Fiber Optic Transillumination

Fiber-Optic Transillumination (FOTI)

Brief Description

Fiber-optic transillumination (FOTI) is an enhanced visual technique that uses the principle of illuminating teeth to detect the presence of caries. The principle behind transilluminating teeth is that demineralized areas of enamel or dentine scatter light more than sound areas. Incipient caries appear as darker areas in the resultant images, which are obtained during screening. (Pretty, Maupomé, 2004)

Working Principle

The keystone of visual inspection of caries is based on the phenomenon of light scattering. Sound enamel is composed of densely-packed, modified hydroxyapatite crystals which give it a transparent structure. Hence, tooth colour is largely influenced by the underlying dentin shade. When enamel is disrupted in the presence of demineralization, the penetrating photons of light are scattered, which results in an optical disruption. In normal visible light, this appears as a ‘white spot’ – an area which looks whiter than the rest of the tooth. The appearance is enhanced in a dried lesion, as water has a similar refractive index (RI) to enamel, but air has a lower RI thus the lesion is more clearly seen. FOTI makes use of these optical properties of enamel and enhances them by using a high intensity white light shone through a small aperture (e.g. 0.3-0.5 mm) of a dental handpiece. The light that is shone through the tooth scatters and observed shadows may indicate the presence of a carious lesion. The reason why shadows may indicate caries is because demineralized areas of enamel or dentine scatter light more than sound areas. Hence, caries appear as darker areas under FOTI. (Pretty, 2006)

The Method

High intensity white light from a fiber optic handpiece coupler attached to the handpiece should be used with dimmed room lighting and without the use of the operating light.

The light source should be of the smallest possible diameter (0.3-0.5mm) and can be from a 150 watt halogen lamp and rheostat.

For posterior approximal caries:
- Light probe position should be above the gingival margin of the tooth
- Light source should be directly perpendicular to the approximal area to prevent direct observation of the beam of light and allow diffraction between demineralized and sound tooth structure
- Approximal decay will produce a dark shadow on the occlusal marginal ridge

For anterior approximal caries:
- Light probe position also above the gingival margin
- Light source should be shone on buccal surface

(Capellini, Mobley, 2008)


Reported in a project by Davies et al. (2001), general dental practitioners (GDP) found more approximal enamel and dentinal lesions when using FOTI than when not. This study showed a trend for all GDPs to detect more approximal enamel and dentinal lesions when FOTI was incorporated into the standard clinical examination. The finding was apparent both with and without the addition of the radiographic assessment.

Table 1
Table 1.
(Davies et al., 2001)

Table 2
Table 2.
(Davies et al., 2001)

FOTI can be used for detection of caries on all surfaces, although it is more useful for proximal lesions. FOTI is also good for early detection of caries.

Sensitivity and Specificity

Sensitivity: proportion of actual positives which are correctly identified as such (e.g. person with caries identified as having caries)
= a/ (a+c)

Specificity: proportion of negatives which are correctly identified (e.g. person with no caries identified as without caries)
= d/ (b+d)

Subject Study Main Findings
Occlusal and approximal surfaces Schneiderman et al. Sensitivity: 0.67 for occlusal and 0.56 for approximal surfaces
Occlusal caries Mitropoulos Sensitivity: 0.85, specificity: 1.00
Buccal surfaces Sidi and Naylor Sensitivity: 0.74, specificity: 0.99
Table 3. Summary of Findings of Sensitivity/Specificity of FOTI
(Pretty, Maupomé, 2004)

References Diagnostic Test Validation method Sensitivity Specificity
Mitropoulos, 1985 FOTI Radiography 0.85 1.00
Pieper and Schurade, 1987 FOTI Radiography 0.71 0.92
Stephen et al., 1987 FOTI Radiography 0.44 0.99
Sidi and Naylor, 1988 FOTI (buccal and lingual) Radiography 0.74 (bucc.); 0.30 (ling.) 0.99 (bucc. and ling.)
Sidi and Naylor, 1988 FOTI Visual 1.00 0.99
Pieper and Schurade, 1987 FOTI Visual 0.96 0.92
Peers et al., 1993 FOTI Histology 0.67 0.97
Table 4. Summary of Findings of Sensitivity/Specificity of FOTI
(van Rijkom et al., 1995)

Sensitivity of FOTI varies between 0.00 and 0.85. Exceptions can be due to the nature of the ordinal scale used to record the subjective visual assessment, or based on the gold standard (e.g. radiography) that is used to validate the FOTI method. (Pretty, Maupomé, 2004) Despite the high positive predictive value of the FOTI method, a recent study has demonstrated a low sensitivity for the detection of small occlusal (Wenzel et al., 1992) and approximal surfaces caries lesions, ranging from 0.00 to 0.08. (Hintze et al.,1997)

FOTI however, shows consistently high specificity of between 0.95 and 1.00.

With low sensitivity and high specificity, the usefulness of FOTI hence lies in the ability to correctly diagnose caries based on exclusion.


However, the system is subjective. Analysis is done by the examiner who makes the call based on the appearance of scattering. There is also no continuous data output and it is not possible to record what is seen in the form of an image. Furthermore, FOTI can only be used for coronal tooth surfaces (occlusal, interproximal, and smooth) and not below the gingiva. (Pretty, 2006)

Fiber Optic Transillumination - Cariology
Figure 1. FOTI equipment
(Pretty, 2006)

Digital Imaging Fiber-Optic Transillumination (DiFOTI)

Brief Description

Digital Imaging Fiber-Optic Transillumination (DiFOTI) is a technique that builds on FOTI but which allows the recording of images of carious lesions during illumination. It employs high intensity light and has an additional grey scale camera.

Fiber Optic Transillumination - Cariology
Figure 2. DiFOTI general overview of system
(Picture credits:
Electro-Optical Sciences, Inc.)

The Method

There are two types of mouthpieces available for use with the DiFOTI:

(a) Proximal surface mouthpiece: It is used for detecting interproximal and smooth surface caries. Light is shone from either the buccal or lingual surface through the tooth and the image is recorded from the opposite surface with the attached camera (Pretty, Maupomé, 2004)

Fiber Optic Transillumination - Cariology
Figure 3. Proximal surface mouthpiece (Pretty, Maupomé, 2004)

(b) Occlusal surface mouthpiece: It is used for detecting caries on the occlusal surface. The mouthpiece illuminates the tooth through both the buccal and lingual surfaces and captures the image from the top of the tooth. (Pretty, Maupomé, 2004)

Fiber Optic Transillumination - Cariology
Figure 4. Occlusal surface mouthpiece
(For picture on left: Pretty, Maupomé, 2004; right:
Electro-Optical Sciences, Inc., 2004)


Reported by Schneiderman, et al. (1997), the DIFOTI technique has superior sensitivity compared to conventional radiological methods for the detection of approximal, occlusal, and smooth-surface caries.
The images can indicate the presence of early decay before either film or digital radiography. Fennis-Ie et al. (1998) verified that 44% of the sites diagnosed as having enamel or dentinal caries by FOTI actually became carious within 2.5 years. (Devlin, 2006, p. 7)

difoti difference
Figure 5. Difference between DIFOTI and conventional Radiography.
(Photo credits: Electro-Optical Sciences, Inc., 2004)

The DIFOTI technique is rapid, since images are instantly available following capture by the dentist. These images can then be discussed with the patient, then stored and reviewed at future visits. Given the visual approach of this technique, patients may be encouraged to take on a preventive approach as they are now aware and able to examine the demineralized enamel and the condition of their teeth.
(Devlin, 2006, p. 7)

Additionally, this modified method is a safe and non-radiation technique for caries identification for pregnant women, children and cancer patients who receive high doses of radiation (as opposed to X-rays).

Sensitivity and Specificity

The DIFOTI technique has superior sensitivity over radiological methods for the detection of approximal, occlusal and smooth-surface caries, although specificity was slightly less in general (Schneiderman et al., 1997). DIFOTI thus is able to detect early surface carious lesions not readily discernable by radiographic film technology. (Devlin, 2006)

However, the greater sensitivity of DIFOTI may result in white-spot carious lesions with intact enamel surface appearing dark and hence erroneously diagnosed as requiring restoration. Nevertheless, the value of this technique can be to encourage a preventive approach since patients can be made aware (visually) of demineralized enamel. (Devlin, 2006)

Gutierrez (2008) recorded sensitivity and specificity values for DIFOTI on various tooth surfaces and found the following data using the sectioned specimens as the gold standard:

Sensitivity Specificity
Smooth surfaces 1.00 0.88
Occlusal surfaces 0.82 1.00
Approximal surfaces 0.44 0.83
Table 5. Sensitivity and Specificity of DIFOTI
(Gutierrez, 2008)

Comparative to conventional radiographs, DIFOTI was found in one study by Stookey and Gonzales-Cabezas to be twice as sensitive in the detection of interproximal lesions and three times as sensitive in the detection of occlusal lesions. Verdonschot et al found the positive predictive value of DIFOTI to be superior to all other diagnostic systems evaluated. (Everett et. al.)

The observation in one study of an area under the curve of 0.85 in a receiver operating characteristics (ROC) analysis of DIFOTI suggests that there is a basis for using this device in diagnostic dntistry. (Pretty, Maupomé, 2004)


A potential problem with DIFOTI is image interpretation. Since results are not directly quantified, the clinician must perform the analysis, giving up to the probable inaccuracy of human error that such analyses entail.(Pretty, Maupomé, 2004) For example, the greater sensitivity of DIFOTI may mean that white-spot carious lesions with an intact enamel surface may appear dark and may be erroneously diagnosed as requiring restoration. (Devlin, 2006, p. 7)

Also, the DIFOTI does not have the capability to determine depths of lesions. (Barnes, 2005)

Fiber Optic Transillumination - Cariology
Figure 6. Caries on interproximal surface
(Picture credits:
Electro-Optical Sciences, Inc., 2004)

Fiber Optic Transillumination - Cariology
Figure 7. Arrows indicate light scattering with mineral loss on (a) occlusal and (b) buccal surfaces.
(Pretty, Maupomé, 2004)

Quick Links
Homepage| Contents Page | Introduction | Visual-Tactile Caries Diagnosis | Radiography| Fiber-Optic Transillumination (FOTI)
Electrical Conductance | Laser Fluorescence And QLF | Towards The Future: Other New And Emerging Technologies | A Summary



1) Barnes, C. M. (2005). Dental hygiene participation in managing incipient and hidden caries. Dent Clin North Am, 49(4), 795-813, vi-vii.

2) Cappelli DP, Mobley CC. Prevention in Clinical Oral Health Care (2008)

3) Davies, G. M., Worthington, H. V., Clarkson, J. E., Thomas, P., & Davies, R. M. (2001). The use of fibre-optic transillumination in general dental practice. British Dental Journal, 191(3), 145-147.

4) Devlin, H. Operative Dentistry: A Practical Guide to Recent Innovations (2006)

5) Everett K, Fuller B, Gaudry D, Gearhart K, Geller N, Grabowski D, Gustavson M, Harrison J, Haws J, Huneke A. A Review of Treatment Options for the Mild to Moderate Carious Lesion: The Lesion-Specific Approach. Retrieved on 20th October 2009 from

6) Fejerskov O, Kidd EAM. Dental Caries: The Disease and its Clinical Management (2008)

7) Gutierrez C. DIFOTI (Digital Fiberoptic Transillumination): Validität In Vitro. Dissertation, LMU München: Faculty of Medicine. Retrieved on 17th October 2009 from 1)

8) Hintze, H., Wenzel, A., Danielsen, B., & Nyvad, B. (1998). Reliability of visual examination, fibre-optic transillumination, and bite-wing radiography, and reproducibility of direct visual examination following tooth separation for the identification of cavitated carious lesions in contacting approximal surfaces. Caries Research, 32(3), 204-209.

9) Mitropoulos, C. M. (1985). A comparison of fibre-optic transillumination with bitewing radiographs. Br Dent J, 159(1), 21-23.

10) Peers, A., Hill, F. J., Mitropoulos, C. M., & Holloway, P. J. (1993). Validity and reproducibility of clinical examination, fibre-optic transillumination, and bite-wing radiology for the diagnosis of small approximal carious lesions: an in vitro study. Caries Res, 27(4), 307-311.

11) Pieper K, Schurade B. Die Untersuchung mit der Kaltlicht-Diagnosesonde. Dtsch Zahnärztl Z 1987; 42:900-903. Retrieved on 19th October 2009 from

12) Pretty, I. A., & Maupome, G. (2004). A closer look at diagnosis in clinical dental practice: part 5. Emerging technologies for caries detection and diagnosis. J Can Dent Assoc, 70(8), 540, 540a-540i.

13) Pretty, I. A. (2006). Caries detection and diagnosis: Novel technologies. Journal of Dentistry, 34(10), 727-

14) Schneiderman, A., Elbaum, M., Shultz, T., Keem, S., Greenebaum, M., & Driller, J. (1997). Assessment of dental caries with Digital Imaging Fiber-Optic TransIllumination (DIFOTI): in vitro study. Caries Res, 31(2), 103-110.

15) Sidi, A. D., & Naylor, M. N. (1988). A comparison of bitewing radiography and interdental transillumination as adjuncts to the clinical identification of approximal caries in posterior teeth. Br Dent J, 164(1), 15-18.

16) Stephen, K. W., Russell, J. I., Creanor, S. L., & Burchell, C. K. (1987). Comparison of fibre optic transillumination with clinical and radiographic caries diagnosis. Community Dent Oral Epidemiol, 15(2), 90-94.

17) van Rijkom, H. M., & Verdonschot, E. H. (1995). Factors involved in validity measurements of diagnostic tests for approximal caries--a meta-analysis. Caries Res, 29(5), 364-370.

18) Wenzel, A., Verdonschot, E. H., Truin, G. J., & Konig, K. G. (1992). Accuracy of visual inspection, fiber-optic transillumination, and various radiographic image modalities for the detection of occlusal caries in extracted non-cavitated teeth. J Dent Res, 71(12), 1934-1937.

19) Electro-Optical Sciences Inc. (2004) Digital Imaging Fiber- Optic Transillumination. Retrieved on 6 October 2009 from

More pages