Technical Report Analysis of the effect of load direction on the stress distribution in dental implant N. Djebbar, B. Serier, B. Bachir Bouiadjra * , S. Benbarek, A. Drai Department of Mechanical Engineering, University of Sidi Bel Abbes, BP 89, Cité Ben M’hidi, Sidi Bel Abbes 2200, Algeria article info Article history: Received 21 March 2009 Accepted 22 October 2009 Available online 25 October 2009 abstract In this work, the finite element method is used to compute the distribution of stresses in dental prosthe- sis. The stress analysis is particularly focused at the interface bone–implant in different positions: distal zone, medial zone and proximal zone of these components. The effects of the intensity and the direction of loading on the stress variation were highlighted. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Successful durable results of dental implants have led to an in- crease in its usage in many clinical situations [1]. Since osseointe- grated implants were introduced for the rehabilitation of the edentulous patient in the late 1980s, a great awareness and subse- quent demand have arisen in the field. In evaluation of the durable success of a dental implant; the reliability and the stability of the implant–abutment and implant–bone interfaces play an essential role. In general, the success of the treatment depends on many fac- tors affecting the bone–implant, implant–abutment and abut- ment–prosthesis interfaces [2]. Stress paths on prosthetic structures and bone tissue are not only caused by occlusal loads but can be also related to inappropriate clinical practice or manu- facturing defects, as in the case of stress induced by misfit for im- plant–supported prosthesis [3]. This problem is well-known in the dental research community and continuously stimulates efforts to develop new procedures for reducing the prosthetic misfit possibil- ity, even ones using computer aided surgical procedures. Nowadays, the dental implants have an aesthetic aim as well as functional. Various operational procedures were developed which privileges the patient comfort. The dynamic, static and fatigue behaviours of the implant were studied [2]. Dynamic loads were applied during five minutes to occlusive surface. For the fatigue analysis of the implant, they used the formula of Goodman, Soderberg and Gerber. Winter et al. [4] showed that one can calculate the non-linear relationship between the torque and the angle of rotation up to the ultimate torque. The final displacement couples, which depend on curative time, are de- scribed by a curative function depending on time. Simsek and Erk- men [1] studied the evaluation of the tensile and compressive stresses for the cortical and cancellous bone under load conditions according to the inter-implants distance, inter-implant distance of 1.0 cm is the optimum distance for the two fixtures implantation. Pegoretti and Migliaresi [5] calculated the long-term effects of age- ing in the water of a new class of the dental compounds available in the polymer traffic on its physical properties. Li et al. [6] devel- oped a new bone remodelling model which can simulate both underload and overload resorptions that often occur in dental im- plant treatments. However, Sevimay and Turhan [7] made a study of the effect of four different bone qualities on stress distribution in an implant–supported mandibular crown, using three-dimensional (3D) finite element analysis (FEA). FEA of Dinaer Bozkaya [8] led to the evaluation of load transfer characteristics for five different im- plants in the compact bone for different loads. Bozkaya and Muftu [9] analyzed the mechanisms of fitting with conical tightening in dental implants; the validity and the applicability of the analytical solution were studied by comparing them with the model designed in finite elements for problem parameters range. Morgan and Jam- est [10] indicated that the force distributions, bending moment and the torque are determined by structural analysis for an osseo- integrated dental implant system. This one is a dental prosthesis rigidly connected to the bone by implants. The immediate result of the structural analysis is that the bending moment due to the vertical component of the applied moment load which has previ- ously been neglected can produce stresses in the implant which are important than the direct axial stresses. Van Schoiack and Wu [11] studied the effect of the bone density on the mechanical damping behaviour of dental implants. The purpose of this study is to evaluate the effects of external loading on the stress distribution in the dental Implant using 3D FEA. Since the bone–implant interface is the critical zone, the dis- tribution of the stresses is analysed in the proximal, medial and distal zones of this region. 2. Geometrical model The three-dimensional geometrical model of the dental struc- ture, illustrated in Fig. 1, is analyzed by the finite element method using ABAQUS code version 6.5. The bone was modelled as full structure (block of bone with size equal to the section of lower 0261-3069/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2009.10.042 * Corresponding author. E-mail address: bachirbou@yahoo.fr (B.B. Bouiadjra). Materials and Design 31 (2010) 2097–2101 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes