Implants

30 I I research_ Single molar restoration implants1_2013 thealveolarboneisclassifiedtoD1,2,3,423in a descending order. So, provided that the edentulous space after the molar extraction permits, it’s rec- ommended in the harder bone quality (D1,2) to use one wide diameter implant and in the softer bone (D3,4) quality two average sized implants. Therefore more detailed study to compromise between the two implants size/ design and intermediate space can put this stress values in safe, acceptable, and control- lable region under higher levels of loading. ** The area under the __-__ curve up to a given value of strain is the total mechanical energyperunitvolumeconsumedbythema- terialinstrainingittothatvalue(Fig.9).Thisis easilyshownasfollowsinequation2: _Summary Restoration of single molar using implants encounters many problems; mesio-distal cantilever due to very wide occlusal table is the most prominent. An increased occlusal force posteriorly worsens the problem and increases failures. To overcome the overload, the use of wide diameter implants or two regular sized implants were suggested. The aim of this study was to verify the best solu- tion that has the best effect on alveolar bone under distributed vertical loading. Therefore, a virtual experiment using Finite Element Analysis was done using ANSYS version 9. A simplified simulation of spongy and cortical bones of the jaw as two co-axial cylinders was utilised. Full detailed with high accuracy simulation for implant, crown, and coating was implemented. The comparison included different types of stresses and deformations of both wide implant and two regular im- plants under the same boundary conditions and load application. The three main stresses compressive, ten- sile, shear and the equivalent stresses in ad- dition to the vertical deformity and the total deformities were considered in the compari- sonbetweenthetwomodels.Theresultswere obtained as percentages using the wide im- plantasareference.Thespongyboneshowed about five per cent less stresses in the two implants model than the one wide diameter implant. The exceptions are the relatively in- crease in maximum compressive stresses and deformations of order 12 per cent and 0.3 per cent respectively. The stresses and displacements on the cortical bone are higher in the two implant model due to having two close holes, which results in weak area in-between. The spongy boneresponsetothetwoimplantswasfound to be better considering the stress distribu- tion (energy absorbed by spongy bone**). Therefore, it was concluded that, using the wide diameter implant or two average ones as a solution depends on the case primarily. Provided that the available bone width is suf- ficient mesio distally and bucco-lingual, the choice will depend on the type of bone. The harder D1,2 types having harder bone qual- ity and thicker cortical plates are more con- venient to the wide implant choice. The D3,4 typesconsist of morespongyandlesscortical bone, are more suitable to the two implant solution._ Editorial note: A complete list of references isavailablefromtheauthor. Fig. 10 Fig. 10_Equation 2 (stress energy). implants Prof. Amr Abdel Azim Professor, Faculty of Dentistry, Cairo University drazim@link.net Dr Amani M. Zaki GBOI. 2009, Egypt amani.m.zaki@gmail.com Dr Mohamed I. El-Anwar Researcher, Mechanical Engineering Department, National Research Center, Egypt anwar_eg@yahoo.com _contact