The Effect of Processing Conditions on the Flexural Strength of Polyetheretherketone (PEEK) Used as Innovative Denture Base Material S. A. MUHSIN 1 , D. J. WOOD 1 , P. V. HATTON 1 , A. JOHNSON 1 , and N. SERENO 2 1 School of Clinical Dentistry, Faculty of Medicine, Dentistry and Health, University of Sheffield, England 2 Juvora Ltd, Thornton Cleveleys, England smuhsin1@sheffield.ac.uk The 2 nd International PEEK Meeting, USA-Washington DC (23-24 th April, 2015) Despite the fact that material scientists and researchers have continued to improve the mechanical properties of denture base materials, none yet meet the ideal requirements. The range of denture biomaterials is small and there is currently considerable interest in the development of new speciality materials. Current materials may not have appropriate mechanical properties for load- bearing dental devices. Flexural properties are a crucial factor in material selection for dental use. Polyetheretherketone (PEEK) has become established in medical engineering as it is resistant to aggressive environments, and it has increasingly been suggested for dental applications. However, it is not known whether PEEK prepared using either thermo-pressing or machining techniques would compromise the benefits of PEEK compared to the conventional denture materials. Therefore, the influence of process parameters on the flexural properties of the PEEK is reported here. To date, there have been no systematic studies of flexural properties to assess PEEK as a denture material. Therefore, the aim of this project was to evaluate the flexural behaviour of PEEK material as a denture base prepared by both machining and thermo-pressing techniques compared to the conventional denture base materials using a static 4-point bend test. CONCLUSIONS INTRODUCTION AIMS Step 1 Step 3 & 4 Step 2 Step 5 Step 7 The following steps are shown in Figure 1: Step 1: A tooth-borne removable partial denture (RPD) framework design was created for Class III modification 1 model using Dental Wings RPD-CAD software. Step 2: A wax pattern was produced by using a Solidscape 3ZLab wax printer. Step 3: The wax pattern was invested to create a mould using a two part flask compatible with the Bredent thermo-pressing unit (Thermopress 400). Step 4: Thermocouples were incorporated in different positions in order to record the actual mould temperature in comparison to the furnace temperature at mould temperature of 100, 150, 175 and 200 ˚C. Step 5: Samples were prepared for flexural strength testing according to ISO standardization (1567: 2005), (n=10): A. Heat-cured PMMA B. Thermo-pressed PMMA C. Cobalt-Chromium (Co-Cr) RPD casting alloy D. Thermo-pressed PEEK PEEK-OPTIMA ® NI1) and E. PEEK-CAD/CAM JUVORA TM  Step 6: Specimen dimensions. Step 7: 4-point bend testing was accomplished at load of 100 N and a crosshead speed of 5(±1) mm/min using Lloyds tester machine of 2.5 KN loading capacity. MATERIALS & METHOD Figure 1: Diagram summarises the experimental approach taken in this study. The main observations in this study were: 1. Both PEEK materials had superior flexural properties compared to traditional PMMA denture base material. 2. PEEK-Juvora TM provides superior flexural behaviour with highest ability to spring ďaĐk to its original shape after load removal. This highly promising data supports the rational for the ongoing development of PEEK for use in the manufacture of tough and resilient dental prosthetics. Flask (Mould Entrance) Anterior Region (Major Connector) Premolar Clasp Region Middle Region (Major Connector) Molar Clasp Region Posterior Region (Major Connector) Step 6 Acknowledgments The Higher Committee for Education Development in Iraq (Baghdad-Iraq ) Invibio Ltd. & JUVORA Ltd., Thornton Cleveleys, Lancashire, United Kingdom Comparison of Four-point Bending Test Results (N=10) Materials Processing Method EM (GPa) FR (N/m 2 ) MD (mm) R (J) PEEK-JUVORA™ CAD/CAM 5.57 7.5x10 -2 3.22 5.6x10 -2 PEEK-OPTIMA®NI1 Thermo-pressed at ϭϬϬ˚C Mould T 4.80 6.3 x10 -2 3.97 3.8 x10 -2 Thermo-pressed at ϭϱϬ˚C Mould T 4.85 6.4 x10 -2 3.94 4.1 x10 -2 Thermo-pressed at ϭ7ϱ˚C Mould T 4.69 6.2 x10 -2 3.95 3.4 x10 -2 Thermo-pressed at ϮϬϬ˚C Mould T 4.91 6.6 x10 -2 3.67 4.2 x10 -2 PMMA Heat-Cured 3.58 4.7 x10 -2 5.49 3.1 x10 -2 Thermo-pressed at ϰϬ˚C Mould T 3.79 5 x10 -2 5.51 3.2 x10 -2 Co-Cr alloy Casting 206.33 276 x10 -2 0.26 0.08 x10 -2 T: Temperature; EM: Elastic Modulus; FR: Flexural Rigidity; MD: Maximum Deflection; and R: Resilience Load (N) Deflection (mm) General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PMMA HC Load (N) Deflection (mm) General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PMMA Injection-40C Load (N) Deflection (mm) General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% Co-Cr RPD casting alloy Load (N) Deflection (mm) General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PEEK-Injection-150C Load (N) Deflection (mm) General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PEEK-Injection-175C Load (N) -10 0 10 20 30 40 50 60 70 80 Deflection (mm) -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Secant Elastic Limit Preload General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PEEK-Injection-200C Load (N) -10 0 10 20 30 40 50 60 70 80 Deflection (mm) -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Secant Elastic Limit Preload General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PEEK (JUVORA) Load (N) Deflection (mm) General Purpose 4 Point Bend Setup Preload: Spans: Section: Stop At: Fracture: 5.00 N About 17.0 mm & 50.0 mm About 2.50 mm x 10.0 mm Load of 100.0 N Load drops to 20.0% PEEK-Injection-100C Thermo-pressed PMMA Cobalt Chromium Casting alloy Thermo-pressed PEEK at ϭϬϬ ˚C Thermo-pressed PEEK at ϭϱϬ ˚C Thermo-pressed PEEK at ϭ7ϱ ˚C Thermo-pressed PEEK at ϮϬϬ ˚C Machined PEEK-JUVORA™ Heat-Cured PMMA Results Figure 2: Flexural properties of tested materials prepared by different processing conditions.