Source: Okayama University (JAPAN), Public Relations Division
For immediate release: 25 December 2020
Okayama University research: Promising imaging method for the early detection of dental caries

(Okayama, 25 December) Researchers at Okayama University report in Scientific Reports that optical coherence tomography, an imaging method based on infrared radiation, can be used for detecting dental caries on the surface of rear teeth. As infrared light is non-ionizing, the method is safer than radiography, which involves X-rays.

Dental caries affects more than 90% of the world’s adult population. And often, dental caries is detected ‘too late’, requiring invasive teeth treatment. Visual examination (by a dentist) and radiography are currently the main tools for diagnosing caries. However, they are not completely efficient for detecting caries in rear teeth (so-called posterior teeth) — moreover, radiography is considered problematic for pregnant women and infants. A promising alternative technique, which is non-invasive and does not involve X-rays, is optical coherence tomography (OCT): an imaging method that can be used to create a 3D representation of teeth. Now, Associate professor SHIMADA Yasushi and Professor YOSHIYAMA Masahiro from Okayama University and colleagues have tested the accuracy of OCT for diagnosing caries in posterior teeth. They found that the method could indeed become a viable alternative for radiography.

In OCT, a sample is irradiated with infrared light; different types of tissue scatter and absorb the infrared radiation differently. Scattering/absorption images (that are 2-dimensional) obtained for many different irradiation angles can then be combined into a 3D visualization of the sample. Because dental caries has a specific response to the radiation, it can be detected on the 3D image — in principle.

To check whether OCT is actually accurate enough for detecting caries in posterior teeth, Associate professor SHIMADA and Professor YOSHIYAMA and colleagues compared radiography and OCT results for 51 proximal surfaces of 36 molars. (The proximal surfaces of teeth are those that are adjacent to other teeth.) The study was performed ex vivo: the molars were mounted in silicone blocks in a way corresponding to their normal anatomical position. The degree of caries present on the surface was marked histologically with a score from 0 to 5, corresponding to “sound tooth surface” and “distinct cavity with visible dentin”, respectively. (Dentin is the material just below the enamel that normally tops a tooth’s surface.)

In order to make a quantitative comparison between radiography and OCT, certain parameters like sensitivity and specificity for the detection of caries were evaluated by 13 dentists. A statistical analysis then led to the conclusion that OCT appears to be a suitable method for diagnosing proximal enamel damage, and for following-up on whether non-invasive treatment — typically based on stopping and reversing the demineralization of the enamel layer — is successful. Quoting the scientists: “OCT can be a safer option for the diagnosis of proximal caries in posterior teeth that can be applied to the patients without X-ray exposure.”

Background
Caries
Dental caries, also known as dental decay or cavities, is the result of the process where acids produced by bacteria break down tooth material. Symptoms of caries can include tooth pain, difficulty with eating; complications can include inflammation of tissue around the affected tooth, its loss, and abscess formation. The acids are produced by bacteria breaking down food rests and/or sugar on the surface of the tooth. The main prevention of dental caries is the regular cleaning of teeth. Treatments of dental caries depend on the extent of destruction. For early-stage caries, non-invasive approaches exist, based on reversing the destruction process by introducing calcium, phosphate and fluoride ions in the oral environment. For later-stage caries, invasive restorative treatments are necessary, or even tooth removal.

To avoid invasive treatments, early detection of caries is crucial. Existing methods are visual examination by a dentist and radiography, but the latter is problematic for pregnant women and infants. Associate professor SHIMADA Yasushi and Professor YOSHIYAMA Masahiro from Okayama University and colleagues have now shown that a technique called optical coherence tomography (OCT) is a promising alternative for the early detection of caries in the rear teeth.

Optical coherence tomography
Optical coherence tomography (OCT) is an imaging technique based on the ability of particular samples, including biological tissue, to scatter or absorb low-coherence radiation. The type of radiation used in OCT is typically near-infrared light. As this is relatively long-wavelength light, it can penetrate well into the scattering sample.

It is possible to combine several 2D images recorded for various irradiation directions into a 3D image (‘3D reconstruction’). Shimada and colleagues applied OCT to examine the surface of teeth, and found that the method allows detecting different stages of caries on the surface of rear teeth.

Reference
Yasushi Shimada, Michael F Burrow, Kazuyuki Araki, Yuan Zhou, Keiichi Hosaka, Alireza Sadr, Masahiro Yoshiyama, Takashi Miyazaki, Yasunori Sumi, Junji Tagami. 3D imaging of proximal caries in posterior teeth using optical coherence tomography. Scientific Reports, (2020) 10:15754.
DOI : 10.1038/s41598-020-72838-2.
https://www.nature.com/articles/s41598-020-72838-2

Correspondence to
Associate professor SHIMADA Yasushi, D.D.S., Ph.D.
Department of Operative Dentistry,
Graduate School of Medicine, Dentistry and Pharmaceutical
Sciences, Okayama University, 2-5-1 Shikata-cho, Kita-ku,
Okayama 700-8525, Japan
e-mail : shimada.ope(a) okayama-u.ac.jp
HP(Japanese) : https://opera.dent.okayama-u.ac.jp/
For inquiries, please contact us by replacing (a) with the @ mark.

Further information
Okayama University
1-1-1 Tsushima-naka , Kita-ku , Okayama 700-8530, Japan
Public Relations Division
E-mail: www-adm(a) adm.okayama-u.ac.jp
For inquiries, please contact us by replacing (a) with the @ mark.
Website: //www.okayama-u.ac.jp/index_e.html
Okayama Univ. e-Bulletin: //www.okayama-u.ac.jp/user/kouhou/ebulletin/
We love OKAYAMA UNIVERSITY: https://www.youtube.com/watch?v=7cXlttQIk3E
Okayama University Image Movie（2020）
https://www.youtube.com/watch?v=BKRoF0tffmA
Okayama University supports the Sustainable Development Goals: https://sdgs.okayama-u.ac.jp/en/


Okayama University Medical Research Updates （OU-MRU）
The whole volume : OU-MRU (1- )
Vol.1：Innovative non-invasive ‘liquid biopsy’ method to capture circulating tumor cells from blood samples for genetic testing
Vol.2：Ensuring a cool recovery from cardiac arrest
Vol.3：Organ regeneration research leaps forward
Vol.4：Cardiac mechanosensitive integrator
Vol.5：Cell injections get to the heart of congenital defects
Vol.6：Fourth key molecule identified in bone development
Vol.7：Anticancer virus solution provides an alternative to surgery
Vol.8：Light-responsive dye stimulates sight in genetically blind patients
Vol.9：Diabetes drug helps towards immunity against cancer
Vol.10：Enzyme-inhibitors treat drug-resistant epilepsy
Vol.11：Compound-protein combination shows promise for arthritis treatment
Vol.12：Molecular features of the circadian clock system in fruit flies
Vol.13：Peptide directs artificial tissue growth
Vol.14：Simplified boron compound may treat brain tumours
Vol.15：Metamaterial absorbers for infrared inspection technologies
Vol.16：Epigenetics research traces how crickets restore lost limbs
Vol.17：Cell research shows pathway for suppressing hepatitis B virus
Vol.18：Therapeutic protein targets liver disease
Vol.19：Study links signalling protein to osteoarthritis
Vol.20：Lack of enzyme promotes fatty liver disease in thin patients
Vol.21：Combined gene transduction and light therapy targets gastric cancer
Vol.22：Medical supportive device for hemodialysis catheter puncture
Vol.23：Development of low cost oral inactivated vaccines for dysentery
Vol.24：Sticky molecules to tackle obesity and diabetes
Vol.25：Self-administered aroma foot massage may reduce symptoms of anxiety
Vol.26：Protein for preventing heart failure
Vol.27：Keeping cells in shape to fight sepsis
Vol.28：Viral-based therapy for bone cancer
Vol.29：Photoreactive compound allows protein synthesis control with light
Vol.30：Cancer stem cells’ role in tumor growth revealed
Vol.31：Prevention of RNA virus replication
Vol.32：Enzyme target for slowing bladder cancer invasion
Vol.33：Attacking tumors from the inside
Vol.34：Novel mouse model for studying pancreatic cancer
Vol.35：Potential cause of Lafora disease revealed
Vol.36：Overloading of protein localization triggers cellular defects
Vol.37：Protein dosage compensation mechanism unravelled
Vol.38：Bioengineered tooth restoration in a large mammal
Vol.39：Successful test of retinal prosthesis implanted in rats
Vol.40：Antibodies prolong seizure latency in epileptic mice
Vol.41：Inorganic biomaterials for soft-tissue adhesion
Vol.42：Potential drug for treating chronic pain with few side effects
Vol.43：Potential origin of cancer-associated cells revealed
Vol.44：Protection from plant extracts
Vol.45：Link between biological-clock disturbance and brain dysfunction uncovered
Vol.46：New method for suppressing lung cancer oncogene
Vol.47：Candidate genes for eye misalignment identified
Vol.48：Nanotechnology-based approach to cancer virotherapy
Vol.49：Cell membrane as material for bone formation
Vol.50：Iron removal as a potential cancer therapy
Vol.51：Potential of 3D nanoenvironments for experimental cancer
Vol.52：A protein found on the surface of cells plays an integral role in tumor growth and sustenance
Vol.53：Successful implantation and testing of retinal prosthesis in monkey eyes with retinal degeneration
Vol.54：Measuring ion concentration in solutions for clinical and environmental research
Vol.55：Diabetic kidney disease: new biomarkers improve the prediction of the renal prognosis
Vol.56：New device for assisting accurate hemodialysis catheter placement
Vol.57：Possible link between excess chewing muscle activity and dental disease
Vol.58：Insights into mechanisms governing the resistance to the anti-cancer medication cetuximab
Vol.59：Role of commensal flora in periodontal immune response investigated
Vol.60：Role of commensal microbiota in bone remodeling
Vol.61：Mechanical stress affects normal bone development
Vol.62：3D tissue model offers insights into treating pancreatic cancer
Vol.63：Promising biomarker for vascular disease relapse revealed
Vol.64：Inflammation in the brain enhances the side-effects of hypnotic medication
Vol.65：Game changer: How do bacteria play Tag ?
Vol.66：Is too much protein a bad thing?
Vol.67：Technology to rapidly detect cancer markers for cancer diagnosis
Vol.68：Improving the diagnosis of pancreatic cancer
Vol.69：Early gastric cancer endoscopic diagnosis system using artificial intelligence
Vol.70：Prosthetics for Retinal Stimulation
Vol.71：The nervous system can contribute to breast cancer progression
Vol.72：Synthetic compound provides fast screening for potential drugs
Vol.73：Primary intraocular lymphoma does not always spread to the central nervous system
Vol.74：Rising from the ashes—dead brain cells can be regenerated after traumatic injury
Vol.75：More than just daily supplements — herbal medicines can treat stomach disorders
Vol.76：The molecular pathogenesis of muscular dystrophy-associated cardiomyopathy
Vol.77：Green leafy vegetables contain a compound which can fight cancer cells
Vol.78：Disrupting blood supply to tumors as a new strategy to treat oral cancer
Vol.79：Novel blood-based markers to detect Alzheimer’s disease
Vol.80：A novel 3D cell culture model sheds light on the mechanisms driving fibrosis in pancreatic cancer
Vol.81：Innovative method for determining carcinogenicity of chemicals using iPS cells
Vol.82：Making memories — the workings of a neuron revealed
Vol.83：Skipping a beat — a novel method to study heart attacks
Vol.84：Friend to Foe—When Harmless Bacteria Turn Toxic