The Use of Optical Coherence Tomography in Dental Diagnostics: A State-of-the-Art Review

Table 1

The OCT facilities and diagnostics in the last 5 years of publications.

Number	Reference number	Author	Title	Significance
(1)	[75]	Shi et al.	Monte Carlo modeling of human tooth optical coherence tomography imaging	This modeling will become a powerful and accurate tool for a preliminary numerical study of the OCT technique on diseases of dental hard tissue in human teeth.
(2)	[76]	Fried et al.	Near-IR imaging of cracks in teeth	Cracks were clearly visible using near-IR imaging at 1300 nm in both in vitro and in vivo images. Cracks and fractures also interfered with light propagation in the tooth aiding in crack identification and assessment of depth and severity.
(3)	[77]	Tom et al.	Near-IR imaging of demineralization under sealants	The wavelength region between 1500–1700 nm yielded the highest contrast of lesions under sealants for near-IR reflectance measurements.
(4)	[78]	Lee et al.	Dental optical coherence tomography: new potential diagnostic system for cracked-tooth syndrome	Crack lines shown in the SS-OCT images had distinct characteristics, and structural crack lines and craze lines could be distinguished in SS-OCT images. Thus, the detection ability of SS-OCT renders it an acceptable diagnostic device for cracked-tooth syndrome.
(5)	[79]	Simon et al.	Near-infrared imaging of secondary caries lesions around composite restorations at wavelengths from 1300–1700 nm	Intensity changes in NIR images at wavelengths ranging from 1300 to 1700 nm correlate with increased mineral loss measured using TMR. NIR reflectance and transillumination at wavelengths coincident with increased water absorption yielded significantly higher () contrast between sound enamel and adjacent demineralized enamel. In addition, NIR reflectance exhibited significantly higher () contrast between sound enamel and adjacent composite restorations than visible reflectance.
(6)	[80]	Chan et al.	Clinical monitoring of smooth surface enamel lesions using CP-OCT during nonsurgical intervention	Even though it appears that most of the lesions manifested little change with fluoride varnish application in the 30 weeks of the study, CP-OCT was able to measure the depth and internal structure of all the lesions including the thickness of the important transparent surface zone located at the surface of the lesions, indicating that CP-OCT is ideally suited for monitoring lesion severity in vivo.
(7)	[81]	Al-Azri et al.	Optical coherence tomography use in the diagnosis of enamel defects	OCT imaging enabled the identification of the type of enamel defect and the determination of the extent of the enamel defects in MIH with the advantage of being a radiation free diagnostic technique.
(8)	[82]	Tezuka et al.	Assessment of cervical demineralization induced by Streptococcus mutans using swept-source optical coherence tomography	The gaps along the dentinoenamel junction were additionally observed in SS-OCT. SS-OCT was capable of monitoring the cervical demineralization induced by a cariogenic biofilm and is considered to be a promising modality for the diagnosis of cervical demineralization.
(9)	[83]	Kang et al.	Enhancement of OCT images with vinyl polysiloxane (VPS)	Vinyl polysiloxane (VPS) impression materials which are routinely used in dentistry can be used to enhance the detection of dentinal lesions on tooth occlusal surfaces.
(10)	[84]	Damodaran; et al.	Optical coherence tomography-based imaging of dental demineralisation and cavity restoration in 840 nm and 1310 nm wavelength regions	Were comparable with that of the widely used 1310 nm OCT system. In the case of restoration with filler material, the 1310 nm OCT imaging displayed better imaging capacity due to lower scattering than 840 nm imaging.
(11)	[85]	Duma et al.	Handheld scanning probes for optical coherence tomography: developments, applications, and perspectives	Two probes are constructed almost entirely from off-the-shelf components, while a third, final variant is constructed with dedicated components, in an ergonomic design. The handheld probes have unidimensional (1D) galvanometer scanners; therefore, they achieve transversal sections through the biological sample investigated—in contrast to handheld probes equipped with bidimensional (2D) scanners that can also achieve volumetric (3D) reconstructions of the samples. These latter handheld probes are therefore also discussed, as well as the possibility to equip them with galvanometer 2D scanners or with Risley prisms. For galvanometer scanners, the optimal scanning functions studied in a series of previous works are pointed out; these functions offer a higher temporal efficiency/duty cycle of the scanning process, as well as artifact-free OCT images.
(12)	[86]	Mahdian et al.	Tissue characterization using optical coherence tomography and cone beam computed tomography: a comparative pilot study	Within the limitations of this ex vivo pilot study, OCT can reliably differentiate between a range of hard and soft tissues.
(13)	[87]	Bakhsh et al.	Ultrastructural features of dentinoenamel junction revealed by focused gallium ion beam milling	The great potential of cryo-FIB in handling different biological tissues having different physical properties, with great precision and accuracy and minimum artefacts.
(14)	[88]	Oguro et al.	The role of enamel thickness and refractive index on human tooth colours	Enamel affected tooth colour, in which n was a statistically significant predictor for tooth colour change.
(15)	[89]	Algarni et al.	Enamel thickness determination by optical coherence tomography: in vitro validation	Human enamel samples were prepared and evaluated with μ-CT and PS-OCT and then sectioned and observed via digital transversal light microscopy. For all methods, a standard transversal section (B-scan) in each sample was selected, and the enamel thickness was measured at three predetermined positions using ImageJ analysis software. The results revealed significant high agreement between all tested methods, indicating the potential of PS-OCT as a clinical tool to effectively measure enamel thickness.
(16)	[90]	Wijesinghe et al.	Bio-photonic detection and quantitative evaluation method for the progression of dental caries using optical frequency domain imaging method	The physicians were able to diagnose the tooth volumetric and thickness changes at an initial stage by considering the obtained results as promising threshold parameters, which will be useful to barricade the progression of caries. To enhance the accuracy of the threshold parameters, quantitative (thickness and volumetric) information of multiple in vivo specimens will be evaluated, averaged, and normalized along with clinical trials in future studies.
(17)	[91]	Watanabe et al.	Resolution characteristics of optical coherence tomography for dental use	This study successfully clarified the resolution characteristics of two types of OCTs. The obtained data may be useful for diagnostic purposes, and the glass chart device used in this study may be useful for OCT quality assurance programmes.
(18)	[92]	Kim et al.	Automatic detection of tooth cracks in optical coherence tomography images	The authors were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.
(19)	[93]	Segarra et al.	Three-dimensional analysis of enamel crack behavior using optical coherence tomography	Crack pattern, tooth type, and the location of the crack on the tooth exhibited a strong correlation. We show that the use of 3D SS-OCT permits for the nondestructive 3D imaging and analysis of enamel crack behavior in whole human teeth in vitro. 3D SS-OCT possesses potential for use in clinical studies for the analysis of enamel crack behavior.
(20)	[94]	Simon et al.	Near-IR and CP-OCT imaging of suspected occlusal caries lesions	Near-IR imaging methods have great potential for improving the early diagnosis of occlusal lesions.
(21)	[61]	Hariri et al.	Effects of structural orientation of enamel and dentine on light attenuation and local refractive index: an optical coherence tomography study.	Unlike enamel, refractive index and OCT signal patterns in dentine vary according to structural orientation, with dentine tubules playing the role. Attenuation of OCT signal intensity was small in enamel. The findings may contribute to a better understanding of the interactions of light with the dental tissue. Precise records of refractive indices and OCT signal patterns may be important for clinical diagnosis of caries and measurement of structural depth for operative purposes using this technology. Effects of dentine structural orientation on refractive index and scattering pattern must be considered when observing human teeth by OCT cross-sectional imaging.