Clinical Applications for Optical Coherence Tomography

In dentistry, optical coherence tomography (OCT) is used to support diagnosis, treatment planning and patient education. Providing a localized, digital image in real time, this modality can help clinicians evaluate the margins of oral lesions, detect caries or tooth fractures, and support the diagnosis of periodontal disease. It is also useful in measuring caries preparations for restorations created by computer-aided design/computer-aided manufacturing (CAD/CAM) technology.

This technique was developed into a cross-sectional imaging modality by Huang et al1 in 1991. It was first applied in ophthalmology with a focus on the retina, optic nerve and coronary arteries.¹ In 1997, Sergeev et al² presented OCT applications in vivo for the respiratory mucosa, gastrointestinal, urinary and genital tracts. Today, OCT is used in medicine in the diagnosis and treatment of glaucoma, during guided surgical procedures, and for intracoronary imaging (Figure 1).

The technology was first used in dentistry in the late 1990s. As one example, Baumgartner et al³ used the technique to better understand the cross-sectional imaging of dental structures. In 2000, Otis et al⁴ described the use of OCT in imaging hard and soft tissues, as well as restorative materials. In 2002, the U.S. Food and Drug Administration approved the use of OCT in dentistry.

Images captured with OCT are presented in a three-dimensional (3D) format. In comparison to two-dimensional radiography, with its limited contrast and resolution, dental OCT offers improved resolution and increased contrast among areas of examination.⁵ This modality uses electromagnetic radiation, which does not emit the same type of mutagenic interaction as traditional radiography technologies.⁶

An OCT unit consists of a small, wand-like apparatus with a tip that is used to acquire the image. In producing an image, a broadband light source is released and then separated, with one light source directed to a mirror, and the other pointed to the specified area in the oral cavity. A reflection is created from the mirror and tissue of the oral cavity. This reflection is recombined at the original splitter to produce a transmission that is sent to a receptor. The receptor configures the transmission and creates an image of the dental tissue via a computerized processor.⁵ As with digital radiography, special software enables manipulation of the image for optimal clinical viewing.

CLINICAL APPLICATIONS

Valuable for the early detection of demineralization,⁵ OCT can be can be particularly useful in evaluating the occlusal surfaces of posterior teeth — which are some of the most difficult areas to assess for caries. What may appear as a stain could actually be the early progression of caries. During a clinical exam, the use of an explorer may not prove adequate for the detection of early caries lesions. And because of their limited resolution and contrast, traditional radiographs may not indicate this initial progression of demineralization. By comparison, OCT provides a real-time image of the specific area in a more detailed format, allowing the dental team to better evaluate the area for specific treatment. It can also help clinicians determine if recurrent decay is present after restoration placement, as OCT enhances margin visualization.

As noted, this imaging modality is helpful for detecting and evaluating fractures within the tooth.⁷ Oral health professionals can also use this technique to ensure success during sealant placement. As the surfaces to be sealed must be free of early demineralization, OCT can be used to evaluate the tooth surface and verify that demineralization is not a factor.⁸ And because caries can sometimes progress under sealants, these images can also provide an enhanced view of questionable areas or early issues that may not be readily apparent, either radiographically or to the unassisted eye.

Clinicians may also utilize OCT during periodontal health assessments. Probing depths, clinical visualization and radiographs are key tools when assessing periodontal health. Bone height and periodontal ligament structure may be altered, yet not ­interpreted, however, due to limited accessibility to these areas. Traditional radiography may not demonstrate the bone loss on one side of the dentition due to superimposition caused by one bone surface being higher than the other.⁹ By comparison, OCT allows a 3D examination of alterations in bone structure to determine where periodontal issues are specifically occurring.

The use of OCT may aid in the detection of oral cancers.⁵ It can provide information about the stage of a tumor, including premalignancy and malignancy status. This modality can also assist clinicians in determining the extent of a lesion through the technology’s improved contrast capabilities and opportunity to evaluate the lesion via 3D imaging.⁵ In addition, it can be helpful when determining recurrence risk and predicting tumor response once treatment begins.⁵

Newer studies have looked at the use of OCT to obtain impressions from intraoral preparations, which would assist in the creation of indirect restorations using in-office CAD/CAM technology.¹⁰ After the preparation is complete, an OCT unit can be used to scan the tooth, depict the margins of the preparation, and send an image to the CAD/CAM unit for design and fabrication of the restoration. This technology would eliminate the need for conventional impressions, which are cumbersome, messy and time consuming, while also reducing the cost of materials.

key takeaways

• First used in dentistry in the late 1990s, optical coherence tomography’s (OCT) enhanced imaging capability supports definitive diagnosis and treatment planning.
• Compared to two-dimensional radiography, OCT images are presented in a three-dimensional (3D) format and offer improved resolution and contrast.⁶
• These images can be used to detect caries or tooth fractures, support the diagnosis of periodontal disease, and evaluate oral lesions.
• This imaging modality can be valuable for early detection of demineralization.⁶ And because it enhances margin visualization, OCT can help clinicians determine if recurrent decay is present after placement of restorations.
• The use of OCT may aid in the detection of oral cancers. It can provide information about the extent of a lesion and tumor stage, including premalignancy and malignancy status.
• Studies have looked at the use of OCT to capture impressions, which would assist in the creation of indirect restorations using computer-aided design/computeraided manufacturing technology.¹¹
• This imaging modality supports patient education efforts, as sharing 3D images may encourage patients to accept — and adhere to — treatment plans.

PATIENT EDUCATION

Patient education efforts are also enhanced through the use of OCT. Charting of probing depths, intraoral photos and radiographs are all used to educate patients about the presence of periodontal disease and proposed treatment. Providing an enhanced 3D image further educates the patient about his or her condition, and directs focus on specific areas that may not be seen in radiographs. Analyses of both bone and the periodontal ligament could help patients understand the importance of the attachment apparatus. This imaging modality may assist oral health professionals in explaining surgical versus nonsurgical treatment.

As the U.S. population of older adults continues to grow, more patients will present with their natural dentition intact. The use of OCT during diagnosis and patient education may encourage older adults to adhere to proposed treatment plans to help them avoid tooth loss. Patients are more likely to agree to treatment and comply with the suggested regimen when enhanced visual aids are used.

In conclusion, OCT’s ability to provide the dental team with a different vantage point and enhanced imaging supports definitive diagnosis and treatment planning. Although this modality has been available in the dental setting for some time, its use in dentistry has not reached its full potential. As with any technology, gradual improvements are being made to boost image quality and reduce cost so OCT can be implemented more easily into daily dental practice.

References

1. Huang D, Swanson EA, Lin CP, et al. Optical coherence tomography. Science. 1991;254:1178–1181.
2. Sergeev A, Gelikonov V, Gelikonov G, et al. In vivo endoscopic OCT imaging of precancer and cancer states of human mucosa. Opt Express. 1997;1:432–440.
3. Baumgartner A, Dichtl S, Hitzenberger CK, et al. Polarization-sensitive optical coherence tomography of dental structures. Caries Res. 2000;34:59–69.
4. Otis LL, Everett MJ, Sathyam US, Colston BW Jr. Optical coherence tomography: a new imaging technology for dentistry. J Am Dent Assoc. 2000;131:511–514.
5. Hsieh Y, Ho YC, Lee SY, et al. Dental optical coherence tomography. Sensors. 2013;13:8928–8949.
6. Azevedo CS, Trung LC, Simionato MR, Freitas AZ, Matos AB. Evaluation of caries-affected dentin with optical coherence tomography. Braz Oral Res. 2011;25:407–413.
7. BioOptics World. Optical Coherence Tomography/Dentistry: Driving OCT into Dentistry. Available at: bioopticsworld.com/articles/ print/volume-7/issue-1/features/optical-coherence-tomography-dentistry-driving-oct-into-dentistry.html. Accessed April 19, 2016.
8. Holtzman JS, Osann K, Pharar J, et al. Ability of optical tomography to detect caries beneath commonly used sealants. Lasers Surg Med. 2010;42:752–759.
9. Freitas AZ, Zezell DM, Vieira ND Jr, Ribeiro AC, Gomes ASL. Imaging carious human dental tissue with optical coherence tomography. J Applied Phys. 2006;99(2):024906.
10. Chityala R, Vidal C, Jones R. Utilizing optical coherence tomography for CAD/CAM of indirect dental restorations. Proc SPIE. 2013;8566.