In part one, we showed that caries detection using basic clinical diagnosis procedures was at best, a 50/50 proposition. Experimental studies have recently been directed towards finding better, more reliable methods, which can then be used, in the clinical setting..

Unfortunately, most dentists are unaware of both the futility of their efforts in diagnosing caries clinically and the advancements in the experimental setting as they apply to them. As with all new technology, these methods of caries detection are not quite at the practical stage for use.

But, what they have done already is to change the way we should think: about the prevalence of caries and itÕs changing lesion morphology. And, how we should modify our actions in the clinical setting both in the way we diagnose caries and how we treatment plan and perform restorations.

This second part will cover the new methods of detection, where the research seems to be headed and what we as clinicians need to know, and what we should be changing in our thinking. The third part of this series will cover the clinical implications of treatment planning, preparation and restoration. The knowledge we have gleaned from just these initial findings SHOULD change the way we practice dentistry.

The new direction of caries detection has taken a path towards three basic areas; electrical resistance, light illumination and digital imaging. Another useful, older diagnostic tool, risk assessment, is making a comeback of sorts in the literature.

Electrical resistance measurements such as a.c. impedance spectroscopy, electrical conductance measurements (ECMs), electrical resistance monitors; light illumination such as laser fluorescence, stereomicroscopy, fiberoptic transillumination; strip mutans test for risk measurement, and ultrasonic imaging have all shown promise if not singly, surely in concert.

Also, there is an effort underway to use less invasive tooth preparation techniques, air-abrasion being the best, as a sort of definitive, conservative caries detection technique. Air abrasion is a very conservative tooth preparation technique and when used as a "caries discovery method", we can easily see the caries most other methods miss.

Combine this method with new bonding techniques and it is a can't miss method of caries detection.

The one thing that should be clear after reading this article is that no one method will be used. A combination of diagnostic tools will help us to diagnose lesions earlier and replace worn restorations sooner, all to avoid more costly, destructive dental procedures and truly take dentistry into the preventive rather than the reactive mode.

This area of study, while having differing sounding methods of detection is based on the simple theory that when an electrical current is passed through a whole, sound, caries-free tooth it will have a differing resistance reading than a decayed, unsound or fracture-filled tooth.

A study by Ricketts, Kidd and Wilson took one hundred teeth and measured them in vivo using two different resistance machines. They then extracted all teeth and remeasured them in vitro.

The in vivo/in vitro comparison showed excellent reproducibility. This is important as some experimental work in this field is still done in vitro and we can comfortably extrapolate the data from these studies in vivo.

They also showed in this same study a comparison between the two machines used with radiographic and visual detection. Radiographic detection showed an accuracy of 6% while visual showed 27%. The two electronic resistance machines showed an accuracy of 81% and 74%. We felt that the rads and visual were low in an experimental setting but are probably more accurate for a clinical setting.

Another study by Longbottom et.al., used A.C. impedence measurements and found an outstanding 100% correlation between these measurements and the actual extent of approximal caries in vitro. This gives the promise not only of identifying lesions but the extent or size of the lesion.

In a study by Wenzel, et.al. the accuracy of stereomicroscopy was compared to radiography. The teeth were first rated for caries by visual then conventional radiographic methods. The teeth were serial sectioned then examined by stereomicroscopy and radiographs. The same four observers were used. What this study compared was the interobserver agreement between the various methods. Radiography showed a 44-76% agreement while stereomicroscopy was in the 47-60% range.

The discrepancies again were found to be not with the methods of caries detection used, (even though stereomicroscopy of sections showed consistantly deeper lesions), but with the evaluators own theories or definitions of a carious lesion.

When these parameters were standardized, (meaning the definition of what is a carious lesion was followed by all observers), the validation-comparison correlations were very close, approaching 95%. This shows up again and again in the literature. The dental profession doesn’t have a definition for its most prevalent disease process. A sad commentary on the state of our profession!

Another problem was the comparison of performances between the various diagnostic systems. A study by Ie and Verdonschot took the data from ten different studies on occulsal caries diagnosis and standardized the results. What they found was that electrical resistance measurements and fiber-optic transillumination had good, while visual and radiographic methods poor performances.

Getting back to electrical resistance methods of caries detection, a study by Verdonshot, et. al., found that when comparing this method with radiography and visual inspection, the results showed ERM to be slightly superior to the other two methods with one examiner showing statistically significantly better with ERM.

Another study by Verdonschot, et. al., compared the performance of various methods of occlusal caries detection; visual, fiber-optic transillumination, fissure disoloration, ERM and radiographic. This study made the diagnosis, then physically removed the decay and then rated the lesions. The only method with an acceptable performance was ERM. It showed 96% accuracy and a very high negative predictive value. All other methods rated either moderately low or very low predictive values.

Again, in this latter study, the definition of what a carious lesion is was standardized, making the study more comparative between the methods.

Finally, a study by Luzzi, et.al., showed an accuracy of 83% with ERM as compared with radiography at 71%. These measurements were taken in vivo on intact third molars without any macroscopic cavitation. They were then extracted and sectioned. The only blip in the study was the 23% false positives from ERM. They suggested combining this method with others to gain more accuracy.

It seems as though ERM for the location and extent of carious lesions in virgin teeth will be a method employed in the future. Even now, in its infancy, the method is displaying superior accuracy to anything now used clinically. Be aware of this technology. It will probably be in use clinically, in Europe, soon.

This method of caries detection uses a light source, preferably bright, to illuminate the tooth. This then shows internal variations of color, shading and morphology which goes undetected when the tooth is exposed to only low, mainly reflective light.

Caries or deminerialized areas in dentin or enamel show up as darkened areas with this technique. You can do this simply with a fiber-optic handpiece and illuminate the tooth from inside to outside the mouth. (Its also a great way to pick up the subtleties of the shading of the tooth for color mapping.)

The light is absorbed more when the decay process disrupts the crystalline structure of enamel and dentin. This in essence gives that area a more darkened appearance.

A study by Ogaard and Ten Bosch, used an optical, light scattering method to measure changes in decalcified enamel. The baseline readings were taken, presumably that of healthy enamel, and throughout the demineralization process. The demineralization was induced then the areas were left to either regress further or to remineralize. They showed that these areas remineralized rather rapidly in the presence of saliva.

What was interesting was that the optical scattering measurements moved down as the areas demineralized and moved back up to baseline readings as the remineralizing process reversed the lesion. This could be a way to monitor white demineralized lesions to see if they will heal instead of restoring immediately.

Fiber-optic transillumination, to find interproximal lesions in their initial stages, has been studied in the literature. In a study by Peers, et. al., it was shown that FOTC was as accurate as bitewing radiographs and far superior to visual examination.

There seems to be a limitation in the advanced lesion where transillumination is concerned. In a study by Vaarkamp, ten Bosch and Verdonschot, using light absorbing and light scattering fluids, it was shown that the radiance change caused by a carious lesion is mainly determined by the enamel part of the lesion. This would preclude this method from detecting the extent of lesions into dentin or detecting some carious lesions where enamel destruction is minimal but dentin invasion is extensive.

Transillumination has not been found to be effective in all studies. One by Choksi, et. al., showed visual and radiographic examination to be superior when compared to fiber-optic transillumination. But, this study measured all clinical manifestations of caries; new occlsual and approximal, recurrent under restorations and secondary caries interproximal in anterior teeth. As we have seen, the scope of FOTI may be very limited.

One interesting study by de Josselin de Jong, et. al., used a CCD camera with a high pass filter to collect the fluorescence image of carious teeth. The teeth were illuminated intraorally with diffuse laser light. Incipient lesions showed a loss in fluorescence. The images were saved on a computer and analyzed with a software program. They showed a direct correlation not only between loss in fluorescence and the presence of caries but also a quantitative correlation of that loss and the amount of caries present.

A second study by Hietala, et. al., showed dentin fluorescence to be a more sensitive indicator of the caries progression than staining with Schiff's reagent, especially in the early phase of the carious process.

The ability to identify caries-susceptible individuals has always been a goal of research. Most studies have focused on the direct cause of caries, bacteria, and also some of the mitigating factors such as salivary pH, protein makeup or home care.

The two tests used for bacterial studies, strip mutans and general acidogenic ability measurements of bacteria, were reviewed in two studies. A study by Twetman, et. al., showed no correlation between caries risk assessment with regards to strep mutans levels and caries rates among preschool children

A second test showed that strep mutans levels alone are a poor indicator for assessing dental caries activity in children and that lactobacilli and other aciduric bacteria, as measured by the Cariostat test, should be considered.

Theorists have often tried various methods to predict those individuals more susceptible to caries-often in vain. Streptococcus mutans has been the focal point of testing, it being the supposed main cause of caries. The Strip Mutans test was evaluated by Twetman, et. al., using a child population of 528 four year olds.

All children were assessed at baseline and again at two years. There was a positive correlation between elevated mutan levels and caries over the two-year period. They don't say to what degree there was a positive correlation, but do mention a median area of overlap where some at-risk children did not develop caries over the two years. This shows strep mutans to be a good predictor of risk but not the only factor in the caries process.

Another similar study by Ansai, et. al., used 250 four and five year olds and assessed two parameters; salivary levels of mutans ( by Mucount test) and the acidogenic ability of dental plaque bacteria (Cariostat test).

There was a significant positive correlation between the two tests. However, there were some conflicting results with the two tests. The group, which showed Mucount negative and Cariostat positive, was an accurate predictor of caries rate whereas; the Mucount positive and Cariostat negative group showed a negative correlation with the caries rate.

The conclusions were that strep mutans levels are not an accurate predictor of caries susceptibility but that lactobacilli and other aciduric bacteria should be considered.

Salivary diagnostics is now entering the clinical setting although no test yet available is so specific or sensitive that caries can be diagnosed from saliva samples only. The present tests are useful for estimating the caries activity due to bad dietary habits (lactobacilli), infection (strep mutans), buffer capacity which shows probably the most important host response against caries and salivary yeast levels to determine an overall medical condition of the patient.

These tests alone, or in combination, are now so easy to perform that they should be used in every dental practice.

Though most practitioners are well aware of the technology, most feel that the radiographs produced by the new digital radiographic systems are inferior to conventional radiographs. This is a misrepresentation of both technologies.

Conventional radiographs, as we have seen in previously mentioned studies, is at best 60% reliable for the diagnosis of caries. But, what most dentists don't realize is that the radiographs taken and developed in a research environment are well controlled for speed, angulation, power, and film speed and development parameters. In other words, these "conventional radiographs" are far superior to that seen routinely in general practice.

With that taken into consideration, digital radiographic systems, with their abilities to modify and enhance the original image, become far more accurate in the caries diagnosis field.

A study by Heaven, et. al., took extracted teeth and visually and radiographically examined them for approximal caries using both radiographic methods. When using the digital radiographic system, all dentists were allowed to enhance the image. Then the teeth were examined histologically for the presence and depth of caries.

The results showed that the computer enhanced group were far superior in all categories of comparison; sensitivity, interexaminer agreement and area under the receiver-operating curve.

Another study by Wenzel and Fejerskov compared visual, conventional radiographs and digital radiographic methods. Using two methods, contrast stretch and filtering enhanced the radiographs. The digital images with contrast stretch performed the best of all four methods at over 70% accuracy. Visual was at 53% and conventional radiographs were at 48%.

This technology is what we will be using in the future. The learning curve is long and getting longer as the process improves. We feel that the sooner dentists get involved with this and other emerging technologies, the better for them and their patients.

This second part of our caries discussion involved the emerging technologies associated with caries detection. As we have shown previously, our diagnostic abilities with regards to caries detection, are at best 50/50. And one of the biggest problems is our lack of a suitable, universal definition of the caries process. Also, the lack of longevity guidelines for existing restorations further complicates the problem of treatment planning the replacement of dental work.

In the next issue of the NewsJournal, PART III of our continuing discussion of caries, our most prevalent disease, we will discuss caries detecting agents, new guidelines for population risk measurements and follow clinical cases, which will enhance the preventive goals of the profession.

We will develop our own NewsJournal Caries Diagnosis and Treatment Planning guide for the discerning practitioner which will help those dentists who strive to provide the most conservative, preventive and highest quality dentistry for their patients.

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