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Purpose: This study determined the effect of sonic and ultrasonic instrumentation on the shear bond strengths of Panavia 21, a popular cement for the luting of resin-bonded restorations. Methods: 84 Ni-Cr cylinders were cemented to randomly selected resin composite substrates using Panavia 21 following the manufacturer's instructions. The Ni-Cr-composite specimens were divided into 7 groups of 12 specimens each based upon the procedure used for removing the excess cement. For Group 1 (Co) specimens the excess cement was removed with microbrushes immediately after cementation. Groups 2 through 7 were based on the use of vibrating instrument and the time period after which the excess material was removed. These included the cement, Panavia 21, three vibrating instruments, Sonic with a universal tip (So), Piezoelectric ultrasonic with a USPIS tip (Pu), Magnetorestrive ultrasonic with a FS1-100 tip (Mu) and two different time periods, soon after cementation (9m) and one hour after cementation (1h). Once excess cement REMOVAL WAS COMPLETED, THE SPECIMENS WERE SUBJECTED TO SHEAR TESTING. Results: Mean Shear Bond strengths ranged from 16.03 MPa (Co) to 19.91 MPa (So 1h). Statistical analysis demonstrated that interaction of the main effects were significant (F = 4.27, p = 0.042). Post-hoc analysis demonstrated that the effect of timing was significant in all the instrumented groups. The majority of the tested specimens failed cohesively compared to mainly adhesive failures for the control group. Conclusions: The effect of type of instrumentation immediately following polymerization setting had no effect on the shear bond strengths however a delay of 1 hour for all types of instrumentation had a beneficial effect of improving observed shear bond strengths.

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Aim: To evaluate the effect of different enamel conditionings on the shear bond strength (SBS) and bond failure patterns of a resin modified glass ionomer cement (RMGIC) used to bond ceramic brackets. Methods: 105 human premolars extracted for orthodontic reasons were divided into 7 groups according to the enamel surface treatments: conditioners (35% phosphoric acid and 10% polyacrylic acid), type of adhesive (Transbond(r) and Fuji Ortho LC Capsule(r)), washing time and drying of the surface. Results: A significant p<0.05 was observed among the shear bond strength values obtained with seven different types of enamel preparation prior to bonding. The group that had the tooth surface conditioned with polyacrylic acid and enamel surface slightly dried before bracket placement showed no significant difference (p>0.05) to the group that had brackets bonded with composite resin. The two groups that had enamel prepared with polyacrylic acid and brackets bonded with GIC on a wet surface showed significantly lower shear bond strength than the control group (p<0.05). Conclusions: Moisture contamination decreased SBS, but not enough to preclude the use of RMGIC as an alternative to composite resin (CR) for direct bonding of ceramic brackets.

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OBJETIVO: A finalidade deste estudo foi quantificar e comparar as propriedades mecanicas de dois materiais restauradores nanocompositos disponiveis comercialmente. MATERIAL E METODO: Especimes de dois nanocompositos, Z350TM e GrandioTM, foram polimerizados com luz LED por 30 segundos e submetidos a testes mecanicos. As propriedades testadas incluiram: resistencia flexural, resistencia tensil diametral, resistencia a fratura e microdureza (topo e fundo). RESULTADOS: O Grandio apresentou valores de resistencia flexural media maiores quando comparados com o Z350 (89.1 MPa vs 61.9 MPa). O Grandio demonstrou maior microdureza das superficies de topo de cada composito quando comparada com sua correspondente superficie de fundo. As propriedades de resistencia a fratura e forca tensil diametral nao foram fatores discerniveis neste estudo em particular. CONCLUSAO: Grandio possui maiores valores para propriedade de resistencia flexural e dureza quando comparado com o Z350. Nao houve diferencas entre os dois materiais em relacao a resistencia a fraturas e resistencia a forcas tenseis diametrais.

OBJECTIVE: The purpose of this study was to quantify and compare the mechanical properties of two commercially available nanocomposite restorative materials. MATERIAL AND METHODS: Specimens of two nanocomposites, Z350TM and GrandioTM, were polymerized with a LED light for 20 seconds and subjected to mechanical tests. Properties tested included: flexural strength, diametral tensile strength, fracture toughness and microhardness (top and bottom). RESULTS: Grandio exhibited significantly higher mean flexural strength values when compared to Z350 (89.1 MPa vs 61.9 MPa). Grandio exhibited significantly higher top microhardness values when compared to Z350. Additionally when microhardness for the top surfaces of each composite were compared with their corresponding bottom surfaces, the bottom surfaces demonstrated significantly lower readings. The properties of fracture toughness and diametral tensile strength were non-discerning factors in this particular study. CONCLUSION: Grandio has greater observed values for the properties of flexural strength and hardness when compared with Z350. There was no difference between the two materials with respect to their fracture toughness and diametral tensile strength.

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OBJECTIVE: The purpose of this study was to quantify and compare the mechanical properties of two commercially available nanocomposite restorative materials. MATERIAL ANDMETHODS: Specimens of two nanocomposites, Z350TM and GrandioTM, were polymerized with a LED light for 20 seconds and subjected to mechanical tests. Properties tested included: flexural strength, diametral tensile strength, fracture toughness and microhardness (top and bottom). RESULTS: Grandio exhibited significantly higher mean flexural strength values when compared to Z350 (89.1 MPa vs 61.9 MPa). Grandio exhibited significantly higher top microhardness values when compared to Z350. Additionally when microhardness for the top surfaces of each composite were compared with their corresponding bottom surfaces, the bottom surfaces demonstrated significantly lower readings. The properties of fracture toughness and diametral tensile strength were non-discerning factors in this particular study. CONCLUSION: Grandio has greater observed values for the properties of flexural strength and hardness when compared with Z350. There was no difference between the two materials with respect to their fracture toughness and diametral tensile strength.

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