Irreversible hydrocolloids (IR) is a dental impression material commonly used in Brazilian and European dental practice because it is inexpensive, easy to handle, has good reproductive detail and is comfortable for the patient. This research aimed to analyze the chemical composition of eight different IRs for dental use. A sample of 0.2 g was weighed and transferred to a Teflon beaker moistened with drops of distilled or deionized water; 5 mL of nitric acid was added until total solubility of the sample; the solution was transferred to a 100 mL volumetric flask, the volume was filled with distilled or deionized water and homogenized. Thirty-five chemical elements were found: Lithium, Beryllium, Boron, Sodium, Magnesium, Aluminum, Silicon, Phosphorus, Potassium, Titanium, Manganese, Cobalt, Nickel, Vanadium, Zinc, Rubidium, Arsenic, Iron, Copper, Strontium, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Cadmium, Tin, Antimony, Barium, Lanthanum, Cerium, Mercury, Lead, Thorium and Uranium. Only one of the samples contained no Nickel, Antimony and Lead; and Arsenic and Uranium were found in 2 samples. This study provided evidence of high toxicity of the IR brands, pointing out the need for better quality control of this product, in order to prevent health damage in dentists, prosthesis technicians and patients.
The aim of this study was to evaluate the effects of cleaning protocols on the presence of residues, open dentinal tubules, and bond strength of a self-etch adhesive plus a dual-cure resin cement to dentin in the fiber-post space. The methods for cleaning utilized were conventional irrigation (CI), rotary brush with continuous rotary movement (RB), and continuous ultrasonic irrigation (CUI). Sixty bovine incisors were used for fiber-post space preparation. Thirty roots were divided into three groups (n = 10) according to the cleaning protocols and submitted to scanning electron microscope to evaluate presence of residues and relative quantity of open dentinal tubules on dentin surface. Similar protocols were performed in the other thirty roots (n = 10) using a self-etching adhesive system (Scotchbond Universal) and a dual-cure resin cement (Relyx Unicem 2). After 6 months cervical, middle, and apical thirds sections of fiber-post space were submitted to push-out testing. To data ANOVA and Tukey's test were employed (α = 5%). RB and CUI showed the lowest presence of residues on dentin surface (p = .015) and the highest bond strength values (p < .001), regardless of the dentin third. CUI presented the highest quantity of open dentinal tubules in middle and apical thirds (p < .001). CI presented the lowest bond strength value of resin cement, regardless of dentin third (p < .001).Mechanical cleaning protocols, such as RB and CUI, presented better surface cleaning capabilities and higher bond strength than CI with dual-cure resin cement employed.The use of a mechanical cleaning protocol seems to cause appropriate condition on the root dentin surface. Mechanical cleaning of root dentin provided greater bond strength of the self-etching system with dual resin cement. Conventional irrigation did not provide adequate root dentin cleaning.
Avaliar a resistência flexural e a adaptação marginal dos materiais restauradores provisórios Clip F (CF),Bifix Temp (BT), Systemp.onlay (SO), Fill Magic Tempo (FT) e Provi Master F (PF), na dentina da coroa dentária de dentes tratados endodonticamente. Métodos: Inicial-mente, foram confeccionados dez espécimes de cada um dos materiais restauradores, que foram individualmente submetidos ao teste de resistência flexural, na máquina de ensaio eletromecânica. Para avaliar a adaptação marginal,a câmara pulpar de cinquenta pré-molares superiores foi restaurada com um dos materiais avaliados (n=10). Após sete dias, a interface entre a dentina e o material restaurador, no terço médio da coroa dentária, foi submetida à análise em microscopia eletrônica de varredura. A extensão de desadaptação dos materiais e os gaps formados com a dentina foram mensurados com o software Image J.Resultados: CF e BT demonstraram o maior e o menor valor de resistência flexural, respectivamente (p<0,05).Os valores demonstrados por SO, FT e PF foram similares entre si (p>0,05). Por outro lado, CF demonstrou a menor extensão de desadaptação marginal (em porcentagem)e extensão de gaps (em μm) (p<0,05) na interface com a dentina. BT apresentou valor intermediário, mas menor do que os dos SO, FT e PF (p<0,05) que, por sua vez, foram similares entre si (p>0,05). Conclusões: O CF demonstrou o maior índice de resistência flexural e menor extensão de desadaptação marginal e gaps, em comparação aos demais materiais restauradores provisórios.
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