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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

  1. 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

  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. NORTHWE NORT 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 World Top 500 Universities (2015): NU 27 ▪ Mechanical Engineering (2016): NU 4 3

  5. Advanced Manufacturing Processes Laboratory ry 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 ESi ™ Implant -Conical Model Abutment 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 ANALOGY Spindle – Toolholder Implant - Abutment Taper errors Stress analysis 8

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

  10. Abutment-Implant In Interaction Objectives Sample Orientation Accelerated aging Observe the wear of reflects ½ year of anodizing coating Conical Connection Hex Connection chewing 1 • Assume 3 episodes • Pattern will of chewing for 15 indicate contact 8 mm minutes per day between abutment Epoxy, 3M DP-100 FR and implant • 500,000 cycles = 5 cm 0.5 years chewing • Gain insight on interaction Aluminum Block 15 cm [1] K. Verplancke, W. De Waele and H. De Bruyn. Dental Implants, what should be known before 10 starting an in vitro study. Sustainable Construction and Design, vol. 2, 2011, p. 360-369.

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

  12. Abutment-Implant In 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 Abutment Abutment Implant Implant Applied Motion 12

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

  14. Abutment-Implant In Interaction Results: Hex Abutment Results: Conical Abutment Before After After Before Wear along length of Wear only on sliver of angled surface shows angled surface shows fully-seated connection minimal connection 14

  15. Im Implant-SAWBone In Interaction Objectives • Observe loosening of implant in SAWBone • Accelerated 1 year of lateral chewing motion Sample Orientation • Measure pull out force to quantify implant loosening Abutment of each model type Implant Bone Type Density 2 Strength 2 Modulus 2 (pcf) (g/cc) (Mpa) (Mpa) 8 mm 10 0.16 2.2 58 SAWBone 40 pcf (Type I) 4 cm II 12 0.19 3.2 81 15 0.24 4.9 123 III 20 0.32 8.4 210 13 cm 30 0.48 18 445 IV 10 mm 40 0.64 31 759 [2] SAWBones “Biomechanical Test 15 Materials”

  16. Im Implant-SAWBone In Interaction Set Up: Lateral Motion Testing • 1,000,000 cycles of chewing is approximately 1 year of chewing Abutments • Test run at 30 Hz for 10 hours at ~15 N transverse load • Implants Lateral motion applied by dynamic shaker exacerbates worst-case SAWBone condition in mesial-distal direction Dynamic Force Abutment Housing Shaker Sensor Abutment Housing Capacitance Sensor Dynamic Shaker Dynamic Force Sensor Aluminum Housing SAWBone with Motion samples 16

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

  18. Implant-SAWBone In Im Interaction Set Up and Results: Pull Out Test 250 Hex 200 Conical Force (N) 150 100 50 0 0 0.5 1 1.5 2 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 𝑒𝑦 𝐵𝐹 𝑒𝑣 𝑒 • 𝑒𝑦 + 𝑐 = 0, 0 < 𝑦 < 𝑚 Stresses • Where are the • Boundary Conditions forces in the part? • 𝜏 𝑦 = 0 = 𝐹 𝑒𝑣 𝑒𝑦 𝑦=0 = − ҧ 𝑢 • 𝑣 𝑦 = 𝑚 = ത Displacements 𝑣 • How does the part 𝑚 𝑥𝑐 𝑒𝑦 move? 𝑚 𝑒𝑥 𝑒𝑣 • ׬ 𝑒𝑦 𝑒𝑦 = 𝑥𝐵 ҧ 𝑒𝑦 𝐵𝐹 𝑢 𝑦=0 + ׬ 0 0 ∀𝑥 𝑥𝑗𝑢ℎ 𝑥 𝑚 = 0 19

  20. Finite Element Model Methods • Abaqus model uses simplified geometry Young’s Poisson Coefficient of • Material Properties Density Yield Strength Takes advantage of symmetry Modulus Ratio Friction • Only interested in abutment-implant and Ti6Al4V 110 GPa 0.34 0.3 4.43E-09 970 MPa implant-bone interaction SAW Bone 15pcf 123 MPa 0.3 1.60E-10 Abutment • Titanium implant and abutment modeled as elastic-perfectly plastic material Implant • Friction defined for contact modeling • Bone modeled as linearly elastic 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 Methods: Applied Forces 1. Occlusal displacement 2. Mesio-distal moment 3. Buccal-lingual moment 1. 2. 3. 23

  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 Conical Connection Hex 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?

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