A time-saving technique for making accurate temporary restorations
JOHN MAMOUN, B.A.
Typically, to make an acrylic temporary restoration, the practitioner fills a one-piece mold with liquid acrylic mixture and overlays it on the tooth preparation. The resulting temporary, once hardened, usually features gross excess of acrylic marginally, buccally and lingually that must be removed in a tedious process. Also, excess interproximal acrylic may destroy the temporary via undercuts as it is removed from the preparation. However, a modification of this procedure systematically yields a temporary with almost perfect interproximal and marginal adaptation, buccolingual and mesiodistal contours, and very minimal acrylic excess, all on the basis of the first temporary impression.
THE METHOD
In this method, the dentist takes four separate impressions of the tooth before preparation, using condensation silicone. One impression captures the lingual portion of the tooth, another the buccal portion and a third (overlaid on the buccal and lingual pieces) the occlusal portion. A fourth, overlaid on the other three, is used to bind the other three in the mouth. At impression time, the lingual and buccal pieces are positioned around the tooth preparation, closely adapted to the lingual and buccal margins of the preparation. The acrylic mixture is placed, and the occlusal portion placed on top of the acrylic. The resulting temporary is so well-adapted to the marginal, interproximal, buccal and lingual surfaces of the tooth that, with minor finishing, it is almost perfect from the initial impression. And with minimal interproximal acrylic excess, there is less threat of undercuts.
This technique for temporary fabrication saves considerable time by yielding a temporary with excellent margins, interproximal adaptation and morphological form almost from the initial setting.
THE TECHNIQUE
– Take separate buccal and lingual impressions of the tooth to be prepared.
– Take an occlusal impression over the lubricated buccal and lingual pieces.
– Take a fourth impression over the buccal, lingual and occlusal impression to act as a jacket to hold the other three pieces in place in the mouth.
– Remove the impressions, prepare the tooth, then replace the buccal and lingual impressions around the tooth (Figure 1
).
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Figure 1. After tooth no. 21 has been prepared with a porcelain-fused-to-metal restoration, it is bordered with the buccal and lingual impression pieces, which form a hole in which a pasty acrylic mixture will be placed to begin making the temporary for the tooth.
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– Place an acrylic/monomer mixture in the compartment formed by the buccal and lingual impression walls, cover it with the occlusal impression piece, then overlay the fourth impression piece on the other three pieces to hold them in place in the mouth while the acrylic sets and hardens.
This step demonstrates the advantages of this technique. The buccal and lingual impression pieces are precisely adapted to the tooth contours. This forms a seal at the marginal area of the tooth that prevents excess acrylic from seeping below the margins, yielding a temporary with almost perfect marginal adaptation that needs minimal finishing with acrylic burs. This also gives the temporary excellent interproximal and intra-arch contours, and it minimizes the possibility of excess acrylic’s building up interproximally and creating undercuts that trap or destroy the temporary as the clinician attempts to remove it from the preparation. If just one piece of condensation silicone is used, intimate interproximal adaptation will result in an undercut.
In addition, the removable occlusal portion allows the clinician to inspect the temporary visually before it has set, and to expose it to air to facilitate evaporation of excess monomer. It also allows the clinician to use slight force to condense the acrylic mixture into the preparation, thus ensuring that the temporary will be free of voids. Also, an opened occlusal surface allows the clinician to gauge visually how much acrylic mixture is needed for the temporary and therefore to control the amount of acrylic added, which reduces the amount of gross acrylic excess.
- – Remove the pieces to inspect and finish the acrylic temporary (Figure 2).
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Figure 2. After a few minutes of setting, the jacket and occlusal portion are removed so that the dentist can inspect the temporary for voids and monitor its hardness. Eventually, the lingual and buccal pieces are removed as well.
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CONCLUSION
This technique for temporary fabrication saves considerable time by yielding a temporary with excellent margins, interproximal adaptation and morphological form almost from the initial setting. It also features a reduced possibility of undercuts destroying the temporary. An added benefit of the technique is that since the patient’s own tooth is used to form the temporary mold, the resulting temporary is a morphological copy of the patient’s own tooth, and therefore it may more likely win the patient’s acceptance. As a side note, if an accurate diagnostic model of the patient’s dentition is available before his or her appointment, the temporary mold pieces may be prefabricated on the model to reduce the chair time needed to make the temporary. This should be done shortly before the visit to reduce the possibility of the condensation silicone’s distorting as a result of being left out for too long.
DO YOU HAVE A TIP TO SHARE
Do you have a time- or work-saving clinical technique to share with your colleagues? Submit it to JADA’s Clinical Directions department. A Clinical Directions item should be a maximum of two double-spaced typed pages and should include no more than one figure or illustration. Submit items to Clinical Directions, JADA, 211 E. Chicago Ave., Chicago, Ill. 60611.
FOOTNOTES
Mr. Mamoun is a third-year dental student at the University of Medicine and Dentistry of New Jersey, Newark. Address reprint requests to Mr. Mamoun at P.O. Box 219, Green Village, N.J. 07935, e-mail "mamounjo{at}umdnj.edu".
