INTRODUCTION
It will be news to no one that new technologies are changing the clinical practice and the dental laboratory workflow. As the profession adjusts, and as individual practitioners determine how or if these technologies have a place in their own offices, we must always consider the value chain in the process. From the initial patient presentation to delivery of a finished prosthesis and the subsequent follow-up, technology has the potential to change the dental value chain; however, it also has limitations.
Impression making is one example where emerging technologies are especially visible, and where many dentists are continually re-evaluating their options. This realm provides an especially good example of the “limitations versus value added” calculation. With in-office digital scanners at a price of $12,000 to $20,000 and more, dentists must carefully weigh their options with this technology. While chairside scanning has been touted for its improvements to productivity and accuracy, the fact remains that it cannot be used with every type of case and, therefore, dentists must stay sharp with their traditional impression-making materials and techniques. Given the state of today’s technology, in many types of restorative cases, an elastomeric impression technique provides the best accuracy, efficiency, and cost for the dentist.
On the laboratory side, a similar situation exists. CAD/CAM tools have improved standards for the design and manufacturing of some dental restorations. Despite these advances, for many dentists and labs, a solid model still provides a very sound method to finish margins, contact points, and occlusion; therefore, the buzz surrounding “model-free” restorations may be premature.
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| Before Image. The patient’s existing dentition was worn and mottled, with a failing crown on tooth No. 12. | After Image. The patient was extremely pleased with the aesthetic improvement and natural color. |
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| Figure 1. The Transcend simulation image showed possible results that could be realized by lengthening the central incisors, altering the smile-line, expanding the arch form, and making a shade change. | Figure 2. The teeth prior to impression-taking for the diagnostic model and provisional. |
When dentists and labs work together to optimize their individual contributions to the restorative process using the most appropriate tools, the result is often preferable to what can be achieved with an over-reliance on a digital workflow. An examination of the value chain for one representative large-scale case helps illustrate this concept: After a patient’s initial presentation to the office requesting an aesthetic makeover, the dentist communicates with the dental lab team to develop a simulation image of what the patient might expect from treatment. Once the patient approves the dentist’s plan, the dentist takes a set of traditional impressions and submits them to the dental lab, where they are used to make and scan a model, design a provisional digitally, and then mill the provisional. The provisional is then finished on the traditional model. At this stage, the case is again handed off to the dentist, who preps the teeth, relines the milled provisional, and captures a final set of impressions. The lab technician follows the same steps as before. A solid cast is digitized, the design of the provisional is carried forward, the restorations are milled and characterized, then finished on a solid cast. At the final appointment in the dentist’s office, the dentist places the restorations, ideally with minimal adjustments.
When a case goes well using a workflow like this, both the dentist and the laboratory can feel confident that they have delivered excellent work that was done with quality and value in mind. The aim with any aesthetic case is to gain a full understanding of the patient’s objective, identify the critical factors to satisfying that objective, and ultimately meet the patient’s expectations. In most cases, patient expectations have very little to do with the technologies used and much more to do with the aesthetic and functional outcomes of treatment. Viewed in this light, it is clear that there are processes that are naturally driven by technology, and there are processes that are better driven by traditional clinical techniques.
This case presentation will demonstrate a workflow merging new technologies with traditional materials and techniques.
CASE REPORT
Diagnosis and Treatment Planning
A 57-year-old female presented, seeking a cosmetic improvement to her smile. Her existing teeth were mottled and worn, with several large restorations (Before Image). Tooth No. 12 had been treated in the past with a crown, which was now failing cosmetically and functionally. The patient stated that she wanted a natural-looking aesthetic improvement while addressing the aspects of her smile that she did not like.
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| Figure 3. Impression captured with a vinyl polysiloxane (VPS) alginate substitute (Position Penta Quick [3M ESPE]) VPS alginate replacement. |
Figure 4. The provisionals were digitally designed using feedback gained from the simulation review. |
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| Figure 5. The polymethyl methacrylate (PMMA) milled provisional. | Figure 6. The provisionals were finished on a solid cast. |
At the first consultation appointment, impressions were made for diagnostic models, and occlusal and face-bow records were taken. A series of digital photos was taken and shared with the dental laboratory team via TransLab. A prescription for a digital treatment simulation was submitted to Transcend.
The patient returned to the office 7 days later to review the simulation and make a final decision on the objectives of treatment and techniques that would be used to accomplish the desired changes. The simulation showed what the patient’s teeth might look like with changes including slight lengthening of the central incisors, the creation of a better smile-line, slight expansion of the arch form, and a brighter shade (Figure 1). To achieve these changes, treatment of the upper arch with 10 lithium disilicate crowns was recommended. The patient and her husband were both positive about the proposed changes, with the exception of the significantly whiter shade. Both stated that it was very important that the final restorations look very natural and closer to her original shade. The treatment plan was approved with this change.
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| Figure 7. The teeth following preparation for provisional. | Figure 8. An intraoral syringe (Rely X Unicem 2 Automix Resin Cement [3M ESPE]) was used to place light-body impression material (Imprint 4 [3M ESPE]). |
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| Figure 9. The final VPS (Imprint 4) impression. | Figure 10. The seated PMMA provisional. |
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| Figure 11. The final crowns were designed using feedback from both the simulation and provisional. | Figure 12. The final lithium disilicate crowns (IPS e.max [Ivoclar Vivadent]) mounted on the solid cast. |
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| Figure 13. Our patient was very happy with the final results. |
Clinical and Laboratory Protocols
A vinyl polysiloxane (VPS) alginate substitute (Position Penta Quick [3M ESPE]) was used to capture an impression of her teeth (Figure 2) for the diagnostic model (Figure 3). Once at the dental laboratory, the impression was poured and the resulting model was digitally scanned. Polymethyl methacrylate (PMMA) provisionals then designed and milled using the feedback provided during the simulation review (Figures 4 and 5). The provisionals were then finished on a solid cast to help improve the articulation and to minimize chairside adjustment time before being shipped back to the dental office (Figure 6).
At the patient’s next appointment, the teeth were prepared and then cleaned with a scrub of chlorhexidine (Figure 7). The VPS light-body impression material (Imprint 4 [3M ESPE]) was dispensed around the preparations with an intraoral syringe (Figure 8), and then a tray with heavy-body material (Imprint 4) was seated. After removal of the set impression (Figure 9), the teeth were cleaned again, then the provisional was relined with PMMA and seated over the preparations (Figure 10). The impression was returned to the dental laboratory team for fabrication of the final restorations.
During the final stage at the lab, the VPS impression was used to create a solid master cast, which was again scanned to enable the digital design (900L Scanner [3Shape]) (Figure 11). Design of the final crowns at this point benefited from feedback received from both the simulation and provisional stages, and the crowns were milled from lithium disilicate (IPS e.max [Ivoclar Vivadent]). After milling, the crowns were characterized, remounted, and finished on a solid cast to refine the contact points, occlusion, and marginal fit (Figure 12).
The crowns were seated (e.max) at the delivery appointment with minimal adjustments. Final cementation was completed with Rely X Unicem 2 Automix Resin Cement (3M ESPE). The patient was very happy with the final outcome (Figure 13 and After Image).
DISCUSSION
Impression-taking tools currently available to dentists are of excellent quality, and when used with proper technique, serve as the backbone to complicated restorative cases. In any step of the value chain, materials and techniques cannot be taken for granted, so it is important for dentists to ensure they are adding the most value by capturing accurate impressions.
Two different VPS materials were used in the case shown in this article, each with its own benefits for its step in the procedure. The first material used, Position Penta Quick VPS alginate replacement, is a very useful material for preliminary impressions. It can be poured multiple times, has a consistent viscosity (thanks to automixing) and, once set, the impressions are dimensionally stable with a long shelf life. In addition, this material’s lack of unpleasant taste and short setting time make it more patient-friendly.
For the final impression, using an intraoral syringe to inject wash material around the preparations brings an extra level of detail. The syringe used here is designed with a very fine tip that enables it to place material directly into the sulcus. The syringes can be filled up to 12 hours before application, so a day’s worth can be prepped in advance and ready for scheduled procedures. The final VPS impression material used for this case (Imprint 4) flows very well into marginal areas to capture subgingival margins. This material also has good patient acceptance due to its taste and removal properties.
Experience has shown many of us that in large-scale cases, traditional impression materials capture impressions quickly and accurately. This experience makes it clear that these materials will continue to have a vital role in the restorative procedure. However, when dentist and lab teams combine traditional and digital tools wisely, they can achieve excellent results that can meet both patient and clinician expectations.
IN SUMMARY
The case described herein illustrates the comfortable interplay that can be achieved between traditional techniques and new technologies. At the patient’s first visit in the dental office, traditional tools can be used to gather records, and an old-fashioned dialogue was employed to determine the patient’s goals for treatment. Creation of a digital treatment simulation by TransLab gives the dentist, dental laboratory team, and the patient a tangible picture to review and discuss. This collaboration helps to ensure that all parties have the same expectations, before proceeding any further with the actual treatment procedures.
At this stage, the dentist again relies on traditional impression-taking materials to capture data, which is then made digital in the dental lab. From here, the laboratory team uses a combination of digital design and traditional finishing procedures to deliver both the provisionals and final restorations. By mixing traditional and new technologies, the dental team can deliver a high-quality product with excellent productivity and a great outcome, even for large cases. Even though in-office digital technologies will still draw attention, doctors should be aware that traditional tools and good technique will continue to serve them, and their patients, very well.
Acknowledgement
The author would like to thank Lee Culp, CDT (Morristown, NC), for the lab work shown in this article.
Dr. Rosen’s background spans all arenas of patient care as a practitioner, administrator, and academician. His specialty from Boston University School of Graduate Dentistry and Sloan Kettering Memorial Cancer Institute was prosthodontics and maxillofacial prosthetics, and he has since added an MBA from Boston University School of Business Administration. He has served as director of hospital dentistry at New England Medical Center Hospital, co-founder and director of the Dental Implant Center at Tufts University School of Dental Medicine, and founder of the Tufts Dental Implant Fellowship Program. He has also worked in telemedicine and teledental technologies for several years as a consultant and as co-founder of the telemedicine company Global Telemedix and founder of Transcend, Inc. He has also been an active consultant in the profession, setting up an implant center in Jeddah, Saudi Arabia; evaluating joint ventures in the Ukraine and Czech and Slovak republics; and designing and project managing training and education centers. He can be reached via email at the address arosen@translab.com.
Disclosure: Dr. Rosen reports no disclosures.
