Mechanical behavior and bond strength of zirconia after surface micro texturing with ultrashort pulsed laser

Author(s)

Stephanie Assimakopoulos Garofalo

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia (FO/SDO)
• Defense date: 2021-03-12

Examining board members

Ana Cecilia Corrêa Aranha; Paulo Francisco Cesar; Mario Fernando de Goes; Marcella Esteves Oliveira

• Advisor: Ana Cecilia Corrêa Aranha

Abstract

The objectives of this study were to evaluate the long-term bond strength of zirconia treated with ultra-short pulsed laser (USPL) to a resin cement, as well as the mechanical behavior of the treated zirconia. After a systematic review of the literature, and the completion of a pilot study, for the bond strength test, sixty zirconia blocks (YTZP) were cleaned and randomly distributed into 4 groups (n = 12) that received the following surface treatments: 1) Sandblasting with aluminum oxide particles (SB); 2) Irradiation with USPL with crossed lines pattern (LC); 3) Irradiation with USPL with random hatching pattern (LR); 4) Irradiation with LPUC with parallel wave pattern (LW). For the surface roughness test (n = 6), a 3D profilometer was used. Representative blocks (n = 3) from each group were analyzed by scanning electron microscopy (SEM). For the bond strength test, specimens were cemented to composite resin replicas with a dual cure resin cement and then cut into 1mm2 sticks. Half of the sticks from each block were stored in distilled water at 37 ° C for 24 hours and the other half for 6 months, and then the test was performed. For the flexural strength test, 160 barshaped specimens of 21x4x2.1 mm3 were prepared from the same zirconia and randomly divided into five groups (n = 32). Four groups received the same surface treatments as for the bond strength test and an additional \"just polished\" group was used as a negative control. The bars were subjected to a four-point bending test and changes in the content of the crystalline phase were identified by X-ray diffraction. The data for roughness, bond strength and flexural strength were statistically analyzed. The roughness and bond strength data were subjected to ANOVA and Tukey\'s test (? = 0.05). Flexural strength data were subjected to nonparametric tests (Kruskal-Wallis) for comparisons between groups. Weibull\'s statistical analysis was used to describe the reliability of the ceramic material. The USPL-treated zirconia showed a statistically higher roughness than SB, except for LR. After 24h and after 6 months, the highest bond strength values (MPa) were achieved by LC (32.8 ± 6.0 / 21.2 ± 5.1) and LW (29.3 ± 5.0 / 21.4 ± 4.4), and both were statistically higher than SB (18.1 ± 5.4 / 6.0 ± 3.2) and LR (22.1 ± 5.4 / 6.6 ± 3 , 7) (p <0.05). All laser groups exhibited higher Weibull modules than NC and SB. A greater increase in the monoclinic phase was observed for SB. USPL proved to be an interesting and contemporary alternative to the treatment of the internal surface of zirconia, creating reproductible and homogeneous surface structures. It was possible to determine irradiation parameters that promoted a significant increase in the bond strength (LC and LW) compared to the positive control (SB), even after 6 months of water storage and that did not promote a decrease in the flexural strength (LR) in comparison to the negative control. (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)