Inside Dental Technology
Removable over Implants
A winning case for the KunstZahnWerk® 2012 North America competition.
Since 2001, the Swiss tooth manufacturer Candulor has organized the biennial “Art of Dental Prosthetics” competition (KunstZahnWerk®), culminating in awards and participant case presentations at the International Dental Society in Cologne, Germany.
In 2011, US technicians were invited to participate in this competition. All US entrants made it through the first round with Andrea Hegedus (Muskegon, MI) placing second in the Digital Documentation category and Jack Edwards (Fullerton, CA) placing 10th in the Overall category. Based on the success of the nine US participants, Candulor organized the first North American competition in 2012.
The patient, a 72-year-old woman, had been a denture wearer for 28 years and had suffered from a very ill-fitting lower denture for the same length of time. During the initial consultation, this very active woman complained especially about problems with speech, chewing, and recurring sore points on the lower jaw. From an esthetic point of view, the patient was bothered by barely visible upper anteriors that looked unnatural.
Following an in-depth clinical and radiological examination, four Camlog implants (Camlog USA, www.camlogus.com) had been placed in the patient’s mandible for a bar construction.
All contestants also received one maxillary edentulous model, one mandibular edentulous model with four Camlog implant analogs, four Camlog implant wax-up abutments, eight Camlog implant screws, an assessment sheet, and a plaster bite rim for articulator mounting.
The author demonstrated a unique removable implant concept that has been a very popular option throughout Europe for many years and was first described by Dr. Arnold Gaerny in Switzerland during 1972.1 The approach involved the use of a 0° bar milled in zirconia using a gold Galvano electroformed telescope for hydraulic retention. The telescope was further reinforced by a non-precious tertiary structure, which strengthened both the Galvano coping and the mandibular prosthesis.
Individual Dentate Character
The first goal was to determine how the artificial teeth would be characterized. The decision was made to cut back each tooth individually and apply a variety of age-appropriate stains to mimic areas of decalcification, incisal translucency, cervical coloring, and abfractions (Figure 2). Mammelons were also highlighted and slight color was added to the body of each tooth. Staining was followed by enamel and incisal build-up using a light-curing composite material.
Next, there was a need to create a new working model upon which the implant bar could be pre-milled in wax for scanning and definitive milling. Polyurethane was used to create a proper working model with a removable mask retained by mini-magnets (Figure 3 through Figure 5).
Once all model work was accomplished, the case was mounted on Candulor’s CA II articulator (Candulor Dental, www.candulor.us) using the provided plaster rim and centering pin. Care was taken to ensure that the models were mounted according to the occlusal plane indicated on the plaster rim, and that this plane directly related to the occlusal notches provided on the CA II articulator using a red rubber band (Figure 6).
With the models mounted, a thorough model analysis using a profile compass and a series of colored indelible pencils was performed (Figure 7 though Figure 9). In addition to this, a matrix was made of the plaster rim, and midline and canine positions were transferred to the matrix in order to set the artificial teeth in ideal locations to meet esthetic demands and provide adequate lip and musculature support (Figure 10 and Figure 11).
This was the only time that the characterized artificial teeth could be set in wax. Using the matrix, not as a rigid guide but as more of a template, allowed some interpretive freedom when deciding on particular rotations of each individual tooth as in nature. For this case, the distal limits of the central incisors were flared labially (Figure 12 through Figure 15), and the lateral incisors were tucked slightly behind the centrals (Figure 16). The posterior teeth were set strictly according to Candulor’s specifications, as there is a very specific way that the Condyloform teeth (Candulor Dental) are designed to inter-cuspate and provide a balanced, lingualized occlusal scheme.
Candulor’s Statik Laser (Candulor Dental) was also used to ensure that the largest masticatory unit of the mandible, the first molar, was ideally placed directly over the residual ridge (Figure 17 and Figure 18). The earlier model analysis also enabled mandibular first molar placement at the lowest point on the mandible accurately.
Primary Bar Construction
After all the artificial dentition had been set up in wax and the final wax contouring had been accomplished, the design of the 0° bar began. Putty matrices were created both on the labial and lingual aspects of the fully contoured mandibular wax-up. Using Passive Fit Ti bases and waxing sleeves (Camlog US, www.camlogimplants.com), milling wax was applied and formed to the desired contours—within the limits of the putty matrices. A hand-milling unit was used to mill the bar wax-up to 0° (Figure 19 through Figure 21).
The bar wax-up was then scanned, milled in zirconia, and sintered (Figure 22 and Figure 23). The removable mask portion of the master working model was removed, and final milling and polishing was carried out using the hand-milling unit. Special care was taken to use a liberal amount of water spray during final milling and to protect the model with a plastic wrap (Figure 24).
Galvano Outer Telescope
The zirconia bar was prepared for Galvano electroforming by screwing the implant analogs into the bar interfaces and temporarily cementing the Passive Fit Ti bases to the zirconia bar. The analogs were protected with insulating wax, and the bar was airbrushed with silver conducting lacquer for the Galvano process. An apron fashioned out of wax was used at the extremities of the bar for a clean border finish
and ledge for easy insertion by the patient (Figure 25 and Figure 26). After Galvano forming, the zirconia bar was removed from the Galvano telescope, and a solution of nitric acid was used to remove any remaining silver lacquer.
The entire assembly was then placed back on the master working model, and undercuts were blocked out in wax. A light film of wax was added to the entire telescope to serve as a spacer for cementation of the non-precious tertiary structure. The fully blocked out master model was then duplicated using duplicating silicone, and the tertiary structure was waxed up on the treated investment duplicate model. The tertiary wax-up was cast in chromium cobalt, checked for accuracy, and fit over the Galvano outer telescope. Vents were placed in the tertiary structure as exit access for excess composite resin cement at the time of cementation of the tertiary structure to the Galvano outer telescope (Figure 27).
Both the Galvano telescope and the tertiary structure were air abraded with 50-micron aluminum oxide at two-bar pressure. The two components were prepared with light-curing metal primer. The structures were then cemented together with light-curing composite resin cement.
The tertiary structure was then covered in a base-pink, light-curing opaque material. This step was repeated twice to achieve an optimum level of opacity and to ensure that the tertiary structure would not show through to the acrylic surface of the prosthesis (Figure 28).
The matrices used earlier for the bar construction were again used in order to relate tooth positions back to the tertiary structure with wax. The mandibular master working model was placed back on the articulator, and the artificial dentition was checked for original fully balanced positions. Once all excursive and protrusive checks were confirmed, the final blocking and waxing of the mandibular prosthesis was carried out for gingival characterization and polymerization. At this time, the maxillary prosthesis was also waxed to the final contours.
The importance of anatomically correct gingival contours and denture base tinting have been highlighted by a number of clinicians, including Earl Pound, DDS; John Frush, DDS; and Dr. Jack Turbyfill, DMD.2
In order to correctly colorize the gingival contours, a polychromatic color scheme was planned and drawn out, followed by a complex and tedious placement of final gingival characterization in the negative mold. Using a special formulation of acrylic polymers and intensifiers specific to this case, the colors were placed in the anatomy of the negative gingival mask according to the drafted color scheme. Differing levels of opacity also played a role in the final appearance of the gingival portion of the prosthesis. The variety of colors were manipulated and blended for a selection of naturally occurring gingival effects.
An appropriate customized base shade blend was decided upon, and final polymerization was carried out with a castable acrylic resin system using a pressurized polymerization unit at 45°C. After polymerization was complete, the maxillary and mandibular prostheses were bench-cooled, removed from the molds, and carefully finished using a variety of fine burs, brushes, and polishing paste. (Figure 29 and Figure 30).
1. Gaerny AA. Removable Closure of the Interdent-al Space (C.I.S.). Hassell TM, trans-ed. Berlin, Germany: Buch und Zeitschriften-Verlag; 1972
2. Pound E. Personalized Denture Procedures: Dentist’s Manual. Anaheim, CA: Denar Corporation; 1973.
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About the Author
Arian Deutsch, CDT
Deutsch Dental Arts