Laser fluorescence (LF) is the most widespread laser diagnostic technology; it is a non-ablative laser device that emits a visible, red light at 655 nm.

When the light is directed towards the occlusal fissures of posterior teeth, it is easily transmitted through the enamel and is absorbed by a specific target. Effectively, bacteria by-products and porphyrins within the carious lesion absorb and simultaneously reflect a red fluorescent light that is detected and rated at a digital display and as an acoustic signal [2, 3] (Figs. 6.3, 6.4, and 6.5).

Iwami et al. reported the relationship between bacterial infection of carious dentin and LF detection (polymerase chain reaction). The values of the LF increased as the bacteria detection rates increased, reinforcing the concept of the relationship between fluorescence values of caries and rates of bacteria by-products and porphyrins present [4]. Later on, Neuhaus et al. also reported that the quantitative measure of fluorescence of the tooth was related more to the presence of bacterial by-products than to the mineral loss subsequent to the development of a caries lesion [5].

Several studies compared different caries detection methods: visual inspection alone, visual inspection with magnification, bitewing x-ray, and laser fluorescence with different results.

Lussi and Francescut confirmed the very high reliability and the diagnostic validity (sum of sensitivity and specificity) of LF for occlusal caries detection and also reported it, as higher than bitewing radiography for proximal caries diagnosis in primary teeth. The authors concluded that LF could be used as an additional tool in the detection of occlusal caries in deciduous teeth and its good reproducibility should enable the laser device to monitor the caries process over time [6]. Another study reported that the reliability, predictability, and the reproducibility of the detection did not result as dependent on operator factor [7].

Olmez et al. (2006) evaluated the sensitivity and specificity of DIAGNOdent, visual examination, and bitewing radiography. Sensitivity measures the proportion of actual positives which are correctly identified as such (e.g., the percentage of decayed teeth who are correctly identified as having the condition). Specificity measures the proportion of negatives which are correctly identified as such (e.g., the percentage of healthy teeth who are correctly identified as not having the condition). Sensitivity and specificity for DIAGNOdent, visual examination, and bitewing radiography were 0.86/0.80, 0.69/1.00, and 0.36/1.00, respectively. The LF showed lower specificity than visual inspection and bitewing radiographs but on the contrary demonstrated significantly higher sensitivity for caries lesions than other conventional methods. Consequently, in case of doubtful diagnosis after clinical examination, LF having high sensitivity may be a useful adjunct to visual inspection with a high specificity to formulate the proper diagnosis of occlusal caries [8, 9].

Chu et al. compared three different methods for fissure caries detection in second permanent molars of young adults (visual examination, bitewing radiographs, and DIAGNOdent) and concluded that the combined approach of the LF and visual examination produced the better results [10].

Diniz et al. conducted an in vivo study to determine clinical cutoffs for a DIAGNOdent, a DIAGNOdent-pen, and a DIAGNOcam (fluorescence camera, FC) and to evaluate the clinical performance of these methods and conventional methods in detecting occlusal caries in permanent teeth. The International Caries Detection and Assessment System (ICDAS), the LF device, and the LF pen demonstrated good performance in helping detect occlusal caries in vivo. BW radiography and FC had the lowest performances in helping to detect the lesions. The study concluded that occlusal caries detection should be based primarily on visual inspection. Fluorescence-based methods may be used to provide a second opinion in clinical practice [11] (Figs. 6.6, 6.7, 6.8, 6.9, 6.10, and 6.11). Recently an in vivo study reported that caries lesions may be detected more accurately by laser fluorescence devices than by clinical visual inspection [12].

Laser fluorescence has been proposed also for monitoring and for appropriate management of dental caries in both primary and permanent molars.

An in vitro study by Mendes et al. reported that LF was neither able to detect the remineralization of incipient caries lesions of primary teeth nor to monitor the quantification of mineral loss in caries lesion development in primary teeth [13]. In a following study of the same group, Braga et al. reported that LF device performed better at the dentin threshold than at the enamel threshold; accordingly the study concluded that LF performed better in predicting the depth of the caries lesions (dentin caries) than the initial mineral loss (early enamel caries) [14].

Khalife et al. in an in vivo study also assessed the correlation between the depth and volume of caries and DIAGNOdent readings and concluded that the DIAGNOdent should be used only as an adjunct to the diagnosis and treatment planning process [15].

Also a more recent in vitro study by Bahrololoomi et al. concluded that LF is an appropriate method for detection of demineralization in smooth enamel lesions, but it was not so efficient in the detection of remineralization [16].

Besides occlusal caries detection performed with DIAGNOdent, a more recent version (DIAGNOdent-pen) has different tip shapes that enable an advanced proximal caries detection.

Novaes et al. compared the performance of various methods for proximal caries detection in primary molars. Both the LF pen and radiographic examination exhibited similar performance in the detection of cavitations on proximal surfaces of primary molars [17].

A recent study investigated in vitro a newly developed LED fluorescence device for proximal caries detection in comparison with DIAGNOdent-pen, bitewing x-rays, and visual inspection (International Caries Detection and Assessment System, ICDAS). Reliability data scored fair to moderate for the LED fluorescence device and good for bitewing radiography and laser fluorescence pen. However, it is the combination of different methods that gives better results, with association of visual inspection (ICDAS) and radiography yielding the best diagnostic performance at the dentine threshold [18] (Figs. 6.12, 6.13, 6.14, and 6.15).

Several studies investigated particular factors that could negatively influence the detection and must be kept in mind when combining the visual inspection and laser fluorescence detection.

The presence of brown or dark spots on fissures tends to overscore specific discolored areas of fissures, giving false positive detection [19].

The presence of plaque or toothpaste residual after teeth cleansing worsens the performance registering false readings [20, 21]; therefore, a careful preparation must precede the laser detection.

The laser reading under whitish dental sealants is unreliable due to inaccurate detection caused by intrinsic fluorescence of sealant material [22, 23]. However, it has been recently reported the possibility of monitoring the sealant procedure over time, when clear sealant is used [24].

To conclude this brief overview on laser diagnostic device guidelines, a study by Mendes et al. was included to give a complete and objective point of view. This study reported that adjunct methods of caries detection would not significantly improve the detection of primary molar lesions in comparison to visual inspection alone. The sensitivity, specificity, accuracy, and utility of diagnostic strategies were calculated. Simultaneous combined strategies increased sensitivities but decreased specificities, and, furthermore, no differences were observed in accuracy and utility, parameters more influenced by caries prevalence. The study concluded that present clinical guidelines should be re-evaluated [25]. In agreement with other studies [11, 18], it is personal opinion of the author that LF may be considered a valuable tool in combination to visual inspection, for caries detection as well as for longitudinal monitoring of caries and for assessing the outcome of preventive interventions during recall session in caries risk patients; LF allows to space out the x-ray examinations, so reducing the radiation dose summation (Tables 6.1, 6.2, and 6.3).

Bacteria present in the infected carious dentin release metabolic products (porphyrins) that emit visible red fluorescence when lighted with a violet laser light (405 nm). Healthy tooth tissue differs in this respect by fluorescing green.

During caries excavation, one of the main problems is to avoid over-excavation saving healthy dentin to be removed. This is also more important when approaching deep caries for the possibility to create a pulp exposure (this topic is discussed in Sects. 7.​7.​2, 7.​7.​3, and 8.​2.​3). SIROInspect utilizes a patented technology (FACE, fluorescence-aided caries excavation) to illuminate the tooth cavity with violet light (405 nm). The advantage of intraoperative laser fluorescence technology is that the dentist can see which areas are carious and which are not, during excavation with a much greater degree of certainty than with dye detector or visual inspection or tactile feedback alone.

The light is delivered through a handy probe that presents an attachable filter fit and aligned on it (Fig. 6.16); this allows to filter out light with wavelengths below 500 nm, making the light with higher wavelengths to remain visible when the tooth is exposed to violet light. Few studies are present in literature on this topic.

The studies of Lennon et al. investigated the ability of fluorescence-aided caries excavation (FACE) to detect and remove infected dentin in primary teeth compared to conventional methods (tactile excavation criteria or a caries detector dye). The quantitative confocal microscopy and histologic investigations showed significantly less remaining infected dentin in FACE samples compared to conventional excavation, resulting in more effective excavation than conventional in removal of infected dentin [26, 27]. The author’s experiences are very positive on the utility of this device as an adjunct valuable instrument to perform minimal invasive cavity preparation.

Although there is evidence of sealants’ effectiveness, one major obstacle on its use is the concern of sealing over active caries lesions, and the decision of whether or not to place a sealant depends largely on the dentist’s assessment of the depth of the occlusal fossae (Figs. 6.23, 6.24, 6.25, and 6.26). Effectively pediatric dentists’ perception (visual examination and tactile perception) of fossa depth in permanent molars correlates moderately well with the actual fossa depth [36], so that clinical and anatomical consideration in combination with laser diagnostic values must be considered before the sealant procedure, because they condition both the clinical choice and the operative procedure, making the treatment plan more reliable (Figs. 6.27 6.28, 6.29, 6.30, 6.31, and 6.32). Anatomical and clinical considerations include the following:

LF permits to diagnose the condition of the fissure and pits, addressing the procedure towards a preventive or therapeutical treatment (see Tables 6.1 and 6.2) (Figs. 6.33 6.34, 6.35, 6.36, 6.37, and 6.38).

When fluorescence diagnosis is combined with erbium lasers (2780 and 2940 nm), it is possible to individualize (personalize) the treatment of the fissure. Erbium lasers can be used as: