Written by James Braun, DDS, MS Tuesday, 01 January 2002 00:00
The final aesthetic restorative outcome of anterior teeth can be significantly influenced by several important factors. These factors include the following:
(1) The extent and needs of the restorative case as it relates to strength, aesthetics, occlusion, and ease of placement.
(2) The underlying dentinal shade. Very often devital or discolored teeth can alter the final coloration when more translucent restorative dental materials are utilized in an overlay application. This darkening can extend into the entire root system.
(3) Pre-existing restorative materials contribute to the overall scheme of color emanating from the dentinal/gingival complex. It is very common with porcelain/metal crowns where metal extends to the labial margin that the free gingival margin takes on a bluish tint. This is because of the shadowing effect into the soft tissue created by the overlying metal substructure.
(4) With devital teeth where significant coronal structure is gone, there is a need to place a post and core. Cast gold posts will contribute to darkening of the root and do not allow for selective shading of the coronal portion. This can be extremely important when placement of an all-ceramic noncore crown is contemplated.
The impact of these factors is relative to the extent and criteria of the treatment plan. For example, if all anterior teeth are being restored, the decision process and material selection may be simplified. Limited intraocclusal space and parafunctional habits may dictate the need for porcelain/metal crowns with porcelain shoulders. Also, in situations where adhesive techniques are difficult because of isolation, preparation depth, or soft tissue health, there exists the need to cement the final restorations. Often, however, in the anterior region the most important criterion is aesthetics. Moreover, this is more evident when performing the most challenging aesthetic restorative task of matching an adjacent artificial crown to a natural central incisor. This challenge is even greater when restoring devital teeth. The clinician must consider the influence and impact of the underlying post and core system.
This case report typifies what can be accomplished with a tooth-colored post and core system to maximize aesthetics.
|Figure 1. The patient presented with a loose and unaesthetic crown on tooth No. 8, with gingival recession. Tooth No. 9 had a fractured incisal edge.|
A 45-year-old female presented with concerns over some existing dental work, specifically a somewhat loose crown on tooth No. 8. The history included placement of this PFM crown approximately 2 years previously. Along the labial margin, a strip of composite resin had been placed recently, following some gingival recession (Figure 1). This composite resin restoration was prompted by exposure of the darkened root and visibility of the crown’s metal substructure.
The history indicated the tooth had been traumatized 10 years earlier, received endodontic therapy, and was subsequently veneered with direct composite to improve the appearance. The access opening had been plugged with amalgam, and no post had been placed. Presently, it was ascertained that probably a portion of the remaining coronal structure had fractured loose. Tooth No. 9 also had a fractured incisal angle. With that in mind, a treatment plan was devised to include the following:
(1) Placement of an aesthetic fiber-reinforced post and appropriate shaded composite core.
(2) Construction of an all- porcelain pressed ceramic crown to replace the existing crown.
(3) Restoration of the incisal angle on tooth No. 9 with composite resin.
|Figure 2. The radiograph is used to determine the appropriate diameter and length of post to place in the root canal.|
The radiograph was evaluated to initially determine the appropriate diameter and length of post to place in the canal (Figure 2).
There are a number of fiber- reinforced resin post systems on the market for use in the anterior region.1 The Para Post Fiber White System (Coltene/Whaledent) was selected because of clinical protocol. This particular post is composed of uni-directional glass fibers embedded in composite resin. This creates a tough, light-colored post with tensile strength of approximately 1,200 Mpa and flexural strength of 990 Mpa. The bis-GMA resin component allows for adhesive bonding of the post. The design itself depicts double undercuts and a rounded antirotational head.
|Figure 3. After the crown was removed, gutta-percha was removed using a Gates Glidden system.|
A very important feature is the fact that the flexural modulus of the post (28 GPA) is very similar to dentin (18 GPA). This allows for potentially greater fracture resistance of the tooth/root complex as it flexes.2 The use of adhesively bonded pre-formed posts can actually aid in root reinforcement.3 After the crown was removed, gutta-percha was drilled out utilizing a Gates Glidden system for nondestructive preparation (Figure 3). The use of a parallel post would allow for maximum retention.4 Care must be taken not to overenlarge the diameter of the post space or overextend the preparation.5
|Figure 4. The black drill contained in the post kit is used to extend the post preparation approximately two thirds down the root and 1.5 mm in diameter.||Figure 5. The Fiber White post is tried in to check length and fit.|
Initially, a rubber dam was placed for isolation. Because of various guidelines and clinical experience, it was determined to extend the post preparation approximately two thirds down the root and approximately 1.5 mm in diameter. The black drill with the post kit was used for this step (Figure 4). After preparation for the post space, the Fiber White post was tried in to check length and fit (Figure 5).
|Figure 6. A polypropylene form is placed over the teeth with the post in place to verify room for the core over the post.||Figure 7. The canal is thoroughly cleaned with a slurry of pumice and a peeso brush.|
From a pre-op model, a 0.020 polypropylene sheet had been vacuformed. This form was placed over the teeth with post in place to verify ample room for the core over the post (Figure 6). The advantage of the core form is that it enables the clinician to re-establish proper tooth form for guided reduction and preparation. After instrumentation, the canal was thoroughly cleaned with a slurry of pumice and a peeso brush (Premier) (Figure 7). This would allow for thorough debridement of the canal prior to the bonding technique. After complete rinsing, 37% phosphoric acid gel was placed in the canal for 30 seconds, and rinsed and partially dried, leaving the dentin only moist. It was decided to utilize a resin cement for placement of the post because of the increased strength and decreased solubility.6
|Figure 8. A periodontal probe is inserted to prevent air entrapment and hydraulic buildup.||Figure 9. The post is placed and covered with resin cement for improved adaptation.|
The Para Post cement kit was utilized for the next two steps. Initially, the dual-cure adhesive was placed into the canal with a paper point. It is essential not to allow any pooling that would prevent seating of the post. Next, the fiber post was silanated for improved bond strength and coated with the adhesive. Following this, the dual-cure resin cement was mixed and injected into the canal. A perio probe was inserted to prevent air entrapment and hydraulic buildup (Figure 8). Next, the post was placed and covered with the resin cement to allow for improved adaptation (Figure 9). The use of adhesive resin cement allows for maximum retention of the post.7 Following the final cure of the resin cement, the next stage was to complete the core buildup.
|Figure 10. The vacuform is loaded with shade A2 and placed over the post.||Figure 11. The vacuform is light cured from the labial and lingual for 30 seconds each for complete polymerization.|
|Figure 12. After injection of local anesthetic, the form is removed and tooth preparation is begun.|
A composite was selected of the appropriate dentin shade to imitate the proper dentin color base. In this case Synergy (Coltene/Whaledent) hybrid was utilized. The physical properties would allow for sufficient strength and would complement the flexural strength and retention in a top-to-bottom operation.8 The vacuform was loaded with shade A2 and placed over the post (Figure 10). This was light cured from the labial and lingual each for 30 seconds with an Optilux 501 light (Kerr), which would allow for complete polymerization (Figure 11). After injection of local anesthetic, the form was then removed and preparation began. This direct system allows for a one-appointment process (Figure 12).
|Figure 13. The preparation of tooth No. 8 included a rounded chamfer finish line extending to the free gingival margin, and rounded internal line angles.|
Because proper tooth dimensions and appropriate density were attained with the composite core, guided reduction was simplified. A rounded chamfer finish line that extended to the free gingival margin was employed, along with rounded internal line angles (Figure 13). It is essential that a 2-mm ferrule be placed onto solid tooth structure to avoid increased stress along the core/root interface.9
|Figure 14. The PVS impression material is injected intrasulcularly around the tooth.||Figure 15. A custom tray improves accuracy and dimensional stability of the impression.|
Upon completion, the impression was made. Ultra Pak Cords No. 2 (Ultradent) moistened with aluminum chloride aqueous solution were first placed in the sulcus. These dampened cords were removed, and the light body polyvinylsiloxane (PVS) impression material Flextime (Kulzer) was automixed. A dispensing syringe (Kerr) was loaded from the tip end to avoid air entrapment. An Access tip (Centrix) was screwed onto the barrel, and impression material was injected intra-sulcularly around the tooth (Figure 14). A final impression was made with mono-phase viscosity to support the light body. Improved accuracy and dimensional stability was achieved with a custom tray (Figure 15). A self-cure bis-acrylic resin provisional Luxatemp-A2 (Zenith Corporation) was constructed by means of a putty matrix from the pre-op model. This allows for much better anatomical definition and fewer intraoral adjustments.
Because of impressive clinical success and optical qualities, Empress (Ivoclar Vivadent) was chosen for the definitive crown.10 This pressed ceramic system also results in decreased abrasion of opposing natural teeth.11 Because of its versatility and improved replication of natural dentition, a Vita 3-D (Vita Corporation) shade guide was utilized for shade matching. Along with this shade designation, digital photography was employed and conveyed to the dental laboratory. This is essential for the technician as a guide to characterize the restoration in the layering technique. Also, having porcelain tabs enables the dentist to select appropriate modifier powders to mimic the dentin and enamel. This replication process is never more crucial than in a clinical situation such as this. After being returned from the lab, the crown was inspected for shade match, fit, and occlusion.
Prior to final seating of the crown, the incisal angle on tooth No. 9 was restored. PQ adhesive (Ultradent) was used as the bonding system, followed by Vitalessence (Ultradent) composite shade A-2, and overlayed with translucent modifier PS. The composite restoration was polished with the Astropol kit (Ivoclar Vivadent). The final crown, which had been etched with hydrofluoric acid, was silanated to improve bond strength.
|Figure 16. The final result is highly aesthetic.|
The protocol in this case was to utilize a resin cement for maximum strength and retention.12 After cleaning and etching the tooth, Single Bond (3M ESPE) was placed and light cured for 10 seconds. The crown was then loaded with dual-cure Rely X ARC Cement (3M ESPE) and placed on the core. After checking occlusion and fit, the excess cement was removed. Both sides of the crown were then light cured to enhance the physical properties of the cement. The final check was made and the patient happily viewed her new smile (Figure 16).
1. Freilich MA, Meiers JC, Duncan JD, et al. Fiber Reinforced Composites in Clinical Dentistry. Coral Stream, Ill: Quintessence Publishing; 2000.
2. Sirmal S, Reis SN, Morgano SM. An in vitro study of the fracture resistance and the incidence of vertical root fracture of pulpless teeth restored with six post and core systems. J Prosthet Dent. 1999;81:262-269.
3. Mendoza DB, Eable WS, Kuhl EA, Ho R. Root reinforcement with a resin bonded preformed post. J Prosthet Dent. 1997;78:10-14.
4. Margano SM. Restoration of pulpless teeth: application of traditional principles in present and future contexts. J Prosthet Dent. 1996;75:375-380.
5. Goodacre CJ, Spoimick KJ. The prosthodontic management of endodontically treated teeth. J Prosthet Dent. 1995;4:51-53.
6. Rosenstiel SF, Land MF, Crispin BJ. Dental luting agents: a review of the literature. J Prosthet Dent. 1998:80:280-301.
7. Duncan JP, Pameijer CH. Retention of parallel-sided titanium posts cemented with six luting agents; an in-vitro study. J Prosthet Dent. 1998;80:423-428.
8. Cohen B, Pagnillo MK, Condos S, et al. Four different core materials measured for fracture strength in combination with five different designs of endodontic posts. J Prosthet Dent. 1996;76:487-495.
9. Libman WJ, Nicholls JL. Load fatigue of teeth restored with cast post and cores and complete crowns. Int J Prosthodont. 1995; 8:155-161.
10. Fradeani M, Aquilano A. Clinical experience with empress crowns. Int J Prosthodont. 1997;10:241-247.
11. Krejci I, Lutz F, Reimer M, et al. Wear of ceramic inlays, their enamel antagonists and luting cements. J Prosthet Dent. 1993;69:425-430.
12. Tjan AH, Li T. Seating and retention of complete crowns with a new adhesive resin cement. J Prosthet Dent. 1992; 67:478-483.
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