Journal of Oral Implantology April 2013 - (Page 123)

RESEARCH Evaluation of Optimal Taper of Immediately Loaded WideDiameter Implants: A Finite Element Analysis Momen A. Atieh, MSc, PhD* Reza A. Shahmiri This study aimed to evaluate the effects of different tapering angles of an immediately loaded wide-diameter implant on the stress/strain distribution in bone and implant after implant insertion in healed or fresh molar extraction sockets. A total of 10 finite element (FE) implant-bone models, including 8.1-mm diameter implant, superstructure, and mandibular molar segment, were created to investigate the biomechanical behavior of different implant taper angles in immediate and delayed placement conditions. The degrees of implant taper ranged from 28 to 148, and the contact conditions between the immediately loaded implants and bone were set with frictional coefficients (l) of 0.3 in the healed models and 0.1 in the extracted models. Vertical and lateral loading forces of 189.5 N were applied in all models. Regardless of the degree of implant tapering, immediate loading of wide-diameter implants placed in molar extraction sockets generated higher stress/strain levels than implants placed in healed sockets. In all models, the von Mises stresses and strains at the implant surfaces, cortical bone, and cancellous bone increased with the increasing taper angle of the implant body, except for the buccal cancellous bone in the healed models. The maximum von Mises strains were highly concentrated on the buccal cortical struts in the extracted models and around the implant neck in the healed models. The maximum von Mises stresses on the implant threads were more concentrated in the non-tapered coronal part of the 118 and 148 tapered implants, particularly in the healed models, while the stresses were more evenly dissipated along the implant threads in other models. Under immediate loading conditions, the present study indicates that minimally tapered implants generate the most favorable stress and strain distribution patterns in extracted and healed molar sites. Key Words: oral implants, finite element analysis, immediate loading, stress distribution, tapering angle INTRODUCTION O ver the past decade, the primary stability of implants was tremendously improved through modifying the surgical protocol, implant surface characteristics, and design. The ability to achieve and maintain a high primary stability has caused a paradigm shift in the way implants were traditionally placed and loaded. Shortening the treatment time has introduced new terms in the oral implant vocabulary. Terms such as ‘‘immediate’’ or ‘‘early’’ placement and loading were used to Sir John Walsh Research Institute, School of Dentistry, University of Otago, Dunedin, New Zealand. * Corresponding author, e-mail: DOI: 10.1563/AAID-JOI-D-11-00104 describe the different treatment modalities that attempted to meet patients’ demands for a shorter period of intervention.1–4 One of the most popular protocols combines immediate implant placement with immediate restoration/loading (the bimodal approach, Figure 1).3 Immediate placement was defined as placing the implant in a fresh extraction socket on the same day of surgery,1 and immediate restoration/loading referred to placing the implant restoration within the first 48 hours after implant placement.4 The bimodal approach offered the shortest treatment time, optimal soft tissue outcomes, and high rates of short-term success.5–11 However, meta-analytic studies showed a higher failure risk associated with immediate placement/ loading of single implants compared with the Journal of Oral Implantology 123

Table of Contents for the Digital Edition of Journal of Oral Implantology April 2013

Evidence-Based Practice or Practice-Based Evidence?
Evaluation of Optimal Taper of Immediately Loaded Wide-Diameter Implants: A Finite Element Analysis
A Prospective, Randomized Controlled Preclinical Trial to Evaluate Different Formulations of Biphasic Calcium Phosphate in Combination With a Hydroxyapatite Collagen Membrane to Reconstruct Deficient Alveolar Ridges
Retention of Implant-Supported Overdenture With Bar/Clip and Stud Attachment Designs
The Clinical and Histologic Outcome of Dental Implant in Large Ridge Defect Regenerated With Alloplast: A Randomized Controlled Preclinical Trial
Fluoride-Treated Bio-Resorbable Synthetic Hydroxyapatite Promotes Proliferation and Differentiation of Human Osteoblastic MG-63 Cells
Resonance Frequency Analysis of 208 Straumann Dental Implants During the Healing Period
A Simplified Technique for Solving the Transfer Problem of Implant-Supported Fixed Partial Dentures for Patients With Microstomia
Esthetic Evaluation of Single-Tooth Morse Taper Connection Implants Placed in Fresh Extraction Sockets or Healed Sites
A Technique for Improving the Retention of Dentures Retained by Ramus Frame Implants
Treatment of Congenitally Missing Maxillary Lateral Incisors: An Interdisciplinary Approach
Use of Titanium Mesh in Lieu of a Fixation Screw to Stabilize an Autogenous Block Graft: A Case Report
A Novel Approach to Preserve the Buccal Wall in Immediate Implant Cases: A Clinical Report
Implant Failure Associated With Actinomycosis in a Medically Compromised Patient
Replacement of Mandibular Posterior Teeth With Implants in a Postmandibular Resection Case: A Case Report
Zygomatic Implants/Fixture: A Systematic Review
An Overview of Immediate Root Analogue Zirconia Implants
Letter to the Editor
Reviews of Current Literature

Journal of Oral Implantology April 2013