Fracture Strength Of Endodontically Treated Teeth with Flared Root Canals and Restored with Different Post Systems
Maccari PC, Cosme DC, Oshima HM, et al. J Esthet Restor Dent. 2007;19(1):30-37.
BACKGROUND: Many post systems are available to clinicians, yet no consensus exists about which one is better for restoring endodontically treated teeth. PURPOSE: This study evaluated the fracture strength of teeth with flared canals and restored with two fiber-reinforced resin systems (glass fiber: FRC Postec [Ivoclar Vivadent, Schaan, Liechtenstein]; quartz fiber: D.T. Light Post [Bisco Dental Products, Schaumburg, IL, USA]); and one custom cast base metal (Ni-Cr) post and core system. METHODS: Thirty anterior teeth had their crowns removed below the cemento-enamel junction and were endodontically treated. The canals were prepared for post fixation, and the canal walls were flared using a taper diamond bur. The prepared roots were randomly divided into three groups according to the post system. All posts were cemented with an adhesive resin cement. For the fiber-reinforced resin posts, cores were built using microhybrid composite. Metallic crowns were luted using zinc phosphate cement. Specimens were loaded at 45 degrees in a universal testing machine at a crosshead speed of 0.5 mm/min until failure. The mode of failure was classified as repairable or nonrepairable. RESULTS: Teeth restored with cast posts had fracture strength twice that of teeth restored with resin posts. Fiber-reinforced posts’ failure at a compressive force is comparable to clinical conditions, but all failures were repairable. CONCLUSION: Fracture strength and mode of failure in anterior teeth with flared canals varied according to the type of post used to support a crown.
There are many options to consider when restoring endodontically treated teeth. Teeth can be weakened by a loss of internal root structure due to the age of the patient (larger, flared canals for the younger patient); overprepared roots from previous post-retained restorations; overpreparation during endodontic treatment; caries; fractures; or internal resorption. For these clinical situations, the use of a fiber-reinforced resin post has become more accepted because of the root-reinforcing capability of this type of post when cemented with an adhesive-resin luting agent. Past studies evaluating different metal, ceramic, and fiber-reinforced posts have many times not restored the tooth being tested with an indirect crown. The researchers of this article provide a more clinically relevant evaluation of a cast post-and-core compared to two different fiber-post systems with the use of a cast-metal crown. One problem with metal posts is that the complication of root or crown fractures can lead to loss of the tooth. In this study, seven of 10 specimens with cast posts had nonrepairable failures (root fracture) while in the two fiber-post systems tested, all of the specimens had failures that would be clinically repairable. The clinical relevance of this study is that while the cast-metal post-and-cores had twice the fracture strength when compared to the fiber posts, the root fractures that occurred with the cast-metal (70%) would lead to tooth extraction. In the flared canals that were restored, the two fiber-post systems would have maintained the survivability of the teeth when failure occurred. Fiber-reinforced posts are a viable alternative to traditional metal posts used to restore endodontically treated teeth.
Howard E. Strassler, DMD