Fiber Bragg grating-based method for measuring mesiodistal tooth displacement and force under physiological...

Real-time measurement of mesiodistal displacement and force on teeth is a classic challenge in dentistry. In this paper, a fiber Bragg grating (FBG) sensor system was developed and evaluated for real-time measurement of mesiodistal tooth displacement and force under physiological conditions. The sensing element was integrated into a 0.018×0.025in. nickel-titanium orthodontic archwire and bonded to the brackets of the maxillary central incisors. Micro-movements of the tooth induce bending of the FBG, producing a measurable wavelength shift that is decoded into displacement and force. System performance was first characterized in vitro using a calibrated dynamometer to apply vertical loads on a dental model, demonstrating a linear response between the applied force and both mesiodistal displacement and force. Under a 1 N vertical load, the system measured a strain deviation of 8.56±2.83µε, corresponding to a displacement of 0.07±0.02µm and a mesiodistal force of 0.20±0.07N. In vivo validation was performed with five healthy volunteers during biting and chewing tasks with foods of varying hardness. Distinct biomechanical patterns were recorded, with significant differences in displacement and force associated with different food types. The FBG-based system successfully captured dynamic intraoral forces and tooth movements, demonstrating its stability and feasibility for direct biomechanical monitoring in the oral environment. This approach provides a quantitative optical sensing tool for studying orthodontic mechanics and dental function in real time.