{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T03:22:43Z","timestamp":1769052163241,"version":"3.49.0"},"reference-count":22,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2024,2,23]],"date-time":"2024-02-23T00:00:00Z","timestamp":1708646400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI)","doi-asserted-by":"publisher","award":["19KK0259"],"award-info":[{"award-number":["19KK0259"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Salivary turbidity is a promising indicator for evaluating oral hygiene. This study proposed a wearable mouthguard-type sensor for continuous and unconstrained measurement of salivary turbidity. The sensor evaluated turbidity by measuring the light transmittance of saliva with an LED and a phototransistor sealed inside a double-layered mouthguard. The sensor was also embedded with a Bluetooth wireless module, enabling the wireless measurement of turbidity. The mouthguard materials (polyethylene terephthalate-glycol and ethylene-vinyl acetate) and the wavelength of the LED (405 nm) were experimentally determined to achieve high sensitivity in salivary turbidity measurement. The turbidity quantification characteristic of the proposed sensor was evaluated using a turbidity standard solution, and the sensor was capable of turbidity quantification over a wide dynamic range of 1\u20134000 FTU (formazine turbidity unit), including reported salivary turbidity (400\u2013800 FTU). In vitro turbidity measurement using a saliva sample showed 553 FTU, which is equivalent to the same sample measured with a spectrophotometer (576 FTU). Moreover, in vivo experiments also showed results equivalent to that measured with a spectrophotometer, and wireless measurement of salivary turbidity was realized using the mouthguard-type sensor. Based on these results, the proposed mouthguard-type sensor has promising potential for the unconstrained continuous evaluation of oral hygiene.<\/jats:p>","DOI":"10.3390\/s24051436","type":"journal-article","created":{"date-parts":[[2024,2,23]],"date-time":"2024-02-23T04:31:23Z","timestamp":1708662683000},"page":"1436","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Mouthguard-Type Wearable Sensor for Monitoring Salivary Turbidity to Assess Oral Hygiene"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5864-0460","authenticated-orcid":false,"given":"Kenta","family":"Ichikawa","sequence":"first","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), Tokyo 101-0062, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5608-8863","authenticated-orcid":false,"given":"Kenta","family":"Iitani","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), Tokyo 101-0062, Japan"}]},{"given":"Gentaro","family":"Kawase","sequence":"additional","affiliation":[{"name":"Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1683-1496","authenticated-orcid":false,"given":"Koji","family":"Toma","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), Tokyo 101-0062, Japan"},{"name":"Department of Electronic Engineering, College of Engineering, Shibaura Institute of Technology, Tokyo 135-8548, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1555-1281","authenticated-orcid":false,"given":"Takahiro","family":"Arakawa","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), Tokyo 101-0062, Japan"},{"name":"Department of Electric and Electronic Engineering, Tokyo University of Technology, Tokyo 192-0982, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6348-0879","authenticated-orcid":false,"given":"Dzung Viet","family":"Dao","sequence":"additional","affiliation":[{"name":"School of Engineering and Built Environment, Griffith University, Southport 4222, Australia"},{"name":"Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan 4111, Australia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0709-4957","authenticated-orcid":false,"given":"Kohji","family":"Mitsubayashi","sequence":"additional","affiliation":[{"name":"Department of Biomedical Devices and Instrumentation, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), Tokyo 101-0062, Japan"},{"name":"Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan"}]}],"member":"1968","published-online":{"date-parts":[[2024,2,23]]},"reference":[{"key":"ref_1","first-page":"30","article-title":"The Effects of Oral Health on Systemic Health","volume":"65","author":"Kane","year":"2017","journal-title":"Gen. Dent."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"547","DOI":"10.1128\/CMR.13.4.547","article-title":"Systemic Diseases Caused by Oral Infection","volume":"13","author":"Li","year":"2000","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"6365","DOI":"10.1038\/s41598-020-63222-1","article-title":"Quantitative Analysis of Salivary Oral Bacteria Associated with Severe Early Childhood Caries and Construction of Caries Assessment Model","volume":"10","author":"Zhang","year":"2020","journal-title":"Sci. Rep."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1111\/prd.12100","article-title":"Salivary Biomarkers for Dental Caries","volume":"70","author":"Gao","year":"2016","journal-title":"Periodontol. 2000"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1111\/j.1600-0757.2010.00361.x","article-title":"Bacterial and Viral Pathogens in Saliva: Disease Relationship and Infectious Risk","volume":"55","author":"Slots","year":"2011","journal-title":"Periodontol. 2000"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1041","DOI":"10.1111\/j.1469-0691.2007.01802.x","article-title":"Oral Infections and Systemic Disease\u2014An Emerging Problem in Medicine","volume":"13","author":"Rautemaa","year":"2007","journal-title":"Clin. Microbiol. Infect."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"577","DOI":"10.1038\/s41415-019-0794-5","article-title":"Periodontitis and Diabetes","volume":"227","author":"Preshaw","year":"2019","journal-title":"Br. Dent. J."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1111\/jcpe.13189","article-title":"Periodontitis and Cardiovascular Diseases: Consensus Report","volume":"47","author":"Sanz","year":"2020","journal-title":"J. Clin. Periodontol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.archger.2005.09.002","article-title":"Oral Hygiene Evaluation for Effective Oral Care in Preventing Pneumonia in Dentate Elderly","volume":"43","author":"Abe","year":"2006","journal-title":"Arch. Gerontol. Geriatr."},{"key":"ref_10","first-page":"116","article-title":"The Role of Dental Plaque Biofilm in Oral Health","volume":"81","author":"Gurenlian","year":"2007","journal-title":"Am. Dent. Hyg. Assoc."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Paqu\u00e9, P.N., Herz, C., Jenzer, J.S., Wiedemeier, D.B., Attin, T., Bostanci, N., Belibasakis, G.N., Bao, K., K\u00f6rner, P., and Fritz, T. (2020). Microbial Analysis of Saliva to Identify Oral Diseases Using a Point-of-Care Compatible QPCR Assay. J. Clin. Med., 9.","DOI":"10.3390\/jcm9092945"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"16124","DOI":"10.1038\/s41598-019-52445-6","article-title":"Comparison of Oral Microbiome Profiles in Stimulated and Unstimulated Saliva, Tongue, and Mouth-Rinsed Water","volume":"9","author":"Jo","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1038\/s41598-021-04612-x","article-title":"Comparison of Oral Metabolome Profiles of Stimulated Saliva, Unstimulated Saliva, and Mouth-Rinsed Water","volume":"12","author":"Maruyama","year":"2022","journal-title":"Sci. Rep."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"183","DOI":"10.3109\/00016357.2011.654258","article-title":"The Relationship between Turbidity of Mouth-Rinsed Water and Oral Health Status","volume":"71","author":"Takeuchi","year":"2013","journal-title":"Acta Odontol. Scand."},{"key":"ref_15","first-page":"133","article-title":"Saliva in the Diagnosis of Diseases","volume":"8","author":"Zhang","year":"2016","journal-title":"Nat. Publ. Group"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Farag\u00f3, P., G\u0103l\u0103tu\u0219, R., Hintea, S., Bo\u0219ca, A.B., Feurdean, C.N., and Ilea, A. (2019). An Intra-Oral Optical Sensor for the Real-Time Identification and Assessment of Wine Intake. Sensors, 19.","DOI":"10.3390\/s19214719"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1016\/S0160-4120(00)00107-0","article-title":"Monitoring Natural Organic Matter in Water with Scanning Spectrophotometer","volume":"26","author":"Wang","year":"2001","journal-title":"Environ. Int."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"906","DOI":"10.1016\/j.talanta.2005.11.033","article-title":"Frequency-Selective Absorbance Detection: Refractive Index and Turbidity Compensation with Dual-Wavelength Measurement","volume":"69","author":"Eom","year":"2006","journal-title":"Talanta"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Ahn, J.-H., and Park, Y.-J. (2020). Estimating Water Reflectance at Near-Infrared Wavelengths for Turbid Water Atmospheric Correction: A Preliminary Study for GOCI-II. Remote Sens., 12.","DOI":"10.3390\/rs12223791"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"265","DOI":"10.5978\/islsm.15-OR-16","article-title":"405 nm diode laser, halogen lamp and LED device comparison in dental composites cure: An \u201cin vitro\u201d experimental trial","volume":"24","author":"Fornaini","year":"2015","journal-title":"Laser Ther."},{"key":"ref_21","first-page":"1315","article-title":"Wireless Unconstrained Monitoring of Intra-Oral Temperature Using Thermistor and Telemeter Sealed in Mouthguard","volume":"35","author":"Iitani","year":"2023","journal-title":"Sens. Mater."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"12201","DOI":"10.1021\/acs.analchem.0c01201","article-title":"A Wearable Cellulose Acetate-Coated Mouthguard Biosensor for In Vivo Salivary Glucose Measurement","volume":"92","author":"Arakawa","year":"2020","journal-title":"Anal. Chem."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/5\/1436\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T14:03:37Z","timestamp":1760105017000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/5\/1436"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,2,23]]},"references-count":22,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2024,3]]}},"alternative-id":["s24051436"],"URL":"https:\/\/doi.org\/10.3390\/s24051436","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,2,23]]}}}