Usure des matériaux dentaires

Abstract

The Application of biomaterials for dental use requires a thorough comprehension of a mechanical properties in the aim to develop more effective materials. These materials (composite, resin and ceramic) are very sensible to mechanical sollicitations. They are submitted to constant wear by friction, to cyclic fatigue and fracture in varied chemical conditions. The objective of this study consists to determine the wear that is caracterized by the height loss with a mechanical deplacement sonsor, a micrometric dial comparator and a long working distance microscope. In addition, the effect of cyclic loading on the growth of an indentation crack on a restoration dental composite (hybride) and the rupture of two resins (Meliodent and Major) is examined. Two wear modes are considered: dry (air) and lubrificated sliding (acid pH1.5, base pH14 and water pH7). On a new made wear device, the natural tooth rotates with regard to the composite sample. The contact is flat on flat. The of applied load and speed on the removal materials or resin and composite dental materials are investigated. In both case, the results show that the accumulated wear of the dental materials increase with the normal load and sliding speed. The results of wear show a low difference in hight loss obtained by the different methods. Put a side the acid, the two other lubricants (base and water) are minimized wear compared to the dry mode. The last lubricant (water) gave the lower wear. The fatigue test for resins indicate that resin Major is more brittle than resin Meliodent. The fatigue research for composite usually studies the nomber of cycles until catastrophic failure. In our case, the fatigue test consists to follow the microcracks introduced by Vickers indentation technique in cyclic shoks between the natural tooth and the dental composite sample. The measures revealed that the cracks in tension grow in a linear manner according to the number of cycles while those in compression decrease. Lasly, by using the finite element method and the computer code CASTEM, we simulated the behavior of a natural tooth under compression loads. For that two cases are proposed: with and without restoration.