PubMed · 10853570
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M Miller. 1999. Finding, using appropriate materials is an ongoing challenge.. https://pubmed.ncbi.nlm.nih.gov/10853570/
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BACKGROUND AND OBJECTIVE: The clinical use of the Er:YAG laser in cavity preparation has become widespread. With respect to cavities prepared with the Er:YAG laser, restorations using composite resins and glass ionomer cements are common. The bond strength of current resin bonding systems to ground enamel is 14-30 MPa, whereas the strength to Er:YAG laser-irradiated enamel, regardless of the use or non-use of phosphoric acid etching is less than 10 MPa. STUDY DESIGN/MATERIALS AND METHODS: In this investigation, an ultrasonic scaler was tested as a technique to increase the bond strength of composite resins to the Er:YAG irradiated enamel surface. RESULTS: The application of the ultrasonic scaler significantly increased bond strength. CONCLUSIONS: The tensile bond strength in the groups treated with the ultrasonic scaler exhibited approximately twice the strength observed in groups treated with laser irradiation alone.
OBJECTIVE: The main goal of this study was the hardness evaluation of a composite resin cured by five LED (Light Emitting Diodes) based devices and a comparison with a conventional curing unit. The hardness test was used to compare the efficacy of both types of light source. METHODS: The LED-based devices were made employing an array of LEDs (Nichia Chem. Ind., Japan) emitting light peaked at 470nm. Composite resin (Z100, shade A3) was cured for 20, 40, 60, 120 and 180s with each LED-based device and for 40s with the halogen lamp. The composite samples were prepared with 0.35, 1.25 and 1.8mm of thickness. Five samples of each set of parameters were done. The hardness evaluation was performed at the non-illuminate surface with three indentations for each sample. RESULTS: All the samples cured by the LED-based devices showed inferior hardness values when compared with the halogen lamp at the typical curing time (40s). The L6 (device composed of six LEDs) was the most efficient one of the LED-based devices. Its obtained irradiance was 79mW/cm(2), whereas the halogen lamp irradiance was of 475mW/cm(2). For the L6 device here presented, longer exposure times or a thinner resin layer are required to achieve reasonable hardness values. SIGNIFICANCE: Besides the difference of irradiance when compared with halogen lamps, LED-based devices show to be a promising alternative curing instrument. Further development in instrumentation may result in devices even more efficient than conventional lamps.
OBJECTIVES: The aim of this study was to investigate the feasibility of using the microbond test (MBT) to probe the durability of the bond between a polymerized dental resin with differently silanized E-glass fibers. METHODS: The E-glass fibers were silanized with equivalent amounts of two types of acrylic-silane coupling agents: 3-methacryloxypropyltrimethoxysilane (MPTMS) and 10-methacryloxydecyltrimethoxysilane (MDTMS), a more hydrophobic silane coupling agent than MPTMS. Unsilanized E-glass fibers were used as the control. Microdroplets of a photo-activated dental resin were applied on the fiber and photocured with visible light irradiation (470 nm). Subsequently, the specimens were tested in shear after 24h storage in air at 23 degrees C or water at 60 degrees C. RESULTS: The mean interfacial shear strength (tau) and the standard deviation in MPa for the three systems in 23 degrees C in air (n>7) were: 33.8(10.1), 33.7(8.9) and 15.3(4.2) for the MPTMS silanized, MDTMS silanized, and unsilanized fibers, respectively. When the three types of fibers were first exposed to 60 degrees C water for 24h prior to having the microdroplets of the resin bonded to them, the strength values of the MDTMS silanized fibers and the control fibers remained essentially unchanged at (n> or =7) 31.8(7.7) and 17.5(4.9)MPa respectively; the MPTMS specimens showed a significant decrease to 15.8(4.8)MPa. Similar trends were observed when the fibers had microdroplets of the resin bonded to them prior to aqueous exposure. SIGNIFICANCE: These results indicate that the microbond test has the sensitivity to measure changes at the interface between polymerized dental resins and variously silanized E-glass fibers. It appears that surface modification of the fibers with the more hydrophobic silane coupling agent MDTMS promotes enhanced resistance to degradation from exposure to water. The microbond test has the potential for studying dental adhesion involving small bonded areas under a variety of conditions with different adhesive systems and substrates.