Internal adaptation of cast titanium crowns

As the adaptation of titanium crowns obtained by Rematitan Plus investment, specific for titanium, is not recognized to be suitable, this study evaluated the effect of the concentration of the specific liquid and the temperature of the mold of investments on the internal misfit of crowns cast on commercially pure titanium. Individual dies of epoxy resin were obtained, representing teeth prepared for full-crown restoration with a 6-degree axial surface convergence angle and shoulder (1.0 mm). For the waxing of each crown, a ring-shaped stainless steel matrix (8.0mm internal diameter; 7.5 mm height) was adapted above the individual dies of epoxy resin. The Rematian Plus investment was mixed according to the manufacturer's instructions using two different concentrations of the specific liquid: 100%, 75%. Casting was performed in a Discovery Plasma Ar-arc vacuum-pressure casting machine with molds at temperatures of 430ºC, 515ºC and 600ºC. The crowns were cleaned individually in a solution (1% HF + 13% HNO3) for 10 min using a ultrasonic cleaner, with no internal adaptations, and luted with zinc phosphate cement under a 5 kg static load. The crown and die assemblies were embedded in resin and sectioned longitudinally. The area occupied by cement was observed using stereoscopic lens (10X) and measured by the Leica Qwin image analysis system (mm²). The data for each experimental condition (n=8) were analyzed by Kruskal-Wallis non-parametric test (á=0.05). The results showed that liquid dilution and the increase in mold temperature did not significantly influence the levels of internal fit of the cast titanium crowns. The lowest means (±SD) of internal misfit were obtained for the 430ºC/100%: (7.25 mm² ±1.59) and 600ºC/100% (8.8 mm² ±2.25) groups, which presented statistically similar levels of internal misfit

Effect of phosphate-bonded investments on titanium reaction layer and crown fit

This study analyzed the reaction layer and measured the marginal crown fit of cast titanium applied to different phosphate-bonded investments, prepared under the following conditions (liquid concentration/casting temperature): Rema Exakt (RE) - 100%/237°C, 75%/287°C, Castorit Super C (CS)-100%/70°C, 75%/141°C and Rematitan Plus (RP)- 100%/430°C (special to titanium cast, as the control group). The reaction layer was studied using the Vickers hardness test, and analyzed by two way ANOVA and Tukey's HSD tests (α = 0.05). Digital photographs were taken of the crowns seated on the die, the misfit was measured using an image analysis system and One-way ANOVA, and Tukey's test was applied (α = 0.05). The hardness decreased from the surface (601.17 VHN) to 150 μm (204.03 VHN). The group CS 75%/141°C presented higher hardness than the other groups, revealing higher surface contamination, but there were no differences among the groups at measurements deeper than 150 μm. The castings made with CS - 100%/70°C presented the lowest levels of marginal misfit, followed by RE -100%/237°C. The conventional investments CS (100%) and RE (100%) showed better marginal fit than RP, but the CS (75%) had higher surface contamination.(FAPESP) São Paulo Research Foundatio

Prevalence of Abutment Teeth for Conventional Fixed Prostheses in a Brazilian Subpopulation

The purpose of this cross-sectional study was to evaluate the prevalence of abutment teeth for conventional fixed prostheses in a Brazilian subpopulation. Panoramic radiographs for a total of 1,401 patients taken from August 2002 to September 2007 were randomly selected from the database of the Radiological Center of Orofacial Images of Cuiabá (Cuiabá, Brazil). A total of 1,401 radiographs were examined to determine the frequency of abutment teeth for conventional fixed prostheses. Data concerning age, sex, and dental group were recorded. Frequency distribution and the chi-square test were used for statistical analysis. The level of significance was set at α = 5%. Of the 29,467 teeth included in the evaluation, 4,967 (16.8%) were abutments for conventional fixed prostheses. A high prevalence of abutment teeth for conventional fixed prostheses was observed in individuals aged between 46 and 60 years (49.9%). Maxillary canines and second premolars were the teeth most often involved in rehabilitation (10.5% and 10.3%). Missing teeth were identified in 24.8% of the sample. The prevalence of abutment teeth for conventional fixed prostheses was 16.8%, and the teeth most frequently used were maxillary canines and maxillary second premolars

Técnica minimamente invasiva para restabelecimento de dimensão vertical de oclusão de dentição com erosão.

INTRODUÇÃO: A erosão dentária caracteriza-se como uma condição multifatorial associada com a perda irreversível de estrutura dentária resultante de processo químico envolvendo fontes ácidas não bacterianas. Nos casos mais severos o grau de dano tecidual pode não raro provocar a redução da dimensão vertical de oclusão (DVO). O amplo desenvolvimento das técnicas adesivas tem favorecido a adoção de procedimentos mais conservadores com preservação de estrutura dentária hígida. OBJETIVO: Relatar um caso clínico de técnica aditiva minimamente invasiva para reanatomização de dentes anteriores superiores como parte integrante do restabelecimento de dimensão vertical de oclusão de arcadas danificadas pelo processo de erosão dentária. RELATO DO CASO: Paciente HGH, 42 anos, gênero feminino, apresentou com queixa de insatisfação com a aparência estética de seu sorriso. As imagens de face apresentam sinais característicos de uma dimensão vertical de oclusão reduzida, associada a desgaste generalizado dos dentes anteriores. Para a reanatomização da face palatal dos dentes 11,12,13, 22 e 23, bastante destruída, optou-se pela técnica aditiva de com resina composta direta associada à faceta cerâmica nas faces vestibular e incisal, conhecida como Técnica de Sanduíche. O emprego de uma matriz de silicone transparente possibilitou uma reprodução fiel, e tecnicamente mais simplificada, da anatomia palatal definida no enceramento. CONCLUSÃO: A técnica Sanduiche apresenta-se como alternativa segura, exequível e efetiva para o restabelecimento de DVO de arcadas severamente danificadas pelo processo de erosão dentária

Efeito da concentração do líquido especial e da temperatura do molde de revestimentos na desadaptação marginal de coroas fundidas em titânio

O objetivo deste estudo foi avaliar o efeito da concentração do líquido especial e da temperatura do molde dos revestimentos Rematitan Plus, específico para titânio, Rema Exakt e Castorit Super C, alternativos, na desadaptação marginal de coroas fundidas em titânio puro. Para o revestimento Rematitan Plus os padrões de cera foram incluídos à vácuo com três diferentes concentrações do líquido especial, 100%, 75% e 50%, diluídos em água destilada. As fundições foram realizadas na máquina Discovery Plasma com os moldes em três temperaturas, 430ºC, 515ºC e 600ºC. Os revestimentos alternativos foram empregados nas condições em que obtiveram expansão total de 0,8%, equivalente à do Rematitan Plus (100%/430ºC), adotado como grupo controle. Conforme as curvas de expansão de presa e térmica foram estabelecidas as condições de concentração e temperatura: Rema Exakt (100%/220ºC, 75%/240ºC e 50%/340ºC) e Castorit Super C (100%/temperatura ambiente e 75%/160ºC).This study had the goal of assessing the effect of the concentration of the special liquid and the temperature of the mold of Rematitan Plus investment, specific for titanium, Rema Exakt and Castorit Super C, alternative investments, on the marginal misfit of crowns cast on pure titanium. For the Rematitan Plus investment, the wax standards were included in vacuum with three different concentrations of the special liquid, 100%, 75% and 50%, diluted in distilled water. The castings were performed on the Discovery Plasma machine with the molds at three temperatures, 430ºC, 515ºC and 600ºC. The alternative investments were employed under conditions in which they obtained a overall expansion of 0.8%, equivalent to that of the Rematitan Plus (100%/430ºC), adopted as the control group. According to the thermal and setting expansion curves the conditions of concentration and temperature were established: Rema Exakt (100%/220ºC, 75%/240ºC and 50%/340ºC) and Castorit Super C (100%/room temperature and 75%/160ºC).Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Efeito de tratamentos térmicos na resistência à tração e na dureza Vickers do Ti c.p. e da liga Ti-6Al-4V obtidos por fundição odontológica

O objetivo desta investigação foi determinar se os tratamentos térmicos podem alterar a resistência à tração e a dureza Vickers do Ti c.p. e da liga Ti-6Al-4V. Trinta corpos-de-prova na forma de halteres com 3,0 mm no segmento central e 42 mm de comprimento, obtidos por meio de uma matriz de alumínio, foram fundidos no sistema Rematitan. Os corpos-de-prova de Ti c.p. e Ti-6Al-4V foram divididos aleatoriamente em três grupos de 10 cada, e submetidos às seguintes condições de tratamento térmico: (1) controle; (2) T1 - aquecimento a 750ºC/2 h; (3) T2 - recozimento a 955ºC/1 h e envelhecimento a 620ºC/2 h. Ambos, aquecimento e resfriamento, foram realizados em atmosfera controlada de argônio. O ensaio de tração foi efetivado na máquina de testes mecânicos MTS modelo 810 à velocidade de 1,0 mm/min. Após o teste de tração uma das extremidades do corpo-de-prova foi embutida em resina acrílica, regularizada e polida antes da medida da dureza Vickers no durômetro Micromet 2100. As médias de resistência à tração e dureza Vickers foram comparadas estatisticamente usando o teste não-paramétrico de Kluskall-Wallis. Nos grupos de Ti c.p. não foram observadas diferenças significativas na resistência à tração, entretanto, na dureza Vickers os resultados do grupo T2 foram significativamente maiores que os outros grupos, que se mostraram iguais entre si. Na liga Ti-6Al-4V os grupos controle e T1 revelaram igualdade estatística em relação à resistência à tração, e significativamente superiores ao grupo T2. Quanto à dureza Vickers, diferenças estatisticamente significantes foram observadas entre os três grupos de tratamento térmico: T2>T1>controle. Não foi observada correlação entre as propriedades de resistência à tração e dureza Vickers....The aim of this investigation was to determine whether heat treatments could change the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy castings. Thirty dumbbell rods, 3.0 mm in diameter at the central segment and 42 mm in length, obtained from an aluminum matrix, were cast for each metal in the Rematitan system. The specimens of CP Ti and of alloy Ti-6Al-4V, were divided randomly into three groups of ten each; then submitted to the following heat treatments: (1) control group, without heat treatment; (2) T2 - heat at 750ºC for 2 h; (3) annealing at 955ºC for 1 h and aged at 620ºC for 2 h. The heat treatments, as well as the cooling process were conducted in the furnace with argon atmosphere. The tensile strength was measured by means of a universal testing machine, MTS model 810, at a strain of 1.0 mm/min. After the tensile testing the specimens were embedded in acrylic resin, grounded and polished prior to hardness measurements, using the Vickers tester Micromet 2100. The means and standard deviations of tensile strength and Vickers hardness were statistically compared using Kruskal-Wallis non-parametric test at a=0.05 significance level. In CP Ti groups, no statistically significant differences in tensile strength were observed; however, in Vickers hardness the results of group T2 were significantly higher than the other groups, which showed similar mean values among themselves. In Ti-6Al-4V alloy, the control and T1 groups revealed statistically higher tensile strength when compared to T2 group, with no significant difference between control and T1 group. Regarding Vickers hardness, statistically significant differences were observed among the three heat-treatment groups: T2>T1>control...(Complete abstract, click electronic access below