Analysis of the diametral compressive bond strength between composite resin and amalgam in different stages of oxidation.
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AIM: Amalcomp is a technique that combines composite resin to amalgam in restorative procedures to improve esthetics and minimize the negative effects of polymerization on dental tissues. The objective of this in vitro study was to measure the diametral compressive bond strength between Fill Magic composite (Vigodent) versus Permite (DFL) or Velvalloy (SS White) amalgams in different oxidation stages. METHODS: Twenty-four cylinders of each amalgam brand were fabricated using a Teflon matrix and divided into 3 groups according to the immersion period in artificial saliva for oxidation: A (1 day), B (7 days) and C (30 days). After immersion, the amalgam cylinders were bonded to the composite specimens using the Scotch Bond Multi Use Plus (3M) bonding system. Diametral compression assays were then carried out in an EMIC-MEM 2000 universal testing machine set to 0.5 mm/min. Statistical analysis was performed using ANOVA and Tukey's test. RESULTS: The mean recorded strength (MPa) for each oxidation group was: A=9.71, B=8.21 and C=6.98 (A>B = C; P<0.01). Permite (7.24) provided significantly less adhesion to the composite than Velvalloy (9.36; P<0.05). There was no interaction between the factors alloy, resin and time. CONCLUSIONS: Under the conditions of this study, the less oxidized amalgam showed the greatest diametral compressive strength values. (+info)
The development of Ti alloys for dental implant with high corrosion resistance and mechanical strength.
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The corrosion behaviors of Ti and Ti-6Al-4V, Ti-6Al-7Nb, Ti-0.5Pt, Ti-6Al-4V-0.5Pt, and Ti-6Al-7Nb-0.5Pt alloys were examined using an electrochemical analyzer in artificial saliva containing 0.1 and 0.2% NaF at a pH of 4.0. The SEM observations revealed that the surfaces of the alloys containing 0.5 wt% Pt were not affected in fluoride-containing environments, whereas the surfaces of Ti, Ti-6A1-4V, and Ti-6Al-7Nb alloys were markedly rough. In artificial saliva containing 0.1% NaF at a pH of 4.0, the amounts of Ti dissolved from the Ti, Ti-6Al-4V, and Ti-6Al-7Nb alloys were about 50 times larger than those of the alloys containing 0.5 wt% Pt. The tensile strengths of the alloys containing 0.5 wt% Pt were equal to or higher than those of pure Ti or the alloys without Pt. The Ti-0.5Pt, Ti-6Al-4V-0.5Pt, and Ti-6Al-7Nb-0.5 alloys are expected to be useful in clinical dentistry as new Ti alloys with high corrosion resistance and mechanical strength. (+info)
Frictional properties of aesthetic brackets.
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The purpose of this study was to compare the frictional properties of two self-ligating aesthetic brackets, Opal (Ultradent Products) and Oyster (Gestenco Int.), with those of four conventionally ligated aesthetic brackets, Transcend (3M Unitek), Inspire (Ormco), Allure (GAC Int.), and Image (Gestenco Int.). Friction was tested with different wire dimensions and qualities [stainless steel (SS) wire 0.017 x 0.025 inches; SS 0.019 x 0.025 inches; TMA 0.019 x 0.025 inches] using a Zwick testing machine. All brackets had a 0.022-inch slot and the prescription of an upper first premolar of the Roth system (tip: 0 degrees, torque: -7 degree). Each bracket/archwire combination was tested 10 times and each test was performed with a new bracket/wire sample that was pulled through twice. Additionally, two sets of 30 Opal brackets each were aged with an ageing machine under standardized conditions for 9-10 and 18-20 months, respectively. Friction of the aged brackets was tested with identical wire dimensions and qualities using the same testing procedure. All data were statistically analysed with unsigned comparisons of all bracket/wire combinations using GLM and the Games-Howell post hoc test. The results showed Opal brackets to have the lowest frictional forces for all wire dimensions and qualities. Furthermore, friction was lower at a significant level (P +info)
Electrochemical behavior and pH stability of artificial salivas for corrosion tests.
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It is assumed that the compositions of artificial salivas are similar to that of human saliva. However, the use of solutions with different compositions in in vitro corrosion studies can lead dissimilar electrolytes to exhibit dissimilar corrosivity and electrochemical stability. This study evaluated four artificial salivas as regards pH stability with time, redox potentials and the polarization response of an inert platinum electrode. The tested solutions were: SAGF medium, Mondelli artificial saliva, UFRJ artificial saliva (prepared at the School of Pharmacy, Federal University of Rio de Janeiro, RJ, Brazil) and USP-RP artificial saliva (prepared at the School of Pharmaceutical Sciences of Ribeirao Preto, University of Sao Paulo, SP, Brazil). It was observed that pH variations were less than 1 unit during a 50-hour test. The SAGF medium, and the UFRJ and USP-RP solutions exhibited more oxidizing characteristics, whereas the Mondelli solution presented reducing properties. Anodic polarization revealed oxidation of the evaluated electrolytes at potentials below +600 mV SCE. It was observed that the UFRJ and USP-RP solutions presented more intense oxidation and reduction processes as compared to the Mondelli and SAGF solutions. (+info)
Retention and penetration of a conventional resin-based sealant and a photochromatic flowable composite resin placed on occlusal pits and fissures.
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This study compares the retention and penetration of a conventional resin-based sealant (Fluroshield) and a photochromatic flowable composite resin (Tetric Flow Chroma) placed on occlusal pits and fissures and submitted to thermal or chemical cycling regimens. Penetration assessment--ten premolars were sealed with each material, isolated (except for the sealed surface) and immersed in 0.2% Rhodamine B. The teeth were serially sectioned in a mesiodistal direction. The images of the sections were digitized and analyzed (ImageLab). The distance between the most superficial and the deepest points on the occlusal central groove was calculated to determine the groove's total depth. The length of the central groove filled with the sealant was divided by its total depth to obtain the percentage of sealing of the occlusal groove. Retention assessment--30 premolars were sealed, their occlusal surfaces were photographed and the area occupied by the sealing materials was demarcated (ImageLab). The teeth were submitted to different treatments: thermocycled, stored in artificial saliva and immersed in acetic acid and saliva (10 cycles/day protocol for 30 days). New photographs were taken to assess the final area occupied by the materials. The difference between the final and initial area was calculated to obtain the material loss. The data was analyzed (two-way ANOVA and Tukey's test P<0.05). Both materials presented similar penetration of the occlusal central groove. After thermal and chemical cycling, the materials did not differ with respect to retention, except for immersion in acetic acid. In this case, Tetric Flow Chroma presented greater retention than Fluoroshield. (+info)
Effect of fluoride released from fluoride-containing dental restoratives on NiTi orthodontic wires.
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The present study investigated the effect of fluoride released from dental restoratives on orthodontic NiTi wires. Five different restoratives (four fluoride-containing and one non-fluoride-containing) and four different NiTi wires were examined in this study. The pH of artificial saliva (AS) was adjusted to 2.5 and 6. Content of released fluoride was determined daily for 10 days. The morphology of wires was observed using a scanning electron microscope. After immersion for 10 days, the initial microhardness of the wires decreased by 0.3-5.6% depending on the test solution. Dyract AP (DA) and F2000 (F2) (compomers) released significantly more fluoride than the other resin products (composite resins) regardless of the test solution. In pH 2.5 solution, both DA and F2 released 40-45 ppm/day fluoride for five to six days. As for the wires in contact, they did not show any visible modification in surface morphology. Therefore, despite the released fluoride, wires in contact with the fluoride-containing restoratives were not damaged regardless of the pH value of test solution. (+info)
Effect of a bonding agent on in vitro biochemical activities of remineralizing resin-based calcium phosphate cements.
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Erosive effects of acidic center-filled chewing gum on primary and permanent enamel.
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BACKGROUND: The higher incidence of dental erosion in children and teenagers possibly reflects a high intake of acidic food and beverages as well as a more frequent diagnosis on this condition. AIM: The aim of this study was to evaluate the erosive potential of acidic filling of chewing gum in primary and permanent enamel. METHODS AND MATERIALS: Eighty enamel blocks (40 primary and 40 permanent teeth) were used and randomly distributed into eight groups. Groups were divided according to types of dental substrates (permanent or primary), frequency of exposure to the acidic substance (2X or 4X/day), and concentration (pure or diluted). Exposure time to the acidic content of the chewing gum was five minutes under agitation, during five days. RESULTS: All groups showed a significant decrease in surface microhardness (P P = 0.002), D3 (pure, 4X/day) and D4 (diluted, 4X/day) (P = 0.009) regarding the concentration, then the diluted acid content was associated with a greater decrease in microhardness. CONCLUSION: It is concluded that the acidic filling of a chewing gum reduced the microhardness of primary and permanent enamel. (+info)