Table of Contents

Cover Story
Practice Building
Roundtable
Continuing Education
Esthetics
Periodontics

Inside Dentistry

July/August 2010, Volume 6, Issue 7
Published by AEGIS Communications

Digital Impressions

John Walker, DDS

Technology gains strength as it offers a gateway to productivity.

A practice’s image is shaped by many things. When patients visit an office for the first time, they observe not only the staff, but also the overall atmosphere in the office. Technology, when used well, can be a valuable tool to enhance a practice’s image. Of course, dentists do not purchase technology simply for the sake of showing it off to patients—it must also be useful in practice and should provide concrete improvements to the care being delivered. Currently, digital impressioning devices are the latest office technology that both interests patients and helps dentists to deliver the best possible care.

The author acquired a 3M™ ESPE™ Lava™ Chairside Oral Scanner C.O.S. (http://www.3mespe.com) in 2008, and has been using it with very positive results. The Lava C.O.S. can be used in place of a conventional impression to create almost any restoration, and the accuracy provided by the digital impression allows the laboratory to craft restorations that fit exceptionally well. In addition to the productivity improvements brought about by better-fitting restorations, the device has helped the author to free up time, which used to be spent taking and checking conventional impressions. The following case illustrates the esthetic results and superb fit that can be achieved using digital impressioning.

Case Presentation

The 56-year-old patient presented to the office with many existing restorations and decay. Teeth Nos. 7 and 10 had existing crowns; however, tooth No. 10 was failing due to recurrent decay. The patient’s two central incisors had decay interproximally and on the facial and gingival surfaces, and the overall esthetic appearance of the teeth was poor (Figure 1). Because of the generalized location of the decay on teeth Nos. 8 and 9, the patient’s history of recurrent decay around fillings, and the need to replace the crown on tooth No. 10 while retaining the crown on tooth No. 7, it was determined that placing new Lava™ zirconia crowns on teeth Nos. 8, 9, and 10 would be the best course of treatment.

Study models were made to wax up the contours of teeth Nos. 8, 9, and 10, and duplicated to create a stent for the temporaries. Preoperative photographs were taken to communicate with the laboratory regarding the shading and shape of the crowns (Figure 2). The patient’s uneven facial structure made this step especially important (Figure 3).

At the scanning appointment, the patient was anesthetized, and an Isolite™ (http://www.isolitesystems.com) and retractors were placed to keep the field dry during the scanning. The assistant lightly powdered the teeth and scanned the opposing arch. Two Ultradent (http://www.ultradent.com) cords (#0 and #2) soaked in Hemodent™ (Premier Dental, http://www.premusa.com) were then placed around the teeth, and shoulder preparations were created with a fine-grit round-end taper diamond bur.

The assistant then powdered the upper arch and scanned the preparations (Figure 4 and Figure 5). After this step, the author returned to the operatory to confirm the scan’s accuracy and check that the entire marginal area had been captured. After verifying this, the assistant was able to scan the rest of the arch and the bite.

The patient was temporized with Protemp™ Plus (3M ESPE) and given postoperative instructions. (On anterior cases, the author prescribes chlorhexidine for use during the weeks between temporization and placement of the final crown to keep the tissue in the best condition.) During the time the patient wore the temporaries, the stereolithographic model and Lava crowns were being created simultaneously at the model construction facility and laboratory, respectively (Figure 6 and Figure 7). The digital data captured by the scan (Figure 8) allowed the laboratory to design the restorations and mill them without the model; the model was used later for the porcelain application and finishing. After the bisque crowns were sent back to the office, the patient returned for a bisque try-in. Shade and contour adjustments were indicated and more photographs were taken and sent back to the laboratory for incorporation in the final glaze. The patient returned approximately 1 week later and the crowns were easily seated with RelyX™ Luting Plus Cement (3M ESPE) with no adjustment needed (Figure 9).

The patient loved the new look of her final crowns (Figure 10). While this case posed an esthetic challenge because of her uneven midline and occlusal plane, the author and his team were able to create a more natural and even appearance with careful attention to these factors. The try-in appointment was especially helpful in refining the appearance of the crowns. Although the author performs a try-in on every anterior case, it was especially critical in this instance to communicate to the laboratory regarding the soft tissue architecture of the patient’s face in relation to the long axis of the teeth. Having the quality and accuracy of the digital impression and bite was a significant help in reducing adjustments and final seating time.

Clinical Applicability

This case illustrates only one of many cases the author has completed using a digital impression. Since acquiring the Lava C.O.S. system in June 2008, his office has performed more than 300 scans with the device, and his team has been extremely pleased with the results. Incorporating the device was a relatively simple process—after 2 days of training with 3M ESPE instructors and his staff, the team returned to the office and felt comfortable performing the procedure on patients. The author would compare learning how to use the system with learning how to work in a mirror, or using an intraoral camera. After committing to understanding the process, users learn quickly and can soon perform the procedure smoothly.

The author also uses a CEREC® (Sirona Dental Systems, http://www.sirona.com) in his office, and so he can appreciate the scanning abilities offered by that system. The major advantage of CEREC is being able to perform single-appointment crowns or onlays. Now with the Lava C.O.S., he has the ability to use a digital scan in a wide variety of cases—whether to create a Lava crown, PFM, full gold crown, partial crown, or bridge. The author does not consider the Lava C.O.S. as a replacement for the CEREC; it is a replacement for conventional impressioning. The versatility offered by the system makes it useful for almost any laboratory-fabricated restoration.

Improved Productivity and Accuracy

The changes the device has made in office productivity have been very valuable. The author is now able to anesthetize and prepare the patient, then leave the room while the assistant performs the scan. He simply returns to confirm the preparation has been correctly captured, which takes just seconds. He no longer has to worry about budgeting his time to take impressions. As many clinicians have experienced, if a retake is necessary with conventional impression material, it can put the office significantly behind schedule. However, with digital impressioning, a retake can be completed in approximately 1 minute. Because the assistant can do all the work, the doctor is freed up to attend to other patients.

The team experiences an additional benefit once the restoration returns from the laboratory, when seating and adjustment times are much faster. The author has found this to be especially true with occlusal adjustments. To capture a bite with a digital scanner, the patient simply has to close his or her teeth together, instead of biting down into a bite tray, which feels unnatural to patients and often causes them to shift their bite. With the Lava C.O.S., the patient closes naturally and the models are set up exactly that way.

The accuracy of the digital data eliminates the inaccuracies that are introduced with conventional impressioning. The traditional process presents many opportunities for distortion to make its way into the restoration, either through the initial impression, the model, or a subsequent step. Digital impressioning and the 3M ESPE model-making process eliminate those issues, meaning that both the initial impression and the model are more accurate, creating restorations that consistently fit better and more predictably.1

Enhancing the Practice Image

Digital impressioning helps boost the image of the practice in an important way. Patients can easily see how high-tech it is, and react very enthusiastically. Those who have had traditional impressions in the past are relieved they do not have to put up with the tray that makes them gag and choke. They also enjoy watching the image modeled back in real time on the screen (Figure 11).

Conclusion

Incorporating digital impressioning works to complement the rest of the messages the practice sends to patients. When used in an inviting, attractive practice with a pleasant and caring staff, it helps to bolster patients’ opinions of the office and their relationship with the staff. Patients take pride in being part of a practice that is cutting-edge and known around the community, and they take pride in referring friends and family. As the author has experienced, the device is a valuable investment not only because of its ability to improve productivity, but also in its enhancement of the practice’s image.

Reference

1. Hirayama H, Chang Y, Kugel G, et al. Fit of zirconia copings generated from a digital impression technique and a conventional impression technique. Tufts University of Dental Medicine Masters Project.

About the Author

John Walker, DDS
Private Practice
Olympia, Washington