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Biomedical subjects

M J Wicht

Publications and source records attributed to M J Wicht.

5 recordsLinked to original sources

Caries detection and quantification with DIAGNOdent: prospects for occlusal and root caries?

A possible consequence of light absorption as the interaction of electromagnetic radiation with molecules of the tooth's hard substances is, apart from the emission of heat, fluorescence. It was demonstrated that the emission spectra of enamel, dentin, and caries look alike upon excitation with red light; however, fluorescence increases with the process of carious destruction. Based on that, the DIAGNOdent System was developed, which simultaneously injects red light into the tooth surface and detects the resulting fluorescence. Due to this design, clinical application is currently limited to accessible occlusal and smooth surfaces. For occlusal caries detection, it was shown that validity and reproducibility could be optimized over classical diagnostic tests for deep dentin lesions with seemingly intact surfaces. The detection of root caries does not play a relevant role in the directly accessible areas, but estimation of the lesion's activity and progression rate is a prerequisite for differentiated lesion management Excellent reproducibility of the laser fluorescence measurements was confirmed for this scenario. Lesions with a soft surface texture show significantly higher fluorescence values than leathery or hard lesions, and values also increase with increasing cavity depth. DIAGNOdent offers the potential to improve follow-ups and estimation of the prognosis and to support clinical management of primary carious lesions.

Dental Caries↗

Influence of displayed image size on radiographic detection of approximal caries.

OBJECTIVES: To evaluate the validity of approximal caries detection on digital bitewing radiographs displayed at different image sizes on either a cathode ray tube (CRT) monitor or a thin film transistor (TFT) monitor. METHODS: Five observers assessed digital radiographs of a charge-coupled device (CCD)-based sensor system (Sidexis) of 160 unrestored premolars and molars for approximal caries using a six category caries rating scale. Images were displayed at ratios of 1:1, 1:2 and 1:7 on a CRT monitor (Nokia 446 XS) and a TFT display (Panasonic LC 50S). Histological assessments of serial sections were used as the validation standard. Diagnostic accuracy was expressed as area under the receiver operating characteristic (ROC) curve (AUC) and was calculated at two levels of caries penetration: presence of caries (I) and presence of a lesion in the dentine (II). The influence of the factors "monitor type", "image size" and "validation threshold" were analysed with repeated measures analysis of variance. RESULTS: The ROC curve areas for approximal caries detection at both histological penetration levels were not influenced by the type of monitor display, whereas image size had a significant impact (P<0.01). AUCs for image size 1:7 (I, 0.62; II, 0.65) were smaller compared with ratios of 1:1 and 1:2 (P<0.01). No differences were observed between image size ratios 1:1 (I, 0.69; II, 0.74) and 1:2 (I, 0.68; II, 0.73). CONCLUSIONS: In this study, the type of monitor did not influence approximal caries detection on digital radiographs. Image sizes with a display ratio of 1:1 and 1:2 resulted in better diagnostic validity than those with a ratio of 1:7.

Analysis of Variance↗

Influence of room lighting on grey-scale perception with a CRT-and a TFT monitor display.

OBJECTIVES: To determine the influence of ambient lighting on grey-scale perception using a cathode-ray tube (CRT) and a thin film transistor (TFT) computer display. METHODS: A cathode ray tube (Nokia XS 446) and a liquid crystal display (Panasonic LC 50S) were used at reduced room lighting (70 lux) and under conditions recommended for a dental operatory (1000 lux). Twenty-seven observers examined twice a modified SMPTE test pattern [0 to 255; 255 to 0] grey-scale values. The corresponding contrast differences were allocated to four ranges of grey levels (I: 0-63; II: 64-127; III: 128-191; IV: 192-255). The influences of monitor type, grey-scale range and illumination were evaluated by means of repeated measures analysis of variance. RESULTS: Detection of differences in monochromatic intensity was significantly earlier with reduced lighting (P<0.0001). When full ambient lighting was used, the TFT display was superior compared to the CRT monitor in ranges II and III (P<0.0001), whereas no differences could be detected for grey intensities between 0 and 63 (P=0.71) and between 192 and 255 (P=0.36). CONCLUSIONS: Background lighting hampers grey-scale perception on computer displays. In this study of one TFT and one CRT monitor, the TFT in full ambient lighting was associated with earlier detection of grey scale differences than CRT.

Adult↗

Does chemomechanical caries removal affect dentine adhesion?

The purpose of this study was to determine whether shear bond strengths (SBS) to chemomechanically excavated dentine (Carisolv) differed from the SBS after conventional caries removal (bur). The following adhesive systems were used: Dyract AP/NRC/Prime & Bond NT; Dyract AP/Prime & Bond NT; Tetric Ceram/ Syntac SC; Tetric Ceram/Syntac SC (no etch) (TC 2); Definite/Etch & Prime 3.0; Definite/experimental. One-hundred and twenty human molars with occlusal caries were assigned to 12 groups. Sequential caries removal was controlled with laser fluorescence. After water storage, the samples were tested in a single-plane shear test assembly. The results demonstrated differences between the bonding systems, whereas the mode of caries removal had no consistent effect. If total etch technique was neglected, the results of the composite resin (TC 2) indicated a tendency to higher SBS in the Carisolv group (18.6 +/- 4.6 MPa) compared with conventional treatment (14.1 +/- 3.9 MPa). The present data demonstrate that chemomechanical caries removal has no adverse effect on bonding of modern adhesive systems to dentine. Smear layer-dissolving or -modifying bonding systems could potentially benefit from chemomechanical pretreatment.

Analysis of Variance↗

Conventional, digital and contrast-enhanced bitewing radiographs in the decision to restore approximal carious lesions.

The purpose of the present investigation was to compare the accuracy of treatment decisions in proximal sites using three intra-oral radiographic systems. Additionally, the impact of an automated non-linear grey-level display was evaluated. Ten observers assessed 84 surfaces on bitewing radiographs for their requirement of restorative treatment using a 6-rank confidence scale. Radiographs were taken with conventional film images (Ultraspeed), a storage phosphor plate (Digora) and a CCD system (Dexis). Additionally, the Dexis software was expanded by a contrast enhancement routine (Dexis+). The restorative treatment threshold was defined as presence of macroscopic cavitation. Regarding the areas below mean ROC curves no significant differences were detected between the groups (p>0.05). Likelihood ratios for positive test results were: 5.29 (Ultraspeed), 8.14 (Digora), 9.67 (Dexis) and 11.37 (Dexis+). The accuracy of restorative treatment decisions based on digital and conventional radiographs is comparable. If a dichotomous treatment decision was requested, the digital systems demonstrated a notable tendency towards higher likelihood of true-positive decisions.

Confidence Intervals↗