Shedding New Light on Early Caries Detection

Dental caries is one of the most prevalent chronic diseases among children and adolescents in North America. At a symposium, “Designing dental programs for high-risk children,” held during the July 2008 International and Canadian Association for Dental Research conference in Toronto, common themes among speakers were (1) caries is preventable and (2) there is value in early caries detection and, thus, preventive approaches. With strategies to control, arrest or reverse the disease process, the economic burden, pain and suffering of placing and replacing restorations can be reduced. An example of a prevention effort that has resulted in decreased incidence and prevalence of caries is fluoridation of community drinking water. This method is endorsed by over 90 national and international professional health organizations including Health Canada, the Canadian Public Health Association, the Canadian Dental Association, the Canadian Medical Association and the World Health Organization.1 In July 2008, Canada's chief dental officer highlighted some of the benefits of fluoridation, caries prevention being the primary one.1 This public health measure has also reached such high caries risk groups as those with low socioeconomic status and the elderly, who are particularly susceptible to root caries. Where prevention is not successful, early detection of caries before it reaches the stage of cavitation offers another opportunity for effective dental care. Early detection and diagnosis will allow dentists to counsel and assist patients to prevent the progression of caries and, thereby, avert the need for invasive, irreversible removal and restoration of tooth structure. Detecting early dental caries and monitoring the dynamic processes of demineralization and remineralization are challenging. Conventional diagnostic methods, such as visual observation and the use of a sharp explorer tool, rely on subjective clinical criteria: for example, colour, “softness” and resistance to removal. Routine dental radiographs cannot detect early enamel white-spot lesions on any surface. Approximately 30%–40% mineral loss is necessary before an early enamel carious lesion is visible radiographically.2 It can take 9 months or longer before demineralization appears radiographically.3 These deficiencies make it difficult to diagnose early approximal, smooth surface enamel lesions as well as occlusal caries. Accurate diagnosis of occlusal caries including assessment of lesion depth is particularly challenging due to the hypermineralized outer enamel surface (possibly as a result of fluoride treatment) that masks the underlying lesion. Conventional diagnostic techniques lack sufficient high sensitivity and specificity for early lesion detection and are not able to provide information on caries activity. In recent years, various techniques have been explored to address the need for better detection tools to aid dentists in the diagnosis of early caries, and several of these methods have been developed into commercial products. The following is a list of various emerging techniques with corresponding commercially available or soon to be released devices in parentheses4–8: direct digital radiography (various devices) digital imaging fibre-optic transillumination (DIFOTI, Electro-Optical Sciences, Irvington, N.Y.] electroconductivity measurements (Electronic Caries Monitor, Lode Diagnostics, Groningen, The Netherlands) impedance spectroscopy (CarieScan, IDMoS, Dundee, Scotland) quantitative light-induced fluorescence (QLF, Inspektor Pro, OMNII Oral Pharmaceuticals, West Palm Beach, Fla.) laser fluorescence (DIAGNOdent devices, KaVo, Lake Zurich, Ill.; Midwest Caries I.D., Dentsply, York, Penn.) photothermal radiometric and modulated luminescence methods (Canary System, Quantum Dental Technologies, Toronto, Ont.) optical coherence tomography (OCT Dental Imaging System, Lantis Laser, Denville, N.J.) ultrasound near-infrared illumination Raman spectroscopy terahertz imaging Despite their potential, some of these techniques and devices also suffer from subjectivity, with high intra- and inter-examiner variability; false-positive results due to stains, calculus or organic deposits; and unsuitability for detection of initial enamel caries at all tooth surfaces.9–17 Furthermore, several of these tools do not allow longitudinal monitoring of caries development or repair (i.e., caries activity) in terms of providing information about mineral loss or gain. For example, the DIAGNOdent device (KaVo) is based on fluorescence of bacterial porphyrins within lesions rather than mineral content. Thus, better, objective diagnostic tools with both high sensitivity and high specificity are still needed for early detection and monitoring of dental caries.