Year : 2013 | Volume
: 4 | Issue : 1 | Page : 17--20
Caries detection in primary teeth is less challenging than in permanent teeth
Fausto M Mendes, Mariana M Braga
Department of Pediatric Dentistry, School of Dentistry, University of Sao Paulo, Av. Lineu Prestes, 2227, Sao Paulo, Brazil
Fausto M Mendes
School of Dentistry, University of Sao Paulo, Av. Lineu Prestes, 2227, Sao Paulo 05508-000
Introduction: Most studies about caries detection methods have been performed using permanent teeth. Primary teeth, however, present significant differences from permanent teeth; hence findings of these studies with permanent teeth cannot be extrapolated. The Hypothesis: Our hypothesis is that the caries diagnosis process in primary teeth is less challenging than in permanent teeth. This assertion is based on the fact that primary enamel is thinner and the caries process progresses faster in this type of teeth when compared to permanent teeth. For these reasons, the majority of caries lesions in primary teeth would be more evident and therefore, easily detected through visual inspection. Only a few number of caries lesions would be missed by visual inspection. Thus, adjunct diagnostic methods, such as radiographs, would be unnecessary for primary teeth. Evaluation of the Hypothesis: To evaluate this hypothesis, researchers should conduct studies about the performance of the caries detection methods avoiding selection bias and defining appropriate settings. Clinical trials randomizing the diagnostic strategies would be worthwhile. The evidence supporting the benefits of adjunct methods in detecting caries lesions in primary lesions is limited. However, clinical guidelines have recommended the use of the radiographic method to detect caries in primary teeth in all symptomless children. The confirmation of our hypothesis would lead to the need to re-evaluate such guidelines.
|How to cite this article:|
Mendes FM, Braga MM. Caries detection in primary teeth is less challenging than in permanent teeth.Dent Hypotheses 2013;4:17-20
|How to cite this URL:|
Mendes FM, Braga MM. Caries detection in primary teeth is less challenging than in permanent teeth. Dent Hypotheses [serial online] 2013 [cited 2019 Jun 19 ];4:17-20
Available from: http://www.dentalhypotheses.com/text.asp?2013/4/1/17/110185
Caries diagnosis process has been more difficult in the last years due to the decline of caries progress observed in most countries. ,, With this decrease, demineralization develops more slowly, and therefore, caries lesions do not cavitate until later stages of the disease progression.  Clinically, intact enamel hampers the visualization of occlusal and approximal caries lesions, complicating their detection.
Traditionally, caries detection has been performed with clinical and radiographic examination. Visual inspection has performed well in terms of specificity, but the method has presented low reliability and sensitivity values.  Radiographs have been indicated to increase the sensitivity of the caries detection process. , However, most studies have been performed in permanent teeth and there is a lack of studies about caries detection methods using primary teeth.  Significant structural differences between primary and permanent teeth ,,,,, make it inaccurate to extrapolate the results obtained for one type of substrate to the other. Our belief that the caries detection process is easier and more accurate in primary than in permanent teeth is based on several principles.
There are considerable differences between permanent and primary teeth which may directly affect the caries process. Firstly, the enamel of primary teeth is thinner than that of the permanent teeth.  Secondly, the primary enamel is more porous,  less mineralized, , and has more carbonate, , less phosphorus,  and calcium phosphates  in its composition. Furthermore, caries lesions progress faster in primary than in permanent teeth. 
Considering all these factors, it is plausible to state that the overlying enamel in dentine caries lesion breaks more easily in primary than in permanent teeth. Therefore, less non-evident caries lesions would occur in primary teeth than in permanent ones. On the other hand, in permanent teeth, since the enamel is approximately twice as thick, it is harder to break and caries lesions remain undetected for longer periods. Some authors named this condition as "hidden caries." ,, Hidden caries have been defined as extensively demineralized occlusal dentin caries lesions not detected through visual inspection, which can be detected by radiographs. ,, Less "hidden caries" would be present in primary teeth probably because the faster progression of caries lesions and thinner enamel. The primary enamel would easily break, making the lesion evident.
The definition of hidden caries can be also applied to approximal lesions where dental caries progresses under the marginal ridge making it difficult for dentists to visually detect them. Even though the marginal ridge is more difficult to break than other regions of the enamel, this fracture also occurs more easily in primary than in permanent teeth.
Therefore, we hypothesized that the caries detection both in approximal and occlusal surfaces of primary molars would be easier than the process in permanent molars due to a greater number of evident caries lesions that can be expected to occur in primary teeth. The evident caries lesion is easily detected during the clinical examination  and adjunct methods are not necessary in such cases. 
The evidence supporting this hypothesis in the literature is still lacking. Few studies have found a better performance of the visual examination method in primary than in permanent teeth. In a systematic review published in 2002, the authors affirmed that there was a lack of studies about the performance of traditional caries detection methods in primary teeth.  In another systematic review assessing the performance of a laser fluorescence device to detect caries lesions, named DIAGNOdent, studies using primary teeth showed a slightly higher specificity than studies in permanent teeth. 
Furthermore, few studies have compared the performance of different methods for detecting caries lesions in primary and permanent teeth. Studies using different methods to detect occlusal caries lesions, such as visual inspection, laser fluorescence and radiographic methods have found only a slightly better performance in primary compared to permanent teeth. ,,
This superiority of caries detection performance in primary teeth is not clear yet. A possible explanation is that the authors usually choose a convenience sample to perform studies about methods of caries detection. For example, the authors select teeth with suspected caries lesions and they usually exclude teeth with evident cavitations. On one hand, this procedure is comprehensible since the inclusion of cavitation's in the sample would increase the performance of the methods.  Changes in the spectrum of the disease usually increase the performance of diagnostic methods , and probably overestimate their performance in a population presenting low caries progression. On the other hand, the exclusion of more advanced caries lesions causes a decrease in the external validity of the studies because the spectrum of the disease does not reflect the actual occurrence of caries in some populations.
Our hypothesis is based on the faster progression of caries and thinner enamel of primary teeth. In the daily clinical practice, primary teeth present a higher prevalence of evident caries lesions than permanent teeth. Therefore, visual inspection would be more accurate in this type of tooth. Adjunct methods of caries detection are indicated to detect non-evident caries lesions, mainly at occlusal (hidden caries) and approximal surfaces.  Therefore, such methods would be more useful in permanent teeth, where a higher prevalence of non-evident caries lesions is expected.
This statement is contrary to current recommendations of the most renowned clinical guidelines in Pediatric Dentistry. Both European and American clinical guidelines concerning dental radiographs in children recommend that the dentists take two radiographs in all symptomless children with primary teeth in order to detect caries lesions missed by visual inspection. , However, the low prevalence of non-evident caries lesions in primary teeth contradicts this recommendation. In fact, we observed a low prevalence of cavitated caries lesions in approximal surfaces of primary teeth (around 5%) and adjunct radiographic or laser fluorescence methods did not have a better performance than that of visual inspection, increasing the number of false positive results. , False positive results are undesirable since they lead to unnecessary operative treatment. Moreover, despite the low-level X-rays used in dental radiographs, any dose of radiation would have the potential to cause biological harm according to the current theory in radiation protection, especially in young children whose cells are highly undifferentiated. 
Therefore, such clinical guidelines should be reviewed, changing the current thinking about caries diagnosis process in primary teeth. For this purpose, new studies need to be performed to prove our hypothesis.
Evaluation of the Hypothesis
To test our hypothesis, researchers should perform clinical studies in both permanent and primary teeth selecting a consecutive or randomized sample of subjects avoiding convenience samples. Furthermore, researchers have to define an appropriate setting for the study. Concerning the caries detection methods, the best setting is the dental office and the study should include subjects who looked for dental treatment at a clinic or dental school.
Another important point is that the performance of the visual inspection method, which is of essential use in all patients,  should be evaluated in all teeth and frank cavitations should not be excluded from sample. Obviously, the method will perform better using these selection procedures. However, if the authors select patients with primary and/or permanent teeth, it will be possible to prove that caries detection in primary teeth is more accurate than in permanent ones. Other methods, such as radiographic and laser fluorescence, should be used only as adjunct to visual inspection in cases when the dentist has doubts about the correct diagnosis. These adjunct methods are more useful in permanent teeth. Furthermore, randomized clinical trials conducted in children to evaluate the two different caries diagnosis approaches: visual inspection alone and visual inspection and radiographic method.
Thus, considering all aspects discussed in the present text, visual inspection probably performs better in detecting caries lesions in primary teeth and the use of adjunct methods may not lead to many benefits. The recommendations of the clinical guidelines that dentists should take two bitewing radiographs in symptomless children with primary teeth in order to detect caries lesions should, therefore, be re-evaluated. New studies should be performed in a sample of consecutive subjects who sought dental treatment, avoiding the selection of a convenience sample. The actual prevalence of non-evident caries lesions in primary teeth is low and therefore, visual inspection probably suffices to obtain a good performance in the caries diagnosis process in children with primary teeth.
The authors wish to thank Dr. Christiana Murakami for English corrections and the valuable critical considerations about the text.
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