Dentistry Today Clinical Insights Prosthetics Improving Accuracy and Simplifying Treatment With Full Arch Removable Prosthetics: A Case Report
Prosthetics

Improving Accuracy and Simplifying Treatment With Full Arch Removable Prosthetics: A Case Report

  • July 1, 2004
  • 17 minutes read
  • 21 years ago

Patients who are currently wearing full arch removable prostheses may present requesting new dentures. The process may be simplified and the number of appointments decreased by using the current dentures as custom trays for master cast construction. The dentures may be duplicated quickly in the office to fabricate custom trays. When time is essential to provide the new dentures, the duplicated dentures can be ready for impression-taking in about 1 hour.

Processing of the dentures with traditional methods has been a time-consuming procedure. This normally delays delivery of the finished dentures following the try-in appointment. This article presents a case report utilizing a new, light-curable material that can reduce processing time to less than 90 minutes.

CASE REPORT
The patient, a 49-year-old white female, presented requesting a duplicate set of dentures. She expressed that she was satisfied with the present dentures but wished to have a duplicate set fabricated.

Impressions and Master Model Fabrication
The patient’s current full maxillary and mandibular dentures were duplicated with a Lang denture duplicator (Lang Dental) using alginate (Tropicaligin; Zhermack). Upon setting of the alginate, the duplicator was opened and the denture removed. A self-cure acrylic (Jet Acrylic; Lang Dental) was mixed and poured into the duplicator. The duplicator was closed and immersed into a bowl of hot water to accelerate set of the acrylic.

The duplicated denture was removed from the duplicator and flash was removed from the flanges with an acrylic bur. The duplicated dentures were tried in the patient to check for fit, and sore spots were adjusted. Occlusion between the maxillary and mandibular duplicate dentures was verified. Three small vent holes were made in the palatal area of the maxillary duplicate denture to eliminate hydrostatic pressure during the impression. Tray adhesive was applied to the tissue side of the duplicate maxillary denture and overlapped on all flanges. A light body polyvinyl siloxane (PVS) impression material was injected into the maxillary denture and inserted. The pa­tient was guided into oc­clusion with the mandibular duplicate denture, and the impression material was allowed to set. The lower duplicate denture was re­moved and tray adhesive applied. A medium body PVS was injected and the denture reinserted, with care taken to guide the patient into occlusion with the maxillary duplicate denture.
Stone master casts were fabricated in the final impressions, and the casts mounted in occlusion (Figure 1).

Fabrication of the Record Base

Figure 1. Master casts are fabricated based on duplicates of the current dentures and mounted in occlusion. Figure 2. The mandibular baseplate is placed on the articulator ready to have teeth set to occlude with the maxillary duplicate denture.
Figure 3. An acrylic bur is used to bevel the flanges with a chamfer. Figure 4. Denture tooth cage for removal of wax residue.
Figure 5. Knife edge diamond creating divergent tissue side cuts in the denture tooth. Figure 6. Collar diamond creating a circumferential groove on the denture tooth.
Figure 7. Setup Eclipse resin being placed on the cured baseplate with an electric spatula. Figure 8. Setup begins with a mandibular central incisor.
Figure 9. Maxillary and mandibular teeth set on baseplates with Setup resin. Figure 10. Occlusal view of the maxillary denture setup. Setup resin is confined to holding the denture teeth to the baseplate only.

After placement of the posterior palatal seal, the master cast was brushed with Al-Cote (DENTSPLY Trubyte) to seal the cast and prevent resin penetration into any micro­defects within the surface of the stone cast. To facilitate adaptation of the Baseplate resin, the master cast was placed in the conditioning oven and allowed to reach 55ºC. A package of Baseplate resin was opened, placed on the warmed cast (convex side toward the cast), and placed back into the conditioning oven to soften the material. The model was removed from the oven and molded with finger pressure to allow the Baseplate resin to melt into the master cast and form the denture base. Air Barrier Coating (ABC; DENTSPLY Trubyte) was brushed over the entire surface to eliminate an air-inhibited layer on the surface of the resin.

The master cast was placed into an Eclipse Pro­cessing Unit and cured for 10 minutes. (Note: The Eclipse system [DENTSPLY Trubyte] consists of a Baseplate resin, Setup resin, and Contour resin. Each is currently available in 4 shades [original, light pink, reddish pink, and dark pink], matching the available shades of Lucitone 199. The Baseplate resin is utilized to fabricate a permanent record base that will be used for records [with a wax rim] and become a permanent portion of the final denture. This allows the dentist to determine the retention and fit of the final denture at the records visit. The Setup resin is utilized to attach the denture teeth to the cured baseplate with the consistency of a hard wax prior to light curing. Contour resin is overlayed on the baseplate, exposed Setup resin, and necks of the denture teeth. This material is highly polishable and is also easily carved like wax prior to being light cured.) 
Following curing, the cast was soaked in water to facilitate removal of the baseplate from the cast (Figure 2). Margins of the baseplate were trimmed with an acrylic bur (Figure 3). An acrylic bur was used to create a chamfer margin along all the flanges of the final denture bases. Removal of the surface of the baseplate will ensure adaptation of the overlaying Contour resin without any interfering wax residue. The maxillary duplicate denture was placed on the master cast, and the lower Eclipse baseplate inserted.

Setting Teeth

Figure 11. Occlusal view showing Eclipse Contour resin has been applied to the exposed baseplate.

 Figure 12. A hot-air gun is being used to smooth the Contour resin.
Figure 13. The electric spatula is used to apply Contour resin and for initial shaping. Figure 14. Carving instruments are used to festoon the material.
Figure 15. Eclipse Contour material has been applied to the dentures and festooned. Figure 16. Dentures at try-in. Note the bubblegum-like appearance of the uncured Eclipse material.
Figure 17. Eclipse gel being applied to the flanges of the conditioned denture prior to processing. Figure 18. Uncured denture in the processing unit awaiting processing.
Figure 19. Final processed denture. Note the change in color of the base material. Figure 20. Finished and inserted dentures.

Teeth were selected to match the shade and mold of the patient’s current dentures, as she was satisfied with the aesthetics. The teeth were placed in a metal tooth cage, and wax residue was dissolved in a boiling water bath (Figure 4). The lower teeth were ground to fit the baseplate. Mechanical retention is required to retain the denture teeth within the Eclipse material following final curing. To facilitate this, divergent cuts were made on the tissue side of the denture tooth utilizing the knife edge diamond in a slow-speed handpiece (Figure 5). A circumferential collar groove was made with an inverted cone diamond in a slow speed (Figure 6). An electric spatula was utilized to place Eclipse Setup material in the grooves/cuts on each denture tooth to ensure that no voids were present between the tooth and baseplate.

A small amount of warmed Eclipse Setup material was placed on the baseplate (Fig­ure 7), and the denture teeth were set in the desired configuration (Figure 8). Sufficient material was used to hold the denture teeth to the baseplate without overbuilding the material (Figures 9 and 10). Excess material can be removed with a clean wax carver. It is imperative that voids be avoided under the denture teeth, as these will not be eliminated after final processing. Should movement of the tooth be necessary during setup, additional setup material should be flowed under the tooth with the electric spatula. The lower denture was set in occlusion with the duplicated maxillary denture. 
An electric waxing pot was used to melt Eclipse Contour material to facilitate placement on the denture. An electric spatula was used to carry Contour material to the denture and flow it over and around the visible areas. All exposed portions of baseplate should be covered by a thin layer of Contour material to eliminate any interface lines between the Contour material and baseplate (Figure 11). Additional Contour material was flowed around the necks of all teeth to create a uniform overlay. To facilitate carving of the contour material, the denture may be placed in a zip-top plastic bag and immersed into a bowl of ice cold water. 
The duplicate maxillary denture was removed from the master cast and the Eclipse baseplate inserted. Maxillary denture teeth were set in a similar manner as the mandibular teeth. The teeth were set in occlusion with the completed new mandibular denture. A hot-air gun was used to create a smooth surface on the Contour material and minimize polishing and finishing after curing (Figure 12). Clean wax carving instruments were used to festoon the Contour material (Figures 13 and 14). Instruments that have been heated in an open flame or used to melt wax should be avoided to prevent incorporation of soot or other undesirable debris into the Eclipse material. 

The finalized Eclipse denture was placed in a light-proof bag and was ready for final try-in (Figure 15). A minimum working time of 60 minutes under typical room illumination is afforded. Exposure of the final denture to direct sunlight prior to processing must be avoided. Eclipse Setup and Contour resins will have a bubblegum-like coloration in their un­cured appearance, and the dentist (along with the patient) should be in­formed so that miscommunication is avoided as to what the final result will be aesthetically (Figure 16). Shade tabs of the cured Eclipse material can be used to demonstrate final cured coloration.

Completion of the Denture

The Eclipse denture setups were tried in and checked for aesthetics and phonetics. Upon approval the dentures were returned to the light-proof bags and were ready for processing. The denture was placed on the master cast and air barrier brushed over the entire surface of the final setup and cast. Air Barrier Coating must be used to prevent air inhibition, which causes staining of the air inhibited layer. It is important to achieve a smooth surface when polishing the denture, since rough, unpolished areas show slight stain retention. Eclipse provides acceptable in vitro stain resistance to both coffee and mustard when properly polished. In vitro mustard stain resistance is similar to L199. Dentures, repairs, and re­lines all show acceptable stain resistance.

The master cast was placed into the conditioning oven for 1 hour. Conditioning prior to final curing is designed to melt any crystals that may have formed within the Setup/Contour material and prevent “snow flakes” within the final cured material. After the cast and denture were conditioned, Eclipse Gel was applied to the margins, locking the denture to the cast and preventing warp­age due to curing shrinkage (Figure 17). It is unnecessary to cure the gel prior to placement of the cast into the Eclipse processing unit. The master cast was placed into the processing unit (Figure 18), and final curing was completed in 13 minutes (Figure 19).
After curing, the cast and denture were allowed to cool to room temperature. The denture was removed from the cast, and Eclipse gel was removed with an acrylic bur. Final polishing and finishing were completed in a standard manner. Due to the very low polymerization shrinkage of Eclipse, occlusal adjustment requirements were nonexistent. Because flasking was not required, finishing time was minimized. The denture was inserted and the patient dismissed (Figure 20).

DISCUSSION
Eclipse provides a denture material that is free of monomer (methyl, ethyl, butyl, or propyl methacrylate) for a more biocompatible product that also eliminates potential hazards to the laboratory technician during fabrication. Potential for leaching of monomer during denture use long term is eliminated, creating a more stable denture for the patient. Flasking and packing are eliminated, making processing faster and easier for the technician. Once the final denture has been ap­proved, the denture can be processed in as little as 1 hour and 15 minutes compared to 4 or more hours using conventional methods. The “wax-like” feel of the thermoplastic material allows the technician experienced at fabrication of fixed prosthetics to use techniques they are comfortable with, thereby shortening any learning curve with the system. Labor time is greatly decreased for the technician, increasing profit and capacity.

Eclipse material shows strength that is similar to Lucitone (DENTSPLY Tru­byte) but with less than half the volumetric curing shrinkage (Eclipse = ~3%, Lucitone = ~7%). Thus, there is less chance of processing errors and changes in vertical dimension. The fit at try-in equals the fit at delivery. The dentist does not require additional equipment to incorporate Eclipse into his or her treatment options. A warm water bath can be used to soften the denture setup at 110ºF (43ºC) and perform minor movements of teeth at the try-in appointment. The denture should only be briefly dipped into the water bath to prevent over-softening. The tooth is moved, then placed under cold water prior to reinsertion in the mouth. The dentist should inform the technician which teeth have been moved so that complete backfill and avoidance of voids in the resin can be accomplished prior to final processing. Instruments heated in an open flame should be avoided by the dentist to prevent incorporation of soot into the resin. Eclipse being more stable than wax, teeth will not move unless the dentist warms the material in a warm water bath to adjust them, or the patient uses excessive biting force.
Conventional dental wax can be used to set teeth in combination with an Eclipse processed baseplate to make a try-in denture. Following try-in, a silicone matrix is made, the wax is boiled off the processed Eclipse baseplate, and the teeth are back filled with Eclipse setup material. Should the baseplate not fit properly at the records appointment, it is recommended the dentist take a wash impression with a light body polyvinyl siloxane. The laboratory will then pour a new master cast and fabricate a new baseplate from Eclipse. If the laboratory does not feel the initial cast or impression adequately reflects the needed areas of the arch, it is recommended that a standard record base and wax rim be fabricated. The dentist can then be instructed to take a wash impression to allow accurate master cast construction. The wash impression should be taken at the occlusal ap­pointment, not at the try-in appointment. Any changes should be made as early in the process as possible.
Should a bite registration be needed at the try-in appointment, a polyvinyl siloxane (PVS) material should be used to avoid contamination of the uncured resin with wax. When more than a minor change in occlusion is required, the dentist can strip off the teeth and uncured resin with a new scalpel blade and record a bite in the desired vertical dimension. If the dentist desires to “plump” gingival areas for increased lip support, a PVS putty or bite material can be applied to communicate needed changes to the laboratory. As with taking a bite registration at try-in, waxes should be avoided. The dentist can accomplish reduction of excess gingival material by carving with a clean instrument.
Although Eclipse and Triad (DENTSPLY Trubyte) are both based on urethane dimethacrylate chemistry and are cured by light and heat, the similarities end there. Eclipse uses different initiator species than Triad Denture Resins, which en­sures high strength. The Eclipse Processing Unit contains 6 lamps and 2 fans and is designed specifically to cure properly the complex, 3-dimensional geometry of devices encountered in prosthodontics. If curing is attempted in a Triad unit or with a handheld curing light, the Eclipse material will minimally harden but will not reach the strengths required. This will be evident by a failure to convert from the bubblegum-like color to the final normal processed acrylic coloration. The Triad Processing Unit only reaches a temperature of 168°F. The Eclipse Processing Unit attains a temperature of 265°F. A denture processed in a Triad Processing Unit will not cure properly, even though it may appear cured when you take it out of the unit. A Triad-cured Eclipse denture will not have the strength required of a denture.
Should relining or repair be desired, conventional materials (monomer free or methylmethacrylate containing) will bond to the Eclipse materials. Permasoft (DENTSPLY Austenal) may be used as a soft liner, placed by the laboratory on a cast or intraorally by the dentist. Disinfection of uncured Eclipse dentures with phenol-type agents should be avoided, as the resin is sensitive to and is softened by some types of disinfectants. It has been shown that uncured Eclipse can be disinfected with glutaraldehyde-based disinfectants with no effect on the material. Cured Eclipse dentures are resistant to common disinfectants, thus a broad range of materials can be used on the finished device, including phenolics, quaternary ammonium chlorides, and glutaraldehyde-based disinfectants. Thus, a dentist or lab technician does not need to be concerned about disinfection of a finished denture whose origin is unknown. (Note: iodine-containing disinfectants are to be avoided; these may stain Eclipse [and probably acrylics] and are not recommended.)
Acrylic or porcelain teeth may be selected for each case. However, since there is no chemical bond between the tooth material and the Eclipse materials, mechanical retention is necessary. Staining at the interface between the Eclipse material and teeth due to a lack of chemical bond between the 2 materials, similar to that seen around porcelain teeth, has not been demonstrated. Porcelain diatorics and retention pins are adequate to retain the teeth within the Eclipse material, and it is important to ensure that setup resin flows into these areas to avoid potential voids. As discussed, when acrylic teeth are utilized, divergent slots are to be placed into the tissue portion of the denture tooth, and a circumferential collar groove placed.
Unlike other monomer-free materials that are known to have color stability concerns, Eclipse has excellent color stability and has undergone rigorous testing, including the standard ADA testing for color stability. In addition, no significant color changes have been noted from the clinical study.

CONCLUSION
Full arch removable prosthetics can be a challenging treatment and time consuming for the dentist. When the patient presents with an existing full arch removable prosthesis, it can be utilized to fabricate a custom tray, improving and simplifying the impression phase of treatment. The technique described affords laboratories the ability to finish and process dentures in less than 90 minutes, compared to more than 4 hours using traditional processing that involves flasking and packing. Additionally, the final processed baseplate fabricated at the initial laboratory appointment allows both the dentist and patient to feel how the final denture will fit and what retention will be present prior to final processing of the denture. Eclipse dentures are repairable using conventional materials, however the optimal repair is completed using Eclipse Baseplate resin. Re­line procedures may be accomplished with any soft or hard conventional materials.

Acknowledgment
The authors would like to thank Drs. Nels Ewoldson and Gary Henkel for their help in reviewing this article.

Dr. Kurtzman is in private practice in Silver Spring, Md, and is an Assistant Clinical Professor at the University of Maryland School of Dentistry, Department of Restorative Dentistry. He has lectured nationally and internationally on the topics of restorative dentistry, endodontics, and dental implant surgery and prosthetics, and has had numerous journal articles published in peer-reviewed publications. Dr. Kurtzman is on the editorial board of the Journal of Oral Implantology, an assistant editor for the International Magazine of Oral Implantology, and editor for the Maryland Academy of General Dentistry. He is a consultant and evaluator for several dental companies. He has earned fellowships in the Academy of General Dentistry, the International Congress of Oral Implantologists (ICOI), and the Pierre Fauchard Academy; masterships in the Academy of General Dentistry and the Implant Prosthetic Section of ICOI; and diplomate status in ICOI. He can be contacted at dr_kurtzman@maryland-implants.com.

Dr. Melton is a prosthodontist who has spoken extensively on a national and international level. He graduated from Baylor University College of Dentistry and received his diploma in fixed prosthetics from the University of Missouri-Kansas City. He is a member of the American College of Prosthodontists, the American Academy of Implant Dentistry, and the International Congress of Oral Implantology. He is a diplomat of the American Board of Oral Implantology/Implant Dentistry and the International Congress of Oral Implantologists, and fellow of the Academy of Dentistry International. His practice is located in Albuquerque and Santa Fe, NM, and is limited to prosthodontics and implant dentistry. He can be contacted at abmeltonnm@aol.com.