The Journal of Prosthetic Dentistry Konstantinidis et al

This article describes an alternative technique for the fabrication of interim restorations. A thermoplastic, vacuum-formed template and translucent vinyl polysiloxane material are combined in the waxed diagnostic cast to fabricate a matrix in which the interim material can be placed. With this matrix, a variety of materials, such as dual-polymerized or light-polymerized resins, can be used in a predictable way. The major advantage of this technique is that it allows for the fabrication of accurate restorations with excellent reproduction of surface anatomy and for alterations of the tooth shape with light-polymerized materials. (J Prosthet Dent 2013;109:198-201)

A novel technique for the direct fabrication of fixed interim restorations

Ioannis Konstantinidis, DDS,a Georgios Kotsakis, DDS,b Konstantinos Pallis, DDS, MSc,c and Michael Horst Walter, Prof Dr med Dentd

School of Dentistry, University Hospital Carl Gustav Carus, Technical University Dresden, Dresden, Germany; School of Dentistry, University of Minnesota, Minneapolis, Minn; Dental School of Athens, Athens, Greece

aDentist, Department of Prosthetic Dentistry, Technical University Dresden.bResident, Advanced Education Program in Periodontology, Department of Developmental and Surgical Sciences, School of Dentistry, University of Minnesota.cPhD student, Department of Prosthodontics, Dental School of Athens.dProfessor, Department of Prosthetic Dentistry, Technical University Dresden.

Fabricating a precise interim res-toration is an important step in con-temporary prosthodontics. An interim restoration should provide for the func-tional, esthetic, and biological needs of the patient until the placement of the definitive restoration.1 Design of the interim prosthesis has an important role in the configuration of the mar-ginal gingiva, especially when dental implants have been placed.2 Moreover, interim restorations may function as a means of communication, convey-ing information regarding the function and esthetics of a restoration between patient, dentist, and dental technician.3 Choosing the appropriate combina-tion of materials and methods for the fabrication of a high quality interim res-toration is important because the only difference between this and the defini-tive restoration should be the material used.4 A precise technique can provide restorations with accurate margins that offer substantial clinical benefits.5

Interim restorations can be fabri-cated directly intraorally, indirectly in the laboratory, or with the direct-in-direct technique when the restoration is formed extraorally and finalized in-traorally.6 Although, according to in vitro data, the indirect method can yield restorations with more accurate marginal adaptation,7 most dentists use the direct method. The matrices for the direct technique are made of thermoplastic, vacuum-formed tem-plates, irreversible hydrocolloid, or elastomeric impression materials,8 but the matrix of choice for each situ-ation depends upon many variables. Factors such as the span of the res-toration, the handling characteristics of the matrix, the ability of the matrix to reproduce fine detail, and the abil-ity to allow direct visual control of the restorative material should be taken under consideration.

A translucent, vacuum-formed matrix enables the use of light-po-

lymerized restorative materials and allows the material to be visualized during its polymerization.9 It also can be used as a guide for tooth prepara-tion, for the fabrication of diagnos-tic tooth arrangements10,11 or for the restoration of severely damaged teeth with composite resin.12 The use of a vacuum-formed template has the dis-advantage of lacking detail relative to the occlusal surfaces and the margins because it is inherently difficult to adjust over the cast with simultane-ous, even pressure. The insertion of visible light-polymerized (VLP) resin between cast and matrix is recom-mended to improve matrix accuracy and achieve better formed occlusal surfaces.13 To make interim restora-tions that are durable enough to stay intact for a protracted period of time, the use of light-polymerized materials is preferable.14,15 Jeroff et al16 reported a technique for the fabrication of in-terim restorations with the aid of a

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translucent matrix formed by using a translucent impression material and a sectional impression tray.

This article describes an alterna-tive technique for fabricating interim restorations by using a translucent matrix made from the combination of a thermoplastic, vacuum-formed template, and translucent impression material.

TECHNIQUE

Fabricating the matrix

1. If the current shape of the teeth to be prepared is acceptable, make an impression including at least 1 adjacent tooth on each side and fabricate a cast

with a Type IV dental stone (Resin Rock; Whip Mix, Louisville, Ky). In this situa-tion, base the fabrication of the interim restoration on the existing partial fixed dental prosthesis in the maxillary left posterior region (Fig. 1). Alternatively, if new information must be transferred from the diagnostic waxing, moisten the diagnostic cast and use it to fabri-cate the matrix. Note that there is no need to duplicate the diagnostic cast.

2. Place the moisturized cast on the thermoforming unit (Erkoform-3; Erkodent Erich Kopp GmbH, Pfalz-grafenweiler, Germany) and activate it. Note that the thermoplastic sheet (Erkodur-3; Erkodent Erich Kopp GmbH) will enter a viscoelastic phase due to the temperature rise.

3. Inject the translucent impres-sion material (Memosil 2; Heraeus Kulzer GmbH, Hanau, Germany) by placing the impression material mix-ing tip onto the occlusal or incisal surfaces of the cast and sliding it in a continuous manner in the posterior-anterior direction over the cast (Fig. 2). Determine the volume of the ap-plied impression material by the di-ameter of the impression tip as it runs over the occlusal or incisal surfaces of the cast. Note that according to the authors’ experience a cylinder of im-pression material with a diameter of 8 to 10 mm is ideal for that purpose. Do not apply either too little or too much impression material as it can jeopardize the accuracy of the matrix.

1 Patient presented with partial fixed dental prosthesis on maxillary left posterior region, which required removal because of secondary caries.

2 Diagnostic cast is placed appropriately on thermo-plastic unit, and vinyl polysiloxane translucent impression material placed on occlusal and incisal surfaces of teeth that are to be included in matrix.

3 View of cast after application of thermoplastic sheet. Remove cast from unit when polymerization of impres-sion material is completed and thermoplastic sheet has cooled.

4 Modified matrix after removal of excess from thermo-plastic sheet. At least 1 tooth adjacent to prepared tooth should be included in matrix. Note detailed reproduction of proximal and incisal surfaces.

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4. Before the working time of the impression material is exceeded, apply the heated sheet of the thermoplastic material over the cast and wait until it cools and the impression material is completely polymerized (Fig. 3).

5. Cut back the matrix excess with the aid of a heated wax knife or scalpel so as to include at least 1 tooth mesi-ally and distally of the prepared teeth.

6. Remove the matrix from the cast and evaluate its surface. Ensure that the impression material adapts to all of the teeth and the matrix and the impression material (Fig. 4).

Fabricating the interim restoration

7. Place the translucent matrix intra-orally and evaluate its fit over the unpre-pared teeth.

8. Lubricate (Vaseline; Corp, Englewood Cliffs, NJ) the teeth and syringe the restorative material, a bis-GMA-based material (Luxatemp; DMG, Hamburg, Germany), into the matrix. Place the material only in the space that the interim restoration will occupy. Note that the excess material will increase the working time, so take care not to overfill the matrix.

9. Place the matrix over the abut-ment teeth (Fig. 5). Apply gentle pressure on the matrix to ensure its precise fit over the unprepared teeth. Note that forceful pressure may dis-place the matrix and alter the form of the interim restoration. When us-ing dual- or light-polymerized interim materials, hold the matrix stable and apply the polymerization light to the matrix surface. Use adjunctive polym-

erization after matrix removal, even though the translucency of the matrix allows light to pass through and po-lymerize the restoration.

10. Wait until the polymerization of the restorative material is complet-ed and then remove the matrix with the restoration from the mouth.

11. Separate the restoration from the matrix (Fig. 6), trim the excess material, and polish the restoration (Fig. 7).

12. Place the restoration over the prepared teeth, and verify that the marginal seating is precise and that there is no occlusal interference. Ce-ment the interim restoration with an interim cement (TempBond; Kerr Corp, Orange, Calif ) (Fig. 8).

5 Fill matrix with interim material of choice and apply it over treatment area. Press occlusal surfaces of matrix to ensure accurate seating. Note potential of visualizing interim material and unprepared teeth through matrix.

7 Interim restoration after removing excess. Minimum chairside contouring was required.

8 Restoration is placed intraorally. Occlusal contacts are controlled, and restoration is cemented with interim cement.

6 After removal from mouth, interim restoration can be easily collected because of flexibility of impression material in matrix. Notice that there is minimum material excess since care was given to avoid overfilling matrix.

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DISCUSSION

This article describes a direct tech-nique for fabricating interim restora-tions. The transparency of the matrix used enables better control of the restoration fabrication process and allows for the use of various interim materials.

The temperature rise caused by some restorative materials such as poly(methyl methacrylate) can be countered by using a matrix that ab-sorbs the increased temperature. The thickness of the presented matrix in-creases its heat capacity compared to a vacuum-formed template, thus achieving a lower temperature rise. Additionally, the clinician can have visual control of the material through the matrix in order to verify that it is properly adapted to the abutment teeth. The accuracy of fit can also be confirmed by evaluating the seating of the matrix on the adjacent teeth.

The impression material inside the vacuum-formed matrix offers not only better reproduction of the occlusal sur-faces but also improves the stability of the matrix during its intraoral applica-tion. This is an important factor when managing long-span restorations.

Because the impression material is in contact with the diagnostic cast during the matrix fabrication process, the thermal energy of the heated ther-moplastic template is not transferred to the wax on the diagnostic cast. As a result, there is no need to duplicate the waxed diagnostic cast, which can be used directly for matrix fabrica-tion. This is both cost and time effi-cient. Even though the elasticity of the matrix allows the removal of the ma-trix from the cast without damaging

the waxed diagnostic cast, the clini-cian should consider that by removing the matrix the surface of waxed teeth may be altered. Thus, if the waxed di-agnostic cast is to be of future use, it may be prudent for the dentist to maintain a duplicated cast of it.

Potential applications of this ma-trix in combination with light-po-lymerized restorative materials may include the fabrication of diagnostic tooth arrangements or the restora-tion of abraded or fractured teeth.

SUMMARY

A new technique for the fabrica-tion of interim restorations with a translucent matrix is described. A thermoplastic, vacuum-formed tem-plate and a translucent vinyl polysi-loxane material are combined in this technique, which allows the use of a wide variety of interim materials, in-cluding light-polymerized resins. The technique leads to the fabrication of accurate, durable, and esthetic inter-im restorations.

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Corresponding author:Dr Ioannis Konstantinidis Universitätsklinikum, ZAPFetscherstraße 74D-01307 DresdenGERMANYE-mail: Ioannis.Konstantinidis@uniklinikum-dresden.de

Copyright © 2013 by the Editorial Council for The Journal of Prosthetic Dentistry.