Donna E. Edwards
Greer, South Carolina
Phone: 864.297.6365
Email:

Abstract

Product manufacturers continue to improve temporary crown materials. Supplementing the traditional products still in use today, new products are regularly introduced, expanding the range of options available. As an assistant, you must update your knowledge of these materials and proper techniques for their use to help the dentist choose the most appropriate treatment for each case. This article will explore the more traditional products and techniques, as well as some newer materials to augment your treatment options and help you provide the best possible care for your patients.

Every day, in dental offices across the country, teeth are prepared for crowns, bridges, or veneers. In each case, one or more temporaries (provisionals) must be made before the patient leaves the office. In most states, it is the dental assistant who does this. (As always, you need to be aware of your state's regulations regarding the assistant's role in this or any other procedure.)

Since the 1930s, acrylic materials have been used for making temporaries. Over the past few years, dental product manufacturers have developed alternatives to supplement acrylic materials, expanding the range of treatment options. You should be familiar with all of the available materials and the proper procedure for each one to provide the best care for your patients.

Temporary Crowns

Restorative dentistry includes placing crowns, fixed bridges, implants, and, with the growing popularity of cosmetic dentistry, veneers and all-porcelain crowns. One of the most important procedures with any of these treatments is the fabrication of the temporary crown, bridge, or veneer. Although patients look forward to the end result, dental assistants must not forget the importance of the temporary restoration.

Most temporaries are worn at least 2 weeks, sometimes longer, while the final restoration is being fabricated. Patient comfort and esthetics are important during this period. The temporary will protect the prepared tooth/teeth (dentin and pulpal tissues) against invasive microorganisms, saliva, and food, which may penetrate the dentinal tubules. It also will help prevent hot and cold sensitivity. Proper marginal adaptation will protect the finished edge of the preparation. Proper occlusion, along with interproximal contacts, will prevent the drifting and extrusion of teeth that can affect the fit of the final restoration. Good interproximal contacts prevent food im­paction into the soft tissues. Proper contouring of the temporary can assist in the maintenance of periodontal health by allowing access to the soft tissues during patients' oral hygiene procedures.¹

Because no temporary material suits every patient's needs, it is important for the dentist and dental assistant to be knowledgeable of the available material options. Using this information, you should be able to determine which material will allow you to make the most functional and esthetic temporary for each patient.

Temporary Crown Materials

Acrylic Materials

Acrylic temporary materials are divided into 2 separate categories: polymethyl methacrylate (PMMA) and polyethyl methacrylate (PEMA). There are advantages and disadvantages in both categories²:

Common advantages

• Can be smoothed and polished
• Can be characterized
• Can be easily repaired
• Can be used for long-span (3 or more) provisionals
• Low cost

Additional advantages of PMMA materials

• Good strength
• Good color stability for a few weeks

Additional advantage of PEMA materials

• Lower exotherm than PMMA, but higher exotherm than bis-acryl resin composite

Common disadvantages

• High exotherm. The high temperature generated during the setting of PMMA materials can be traumatic to the dental pulp if not dissipated with cool water and air during the polymerization stage. PEMA materials have a lower exotherm, but care still should be taken during the setting phase to keep the tooth cool.
• Odor objectionable to many patients

Disadvantages of PEMA material

• Bodily discoloration over a 2-week period
• Weaker than PMMA material

To make an acrylic temporary, a silicone putty matrix, vacuuform matrix, or preliminary impression made with a vinyl polysiloxane material, alginate, or alginate alternative will be needed. If an alginate impression will be used, it will need to be kept wrapped in damp paper towels so the material will not dry out and distort. A vacuuform matrix works well because the material can be seen, even in anterior cases, making it possible to note how the material flows and if any air bubbles are present. Using an explorer to make small holes at the incisal edges or occlusal surfaces of the matrix will help eliminate bubbles during seating. If not watched carefully, acrylic material can and will attach to any undercuts on the prepared teeth. To help avoid this, petroleum jelly or glycerin should be placed on the teeth and surrounding tissues.¹

Acrylic materials are purchased as a powder and a liquid that must be mixed together according to the manufacturers' guidelines at the time of use. Some acrylic materials are avail­able in a wider variety of shades than others. To get the desired shade, 2 shades of powder may need to be mixed together. Two different shades also can be used to add character to the temporary, for example, a lighter shade at the incisal edge and a darker shade for the remaining tooth.¹

The powder and liquid are mixed together, usually in a dappen dish, and when the material has a putty consistency it can be loaded in the matrix and placed over the prepared tooth/teeth. Attention must be paid to the material at this time. Keep a pea-sized amount of the material to the side to monitor the polymerization (ie, curing) process. As they cure, acrylic materials give off heat. Remember, PMMA materials have a higher exo­therm than PEMA materials, which can cause da­mage to the pulp of the tooth and also could burn the tissue. As the material begins to set, usually 1 to 1.5 minutes after the matrix is seated, begin to remove the matrix along with the acrylic material from the teeth. The matrix should be reseated several times during polymerization to prevent the acrylic from locking onto the prepared teeth and to offset shrinkage. To keep the acrylic and teeth cool, irrigate with water during the polymerization process. After the acrylic has hardened, check the margins, making sure they are well defined and cover the entire preparation. The material can be removed from the matrix at this time.

Using a lead pencil, mark the margins and contact areas on the temporary restoration.1 Trim the temporary with the acrylic burs of choice. There are several acrylic trimming and polishing kits available. The manufacturer may recommend the best trimming and polishing techniques for its acrylic material. When trimming, be sure to open the interproximal em­brasures so the patient can floss between the teeth. This is important to maintain healthy periodontal tissue. For your safety and protection, safety glasses, gloves, and a mask should be worn while trimming the temporary. After trimming the temporary, try it in and check the margins. If they are short, most often caused by shrinkage during polymerization, additional acrylic material can be added.

Remove the temporary from the mouth and, using an acrylic bur, remove 1 mm of material. This will allow space for the additional acrylic material. Place the temporary back on the prepared tooth/teeth and, using a small brush, paint some of the liquid around the margin to be repaired. Rewet the brush tip in the liquid and pick up a small amount of powder. Place the acrylic at the marginal area where it is short. If needed, additional acrylic can be added. Using additional liquid, lightly paint it over the set acrylic to smooth any air bubbles. After the acrylic has set, remove it from the prepared tooth/teeth. Mark the margins again with the lead pencil and retrim. Try the temporary in again and recheck the margins. Check the patient's occlusion, making any necessary occlusal adjustments. After proper occlusion is achieved, the temporary is ready to polish.

The temporary restoration can be polished in the laboratory using a wet rag wheel, and a slurry of fine pumice. To obtain a high polish, a chamois wheel, and an acrylic polishing compound can be used. When polishing the temporary restoration, care should be taken to avoid frictional heat damage to the acrylic. When using the rag wheel, take care not to damage the margins and contours. The temporary is now ready to cement. Several luting agents have been recommended as cements for acrylic temporaries. These include resin-based, zinc oxideeugenol, or noneugenol.¹

Before dismissing your patient, postoperative instructions on caring for the temporary should be given and also, if available, a written copy to take home.

Bis-Acryl Composites

In 1962, Rafael Bowen developed Bis-GMA, the thermoset resin complex used in most modern composite resin restorative materials.³ This was the beginning of the most popular temporary materials, bis-acryl resin composites. All bis-acryl composites are self-curing.

Some advantages²:

• Low exotherm during setting
• Lacks objectionable smell or taste
• Minimal shrinkage allows good marginal fit
• Delivered through a syringe
• Can be smoothed and polished
• Available in a variety of shades, including bleach shades
• Most can be repaired with flowable composite

Some disadvantages²:

• Can break when placed in areas of moderate stress
• High cost compared with other temporary materials

Like acrylic materials, bis-acryl tem­porary materials are used in a direct technique, meaning the procedure is preformed inside the mouth.⁴ To make a temporary, bis-acryl can be syringed into preliminary impressions made with vinyl polysiloxane material, alginate or alginate alternative, silicone putty splints, or vaccuform matrices.

Bis-acryl materials come in cartridge dispense systems, with auto­mix tips, that are loaded into a dispensing gun. No hand mixing is required; the assistant simply pulls the trigger. The mixing tip creates a perfect mix every time. This also prevents any crosscont­a­mination. To help with removal, before loading the temporary material in the preliminary impression, the prepared tooth/teeth can be lubricated with petroleum jelly or a similar lubricant. The author has found lubrication to be very useful when making anterior veneer temporaries, long-span temporaries (6 or more), and where a composite material was used as a build-up material. To avoid air bubbles, keep the mixing tip in the temporary material until you are finished loading the impression or matrix. After loading the tray, either recap the cartridge or leave the mixing tip on the syringe. After the temporary crown material is syringed into the preliminary impression, it is placed in the patient's mouth and the patient is asked to bite down into the impression. Timing depends on the particular product. After being placed in the mouth, for example, Integrity (Dentsply Caulk, Milford, Del, www.caulk.com) can be removed after 45 seconds; Access Crown (Centrix, Inc, Shelton, Conn, www.centrixdental.com) in 1 minute, and Luxatemp (Zenith/DMG, Englewood, NJ, www.zenithdental.com) in 2 to 3 minutes. The final set time ranges from 3 minutes for Access Crown to 6 and 7 minutes for Luxa­temp and Integrity.⁵ A smear layer, or oxygen-inhibited layer, forms during setting and must be removed with alcohol-soaked gauze before trimming. A smear layer is a thin layer of uncured composite that forms from air inhibition. The composite will not cure in the presence of air.

These materials can be trimmed with sandpaper discs, slow-speed rotary instruments, or fine-grit diamond burs.6-8 As mentioned earlier, mark the margins and contacts with a lead pencil before trimming. Don't trim the pencil marks; these can be removed with alcohol-soaked gauze after trimming. After trimming the temporary, try it on the prepared tooth/teeth and check the margins and contacts. If the margins are short, bis-acryl temporaries can be repaired with flowable or paste composite material. Add the additional material while the temporary is in the mouth and cure the composite material with a light-emitting diode (LED) curing light. After the additional composite is cured, remove the temporary from the mouth, mark the margins with a lead pencil, and retrim. Retry the temporary, adding more composite as needed. Zenith/DMG makes a flowable, light-cured composite, LuxaFlow, that can be used with Luxatemp.⁹ Integrity and Access Crown can be repaired with the composite material used in the office.^6,7

Bis-acryl temporaries can be polished with fine pumice, a rubber polishing wheel, a goat hair brush, or a composite glaze.^6-8 A wide variety of acrylic trimming burs and polishing wheels is available from different manufacturers. Bis-acryl temporaries can be cemented with the temporary cement of your choice. Dentsply does recommend that eugenol cements not be used with Integrity,⁶ Centrix states that Access Crown is compatible with eugenol and noneugenol cements,⁷ and Zenith/DMG also recommends zinc oxide-eugenol or noneugenol. Temporary cements containing eu­genol may inhibit the polymerization of resin-based luting cements.⁸

Other Composite Crowns

The newest temporary crown material on the market is Protemp Crown Temporization Material (3M ESPE, St Paul, Minn, www.3mespe.com). These crowns are available in 9 preformed sizes, saving valuable chair time. For a detailed description of Protemp Crown Temporization Material, see the July/August 2007 issue of Contemporary Dental Assisting.

Case Study—Making a Temporary Crown

The patient presented needing a crown for tooth No. 30. After the pa­tient was seated, the tooth was checked for any broken cusps that needed to be repaired be­fore the preliminary im­pres­sion could be made. The tooth was found to be intact. Before anesthesia was given and the preliminary impression made, the patient was asked to close, in his normal bite, and instructed to close in this manner when the preliminary impression is made. If the preliminary impression is made after anesthesia is given, the patient may not know if he or she is closing normally because of numbness. Blu-Mousse (Parkell, Inc, Edgewood, NY, www.parkell.com) was syringed into a posterior Triple Tray (Premier Products Co, Plymouth Meeting, Pa, www.premusa.com) (Figure 1) and placed in the patient's mouth. The patient was asked to bite down into the impression material, and the material was allowed to set according to the manufacturer's guidelines. It is a good idea to check the occlusion on the side opposite of the impression tray to be sure the patient has closed correctly. After the tray was removed from the mouth, the impression was checked to ensure that the margins were distinct and no pulls were present in the material (Figure 2). Anesthesia was given and the tooth was prepared for a single-unit crown. After preparing the tooth and achieving hemostasis, Access Crown temporary crown material was loaded into the preliminary impression (Figure 3) and placed in the patient's mouth. The patient was asked to bite down and, after 1 minute, the impression was removed (Figure 4). Then the retraction cord was placed and the final impression made. During this time, the temporary material set completely. After the final impression was made, the temporary was removed from the preliminary impression, the smear layer was removed with alcohol-soaked gauze, and the temporary was rinsed with water and air dried. The margins were then marked with a pencil (Figure 5). Marking the margins helps make them clear, so they can be trimmed to the margin and not beyond. This helps ensure that the temporary fits well, helps keep the tissue healthy, and matches the final crown as closely as possible. This is especially important with anterior veneer cases. The temporary was trim­med using the slow-speed handpiece with a Moore's 0.75-inch sandpaper disc placed on a mandrel (Figure 6) and a Robot Point Diamond No. 881 (Shofu Dental Corp, San Marcos, Calif, www.shofu.com) at the margin. (A good way to check and see how well you are trimming the margins of your temporaries is to try them on the models after you have cemented the permanent crowns.) The diamond also was used to add occlusal anatomy. The temporary was taken to the laboratory and polished with a wet rag wheel and a slurry of fine pumice. The temporary was tried in, the occlusion checked, and the contacts flossed. Slight adjustments, as well as a final polish, were made chairside with a Jiffy polishing brush (Ultradent Products, Inc, South Jordan, Utah, www.ultradent.com) (Figures 7 and 8). Zone Temporary Cement (Dux Dental, Oxnard, Calif, www.duxdental.com) was used to ce­ment the temporary restoration (Figure 9). The patient was asked to bite on a cotton roll while the cement set, the excess was removed, and the contacts were flossed again to remove the remaining interproximal cement. The patient's occlusion was rechecked, slight adjustments were made, and the temporary was repolished. Postoperative instructions on temporary care were given and the patient was dismissed.

Figure 1—Blu-Mousse being syringed into a posterior Triple Tray.	Figure 2—Blu-Mousse preliminary impression. Note the margin detail.	Figure 3—Access Crown temporary material being syringed into the preliminary impression.
Figure 4—Temporary crown after being removed from the mouth.	Figure 5—Margins after being marked with lead pencil.	Figure 6—Trimming the temporary with a sandpaper disc.
Figure 7—Polishing the temporary with a Jiffy brush.	Figure 8—Instruments used to trim and polish the temporary: Moore’s 0.75-inch sandpaper disc, Robot Point Diamond No. 881, Jiffy polishing brush.	Figure 9—The cemented temporary on tooth No. 30.

Patient Instructions—Taking Care of Temporaries

During the 2- to 3-week period while the final crown is being made at the laboratory, it is important for patients to know how to care for their temporary crowns. Instructions should include:

• No chewing gum or sticky candy. These will stick to the temporary and could pull it off.
• Do not chew anything hard be­cause your temporary could break.
• The tissue around the temporary could be sore for a few days. Rinsing with dilute, warm salt water (0.5 tea­spoon of salt to 8 ounces of warm water) twice a day for 2 to 3 days will help the tissue heal. Avoid any mouthwashes containing alcohol because they could sting.
• There may be some hot or cold sensitivity.
• Unless contraindicated for particular patients, ibuprofen or acetaminophen may be taken for discomfort.
• Proper brushing and flossing are necessary to keep the tissue healthy. When flossing, pull the floss out to the side to avoid pulling off the temporary.
• If the temporary should come off, you can put it back on with toothpaste or denture cream. Some stores now carry temporary filling/crown cement. You can try these, but do not use glue. Call the office to schedule an appointment to have your temporary recemented. The temporary is very important because it holds the space for your new crown. If you do not have it recemented, you run the risk of your permanent crown not fitting properly.

Conclusion

One of the most important procedures when placing crowns, bridges, or veneers is the fabrication of the temporary. A well-made temporary not only saves valuable chair time at the final seating appointment, but also helps protect the prepared tooth/teeth against microorganisms, saliva, and food. Additionally, proper marginal ad­aptation will help protect the finished edge of the preparation, and proper occlusion and interproximal con­tacts will help prevent drifting and extrusion of teeth that can affect the fit of the final restoration.

Because no temporary material suits every patient's needs, it is important for dental assistants to know the available material options. By staying up-to-date with these materials and techniques, you can provide the best possible care to each patient and in­crease the value of your contributions as a team member.

References

1. Schwedhelm ER. Direct technique for the fabrication of acrylic provisional restorations. J Contemp Dent Practice.2006;7:157-173. Available at: www.thejcdp.com/issue025/schwedhelm/01schwedlhelm.htm. Accessed Aug 26, 2007.
2. Christensen GJ. The fastest and best provisional restorations. J Am Dent Assoc [serial online]. 2003;134:637-639. Avail­able at: jada.ada.org/cgi/content/full/134/5/637?maxtoshow=&HITS=10&hits=10&RESULT. Accessed Aug 6, 2007.
3. History of dentistry. Innovations in techniques and technology—the 20th century. American Dental Association Web site. Available at: www.ada.org/public/resources/history/timeline_20cent.asp. Accessed Aug 27, 2007.
4. Glossary of dental terms. American Dental Association Web site. Available at: www.ada.org/public/resources/glossary.asp#d. Accessed Sept 4, 2007.
5. Provisional materials—indirect: Access Crown/Integrity/Luxatemp. dentalcompare: The Buyers Guide for Dental Professionals Web site. Available at: www.dentalcompare.com/matrix.asp?catid=30. Accessed on Jul 14, 2007.
6. Integrity [package insert]. Milford, Del: Dentsply Caulk; 2005.
7. Access crown. Centrix, Inc Web site. Available at: www.centrixdental.com/temporary-crown-bridge_details.asp. Accessed Jul 5, 2007.
8. Luxatemp [package insert]. Englewood, NJ: Zenith/DMG; 2005.
9. LuxaFlow [package insert]. Englewood, NJ: Zenith/DMG; 2005.