Compact and portable device for caries diagnosis

We are developing a compact and portable device named "HAMILTOM (Hardness Meter using Indenter with Light for Tooth Monitoring)," which can easily measure tooth hardness using light. In the super-aging society, the management of root caries is an important issue because the gingiva of over 40s generation recedes, resulting in the root of the tooth exposed and caries is easily occurred at the root that is not covered with hard enamel. Although X-ray radiography, laser-induced fluorescence, and optical coherence tomography are used to examine caries at the crown covered with enamel, they are not suitable for root caries. Therefore, the diagnosis of root caries is based on visual examination and palpation. However, there is no clear color change in early root caries and palpation with a probe is dependent on the dentist's skills.
In the HAMILTOM system, light from an LED is injected into a transparent, 90-degree conical indenter, and the light reflected by the indenter is reflected toward the camera by a beam splitter, and the indenter tip is magnified by a lens to form an image on the camera. If nothing touches the indenter, total reflection occurs at the boundary between the indenter and air, and the indenter appears bright. On the other hand, when a tooth touches the indenter, total reflection does not occur because the refractive indices of the indenter and the tooth are both about 1.5, and the reflectance significantly decreases. The indenter is brought into contact with the tooth while the load applied to the indenter tip is measured. When the load reaches the specified value, the camera captures the image and the contact area appears dark. If the contact load is constant, the contact area is small on a healthy hard tooth, and the darkened area is small, but on a soft caries tooth, the contact area becomes large and the darkened area increases. Therefore, the area of the darkened area can be measured to determine the hardness. Since the measurement is performed with a small hand-held device, it is possible to measure the hardness of living teeth.
This device will make it possible to measure the hardness of living teeth in a clinical setting and to measure changes in hardness over time. It is expected to improve our understanding of the mechanisms of caries progression and treatment from physical and chemical perspectives. Based on this knowledge, development of minimally invasive dental diagnosis and treatment based on scientific evidence can be expected.