Selecting the Appropriate Core Material for Immediate Post and Core Buildup
Avishai Sadan, DMD
In the case of root canal therapy and moderate to extensive coronal tooth destruction, a post and core buildup procedure is required to provide a solid foundation for the future crown. The prefabricated circular post is an appropriate treatment modality if the canal can be prepared to receive a circular post without considerably compromising the root strength. The purpose of this discussion is to compare composite resin and amalgam as core materials. Amalgam must be ferruled and must be applied with sufficient bulk to provide optimal strength. Composite resins, however, are not limited by these considerations. It is difficult to locate anterior teeth that provide an adequate bed for ferruling and that have sufficient volume; even many premolars are not adequate for amalgam buildups. While the use of amalgam in anterior teeth raises aesthetic concerns, it is the limitations associated with the mechanical properties of the material that focus the discussion primarily on posterior dentition (molars). In order to provide optimal strength and minimal shrinkage, a highly filled composite resin is required for buildups.
Amalgam vs. Composite Resin in Molar Buildups
While amalgam can be utilized successfully for molar buildups, even without the use of a post,1 a number of factors can be addressed when using this application.
While a number of clinicians advocate the addition of amalgam bonding agents due to their ability to provide enhanced retention and marginal seal for the core,2 this bond strength is relatively inferior to that achieved with composite resin.3,4 Bonding procedures for composite resin and amalgam must be completed under meticulous moisture and contaminant control. In the presence of contaminants, bond strength is significantly reduced, and the risk of leakage is increased. If ideal moisture control cannot be achieved, the use of a composite resin buildup or even an amalgam bonding agent is not recommended. For the author, the inability to control moisture is the primary indication for the use of amalgam in the "traditional" manner for a buildup procedure.
This phenomenon is associated with amalgam and not with composite resin.
Although most new amalgams set rapidly and achieve high strength shortly after condensation, it is safer to prepare composite resin immediately following curing, and thus enable the clinician to build up and immediately prepare the tooth.
The need for optimal moisture control, multiple bonding steps (even with latest generation bonding agents), incremental buildup with multiple curing, and the use of a reliable light source render the use of composite resins much more cumbersome in comparison to "traditional" amalgam buildup.
Whenever appropriate moisture control can be achieved, highly filled composite resins provide strong foundations that can be safely prepared immediately following curing without any aesthetic compromises and the risk of tissue tattooing. The clinician must remember, however, that the traditional amalgam buildup procedure (without bonding agents) is indicated when moisture control is a concern. If amalgam is still a clinician's core material of choice, he or she should consider using it in conjunction with amalgam bonding agents.
* Dean, University of Southern California, Ostrow School of Dentistry, Los Angeles, CA.
- Nayyar A, Walton RE, Leonard LA. An amalgam coronal-radicular dowel and core technique for endodontically treated posterior teeth. J Prosthet Dent 1980;43(5):511-515.
- Eakle SW, Staninec M, Yip RL, et al. Mechanical retention versus bonding of amalgam and gallium alloy restorations. J Prosthet Dent 1994;72(4):351-354.
- Miller B, Burgess JO. Shear bond strength of amalgam bonded to dentin. J Dent Res 1997;76:68(Abstract No. 439).
- Gallo J, Xu X, Burgess JO. Dentin bond strength of three composite resins using five adhesives. J Dent Res 1998;77:945(Abstract No. 2508).