Analysis of enamel and material wear by digital microscope: an in-vitro study

Abstract: The objective of the study was to analyze the surface area (SA) of the wear caused by simulated chewing on human enamel and opposing restorative material, namely: composite resin (CR), porcelain fused to metal (PFM), lithium disilicate (LD), or monolithic zirconia (MZr). Forty-eight premolars were selected as enamel specimens and divided randomly into 4 groups (n = 48; n =12) used as antagonists in chewing simulation (250,000 loading cycles) against one of the four selected test materials. Enamel and material specimens were scanned and evaluated under digital microscope, and wear SA (mm2) were recorded. Descriptive statistics, paired t-test, one-way ANOVA, and post-hoc Tukey-HSD tests were used for statistics (p < 0.05). The smallest and largest SA were exhibited by enamel against LD (0.80 mm2) and PFM (1.74 mm2), respectively. PFM (3.48 mm2) showed the largest SA and CR (2.28 mm2) showed the smallest SA. Paired t-test for SA values showed significant difference (p < 0.05) in all wear comparisons between materials and enamel antagonists. The wear of materials were greater than that of their respective enamel antagonists (p < 0.05). One-way ANOVA of the logarithmic means of wear SA revealed significant differences (P<0.05). Post-hoc Tukey test revealed significance for PFM (p < 0.05) with other materials. Wear of all test materials was greater compared to the wear of enamel antagonists. PFM and LD caused the largest and the smallest enamel wear, respectively. CR, LD, and MZr are more resistant than PFM to wear after simulated chewing against enamel.

Deformações geradas no intermediário e região peri-implantar após aplicação de cargas inclinadas em coroas unitárias / Deformation generated in the abutment and peri-implant bone after application of an oblique load or metal-ceramic crowns

A reabilitação protética de pacientes desdentados é uma área da Odontologia amplamente estudada por pesquisadores do mundo todo, e com o desenvolvimento dos implantes osseointegrados surgiram muitas perguntas sobre o desempenho das próteses instaladas sobre estes. Conhecer o comportamento mecânico do conjunto coroa unitária, intermediário, implante e tecido de suporte é importante para entender o processo de transmissão de forças e suas consequências, processos estes que ainda não estão totalmente compreendidos. O objetivo deste trabalho foi verificar a deformação gerada no intermediário e no osso peri-implantar após aplicação de uma carga inclinada sobre coroas unitárias metalocerâmicas. Foi utilizado um modelo mestre de poliuretano, simulando o osso mandibular, com um implante hexágono externo de 3,75mm x13 mm de comprimento, no qual foi fixado um intermediário multi-unit. O trabalho foi realizado com 3 grupos de 4 coroas cada, divididos de acordo com o tipo de cilindro e liga de fundição (cilindros de ouro sobrefundidos com liga de PdAg, cilindro de acrílico fundido com liga de NiCoCr e cilindros de CoCr usinado sobrefundidos com liga de NiCoCr). Cada corpo de prova foi submetido cinco vezes à aplicação de carga oblíqua de 15 e 30 graus no centro da oclusal de cada coroa com uma força de 300N em uma máquina universal de ensaios. Foram realizadas leituras das deformações geradas no intermediário e no poliuretano, com o uso de extensômetros lineares elétricos (strain gauges) os quais foram colados em três faces do intermediário (Disto lingual, Mesio lingual, Vestibular) e nas superfícies mesial, vestibular, distal e lingual do osso simulado ao redor do implante. Os dados obtidos foram submetidos à análise de variância a 3 critérios (ANOVA) e o teste de Tukey, utilizando um nível de significância (p<0,05). Os resultados mostraram que entre as duas angulações utilizadas existiram diferenças estatísticas significantes. Os valores médios de deformação se...

The prosthetic rehabilitation of edentulous patients is a dental area widely studied by worldwide researchers, and through the development of dental implants, appear many questions about the performance of prostheses installed on them. Knowledge of the mechanical behavior of the integration between single crown, abutment, implant and support tissue is very important to understand the forces transmission process and its consequences but these processes are not fully understood. The objective of the present study was to evaluate the deformation generated in the abutment and simulated peri-implant bone after application of an oblique load on metal-ceramic crowns. A polyurethane master model was used to simulate the jawbone with an implant external hexagon 3.75 mm x13 mm length, which was fixed in a multi-unit abutment. The study was conducted with twelve metal ceramic crowns divided according to type of cylinder and casting alloy, Group 1: Gold cylinder cast with PdAg alloy; Group 2: Acrylic cylinder cast with NiCoCr alloy; Group 3: CoCr cylinder cast with NiCoCr alloy, thus forming three groups of four sample each. Each specimen was subjected five times the application of oblique load of 15 and 30 degrees in the center of the occlusal of each crown with a 300N force in a universal testing machine. Readings were taken of the deformations generated in the abutment and bone simulated by polyurethane, with the use of electric linear strain gauges which have been positioned on three sides equidistant to each other to measure microstrains at abutment (disto-lingual, meso-lingual, Vestibular) and the simulated bone around each implant received four strain gauges, positioned on the mesial, distal, buccal and lingual aspects. The data were submitted to analysis of variance to 3 criteria (ANOVA) and Tukey test, using a significance level (p <0.05). The results showed that between the two angles tested there were significant statistical differences...

Does the casting mode influence microstructure, fracture and properties of different metal ceramic alloys?

The aim of the present study was to evaluate the tensile strength, elongation, microhardness, microstructure and fracture pattern of various metal ceramic alloys cast under different casting conditions. Two Ni-Cr alloys, Co-Cr and Pd-Ag were used. The casting conditions were as follows: electromagnetic induction under argon atmosphere, vacuum, using blowtorch without atmosphere control. For each condition, 16 specimens, each measuring 25 mm long and 2.5 mm in diameter, were obtained. Ultimate tensile strength (UTS) and elongation (EL) tests were performed using a Kratos machine. Vickers Microhardness (VM), fracture mode and microstructure were analyzed by SEM. UTS, EL and VM data were statistically analyzed using ANOVA. For UTS, alloy composition had a direct influence on casting condition of alloys (Wiron 99 and Remanium CD), with higher values shown when cast with Flame/Air (p < 0.05). The factors 'alloy" and 'casting condition" influenced the EL and VM results, generally presenting opposite results, i.e., alloy with high elongation value had lower hardness (Wiron 99), and casting condition with the lowest EL values had the highest VM values (blowtorch). Both factors had significant influence on the properties evaluated, and prosthetic laboratories should select the appropriate casting method for each alloy composition to obtain the desired property.

Internal fit of two all-ceramic systems and metal-ceramic crowns

OBJECTIVES: The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA - In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD), and metal-ceramic (MC - Ni-Cr alloy) crowns. MATERIAL AND METHODS: Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey ’s multiple comparison test (p<0.05). RESULTS: No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. CONCLUSIONS: The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS.

Assessment of convergence angle of full-coverage porcelain fused to metal crowns in clinical practice.

Background: Full-coverage porcelain fused to metal crowns is commonly recommended for restoration of extensively damaged teeth. Ability of the dentist to adequately prepare teeth is fundamental to success and longevity of these restorations. Aims: This study was designed to compare recommended convergence angle and taper values of tooth preparation with clinically practiced values and to assess the factors such as tooth position, operator experience, vitality, and restorative status on convergence angle of prepared teeth. Setting and Design: It was a descriptive, cross-sectional study design and held at The Aga Khan University Hospital, Dental Section, for a period of 1 year. Materials and Methods: A minimum of 197 crown preparation models of molar and premolar teeth prepared by residents and specialists were collected in order to achieve the objectives of the study on the basis of convenient sampling technique. Statistical Analysis: One sample t-test used to compare the mean practiced convergence angle values with its recommended values. Independent sample t-test and one-way ANOVA was used to see difference in the convergence angle values of the teeth prepared by different operators, tooth type, vitality status, and restorative status of teeth. Results: Mean reported convergence angle and axial wall taper values were 23.7°±8.9° and 11.3°±7.8°, respectively, which is significantly greater (P<0.001) than the recommended values. Convergence angle values were greater for molars as compared to premolars. Conclusion: There was a considerable disparity between the convergent angles values recorded in this study and the recommended guidelines and are affected by tooth type, vitality, and restorative status of tooth.

A finite element thermal analysis of various dowel and core materials.

Aim: Thermal analysis of the temperature and stress distribution of parallel sided, threaded and non-threaded dowels and core materials under thermal loading within a maxillary central incisor using a three dimensional finite element study. Materials and Methods: 3D models of endodontically treated maxillary central incisor with parallel sided, threaded and non- threaded post and core materials were simulated using the ANSYS software. Materials simulated were parallel sided cast gold post and core, parallel sided fibre reinforced composite (FRC) post and core, and parallel sided, threaded, prefabricated stainless steel post and amalgam core. Thermal loads simulating hot (60 degree C/ 333K) and cold (15 degree C/288K) liquid were applied for 15 seconds at the incisal edge. The temperature changes at the selected nodes were obtained on the various post and core materials, interface between post and dentin, interface between core and dentin, within the dentin and within the cement layer. Results: Temperature and stress distribution pattern were represented in numerical and color coding and results interpreted. Thermal stresses arises as a result of temperature changes. A decreased temperature gradient of the metallic dowels and core (T1 hot - 0.002K, T3 hot - 1.071K, T1 cold -0.99K, T3 cold - 0K) were obtained than that of the FRC dowel and core of 1.982K(hot) and1.55K(cold) respectively due to the higher thermal conductivity of the metals. Higher thermal stress values of 3.567 Mpa(hot) and 3.092 Mpa(cold) respectively were obtained for the FRC dowels and higher stress values of 39.679 Mpa(hot) and 57.855 Mpa(cold) respectively were also obtained for the FRC cores. These values indicated that thermal stresses of the FRC dowel and core were greater than that of cast gold dowel and core and prefabricated stainless steel dowel and amalgam core due to its high coefficient of thermal expansion. Maximum stress values of the FRC dowel and core of 1.87 Mpa(hot) and 2.57 Mpa(cold) respectively were also generated in the cement layer, core and metal ceramic crown. The junction of the metal ceramic crown and dentin demonstrated the maximum stress. Higher thermal stress values of 59.162 ± 10 Mpa were obtained in the restoration and the coronal portion of the dentin than the stress levels of .0039 ± 10Mpa in the supporting bone due to an increased thermal expansion. Conclusion: Non-metallic dowel and core materials such as fibre reinforced composite dowels (FRC) generate greater stress than metallic dowel and core materials. This emphasized the preferable use of the metallic dowel and core materials in the oral environment.

Impact of rehabilitation with metal-ceramic restorations on oral health-related quality of life

Dental ceramics present excellent ability to reproduce the natural teeth regarding esthetic and biomechanics. Recently, due to the advancement of ceramic technology, metal-free restorations were developed. However, the traditional metal-ceramic restorations still present the requirements of high strength, long survival in the oral environment and favorable aesthetics. In this context, it is essential to know the specificity of each ceramic system available in order to apply it properly to various clinical situations. This report describes an integrated rehabilitation using metal-ceramic restorations of a patient at 50 years of age, who presented edentulous spaces, and previous unsatisfactory composite and amalgam restorations, and indirect metallic restorations, leading to compromised quality of life in both functional and psychosocial aspects. The impact on quality of life was measured using a generic instrument, OHIP-14, validated for the World Health Organization, which covers both the biological and the psychosocial dimensions. This instrument was applied to the patient before and after treatment. The patient had an overall OHIP-14 score of 28 before the treatment and after treatment the score decreased to 0, showing that dental and oral health conditions are factors that do impact on the quality of life. Rehabilitation has provided functional and aesthetic restorations, harmony of the stomatognathic system and improvement of life quality.

As cerâmicas dentais são conhecidas pela excelência em reproduzir artificialmente dentes naturais. Recentemente, devido ao aprimoramento da tecnologia cerâmica, surgiram as restaurações livres de metal. Entretanto, as tradicionais metalocerâmicas ainda preenchem adequadamente os requisitos de alta resistência, longa sobrevida em meio bucal e estética favorável. Neste contexto, é fundamental conhecer a especificidade de cada sistema cerâmico a fim de indicá-lo adequadamente às diversas situações clínicas. Este artigo relata um caso de reabilitação integral e integrada de paciente de 50 anos de idade, portador de espaços edêntulos, restaurações protéticas posteriores e restaurações diretas anteriores insatisfatórias, resultando em comprometimento da qualidade de vida nos âmbitos funcional e psicossocial, utilizando coroas metalocerâmicas. O impacto na qualidade de vida foi mensurado utilizando um instrumento genérico, OHIP-14, validado pela Organização Mundial de Saúde, que abrange tanto a dimensão biológica, como a dimensão psicossocial. Este instrumento foi aplicado à paciente antes e após o tratamento, obtendo pontuação total de 28 e 0 respectivamente, o que mostra que a condição de saúde oral representa fator de grande impacto sobre a qualidade de vida. A reabilitação oral proporcionou restabelecimento funcional e estético, harmonia do sistema estomatognático e melhoria da qualidade de vida da paciente.

Oxidation heat treatment affecting metal-ceramic bonding.

Aim of the Study: There is dearth of literature regarding the effects of oxidation heat treatment (OHT) as surface pretreatments on bond strength of base metal alloys and porcelain. Materials and Methods: Forty-five bar specimens of each two commercially available base metal alloys Mealloy and Wirorn-99 (were fabricated. Dimensions of each specimen were 15.0 × 2.0 × 0.5 mm (according to the ISO 6872-1984). According to the surface pretreatments the samples of the two groups were categorized into three subgroups: With OHT only, with sandblasting only (with Al 2 O 3 of 110 μm) and with OHT and sandblasting. Application of commercially available Duceram porcelain in thickness of 2.00 mm was applied over the surface of metal with the pretreatments. Samples were then placed under SEM for EDX examination to evaluate ionic changes that occurred at the metal-ceramic interface. Flexural bond strength of each sample was calculated under Universal Testing Machine. Results: The one-way ANOVA indicated no significant influence of either metal type (P=0.811) or any surface pretreatment (P=0.757) on the metal-ceramic bond strength. Conclusion: OHT resulted in the increase in amount of oxides at the metal-ceramic interface. However, neither metal type nor surface pretreatments affected bond strength.

Effect of laser welding on the titanium ceramic tensile bond strength

Titanium reacts strongly with elements, mainly oxygen at high temperature. The high temperature of titanium laser welding modifies the surface, and may interfere on the metal-ceramic tensile bond strength. OBJECTIVE: The influence of laser welding on the titanium-ceramic bonding has not yet been established. The purpose of this in vitro study was to analyze the influence of laser welding applied to commercially pure titanium (CpTi) substructure on the bond strength of commercial ceramic. The influence of airborne particle abrasion (Al2O3) conditions was also studied. MATERIAL AND METHODS: Forty CpTi cylindrical rods (3 mm x 60 mm) were cast and divided into 2 groups: with laser welding (L) and without laser welding (WL). Each group was divided in 4 subgroups, according to the size of the particles used in airborne particle abrasion: A - Al2O3 (250 µm); B - Al2O3 (180 µm); C - Al2O3 (110 µm); D - Al2O3 (50 µm). Ceramic rings were fused around the CpTi rods. Specimens were invested and their tensile strength was measured at fracture with a universal testing machine at a crosshead speed of 2.0 mm/min and 200 kgf load cell. Statistical analysis was carried out with analysis of variance and compared using the independent t test (p<0.05). RESULTS: Significant differences were found among all subgroups (p<0.05). The highest and the lowest bond strength means were recorded in subgroups WLC (52.62 MPa) and LD (24.02 MPa), respectively. CONCLUSION: Airborne particle abrasion yielded significantly lower bond strength as the Al2O3 particle size decreased. Mechanical retention decreased in the laser-welded specimens, i.e. the metal-ceramic tensile bond strength was lower.

In in-vitro evaluation of effect of different finish lines on marginal adaptation in metal-ceramic restorations under thermo-mechanical loading.

The aim of this study was to evaluate the marginal gap in terms of cement film thickness associated with shoulder, shoulder with 45° bevel, shoulder with 30° bevel and chamfer, under thermo-mechanical loading. Forty human mandibular molars were prepared and restored with ceramo-metal crowns. Teeth were thermo-mechanically loaded and vertically sectioned to evaluate the cement film thickness. Shoulder with 45° bevel provided the least marginal gap as compared with all the tested finish lines.

Esthetic correction in open bite.

Deleterious oral habits, which are persistent, can lead to poor esthetics of a beautiful face. Conventional treatment modalities for an open bite usually include orthodontic treatment and/or skeletal surgery. This article focuses on a different treatment modality for an anterior open bite.

Collarless metal ceramic restorations to obscure the umbrella effect.

Esthetics with porcelain fused to metal restoration in the anterior region can be adversely affected due to the inadequate teeth preparations and design of the prosthesis. We presented here a case report where esthetics was compromised due to darkening of the interdental papilla and marginal gingival and overcontoured restorations in relation to porcelain fused to metal restorations. Good esthetic results were obtained by using basic principles of tooth preparation and using collarless metal ceramic restorations.

Porcelain application and simulation of firing cycle: effect on marginal misfit of implant-supported frameworks

Aim: Success of implant-supported prostheses is related to the frameworks’ passive fit, henceinaccuracies can generate stress, leading to bone resorption and rehabilitation failure. This study evaluated misfit levels of implant-supported frameworks after different coverage treatments.Methods: Twenty commercially pure titanium (CP Ti) frameworks were manufactured with 5Branemark type multi-unit abutments. Frameworks were distributed in two groups as follows: G1- porcelain application (n=10); G2 - porcelain firing cycle simulation (n=10). Using a traveling microscope, marginal misfit was measured before and after undertaking the techniques, following the single-screw test protocol. All data were submitted to ANOVA and Tukey’s test (p<0.05).Results: Initial marginal misfit values were not significantly different, but both groups presented significantly higher misfit values after treatment: G1: 233.99 ìm (p=0.0003); G2: 119.75 ìm(p<0.0001). In addition, G1 presented higher misfit than G2 (p<0.0001). Conclusions: Porcelain application promoted significantly higher increase of misfit, which indicates that such procedure should be considered on misfit analysis of implant-supported prostheses.

Influência da ciclagem térmica e diferente tipos de solda na resistência da interface metalo-cerâmica / Influences of thermocycling and different kinds of weld on metal-ceramic interface resistance

O efeito da soldagem e termociclagem na união metalo-cerâmica foi avaliado pela fundição de sessenta barras metálicas em NiCr nas dimensões estabelecidas para o teste de flexão (ISO 9693:1999E). Destas, 20 barras formaram o grupo controle (GC) e 40 foram segmentadas: 20 unidas por brasagem (GB) e 20 soldadas a laser (GL). Uma camada de 1,0mm de cerâmica foi aplicada sobre as barras, as quais receberam (0,1mm de opaco e 0,9mm de dentina) na sua área central e inferior. A área total testada foi de 20mm com carga central. Os tratamentos de superfície do metal, a temperatura e tempos de queima da cerâmica foram os recomendados pelos fabricantes. A metade dos corpos-de-prova foi termociclada (GCT, GBT e GLT). Todos os corpos-de-prova foram submetidos ao teste de flexão de três pontos com célula de carga de 10Kg e velocidade 1,5±0,5mm/min em uma máquina de ensaios universal, e as cargas máximas até a falha inicial foram anotadas. Os dados foram submetidos à análise de variância e ao teste de Tukey. Não houve diferença significante estatisticamente com relação à força máxima até a falha de união metalo-cerâmica para os grupos GB (10,55±1,37N), GL (9,87±1,22N) e grupo controle GC (14,5±2,11N), que apresentou a força mais alta até falha, estatisticamente significante em relação aos demais grupos, com p=0,001. Para a termociclagem, não houve diferença significativa estatisticamente dentro de todos os grupos estudados. Após o teste, um corpo-de-prova de cada um dos grupos, foi observado por MEV associado ao EDX.

Among these ones, 20 bars formed the control group (CG) and 40 were divided: 20 were attached by the use of brazing (BG) and 20 were laser welded (LG). A 1,0mm ceramic layer (0,1mm of opaque ceramics and 0,9mm of dentine ceramics) was applied over the bars, on its central and bottom area. The total area tested had 20mm2, with central load. The metal surfaces treatments, the temperature, and the times of ceramics coccion were recommended by the manufacturers. Half of the specimens were thermocycled (CGT, BGT, LGT). All the specimens underwent the three point bending test with a 10-kilo load cell and speed of 1,5±0,5mm/min in an universal testing machine and the maximum load up to initial failure was marked. Data underwent statistical analysis (ANOVA and Tukey Test). There was no relevant static difference concerning the maximum load to metal-ceramic failure of the groups BG (10,55±1,37N) and LG (9,87±1,22N), but CG had the highest load up to failure (14,5±2,11N), statistically relevant, of all the groups, with p=0,001. When it comes to thermocycling, there were no relevant differences statistically, among all the studied groups. After the test, one specimen of each one of the groups was observed by MEV associated to EDX.

Shear bond strenght between metal alloy and a ceramic system, submitted to different thermocycling immersion times

El objetivo de este estudio fue evaluar la resistencia a cizallamiento de aleaciones metálicas de Co-Cr y Ni-Cr; con un mismo tipo de cerámica, sometidos a diferentes tiempos de inmersión en el termociclaje. Sesenta especímenes fueron confeccionados de forma standarden formato cilindrico. Tres condiciones de termociclaje fueron evaluadas: sin termociclaje, 3000 ciclos (5ºC/55ºC±1) con 30s y 3.000 ciclos (5ºC/55ºC±1) con 60s de tiempo de inmersión. El ensayo de cizallamiento fue realizado en una máquina universal usando un dispositivo para concentrar la tensión en la interfase metalocerámica durante el test. La carga fue aplicada hasta que ocurra la fractura de los especimenes. La información fue estadísticamente analizada por ANOVA(two-way) y el test de Tukey (p<0,05). Los resultados no mostraron diferencia estadísticamente significante entre las combinaciones metal-porcelana. Sin embargo, ambas combinaciones metalocerámicas sometidas a 60s de tiempo de inmersión mostraron valores más bajos en comparación con los especimenes del grupo sin termociclaje. Fue concluido que el tiempo de inmersión de termociclaje de 1 minuto afectó los valores de resistencia de cizallamiento en los grupos de Ni-Cr/porcelana y Cr-Co/porcelana.

Effects of elevated temperatures on various restorative materials: an in vitro study.

In cases of mass disasters associated with fire, identification of the burnt victims can be a real challenge to the forensic team. Teeth and their restorations play a significant role to aid in the identification process, as various restorative materials have varying resistance to high temperatures. A study was undertaken to evaluate the changes taking place on teeth restored with amalgam, composites, glass ionomers, heat cure acrylic, and ceramics. The specimens were placed in a furnace and heated to predetermined temperatures of 200, 400, 600, 800, and 1000 degrees C and the changes were examined using a digital camera and stereomicroscope. Our observations show that while some restorations were able to withstand elevated temperatures, others were reduced to an unrecognizable mass at relatively low temperatures.

Avaliação das condutas adotadas por profissionais na utilização de coroas metalo-cerâmicas / Assessment of clinical proceedings adopted by dental professionals regarding the employment of ceramic fused to metal crowns

A fim de avaliar a opinião da classe odontológica sobre a utilização das coroas metalo-cerâmicas na prática odontológica, aplicou-se um questionário de 20 questões a cirurgiões-dentistas da cidade de Aracaju - SE, e a cirurgiões-dentistas e estudantes de pós-graduação em odontologia, na área de prótese dental, da cidade de Bauru-SP. Concluiu-se que: 1. As coroas metalo-cerâmicas são o tipo de restauração protética mais empregado em Odontologia. 2. A maioria dos dentistas refere-se às coroas metalo-cerâmicas como restaurações bem sucedidas, indicando superfícies oclusais metálicas para a maioria dos pacientes. 3. Apesar da maior parte dos profissionais utilizar as ligas de níquel-cromo nas coroas metalo-cerâmicas de seus pacientes, os mesmos prefeririam que ligas nobres ou semi-nobres fossem empregadas em suas próprias restaurações. 4. A maioria dos entrevistados emprega as coroas metalo-cerâmicas na restauração de dentes anteriores (57,23 por cento). Entretanto, esse valor se deve à preferência dos dentistas de Aracaju (78 por cento) por esse tipo de restauração, ao passo que, em Bauru, prevaleceu o número de respostas favoráveis às coroas de porcelana pura. 5. O cimento de fosfato de zinco foi o cimento de escolha da maioria dos profissionais. 6. A preferência da maior parte dos entrevistados, com relação à porcelana utilizada foi pela porcelana Vita (34,34 por cento), em comparação às porcelanas Noritake e Dulceram Plus (13,86 por cento). 6. Ficou evidente o desejo dos entrevistados quanto ao desenvolvimento de mecanismos que facilitem o reparo das coroas metalo-cerâmicas.

Evaluation of low-fusing ceramic systems combined with titanium grades II and V by bending test and scanning electron microscopy / Avaliação de sistemas cerâmicos de baixa fusão combinados com titânio grau 2 e 5 por ensaio flexão e microscopia eletrônica de varredura

Foram avaliados dois substratos metálicos (titânio comercialmente puro ou grau 2 e a liga Ti-6Al-4V ou grau 5) combinados com a três sistemas cerâmicos de baixa fusão (PBF) sobre a resistência de união pelo teste de flexão de três pontos e a natureza da fratura porcelana-metal através da microscopia eletrônica de varredura (MEV). Os resultados foram comparados a combinação da liga paládio-prata (Pd-Ag) com porcelana convencional (Duceram VMK68). Foram confeccionadas sessenta tiras de metal medindo 25x3x0.5mm, sendo 30 de titânio grau 2 e 30 de titânio grau 5 sobre os quais foram aplicadas as porcelanas: Vita Titankeramik, Triceram e Duceratin (10 espécies de cada porcelana) nas dimensões de 8x3x1mm. O grupo controle era composto de 10 especies de Pd-Ag alloy/ com a porcelana Duceram VMK68. Na análise estatística utilizou-se análise de variância (ANOVA) e o teste de Tukey em nível de significância de 5 por cento. Os resultados indicaram que a resistência de união do grupo controle (48.0 + 4.0) foi estatisticamente significante maior que nos substratos Ti-2 (26.7 + 4.1) e Ti-5 (25.2 + 2.2). Os resultados dos substratos de Ti-2 e Ti-5 com a porcelana Duceratin foram estatisticamente significante menores quando comparados ao Ti-2 com a porcelana Vitatitankeramik. A análise pela MEV indicou fraturas predominantemente do tipo adesiva para as amostras de Ti-2 e Ti-5, e coesivas para o grupo controle PdAg/Duceram. O grupo controle apresentou maior resistência de união comparadas às amostras que empregaram as PBF. Entre as porcelanas de baixa fusão, os menores resultados foram obtidos com a porcelana Duceratin em ambos os substratos. A análise pela MEV confirmou os resultados do teste de flexão.

Pernos preformados ¿por qué resistirse? / Prefabricated posts, why to resist?

Los sistemas de pernos preformados para la reconstrucción de elementos tratados endodónticamente son variados y pueden aplicarse a distintas situaciones clínicas. Estos pernos preformados pueden ser de estructura metálica o libres de metal. Estos últimos pueden ser utilizados en restauraciones que tienen alto requerimiento estético como las cerámicas puras. Para lograr el éxito clínico utilizando algunos de estos sistemas es necesario seguir las indicaciones precisas que cada sistema propone

Uniäo da cerâmica ao metal: uma comparaçäo utilizando testes de cisalhamento / Bonding ceramic to metal: a comparison using shear tests

Muitos dentistas e técnicos usam cerâmicas dentais com diferentes ligas sem se preocupar com as características de compatibilidade desses materiais. É muito importante para o profissional, conhecer as propriedades das ligas e cerâmicas utilizadas em restaurações metalocerâmicas. O objetivo deste estudo foi de avaliar a resistência de uniäo de uma liga de paládio-prata (Pors-On 4) com três cerâmicas (Ceramco, Noritake e Vita VMK-68) utilizando forças de cisalhamento na interface meta/cerâmica, além de testar a metodologia e as características de manipulaçäo dos materiais estudados. Uma matriz cilíndrica foi utilizada para a preparaçäo dos padrões metálicos, aplicaçäo das cerâmicas e execuçäo dos testes de cisalhamento. Trinta padrões metálicos receberam duas camadas de opaco e duas camadas de porcelana de corpo. Os testes de cisalhamento foram executados em uma máquina de ensaios universal a uma velocidade de 0.5mm/min. Os valores de resistência de uniäo foram: 28.21MPa (Ceramco), 28.96MPa (Noritake) e 24.11MPa (Vita VMK-68). A ANOVA a um critério determinou näo existirem diferenças estatisticamente significativas entre os grupos (p < 0.05). Os resultados mostraram que os três sistemas cerâmicos säo satisfatórios para a utilizaçäo com a liga selecionada