February 2011, Volume 7, Issue 2
Published by AEGIS Communications
New Gel Retraction Material
Increasing the success and predictability of fixed prosthodontic impressions.
In fixed prosthodontics, clinically acceptable impressions are an absolute necessity (Figure 1). The laboratory fabricating the restoration is limited in its final quality by the quality of the incoming impression. The unfortunate reality is that most impressions are clinically unacceptable.1
Some of the most common errors seen in impressions include tears, bubbles, voids, debris entrapment, tray burn-through, material/tray separation, and lack of catalyzation of the material.2 Unfortunately, many of these errors are most evident at the restorative margin. Any lack of detail at the margin forces the laboratory technician to guess during die trimming. This area is highly susceptible to the collection of blood, debris, and lymphatic exudate. Considering the limited hydrophilic nature of most impression materials, issues can quickly compound.
The most predictable way to obtain a quality impression is to start with healthy tissue. Pre-restorative planning should include any necessary periodontal treatment, patient hygiene instruction, and caries control.3 Different options exist to aid in tissue management. These would include the use of retraction cord, chemical hemostatic agents, a soft tissue laser, and tissue gels or pastes, either alone or in various combinations.
Attention should also be given to the position of the osseous crest and the compensating gingival biotype. In a normal crest relationship, the depth from the gingival margin to the bony crest is 3 mm to 4 mm apart. A distance greater than this would indicate a low-crest relationship. Depths of less than 3 mm would be indicative of a high-crest relationship.4 Tissue with a low-crest position would be less supported, more flaccid, and more prone to recession as a result of trauma or over-manipulation. Tissue associated with high crestal bone is usually thicker, more fibrous, and more forgiving of damage. However, high-crest bone is at higher risk of biologic width violations.
This article will discuss impression techniques using a new gel retraction and hemostatic aid called Racegel (Figure 2). The features of the Racegel include:
- Thermodynamic chemistry that provides increasing viscosity in the oral cavity. The thermal effect is reversed when rinsed with water for ease of removal.5
- 25% aluminum chloride for optimal control of bleeding and crevicular fluid.
- An orange color for easy viewing during placement and for confirming complete removal.
- Can be used in conjunction with cord or simple control of gingival bleeding.
Clinical Example One
This posterior crown is a common example of a low crest and deep sulcus restorative situation (Figure 3). Because of the sulcus depth, often one cord is not adequate to fully displace the tissue and obtain a quality impression. Instead of traumatizing the tissue with two cords, one small cord was placed and then Racegel was injected into the sulcus. This provided the necessary retraction and hemostasis.
All-ceramic preparation margin designs will often be at the level of the gingival margin (Figure 4). The premolar seen in this figure, which has a normal gingival biotype, can be readied for impression with Racegel as the sole source of retraction.
Clinical Example Two
Preoperatively, this case had generalized interproximal decay and decalcification (Figure 5), which resulted in residual interproximal inflammation and bleeding at the preparation visit. Dry cords were placed in the sulcus, and Racegel was placed on the bleeding areas. By controlling the tissue and obtaining a high-quality impression (Figure 6), properly fitting restorations were created that allowed optimal health postoperatively (Figure 7).
Clinical Example Three
This anterior crown preparation was associated with a thin gingival biotype and low bone crest. To keep tissue trauma to a minimum, Racegel was used as the only source of retraction (Figure 8). After 2 minutes of setting, the material was easily rinsed away, leaving a clearly exposed margin (Figure 9). The resulting impression had crisp 360º margins and captured past the margin end point (Figure 10).
There is no doubt that modern dental materials can improve the efficiency of restorative care. However, there is no replacement for good clinical judgment and proper diagnosis. Only when these types of materials are applied in the proper circumstances will predictability and uncompromised quality complement the efficiency gained.
1. Samet N, Shohat M, Livny A, et al. A clinical evaluation of fixed partial denture impressions. J Prosthet Dent. 2005;94(2):112-117.
2. Hess L. Creating restorative success with clinical zirconia. Inside Dentistry. 2006;2(8):62-66.
3. Hess L. The biologic and restorative interface. Contemporary Esthetics and Restorative Practice. 2005;9(3):46-51.
4. Kois JC, Vakay RT. Relationship of the periodontium to impression procedures. Compend Cont Educ Dent. 2000; 21(8):684-692.
5. Data on file. Laboratory Matiere of Systems Complexes. 2008; University of Paris.
About the Author
Leonard A. Hess, DDS
Monroe, North Carolina
The Dawson Academy
St. Petersburg, Florida