Effect of the type of resin cement on the fracture resistance of chairside CAD-CAM materials after aging.

PURPOSE: The study objective was to evaluate the influence of the type of resin cement on the flexural strength and load to fracture of two chairside CAD-CAM materials after aging. MATERIALS AND METHODS: A polymer-infiltrated ceramic network (PICN) and a nanoceramic resin (RNC) were used to produce the specimens. Two types of dual-cure resin cements, a self-adhesive and a universal, were investigated. Bilayer specimens were produced (n = 10) and aged for 6 months in a humid environment before the biaxial flexural strength test (σf). Bonded specimens were subjected to a mechanical aging protocol (50 N, 2 Hz, 37℃ water, 500,000 cycles) before the compressive load test (Lf). σf and Lf data were analyzed using two-way ANOVA and Tukey tests (α = .05). Chi-square test was used to analyze the relationship between failure mode and experimental group (α = .05). RESULTS: The type of resin cement and the interaction between factors had no effect on the σf and Lf of the specimens, while the type of restorative material was significant. RNC had higher σf and Lf than PICN. There was a significant association among the type of cracks identified for specimens tested in Lf and the restorative material. CONCLUSION: The type of resin cement had no effect on the flexural strength and load to fracture of the two investigated CAD-CAM chairside materials after aging.

Fatigue resistance of polymeric restorative materials: effect of supporting substrate.

The objective of this study was to investigate the effect of mismatch between the elastic properties of substrate and restorative material on the fatigue resistance and stress distribution of multilayer structures. The tested hypotheses were that (1) both an indirect composite resin (IR) and a polymer-infiltrated ceramic network (PICN) would show a higher survival rate after cyclic loading when cemented to a substrate with a high elastic modulus (E); and (2) PICN structures would have higher survival rates than IR structures regardless of the supporting substrate. Blocks of PICN and IR were cut to obtain 1.0-mm-thick sections, which were cemented to substrates with different E values: c, core resin cement (low E); r, composite resin (intermediate E); and m, metal (nickel-chromium alloy; high E). The resulting 6 groups of specimens (n = 20 per group) were subjected to a cyclic fatigue test (106 cycles). Stress distribution was verified using finite element analysis, and the risk of failure was estimated. Fatigue data were analyzed using Kaplan-Meier and Holm-Sidák tests. The χ2 test was used to evaluate the type of crack. The groups IRc, IRr, and PICNm had the highest survival rates after cyclic loading and were statistically similar to each other. Their survival rates were significantly greater than those of the IRm, PICNr, and PICNc groups (P < 0.001), which were all significantly different from each other (P < 0.001). There was a significant relationship between the experimental group and type of crack (P < 0.001). Specimens cemented to core resin cement and composite resin substrates showed predominantly radial cracks, while those cemented to nickel chromium alloy had predominantly cone cracks. The risk of failure values revealed that PICN was more sensitive to the type of substrate than IR. PICN has greater fatigue-resistant behavior when cemented to a substrate with a high E value, while IR has superior performance when substrates with lower and intermediate E values are used.

Assessment of the survival and success rates of lithium disilicate crowns after different surface finishing procedures: An in vitro study.

STATEMENT OF PROBLEM: Evidence is limited for the impact of clinical adjustments and polishing on the longevity of glazed lithium disilicate restorations. PURPOSE: The purpose of this in vitro study was to evaluate the influence of surface finishing on the survival and success rates of lithium disilicate restorations based on fatigue resistance and failure mode. MATERIAL AND METHODS: Lithium disilicate (IPS e.max CAD) maxillary premolar crowns (N=54) were cemented on a dentin analog. The restorations were divided into 3 groups: overglaze (OG), abrasion (GA), and abrasion and polishing (AP). The crowns were submitted to cyclic fatigue in 37 oC water at 100 N and 2 Hz in 2 lifetimes. The load was applied to the occlusal surface by using anatomic pistons to simulate a clinical tripod occlusal contact. After cycling, the crowns were examined for failure (cracking, chipping, or catastrophic fractures) under optical and scanning electron microscopy. Cracking was considered either a structural failure (success analysis) or a survival (clinical criteria - survival analysis). Data were analyzed by using the log rank Kaplan-Meier and Holm-Sidak tests (α=.05). RESULTS: Surface finishing had no influence on the structural integrity of lithium disilicate, with similar success rates (P=.720). The calculated survival rate was higher for AP than that for other groups (P=.028). Cracking was found for GA and AP crowns, mostly initiating from the external surface. Chipping occurred in all experimental groups, and AP crowns did not show catastrophic failures. CONCLUSIONS: Although surface treatments had no influence on the success of lithium disilicate, polishing showed a positive effect on the survival rate of the crowns based on the clinical implications of cracking (no need for replacement).

Optimization of Lithium Disilicate Glass-Ceramic Crowns: Finish Line, Scanning, and Processing Methods.

PURPOSE: To investigate the optimal combination of factors (finish line, scanning, and ceramic processing) to achieve the best values of both adaptation and fracture load for lithium disilicate crowns (LD). MATERIALS AND METHODS: Two abutment preparations, chamfer (C) and rounded shoulder (S), were produced with a dentin analog material and scanned with either extraoral (E) or intraoral (I) scanners. Images were processed using CAD software to design a premolar. Blocks of LD were milled using a CAD/CAM system (CAD). For the press technique (PRE), crowns were first 3D printed using a polymeric material, then heat-pressing protocol was performed. Design of experiments was used to plan four experimental groups (n = 10): CAD-CI, CAD-SE, PRE-CE, and PRE-SI. Two dependent variables were analyzed: adaptation, measured using the replica technique; and fracture load of the cemented crowns. Fractographic analysis was performed. Data were analyzed using ANOVA and regression statistical analyses. RESULTS: There was no significant effect of the scanning method and finish line on the gap thickness in the different regions. For the processing method, CAD resulted in larger gap thickness in the occlusal, axial angle, and marginal areas and a smaller gap in the axial area (P < .001). The investigated factors had no effect on the fracture load. Yet, PRE-CE was considered the optimum design because it achieved 100% of the desired fracture load (>1000 N) and 40% adaptation (< 200 µm). CONCLUSIONS: The optimum combination of factors for all-ceramic crowns is chamfer abutment preparation, extraoral scanning, and the press technique (combined with 3D printing). Int J Prosthodont 2023;36:e103-e118.

Pain factors related to dental implant surgery: A 7-day observational clinical study

This article aims to associate patient-reported pain intensity in the immediate seven days after dental implant surgery with surgical factors, sex and patient age. The sample was composed of 108 patients from a dental school in southern Brazilian, between 2018 and 2020. The variables torque, pre- and postoperative medication, healing of first and second intention, gender, age, number of quadrants, number of implants and type of surgery were related to the outcome pain. Pain was reported every day by the patient until the seventh day after surgery, using a visual analogic scale (VAS). Univariate Poisson regression models were used to assess the relationship among pain and the factors. Rate ratios were obtained with 95% of confidence intervals. Overall pain was reported as moderate/intense (VAS: 3-10) by 30.56% of patients, mild pain (VAS: 1-3) by 55.56%, and no pain symptoms were reported by 13.89% of patients. Individuals which the implants were installed with high torques (50-80 N) showed more pain (p=0.03) compared to patients which the implants were installed with regular torque (30-45 N). The other factors evaluated were not significant. The torque was the most relevant factor related to pain among the evaluated by the study. High torque generates more postoperative pain than lower torque. The factors gender, age, number of operated quadrants, number of installed implants, type of surgery and pre and postoperative analgesic did not interfere in the patient's pain during the first week after surgery.

Influence of photodynamic therapy, different final irrigants, and ultrasonic activation on the bond strength of glass fiber posts to root dentin.

OBJECTIVE: To evaluate the influence of photodynamic therapy (PDT), different final irrigants, and ultrasonic activation (US) on the bond strength of glass fiber posts (GFP) to root dentin. METHODS: One hundred twenty bovine roots were divided into 12 groups according to PDT application, the type of final endodontic irrigant, and US. The samples were divided into 12 groups (n = 10): G1-DW(distilled water); G2-DW+US; G3-17% EDTA; G4-17% EDTA+US; G5-17% GA (glycolic acid); G6-17% GA+US; G7-PDT+DW; G8-PDT+DW+US; G9-PDT+17% EDTA; G10-PDT+17% EDTA+US; G11-PDT+17% GA; G12-PDT+17% GA+US. After cementing the glass fiber posts with resin cement, roots were sectioned into 2-mm-thick slices. One slice from the cervical third and another from the middle third were used for the push out test (PO), and the other two for the diametral compression test (DC). Thus, 10 samples were obtained per third for each mechanical test (n = 10). Kruskal-Wallis and Student-Newman-Keuls tests were used to analyze PO and DC data, and Pearson's correlation test was used to verify the relationship between the variables. Failure patterns were analyzed with chi-square test. RESULTS: Significant differences were found in the PO test among the experimental groups (p < 0.001; power=1.00). PDT improved bond strength when using EDTA. PDT and US increased bond strength when using GA. Favorable failure patterns occurred more frequently in Group GA+US. There was no correlation between data obtained with PO and DC tests (r = 0.112; p = 0.729). CONCLUSION: PDT provided the highest bond strength values of GFP to root dentin when associated with GA and US or when associated only with EDTA.

Fiberglass versus cast metal posts: a practical review based on mechanical properties / Pinos de fibra de vidro versus metal fundido: uma revisão prática baseada em propriedades mecânicas

The current review aimed to compare the mechanical properties and clinical behavior of fiberglass and cast metal posts. It included in-vitro studies, finite element analysis, clinical studies, and systematic reviews that evaluated fiberglass and metal posts with reliable methodologies. The reports in the literature diverge on tooth failure modes and stress distributions in the root according to different posts. Investigations suggest that fiberglass posts are preferable because their elastic modulus is similar to dentin. Other studies mention that the flexibility of fiber posts may damage the interface. The fracture load values of different studies could not be compared. The presence of a ferrule seems beneficial. Cast metal posts provide higher characteristic strength to the set but with more unfavorable failures. Intraradicular posts with a lower elastic modulus produce more stress between the cement layer and dentin. In conclusion, fiberglass and cast metal posts can be used with a ferrule. Cast metal posts seem more appropriate for weakened teeth. The presence of a ferrule benefits the system. Weakened teeth tolerate higher loads when restored with cast metal posts, but when these posts fail, the only solution is tooth extraction. Clinical follow-ups cannot yet detect differences between the survival rates of intraradicular fiberglass and cast metal posts (AU)

O objetivo da presente revisão foi comparar as propriedades mecânicas e o comportamento clínico de pinos de fibra de vidro e núcleos metálicos fundidos. Estudos laboratoriais, analise por elementos finitos, estudos clínicos e revisões sistemáticas que avaliaram pinos de fibra de vidro e metálicos, com metodologia confiável foram selecionados. A literatura mostra-se bastante controversa sobre os modos de falha do dente e a distribuição de tensões na raiz de acordo com diferentes tipos de pinos. Algumas investigações sugerem que pinos de fibra de vidro são preferíveis porque seu módulo de elasticidade é semelhante ao da dentina, enquanto outras mencionam que a flexibilidade do pino de fibra pode ser prejudicial à interface adesiva. Os valores de carga de fratura em diferentes estudos não podem ser comparados. A presença de férula é benéfica. O núcleo metálico fundido resulta em maior resistência característica do conjunto, mas falhas mais desfavoráveis. Também, pinos com menor módulo geram mais tensão entre a camada de cimento e a dentina. Em conclusão, verificou-se que tanto pino de fibra de vidro como núcleo metálico fundido podem ser utilizados quando a férula está presente. Os núcleos metálicos fundidos parecem ser mais indicados para dentes fragilizados. É evidente que a presença de férula é benéfica para o sistema. Dentes fragilizados toleram cargas maiores quando restaurados com núcleos metálicos fundidos; porém, quando falham, a única solução é a extração do dente. Os acompanhamentos clínicos ainda não são capazes de detectar diferença entre as taxas de sobrevivência dos pinos de fibra de vidro e núcleos metálicos (AU)

Hydrogen peroxide as an auxiliary treatment for COVID-19 in Brazil: a randomized double-blind clinical trial.

OBJECTIVES: This study evaluated the effectiveness of hydrogen peroxide (H2O2) as mouthwash and nasal spray on symptom relief in coronavirus disease 2019 (COVID-19) patients. METHODS: Patients positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), who were treated in a hospital or at home, and patients' family members (not positive for SARS-CoV-2), were randomized into 2 groups: experimental (1% H2O2 for gargling, 0.5% H2O2 for nasal wash), and control. Patients gargled the solution 3 times a day, and applied the nasal spray twice a day, for a 7-day period. Family members received the same treatment as the treated COVID-19 patient. The researchers contacted patients every 2 days over an 8-day period. An average post-treatment interval of 8 days passed before testing family members. RESULTS: The most frequent symptoms on day 0 were cough, loss of taste, and hyposmia; there were no significant differences between groups, independent of the period. The symptom of dyspnea presented a significant difference between days 2 and 4 (p<0.05). Among family members, 86.0% had no antibodies, 2.3% had antibodies, and 11.6% had active infections (4 in the experimental group and 6 in the control group). The most frequent adverse effects in the H2O2 group were a burning throat and nose. CONCLUSIONS: H2O2 was not effective for the relief of COVID-19 symptoms and was associated with reports of transient adverse effects.

Effectiveness of hydrogen peroxide as auxiliary treatment for hospitalized COVID-19 patients in Brazil: preliminary results of a randomized double-blind clinical trial.

OBJECTIVES: To evaluate the effectiveness of hydrogen peroxide (H2O2) in the form of mouthwash and nasal spray as an auxiliary treatment for coronavirus disease 2019 (COVID-19). METHODS: Forty hospitalized patients who tested positive for severe acute respiratory syndrome coronavirus 2 using a reverse-transcription polymerase chain reaction test were evaluated. They were randomly divided into an experimental group (n= 20; gargling with 1.0% H2O2 and nasal wash with 0.5% H2O2) or a control group (n= 20). The solutions were used for 7 days and the patients were monitored every 2 days, for a total of 8 days. At check-ups, patients were asked about their symptoms and possible adverse effects of the solutions. The presence and severity (mild, moderate, or severe) of symptoms were recorded. Data were compared using the Student test and the Fisher exact test (α= 0.05). RESULTS: There was no significant difference between the 2 groups in the length of hospital stay (p= 0.65). The most frequent symptom on day 0 was coughing (72.0% in the experimental group and 76.5% in the control group), which abated over time. There was no significant difference between the groups in the evaluated symptoms. Most (75.0%) of the patients in the experimental group presented a reduction in dyspnea between days 0 and 2. Few patients reported adverse effects from the use of the solutions. CONCLUSIONS: H2O2 as a mouthwash and nasal spray is safe to use. There is insufficient evidence to demonstrate that H2O2 is effective as an auxiliary treatment for hospitalized COVID-19 patients.

Comparisons between photographic equipment for dental use: DSLR cameras vs. smartphones / Comparações entre equipamento fotográfico para uso odontológico: câmeras DSLR vs. smartphones

Objective: to compare the image quality obtained by six cameras used for dental documentation, including four DSLR cameras and two smartphones with different sensor size. Methods: the equipment determined the groups: APSCcan18-55 ­ Sensor APS-C Canon (EOS T5i) + 18-55 mm lens; APSCcan100 ­ Sensor APS-C Canon (EOS T5i) + 100 mm macro lens; APSCnik18-55 ­ Sensor APS-C Nikon (D5100) + 18-55 mm lens; APSCnik100 ­ Sensor APS-C Nikon (D5100) + 100 mm macro lens; ip1/3" ­ iPhone with 1/3-inch sensor; ga1/2.6"- Galaxy with 1/2.6-inch sensor. Two set of images -"dental documentation" and "small objects"- were obtained. The photographs were evaluated by three groups: US, undergraduate students; DS, dentists; and DP, dentists with photography experience. Scores between 0 and 10 were assigned. The results were compared by RM Anova and Tukey (α = 0.05). Results: the highest overall scores were obtained with APSCnik100 (8.5). For "dental documentation", APSCcan18-55 and APSCnik18-55 showed the lowest values, even compared to ga1/2.6" (for US, DS and DP evaluators) and ip1/3" (for US evaluators). For "small objects", DSLRs resulted in higher mean values compared to smartphones for US and DS. Conclusions: DSLR cameras with 18-55 mm lens and no circular flash should not be used for documentation photographs. DSLR cameras, regardless of lens, are superior to smartphones for small objects photographs. (AU)

Objetivo: comparar a qualidade da imagem obtida por seis câmeras utilizadas para documentação odontológica, incluindo quatro câmeras DSLR e dois smartphones com diferentes tamanhos de sensor. Métodos: a divisão dos grupos foi realizada pelo tipo de equipamento: APSCcan18-55 - Sensor APS-C Canon (EOS T5i) + lente 18-55 mm; APSCcan100 - Sensor APS-C Canon (EOS T5i) + lente macro de 100 mm; APSCnik18-55 - Sensor APS-C Nikon (D5100) + lente 18-55 mm; APSCnik100 - Sensor APS-C Nikon (D5100) + lente macro de 100 mm; ip1 / 3 "- iPhone com sensor de 1/3 de polegada; ga1 / 2.6 "- Galaxy com sensor de 1 / 2,6 polegadas. Dois conjuntos de imagens ­ "documentação odontológica" e "pequenos objetos" ­ foram realizados. As fotografias foram avaliadas por três grupos de examinadores: estudantes de graduação (US); dentistas (DS); e dentistas com experiência em fotografia (DP). Foram atribuídas pontuações entre 0 e 10. Os resultados foram comparados por Anova e Tukey (α = 0,05). Resultados: os maiores escores foram obtidos com o APSCnik100 (8,5). Para "documentação odontológica", APSCcan18-55 e APSCnik18-55 apresentaram os menores valores. Para "objetos pequenos", as DSLRs resultaram em valores médios mais altos em comparação aos smartphones. Conclusões: as câmeras DSLR com lentes de 18 a 55 mm e sem flash circular não devem ser usadas para fotografias de documentação. As câmeras DSLR, independentemente da lente, são superiores aos smartphones para fotografias de objetos pequenos. (AU)

The critical bond strength of orthodontic brackets bonded to dental glass-ceramics.

OBJECTIVES: To evaluate the critical bond strength (σ) of ceramic and metal brackets to a lithium disilicate-based glass-ceramic. MATERIALS AND METHODS: Two hundred and forty ceramic specimens (IPS e-max CAD) were randomly distributed in 12 experimental groups (n = 20). Two ceramic brackets (monocrystalline, BCm; and polycrystalline, BCp) and a metal bracket (BM) were bonded to glass-ceramic specimens after one of the following surface treatments: HF-hydrofluoric acid applied for 60 s; S-silane applied for 3 min; HFS-HF followed by S; and MDP-application of an adhesive containing a phosphate monomer (MDP). All brackets were bonded to the treated glass-ceramic using a resin cement, stored in 37 °C water for 48 h before shear bond strength testing. Optical (OM) and scanning electron (SEM) microscopies were used for fractographic analysis. Data was statistically analyzed using Kruskal-Wallis and Student-Newman-Keuls (α = 0.05). RESULTS: BCm bonded to glass-ceramic treated with either HFS or HF showed the highest median σ values, respectively, 10.5 MPa and 8.5 MPa. In contrast, the BCp bonded to glass-ceramic treated with MDP showed the lowest median σ value (0.8 MPa), which was not statistically different from other MDP-treated groups. CONCLUSIONS: The failure mode was governed by the glass-ceramic surface treatment, not by the bracket type. Quantitative (σ values) and qualitative (fracture mode) data suggested a minimum of 5 MPa for brackets bonded to glass-ceramic, which is the lower critical limit bond strength for a comprehensive orthodontic treatment. CLINICAL RELEVANCE: Bonding brackets to glass-ceramic requires micromechanical retention.

Effect of supporting substrate on the failure behavior of a polymer-infiltrated ceramic network material.

STATEMENT OF PROBLEM: Restorative materials are cemented on different types of substrates, such as dentin, metal, and glass-fiber posts with composite resin cores. PURPOSE: The purpose of this in vitro study was to evaluate the failure behavior after cycling fatigue of a polymer-infiltrated ceramic network material (PICN; VITA ENAMIC) cemented on different supporting substrates. MATERIAL AND METHODS: PICN plates (N=80) were obtained from computer-assisted design and computer-assisted manufacturing (CAD-CAM) blocks and cemented with a resin cement to 4 different supporting substrates (n=20): (1) human dentin (PICNDen); (2) dentin analog (PICNDenAn); (3) nickel-chromium alloy (PICNNiCr); and (4) composite resin plus fiberglass post (PICNRc). For comparison, the fracture behavior of a feldspathic ceramic (FelDenAn; VITABLOCS Mark II) and an indirect composite resin (ResDenAn; Opallis LAB Resin) cemented to the DenAn substrate was investigated (n=20). Thus, specimens were composed of the restorative material layer (1-mm thick) resin cemented (0.1-mm-thick layer) to a 2-mm-thick supporting substrate. All specimens were subjected to mechanical cycling (MC) using a pneumatic cycling machine (500 000 cycles, 2 Hz, 50 N). Specimens that did not fracture during cycling were tested under compression using a universal testing machine at a cross-head speed of 0.5 mm/min until the sound of the first crack was detected using an acoustic system. Failure data were statistically evaluated using Weibull distribution. Failures were classified as radial crack, cone crack, combined, and catastrophic fracture. RESULTS: All FelDenAn specimens were fractured during MC. Only 4 PICNRc specimens survived MC, so their fracture load data were not statistically analyzed. PICNNiCr showed the greatest characteristic load (L0) value, followed by ResDenAn. Groups PICNDenAn and PICNDen showed lower and similar L0 but statistically different Weibull modulus (m). There was a significant relationship between experimental group and failure mode (P<.001). FelDenAn and PICNRc had a higher frequency of radial cracks, whereas PICNNiCr failed from cone cracking. CONCLUSIONS: The supporting substrate influenced the failure behavior of PICN. When the substrate had a higher elastic modulus than the restorative material, better mechanical behavior was observed.

A literature review on the new polymer-infiltrated ceramic-network material (PICN).

OBJECTIVES: Ceramics and composites are the most used materials for dental application. Recently, the characteristics of both were combined on the called "polymer-infiltrated ceramic-network" (PICN). The aim of this review is to report the behavior of PICN, comparing the findings that may support the correct clinical application. OVERVIEW: The PICN material is a structure with a sintered ceramic matrix infiltrated with a polymer matrix. Studies evaluated this material microstructure and composition, mechanical properties and adhesive behavior. The most cited mechanical properties are flexural strength, compressive strength, elastic modulus, Weibull modulus, hardness, fracture toughness and fatigue resistance. Most studies compared PICN with feldspathic porcelain, lithium disilicate glass-ceramic, lithium silicate, zirconia-reinforced glass-ceramic, leucite reinforced glass-ceramic, polycrystalline alumina and zirconia. Other studies evaluated a similar material (a nanoceramic resin). CLINICAL SIGNIFICANCE: The mechanical properties of the PICN are equivalent to the properties of nanoceramic resins, lower to lithium disilicate glass ceramic and superior to feldspathic porcelain. Yet, the findings suggest a highly resistant material to degradation at low loads (close to physiological situation) when cemented on a substrate.

Influência da manipulação da resina composta na resistência adesiva à dentina

Objetivo: avaliar a influência da manipulação de uma resina composta (RC) com diferentes luvas na sua resistência adesiva à dentina. Materiais e método: 25 terceiros molares hígidos foram seccionados 2 mm abaixo do sulco central, expondo a dentina (D). A D foi condicionada com ácido fosfórico 35% e lavada, e o sistema adesivo Single Bond Universal (3M ESPE) foi aplicado. Os dentes foram distribuídos aleatoriamente em cinco grupos, de acordo com o tipo da manipulação da RC: C (controle) ­ RC inserida diretamente do tubo para a D; LL ­ RC manipulada com luvas de látex antes da inserção; LV ­ RC manipulada com luvas de vinil; LC ­ RC manipulada com luvas de látex contaminadas; VC ­ RC manipulada com luvas de vinil contaminadas. Após, o conjunto foi seccionado em uma máquina de corte para a obtenção dos palitos com área aproximada de 1 mm², que foram armazenados em água destilada a 37°C por 6 meses. O teste foi realizado em uma má- quina de ensaio (EMIC), com velocidade de 0,5 mm/ min. Os valores de resistência adesiva foram calculados (MPa) e comparados por uma análise de Weibull. Resultados: o grupo com maior resistência adesiva foi o LV (38,7 MPa). A análise de Weibull apenas das falhas adesivas demonstrou que a resistência característica de LV e VC foi superior que a LL. Conclusão: a manipulação da RC com luvas de vinil resulta em maior resistência de união à dentina se comparada à manipulação com luvas de látex limpas.

Influence of surface finishing on fracture load and failure mode of glass ceramic crowns.

STATEMENT OF PROBLEM: Ceramic restorations often require adjustments using diamond rotary instruments, which damage the glazed surface. The effect of these adjustments on the fracture behavior of these restorations is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the influence of induced surface defects on the fracture load and mode of failure of lithium disilicate-based (LDS) glass ceramic restorations. MATERIAL AND METHODS: Premolar crowns were obtained from LDS computer-aided design and computer-aided manufacturing blocks (n=60) and glazed. The crowns were bonded to dentin analog dies and divided into 5 groups (n=12), as follows: glaze; abrasion (diamond rotary instrument 2135); abrasion and reglaze; abrasion and polishing (diamond rotary instrument 2135F, 2135 FF, and polishing devices); and polishing. The topography of the crowns was examined by scanning electron microscopy, and roughness was measured. A compressive load (0.5 mm/min) was applied by a piston to the center of the lingual cusp until fracture. The fracture load was recorded and data were statistically analyzed by ANOVA and the Tukey HSD test (α=.05). Fractured crowns were examined to determine the fracture origin. RESULTS: Polishing and/or reglazing resulted in lower roughness than for the abraded group (P<.05), which did not affect the fracture loads (P=.696). Catastrophic fracture with origin at the intaglio surface was the mode of failure for all the crowns. CONCLUSIONS: The experiment design successfully submitted the crowns to a clinical stress state, resulting in a clinically relevant failure. Reglazing or polishing were effective in reducing surface defects. Surface treatments had no effect on the immediate catastrophic failure of LDS crowns.

Reliability and mode of failure of bonded monolithic and multilayer ceramics.

OBJECTIVES: To evaluate the reliability of monolithic and multilayer ceramic structures used in the CAD-on technique (Ivoclar), and the mode of failure produced in ceramic structures bonded to a dentin analog material (NEMA-G10). METHODS: Ceramic specimens were fabricated as follows (n=30): CAD-on- trilayer structure (IPS e.max ZirCAD/IPS e.max Crystall./Connect/IPS e.max CAD); YLD- bilayer structure (IPS e.max ZirCAD/IPS e.max Ceram); LDC- monolithic structure (IPS e.max CAD); and YZW- monolithic structure (Zenostar Zr Translucent). All ceramic specimens were bonded to G10 and subjected to compressive load in 37°C distilled water until the sound of the first crack, monitored acoustically. Failure load (Lf) values were recorded (N) and statistically analyzed using Weibull distribution, Kruskal-Wallis test, and Student-Newman-Keuls test (α=0.05). RESULTS: Lf values of CAD-on and YZW structures were statistically similar (p=0.917), but higher than YLD and LDC (p<0.01). Weibull modulus (m) values were statistically similar for all experimental groups. Monolithic structures (LDC and YZW) failed from radial cracks. Failures in the CAD-on and YLD groups showed, predominantly, both radial and cone cracks. SIGNIFICANCE: Monolithic zirconia (YZW) and CAD-on structures showed similar failure resistance and reliability, but a different fracture behavior.

A new operative method for obtaining full-arch prostheses for immediate loading dental implants.

PURPOSE: Implant supported full-arch immediate prosthesis (also called the immediate Brånemark protocol) revolutionized dental clinical practice due to the aesthetic/functional benefits it offers to the patient. This work presents a simplified and efficient technique for implant supported full-arch immediate prosthesis fabrication. METHODS: After diagnosing the necessity of the protocol, the implants were installed with a minimum torque of 35Ncm. For implant impression, the use of previously prepared castable cylinders (dispensing with impression posts), and a U-shaped acrylic (Mello technique) generated a cast without distortion. The Brånemark protocol was fabricated on this cast without the metal test specimen. CONCLUSION: The simplified technique proposed in this article for Brånemark protocol fabrication seemed to be effective.

Influence of drying time of adhesive systems on the bond strength between resin cement and feldspathic ceramic / nfluência do tempo de secagem de sistemas adesivos na resistência de união entre cimento resinoso e cerâmica feldspática

Objetivo: Este estudo se propôs avaliar o efeito de diferentes tempos de secagem de dois adesivos tipo ‘total-etch & rinse’ e ciclagem térmica na resistência adesiva entre cerâmica feldspatica e cimento resinoso. Material e Métodos: Trinta e dois blocos (12×10×4 mm) de cerâmica feldspática e respectivos blocos (32) de resina composta foram obtidos. A superfície de cimentação de cada bloco cerâmico foicondicionada por ácido fluorídrico (HF), silanizada (S), e recebeu a aplicação de um dos dois sistemas adesivos testados (SB - Single Bond 2, 3M-ESPE; ou PB – Prime & Bond NT, Dentsply). Então a superfície com o adesivo foi seca em diferentes tempos (5, 10 e 15s) antes da cimentação. Após, um cimento resinoso foi aplicado sobre a superfície de cimentação e o bloco correspondente de resina foi cimentado. Os palitos para microtração foram obtidos, sendo que metade deles foram imediatamente testados, enquanto os demais foram submetidos à ciclagem térmica e armazenagem (150 dias). Para os grupos sem envelhecimento, o tempo de secagem mais longo (15s) aumentou a resistência para o adesivo SB, enquanto que reduziu a resistência para o adesivoPB. Resultados: Para os grupos envelhecidos, as resistências adesivas dos diferentes tempos de secagem não foram diferentes estatisticamente, independente do adesivo. A falha predominante foi coesiva do cimento resinoso, seguido pela falha na interface cerâmica cimento. Conclusão: Conclui se que tempos mais longos de secagem podem melhorar a resistência adesiva à cerâmica testada, usando o adesivo SB. Por outro lado, tempos mais curtos podem otimizar a adesão para o adesivo PB. O envelhecimento afetou a adesão somente nos grupos do adesivo SB

Objective: This study evaluated the effect of drying times of two total-etch & rinse adhesives on the resin bond strength to a feldsphatic ceramic, before and after aging. Material and Methods:Feldsphatic-ceramic CAD-CAM bars were cut into blocks (12×10×4 mm) with a cutting machine (N = 32). Impressions were made of each ceramic block with silicone putty material and the negativespace was filled with a composite resin. The bonding ceramic surface was etched with hydrofluoric acid, silanized, and the adhesive system (SB- Single Bond 2, 3M-ESPE; or PB- Prime & Bond NT, Dentsply) was applied. The samples were dried at different times (5, 10 and 15 s) before the cementation. The resin and ceramic blocks were cemented bya dual cure resin cement. All samples were stored in distilled water at 37 °C for 24 h. For the μ-TBS test, the samples were sliced into microbars. Half of the bars of each block was tested after 24 h and, the other bars were submitted to thermocycling (12,000×) and water storage (150 d). For the 24 h groups, the longer drying time increased (p < 0.05) the bond strength of SB (water/alcohol adhesive), while reduced (p < 0.05) for the PB group (acetone based adhesive). Results: For the aged groups, the bond strength for the different drying times had no significant difference, for the both adhesives. Conclusion: Longer drying times increased the bond strength values of SB. Smaller drying times increased the bond strength values of PB. The aging protocol influenced the bond strength of SB groups.

Influence of CAD-CAM diamond bur deterioration on surface roughness and maximum failure load of Y-TZP-based restorations.

PURPOSE: To investigate the influence of CAD-CAM diamond bur deterioration on surface roughness (Ra) and maximum failure load (Lf) of Y-TZP-based ceramic (YZ) substructures (SB) veneered with a feldspathic porcelain. METHODS: Two sets of burs (B1 and B2) were used to fabricate 30 YZ SB each in a CAD/CAM system (Cerec InLab). The SB were identified (1-30) according to the milling sequence (MS). SEM images of the burs were recorded before milling, and after milling 15 and 30 SB. The SB Ra was measured. All SB were veneered, cemented onto a fiber reinforced epoxy resin die, and loaded to failure. Specimens from B1 group were cyclic fatigued (106 cycles) before loading to failure. Fractographic analysis was performed. Data were statistically analyzed using Student's t-test, Weibull analysis, Pearson's correlation and ANOVA (α= 0.05). RESULTS: The mean Ra value of B1 specimens was statistically greater than B2. Weibull modulus of B1 and B2 were statistically similar. The correlation between MS and Lf was not statistically significant for the groups. MS and Ra had significant correlation for both groups (B1: r= -0.514, P= 0.015; B2: r= -0.462, P= 0.03). Although the visual aspect (SEM) of the burs was similar after 30 millings, the mean Ra values were significantly different after 27 millings for B1 and 24 millings for B2.

Finite element analysis of the influence of geometry and design of zirconia crowns on stress distribution.

PURPOSE: To evaluate the influence of the geometry and design of prosthetic crown preparations on stress distribution in compression tests, using finite element analysis (FEA). MATERIALS AND METHODS: Six combinations of 3D drawings of all-ceramic crowns (yttria-stabilized zirconia framework and porcelain veneer) were evaluated: F, flat preparation and simplified crown; FC, flat preparation and crown with contact point; FCM, flat preparation and modified crown; A, anatomical preparation and simplified anatomical crown framework; AC, anatomical preparation and crown with contact point; and ACM, anatomical preparation and modified crown. Bonded contact types at all interfaces with the mesh were assigned, and the material properties used were according to the literature. A 200 N vertical load was applied at the center of each model. The maximum principal stresses were quantitatively and qualitatively analyzed. RESULTS: The highest values of tensile stress were observed at the interface between the ceramics in the region under the load application for the simplified models (F and A). Reductions in stress values were observed for the model with the anatomical preparation and modified infrastructure (ACM). The stress distribution in the flat models was similar to that of their respective anatomical models. CONCLUSIONS: The modified design of the zirconia coping reduces the stress concentration at the interface with the veneer ceramic, and the simplified preparation can exert a stress distribution similar to that of the anatomical preparation at and near the load point, when load is applied to the center of the crown.