Presentation

OUTLINE

• The FEA of the 3.5 mm Bicon Implant-Abutment-Bone system under central occlusal loads

• Mechanics of the Tapered Interference Fit in a 3.5 mm Bicon Implant

WHAT IS A DENTAL IMPLANT?

Dental implant is an artificial titanium fixture (similar to those used in orthopedics)

which is placed surgically into the jaw bone to substitute for a missing tooth and its root(s).

Surgical Procedure

STEP 1: INITIAL SURGERY

STEP 2: OSSEOINTEGRATION PERIOD STEP 3: ABUTMENT CONNECTION STEP 4: FINAL PROSTHETIC RESTORATION

Success Rateslower jaw, front – 90 – 95%lower jaw, back – 85 – 90%upper jaw, front – 85 – 95%upper jaw, back – 65 – 85%

History of Dental Implants

In 1952, Professor Per-Ingvar Branemark, a Swedish surgeon, while conducting research

into the healing patterns of bone tissue, accidentally discovered that when pure titanium comes into direct contact with the living bone

tissue, the two literally grow together to form a permanent biological adhesion. He named this

phenomenon "osseointegration".

First Implant Design by Branemark

All the implant designs are obtained by themodification of existing designs.

John Brunski

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Bicon

OUTLINE



The FEA of the 3.5 mm BiconImplant-Abutment-Bone system under

central occlusal loads

Assumptions:

• Analyses were linear, static and assumed that materials were elastic, isotropic and homogenous.

• 100% osseointegration is assumed between bone and implant. Bone and implant are assumed to be perfectly bonded.

• The stresses in the bone due to the interference fit betweenimplant and abutment is assumed to be relaxed after the insertion of the abutment.

Finite Element Model

29117 Solid 45 Brick Elements (32000 limit)

Symmetry boundary conditions on two cross-sections

and fixed in all dofs from the bottom of the bone.

V

H

RESULTS

Effect of bone’s elastic modulus on the overall stress distribution: Different finite element analyses are run by varying bone mechanical properties surrounding the implant. (1-16 GPa)

The properties of the bone depends on the location in the jaw, the gender and age of the patient.

Force: Vertical 100 N Bone Modulus: 16 GPa


Force: Lateral 20 N Bone Modulus: 16 GPa


• Both the stress distribution and the stress levels are effected significantly as the bone modulus is varied.• CT scan data may be a good source for obtainingpatient dependent implant designs.

Maximum vertical and lateral load carrying capacity ofthe bone: The failure limit of the bone due to fatigue is 29 MPa. [Evans et al.]



Lateral loads cause approximately 25 times higher stresses in the bone than the vertical loads.

OUTLINE



Mechanics of the Tapered Interference Fitin a 3.5 mm Bicon Implant

Perfectly elastic large displacement non-linear contact finite element analysis for different insertion depths.

Elastic-plastic large displacement non-linear contactfinite element analysis for different insertion depths.

Different implant-abutment assemblies are performedfor 0.002”, 0.004”, 0.006”, 0.008” and 0.010” insertiondepths.

Axisymmetric model is used.

100% osseointegration is assumed between bone and implant. Bone and implant are assumed to be perfectly bonded.

Bone is assumed to be elastic, isotropic and homogenouswith a Young’s modulus of 10 GPa.

Finite Element Model

Perfectly elastic large displacement non-linear contact finite element analysis for different

insertion depths.

Perfectly Elastic Finite Element Results

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0.47 0.49 0.51 0.53 0.55 0.57 0.59Vertical Position

Co

nta

ct

Pre

ss

ure

(P

) p

si

Interference depth: 0.002 in



Contact pressure increases linearly with insertion depth.

After 0.004” insertion depth, it is seen that plastic deformation occurs in the implant.

An elastic-plastic model is needed.

Yield Strength of Ti-6Al-4V 139,236 Psi

Elastic-plastic large displacement non-linear contact finite element analysis for different

insertion depths

Stress(MPA)

% Strain

Bilinear Isotropic Hardening Model

Contact Pressure Distribution for Different Insertion Depths

Elastic-Plastic Finite Element Results

0

50000

100000

150000

200000

250000

300000

0.45 0.47 0.49 0.51 0.53 0.55 0.57 0.59Vertical Position

Co

nta

ct

Pre

ss

ure

(P

) p

si





Contact pressure increases non-linearly with largerinsertion depths.

Von

Mis

es S

tres

s D

istr

ibut

ion

in th

e Im

plan

tYield Strength of Ti-6Al-4V 139,236 Psi

Von

Mis

es S

tres

s D

istr

ibut

ion

in th

e B

one

Yield Strength of Bone 8,702 Psi

FUTURE WORK

Comparison of different implant designs in terms of stress distribution in the bone due to occlusal loads.

Modeling non-homogenous bone material properties by incorporating with CT scan data.

Comparison of different implant-abutment interfaces

Presentation

Health & Medicine

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