Visual inspection with magnification VIM

Visual inspection with magnification (VIM) involves all the criteria and arguments defined for visual inspection (VI) without magnification. In the same way as with VI, the reported sensitivity data differ greatly, and can be as low as 0.20 (Lussi, 1993) - though accompanied by high specificity in most studies (Lussi, 1991). Magnification can improve the diagnostic performance of the test (Ekstrand et al., 1998; Lussi & Francescut, 2003). In this context, different studies have compared both methods (Lussi, 1993; Lussi, 1991; Lussi & Francescut, 2003), with the observation of superior sensitivity and specificity for VIM, though without reaching statistically significant differences versus VI. We obtained similar results, with a sensitivity rating for VIM (x2.6 magnification) of 0.76, versus 0.71 for VI (Guerrero, 2011). Our observed specificity (Guerrero, 2011) in turn is high, with a value of 0.84. In line with these results, Lussi (Lussi & Francescut, 2003) reported moderate sensitivity (0.65) and high specificity (0.96). Figure 3 simulates the view we would have of the occlusal surface of a lower second premolar without magnification (i.e., real size) and under x3.5 magnification. We can see that visual examination is easier with VIM; thus, although the literature reports no significant differences in performance between the two techniques, VIM is the preferred option, since it allows better appreciation of the possible signs of caries.

The importance of VI and VIM is attributable to their positive predictive value (PPV), which exceeds 90%(Guerrero 2011). In other words, when a positive diagnosis is established, caries is almost sure to be present. The same cannot be said of a negative diagnosis, however, since the negative predictive value (NPV) of the test is not so high. Therefore, we are unable to rule out the possibility of a false-negative diagnosis, since with this test it is often impossible to examine the depths of the fissures. In this sense, according to Lundberg (Lundberg et al., 2007), in the permanent first molars we observe a relationship between pit depth and bacterial colonization. Specifically, central pits are deeper and more varied in their morphology than less deeper mesial pits. There is an interesting correlation between central pits and colonization by Streptococcus mutans, and trapped organic material moreover may contribute to a faster evolution of hidden caries (Lundberg et al., 2007). In this sense, despite the use of magnification, visual inspection is far from being able to detect these etiopathogenic factors. In this sense, the visual diagnostic techniques require improvement or combination with other diagnostic methods in order to detect these early or incipient stages of caries. In conclusion, and in agreement with the studies of Forgie (Forgie et al., 2002) regarding the use of magnification in relation to other diagnostic techniques, VIM is the method of choice for the detection of occlusal non-cavitated caries, despite the limitations commented above.

Fig. 3. Visual inspection of the occlusal surface of a second premolar (A: real size, and B:under x3.5 magnification).

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