Dental Implants: Hex or Conical Connection?

Transcription

1 Dental Implants: Hex or Conical Connection? ARDII Inaugural Global Symposium Toronto, May 17-19, 2018 Samantha Webster & Dr. Kornel Ehmann Northwestern University Department of Mechanical Engineering Dr. Jonathan Yahav & Khasim Ali Khan SpiralTech

2 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 2

3 NORTHWESTERN UNIVERSITY 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 World Top 500 Universities (2015): NU 27 Mechanical Engineering (2016): NU 4 3

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5 Advanced Manufacturing Processes Laboratory Flexible Manufacturing Additive Manufacturing Surface Engineering Incremental Forming Laser Micro-machining Cutting/Machining Cyber Physical Systems ICME Composites Engineering 5

6 SpiralTech ESi Implant 6

7 Connection Types ESi Implant-Hex Model Abutment ESi Implant-Conical Model Abutment Screw Screw Jaw Implant Jaw Implant 7

8 Why are Conical Connections Preferable? CAT Taper joints provide: Accurate location Uniform stress distribution Reduced wear HSK Collets Taper errors ANALOGY Spindle Toolholder Implant - Abutment Stress analysis 8

9 Problem Analysis Experimental Simulation Abutment-Implant Interaction Implant-Bone Interaction Finite Element Model Abaqus Simulation 9

10 Abutment-Implant Interaction Objectives Accelerated aging reflects ½ year of chewing 1 Observe the wear of anodizing coating Sample Orientation Conical Connection Hex Connection Assume 3 episodes of chewing for 15 minutes per day 500,000 cycles = 0.5 years chewing Pattern will indicate contact between abutment and implant Gain insight on interaction 8 mm Aluminum Block Epoxy, 3M DP-100 FR 5 cm 15 cm 10 [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

11 Abutment-Implant Interaction Set Up: Surface Wear Test Capacitance Displacement Sensor Aluminum Housing Dynamic Force Sensor Abutment Housing Capacitance Sensor Shaker Motion Electrodynamic Shaker Samples Aluminum Block with Samples Abutment Implant Dynamic Force Sensor 11

12 Abutment-Implant Interaction Set Up: Surface Wear Test Capacitance sensor measures relative displacement Dynamic force sensor measures load 45 o mounting reflects occlusal and mesial-distal loading conditions Test run for 5 hours at 30 Hz with ~50 N of force Applied Motion Implant Abutment Applied Motion Implant Abutment 12

13 Abutment-Implant Interaction Before Results: Hex Implant Wear mainly identified on upper implant surface Anodizing coating partially removed After Results: Conical Implant Before Similar wear on upper portion of implant Area of wear more concentrated After 13

14 Abutment-Implant 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 14

15 Implant-SAWBone Interaction Objectives Observe loosening of implant in SAWBone Accelerated 1 year of lateral chewing motion Measure pull out force to quantify implant loosening of each model type Sample Orientation Abutment Implant Bone Type Density 2 Strength 2 Modulus 2 (pcf) (g/cc) (Mpa) (Mpa) II mm SAWBone 40 pcf (Type I) 4 cm III IV cm 10 mm 15 [2] SAWBones Biomechanical Test Materials

16 Implant-SAWBone Interaction Set Up: Lateral Motion Testing 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 Implants Abutments SAWBone Abutment Housing Dynamic Force Sensor Abutment Housing Shaker Capacitance Sensor Aluminum Housing Motion Dynamic Shaker SAWBone with samples Dynamic Force Sensor 16

17 Implant-SAWBone Interaction Results: Force and Displacement Measurements Hex Connection Conical Connection 17

18 Force (N) Implant-SAWBone Interaction Set Up and Results: Pull Out Test Hex Conical Crosshead Displacement (mm) Sintech 20/G Tensile Test Machine Conical connection maximum pull out force was 20N larger than hex connection 18

19 Finite Element Model Background and Objectives Differential equation d dx du AE dx Boundary Conditions 0 l dw dx σ x = 0 = u x = l = തu + b = 0, 0 < x < l E du = tҧ dx x=0 AE du dx dx = wa ҧ t x=0 + 0 l wb dx Stresses Where are the forces in the part? Displacements How does the part move? w with w l = 0 19

20 Finite Element Model Methods Material Properties Young s Modulus Poisson Ratio Coefficient of Friction Density Yield Strength Ti6Al4V 110 GPa E MPa SAW Bone 15pcf 123 MPa E-10 Abaqus model uses simplified geometry Takes advantage of symmetry Only interested in abutment-implant and implant-bone interaction Titanium implant and abutment modeled as elastic-perfectly plastic material Friction defined for contact modeling Bone modeled as linearly elastic Abutment Implant Bone 20

21 Finite Element Model Methods: Mesh Four-node tetrahedral elements Total elements: 430,000 Tetrahedral elements used based on complicated geometry Hex Connection Conical Connection 21

22 Finite Element Model Methods: Boundary Conditions 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 22

23 Finite Element Model 1. Occlusal displacement 2. Mesio-distal moment 3. Buccal-lingual moment Methods: Applied Forces

24 Finite Element Model Results: Stress Distributions in Bone Hex Connection Conical Connection 24

25 Finite Element Model Results: Stress Distributions in Abutment Hex Connection Conical Connection 25

26 Finite Element Model Results: Stress Distributions in Jaw Implant Main Resulting Force Hex Connection Conical Connection 26

27 Finite Element Model Results: Displacement Field in Bone Hex Connection Conical Connection 27

28 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 28

29 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 29

30 Acknowledgements: Dr. Jian Cao, advisor Dohyun Leem, AMPL PhD Student Grant Schneider, BME Master s Student Thank You Questions?