The selection of the best restoration for an endodontically treated tooth in the aesthetic zone depends on strength and the ability to recreate the form, function, and aesthetics of the natural tooth. The increased use of all-ceramic materials is a result of improved ceramic materials and adhesive systems. However, the advent of the current variety of translucent ceramic systems makes the shade of the abutment important in achieving the desired aesthetic outcome. This article discusses the different types of posts used in the restoration.
The selection of the best restoration for an endodontically treated tooth in the aesthetic zone depends on strength and the ability to recreate the form, function, and aesthetics of the natural tooth. The increased use of all-ceramic materials is a result of improved ceramic materials and adhesive systems. However, the advent of the current variety of translucent ceramic systems makes the shade of the abutment important in achieving the desired aesthetic outcome. Carossa and colleagues studied different posts and cores and thought that, although there were significant differences spectrophotometrically, clinically these differences were not noticeable. Deger and colleagues, Vichi and colleagues, and Nakamura and colleagues arrived at different conclusions. They found that translucent ceramic crowns thinner than 1.6 mm are affected by the color of the core. Vichi and colleagues found that when the thickness of the ceramic crown was 1 mm, color differences with the adjacent teeth are visually noticeable. Color differences decreased when the thickness was increased to 1.5 mm, and at 2.0 mm, no differences were noticeable. Michalakis and colleagues found that cast posts can result in root discoloration and have a blue-gray effect if the overlying bone and soft tissue are thin, which would be especially important if a high lip line or broad smile exposes the restoration. De Rouffignac and de Cooman suggested using cast metal posts and cores with 2 thin metal tags to retain a ceramic for the core. However, this only addressed the optical effects in the coronal aspect, not in the root. If cast gold is used for the post and core, Carossa and colleagues found greater luminance with a polished core compared with a matte-finished one.
Because the shade of the final restoration is affected by the color of the abutment, the need for a post and the nature of the post must be considered. Previously, a post was considered necessary for reinforcing an endodontically treated tooth, but most recent studies demonstrate a weakening effect rather than reinforcement. Some clinicians feel that the use of adhesive materials allow the clinician to bond the post to the dentin, the core to the post, and the ultimate restoration to the post-core and remaining tooth structure. Theoretically, when the various components with analogous properties are bonded together, the root can be strengthened, but this theory has not been proved. However, when there is insufficient tooth structure present, full coverage restorations may need a post to provide adequate retention.
Need for a post
Post preparation may increase the risk of root fracture. Teeth that have been debilitated by trauma, caries, or previous restoration are often those that require endodontic treatment. Endodontic access forms require straight-line entrance and the “crown down” technique requires adequate removal of both coronal and radicular dentin to provide a continuously tapered preparation to the apex. The remaining tooth structure needs to be evaluated on its ability to retain and support the final restoration. The type of post and adhesive system that provides the best strength, reliability, aesthetics, and ease of handling should be selected. Peroz and colleagues formulated a classification of the amount of remaining tooth structure that is related to the remaining walls. Class I has all 4 axial walls remaining and only the access preparation, class II has 1 cavity wall removed and could be either an mesial-occlusal or distal-occlusal. Class III is an mesial-occlusal-distal cavity with 2 remaining walls, and class IV has only 1 remaining wall (either a buccal or lingual). Class V has no remaining walls. Dietschi and colleagues delineated the modifications that occur in dentin composition, physical characteristics, fracture resistance, tooth stiffness, and restorative materials and techniques that would be required to effectively restore an endodontically treated tooth. He also determined that there is a change in not only the water content but also the Young modulus, and proportional limit are modified slightly. There is no resulting decrease in compressive strength and tensile strength.