Written by Martin B. Goldstein, DMD Friday, 10 September 2010 12:45
Aesthetic restorative dentistry continues to grow in importance to dental patients and professionals alike. In light of continued advances in material science and consumers’ awareness of the potential results that can be achieved through contemporary dental care, it’s crucial to have a detailed understanding of today’s restoratives and sufficient experience in their clinical use in order to provide long-term success.
When indirect restorations are involved, it is the impression-taking process that is the critical link between the preparations that we create intraorally, and our dental laboratory technicians, who are then responsible for making us look good and our patients happy. While immersed in the tense and often grueling task of preparing multiple teeth, I often liken the process to a drama, the climax of which is the moment the impression tray is withdrawn from the patient’s mouth. It is at that very moment that we are prepared to either rejoice and relax, or shake our heads in disgust while preparing to do it over again as the prospect of taking a lunch break dims. And, of course, there’s the usual “teetering” as we deliberate whether our impression will suffice, despite the obvious technical defects (voids, marginal tears, drags, and/or pulls, etc) that may not provide the dental laboratory technicians with the accurate details needed for a great result. We’ve all been there!
Contemporary impression materials continue to evolve, purportedly developed by dental manufacturers to eliminate the technique sensitivities associated with previous generations of such materials. (Have you been practicing long enough to remember polysulfide rubber impression materials?) Regarding the ideal properties of an elastomeric impression material, we can all agree that we look for the following points:
- The material should be as hydrophilic as possible. While vinyl polysiloxane (VPS) materials are not truly hydrophilic, components can be added to them that enable such materials to emulate this desirable characteristic, as will be discussed shortly.
- It should accurately reproduce the details that present intraorally.
- The material should exhibit dimensional stability, even with multiple pours.
- It should demonstrate viscosity that is conducive to material placement and clinical management of the patient.
- It should have tear resistance and elasticity, enabling the clinician to easily remove the set impression without distortion or leaving behind remnants.
- The material should have working and setting time appropriate for the chosen technique (ie, multiple preparations may benefit from a material with a longer working time).
VPS is generally regarded as the most popular elastomeric impression material in fixed prosthodontics due to its precision, elasticity, dimensional stability, and odorless and tasteless characteristics. Often overlooked is “ease of removal.” I still recall embarrassing moments experienced when attempting to remove excessively rigid and sticky alternatives that refused to budge without using excessive force or even an extra set of hands!
The importance of matching the right impression material properties to the task at hand will be demonstrated and discussed in the context of the case to follow.
Diagnosis and Treatment Planning: Inspiration Instilled
From Figures 1 and 2, it is evident that Ira, a patient relatively new to my practice, was a potential candidate for an aesthetic rehabilitation. Until the time that this case formally began, Ira presented mostly for crisis-based dentistry which typically involved repairing failing posterior restorations. During one of those visits, I elected to expose Ira to the possibilities of smile rehabilitation. This involved a quick digital portrait that was forwarded to Smile-Vision (Smile-Vision). In a few days, I received a notice that Ira’s simulation was ready for viewing and subsequent downloading. Upon doing so, I printed and placed the simulation in Ira’s chart in preparation for his next unscheduled visit (Figures 3a and 3b). (Note: If you prefer, Smile-Vision can also print a copy of the simulation for you.)
|Figure 1. Preoperative retracted view of the patient’s smile.||Figure 2. Occlusal view of the compromised maxillary dentition.|
|Figures 3a and 3b. Preoperative portrait view of the patient (a). Smile-Vision preview of the anticipated treatment result (b).|
Ira’s next visit was necessitated by pulpitis in a lower molar that prompted endodontic therapy and a subsequent crown. During that visit, I gave Ira a copy of his simulation. His reaction ranked among the most exuberant of those I have ever witnessed upon viewing of their simulation: he was smiling ear to ear at the prospect of what might be accomplished. To put it simply: “You can make me look like this picture?” To which I replied, “Yes!”
|Figure 4. Virtual study models (diagnostic wax-up [or mock-up] created by the digital imaging software).|
|Figure 5. Mounted study models with diagnostic wax-up on the articulator.|
This preview prompted a more extensive discussion between Ira and me, ultimately resulting in the formulation and patient acceptance of a treatment plan that would guide the case to its successful completion. In all, Ira’s treatment plan included orthodontic, endodontic, periodontal, and oral surgical care in addition to the prosthodontic treatment needed to restore his smile.
Prior to instituting any restorative procedure, Ira’s simulation was used by Smile-Vision to generate a virtual wax-up (or mock-up) (Figure 4), a preparation guide, and a hard/soft template that would subsequently enable the chairside fabrication of acrylic provisional restorations. The “Resin-Replica” created from the mock-up was mounted on a Panadent articulator (Panadent) to enable all functional criteria to be reconciled preoperatively (Figure 5). Tooth No. 9, which, as determined during endodontic consultation, exhibited an advanced periodontal lesion with a poor prognosis, was ultimately extracted prior to restorative treatment. It would be allowed to heal for approximately 6 weeks while the socket stabilized. During that same time, tooth No. 23 was removed, and orthodontic therapy performed to align Ira’s lower anterior teeth in preparation for porcelain veneers.
Tooth Preparation, Tissue Management, and Impressions
Following completion of Ira’s preparatory specialty care (lasting approximately 8 months in total), the maxillary dentition was prepared for full-coverage crowns and a fixed partial denture (Figures 6 and 7), taking care to expose the margins for taking the final impression and the anticipated restorations. Having completed periodontal care in advance of restorative treatment, no exudates, blood, or other crevicular fluids that would have compromised the final impression were detected.
|Figure 6. Facial view of the completed preparations for the dentition of the maxillary arch.||Figure 7. Occlusal view of the repaired anterior dentition.|
|Figure 8. Placement of the preliminary retraction cord.||Figure 9. Insertion of the impression cords (double-cord technique was used).|
Achieving proper hemostasis was critical to capturing a precise impression. A dual-cord technique and laser-troughing ezlase (BIOLASE) were used in order to ensure that the gingival tissues were sufficiently deflected from the preparation margins for accurate registration of these critical areas. The first epinephrine-soaked cords (size No. 0, Gingibraid [Dux]) were placed circumferentially around the prepared teeth (Figure 8). Then, a second continuous cord (size No. 1) was inserted around all the teeth to further facilitate retraction (Figure 9). In areas where the margins were not fully exposed using the dual-cord technique, a soft-tissue diode laser was also applied to improve access of the impression material to all the details of the margins (Figure 10). The second cord would be removed just prior to the injection of the light-body material, leaving the sulcular cord in place throughout the process.
|Figure 10. A soft-tissue diode laser (ezlase [BIOLASE]) was used to optimize the position of the gingival tissue for impression making.||Figure 11. Application of a surfactant (B4 Pre-Impression Surface Optimizer [DENTSPLY Caulk]), done prior to the application of the vinyl polysiloxane impression material.|
|Figure 12. Injection of wash material around prepared dentition.||Figure 13. Flowing the impression material (Aquasil Ultra Xtra Smart Wetting Impression Material [DENTSPLY Caulk]) into the custom resin impression tray.|
|Figure 14. Seating of the impression tray.||Figure 15. Occlusal view of the resulting impression.|
|Figure 16. Provisionalized maxillary dentition.||Figure 17. The definitive restorations were polished on the model and forwarded for try-in, cementation, and final finishing/polishing.|
Next, a surfactant (B4 Pre-Impression Surface Optimizer [DENTSPLY Caulk]) was then applied to the prepared teeth. This important new clinical step was done to break the surface contact tension, thus providing a lubricating effect for the light-body impression material (Figure 11) that was subsequently syringed around the prepared dentition (Figure 12). An elastomeric impression material (Aquasil Ultra Xtra Smart Wetting Impression Material [DENTSPLY Caulk]) was selected for the procedure for a variety of reasons. Its extended working time afforded me 45 additional seconds for syringing the material around the preparations, enabling full capture of the margins minus the undesired voids, air bubbles, or draws. I like to use a resin custom tray with an open palate design which makes it easy to retrieve any excess impression material that may escape down a patient’s throat. It’s worth mentioning that the thixotropic (yet flowable) consistency of the Ultra Xtra tray material all but eliminated any concerns of tray run-off. (Figures 13 and 14 demonstrate loading of the custom tray followed by its intraoral seating.) In addition, this impression material would also be easy to remove upon setting, thus eliminating but one more source of stress when impressing multiple teeth in a close-fitting custom tray. Upon removal from the patient’s mouth (Figure 15), the impression was easy to read and was sent to the dental laboratory with all the diagnostic information gathered during preoperative consultation and at the chair.
Bisacrylic (Protemp Garrant [3M ESPE]) provisional restorations, fabricated from the template demonstrating the ideal position of the patient’s dentition (determined preoperatively in the Smile-Vision wax-up and mockup), were delivered to the patient at this time (Figure 16). The provisional restorations would enable proper function during laboratory fabrication of the definitive restorations and ensure evaluation of patient function, phonetics, and aesthetics during this 2-month period.
The impressions of the patient’s maxillary and mandibular arches were used to pour accurate working models and were used to create the restorations required to satisfy the patient’s aesthetic objectives. The impressions were forwarded to the dental technician along with digital photographs (eg, of the preoperative condition, preparations, the seated provisional restorations) and the 3-dimensional Smile-Vision mock-up itself. Single-unit, full-coverage, porcelain-fused-to-metal (PFM) crowns were created for teeth Nos. 3 to 7, as well as teeth Nos. 13 and 14 (Figure 17). A PFM bridge was seated for teeth Nos. 8 to 12 (with pontics at teeth Nos. 9 and 11).
Delivery of the Final Restorations
Teeth Nos. 22 to 27 received orthodontic care (during which tooth No. 23 was also extracted) to align with the anticipated position of the maxillary anterior teeth. Six veneers (including one for a lower premolar tooth) would be delivered for the anterior mandibular arch to restore it to ideal form, position, and aesthetics. These restorations would be seated with the combination of a self-etching, self-priming, light-cured adhesive system and resin cement (BiFix QM [VOCO]).
|Figure 18. Occlusal view of the maxillary dentition following insertion of the definitive restorations.||Figure 19. Final view of the patient (4 weeks postoperatively).|
|Figure 20. Retracted postoperative view.||Figure 21. Postoperative view of the anterior maxilla demonstrating the predictable results achievable when using the proper collaborative (interdisciplinary) techniques.|
Delivery of the definitive maxillary restorations was conducted at a second appointment in order to provide sufficient time for the healing of the gingival tissues and extraction sockets. The single-unit PFM crowns and bridge were accomplished with self-etching resin cement. Final occlusal adjustments were performed, and then the restorations were polished to a natural luster (Figure 18).
The patient was recalled approximately 3 weeks postoperatively for follow-up, including taking the final case photos (Figures 19 to 21) and to confirm success of the treatment.
The precision of the resulting indirect restorations was directly influenced by the accuracy (defined as the ability to properly relate all the details of the prepared teeth) of the impressions taken in this case. Consequently, it was imperative that I obtain an impression that duplicated the prepared teeth as well as the uncut tooth surfaces beyond the margins. The 2 combined would enable the dental laboratory technicians to ascertain the exact position and configuration of the finish line. The adjacent teeth and gingival tissues were also encompassed and reproduced in the void-free impression, which consequently allowed the casts to be properly articulated and the restorations to be naturally contoured.
Multiple factors contribute to the success of any case, including the one presented in the following description:
One was the digital simulation from Smile-Vision, which aided considerably in gaining patient acceptance of the treatment plan. It also allowed for efficient treatment planning (as well as yielding the resin replica, preparation guide, and template for the provisional restorations).
The impression material chosen, with its extended working time and accompanying surfactant, made it conducive to multiple treatment sites, enabling me to proceed with confidence through this otherwise technique-sensitive process. Ultimately, we are only as good as our impressions, no matter how many hours are spent preparing the dentition.
Finally, the collaborative approach—involving our periodontist, orthodontist, endodontist, and dental laboratory technicians—allowed each professional to optimize the health, position, and function of the dentition prior to restorative care. All involved provided valuable contributions to the outcome depicted herein.
The author would like to thank the excellent team of dental technicians at Aesthetic Porcelain Studios, Los Angeles, Calif, for the beautiful technical work presented in this article, and a special thanks to Smile-Vision for their excellent diagnostic workup.
Disclosure: Dr. Goldstein reports no conflicts of interest.
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