ABSTRACT
There is no consensus in literature regarding the best plan for prosthetic rehabilitation with partial multiple adjacent implants to minimize stress generated in the bone-implant interface. The aim of this study was to evaluate the biomechanical behavior of cemented fixed partial dentures, splinted and nonsplinted, on Morse taper implants and with different types of coating material (ceramic and resin), using photoelastic stress analysis. A photoelastic model of an interposed edentulous space, missing a second premolar and a first molar, and rehabilitated with 4 different types of cemented crowns and supported by 2 adjacent implants was used. Groups were as follows: UC, splinted ceramic crowns; IC, nonsplinted ceramic crowns; UR, splinted resin crowns; and IR, nonsplinted resin crowns. Different vertical static loading conditions were performed: balanced occlusal load, 10 kgf; simultaneous punctiform load on the implanted premolar and molar, 10 kgf; and alternate punctiform load on the implanted premolar and molar, 5 kgf. Changes in stress distribution were analyzed in a polariscope, and digital photographs were taken of each condition to allow comparison of stress pattern distribution around the implants. Cementation of the fixed partial dentures generated stresses between implants. Splinted restorations distributed the stresses more evenly between the implants than nonsplinted when force was applied. Ceramic restorations presented better distribution of stresses than resin restorations. Based on the results obtained, it was concluded that splinted ceramic restorations promote better stress distribution around osseointegrated implants when compared with nonsplinted crowns; metal-ceramic restorations present less stress concentration and magnitude than metal-plastic restorations.
Subject(s)
Dental Implants , Dental Prosthesis, Implant-Supported , Dental Stress Analysis/methods , Denture, Partial, Fixed , Jaw, Edentulous, Partially/rehabilitation , Acrylic Resins , Biomechanical Phenomena , Bite Force , Ceramics , Crowns , Denture Design , Humans , Models, Dental , PhotographyABSTRACT
PURPOSE: The purpose of this study was to compare the tensile strength of commercially pure titanium dowels and cores cemented with zinc phosphate or resin cements. METHODS: Twenty-one extracted human canines were endodontically treated. The root preparations were accomplished using Largo reamers (10mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the dowel and cores were made, and specimens were cast in commercially pure titanium (n=7) and divided in three groups: TZ-CP Ti dowels luted with zinc phosphate luting agent, TP-CP Ti dowels luted with Panavia F and TR-CP Ti dowels luted with RelyX U100. Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5mm/min. The results (N) were statistically analyzed by ANOVA and Tukey tests (α=0.01). RESULTS: The ANOVA indicated that there were significant differences among the groups tested. A Tukey multiple comparison procedure was performed and revealed statistically significant higher retention values for the dowel luted with RelyX U100 when compared with zinc phosphate or Panavia F. CONCLUSION: Cast commercially pure titanium dowels and cores fixed with RelyX U100 cement presented superior bond strength retention when compared to zinc phosphate and Panavia F.
Subject(s)
Dental Cements , Post and Core Technique/standards , Tensile Strength , Titanium , Humans , In Vitro Techniques , Phosphates , Zinc CompoundsABSTRACT
STATEMENT OF PROBLEM: In vitro studies on the retentive strengths of various cements used to retain posts have reported conflicting results. PURPOSE: The purpose of this study was to compare the tensile strength of commercially pure titanium and type III cast gold-alloy posts and cores cemented with zinc phosphate or resin cement. MATERIAL AND METHODS: Forty-two extracted human canines were endodontically treated. The root preparations were accomplished using Largo reamers (10 mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the posts and cores were made, and specimens were cast in commercially pure titanium and in type III gold alloy (n=7). Fourteen titanium cast posts and cores were submitted to surface treatment with Kroll acid solution and to scanning electron microscopy (SEM), before and after acid etching. The groups (n=7) were cemented with zinc phosphate cement or resin cement (Panavia F). Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The results (Kgf) were statistically analyzed by 2-way ANOVA (alpha=.05). RESULTS: The 2-way ANOVA indicated that there were no significant differences among the groups tested. Retentive means for zinc phosphate and Panavia F cements were statistically similar. The bond strength was not influenced by the alloy, the luting material, or the etching treatment. SEM analysis indicated that the etched surfaces were smoother than those that did not receive surface treatment, but this fact did not influence the results. CONCLUSIONS: Commercially pure titanium cast posts and cores cemented with zinc phosphate and resin cements demonstrated similar mean tensile retentive values. Retentive values were also similar to mean values recorded for cast gold-alloy posts and cores cemented with zinc phosphate cement and resin cements.
Subject(s)
Dental Bonding , Dental Casting Investment/chemistry , Dental Cements/chemistry , Dental Materials/chemistry , Gold Alloys/chemistry , Post and Core Technique , Titanium/chemistry , Acid Etching, Dental , Cementation , Dental Prosthesis Design , Dental Prosthesis Retention , Humans , Materials Testing , Microscopy, Electron, Scanning , Resin Cements/chemistry , Root Canal Preparation/methods , Stress, Mechanical , Surface Properties , Tensile Strength , Tooth, Nonvital/therapy , Zinc Phosphate Cement/chemistryABSTRACT
O objetivo deste estudo foi avaliar a ação de três agentes isolantes aplicados sobre a superfície de núcleos metálicos fundidos para a confecção de coroas provisórias e a sua influência na fixação com diferentes agentes cimentantes temporários. A partir de uma matriz foram confeccionados 45 padrões em resina acrílica autopolimerizável (Duralay), fundidos com liga de cobre-alumínio (Novelli) e divididos em 9 grupos (n=5). Os núcleos foram isolados com saliva artificial (grupo controle), gel aquoso à base de glicerina (K-Y®) ou vaselina pastosa (Rioquímica), e a seguir confeccionadas as coroas provisórias em resina acrílica autopolimerizável (Vipiflash). Os núcleos eram posicionados em um dispositivo e realizada a cimentação das coroas, com carga padronizada de 300g, com os cimentos Dycal, Provicol e Temp bond. Removidos os excessos, as amostras foram armazenadas em água destilada a 37°C por 40 horas; após esse período foi realizado o ensaio de tração em uma máquina universal EMIC-DL2000 (velocidade = 5mm/minuto e célula de carga = 50 Kgf). A análise de variância evidenciou diferenças estatisticamente significantes para os fatores individuais (p≤0,0l) e para a interação (p≤0,05). Os testes complementares de Tukey e Scheffé indicaram diferenças entre os três agentes isolantes (saliva=8,73; K-Y®= 7,03 e Vaselina= 6,26) e para os cimentos a diferença entre o par formado por Temp Bond/Dycal e Provicol, respectivamente 8.47, 7.60 e 5.95 Kgf. Pelos resultados conclui-se que a saliva deve ser o agente isolante usado na confecção de coroas provisórias a serem cimentadas com Dycal ou Temp bond.
Subject(s)
Cementation , Dental Cements , Denture, Partial, Fixed , Dental Restoration, TemporaryABSTRACT
A análise da dentição mista, mais precisamente a predição do espaço para erupção de caninos e pré-molares, é fundamental para que o Ortodontista possa realizar o diagnóstico e tratamentos criteriosos. O objetivo do estudo consiste em verificar a confiabilidade do método de predição das larguras mesiodistais de caninos e pré-molares propostos pelas análises de Moyers¹ e Tanaka & Johnston². Para a realização desta investigação, foram selecionados 37 pacientes dos arquivos da Faculdade de Odontologia de Ribeirão Preto - Universidade de São Paulo, em fase de dentição mista e permanente. Os procedimentos técnicos empregados para esta análise foram: 1 - Medição das larguras mesiodistais dos incisivos inferiores, 2 - previsão da soma dos diâmetros mesiodistais de caninos e pré-molares com auxílio da "Tabela de Probabilidades" proposta por Moyers¹ e, 3 - previsão da soma dos diâmetros mesiodistais de caninos e pré-molares proposta por Tanaka & Johnston². Os dados foram submetidos à análise estatística para verificar a correlação existente entre as medidas obtidas por meio dos referidos métodos de predição e as medidas reais de caninos e pré-molares. Pode-se constatar que não houve diferenças estatisticamente significantes no tamanho de canino e pré-molares (p>.05). O erro envolvendo o uso dos métodos de predição de Moyers¹ e Tanaka & Johnston², em relação ao tamanho real, é expresso como estimativa de erro padrão (EEP), indicando que o erro para a utilização do método de Moyers¹ foi de 1.28mm e para o de Tanaka & Johnston² de 1.07mm.
