PubMed · 282933
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E Jaoui. [Composites for dental obturations. Scanning electron microscope study].. https://pubmed.ncbi.nlm.nih.gov/282933/
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OBJECTIVES: To use the technique of infrared thermography for non-invasive monitoring of temperature changes during polymerization of resin composite by measuring the infra-red emission from the surfaces of resin composite restorations during photocuring. METHODS: In this study 10 patient volunteers had resin composite restorations placed in upper incisor teeth and during photocuring the temperature rise within the composite was measured using the Thermovision 900 infra-red scanning system. RESULTS: The results demonstrate that the exotherm is almost instantaneous, occurring as soon as the light source is activated and rising to a peak at approximately 30 s before levelling off. The measurements suggest that a maximum temperature increase of 12 degrees C could occur, although this may only be for a short period (< 15 s). CONCLUSION: The range of temperature rise measured in this study (mean 5.4 degree C +/- 2.5 degree C) would suggest that the pulp may be endangered by the temperature rise which occurs during resin composite polymerization in vivo.
OBJECTIVES: The purpose of this investigation was to assess the effectiveness of five commercially available hand-held dental radiometers and a computer-based experimental radiometer. METHODS: Light intensity of five visible light activation units was determined using the dental radiometers. The influence of curing light intensity on depth of cure of a hybrid composite material was determined using a digital penetrometer. RESULTS: The radiometers evaluated varied with respect to sensor aperture diameter, scale readings (analogue or digital) and the units of measurement (arbitrary or mW cm2). The experimental computer-based radiometer allowed continuous recording of intensity against time; thus the light output could be monitored over the entire irradiation period. CONCLUSIONS: When light intensity readings were normalized with regard to a standardized light sensing device aperture of 4 mm diameter, a linear relationship was found between depth of cure and the logarithm of the intensity of the light. The results of this investigation support the use of dental radiometers for periodically monitoring visible light activation units.
Since the introduction in the 1970s of single paste composite materials, there has been a rapid increase in the range of both materials and activation light units. This investigation is being undertaken as part of a larger study where the characteristics of both composite materials, light activation units and composite material/light activation unit combinations, are being evaluated. This section of the study was undertaken to determine the characteristics of four light activation units. The equipment was developed to measure radiation energy over a wide range of illumination. This range can be from the relatively low intensity of radiation transmitted through restorative materials to the intensities of direct radiation from light activation units. The four light units tested had various radiation outputs between 225,000 lx and 75,000 lx. All the units, apart from one, showed a decrease in light output with successive applications. The units emitted radiation outside the optimum range of 440-500 nm, which may produce damaging radiation and glare. Although the extreme intensities varied threefold the effect on depth of cure of one-material varied by only 16%.