A new method for the in vivo assessment of changes in initial enamel caries lesions was developed and tested. A CCD camera equipped with a high-pass filter (λ > 520 nm) collects the fluorescence image of carious teeth, illuminated intraorally with diffuse laser light (λ=488 nm). Incipient lesions show a loss in fluorescence to be expressed as a percentage of fluorescence radiance of sound tissue. A PC program (Inspektor, model QLF 1.0) is used for display, storage, and subsequent analysis of images. To enable the calculation of fluorescence loss, the fluorescence of sound tissue at the lesion site is reconstructed from the radiances of sound tissue bordering the lesion. This method was tested on 19 visually sound buccal surfaces in vivo. The differences between actual and reconstructed radiance was -1.6 ± (SD) 1.1%, over areas varying between 8 and 14 mm2. The repeatability of the caries quantification was tested by measuring one arrested initial caries lesion 25 times in vivo. The lesion area was 0.56 ± 0.20 mm2, and the loss of fluorescence was 17.6 ± 0.7%, corresponding to a lesion depth of 17 ± 2 μm. The new quantitative method was applied for the testing of an in vivo caries model using plaque-accumulating brackets on premolars scheduled for extraction. Videoimages were recorded in vivo before bracketing and 0, 2, 3, and 5 weeks after debracketing. Clear changes between the different time points were recorded for both lesion size and mineral content. Thus, the method seems suitable for in vivo measurement of mineral changes in natural enamel lesions on smooth surfaces and might be useful for clinical trials and evaluation of preventive measures.
A new quantitative, non-destructive method using laser-induced fluorescence (LAP) was compared with longitudinal microradiography (LMR) for assessment of mineral changes in enamel slices using an in vitro caries model. Ten enamel slices, cut longitudinally from sound natural smooth surfaces of human teeth, were exposed to de- and remineralization in a pH-cycling model. The enamel slices were subjected to LAF and LMR measurements before and at 2, 4, 7, and 9 days of demineralization. For LAF, the average fluorescence radiance decreased during the demineralization period with 11% by day 2 and 49% by day 9. For LMR, the corresponding average loss of mineral content changed with 0.01 and 0.10 kg m––2 over the same time period. The mineral losses in each individual enamel slice measured with the two techniques were strongly correlated, r = 0.97. The Spearman rank correlation coefficient for all LAF and LMR demineralization results was 0.86. The precision (coefficient of variation) for LAF was 3.1%, corresponding to 0.005 kg m––2, and the repeatability error for LMR was 0.02 kg m-2 indicating a lower discrimination threshold for LAF compared to LMR. It was concluded that the new, sensitive, nondestructive LAF method provides possibilities for further improvement in the quantification of initial caries lesions in natural smooth enamel surfaces for use in in vitro studies. Furthermore, it offers potential in in situ caries studies as well as a tool in the diagnosis of early enamel caries in vivo.
Månsson (1996) Mineral loss in incipient caries lesions quantified with laser fluorescence and longitudinal microradiography: A methodologic study, Acta Odontologica Scandinavica, 54:1, 8-13To link to this article: http://dx.loss in incipient caries lesions quantified with laser fluorescence and longitudinal microradiography. A methodologic study. Acta Odontol Scand 1996;54:8-13. Oslo. ISSN 0001-6357.
The flexure strength of three resin-modified glass ionomer cements and one conventional glass ionomer cement and their bond strength to dental composites were studied by measuring the three-point bending and the shear strengths. The bond strengths between the dental composite and the resin-modified glass ionomer cements were dependent on the curing modes. Resin-modified glass ionomer cements bonded significantly more strongly to cured dental composites than dental composites bonded to cured resin-modified glass ionomer cements. However, the dental composites showed a significantly stronger bonding to the resin-modified glass ionomer cements than to the cured conventional glass ionomer cement, to which the dental composite did not adhere without acid etching. The flexure strengths of the resin-modified glass ionomer cements were significantly improved compared with the conventional one but were still significantly lower than that of the dental composites.
Diametral tensile strength (DTS), fracture strength, and Vickers microhardness were tested in three resin-modified glass ionomer cements (GICs), one chemically set GIC, and one dental composite. For the DTS studies test discs were immersed in deionized water at 37 degrees C for 10 min, 1 day, and 28 days, respectively. Cured discs were also implanted in back muscles of rats for 28 days before testing. The effects of light irradiation time and delayed curing on the DTS of the cements were also studied. Significantly higher strength was observed in the resin-modified GICs in comparison with the chemically set GIC at all observation period. K71 showed the highest strength among the GICs. No strength reductions were detected after 28 days for the specimens in vivo. An illumination time of 20 sec was enough to obtain final strength in the PFA and K71 specimens, and 40 sec was needed in the VI specimens. The strength of the resin-modified GICs when light-cured was significantly higher than when the same cements were allowed to set without irradiation. The microhardness of the light-cured GICs was similar to that of the dental composite. Considering the improved fracture strength and surface hardness, it was concluded that the resin-modified GICs present an interesting material for further development.
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