Effect of Finishing Protocols on the Surface Roughness and Fatigue Strength of a High-Translucent Zirconia.

Purpose: In case of need for esthetical improvement of zirconia restorations, an individualization using extrinsic staining can be applied. This study aimed to evaluate the surface roughness and fatigue strength (survival) of high-translucency zirconia (3Y-TZP, YZ®HT, Vita Zanhfabrik) with extrinsic characterization and/or glaze. Methods: Sixty (60) zirconia discs (12 × 1.2 mm) were obtained, sintered, and randomly distributed among three groups (n = 20) according to the surface finishing protocol: C (control), C + G (extrinsic characterization followed by a glaze layer), and G (glaze layer). The surface roughness (Ra) was analyzed with a contact profilometer. Subsequently, the specimens were subjected to a fatigue load profile starting at 120 N during 20,000 cycles at 4 Hz frequency, with a 5% increase at each step until failure. The failed specimens were evaluated under a stereomicroscope. Surface roughness analysis was evaluated by using one-way ANOVA and post hoc Tukey tests (95%); while fatigue survival probability was analyzed with Kaplan-Meier and Mantel-Cox (log- rank, 95%). Results: One-way ANOVA revealed that surface roughness was affected by the finishing protocol, where C + G showed the highest mean value (0.46 ± 0.18 µm)A followed by G (0.30 ± 0.10 µm)B, and C (0.19 ± 0.02 µm)C. While for fatigue strength, the G protocol presented a higher mean value (243.00, and 222.36-263.63)A, followed by C + G (192.75 and 186.61-198.88)B and C (172.50 and 159.43-185.56)C. Conclusion: Surface finishing protocols modify the surface roughness and fatigue strength of high-translucent zirconia. Regardless of the surface roughness, both glazing protocols improved the ceramic fatigue strength, favoring the restoration's long-term survival.

High-Translucency Zirconia Following Chemical Vapor Deposition with SiH4: Evidence of Surface Modifications and Improved Bonding.

PURPOSE: To evaluate the effect of plasma-enhanced chemical vapor deposition (PECVD) with silicon hydride (SiH4) at different times on HT-zirconia surface characteristics and bonding of composite cement before and after thermocycling. MATERIALS AND METHODS: Blocks of HT zirconia were obtained, polished, sintered and divided into five groups, according to PECVD time (n = 31): Zr-30 (30 s), Zr-60 (60 s), Zr-120 (120 s) and Zr-300 (300 s). The control group (Zr-0) did not receive PECVD. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS) in conjunction with field-emission scanning electron microscopy (FE-SEM), x-ray photoelectron spectroscopy (XPS), goniometry, and profilometry tests were used for chemical and topographic characterization. Monobond N silane (Ivoclar Vivadent) was applied to the surface, and a cylinder of composite cement (Variolink N) was made (3 x 3 mm). Half of the specimens of each group were stored for 24 h or subjected to thermocycling (6 x 103 cycles). A shear bond strength (SBS) test was performed. Results were subjected to one-way ANOVA and Tukey's tests (α = 0.05). RESULTS: For experimental groups, XPS showed that formation of Si-O bonds contributed to increased surface free energy (SFE). FE-SEM and EDS showed that the longer the deposition time, the greater the amount of silicon on the surface. Zr-60 and Zr-300 presented higher and lower surface roughnesses, respectively. The silicon penetrated the microstructure, causing higher stress concentrations. The bond strength to composite cement was improved after all PECVD deposition times. CONCLUSION: The PECVD technique with SiH4, associated with chemical treatment with primer based on silane methacrylate, is a solely chemical surface treatment capable of maintaining bonding between composite cement and HT zirconia.

Effect of hydrothermal and mechanical aging on the fatigue performance of high-translucency zirconias.

OBJECTIVES: This study aimed to evaluate the impact of mechanical fatigue cycling using the step-stress approach along with hydrothermaldegradation (134 ºC with a constant pressure of 2 bars for 20 h), and a novel intercalated hydrothermal/fatigue aging protocol on different aspects of the aging resistance of three generations of dental zirconias. METHODS: "Y"Z T (VITA), INCORIS "T"ZI (Dentsply Sirona) and "K"ATANA UTML (Noritake Kuraray) - 1st, 2nd and 3rd generation, respectively-, zirconia disks (N = 153), were divided into 6 groups (n = 3) for monotonic testing and 9 groups (n = 15) for mechanical fatigue testing, according to 3 proposed treatments for each zirconia: CF (control - only mechanical fatigue cycling); AF (aging in hydrothermal reactor at 134 °C for 20 h + mechanical fatigue cycling); AFA (Alternating protocol: 4 steps of 5 h of hydrothermal aging intercalated with mechanical fatigue cycling). Mechanical fatigue aging was performed according to the step-stress approach through biaxial flexural setup (piston-on-3-balls, initial strength: 100 MPa, step: 50 MPa/10,000, frequency: 20 Hz) until failure. Data were analyzed using Kaplan-Meier and Mantel-Cox test (α = 0.05), in addition to Weibull analysis. Fractured disks were analyzed in stereomicroscope, Scanning Electron Microscopy and X-Ray Diffraction. RESULTS: Continuous hydrothermal and mechanical fatigue cycling decreased the fatigue strength of YAF group (516 ± 38 MPa), while the alternating protocol increased it (730 ± 58 MPa). KATANA UTML showed no differences for both treatments and did not undergo t-m phase transformation. The TAF group showed the highest fatigue strength (810 ± 76 MPa) and cycles for failure (147,000.00 cycles). The fracture origin for all specimens was on the tensile side in pre-existing defects. SIGNIFICANCE: INCORIS TZI zirconia had higher fatigue strength and survival rates after hydrothermal and mechanical fatigue aging. Although less resistant, KATANA UTML did not suffer chemical degradation.

Posterior rehabilitation using 3D-printed dental implants and synthetic regenerative biomaterials / Reabilitação posterior com implantes impressos e biomateriais sintéticos

Aim: To describe through a clinical case report the surgical sequence of rehabilitation with 3D-printed implants associated with maxillary sinus floor lift with synthetic regenerative materials, including biphasic bioceramic. Case Report: Patient had an agenesis of the upper left premolars (#12 and #13), a vertical bone deficiency caused by maxillary sinus' pneumatization, and a horizontal alveolar resorption around the missing teeth area. During the surgical procedures, incisions, detachment, and osteotomy were performed in the lateral region of the maxillary sinus. The sinus membrane was detached and lifted 10 mm. Then, a thick poly(dioxanone)-based synthetic resorbable membrane (Plenum) was inserted and adapted inside the sinus to protect the sinus membrane. After the osteotomies with sub-instrumentation, 3D-printed implants (Plenum) were installed in the #12 area (3.5mm x 11.5 mm; 30N) and #13 area (4.0mm x 10mm; 20N). The maxillary sinus was entirely filled with a biphasic bioceramic, HA/ß-TCP (70:30) 500-1000 µm (Plenum) and covered by the same synthetic resorbable membrane. Connective tissue graft from the palatal area was positioned internally to the flap and stabilized with sutures to improve the vestibular tissue architecture. The entire surgical wound was sutured, and the tissues stabilized. No complications occurred in the postoperative period. Conclusion: The use of synthetic regenerative memberane and 3D-printed implants seems to be a promising option in areas of deficient bone remnants (AU)

Objetivo: Descrever por meio de um relato de caso clínico a sequência cirúrgica de reabilitação com implantes obtidos por impressão 3D associados à elevação do assoalho do seio maxilar com materiais regenerativos sintéticos, incluindo uma biocerâmica bifásica. Relato de Caso: Paciente apresentava agenesia dos pré-molares superiores esquerdos (24 e 25), deficiência óssea vertical causada pela pneumatização do seio maxilar e reabsorção alveolar horizontal ao redor da área dos dentes ausentes. Durante os procedimentos cirúrgicos foram realizados incisões, descolamento e osteotomia na região lateral do seio maxilar. A membrana sinusal foi descolada e elevada 10 mm. Em seguida, uma membrana reabsorvível sintética à base de poli(dioxanona) espessa (Plenum) foi inserida e adaptada dentro do seio para proteger a membrana do seio. Após as osteotomias com subinstrumentação, implantes impressos em 3D (Plenum) foram instalados na área do 24 (3,5mm x 11,5mm; 30N) e na área do 25 (4,0mm x 10mm; 20N). O seio maxilar foi inteiramente preenchido com biocerâmica bifásica, HA/ß-TCP (70:30)500-1000 µm (Plenum) e recoberto pela mesma membrana sintética reabsorvível. O tecido conjuntivo da região palatina foi posicionado internamente ao retalho e estabilizado com suturas para melhorar a arquitetura do tecido vestibular. Toda a ferida cirúrgica foi suturada e os tecidos estabilizados. Não ocorreram complicações no pós-operatório. Conclusão:A utilização de biomateriais regenerativos sintéticos e implantes impressos parece ser uma opção promissora em áreas de remanescentes ósseos deficientes.(AU)

Efeito do envelhecimento hidrotérmico e mecânico na performance à fadiga de zircônias de alta translucidez / Effect of hydrothermal and mechanical aging on the fatigue performance of high-translucency zirconias

O objetivo deste trabalho foi avaliar a resistência à fadiga e ciclos até a falha de 3 zircônias odontológicas após envelhecimento hidrotérmico isolado e um novo protocolo alternado. Discos de zircônia "Y"Z T (VITA), INCORIS "T"ZI (Dentsply Sirona) e "K"ATANA UTML (Noritake Kuraray) (N=135) ­ 1ª, 2ª e 3ª gerações, respectivamente ­, foram divididos em 9 grupos (n=15), com 3 tratamentos para cada zircônia: CF ­ Controle, somente com fadiga mecânica; EF ­ Envelhecido em reator hidrotérmico a 134 ºC por 20 h + Fadiga; EFA: 4 passos de envelhecimentos de 5h alternados com fadiga. O teste de fadiga em flexão biaxial foi realizado com configuração de pistão sob 3 esferas, utilizando o método step-stress (carga inicial: 100 Mpa, step: 50 MPa/10.000 ciclos, frequência: 20 Hz). Os dados foram analisados através de teste Kaplan-Meir e Mantel-Cox com α=0,05, além da análise de Weibull. Discos fraturados foram analisados em estereomicroscópio, Microscopia Eletrônica de Varredura (MEV) e Difratômetro de Raios-X (DRX). O envelhecimento isolado com fadiga aumentou a resistência do grupo TEF (810 ± 76 MPa), enquanto diminuiu a do YEF (516 ± 38 MPa), o protocolo alternado aumentou a resistência apenas para a YZ T (730 ± 59 MPa). A KATANA UMTL não apresentou diferenças para ambos os tratamentos. Igualmente, foi a única a não sofrer transformação de fase T-M. O grupo TEF apresentou maior taxa sobrevivência à fadiga (147,000.00 ciclos). A origem de fratura para todos os espécimes deu-se no lado de tração em defeitos pré-existentes. Zircônias de 2ª geração possuem melhor comportamento mecânico e longevidade pós-envelhecimento e fadiga. Embora seja menos resistente, a KATANA UTML não sofreu degradação

This study aimed to evaluate the fatigue strength and cycles for failure of 3 dental zirconias after isolated and a novel hydrothermal and mechanical fatigue cycling aging protocol. "Y"Z T (VITA), INCORIS "T"ZI (Dentsply Sirona) and "K"ATANA UTML (Noritake Kuraray) zirconia discs (N=135), were divided into 9 groups (n=15), according to 3 proposed treatments for each zirconia: CF (control ­ only mechanical fatigue cycling); AF (aging in hydrothermal reactor at 134°C for 20 h + mechanical fatigue cycling ); AFA (Alternating protocol: 4 steps of 5 h of hydrothermal aging intercalated with mechanical fatigue cycling). Mechanical fatigue aging was performed according to the step stress approach through biaxial flexural setup (piston-on-3-balls, initial strength: 100 MPa, step: 50 MPa/ci000, frequency: 20 Hz) until failure. Data were analyzed using KaplanMeier and Mantel-Cox test (α=0.05), in addition to Weibull analysis. Fractured discs were analyzed in stereomicroscope, Scanning Electron Microscopy and XRay Diffraction. Continuous hydrothermal and mechanical fatigue cycling decreased the fatigue strength of YAF group (516 ± 38 MPa), while the alternating protocol increased it (730 ± 59 MPa). KATANA UTML showed no differences for both treatments and did not undergo T-M phase transformation. The TAF group showed the highest fatigue strength (810 ± 76 MPa) and cycles for failure (147,000.00 cycles). The fracture origin for all specimens was on the tensile side in pre-existing defects. INCORIS TZI zirconia have higher fatigue strength after hydrothermal and mechanical fatigue aging. Although less resistant, KATANA UTML did not suffer chemical degradation

Degradation kinetics of high-translucency dental zirconias: Mechanical properties and in-depth analysis of phase transformation.

This study aimed to evaluate the effects of low temperature degradation (LTD) on commercial dental zirconias (conventional and high-translucent - HT) with different microstructures, as well as on their mechanical properties and t-m phase transformation. The amount of monoclinic zirconia in different depths was quantified using X-ray diffraction (XRD) with different anode tubes (Cr, Co and Cu). XRD was also used to measure the residual stress of the materials at 0 h, 26 h and 140 h aging times. Vickers microhardness and biaxial flexural strength tests were performed. Data were subjected to two-way ANOVA and Tukey's post-hoc test, both with α = 0.05 for means comparisons. Weibull parameters were calculated and compared based on the overlapping of confidence intervals (CI = 95%). HT Zirconia presented smaller grain sizes and had a higher rate of t-m transformation over time. The microstructure of the conventional zirconia showed an expressive increase of the grain size and consequently greater morphological variation with the LTD. The non-aged samples (control) did not present any residual stress and the aged ones presented compression stress. All zirconia showed a residual stress increase with the increase of LTD time, but the conventional one showed a decrease after 140 h. HT zirconia showed no significant change in flexural strength over LTD time, but the conventional one showed a strength decrease after 140 h (681.78 ±â€¯121.18 MPa). Vickers hardness decreased for all zirconia samples after 26 h. The mechanics of LTD is significantly altered in different zirconia microstructures. Zirconias with smaller grains are more prone to t-m phase transformation, but present lower variation of residual stress, while larger grains zirconias have a lower surface area and therefore a more pronounced increase in stress over LTD time. Stress values close to the maximum compression stress generates ejection of the zirconia grains, producing defects and causing reduction of the compression stress and consequently decrease of flexural strength.

Impact of Acid Concentration and Firing on the Long-term Bond Strength of a Zirconia-Lithium Silicate Ceramic Following Adhesive Cementation.

PURPOSE: To evaluate the effect of different firing stages (without firing, additional crystallization and glaze firings), hydrofluoric acid (HF) concentrations (5% and 10%), and thermocycling on the bond strength between resin cement and a zirconia-lithium silicate (ZLS) ceramic. MATERIALS AND METHODS: ZLS ceramic (Celtra Duo, Dentsply Sirona) blocks were cut into smaller blocks and divided into 12 groups (N = 72), according to the HF concentration used, firing stage, and thermocycling (n = 6). All specimens were silanized (Monobond N, Ivoclar) and cemented with resin cement (Multilink N, Ivoclar) onto blocks of composite resin (Filtek Z250 XT, 3M). The specimens were immersed in distilled water for 24 h. The blocks were cut into sticks and tested immediately or thermocycled for 10,000 cycles in water (5°C-55°C). Microtensile bond strength (µTBS) testing was then performed in a universal testing machine (0.5 mm/min, 50 kgf load cell). The failure modes of the sticks were examined using SEM and classified as adhesive, predominantly adhesive, or cohesive. Fracture surfaces were topographically evaluated using SEM. The 5% and 10% HF groups were analyzed separately and the data submitted to two-way ANOVA and Tukey's test (p < 0.05). Additional samples were used for SEM topographic analysis of representative ceramic surfaces. RESULTS: The most frequent types of failure were predominantly adhesive between cement and ceramic and adhesive (cement completely covered the composite). Statistically significant differences were found only for the thermocycling factor (p < 0.05) for both HF concentrations. However, for the 10% HF groups, a marked decrease in µTBS was observed after firing and thermocycling. SEM showed superficial irregularities on ZLS without etching, partial and total dissolution of the vitreous matrix and exposure of the crystals using 5% and 10% HF, respectively. CONCLUSION: The crystallization and glaze firings of ZLS ceramics conditioned with 5% HF promoted bond strength maintenance after thermocycling. Thermocycling decreased the bond strength in all groups, but mainly for fired ZLS conditioned with 10% HF.

The performance of sol-gel silica coated Y-TZP for veneered and monolithic dental restorations.

OBJECTIVES: The purpose of the study was to characterize the microstructure, constituents, and mechanical properties of mono and bilayered zirconia specimens infiltrated with silica by the sol gel method. METHODS: 180 zirconia discs (14-mm diameter) were divided in 3 groups (n = 60) according to thickness (1.2, 0.5 mm) and further divided in two groups (n = 30) according to treatment (infiltrated or not). Disk thickness was 1.2 mm for the control samples. Veneering feldspathic porcelain had two thicknesses (0.5 mm and 1 mm) at the tops of the zirconia discs. All groups were subjected to the biaxial flexural test in an aqueous medium. Weibull analysis was performed for determination of the Weibull modulus (m) and characteristic strength (σ0). The specimens were characterized by SEM and EDS and XRD. Hardness and elastic modulus were measured by nano-indentation and pulse-echo methods, respectively. Fracture toughness was determined by the nano-indentation technique. A scratch test was used for evaluation of the adhesion between the zirconia and porcelain. RESULTS: There was less variability (higher Weibull modulus) in the infiltrated monolithic specimens; biaxial flexural strength was not statistically higher in the veneered infiltrated specimens and was decreased for the 1-mm veneered infiltrated group. The diffractograms showed formation of ZrSiO4 crystal phase. Hardness also increased in the infiltrated monolithic zirconia, whereas fracture toughness decreased. Adhesion between zirconia and porcelain was superior in the non-infiltrated monolithic specimens. CONCLUSIONS: Infiltration increased the structural homogeneity and hardness of the monolithic zirconia, but it reduced fracture toughness, and the adhesion to porcelain. CLINICAL SIGNIFICANCE: Within the limitations of the present study, it is possible to recommend the infiltration of silica gel in zirconia only for monolithic restorations.