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  Ever since the development of the casting technique by Taggart (1907), gold cast posts have been receommendd for the retention of coronal restorations. In recent years the prefabricated post has been suggested as a replacement for the traditional apporoach. The prefabricated post not only eliminated a great deal of preparatory procedures (i.e. pattern fabrication, casting, etc.) but permitted the operation to be accomplished in one appointment.

   Functionally there are two types of posts:active and passive. The former (Flexipost)requires some type of energy to force the device into the prepared canal. The passive post (Parapost) on the other hand necessitates the use of a luting agent (with or without and adhesive). The active post has somewhat fallen into disfavor. The reason of course, relates to the energy incorporated into the root during insertion. This energy may either weaken the root or may exist latently until at a later time may be sufficient to cause a fracture of the root.

   The passive type ost may consis of several materials including base metal alloys, titanium, stainless steel, percelain, carbon fiber or glass fiber. Most all of the above have given way to the glass fiber post. While there are numerous reasons for the final selection, the most importnat relate to the matched properties between the post and the root itself. As clinical studies have demonstrated, this most important property is the modulus of elasticity. Both tooth structure and the glass fiber post range between 11 adn 14 Gpa.

   While it could be imagined that a post with strength properties superior to the root woud create a condition for enhancing root fracture resistance, the opposite is true, When a post of similar elastic modulus to tooth structure is used, externally applied forces are transmitted uniformly throughout the root thereby minimizing root fracture. Since the elastic modulus of such agents as porcelain, titanium and base metal alloys may be several times greater than the tooth into which they may be inserted, they are contraindicated.

    In addition to excellent resistance to root fracture, the glass posts are readily retrievable form the canal. This commonly is accomplished with the appropriate instruments or drills. Due to the nature of the post, the removal process grinds it into a powder which can be readily flushed from its location.

   Another feature of the glass fiber post is the potential for bonding. This relates not only to the surface of the post but the walls of the canal as well. It facilitates the potential for bonding the core to the post which can be in turn bonded to the cervical section of the prepared tooth as well.

    Regardless of the material comosition of the post, there is a potential problem associated with the adhesion of the luting agent. As reported by CRA (2003), all generations beyond the fouth generation tend to be incompatible with the dual or self-cured luting agents. This same relationship can also be experienced with the dual ro self-cure composite resin core materials. Adhesion values reported for generations five and six fall into the range of 0-8 MPa. Unfortunately, this means that there may be a fairly large number of bonded posts and cores with poor to non existnet adhesion.

    All of this has lead to the development and marketing of light-transmittable glass posts such as DT (Bisco). Assuming a realistic light transfer to the apical portion of the post, this approach would eliminate the real concern of deminished to non-existent bonding. Unfortunately, very little or no reliable information has been published regarding the efficacy of the light transmitting posts.