June 2013, Volume 9, Issue 6
Published by AEGIS Communications
A Simplified Characterization of Temporary Restorations
Material selection and technique keep function and esthetics in mind
Often provisionalization is squeezed into the little time remaining at the end of a crown-and-bridge appointment.1 This can create frustration and anxiety if the method used is not predictable or is overly time intensive, or if the resulting temporary restoration requires a lot of trimming, fitting, and occlusal adjustment before or at insertion. Temporary fixed prostheses must usually function for a short period of time; however, there are instances when these temporaries must survive clinically for a protracted period of time and, if in the anterior region, must not only succeed from a functional point of view, but must also be esthetic.
Choosing Temporary Materials
There are many provisional materials available to the clinician. Preformed crowns of polycarbonate, aluminum, and nickel chrome are time consuming and difficult to adapt not only to the interproximal contacts, but also to the occlusal contacts and the gingival margins, even when they are available in multiple sizes. This can result in many clinical complications when attempting to seat the crown-and-bridge prosthesis.2 They may be lined with various resins for better adaptation, but their use is limited.
Preformed crown forms or celluloid shells that can be filled with tooth-colored temporary materials inevitably need major contouring of the cavo surface margins, adjustment or addition of interproximal contacts due to the thickness of the crown form, and more occlusal adjustment than temporaries made from accurate matrices. Protemp™ crowns (3M ESPE, www.3mespe.com) comprise a bis-GMA light-cured composite that come in single units, are adaptable, have a single shade only, and have good wear resistance and good polishability. Due to their single shade, however, their use is somewhat limited unless one is prepared to custom stain.
Various types of resins are extensively used in the fabrication of single or multiple unit provisionals. Polymethyl methacrylates (self- or heat- cured) such as Jet (Lang Dental, www.langdental.com), ALIKE™ (GC America, www.gcamerica.com), and Trim® Plus (Harry J. Bosworth Co, www.bosworth.com) have a high exothermic reaction,3 high shrinkage resulting in fair marginal adaptation, good color stability, and sometimes residual-free monomer that can damage the pulp. Polyethyl methacrylates such as SNAP™ (Parkell, http://parkell.com) or Trim® (Harry J. Bosworth Co) shrink less, and have less of an exotherm but have less strength, less fracture toughness, less color stability, and are not as durable.4
Most temporary materials currently in use fall under the grouping of bis-acryl composites. These include Temptation® Now (Clinician’s Choice, www.clinicianschoice.com), Luxatemp® (DMG America, www.dmg-america.com), Protemp™ II (3M ESPE), Integrity® (DENTSPLY Caulk, www.caulk.com), and Stuctur 3 (VOCO America, www.voco.com). These materials show a low exothermic reaction, are easy to work with intraorally, have a relatively low shrinkage resulting in a better marginal fit, have good abrasion resistance especially when a glaze is applied, come in multiple shades, can be added to a flowable composite, and have reasonable esthetics with color stability.5,6 However, they can be brittle when overly thin (some are designed with more flex for longer span provisionals), can have an oxygen-inhibited layer on the surface that must be removed with alcohol,7 tend to feel somewhat porous or rough to a patient’s tongue if not polished or surface treated with a glaze, and are more expensive than polymethyl methacrylates and polyethyl methacrylates.
Methods of Fabrication
Many dentists prefer the use of matrices for the fabrication of provisional restorations because they can be easily created intraorally from the existing dentition and easily created intraorally for simple bridges if a single tooth is missing; in more complex restorative cases, they can transfer data accurately from esthetic or functional mock-ups.1 The use of an alginate impression matrix has the limitation of one-time use only; alginate is not dimensionally stable due to syneresis and can imbibe water when wrapped, thus creating distortion.8 The use of a softened hard pink base-plate waxy impression as a matrix has been described,2 but due to the difficulty in stability and adapting gingivally and interproximally, finishing and trimming the temporary is much more time consuming than other methods.
The creation of a suck-down matrix necessitates many steps and the use of valuable dental team member time. The accuracy of this suck-down matrix is limited by the accuracy and flow of the alginate impression, which is variable depending on the water-to-powder mix and the water temperature used; it is nearly impossible to achieve adaptation of the plastic matrix to the occlusal surfaces, and occlusal adjustment is necessary. Many times, the taking of these impressions needlessly ties up chair time. Because the majority of crown-and-bridge work performed involves single units,9 study models for these cases are often not necessary, and the direct matrix technique is more practical and economical.10 However, a suck-down clear matrix is a good adjunct when doing major restorative work using esthetic wax-ups. A putty matrix can take a relatively long time to set, and may not have the flow necessary to accurately capture the detail of occlusal surfaces or pick up gingival contour and interproximal surfaces, so that temporaries fabricated from these types of matrices often need extensive trimming and adjustment.
Bite registration materials are designed to be stiff and have no bounce to allow for accurate articulation of models, and thus as a matrix material lack the flex needed to be easily removed from interproximal areas. Polyvinyl substitutes for alginate can be used as a matrix in an impression tray. These alginate substitutes are essentially low-cost polyvinyl siloxanes (PVSs) and offer the benefits of good flow, excellent detail reproduction, and the ability to be reused because of their long-term stability.8 They can take 3 to 4 minutes to polymerize and the cost for creating a single-unit temporary can be minimized by using a sectional tray rather than taking a full-arch impression.
Regular PVS materials can have either clear or colored opaque formulations and demonstrate excellent flow, stability, dimensional accuracy, and flex to aid in removal. There are multiple variations in working and setting times. Some clinicians have used a PVS material for the matrix and then relined it with a high-flow PVS for the final impression. This technique is not recommended, because the surface of the tray material is contaminated with the bis-acryl, preventing the high-flow material from chemically bonding to the tray material and resulting in separation when a model is poured and removed. In addition, a two-part impression technique for crown and bridge is not as accurate as an all-in-one, due to the difficulty of reseating the impression with accuracy with a reline technique.
The dental literature is replete with confirmation of the reinforcement effects of composite reinforcement fibers on composites and bis-acryls. The inclusion of fibers in provisional restorations increases the fracture toughness and flexural strength of temporary fixed prostheses.11 Clinically, there is a reduced incidence of fixed provisional restoration failure12 due to enhanced fracture resistance.13 The mean flexural modulus for including horizontally-oriented fibers is significantly greater than interim restorations without incorporated fibers.14 Therefore, if a provisional restoration is to be in clinical service for more than the typical 2 to 3 weeks, or if a large full-mouth rehabilitation needs to be temporized, fiber reinforcement will ensure longer-term survival.
Technique with Quick-Setting PVS
When fabricating a matrix for a temporary restoration, the tray you choose can be a major factor in whether the procedure is a success or failure. The tray has to be customizable, cost effective, and useable in all four quadrants and the anterior sextants, and must not distort. The metal TempTrayTM (Clinician’s Choice) is used for this technique because it is designed to be a customizable, distortion-free, and disposable temporary tray. When used as a posterior matrix tray, the handle that is facing the retro-molar area is bent over on top of the tray, so as not to impinge on the tissue, and the anterior is bent at a 45° angle to facilitate insertion, providing a convenient handle. When used anteriorly, the lingual wall is bent slightly toward the palate and both ends are bent at 45° angles to provide a handle on both ends.
The material that makes this technique so user friendly is Template® (Clinician’s Choice), an ultra-quick-setting PVS matrix material that provides good flow for superior detail and accuracy. Template sets in 30 seconds, flows well into the embrasure areas and into the finest morphology, minimizing flash, and yet will release easily when cured. As a PVS, it will maintain its form and accuracy indefinitely, which allows for it to be reused if the patient should fracture or lose their temporary restoration.
To begin, Template is injected into the TempTray (Figure 1) (after dispensing a small portion that may not be mixed completely on a pad, as with all materials using mixing tips). It is quickly inserted over the tooth or teeth to be restored or over a cast fabricated from a diagnostic wax-up and then removed after 30 seconds (Figure 2). The mixing tip is left on until the next use, so as not to cross contaminate the ports of the cartridge. The extensions of the Template that go into the area of the pontic lingual embrasure are removed, to give more bulk in the area of the connectors, increase strength, and facilitate adaptation of the reinforcing fiber (Figure 3). The fiber reinforcement is then cut to length and placed into the PVS matrix to verify fit before injecting the bis-acryl (Figure 4).
A product like Ribbond® THM or Ribbond® Triaxial (Ribbond, www.ribbond.com) needs to be wetted with an unfilled bonding resin (Figure 6) before placement and adaptation into the bead (Figure 7). Quartz Splint™ UD 1.0 mm and 1.5 mm and Quartz Splint™ Woven 2.5 mm (RTD, http://rtddental.com) are uniformly impregnated in a light-curable resin matrix, eliminating this wetting step.
After dispensing a pea-sized amount on a mixing pad, the fast-setting bis-acryl Temptation Now is injected into the matrix (Figure 8) and reseated over the final preparation. When fabricating anterior temporaries, the authors often use one shade darker for the cuspid to give a more lifelike colour gradation. With an initial cure (mouth removal time) of 45 seconds to 1 minute and a complete cure in 4.5 minutes, the overall temporization procedure time is reduced, as it allows for trimming earlier (Figure 9). The resin-impregnated reinforcement fibers in the provisional bridge are light cured lingually prior to removing the temporary Figure 10). The small amount of flash can be removed with a disc, but the authors find that the pointed Contours™ Coarse Anatomy Trimmers (Clinician’s Choice) are faster and easier to use and control (Figure 11).
All bis-acryl temporary materials can be added to a flowable composite resin after the temporary is fabricated. This modification can easily add contour and interproximal and occlusal contact points, minimize gingival discrepancies, and buttress the connector areas. As some bis-acryl temporary materials can shrink by more than 4%, it is an advisable technique to try in all temporaries before cementation and assess the gingival adaptation. If there is any amount of drawback from the margin, a small amount of flowable composite can be injected over the margins, the bis-acryl temporary seated, and the excess flowable brushed over the provisional; after light curing, the provisional is then removed. This recapitulation step significantly decreases the marginal gap, decreasing the amount of temporary cement that is exposed for potential wash out, and increases gingival health. Also check the contact areas between the teeth with floss before cementation. If the contact is open or light, add a small drop of flowable to the contact area, insert the temporary, and light cure, and the contact will be readapted properly. Some excess may need to be polished if the contour is rough.
In the anterior region, a monochromatic temporary restoration is no longer acceptable for the esthetically demanding patient. It only takes a few minutes to do a very simple characterization that makes the restoration not only look esthetic but blend into the existing dentition. Photographs were taken on a model for ease of photography, but this process can be easily accomplished intraorally.
The first step is to coat the bis-acryl with a bonding resin, as this fills in any voids and provides a surface that will allow control of the characterization. In this case, one coat of MPa™ (Clinician’s Choice) was placed and light cured for 10 seconds with a VALO® LED light curing unit (Ultradent Products Inc., www.ultradent.com) (Figure 12). A 50/50 mix of Vit-l-essence® (Ultradent) colors dark brown and clear was minimally applied with a #15 Bard Parker™ scalpel (BD Medical, www.bd.com/us) interproximally to provide the illusion of separation (Figure 13 and Figure 14) and light cured. With a fine sable hair brush, a 2/1 mixture of ochre/clear was then applied for gingival down toning and warmth and also light cured (Figure 15). This application can be as much or as minimal as the adjacent teeth dictate. If the incisal one third has some semblance of “clouds” or characterization, then a 2/1 mixture of clear and white can be applied with a microbrush to give this illusion (Figure 16). The final application in this example included placing white calcification marks on the cusp tips and incisal edges (Figure 17).
Because bis-acryls are somewhat rough and tend to wear if left for any protracted amount of time, a glaze must be placed over the temporary bis-acryl material. The application of a glaze totally eliminates the need for any polishing, thereby significantly decreasing procedure time, and also creates a smoother surface for the patient’s tongue, increases wear resistance, and facilitates easier temporary cement removal (Figure 18).
Figure 19 and Figure 20 show the development of pontic form and tissue health that can be created with the use of a properly adapted long-term provisional. The fabrication of a personalized, esthetic temporary restoration or temporary fixed prosthesis can be user friendly, predictable, and efficient. Using a highly accurate, quick-setting specialized PVS matrix material and its adjustable tray with a fast-setting bis-acryl temporary material and supplying internal reinforcement, surface characterization, and a glaze as described above should eliminate much of the frustration and time required to create an esthetic provisional prosthesis that meets all the required criteria for a good long-term temporary.
Note: Portions of this article were previously published in the January/February 2011 issue of Inside Dental Assisting as “Temporization Simplified.”
Leendert (Len) Boksman, DDS, BSc, FADI, FICD, is retired from private practice and consults part time for a number of dental manufacturers. Gregg Tousignant, CDT, is currently serving as technical support manager for Clinical Research Dental, where he provides technical support and hands-on courses consistent with the company’s philosophy of teaching better dentistry.
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Leendert (Len) Boksman, DDS, BSc, FADI, FICD
Retired from Private Practice
London, Ontario, Canada
Gregg Tousignant, CDT
Technical Support Manager
Clinical Research Dental
London, Ontario, Canada