Modern Concepts in Provisionalization

Among the many material options available for provisional fabrication are methyl methacrylate, ethyl methacrylate, bis-acryl composite, and light-cured resin. Although each material has its own advantages and disadvantages, they can all be used successfully to accomplish the goals of provisionalization. It is typically not the material that makes the difference, but rather the provisionalization technique and how the restorations are trimmed and polished.

There are three main techniques for fabricating provisionals. The first and most common technique is “direct in the mouth.”^2,3 The overwhelming majority of provisionals are fabricated in this manner using a matrix from a diagnostic model or wax-up, filling it with provisional material, seating it over the preparations in the mouth, and then removing to trim and polish. Another technique is “indirect on a model.” The same type of matrix is used, but the provisional is made on a silicone or stone model of the preparations.⁴ This can be beneficial with a larger number of units, as it is easier to control the fit, form, and esthetics. The last technique would be a combination of the previous two techniques, where a “preformed shell” is then relined over the preparations directly in the mouth.⁵

By far the most important part of fabricating provisionals is the process of trimming and polishing. The technique of trimming provisionals is linear and consistently follows the same sequence. That trimming sequence is: buccal/palatal margins, interproximal embrasures, facial/incisal embrasures, facial surface, and incisal edges.

Buccal/Palatal Margins

The starting point when trimming provisional restorations is to identify and trim the buccal and palatal margins. Prior to any trimming of the provisionals (bisacryl), it is advisable to clean the provisionals with alcohol (Figure 4 and Figure 5). The purpose of this is to remove the sticky air-inhibited layer. If this is not done, the burs and discs will immediately become gummed up and no longer cut efficiently.

For rapid removal of material, the author primarily uses a large acrylic bur (H78E) (Figure 6). However, it is not uncommon for acrylic burs to “chatter” and possibly gouge margins. For a more refined removal of material at the marginal areas, the clinician can use a fine acrylic bur (H79EF) (Figure 7) or a silicone polishing wheel (RWGPP green) (Figure 8). This benefit of the silicone wheel is that it creates a very smooth, polished margin with no risk of chatter (Figure 9).

Interproximal Gingival Embrasures

In order to open and adjust the interproximal gingival embrasure, the use of a thin, flexible diamond disc is necessary (Vision Flex 934 or Hyper Flex 911H) (Figure 10 and Figure 11). The key to using diamond discs is to run them at a fairly slow speed. If the speed is too high, there is a loss of tactile sensation and the discs will cut too aggressively.

It is important when carving gingival embrasures to always keep the disc parallel to the tooth being worked on, to allow the proper emergence profile to be created from the preparation to the restoration, and help the interproximal embrasure flow into the facial embrasure (Figure 12 and Figure 13). Orienting the disc “straight” into the embrasure should be avoided, as this does not allow the proper emergence profile to be created and does not create adequate room for hygiene. In order to carve the embrasure for the midline, the clinicians should start by “notching” the gingival embrasure halfway between each preparation and then angling the disc from each preparation into this area. This allows the adjustment to end up dividing the space equally between the teeth.

It is always desirable to leave the gingival embrasures slightly open when carving them, because the provisionals are typically made after some sort of gingival displacement is performed to get the impressions. If they are kept too closed, the tissue has no room to rebound after it has been displaced. As a result, inflammation of the tissue will be present due to inadequate room for hygiene.

Facial/Incisal Embrasures

To address the facial/incisal embrasures, the practitioner should start by determining the appropriate width desired for the incisal edge and use a disc to carve (Vision Flex 934 or Hyper Flex 911H). The facial embrasure is then a direct extension between the gingival and incisal embrasures. Leaving the facial embrasures more closed will give the perceived appearance of a wider tooth, as the line angles will be pushed out toward the lateral aspects of the tooth thereby creating more surface for light reflection. A more open facial embrasure will move the line angles toward the middle of the tooth, giving the perception of a narrower tooth.

Facial Surface/Incisal Edge

In conjunction with carving the facial embrasures, the next step in the process is to adjust the facial surfaces and incisal edge. The facial surface can be adjusted with either a silicone polishing wheel (RWGPP green) (Figure 14) or a fine acrylic bur (H79EF) (Figure 15), depending on how much adjustment is necessary (Figure 16). For anterior teeth, it must be remembered that the facial surface is composed of three planes (cervical, middle, incisal) and typically has surface anatomy to help break up the light. The incisal edge can easily be adjusted with the same green silicone. Any minor refinements to the contour can then be accomplished with a fine silicone wheel (RWPPP pink).

Polishing

Traditional polishing techniques using pumice on a wet rag wheel (slow speed) followed by a high shine polishing paste on a dry rag wheel (high speed) still produces the best surface finish. However, use of the aluminum-oxide-impregnated felt wheels (SWR22M and SWR22F) is a quick way to produce a very nice surface chairside (Figure 17 and Figure 18).

In summary, the key to fabricating natural, esthetic provisionals is “time” and “attention to details” with the trimming and polishing techniques, as can be seen in the completed provisional restorations after finishing and polishing (Figure 19).

Greggory Kinzer, DDS, MSD
Faculty
Spear Education at the Scottsdale Center for Dentistry
Scottsdale, Arizona 


Private Practice

Seattle, Washington