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Inside Dentistry

February 2012, Volume 8, Issue 2
Published by AEGIS Communications


E4D CAD/CAM Restorative System

Placing a Maryland bridge using the in-office system to achieve a long-term temporary restoration.

By Dino Javaheri, DDS | Roxanna Shahnavaz

Options for replacing a missing anterior tooth in a 14-year-old patient are very limited. The ideal final treatment modality is to place an implant; however, this cannot be accomplished in a child or adolescent until he or she has stopped growing. Maintaining the space until an implant can be placed is achievable with a temporary removable partial denture (RPD), an Essix retainer, or a fixed resin-reinforced ceramic Maryland (FRRCM) bridge. Although temporary removable partial dentures and Essix retainers (DENTSPLY Raintree Essix, www.essix.com) are relatively cost-effective, both can be uncomfortable. Talking and eating with such restorations can be challenging. Also, there often is an esthetic compromise with a removable prosthesis. In contrast, a fixed Maryland bridge can provide a comfortable, strong, and esthetically pleasing long-term temporary solution. The restoration can be fabricated using an in-office CAD/CAM system (eg, E4D, D4D Technologies, www.e4d.com; or CEREC® 3D (Sirona Dental Systems, www.sirona.com). Such systems offer both the dentist and the patient the options of a quick turnaround time, an accurate fit, and direct control of color and shape.

The E4D in-office CAD/CAM system is a comprehensive scanning, designing, and milling system for chairside use. Both preoperatively and during preparation, E4D can scan the soft tissues and tooth structure, as well as all bite registration materials, without the need for a contrast agent or opaque medium such as powders or sprays. After intraoral scanning, the software creates a model, after which the design process can begin. Autogenesis provides an optimized restoration design using information from the opposing dentition (bite), preoperative condition, wax-up, or scans of provisional restorations. For patients who require a detailed or unique design, a full suite of design tools provides unlimited control of every aspect of design.

The approved restoration is sent wirelessly to the E4D mill, which then fabricates a high-strength ceramic or composite restoration (eg, IPS Empress® CAD and IPS e.max® CAD, Ivoclar Vivadent Inc., www.ivoclarvivadent.com; Paradigm™ C and Paradigm™ MZ100, 3M ESPE, www.3mespe.com). After polishing, staining, and glazing, this system can provide excellent restorative and esthetic care.

To fabricate the CAD/CAM FRRCM bridge, a two-part system that consisted of a composite framework using Paradigm MZ100 and a porcelain veneer using IPS Empress CAD Multi block was used. The composite framework was used because it is more flexible than porcelain and can better resist stress in multiple directions. Composite is less brittle than porcelain, so it is less likely to fracture under flexion stress. Esthetics is an issue with composite restorations, as the material is monochromatic. To improve the esthetic outcome, a porcelain veneer was created to overlie the framework. Combined, the composite framework and porcelain veneer provide the flexibility and esthetics required for success.

Case Presentation

Prior to completion of orthodontic treatment, the patient and her parents presented to discuss options to replace a congenitally absent right lateral maxillary incisor. After reviewing all treatment options, the ultimate goal was deemed to be an implant. However, given the patient’s age, this goal was considered unattainable for several years. Consequently, a long-term, temporary solution was needed. The patient and parents expressed a desire for an option other than a temporary RPD to replace the missing tooth, based on the experience of a family friend who had received a temporary RPD under similar circumstances. In addition to the friend’s dissatisfaction with the fit and esthetics, the denture had fractured several times. After discussing options, a decision was made in favor of having a FRRCM bridge fabricated.

The procedural objective was to completely avoid reduction of tooth structure for the temporary restoration. Instructions were forwarded to the orthodontist to tilt the opposing mandibular teeth slightly toward the lingual aspect, leaving approximately 1 mm clearance of occlusion for the teeth adjacent to the missing tooth to allow for the material thickness of the wings of the bonded bridge.

The patient came in 1 day after having her braces removed (Figure 1). No tooth preparation was done. Using the E4D digital scanner, a scan was performed of her anterior maxillary dentition and for bite registration (Figure 2). No powder or contrast agent was required, as the E4D system can directly scan the tooth structure to prepare an accurate 3-D image. An outline was made of the proposed margins of the wings on the adjacent teeth (Figure 3). Care was taken not to exceed the largest block size when determining the overall length of the restoration. Once the margins were defined, the software was able to design the composite framework (Figure 4). Some adjustment was done to the design to leave room for a porcelain veneer. The final design was sent to the milling machine, and was milled in about 9 minutes (Figure 5). The sprue was sectioned and the restoration checked for fit and occlusion. No adjustments were necessary; consequently, the first part of the restoration was bonded using a resin cement. The facial area of the restoration was altered slightly to provide an ideal veneer preparation (Figure 6).

A second digital scan of the maxillary anterior was performed with the framework in place (Figure 7). This time, after the margins were marked, the E4D software was instructed to design a standard porcelain veneer over the framework (Figure 8). The veneer was milled out of an IPS Empress Multi block in approximately 11 minutes. The Multi block is considered to be more esthetic than a standard porcelain block, because it shows a natural shade and translucency gradient from the cervical to the incisal areas. After the design was approved, it was milled, placed, and examined in position. Slight changes were made to the line angle to match the other maxillary lateral incisor (Figure 9). The restoration was then stained and glazed in a porcelain oven to optimize the esthetic outcome. With the final approval of the patient and her parents, the porcelain veneer was cemented into place using a light-cured resin cement over the framework. All excess cement was removed, and the restoration was polished with composite polishing rubber cups. The final restoration demonstrated esthetic harmony with the natural dentition and satisfied the esthetic and functional requirements of a long-term temporary (Figure 9, Figure 10, and Figure 11). The patient was very pleased with the results and was sent back to the orthodontist to have a retainer fabricated.

Conclusion

As digital dentistry continues to grow, CAD/CAM technology can be increasingly applied to restorative procedures. In this case, it was of great benefit to the patient to be able to have her restoration within an hour, instead of the traditional 2-week turnaround. In addition, matching a single anterior tooth is often challenging for dentists and laboratory technicians, sometimes requiring multiple adjustment appointments. By maintaining control over design and shade matching, the likelihood of success with the first attempt was optimized.

About the Authors

Dino Javaheri, DDS
Private Practice
Danville, California

Roxanna Shahnavaz
Dental Student
The Arthur A. Dugoni School of Dentistry
University of the Pacific
San Francisco, California


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Image Gallery

Figure 1  Preoperative photograph of a missing maxillary right lateral incisor.

Figure 1

Figure 2  3-D digital model created with the E4D system.

Figure 2

Figure 3  Outline of the margins for the composite framework.

Figure 3

Figure 4  Design of the composite framework.

Figure 4

Figure 5  The composite framework upon completion of milling.

Figure 5

Figure 6  The cemented framework with a veneer preparation.

Figure 6

Figure 7  3-D digital model of teeth with the framework in place.

Figure 7

Figure 8  Design proposal for a porcelain veneer to fit over the framework.

Figure 8

Figure 9  The veneer milled from an IPS Empress Multi-block prior to staining and glazing.

Figure 9

Figure 10  Facial view of the final restoration.

Figure 10

Figure 11  Lingual view of the final restoration.

Figure 11