Artificial Caries-Like Lesions Analysed by the Optical Caries Monitor: An In Vitro Investigation

Wilhelm, Nikolas (1996) Artificial Caries-Like Lesions Analysed by the Optical Caries Monitor: An In Vitro Investigation. Master of Science thesis, University of Glasgow.

Abstract

Optical methods are one of many non-destructive methods investigated at the current time for the early detection of decalcification around orthodontic brackets. The visual method of von der Fehr was used firstly to assess decalcification. The results of the optical method were then compared with those from microradiography and microdensitometry. This study investigates the use of an optical probe in vitro (SENSOPTIC optical caries monitor) which works on the principle of light scattering by enamel crystals in relation to their surrounding environment. The optical caries monitor employs a narrow beam of white light illuminating a circular spot of ~1mm diameter. The light which emerges from the same spot is recollected and measured. The optical caries monitor was investigated with regard to its capability to produce repeatable and reproducible measurements of mineralised and demineralised tooth surfaces. For this purpose, 60 bovine incisors were obtained and prepared. All teeth were exposed to a demineralisation solution to create enamel surface lesions in specially designed areas. The lesions, exhibiting varying grades of white spot intensity, were assessed visually under a microscope and photographed for later visual assessment. Optical caries monitor readings were taken in the lesion areas which formed two bands on the mid labial surface of the crown aligned in two horizontal bands being ~5-6 mm long 1 mm wide and running ~1 mm parallel apart from each other. In each of the two lesion bands described as upper and lower carious lesion bands, four measurements were taken in each band at different locations. These measurements were each repeated four times and one average value was calculated for each of the spots. This value represented 16 measurents in total for each of the two carious lesion bands. The collection of the data for the sound enamel surface followed the same technique by using the area above the upper lesion band and below the lower lesion band as a control area. A total of 64 measurements were collected for each tooth grid provided data which consisted of 3776 measurements. One tooth was excluded from the sample because of excessive decalcification. To assess the reliability of the optical caries measurements, all 59 samples were subjected to further laboratory investigations. To assess the mineral changes which had occurred due to the demineralisation procedure the samples underwent examination by microradiography and microdensitometry. Von der Fehr Index assessment was made using photographic slides of the samples after demineralisation. Visual scoring was carried out on two different occasions, by two examiners, giving a time interval of one week before the second assessment. The slides were projected onto a screen for each scoring session. The slides were precoded prior to the scoring session and randomly arranged by the author for each of the sessions. At the end of the scoring sessions the code was broken for analysis of the scores. The results of the study demonstrated the capability of the caries monitor to differentiate differences between sound enamel areas and decalcified lesion areas. The caries lesion bands and non-caries lesion areas did not show any significant difference. The visual assessment scoring, based on the von der Fehr Index, showed reproducible results only for one examiner who had a clinical background, whereas for the non-clinical examiner they were not strong enough to show a consistent assessment during both scoring sessions. The results of this investigation, indicate that microdensitometry / microradioraphy was considered to be the most accurate method of lesion assessment. Comparisons between optical caries monitor scores and microdensitometry showed good correlations, although the prediction interval had a wide range. Furthermore, Delta Z and Lesion Depth showed good correlation values when compared to the caries monitor readings. When Surface Zone and Lesion Body were compared to the optical caries monitor readings, there was a poor correlation. There is great potential for future use of the optical caries monitor if some of the handling procedures, such as calibration, could be more simplified and the design of the apparatus more orientated towards future clinical use.

• Item Type: Thesis (Master of Science)
• Qualification Level: Masters
• Additional Information: Adviser: W J S Kerr
• Keywords: Dentistry
• Date of Award: 1996
• Depositing User: Enlighten Team
• Unique ID: glathesis:1996-76117
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 16:38
• Last Modified: 19 Nov 2019 16:38
• URI: https://theses.gla.ac.uk/id/eprint/76117