Connectio ion? Samantha Webster & Dr. Kornel Ehmann - - PowerPoint PPT Presentation

Dental l Im Impla lants: Hex or Conic ical l Connectio ion?

Samantha Webster & Dr. Kornel Ehmann

Northwestern University Department of Mechanical Engineering

• Dr. Jonathan Yahav & Khasim Ali Khan

SpiralTech

ARDII – Inaugural Global Symposium Toronto, May 17-19, 2018

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Outline

Introduction

• Northwestern University AMPL Lab
• SpiralTech Implants

Experiments

• Abutment and Implant Interaction
• Implant and SAWBone Interaction

Finite Element Model

• Abaqus Simulations
• Displacement and Stress Distributions

Conclusions and Future Work

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World Top 500 Universities (2015): NU 27

▪ Mechanical Engineering (2016): NU 4

NORT NORTHWE HWEST STERN ERN UNI UNIVERS VERSIT ITY

Founded in 1851, three campuses with 12 schools and colleges:

• Evanston: 379-acre campus 12 miles

north of Chicago ~17,000 total enrollment

• ~ 8,500 graduate students

Research & Finances:

• > $650 M in research awards and grants
• $10.5 B total endowment

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Advanced Manufacturing Processes Laboratory ry

Flexible Manufacturing Additive Manufacturing Surface Engineering Incremental Forming Laser Micro-machining Cutting/Machining Cyber Physical Systems ICME Composites Engineering

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SpiralTech ESi™ Implant

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Connection Types

ESi™ Implant-Hex Model ESi™ Implant-Conical Model Abutment Jaw Implant Screw Abutment Jaw Implant Screw

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Why are Conical Connections Preferable?

CAT Collets HSK ANALOGY Spindle – Toolholder Implant - Abutment Taper joints provide:

• Accurate location
• Uniform stress distribution
• Reduced wear

Taper errors Stress analysis

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Problem Analysis

Experimental

• Abutment-Implant Interaction
• Implant-Bone Interaction

Simulation

• Finite Element Model
• Abaqus Simulation

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Objectives

Accelerated aging reflects ½ year of chewing1

• Assume 3 episodes
• f chewing for 15

minutes per day

• 500,000 cycles =

0.5 years chewing Observe the wear of anodizing coating

• Pattern will

indicate contact between abutment and implant

• Gain insight on

interaction

Abutment-Implant In Interaction

[1] K. Verplancke, W. De Waele and H. De Bruyn. Dental Implants, what should be known before starting an in vitro study. Sustainable Construction and Design, vol. 2, 2011, p. 360-369.

Hex Connection Conical Connection

Epoxy, 3M DP-100 FR Sample Orientation

15 cm 5 cm 8 mm

Aluminum Block

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Set Up: Surface Wear Test

Abutment-Implant In Interaction

Abutment

Shaker Capacitance Sensor Dynamic Force Sensor

Samples Capacitance Displacement Sensor Dynamic Force Sensor Aluminum Housing Aluminum Block with Samples Abutment Housing

Motion

Electrodynamic Shaker

Implant

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Set Up: Surface Wear Test

Abutment-Implant In Interaction

• Capacitance sensor measures relative

displacement

• Dynamic force sensor measures load
• 45o mounting reflects occlusal and mesial-distal

loading conditions

• Test run for 5 hours at 30 Hz with ~50 N of force

Applied Motion

Abutment

Applied Motion

Implant Abutment Implant

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Abutment-Implant In Interaction

Results: Hex Implant Results: Conical Implant

Before After Before After

• Wear mainly identified on

upper implant surface

• Anodizing coating partially

removed

• Similar wear on upper

portion of implant

• Area of wear more

concentrated

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Abutment-Implant In Interaction

Results: Hex Abutment Results: Conical Abutment

Before After Before After Wear only on sliver of angled surface shows minimal connection Wear along length of angled surface shows fully-seated connection

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Objectives

Im Implant-SAWBone In Interaction

[2] SAWBones “Biomechanical Test Materials”

• Observe loosening of implant in SAWBone
• Accelerated 1 year of lateral chewing motion
• Measure pull out force to quantify implant loosening
• f each model type

Bone Type Density2 Strength2 Modulus2 (pcf) (g/cc) (Mpa) (Mpa) II 10 0.16 2.2 58 12 0.19 3.2 81 III 15 0.24 4.9 123 20 0.32 8.4 210 IV 30 0.48 18 445 40 0.64 31 759

SAWBone 40 pcf (Type I)

13 cm 4 cm 8 mm

Abutment Implant

10 mm

Sample Orientation

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Set Up: Lateral Motion Testing

Im Implant-SAWBone In Interaction

Shaker Dynamic Force Sensor Abutment Housing SAWBone with samples Motion Dynamic Shaker Capacitance Sensor Aluminum Housing Dynamic Force Sensor Abutment Housing

• 1,000,000 cycles of chewing is approximately 1 year of chewing
• Test run at 30 Hz for 10 hours at ~15 N transverse load
• Lateral motion applied by dynamic shaker exacerbates worst-case

condition in mesial-distal direction

SAWBone Implants Abutments

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Results: Force and Displacement Measurements

Im Implant-SAWBone In Interaction

Hex Connection Conical Connection

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Set Up and Results: Pull Out Test

• Sintech 20/G Tensile Test Machine
• Conical connection maximum pull out force

was 20N larger than hex connection

Im Implant-SAWBone In Interaction

50 100 150 200 250 0.5 1 1.5 2 Force (N) Crosshead Displacement (mm) Hex Conical

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Background and Objectives

• Differential equation
• 𝑒

𝑒𝑦 𝐵𝐹 𝑒𝑣 𝑒𝑦 + 𝑐 = 0, 0 < 𝑦 < 𝑚

• Boundary Conditions
• 𝜏 𝑦 = 0 = 𝐹 𝑒𝑣

𝑒𝑦 𝑦=0 = − ҧ

𝑢

• 𝑣 𝑦 = 𝑚 = ത

𝑣

• ׬

𝑚 𝑒𝑥 𝑒𝑦 𝐵𝐹 𝑒𝑣 𝑒𝑦 𝑒𝑦 = 𝑥𝐵 ҧ

𝑢 𝑦=0 + ׬

𝑚 𝑥𝑐 𝑒𝑦

∀𝑥 𝑥𝑗𝑢ℎ 𝑥 𝑚 = 0

Finite Element Model

Stresses

• Where are the

forces in the part?

Displacements

• How does the part

move?

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Methods

Finite Element Model

Material Properties Young’s Modulus Poisson Ratio Coefficient of Friction Density Yield Strength Ti6Al4V 110 GPa 0.34 0.3 4.43E-09 970 MPa SAW Bone 15pcf 123 MPa 0.3 1.60E-10

• Titanium implant and abutment modeled as

elastic-perfectly plastic material

• Friction defined for contact modeling
• Bone modeled as linearly elastic
• Abaqus model uses simplified geometry
• Takes advantage of symmetry
• Only interested in abutment-implant and

implant-bone interaction Abutment Implant Bone

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Methods: Mesh

Finite Element Model

Hex Connection Conical Connection

• Four-node tetrahedral elements
• Total elements: 430,000
• Tetrahedral elements used

based on complicated geometry

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Methods: Boundary Conditions

Finite Element Model

• 1. Assembly fully fixed in jaw
• 2. Half-model symmetry
• 3. Full osseointegration is

assumed and implemented with a tie constraint between the implant and the bone

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Methods: Applied Forces

Finite Element Model

• 1. Occlusal displacement
• 2. Mesio-distal moment
• 3. Buccal-lingual moment

3. 1. 2.

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Results: Stress Distributions in Bone

Finite Element Model

Hex Connection Conical Connection

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Results: Stress Distributions in Abutment

Finite Element Model

Hex Connection Conical Connection

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Results: Stress Distributions in Jaw Implant

Finite Element Model

Hex Connection Conical Connection

Main Resulting Force

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Results: Displacement Field in Bone

Finite Element Model

Hex Connection Conical Connection

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Conclusions

Conical connection does not rely on the machining tolerance to make a full, stiff connection between the abutment and the jaw implant Wear surfaces indicate level of contact between the abutment and implant of hex and conical connections Finite element model illuminates larger displacements in bone when using hex connection

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Future Work

• Experimental Improvements
• Repeated tests for statistical data
• Fine-tune experimental setup (load application point)
• Accurate drilling in SAWBone samples
• Further testing and characterization of implants after

testing

• Surface roughness measurements of wear surfaces
• Larger sample size for pull-out tests
• Model improvements
• Higher-order elements
• Hyperelastic material model for bone
• Addition of connecting screw

Baseplant

Thank You

Questions? Acknowledgements:

• Dr. Jian Cao, advisor

Dohyun Leem, AMPL PhD Student Grant Schneider, BME Master’s Student