Direct Procedure

1. Lightly lubricate the canal and notch a loose-fitting plastic dowel (Fig. 12-33, A). It should extend to the full depth of the prepared canal.

2. Use the bead-brush technique (Fig. 12-33, B) to add resin to the dowel (Fig. 12-33, C) and seat it in the prepared canal. This should be done in two steps: Add resin only to the canal orifice first. An alternative is to mix some resin and roll it into a thin cylinder. This is introduced into the canal and pushed to place with the monomer-moistened plastic dowel.

3. Do not allow the resin to harden fully within the canal. Loosen and reseat it several times while it is still rubbery.

4. Once the resin has polymerized, remove the pattern (Fig. 12-33, D).

5. Form the apical part of the post by adding additional resin and reseating and removing the post, taking care not to lock it in the canal.

6. Identify any undercuts that can be trimmed away carefully with a scalpel.

The post pattern is complete when it can be inserted and removed easily without binding in the

Fiber Post Placement

Fig. 12-30. Carbon fiber posts. A, The C-Post system is available in various sizes and configurations. B, Gutta-percha is removed with hot instruments or a Gates Glidden drill. The canal is prepared sequentially with the drills provided by the manufacturer. C, The post is seated in the canal and shortened with a diamond rotary instrument or disk. Wire cutters should never be used to cut carbon fiber composites, because they crush and weaken the composite structure. D, The canal is prepared by etching and priming according to the manufacturer's recommendations. The n the post is prepared by airborne particle abrasion. E, The luting resin is introduced into the canal with a lentulo spiral. F, The post is seated and the core built up with the recommended core resin. G, The preparation is finalized. H, The completed restoration. (Courtesy Bisco, Inc.)

Fig. 12-30. Carbon fiber posts. A, The C-Post system is available in various sizes and configurations. B, Gutta-percha is removed with hot instruments or a Gates Glidden drill. The canal is prepared sequentially with the drills provided by the manufacturer. C, The post is seated in the canal and shortened with a diamond rotary instrument or disk. Wire cutters should never be used to cut carbon fiber composites, because they crush and weaken the composite structure. D, The canal is prepared by etching and priming according to the manufacturer's recommendations. The n the post is prepared by airborne particle abrasion. E, The luting resin is introduced into the canal with a lentulo spiral. F, The post is seated and the core built up with the recommended core resin. G, The preparation is finalized. H, The completed restoration. (Courtesy Bisco, Inc.)

Cosmopost Inlay Core

Fig. 12-31. A, Zirconia posts, such as the CosmoPost, shown with the corresponding rotary instruments, are esthetic and strong. B, Special pressable ceramics are available to form the core (composite resin can also be used). (See also Fig. 25-19.)

(Courtesy Ivoclar North America.)

Fig. 12-31. A, Zirconia posts, such as the CosmoPost, shown with the corresponding rotary instruments, are esthetic and strong. B, Special pressable ceramics are available to form the core (composite resin can also be used). (See also Fig. 25-19.)

(Courtesy Ivoclar North America.)

Acrylic Fiber Cross Section
Fig. 12-32. Ceramic composite post. A, The ^Estheti-plus post system uses ccramic fibers in a resin matrix. B, Cross-section a i and C, longitudinal sections of the fiber composite.
Fig. 12-33. Fabrication of an acrylic resin pattern for a custom-made post. (Courtesy Dr. R. Webber.)

canal. Once the pattern has been made, additional resin or light-polymerized resin* is added for the core.

Pattern Fabrication with Thermoplastic

1. Fit the plastic rod to the prepared post space. Trim the rod until the bevel area is approximately 1.5 to 2 mm occlusal to the finish line for the core.

2. Lubricate the canal with a periodontal probe and petroleum jelly.

3. Heat the thermoplastic resin over a flame until the material turns clear or heat the resin in a low-temperature glue gunt.

4. Apply a small amount of the heated resin to the apical end of the rod to cover two thirds of the anticipated length of the post pattern.

5. Fully insert the rod into the prepared post space. Lift after 5 to 10 seconds and reseat. Inspect the post pattern for completeness and remove any projections that result from undercuts in the canal with a scalpel blade.

*LX Gel, Dentatus: New York; Palavit G LC, Heraeus f; h-- Tu^nf. l.ikvk -.md Vkxlvr, HuiK V^il-y. K'hi Kulzer, Inc.: South Bend, Indiana.

Merritt Cast Post

Fig. 12-34. The Merritt EZ Cast Post system. A, The canal is lubricated and excess lubricant removed with paper points. The post was previously trimmed until its beveled portion protrudes about 1.5 to 2 mm above the tooth preparation. B, A stick of the thermoplastic material is heated. C, The plastic rod is covered for about two thirds of the anticipated post length. D, The coated post is inserted and can be removed in 5 to 10 seconds. E, After any protrusions have been removed, the core is built from autopoly-merizing resin and trimmed to ideal tooth preparation form. F, The completed custom post-and-core. (From RosenstielSFetal: J Prosthet Dent 77:209, 1997.)

Fig. 12-34. The Merritt EZ Cast Post system. A, The canal is lubricated and excess lubricant removed with paper points. The post was previously trimmed until its beveled portion protrudes about 1.5 to 2 mm above the tooth preparation. B, A stick of the thermoplastic material is heated. C, The plastic rod is covered for about two thirds of the anticipated post length. D, The coated post is inserted and can be removed in 5 to 10 seconds. E, After any protrusions have been removed, the core is built from autopoly-merizing resin and trimmed to ideal tooth preparation form. F, The completed custom post-and-core. (From RosenstielSFetal: J Prosthet Dent 77:209, 1997.)

6. For the direct technique, fabricate the core of the post space. If the fit is too tight, the im-with conventional autopolymerizing resin pression material will strip away from the using the brush-bead technique or syringe wire when the impression is removed.

a light polymerized pattern resin (an easier 3. Coat the wire with tray adhesive. If subgingi-

technique). val margins are present, tissue displacement

7. If the indirect technique is preferred, pick up may be helpful. Lubricate the canals to facili the pattern with an elastomeric impression material, which can be poured in the conven tional manner. Soak the cast in warm water to help release the pattern. Reseat the post pattern and wax the core.

8. Invest and cast the post-and-core. Phosphate-bonded investment is recommended because of its higher strength.

Indirect Procedure (Fig. 12-35). Any elastomeric material will make an accurate impression of the root canal if a wire reinforcement is placed to prevent distortion.

1. Cut pieces of orthodontic wire to length and shape them like the letter J (Fig. 12-35, A).

2. Verify the fit of the wire in each canal. It should fit loosely and extend to the full depth tate removal of the impression without distortion (die lubricant is suitable).

4. Using a lentulo spiral, fill the canals with elastomeric impression material. Before loading the impression syringe, verify that the lentulo will spiral material in an apical direction (clockwise). Pick up a small amount of material with the largest lentulo spiral that fits into the post space. Insert the lentulo with the handpiece set at low rotational speed to slowly carry material into the apical portion of the post space. Then increase handpiece speed and slowly withdraw the lentulo from the post space. This technique prevents the impression material from being dragged out. Repeat until the post space is filled.

Indirect Post Impression
Fig. 12-35. Indirect procedure for post-and-cores.

5. Seat the wire reinforcement to the full depth of each post space, syringe in more impression material around the prepared teeth, and insert the impression tray (see Fig. 12-35, B).

6. Remove the impression (see Fig. 12-35, c, evaluate it, and pour the working cast (see Fig. 12-35, D) as usual (see Chapter 17).

NOTE: Access for waxing is generally adequate without placement of dowel pins or sectioning of the cast.

7. In the laboratory, roughen a loose-fitting plastic post (a plastic toothpick is suitable) and, using the impression as a guide, make sure that it extends into the entire depth of the canal.

8. Apply a thin coat of sticky wax to the plastic post and, after lubricating the stone cast, add soft inlay wax in increments (Fig. 12-36). Start from the most apical and make sure that the post is correctly oriented as it is seated to adapt the wax. When this post pattern has been fabricated, the wax core can be added and shaped.

9. Use the impression to evaluate whether the wax pattern is completely adapted to the post space.

Was this article helpful?

+1 0

Post a comment