Influence of photoactivation protocol and ceramic thickness on mechanical properties of cementation agents

Abstract

The objective of this work was to evaluate the influence of photoactivation protocol and ceramic thickness on the Knoop microhardness (KHN) and the diametrical tensile strength (DTS) of a dual resin cement (Rely X ARC 3M ESPE (RL)) and a low viscosity composite resin (Filtek Z350 Flow 3M ESPE (Z)). Thereunto, cementation agents were photoactivated under ceramic discs of lithium disilicate with thickness of 1 and 2mm, and a glass slide (control group). The photoactivation was performed with halogen light-curing unit in continuous mode (XL 3000 3M Espe,) (XL) 500 mW/cm2 X 38 s, and with third generation LED light-curing unit (Valo Ultradent) in Standard mode (S) 1000 mW/cm2 X 19 s and Plasma Emulation mode (PE) 3200 mW/cm2 X 6 s, all them providing approximately 19 J/cm2. For KHN measurement, samples (5mm X 1mm) were made (n=8) and submitted to the KHN test on the top surface under a load of 10g applied for 10 seconds. For the DTS (n=8), samples (5mm X 3mm) were made and submitted to a compressive load of 0.5 mm/s until fracture. The data obtained were submitted to the statistical analysis. For KHN, there was statistically significant effect for interactions cementation agent X ceramic thickness, where RL presented higher values of KHN than Z. Comparing inside of cementation agent, RL presented higher values of KHN when photoactivated under 1 mm of ceramic thickness, different from the others. For Z, there was no statistically significant difference between different thickness and the control. The interaction cementation agent X photoactivation protocol was also significant, where for all the photoactivation protocols RL presented higher values of KHN than Z. For the cementation agent there was no significant difference in the values of KHN in all the photoactivation protocols for RL. For Z, the higher values of KHN were obtained by XL protocol and the lower values by S. For DTS, there was significant effect for the interaction cementation agent X photoactivation protocol, where in the photoactivation protocol factor, RL presented higher DTS when photoactivated by XL protocol. For cementation agent factor, the higher values of DTS for RL were obtained with XL, and the lower ones with S. For Z, similar values of DTS were obtained among photoactivation protocols evaluated. It was possible conclude that ceramic thickness and the photoactivation protocols exerted influence on the mechanical properties of  cementation agents evaluated.