mJ with pulse duration 0.58 msec. and the energy will be 24 J. The laser apparatus was run in a dynamic mode and the tip of laser was held manually perpendicular to the zirconia surface in lateral direction at distance 3 cm with frequency 200 HZ (pulse per second) and irradiation time 10 sec, and then all specimens were ultrasonically cleaned in de-ionized water bath for 10 minutes and gently air- dried. The resin was applied by using plastic tubes (catheters) with internal diameter 2mm and sectioning them to 2mm height then the tubes were stabilized on the plates by applying bonding agent on the peripheries of the tubes with micro brush and the resin was applied by using auto mix tip then the specimen was light cured with a high intensity LED device for 40 sec. then the plastic tubes were cut with a scalpel blade and removed. The bonded specimens were stored in distilled water for 24 hours before the shear bond strength test step. Half of each group (n=7) was subjected to thermo-cycling for 5000 cycles between 5 and 55 OC. The dwell time at each temperature was 30 seconds and the transfer time was 2 seconds The specimens were tested in a universal testing machine. The shear force was applied parallel to the interface of the bonding surface at a cross- head speed of 1 mm/min by using a mono-beveled chisel shaped metallic rod, until bonding failure of the specimens occurred. The maximum force needed for de-bonding was recorded and the bond strength was calculated by dividing the maximum force over the area of the bonding surface. The load-deflection curves were recorded using computer software.