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Inside Dental Technology
March 2016
Volume 7, Issue 3
Peer-Reviewed

Case in Point

A patient presented with five maxillary implants (MIS) to which custom abutments were attached, supporting a cement-retained bridge, and two recently placed posterior implants (MegaGen USA, megagen.us) that were not yet connected (Figure 3).

The prosthodontist provided a great deal of information at the first step, including casts of the implant abutments, bridge in place, implant-level verified cast, and opposing cast (Figure 4 through Figure 8).

Additionally, patient photos and expectations were provided. An initial analysis of the photos and models revealed that a great deal of planning was lacking in the initial porcelain bridge solution, and a large discrepancy existed between the tooth positions of the porcelain bridge and the proposed tooth positions according to an in-depth edentulous cast analysis (Figure 9). This was confirmed by patient photos, which presented a lack of any buccal corridor (Figure 10).

More Is Better

Regarding information, more is better. Due to the immaculate condition of the impressions that were provided, the laboratory was able to make a cast transfer accurately and quickly by mounting the existing cast of the maxillary bridge against the antagonist cast and creating a silicone putty index (Matrix Form 70, anaxdent North America, anaxdentusa.com) (Figure 11). This index was then used to cross-mount the verified implant-level maxillary cast to the antagonist cast using the hard palate as a solid reference (Figure 12).

This approach enabled the dental team to perform a bilaterally screw-retained try-in with teeth in wax at the second patient appointment, completely avoiding centric and vertical recording (Figure 13 and Figure 14).

The wax try-in clearly illustrated the contrast between the previous cement-retained ceramic bridge and the newly proposed tooth positions. With the addition of a high-quality artificial dentition, using five-layer PMMA (artegral, Merz Dental, merzdental.de), the dental team and the patient could realize a vast improvement. A natural smile was restored, and natural-looking surface texture returned to the patient’s smile (Figure 15 and Figure 16).

Telescopic Protocols

After tooth positions are approved and a centric and vertical record were confirmed, a phonetics and function test was performed, and a double scan was carried out to enable design of the primary telescopic abutments within the volume of the approved tooth positions (Figure 17). Scan, design, and primary milling were performed by Dental Creations Laboratory Inc. in Tucson, Arizona.

The abutments were milled in zirconia, sintered, and hand-milled with a high-speed water turbine and a series of five progressive diamond milling burs down to 4 microns so that no microfracturing took place (Figure 18 and Figure 19). The abutments were then hand polished on the hand mill with a series of three dry diamond impregnated polishers, which were consistently dressed at either 0° or 2°, depending on the specific case, thus ensuring a perfectly polished surface, with walls remaining intact at the desired 0° or 2°.

Galvano Process

One of the most important aspects of a telescopic prosthesis is the fit tolerance from secondary to primary component. No technology that is currently employed is quite as accurate as the Galvano method, or electroforming of a high-purity gold (99.9%) to the primary telescopic abutment surface. This method achieves a 4- to 5-micron fit consistently.

This process can be carried out in both a direct and indirect method, either directly to the abutment surface or to a duplicate die using duplicating silicone and Fujirock® IMP (GC America Inc., gcamerica.com). Once the Galvano process for this case was completed, the electroformed abutments or dies were removed from the Galvano unit (Gammat® free, Gramm Technik, gramm-technik.de) and separated (Figure 20). The remaining silver lacquer residue was then removed with 40% nitric acid solution under ultrasonic waves (Figure 21). The secondary Galvano telescopes were refined and fit to the primary zirconia telescopic abutments (Figure 22).

Tertiary Structure

A tertiary structure served to cement the gold copings, and as a substantial reinforcement lending a great deal of strength to the prosthesis. It was digitally designed within the volume of the approved prosthesis volume, which was checked in wax (Figure 23). The tertiary structure design, which was scanned and designed by Alexander Wünsche, CDT, of Zahntechnique in Miami, Florida, was then transmitted to an SLM production facility (Bego USA, begousa.com) and the selective laser melting process was completed, providing a very accurate tertiary structure with a perfect cement gap (Figure 24).

The tertiary structure can be cemented on the verified cast or intraorally to the gold secondary copings (Figure 25 and Figure 26). Once this was completed, a processing duplicate was made using duplicating silicone (GC America Inc.), and a processing duplicate was vacuum mixed and poured in a type IV resin reinforced gypsum (Fujirock IMP, GC America Inc.).

Final Processing

Another critical aspect of restoring a patient’s dentition is creating lifelike, natural-looking tissues. Many materials are on the market, and newer materials are becoming available all the time. In the author’s experience, utilizing a variety of colorized heat-cured acrylics provides a very natural appearance and is durable and color stable long term. It is important to select an acrylic that has a high impact resistance. Nature-Cryl® Super Hi Impact acrylics (GC America Inc.) can be traditionally press packed or injected and demonstrate such properties. The acrylic tissue can also be modified by removing the artificial veins, and placed and blended strategically to mimic gingival tissues very closely.

One technique that has been very successful utilizes disposable syringes in order to place the differing colors of acrylic exactly where desired (Figure 27), and then to manipulate with a Kolinsky brush to blend the colors. This technique prevents transition lines that may look artificial.

Conclusion

The patient in this case experienced a vast improvement in esthetics, comfort, and cleansability (Figure 28), with a very minimal volume of acrylic, which only replaced the dentition and structures that were lost (Figure 29).

Telescopic implant prosthetics have a long, rich, well-proven tradition in Europe.6 Compared to the current screw-retained acrylic hybrid solutions available, the implants offer a compelling alternative to such solutions and warrant further examination for use in the implant market. For the purposes of this article, special focus was placed on the cleansability aspect of telescopic implant prostheses.

However, many additional benefits to this solution exist, such as less restorative space requirements, implant angulation corrections without need of an angled multi-unit abutment, and easy and economic repairability. The author plans to cover these and other benefits in depth in future articles and hands-on courses.

Disclosure

The authors had no disclosures to report.

References

1. Schnitman PA; Wöhrle PS; Rubenstein JE. Immediate fIxed interim prostheses supported by 2-stage threaded implants: Methodology and results. 1990 J Oral Implanto|(16; 2,; 96-105) Brånemark P-I, Svensson B, van Steenberghe D. Ten-year survival rates of fixed prostheses on four or six implants ad modum Brånemark in full edentulism. Clin Oral Impl Res 1995; 6:227-231. Schnitman PA; Wöhrle PS; Rubenstein JE; DaSilva JD; Want NH. Ten-year results for Brånemark implants immediately loaded with fixed prostheses at implant placement. Int J Oral Maxillofac Implants. 1997|(12; 4; 495-503)

2. Gaerny, Arnold. Removable Closure of the Interdental Space (CIS). Quintessenz, 1972.

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