FIXED PROSTHODONTICS OPERATIVE DENTISTRY HENRY

E. EBEL,

SAMUEL

A systematic

E. GUYER,

approach

Jack D. Preston, D.D.S.* Wadsworth Veterans Administration

WILLIAM

LEFKOWITZ,

to the control

Hospital,

Section editors

of esthetic

Los Angeles,

form

Calif.

T

o provide a fixed prosthodontic service, the dentist must possess diagnostic skill, technical ability, and a clear concept of what constitutes an acceptable prosthesis for the patient receiving treatment. A diagnostic wax-up can prevent many embarrassing diagnostic waxing is not a routine procedure treatment problems. r, * Unfortunately, in most practices, because it takes tinie and does not immediately manifest obvious tangible benefits. Also, the results obtained in the diagnostic waxing are sometimes not carried through in delivery of the prosthesis. This article describes a system wherein esthetic form is established in advance of treatment as part of the diagnostic phase. It is tested in the provisional (treatment) restoration and maintained in the completed prosthesis. This method of esthetic control offers a systematic approach to providing a fixed prosthodontic service and allows the dentist to recover the initial investment of time with additional benefits accruing. I have tested this procedure for 4 years and have implemented it as a matter of routine. This esthetic control system can be thought of in five stages-two primarily laboratory steps and three clinical: ( 1) preparatory procedures (laboratory and clinical), (2) trial restoration (clinical), (3) preparation guide (clinical), (4) treatment (provisional) restoration (clinical), and (5) d evelopment of metal substructure and veneering (laboratory). Not all patients will require all phases, but the concept can be applied to most. PREPARATORY

PROCEDURES

Accurate complete-mouth impressions are made and poured in artificial stone (Fig. 1). It is desirable to duplicate these original casts and retain them while the duplicates are used for diagnostic waxing. The casts are mounted on the articulator in the position at which the the patient’s mouth is to be restored. The wax-up is developed with the use of information gleaned from the patient and from observation of previous prosthodontic restorations, and it should embody the dentist’s concept of Read

before

*Director,

the Pacific

Coast

Resident Training

Society

of Prosthodontists,

San Diego,

Calif.

Program in Fixed Prosthodontics. 393

394

J. Prosthet: Dent. April, 1976

Preston

Fig. 1. Diagnostic mandibular lateral

casts of Patient 1. Teeth were lost incisors are indicated for extraction.

Fig.

2. Diagnostic

wax-up

Fig.

3. Cast made

from

for

Patient

wax-up.

through

facial

trauma.

Maxillary

and

1.

Matrices

will

be thermoformed

on this cast.

what is ultimately desired in the patient’s prosthesis (Fig. 2). Depending upon the complexity and the extent of the restoration needed, much of the work may be completed by the dental laboratory technician. It is often during this waxing procedure that awkward edentulous spaces with too much or too little space for pontics are first discovered. Also, other problems such as cross-bites, difficult tooth-ridge relationships, and the need for atypical contours often are present. The detection of these situations in advance of preparation of the teeth can alone be a justifying indication for diagnostic waxing. I prefer to complete the wax-up with ivory wax for the form of anterior teeth and inlay wax for occlusal modification. Once the wax-up is completed, the waxed cast is duplicated with either reversible or irreversible hydrocolloid impression material and artificial stone (Fig. 3). FABRICATION

OF MATRICES

Three clear plastic matrices (bridge splints) are thermoformed over each cast. I strongly prefer material such as the No. 0.020 inch polypropylene bridge splint material* to the polyvinyl. The polypropylene is strong yet flexible and resists tearing or cracking when withdrawn from pronounced undercuts. Pressure forming has, in my experience, yielded better detail than has vacuum forming, although either may be used. This may be accomplished by one of the commercial systemst or by a simple and inexpensive procedure employing a soft material (blockout cornpoundS) as the pressure-forming material after the manner described by Ellman.3 The initial fabrication of three matrices has proved necessary to accomplish all the tasks for which the system is designed (Fig. 4). *Bridge splint material No. 0.020 inch, Howmedica, Inc., Los sheets, Ellman Dental Mfg. Company, Hewlett, N. Y.; Vacu-Press (a very modified styrene), Dentsply International, York, Pa. tional,

tMicroform York, SOmnident

press,

Howmedica,

blockout

compound,

Inc.,

Los

Angeles,

Calif.;

Angeles, Calif.; Press-Form temporary splint material

Vacu-Press,

Dentsply

Pa. Buffalo

Dental

Mfg.

Company,

Brooklyn,

N. Y.

Interna-

Systematic

Fig.

4. Polypropylene

Fig.

5. Trial

restoration

control

of esthetic

form

3%

matrices. for

Patient

1.

IMPLEMENTATION OF THE SYSTEM Trial restoration. The importance of esthetic form and the influence of the anterior teeth on phonetics cannot be minimized in fixed prosthodontics. Esthetics is frequently the motivating factor for patients who seek a fixed prosthodontic service. Unfortunately, the dentist’s concept of esthetic form and position and the patient’s expectations are not always in concert. A patient’s lack of tolerance of the esthetic inadequacies found in a fixed partial prosthesis may necessitate a removable or fixed-removable unit. The concept of an esthetic try-in of anterior pontics has largely been abandoned with the decreased use of prefabricated pontics and facings (i.e , flat-back, Tru-pontic, or long-pin pontics). Likewise, many of the phonetic tests by which anterior teeth are selected for complete dentures are never applied in the consideration of anterior tooth position for fixed partial dentures. These considerations, which have been well discussed by Pound and Murrell” and others, may also be used in anterior fixed partial restorations. The use of a trial restoration employing the clear matrix allows evaluation of the intended result before tooth preparation and without the encumbrance of a palatal trial base. Technique. The anterior edentulous spaces and adjacent teeth of the original diagnostic cast are painted with an alginate tinfoil substitute. The pontic spaces of the matrix are filled with incisal- and body-shade autopolymerizing acrylic resins. The matrix is removed (polypropylene does not adhere to the acrylic resin), and the pontics are trimmed to the same gingival and embrasure form they will display in the completed fixed prosthesis. The pontics are reinserted in the clear matrix, and the gingival aspect of the matrix is trimmed to follow the pontic form (Fig. 5). The unit may be appraised by the patient at the next appointment. The pontics are held in place by the adaptation of the matrix to the remaining teeth. This matrix, having been stretched and thinned by the forming procedure, will be approximately 0.007 inch thick and will manifest very little alteration of the interocclusal distance during speech. The vertical and horizontal overlap, general form, lip support, and estheticphonetic presentation of the pontics are evaluated (Fig. 6) . Once the dentist’s criteria

396

J. Pronthet. Dent. April, 1976

Preston

Fig.

6. Intraoral

views

of trial

restoration:

(A)

retracted

and

(B)

lips parted

naturally.

for acceptance are met, the trial restoration is shown to the patient. This involvement of the patient is very beneficial toward his acceptance of the final prosthesis.5 Should the patient not accept the result that can be obtained with a fixed restoration, a removable or fixed-removable prosthesis must be considered. The fact that this decision can be made prior to preparation of the teeth is a major advantage of preplanning. PREPARATION

GUIDE

The requirements of the materials used in porcelain-fused-to-metal appliances dictate adequate tooth reduction. Depth-gauging cuts help appraise adequate removal but, at times, offer no aid. When previous castings must be removed or when gross alteration of form is necessary, gauging cuts are of no value (Fig. 7). Since the clear matrix outlines the form to be desired in the final restoration, it is the logical guide for judging the adequacy of tooth reduction (Fig. 8). The matrix itself does have some thickness, but it can be split and the amount of space available for restorative material can be measured directly with a periodontal probe or depth-gauging instrument* such as described by Krug.6 TREATMENT

RESTORATION

Probably the most satisfying use of this system is its application in the fabrication of the treatment (provisional) restoration. Many techniques have been described, and most prosthodontists have tried many of them. Whereas the technique is not presented as the “universal solution” to the problems of provisional coverage, it most nearly meets the author’s criteria for this situation and is used in most treatment situations. The method is a modification of that described by Fisher, Schillingburg, and Dewhirst.’ After the preparations are completed, the gingival tissues are displaced and a master impression (or impressions) is made. While the gingival tissues are still somewhat distended, another impression is made. If the margins are all supragingival, irreversible hydrocolloid is adequate. Usually a silicone putty-wash technique is best. *Omnidepth

instrument,

Whaledent,

Inc.,

Brooklyn,

N. Y.

Volume Number

35 4

Systematic

Fig. 7. Patient 2 requires anterior ceramic veneers Fig.

8. Matrix

in place

esthetic and functional are to be removed, and

as a preparation

alteration a six-unit

control

of esthetic form

3% 7

of anterior restorations. The four splinting prosthesis is to be placed.

guide.

A cast is then poured with a rapid-set plaster. * The final set of this material is completed within 5 minutes, and the cast is carefully recovered. The second matrix (which can be the same as the one used for the preparation guide if no perforations for measurement were used) is tried on the plaster cast and trimmed to allow complete seating. The plaster cast is then painted with alginate tinfoil substitute diluted with an equal amount of water. This should be done carefully to avoid puddling in the gingival sulcus. Autopolymerizing (methyl methacrylate) tooth-shade acrylic resins? are selected. For an anterior six-unit fixed partial denture, for example, usually two body shades and an incisal shade3 are selected. The incisal resin is mixed first. It should be very fluid and is flowed into the matrix from a brush or instrument. This incisal shade should extend one half to two thirds of the length of the labial surface and should feather out to avoid any sharp line of demarcation. Next, the darkest body shade is mixed-again, very loosely-and placed in the canine region and around the gingival aspect of the preparations. The other body shade is used to fill the remaining pontic spaces. Imagination and artistic desires are the only limiting factors in this procedure. Then, the matrix is seated over the plaster cast and, if need be, secured lightly with elastic bands. The unit is next placed in a pressure pots partly filled with warm water, and 20 to 30 pounds of air pressure are applied. The restoration will polymerize in about 5 minutes, whereupon it is removed. The matrix is easily lifted free, and the treatment restoration is evaluated. Thir. regions or previously undetected voids may be corrected with a mix of the appropriate resin. The restoration is then separated from the cast. If the preparation areas do not break free, they usually can be blown from the splint with a stream of compressed air. The unit is trimmed with disks, acrylic trimmers, and rubber wheels. The marginal integrity should be maintained and bevels should be clearly visible. *Snow

White

plaster

No.

+Jet acrylic

tooth

shades,

$Light

dark

incisal

§Sure-Cure

and

pressure

unit,

2, Kerr Lang

Mfg.

Dental

cold-cure Howmedica,

tooth

Company, Mfg.

plastic, Inc.,

Romulus,

Company, Unitek

Los Angeles,

Chicago, Corp., Calif.

Mich. 111. Los Angeles,

Calif.

398

J. Prosthet. Dent. April, 1976

Preston

. Fig. 9. Treatment Fig. 10. Matrix a plastic

sprue

restoration

in place on master bar has been placed.

Fig. 11. Molten wax diagnostic waxing.

Fig. 12. Matrix

for Patient

is flowed

is used

into

to evaluate

cast.

2. Abutment

the lubricated casting

and

copings

matrix assure

and

margins

to re-establish adequate

space

have

been waxed,

form

developed

for

veneering

and

in the material.

The underside of the pontics is given special attention. The pontic form intended for the finished restoration must be incorporated in this treatment restoration. This not only allows for adequate patient hygiene but also enables the patient to test the pontic for comfort as well as esthetics. This is especially helpful in the posterior region when a noncontacting pontic form (“sanitary pontic”) is planned. The unit is then carefully finished with wet pumice and a rag wheel with a high-gloss polish. The lathe should be run at low speed to avoid throwing and subsequent fracture of the unit. The resulting treatment restoration will easily go into place in the mouth but may require occlusal adjustment. The unit offers excellent protection of the abutments and affords a most esthetic and functional unit. Many advantages accrue from this procedure. ( 1) There is no exposure of the gingiva or freshly prepared dentin to acrylic monomer or heat of polymerization. (2) The unit is fabricated away from the patient and is therefore more comfortable and neater.

thetic

Fig. 13.

Patient

1 with

completed

prostheses:

(A) maxillary

and

form

399

(B) mandibular.

(3) Auxiliary personnel can be trained to perform the entire procedure. (4) There is no locking of the resin in undercuts or in adjacent interproximal spacessuch as is encountered in direct procedures. (5) Undercuts where caries or previous restorations were removed can be blocked out on the plaster “dies.” (6) There is complete extraoral control of materials. (7) The seating of the clear matrix on the plaster cast is positive and under complete visual control. (8) Voids can be detected and eliminated while the massis still workable. Simply remove the matrix, add new resin, and reseat the matrix. (9) The surface of the restoration is greatly improved when polymerized agains-t the plastic matrix in a pressurepot. (10) The duplication of the diagnostic wax-up is excellent. ( 11) Esthetics are excellent. (12) The pontic form can be tested by the patient for acceptability. After the unit is placed with a sedative luting agent and when the dentist is satisfiedwith the esthetics and function, the patient is shown the restoration and told that the unit approximates the anticipated prosthesisin form and position (Fig. 9). If the patient has any objections or if family comments on estheticsare negative, these are taken into account before the fixed prosthesisis fabricated. This communication reduces patient dissatisfaction or misunderstanding and prepares the patient for acceptance of the finished metal-ceramic unit.

LABORATORY FABRICATION In the past, it has been difficult to achieve the same form and tooth position in the final unit as were planned in the diagnostic wax-up. This end is rather simply obtained in this esthetic control system, and it is here that some of the time lost in diagnostic waxing is recouped. A master cast with removable dies is fabricated from the final impression, and the casts are mounted on the articulator in any conventional manner. Vinyl copings are thermoformed” on the abutment dies and trimmed 1 mm. short of the margins. ‘Resin

coping

kit,

J. Aderer,

Inc.,

Long

Island

City,

N. Y.

400

Preston

J. Prosthet. Dent. April, 1976

Pig. 15. Patient requiring extensive periodontal and restorative care: (A) preoperative condition and (B) with provisional restoration during periodontal therapy.

The margins are carefully waxed, and a thin layer of wax is laid down over the copings. No attempt is made to achieve form or bulk. A 10 or 12 gauge solid plastic sprue bar* is heated and conformed to the curve of the edentulous ridge. (If one sprue bar is too short, two may be joined by merely heating one end of each and sticking them together.) This sprue bar is placed in the desired connecting position between the two abutments and attached with sticky wax. A matrix is placed over the cast and dies and the position of the sprue bar appraised (Fig. 10). The matrix is removed and the lingual aspect of the pontic areas of the matrix trimmed to within about 3 mm. of the incisal edge. The matrix and cast are painted with a wax pattern lubricant, and the sprue bar is lightly scored with a hot instrument. The matrix is replaced, and molten inlay wax is flowed into the matrix, filling the abutment form and the labial, incisal, and gingival aspects of the pontics (Fig. 11). Another approach? is to use a glass syringe with a large-gauge blunt needle in which the wax can *Plastic sprues, Williams Gold Refining Company, Buffalo, N. Y. tPersona1 communication from Dr. Richard Harrison, September, 1974.

pI;Lm& u

?f

Systematic

control

of esthetic

form

401

be melted and then injected into the matrix. Both methods rapidly fill the matrix and develop a full-form wax-up. When the wax is thoroughly cooled, the matrix is slipped off. The excesswax can be quickly trimmed away, any defects corrected, and the lingual aspects of the pontics developed. The sprue bar adds great rigidity to the pattern, and the vinyl copings help resist distortion. The full-form wax-up is then dewaxed to allow for veneering material. Before the unit is sprued and invested, however, the matrix should be r-e-placedto insure that enough cutback was allowed. If it is not thought desirable to cast in one unit, the span may be carefully separated with a jeweler’s saw. The units are then conventionally invested and cast. The castings are recovered, the spruesare removed, and the metal is finished to receive porc’elain. The matrix is once again seated on the cast, and the castings are evaluated 1:o insure that the substructure is, indeed, ready to receive the veneering material (Fi,g. 12) . Embrasuresand incisal edgesare especially evaluated, and any final shaping may be accomplished. In this manner, the substructure is fabricated toward a definiize end-an end which can be visually perceived throughout its entire construction. Veneering with porcelain is thus simplified, since all connectors are definitely placed and sufficient space remains for ceramic material (Figs. 13 and 14). ADJUNCTWE

SUPPORT

IN PERIODONTAL

THERAPY

A serendipitous use of this systematic development of form has been for patient: requiring integrated periodontal and prosthodontic therapy. Those patients for whorr a fixed prosthesisis planned and who require stabilization, alteration of contour, 01 gross occlusal modification can derive benefits from a modification of the system After the initial phasesof periodontics are completed, modified shoulder preparation! are made. No attempt is made at beveling. The treatment restoration is then made in the conventional manner as described previously (Fig. 15). These have been placed for periods of 8 and 9 months with excellent tissueaccommodation. None has broken in service nor have there been any signsof deterioration of the acrylic resin by thme eugenol of the luting agents. The periodontal therapy is made easier, becausewhen the unit is removed, there is excellent interproximal access.Treatment restorations of this nature offer good splinting qualities and apparently offer excellent support during bone augmentation procedures or similar efforts at pocket reduction and decreasing mobility. When the periodontal phase is completed, the margins are finalized in relation to the healed tissuesand a beveled shoulder and chamfer placed. Either a new treatment restoration is then made or, if the correction of the margins is minor, the old unit is altered directly with acrylic resin or epimine plastic.” SUMMARY

A systematic, orderly approach to the problem of establishing harmonious phone.. tics, esthetics, and function in fixed restorations has been described. The system re.. quires an initial investment of time in performing an adequate diagnostic waxing, but recoups that time in many clinical and laboratory procedures. The method has. proved a valuable assetin fixed prosthodontic care. The technique can be expanded and combined with other techniques with a little imagination and artistic bent. “Scutan temporarysplintingmaterial,Premier

Dental

Products

Company,

Philadelphia,

Pa.

402

J. Prosthet. Dent. April, 1976

Preston

References 1. 2. 3. 4. 5. 6. 7.

Braly, B. V.: A Preliminary Wax-up as a Diagnostic Aid in Occlusal Rehabilitation, J. PROSTHET. DENT. 16: 728-730, 1966. Wax-up Technique, J. Morgan, D. W., Comella, M. C., and Staffanou, R. S.: A Diagnostic PROSTHET. DENT. 33: 169-177, 1975. Ellman, J.: Compression Formed Plaster Shells for Temporary Splints, Dent. Dig. 77: 334-339, 1971. Pound, E., and Murrell, G.: An Introduction to Denture Simplification, J. PROSTHET. DENT. 26: 571-580, 1971. Hirsch, B., Levin, B., and Tiber, N.: Effects of Dentist Authoritarianism on Patient Evaluation of Dentures, J. PROSTHET. DENT. 30: 745-748, 1973. Krug, R. S.: Multiple Uses of Plastic Template in Fixed Prosthodontics, J. PROSTHET. DENT. 30: 838-842, 1973. Fisher, D., Schillingburg, H. T., and Dewhirst, R. B.: Indirect Temporary Restorations, J. Am. Dent. Assoc. 82: 160-163, 1971. 5062 AMESTOY ENCINO, CALIF.

AVE. 91316

ARTICLES Titanium A 2 year I. M.

TO APPEAR

endosteal study

Gourley,

D.V.M.,

Observations Rafael

Oscar

results

wear, tensile a relationship?

Harrison,

B.D.S.,

J. Hoard,

D.D.S.,

F.D.S.,

D.M.D.,

molds

of bevels D.D.S.,

ISSUES

mandibles and

of beagle

D. R. Cordy,

D.V.M.,

Ph.D.

resin restorations and Maya

Zalkind,

D.M.D.

used in constructing

and Ken

dogs:

facial

prostheses

Canada

of occlusal

wear

of complete

dentures

R.C.S.

strength,

F.D.S.,

D.D.S.,

for composite

Hirschfeld,

of the measurement B.D.S.,

in the

L. W. Richards,

for metal

M.S.P.H.,

The relationship Richard

Zvia

technique

Harrison,

Abrasive Is there Alan

Ph.D.,

N. Guerra,

Clinical Alan

Ph.D.,

implants

on cavity liners

Grajower,

Open-cast

dental

IN FUTURE

R.C.S.,

and hardness and Robert

to the adaptation

and Jay Watson,

D.D.S.

of dental

A. Draughn,

composite

D.Sc.

of intracoronal

inlays

resins-