Feldspathic and Lithium Disilicate Onlays with a 2-Year Follow-Up: Split-Mouth Randomized Clinical Trial.

The present study was a prospective, controlled, randomized, clinical short-term trial aiming to evaluate the clinical performance of adhesively luted, lithium disilicate and feldspathic glass-ceramics onlays over a period up to 2 years. A total of 11 patients (7 female, 4 male; age range: 18-60 years, mean age: 39 years) were selected for this study. Each patient received a maximum of two restorations per group in a split-mouth-design. LD: Eleven onlays, performed with lithium disilicate-based ceramic (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein), and FP: Eleven onlays, performed with feldspathic ceramic (Vita Mark II, Vita Zanhfabrik, Bad Säckingen). Recalls were performed at 2 weeks (baseline = R1), 1 year (R2) and 2 years (R3) after the cementation by three calibrated blinded independent investigators using mirrors, magnifying eyeglasses, probes and bitewing radiographs. The postoperative sensitivity, secondary caries, marginal integrity, marginal discoloration, color match, surface roughness, tooth integrity, and restoration integrity were evaluated. The Friedman test was used to determine if there was a statistically significant difference in time-to-time comparison of the parameters in the ceramics restorations. A total of 95.4% of the restorations were clinically acceptable at the 2-year recall, without a difference for any evaluation parameter for both ceramic materials. Based on the 2-year data, the CAD-CAM onlays manufactured with feldspathic and lithium-disilicate based ceramics showed similar clinical performance.

Feldspathic and Lithium Disilicate Onlays with a 2-Year Follow-Up: Split-Mouth Randomized Clinical Trial

Abstract The present study was a prospective, controlled, randomized, clinical short-term trial aiming to evaluate the clinical performance of adhesively luted, lithium disilicate and feldspathic glass-ceramics onlays over a period up to 2 years. A total of 11 patients (7 female, 4 male; age range: 18-60 years, mean age: 39 years) were selected for this study. Each patient received a maximum of two restorations per group in a split-mouth-design. LD: Eleven onlays, performed with lithium disilicate-based ceramic (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein), and FP: Eleven onlays, performed with feldspathic ceramic (Vita Mark II, Vita Zanhfabrik, Bad Säckingen). Recalls were performed at 2 weeks (baseline = R1), 1 year (R2) and 2 years (R3) after the cementation by three calibrated blinded independent investigators using mirrors, magnifying eyeglasses, probes and bitewing radiographs. The postoperative sensitivity, secondary caries, marginal integrity, marginal discoloration, color match, surface roughness, tooth integrity, and restoration integrity were evaluated. The Friedman test was used to determine if there was a statistically significant difference in time-to-time comparison of the parameters in the ceramics restorations. A total of 95.4% of the restorations were clinically acceptable at the 2-year recall, without a difference for any evaluation parameter for both ceramic materials. Based on the 2-year data, the CAD-CAM onlays manufactured with feldspathic and lithium-disilicate based ceramics showed similar clinical performance.

Resumo O presente estudo é um estudo clínico prospectivo, controlado, randomizado e de longo curto prazo, com o objetivo de avaliar o desempenho clínico de restauraç ões adesivas cerâmica vítrea reforçada com dissilicato de lítio e cerâmica feldspática por um período de até 2 anos. Um total de 11 pacientes (7 mulheres, 4 homens; faixa etária: 18-60 anos, idade média: 39 anos) foram inseridas para este estudo. Cada paciente recebeu duas restaurações por grupo em um delineamento de boca dividida. LD: Onze onlays, realizados com cerâmica à base de dissilicato de lítio (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein); e FP: Onze onlays, realizados com cerâmica feldspática (Vita Mark II, Vita Zanhfabrik, Bad Säckingen). Os retornos foram realizados em 2 semanas (linha de base = R1), 1 ano (R2) e 2 anos (R3) após a cimentação, por três investigadores independentes, cegos e calibrados, usando espelhos, óculos de aumento, sondas e radiografias interproximais. Foram avaliadas a sensibilidade pós-operatória, cárie secundária, integridade marginal, descoloração marginal, correspondência de cores, rugosidade da superfície, integridade dentária e integridade da restauração. O teste de Friedman (95%) foi utilizado para determinar se havia uma diferença estatisticamente significante na comparação periódica dos parâmetros nas restaurações cerâmicas. Um total de 95,4% das restaurações estava clinicamente aceitável no retorno de 2 anos, sem diferença para qualquer parâmetro de avaliação para ambos os materiais cerâmicos. Com base nos dados de 2 anos, as restaurações CAD-CAM fabricados com cerâmica feldspática e à base de dissilicato de lítio apresentaram desempenho clínico semelhante.

Efficacy of fluoride varnishes with different compositions on white spot lesions remineralization / Eficácia de vernizes fluoretados com diferentes composições na remineralização de manchas brancas

Objective: To evaluate the efficacy of different fluoride varnishes on white spot lesions (WSL) remineralization. Material and Methods: Polished bovine enamel specimens were obtained (n = 60) and had their initial surface Knoop microhardness (SMH) determined. WSL were created and the SMH was measured again. Then, specimens were allocated into six groups: C ­ Control (without varnish); BF ­ Bifluorid 12 (6% NaF + 6% CaF2); DP ­ Duraphat (5% NaF); PF ­ Profluorid (5% NaF); FP - Fluor Protector (0.2% NaF + 0.9% difluorsilane); CW - Clinpro White Varnish (5% NaF + 5% TCP). After varnishes application, specimens were immersed in artificial saliva for 24 h. Then, pH-cycling was performed for 8 days and SMH was measured. Data were analyzed by one-way ANOVA and Tukey's test. Results: Non-significant differences were observed among the groups at baseline (p = 0.187) and after WSL formation (p = 0.999). After treatments, significant differences were observed among the groups (p = 0.001). Mean % of alteration (SD) and results of Tukey test were: C- 92.40 (12.10)a; PF- 88.66 (10.66)a; FP- 85.90 (14.49)ab; BF- 67.85 (17.86)bc; CW- 66.60 (18.48)c; DP- 58.62 (8.69)c. Conclusion: Bifluorid 12, Clinpro White Varnish, and Duraphat showed higher efficacy than artificial saliva in promoting the remineralization of WSL, nevertheless, none of the treatments were able to recover sound enamel baseline microhardness (AU)

Objetivo: Avaliar a eficácia de diferentes vernizes fluoretados na remineralização de lesões de mancha branca (LMB). Material e métodos: Espécimes de esmalte bovino polido (n = 60) foram submetidos à análise de microdureza superficial Knoop (KMH) inicial. Foram então criadas LMB artificialmente e os espécimes foram alocados em seis grupos: C ­ Controle (sem aplicação de verniz); BF ­ Bifluorid 12 (6% NaF + 6% CaF2); DP ­ Duraphat (5% NaF); PF ­ Profluorid (5% NaF); FP - Fluor Protector (0.2% NaF + 0.9% difluorsilano); CW - Clinpro White Varnish (5% NaF + 5% TCP). Após a aplicação dos vernizes, os espécimes ficaram imersos em saliva artificial por 24h e uma ciclagem de pH foi realizada por 8 dias. Após a ciclagem, KMH final foi realizada. Os dados foram analisados por ANOVA e teste de Tukey (5%). Resultados: Não foi observada diferença significante para os grupos após a KHM inicial (p = 0.187) e após a formação de LMB (p = 0.999). Após os tratamentos, diferenças significativas foram observadas entre os grupos (p = 0.001). Valores de média de % de alteração superficial (desvio-padrão) e resultados do teste de Tukey foram: C- 92.40 (12.10)a; PF- 88.66 (10.66)a; FP- 85.90 (14.49)ab; BF- 67.85 (17.86)bc; CW- 66.60 (18.48)c; DP- 58.62 (8.69)c. Conclusão: Os vernizes Bifluorid 12, Clinpro White Varnish e Duraphat apresentaram maior eficácia na remineralização das LMB quando comparados à saliva artificial, entretanto, nenhum dos produtos testados foi capaz de recuperar os valores iniciais de microdureza. (AU)

Effect of framework type on survival probability of implant-supported temporary crowns: An in vitro study.

BACKGROUND: This in vitro study evaluated the effect of framework type on the survival probability of temporary implant-supported crowns and on the implant platform structure after dynamic fatigue. MATERIAL AND METHODS: Thirty (30) external hexagon implants (3.75 x 10 mm) were embedded in acrylic resin following the ISO-14801. Standardized temporary crowns (n=10, N=30) were manufactured in acrylic resin and divided according to the framework type: Total plastic, Plastic with CoCr base and Titanium. The crowns were installed onto the implants (20N.cm) and fatigued (100N, 2 Hz) to determine the crowns' survival probability for missions of 300.000 and 600.000 cycles. Fatigue data were submitted to the Kaplan-Meier test followed by Wilcoxon and Log Rank, all with α = 5%. The implant platforms were parametrically inspected based on the scanning before and after the fatigue to evaluate the damage. The strain values were analyzed using One-way ANOVA and Tukey test, all with α = 5%. RESULTS: ANOVA revealed that the Total plastic showed less implant damage (-0.07 ± -0.03 mm) than the Plastic with CoCr base (-0.08 ± -0.04 mm) and the Titanium (-0.10 ± -0.01 mm) frameworks. Therefore, the framework type to manufacture implant-supported temporary crowns influences the fatigue survival of the restoration and the implant platform damage. The Plastic with CoCr base and Titanium frameworks showed superior reliability than the Total plastic framework which could not survive 600,000 cycles. CONCLUSIONS: The Plastic with CoCr base and the Titanium framework are suitable for restorations over 3 months in use, without a difference in the implant platform damage. Key words:Implant dentistry, axial loading, occlusion, methodo-logical study.

Does the prosthesis weight matter? 3D finite element analysis of a fixed implant-supported prosthesis at different weights and implant numbers.

PURPOSE: This study evaluated the influence of prosthesis weight and number of implants on the bone tissue microstrain. MATERIALS AND METHODS: Fifteen (15) fixed full-arch implant-supported prosthesis designs were created using a modeling software with different numbers of implants (4, 6, or 8) and prosthesis weights (10, 15, 20, 40, or 60 g). Each solid was imported to the computer aided engineering software and tetrahedral elements formed the mesh. The material properties were assigned to each solid with isotropic and homogeneous behavior. The friction coefficient was set as 0.3 between all the metallic interfaces, 0.65 for the cortical bone-implant interface, and 0.77 for the cancellous bone-implant interface. The standard earth gravity was defined along the Z-axis and the bone was fixed. The resulting equivalent strain was assumed as failure criteria. RESULTS: The prosthesis weight was related to the bone strain. The more implants installed, the less the amount of strain generated in the bone. The most critical situation was the use of a 60 g prosthesis supported by 4 implants with the largest calculated magnitude of 39.9 mm/mm, thereby suggesting that there was no group able to induce bone remodeling simply due to the prosthesis weight. CONCLUSION: Heavier prostheses under the effect of gravity force are related to more strain being generated around the implants. Installing more implants to support the prosthesis enables attenuating the effects observed in the bone. The simulated prostheses were not able to generate harmful values of peri-implant bone strain.

Effect of Framework Type on the Biomechanical Behavior of Provisional Crowns: Strain Gauge and Finite Element Analyses.

The aim of this study was to evaluate the effects of different frameworks on the biomechanical behavior of implant-supported provisional single crowns to indicate or not the use of plastic framework as infrastructure. For finite element analysis, a hemi-jaw stone model was scanned and modeled with an external hexagon implant. A framework was screwed onto the implant and a crown was constructed over it. The set was made in triplicate according to framework type: plastic, cobalt-chromium (CoCr), and titanium. Models were exported in volumetric format to analysis software where structures were considered isotropic, linear, elastic, and homogeneous. Axial loads (100, 200, and 300 N) were applied to the fossa bottom, and the system's fixation occurred on the bone base. For strain-gauge analysis, the same hemi-jaw model was built in polyurethane and an implant was placed on it. Three crowns were made, each one with a different framework. Four strain gauges were glued around the implant to obtain microstrain values. The data were analyzed by three-way analysis of variance (ANOVA) and Tukey tests (P < .05). Finite element analysis exhibited microstrain results for bone, von Mises stress values for the implant and screw, and maximum principal stress values for the crown. For computational method, as the applied load increased, so did the stress generated. Titanium frameworks concentrated more stress in the crown and bone, while plastic ones concentrated more in the implant and screw. ANOVA showed that the higher the load value and the framework elastic modulus, the higher the generated microstrain in bone. It can be concluded that all evaluated framework types can be used in the manufacturing of provisional crowns.

Influence of different alcohol intake frequencies on alveolar bone loss in adult rats: A sem study.

BACKGROUND: Alcohol intake is associated with oral diseases and bone changes including alveolar bone loss in humans and in experimental animals. The main aim of the present study is to assess the effect of long-term alcohol intake, at different frequencies, on periodontal bone loss (PBL) in adult rats. MATERIAL AND METHODS: Thirty-six (36) rats were divided into 3 groups: Control (daily water intake, n=12), daily alcohol intake (20% ethanol, n=12), and social alcohol intake (20% ethanol twice a week, n=12). The rats were sacrificed after 90 days and their right maxillae were removed. Initially, a random portion from each group was analyzed through SEM (scanning electron microscope) to assess surface topography. Next, all pieces were dissected and stained with methylene blue 1% and photographed in stereomicroscope at 10x magnification. The PBL was assessed by measuring the distance between cement-enamel junction and alveolar bone crest. RESULTS: Results showed higher (p=0.0368) alcohol solution amount in the daily intake group than in the twice week intake one. The SEM showed qualitatively flat bone surface in the control group, the social intake group presented surface with few minor hollows, and the daily intake group evidenced increased number and diameter of wells. The comparison between groups showed higher bone loss (p<0.05) in both frequencies than in the control, but the bone loss was lower (p<0.05) in the social alcohol intake group than in the daily intake one. CONCLUSIONS: Alcohol intake may cause alveolar bone loss in periodontitis-free rats depending on the frequency. Key words:Alcohol intake, alveolar bone loss, alcohol-induced periodontitis, alcoholic rats.

Biomechanical effect of inclined implants in fixed prosthesis: strain and stress analysis / Efeito biomecânico de implantes inclinados em prótese fixa: analise das tensões e deformações

Introduction: Implant inclinations can be corrected using mini abutments at different angulations. Objective: To analyze the influence of external hexagon implants in different inclinations (3 levels) on the microstrain distribution generated around three implants. Method: A geometric bone model was created through Rhinoceros CAD software (version 5.0 SR8, Mcneel North America, Seattle, WA, USA). Three implants (4.1 × 13 mm) were modeled and inserted inside the substrate at three different inclinations: 0º, 17º and 30º. Next, all groups received mini conical abutments, fixation screws and a simplified prosthesis. The final geometry was exported in STEP format to analysis software and all materials were considered homogeneous, isotropic and linearly elastic. An axial load (300N) was applied on the center of the prosthesis. An in vitro study was conducted with same conditions and groups for validating the tridimentional model. Result: Stress was concentrated on the external area of the implants, in contact with the cortical bone and external hexagon. For the bone simulator, the strain increased in the peri-implant region according to the increase in the implant's inclination. The difference between groups was significant (p = 0.000). The 30º group presented higher stress and strain concentration. Conclusion: The microstrain and stress increase around implants directly proportional to the increase of the installation angle.

Introdução: A inclinação dos implantes pode ser corrigida através de mini-pilares de diferentes angulações. Objetivo: Analisar a influência de implantes com hexágono externo em diferentes inclinações (3 níveis) na distribuição de microdeformações geradas em torno de três implantes. Método: Um modelo geométrico de osso foi criado através do software CAD Rhinoceros (versão 5.0 SR8, Mcneel North America, Seattle, WA, EUA). Três implantes (4,1 × 13 mm) foram modelados e inseridos no interior do substrato em três diferentes inclinações: 0º, 17º e 30º. Em seguida, todos os grupos receberam mini-pilares cônicos, parafusos de fixação e prótese simplificada. A geometria final foi exportada em formato STEP para software de análise e todos os materiais foram considerados homogêneos, isotrópicos e linearmente elásticos. Uma carga axial (300N) foi aplicada no centro da prótese. Um estudo in vitro foi conduzido com as mesmas condições e grupos para validar o modelo tridimensional. Resultado: A concentração de tensão ocorreu na área externa dos implantes, em contato com o osso cortical e o hexágono externo. Para o simulador ósseo, a deformação aumentou na região peri-implantar de acordo com o aumento da inclinação do implante. A diferença entre os grupos foi significativa (p = 0.000). O grupo de 30º apresentou maior concentração de tensão e deformação. Conclusão: O aumento da microdeformação e das tensões ao redor dos implantes aumenta diretamente proporcional ao aumento do ângulo de instalação.

The importance of correct implants positioning and masticatory load direction on a fixed prosthesis.

BACKGROUND: Through the biomechanical study of dental implants, it is possible to understand the dissipation effects of masticatory loads in different situations and prevent the longevity of osseointegration. Aims: To evaluate the microstrains generated around external hexagon implants, using axial and non-axial loads in a fixed four-element prosthesis with straight implants and implants inclined at 17°. MATERIAL AND METHODS: Three implants were modeled using CAD software following the manufacturer's measurements. Then, implants were duplicated and divided into two groups: one with straight implants and respective abutments, and the other with angled implants at 17° and respective abutments. Both groups were arranged inside a block simulating bone tissue. A simplified fixed prosthesis was installed on both groups and the geometries were exported to CAE software. Five loads of 300N were performed at axial and non-axial points on the fixed prosthesis. Stress on the implants and strain on the block were both analyzed. An in vitro experiment was performed following all structures made in FEA in order to validate the model. In each experimental block, 4 strain gauges were linearly placed between the implants and the same loads were repeated with a loading applicator device. RESULTS: The deformations computed by the gauges were correlated with the FEA results, showing that the group with inclined implants had more damaging biomechanical behavior and was significantly different from the group with straight implants (P<0.005). CONCLUSIONS: The mathematical model used is valid and inclined implants can induce unwanted bone remodeling. Key words:Finite Element Analysis, Dental Implants, Fixed Prosthesis.

Validation of a Simplified Implant-Retained Cantilever Fixed Prosthesis.

PURPOSE: To evaluate the stress and strain generated in a fixed four-element prosthesis under the application of axial and nonaxial loads using a simplified implant-supported fixed prosthesis model. MATERIALS AND METHODS: A 3-dimensional model was constructed containing 3 implants with a conventional anatomical prosthesis (G1). The second model with the same implant system received the simplified prosthesis (G2). A load of 300 N was applied at an axial point and a nonaxial point through finite element analysis software. RESULTS: The G2 group showed different values of stress concentration in the prosthesis, fixation screw, retention screw, and abutments when compared with G1. Within a limit of 10% degrees of acceptability, the stress on the implants and the bone strain were enclosed for both models of prostheses. CONCLUSION: The simplified fixed prosthesis evaluated presents biomechanical behavior similar to an anatomical prosthesis in the implants and in the surrounding bone structure.