ABSTRACT
This study evaluated the tensile and flexural strength of tungsten inert gas (TIG) welds in specimens made of commercially pure titanium (CP Ti) compared with laser welds. Sixty cylindrical specimens (2 mm diameter x 55 mm thick) were randomly assigned to 3 groups for each test (n=10): no welding (control), TIG welding (10 V, 36 A, 8 s) and Nd:YAG laser welding (380 V, 8 ms). The specimens were radiographed and subjected to tensile and flexural strength tests at a crosshead speed of 1.0 mm/min using a load cell of 500 kgf applied on the welded interface or at the middle point of the non-welded specimens. Tensile strength data were analyzed by ANOVA and Tukey's test, and flexural strength data by the Kruskal-Wallis test (α=0.05). Non-welded specimens presented significantly higher tensile strength (control=605.84±19.83) (p=0.015) and flexural strength (control=1908.75) (p=0.000) than TIG- and laser-welded ones. There were no significant differences (p>0.05) between the welding types for neither the tensile strength test (TIG=514.90±37.76; laser=515.85±62.07) nor the flexural strength test (TIG=1559.66; laser=1621.64). As far as tensile and flexural strengths are concerned, TIG was similar to laser and could be suitable to replace laser welding in implant-supported rehabilitations.
Este estudo avaliou a resistência à tração e à flexão de soldas feitas com gás inerte de tungstênio (TIG) em amostras de titânio comercialmente puro (Ti CP) em comparação com a solda a laser. Sessenta amostras cilíndricas (diâmetro de 2 mm e espessura de 55 mm) foram distribuídas aleatoriamente em três grupos para cada ensaio (n=10): sem solda (controle), solda TIG (10V, 36A, 8 s) e solda com laser de Nd:YAG (380 V, 8 ms). As amostras foram radiografadas e submetidas aos testes de resistência à tração e à flexão em máquina de ensaios mecânicos à velocidade de 1mm/min com célula de carga de 500 kgf aplicada na interface soldada ou no ponto médio das amostras controle. Os dados de resistência à tração foram analisados estatisticamente por ANOVA e teste de Tukey e os dados de resistência à flexão pelo teste de Kruskal-Wallis (α=0,05). Espécimes não-soldados apresentaram resistência à tração (controle=605,84±19,83) (p=0,015) e resistência à flexão (controle=1908,75) (p=0,000) significantemente maiores que os solados com TIG ou laser. Não houve diferença estatisticamente significante (p>0.05) entre os tipos de solda no teste de resistência à tração (TIG=514,90±37,76; laser=515,85±62,07) nem no teste de resistência à flexão (TIG=1559,66; laser=1621,64). As resistências à tração e à flexão foram similares quando as amostras foram soldadas com TIG e a laser.
Subject(s)
Lasers , Tungsten , Titanium/chemistry , Welding/methods , Porosity , Shear Strength , Tensile StrengthABSTRACT
OBJECTIVE: To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems. Materials and Methods: Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37 percent phosphoric acid; groups II/IV - self-priming etchant (Tyrian-SPE). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50 percent silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey's test (α=0.05). RESULTS: Marginal seal provided by air abrasion was similar to high-speed handpiece, except for group I. There was SIGNIFICANT difference between enamel and dentin/cementum margins for to group I and II: air abrasion. The etch-and-rinse adhesive system promoted a better marginal seal. At enamel and dentin/cementum margins, the highest microleakage values were found in cavities treated with the self-etching adhesive system. At dentin/cementum margins, high-speed handpiece preparations associated with etch-and-rinse system provided the least dye penetration. CONCLUSION: Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins.
Subject(s)
Humans , Air Abrasion, Dental/methods , Dental Cavity Preparation/methods , Dental Leakage/classification , Acid Etching, Dental/methods , Aluminum Oxide/chemistry , Composite Resins/chemistry , Dental Bonding , Dental High-Speed Equipment , Dental Marginal Adaptation , Dental Polishing , Dental Cavity Preparation/instrumentation , Dental Cementum/ultrastructure , Dental Enamel/ultrastructure , Dental Restoration, Permanent/methods , Dentin-Bonding Agents/chemistry , Dentin/ultrastructure , Materials Testing , Methacrylates/chemistry , Phosphoric Acids/chemistry , Silver Staining , Surface Properties , TemperatureABSTRACT
A iniciação profissional representa uma etapa difícil para todo recém-formado na área de Odontologia, porque muitas decisões tomadas nesse momento refletirão na satisfação profissional do novo cirurgiãodentista. Por esse motivo, torna-se fundamental efetuar a escolha mais correta do caminho a seguir, seja na área privada ou pública, sabendo-se as vantagens e dificuldades de cada área.
The start of one's professional practice is a difficult phase for all newly-graduated dental professionals. Since many decisions made at this point may reflect in the professional satisfaction of the new dental surgeon. Due to such, it is fundamental to make the most correct choice with regard to the path to be followed, whether in private or public practice, aware of the advantages and difficulties that each present.
Subject(s)
Education, Dental , Marketing of Health Services , Job Market , Professional PracticeABSTRACT
O objetivo deste trabalho foi avaliar quantitativamente in vitro a microinfiltração nas margens oclusal (O) e cervical (C) em restaurações com amálgama aderidocom diferentes sistemas ionoméricos: Vidrion F (VF), Vitremer C (VC) e ProTec CEM (PC), no grupo controle foi utilizado o verniz cavitário Copalite (Co). Foram realizados 40 preparos cavitários Classe V em pré-molares, divididos aleatoriamente em quatro grupos (N=10), todos os espécimes foram restaurados com Dispersalloy. O polimento foi realizado após 24 horas e, então, os corpos-de-prova foram isolados, termociclados, imersos em Rodamina B a 0,2 por cento durante 24 horas, lavados, incluídos em resina acrília e seccionados. Para análise da microinfiltração foi utilizado um microscópio óptico acoplado a uma câmera e computador, para obtenção da imagem digitalizada, na qual mediu-se quantitativamente, em milímetros, a penetração do corante. Os dados foram submetidos aos testes de Wilcoxon e Kruskal-Wallis...