ncreasing dental zirconia micro-retentive aspect through ultra-short pulsed laser microstructuring: study on flexural strength and crystal phase characterizatio

Author(s)

Garofalo, Stephanie Assimakopoulos ^[1] ; Wehner, Martin ^[2] ; Dohrn, Andreas ^[2] ; Bilandzic, Marin Dean ^[3] ; Roos, Christian ^[3] ; Wierichs, Richard Johannes ^[4] ; Meyer-Lueckel, Hendrik ^[4] ; Aranha, Ana Cecilia Correa ^[5] ; Esteves-Oliveira, Marcella ^{[4, 6]}

Affiliation

^[1] Univ Sao Paulo, Sch Dent, Dept Restorat Dent, Sao Paulo - Brazil

^[2] Rhein Westfal TH Aachen, Fraunhofer Inst Laser Technol ILT, Aachen - Germany

^[3] Rhein Westfal TH Aachen, Inst Mineral Engn GHI, Aachen - Germany

^[4] Univ Bern, Zmk Bern, Dept Restorat Prevent & Pediat Dent, Bern - Switzerland

^[5] Univ Sao Paulo, Sch Dent, Dept Restorat Dent, Special Lab Lasers LELO, Sao Paulo - Brazil

^[6] Univ Leipzig, Dept Cariol Endodontol & Periodontol, Leipzig - Germany

• Document type: Journal article
• Source: CLINICAL ORAL INVESTIGATIONS; v. 26, n. 1 AUG 2021.
• Web of Science Citations: 0

Abstract

Objectives Although ultra-short pulsed laser (USPL) microstructuring has previously improved zirconia bond-strength, it is yet unclear how different laser-machined surface microstructures and patterns may influence the material's mechanical properties. Therefore, the aim of this study was to assess the flexural strength of zirconia after different USPL settings creating three different geometrical patterns with structures in micrometer scale. Methods One hundred sixty zirconia bars (3Y-TZP, 21 x 4 x 2.1 mm) were prepared and randomly divided into five groups (n = 32): no surface treatment (negative control-NC); sandblasting with Al2O3 (SB); and three laser groups irradiated with USPL (Nd:YVO4/1064 nm/2-34 J/cm(2)/12 ps): crossed-lines (LC), random-hatching (LR), and parallel-waves (LW). Bars were subjected to a four-point flexural test (1 mm/min) and crystal phase content changes were identified by X-ray diffraction. Surface roughness and topography were analyzed through 3D-laser-profilometry and SEM. Data were analyzed with parametric tests for roughness and Weibull for flexural strength (alpha = 5%). Results LR (Mean{[}95%CI]: 852.0 MPa, {[}809.2-894.7]) was the only group that did not show a significantly different flexural strength than NC (819.8 MPa, {[}796.6-842.9]), (p > 0.05). All laser groups exhibited higher Weibull moduli than NC and SB, indicating higher reliability and homogeneity of the strength data. An increase of monoclinic phase peak was only observed for SB. Conclusion In conclusion, USPL created predictable, homogeneous, highly reproducible, and accurate surface microstructures on zirconia ceramic. The laser-settings of random-hatching (12 ps pulses) increased 3Y-TZP average surface roughness similarly to SB, while not causing deleterious crystal phase transformation or loss of flexural strength of the material. Furthermore, it has increased the Weibull modulus and consequently material's reliability. Clinical significance Picosecond laser microstructuring (LR conditions) of 3Y-TZP ceramic does not decrease its flexural strength, while increasing materials realiability and creating highly reproducible and accurate microstructures. These features may be of interest both for improving clinical survival of zirconia restorations as well as enhancing longevity of zirconia implants. (AU)

• FAPESP's process: 16/20935-2 - Immediate and long-term microtensile bond strength of a resin cement to zirconia ceramic after ultra-short pulsed laser treatment
• Grantee: Stephanie Assimakopoulos Garófalo
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 17/17808-1 - Effect of different artificial aging methods on the durability of the bond strength of laser- treated zirconia to a resin cement
• Grantee: Stephanie Assimakopoulos Garófalo
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)