Alternative Method of Gingival Displacement for Crown Impressions
Mary A. Baechle; Kanokraj Srisukho; Ronald E. Kerby
Quick considerations for treatment success.
Most dentists would agree that in addition to a correctly prepared tooth, an accurate impression is imperative for the laboratory technician to create a functional and esthetic restoration. One of the hallmarks of a good impression is accurately captured margins. When preparation margins are not supragingival and gingival tissue displacement is necessary to capture the margins in the final impression, one can use a variety of methods and materials. The three primary types of gingival displacement techniques are mechanical, chemical, and surgical.1
Mechanical displacement includes placing cord and paste systems.1 To achieve gingival displacement with a cord, which can be of a braided or knitted variety, a cord is placed directly into the gingival sulcus surrounding the preparation margins. With paste systems, a paste, frequently along with directed pressure, is applied in the area of the preparation margins and gingival sulcus.1 Chemical gingival tissue displacement involves applying a hemostatic agent, such as aluminum sulfate or aluminum chloride, or a vasoconstrictor, such as epinephrine.1 These chemicals can produce shrinkage of the soft tissues immediately surrounding the preparation.1 Finally, in some situations, an impression is best captured by surgical removal of gingival tissue. This can be accomplished with curettage, scalpel excision, or electrosurgery.1 However, gingival retraction cord with a hemostatic agent—a combination of both mechanical and chemical means—is the most common gingival displacement technique.2
One of the newer products on the market that uses the mechanical method of gingival tissue displacement, specifically as a paste system, is Magic FoamCord® (Coltène/Whaledent, Inc, Cuyahoga Falls, OH). Two other paste system products dentists may choose are Expasyl™ (Kerr Corporation, Orange, CA) and GingiTrac™ (Centrix, Inc, Shelton, CT). These products are similar in their method of application; however, unlike Magic FoamCord, both contain a hemostatic agent.1,3
According to the manufacturer, Magic FoamCord consists of a base and catalyst that when mixed together form a blue, low-viscosity, polyvinyl siloxane (PVS) addition-type silicone elastomer.4,5 This product may be used with the putty technique or the Comprecap Anatomic technique. The latter system uses the PVS paste in conjunction with Roeko Comprecap Anatomic (Coltène/Whaledent, Inc), compression caps composed of rayon, cellulose, adhesive, and cotton.
Case Report
A 43-year-old man presented with recurrent decay on his maxillary left first molar under the distal portion of a gold onlay and a perforation on the occlusal surface of the restoration. On removal of the onlay, decay was found to extend subgingivally on the distal, requiring crown lengthening to avoid violating the biologic width with the final restoration. After the decay was removed, Dycal® (DENTSPLY Caulk, Milford, DE) and Fuji II™ LC light-cured resin reinforced glass ionomer (GC America, Inc, Alsip, IL) were placed. The tooth was then prepared for a porcelain-fused-to-metal crown and temporized with a provisional restoration. Crown lengthening was performed by a periodontist. After healing, the patient returned for the final impression of the crown.
After administering local anesthetic and removing the provisional crown, some minor hemorrhaging occurred. To obtain maximum results with the Magic FoamCord and Comprecap Anatomic, the manufacturer recommends first obtaining hemostasis.4 Therefore, after refining the preparation, ViscoStat® (Ultradent Products, Inc, South Jordan, UT) was applied to the sulcular gingival tissues surrounding the preparation margins and then rinsed off, followed by drying of the preparation. Hemostasis was achieved (Figure 1). The blue PVS paste was syringed around the preparation margins (Figure 2), followed by the placement of the prefitted Comprecap Anatomic onto the prepared tooth. The patient was instructed to bite down firmly for 5 minutes (Figure 3). A unique feature of the Comprecap Anatomic, as opposed to the regular Comprecap, is that it has been cut back in a semicircular fashion on two opposite sides of the cap, which allows it to be placed on prepared teeth adjacent to one another. Gingival displacement was accomplished by the expansion of the addition silicone in the sulcus after the cap and occlusal force had been applied. Hemostasis and moisture control also were achieved, providing for a dry impression field.
After removing the cap and adherent, set PVS paste in one piece (Figure 4), it was noted that soft tissue displacement had been produced, all of the margins of the preparation were visible, and excellent hemostasis had been achieved (Figure 5). Although a hemostatic agent was used before applying the Magic FoamCord, the authors have noticed that when using hemostatic agents along with cord, some bleeding can still occur when the cord is removed. However, in this case, no bleeding occurred when the cap and set paste were removed.
For the final impression, Reprosil® light-body PVS impression material (DENTSPLY Caulk) was used for the wash material. An initial amount of the wash material was syringed around all of the preparation margins. Additional light-body material was then placed on the remainder of the tooth until it completely covered the preparation. As the light-body material was being applied, Reprosil heavy-body PVS impression material was loaded into a quadrant dual-arch Tri-Bite® plastic impression tray (Direct Dental Service, Milwaukee, WI). The tray was then placed into the patient’s mouth, which the patient held in maximum intercuspation until the material was set. After removal from the patient’s mouth, the impression was disinfected (Figure 6).
Clinical Impression
The authors found that the Magic FoamCord system produced a very dry field and, although there could have been a little more tissue displacement, it prepared the tissues in such a way that the final impression captured not only the deep subgingival distal margin, but also some of the unprepared tooth structure below it. In the past, the authors have sometimes found it difficult to achieve this even with multiple impressions using hemostatic agents and cord. Likewise, gingival tissue may recede if subjected to too much pressure during the placement of the retraction cord.6 The Magic FoamCord Comp-recap Anatomic technique can be relatively atraumatic to the tissues and still result in adequate gingival displacement and good hemostasis for final impressions. This can be especially important for preparations in the esthetic zone.
Regarding gingival displacement, Donovan and Chee state that "no scientific evidence has established the superiority of one technique over the others, so the choice of technique depends on the presenting clinical situation and operator preference."2 Therefore, Magic FoamCord with Comprecap Anatomic is another clinical option dentists may choose when considering what technique to use for gingival tissue displacement for final impressions.
Disclosure
The authors received material support from Coltène/Whaledent.
Acknowledgment
The authors would like to thank Robert Rashid, DDS, MAS, for converting the photographs for publication.
References
1. Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics. 4th ed. St. Louis: Mosby Elsevier; 2006: 431-465.
2. Donovan TE, Chee WW. Current concepts in gingival displacement. Dent Clin North Am. 2004;48(2):433-444.
3. Strassler HE, Polhaus JP. Cordless gingival retraction and hemostasis. Contemporary Esthetics. Aug 2006;10(8):64-67.
4. Data on file. Coltène/Whaledent. Available at: www.coltenewhaledent.biz/download.php?file_id=1705. Accessed January 14, 2008.
5. Data on file. Coltène/Whaledent. Available at: www.coltenewhaledent.biz/download.php?file_id=2417.
6. Shannon A. Expanded clinical uses of a novel tissue-retraction material. Compend Contin Educ Dent. 2002;23(1 suppl):3-6.
About the Authors
Mary A. Baechle, DDS
Assistant Professor of Clinical Dentistry
Section of Primary Care
The Ohio State University Health Sciences Center
College of Dentistry
Columbus, Ohio
Kanokraj Srisukho, DDS, MS
Assistant Professor of Clinical Dentistry
Section of Restorative and Prosthetic Dentistry
The Ohio State University Health Sciences Center
College of Dentistry
Columbus, Ohio
Ronald E. Kerby, DMD
Associate Professor
Section of Restorative and Prosthetic Dentistry
The Ohio State University Health Sciences Center
College of Dentistry
Columbus, Ohio
