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An indirect technique to prepare a multirooted pulpless tooth to receive a crown is presented. The crown also may be made on the newly completed core and its die. The procedure promotes the use of a commercial dental laboratory. The system, which uses divergent roots, results in a cast core having maximum retention.
The technique described results in a well adapted cast post and core with good retention (Figs. 18 and 19). The chances of perforation of the root and trauma to the patient are reduced, and the expense of the procedure is minimal. This system is adaptable to single- or multirooted teeth and continually produces good results with minimal problems.
A practical direct technique for making post and core impressions with a T-pin and self-curing acrylic resin was described. Emphasis was placed on the function of the T-shaped plastic pin in fabricating the pattern. Clinical procedures for each step were described in detail. The unique characteristic of the T-pin of softening and becoming very sticky when exposed to direct contact with acrylic resin monomer allows soft acrylic resin to adhere to it, resulting in an accurate direct impression of the canal.
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A laminated single impression technique for cast post and core has been described. Its advantages are the ease and versatility with prefabricated or customized post techniques (Fig. 14) and the one-step registration of single or multiple divergent canals. Its disadvantage is the necessity for additional laboratory procedures.
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Casting a core to a prefit post reduces the need for adjustments at cementation. This study compared two-piece post and core castings to one-piece castings of the same geometric configuration. The specimens were made with 0.070-inch Whaledent laboratory burnout posts invested in a phosphate investment and cast with Midas, Sturdicast, or Rexillium III alloys. Three groups (n = 10) with two-piece castings had the post cast followed by a second casting of a 1 mm thick core to the post head. Three groups (n = 5) were cast in one piece. The specimens were tested for tension at a head speed of 1 cm/min. One Midas alloy two-piece casting was dislodged at the post head-to-core interface whereas the other specimens failed within the post. There was no significant difference between the two techniques using a generalized linear model (p less than 0.05).
An accelerated technique for casting a direct-pattern post and core restoration is presented. The entire clinical and laboratory procedure may be completed within 1 hour. The necessity for two appointments for completion of the restoration as well as the necessity of making two provisional restorations may be eliminated.
Carbon fibre reinforced carbon (CFRC) in the form of a prefabricated post has recently been developed and is theoretically acceptable for consideration in an endodontic post-retained crown system. This study compared four different types of postcore system cemented into 40 extracted anterior human teeth. The test groups consisted of CFRC posts cemented with a composite resin luting agent, and used with either a cast gold alloy core (Group B) or a composite resin core (Group C). Two existing post-core techniques were used as controls for comparison with the CFRC groups. One control was a prefabricated wrought precious alloy post having a cast gold alloy core, and cemented with zinc phosphate cement (Group A). The other was a prefabricated stainless steel post with a composite resin core, and cemented with a composite resin luting agent (Group D). All specimens were restored with a gold alloy crown and tested to failure with an obliquely applied compressive load at 130 degrees in an Instron using a cross-head speed of 5 cm min-1. The results showed that post-retained crowns using a prefabricated CFRC post exhibited properties comparable with, and in some cases better than, those of existing prefabricated posts. The mode of failure of specimens restored with a CFRC post was more favourable to the remaining tooth tissue than was that of specimens restored with a metallic post.
A technique to make a post and core pattern that can be used to save an existing crown has been presented. The technique should become an additional tool in the treatment armamentarium.
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A barbed broach covered by cotton fibers is used as a matrix to carry blue inlay wax into the canal prepared for a post. This simple, direct technique of post fabrication lends itself to various clinical situations. The technique requires no special armamentarium.
A technique for the construction of a cast post and core with a nonprecious metal is described. The technique is a practical and inexpensive approach to the construction of this type of restoration.
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Fabrication of posts and cores for fixed partial denture (FPD) and removable partial denture (RPD) abutment restorations is common in dentistry. The biocompatibility of various post and core techniques with the restorations was clinically evaluated according to location and function. In this study, 154 post and core constructions for 150 patients were observed for a 3-year period to determine if the function of the original restorations remained unsatisfactory. The following techniques were included: (1) screw post and light-curing composite resins, (2) cemented post with parallel sides and light-curing composite resins, and (3) a cast and core technique. Seventeen of the 154 restorations failed; four failures were attributed to root fractures, three to radicular caries, and five to crown dislodgement, while five failures were from detachment of the post and core from the root. The statistical analysis revealed that only the factor "type of abutment" (RPDs and FPDs) had some effect on the failure of the restorations.
A technique to provide cement spacing for cast post-cores prior to construction of their crowns is described. The axial lift of crowns cemented with zinc phosphate was greater, but not significantly, for crowns constructed on non-spaced post-cores compared with crowns constructed on spaced post-cores. Three materials were evaluated to determine their effectiveness in providing cement spacing for post-cores. The phenomenon of post-core 'wedging' during luting was identified.
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