476 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 83 NUMBER 4

An approach to achieving mandibular denture sta-bility is to place the peripheral extension of the dentureborder superior to the muscle attachments (Fig. 1),namely, in a myostatic position.1 Myostatic is a termdefined by Frush to describe an area or location on themandible that remains static or immobile regardless ofmuscle activity.1 In addition, if the occlusal forces canbe confined within an area that does not cause torquingor tilting of the denture during function,2 a remarkablystable prosthesis can be provided.

With this approach, the anterior segment of theprosthesis is superior to the buccal frenums, mentalismuscle, and lingual frenum attachments. In situationswhere extensive resorption of the residual ridge hasoccurred, it is not uncommon to have a buccolingualwidth of 5 mm or less. The potential for denture frac-ture is therefore inherent. Coupled with the fact thatmany persons having this condition are geriatric andhandicapped by arthritis and other infirmities that limittheir dexterity, the risk of breakage increases.

The use of a metal base or metal mesh within theprosthesis is not a new or original concept.3-5 Theapproach advocated by the author is a modification ofthe technique to reinforce silicone-lined denturesdescribed by Morrow.6 It differs in that this approachpermits treatment to proceed normally while, con-currently, the metal frame is being fabricated, andthen incorporated accurately just before finalizing thewax-up for processing without altering the prosthetictooth arrangement or relationship of the teeth to themaster cast.

In the technique advanced by Morrow,6 the artificialteeth are set and approved for processing and finishing.A stone occlusal index is made on the articulator of theocclusal and incisal surfaces of the lower teeth. The waxis then eliminated from the master cast and the reinforc-ing metal frame with 8 positioning struts to keep theframe suspended above the residual ridge is fabricated.When this has been accomplished, it is placed on themaster cast and returned to the articulator. It is thenincluded in the lower denture wax-up using the occlusal

index with the teeth attached. The occlusal index isremoved, the maxillary wax denture returned to thearticulator and the occlusion modified and refined asneeded. It is my opinion that this technique is moretime-consuming and requires a duplication of effort.

The solid metal base with beads or latticework foracrylic retention as described by Massad1 must be fab-ricated with metal anterior and posterior tissue stopsbefore determining the vertical dimension and centricrelation because the metal base will be incorporatedinto the recording trial base. This delays the clinicalprocedures until the metal work is accomplished. It isthen necessary to flow wax beneath the metal base onthe master cast for tissue contact to be stable. This isdifficult and more prone to inaccuracy than building abase over sheets of baseplate wax adapted and sealed tothe master cast. It is also a more difficult laboratoryprocedure to flow refractory material between the ele-vated beaded baseplate wax and the refractory castwithout trapping air bubbles when investing for cast-ing, as required with this technique.

An added advantage of the proposed technique isthat a predetermined amount of space between the

Fabrication and use of a metal reinforcing frame in a fracture-pronemandibular complete denture

William S. Jameson, DDSa

Tucson, Ariz.

A procedure to reinforce mandibular complete dentures with a rigid internal horseshoe-shaped frame isdescribed. Sequential clinical and laboratory procedures to incorporate a metal frame at a predeter-mined, controlled position within the prosthesis are presented. This procedure provides not onlystrength but ensures adequate space for a resilient liner if required. (J Prosthet Dent 2000;83:476-9.)

aConsultant, Department Of Veterans Affairs.

Fig. 1. Myostatic outline for mandibular denture is indicatedin red. Areas to be “dimpled” are indicated by solid red dots.Outline of tissue stop in anterior is indicated by open blackrectangle.

metal and the residual ridge can be provided. Subse-quent relining with hard or resilient material can beaccomplished without exposing the metal. When theuse of a resilient liner is anticipated, this techniqueensures the recommended material thickness requiredfor optimal results.7 The required space is ensured byforming a relief spacer with a predetermined number ofbaseplate wax sheets of known thickness before dupli-cation and production of the refractory cast.

With a narrow, flat ridge-and-border configuration,rigidity of the metal frame can be ensured with solidmetal approximately 0.75 to 1 mm thick rather thanopen mesh in the anterior region. The actual thickness issomewhat a matter of personal judgment. With the prin-ciples used when designing a maxillary removable partialdenture major connector, a broad palatal strap in 2planes can be kept thin, whereas a palatal bar must bethick to achieve rigidity. Another concern is the poten-tial for the metal frame to show through the somewhattranslucent high-impact resin. To overcome this unde-sirable esthetic caveat, pink opaque should be applied tomask the metal. If the metal frame is to be fabricated ata second laboratory, it will be prudent to make a dupli-cate stone cast of the altered master cast. This can beperformed accurately by the dentist with irreversiblehydrocolloid and an oversized impression tray, a 2.5:1water-to-powder ratio of irreversible hydrocolloid and aduplicating flask, or using polyvinyl-siloxane duplicatingmaterial (Silflex III, Austenal, Inc, Chicago, Ill.). Thedesign can be drawn on the resultant stone cast and for-warded for fabrication without having to delay treat-ment until the master cast is returned with the frame.

This article describes a procedure to reinforcemandibular complete dentures with a rigid internal horse-shoe frame. Not only will the denture be reinforced, butthe metal frame can be positioned at a predetermined,

controlled position within the prosthesis. By doing so, theprosthesis is not only strengthened, but, should it berequired, adequate space for a resilient line is ensuredwithout compromising the integrity of the frame.

PROCEDURE

1. Fabricate maxillary and mandibular master castswith the technique of choice.

2. Locate the anatomic landmarks and draw the myo-static outline for the mandibular denture base onthe cast. This should be verified visually by theoperator intraorally with the patient.

3. For 2-mm available relief space, 2 sheets of1.3-mm thick baseplate wax (Geneva 2000 Set-UpWax, Geneva Dental, Inc, Beverly Hills, Calif.)should be placed and sealed to the cast at thescribed outline, but short of the retromolar pads.Cut a window through the wax to the cast in theanterior midline area. Prepare 4 “dimples” in thecast with a No. 12 bur on either side of the archlateral to the myostatic outline (Fig. 2). (These“dimples” will facilitate placement of the reinforc-ing frame before processing the denture.)

4. Duplicate the master cast with the wax spacer. Fillthe negative space with stone for the production ofa diagnostic cast. (The design is drawn on thestone cast to augment the written prescription.This stone cast will be duplicated for the produc-tion of the refractory cast.) Perform wax-up, cast-ing, and finishing procedures for the metal framewhile the customary clinical and laboratory proce-dures are being executed by the operator8 (Fig. 3).

5. After duplication and production of the diagnosticcast, (the operator or laboratory technician) add anadditional sheet of baseplate wax to those previ-ously applied to the master cast and a stable trialbase is fabricated (VLC material or C-Plast methylmethacrylate, Geneva Dental Inc). (This addition-

JAMESON THE JOURNAL OF PROSTHETIC DENTISTRY

APRIL 2000 477

Fig. 2. Wax spacer short of retromolar pads and withinperipheral outline; cast is exposed in anterior midline area.Eight positioning dimples lateral to wax spacer have alsobeen prepared.

Fig. 3. Finished chrome-cobalt frame on master cast, withspace between frame and cast.

al sheet of wax will produce the space necessary toaccommodate the metal frame during final wax-up.) Ensure the anterior “window” is completelyfilled with the trial base material and the retromo-lar pads covered (Fig. 4).

6. Vertical dimension and centric relation are deter-mined and recorded with the operator’s techniqueof choice. Mount the master casts in the articula-tor of choice and arrange the prosthetic teeth. Theverification and acceptance appointment is thenaccomplished (Fig. 5).

7. After receiving the patient’s permission to processthe denture, remove the wax spacer from the tissueside of the stable trial base and “bead” or score thecast with a No. 2 bur just lateral to the scribed out-line. Place the metal-reinforcing frame with its 8positioning struts or legs in the indentations onthe cast. (Because of the narrow anterior width andthe required “window” opening, the metal frameshould be solid in this area for strength with beadsfor resin retention.) Prepare the metal frame withSiloc bonding method (silica coating, HeraeusKulzer, Inc, Irvine, Calif.) to achieve a chemical-micromechanical bond between the denture basematerial and the dental alloys. (The Siloc methodis similar to silicoating but, according to the man-ufacturer, is improved to eliminate debonding. Apink opaquer is applied to reduce metal visibilitythrough the high-impact, but somewhat translu-cent, resin.) The additional space provided by thesheet of baseplate wax that was added after dupli-cation will permit placement of the trial base overthe frame without interference (Fig. 6).

8. Seal the base to the cast and finalize the wax-up(Fig. 7). To prevent dislodgment of the denturefrom the cast after processing and during recoveryand divesting, make undercuts in the stone castbeneath the mylohyoid ridge on each side and inthe genial tubercle area. Fill these cut areas withwax and join to the denture wax-up.

9. If the base is to be tinted or color characterized,either by the Pound9 or reverse Pound techniqueused by Hardy,10 invest the metal frame to be

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Fig. 4. Tissue side of stable trial base revealing tissue stopson retromolar pads and in anterior midline region.

Fig. 5. Complete set-up verified in mouth and maxillary trialdenture has been sealed to cast. Wax spacer is still in placeon tissue side of mandibular trial base. Linear occlusion wasused for this denture set-up, which dictated 0.020-in. anteri-or separation of teeth. With this occlusal concept, it isbelieved that rotation of dentures on anterior ridges with pro-trusive contact is prevented due to bilateral fulcrum of pro-trusive stability in first or second premolar area. This producesvertical seating forces behind anterior ridges, creating stabili-ty rather than rotational forces with anterior tooth contact.

Fig. 6. Metal frame in position on master cast after treatmentwith Siloc and application of pink opaque. Positioningstruts, which will be removed during finishing, need not beopaqued. Wax spacer has been removed and trial base posi-tioned over metal frame. Base is in contact with cast, both inanterior and posterior regions. Beading of cast for accurateborder determination during finishing is visible lingual tobuccal struts.

retained in the lower, or drag, portion of the flask.If a resilient liner is to be processed simultaneous-ly with the base resin using compression moldingprocedures, it will be necessary for the frame to beretained in the upper, or cope, half of the flask.(This permits the use of a spacer beneath theframe, producing a void that is filled with resilientmaterial after the resin has stiffened sufficiently andbefore final closure.6)

10. After processing, remount and correct the occlusionto eliminate processing errors. Recover the denturesfrom the master casts, then finish and polish. As apart of the finishing procedures, cut the frameworkstruts flush with the acrylic resin. If the exposedmetal is objectionable, it can be countersunk andcovered with autopolymerizing resin (Fig. 8).

DISCUSSION

A sequential approach in fabricating a stablemandibular denture with a reinforcing metal frame ispresented. Weight, resistance to midline fracture, andsufficient available denture thickness for subsequentrelining are advantages achieved with this technique.This procedure will reduce the possibility of midlinefracture in the myostatic mandibular denture. Althoughimplementing this procedure might be consideredunnecessary if high-impact denture base material (Ivo-cap, Ivoclar Williams, Amherst, N.Y.; Lucitone 199,Dentsply International, Inc, York, Pa.; Microfit VR 90,Vynacron Co, Matawau, N.J.) is to be used, it could bea timely precaution to avoid a potential disaster.

The disadvantage of this procedure would be theadded cost for the metal frame and the additional stepsneeded for its inclusion. If the dentist is not using afull-service laboratory, it will be necessary to arrange

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APRIL 2000 479

for the metal frame to be produced at a remote locationto the denture laboratory. The communication andcoordination necessary should be no more difficultthan coordinating a removable partial framework inconjunction with a complete denture when both arerequired to restore a patient.

REFERENCES

1. Massad JJ. A metal-based denture with soft liner to accommodate theseverely resorbed mandibular alveolar ridge. J Prosthet Dent 1987;57:707-11.

2. Lang BR, Kelsey CC. International prosthodontic workshop on completedenture occlusion. Ann Arbor: The University of Michigan School of Den-tistry; 1973. p. 154-8.

3. Strahl RC, Streckfus CF. The utilization of mandibular metal base denturesfor patients with severe mandibular alveolar bone atrophy. J Md StateDent Assoc 1984;27:68-71.

4. Faber BL. Lower cast metal denture. J Prosthet Dent 1957;7:51-4.5. Grunewald AH. Gold base lower dentures. J Prosthet Dent 1964;14:432-41.6. Morrow RM, Reiner PR, Feldman EE, Rudd KD. Metal reinforcing silicone-

lined dentures. J Prosthet Dent 1968;19:219-29. 7. Marginis MJ, Gauber GT. Soft liners. In: Morrow RM, Rudd KD, Eissmann

HF, editors. Dental laboratory procedures complete dentures. Vol I. StLouis: Mosby; 1980. p. 432-46.

8. Brudvik JS. Metal bases. In: Morrow RM, Rudd KD, Eissmann HF, editors.Dental laboratory procedures complete dentures. Vol I. St Louis: Mosby;1980. p. 447-65.

9. Pound E. Esthetic dentures and their phonetic values. J Prosthet Dent1951;1:98-111.

10. Hardy IR. Problem-solving in denture esthetics. In: Payne SH, editor. DentalClinics of North America. Philadelphia: WB Saunders; 1960. p. 305-20.

Reprint requests to:DR WILLIAM S. JAMESON

11401 CALLE VAQUEROS

TUCSON, AZ 85749-8483FAX: (520)749-1511E-MAIL: bbjameson@dakotacom.net

Copyright © 2000 by The Editorial Council of The Journal of ProstheticDentistry.

0022-3913/2000/$12.00 + 0. 10/1/105882doi:10.1067/mpr.2000.105882

Fig. 7. Final wax-up is ready for processing. This lingual viewof final wax-up reveals wax extensions into prepared retain-ing areas in retromolar and genial tubercle areas. Exposedstruts will be captured in investing stone.

Fig. 8. Completed, color-characterized mandibular denture.Anterior strut has been countersunk and covered withautopolymerizing resin. Nonobtrusive posterior strut hasbeen cut flush with base, then smoothed and polished.