Summary: Occlusal surfaces of molars are especially susceptible to the development of caries because of their anatomical structure - pits and deep fissures. In the study a new high technology fluorescence laser system KaVo Diagnodent was used for detecting and diagnosis caries on the occlusal surfaces of molars. The visual examination of fissures was based on a classification by K. Ekstrand. The material consisted of 237 permanent molar teeth in 84 children aged 6-7 years. The results showed strong relationship between the visual inspection and examination with DIAGNOdent. In conclusion authors recommend LFS in the diagnosis of occlusal caries as a sensitive and non-invasive method useful especially for children.
1.1. Occlusal surfaces of molars are especially susceptible to the development of caries because of their anatomical structure (Weerheijm et al. 1989, Weerheijm et al. 1992). Deep fissures are naturally predisposed to the accumulation and multiplication of microbes over a period of time. In deep fissures caries lesions are hidden, develop along the walls, progress symmetrically and spread laterally until they reach the enamel-dentin junction undermining the sound enamel. Microscopic examinations prove that only about 50% of fissures assessed in a routine visual examination as "sound" are really free from demineralization (Ekstrand et al. 1987, Ekstrand et al. 1995, Lussi 1991). Traditionally, the diagnosis of occlusal caries has been carried out with the use of explorer and dental mirror. Cavities are often located at the bottom of deep fissures or in their walls and difficult to detect during visual examination and with the aid of a probe (Figure 1). Moreover, researchers turn their attention to the possibility of iatrogenic damage of enamel while probing the teeth of children especially in newly erupted permanent molars (Ekstrandt et al. 1987, van Dorp et al. 1988). Therefore other modern diagnostic methods have been used in the detection of caries, for example visual examination with magnifying glass, conventional bite-wing radiography or digital radiography and caries risk assessment. In recent years clinicans and researches have explored new technologies - fiber optic translumination (FOTI), electrical resistance measurement, and finally, used in our study- laser fluorescence system (LFS) (Ekstrand et al. 1997, Kruszyńska-Rosada 1998, Lussi 1993, Mielczarek et al. 2000, Verdonschot et al. 1999).
1.2. The DIAGNOdent device currently available on the market is equipped with two diagnostic tips: cone-shaped A designed for fissures and B - broad tip for smooth, buccal and lingual surfaces of teeth (Figure 2). A laser diode provides pulsed light of a defined wavelength (λ=655nm) directed onto the tooth inducing fluorescence. The laser-light is absorbed by organic and inorganic tooth substance and by metabolites of oral bacteria (Hibst and Paulus 2000, Lussi et al. 1999, Reich et al. 1998). Decalcified areas in the enamel structure stimulate fluorescent light of a different wavelength, which is evaluated by an appropriate electronic system in the DIAGNOdent unit. Fluorescence values are displayed in the 0-99 range and translated into an acoustic signal.
2.1. Patients were selected for this study from the first form of primary schools. The material consisted of 237 permanent molar teeth in 84 children aged 6-7 years (mean age 6.74 ± 0.63). The study included first permanent molars, not sealed and non-cavitated due to caries.
3.1. The clinical examinations were conducted under standardized conditions using dental unit, equipped with operating halogen light, compressed air (3-in-1 air syringe) and suction device, in school dental surgery. The visual appearance of each permanent molar was recorded by one examiner (TM) and another dentist rescored ten percent of cases on a separate occasion (WE). Immediately before visual detection, the occlusal surface of tooth was mechanically cleaned using a rotating bristle and copious water. The condition of occlusal surface was evaluated visually with dental mirror by means of Ekstrand classification according to the criteria in the Table 1 (Ekstrand et al. 1998).
4.1. Then the fissures were examined by means of DIAGNOdent-laser using the "conic probe A" by the same examiner (TM). The occlusal surface was briefly air-dried using a 3-in-1 air syringe. The measurements were made while moving the tapered fibre-optic tip along the fissure lines and the peak value (maximum fluorescence reading) was registered within 0-99 range. The tip of the laser device was placed perpendicularly to the long axis of the tooth. Ten percent of the teeth were examined separately again by another examiner (WE).
5.1. Visual examinations of fissures by Ekstrand's scoring system were compared with maximal laser measurements as shown in Table 2. Collected data were considered according to Diagnodent manufacturer criteria: 0-14 - no caries and no care advised, 15-20 - enamel caries and preventive care advised, >20 dentinal caries and preventive or operative treatment advised depending on patient's caries risk, >30 operative treatment required.
5.2. The obtained results were analysed statistically using computer software Statistica (Version 8.0) and presented in the form of table. Spearman rank-order correlation coefficient (r e ) was used to measure the correlation between the visual examination (VE) and examination by laser fluorescent system (LFS). The intraexaminer reliability was tested using Kappa values.
6.1. Based on visual examination, 61 teeth were evaluated as clinically sound VE-0 without changes in the fissures, in all these cases maximum values by means of DIAGNOdent were under 20; the average being 13,14. Opacity (white or brown) distinctly visible after air drying on occlusal surfaces of 83 teeth were observed in the fissures (clinically VE-1 and VE-1a). In 27.7% of these cases maximum measurements did not exceed 20, in 29 cases (34.9%) despite only slight clinical symptoms caries undermining the enamel was found by Diagnodent. In the group of fissures with distinct white or brown discoloration visible on the wet surface - clinically category VE-2 and VE- 2a - the presence of dentinal caries was confirmed in 48% whereas in 34% no fluorescence change related to caries was found. In the fissures categorized as 3 and 4 high fluorescence values related to caries were noted, the mean fluorescence values being 43.3 and 51.0 respectively. In four of examined molars in category VE=3, measurements of maximum laser fluorescence did not indicate presence of caries on occlusal surface. These cases will still be monitored. In teeth with cavitation in opaque or discoloured enamel exposing the dentine beneath - score 4 - caries was shown by Diagnodent too.
6.2. The results of measurements are shown in Table 3 and statistical analyses have been done. Using the correlation of Spearman ranks, the relationship between two methods of evaluation, namely visual examination and laser fluorescence measurement, has been determined. It follows from the study that there is a positive correlation statistically significant between the analysed variables (r e = 0.61; p<0.001). More advanced changes within the fissures found during visual examination are represented by higher DIAGNOdent records.
7.1. In clinical assessment, most doubts arise in the case of occlusal surfaces where fissures have distinct brown discoloration (belonging to category 2, 2a or 3) and the so called "sticky" fissures during clinical probing. In order to limit diagnostic errors resulting not only from failure to detect caries, but also from unnecessary preparing of healthy fissures, it is vital to supplement the visual examination with other sensitive and specific methods. According to Lussie (1993) and other authors (Creanor et al. 1990, Pitts 1991), the dental explorer does not significantly improve effectiveness of caries detection hidden in the occlusal pits. The same is true for visual examination with doubly magnifying glasses when compared with just naked eye (Lussi 1993, Pitts 1992). The "sticky" fissure is more often a result of fissure morphology "natural entrapment areas", than the presence of caries (Lussi 1991). The clinical picture is completed by bitewing radiography useful for caries detection not only for aproximal surfaces but also occlusal (Creanor et al. 1990, Lussi 1993). The method improves detectability by about 11% and enables assessment of cavity size. Yet the early stages of demineralization are not visible in radiographs (Ekstrand 1995). Diafanoskopia, which extends diagnostic possibilities in the assessment of hard tissues, is a noninvasive method helpful in detecting caries of approximal surfaces and fissure caries, but is not accurate enough to assess its extent (Ekstrand 1995, Kruszyńska-Rosada 1998, Lussi et al. 1995, Verdonschot 1992).
7.2. In modern dentistry, the significance of caries prophylaxis is growing in comparison with conservative treatment, hence the need for improving diagnostic methods for detection or unequivocal ruling out of early carious lesions. In the case of caries the most sensitive and specific were the measurement of electric resistance and laser fluorescence (Pitts 1991, Pitts 1992, Rock and Kidd 1988, Kruszyńska-Rosada and Borysewicz-Lewicka 2000).
8.1. (1) Occlusal surfaces are the most vulnerable location for the development of dental caries but fissure morphology and fissure brown discoloration were not useful for correct caries diagnosis by means of visual inspection.
8.2. (2) The measurement of laser fluorescence by means of DIAGNOdent is a modern, noninvasive and sensitive method helpful in the accurate assessment of fissures complementary to traditional dental examination.
8.3. (3) The use of DIAGNOdent in diagnosis makes it easier to detect initial diagnosis within fissures and at the same time to limit the unnecessary preparation of healthy teeth in cases where the visual examination alone is not adequate.
Ekstrand KR, Ricketts DNJ, Kidd EAM (1997) Reproducibility and accuracy of three methods for assessment of demineralization depth on the occlusal surface: An in vitro examination. Caries Res 31:224-231
Ekstrand KR, Ricketts DNJ, Kidd EAM, Qvist E, Schou S (1998) Detection, diagnosing, monitoring and logical treatment of occlusal caries in relation to lesion activity and severity: An in vivo examination with histological validation. Caries Res 32:247-254
Verdonschot EH, Angmar-Månsson B, ten Bosch JJ, Dery CH, Huysmans MCDNJM, Pitts NB, Waller E (1999) Developments in caries diagnosis and their relationship to treatment decisions and quality of care. Caries Res 33:32-40.