The diagnosis of pits, grooves and fissures is one of the main challenges facing dentists in their professional activity, since the existence of an intact enamel surface may hide deep caries in dentin. Lesions of this kind were described by Weerheijm et al. (1992) as "hidden caries". Over 70 years ago a high incidence of caries was confirmed in grooves and fissures (Hyat, 1923), in coincidence with more recent observations (Bragamian & Garcia-Godoy, 2009). In order to understand and explain this high incidence and the morphological peculiarities involved, it is essential to know the physiopathology of the tooth and of the carious lesion.
Caries is a "multifactorial disease causing dissolution of the organic component and demineralization of the inorganic component of the hard dental tissues" (Bonilla, 1998). In the chronology of this process is must be noted that the enamel is a filtering membrane allowing the transit of substances from the exterior to the interior, and vice versa (Llamas et al., 2000). This is because the enamel contains areas with increased water and organic material contents, such as the lamellae or cracks, striae of Retzius, adamantine rod sheath, inter-rod space, and inter-crystalline areas, among others. These zones allow the flow of acids from bacterial plaque, giving rise to disintegration of the organic material and posteriorly conditioning demineralization of the inorganic component - thus supporting the proteolysis - chelation theory of dental caries. These enamel areas with disintegration of the organic material, and the large structural defects such as cracks, which are rich in organic material, can facilitate the penetration of bacteria into deep areas of the enamel, without the existence of superficial cavitation (Brannstrom et al., 1980).
The unpredictable, irregular and varied morphology of the grooves and fissures is well known and makes it impossible to pre-determine the structure; however, it is known that over 50% of all studied teeth have cracks in the depths of the fissures that facilitate the rapid transit of substances and/or bacteria from the depth of the sulcus to the dentin (Pastor et al., 1998). On furthermore considering that enamel thickness from the depth of the sulcus to the dentin is variable and in some cases inexistent, it can be understood why a carious lesion beginning within a fissure can develop in enamel and even in dentin without any external clinical or morphological signs of caries. This in turn explains how in some cases we can observe grooves and fissures that are apparently norma! or with a discrete brown or blackish color, but with no cavitations reflecting an incipient or consolidated lesion affecting even the dentin (Fig.1). In view of the above, how can we know if we are dealing with a true initial dentinal carious lesion if the tooth appears to be healthy? Or how can we diagnose something in depth based on the surface appearance? On the other hand, how and when do we decide to open the fissure or not? If we fail to open the fissure dentin caries may exist and progress rapidly; alternatively, a decision to open the fissure may cause us to needlessly damage an intact tooth. We thus face a diagnostic dilemma.
This problem could be a minor concern if the disorder in question were of low prevalence. However, despite the decrease in the frequency of caries in the industrialized world over the last 20 years (Mejare et al., 2004), not all clinical forms of caries have evolved equally; indeed, caries of grooves and fissures are those showing the greatest prevalence at the present time, since the most notorious decrease has corresponded to caries of smooth surface (Bagramian & Garcia-Godoy, 2009). The form of presentation has also changed; in effect, enamel presently takes longer in becoming affected, thanks mainly to continuous exposure to fluor. As a result, caries develops more slowly, with preservation of enamel integrity for longer periods of time. At present, caries of grooves and fissures affect between 10-50% of the permanent molars of adolescents (Weerheijm et al., 1992), these being the locations where most carious lesions are found, and non-cavitation persists for a longer period of time. Based on the above, it can be concluded that we are not only facing a diagnostic problem, with a high prevalence in adolescents and young adults, but are also facing a buccodental health problem.
The objective of modern Odontology should be to ensure the prevention of caries, avoiding invasive treatments as far as possible. However, this is only possible if full restitution of the affected tissue is achieved (Hibst et al., 2001). In this context, diagnostic tools should evolve in order to allow us to detect the first signs of enamel demineralization. In other words, the tendency should be to facilitate the early detection of caries, with a view to adopting noninvasive treatments and the corresponding preventive measures. On the other hand, we fundamentally should center on common diagnostic techniques that are accessible to dentists, in order for such strategies to be applicable to routine clinical practice.
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