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Biomedical subjects

P E Benson

Publications and source records attributed to P E Benson.

9 recordsLinked to original sources
PubMed2000

Enamel demineralisation assessed by computerised image analysis of clinical photographs.

OBJECTIVES: To investigate the use of computerised image analysis to measure the area of demineralisation on the buccal surface of a tooth and to analyse the effect on that measurement of varying the angle at which a photographic image of the buccal surface of a tooth is taken. METHODS: Twenty-two teeth with areas of incremental demineralisation on the buccal surface were photographed perpendicular to the buccal surface and at angles of 20 and 40 degrees, above (Cuspal) and below (Gingival) the perpendicular. The images were captured and analysed using computerised image analysis. RESULTS: The Gingival views showed lower limits of agreement than the Cuspal views, probably due to the positioning of the masking on the lower part of the flash, to reduce reflection. There was a significant difference between the areas of demineralisation measured for the three angles from the Gingival views (p<0.001). The mean differences in areas measured were not linear, but there was a significantly greater reduction in area measured for the 40 degrees views. CONCLUSIONS: Computerised image analysis to measure areas of demineralisation from a captured 35mm slide is reproducible. The position of the masking on the camera flash and the angle of the camera makes a difference to the area measured and the grey scales recorded. Images taken at a larger angle than 20 degrees to the perpendicular will record a significantly reduced area of demineralisation. Standardisation of photographs with the use of calibration markers and manipulation of images is discussed.

Analysis of Variance↗
PubMed1999

An in situ caries model to study demineralisation during fixed orthodontics.

OBJECTIVES: To investigate de/remineralization of enamel during the early stages of orthodontic treatment using the in situ caries model. DESIGN: A prospective, longitudinal study, using the in situ caries model. SETTING AND SAMPLE POPULATION: The Department of Orthodontics at the University of Liverpool School of Dentistry. Fifteen orthodontic patients undergoing fixed appliance treatment with extraction of premolar teeth. EXPERIMENTAL VARIABLE: Two enamel samples with pre-formed caries-like lesions were placed bilaterally, in specially constructed holders, on an orthodontic fixed appliance. One sample was bonded with a small bracket base. OUTCOME MEASURE: The parameters of the pre-formed carious lesion, expressed as mineral loss (delta Z), lesion depth (ld), lesion width (lw) and ratio (delta Z/ld) were compared between the bracketed, the non-bracketed and a control sample that had not been placed in the mouth. The difference between brackets place on the dominant (toothbrush hand) side and non-dominant side were also investigated. The correlation between mineral loss and length of time the sample was in the mouth was also analysed. RESULTS: There was considerable individual variation; however, a one-factor repeated analysis of variance showed a significant difference in ratio values between the three groups (p = 0.006). A pairwise comparison showed a significant reduction in ratio value for the non-bracketed sample compared with the control, but not the bracketed sample. There was no significant difference in mineral loss between the dominant and non-dominant sides. There was no linear correlation between the length of time the sample was in the mouth. CONCLUSION: An enamel sample with a pre-formed carious lesion, when placed in the mouth of an orthodontic patient, showed reduced remineralization in the presence of a simulated orthodontic bracket. Consistently effective preventive regimes to prevent demineralization in patients with fixed orthodontic appliances need to be developed. The technique described will be a valuable tool in this process.

Analysis of Variance↗
PubMed1998

Morphometric assessment of enamel demineralisation from photographs.

OBJECTIVES: To investigate the validity and reproducibility of a method of morphometric assessment of enamel demineralisation. METHODS: An in vitro investigation was carried out on 22 human teeth. One investigator coated the crowns of the teeth with an acid-resistant varnish, leaving a small window on the buccal surface. This was incrementally occluded by varnish over a 14-day period, during which the teeth were placed in a demineralising gel at pH 4.5. After varnish removal, a second investigator blindly quantitated the demineralised area by three methods of examination; direct visual, microscopic and from photographs. The microscopic and photographic measurements were carried out using a morphometric assessment with a 121-dot array. Photographs and assessments were repeated after 1 week. The readings were analysed using the kappa statistic, the limits of agreement and the coefficient of repeatability. RESULTS: Photographic assessments demonstrated excellent agreement for grid positioning (kappa > 0.81) and substantial agreement for reading reproducibility (kappa = 0.61-0.80). The coefficients of repeatability were found to be the same for repeat readings of the same slide and the repeated slides (5.0 mm2). They were higher for the microscopic technique (6.8 mm2) and for the direct visual technique (7.8 mm2). The limits of agreement are presented graphically. CONCLUSIONS: The photographic technique used was a reproducible method of measuring artificial enamel demineralisation. Measurement from photographs was more reproducible than direct measurement with the naked eye. Subjectiveness of the index leads to most variation and more objective means of assessing enamel demineralisation need to be found.

Humans↗
PubMed1997

A critical appraisal of measurement of the soft tissue outline using photographs and video.

Radiographs are essential in the planning and assessment of treatment, as well as the study of growth patterns, but before subjecting a child to X-rays, the clinician must ensure that it is justifiable on clinical grounds. The use of cephalometric radiography, particularly in the young patient with a cleft of the lip and/or palate, has been questioned. The aim of this project was to investigate the validity and reproducibility of using a photograph or video image, compared with a radiograph, for measurement of the soft tissue profile of the face. A radiographic phantom head was used, which consisted of a dry bone skull encased in a soft tissue substitute. The method involved comparing direct measurement of the head in a Reflex Metrograph with the results of computerized digitizing of a cephalometric radiograph, digitizing a video image from a computer screen and measurement of a photograph. It was found that digitizing of the soft tissue outline of a radiographic phantom head from a video image was neither a valid, nor a reproducible method of replacing cephalometric radiographs in the measurement of the soft tissue profile of the face. A photograph may be a clinically acceptable alternative, but errors from this method are likely to be larger than those due to digitization of a radiograph.

Analysis of Variance↗
PubMed1983

Longitudinal age changes in vigilance over an eighteen year interval.

An 18-year longitudinal repeat of the Mackworth Clock vigilance experiment was conducted. Skin potential response latencies (SPRL) and reaction times were taken from 33 men during the vigilance task. The longitudinal change in this study reproduced the earlier cross-sectional relationship. The 51 to 69 year olds showed faster reaction times, the 70 to 88 year olds showed slower reaction times and, the 70 to 88 year olds detected significantly fewer targets than when 18 years younger. It was found that the greater the change noted in this study reflected previously determined cross-sectional SPRL effect. However, the SPRL outcome was equivocated by a time-of-measurement effect. It was concluded that at about age 70 years a noticeable reduction in vigilance performance occurs, and this is accompanied by a reduction in autonomic and central nervous system reactivity.

Adult↗
PubMedDate not supplied

Reproducibility of quantitative measurement of white enamel demineralisation by image analysis.

The reproducibility of measuring artificial enamel white spot lesions from captured photographic images using computerised image analysis was assessed. Enamel lesions were induced on the buccal surface of 22 human teeth over periods of 3, 7 and 14 days. Standardised photographs were taken from above and below the occlusal plane. These were repeated after 2 weeks. The photographs were converted into TIFF images and mean grey scale levels of the areas of etched enamel were measured using computerised image analysis. Assessment of repeat readings of the same slide showed good reproducibility for photographs taken below the occlusal plane. The limits of agreement showed reasonable agreement between readings carried out on two slides of the same tooth. Capturing TIFF images via 35-mm film and measuring grey scale levels by computerised image analysis is a useful method of quantitative study of early enamel demineralisation. This may be developed for application in the clinical setting.

Adult↗