applied fracture mechanics

Chapter 4Fracture of Dental MaterialsKarl-Johan SöderholmAdditional information is available at the end of the chapterhttp://dx.doi.org/10.5772/483541. IntroductionFinding a material capable of fulfilling all the requirements needed for replacing lost toothstructure is a true challenge for man. Many such restorative materials have been exploredthrough the years, but the ideal substitute has not yet been identified. What we use todayfor different restorations are different metals, polymers and ceramics as well as combinationsof these materials. Many of these materials work well even though they are not perfect.For example, by coating and glazing a metal crown shell with a ceramic, it is possible tomake a strong and aesthetic appealing crown restoration. This type of crown restoration iscalled a porcelain-fused-to-metal restoration, and if such crowns are properly designed, theycan also be soldered together into so called dental bridges. The potential problem with thesecrowns is that the ceramic coating may chip with time, which could require a complete remakeof the entire restoration. Another popular restorative material consists of a mixture ofceramic particles and curable monomers forming a so called dental composite resin. Thesecomposites resins can be bonded to cavity walls and produce aesthetic appealing restorations.A potential problem with these restorations is that they shrink during curing and sometimesdebond and fracture. In addition to porcelain-fused-to-metal crowns and composites, allceramicand metallic restorations as well as polymer based dentures are also commonly used.These constructions have their inherent limitations too.The reason it is difficult to make an ideal dental material is because such a material has to bebiocompatible, strong, aesthetic, corrosion resistant and reasonable easy to process,properties that are difficult to find in one single material. Besides, material as well asprocessing costs of such a material should be relatively low in order to make the use of thematerial wide among all social-economical groups. That demand makes the ideal materialidentification process even more challenging.Today, dentistry to a great deal is driven by aesthetic demands, restricting the selectablematerials mainly to tooth colored materials. Because of that demand, dentists are moving© 2012 Söderholm, licensee InTech. This is an open access chapter distributed under the terms of theCreative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permitsunrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.