Meditech Meeting on: “Innovations in Materials and Manufacturing of Dental Devices”

Cardiff MediCentre,29th March 2007 Meditech Meeting on: “Innovations in Materials and Manufacturing of Dental Devices” Thermal-mechanical reliability of Ti/HAp-based endosseous dental implant in severe conditions of Bruxism Giuseppe Cevola

Outline • Introduction • 3D FEM Modelling • mandibular bone • FGMs (Functionally Graded Materials) endosseous dental implant • Mechanical loading conditions • occlusive loading • bruxism loading • FGMs composition’s parametric studying • Thermal-mechanical Studying & Bruxism conditions • Conclusions and future developments

Introduction Bruxism is a disorder of the masticatory system characterized by teeth grinding and clenching Bruxism is considered • aetiological factor for temporomandibular disorders (TMD) • tooth wear (attrition) • loss of periodontal support • failure of dental restorations

Introduction The most common current dental implants are: Sub-PERIOSTEAL ENDOSSEOUS

Introduction Endosseous dental implant performance requirements: • biocompatibility: osteointegration • thermal/mechanical reliability: residual stress due to • production (Hot Isostatic Pressing, Spark Sintering)

Introduction • The success of the endosseous dental implant integration is due to: • Lack of clinical signs and symptoms of pathology • Lack of mobility • Radiographically stable interface Radiographically stable interface • Dynamic Modeling process • Remodeling process Adaptive capacity: load-bearing biological structures that bond with bone Clark M. Stanford Biomechanical and functional behavior of implants Adv Dent Res 13:88-92, June, 1999

Introduction Used Materials • Titanium and its alloys • Bioceramics : Hydroxyapatite (HAp) as coating, Zirconia Groundbreaking dental implants are designed using Functionally Graded Materials (FGM’s) made of Ti/HAp – Graduality along vertical direction: • Titanium: upper part (occlusive loading) • HAp: lower part (bone contact)

Outline • Introduction • 3D FEM Modelling • mandibular bone • FGMs (Functionally Graded Materials) endosseous dental implant • Mechanical loading conditions • occlusive loading • bruxism loading • FGMs composition’s parametric studying • Thermal-mechanical studying & Bruxism conditions • Conclusions and future developments

Modelling 3DFEM models FGM’s endosseous dental implant (first lower molar) Mandibular bone segment (35.25 mm) obtained by Computed Tomography (CT) images of Titanium dental implant (Bioform®) Computed Tomography (CT) images of Human mandibular bone

Modelling Mandible Computed Tomography image

Modelling Completed Model The materials are supposed isotropic with linear-elastic behaviour Toparli M, Sasaki S. Finite element analysis of the temperature and thermal stress in a postrestored tooth. J Oral Rehabil 2003;30:921–926.

Modelling Mesial-Distal section Buccal-Lingual section • Higher peri-implant tensile and compressive stresses would imply: • implant-bone bond failure • bone absorption S.C.Huang, C.F.Tsai Finite element analysis of a dental implant Biomedical Engineering-Applications, Basis & communications Vol.15 No.2 April 2003 • Implant mechanical performances are evaluated by means peri-implant-bone stresses: • von Mises stress • First principal stress • Third principal stress

Mechanical loading conditions:Experimental data Normal bilateral occlusive loading: Molar region : 400-650 N Premolar region : 222-445 N Canine region : 133-334 N Incisive region : 89-111 N K.J. Anusavice, Phillips Science of Dental Materials, W.B.Saunders Co., New York, (1996) Molar region unilateral occlusive loading : 30% smaller than one obtained during bilateral loading TWENTY-SECOND BIENNIAL MEETING 7–10 June 2001, Lugano, Switzerland Journal of Oral Rehabilitation 2002 29; 872–889 Upper and lower dental appliances containing miniaturestrain-gauge transducers.

Mechanical loading conditions:Experimental data Bruxist bilateral clenching loading molar region : 790 N transversal force: 50 N First lower molar Journal of Oral Rehabilitation 2001 28; 485-491 K. Nishigawa Department of Fixed Prosthodontics, The University of Tokushima School of Dentistry, Tokushima, Japan

FGMs composition’s parametric studying Exponential law between composition and longitudinal coordinate h = hydroxyapatite t = titanium Increasing value of Ti along the implant lenght

m=0.1 m=0.2 m=0.5 m=1 m=2 m=5 m=10 Ti Thermal-mechanical Studying Changing temperature implant performances: ΔT = 0°C

Thermal-mechanical Studying Changing temperature implant performances: ΔT= + 20°C and -20°C

Thermal-mechanical Studying Bruxism Conditions: Clenching load & grinding force

Conclusions and future developments So far m = 2 composition withstands the highest von Mises and first principal stresses in all the implants, with temperature reduction of 20°C In progress On the basis of provided experimental data (K. NISHIGAWA School of Dentistry, Tokushima, Japan ) the bruxism behaviour is in progress Future works Would be desirable to carry-out fatigue analysis for the implant-bone bond The residual stresses due to the technological processes can neglect the hosting oral changing temperature effect?

Acknowledgment • Dr. WANG Fang, PhD. Institute of High Performance Computing Singapore, • External Advisor • Prof. Estevam Barbosa de Las Casas, Universidade Federal de Minas Gerais, • Belo Horizonte, BRASIL • Prof. K. Nishigawa, School of Dentistry, Tokushima, Japan • Prof. F. Lobbezoo, Department of Oral function, Academic Centre for Dentistry • Amsterdam (ACTA), Amsterdam, The Netherlands • Are gratefully acknowledged for their assistance and contributions • Prof. Roberto Contro, Prof. of Biomechanics, Politecnico di Milano, Italy • Prof. Pasquale Vena, Assoc. of Biomechanics, Politecnico di Milano, Italy • Dr. Dario Gastaldi, PhD. of Material Engineering, Politecnico di Milano, Italy • Are also acknowledged for their kind assistance and useful discussions

Thankyou!

Meditech Meeting on: “Innovations in Materials and Manufacturing of Dental Devices”