Visual inspection VI

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Visual inspection is the most widely used diagnostic method. VI has a long history, but is subjective and depends on the experience of the examiner (Pretty, 2006; Zandona & Zero, 2006). The diagnosis of a cavitated lesion poses no diagnostic difficulty of any kind; it is in the case of the so-called "hidden caries" where doubts arise, together with the impossibility of determining whether a dark fissure presents underlying caries or merely corresponds to surface staining. In their first stages, caries of grooves, pits and fissures appear as a milky or darkish stain indicating demineralization of the walls of the fissure and implying enamel opacity. In addition, there may be decoloration of the dentin through the enamel, as well as defects in the bottom or depth of the pit, which would confirm the diagnosis of dentin caries. Accordingly, clinical inspection is based on evaluation of the transparency changes of the enamel, loss of brightness, an opaque appearance, and integrity of the fissure (Thylstrup et al., 1994; Ekstrand et al., 1997). In order to appreciate these changes, the occlusal surfaces must be clean and dry during inspection of the grooves and fissures. Drying the enamel reduces the refraction index of the inter-rod spaces (from 1.33 in the case of humid or moist demineralized surfaces to 1.0 in the case of dry demineralized surfaces) - this making it possible to easily visualize the opaque appearance of enamel demineralization caused by the bacterial plaque acids (Kidd et al., 1993). We can also evaluate pigmentations, the presence or absence of soft tissues, or changes in enamel texture according to the degree of demineralization. According to some authors (Thylstrup et al., 1994), we are also able to establish whether the caries are active or inactive. The evaluation of these findings must be made following some classifying method or criterion capable of correlating the observed signs to the stage of the lesion. The system developed from the studies of Thylstrup in 1994 (Thylstrup et al., 1994) and posteriorly structured by Ekstrand in 1997 (Ekstrand et al., 1997) and modified in 1998 (Ekstrand et al., 1998) is one of the most widely used options. The criteria established by Ekstrand et al. (1997) are the following: 0 = no or slight change in enamel translucency after prolonged air drying; 1 = opacity or discoloration hardly visible on the wet surface, but distinctly visible after air drying; 2 = opacity or discoloration distinctly visible without air drying; 3 = localized enamel breakdown in opaque or discolored enamel and/or grayish discoloration from underlying dentin; and 4 = cavitation in opaque or discolored enamel exposing the dentin (Fig. 2). Other criteria have also been developed, however, such as those of Nyvad (Nyvad et al., 1999), the ICDAS (International Caries Detection and Assessment System (Pitts, 2004), the UniViSS (Universal Visual Scoring System for Caries Detection and Diagnosis) (Kuhnisch et al., 2009), or even the International Consensus Workshop on Caries Clinical Trials (ICW-CCT), where caries activity and inactivity are taken into consideration (Pitts & Stamm, 2004).

A

m ^

fcr

B: Superficial enamel caries

C: Deep enamel caries

D,E: Dentin caries

Fig. 2. Representative signs of caries in cracks and fissures, according to the Ekstrand criteria.

The sensitivity of visual inspection varies greatly depending on the literature source. Our review of the existing publications yielded values between 0.12 and 0.97. A sensitivity of 0.62 to 0.90 is common when there are visible cavities in the fissures. However, in hidden dentin caries, different studies (Lussi, 1993; Wenzel et al., 1991) have reported sensitivity values as low as 0.12. This low sensitivity is due to the fact that we cannot inspect beneath an apparently healthy enamel layer. Some authors (Ekstrand et al., 1997; Pereira et al., 2001) have obtained high sensitivity values that may be justified in part by elimination of a portion of the study sample due to validation problems or because of the presence of stained fissures. Application of the Ekstrand criteria tends to increase the sensitivity of the test both in vitro (Ekstrand et al., 1997; Tran^us et al., 2005) and in vivo (Angnes et al., 2005; Reis et al.,

2006). Some studies do not draw these conclusions, however (Heinrich-Weltzien et al., 2002). In effect, Lussi (Lussi et al., 2001) reported that visual inspection alone does not offer good sensitivity in detecting occlusal dentin caries. The width of the fissure also influences sensitivity; in this sense, a diagnosis is more difficult to establish in the presence of narrow fissures than in the case of wide fissures (Lussi, 1991). In vivo studies pose the inconvenience of incomplete sample validation, or the use of samples comprising third molars or premolars, with anatomical features different from those of the permanent first and second molars. Most studies indicate that visual inspection offers low-medium sensitivity and high specificity in the diagnosis of occlusal non-cavitated caries (Kidd et al., 1993; Wenzel et al., 1991; Reis et al., 2006; Heinrich-Weltzien et al., 2002) (Table 1).

AUTHOR

LEVEL

STUDY

SENSITIVITY

SPECIFICITY

Lussi 1993

dentin

in vitro

0.12

0.93

Ektrand 1997

dentin

in vitro

0.92 - 0.97

0.85 -0.93

Reis 2006

dentin

in vitro

0.69

0.88

Ashley 1998

enamel

in vivo

0.60

0.73

Angnes 2005

dentin

in vivo

0.75 / 0.68

0.84 / 0.81

Table 1. Sensitivity and specificity values for visual inspection.

Table 1. Sensitivity and specificity values for visual inspection.

In our studies (Abalos et al., 2009, 2011; Guerrero, 2011) of laser fluorescence, we obtained a sensitivity for visual inspection of over 0.70, in application to both enamel caries and dentin caries. In contrast to other authors, we achieved total validation of the sample of first and second molars in vivo, since we used teeth that were to be prepared for fixed prostheses. This afforded more realistic sensitivity and specificity values for the studied tests. However, in the case of VI, we consider that our results exceed those obtainable in the real life scenario, since as has been explained in our studies (Abalos et al., 2009, 2011; Guerrero, 2011), in our selection of the sample we aimed to secure a sufficient proportion of teeth that were clearly healthy or with enamel caries - a fact that may have influenced the recorded high sensitivity for VI. However, when using the criteria of Ekstrand (Ekstrand et al., 1997), with drying of the tooth (Tran^us et al., 2005; Ekstrand et al., 1997; Angnes et al., 2005; Reis et al., 2006), the sensitivity of the test increases. Many studies of VI have been published, and the results differ greatly according to the type of methodology used (Bader & Shugars, 2004). Despite this fact, VI is a technique that will continue to be used in routine clinical practice. However, rather than focusing on the true diagnostic performance of VI, which is clearly influenced by the examiner and the inaccessible depth of the fissures, future research should attempt to establish which tests are really useful, and to what extent, as coadjutants to visual inspection.

The mentioned moderate sensitivity is accompanied by high specificity (Table 1). In other words, while we must accept the probability of false-negative findings (Costa et al., 2008), the high specificity of the test and its important positive predictive value (PPV) (Guerrero, 2011) point to the advisability of opening all fissures with scores of 3 or 4 on the Ekstrand scale (Fig.2D,E). This is where the true usefulness of the test is found: when signs of caries are identified, caries may very well be present.

Regarding the reproducibility of the test, the studies that determine inter-examiner agreement or concordance (Lussi, 1991; Anttonen et al., 2003; Costa et al., 2008) report kappa

(k) values of >0.61 to >0.81. The reported intra-examiner reproducibility (Lussi, 1991; Anttonen et al., 2003; Costa et al., 2008) in turn yields k values of >0.41 to >0.81. This scale was developed by Landis and Koch (Landis & Koch, 1977), who scored the concordance values for the k index from <0 (no concordance) to 0-0.20 (insignificant or slight concordance), 0.21-0.40 (discrete concordance), 0.41-0.60 (moderate concordance), 0.61-0.80 (substantial concordance) and 0.81-1 (near-perfect concordance).

In sum, it is important for dentists to become familiarized with this exploration modality, without being too conditioned by superficially stained fissures that do not meet the specified criteria and which can lead to over-treatment. The prevalence of caries and the potential patient risk are important aspects that must be taken into account. A low caries prevalence with good molar hygiene and no bacterial plaque improve the reliability of the test, since there is a lesser probability of establishing an incorrect diagnosis. Visual inspection is the first method to be used in application to hidden dentin caries. In the case of a positive diagnosis, we should open the fissure and use a probe to explore the hardness of the dentin (Kidd et al., 1996). However, a negative diagnosis does not rule out the existence of caries, and other tests must be used together with VI in such situations - particularly in the presence of stained fissures.

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