Imaging textural variation in the acoustoelastic coefficient of aluminum using surface acoustic waves.

Much interest has arisen in nonlinear acoustic techniques because of their reported sensitivity to variations in residual stress, fatigue life, and creep damage when compared to traditional linear ultrasonic techniques. However, there is also evidence that the nonlinear acoustic properties are also sensitive to material microstructure. As many industrially relevant materials have a polycrystalline structure, this could potentially complicate the monitoring of material processes when using nonlinear acoustics. Variations in the nonlinear acoustoelastic coefficient on the same length scale as the microstructure of a polycrystalline sample of aluminum are investigated in this paper. This is achieved by the development of a measurement protocol that allows imaging of the acoustoelastic response of a material across a samples surface at the same time as imaging the microstructure. The development, validation, and limitations of this technique are discussed. The nonlinear acoustic response is found to vary spatially by a large factor (>20) between different grains. A relationship is observed when the spatial variation of the acoustoelastic coefficient is compared to the variation in material microstructure.

School-based intervention for improving the oral health of children in southern Thailand.

OBJECTIVE: A two-year study assessed the benefit of an enhanced oral health promotion program combined with a closely supervised tooth brushing program in schools, using toothpaste containing 1,450 ppm F- and 1.5% arginine, on oral health and dental caries. METHODS: 15 southern Thailand schools and 3,706 pre-school children were recruited: 8 schools with 1,766 children as controls; 7 schools with 1,940 children in the intervention groups. Of the intervention schools five were classified as cooperative school and two as non-cooperative schools, based on the criteria of 80% participation in the prescribed tooth brushing activities. RESULTS: The DMFT and DMFS increments ("enamel and dentine") were 1.19 and 1.91 for the control group and 1.04 and 1.59 for the intervention groups. These represent 12.6% and 16.8% reductions in caries respectively. The DMFT and DMFS increments ("dentine threshold") were 0.26 and 0.44 for the control group and 0.19 and 0.29 for the intervention group, representing 26.9%, and 34.1% reductions in caries incidence respectively. For the more cooperative schools the benefits were greater: up to a 40.9% reduction in caries for DMFS ("dentine threshold"). At the 24 month examination there were significant improvements in dental plaque scores with greater improvements seen in the intervention group, greater still in the cooperative schools. CONCLUSIONS: This study documents the positive effect from use of fluoridated toothpaste (1,450 ppm F- and 1.5% arginine) administered by schoolteachers and undertaken via an enhanced school oral health program. Optimising oral health interventions for young children in Thai schools may have a significant impact on caries incidence resulting in reductions of up to 34% reductions in caries for all schools included in the study and up to 41% for the most cooperative.

Measuring initial enamel erosion with quantitative light-induced fluorescence and optical coherence tomography: an in vitro validation study.

BACKGROUND: Measurement of initial enamel erosion is currently limited to in vitro methods. Optical coherence tomography (OCT) and quantitative light-induced fluorescence (QLF) have been used clinically to study advanced erosion. Little is known about their potential on initial enamel erosion. OBJECTIVES: To evaluate the sensitivity of QLF and OCT in detecting initial dental erosion in vitro. METHODS: 12 human incisors were embedded in resin except for a window on the buccal surface. Bonding agent was applied to half of the window, creating an exposed and non-exposed area. Baseline measurements were taken with QLF, OCT and surface microhardness. Samples were immersed in orange juice for 60 min and measurements taken stepwise every 10 min. QLF was used to compare the loss of fluorescence between the two areas. The OCT system, OCS1300SS (Thorlabs Ltd.), was used to record the intensity of backscattered light of both areas. Multiple linear regression and paired t test were used to compare the change of the outcome measures. RESULTS: All 3 instruments demonstrated significant dose responses with the erosive challenge interval (p < 0.05) and a detection threshold of 10 min from baseline. Thereafter, surface microhardness demonstrated significant changes after every 10 min of erosion, QLF at 4 erosive intervals (20, 40, 50 and 60 min) while OCT at only 2 (50 and 60 min). CONCLUSION: It can be concluded that OCT and QLF were able to detect demineralization after 10 min of erosive challenge and could be used to monitor the progression of demineralization of initial enamel erosion in vitro.

Quantitative light-induced fluorescence to measure enamel remineralization in vitro.

UNLABELLED: The aim of this study was to compare the ability of quantitative light-induced fluorescence (QLF) and surface microhardness (SMH) to measure the remineralization of enamel subsurface lesions, using a pH-cycling model including treatment with 0-ppm, 550-ppm or 1,100-ppm sodium fluoride (NaF) dentifrices. METHODS: Subsurface lesions were created in human enamel specimens (n = 36) and exposed to a remineralization pH-cycling model for 14 days. The pH-cycling model was performed in an automated system where specimens were subjected to a demineralizing solution for 20 min and treatment for 1 min and were then remineralized for 7 h 39 min, 3 times daily. The treatments consisted of 3 NaF, silica-containing dentifrices (0 ppm F; 550 ppm F; 1,100 ppm F). The outcome variables were: change from baseline in surface hardness and percentage change from baseline in fluorescence. An ANCOVA explored differences between different treatment groups (at the p < 0.05 level). Associations between QLF and SMH were evaluated using Spearman's correlation coefficient. RESULTS: The percentage SMH changes were 14.9 ± 2.1%, 56.6 ± 9.6% and 103.9 ± 14.6% for the 0-, 550- and 1,100-ppm F dentifrices, respectively. The percentage fluorescence changes were 15.6 ± 7.1%, 59.8 ± 11.9% and 85 ± 13.2%, respectively. The differences between all pairwise comparisons were statistically significant for both methods (p = 0.001). QLF correlated with SMH (r = 0.67). CONCLUSIONS: Both the SMH and QLF methods demonstrated a significant F dose response for toothpaste in this in vitro remineralization model, and both methods were able to distinguish treatments with different F levels.

Determination of the acoustoelastic coefficient for surface acoustic waves using dynamic acoustoelastography: an alternative to static strain.

The third-order elastic constants of a material are believed to be sensitive to residual stress, fatigue, and creep damage. The acoustoelastic coefficient is directly related to these third-order elastic constants. Several techniques have been developed to monitor the acoustoelastic coefficient using ultrasound. In this article, two techniques to impose stress on a sample are compared, one using the classical method of applying a static strain using a bending jig and the other applying a dynamic stress due to the presence of an acoustic wave. Results on aluminum samples are compared. Both techniques are found to produce similar values for the acoustoelastic coefficient. The dynamic strain technique however has the advantages that it can be applied to large, real world components, in situ, while ensuring the measurement takes place in the nondestructive, elastic regime.

Dentists' perspectives on caries-related treatment decisions.

OBJECTIVE: To assess the impact of patient risk status on Colombian dentists' caries related treatment decisions for early to intermediate caries lesions (ICDAS code 2 to 4). METHODS: A web-based questionnaire assessed dentists' views on the management of early/intermediate lesions. The questionnaire included questions on demographic characteristics, five clinical scenarios with randomised levels of caries risk, and two questions on different clinical and radiographic sets of images with different thresholds of caries. RESULTS: Questionnaires were completed by 439 dentists. For the two scenarios describing occlusal lesions ICDAS code 2, dentists chose to provide a preventive option in 63% and 60% of the cases. For the approximal lesion ICDAS code 2, 81% of the dentists chose to restore. The main findings of the binary logistic regression analysis for the clinical scenarios suggest that for the ICDAS code 2 occlusal lesions, the odds of a high caries risk patient having restorations is higher than for a low caries risk patient. For the questions describing different clinical thresholds of caries, most dentists would restore at ICDAS code 2 (55%) and for the question showing different radiographic thresholds images, 65% of dentists would intervene operatively at the inner half of enamel. No significant differences with respect to risk were found for these questions with the logistic regression. CONCLUSION: The results of this study indicate that Colombian dentists have not yet fully adopted non-invasive treatment for early caries lesions.

A randomized clinical trial of the anti-caries efficacy of 5,000 compared to 1,450 ppm fluoridated toothpaste on root caries lesions in elderly disabled nursing home residents.

Root caries is prevalent in elderly disabled nursing home residents in Denmark. This study aimed to compare the effectiveness of tooth brushing with 5,000 versus 1,450 ppm of fluoridated toothpaste (F-toothpaste) for controlling root caries in nursing home residents. The duration of the study was 8 months. Elderly disabled residents (n = 176) in 6 nursing homes in the Copenhagen area consented to take part in the study. They were randomly assigned to use one of the two toothpastes. Both groups had their teeth brushed twice a day by the nursing staff. A total of 125 residents completed the study. Baseline and follow-up clinical examinations were performed by one calibrated examiner. Texture, contour, location and colour of root caries lesions were used to evaluate lesion activity. No differences (p values >0.16) were noted in the baseline examination with regards to age, mouth dryness, wearing of partial or full dentures in one of the jaws, occurrence of plaque and active (2.61 vs. 2.67; SD, 1.7 vs.1.8) or arrested lesions (0.62 vs. 0.63; SD, 1.7 vs. 1.7) between the 5,000 and the 1,450 ppm fluoride groups, respectively. Mean numbers of active root caries lesions at the follow-up examination were 1.05 (2.76) versus 2.55 (1.91) and mean numbers of arrested caries lesions were 2.13 (1.68) versus 0.61 (1.76) in the 5,000 and the 1,450 ppm fluoride groups, respectively (p < 0.001). To conclude, 5,000 ppm F-toothpaste is significantly more effective for controlling root caries lesion progression and promoting remineralization compared to 1,450 ppm F-toothpaste.

Two-year caries clinical study of the efficacy of novel dentifrices containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm fluoride.

A 2-year double-blind randomized three-treatment controlled parallel-group clinical study compared the anti-caries efficacy of two dentifrices containing 1.5% arginine, an insoluble calcium compound (di-calcium phosphate or calcium carbonate) and 1,450 ppm fluoride (F), as sodium monofluorophosphate, to a control dentifrice containing 1,450 ppm F, as sodium fluoride, in a silica base. The 6,000 participants were from Bangkok, Thailand and aged 6-12 years initially. They were instructed to brush twice daily, in the morning and evening, with their randomly assigned dentifrice. Three trained and calibrated dentists examined the children at baseline and after 1 and 2 years using the National Institute of Dental Research Diagnostic Procedures and Criteria. The number of decayed, missing and filled teeth (DMFT) and surfaces (DMFS) for the three study groups were very similar at baseline, with no statistically significant differences among groups. After 1 year, there were no statistically significant differences in caries increments among the three groups. After 2 years, the two groups using the dentifrices containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm F had statistically significantly (p < 0.02) lower DMFT increments (21.0 and 17.7% reductions, respectively) and DMFS increments (16.5 and 16.5%) compared to the control dentifrice. The differences between the two groups using the new dentifrices were not statistically significant. The results of this pivotal clinical study support the conclusion that dentifrices containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm F provide significantly greater protection against caries lesion cavitation, in a low to moderate caries risk population, than dentifrices containing 1,450 ppm F alone.

A clinical investigation using quantitative light-induced fluorescence (QLF) of the anticaries efficacy of a dentifrice containing 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate.

OBJECTIVE: The purpose of this study was to assess the ability of a new dentifrice containing arginine, an insoluble calcium compound, and fluoride to arrest or reverse naturally occurring buccal caries lesions measured using Quantitative Light-induced Fluorescence (QLF). METHODS: Three study groups used dentifrices which contained 1) 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate (experimental), 2) 1450 ppm fluoride as sodium monofluorophosphate (positive control), and 3) no fluoride (negative control). All three dentifrices were formulated in the same calcium base. The study participants were from three schools in the city of Chengdu, Sichuan Province, China. A total of 446 of 450 recruited subjects completed the study. Of these, 147 were in the experimental, 148 in the positive control, and 151 in the negative control groups. The initial age of the children was 10-12 years (mean 11.4 +/- 0.54); 47.5% were female. RESULTS: Using QLF, assessments of buccal caries lesions were made at baseline and after three and six months of product use. For AQ, representing lesion volume, the baseline mean value for the three groups was 27.30, and at the three-month examination the mean values were 16.76, 19.25, and 25.89 for the experimental, positive, and negative control dentifrices, respectively. This represents improvements from baseline of 38.6%, 29.5%, and 5.2%. At six months, the deltaQ values for the three groups were 13.46, 18.47, and 24.18, representing improvements from baseline of 50.7%, 32.3%, and 11.4%. For all QLF metrics, deltaF (loss of fluorescence), area, and deltaQ, the differences between the negative control and both the experimental and positive control groups were statistically significant (p < or = 0.01). The differences between the experimental and positive control groups attained statistical significance for deltaQ (p < or = 0.003) at the six-month examination. CONCLUSION: It is concluded that both of the fluoride-containing toothpastes are significantly better at arresting and reversing buccal caries lesions than the non-fluoride toothpaste. Furthermore, it is concluded that the new dentifrice containing arginine, an insoluble calcium compound, and fluoride provides significantly greater anticaries benefit than a dentifrice containing fluoride alone.

A clinical investigation of the efficacy of a dentifrice containing 1.5% arginine and 1450 ppm fluoride, as sodium monofluorophosphate in a calcium base, on primary root caries.

OBJECTIVE: The purpose of this six-month study was to assess the ability of a new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, as sodium monofluorophosphate, to arrest and reverse primary root caries lesions in adults. METHODS: Three test groups used dentifrices which contained either: 1) 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate in a calcium base (experimental); 2) 1450 ppm fluoride as sodium fluoride in a silica base (positive control); or 3) no fluoride in a calcium base (negative control). The study participants were residents of the city of Chengdu, Sichuan Province, China. In order to take part, subjects had to have at least one non-cavitated primary root caries lesion. A total of 412 subjects completed the study. They were aged from 50 to 70 years (mean age 64 +/- 4.1 years) and 53.6% were female. Efficacy for arresting and reversal of primary root caries was assessed by clinical hardness measures and through the use of the Electrical Caries Monitor. RESULTS: After three months of product use, clinical hardness measures showed that 27.7%, 24.6%, and 13.1% of lesions had improved in the experimental, positive, and negative control groups, respectively, and 0.7%, 4.5%, and 16.8% had become worse, respectively. The differences in the distribution of lesion change between the negative control group and both the experimental (p < 0.001) and positive control (p = 0.001) were statistically significant. The Electrical Caries Monitor was also used as an objective measure of lesion severity. The end values increased from baseline to the three-month examinations, but none of the differences between the groups attained statistical significance. After six months, clinical hardness measures showed that only one lesion (0.7%) was worse than at the baseline examination-in the experimental group compared to 9.0% and 18.2% in the positive and negative control groups, respectively. In addition, 61.7%, 56.0%, and 27.0%, respectively, showed improvement for the three groups. The differences in the distribution of lesion change scores between the negative control group and both the experimental (p < 0.001) and positive control (p < 0.001) were statistically significant, as was the difference between the experimental group and the positive control (p = 0.006). The Electrical Caries Monitor end values for the experimental, positive, and negative control groups at the six-month examination were 7.9, 1.9 mega omega(s), and 387 kilo omegas(s), respectively. The differences between the negative control group and both the experimental (p < 0.001) and positive control (p < 0.001) were statistically significant. The difference between the experimental and positive control groups was also statistically significant (p = 0.03). CONCLUSION: It is concluded that the new toothpaste containing 1.5% arginine and 1450 ppm fluoride, as sodium monofluorophosphate in a calcium base, provided greater anticaries benefits than a conventional toothpaste containing 1450 ppm fluoride. Both fluoride toothpastes demonstrated greater benefits than non-fluoride toothpaste.

Caries clinical trial methods for the assessment of oral care products in the 21st century.

Traditionally, caries clinical trials of oral care products have focused on the prevention of caries in children and adolescents at the "cavitation" level. Because of a general reduction in caries incidence and the use of positive control comparators, studies have grown both in size and duration to improve statistical power. Currently, they tend to be of 2 to 3 years' duration, with up to 2,000 high-risk individuals per group. During the past decade, there has been a shift in emphasis from a restorative approach to the treatment of dental caries to a therapeutic approach focused on the remineralization of early caries lesions. However, caries clinical trials of oral care products have not often reflected this paradigm change. This manuscript reviews alternative caries clinical trial methods for oral care products. It is concluded that methods focused on the detection and monitoring of enamel caries and root caries, by visual approaches such as ICDAS and instrumental methods such as QLF, Diagnodent, and Electrical Caries Monitors, provide viable alternatives to traditional methods. In particular, such approaches more accurately reflect the modes of action of many therapeutic agents and formulations and may reduce the cost and duration of product innovation.

Effect of post-brushing mouthwash solutions on salivary fluoride retention--study 2.

OBJECTIVE: This study evaluated the effects of three post-brushing mouthwashes containing 0 ppm F, 225 ppm F, and 500 ppm F, respectively, on salivary fluoride retention after brushing with 1450 ppm fluoride (as NaF) toothpaste and rinsing with water immediately after brushing. METHODS: In this three-phase, randomized, cross-over study, an ion-specific electrode was used to measure salivary F levels in thirty trial participants before brushing (Time 0), and after brushing, rinsing with water, and then rinsing with one of the three mouthwashes. Time points evaluated after brushing were one, three, five, 10, 20, 30, 45, and 60 minutes. For saliva sample collections, subjects were asked to pool saliva in their mouths for 10 seconds before spitting out into a container for each of the time points. RESULTS: The AUC0-60 means for F in saliva were 554, 252, and 20 for the 500, 225, and 0 ppm F mouthwash groups, respectively. The 500 ppm F mouthwash resulted in a 2660% increase in total fluoride salivary retention over 60 minutes when compared with the 0 ppm F group, and a 120% increase when compared with the 225 ppm F group. A significant difference (p < 0.001) in the AUC0-60 means between the three groups was observed using analysis of variance (ANOVA). Paired t-tests also showed significant differences in the mean fluoride retention over 60 minutes for all three pair-wise group comparisons (p < 0.001). CONCLUSION: Use of a fluoride mouthwash containing 225 ppm F or 500 ppm F produced a significant increase in salivary fluoride retention following brushing with a 1450 ppm F toothpaste and rinsing with water compared to rinsing without fluoride. The use of the 500 ppm F mouthwash may be of particular benefit to those at high caries risk.

Clinical studies of dental erosion and erosive wear.

We define erosion as a partial demineralisation of enamel or dentine by intrinsic or extrinsic acids and erosive tooth wear as the accelerated loss of dental hard tissue through the combined effect of erosion and mechanical wear (abrasion and attrition) on the tooth surface. Most experts believe that during the last decade there has been a significant increase in the prevalence and severity of erosive tooth wear, particularly in adolescents. Even when erosive wear occurs in its milder forms, this is a matter of concern, as it may compromise the integrity of an otherwise healthy dentition in later life. The erosive wear process is complicated and modified by many chemical, behavioural and associated processes in the mouth. If interventions are to be developed it is therefore important that in vivo methods are developed to assess the outcomes of the erosion and erosive wear processes and the effects of interventions upon them. This paper discusses potential methods of investigating erosion and erosive wear in vivo and the difficulties associated with clinical studies.

Brain Functional Changes before, during, and after Clinical Pain.

This study used an emerging brain imaging technique, functional near-infrared spectroscopy (fNIRS), to investigate functional brain activation and connectivity that modulates sometimes traumatic pain experience in a clinical setting. Hemodynamic responses were recorded at bilateral somatosensory (S1) and prefrontal cortices (PFCs) from 12 patients with dentin hypersensitivity in a dental chair before, during, and after clinical pain. Clinical dental pain was triggered with 20 consecutive descending cold stimulations (32° to 0°C) to the affected teeth. We used a partial least squares path modeling framework to link patients' clinical pain experience with recorded hemodynamic responses at sequential stages and baseline resting-state functional connectivity (RSFC). Hemodynamic responses at PFC/S1 were sequentially elicited by expectation, cold detection, and pain perception at a high-level coefficient (coefficients: 0.92, 0.98, and 0.99, P < 0.05). We found that the pain ratings were positively affected only at a moderate level of coefficients by such sequence of functional activation (coefficient: 0.52, P < 0.05) and the baseline PFC-S1 RSFC (coefficient: 0.59, P < 0.05). Furthermore, when the dental pain had finally subsided, the PFC increased its functional connection with the affected S1 orofacial region contralateral to the pain stimulus and, in contrast, decreased with the ipsilateral homuncular S1 regions ( P < 0.05). Our study indicated for the first time that patients' clinical pain experience in the dental chair can be predicted concomitantly by their baseline functional connectivity between S1 and PFC, as well as their sequence of ongoing hemodynamic responses. In addition, this linked cascade of events had immediate after-effects on the patients' brain connectivity, even when clinical pain had already ceased. Our findings offer a better understating of the ongoing impact of affective and sensory experience in the brain before, during, and after clinical dental pain.

Comparison of paired visual assessment and software analyses of changes in caries status over 6 months from fluorescence images.

Images captured using light-induced fluorescence systems are generally analysed using proprietary software. The purpose of this study was to determine if such images could be scored visually and to compare these data with those metrics produced by the software. A total of 171 lesions were selected from a pool of images to provide a range of lesions which were reported as having remained static, increased or decreased in fluorescence using the QLF analysis software. The baseline and 6-month images were then assessed side by side on a computer screen by 10 examiners who were asked to rate the lesions to determine if the lesion had become better or worse, or had stayed the same. There was generally poor correlation between clinical visual image assessments and all QLF analysis outcomes for all examiners. The agreement amongst the visual image assessments for the 10 examiners compared to the average score ranged from kappa 0.22 to 0.59 and the rank correlations from -0.01 to 0.73. This study suggests that the visual assessment of lesion images by the examiners in this study was based upon different characteristics of lesion change than those utilised by the QLF analysis software. A clearer understanding of lesion characteristics that are indicative of positive and negative changes may be required before this technology can be exploited to its full potential.

Reliability of quantitative laser fluorescence analysis of smooth surface lesions adjacent to the gingival tissues.

The aim of this study was to determine the impact of analysis patch border inclusion or exclusion on the reliability of quantitative laser fluorescence (QLF) analyses of lesions close to the gingival margin. Ninety-three lesions on the maxillary anterior teeth were imaged using a fluorescent capturing system. All the lesions were located on the gingival third of the teeth. One examiner undertook two analyses of the images 1 week apart and another examiner undertook a single analysis. Analyses were undertaken using QLF 2.00 g with four patch borders. Each border was assessed as active or inactive. QLF metrics DeltaF, DeltaQ and area were exported. Kappa statistics were used to measure the agreement of border inclusion between all three analyses, and intra-class correlation coefficients (ICCs) were used to determine the intra- and inter-examiner reliability of the QLF metrics. Agreement on border exclusion was poor; with intra-examiner kappa of 0.48 and inter-examiner at 0.20. However, despite the inconsistencies in border exclusions the ICCs for each QLF metric were high; intra-examiner DeltaQ 0.91, DeltaF 0.80 and area 0.92; inter-examiner DeltaQ 0.86, DeltaF 0.68, area 0.88. Lesions adjacent to the gingival margin will often require a patch analysis border to be excluded in order to ensure a satisfactory reconstruction and thus accurate analysis. The decision to include or exclude a border and, if excluded, which border to select appears to be highly variable between examiners. Nevertheless, the QLF metrics appear to be robust as demonstrated by the high ICCs noted in this study.

Assessment of autofluorescence to detect the remineralization capabilities of sodium fluoride, monofluorophosphate and non-fluoride dentifrices. A single-blind cluster randomized trial.

The purpose of the study was to determine if longitudinal measurements of enamel autofluorescence (quantitative light-induced fluorescence, QLF) could detect differences in remineralization of early enamel caries on buccal surfaces of anterior teeth following supervised daily brushing with either sodium fluoride (NaF; 1,450 ppm F), sodium monofluorophosphate (MFP; 1,450 ppm F) dentifrices or a herbal, non-fluoride placebo dentifrice. The study was a pragmatic cluster-randomized controlled trial with schools as the unit of randomization. Twenty-one schools in Chengdu, China, comprised the clusters; 296 children with at least 1 visible white-spot lesion were examined using QLF at baseline and after 3 and 6 months. Each of the 21 clusters was randomly assigned 1 of the 3 dentifrices, and the children brushed under supervision once per day for 2 min. The primary outcome measure was deltaQ (product of fluorescence loss and area) at a 5% threshold after 6 months of product use. A multi-level model was fitted to the data at the site level, taking into account the hierarchical structure with baseline deltaQ, age and sex as covariates. After 3 months there was a significant difference between the MFP group and placebo (p = 0.02) and after 6 months between the NaF group (p = 0.002), MFP group (p < 0.001) and the placebo. QLF methodology could detect, within 3- and 6-month periods of supervised brushing, a difference in remineralization between fluoride-containing and non-fluoride-containing dentifrices. Typically lesions in all 3 treatment groups demonstrated improvement. Groups receiving fluoride experienced a more rapid and more substantial remineralization than those in the placebo group.

Accuracy and reproducibility of conventional radiographic assessment and subtraction radiography in detecting demineralization in occlusal surfaces.

Subjective interpretation of paired digital radiographic images viewed side by side to assess occlusal lesion progression, arrest or remineralization is difficult. The aim of this study was to compare the accuracy and reproducibility of a digital subtraction radiography technique and visual assessment of paired digital images in detecting changes in mineral content within occlusal cavities. Forty molar teeth with occlusal cavities were placed in arches and baseline digital radiographs taken. Nineteen teeth were randomly selected and had acid placed in the cavities and digital images taken after 3, 6, 12, 18 and 24 h of acid exposure. Paired baseline images and those taken at the various time intervals were examined side by side and assessed for demineralization by five examiners. Subtraction images prepared from the paired images were assessed in the same way. One fifth of the images were re-examined to determine intra-examiner reproducibility. After 12 h or longer the diagnostic accuracy (mean area under the ROC curve = 0.92-0.98 for subtraction radiography), intra-examiner and inter-examiner reproducibility for detection of demineralization from the subtraction images was significantly better than viewing the paired images side by side (p < 0.01). The subtraction radiography system used was found to be more accurate and reproducible than visual assessment of paired digital images. As such the technique shows promise for monitoring occlusal lesion progression in clinical studies.

Agreement amongst examiners assessing dental fluorosis from digital photographs using the TF index.

OBJECTIVE: To compare the scoring of dental fluorosis by experienced examiners from digital photographs using the TF index. BASIC RESEARCH DESIGN: 120 images were selected from 703 photographs obtained during a clinical trial (Tavener et al., 2004). The selection process was stratified so that the full range of defects seen in the main study was included. The children, aged 8-10 years, were from deprived areas of Manchester, England with fluoride levels in the drinking water of less the 0.1 ppm F. The photographs of the upper and lower anterior sextants were taken after cleaning and drying the teeth. The examiners were identified by searching Medline for individuals who had previously used the TF index or had experience of scoring dental fluorosis. Of the 12 examiners identified, 10 agreed to take part. Each examiner was provided with identical CDs containing a PowerPoint presentation of the images. Twelve images were duplicated and interspersed amongst the 120 images to assess intra examiner agreement. Each examiner was also supplied with a table listing the criteria and illustrations for each of the TF index scores (Fejerskov et al., 1988). RESULTS: The prevalence of fluorosis (TF > 0) amongst the 10 examiners ranged from 43% to 70% and from 2% to 13% for the more severe scores (TF 3 or 4). Paired agreements amongst subject scores for the 10 examiners, measured using a weighted Kappa score, ranged from 0.40 to 0.71. CONCLUSION: It is concluded that although the criteria for the TF index are well defined, it is possible that examiners may interpret the criteria in different ways and conditions in which images are viewed may need to be standardised. This study may explain some of the differences in the prevalence and severity of fluorosis reported in different studies. There is a need to standardise the methods used to score dental fluorosis.