Biomedical subjects

Susan M Higham

Publications and source records attributed to Susan M Higham.

9 recordsLinked to original sources

PubMed2004

Quantification of root caries using optical coherence tomography and microradiography: a correlational study.

PURPOSE: The use of transverse microradiography (TMR) to quantify the amount of mineral lost during demineralization of tooth tissue has long been established. In the present study, the use of an en-face Optical Coherence Tomography (OCT) technology to detect and quantitatively monitor the mineral changes in root caries was investigated and correlated with TMR. MATERIALS AND METHODS: We used an OCT system, developed initially for retina imaging, and which can collect A-scans, B-scans (longitudinal images) and C-scans (en-face images) to quantitatively assess the development of root caries. The power to the sample was 250 microW, wavelength lambda = 850 nm and the optical source linewidth was 16 microm. RESULTS: Both the transversal and longitudinal images showed the caries lesion as volumes of reduced reflectivity. Quantitative analysis using the A-scan (reflectivity versus depth curve) showed that the tissue reflectivity decreased with increasing demineralization time. A linear correlation (r = 0.957) was observed between the mineral loss measured by TMR and the percentage reflectivity loss in demineralized tissue measured by OCT. CONCLUSION: We concluded that OCT could be used to detect incipient root caries, and that the reflectivity loss in root tissue during demineralization, measured by OCT, could be related to the amount of mineral lost during the demineralization.

Analysis of Variance↗

PubMed2003

The recharge of esthetic dental restorative materials with fluoride in vitro-two years' results.

OBJECTIVES: A range of esthetic restorative dental materials are now available to dental clinicians. The aim of this study was to evaluate the relative fluoride recharge potential of a number of these materials in vitro over two years. METHODS: Disc samples (12 mm x 2 mm) of each of the materials were placed into artificial saliva at neutral pH. The materials tested were: two glass ionomers (Chemfil; Ketac-Fil), two resin-modified glass ionomers (Photac-Fil Aplicap; Vitremer), two compomers (Dyract; Compoglass) and two composites (Heliomolar; Concise). At 13 intervals over a two years period the discs were subjected to a 2 min fluoride recharge by exposure to sodium fluoride (500 ppm F). The pre- and post-recharge fluoride release values were determined using an ion sensitive electrode. RESULTS: At all time intervals the post-recharge fluoride release of the materials was significantly different (MANOVA p<0.0001). The mean values for post-recharge fluoride release after two years were: Chemfil 10.3, Ketac 3.0, Vitremer 9.0, Photac-Fil Aplicap 12.1, Compoglass 5.0, Dyract 3.6, Concise 0.3, Heliomolar 0.2 (units = microgF/cm(2)/h). SIGNIFICANCE: Esthetic fillings vary significantly in their capacity to absorb and re-release fluoride. The glass ionomer-based materials displayed a far greater potential for fluoride recharge than the composites, in which the recharge was virtually negligible. Whilst it cannot be assumed that fluoride release is directly proportional to cariostatic potential, these results suggest that, where possible, glass ionomer-based materials should be used in patients who have a high caries rate.

Analysis of Variance↗

PubMed2003

Quantifying enamel demineralization from teeth with orthodontic brackets--a comparison of two methods. Part 1: repeatability and agreement.

The aim of this investigation was to compare the repeatability of measuring enamel demineralization surrounding an orthodontic bracket using two techniques: computerized image analysis from digitally converted photographic slides and quantitative light-induced fluorescence (QLF). Fifteen human molars were halved and shaped to look like incisors. The teeth were individually numbered and orthodontic brackets bonded to the buccal surface. The crowns were covered with acid resistant varnish, except for windows approximately 1.5 x 3 mm adjacent to the gingival, occlusal, mesial, and distal edges of the bracket. The windows were variously exposed to a demineralizing gel for 0, 3, 7, or 14 days, and the acid resistant varnish was removed. Standardized photographic slides and QLF images of the teeth were taken. These were repeated after 1 week. The slides were converted to grey scale digital format and analysed using Image-Pro Plus 3.0. The QLF images were stored, processed, and analysed using customized software. All images were recoded for blind analysis. The four surfaces of the bracket were inspected and only areas of suspected demineralization were analysed. This was repeated after 1 week. The limits of agreement and mean difference between repeat readings of the area of demineralization were similar for both techniques (-0.04 +/- 0.43 for photographs and -0.10 +/- 0.63 for QLF). Mean grey level (photographs) and mean loss of fluorescence from that area (deltaF) (QLF) showed acceptable limits of agreement. The Intra Class Correlation (ICC) was below 0.81 for the measurement of area from QLF, suggesting that random error needs to be reduced. There was evidence of systematic bias for the repeat readings of the grey levels from the photographs (P < 0.001). Enamel demineralization surrounding an orthodontic bracket can be measured reproducibly using these two techniques.

Bias↗

PubMed2003

Quantifying enamel demineralization from teeth with orthodontic brackets--a comparison of two methods. Part 2: validity.

This is Part 2 of an in vitro study investigating two techniques for recording and quantifying demineralization surrounding orthodontic brackets. In Part 1 the repeatability of computerized image analysis from digitally converted photographic slides and quantitative light-induced fluorescence (QLF) was explored. In Part 2 of the investigation the validity of each technique was examined. Thirty halved human molars, shaped to look like incisors and with an orthodontic bracket bonded to the buccal surface were used. A small area of each of the four edges of the bracket was variously exposed to a demineralizing gel for 0, 3, 7, or 14 days. Images of the teeth were taken and analysed using the two techniques. Repeat images and analysis were carried out blind. The sensitivity, specificity, positive, and negative predictive values were calculated. A negative result confirmed that there was no demineralization present in the majority of cases. A positive result was less reliable particularly for the occlusal and gingival regions. The 7- and 14-day demineralization patterns were detected every time using the photographic technique. The discrimination of the 0- and 3-day patterns was less reliable. The results of this study were extrapolated to allow for the prevalence of the condition following orthodontic treatment, and the implications of this for a putative clinical trial are discussed, together with the advantages and disadvantages of each method. Either technique would be applicable to use in a clinical trial.

Dental Bonding↗

PubMed2003

Correlation of quantitative light-induced fluorescence and optical coherence tomography applied for detection and quantification of early dental caries.

Fluorescence loss in enamel following demineralization has been correlated with the amount of mineral lost during the demineralization. The correlation between fluorescence loss measured by quantitative light-induced fluorescence (QLF) and the reflectivity loss measured by a versatile en face optical coherence tomography (OCT) system was investigated in a demineralization process to produce artificial dental caries. We used an OCT system that can collect A-scans (reflectivity versus depth), B-scans (longitudinal images), and C-scans (en face images). The power to the sample was 250 microW, the wavelength lambda = 850 nm, and the depth resolution in air 16 microm. A-scans, which show the profile of the reflectivity versus the depth of penetration into the tooth tissue, were used for quantitative analysis of the reflectivity loss. The results have shown that both the fluorescence radiance and reflectivity of the enamel decrease with increasing de- mineralization time. A linear correlation was observed between the percentage of fluorescence loss measured by QLF and the percentage of reflectivity loss measured by OCT. It was concluded that the decrease in reflectivity of the enamel during demineralization, measured by OCT, could be related to the amount of mineral lost during the de- mineralization process.

Algorithms↗

PubMed2002

Fluoride-releasing elastomeric ligatures assessed with the in situ caries model.

The in situ caries model was used to assess the clinical benefit of fluoride-releasing elastomeric ligatures. The design of the experiment was a longitudinal, prospective, randomized, crossover clinical trial. Fourteen individuals starting orthodontic treatment with fixed appliances were recruited. Three in situ enamel specimens, with preformed subsurface carious lesions, were prepared for each patient, from human premolars. Two were placed in customized holders and one was retained as a control specimen. A crossover design was used so that patients had two experimental periods of six weeks with either fluoridated or non-fluoridated elastomerics, and a washout between. Elastomerics were randomly allocated at the first visit and one enamel specimen was placed at the beginning and collected at the end of each experimental period. The specimens were sectioned and ground to 100 microns, and transverse microradiography was carried out. They were analysed using dedicated computer software. The outcome measure was the change in 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) between the three specimens. The mean mineral loss (vol %.micron) for the control specimen was 403.7 (+/- 139.5), compared with 599.3 (+/- 515.4) for the non-fluoridated ligatures and 477.2 (+/- 298.4) for the fluoridated ligatures. A one-factor within subjects ANOVA showed no statistical difference between the groups (P = 0.376). Fluoride-releasing ligatures do not provide a significant anti-cariogenic benefit in patients undergoing orthodontic treatment. This may be due to the short-term nature of the fluoride release. However, they might affect the local environment surrounding the bracket.

Adolescent↗

PubMed2002

Quantitative light-induced fluorescence: a potential tool for general dental assessment.

Current dental diagnostic methods can detect caries but cannot quantify the mineral status of a lesion. Quantitative light-induced fluorescence (QLF) measures the percentage of fluorescence change of demineralized enamel with respect to surrounding sound enamel, and relates it directly to the amount of mineral lost during demineralization. Development of caries-like lesions and subsequent remineralization of the lesions were monitored by QLF. The results showed that the percentage of fluorescence change (Delta Q) increased linearly with the demineralization time and decreased with increased remineralization time. Stained teeth were whitened with a bleaching agent and the change in stain intensity (Delta E) was quantified using QLF. The results showed that Delta E decreased linearly as the tooth regained its natural color. Factors that might affect the use of QLF to detect and quantify caries were also examined. It was concluded that QLF could be used to detect and longitudinally monitor the progression or remineralization of incipient caries, however lesion detection may be limited by the presence of saliva or plaque and enhanced by staining. The change in shade of discolored teeth by whitening agents could be quantitatively measured by QLF.

Dental Caries↗

PubMed2002

Development of a quantitative method to monitor the effect of a tooth whitening agent.

This study demonstrated a quantitative method for assessing the effect of a tooth whitening agent. Forty human teeth were stained with a tea solution, and randomly assigned to two groups (A, B) of twenty teeth. The teeth were subsequently treated with either sodium hypochlorite (NaOCL) or deionized distilled water (DDW) by intermittent immersion (60 seconds on each occasion) in a 1:10 dilution of NaOCL (group A) or DDW (group B). Prior to whitening and following each immersion, the color of the teeth at the stained spot was measured using ShadeEye-Ex Dental Chroma Meter and quantitative light-induced fluorescence (QLF). ShadeEye-Ex instantly gave a numerical value for the stain intensity, chroma (C), which is the average of three measurements taken automatically by the machine. QLF gave a quantitative value for the stain, delta Q (% mm2), following analysis of the fluorescence image of the tooth. Immersion was stopped after four readings when one specimen, in group A, was observed to have regained its natural color. There was a good correlation between C and delta Q with either NaOCL (Pearson correlation coefficient (r) = 0.974; p < 0.05) or DDW (r = 0.978; p < 0.05). With NaOCL, an inverse relationship observed between stain measurements, C (Linear fit correlation (R) = -0.982; p < 0.05) or delta Q (R = -0.988; p < 0.05) and exposure time correlated to a linear fit, but not with DDW. ANOVA showed a significant difference between the means (n = 20) of the reading at the measurement intervals (0, 60, 120 and 180 seconds) for both C (p < 0.001) and delta Q (p < 0.001) with NaOCL but not with DDW. In conclusion, the study highlighted the potential of ShadeEye-Ex Dental Chroma Meter as a tool for the quantitative assessment of the gradual change in shade of discolored teeth by tooth whitening products.

Analysis of Variance↗

PubMed2002

The use of quantitative light-induced fluorescence (QLF) to identify composite restorations in forensic examinations.

There has been a large increase in the number of tooth colored restorations "white fillings" placed in recent years. An increased demand from the public for more aesthetic dental restorations causes a potential problem for forensic dentists who may find the fillings difficult to identify and hence include in postmortem odontograms. This has implications for the accuracy of dental identifications, particularly in situations where limited time is available for postmortem identification, e.g., mass casualty incidents. A new method for the detection of composite restorations is presented. Quantitative Light-induced Fluorescence (QLF) is a technique currently employed to detect small changes in enamel mineral content. An experiment was conducted to determine if the technique would afford a greater degree of contrast between composite and enamel and thus enable the accuracy of composite identification in enamel. Twenty-four previously extracted human premolars were gently cleaned with pumice and wet-and-dry paper. Twelve were subsequently randomly selected and restored on their buccal surfaces with Spectrum (a composite) following manufacturer's instructions. No attempt was made to color match the teeth and all were filled with shade B3. Twelve teeth were left unrestored. QLF and normal white light images were taken of both restored and non-restored surfaces with teeth wet and then dried. Ten forensic dentists were asked on two separate occasions (one month between each attempt) to indicate whether or not they thought the surface was: a) restored or b) unrestored. Results indicate that forensic dentists detected a significantly higher proportion (p<0.005) of filled surfaces with QLF.

Autopsy↗