Stabilized accurately fitting trial bases

MAKING

RECORD

BASE WITH

SURVEYOR

16. Apply sticky wax on the resin over the ridge. 17. Heat two sheets of medium-hard baseplate wax until they are dead soft and roll them into a rope (Fig. 7). 18. Place wax on the ridge and push it into place labially and into the vestibule (Fig. 8). 19. Add wax to the rim so that it tapers both from the buccal and lingual toward the occlusal surface in the regions distal to the canines (Figs. 9 and 10). 20. In the anterior part of the rim, the wax must flare labially so that proper lip support can be maintained (Fig. 11). 21. The occlusal width of the posterior wax rim should be about 8 mm and the incisal width of the anterior rim about 4 to 6 mm. 22. The 1eng:thof the wax rim in the anterior region should be ab0u.t 24 mm. 23. Taper distal surfaces of the wax rims parallel to the anterior surfaces so that there will be less possibility of interference when occlusal records are made (Fig. 12).

substitute prior to blocking out the posterior undercuts, the rope wax will adhere to the resin: On initial removal from the cast, the wax will yield enough to clear the undercuts. The wax in the anterior portion of the base will also flex enough to clear the undercut. The cast will not break, and maximum utilization of the labial vestibule will be realized. This technique produces a maxillary record base that is stable, retentive, and allows anterior teeth to be properly positioned without problems of resin interference. REFERENCES I.

Academy of Denture Prosthetics: Glossary of Prosthodontic Terms, ed 3. St. Louis, 1968, The C. V. Mosby Co. 2. Ellinger. C. W.. Rayson, J. H., Terry, J. M., and Rahn. A. 0.: Synopsis of Complete Dentures. Philadelphia, 1975, Lea & Frbiger. 3. hlrCracken, W.: Auxiliary uses of cold curing acrylic resins in prosthetic dentistry. J Am Den: Assoc 47:298, 1953. 4. liar&, L.: An advanced use of impression trays. J PR~STHET DEXT 3:150, 1953. 5. Bailey. L. R.: Permanent-type bases for transferring records to an articulator. Dent Clin North Am November 1964, p 623. 6. LaVere, A. M., and Freda, A. L.: Accurate-fitting record bases. J PROSTHETDENT 32:335. 1974.

SUMMARY A technique has been described that will allow more intimate contact of a maxillary record base to the tissues and the casts. A dental surveyor is used to determine a path of insertion that minimizes the amount of undercut to be blocked out. By coating the cast with tinfoil

Stabilized T. Hewitt

McElroy,

accurately D.D.S.,*

fitting

and Kenneth

Ke~mm wqtLd\ lo: DR. JOHN R. SHERMAN.JR. LOUISIAN\

ST.\TE UNIVERSITY

MEDICAL

CENTER

Sc~o01. OF DENTISTRY NE\z. ~)RI.F.hNS. LA 701 19

trial bases

W. Canada**

Ellis Fischel State Cancer Center, Columbia, MO.

P

rosthodontic treatment can fail because of one “weak link” in the chain of procedures. Jaw relation registration is enhanced by accurately fitting and stable trial bases. While the accuracy of trial bases is affected by the accuracy of final impressions and master casts, the technique and materials used in trial base fabrication also determine the efficiency of the bases. MATERIAL

AND

TECHNIQUES

Jones’ listed the ideal qualities of trial bases and compared the advantages and disadvantages of various *Associate Dental Oncologist and Maxillofacial Prosthodontist, Department of Dental Oncology. **Maxillofacial Prosthetics Technician, Department of Dental Oncol%Y. THE JOURNAL

OF PROSTHETIC

DENTISTRY

materials and techniques used. He concluded that autopolymerized acrylic resin bases made with the sprinkle technique as described by McCracken2 are more ideal than shellac, shellac stabilized with zinc oxide and eugenol paste, or heat-processed acrylic resin bases. A disadvantage of the autopolymerized acrylic resin base is an inaccuracy of fit in undercuts, which are necessarily blocked out with wax on the master cast to prevent breakage and abrasion of the cast. Burnett) described the application of autopolymerized soft acrylic resin into undercuts and other irregularities prior to the addition of sprinkled-on acrylic resin. The soft liner bonds to the base to allow safe removal and replacement onto the master casts as well as improving fit and stability in the mouth. We have found modification of the technique described by Burnett3 to be helpful. 753

Fig. 3. Autopolymerizing soft acrylic resin placed into undercuts and over irregularities. Anchoring holes in posterior land area of maxillary cast enhance close adaptation of autopolymerization acrylic resin on curing. Fig. 1. Maxillary master cast. Posterior palatal seal area scraped prior to trial base fabrication.

Fig. 4. Tissue surface view of trial bases shows soit acrylic resin bonded to bases.

Fig. 2. Casts are saturated prior to painting with foil substitute. To prevent dissolution and distortion, tissue surfaces are not submerged.

Technique of fabrication 1. Determine the posterior extension of the maxillary prosthesis during final impression making. 2. Scrape the posterior palatal seal area into the master cast prior to trial base fabrication. The scraping of the posterior palatal seal is done in the tapering fashion described by Swenson4 but modified with a double bead as recommended by Jones* (Fig. 1). The posterior palatal seal is incorporated into the maxillary trial base; and the efficiency of the seal, which will later be incorporated into the completed prosthesis, can be tested during jaw relation procedures. 3. Apply foil substitute (Modern Foil, Modern Materials Mfg. Inc.,St. Louis, MO.) to the master casts. Casts can be moisture-saturated without dissolution and distortion of tissue detail by setting the casts flat in water *Jones, P. M.: Personal communication, 1976. 754

that extends just short of the land area of the casts (Fig. 2). The foil substitute seems to be more effective on moistened casts. 4. Drill holes into the cast posterior to the palatal seal area. Often during polymerization of acrylic resin, curing shrinkage causes a loss of intimate contact between trial base and master cast in the posterior palatal seal area. This “pulling away” phenomenon can be minimized by providing “anchorage” for the acrylic resin in the form of holes in the posterior land of the cast (Fig. 3). 5. Place autopolymerizing soft acrylic resin (Softone, Harry J. Bosworth Co., Chicago, Ill.) into undercuts and over irregularities such as the palatal rugae and knife-edge ridges (Figs. 3 and 4). 6. Sprinkle autopolymerizing acrylic resin base material onto the casts to the morphology and thickness desired, and extend into the anchoring holes in the posterior land area of the maxillary cast. 7. Cure the bases in water at approximately 110” F under 30 psi in a pressure pot. 8. Finish and polish the hydrophilic trial bases after curing, and store in water to prevent distortion (Figs. 4 and 5). NOVEMBER

1984

VOLUME

52

NUMBER

5

impressions, master casts, or marginal seals that can be assessedand corrected early in treatment. Well-fitting trial bases will eliminate the need for denture adhesives during jaw relation procedures, which otherwise may prove detrimental by causing the patient to assume that adhesives will be required for the completed prostheses. Retentive trial bases will enhance the patient’s confidence in the dentist and will add to the reliability of the jaw relation records. REFERENCES Fig. 5. Finished trial bases. Good posterior adaptation of maxillary trial base. Trial bases should be stored in water to prevent distortion.

DISCUSSION Trial bases made of autopolymerizing acrylic resin with the sprinkle technique and the use of soft acrylic resin in undercuts and over irregularities are quick, easy, and efficient. They are accurate and stable in the mouth and do not mar the master casts. They are not subject to heat-induced distortion as shellac bases may be during set-up and waxing procedures. Their retention, particularly as affected by the posterior palatal seal, is essentially that which will be exhibited by the final prostheses. If the trial base is nonretentive it may indicate errors in

Duplicating

maxillary

1. Jones, J. D.: A qualitative comparison of various record base materials. J PROSTHET DENT 49~130, 1983. 2. McCracken, W. L.: Auxiliary uses of cold-curing acrylic resins in prosthetic dentistry. J Am Dent Assoc 47:297, 1953. 3. Burnett, J. V.: Accurate trial denture bases. J PROSTHET DENT 19:338, 1968. 4. Swenson, M. G.: Post Dam, Check of Esthetics. Complete Dentures. St. Louis, 1940, The C. V. Mosby Co., p 89. We would like to thank Mr. Charles Hernandez, medical photographer, for his assistance. Reprint

requests to:

DR. T. HEWITT MCELROY ELLIS FISCHEL STATE CANCER CENTER DEPARTMENT OF DENTAL ONCOL~CY 115 BUSINESS LOOP 70 WEST COLUMBIA, MO 65201

complete dentures

Joseph Nassif, D.D.S., M.Sc.,* and Russell Jumbelic, D.M.D., MS.** Georgetown

University,

College

of Dentistry,

and Howard

M

any edentulous patients are apprehensive about the possibility that their dentures might be broken or lost. They also have grave misgivings about being without them during required relining or repair. For this reason, a valuable service for the complete denture patient is the provision of a duplicate denture. Many techniques have been presented for duplicating complete dentures with a variety of impression materials.‘-I3 This article describes a technique that is similar to one reported by Morrow et a1.9The procedure involves

Read before the National Capir.al Area section of the American College of Prosthodontists, Washington, D.C. *Associate Profe:ssor, Department of Removable Prosthodontics, Georgetown University, College of Dentistry. **Associate Professor, Department of Removable Prosthodontics, Howard University, College of Dentistry. THE JOURNAL

OF PROSTHETIC

DENTISTRY

University,

College of Dentistry,

Washington,

D.C.

the use of irreversible hydrocolloid, a modified Hanau denture flask (Hanau Engineering Co., Inc., Buffalo, N.Y.), and autopolymerizing acrylic resin for both teeth and denture base.

PROCEDURE An oral examination and evaluation of the patient and the prosthesis is completed prior to the duplication procedures. The denture should be examined and evaluated for existing or repaired fractures, craze lines, and missing or replaced teeth. Esthetics, phonetics, accuracy of fit, and vertical and centric relation must also be verified. The patient is then advised whether the existing denture(s) should be duplicated or remade.

Fabrication of the teeth 1. Select a shade that harmonizes with the existing denture (Fig. 1). 755