Surface characterization of monolithic zirconia submitted to different surface treatments applying optical interferometry and raman spectrometry

Abstract

This study evaluated roughness parameters and phase transformation of monolithic zirconia ceramics after various mechanical and laser thermal treatments. Fully sintered monolithic zirconia cylinder specimens were divided to five groups, according to the applied surface treatment: CL: control, GB: grit-blasted with glass particles. AL50: grit-blasted with 50 μm alumina particles, AL90: gritblasted with 90 μm dyed-alumina particles and FEML: subjected to femto laser thermal treatment. Six roughness parameters (Sa, Sq, Sz, Sci, Svi and Sdr) were measured by optical profilometry. Phase transformation in zirconia was determined by micro-Raman spectroscopy. The highest roughness values were recorded in AL90 and FEML groups, followed by AL50. AL90 presented statistically higher monoclinic phase content compared to all other groups. Control and GB groups presented similar roughness without phase transformation. Laser thermal treatment causes minimal destruction of the zirconia surface, and can be suggested as an alternative to other roughening treratments, for enhancing the adhesive potential to dentin.

Novel Femto Laser Patterning of High Translucent Zirconia as an Alternative to Conventional Particle Abrasion

“…It was expected that alumina abrasion with particles of larger size would result in a rougher surface, assisting micromechanical retention [32]. Indeed, the SEM micrographs and roughness measurements reported in our previous study showed that AL90 specimens had rougher surfaces (AL50 = 340.3 ± 49.2 nm) as compared to AL50 (AL90 = 1155.1 ± 97.76 nm) [27]. EDS analysis showed the increased Al and O content in both groups, probably due to the inclusion of Al 2 O 3 particles onto the ceramic surfaces during alumina air-abrasion.…”

“…The GB group presented very low shear strengths and very small percentages of the resin material remained on the surface, resulting in a high percentage of adhesive fracture mode. Based on our previous study and SEM analysis, it was observed that GB created a smooth surface with slightly higher toughness than the control (GB = 99.4 ± 16.6 nm, CL = 73.9 ± 10.7 nm) [27], likely because glass particles are much softer than alumina or zirconia. Therefore, another mechanism, irrespective of roughness, was responsible for these values.…”

“…The highest average values of shear bond strength (23.97 ± 3.7 MPa) were observed in specimens of the FEMTO group, which presented a moderated surface roughness of 307.3 ± 32.7 nm [27], which was similar to AL50 (AL50 = 340.3 ± 49.2 nm) but significantly higher compared to CL (CL = 73.9 ± 10.7 nm) [27]. Similar results were obtained by Vicente Prieto et al [28], who reported superior values of Shear Bond Strength (SBS) in specimens that underwent femto-laser surface patterning as compared with airborneparticle abrasion (APA) and tribochemical coating of conventional zirconia.…”

“…In this respect, ultrafast laser patterning is effective in creating an uncontaminated surface, as it can produce surfaces without any impurities. Besides, FS laser processing is a gentle and precise procedure, as it allows for the creation of different surface patterns without causing damage to the bulk material or significantly increasing the monoclinic phase [27], which makes it an appropriate method for HTZ ceramics surface conditioning. The feasibility to produce and alter zirconia surface patterning with the use of an FS laser is a wide-open field for future research, as many interesting retentive features can be created, with the aim of optimizing the bond strength.…”

“…Femtosecond laser application creates rough zirconia surfaces without triggering phase transformations [25,26]. Moreover, in our previous study it was demonstrated that femtosecond laser patterning of HTZ surface resulted in a rough surface pattern in laser affected areas and the laser-induced grooves presented a repetitive morphology with parallel lines [27].…”