1
Experimental FBG Sensing System and FEA for the Analysis of Dental Macro Implants Paulo A. Lopes, Ilda Abe, Marcelo W. Schiller Paulo A. Lopes, Ilda Abe, Marcelo W. Schiller Department Department of of Physics Physics , , University University of of Aveiro Aveiro Campus Universitário de Santiago, 3810 Campus Universitário de Santiago, 3810-193 Aveiro, Portugal 193 Aveiro, Portugal e-mail : mail : [email protected] [email protected] ABSTRACT: In this work Fiber Bragg Grating sensors (FBG) are used to assess the strain profile of macro dental implants under external loads and the results are compared to the BGPP/SENSORS Joint Poster Session - Session: JThA (Pres. number: JThA3) Optical Sensors (Sensors) OSA Optics & Photonics Congress of macro dental implants under external loads and the results are compared to the corresponding Finite Element Analysis (FEA). FBG vs. Finite Element Analysis Macro dental implants under study Comparison between numerical and experimental results for a 50N static load Metal-plastic implant was used 5 specific locations of interest along an axis paralel to the implant A 6×6×6 cm 3 cube made of bovine fresh bone was used as surrounding media FEA and experimental results agree very reasonably Load transfer is higher around the lower part of the implant FBG are being applied to assess strains in different types of engineering applications. Some Biomechanic studies have also used these sensing elements which present, relatively to conventional strain gauges, some advantages: FBG are non electric devices, less intrusive and of small dimensions. FBG were used to measure the strain pattems, at several locations, in bone surface, around implants attached to bovine fresh bones. FBG FBG is a periodic perturbation of the refractive index along the fiber length which is formed by exposure of the core to an intense optical interference pattern The first one was made only in steel alloy, the second was made combining steel alloy and plastic ABS and the third one was 3 dental macro-implants Component Material Young modulus (E) Poisson coeficient (n) Dental implant ABS Plastic 2,32 GPa 0,3 Bone Cancellous bone 1,37 GPa 0,33 51 FBG FBG in horizontal Optical Fibers 30 40 50 60 Y (mm) H11 H12 H13 H14 V15 V14 H15 H21 H31 H41 H22 H32 H42 V25 V24 H23 H33 H43 H24 H34 H44 H25 H35 H45 0 20 40 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Z (mm) H61 H51 H41 H31 H21 H62 H52 H42 H32 H22 H63 H53 H43 H33 H23 H64 H54 H44 H34 H24 V 23 V 24 V 25 H65 H55 H45 H35 H25 X (mm) V31 V32 V33 H11 H81 H71 H12 H82 H72 H13 V11 V12 V13 V14 V15 H83 H73 H14 H84 H74 H15 H85 H75 Y (mm) H1n H2n H3n H4n H5n H6n H7n H8n FBG in vertical Optical Fibers and the third one was made only in plastic ABS. Three types of dental implant macro models, manufactured based on the Brânemark system of Nobel Biocare, have been used. 40 FBG distributed by 8 optic fibers were used (see figure) to evaluate the occurrence of transverse strain around the implant In this work the performance of 3 dental implants composed of different materials (ABS plastic, a combination of metal and plastic and metal) are to be compared for future selection. Their performance is evaluated by measuring the load transfer distribution around the implant caused by static loads of several magnitudes. That load distribution is measured by 51 FBG in 8 different optical fibers, 3 of which were inserted vertically and the remaining 5, horizontally As surround media a nylon cube with dimensions 6,5×6,5×6,5 has been used (more homogeneous than bone) 0 20 40 60 0 10 20 30 40 50 60 0 10 20 30 X (mm) H71 H81 H72 H82 H73 H83 V13 V12 V11 V33 V32 V31 H74 H84 H51 H61 H75 H85 H52 H62 V23 H53 H63 H54 H64 H55 H65 Z (mm) 0 10 20 30 40 50 60 0 20 40 60 0 10 20 30 40 50 60 H85 H75 H65 H55 H45 H35 H25 H15 H84 H74 H64 H54 H44 H34 H24 V11 V12 V13 V14 V15 H14 H83 H73 H63 H53 H43 H33 H23 V23 V24 V25 H13 V31 V32 V33 H82 H72 H62 H52 H42 H32 H22 H12 H81 Z (mm) H71 H61 H51 H41 H31 H21 H11 Y (mm) X (mm) V 1 n V 3 n Micro-strain measured by the 11 FBG of the 3 vertical optical fibers Analysis of the main results For V3m FBG (below the implant) strain increases with depth ⇒ confirms that load is transmitted downwards by the screw thread and not by the bottom tip. For V2m and V3m strain increases with load while keeping the relative distribution ⇒ confirming that distribution For V2m (by the side of the implant) strain decreases with depth ⇒ confirms that the screw thread transmits load efficiently (the collar has no contact with the bone) For V12 and V14 (metal) traction replaces compression which may be explained by the finite surrounding media and their proximity to the face of the cube As for horizontal FBG, H13 and H23 (near the collar) show high strain as expected but all other FBG (H1m to H8m) show very low and random strain making them meaningless V3m are 3 FBG in a single optical fiber inserted vertically and glued inside the nylon cube right below the implant. V2m are 3 FBG in a single optical fiber located vertically at the side of the implant. V1m are 3 FBG in a single optical fiber located at the far side of the implant. CONCLUSIONS The load transfer is not homogeneous for the metal implant being much higher below it while the plastic and metal-plastic implants exhibit a much more homogeneity which favours a good bone remodelling and consequently long implant life.
