PubMed · 6597822
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T Habu. 1984. [Surface-curing system for resin prostheses].. https://pubmed.ncbi.nlm.nih.gov/6597822/
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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.
PURPOSE: Develop a methodology to correlate microtensile bond strength (microTBS) and leakage within the same site of a specimen and evaluate the predominate debond and leakage pathways. MATERIALS AND METHODS: A Class II (MO) slot cavity was prepared in 37 extracted human molars and restored with indirect resin composite restorations. The restored teeth were thermocycled 300X between 5 and 55 degrees C and then stained with silver. Two specimens per tooth were obtained by diamond saw sectioning for measurement of leakage (microm) and microtensile bond strength (MPa) at the gingival wall and then tested for association with regression analysis. Scanning electron microscopy techniques and energy dispersive spectroscopy (EDS) were used to evaluate the debond and leakage pathways. RESULTS: Association between leakage and bond strength was not significant (t=1.31, p=0.198). All 74 samples debonded within the joint, predominantly at the hybrid layer-adhesive resin region with only one specimen including a small portion of resin cement in the debond pathway. Secondary and backscatter imaging and EDS analysis showed leakage in all samples that involved the hybrid layer. CONCLUSION: This study demonstrates a feasible method for evaluating leakage and bond strength at the joint interface within the same specimen.