title: Fiber Bragg grating sensor for measurement of impact absorption capability of mouthguards.
abstract: BACKGROUND
  There is no standard technique to monitor impact absorption capability of mouthguards. Earlier investigations have established that strain transferred to the teeth through mouthguard is a good indication of their efficiency. In the present study, a unique experimental scheme utilizing fiber Bragg gratings (FBGs) as distributed strain sensors is proposed and investigated to estimate impact absorption capability of custom-made mouthguard. The proposed methodology is useful due to advantages such as, very small size and flexibility for ease of bonding, self-referencing, and multiplexing capability of using FBG sensors.
  
  
  METHODS
  Finite-element analysis was performed to simulate the stress distribution due to impact on the mouthguard. The FBGs were fabricated by exposing the core of photosensitive fiber to intense Ultra-Violet light through a 'phase mask'. One FBG sensor was bonded on the jaw model and another on the mouthguard surface at similar positions, so that both gratings are simultaneously affected by impact. Two different sets of the sensors were used, one for the anterior region and another for posterior region. The impact was produced using customized pendulum device with interchangeable impact objects i.e. cricket ball, hockey ball, and steel ball. Response of gratings was monitored using optical spectrum analyzer and strain induced due to each impact was determined from the Bragg wavelength shifts for each grating.
  
  
  CONCLUSIONS
  Strain induced due to impact was calculated from the Bragg wavelength shifts. Difference in the strain values for the two gratings is interpreted as impact energy absorbed by the mouthguard. The Bragg wavelength shifts (induced strain) for FBG bonded on the jaw model was much lower than the shift for FBG bonded on the mouthguard, indicating that most of the impact energy is absorbed by the mouthguard.
authors.affiliation: Central Scientific Instruments Organisation (Council of Scientific and Industrial Research, New Delhi), Chandigarh, India.
authors.forename: Umesh
authors.initials: U
authors.lastname: Tiwari
authors.forename: Vandana
authors.initials: V
authors.lastname: Mishra
authors.forename: Ashish
authors.initials: A
authors.lastname: Bhalla
authors.forename: Nahar
authors.initials: N
authors.lastname: Singh
authors.forename: Subhash C
authors.initials: SC
authors.lastname: Jain
authors.forename: Harry
authors.initials: H
authors.lastname: Garg
authors.forename: Suryanarain
authors.initials: S
authors.lastname: Raviprakash
authors.forename: Navneet
authors.initials: N
authors.lastname: Grewal
authors.forename: Pawan
authors.initials: P
authors.lastname: Kapur
mesh_terms: D000042:Absorption; D003198:Computer Simulation; D003799:Dental Stress Analysis / Q000295:instrumentation* / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D008953:Models, Anatomic; D009064:Mouth Protectors; D055100:Optical Fibers; D012815:Signal Processing, Computer-Assisted; D013314:Stress, Mechanical; D014466:Ultraviolet Rays