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Biomedical subjects

F Lutz

Publications and source records attributed to F Lutz.

322 records · Page 18Linked to original sources
PubMedDate not supplied

In vitro assessment of incipient approximal carious lesions using computer-assisted densitometric image analysis.

OBJECTIVES: To investigate the use of computer-assisted densitometric image analysis (CADIA) to detect incipient approximal carious lesions in vitro and to compare areas of demineralization and mechanically induced lesions by radiographic visual inspection. METHODS: Thirty-six extracted non-carious human molars were demineralized in a defined approximal area of interest (AOI) using a gel system (pH 4.8) applied over 15 weeks. Standardized digital radiographs were taken before and after creation of caries-like lesions and grayscale values were measured within the AOI. For another group of eight teeth, artificial defects were mechanically induced by a diamond bur and densitometric analysis was performed. Statistical significance was tested using the Wilcoxon test and set at p < or = 0.05. In addition, radiographs were interpreted by visual examination by six experienced dentists. The sensitivity and specificity for both study groups were determined in comparison to a baseline group of untreated teeth. Polarized light microscopy and SEM analysis were used to evaluate changes in the subsurface mineralization pattern and surface micromorphology. RESULTS: Densitometric comparison of images from identical regions in control teeth revealed no significant grayscale value differences within the AOI, whereas a significant decrease (p < or = 0.05) was observed in the demineralized group. Mechanically induced lesions also showed a significant densitometric decrease (p < or = 0.05). The sensitivity of visual inspection of radiographs of demineralized areas was 0%. In contrast, the sensitivity for the detection of a mechanical defect of 0.1mm, which was the same subsurface extension as the histologically determined demineralization, increased to 52%. Specificity was 100% for all groups. CONCLUSIONS: CADIA is able to detect very small changes in mineralization of incipient carious approximal lesions in vitro. The findings presented in this investigation may improve the subtraction method used for diagnosis and monitoring of approximal caries, as well as prophylactic measures.

Absorptiometry, Photon↗
PubMedDate not supplied

Microhardness of resin composites polymerized by plasma arc or conventional visible light curing.

This study evaluated the effectiveness of the plasma arc curing (PAC) unit for composite curing. To compare its effectiveness with conventional quartz tungsten halogen (QTH) light curing units, the microhardness of two composites (Z100 and Tetric Ceram) that had been light cured by the PAC or QTH units, were compared according to the depth from the composite surface. In addition, linear polymerization shrinkage was compared using a custom-made linometer between composites which were light cured by PAC or QTH units. Measuring polymerization shrinkage for two resin composites (Z100 and Tetric Ceram) was performed after polymerization with either QTH or PAC units. In the case of curing with the PAC unit, the composite was light cured with Apollo 95E for two (Group 1), three (Group 2), six (Group 3) or 2 x 6 (Group 4) seconds. For light curing with the QTH unit, the composite was light cured for 60 seconds with Optilux 500 (Group 5). The linear polymerization shrinkage of composites was determined in the linometer. Two resin composites were used to measure microhardness. Two-mm thick samples were light cured for three seconds (Group 1), six seconds (Group 2) or 12 (2 x 6) seconds (Group 3) with Apollo 95E or they were conventionally light cured with Optilux 500 for 30 seconds (Group 4) or 60 seconds (Group 5). For 3 mm thick samples, the composites were light cured for six seconds (Group 1), 12 (2 x 6) seconds (Group 2) or 18 (3 x 6) seconds (Group 3) with Apollo 95E or they were conventionally light cured with Optilux 500 for 30 seconds (Group 4) or 60 seconds (Group 5). Twenty samples were assigned to each group. The microhardness of the upper and lower surfaces was measured with a Vickers hardness-measuring instrument under load. The difference in microhardness between the upper and lower surfaces in each group was analyzed by paired t-test. For the upper or lower surfaces, one-way ANOVA with Tukey was used. For Tetric Ceram, the amount of polymerization shrinkage was lower when cured with the Apollo 95E for two or three seconds than when cured for six and 12 (2 x 6) seconds, or for 60 seconds with Optilux 500 (p<0.05). For Z100, the amount of linear polymerization shrinkage was lower when cured with the Apollo 95E for two, three and six seconds than for 12 (2 x 6) seconds with Apollo 95E or for 60 seconds with the Optilux 500 (p<0.05). The results of the microhardness test indicated that there was no statistically significant difference in microhardness between groups for the upper surface. However, for the lower surface, when the composites were light cured with Apollo 95E for three seconds as recommended by the manufacturer, microhardness of the lower surface was usually lower than that of the upper surface and did not cure sufficiently. Conclusively, when compared with conventional QTH unit, the PAC unit, Apollo 95E did not properly cure the lower composite surface when the layer thickness exceeded 2 mm. In addition, three seconds of curing time, which the manufacturer recommended, was insufficient for optimal curing of composites.

Analysis of Variance↗
PubMedDate not supplied

Fluoride retention by human enamel after in vitro application of nicomethanol hydrofluoride.

Fluoridated dentifrices generally contain sodium monofluorophosphate or sodium fluoride--alone or in combination--or a group of organic fluorides, the amine fluorides. The purpose of this study was to determine the fluoride and retention in vitro by human enamel, after brushing with a dentifrice containing the amine fluoride, nicomethanol hydrofluoride, the fluoride salt of nicotinyl alcohol.

Administration, Topical↗
PubMedDate not supplied

In vitro dissolution of human enamel after application of a mixture of stannous fluoride and amine fluoride 297: a pilot study.

Human enamel specimens were topically treated in vitro, using either a clear, aged aqueous mixture consisting of SnF2 and amine fluoride 297, or SnF2 alone, amine fluoride 297 alone, NaF, or water (as the negative control). The fluoride concentrations used were 250 ppm F1/n. The topically treated enamel specimens were then acid-etched for 5, 10, 15, and 15 seconds, respectively, in 2NHC1. The amount of phosphorous dissolved from the enamel and the depth of etch were both significantly less for the groups treated with SnF2/AmF297 and SnF2 alone, which indicated better protection against acid dissolution than the other three groups.

Acid Etching, Dental↗
PubMedDate not supplied

The postamalgam age.

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Dental Amalgam↗