Current trends in radiographic caries imaging

Current trends in radiographic caries imaging A n n Wenzel, DDS, PhD, DrOdont, a Aarhus, Denmark ROYAL DENTAL COLLEGE, UNIVERSITY OF AARHUS

Caries prevalence, lesion site, and lesion behavior have changed over the past decade. This review looks at the impact of these changes on radiographic caries imaging. (ORALSURGOral MED ORALPATHOI.ORALRADIOLENDOD 1995;80:527-39)

Caries prevalence, lesion site preference, and lesion behavior have changed during the last decades. This results in a number of problems that should be faced by the clinician when radiography is used for the detection and monitoring of caries lesions. (1) The decline in caries prevalence will theoretically lead to a fall in the positive predictive value of a diagnostic test. This means that the lower the disease prevalence, the less trustworthy a positive outcome of the test may be. 1 (2) The higher occlusal/approximal caries ratio makes it important to emphasize the detection of occlusal lesions. (3) The behavior of the lesions has changed most probably because of the widespread use of fluoride dentifrices so that progression rates are on average slow, 2 and lesions may arrest or remineralize. The presence of fluoride even in low concentrations has a strong effect on enamel solubility as it makes the outer enamel apatite less soluble) Evidence exists that the availability of fluoride in the oral environment has a profound impact on enamel repair. 4 As a consequence, a most important feature in the change in lesion behavior may therefore be that lesions do not cavitate until at late stage in disease progression. Thus, demineralizations may develop slowly, even deep into the dentin, underneath a clinically intact enamel surface. On the other hand, lesions may arrest after a phase of demineralization and leave a " s c a r , " a demineralized zone in the inner enamel and the dentin. 5 The outer part of the enamel demineralization may be well remineralized. 4 The dynamics of the caries lesion should be kept in mind when caries diagnostics and treatment decisions are based on radiography. For individual treatment planning, caries in approximal surfaces has traditionally been diagnosed by clinical examination combined with radiography. Occlusal caries lesions have been diagnosed by clinical examination alone as radiography has been c o n -

sidered to be of little value. 6-8 The era for the use of the probe as a diagnostic tool for fissure lesions has ended as more studies have shown that it has a low sensitivity9-11 and does not improve the validity of the diagnosis compared with mere visual inspection. 12, 13 Rigorous probing may even produce traumatic defects of the enamel surface corresponding to subsurface demineralizations, 14, 15 and the use of the explorer for this purpose is therefore obsolete. Currently, there are several new and some rediscovered caries diagnostic methods under development and evaluation, for example, optical methods such as fiber-optic transillumination, ultraviolet light, fluorescent dye uptake, laser fluorescence, and light scattering, 16 and the electricity-based method, electrical resistance measurement.17 The present article will deal, however, merely with the current trends in the use of radiographic methods in caries diagnosis and its relationship with clinical (visual) diagnosis and treatment decision. Recently, a number of reviews have been published on radiographic caries diagnosis and monitoring 17-19 and on the developments in advanced radiographic techniques, z~ The flow of reviews reflects the fact that caries has become more difficult to diagnose in clinical dental practice, and that when a lesion is detected treatment decisions have also changed. The aims of the present article are therefore (1) to give a short review of various radiographic techniques with emphasis on newly developed image receptors; (2) to briefly describe study designs for testing the validity of caries diagnostic methods with comments on existing models; (3) to discuss indications for radiographic examination and the appropriateness of routine screening programs; and finally, (4) to suggest diagnostic a n d treatment planning strategies in the light of the changes that have occured in the caries disease pattern.

METHODS Recording techniques RADIOGRAPHIC

aAssociate Professor, Department of Oral Radiology. Received for publication Feb. 8, 1995; revised via E-mail; accepted for publication May 10, 1995. Copyright 9 1995 by Mosby-Year Book, Inc. 1079-2104/95/$5.00 + 0 7/16/66351

The use of panoramic radiography has increased immensely in general dental practice over the years. 21 Several studies have compared the diagnostic perfor527

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Fig. 1. A and B, Subtraction images reveal close to identical recording geometry in two sets of bite-wing radiographs taken 2 years apart with Kwik-BiteR film holder. Approximal caries lesion is seen in B. mance of intraoral and panoramic radiography for the detection of caries. Although most of the studies have been conducted without a true validation for the presence or absence of disease, the conclusion has been that panoramic radiography is inferior to intraoral radiography. 22-26 The ability to diagnose approximal enamel lesions has been demonstrated to be particularly low in the panoramic image. 27-3~ It has further been shown that lesion detection in the panoramic radiograph varies within the dentition with lowest values for the incisor region. 3~ 31 Others have found that the probability for a false-positive diagnosis is higher in panoramic images than in intraoral radiographs.30, 32 It may therefore be concluded that the panoramic technique is not suitable for caries diagnosis. The intraoral bite-wing technique should therefore still be considered the most appropriate radiographic method for diagnosis of caries. The problems in-

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volved in this recording technique are well known, and in the future focus should also be set on securing image quality throughout the radiographic recording process. 33 To monitor the caries lesion, emphasis should be put on obtaining reproducible recording geometry. The use of a simple film holder with an aiming device may provide an acceptable standardization. 34-36 An indication for this can be obtained from two recent studies in which traditional bite-wing radiographs of school children had been taken with a conventional film holder at 1-year intervals. The radiographs were used for the evaluation of the subtraction radiography method (Fig. 1) as a tool in forensic dentistry based on conventional bite-wing radiographs. 37, 38 Various devices for serial recordings have been suggested including a totally fixed alignment between the film, the film holder, the tooth, and the tube.34, 39-44 The mechanical coupling of film holder and tube for identical geometry may be a very cumbersome and rigid system for use in general practice, and it may be expected that it will soon be exchanged by more easily operable systems facilitating reproducible recording of radiographs. It m a y be predicted that the trend in standardizing intraoral radiographic recording will be the development of devices for optical alignment provided by light beams and fixed points (Fig. 2) 45 and eventually robot recording. 46 Until automated recording takes over, however, there will still be a need for well-trained personel to take the radiographs. Human skills may be the weakest link with respect to assuring quality in the process of radiographic recording. In the early 1980s, the need for standardized teaching programs for education in oral radiology was emphasized, 47-49 and a decade ago, it was suggested that computer-based learning may have many advantages over traditional teaching. 5~ Control over the sequence in the computer programs was shown to improve radiographic image quality. 52 It m a y be anticipated that students will be more motivated when the education is learner-controlled (Fig. 3) and that it will eventually result in radiographic images of better quality in the dental practice. Several universities are currently introducing multimedia and computer-assisted learning to the supply of teaching materials offered to students together with studentdirected courses. The trend seems thus to be that multimedia will be part of the dental curriculum in the future and, as has been previously stated, computerassisted learning " a challenge for the nineties."53, 54 Image receptors Film. The silver-halide based dental film has a high spatial resolution (approximately 10 to 12 lp/mm, 55

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Fig. 2. Schematic drawing of optical alignment device for reproducible recording of radiographs. (Courtesy of Lone Sander, Department of Periodontology, Royal Dental College, University of Aarhus.) and its sensitivity to x-radiation has increased during the years. 56 Several studies have compared the performance of various film types for the detection of caries. Some have found that D-speed (Kodak Ultraspeed, Eastman Kodak Co., Rochester, N.Y.) film p e r f o r m e d better than E-speed (Kodak Ektaspeed) film, 57 but the opposite has also been demonstrated. 5s A large number of studies have shown, however, that the two film speeds perform equally well. 59-64Two recently marketed dental films, M2 Comfort (Agfa-Gevaert, Mortsel, Belgium) and Ektaspeed Plus (Kodak) have shown to perform as accurately as the older films, the Ektaspeed Plus even somewhat better for detection of particularly small approximal caries lesions. 65 The Ektaspeed Plus is the more sensitive film (same exposure parameters as the old Ektaspeed film) and has increased in quality compared with the older film. This film should therefore be recommended for caries diagnostics. CCD-based sensors and storage phosphor plate. One conventional bite-wing film radiograph that covers the first and second premolar and first molar in the upper and lower jaw gives a high information/ dose ratio. The charge-coupled device based (CCD) sensors (Fig. 4, A) display less information than the film in one exposure, and it is not an easy task to make a traditional bite-wing exposure. 66 Often, several exposures are needed with the CCD systems to obtain the same information as from one bite-wing film. The newly marketed storage phosphor plate (Fig. 4, B) has the same shape and dimensions as the current dental film67, 68 and can therefore be used for a traditional bite-wing projection. Conventional aiming devices can and should be used, and the only limitation is that the plate is harder than the film and cannot be bent. Although the radiation dose needed for the CCD sensors is 20% to 25% of that needed for a D-speed film,

Fig. 3. Students work with Digora and conventional film after receiving computer-assisted instruction in a course of intraoral radiography. the phosphor plate starts to create an image at much lower doses and has a much higher tolerance to variations in exposure dose. 69 Depending on the diagnostic task, doses from 5% to 20% of a D-speed radiograph are necessary. 7~ From the point of radiation protection, the digital systems should therefore be recommended in caries diagnosis. A detailed de-

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Fig. 4. A, Three CCD-based sensors and B, the storage phosphor plate.

scription of the digital systems is included in the present journal volume. Only few caries detection studies with digital radiography have been performed so far. It h a s been shown that lesions were detected as accurately on images taken by the RadioVisioGraphy (Trophy Radiologie, Vincennes, France) system as on conventional films 72' 73 whereas paper-print images were less accurate than films.74 A recent report 75 that compared three CCD-based receptors [RadioVisioGraphy, Sens-A-Ray (Regam Medical Systems, AB, Sundsvall, Sweden), and Visualix/Vixa (Philips Medical Systems, Inc., Gendex, Monza, Italy)] and the one storage phosphor plate system (Digora, Soredex Medical Systems, Helsinki, Findland) found no statistically significant differences in the detection of occlusal and approximal caries lesions between the four systems. It seems however, that particularly for

detection of small initial lesions (histologically confined to enamel), the Visualix system has a lower sensitivity (true-positive detection rate) than other digital systems and film. 64' 75 The spatial resolution (lp/mm) is lower in the digital systems than in conventional dental films, but, as stated by Benn, 19 line pair resolution is probably not the appropriate measure for predicting caries visibility. It seems that high contrast is a more important prerequisite for increasing caries diagnostic accuracy. 76 The trend in caries radiographic imaging seems for several reasons to go in the direction of digital systems.

Image quality enhancement Radiographs need to be quite dark with a good contrast to provide the optimal basis for caries diagnosis. In film radiography, an increase in density without deteriorating contrast can only be achieved

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by increasing radiation dose (longer exposure time, higher mA, or shorter focus-film distance). Light radiographs m a y result in poorer diagnostic performance than images of optimal density and contrast76, 77 whereas very dark radiographs may also result in a decreased true-positive detection rate. 78 A film radiograph of nonoptimal density should be retaken whereas in a digital image, contrast and density may be enhanced numerically, optimizing quality and thus diagnostic accuracy. 76,79,80 As much as 30% of all retakes in radiology departments may be due to improper image density. 81 In addition, a large fraction of radiographs with suboptimal quality are a result of improper film processing. 82 In digital imaging, no wet processing is involved, and in all systems on the market, facilities for density correction and contrast enhancement are available. The use of such facilities may be dose saving as retakes are avoided. Radiographs also need to be quite sharp for the purpose of caries diagnosis to detect the boundaries between sound and diseased tissue. 33 Edge enhancement filters m a y reduce blur s3 but leave the image with a grainy appearance. Edge enhancement applied to digital images did not give rise to a more accurate performance than when caries diagnosis was made with conventional films. 76 When various filters were applied to images of periapical bone destruction and bite-wing radiographs with and without caries, dentists preferred a heavily edge-enhanced image for the periapicals, but a more smoothed image for the bitewings. 84 This finding suggests that task-dependent enhancement routines should be provided in future digital systems. Recently a review was published on computeraided image manipulation facilities, s5 Nothing has been published so far, however, on dentists' actual use of the provided enhancement facilities during image interpretation. It may be anticipated that such procedures would not be used if they are very time consuming. A recent study focused on the use of brightness, contrast, and gamma curve manipulations during observers' scorings of approximal and occlusal caries lesions in digital images taken with four intraoral systems. The observers were not aware that their behavior was recorded, s6 It was demonstrated in this study that all observers used at least one of the enhancement facilities in almost all digital images independent of the system behind the image. Further there was no direct relationship between time spent scoring one image and the number of enhancement facilities used. This result indicates that routines for enhancing density and contrast ought to be provided when digital radiographic systems are developed and that factors other than enhancement time determine the diagnostic time use.

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Fig. 5. A, Digital radiograph of extracted tooth with occlusal caries lesion and B, histologic section of tooth as seen in stereomicroscope.

The interobserver variation in detecting dental caries on radiographs is well known, 87 and the influence on observer performance of information given before the examination has previously been described. 78 Automated computer interpretation of radiographs was tried out in the 1980s for detecting and monitoring approximal caries lesions. 88-92 When validated histologically, the system proved more sensitive than did human observers, but it had a relatively low specificity. 9~ When very sensitive methods are used, a high number of false-positive results will be unavoidable. Automated caries diagnosis faces a number of problems, for example, an even higher necessity for a standardization of exposure geometry when monitoring lesions. Recently a new system has been described for automated caries detection93 that still needs proper evaluation before it can be recommended to clinicians. DESIGN OF STUDIES TO EVALUATE DIAGNOSTIC METHODS FOR RADIOGRAPHIC CARIES DETECTION Several textbooks have described the principles for evaluating diagnostic tests, i, 94, 95 It is important that

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new diagnostic methods are evaluated in the laboratory before they are released to be used on patients. Emphasis has been put on expressing the performance of a test in terms of accuracy and precision. 1, 96 Accuracy may be expressed in several ways, tradition: ally by sensitivity, specificity, and predictive values. In theory, the sensitivity and specificity are independent of the disease prevalence although the predictive values are influenced. 1'78 However, no controlled studies have documented that this is in fact true. It is important in studies of diagnostic test performance that the threshold for disease is always described because this naturally has a heavy impact on disease prevalence 97 and therefore will also influence performance. 65 In most of the aforementioned studies to evaluate radiographic methods for caries detection, the diagnostic threshold level D 1 (incipient enamel lesions) was used for approximal lesions whereas occlusal lesions are most often diagnosed at the dentin level because enamel demineralizations cannot be perceived in radiographs. A new diagnostic system should be tested at the diagnostic level at which it is intended to operate in practiceJ 9 W h e n recording caries in radiographs, lesions should be classified according to their progression from the outer toward the inner dental hard tissues on a well-defined disease severity rating scale. Alternatively, disease can be classified according to the certainty by which it is perceived on a socalled confidence or likelihood rating scale at a defined diagnostic threshold. It has been demonstrated that for assessment of diagnostic accuracy in caries detection, both the disease severity scale and the confidence scale can be used as basis for calculation of receiver operating characteristics (ROC) curve areas 98, 99 with no difference between the outcomes in terms of accuracy. The ROC curve area approach allows for an easy comparison between more diagnostic tests, but it is only appropriate in studies with a solid validation (thus mostly in vitro). It is further important in in vitro studies that the validation method and the validator(s) are thoroughly described as this has been shown to influence the results for the diagnostic tests under study.l~176 101 For an in vitro evaluation of the accuracy of caries diagnostic methods, sectioning of the teeth with a subsequent assessment of the sections in a stereomicroscope (Fig. 5) has been demonstrated to be an accurate validation. 100 Some considerations on the evaluation of diagnostic tests with suggestions for designs have recently been published. 96 A trend in research on the performance of diagnostic methods is the use of the likelihood ratio that has not gained a footing in studies on radiographic caries detection.13, 80 This ratio is an expression of the probabil-

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ity for a positive test result that occurs in a patient with the disease as opposed to a patient without the disease; it can be obtained directly to calculate the posttest probability of disease in patients from other populations than the one that has been studied. 1~ The likelihood ratio may be easier to understand and to use than ROC curves and may attract more attention in future caries diagnostic studies, Several models exist for in vitro evaluation of caries lesion behavior or caries diagnostic methods. In s o m e study designs, lesions in digital radiographs have been simulated by computer software and lesion detection related to image noise degradation. 1~ Another design has been to drill holes in teeth to represent c a r i e s 104-106 in the evaluation of projection geometry on lesion detection. 1~ Such method designs give rise to lesion simulations that are far from the biologic appearance of true caries lesions and thus cannot be recommended in studies evaluating caries diagnostic methods. Various acid-gel models have been developed for producing artificial caries lesions in the laboratory. 108 Acid-gel models may be valid in studies of the demineralization and remineralization processes in the dental enamel, but the lesions produced extend only approximately 200 pm deep into the enamel and do not mirror the lesions that need to be diagnosed in the clinic. Such models are not appropriate in studies of the validity of radiographic methods for caries detection. In in vitro studies that evaluate diagnostic tests for caries detection or monitoring, extracted human teeth with true lesions should therefore be preferred. However, attention should be paid to the relationship between the in vitro and in vivo study designs as a translation of laboratory results into the clinical situation will not be straightforward. A recent metaanalysis of the factors that determine the validity of diagnostic tests for caries revealed that the study design had a greater impact on the results than any differences between the diagnostic tests under study. 1~ Investigations are needed that relate resuits from radiographic caries detection performed first in vivo and thereafter in vitro in the same population.

RADIOGRAPHIC SCREENING A N D GUIDELINES In previous epidemiologic investigations, it has been estimated that radiography on average reveals twice as many approximal caries lesions extending into the dentin as observed in a clinical examination alone.110-112 In recent years, occlusal dentin caries has also been reported to remain undetected by clinical examination because of the absence of cavitation,

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whereras radiography has been shown to increase the detection rate. t3, 76, 80, 113-116 On this basis, it has been widely recommended that bite-wing screening radiography be undertaken in both the deciduous and the permanent dentition.ill, 117, 118 A broad literature search on the value of bite-wing radiographs reported that the use of bite-wings compared with a clinical examination alone doubled the number of lesions detected, u2 It was concluded from this review that: " I f diagnosis of small approximal lesions in posterior teeth is important, a bite-wing radiograph is an essential diagnostic aid. " T h e less fastidious the clinical examination, the more important is the radiographic examination. . . . In epidemiological studies where radiographs are not included, the findings will grossly underestimate the total caries prevalence of the population surveyed . . . . In clinical trials where radiography is not included, the necessary basis for treatment decision, preventive or restorative treatment, will be missing." These statements may give rise to the assumption that routine radiographic screening programs should be conducted with regular intervals in various age groups. For example, in the United States guidelines have been published for prescribing dental radiographs with the purpose of caries detection. 118 These guidelines recommend that all new patients irrespective of age and findings from the clinical examination should have a posterior bite-wing examination and that even low-risk (no clinical caries) recall patients should undergo repetitive radiographic examinations every 1 to 2 years from the age of 3 years until adolescence and every 2 to 3 years for the rest of their dentulous l i f e . 119' 120 However, several factors should be considered when such programs are advocated: caries lesion behavior and reliability of the radiographic findings.

Caries lesion behavior It seems that general practitioners perform more radiographic examinations than prescribed in the guidelines.a20, 121 It has been shown that dentists estimate the progression rate through primary tooth enamel to be from 6 months to 1 year and through permanent tooth enamel 1 to 2 years. 121 This estimated speed of progression seems to determine the interval between their conducted bite-wing examinations. 121 This progression rate may, however, be grossly overestimated in western countries with a fluoridated environment. Based on older studies, the caries progression rate for approximal lesions has been estimated to be 3 to 4 years for 50% of lesions to progress through enamel as observed on radio-

Fig. 6. Microradiograph of tooth section shows demineralized area in enamel with well-mineralized intact outer surface zone covering body of lesion. (Courtesy of Mogens Joost Larsen, Department of Dental Pathology, Operative Dentistry and Endodontics, Royal Dental College, University of Aarhus.) graphs 122-126 whereas today it has been calculated to take even longer. 127 With this slow progression rate, the short intervals b e t w e e n bite-wing examinations recommended in the guidelines seem not to be reasonable because the high measurement accuracy needed to observe progression can hardly be obtained in 6-month or yearly radiographic examinations. 19 Knowledge of the behavior of the caries lesion should constitute the basis for prescribing bite-wing examinations. As suggested recently by Chan, 128 it m a y be time for another update of the U.S. guidelines.

Reliability of the radiographic findings Accuracy. The findings from epidemiologic or clinical studies are based on observers' recordings of radiographic images without the possibility of validating the interpretation of a caries lesion. Depending on disease prevalence, a fraction of the lesions detected in such studies will be false-positive recordings. 1 Most in vitro investigations have shown that the false-positive detection rate in radiographs range from 3% to 30%. 58, 72, 80, 129, 130 The accuracy for radiographically detecting small approximal lesions that are histologically in the enamel has been reported to be not much higher than can be obtained by chance. 64 That is, half of the existing Small approximal lesions are not perceived on radiographs (low sensitivity), and half the ones that are observed are false-positive results (low positive predictive value). Validity increases with increasing lesion depth. 131

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Fig. 7. Tooth separation between maxillary second premolar and first molar to diagnose clinical state of demineralization seen on bite-wing radiograph (A). B, spring inserted between two teeth; C, occlusal view after removal of spring; and D, close-up view of surface cavitation. (Courtesy of Bo Danielsen, Dental Auxiliary Division, Royal Dental College, University of Aarhus.)

Precision. Several studies from different parts of the world have shown that dentists differ immensely in the number caries lesions they record in the same radiographs.87, 130, 132, 133 Three dentists, who had worked for many years in t h e same clinic for child dental health care, varied approximately 50% in the number of caries lesions detected in radiographs, not only for enamel but also dentinal lesions. 132 It is therefore doubtful that radiography is an essential aid for detection of small approximal caries lesions as they cannot be accurately and reproducibly observed in radiographs. When guidelines advocate frequent routine screening programs, overtreatment may be the result. 18 The frequent use of sensitive diagnostic tests can be justified only if dentists would adopt to a high threshold for operative therapy and to clinical routines by which the treatment decision is not solely based on the radiographic appearance of the lesion.

TREATMENT DECISIONS The outcome of the caries diagnostic process is the decision for treatment. The decision comprises severa] diagnostic elements including detection of the lesion, determination of lesion activity and state, and evaluation of patient factors that might influence a change in lesion state. TM New diagnostic criteria are needed to classify the caries lesions into categories keyed to treatment strategies. 135 As stated here, approximal caries lesions are traditionally diagnosed on radiographs, and treatment decisions are made from the radiographic appearance. Very few studies have compared the number of detected caries lesions after a thorough clinical examination combined with bite-wing radiographs in cases where lesions were suspected with the number of detected lesions after radiographic screening of all persons. In a low prevalence western society, it has been demonstrated that only approximately 1% of the sur-

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faces with radiographically detectable dentin caries were overlooked in a fastidious clinical examination combined with selective radiography in cases in which caries was suspected. 132 Selective radiography was performed in approximately 5% of surfaces. In the same study, 9% of approximal enamel caries was not detected. Thus, these figures do not come close to the 50% of caries lesions stated to be overlooked in older studies if routine radiography is not performed. 112 A fastidious clinical examination must therefore precede a radiographic examination in individual treatment planning, and selective radiography should be performed in cases in which a clinical examination has led to suspecting a lesion. In these cases the bite-wing radiograph can be a diagnostic aid to detect the nonclinically observable dentinal lesions. Lesion detection is known to differ between dentists. However, even when a lesion is agreed upon, various opinions exist on how to treat it. 136, 137 In many western countries it has been considered overtreatment to perform operative therapy on lesions that radiographically were confined to enamel and when no other information exists. Despite this fact, it has been reported that approximately 25% of Canadian dentists would restore the approximal surface when a radiolucency was observed in the enamel. Fifty percent would fill the tooth when a radiolucency was seen at the dentino-enamel junction; 25% would wait until the lesion had penetrated into dentin. 121 Approximately 90% of Norwegian and Australian dentists would fill a surface if the diagnosis dentinal caries is given, whereas only 10% and 18%, respectively, would if the lesion is seen in enamel. 138 The radiograph per se, however, may not be the appropriate diagnostic tool for treatment decision. It should be noted that in the radiograph, a distinction between the active caries lesion and the arrested lesion with a well-mineralized outer surface cannot be made. It is well known that fluoride facilitates the maintenance of an intact outer enamel surface. 3 A very recent study has indicated that fluoride in high concentrations is taken up in the outer enamel that has easy access to the environment whereas little fluoride diffuses into the body of the demineralized area (Fig. 6) unless the surface is thin or lost. 4 A scar is left in the tissue. Therefore the radiographic appearance of the lesion may well be similar in the active state and in the arrested state. Only a clinical inspection of the tooth surface can verify disease activity and state. Active caries lesions are chalky white and rough whereas arrested lesions may be opaque white or brownish with a shiny surface. 5 In principle, a carious lesion may be arrested if

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plaque accumulation on the surface can be sufficiently controlled. Even though lesions with a cavitated surface can also arrest, this has seemingly been verified mostly for free surfaces where plaque can be readily removed. 139 In approximal surfaces where plaque removal in a cavity will not be possible, lesion arrest seems to be dubious for a cavitated surface. In approximal tooth surfaces, immediate operative treatment is thus only appropriate for active lesions that exhibit an outer surface cavity. It has been reported that only 10% of restored surfaces exhibited a true cavitation before restoration. 140 Previously, the radiography-based treatment decision strategy for approximal caries lesions seems to have been justified because radiographic dentinal lesions were shown to be strongly connected with surface cavitation; 80% to 90% of such lesions had cavities. 141-144In more recent years, however, it has been demonstrated that the relationship between the radiographic appearance and the clinical state of disease is not unequivocal. In low prevalence populations, it has been found that only 40% to 50% of lesions that exhibited a radiolucency into dentin were clinically cavitated 145 , 146 whereas in populations with higher caries prevalences, the 90% still seem to be valid. 147 Radiographic appearance is thus not a good predictor for the presence of cavitation. 1 The radiographic method seems to possess a higher specificity for detecting sound surfaces as only 3% of surfaces without dentinal lesions on radiographs had cavities when validated by tooth separation. 148 When a dentinal approximal lesion is detected by radiography (Fig. 7, A), the patient may thus be offered temporary tooth separation (Fig. 7, B), which provides the possibility for direct visual inspection of the surfaces. 146, 147, 149 By direct inspection, it can be determined whether the lesion is in an active or inactive state, cavitated or noncavitated (Fig. 7, C and D). If the surface is not cavitated and the patient is appropriately motivated, instructions for oral hygiene with emphasis on the lesion site may be given. If the surface is cavitated, operative treatment should be performed. There is a lack of longitudinal studies investigating the behavior of noncavitated approximal dentinal lesions observed in radiographs and the relationship between lesion depth and possible arrest or eventual cavitation of the demineralized area. Future research should look into this. In occlusal surfaces, a fastidious clinical examination will be able to determine caries activity along the fissure systems in the same way as it does for approximal surfaces. When caries is suspected (white, rough, or discolored fissures), radiography may re-

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veal the presence of a dentinal lesion even when no clinically visible breakdown of the outer surface exists. It is difficult to imagine that lesions that have penetrated into dentin along the surfaces of deep fissures can be arrested as they can hardly be kept free from microorganisms. Thus an operative treatment or, for questionable cases, fissure sealants are indicated. N o studies, however, have monitored such lesions systematically over time to determine if they continue to progress under a strict oral hygiene program. It is not k n o w n how far an individual dentinal lesion may progress before cavitation occurs. There are no studies at the site level that have shown that for any particular lesion one can predict the progression rate. 19 Thus, monitoring such lesions may still be dependent on radiography or tooth separation with clinical inspection. The tooth separation technique may, however, be somewhat time consuming (two visits are needed), and at times difficult in adults probably because of bone inflexibility; springs (Fig. 7, B) are more appropriate than elastics. There are therefore reasons to believe that monitoring dentinal approximal caries lesions will also in the future need radiographic examination. CURRENT TRENDS The current trends in the diagnostic and treatment decision strategies concerning dental caries may therefore be the following: 1. Radiographic screening before clinical examination with the aim o f detecting caries should not be performed. 2. A meticulous clinical examination should precede radiographic examination and identify surfaces with lesions or where lesions are suspected. The latter should be radiographed. 3. Approximal lesions in outer enamel cannot be diagnosed accurately and precisely in radiographs, and it may therefore be questionable to spend many resources on preventive programs at the site level. 4. Approximal lesions in dentin observed in radiographs may be active or inactive (arrested). Half the dentinal lesions are not cavitated and can theoretically be arrested if active. Radiography cannot distinguish between active and inactive, cavitated and noncavitated lesions. Only tooth separation can provide the basis for this distinction. 5. Approximal surfaces with a clear cavitation should be treated surgically, surfaces without cavitation should be monitored by standardized radiography or tooth separation and plaque accumulation should be controlled.

6. Occlusal lesions observed in dentin in radiographs should be treated surgically as the ability to keep the surface (fissures) plaque-free and arrest the lesion seems at present to be limited. More research is needed into the behavior of occlusal and approximal dentinal lesions. REFERENCES 1. Grrndahl H-G. Radiologic diagnosis in caries management. In: Thylstrup A, Fejerskov O, eds. Textbook of clinical cariology. 2nd ed. Copenhagen: Munksgaard, 1994:367-82. 2. Pitts NB, Kidd EAM. The prescription and timing of bitewing radiography in the diagnosis and management of dental caries: contemporary recommendations. Br Dent J 1992;172:225-7. 3. Larsen MJ, Bruun C. Caries chemistry and fluoride: mechanisms of action. In: Thylstrup A, Fejerskov O, eds. Textbook of clinical cariology. 2nd ed. Copenhagen: Munksgaard, 1994:231-58. 4. Pearce EIF, Coote GE, Larsen MJ. The distribution of fluoride in carious human enamel. J Dent Res (In press.) 5. Thylstrup A, Fejerskov O. Clinical and pathological features of dental caries. In: Thylstrup A, Fejerskov O, eds. Textbook of clinical cariology. 2nd ed. Copenhagen: Munksgaard, 1994:111-58. 6. King NM, Shaw L. Value of bite-wing radiographs in detection of occlusal caries. Community Dent Oral Epidemiol 1979;7:218-21. 7. Marthaler TM. Improvement of diagnostic methods in clinical caries trials. J Dent Res 1984;63:746-50. 8. Flaitz CM, Hicks MJ, Silverstone LM. Radiographic, histologic, and electronic comparison of occlusal caries: an in vivo study. Pediatr Dent 1986;8:24-8. 9. Howat AP. A comparison of the sensitivity of caries diagnostic criteria. Caries Res 1981;15:331-7. 10. Penning C, van Amerongen JP, Seef RE, ten Care JM. Validity of probing for fissure caries diagnosis. Caries Res 1992;26:445-9. 11. Van Amerongen JP, Penning C, Kidd EAM, ten Cate JM. An in vitro assessment of the extent of caries under small occlusal cavities. Caries Res 1992;26:89-93. 12. Lussi A. Validity of diagnostic and treatment decision of fissure caries. Caries Res 1991;25:296-303. 13. Lussi A. Comparison of different methods for the diagnosis of fissure caries without cavitation. Caries Res 1993;27:40916. 14. Bergmann G, Lindrn L-.A. The action of the explorer on incipient caries. J Swed Dent Assoc 1969;62:629-34. 15. Ekstrand K, Qvist V, Thylstrup A. Light microscope study of the effect of probing in occlusal surfaces. Caries Res 1987;21:368-74. 16. Angmar-Mgmsson B, ten Bosch JJ. Optical methods for the detection and quantification of caries. Adv Dent Res 1987;1: 14-20. 17. Wenzel A. New caries diagnostic methods. J Dent Educ 1993;57:428-32. 18. Brown JP. Dilemmas in caries diagnosis. Introduction to the symposium. J Dent Educ 1993;57:407-8. 19. Benn DK. Radiographic caries diagnosis and monitoring. Dentomaxillofac Radiol 1994;23:69-72. 20. Wenzel A, Pitts N, Verdonschot EH, Kalsbeek H. Developments in radiographic caries diagnosis. J Dent 1993;21:131-40. 21. Osman F, Scully C, Dowell TB, Davies RM. Use of panoramic radiographs in general dental practice in England. Community Dent Oral Epidemiol 1986;14:8-9. 22. Stewart JL, Bieser LF. Panoramic roentgenograms compared with conventional intraoral roentgenograms. ORAL SURG ORAL MED ORAL PATHOL 1968;26:39-42.

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 80, Number 5 23. Ohba T, Katayama H. Comparison of orthopantomography with conventional periapical dental radiography. ORALSURG ORAL MED ORAL PATHOL 1972;34:524-30. 24. Horton PS, Sippy FH, Kerber PE, Paule CL. Analysis of interpretations of full-mouth and panoramic surveys. ORAL SURG ORAL MED ORAL PATHOL 1977;44:468-75. 25. Stephens RG, Kogon SL, Reid JA, Ruprecht A. A comparison of Panorex and intraoral surveys for routine dental radiography. J Can Dent Assoc 1977;43:281-6. 26. Muhammed AH, Manson-Hing LR. A comparison of panoramic and intraoral radiographic surveys in evaluating a dental clinic population. ORAL SURG ORAL MED ORAL PATHOL 1982;54:108-17. 27. Hurlburt CE, WuehrmannAH. Comparison ofinterproximal carious lesion detection in panoramic and standard intraoral radiography. J Am Dent Assoc 1976;93:1154-8. 28. Balis S. Error and accurate rates of panoramic radiography as a screening method for mass surveying of children. J Public Health Dent 1991 ;41:220-34. 29. Ahlqwist M, Hailing A, Hollender L. Rotational panoramic radiography in epidemiological studies of dental health. Swed Dent J 1986;10:79-84. 30. Molander B, Ahlqwist M, Gr6ndahl H-G, Hollender L. Comparison of panoramic and intraoral radiography for the diagnosis of caries and periapical pathology. Dentomaxillofac Radiol 1993;22:28-32. 31. Douglass CW, Valachovic RW, Wijesinha A, Chauncey HH, Kapur KK, McNeil BJ. Clinical efficacy of dental radiography in the detection of dental caries and periodontal diseases. ORAL SURG ORAL MED ORAL PATHOL 1986;62: 330-9. 32. Valachovic RW, Douglass CW, Reiskin AB, Chauncey HH, McNeil BJ. The use of panoramic radiography in the evaluation of asymptomatic adult dental patients. ORAL SURG ORAL MED ORAL PATHOL 1986;61:289-96. 33. Wenzel A. Influence of computerized information technologies on image quality in dental radiographs [Thesis]. Dan Dent J 1991;95:527-59. 34. Pitts NB. Film holding, beam-aiming, and collimating devices as an aid to standardization in intra-oral radiography: a review. J Dent 1984;12:36-46. 35. Harrison R, Richardson D. Bite-wing radiographs of children taken with and without a film-holding device. Dentomaxillofac Radiol 1989; 18:97-9. 36. M~bystad A, Larheim TA. Reproducibility and overlapping of bite-wing radiographs: comparison of Eggen-bite with Kwik-bite. Community Dent Oral Epidemiol 1989; 17: 65 -7. 37. Wenzel A, Andersen L. A quantitative analysis of subtraction images based on bite-wing radiographs for simulated victim identification in forensic dentistry. J Forensic Odontostomatol 1994;12:1-5. 38. Andersen L, Wenzel A. Individual identification by means of conventional bite-wing film and subtraction radiography. Forensic Sci Int 1995;72:55-64. 39. McHenry K, Hausmann E, Wikesj6 U, Dunford R, LyonBottenfield E, Christersson L. Methodological aspects and quantitative adjuncts to computerized subtraction radiography. J Periodontal Res 1987;22:125-32. 40. Gr6ndahl K, Gr6ndahl H-G, Webber RL. Influence of variations in projection geometry on the detectability of periodontal bone lesions. J Clin Periodontol 1984;11:411-20. 41. Janssen PTM, van Palenstein Helderman WH, van Aken J. The effect of in-vivo-occurring errors in the reproducibility of radiographs on the use of the subtraction technique. J Clin Periodontol 1989;16:53-8. 42. Duckworth JE, Judy PF, Goodson JM, Socransky SS. A method for the geometric and densitometric standardization of intraoral radiographs. J Periodontol 1983;54:435-40. 43. Rudolph DJ, White SC. Film-holding instruments for intraoral subtraction radiography. ORAL SURG ORAL MED ORAL PATHOL 1988;65:767-72.

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44. Sewerin I. Device for serial intraoral radiography with controlled projection angles. Danish Dent J 1990;94:613-7. 45. Sander L, Wenzel A, Hintze H, Karring T. Comparison of image homogeneity with two techniques for serial intraoral radiography [Abstract]. 72nd Annual Meeting of the Scandinavian Division of the International Association of Dental Research. Gothenburg, Sweden, 1994:58. 46. Burdea GC, Dunn SM, Immendorf CH, Mallik M. Real-time sensing of tooth position for dental digital subtraction radiography. IEEE Trans Biomed Eng 1991;38:366-78, 47. Farman AG, Hunter N, Grammer S. Dental radiology instructors in United States dental hygiene programs. ORAL SURG ORAL MED ORAL PATHOL 1985;60:335-40. 48. Farman AG, Hunter N, Grammer S. Radiology requirements in United States dental hygiene programs. ORALSURGORAL MED ORAL PATHOL 1986;60:341-5. 49. Patel JR, Greer DF. Evaluating student progress through error reduction in intraoral radiographic technique. ORALSURG ORAL MED ORAL PATHOL 1986;62:471-4. 50. Wenzel A, Gotfredsen E. Computer-assisted instruction for intraoral radiography: Part II. evaluation of program effectiveness. Dentomaxillofac Radiol 1985;14:129-32. 51. Wenzel A, Gotfredsen E. Computer-assisted instruction for intraoral radiography: Part HI. evaluation of time comsumption. Dentomaxillofac Radiol 1986;15:73-7. 52. Wenzel A, Gotfredsen E. Learner- versus teacher-control in computer-assistedinstruction for intraoral radiography. Dentomaxillofac Radiol 1988;17:49-55. 53. Aronberg DJ, Rodewald SS, Jost RG. Computer-assisted instruction in radiology. Radiology 1985;154:345-7. 54. Squire LF. On teaching radiology to medical students: challenges for the nineties. AJR Am J Roentgenol 1989; 152:45761. 55. Sivasriyanond C, Mansong-Hing LR. Microdensitometric and visual evaluation of the resolution of dental films. ORAL SURG ORAL MED ORAL PATHOL 1978;45:811-22. 56. Svenson B, Lindvall A-M, Gr6ndahl H-G. A comparison of a new dental x-ray film, Agfa Gevaert Dentus M4, with Kodak Ektaspeed and Ultraspeed dental x-ray films. Dentomaxillofac Radiol 1993;22:7-12. 57. Sanderink GC, Scholte CM. A comparison between two dental films and two film-screen combinations in detecting low contrast defects and initial caries. Dentomaxillofac Radiol 1985;14:113-22. 58. White SC, Hollender L, Gratt BM. Comparison of xeroradiographs and film for detection of proximal surface caries. J Am Dent Assoc 1984;108:755-9. 59. Kogon SL, Stephens RG, Reid JA, Donner A. Ektaspeed and a screen/film system compared with Ultra-Speed in the interpretation of early proximal caries. J Can Dent Assoc 1984;50:397-401. 60. Svenson B, Gr6ndahl H-G, Petersson A, Olving A. Accuracy of radiographic caries diagnosis at different kilovoltages and two film speeds. Swed Dent J 1985;9:37-43. 61. Kantor ML, Reiskin AB, Lurie AG. A clinical comparison of x-ray films for detection of proximal surface caries. J Am Dent Assoc 1985;111:967-9. 62. Kleier DJ, Hicks ML Flaitz CM. A comparison of Ultraspeed and Ektaspeed dental x-ray film: in vitro study of the radiographic appearance of interproximal lesions. ORAL SURG ORAL MED ORAL PATHOL 1987;63:381-5. 63. Waggoner WF, Ashton JJ. Predictability of cavitation based upon radiographic appearance: comparison of two film types. Quintessence Int 1989;20:55-60. 64. Hintze H, Wenzel A,/ones C. In vitro comparison of D and E speed film radiography, RVG, and Visualix digital radiography for the detection of enamel approximal and dentinal occlusal caries lesions. Caries Res 1994;28:363-7. 65. Hintze H, Christoffersen L, Wenzel A. In vitro comparison of Kodak Ultraspeed, Ektaspeed and Ektaspeed Plus, and Agfa M2 Comfort dental x-ray films for the detection of

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66. 67. 68.

69. 70.

71.

72.

73. 74. 75.

76. 77.

78. 79.

80.

81. 82.

83.

84.

85.

86.

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caries. ORAL SURGORAL MED ORAL PATHOLORAL RADIOL ENDOD 1995;45:27-34. Sanderink GCH. Imaging: new versus traditional technological aids. Int Dent J 1993;43:335-42. Wenzel A, Grtindahl H-G. Direct digital radiography in the dental office. Dental World 1995;45:27-34. GrNndahl H-G, Wenzel A, Borg E, Tammisalo E. An image plate system for digital intraoral radiography - the Digora. Dental Update (In press.) Borg E, GrOndahl H-G. Dynamic range of film and digital systems for image acquisition in intraoral radiography. Dentomaxillofac Radiol 1995 ;24:104. Velders XL, Sanderink GCH, van der Stelt PF. The effect of different exposure times on the detectability of endodontic files in the new Digora indirect digital oral x-ray system [Abstract]. The 10th Congress of the International Association of Dento-Maxillo-Facial Radiology. Seoul, Korea, 1994. GrNndahl H-G, Borg E. Endodontic measurements with an intraoral image plate technique: the Digora system [Abstract]. The 10th Congress of the International Association of Dento-Maxillo-Facial Radiology. Seoul, Korea, 1994. Wenzel A, Hintze H, Mikkelsen L, Mouyen F. Radiographic detection of occlusal caries in noncavitated teeth: a comparison of conventional film radiographs, digitized film radiographs, and RadioVisioGraphy. ORAL SURG ORAL MED ORAL PATHOL 1991;72:621-6. Russell M, Pitts NB. Occlusal caries diagnosis: radiovisiography vs bite-wing radiography. Caries Res 1991;25:217. Russell M, Pitts NB. Radiovisiographic diagnosis of dental caries: initial comparison of basic mode videoprints with bite-wing radiography. Caries Res 1993;27:65-70. Wenzel A, Borg E, Hintze H, Gr6ndahl H-G. Accuracy of caries diagnosis in digital images from charge-coupled device and storage phosphor systems: an in vitro study. Dentomaxillofac Radiol (In press.) Wenzel A, Fejerskov O. Validity of diagnosis of questionable carious lesions in occlusal surfaces of extracted third molars. Caries Res 1992;26:188-94. Wenzel A. Effect of image enhancement for detectability of bone lesions in digitized intraoral radiographs. Scand J Dent Res 1988;96:149-60. GrNndahl H-G. Some factors influencing observer performance in radiographic caries diagnosis. Swed Dent J 1979;3: 157-72. Wenzet A, Fejerskov O, Kidd E, Joyston-Bechal S, Groeneveld A. Depth of occlusal caries assessed clinically, by conventional film radiographs, and by digitized, processed radiographs. Caries Res 1990;24:327-33. Wenzel A, Larsen MJ, Fejerskov O. Detection of occlusal cm'ies without cavitation by visual inspection, film radiographs, xeroradiographs, and digitized radiographs. Caries Res 1991;25:365-71. Goldman L, Vucich JJ, Beech S, Murphy LW. Automatic processing quality assurance program: impact on a radiology department. Radiology 1977;125:591-5. Kantor ML, Hunt RJ, Morris AL. An evaluation of radiographic equipment and procedures in 300 dental offices in the United States. J Am Dent Assoc 1990;120:547-50. Klinger HG, Wiedemann W. A method for radiographic longitudinal study of mineral content during in vitro de- and remineralization of dental enamel. Arch Oral Biol 1985;30: 373-5. Wenzel A, Hintze H. Perception of image quality in direct digital radiography after application of various image treatment filters for detectability of dental disease. Dentomaxillofac Radiol 1993;22:131-4. Wenzel A. Computer-aided image manipulation of intraoral radiographs to enhance diagnosis in dental practice: a review. Int Dent J 1993;43:99-108. Gotfredsen E, Wenzel A, GrNndahl H-G. Observers' use of

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY November 1995

87. 88.

89.

90.

91. 92.

93.

94. 95. 96.

97. 98.

99.

100.

101. 102. 103. 104.

105.

106.

107.

image enhancement in assessing caries in radiographs taken by four intraoral digital systems. Dentomaxillofac Radiol (In press.) GrNndahl H-G. The influence of observer performance in radiographic caries diagnosis. Swed Dent J 1979;3:101-7. Pitts NB. Detection and measurement of approximal radiolucencies by computer-aided image analysis. ORAL SURe ORAL MED ORAL PATHOL 1984;58:358-66. Pitts NB, Renson CE. Reproducibility of computer-aided image-analysis-derived estimates of the depth and area of radiolucencies in approximal enamel. J Dent Res 1985;64: 1221-4. Pitts NB. Renson CE. Image analysis of bite-wing radiographs: a histologically validated comparison with visual assessments of radiolucency depth in enamel. Br Dent J 1986;160:205-9. Pitts NB, Renson CE. Further development of a computeraided image analysis method of quantifying raidolucencies in approximal enamel. Caries Res 1986;20:361-70. Pitts NB, Renson CE. Monitoring the behaviour of posterior approximal carious lesions by imaging analysis of serial standardized bite-wing radiographs. Br Dent J 1987; 162:1521. Heaven TJ, Weems RA, Firestone AR. The use of a computer-based image analysis program for the diagnosis of approximal caries from bite-wing radiographs. Caries Res 1994;28:55-8. Swets JA, Pickett RM. Evaluation of diagnostic systems: methods from signal detection theory. New York: Academic Press, 1982. WulffHR. Rationaldiagnosis and treatment: an introduction to clinical decision-making. Oxford: Blackwell Scientific Publications, 1981. Wenzel A, Verdonschot EH. Some considerations in the evaluation of diagnostic tests in dentistry. Dentomaxillofac Radiol 1994;23:179-82. Pitts NB, Fyffe HE. The effect of varying diagnostic thresh, olds upon clinical caries data for a low prevalence group. J Dent Res 1988;67:592-6. Verdonschot EH, Wenzel A, Bronkhorst EM. Assessment of diagnostic accuracy in caries detection: an analysis of two methods. Community Dent Oral Epidemiol 1993;21:203-8. Verdonschot EH, Wenzel A, Bronkhorst EM. Applicability of receiver operating characteristic (ROC) analysis on discrete caries depth ratings. Community Dent Oral Epidemiol 1993;21:269-72. Hintze H, Wenzel A, Larsen MJ. Stereomicroscopy, film radiography, microradiography, and naked eye inspection of tooth sections as validation for occlusal caries diagnosis. Caries Res (In press.) Wenzel A, Verdonschot EH, Truin GJ, KNnig KG. Impact of the validator and the validation method on the outcome of occlusal caries diagnosis. Caries Res 1994;28: 373-7. Radach KL, Rouan G, Hedges J. The likelihood ratio. Arch Pathol Lab Med 1986;110:689-93. GrNndahl H-G, GrSndahl K, Okano T, Webber RL. Effect of quantum noise on the detection of incipient proximal caries. ORAL SURG ORAL MED ORAL PATHOL 1982;53:219-23. Ten Bosch JJ, Noordmans J, Arnold LU, Borsboom PCF. Effect of a decrease of interproximal overexposure of bitewing radiographs on the diagnosis of approximal caries. Caries Res 1989;23:328-33. Goshima T, Goshima Y. Radiographical detection of recurrent carious lesions associated with composite restorations. ORAL SURG ORAL MED ORAL PATHOL 1990;70:236-9. Nummikoski PV, Martinez TS, Matteson SR, McDavid WD, Dove SB. Digital subtraction radiography in artificial recurrent caries detection. Dentomaxillofac Radiol 1992;21:5964. van der Stelt PF, Ruttiman UE, Webber RL, Heemstra P. In vitro study into the influence of x-ray beam angulation on

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ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 80, Number 5 the detection of artificial caries defects on bite-wing radiographs. Caries Res 1989;23:334-41. 108. Silverstone LM. The surface zone in caries and in caries-like lesions produced in vitro. Br Dent J 1968;125:145-56. 109. van Rijkom H, Verdonschot EH. Factors involved in validity measurements of diagnostic tests for approximal caries: a meta-analysis. Caries Res (In press.) 110. Mann J, Pettigrew JC, Revach A, Arwas JR. Assessment of the DMF-S index with the use of bite-wing radiographs. ORAL SURG ORAL MED ORAL PATHOL 1989;68:661-5. 111. DeVries HCB, Ruiken HMHM, Krnig KG, van't Hof MA. Radiographic versus clinical diagnosis of approximal carious lesions. Caries Res 1990;24:364-70. 112. Kidd EAM, Pitts NB. A reappraisal of the value of bite-wing radiograph in the diagnosis of posterior approximal caries. Br Dent J 1990;169:195-200. 113. Weerheijm KL, Groen HJ, Bast AJJ, Kieft JA, Eijkman MAJ, van Amerongen WE. Clinically undetected occlusal dentine caries: a radiographic comparison. Caries Res 1992; 26:305-9. 114. Creanor SL, Russell JI, Strang DM, Stephen KW, Burchell CK. The prevalence of clinically undetected occlusal dentine caries in Scottish adolescents. Br Dent J 1990;169:126-9. 115. Kidd EAM, Naylor MN, Wilson RF. Prevalence of clinically undetected and untreated molar occlusal dentine caries in adolescents on the Isle of Wight. Caries Res 1992;26:397-401. 116. Wenzel A, Verdonschot EH, Truin GJ, Krnig KG. Accuracy of visual inspection, fiber-optic transillumination, and various radiographic image modalities for the detection of occlusal caries in extracted non-cavitated teeth. J Dent Res 1992;71:1934-7. 117. Holt RD, Abdulkarim NTA, Rule DC. An evaluation of bite-wing radiographs in 5-year-old children. Community Dent Health 1990;7:389-94. 118. Guidelines for prescribing dental radiographs. Pediatr Dent 1994;15:29-30. 119. Ferguson F. Radiography for children and adolescents. N Y State Dent J 1993;59:25-9. 120. Hollender L. Decision making in radiographic imaging. J Dent Educ 1992;56:834-43. 12i. Swan ESC, Lewis DW. Ontario dentists: 2. bite-wing utilization and restorative treatment decisions. J Can Dent Assoc 1993;59:68-75. 122. Zamir R, Fisher D, Fishel D, Sharav Y. A longitudinal radiographic study of the rate of spread of human approximal dental caries. Arch Oral Binl 1976;21:523-6. 123. Granath L, Kahlmeter A, Matsson L, Schrrder U. Progression of proximal enamel caries in early teens related to caries activity. Acta Odontol Scand 1980;38:247-51. 124. Pitts NB. Monitoring of caries progression in permanent and primary posterior approximal enamel by bite-wing radiography: a review. Community Dent Oral Epidemiol 1983; 11: 228-35. 125. Shwartz M, Grrndahl H-G, Pliskin JS, Boffa J. A longitudinal analysis from bite-wing radiographs of the rate of progression of approximal carious lesions through human dental enamel. Arch Oral Biol 1984;29:529-36. 126. GrOndahl H-G, Andersson B, Torstensson T. Caries increment and progression in teenagers when using a prevention rather than restoration-oriented treatment strategy. Swed Dent J 1984;8:237-42. 127. Pitts NB, Kidd EAM. Some of the factors to be considered in the prescription and timing of bite-wing radiography in the diagnosis and management of dental caries. J Dent 1992;20: 74-84. 128. Chan DCN. Current methods and criteria for caries diagnosis in North America. J Dent Educ 1993;57:422-7. 129. Nytun RB, Raadal M, Espelid I. Diagnosis of dentin involvement in occlusal caries based on visual and radiographic examination of the teeth. Scand J Dent Res 1992; 100: 144-8.

130. Espelid I, Tveit AB, Fjelltveit A. Variations among dentists in radiographic detection ofocclusal caries. Caries Res 1994; 28:169-75. 131. Espelid I, Tveit B. Diagnostic quality and observer variation in radiographic diagnosis of approximal caries. Acta Odontol Scand 1986;44:39-46. 132. Hintze H, Wenzel A. Clinically undetected dental caries assessed by bite-wing screening in children with little caries experience. Dentomaxillofac Radiol 1994;23:19-23. 133. Firestone AR, Lussi A, Weems RA, Heaven TJ. The effect of experience and training on the diagnosis of approximal coronal caries from bite-wing radiographs. Schweiz Monatsschr Zahnmed 1994; 104:719-23. 134. Bader JD, Shugars DA. Need for change in standards of caries diagnosis: epidemiology and health services research perspective. J Dent Educ 1993;57:415-21. 135. Bader JD, Brown JP. Dilemmas in caries diagnosis. J Am Dent Assoc 1993;124:48-50. 136. Bader J, Shugars D. Agreement among dentists' recommendations for restorative treatment. J Dent Res 1993;72:891-6. 137. Bader J, Shugars D, Rozier R. Relationship between epidemiologic coronal caries assessments and practitioners' treatment recommendations in adults. Community Dent Oral Epidemiol 1993;21:96-101. 138. Espelid I, Tveit AB, Riordan PJ. Radiographic caries diagnosis by clinicians in Norway and Western Australia. Community Dent Oral Epidemiol 1994;22:214-9. 139. Nyvad B, Fejerskov O. Active root surface caries converted into inactive caries as a response to oral hygiene. Scand J Dent Res 1986;94:281-4. 140. Thylstrup A, Bille J, Qvist V. Radiographic and observed tissue changes in approximal carious lesions at the time of operative treatment. Caries Res 1986;20:75-84. 141. Leijon G. Initial approximal prim/irkaries i rrntgenbilden Del I. J Swed Dent Assoc 1969;62:227-37, 142. Marthaler TM, Germann M. Radiographic and visual appearance of small smooth surface caries lesions studied on extracted teeth. Caries Res 1970;4:224-42. 143. Rugg-Gunn AJ. Approximal carious lesions: a comparison of the radiological and clinical appearances. Br Dent J 1972; 133:481-4. 144. Mej~e I, Malmgren B. Clinical and radiographic appearance of proximal carious lesions at the time of operative treatment in young permanent teeth. Scand J Dent Res 1986;94:19-26. 145. Bille J, Thylstrup A. Radiographic diagnosis and clinical tissue changes in relation to treatment of approximal carious lesions. Caries Res 1982;16:1-6. 146. Pitts NB, Rimmer PA. An in vivo comparison of radiographic and directly assessed clinical caries status of posterior approximal surfaces in primary and permanent teeth. Caries Res 1992;26:146-52. 147. Araujo BF de, Rosito DB, Toigo E, Santos KC. Diagnosis of approximal caries: radiographic versus clinical examination using tooth separation. Am J Dent 1992;5:245-8. 148. Palma RG, Figueiredo MC, Navarro MF, Gerdullo ML. Comparison of clinical and radiographic exams for diagnosing approximal and occlusal caries [Abstract]. 72rid General Session of the International Association for Dental Research. Seattle, Washington. 1994:268. 149. Pitts NB, Longbottom C. Temporary tooth separation with special reference to the diagnosis and preventive management of equivocal approximal carious lesions. Quintessence Int 1987;18:563-73.

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