Experimental FBG Sensing System and FEA for the

Analysis of Dental Macro Implants

Paulo A. Lopes, Ilda Abe, Marcelo W. SchillerPaulo A. Lopes, Ilda Abe, Marcelo W. Schiller

DepartmentDepartment ofof PhysicsPhysics , , UniversityUniversity ofof AveiroAveiro

Campus Universitário de Santiago, 3810Campus Universitário de Santiago, 3810--193 Aveiro, Portugal193 Aveiro, Portugal

ee--mail : mail : paulo@ua.ptpaulo@ua.pt

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

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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 cm3

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 MaterialYoung 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)

H11H12H13H14

V15

V14

H15

H21

H31

H41

H22

H32

H42

V25

V24

H23

H33

H43

H24

H34

H44

H25

H35

H45

0

20

40

600102030405060

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

V23

V24

V25

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)

020

4060

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

V23H53

H63

H54

H64

H55

H65

Z (mm)

0 10 20 30 40 50 600

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)

V1n

V3n

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.