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Detection of Occlusal Caries by Laser Fluorescence: Basic and Clinical Investigations
Med. Laser Appl. 16: 205–213 (2001) © Urban & Fischer Verlag http://www.urbanfischer.de/journals/lasermed
Detection of Occlusal Caries by Laser Fluorescence: Basic and Clinical Investigations RAIMUND HIBST, ROBERT PAULUS, and ADRIAN LUSSI1 Institut für Lasertechnologien in der Medizin und Messtechnik (ILM), Ulm, Germany 1 Department of Operative, Pediatric and Preventive Dentistry, University of Berne, Switzerland Submitted: May 2001 · Accepted: June 2001
Summary Objectives: Motivated by the poor sensitivity of visual inspection and radiography in the detection of occlusal caries hidden under a macroscopically sound surface, we explored the implementation of fluorescence as an alternative diagnostic tool. Methods and Results: Fluorescence spectroscopic investigations revealed considerable contrast between sound and carious tooth hard tissue when excited by red (655 nm) light. For this excitation wavelength on inorganic tooth components only negligible fluorescence was observed. Advanced caries, however, show readily detectable fluorescence. The latter, at least in part, originates from porphyrins produced by bacteria. Based on red excited fluorescence a novel caries detector was constructed (DIAGNOdentTM, KaVo, Biberach). The system measures fluorescence quantitatively. The minimum amount of protoporphyrin IX that can be detected is approximately 1 pmol. Clinical investigations yielded a sensitivity ≥ 0.92 in detection of occlusal caries, compared to 0.63 for bitewing radiography, and ≤ 0.62 for visual inspection. Intra- and interexaminer reproducibility tests resulted in Cohen’s Kappa value of 0.93 in vivo. Conclusions: Detection of occlusal caries with the DIAGNOdentTM system has a much better sensitivity than conventional methods. Because the readings are correlated to the status of the carious lesion, treatment decisions can be aided by the measurement. Additionally, excellent reproducibility allows monitoring of lesions over time to facilitate preventive based management of dental decay.
Key words Caries, diagnosis, DIAGNOdentTM, fluorescence, laser diode
Introduction The onset of caries is characterised by only microscopically visible surface demineralisation on dental hard tissues. Changes of diet and/or oral hygiene habits in combination with optimal fluoridation may stop the progression of a lesion and even allow its remineralisation. The aim of modern dentistry must be a preventive approach rather than invasive repair of the disease. This is only possible if the remaining structural organisation of the attacked tissue will still
allow ‘restitutio ad integrum’ providing early detection and respective preventive measures. Some of today’s diagnostic tools are not sensitive enough to detect this early onset of destruction. Therefore, oftentimes remineralisation or stabilisation is not possible any more at the time of detection and restoration is inevitable. This, in turn, is the start of the vicious circle of restorative therapy due to the limited life expectancy of all restorative materials. Historically, the detection of occlusal caries has been carried out with the use of mirror, light and 1615-1615/01/16/03-205 $ 15.00/0
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explorer. The tactile sign of resistance while withdrawing the explorer has been considered diagnostic for caries (20, 23). The value of the explorer or probe in the detection of occlusal caries has recently been called into question by a number of investigators (13, 6, 22, 14, 15, 27). It has been conclusively demonstrated that conventional clinical methods result in remarkably low values for sensitivity when attempting to detect occlusal caries (26, 14, 15, 16, 8). In the face of this evidence, it is difficult to defend the potential for iatrogenic damage of otherwise remineralizable lesions in fissures when using visual-tactile methods (3). For occlusal surfaces the specificity of clinical examination is beyond 90%, i.e. sound surfaces are most often correctly recognised (26, 14, 15, 16). This is very important in the light of today’s relatively small caries prevalence. Surfaces which can be maintained sound for years with adequate preventive measures must not be treated prematurely by restorative dentistry. The sensitivity at the D3 level (dentinal caries), i. e. the ability to recognise with clinical examination methods diseased surfaces as diseased varies between 12%–82% (26, 14, 15, 16). The significant differences in the performance of the different “classical” clinical methods is due to different statuses of the occlusal surface. Dentinal caries in teeth with a macroscopically intact occlusal surface is difficult to detect in daily practice. Indeed, the lowest sensitivities were found with teeth exhibiting macroscopically intact occlusal surfaces showing underlying dentinal caries histologi-
cally (Table 1). This phenomenon characterises the socalled ‘hidden caries’ found in between 10–50% of the teeth with dentinal caries (5, 11, 17, 24, 25). These problems were the motivation to search for devices more sensitive in detection of caries, especially when covered by a layer of nearly intact enamel. The limitation of visual inspection in these cases is due to light scattering within the tooth. Light being remitted from the surface cannot be attributed to a definite tooth region but reflects the optical properties of a large volume. Thus an increase of absorption in a small carious lesion beneath the surface does not change the overall backscattered light very much: the lesion is “hidden”. Compared to absorption a much higher sensitivity can be expected by detecting the fluorescence light being emitted by some of the molecules following absorption. Already in 1928, fluorescence on UV excitation of enamel and dentine and its loss due to decalcification was reported (2). About 20 years ago, first experiments with excitation in the visible (410 nm, 488 nm, 530 nm) were carried out, and again differences between sound and diseased dental tissue were observed (1, 4). A comparative study on sound and carious tooth substance fluorescence for various excitation wavelengths (337, 488, 515, and 633 nm) revealed maximum contrast for the detection of initial caries at 488 nm excitation (21). No fluorescence was visible when excitation was by red (633 nm) light. Further research then was concentrated on 488 nm in-
Table 1. In vitro validity of different ‘classical‘ diagnostic methods employed by practising dentists for occlusal surfaces on the D3 level (15, 16). No caries (D0) or enamel caries (D1, D2) Visual inspection (n = 26 dentists) Visual inspection combined with probing (n = 23) Visual inspection with a magnifying glass (n = 26) Bitewing radiography (BW) (n = 24) Visual inspection combined with BW (n = 10) Dentinal caries (D3, D4)
Visual inspection (n = 26 dentists) Visual inspection combined with probing (n = 23) Visual inspection with a magnifying glass (n = 26) Bitewing radiography (BW) (n = 24) Visual inspection combined with BW (n = 10)
Specificity 0.93 0.93 0.89 0.83 0.87 Sensitivity –––––––––––––––––––––––––––––––––– macroscopically cavitated intact surface surface –––––––––––––––––––––––––––––––––– 0.12 0.62 0.14 0.82 0.20 0.75 0.45 0.79 0.49 0.90
Detection of Occlusal Caries by Laser Fluorescence
duced fluorescence to quantify initial caries (see Tranaeus et al, this issue). A few years ago, for the first time, the successful use of red light (638 nm, 655 nm) induced fluorescence was reported to differentiate between sound and carious tooth tissue (9, 10). Based on this idea a novel caries detector was implemented, which has been in practical clinical use now for approximately 3 years. The following article summarises the research, including latest results.
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In order to continue the prior work on caries fluorescence we recorded fluorescence emission spectra on sound enamel surfaces and visible brown carious
spots of extracted human teeth. Test sites were irradiated by the radiation from a cw argon ion laser or a dye laser via an optical fibre. Fluorescence and backscattered light was collected by a fibre bundle and transmitted to an optical spectrometer. At the spectrometer site, the fibres were arranged linearly parallel to the entrance slit. To suppress distortions by higher order transmission and scattering within the spectrometer, short wavelength light was cut off by a band pass filter in front of the entrance slit. The spectra shown in Fig. 1 are original data, not corrected for fiber, filter, or spectrometer transmission. The fluorescence intensity is given in arbitrary units, but by ensuring a reproducible sample positioning and normalising the signals with respect to the input power, spectra taken at different excitation wavelengths can be compared quantitatively.
a
b
Fig. 1. Fluorescence spectra of sound and carious tooth area (original data, not corrected for system response; intensities among the different spectra can be compared quantitatively). a) 488 nm excitation b) 655 nm excitation c) as b), but normalised to peak intensity.
c
Spectroscopic investigations
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2a 2b 3a 3b 3c 4a
Fig. 2. Hemi-sectioned tooth with approximal and occlusal caries. a) normal image with white light illumination; b) fluorescence image in false colours (655 nm excitation).
b Fig. 3. Fluorescence caries detector. a) optical set-up; b) fibre tips; c) DIAGNOdentTM system (KaVo, Biberach).
Fig. 4. Longitudinal section of a tooth with macroscopically intact surface and dentinal caries, DIAGNOdent tip in place.
Detection of Occlusal Caries by Laser Fluorescence
For excitation with the blue argon ion laser radiation (l= 488 nm) relatively intense fluorescence in the yellow spectral region is found for sound surfaces (Fig. 1a). In accordance with earlier observations (4), this fluorescence decreases when the teeth become carious. Additionally, in the red and infrared part of the spectrum (λ > 645 nm), carious spots exhibit a stronger fluorescence than sound ones. To differentiate between healthy and carious tissue either the fluorescence decrease below 645 nm or the increase for longer wavelengths could be used. When irradiating with red light for excitation, e.g. at 640 nm or 655 nm (Fig. 1b), fluorescence intensity decreases when compared to 488 nm excitation. However, this decrease is much more pronounced for sound surfaces than for caries, so that now caries fluoresces much stronger. As the normalised spectra (relative to the peak intensity, Fig. 1c) indicate, the intensity relation between carious and sound areas is the same across the entire wavelength range. Thus all fluorescence can be used for differentiation of healthy and diseased tissue. The utilisation of the total fluorescence light compensates in part for the lower intensities compared to excitation with shorter wavelengths. The considerable contrast between caries and enamel, or dentine, respectively, obtained for red excitation is demonstrated in Fig. 2, which shows a hemi-sectioned tooth and the corresponding fluorescence image. Both carious sites are clearly marked on the very low background fluorescence level. This offers a very elegant way for caries detection, because only the bright fluorescence spots in an otherwise dark environment have to be found. This does not require 2-dimensional images and analysis. Additionally, now also the detection of hidden caries is possible, since the weaker enamel fluorescence does not cover completely the signal from a deeper lesion. Red light, and also the infrared fluorescence radiation, is less absorbed and scattered by enamel than light of shorter wavelengths, so that it penetrates deeper into the tooth. This also helps to increase the depth that can be examined.
Fluorophore identification In order to find the origin of fluorescence, one has to consider both the baseline fluorescence of sound den-
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tal tissue, and its increase during the carious process. The dominant components of enamel and dentine are calcium phosphates, mainly substituted hydroxyapatite (HA). To test whether the inorganic components contribute to the signal, we compared the fluorescence of various calcium phosphates (pellets pressed out of pure (> 97%) powder) to that of enamel. From the results (Table 2) it seems unlikely that calcium phosphates are responsible for the baseline fluorescence of sound teeth. By comparing teeth with different colour one can observe that whiter teeth exhibit less fluorescence compared to darker ones. Presumably the same stains cause colour and fluorescence. The caries process starts as a loss of calcium and other ions out of enamel. Fluorescence microscopy of such lesions (white spots in Fig. 2) shows that decalcification does not lead to enhanced signals. This corresponds to the finding of low calcium phosphate fluorescence described above. However, fluorescence is found along the dentinal tubules from the occlusal caries lesion towards the pulp (Fig. 2). This leads to the assumption that bacteria could contribute to the caries fluorescence signal. To test this hypothesis, we incubated bacteria from caries on blood agar and analysed the grown colonies by fluorescence microscopy. Interestingly, not only the bacteria colonies show fluorescence, but also the surrounding agar. Agar fluorescence decreases with increasing distance from the colonies, indicating that there are diffusible bacteria metabolites fluorescing under red light excitation. Candidates for bacterial metabolites that fluoresce could be porphyrins. Porphyrins occur as intermediate steps in the synthesis of haeme, and are also produced by several types of oral bacteria, such as Prevotella intermedia, or Porphyromonas gingivalis. In earlier work porphyrins indeed could be extracted from cariTable 2. Fluorescence signals from calcium phosphates relative to enamel with excitation at 655 nm. material
relative signal
enamel Ca5(PO4)3OH β-Ca3(PO4)2 CaHPO4 2H2O CaCO3 CaHPO4
1 0.06 0.12 0.05 0.03 0.10
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ous lesions and were demonstrated to be useful in differentiating caries from sound tooth by violet (406 nm) excited fluorescence (12). Although fluorescence yield is maximal for this short wavelength excitation, porphyrins were known to also show some fluorescence when excited by red light. In order to check whether porphyrins were also present in our actual samples, we extracted carious material from human teeth, dissolved it either in acetone/ methanol TBP or 3-M HCL, and analysed it by high performance liquid chromatography (HPLC). The fractions were excited by 406 nm and 655 nm radiation and investigated for fluorescence. For additional confirmation porphyrin reference solutions were used. Red excited fluorescence was observed by the reference solutions, but concentration in our caries extractions was too small to result in a signal clearly distinguishable from background. With 406 nm induced fluorescence, however, we found protoporphyrin IX (PPIX), meso-porphyrin, and copro-porphyrin present in the samples. Solutions of these molecules do fluoresce on 655 nm excitation too, and their emission spectra are very similar to those found for caries (Fig. 1b). Thus we have identified molecules that contribute to the signal obtained from caries. Whether these are the dominant or even only fluorophores, or whether there are also other components resulting in red excited caries fluorescence, has to evaluated in further research.
Detector system On the basis of the investigations described above we constructed a novel optical caries detector sketched in Fig. 3. In a joint project between ILM and Kaltenbach and Voigt (KaVo, Biberach, Germany) this system was developed to maturity. It is available on the market under its trade name DIAGNOdent. The set-up and function are as follows. Light from a laser diode (655 nm) is coupled into an optical fibre and transmitted to the tooth. The excitation fibre is surrounded by a bundle of 9 thin concentric fibres, which gather fluorescence as well as backscattered light and guide it to the detection unit. To achieve maximum collection efficiency, the tips of the detection fibres are bevelled such that irradiation and detection field of view overlap (Fig. 3b, 4). By a band
pass filter in front of the photo diode detector the backscattered excitation and short wavelength ambient light is absorbed. To discriminate the fluorescence from the ambient light in the same spectral region, the laser diode is modulated. Due to its relatively short lifetime, fluorescence follows this modulation. By amplifying only the modulated portion of the signal, the ambient light is suppressed. The remaining signal is proportional to the detected fluorescence intensity and displayed as a number (0...99; in arbitrary units). In order to compensate for potential variations of the system (e.g. laser diode output power) it can be calibrated by a standard of known and stable fluorescence yield. This makes the measurement absolute (although in arbitrary units) and allows comparisons of fluorescing tooth spots over time. In order to test the linearity and sensitivity of the DIAGNOdentTM, we made solutions of varying PPIX concentrations and measured the signals. These increase linearly with concentration (slope of 4.3 units per µmol/l). Intersection with baseline, which gives the minimum detectable concentration, is 1.5 to 2 µmol/l (Fig. 5). Within a tooth, overall fluorescence yield is increased due to light scattering. This would result in even higher sensitivity in the clinical situation. To test this, we applied a droplet of 1 µl PPIX solution of 5 and 11 µmol/l, respectively, concentration, onto the enamel and dentine area of a hemi-sectioned tooth. The resulting DIAGNOdentTM readings are reported in Table 3. On average, 1 pmol of PPIX results in an signal increase of 4 units. This compares to the baseline levels of sound teeth, and would be the detectable amount of porphyrins in superficial carious lesions.
Fig. 5. DIAGNOdentTM readings versus protoporphyrin IX concentration.
Detection of Occlusal Caries by Laser Fluorescence Tabele 3. DIAGNOdentTM signals of hemi-sectioned teeth before and after applying 1 µl of PPIX solution.
enamel dentin
before
4.8 µmol/l (4.8 pmol/l)
10.7 µmol/l (10.7 pmol/l)
1 8
20 25
29 77
Clinical investigations The assessment of a tooth with the laser fluorescence system is as follows: After calibration with a ceramic standard the fluorescence of a sound spot on the smooth surface of the tooth is measured in order to provide a baseline value. This value is then subtracted electronically from the fluorescence of the site to be measured. In order to get the maximum extension of caries, the instrument has to be tilted around the measuring site. This ensures that the tip picks up fluorescence from the slopes of the fissure walls where the carious process often begins. A rising tone helps the examiner to find the maximum fluorescence value of the site under study. In order to receive information about cut-off values in vivo 7 dental practitioners were asked to judge 332 occlusal surfaces from 240 patients (mean age 19.8 yr.) either by visual inspection, bitewing radiography or by the DIAGNOdent. Prior to the study the dentists had an audit meeting concerning caries detection. When a dentist decided to open a tooth, the extension of caries was assessed using a sharp probe. Using statistical methods, the best cut-off limits were determined and the guidelines given in table 4 for the clinical use were advised (19). Table 5 gives an overview of the performance of the various diagnostic methods used after caries extent was determined
Table 4. Guidelines for the clinical use of the DIAGNOdent for adult patients (19). Values Values Values
Over
0 – 13: No active care is advised (NCA) 14 – 20: Preventive care is advised (PCA ) 21 – ~29: Preventive or operative care is advised depending on the patient’s caries risk, the recall interval etc. (PCA or OCA) ~ 30: Operative (and preventive) care is advised (OCA)
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Table 5. Specificity and sensitivity for the diagnosis of occlusal caries (all lesions) (19). Visual inspection
Bitewing radiography
DIAGNOdent
Specificity Cut-off: dentine2
–
0.99
0.86
Sensitivity Cut-off: enamel1 Cut-off: dentine2
0.62 0.31
0.63
0.96 0.92
1 cut-off enamel: no caries (D0) was classified as ‘sound’; enamel caries (D1, D2) and dentinal caries (D3, D4) was classified as ‘decayed’. 2 D0, D1, D2 : ‘sound’; D3, D4 : ‘decayed’.
Table 6. Occlusal dentine lesions assessed by all methods (n = 100) (19). Lesions detected by clinical inspection only Lesions detected radiographically only Lesions detected by laser fluorescence only Lesions detected by inspection and radiography Lesions detected by inspection and laser fluorescence Lesions detected by radiography and laser fluorescence Lesions detected common for all 3 methods Lesions not detected by any method Percentage of lesions detected by visual inspection (first opinion) (n = 1 + 1 + 8 + 19 = 29) Percentage of additional lesions detected when radiography was the second opinion (n = 2 + 40 = 42) Percentage of additional lesions detected when laser fluorescence was the second opinion (n = 23 + 40 = 63)
1 2 23 1 8 40 19 6 29% 45% 117%
after operative intervention. Visual inspection achieved a sensitivity of 31% (D3-level) and of 62% (D2-level) whereas the DIAGNOdent device showed a sensitivity ≥ 92%. The McNemar test revealed a better performance of the laser fluorescence device (p < 0.001) compared with visual inspection and bitewing radiography. One hundred occlusal lesions were assessed by all methods. Only one lesion was detected clinically but not by the other methods (Table 6). The additional diagnostic yield from bitewing radiography was 45%. Using laser fluorescence as the additional tool, this value increased to 117%. The reproducibility was also determined in vitro and in vivo (18, 19). The dentists were asked to assess first the fluorescence of a sound smooth surface site (internal calibration of the tooth) and then of the site under study. Later in the same session each measurement was repeated. The quality of the intra- and in-
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terexaminer reproducibility was calculated using Cohen’s Kappa statistic. The Kappa values were determined using the previously established cut-off levels. Cohen’s Kappa was on average 0.90 in the in vitro study and 0.93 in the in vivo study. Combined with the high caries detection performance of the new device, the excellent reproducibility indicates that the laser-based method may be suitable for the longitudinal monitoring of caries and thus also, for assessing the caries activity and the outcome of preventive interventions. Its potential utility is to facilitate preventive based management of dental caries, not merely as a device to aid in the location of dentinal lesions requiring fillings.
Clinical Recommendations It is advised that a patient should always be inspected clinically first using a mirror and air (3-in-1 syringe) instead of a dental explorer. Drying makes decalcifications visible. If there is doubt about the status of health at any particular site then this more sensitive equipment should be used as a second opinion. This approach allows the dentist to combine the advantages of higher specificity and speed of clinical inspection with the higher sensitivity of the new device. Experience with the device demonstrated that deposits like plaque or calculus in the fissure and/or on the tip as well as staining or composites could give rise to a false positive reading. Thus, for this device, as well as for clinical detection, thorough cleaning is a prerequisite for accurate caries diagnosis. Histological involvement of dentine should not, in any case, indicate immediate operative intervention in all circumstances. The decision triggering restorative treatment is dependent upon a range of other variables, such as the patient’s case history, fluoride and dietary status, as well as perceived caries activity and the status of the surface. In no case should early detection of the carious process be an excuse for early operative intervention.
Conclusions and Outlook Red excited fluorescence is well suited for the detection of hidden occlusal caries. Sensitivity is
much better than for conventional methods, and quantitative output allows easy monitoring of lesions. In principle the same technique could be used also for the detection of approximal caries. To achieve optimal sensitivity in this case also, smaller probes have to be developed which would allow a closer access to the lesion. Another additional application can be found in periodontics. Because calculus contains large amounts of porphyrins, these deposits also cause a bright fluorescence signal. This allows calculus detection as well as control of calculus removal. Again, a special fibre tip would be helpful.
Detektion von Okklusal-Karies durch Fluoreszenz Experimentelle und klinische Untersuchungen Einleitung: Die visuelle Inspektion und auch Bißflügel-Röntgenaufnahmen haben eine recht geringe Sensitivität beim Aufspüren von Okklusal-Karies, besonders wenn diese unter einer makroskopischen intakten Schmelzdecke verborgen ist („versteckte Karies“, „hidden caries“). Als Alternative haben wir die Verwendung Laser-angeregter Fluoreszenz untersucht . Methoden und Ergebnisse: Fluoreszenzspektroskopische Untersuchungen ergaben einen besonders guten Kontrast zwischen gesunden und kariösen Hartgeweben, wenn diese mit rotem Licht (655 nm) angeregt wurden. Bei dieser Anregungswellenlänge fluoreszieren die anorganischen Bestandteile des Zahnes fast gar nicht, Karies hingegen deutlich. Ursprung dieser Fluoreszenz sind, zumindest zum Teil, von Bakterien produzierte Porphyrine. Auf der Grundlage rotangeregter Fluoreszenz wurde ein neuartiger Kariesdetektor entwickelt (DIAGNOdentTM, KaVo, Biberach). Mit dem Gerät wird die Fluoreszenz des Zahnes quantitativ erfasst. Auf Zahnscheiben kann bereits eine Menge von 1 pmol Protoporphyrin IX nachgewiesen werden. Klinische Studien ergaben bei der Detektion von Okklusal-Karies eine Sensitivität von ≥ 0,92, verglichen mit 0,63 für Bißflügel-Aufnahmen bzw. von ≤ 0,62 für die visuelle Inspektion. Die Reproduzierbarkeit in vivo betrug bei Vergleichen zwischen verschiedenen Messungen desselben Beobachters 0,93. Schlußfolgerungen: Die Detektion von Okklusal-Karies mit dem DIAGNOdentTM ist erheblich empfindlicher als mit konventionellen Methoden. Dadurch, dass die Fluoreszenz-Messwerte mit dem Status der Karies korreliert sind, geben sie einen zusätzlichen Anhaltspunkt für die Therapieentscheidung. Darüber hinaus erlaubt die exzellente Reproduzierbarkeit der Messung ein zeitliches Monitoring von Läsionen und damit eine Kontrolle auch präventiver Maßnahmen.
Schlüsselwörter Karies, Diagnostik, DIAGNOdent, Fluoreszenz, Laser-Diode
Detection of Occlusal Caries by Laser Fluorescence
References 1. ALFANO RR, YAO SS: Human teeth with and without dental caries studied by visible luminescence spectroscopy. J Dent Res 60: 120–122 (1981) 2. Benedict HC: Note on the fluorescence of teeth in ultraviolet rays. Science 67: 442 (1928) 3. BERGMAN G, LINDÉN LA: The action of the explorer on incipient caries. Svensk Tabdläkare Tetisskrift: 62: 629–634 (1969) 4. BJELKHAGEN H, SUNDSTRÖM F, ANGMAR-MANSSON B, RYDEN H: Early detection of enamel caries by the luminescence excited by visible laser light. Swed Dent J 6: 1–7 (1982) 5. CREANOR SL, RUSSELL JI, STRANG DM, STEPHEN KW, BURCHELL CK: The prevalence of clinically undetected occlusal dentine caries in Scottish adolescents. Br Dent J169: 126–129 (1990) 6. EKSTRAND K, QVIST V, THYLSTRUP A: Light microscope study of the effect of probing in occlusal surfaces. Caries Res 21: 368–374 (1987) 7. EKSTRAND K, RICKETTS DNS, KIDD EAM: Reproducibility and accuracy of three methods for assessment of demineralization depth on the occlusal surface: An in vitro examination. Caries Res 31: 224–231 (1997) 8. FERREIRA ZANDONA AG, ANALOUI M, BEISWANGER BB, ISAACS RL, KAFRAWY AH, ECKERT GJ, STOOKEY GK: An in vitro comparison between laser fluorescence and visual examination for detection of demineralization in occlusal pits and fissures. Caries Res 32: 210–218 (1998) 9. HIBST R, GALL R: Development of a diode laser-based fluorescence caries detector. Caries Res 32: 294 (1998) 10. HIBST R: Optische Meßmethoden zur Kariesdiagnose. ZWR 108: 50–55 (1999) 11. KIDD EAM, NAYLOR MN, WILSON RF: Prevalence of clinically undetected and untreated molar occlusal dentine caries in adolescents on the Isle of Wight. Caries Res 26: 397–401 (1992) 12. KÖNIG K, HIBST R, MEYER H, FLEMMING G, SCHNECKENBURGER H: Laser-induced autofluorescence of carious regions of human teeth and caries-involved bacteria in: ALTSHULER G, HIBST R (Eds.): Dental Applications of Lasers; Proc SPIE 2080: 170–180 (1993) 13. LOESCHE WJ, SVANBERG ML, PAPE HR: Intraoral transmission of streptococcus mutans by a dental explorer. J Dent Res 58;1765–1770 (1979) 14. LUSSI A: Validity of diagnostic and treatment decisions of fissure caries. Caries Res 25: 296–303 (1991) 15. LUSSI A: Comparison of different methods for the diagnosis of fissure caries without cavitation. Caries Res 27: 409–416 (1993)
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16. LUSSI A: Impact of including or excluding cavitated lesions when evaluating methods for the diagnosis of occlusal caries. Caries Res 30: 389–393 (1996) 17. LUSSI A, MENGHINI G, STEINER M, MARTHALER TM: The impact of radiography and electrical conductivity measurements on the prevalence of occlusal caries in epidemiological surveys. Abstract 124. Caries Res 31: 322 (1997) 18. LUSSI A, IMWINKELRIED S, PITTS NB, LONGBOTTOM C, REICH E: Performance and reproducibility of a laser fluorescence system for detection of occlusal caries in vitro. Caries Res 33: 261–266 (1999) 19. LUSSI A, MEGERT B, LONGBOTTOM C, REICH E, FRANCESCUT P: Clinical performance of a laser fluorescence device for detection of occlusal caries lesions. Eur J Oral Sci 109: 14–19 (2001) 20. NEWBRUN E, BRUDEVOLD F, MERMAGEN H: A microradiographic evaluation of occlusal fissures and grooves. J Am Dent Assoc 58: 26–31 (1959) 21. SUNDSTRÖM F, FREDRIKSSON K, MONTAN S, U HAFSTRÖMBJÖRKMAN, STRÖM J: Laser-induced fluorescence from sound and carious tooth substance: Spectroscopic studies. Swed Dent J 9: 71–80 (1985) 22. VAN DORP CSE, EXTERKATE AM, TEN CATE JM: The effect of dental probing on subsequent enamel demineralization. J Dent Child 55: 343–347 (1988) 23. WEERHEIJM KL, VAN AMERONGEN WE, EGGINK CO: The clinical diagnosis of occlusal caries: a problem. J Dent Child 56: 196–200 (1989) 24. WEERHEIJM KL, GRUYTHUYSEN RJM, VAN AMERONGEN WE: Prevalence of hidden caries. J Dent Child 59: 408–412 (1992a) 25. WEERHEIJM KL, GROEN HJ, BAST AJJ, KIEFT JA, EIJKMAN MAJ, VAN AMERONGEN WE: Clinically undetected occlusal dentine caries: A radiographic comparison. Caries Res 26: 305-309 (1992b) 26. WENZEL A, LARSEN MJ, FEJERSKOV O: Detection of occlusal caries without cavitation by visual inspection, film radiographs, xeroradiographs, and digitized radiographs: Caries Res 25: 365–371 (1991) 27. YASSIN OM: In vitro studies of the effect of a dental explorer on the formation of an artificial carious lesions. J Dent Child 62: 111–117 (1995)
Correspondence address: Prof. Dr. RAIMUND HIBST, Institut für Lasertechnologien in der Medizin und Meßtechnik, Helmholtzstraße 12, D - 89081 Ulm, Germany Tel.: ++49-731-14 29 12; Fax: ++49-731-12 29 42 e-mail: [email protected]
Detection of Occlusal Caries by Laser Fluorescence: Basic and Clinical Investigations RAIMUND HIBST, ROBERT PAULUS, and ADRIAN LUSSI1 Institut für Lasertechnologien in der Medizin und Messtechnik (ILM), Ulm, Germany 1 Department of Operative, Pediatric and Preventive Dentistry, University of Berne, Switzerland Submitted: May 2001 · Accepted: June 2001
Summary Objectives: Motivated by the poor sensitivity of visual inspection and radiography in the detection of occlusal caries hidden under a macroscopically sound surface, we explored the implementation of fluorescence as an alternative diagnostic tool. Methods and Results: Fluorescence spectroscopic investigations revealed considerable contrast between sound and carious tooth hard tissue when excited by red (655 nm) light. For this excitation wavelength on inorganic tooth components only negligible fluorescence was observed. Advanced caries, however, show readily detectable fluorescence. The latter, at least in part, originates from porphyrins produced by bacteria. Based on red excited fluorescence a novel caries detector was constructed (DIAGNOdentTM, KaVo, Biberach). The system measures fluorescence quantitatively. The minimum amount of protoporphyrin IX that can be detected is approximately 1 pmol. Clinical investigations yielded a sensitivity ≥ 0.92 in detection of occlusal caries, compared to 0.63 for bitewing radiography, and ≤ 0.62 for visual inspection. Intra- and interexaminer reproducibility tests resulted in Cohen’s Kappa value of 0.93 in vivo. Conclusions: Detection of occlusal caries with the DIAGNOdentTM system has a much better sensitivity than conventional methods. Because the readings are correlated to the status of the carious lesion, treatment decisions can be aided by the measurement. Additionally, excellent reproducibility allows monitoring of lesions over time to facilitate preventive based management of dental decay.
Key words Caries, diagnosis, DIAGNOdentTM, fluorescence, laser diode
Introduction The onset of caries is characterised by only microscopically visible surface demineralisation on dental hard tissues. Changes of diet and/or oral hygiene habits in combination with optimal fluoridation may stop the progression of a lesion and even allow its remineralisation. The aim of modern dentistry must be a preventive approach rather than invasive repair of the disease. This is only possible if the remaining structural organisation of the attacked tissue will still
allow ‘restitutio ad integrum’ providing early detection and respective preventive measures. Some of today’s diagnostic tools are not sensitive enough to detect this early onset of destruction. Therefore, oftentimes remineralisation or stabilisation is not possible any more at the time of detection and restoration is inevitable. This, in turn, is the start of the vicious circle of restorative therapy due to the limited life expectancy of all restorative materials. Historically, the detection of occlusal caries has been carried out with the use of mirror, light and 1615-1615/01/16/03-205 $ 15.00/0
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explorer. The tactile sign of resistance while withdrawing the explorer has been considered diagnostic for caries (20, 23). The value of the explorer or probe in the detection of occlusal caries has recently been called into question by a number of investigators (13, 6, 22, 14, 15, 27). It has been conclusively demonstrated that conventional clinical methods result in remarkably low values for sensitivity when attempting to detect occlusal caries (26, 14, 15, 16, 8). In the face of this evidence, it is difficult to defend the potential for iatrogenic damage of otherwise remineralizable lesions in fissures when using visual-tactile methods (3). For occlusal surfaces the specificity of clinical examination is beyond 90%, i.e. sound surfaces are most often correctly recognised (26, 14, 15, 16). This is very important in the light of today’s relatively small caries prevalence. Surfaces which can be maintained sound for years with adequate preventive measures must not be treated prematurely by restorative dentistry. The sensitivity at the D3 level (dentinal caries), i. e. the ability to recognise with clinical examination methods diseased surfaces as diseased varies between 12%–82% (26, 14, 15, 16). The significant differences in the performance of the different “classical” clinical methods is due to different statuses of the occlusal surface. Dentinal caries in teeth with a macroscopically intact occlusal surface is difficult to detect in daily practice. Indeed, the lowest sensitivities were found with teeth exhibiting macroscopically intact occlusal surfaces showing underlying dentinal caries histologi-
cally (Table 1). This phenomenon characterises the socalled ‘hidden caries’ found in between 10–50% of the teeth with dentinal caries (5, 11, 17, 24, 25). These problems were the motivation to search for devices more sensitive in detection of caries, especially when covered by a layer of nearly intact enamel. The limitation of visual inspection in these cases is due to light scattering within the tooth. Light being remitted from the surface cannot be attributed to a definite tooth region but reflects the optical properties of a large volume. Thus an increase of absorption in a small carious lesion beneath the surface does not change the overall backscattered light very much: the lesion is “hidden”. Compared to absorption a much higher sensitivity can be expected by detecting the fluorescence light being emitted by some of the molecules following absorption. Already in 1928, fluorescence on UV excitation of enamel and dentine and its loss due to decalcification was reported (2). About 20 years ago, first experiments with excitation in the visible (410 nm, 488 nm, 530 nm) were carried out, and again differences between sound and diseased dental tissue were observed (1, 4). A comparative study on sound and carious tooth substance fluorescence for various excitation wavelengths (337, 488, 515, and 633 nm) revealed maximum contrast for the detection of initial caries at 488 nm excitation (21). No fluorescence was visible when excitation was by red (633 nm) light. Further research then was concentrated on 488 nm in-
Table 1. In vitro validity of different ‘classical‘ diagnostic methods employed by practising dentists for occlusal surfaces on the D3 level (15, 16). No caries (D0) or enamel caries (D1, D2) Visual inspection (n = 26 dentists) Visual inspection combined with probing (n = 23) Visual inspection with a magnifying glass (n = 26) Bitewing radiography (BW) (n = 24) Visual inspection combined with BW (n = 10) Dentinal caries (D3, D4)
Visual inspection (n = 26 dentists) Visual inspection combined with probing (n = 23) Visual inspection with a magnifying glass (n = 26) Bitewing radiography (BW) (n = 24) Visual inspection combined with BW (n = 10)
Specificity 0.93 0.93 0.89 0.83 0.87 Sensitivity –––––––––––––––––––––––––––––––––– macroscopically cavitated intact surface surface –––––––––––––––––––––––––––––––––– 0.12 0.62 0.14 0.82 0.20 0.75 0.45 0.79 0.49 0.90
Detection of Occlusal Caries by Laser Fluorescence
duced fluorescence to quantify initial caries (see Tranaeus et al, this issue). A few years ago, for the first time, the successful use of red light (638 nm, 655 nm) induced fluorescence was reported to differentiate between sound and carious tooth tissue (9, 10). Based on this idea a novel caries detector was implemented, which has been in practical clinical use now for approximately 3 years. The following article summarises the research, including latest results.
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In order to continue the prior work on caries fluorescence we recorded fluorescence emission spectra on sound enamel surfaces and visible brown carious
spots of extracted human teeth. Test sites were irradiated by the radiation from a cw argon ion laser or a dye laser via an optical fibre. Fluorescence and backscattered light was collected by a fibre bundle and transmitted to an optical spectrometer. At the spectrometer site, the fibres were arranged linearly parallel to the entrance slit. To suppress distortions by higher order transmission and scattering within the spectrometer, short wavelength light was cut off by a band pass filter in front of the entrance slit. The spectra shown in Fig. 1 are original data, not corrected for fiber, filter, or spectrometer transmission. The fluorescence intensity is given in arbitrary units, but by ensuring a reproducible sample positioning and normalising the signals with respect to the input power, spectra taken at different excitation wavelengths can be compared quantitatively.
a
b
Fig. 1. Fluorescence spectra of sound and carious tooth area (original data, not corrected for system response; intensities among the different spectra can be compared quantitatively). a) 488 nm excitation b) 655 nm excitation c) as b), but normalised to peak intensity.
c
Spectroscopic investigations
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2a 2b 3a 3b 3c 4a
Fig. 2. Hemi-sectioned tooth with approximal and occlusal caries. a) normal image with white light illumination; b) fluorescence image in false colours (655 nm excitation).
b Fig. 3. Fluorescence caries detector. a) optical set-up; b) fibre tips; c) DIAGNOdentTM system (KaVo, Biberach).
Fig. 4. Longitudinal section of a tooth with macroscopically intact surface and dentinal caries, DIAGNOdent tip in place.
Detection of Occlusal Caries by Laser Fluorescence
For excitation with the blue argon ion laser radiation (l= 488 nm) relatively intense fluorescence in the yellow spectral region is found for sound surfaces (Fig. 1a). In accordance with earlier observations (4), this fluorescence decreases when the teeth become carious. Additionally, in the red and infrared part of the spectrum (λ > 645 nm), carious spots exhibit a stronger fluorescence than sound ones. To differentiate between healthy and carious tissue either the fluorescence decrease below 645 nm or the increase for longer wavelengths could be used. When irradiating with red light for excitation, e.g. at 640 nm or 655 nm (Fig. 1b), fluorescence intensity decreases when compared to 488 nm excitation. However, this decrease is much more pronounced for sound surfaces than for caries, so that now caries fluoresces much stronger. As the normalised spectra (relative to the peak intensity, Fig. 1c) indicate, the intensity relation between carious and sound areas is the same across the entire wavelength range. Thus all fluorescence can be used for differentiation of healthy and diseased tissue. The utilisation of the total fluorescence light compensates in part for the lower intensities compared to excitation with shorter wavelengths. The considerable contrast between caries and enamel, or dentine, respectively, obtained for red excitation is demonstrated in Fig. 2, which shows a hemi-sectioned tooth and the corresponding fluorescence image. Both carious sites are clearly marked on the very low background fluorescence level. This offers a very elegant way for caries detection, because only the bright fluorescence spots in an otherwise dark environment have to be found. This does not require 2-dimensional images and analysis. Additionally, now also the detection of hidden caries is possible, since the weaker enamel fluorescence does not cover completely the signal from a deeper lesion. Red light, and also the infrared fluorescence radiation, is less absorbed and scattered by enamel than light of shorter wavelengths, so that it penetrates deeper into the tooth. This also helps to increase the depth that can be examined.
Fluorophore identification In order to find the origin of fluorescence, one has to consider both the baseline fluorescence of sound den-
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tal tissue, and its increase during the carious process. The dominant components of enamel and dentine are calcium phosphates, mainly substituted hydroxyapatite (HA). To test whether the inorganic components contribute to the signal, we compared the fluorescence of various calcium phosphates (pellets pressed out of pure (> 97%) powder) to that of enamel. From the results (Table 2) it seems unlikely that calcium phosphates are responsible for the baseline fluorescence of sound teeth. By comparing teeth with different colour one can observe that whiter teeth exhibit less fluorescence compared to darker ones. Presumably the same stains cause colour and fluorescence. The caries process starts as a loss of calcium and other ions out of enamel. Fluorescence microscopy of such lesions (white spots in Fig. 2) shows that decalcification does not lead to enhanced signals. This corresponds to the finding of low calcium phosphate fluorescence described above. However, fluorescence is found along the dentinal tubules from the occlusal caries lesion towards the pulp (Fig. 2). This leads to the assumption that bacteria could contribute to the caries fluorescence signal. To test this hypothesis, we incubated bacteria from caries on blood agar and analysed the grown colonies by fluorescence microscopy. Interestingly, not only the bacteria colonies show fluorescence, but also the surrounding agar. Agar fluorescence decreases with increasing distance from the colonies, indicating that there are diffusible bacteria metabolites fluorescing under red light excitation. Candidates for bacterial metabolites that fluoresce could be porphyrins. Porphyrins occur as intermediate steps in the synthesis of haeme, and are also produced by several types of oral bacteria, such as Prevotella intermedia, or Porphyromonas gingivalis. In earlier work porphyrins indeed could be extracted from cariTable 2. Fluorescence signals from calcium phosphates relative to enamel with excitation at 655 nm. material
relative signal
enamel Ca5(PO4)3OH β-Ca3(PO4)2 CaHPO4 2H2O CaCO3 CaHPO4
1 0.06 0.12 0.05 0.03 0.10
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ous lesions and were demonstrated to be useful in differentiating caries from sound tooth by violet (406 nm) excited fluorescence (12). Although fluorescence yield is maximal for this short wavelength excitation, porphyrins were known to also show some fluorescence when excited by red light. In order to check whether porphyrins were also present in our actual samples, we extracted carious material from human teeth, dissolved it either in acetone/ methanol TBP or 3-M HCL, and analysed it by high performance liquid chromatography (HPLC). The fractions were excited by 406 nm and 655 nm radiation and investigated for fluorescence. For additional confirmation porphyrin reference solutions were used. Red excited fluorescence was observed by the reference solutions, but concentration in our caries extractions was too small to result in a signal clearly distinguishable from background. With 406 nm induced fluorescence, however, we found protoporphyrin IX (PPIX), meso-porphyrin, and copro-porphyrin present in the samples. Solutions of these molecules do fluoresce on 655 nm excitation too, and their emission spectra are very similar to those found for caries (Fig. 1b). Thus we have identified molecules that contribute to the signal obtained from caries. Whether these are the dominant or even only fluorophores, or whether there are also other components resulting in red excited caries fluorescence, has to evaluated in further research.
Detector system On the basis of the investigations described above we constructed a novel optical caries detector sketched in Fig. 3. In a joint project between ILM and Kaltenbach and Voigt (KaVo, Biberach, Germany) this system was developed to maturity. It is available on the market under its trade name DIAGNOdent. The set-up and function are as follows. Light from a laser diode (655 nm) is coupled into an optical fibre and transmitted to the tooth. The excitation fibre is surrounded by a bundle of 9 thin concentric fibres, which gather fluorescence as well as backscattered light and guide it to the detection unit. To achieve maximum collection efficiency, the tips of the detection fibres are bevelled such that irradiation and detection field of view overlap (Fig. 3b, 4). By a band
pass filter in front of the photo diode detector the backscattered excitation and short wavelength ambient light is absorbed. To discriminate the fluorescence from the ambient light in the same spectral region, the laser diode is modulated. Due to its relatively short lifetime, fluorescence follows this modulation. By amplifying only the modulated portion of the signal, the ambient light is suppressed. The remaining signal is proportional to the detected fluorescence intensity and displayed as a number (0...99; in arbitrary units). In order to compensate for potential variations of the system (e.g. laser diode output power) it can be calibrated by a standard of known and stable fluorescence yield. This makes the measurement absolute (although in arbitrary units) and allows comparisons of fluorescing tooth spots over time. In order to test the linearity and sensitivity of the DIAGNOdentTM, we made solutions of varying PPIX concentrations and measured the signals. These increase linearly with concentration (slope of 4.3 units per µmol/l). Intersection with baseline, which gives the minimum detectable concentration, is 1.5 to 2 µmol/l (Fig. 5). Within a tooth, overall fluorescence yield is increased due to light scattering. This would result in even higher sensitivity in the clinical situation. To test this, we applied a droplet of 1 µl PPIX solution of 5 and 11 µmol/l, respectively, concentration, onto the enamel and dentine area of a hemi-sectioned tooth. The resulting DIAGNOdentTM readings are reported in Table 3. On average, 1 pmol of PPIX results in an signal increase of 4 units. This compares to the baseline levels of sound teeth, and would be the detectable amount of porphyrins in superficial carious lesions.
Fig. 5. DIAGNOdentTM readings versus protoporphyrin IX concentration.
Detection of Occlusal Caries by Laser Fluorescence Tabele 3. DIAGNOdentTM signals of hemi-sectioned teeth before and after applying 1 µl of PPIX solution.
enamel dentin
before
4.8 µmol/l (4.8 pmol/l)
10.7 µmol/l (10.7 pmol/l)
1 8
20 25
29 77
Clinical investigations The assessment of a tooth with the laser fluorescence system is as follows: After calibration with a ceramic standard the fluorescence of a sound spot on the smooth surface of the tooth is measured in order to provide a baseline value. This value is then subtracted electronically from the fluorescence of the site to be measured. In order to get the maximum extension of caries, the instrument has to be tilted around the measuring site. This ensures that the tip picks up fluorescence from the slopes of the fissure walls where the carious process often begins. A rising tone helps the examiner to find the maximum fluorescence value of the site under study. In order to receive information about cut-off values in vivo 7 dental practitioners were asked to judge 332 occlusal surfaces from 240 patients (mean age 19.8 yr.) either by visual inspection, bitewing radiography or by the DIAGNOdent. Prior to the study the dentists had an audit meeting concerning caries detection. When a dentist decided to open a tooth, the extension of caries was assessed using a sharp probe. Using statistical methods, the best cut-off limits were determined and the guidelines given in table 4 for the clinical use were advised (19). Table 5 gives an overview of the performance of the various diagnostic methods used after caries extent was determined
Table 4. Guidelines for the clinical use of the DIAGNOdent for adult patients (19). Values Values Values
Over
0 – 13: No active care is advised (NCA) 14 – 20: Preventive care is advised (PCA ) 21 – ~29: Preventive or operative care is advised depending on the patient’s caries risk, the recall interval etc. (PCA or OCA) ~ 30: Operative (and preventive) care is advised (OCA)
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Table 5. Specificity and sensitivity for the diagnosis of occlusal caries (all lesions) (19). Visual inspection
Bitewing radiography
DIAGNOdent
Specificity Cut-off: dentine2
–
0.99
0.86
Sensitivity Cut-off: enamel1 Cut-off: dentine2
0.62 0.31
0.63
0.96 0.92
1 cut-off enamel: no caries (D0) was classified as ‘sound’; enamel caries (D1, D2) and dentinal caries (D3, D4) was classified as ‘decayed’. 2 D0, D1, D2 : ‘sound’; D3, D4 : ‘decayed’.
Table 6. Occlusal dentine lesions assessed by all methods (n = 100) (19). Lesions detected by clinical inspection only Lesions detected radiographically only Lesions detected by laser fluorescence only Lesions detected by inspection and radiography Lesions detected by inspection and laser fluorescence Lesions detected by radiography and laser fluorescence Lesions detected common for all 3 methods Lesions not detected by any method Percentage of lesions detected by visual inspection (first opinion) (n = 1 + 1 + 8 + 19 = 29) Percentage of additional lesions detected when radiography was the second opinion (n = 2 + 40 = 42) Percentage of additional lesions detected when laser fluorescence was the second opinion (n = 23 + 40 = 63)
1 2 23 1 8 40 19 6 29% 45% 117%
after operative intervention. Visual inspection achieved a sensitivity of 31% (D3-level) and of 62% (D2-level) whereas the DIAGNOdent device showed a sensitivity ≥ 92%. The McNemar test revealed a better performance of the laser fluorescence device (p < 0.001) compared with visual inspection and bitewing radiography. One hundred occlusal lesions were assessed by all methods. Only one lesion was detected clinically but not by the other methods (Table 6). The additional diagnostic yield from bitewing radiography was 45%. Using laser fluorescence as the additional tool, this value increased to 117%. The reproducibility was also determined in vitro and in vivo (18, 19). The dentists were asked to assess first the fluorescence of a sound smooth surface site (internal calibration of the tooth) and then of the site under study. Later in the same session each measurement was repeated. The quality of the intra- and in-
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terexaminer reproducibility was calculated using Cohen’s Kappa statistic. The Kappa values were determined using the previously established cut-off levels. Cohen’s Kappa was on average 0.90 in the in vitro study and 0.93 in the in vivo study. Combined with the high caries detection performance of the new device, the excellent reproducibility indicates that the laser-based method may be suitable for the longitudinal monitoring of caries and thus also, for assessing the caries activity and the outcome of preventive interventions. Its potential utility is to facilitate preventive based management of dental caries, not merely as a device to aid in the location of dentinal lesions requiring fillings.
Clinical Recommendations It is advised that a patient should always be inspected clinically first using a mirror and air (3-in-1 syringe) instead of a dental explorer. Drying makes decalcifications visible. If there is doubt about the status of health at any particular site then this more sensitive equipment should be used as a second opinion. This approach allows the dentist to combine the advantages of higher specificity and speed of clinical inspection with the higher sensitivity of the new device. Experience with the device demonstrated that deposits like plaque or calculus in the fissure and/or on the tip as well as staining or composites could give rise to a false positive reading. Thus, for this device, as well as for clinical detection, thorough cleaning is a prerequisite for accurate caries diagnosis. Histological involvement of dentine should not, in any case, indicate immediate operative intervention in all circumstances. The decision triggering restorative treatment is dependent upon a range of other variables, such as the patient’s case history, fluoride and dietary status, as well as perceived caries activity and the status of the surface. In no case should early detection of the carious process be an excuse for early operative intervention.
Conclusions and Outlook Red excited fluorescence is well suited for the detection of hidden occlusal caries. Sensitivity is
much better than for conventional methods, and quantitative output allows easy monitoring of lesions. In principle the same technique could be used also for the detection of approximal caries. To achieve optimal sensitivity in this case also, smaller probes have to be developed which would allow a closer access to the lesion. Another additional application can be found in periodontics. Because calculus contains large amounts of porphyrins, these deposits also cause a bright fluorescence signal. This allows calculus detection as well as control of calculus removal. Again, a special fibre tip would be helpful.
Detektion von Okklusal-Karies durch Fluoreszenz Experimentelle und klinische Untersuchungen Einleitung: Die visuelle Inspektion und auch Bißflügel-Röntgenaufnahmen haben eine recht geringe Sensitivität beim Aufspüren von Okklusal-Karies, besonders wenn diese unter einer makroskopischen intakten Schmelzdecke verborgen ist („versteckte Karies“, „hidden caries“). Als Alternative haben wir die Verwendung Laser-angeregter Fluoreszenz untersucht . Methoden und Ergebnisse: Fluoreszenzspektroskopische Untersuchungen ergaben einen besonders guten Kontrast zwischen gesunden und kariösen Hartgeweben, wenn diese mit rotem Licht (655 nm) angeregt wurden. Bei dieser Anregungswellenlänge fluoreszieren die anorganischen Bestandteile des Zahnes fast gar nicht, Karies hingegen deutlich. Ursprung dieser Fluoreszenz sind, zumindest zum Teil, von Bakterien produzierte Porphyrine. Auf der Grundlage rotangeregter Fluoreszenz wurde ein neuartiger Kariesdetektor entwickelt (DIAGNOdentTM, KaVo, Biberach). Mit dem Gerät wird die Fluoreszenz des Zahnes quantitativ erfasst. Auf Zahnscheiben kann bereits eine Menge von 1 pmol Protoporphyrin IX nachgewiesen werden. Klinische Studien ergaben bei der Detektion von Okklusal-Karies eine Sensitivität von ≥ 0,92, verglichen mit 0,63 für Bißflügel-Aufnahmen bzw. von ≤ 0,62 für die visuelle Inspektion. Die Reproduzierbarkeit in vivo betrug bei Vergleichen zwischen verschiedenen Messungen desselben Beobachters 0,93. Schlußfolgerungen: Die Detektion von Okklusal-Karies mit dem DIAGNOdentTM ist erheblich empfindlicher als mit konventionellen Methoden. Dadurch, dass die Fluoreszenz-Messwerte mit dem Status der Karies korreliert sind, geben sie einen zusätzlichen Anhaltspunkt für die Therapieentscheidung. Darüber hinaus erlaubt die exzellente Reproduzierbarkeit der Messung ein zeitliches Monitoring von Läsionen und damit eine Kontrolle auch präventiver Maßnahmen.
Schlüsselwörter Karies, Diagnostik, DIAGNOdent, Fluoreszenz, Laser-Diode
Detection of Occlusal Caries by Laser Fluorescence
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Correspondence address: Prof. Dr. RAIMUND HIBST, Institut für Lasertechnologien in der Medizin und Meßtechnik, Helmholtzstraße 12, D - 89081 Ulm, Germany Tel.: ++49-731-14 29 12; Fax: ++49-731-12 29 42 e-mail: [email protected]