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Inside Dentistry

May 2011, Volume 7, Issue 5
Published by AEGIS Communications


Using Compartis ISUS in Conjunction with ANKYLOS

CAD/CAM technology increases predictability in implant prosthetics.

By Troy Aparicio, CDT; and David A. Little, DDS

Complete dentures are an established method to restore esthetics, phonetics, and function to partially or completely edentulous patients. Economically, it continues to be widely used to provide both soft and hard tissue replacement for the edentulous patient with some drawbacks.1 Issues that plague the denture patient usually include the lack of stability, decreased masticatory force, decreased taste sensations, and bulkiness. The advent of implants, however, helped to meet the demands and satisfaction of many completely edentulous patients.2 The treatment modalities include tissue-supported, stud-type attachments (ball, locator) or bar-type prostheses (Hader or hybrid).

The hybrid denture provides patients with the necessary stability similar to that of natural dentition because it is anchored to the integrated implants.3 It also provides the dentist with the ease of retrievability, which is important when maintenance is needed. Usually custom-made in the dental laboratory by highly skilled technicians using alloys containing high levels of precious metal content, these economic conditions have caused dentists to rethink their approach. Traditionally, the fabrication of a hybrid denture was very time-consuming, expensive, very technique-sensitive, stressful to say the least, and, in a majority of cases, yielded less than satisfactory results both mechanically and esthetically. Corrective techniques have to be employed after casting in many cases.4

New Technologies in CAD/CAM Implant-Retained Overdentures

Technology influences the way we think and the way we do things. Computers are being used to assist and shape our daily lives, including in the dental laboratory. The level of sophistication and ease of use in the capture and design software and CAD/CAM services allows the laboratory several options in design and material choices. A stronger, more accurately fitting prosthesis is provided. Compatibility with a variety of implant platforms, achievement of a passive fit, and control of divergences are also enhanced.5

In the case presented in this article, treatment planning and diagnosis was enhanced using a CBCT-scan derived surgical guide (SimPlant®, Materialise, www.materialise.com). A CAD/CAM service platform (Compartis® ISUS, DENTSPLY Prosthetics, www.dentsply.com) provided many options supporting a wide variety of implant systems and platform designs. In this case, the ANKYLOS® (DENTSPLY Tulsa Dental Specialties, www.tulsadental.com) implant system was used; it is easily supported when using this software without changing the protocol in capture, design, and manufacturing process. This report describes the treatment protocol and the authors' experiences with this technology.

Patient Background and Evaluation

The patient, in her 60s, presented to the office with partial edentulism on both arches and poor oral health. During the initial evaluation a severe collapse of occlusion was noted, as well as multiple caries lesions, broken-down amalgams, and the presence of calculus along with periodontal involvement with associated mobility; our insights into diagnosis were enhanced with a cone beam computed tomography (CBCT) scan (Figure 1 and Figure 2). Radiographic guides and a SimPlant surgical guide were used (Figure 3) to enhance implant placement in the maxilla. The patient went through an uneventful osseointegration process.

Implant Suprastructure Planning and Design

In order to support the removable prosthesis over implants, an implant suprastructure provided by the Compartis ISUS service was indicated. Current protocol calls for an abutment-level restoration of the ANKYLOS system. Protocol requires an abutment-level scan of the master cast. ANKYLOS Balance Base stock abutments with the unique tissue care connection were used to provide a platform for the bar. Though the initial plan as seen from the surgical guide was for 10 implants, it provided the surgeon the flexibility needed and only six were used without loss of integrity and stability.

The necessary preparatory tasks were accomplished prior to the ISUS scanning and design process. The abutments were placed (Figure 4) and a final impression was taken. The laboratory fabricated a final cast using a low expansion stone (Figure 5).

After this step, a verification jig was fabricated and used for checking the accuracy of the master cast against the intraoral situation (Figure 6). This essential verification step satisfied the authors with the accuracy of the master cast, and they were ready to proceed. The ISUS protocol requires a denture set-up to be submitted along with the master cast, used to serve as a point of reference during the scanning process. The casts are scanned with, and without (double scanned) the denture set-up (Figure 7 and Figure 8).

Once captured, the data provides a virtual model and the limits of the set-up. By carefully extracting the components, a design technician manipulates the software for the desired results as requested on the prescription. Taking into consideration the labio–lingual and occlusal limits of the teeth and the position of the implant, the design provides for components that strengthen, support, and integrate mechanical retention for resin within the structure (Figure 9, Figure 10 and Figure 11). The bar is then milled from a choice of solid titanium block or chrome cobalt alloy block and returned to the laboratory for final processing; in this case, titanium was preferred (Figure 12).

Processing the Prosthesis

A final wax-up was completed for processing. Removed from the cast, the waxed-up hybrid was fitted with ANKYLOS Balance Base soldering analogs secured with long wax-up screws (Figure 13) and subsequently flasked for molding.

Wax elimination followed and a thorough cleaning of the bar was done, first treating the acrylic retaining surface by blasting with alumina and steam. The surface was chemically treated and a light-cured masking and bond-enhancing agent was used (Figure 14).

The hybrid denture prosthesis was then packed, processed, recovered, and final-polished for delivery. A high-impact denture base acrylic and wear-resistant artificial teeth with an interpenetrating polymer network (Lucitone 199, Portrait IPN, DENTSPLY Prosthetics) were used (Figure 15 and Figure 16). Enhanced wear resistance is necessary as the implant-supported restoration undergoes higher masticatory forces.

The final results and a very happy patient are subsequently illustrated in Figure 17 and Figure 18.

Conclusion

The complexities of treatment coupled with economic concerns, especially in these times, can be very challenging for both the dentist and the laboratory professional. Service-based approaches such as Compartis ISUS provide a clinically sound solution that enhances predictability. Using the virtual design approach, the authors were able to visualize the end result before prosthetic treatment was started. The system provides solutions over a wide variety of implant platforms while eliminating the need for expensive precious metal alloys and the 11th hour miscasts and corrections. Porosity-free ISUS structures, milled with a stress-free passive fit, provide peace of mind and time savings for the laboratory and the dentist. The system provides the accuracy and strength necessary in the framework against the abutments or implants. This is necessary for the longevity of both implants and the prosthesis and results in very satisfied patients.

References

1. Carlsson GE, Omar R. The future of complete dentures in oral rehabilitation. A critical review. J Oral Rehabil. 2010;37(2):143-156.

2. Thomason JM. The use of mandibular implant-retained overdentures improve patient satisfaction and quality of life. J Evid Based Dent Pract. 2010;10(1):61-63.

3. Davodi A, Nishimura R, Beumer J 3rd. An implant-supported fixed-removable prosthesis with a milled tissue bar and Hader clip retention as a restorative option for the edentulous maxilla. J Prosthet Dent. 1997;78(2):212-217.

4. Romero GG, Engelmeier R, Powers JM, Canterbury AA. Accuracy of three corrective techniques for implant bar fabrication. J Prosthet Dent. 2000;84(6):602-607.

5. Rinke S. The Treatment of Toothless Jaws—A Case for CAD/CAM. CAD/CAM English. 2010;
1(2):14-17.

About the Author

Troy Aparicio, CDT
San Antonio, Texas

David A. Little, DDS
Private Practice
San Antonio, Texas
Adjunct Clinical Professor
University of Texas Health Sciences Center San Antonio Dental School
San Antonio, Texas


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Image Gallery

Figure 1  The diagnostic CT scan.

Figure 1

Figure 2  The patient at initial presentation.

Figure 2

Figure 3  The surgical guide.

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Figure 4   Implant abutments in situ.

Figure 4

Figure 5  The laboratory model.

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Figure 6  Verification jig.

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Figure 7  Scan of the model base.

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Figure 8  Scan with set-up in place.

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Figure 9: Visualization composite.

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Figure 10  Virtual design with scan.

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Figure 11  Virtual design of the bar.

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Figure 12  Milled titanium implant supra-structure

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Figure 13  Waxed-up hybrid.

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Figure 14  The framework was ready for processing.

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Figure 15  The final denture on the model.

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Figure 16  Finished ISUS hybrid denture.

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Figure 17  The hybrid denture in place.

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Figure 18  The patient was satisfied with the final results.

Figure 18