July 1, 2011
by Howard E. Strassler, DMD, FAGD, FADM and Leendert (Len) Boksman DDS, BSc, FADI, FICD
The oral cavity is a difficult area to treat in restorative dentistry because of the constraints of the lips, tongue, cheeks, challenges for access to visualize and manipulate instruments, as well as, the position of the teeth that are being treated relative to the gingival tissues, which if improperly managed, bleed. While for operative dentistry and single tooth restorations, the use of the dental dam provides control of the field and access to tooth preparation and restoration, there are many times in restorative dentistry that use of the dental dam is precluded. When caries or non-carious cervical lesions are at or below the free margin of the gingiva other tissue management techniques with gingival retraction must be used. (Fig. 1). For fixed prosthodontics, crown or inlay/onlay margins are at or below the free margin of the gingiva and access to them for both preparation, impressioning, and cementation is impossible without additional techniques to displace the gingival tissues and control gingival hemorrhage and sulcular fluids. (Fig. 2).
One of the most challenging aspects of crown and bridge is management of the gingival tissues when making an impression. Tissue management includes placing the gingival tissues away from the preparation margins so they can be impressed combined with providing for hemostasis when the gingival tissues are susceptible to bleeding.1,2 The rationale for tissue management is a critical aspect of impression making whether the impression is made with a conventional impression material or by a digital impression technique so that all tooth preparation margins are captured in the impression to assure an excellent marginal fit of a laboratory fabricated restoration.1,3
Methods And Materials For Soft Tissue Management, Displacement-Retraction Aand Hemorrhage Control
Mechanical methods Among the first techniques developed and available to clinicians for displacement of gingival tissues, especially for crown and bridge impressions, were mechanical displacement. Mechanical displacement refers to physically moving the gingival tissues aside from the tooth/tooth preparation margins to allow for visualization and access for treatment.1,2,4,5 In many cases, the materials used for gingival retraction can be used by themselves or in combination with other materials and techniques.
Among the most popular methods of gingival displacement is the use of gingival retraction cord.1,2,4,5,6-8 Gingival retraction cords can be woven, braided or twisted in a variety of configurations to provide for different diameters and thicknesses.
The choice of gingival retraction cord has proven itself to be one of personal preference by the clinician. Keep in mind that different cord types offer a variety of properties that to some make them more desirable. Also many manufacturers have a range of options of non-impregnated and chemically impregnated cords. Of importance, when handling gingival retraction cord one should use latex-free gloves. Indirect latex contamination can have an inhibitory effect on the setting of vinyl polysiloxane impressions materials. This is especially critical in the gingival sulcus, where a minimal amount of light body is placed as an incomplete cure may result in gingival tears of the impression materials.(9)
Clinician preference to braided cords relates to their tight and consistent weave, e.g, First String Retraction Cord, (Clinical Research Dental) and GingiBraid (Dux Dental). Braided cords for many clinicians are easier to place in the gingival sulcus with packing-placement instruments, both serrated and smooth, non-serrated, because they are solid and can be pushed to place. Knitted cords have increased in popularity. Knitted cords when saturated with astringents and when placed in the gingival sulcus expand creating a physical effect of enlarging the sulcus for access for impressions or to displace the gingival tissues when placing direct restorative materials. Also the unique knitted weave (UltraPak, Ultradent) (Fig. 3). minimizes unraveling and fraying after cutting and during cord placement. Knitted cords offer an ease in their placement and they expand when wet opening up the sulcus greater than the original diameter of the cord.1,2 The knitting and yarn selection allows for a greater range of knitted cotton cord diameters/sizes. In the authors’ experience, when using knitted cord, a smooth, non-serrated placement instrument allows for precise placement without pulling the cord out of a gingival sulcus. Also, the range of sizes/diameters allow for placement in both the easy to access gingival sulcus and the tighter, healthier gingival sulcus. (Fig. 4)
When describing mechanical displacement of gingival tissues with gingival retraction cords, one would be remiss if there was no mention of retraction cord placement, packing instruments. Key to placement of cord with instruments is that the end of the cord packer be thin enough to be placed in the gingival sulcus without damaging the gingival tissue and potentially causing bleeding, the angle of the instrument allow for orientation so that cord placement can be accomplished around all surfaces of the tooth. Most commonly, the clinician will use double-ended instruments. Recently a novel double-ended instrument with multiple orientations of a dual- packing blade (TN010 Double Cord Packer, Garrison Dental Solutions) has been introduced so that the instrument does not need to be twirled to get the end orientation needed. (Fig. 5). A good friend, Dr. Bob Margeas designed this instrument because when using magnification, he found that this design maintains the instrument in the field of view while packing cord around the tooth.
Mechanicochemical methodsA variety of chemical solutions and gels have been recommended for use with gingival retraction cords because of the properties as drugs to act as an astringent or hemostatic agent.1,2,4 In most cases these drugs are both astringent, causing contraction-retraction of the gingival tissues, and hemostasis, constricting blood flow through coagulation. When these reagents are placed on a retraction cord they cause a transient ischemia shrinking the gingival tissue and blood vessel coagulation. Common astringent-hemostatic agents include ferric sulfate, aluminum chloride, and racemic epinephrine, aluminum potassium sulfate, aluminum sulfate, and zinc phenolsulfonate/racemic epinephrine. Gingival retraction cords are available unimpregnated or impregnated with astringent-hemostatic agents. Chemically impregnated cords offer greater sulcus displacement with the combined physical and chemical effect.1 Also, cord diameter, astringent-hemostatic agent, and cord type have a direct effect on the physical properties of the cord.10 In some cases both solutions and gel formulations are recommended for direct placement into the gingival sulcus with specialized tips (Tissue Goo, Clinical Research Dental, Astringedent, Ultradent; ViscoStat, Ultradent; Racecord, Septodont) to achieve an excellent hemostatic effect with some ischemic effect before cord placement.
A 20-25% aluminum chloride and 15.5-20% ferric sulfate are among the most popularly used chemical reagents. When used for durations within the gingival sulcus of less than 10 minutes, they cause minimal tissue damage.1,2,11 Ferric sulfate has been shown to interfere with surface detail of impression materials, as well as, it can discolour dentin by precipitating ferric sulfide in an anaerobic environment.12 It has been suggested that both ferric sulfate and aluminum chloride can have a negative effect on adhesion.12,13 When using these materials, before cementing the final restoration with a composite resin cement, both etch and rinse and self-etch, one should thoroughly clean the dentin surface with a pumice-water paste to create a dentin smear layer. There has been concern with the use of an 8% racemic epinephrine impregnated cord.4,14-18 It has
been reported that epinephrine impregnated cords should be used with care. It has been reported that an 8% racemic epinephrine cord can cause elevation in blood pressure and tachycardia, especially if the gingival tissue is bleeding due to laceration.15 In fact it has been demonstrated that no clinical benefit in gingival retraction could be recognized between an epinephrine containing cord and other cords.16.
Of special note, the solutions that are used as astringents and for hemostasis, are acidic (pH range of 0.7-2.0). There has been evidence demonstrating that the use of these products remove the smear layer.18,19 There has been some concern that if the root surfaces beyond the crown preparation margins, as well as, the dentin of tooth preparations are exposed to these solutions that there may be an increase in postoperative sensitivity. If as a clinician you have this problem, it is recommended that after making the impression and before cementation of the provisional restoration, the preparations be treated with a desensitizing agent, e.g., G5 Desensitizer, (Clinical Research Dental) or Gluma (Heraeus-Kulzer).
Cordless retractionIn most cases, gingival retraction cord is the most effective method for retracting tissue to the depth of the sulcus. Unfortunately, many times on the day of the tooth preparation, gingival bleeding is difficult to control or when packing a cord into the sulcus, the tissues start to bleed making impression difficult or impossible. For this reason a new class of gingival retraction materials have been introduced. These cordless retraction materials, e.g, Expasyl (Kerr); Racegel (Septodont) Traxodent (Premier); GingiTrac (Centrix) provide for excellent hemostasis and some gingival retraction.20-23 Some of the materials incorporate the use of a compression cap GingiTrac (Centrix) to enhance the retraction effects of the material. (Fig. 6) Using these cordless retraction techniques provide for a non-traumatic, non-invasive tissue management and hemostasis in the gingival sulcus for fixed prosthodontic impressions. These materials and techniques can be used by themselves or in combination with the use of gingival retraction cord, electrosurgery or laser tissue sculpting when bleeding is difficult to control.
Clinical Technique For Predictable Gingival Retraction and Hemostasis With Gingival Retraction CordWhen deciding which technique to use with gingival retraction cord, it is important to evaluate the health of the gingiva and the depth of the gingival sulcus. When there is minimal sulcus depth, the clinician is limited in many cases to placing only a single cord. When possible, recommendations for improved gingival retraction with cord include use of a double cord technique where a thin cord is placed flush in the sulcus, followed by a wider diameter cord. Both braided and knitted cords can be used with this technique. It is advisable to use a chemical astringent-hemostatic agent in combination with the gingival retraction cord. These two authors prefer high viscosity hemostatic gel that can be placed in the sulcus to both help with hemostasis and act as a lubricant for atraumatic placement of the gingival retraction cord and can be placed on the cord itself.
For this case a 25% aluminum sulfate hemostatic gel (Tissue Goo, Clinical Research Dental) was used to impregnate and lubricate a knitted cord (Fig. 7). Using an atraumatic cord placement technique, a thin diameter knitted cord (UltraPak, Ultradent) is placed to the base of the gingival sulcus without overlap (Fig. 8) and cut with a small tipped suture scissors (Micropoint Scissors, Clinical Research Dental) to be flush within the sulcus. (Fig. 9) This cord will be maintained during the impression to control any bleeding from the base of the sulcus. A second wider diameter UltraPak cord was then placed on top of the first cord to achieve tissue displacement. (Fig. 10) Immediately before making the impression and before the wider diameter cord’s removal, the cord should be wetted with water so as not to grab and tear the gingival tissues when the cord is removed which can create bleeding. The wider diameter cord was then removed leaving excellent tissue displacement and hemorrhage control for the impression. Once the cord is removed the retraction is maintained for only 30 seconds.1 Before making the impression, it is important there are no contaminants on the tooth preparation surface. By using a 10% EDTA cavity cleanser (Detail, Clinical Research Dental) one can be assured that the tooth surface is free of hemostatic agent contaminants and any associated debris. The EDTA leaves the dentin tubules plugged and decreases the surface tension of the dentin facilitating flow of light body impression material resulting better adapatation of the impression material to the preparation and in better surface detail of the impression. Clinical tip: If bleeding is persistent when the first cord is removed continue with the impression making certain to syringe the impression material within the sulcus. Even with the expectation that the impression will be unsuccessful this impression will maintain the retraction while allowing for hemostasis. Remove the first impression and DO NOT look at it. Immediately make a second impression. The sulcus will still be open and will not be bleeding.
ConclusionThere are a variety of techniques and materials that allow the clinician to manage the gingival tissues during restoration and when making an impression. These include gingival retraction cords, chemical reagents, electrosurgery, laser tissue sculpting, copper tube impressions, hydraulic impressions, and non-invasive, atraumatic displacement/hemostatic materials. In most cases gingival retraction cord is the most effective method for retracting tissue to the depth of the sulcus. The other methods have their advantages and indications. In any case, the control of the soft tissue for exposing the margins of the tooth preparation for restoration and impressioning is critical. It would be worthwhile for the clinician to understand all the choices available.OH
Dr. Howard Strassler is Professor, Division of Operative Dentistry at the University of Maryland Dental School in the Department of Endodontics, Prosthodontics and Operative Dentistry. He is a consultant and clinical evaluator to more than 15 dental manufacturers. Dr. Strassler’s focus in his 30 years in dental education continues to be innovative teaching using technologyDr. Leendert (Len) Boksman is the Director of Clinical Affairs at Clinical Research Dental/Clinician’s Choice. He is also Adjunct Clinical Professor at the Schulich School of Medicine and Dentistry, London, Ontario, Canada.
Oral Health welcomes this original article.
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