An Experimental Review of Optical Coherence Tomography Systems for Noninvasive Assessment of Hard Dental Tissues.

Optical coherence tomography (OCT) is a noninvasive, high-resolution, cross-sectional imaging technique. To date, OCT has been demonstrated in several areas of dentistry, primarily using wavelengths around 1,300 nm, low numerical aperture (NA) imaging lenses, and detectors insensitive to the polarization of light. The objective of this study is to compare the performance of three commercially available OCT systems operating with alternative wavelengths, imaging lenses, and detectors for OCT imaging of dental enamel. Spectral-domain (SD) OCT systems with (i) 840 nm (Lumedica, OQ LabScope 1.0), (ii) 1,300 nm (Thorlabs, Tel320) center wavelengths, and (iii) a swept-source (SS) OCT system (Thorlabs OCS1300SS) centered at 1,325 nm with optional polarization-sensitive detection were used. Low NA (0.04) and high NA (0.15) imaging lenses were used with system (iii). Healthy in vivo and in vitrohuman enamel and eroded in vitro bovine enamel specimens were imaged. The Tel320 system achieved greater imaging depth than the OQ LabScope 1.0, on average imaging 2.6 times deeper into the tooth (n = 10). The low NA lens provided a larger field of view and depth of focus, while the high NA lens provided higher lateral resolution and greater contrast. Polarization-sensitive imaging eliminated birefringent banding artifacts that can appear in conventional OCT scans. In summary, this study illustrates the performance of three commercially available OCT systems, objective lenses, and imaging modes and how these can affect imaging depth, resolution, field of view, and contrast in enamel. Users investigating OCT for dental applications should consider these factors when selecting an OCT system for clinical or basic science studies.

European Organization for Caries Research Workshop: Methodology for Determination of Potentially Available Fluoride in Toothpastes.

Toothpastes are the most universally accepted form of fluoride delivery for caries prevention. To provide anti-caries benefits, they must be able to release fluoride during the time of tooth brushing or post brushing into the oral cavity. However, there is no standard accepted procedure to measure how much fluoride in a toothpaste may be (bio) available for release. The European Organization for Caries Research proposed and supported a workshop with experts in fluoride analysis in toothpastes and representatives from industry. The objective of the workshop was to discuss issues surrounding fluoride analysis in toothpaste and reach consensus on terminology and best practices, wherever the available evidence allowed it. Participants received a background paper and heard presentations followed by structured discussion to define the problem. The group also reviewed evidence on the validity, reliability and feasibility of each technique (namely chromatography and fluoride electroanalysis) and discussed their strengths and limitations. Participants were able to reach a consensus on terminology and were also able to identify and summarize the advantages and disadvantages of each technique. However, they agreed that most currently available methods were developed for regulatory agencies several decades ago, utilizing the best available data from clinical trials then, but require to be updated. They also agreed that although significant advances to our understanding of the mechanism of action of fluoride in toothpaste have been achieved over the past 4 decades, this clearly is an extraordinarily complex subject and more work remains to be done.

Feasibility of a Real-Time Clinical Augmented Reality and Artificial Intelligence Framework for Pain Detection and Localization From the Brain.

BACKGROUND: For many years, clinicians have been seeking for objective pain assessment solutions via neuroimaging techniques, focusing on the brain to detect human pain. Unfortunately, most of those techniques are not applicable in the clinical environment or lack accuracy. OBJECTIVE: This study aimed to test the feasibility of a mobile neuroimaging-based clinical augmented reality (AR) and artificial intelligence (AI) framework, CLARAi, for objective pain detection and also localization direct from the patient's brain in real time. METHODS: Clinical dental pain was triggered in 21 patients by hypersensitive tooth stimulation with 20 consecutive descending cold stimulations (32°C-0°C). We used a portable optical neuroimaging technology, functional near-infrared spectroscopy, to gauge their cortical activity during evoked acute clinical pain. The data were decoded using a neural network (NN)-based AI algorithm to classify hemodynamic response data into pain and no-pain brain states in real time. We tested the performance of several networks (NN with 7 layers, 6 layers, 5 layers, 3 layers, recurrent NN, and long short-term memory network) upon reorganized data features on pain diction and localization in a simulated real-time environment. In addition, we also tested the feasibility of transmitting the neuroimaging data to an AR device, HoloLens, in the same simulated environment, allowing visualization of the ongoing cortical activity on a 3-dimensional brain template virtually plotted on the patients' head during clinical consult. RESULTS: The artificial neutral network (3-layer NN) achieved an optimal classification accuracy at 80.37% (126,000/156,680) for pain and no pain discrimination, with positive likelihood ratio (PLR) at 2.35. We further explored a 3-class localization task of left/right side pain and no-pain states, and convolutional NN-6 (6-layer NN) achieved highest classification accuracy at 74.23% (1040/1401) with PLR at 2.02. CONCLUSIONS: Additional studies are needed to optimize and validate our prototype CLARAi framework for other pains and neurologic disorders. However, we presented an innovative and feasible neuroimaging-based AR/AI concept that can potentially transform the human brain into an objective target to visualize and precisely measure and localize pain in real time where it is most needed: in the doctor's office. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/13594.

Role of microbial biofilms in the maintenance of oral health and in the development of dental caries and periodontal diseases. Consensus report of group 1 of the Joint EFP/ORCA workshop on the boundaries between caries and periodontal disease.

BACKGROUND AND AIMS: The scope of this working group was to review (1) ecological interactions at the dental biofilm in health and disease, (2) the role of microbial communities in the pathogenesis of periodontitis and caries, and (3) the innate host response in caries and periodontal diseases. RESULTS AND CONCLUSIONS: A health-associated biofilm includes genera such as Neisseria, Streptococcus, Actinomyces, Veillonella and Granulicatella. Microorganisms associated with both caries and periodontal diseases are metabolically highly specialized and organized as multispecies microbial biofilms. Progression of these diseases involves multiple microbial interactions driven by different stressors. In caries, the exposure of dental biofilms to dietary sugars and their fermentation to organic acids results in increasing proportions of acidogenic and aciduric species. In gingivitis, plaque accumulation at the gingival margin leads to inflammation and increasing proportions of proteolytic and often obligately anaerobic species. The natural mucosal barriers and saliva are the main innate defence mechanisms against soft tissue bacterial invasion. Similarly, enamel and dentin are important hard tissue barriers to the caries process. Given that the present state of knowledge suggests that the aetiologies of caries and periodontal diseases are mutually independent, the elements of innate immunity that appear to contribute to resistance to both are somewhat coincidental.

Toothpaste prevents debonded brackets on erosive enamel.

UNLABELLED: This study evaluated the effect of high fluoride dentifrice on the bond strength of brackets after erosive challenge. Eighty-four enamel specimens were divided into seven groups (n = 12): WN (distilled water/no acid challenge), W3C (distilled water/3 cycles of acid challenge), and W6C (distilled water/6 cycles of acid challenge) were not submitted to dentifrice treatment. Groups RF3C (regular fluoride dentifrice/3 cycles of acid challenge) and RF6C (regular fluoride dentifrice/6 cycles of acid challenge) were treated with dentifrices containing 1450 µg F(-)/g and HF3C (high fluoride dentifrice/3 cycles of acid challenge) and HF6C (high fluoride dentifrice/6 cycles of acid challenge) were with 5000 µg F(-)/g. Acid challenges were performed for seven days. After bond strength test, there was no significant difference among groups submitted to 3 cycles of acid challenge (P > 0.05). Statistically significant difference was found between the regular and high fluoride dentifrices after 6 cycles of acid challenge (<0.05). Similar areas of adhesive remaining were found among control groups and among groups W6C, RF3C, RF6C, HF3C, and HF6C. The high fluoride dentifrice was able to prevent the reduction of bond strength values of brackets submitted to acid challenge. CLINICAL RELEVANCE: the high fluoride toothpaste prevents debonded brackets on erosive enamel.

Prevention in practice--a summary.

BACKGROUND: This paper is a summary document of the Prevention in Practice Conference and Special Supplement of BMC Oral Health. It represents the consensus view of the presenters and captures the questions, comments and suggestions of the assembled audience. METHODS: Using the prepared manuscripts for the conference, collected materials from scribes during the conference and additional resources collated in advance of the meeting, authors agreed on the summary document. RESULTS: The Prevention in Practice conference aimed to collate information about which diseases could be prevented in practice, how diseases could be identified early enough to facilitate prevention, what evidence based therapies and treatments were available and how, given the collective evidence, could these be introduced in general dental practice within different reimbursement models. CONCLUSIONS: While examples of best practice were provided from both social care and insurance models it was clear that further work was required on both provider and payer side to ensure that evidence based prevention was both implemented properly but also reimbursed sufficiently. It is clear that savings can be made but these must not be overstated and that the use of effective skill mix would be key to realizing efficiencies. The evidence base for prevention of caries and periodontal disease has been available for many years, as have the tools and techniques to detect, diagnose and stage the diseases appropriately. Dentistry finds itself in a enviable position with respect to its ability to prevent, arrest and reverse much of the burden of disease, however, it is clear that the infrastructure within primary care must be changed, and practitioners and their teams appropriately supported to deliver this paradigm shift from a surgical to a medical model.

The elderly as a market--challenges to evidence.

OBJECTIVE: To review the role of the oral care industry in the oral health of elders and opportunities for partnership with other key stakeholders. BACKGROUND: The elder population is growing at a faster rate than any other segment of the population. This is coupled with a greater probability of maintaining the dentition into later life and an increase in complex restorative work. If an elder's situation changes, they are highly vulnerable to a rapid onset of oral disease that can be devastating and extremely difficult to address. MATERIALS AND METHODS: This manuscript reviews the role of the oral care industry in understanding this population as a market and the different approaches that might be used in promoting health. RESULTS: Two key market segments were identified, the vulnerable elders with high levels of chronic oral disease, systemic complications, medications and often inability to maintain good standards of oral hygiene and a wealthier, health and beauty conscious group with a keen interest in maintaining a healthy, aesthetically pleasing and functional dentition throughout their lives. CONCLUSIONS: It is likely that within current healthcare models, the oral care of elders will be unsustainable, with a smaller working population funding ever-increasing health care needs. 'Home care' combined with effective professional preventive and effective therapeutic options are essential. Partnerships between the oral care industry and oral care providers, to deliver education and engagement of care workers, medical practitioners, pharmacists and social services, are essential over the next few decades.

The Seattle Care Pathway for securing oral health in older patients.

There is a need for a structured, evidence based approach to care for older dental patients. The following article describes the development of the Seattle Care Pathway based upon a workshop held in 2013. An overview is provided on the key issues of older persons dental care including the demography shift, the concept of frailty, the need for effective prevention and treatment to be linked to levels of dependency and the need for a varied and well educated work force. The pathway is presented in tabular form and further illustrated by the examples in the form of clinical scenarios. The pathway is an evidence based, pragmatic approach to care designed to be globally applicable but flexible enough to be adapted for local needs and circumstances. Research will be required to evaluate the pathways application to this important group of patients.

The association between social deprivation and the prevalence and severity of dental caries and fluorosis in populations with and without water fluoridation.

BACKGROUND: To determine the association between social deprivation and the prevalence of caries (including caries lesions restricted to enamel) and enamel fluorosis in areas that are served by either fluoridated or non-fluoridated drinking water using clinical scoring, remote blinded, photographic scoring for caries and fluorosis. The study also aimed to explore the use of remote, blinded methodologies to minimize the effect of examiner bias. METHODS: Subjects were male and female lifetime residents aged 11-13 years. Clinical assessments of caries and fluorosis were performed on permanent teeth using ICDAS and blind scoring of standardized photographs of maxillary central incisors using TF Index (with cases for fluorosis defined as TF > 0). RESULTS: Data from 1783 subjects were available (910 Newcastle, 873 Manchester). Levels of material deprivation (Index of Multiple Deprivation) were comparable for both populations (Newcastle mean 35.22, range 2.77-78.85; Manchester mean 37.04, range 1.84-84.02). Subjects in the fluoridated population had significantly less caries experience than the non-fluoridated population when assessed by clinical scores or photographic scores across all quintiles of deprivation for white spot lesions: Newcastle mean DMFT 2.94 (clinical); 2.51 (photo), Manchester mean DMFT 4.48 (clinical); 3.44 (photo) and caries into dentine (Newcastle Mean DMFT 0.65 (clinical); 0.58 (photo), Manchester mean DMFT 1.07 (clinical); 0.98 (photo). The only exception being for the least deprived quintile for caries into dentine where there were no significant differences between the cities: Newcastle mean DMFT 0.38 (clinical); 0.36 (photo), Manchester mean DMFT 0.45 (clinical); 0.39 (photo). The odds ratio for white spot caries experience (or worse) in Manchester was 1.9 relative to Newcastle. The odds ratio for caries into dentine in Manchester was 1.8 relative to Newcastle. The odds ratio for developing fluorosis in Newcastle was 3.3 relative to Manchester. CONCLUSIONS: Water fluoridation appears to reduce the social class gradient between deprivation and caries experience when considering caries into dentine. However, this was associated with an increased risk of developing mild fluorosis. The use of intra-oral cameras and remote scoring of photographs for caries demonstrated good potential for blinded scoring.

Quantitative light fluorescence (QLF) and polarized white light (PWL) assessments of dental fluorosis in an epidemiological setting.

BACKGROUND: To determine if a novel dual camera imaging system employing both polarized white light (PWL) and quantitative light induced fluorescence imaging (QLF) is appropriate for measuring enamel fluorosis in an epidemiological setting. The use of remote and objective scoring systems is of importance in fluorosis assessments due to the potential risk of examiner bias using clinical methods. METHODS: Subjects were recruited from a panel previously characterized for fluorosis and caries to ensure a range of fluorosis presentation. A total of 164 children, aged 11 years (±1.3) participated following consent. Each child was examined using the novel imaging system, a traditional digital SLR camera, and clinically using the Dean's and Thylstrup and Fejerskov (TF) Indices on the upper central and lateral incisors. Polarized white light and SLR images were scored for both Dean's and TF indices by raters and fluorescence images were automatically scored using software. RESULTS: Data from 164 children were available with a good distribution of fluorosis severity. The automated software analysis of QLF images demonstrated significant correlations with the clinical examinations for both Dean's and TF index. Agreement (measured by weighted Kappa's) between examiners scoring clinically, from polarized photographs and from SLR images ranged from 0.56 to 0.92. CONCLUSIONS: The study suggests that the use of a digital imaging system to capture images for either automated software analysis, or remote assessment by raters is suitable for epidemiological work. The use of recorded images enables study archiving, assessment by multiple examiners, remote assessment and objectivity due to the blinding of subject status.

Adolescents' perceptions of the aesthetic impact of dental fluorosis vs. other dental conditions in areas with and without water fluoridation.

BACKGROUND: The use of fluorides for caries prevention is well established but is linked with an increased risk of dental fluorosis, some of which may be considered to be aesthetically objectionable. Patient opinion should be considered when determining impact on aesthetics. The aim of this study was to assess participant rating of dental aesthetics (from photographic images) of 11 to 13 year olds participating in an epidemiological caries and fluorosis survey in a fluoridated and a non-fluoridated community in Northern England. METHODS: Consented participants were invited to rank in order of preference (appearance) a collage of 10 computer generated images on a touch-screen laptop. The images comprised an assortment of presentations of teeth that included white teeth, a spectrum of developmental defects of enamel and dental caries. Data were captured directly and exported into SPSS for analysis. RESULTS: Data were available for 1553 participants. In general, there were no significant differences in the rank positions between the fluoridated and non-fluoridated communities, with the exception of teeth with caries and teeth with large demarcated opacities. Very white teeth had the highest rating in both localities. Overall, there was a trend for teeth with fluorosis to be ranked more favourably in the fluoridated community; for TF 1 and TF 2 this preference was significant (p < 0.001). CONCLUSIONS: The results of this study suggest teeth that are uniformly very white have the highest preference. The rankings suggest teeth with a fluorosis score of TF 1 may not be considered aesthetically objectionable to this population and age group. The image depicting a tooth with caries and the image with large demarcated opacities were deemed to be the least favoured. Participant preference of images depicting fluorosis falls with increasing severity of fluorosis.

Dental fluorosis in populations from Chiang Mai, Thailand with different fluoride exposures - paper 1: assessing fluorosis risk, predictors of fluorosis and the potential role of food preparation.

BACKGROUND: To determine the severity of dental fluorosis in selected populations in Chiang Mai, Thailand with different exposures to fluoride and to explore possible risk indicators for dental fluorosis. METHODS: Subjects were male and female lifetime residents aged 8-13 years. For each child the fluoride content of drinking and cooking water samples were assessed. Digital images were taken of the maxillary central incisors for later blind scoring for TF index (10% repeat scores). Interview data explored previous cooking and drinking water use, exposure to fluoride, infant feeding patterns and oral hygiene practices. RESULTS: Data from 560 subjects were available for analysis (298 M, 262 F). A weighted kappa of 0.80 was obtained for repeat photographic scores. The prevalence of fluorosis (TF 3+) for subjects consuming drinking and cooking water with a fluoride concentration of <0.9 ppm was 10.2%. For subjects consuming drinking and cooking water >0.9 ppm F the prevalence of fluorosis (TF 3+) rose to 37.3%. Drinking and cooking water at age 3, water used for infant formula and water used for preparing infant food all demonstrated an increase in fluorosis severity with increase in water fluoride level (p < 0.001). The probability estimate for the presentation of aesthetically significant fluorosis was 0.53 for exposure to high fluoride drinking (≥0.9 ppm) and cooking water (≥1.6 ppm). CONCLUSIONS: The consumption of drinking water with fluoride content >0.9 ppm and use of cooking water with fluoride content >1.6 ppm were associated with an increased risk of aesthetically significant dental fluorosis. Fluoride levels in the current drinking and cooking water sources were strongly correlated with fluorosis severity. Further work is needed to explore fluorosis risk in relation to total fluoride intake from all sources including food preparation.

Evaluating the use of fluorescent imaging for the quantification of dental fluorosis.

BACKGROUND: The quantification of fluorosis using fluorescence imaging (QLF) hardware and stain analysis software has been demonstrated in selected populations with good correlation between fluorescent image metrics and TF Index scores from photographs. The aim of this study was to evaluate the ability of QLF to quantify fluorosis in a population of subjects (aged 11-13) participating in an epidemiological caries and fluorosis survey in fluoridated and non-fluoridated communities in Northern England. METHODS: Fluorescent images of the maxillary incisors were captured together with standardized photographs were scored blind for fluorosis using the TF Index. Subjects were excluded from the analysis if there were restorations or caries on the maxillary central incisors. RESULTS: Data were available for 1774 subjects (n=905 Newcastle, n=869 Manchester). The data from the fluorescence method demonstrated a significant correlation with TF Index scores from photographs (Kendall's tau = 0.332 p<0.0001). However, a number of additional confounding factors such as the presence of extrinsic stain or increased enamel translucency on some subjects without fluorosis or at low levels of fluorosis severity had an adverse impact on tooth fluorescence and hence the outcome variable. This in conjunction with an uneven distribution of subjects across the range of fluorosis presentations may have resulted in the lower than anticipated correlations between the fluorescent imaging metrics and the photographic fluorosis scores. Nevertheless, the fluorescence imaging technique was able to discriminate between a fluoridated and non-fluoridated population (p<0.001). CONCLUSIONS: Despite confounding factors the fluorescence imaging system may provide a useful objective, blinded system for the assessment of enamel fluorosis when used adjunctively with photographic scoring.

Dental fluorosis in populations from Chiang Mai, Thailand with different fluoride exposures - paper 2: the ability of fluorescence imaging to detect differences in fluorosis prevalence and severity for different fluoride intakes from water.

BACKGROUND: To assess the ability of fluorescence imaging to detect a dose response relationship between fluorosis severity and different levels of fluoride in water supplies compared to remote photographic scoring in selected populations participating in an observational, epidemiological survey in Chiang Mai, Thailand. METHODS: Subjects were male and female lifetime residents aged 8-13 years. For each child the fluoride content of cooking water samples (CWS) was assessed to create categorical intervals of water fluoride concentration. Fluorescence images were taken of the maxillary central incisors and analyzed for dental fluorosis using two different software techniques. Output metrics for the fluorescence imaging techniques were compared to TF scores from blinded photographic scores obtained from the survey. RESULTS: Data from 553 subjects were available. Both software analysis techniques demonstrated significant correlations with the photographic scores. The metrics for area effected by fluorosis and the overall fluorescence loss had the strongest association with the photographic TF score (Spearman's rho 0.664 and 0.652 respectively). Both software techniques performed well for comparison of repeat fluorescence images with ICC values of 0.95 and 0.85 respectively. CONCLUSIONS: This study supports the potential use of fluorescence imaging for the objective quantification of dental fluorosis. Fluorescence imaging was able to discriminate between populations with different fluoride exposures on a comparable level to remote photographic scoring with acceptable levels of repeatability.

Effect of post-brushing mouthwash solutions on salivary fluoride retention--study 1.

OBJECTIVE: The aim of the present study was to evaluate the effects on post-brushing salivary F retention of rinsing with mouthwashes containing either 500 or 225 ppm F compared to not rinsing. METHODS: The study was a randomized, investigator-blind, cross-over trial with three treatment arms. Thirty volunteers brushed with 0.5 g of 1450 ppm F paste for 40 seconds and then spat out the waste slurry. They then rinsed for one minute with 10 mL of their allocated mouthwash or they did not rinse after the brushing. Saliva samples were collected before brushing (0 minutes) and at one, three, five, 10, 20, 30, 45, and 60 minutes after brushing. The subjects were not allowed to speak, eat, or drink during these 60-minute test periods. The F levels in saliva were then calculated for each time point and the integrated area under the curve calculated (AUC0-60). RESULTS: The mean AUCs were 626, 380, and 237 for the 500 ppm F, 225 ppm F, and no rinse treatments, respectively, and all pair-wise comparisons were statistically significant (p < 0.01). CONCLUSION: It is concluded that rinsing with either 500 or 225 ppm F mouthwash significantly increases the level of F in saliva compared to not rinsing after brushing with 1450 ppm F toothpaste. The 500 ppm F mouthwash provided a significant increase in F retention compared to the 225 ppm F rinse (p = 0.001).

Evaluation of the sensitivity of a digital plaque imaging system on different tooth surfaces.

OBJECTIVE: The study aimed to test the sensitivity of digital plaque imaging in distinguishing the effectiveness of test and control mouthwashes for different groups of tooth surfaces. METHODS: The study was a double-blind, parallel, randomized, controlled clinical trial. Sixty subjects underwent scaling and polishing after recruitment, and attended their baseline examination after a washout phase of a minimum of seven days. They were then randomly assigned to one of two mouthwashes: 1) 0.05% CPC mouthwash; and 2) matching placebo mouthwash without CPC. Both groups were asked to use their assigned mouthwash and to refrain from any other oral hygiene measures for a period of eight days. At the baseline and day 8 visits, digital images of tooth surfaces were captured using Quantitative Light-induced Fluorescence (QLF) imaging, and plaque area as a percentage of the tooth surface was measured. Comparisons were carried out between the products for different groups of tooth surfaces. The data generated by the software were validated by a manual plaque outlining technique. RESULTS: Fifty-eight (58) subjects completed the study. More plaque was detected on the facial surfaces for the whole mouth (42.88% coverage for CPC and 46.45% for placebo) than the whole mouth lingual surfaces (7.23% coverage for CPC and 11.10% for placebo). Significant differences were observed between the products for the following areas: all tooth surfaces (p = 0.032), anterior lingual (p = 0.005), posterior lingual (p = 0.003), and whole mouth lingual (p = 0.001), whereas there were no differences between the products for anterior facial, anterior (facial & lingual), posterior facial, posterior (facial & lingual), and whole mouth facial. A strong correlation (R = 0.793, p < 0.001) was observed between the data (mean difference of percentage plaque coverage) generated by the analyzing program and that from the manual plaque outlining technique. CONCLUSION: The digital plaque imaging system was able to distinguish between the products when looking at the whole mouth. Digital imaging was better able to separate the groups when examining the lingual surfaces than facial.

The water fluoridation debate.

UNLABELLED: Water fluoridation schemes have been employed for over 50 years. Water fluoridation has been a source of continuous debate between those who advocate its use as a public health measure and those who oppose it. There have been no new fluoridation schemes in the U.K. for nearly 30 years owing to principally legislative, but also geographic, financial, and political reasons. However, in early 2008, the U.K. Secretary of State for Health promoted the use of water fluoridation schemes for areas in England with the highest rates of decay. This article, the third and final article of three, aims to discuss the arguments surrounding water fluoridation and its continued relevance as a public health measure. CLINICAL RELEVANCE: This article aims to provide an update for general practitioners for the background and the current status of the water fluoridation debate and to enable them to answer non-clinical questions raised by patients.

An automated assessment algorithm for micro-CT images of occlusal caries.

OBJECTIVES: To produce and test an algorithm to automatically quantify natural occlusal caries lesions in micro-computed tomography (micro-CT) scans of human teeth. METHODS: The algorithm presented divides the occlusal surface into regions of enamel and dentine by looking for sharp increases and decreases in radiopacity characteristic of step changes between materials. The accuracy of an automatic occlusal caries assessment based on these regions is assessed against serial histological assessment and manual examination of the same micro-CT images, using data from 68 previously scanned and sectioned teeth with varying levels of natural occlusal caries. RESULTS: Only three teeth were found to be free of caries by histology. The results of the automated analysis correlate well with histological assessment with a ρ of 0.80 (p < 0.001), and with manual CT assessment with a ρ of 0.85 (p < 0.001). The depth of dentine lesions correlated with histology with an intra-class correlation coefficient of 0.82 (p < 0.001; N = 45) and with manual assessment with an ICC of 0.93 (p < 0.001; N = 39). Micro-CT is found to generally underestimate caries compared to histological assessment. CONCLUSIONS: The algorithm presented can successfully segment micro-CT scans into occlusal enamel and dentine regions, and the results show that the depths of dentine caries lesions can be accurately and objectively measured automatically using micro-CT. However, if enamel caries is to be accurately assessed by a computer, better scans will be required than those used here.