Fiber Optic Displacement Sensor for Scanning and Reconstructing Occlusal Surface of Human Tooth A. I. Che Ani, M. H. Abbas, Siti Salwa Mat Isa, R. Baharudin Faculty of Electrical Engineering Universiti Teknologi MARA Pulau Pinang, Malaysia email@example.com Husna Abdul Rahman, Sulaiman Wadi Harun Photonics Research Centre, Department of Physics Faculty of Science, University of Malaya Kuala Lumpur, Malaysia Abstract — In dentistry, often dental radiography is related to teeth occlusal surface, which can be used for diagnostic and treatment purposes. Nonetheless the exposure of X-Ray dose may limit the usage of this technique. This paper presents the image construction from the occlusal surface of human teeth. The principle of the surface construction is from the exploitation of reflected light intensities along the occlusal surface of human teeth. The image of occlusal surface is constructing back using simple MatLab software. The measured diameter from the images of occlusal surface for molar A and molar B is to be 7.0 mm and 7.5 mm, respectively, which is exactly the same when measured with micrometer. The average surface roughness for each tooth sample namely molar A and molar B is obtained to be 742 μm and 975 μm, respectively. Such results are useful for detecting the occlusal topography and surface profile of human teeth.
Keywords:Fiber optic displacement sensor,Occlusalsurface, dental laser tips
In modern orthodontic, the accurate representation of occlusal surface for human teeth is required for diagnostic and treatment purposes. The accurate representation of human teeth will integrates examination of malocclusion correction, design for prosthetic tooth thus repair for patient tooth and restore the shape and function of the tooth . Nowadays, despite of X-ray which is dominant as scanning method , several type of dental CAD/CAM systems are also available in the world . But, the widespread of these methods are still hindered due to factors such as cost and complex of operation . One of the human teeth surface reconstruction technique is using shape-from-shading (SFS) but the image representation hindered by non-friendly image acquisition environment. A. Abdelrahim et.al has introduced a more realistic formulation of SFS taking into account the non -friendly factors such as the camera, the light source and the surface reflectance . Others technique used hybrid differential method (HDM) is proposed to handle the search and pattern matching for a specific picture. Z. Xitao et.al has proposed an extended HDM for image reconstructing of teeth occlusal view with further analysis of the HDM chart so the more appealing feature of the match point can be revealed. The technique is proved to be effective for single tooth recognition but limited to the anterior view of the teeth searching and recognition . Furthermore S.-X. Zheng et.al addressed a novel technique of 3D morphing for occlusal tooth surface reconstruction . However the 3D morphing algorithm needs to be optimized to add more feature points to improve the surface deformation accuracy.
Biophotonics is the study of the interaction of light with biological materials. Among the biophotonics applications, optical sensors possess various advantages in electrical sensing technologies, which make it interesting for many other areas especially dentistry. The advantages include the safety in chemically or explosive environment and most important is low susceptibility to electromagnetic interference. Development of optical based sensor in dentistry includes the visual technique using the fiber optic sensor technology. The advantages of this method are the ability to help discriminate between early enamel and early dentin lesions. Furthermore it can be used for the detection of caries on all surfaces and is particularly useful at proximal lesions make it one would expect this method to be at least as effective as a visual examination . In other hand, researchers  used polymer optical fiber on the measurement of orthodontic forces. The suggested polymer optical fiber had allowed to control the applied forces that displace a tooth or segment of teeth may cause permanent damage at periodontal ligament.
Fiber optic displacement sensor (FODS) has potential into a new choice of technique for scanning and reconstructing the image of tooth surface [10, 11]. The FODS has shown its potential for various dental application and offer the benefit of low optical signal transmission loss, low production cost, and suitable for employment in harsh environments . This paper intends to use FODS as a quantitative technique for the image of occlusal surface of human tooth. In our proposed technique it uses multimode plastic fibers as the probe together with a red He-Ne laser as a transmitter. The intensity of the reflected light from the tooth surface is recorded and used to determine the distance between the tooth surface and probe. In our approach, the occlusal surface of the tooth namely molar is achieved from the function of lateral movement ( x and y axis) along the tooth surface while being maintained in perpendicular and constant in axial position ( z axis). The image is constructing into 2D and 3D images using the Matlab 3D mesh surface plots.
he experiment prove that FODS can distinguish the intensity of reflected light on the occlusal surface of human tooth namely molar, which is useful for scanning and reconstructing the occlusal surface image. The scanning method can be classified as a non-destructive for quantitative scanning and imaging of molar occlusal surface in a non- contact mode. Dental practitioner may utilize this method to determine abnormalities on the tooth occlusal surface. There will be different reflected light intensity value on abnormalities such as dental cavity thus can lead to distinguish the abnormalities region. However the main limitation of proposed FODS is longer data scanning time when about 30 minutes was taken for each tooth sample and the high equipment and maintenance cost involved in the devices. These limitations can solved with aid of picomotor actuators which can reduce the scanning time. Furthermore the use of computer image processing will increase the accuracy of reconstructing the occlusal surface image.
This paper has introduced a fiber optic sensor for scanning and reconstructing images of occlusal surface for human tooth namely molar. The system of the sensor used He-Ne laser as the light source that transmit via a multimode plastic bundled fiber and a silicon photo detector to detect the intensity of reflected light. The recorded intensity of reflected light is used to construct the 3D and 2D occlusal surface image by using Matlab software. The results indicate the same diameter value measured with micrometer of the occlusal surface for molar A and molar B to be 7.0 mm and 7.5mm, respectively. Furthermore the average surface roughness for both molar A and molar B tooth sample is calculated to be 742 μm and 975 μm, respectively. The results show that with propose displacement sensor technique can visualize the occlusal surface of human tooth. This will help the dental researcher in the characterization and evaluation of occlusal surface for human tooth.