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Biomedical subjects

P C Borsboom

Publications and source records attributed to P C Borsboom.

16 recordsLinked to original sources
PubMed2001

Investigation of applicability of a mid-infrared spectroscopic method using an attenuated total reflection accessory and a new near-infrared transmission method for determination of faecal fat.

In many laboratories, the titrimetric method of Van de Kamer is used for the analysis of faecal fat content of patients suspected of steatorrhoea. We investigated the applicability of a mid-infrared (MIR) spectroscopic method, using an attenuated total reflection (ATR) accessory, and a new near-infrared (NIR) spectroscopic method. For the NIR method, sealed plastic bags containing the stool samples were used as transmission cells. Standardization was obtained using a previously described MIR method, with a NaCl flow-cell, as reference method. Partial least-squares regression was used for the calibration of each method. Full cross-validation of the calibration set was used for the internal validation of each method. Fifteen per cent of the stool samples could not be estimated with the ATR method within reasonable accuracy limits compared with the reference. The standard error of prediction of the NIR method was 1.1 g/dL. We conclude that the new NIR method is a promising technique for routine use. However, further experiments need to be done with triplicate measurements of each sample and the use of an external validation set.

Calibration↗
PubMed1990

A comparison of new and conventional methods for quantification of tooth color.

Tooth color is caused by volume reflection, that is, passage of incident light through the tooth followed by backward emergence. This passage is concurrent with sideward displacement of photons that, in effect, influences the result of usual instrumental methods of determining tooth color. This problem is overcome by the use of large-field illumination and small-field observation. A fiber-optics colorimeter based on this principle is described. The color observed through two holes in a double box was visually matched by subtractive adjustment of the illuminating color in one box, whereas the other box showed the central part of the tooth diffusely illuminated by illuminant C light. This colorimeter was tested on wet, extracted human incisors in the tooth arch of a phantom-head. Results were compared with a visual standard-strip method described previously and with a conventional spectrophotometer. It was concluded that the fiber-optics colorimeter is a promising instrument, although technical improvement is necessary.

Acrylic Resins↗
PubMed1990

Measurement of the uniaxial elasticity of oral mucosa in vivo after CO2-laser evaporation and surgical excision.

The stress-strain relation of oral mucosa of dogs was measured before and 6 weeks after surgical removal of mucosa. Both CO2-laser evaporation and excision were employed. Measurements were done with a miniature tensile tester, especially developed for this purpose. The load-strain ratio of the healed mucosa was proportional to the histologically determined thickness of the healed epithelium and scar tissue together. Laser evaporation caused a 75% increase, excision almost a threefold increase of the load-strain ratio compared with untreated tissue.

Animals↗
PubMed1989

Effect of a decrease of interproximal overexposure of bitewing radiographs on the diagnosis of approximal caries.

In bitewing radiographs the approximal enamel is always overexposed because of the short X-ray beam path in this area. This expectedly leads to a deteriorated detectability of lesions. Abrogation of this overexposure by application of X-absorbing paste in the interproximal space will presumably relieve the deterioration of lesion detection. This principle is demonstrated with aluminum cylinders in which a groove simulates a lesion. The principle is also applied to a phantom head with 0.1- to 0.7-mm lesions in the bicuspids. The resulting bitewing radiographs were scored by dentists, and a lesion detection score as used before was calculated. No score improvement resulted from the relieving of overexposure. This is ascribed to the predominant role of recognition processes in the ability to detect a lesion.

Absorption↗
PubMed1988

Determination of mineral changes in human dental enamel by longitudinal microradiography and scanning optical monitoring and their correlation with chemical analysis.

Both longitudinal microradiography (LMR) and scanning optical monitoring (OM) are non-destructive methods for measuring mineral changes in dental tooth enamel slices with time at 169 locations on the slice. Average calcium losses from four human tooth enamel slices (300-400 micron thickness), etched in HClO4, were determined by LMR and chemical analysis (C). As predicted from theory, LMR and C correlate very well (r = 0.99), but the appearance of a systematic error of unknown source of 30% made with LMR, C, or both could not be avoided. Another, more complex, experiment concerned six human tooth enamel slices of the same thickness which were demineralized in an aqueous buffered acid solution containing Ca and PO4. From this experiment it was found that average calcium loss as measured by C and LMR correlated well with the optical scattering as measured with scanning OM (Spearman rank correlation rs approximately equal to 0.79). It was also found that three-dimensional plots of local calcium loss by LMR and scanning OM as a function of tooth slice surface position show a well-defined tooth-dependent increase due to local demineralization and rather similar behaviour with time. From the experiments it follows that LMR and scanning OM are reliable methods to determine the mineral change in a tooth tissue as a function of local tooth slice surface position and of time and that with LMR and scanning OM time- and position-dependent measurements with an oral device become feasible.

Acid Etching, Dental↗
PubMed1988

Optical quantitation of natural caries in smooth surfaces of extracted teeth.

An optical instrument is described which quantitates incipient smooth surface caries lesions in vivo. The possible role of such quantitation in caries management and in clinical caries research is discussed. The instrument uses a bundle of small fibres in an 'optical needle' with a flat end that is placed on the lesion. Half the fibres are used to illuminate the lesion and the other half to collect the light backscattered by the lesion interior. In this geometry, lesions reflect much more light than does sound enamel. The instrument has been validated against natural lesions in extracted teeth, and the depth of these lesions and their mineral loss were measured by microradiography. The correlation coefficient between these two parameters was 0.96 and the correlation between optical measurement and lesion depth 0.71.

Calibration↗
PubMed1987

A machine for sawing 80-micrometer slices of carious enamel.

Design and construction of a machine that cuts 80-microns slices of sound and carious dental enamel and other calcified tissues is described. These slices can be used for quantitative microradiographic studies. Preparation takes minutes. Thickness for a given slice is uniform within 2 microns, mean thickness is within 4 microns of the intended value and roughness is about 0.1 micron. Commercial components have been used where possible. Information is provided to permit purchase of the components of the machine and its construction in the average university workshop.

Animals↗
PubMed1985

Decreased scattering coefficient of blue sclerae.

The optical scattering properties of blue and normal sclerae were studied with a fiber optic scattering monitor. The scattering was clearly reduced in two osteogenesis imperfecta patients with blue sclerae, and low normal in one osteogenesis imperfecta patient without blue sclerae.

Adult↗
PubMed1985

A new method for matching tooth colors with color standards.

A new method for quantitative intra-oral tooth color determination is presented. Basically, the tooth color is assessed by visual comparison with opaque color standards, which are logically arranged according to three visual color dimensions. The standards were analyzed spectrophotometrically, and the C.I.E. color coordinates were computed. Illumination and observation were standardized during the matching procedure. Two distinct situations, method 1 and method 2, were investigated. The situation in method 1 is to be considered as large window illumination and small window collection of the reflected light. For method 2, the same small window was used for both illumination and observation. Using both methods, the color of a tooth could be quantified into three separate color dimensions. Using method 1, the consistency among 25 examiners was high in determining the color of ten teeth; using method 2, the inter-examiner agreement was low. For the same tooth, different color standards were selected with method 1 or method 2. The standard selected with method 2 often appeared to be in disagreement within clinical expectations. The differences in results between method 1 and method 2 are explained by the optical properties of the translucent dental enamel (e.g., volume reflection). Method 1 allows for reproducible quantification of clinical tooth discoloration according to C.I.E. color specifications and can possibly be applied in prosthetic dentistry.

Color↗
PubMed1979

A non-destructive optical method to study de- and remineralization of enamel.

The absorption and scattering of light in dental enamel or in a carious lesion have been studied quantitatively by using thin slabs. The method thus required destructive preparation techniques. In this paper we describe how the scattering by a bulk sample can be used to obtain semi-quantitative information.

Animals↗