Dental caries diagnosis using terahertz spectroscopy and birefringence

Abstract

Dental caries is a widespread chronic infectious disease which may induce a series of oral and general problems if untreated. As a result, early diagnosis and follow-up following radiation-free dental caries therapy are critical. Terahertz (THz) waves with highly penetrating and non-ionizing properties are ideally suited for dental caries diagnosis, however related research in this area is still in its infancy. Here, we successfully observe the existence of THz birefringence phenomenon in enamel and demonstrate the feasibility of utilizing THz spectroscopy and birefringence to realize caries diagnosis. By comparing THz responses between healthy teeth and caries, the transmitted THz signals in caries are evidently reduced. Concomitantly, the THz birefringence is also unambiguously inhibited when caries occurs due to the destruction of the internal hydroxyapatite crystal structure. This THz anisotropic activity is position-dependent, which can be qualitatively understood by optical microscopic imaging of dental structures. To increase the accuracy of THz technology in detecting dental caries and stimulate the development of THz caries instruments, the presence of significant THz birefringence effect induced anisotropy in enamel, in combination with the strong THz attenuation at the caries, may be used as a new tool for caries diagnosis.

Terahertz technology for biophotonics: a general overview and recent advances in THz spectroscopy toward biology

“…Among other examples, one can cite the use of THz imaging for diabetes foot syndrome analysis [4] or [5], and for burn wound cicatrization [6,7]. Another application envisioned from the early beginning is the cavity detection in dentistry [8,9]. Still in biology, but on plants, several reports have mentioned the capability of Terahertz imagining and hyperspectral imaging to retrieve the hydration of plant leaves [10,11].…”

Absorption Spectroscopy in Dental Tissue Analysis

“…To prevent problems with dental caries [1]- [4], dental lesions should be identified as soon as possible so that minimally invasive treatment procedures can be implemented [5]. Besides the most common visual-tactile method, further procedures, including diffuse reflectance spectroscopy, quantitative light-induced fluorescence, and vibrational spectroscopic techniques [6]- [10], can be applied for studies of the structural or elemental features of hard dental tissues. These methods offer safer, objective, and reliable options that can be applied to patients without X-ray exposure.…”

Non-destructive testing of human teeth using microwaves: a state-of-the-art review

“…The diagnosis using conventional methods like staining with a blue dye, examination with a magnifying glass, probing and cold stimulation strongly depends on the experience of the endodontists. Several non-destructive testing (NDT) methods have also been employed, such as ultrasonics [2], oral X-ray, computed tomography (CT), cone-beam computed tomographic (CBCT) imaging [3], micro-CT, magnetic resonance imaging (MRI) [4] and terahertz imaging [5], [6]. Each method has advantages, limitations and field of application.…”