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Feature Article: Caries Detection

© Dr Julian Holmes

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Feature Article: Caries Detection Q&A
  • Effective Clinical Diagnosis Of Incipient Caries.
  • The Role Of Radiography In Caries.
  • The Role Of Fiber Optic Transillumination (FOTI).
  • The Role Of Electrical Caries Monitor (ECM)?
  • Diagnodent Laser Caries Detection/A>
  • Current State Of Art
  • The Etiology Of Dental Caries
  • The Systemic Consequences Of Caries
  • References

  • Feature Article: Caries Detection - Q&A

    Author; Layla Abu Nabaa,Edward Lynch. 2004.
    Feature Article: Caries Detection

    Q: What is the most effective clinical modality for diagnosing beginning caries formation on the occlusal surfaces and smooth surfaces of the teeth?

    A: Diagnosing reversible-stage caries under conventional clinical conditions is a difficult task. Caries on the obscured approximal areas of teeth is as difficult to detect as decay in occlusal surface pits and fissures, which has long been recognized as a problem.

    Diagnosis becomes even more difficult when the carious lesion is in the initial stage of formation (Weerheijm et al, 1989; Sawle and Andlaw, 1988). Detection difficulties can be partly explained by the presence of fluoride (Sawle and Andlaw, 1988). Referred to as "the fluoride syndrome", increased fluoride intake causes the highly caries-resistant occlusal enamel to obscure underlying dentinal lesions (Creanor et al, 1990; Marthaler, 1990; Weerheijm, 1997).

    Many scientific principles have been used to test and measure the differences between the properties of mineralized tissue of sound teeth and diseased dentition. In the case of fissure caries, tactile-visual detection criteria based on the presence or absence of cavitation and surface texture have shown low sensitivity but high specificity (ten Cate et al., 1996). Similarly, studies also have demonstrated that conventional clinical methods to detect occlusal caries resulted in remarkably low values for sensitivity (Wenzel et al., 1991; Lussi, 1996). Nevertheless, these caries detection methods are of value when performed under good clinical conditions, with careful eye inspection (with or without magnification) using good operatory lighting, and on cleaned and dried tooth surfaces (Ekstrand 1998 and 1995).

    One concern surrounding traditional methods of caries detection is that probing may disrupt the tooth surface and predispose the tooth to cavitation (Kidd et al., 1993; Prinz et al, 1999). One study (Yassin 1995) showed that initial lesions could be converted into cavities following probing, depending upon the size of the defect and the pressure applied. Using a probe to detect fissure lesions also can result in misdiagnosis because the stickiness detected by the probe may be due to fissure morphology or probe pressure rather than the existence of a carious lesion. Lussi (1991) assessed the traditional probing method for detecting occlusal and fissure caries and concluded that it does not aid in caries diagnosis.

    Q: What about the use of radiography for detecting and diagnosing smooth surface and occlusal caries?

    A: The importance of radiographs to diagnose initial carious lesions in approximal surfaces is well established (Kidd and Pitts 1990). However, radiographic evaluation of occlusal surfaces has been found of minimal diagnostic value for detecting enamel caries and superficial dentinal caries (McKnight-Hanes et al., 1990; Flaitz et al., 1986). In deeper lesions reaching the dentin, radiographs show a high specificity (Russel and Pitts, 1991; Tviet et al., 1991; Ricketts et al., 1997). On the other hand, radiographs have been shown to underestimate the size of the lesion considerably (Van Amerongen et al., 1992). Using computer technology to enhance images from a video camera or from a digital X-ray sensor has been proven to be an objective and reproducible methodology (Pitts 1985, 1986 and 1987). A further use for radiographs is to monitor lesion progression. The main disadvantage is the high false-positive results when used for occlusal caries detection (Ricketts, 1995).

    Q: Is fiber optic transillumination (FOTI) a reliable technique? What is the basis for the technology?

    A: This technology is based on the fact that carious enamel has a lower index of light transmission than sound enamel. Diagnostic results from this technology are conflicting. For occlusal caries, one study (Crentor et al., 1990) compared fiber-optic transillumination (FOTI) with radiographic examinations and concluded that radiographic examinations were a better diagnostic tool than FOTI. The opposite was found in a study conducted in 1992 (Wenzel et al). According to another study conducted (Verdonschot et al.) in 1992, transillumination exhibited a low sensitivity to caries detection but showed a high predictive positive value.

    Q: How effective is the use of an electrical caries monitor (ECM)?

    A: Electrical Caries Monitor (ECM) technology is based on the electrical conductivity differences between sound dental tissues and carious dental tissues. Studies have demonstrated a satisfactory performance of ECM when used to detect occlusal caries in-vivo and ex-vivo (Rock and Kidd, 1988; Verdonschot et al., 1992; Ricketts et al., 1995; Ashley, 1998; Fennis-Ie et al., 1998). The (ECM) (Figures 1 and 2) measures the electrical resistance of a site on the tooth during controlled drying. By drying the surface, the resistance is determined by the tooth structure, avoiding electrical guiding from surface liquid (saliva). High measurements indicate well-mineralized tissue, while low values indicate demineralized tissue.

    The electrical conductivity of a tooth changes with demineralization, even when the surface remains macroscopically intact. A major advantage of the ECM is to present objective readings, which have the potential for monitoring lesion progression, arrest, or remineralization. A strong relationship between both lesion depth and mineral content in enamel has been shown with ECM readings (Ricketts et al., 1996).

    Using the ECM to diagnose occlusal caries in a clinical trial (Ashley) concluded that ECM is an accurate and repeatable tool for the diagnosis of early occlusal caries in-vitro and in-vivo. Although the ECM reading maybe susceptible to post-eruptive maturation effects, it did not affect the study. The ECM in this study showed a sensitivity of 0.75 and a specificity of 0.77, indicating that it is a valid indicator for detecting presence or absence of lesion porosity.

    Q: One of the newer technologies on the market is the Diagnodent laser caries detection system. What have the clinical studies shown about its effectiveness?

    A: This laser fluorescence system (Figure 3) detects caries-induced changes in the tooth that cause an increase in the fluorescence at specific excitation wavelengths. The intensity of the fluorescence depends upon the wavelength of the light as well as the structure and condition of hard dentinal tissues. Red light, with a wavelength of 655 nm, is transported to the angulated tip of the device by a central fiber. Around the central fiber, additional light fibers are concentrically arranged; a filter eliminates ambient light. A photodiode measures the amount of fluorescent light passing through the filter. A digital display shows both a real-time and a maximum value. Two fiber-optic tips, a tapered one designed for fissure caries and a flat one for smooth-surface caries, come with the system.

    In an in-vitro study (Lussi et al., (1999) it was concluded that the new laser device had a higher diagnostic validity than the ECM and may be a valuable tool in the longitudinal monitoring of caries and in assessing the outcome of preventive interventions.

    DIAGNOdent readings vs. recommended treatment chart by manufacturer KaVo DIAGNOdent
    Correlation of DIAGNOdent Values to Possible Course of Action Possible Course of Action*

    No Action
    Record &
    0 - 5
    5 - 10
    10 - 15
    15 - 20
    20 - 25
    25 - 30

  • Taken from Lussi
  • ** In unusual cases of virulent disease, preparation may be a course of action when a value between 20 - 30 is recorded.
  • *** Regardless of course of action taken to treat a specific lesion, preventive therapy may be indicated based upon caries risk.

    Q: So where does this leave us? Is there a single tool dentists can use to detect smooth surface or occlusal carious lesions?

    A: Early detection of fissure caries is a prerequisite for effective management. Clinical decisions regarding the type of agent most appropriate for the prevention and chemotherapeutic treatment of root caries depend primarily on the professional assessment of risk for the lesions (Anusavice, 1995).

    For approximal tooth surfaces, the results of several in-vivo studies were reviewed (Ismail 1997). The study evaluated the diagnosis of different stages of dental caries in the proximal surface area and found precavitated lesions to be the most common. Probing was found to be the least effective method for the detection of carious lesions. The FOTI exhibited a better sensitivity than clinical inspection in detecting precavitated lesions that had a shadow or opacity underneath the marginal ridge.

    Another study (Van Rijkom and Verdonschot 1995) also reviewed the diagnosis of caries on proximal surfaces and found that FOTI was superior to visual inspection and radiography. However in a previous review (Verdonschot 1991) radiography was superior to FOTI. A conclusion can be obtained from some of the previous studies that FOTI is a cost efficient non-invasive adjunct to a clinical examination in the detection of posterior dental caries (Pine CM 1996).

    In a statement issued by the National Institutes of Health Consensus Development Conference(2001) on the diagnosis of caries, each of these detection methods were reviewed by an independent, non-Federal Consensus Development Panel. After weighing the scientific evidence, the panel’s draft statement concluded that the differences in caries presentations and behavior in different anatomical sites makes it unlikely that any one diagnostic modality will have adequate sensitivity and specificity of detection for all sites.

    Existing diagnostic modalities appear to have satisfactory sensitivity and specificity in diagnosing substantial, cavitated, dental caries; specifically radiographic methods are essential in diagnosing approximal carious lesions. However, these modalities do not appear to have sufficient sensitivity or specificity to efficaciously diagnose noncavitating caries, root caries, or secondary caries. Currently, there is no diagnostic modality that can differentiate between microbiologically active caries and demineralized dentin without caries activity beneath a restoration. This is a critical weakness in view of the significant percentage of restorations inserted to replace existing restorations.

    The need for the identification and clinical staging of the presence, activity, and severity of dental caries is of paramount importance in the deployment of treatment strategies that employ increasingly important nonsurgical modalities, such as fluoride, antimicrobials, sealants, and no treatment. New diagnostic modalities that are currently in various stages of development and testing will need to be evaluated using rigorously controlled clinical trials. Such studies will promote true staging of carious lesions, based on highly sensitive and specific diagnoses, followed by appropriate, linked, treatment-planning decision algorithms.

    A review conducted by Dodds (1993) on the effective application of various diagnostic systems were tabulated as follows: The Relative Utility of the Available Diagnostic Systems in Diagnosing Early Noncavitated Lesions.

    Clinical observations suggest that carious lesions can be arrested at any stage of lesion development i.e., even at the cavitation stage if plaque-free conditions are maintained (Nyvad and Fejerskov, 1997). The remineralization observed in clinically arrested lesions and the conversion of clinically active to inactive lesions supports the non-restorative management of carious lesions (Nyvad and Fejerskov, 1986). Therefore, sensitive diagnostic techniques are needed to provide acceptable compromises between sensitivity and specificity for a wide range of applications for individual patient care as well as for research purposes.

    However, existing diagnostic techniques generally rely on subjective judgements and can only provide semi-quantitative measures and some of the diagnostic systems are unable to detect small lesions. The ECM is capable of detecting PFCLs, which may be missed with conventional visual examination.

    Q: Can you give us a synopsis of the current thinking regarding the etiology of dental caries?

    A: Enamel is a secretion rather than a true tissue because no viable ameloblasts exist after the eruption of the teeth. Caries, a disease of mineralized tissues, is caused by the action of micro-organisms on fermentable carbohydrates in the diet, which cause demineralization of the mineral portion of these tissues. This is followed by disintegration of organic material. (Thylstrup and Fejerskov, 1994). The classic causal prescription for dental caries includes these three factors.

  • A susceptible tooth surface colonized with cariogenic bacteria and the presence of a dietary source of nutrients.
  • Microbial pathogens producing lactic acid from the fermentation of carbohydrates
  • Lactic acid dissolving the crystal structure of the tooth Many bacterial species take part in the microbiota of the fissures. However, only two species have proved to be strongly associated with the initiation of the caries process specific to the fissure area. These are: Mutans streptococci and Lactobacilli. Both are strongly acidogenic and aciduric, combined with the ability to produce intra–cellular polysaccharides and extracellular glucans.

    In human cross-sectional epidimiological studies, S. mutans has been correlated with caries and presumed to play a major role in the initiation of the lesion, although it is not the first to colonize the tooth surface (Loesche et al., 1975). Lactobacilli have also been correlated with dental caries. However, these species are minimally involved in the initiation of the lesion but play a major role in the progression of it.

    Millar (1890) postulated the theory of multiple bacteria-causing caries rather than a single group, a theory supported by others to date. When comparing the microbial composition of dental plaque from persons with low caries activity with those having high caries activity, the number of acidogenic bacteria was greater in the latter group.

    Cariogenic bacteria utilize sugar (by possessing special enzymes) in its metabolism. The resultant energy is used to produce special intracellular and extracellular glucans (polymers) that help it populate and grow in large numbers or masses. The formation of these masses is important for the initiation of the carious process.

    Fermentation of the carbohydrates in these anaerobic conditions causes an increase in the concentration of organic acids, mainly lactic acid, in the plaque and in the carious lesion. The resulting drop in pH causes demineralization while the acid-free periods in the absence of carbohydrates (resting periods) have no demineralization activity. The balance against those continuous attacks is a function of multiple complex factors. The content of the food intake, plaque quantity and quality, the quantity and quality of saliva, the susceptibility of the tooth surface, and fluoride concentration in the environment are among the important factors that interact with each other to produce caries or inhibit caries. This is one of the reasons for the importance of controlling the intake of fermentable carbohydrates in the diet.

    Caries is an etiologically complex disease process. It is likely that numerous microbial, genetic, immunological, behavioral, and environmental contributors to risk are at play in determining the occurrence and severity of clinical disease. Assessment tools based on a single risk indicator are therefore unlikely to accurately discriminate between those at high and low risk. Multiple indicators, combined on an appropriate scale and accounting for possible interactions, will certainly be required.

    Q: Since this is an infective disease process, are there any systemic consequences to the progression of this disease?

    A: Dental caries produces its effects locally by spreading in the mineralized tissue with no symptoms. Once the process reaches the vital pulp then pain may be felt from sensitivity to cold or osmotic stimuli from foods. If the decay is left to progress, then an infection is established in the pulp chamber and spontaneous pain is produced. The immune response usually can contain the bacteria within the pulp chamber, but a fistula may be established between the tooth apex and the oral cavity, which drains pus.

    Systemic effects of the caries process can occur when the infection is not drained. The building pressure of the infection and bacterial products spread internally within the adjacent tissue, and a swelling can be produced in the facial tissue surrounding the offensive tooth. This might be associated with fever, malaise, and in some cases erythema of the skin. A further serious complication appears when the infection reaches critical areas such as around the eye or down to the neck that might endanger the air passageways or risk a brain infection. In cases where the immunity is reduced by drugs or disease, the total body spread of infection is called septicaemia and risks the life of the patient.

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    January 2015
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