Influência do tratamento laboratorial com líquidos de pigmentação e fluorescência e do envelhecimento acelerado na resistência à fratura de uma zircônia odontológica

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Odontologia, Florianópolis, 2016Para alcançar estética satisfatória em próteses confeccionadas com zircônia tetragonal policristalina (3Y-TZP), tratamentos laboratoriais, tais como a imersão em líquidos de pigmentação e/ou fluorescentes, podem ser realizados. É importante conhecer a influência desses tratamentos na resistência desse material, assim como a influência do envelhecimento nas propriedades mecânicas de zircônia pigmentadas e/ou fluorescentes. O objetivo deste estudo foi avaliar a resistência mecânica de uma 3Y-TZP tratada com líquidos de pigmentação e/ou fluorescência antes e após protocolo de envelhecimento acelerado. Oitenta discos de zircônia (Prettau Zirkon, Zirkonzahn, Itália) com 14x2,5mm foram usinados, divididos em quatro grupos (N=20) de acordo com o tratamento laboratorial: ZN (sem tratamento); ZC (imersão em líquido de pigmentação A2); ZF (imersão em líquido fluorescente); ZFC (imersão em líquido fluorescente e de pigmentação A2) e sinterizados. Dez discos de cada grupo foram submetidos a um protocolo de envelhecimento acelerado em autoclave por 5 horas. Após, os discos foram submetidos ao teste de resistência flexural (Ball-on-three-balls test). Os valores de resistência obtidos foram analisados pelos testes ANOVA a dois critérios e Tukey?s HSD (pAbstract : In order to achieve satisfactory aesthetic in yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), laboratory treatments such as immersion in coloring and/or fluorescent liquids, can be used. It is important to know the influence of such treatments on the strength of the material as well as the influence of aging on mechanical properties of pigmented and/or fluorescent zirconia. The aim of this study was to evaluate the mechanical strength of a pigmented and/or fluorescent 3Y-TZP before and after accelerated aging protocol. Eighty zirconia discs (Prettau Zirkon, Zirkonzahn, Italy) of 14x2,5mm were machined and divided into groups (N=20) according to the laboratory treatment: ZN (no treatment); ZC (immersion in coloring liquid); ZF (immersion in fluorescent liquid); ZFC (immersion in coloring and fluorescent liquid) and sintered. Ten disks of each group were subjected to accelerated aging protocol in an autoclave for 5 hours. All discs were subjected to flexural strength testing (Ball-on-three-balls test). The resistance values obtained were analyzed by two-way ANOVA and Tukey?s HSD (p<0.05). The Weibull modulus (??) was used to analyze the probability of fracture. The content of tetragonal and monoclinic phase was observed by XRD and the microstructure observation was made by SEM. There was a significant increase in resistance of the discs after aging (p<0.001), however, when the laboratory treatments employed were evaluated, no difference was observed (p=0.27). At XRD analysis, the discs subjected to accelerated aging showed the presence of monoclinic content of 30%, while the non-aged samples did not show this phase. The increase in the flexural strength of the groups subjected to accelerated aging for 5 hours suggests that the increase of the monoclinic content concentrated on the surface generated compressive stresses that strengthened the material. Regarding laboratory treatments, there was no significant difference in flexural strength, demonstrating that the use of coloring and fluorescence agents did not influence the mechanical resistance of 3Y-TZP studied

Esthetic and functional rehabilitation of bilateral congenital absence of maxillary lateral incisors: Minimally invasive surgical and prosthetic approach

Congenital absence of maxillary lateral incisors is a frequent clinical challenge which must be solved by a multidisciplinary approach in order to obtain an esthetic and functional restorative treatment. Noninvasive treatments, that are in accordance with the patients' expectations, should be the first therapeutic alternative. If the deciduous tooth is present, minimally invasive dental extraction followed by immediate dental implant placement and provisional restoration is indicated. In this restorative treatment, an adequate emergency profile can be achieved by peri‐implant soft‐tissue‐conditioning techniques. Moreover, the association of restorative materials, such as composite resins and dental ceramics, provides more predictable esthetic results. Clinical Considerations The present case report presents a rehabilitation of bilateral congenital absence of maxillary lateral incisors through a multidisciplinary approach. Dental implants, long‐term provisional restoration, tooth bleaching, minimally veneered high‐translucent monolithic zirconia crowns, feldspathic veneers, and composite restorations were used by the dental team to achieve the expected functional and esthetic outcomes. Conclusions Different treatment modalities are available for the rehabilitation of congenital absence of teeth. However, it is important that a dental team consider performing minimally invasive treatments, as many of these treatments are done on young patients. Clinical Significance Patient‐centered treatments involving minimally invasive approaches in a multidisciplinary environment would be appropriate in order to achieve predictable results