ABSTRACT
This study evaluated the compression strength of gypsum type IV and V according to 2 variables: 1) water proportioned randomly or as recommended by the manufacturer and 2) according to 3 (three) different groups of operators (dentists, technicians and dental students). 180 specimens, produced according to ADA regulation nr. 25 underwent, after seven days (dry resistance), the compression strength test in an universal testing machine. After statistical analyses of the data, there was no statistical significant difference regarding the group of operators. Regarding the variable proportion, the specimens manufactured using a random proportion of water/gypsum powder presented a lower compression value (626,2 Kgf/cm2) when compared to the group where the amount of water/gypsum powder followed the recommendation of the manufacturer (741,7 Kgf/cm2). This difference was statistically significant (p<0.01)
Subject(s)
Alginates , Calcium Sulfate , Dental Impression Materials , Analysis of VarianceABSTRACT
Aim of the study was to compare the trimming and non-trimming variants of the microtensile technique with the 'micro' push-out test in the ability to measure accurately the bond strength of fiber posts luted inside root canals. In 15 endodontically treated teeth (Group A), fiber posts were cemented with Excite DSC in combination with Variolink II (Ivoclar-Vivadent). In 15 roots RelyX Unicem (3M-ESPE) was used for fiber post luting (Group B). Within each group, the bond strength of cemented fiber posts was assessed with the trimming and non-trimming microtensile technique, as well as with the push-out test. The great number of premature failures (16.9% in Group A, 27.5% in Group B) and the finding of high standard deviation values make questionable the reliability of the trimming microtensile technique. With the non-trimming microtensile technique, only five sticks were obtained from a total of six roots. The remaining specimens failed prematurely during the cutting phase. With the push-out test no premature failure occurred, the variability of the data distribution was acceptable, and regional differences in bond strength among root levels could be assessed. Relatively low values of bond strength were, in general, recorded for luted fiber posts. In conclusion, when measuring the bond strength of luted fiber posts, the push-out test appears to be more dependable than the microtensile technique.
Subject(s)
Dental Bonding/methods , Dental Stress Analysis/methods , Post and Core Technique , Resin Cements , Dental Restoration Failure , Glass , Humans , Incisor , Materials Testing/methods , Maxilla , Methacrylates , Random Allocation , Reproducibility of Results , Statistics, Nonparametric , Tensile StrengthABSTRACT
The difficulty with comparing data obtained from different research centers calls for the standardization of laboratory procedures. This in vitro study compared the shear bond strength (SBS) of two adhesive systems--a self-etching system, Etch&Prime 3.0 and a one-bottle total-etch system, Single Bond--using two methods of load application (orthodontic edge wire loop and knife-edge blade). The hypothesis of substrate influence on the results obtained for both tests was also investigated. Twenty-four recently extracted human teeth were embedded in PVC tubes using acrylic resin and divided into two groups (n=12). A proximal surface of each tooth was wet-ground flat to expose dentin. Etch&Prime 3.0 and Single Bond adhesive systems were applied according to the manufacturers' instructions, and cone-shaped restorations were then built using Z100 resin composite. After storage in distilled water at 37 degrees C for 24 hours, the specimens were submitted to SBS testing using an orthodontic edge wire loop. The same teeth were again embedded in PVC tubes using acrylic resin and the other proximal surface was wet-ground flat to expose dentin. The specimens were prepared as explained above, and after storage in distilled water under the same previous conditions, they were submitted to SBS testing using a knife-edge blade. Two-way ANOVA and Tukey's tests were performed to determine any statistically significant differences among testing conditions. Results indicated that SBS values obtained for Etch&Prime 3.0 were significantly lower than Single Bond for both methods of load application (p<0.001). Regarding the load application method, statistically significant higher values (p<0.01) were obtained for Etch&Prime 3.0 when the knife-edge blade was used, whereas, no significant difference was observed between the two methods for Single Bond. There was a significant correlation between the bond strength values obtained on the same tooth (p<0.05). SEM examination found that Etch&Prime 3.0 demonstrated narrower tags than Single Bond. Moreover, the peritubular dentin was not adequately decalcified when Etch&Prime 3.0 was used.
Subject(s)
Dental Bonding , Dental Stress Analysis/methods , Dentin-Bonding Agents , Resin Cements , Analysis of Variance , Bisphenol A-Glycidyl Methacrylate , Composite Resins , Dentin/ultrastructure , Dentin Permeability , Ethanol , Humans , Materials Testing/methods , Methacrylates , Microscopy, Electron, Scanning , Molar , Phosphates , Random Allocation , Shear Strength , Silicon Dioxide , Statistics, Nonparametric , ZirconiumABSTRACT
O objetivo deste estudo in vitro foi avaliar o desgaste de três materiais restauradores diretos (dispesalloy, Surefil e Z250), através de dois metodos: visual (escala M-L) e quantitativo (perfilografo). Superficies ocludais de doze terceiros molares humanos foram aplainadas com disco diamantado e cavidades cilíndricas padronizadas foram confeccionadas no centro delas, com uma ponta diamantada nº721PM, e restauradas conforme instruções dos fabricantes. As restaurações foram armazenadas em agua destilada a 37ºC durante 24 horas, polidas, moldadas e submetidas à ciclagem mecanica. A avaliacao do desgaste foi feita através utilizando a escalaM-L e o perfilografo. Foram encontrados materiais diferentes para os materiais testados, dependento do metodo de avaliacao utilizado. Na escala M-L o desgate entre Dispersalloy, Surefil e Z250 nao foi diferente, enquanto que no perfolografo o Dispersalloy apresentou menos desgaste que as resinas Surefil e Z250 (p<0,01). A avaliação do desgaste pela escala M-L foi subestimada em relação ao método do perfilógrafo (p<0,05).
Subject(s)
Composite Resins , Dental Amalgam , Dental Restoration WearABSTRACT
O objetivo desse estudo foi invertigar o efeito do armazenamento de 4 sistemas adesivos de frasco único por 1 ano sobre a resistência de união à dentina, através do teste de microtração. O esmalte oclusal de 16 molares humanos foi removido expondo superfície. Uma camada de "smear" padrão foi criada pela abrasão em lixas de granelação decrescente. Os dentes foram divididos em quatro grupos: [EX] - Excite (Ivoclar - Vivadent); [SB] - Single Bond (3M-ESPE); [OS] - Optibond Solo Plus (Kerr Corporation), [PB] - Prime & Bond NT (Dentsply-DeTrey). Blocos de resina com 5 mm de altura foram construídos nas superfícies dentárias tratadas com os adesivos. Após 24 horas de armazenamento, os corpos foram selecionados para obter uma série de "palito" em uma máquina de testes universal a 0,5mm/min. Os adesivos foram armazenados, por 1 ano, em estufa a 33oC, sendo abertos uma vez por dia e pressionados expondo 1 gota. Após esse período, todos os procedimentos para o teste de microtração foram repetidos para outros 16 molares. Os dados foram analisados utilizando os testes de Análise de Variância de 2 fatores e Tukey. Os valoresmédios obtidos (imediato/1ano) em MPa foram: [EX] 40,1ª/39,4ª; [SB] 42,8ª/46,7ª, [OS] 35,3ª/39,4ª, [PB] 22,5b/0,0c. Conclusões: Os resultados imediatos mostraram valores de resistência inferiores para o adesivo Prime & Bond NT, que sofreu influência significativa do tempo de armazenados por 1 ano.
