Gingival Retraction PDF

GINGIVAL RETRACTION Learning Outcomes: After the completion of this subject, student will be able to: 1) Decides on the gingival retraction method and material according to the treatment. 2) Explains the importance of gingival retraction in fixed prosthesis treatment. -------------------------------...

GINGIVAL RETRACTION Learning Outcomes: After the completion of this subject, student will be able to: 1) Decides on the gingival retraction method and material according to the treatment. 2) Explains the importance of gingival retraction in fixed prosthesis treatment. --------------------------------------------------------------------------------------------------------------The aesthetics and longevity of restorations is significantly dependent on gingival and periodontal factors. The intimate interaction between the restorations and the surrounding soft tissues means that all procedures performed should keep the health of the gingiva and periodontium under consideration. Restorations placed in close proximity to the soft tissues sometimes require consideration of subgingival margins, otherwise the subsequent restorations may have a high chance of failure. The retraction of the gingival tissue is a long established technique. It can be defined as the process of deflection of the marginal gingiva away from a tooth. Periodontal factors influence the quality of the marginal fit of a restoration. A good quality impression is influenced by location of finish lines, periodontal health and sulcus bleeding during impression making. The aim of gingival retraction is to allow access for the impression material beyond the abutment margins and to create space for the impression material to be sufficiently thick. Tear resistance of the impression material can be affected by the material thickness. Gingival retraction should be mandatory prior to impression so as to expose the prepared tooth surfaces. Impression with less sulcular width have higher incidences of voids, tearing of impression materials and reduction in marginal accuracy. Need for the gingival retraction 1. To widen the gingival sulcus in order to provide access for impression material to reach the subgingival margins and to record adequately the finish line. 2. Helps in obtaining the perfect die with accurate margins, which helps in margin placement and contouring of the restoration. 3. Helps in blending of the restoration with the unprepared tooth surface. 4. Helps in placement and finishing of the margins on the prepared tooth. 5. During cementation it helps in easy removal of cement without tissue damage. 6. It helps the dentist in visually assessing the marginal fit and any caries if present. 7. In situations when it is necessary to extend the restoration below the gingival margin to enhance retention. 8. To enhance access and to prevent damage to the soft tissue during cavity preparation procedure, it may be desirable to carry out some degree of gingival retraction prior to commencement of preparation. Pre-retraction assessment of gingival tissues Before any gingival retraction is contemplated, and ideally before any restoration with subgingival margins is planned, it is important to assess the gingival tissues and adjacent supporting structures thoroughly. This is essential because the placement of subgingival margins and the procedures undertaken to record these margins can damage the delicate gingiva. If the tissues are already compromised, any traumatic retraction method can further damage the tissues. When a gingival retraction technique is utilized, forces act in four directions on the gingival tissues. These are the retraction, displacement, collapsing and relapsing forces (Figure 1). 1. Retraction is the downward and outward force exerted on the gingival tissues by the retraction technique or material; 2. Displacement is the downward force resulting from excessive pressure during retraction or in unsupported gingival tissues; 3. Relapse is when the gingival tissues rebound to their original position; and 4. Collapse is when the gingival tissues are further compressed towards the tooth as a result of using close-fitting trays for impression. When the soft tissues are healthy,with a fibre-rich connective tissue supporting the delicate epithelium, there is less chance of damage to, and collapse of, the gingiva when the retracting agent is removed. The following evaluation should be undertaken prior to retracting or displacing the gingival tissue. Clinical Assessment The gingival tissues intended to be retracted should be pink in colour and firm. The gingival biotype should be identified, which is a useful indicator of the behaviour of the gingiva to operative procedures and gingival displacement. Gingival tissue has been described as mainly having thick or thin biotype, although any variation of the two can be seen clinically, and their characteristics are given. Thin gingival biotypes are more likely to be adversely affected with a subgingivally placed restoration and hence, the treatment and restoration should be planned accordingly.The contour, consistency and any pain originating from the gingiva or supporting tissues should be evaluated. There should be minimum or no bleeding on probing. Bleeding indicates inflamed and damaged gingiva, which is difficult to isolate and is more likely to get damaged during the retraction and displacement process. Gingival indices can be utilized to identify healthy and diseased gingival tissues. Gingival sulcus is also an important parameter to assess the placement of restoration margins. Margins placed too deep in the sulcus require more retraction of the gingival tissue, resulting in damage to the supporting structures of the tooth. If margins are to be placed subgingivally, it is recommended to place the margins 0.5−1mm below the gingival margin, especially where the probing depth is less than 1.5 mm, and ideally to control the apical extent of the preparation so as not to encroach on the epithelial and connective tissue attachment. Radiographic Assessment Both peri-apical and bitewing radiographs can be utilized to assess interproximal bone levels and crestal bone height, as well as infra-bony pockets and boss loss. Unsupported soft tissue, with underlying deficient bone, has a greater chance of recession when gingival tissue is traumatically displaced to record subgingival margins. Methods of Gingival Retraction For the retraction of soft tissue, three principle methods are available for use today: 1) mechanical; 2) chemo- mechanical; and 3) electrosurgical. The chemo- mechanical technique is probably the most widely used but its limitations are time consuming, painful, need for local anesthesia and injury to epithelial tissue and gingival recession. The mechanical aspect of this method involves placement of a string into the gingival sulcus to displace the tissues physically. The chemical aspect of the method involves treatment of the string with one or more of a number of compounds that will induce temporary shrinkage of the tissues and should also control the hemorrhage and fluid seepage that often accompany sub gingival margin preparation. Mechanical Retraction These techniques involve physically retracting and displacing the soft tissues, making space for the impression material to reach the recess of the subgingival preparation, as well as providing haemostasis and controlling crevicular fluid during direct composite restoration placement or cementation of deep subgingival indirect restorations. – Cord They are considered the most popular method for displacement of gingival tissue. According to fabrication, they can be knitted, twisted or braided and can also be classified as impregnated (if already containing medicament or haemostatic agent) or non- impregnated. Any configuration of the cord can be used according to the clinician’s preference, as all different types of cords lack standardization in size. They are, however, colour-coded and vary in diameter (usually indicated by numbers 000, 00, 0−3), to be used in different clinical situations and gingival sulcus depths. They come pre-cut (according to the diameter of teeth) or can be dispensed from a container or a clicker. Ideal properties of retraction cords include: 1. Biocompatible, non-toxic material; 2. Ability to absorb blood, crevicular fluids and medicaments; 3. Easy to apply and remove; 4. Contrasting colour with the surrounding tissue; 5. Does not cause damage to the supporting tissues. But, cords can be painful and uncomfortable for the patient. Also the sulcus collapses soon after the removal of the cord. Hemostasis achieved is limited and the placement of the cord in the sulcus takes time. There are two techniques for mechanical retraction, namely, single-cord and double- cord technique. - Single cord technique This is a relatively straightforward method, usually employed for single teeth, with healthy gingival tissue. A single piece of retraction cord is packed into the gingival sulcus, followed by removal after adequate gingival displacement has been achieved. The impression of the tooth preparation margins can then be made. It is a useful technique when there is little or no haemorrhage from the gingival sulcus, and the preparation margins on the tooth are either gingival or slightly subgingival hydrated potassium aluminium sulfate. - Double cord technique As the name indicates, two retraction cords are placed in the gingival sulcus, which is too deep to be sufficiently displaced with a single cord or where the tissue would collapse with the use of only a single cord. The margins of the tooth preparation in such cases may also be subgingival and hence require additional displacement of the gingival tissues. The technique describes placing a smaller diameter cord soaked with a haemostatic agent into the depth of the sulcus, causing some lateral tissue displacement but primarily controlling haemorrhage. The second larger diameter cord is then packed into the sulcus, causing further lateral tissue displacement (Figure 2). The first deeper placed cord stays in place when the impression is made, after removal of the top, larger diameter cord. Care must be taken not to cause drying of the retraction cords, as they would then adhere to the gingival tissue and cause haemorrhage when removed. - Cord positioning force It is essential that non-damaging minimal force is utilized to insert the cord into the gingival sulcus, otherwise the displacement procedure can lead to haemorrhage and damage to the sulcular and junctional epithelium. Injudicious use of force during cord placement can lead to gingival recession later, due to disruption in blood supply and damage to the periodontal attachment fibres. there may be inadvertent excessive use of force while tucking the cord in the sulcus, particularly when the patient is anaesthetized. - Cord retraction time The time for which the cord is placed in the sulcus is also an important consideration. If the cord is placed for less than the recommended time, the gingival tissues may not be adequately displaced for the impression material to record the subgingival preparation margin. If the cord is placed for only two minutes, the sulcus width is reduced to 0.1 mm within 20 seconds of cord removal. On the other hand, if the retraction cord is placed for a longer time, this could result in damage to the gingival tissue and recession. This is especially relevant for preimpregnated cords or cords used with haemostatic agents. Cords placed in the gingival sulcus for too long also have a chance of drying. If that happens, they adhere to the sulcular epithelium and tear the sulcular epithelium at the time of removal. The recommended time according to several studies ranges from 1–30 minutes. Also, the gingival sulci of all the prepared teeth should be checked after an impression has been made, so that no piece of cord is inadvertently left in the gingival sulcus. - Special cords One product, the Stay-put retraction cord, has a thin wire incorporated into the centre of the retraction cord. Available as both plain and pre-impregnated, this cord offers the advantage of maintaining its shape once inserted inside the gingival sulcus. The pliability of the cord also makes it easier to place in the sulcus and the cord can also be pre-shaped. The pre-impregnated cord uses aluminum chloride, which diminishes the chances of cardiovascular symptoms. It comes in four sizes, according to width (0−3), and can also be used in conjunction with compression caps, which come in regular and anatomic shapes. The anatomic compression caps have a semi-circular shape on the facial and lingual surfaces, hence they can be placed on adjacent teeth for retraction. After the cord is placed, the compression cap is placed on the tooth and the patient is asked to bite. This helps in further retraction of the sulcus. - Rubber dam The use of heavy, extra heavy and special heavy rubber dam, together with specialized clamps (eg Ferrier 212, Schultz, Brinker’s clamp B5, B6), help to retract and protect the gingival tissues during the preparation of the tooth as well as providing isolation for subsequent restoration placement. Inversion of the dam also aids in isolating the gingival tissues. With the help of modified trays, impressions can be made with the clamps in place but it is difficult and cannot be applied to full mouth impressions. Also, some components of the rubber dam, like sulfide, can retard the setting of polyvinyl siloxane elastomeric impression material and, therefore, the two should not be used together. - Matrix band and wedges Matrix bands can provide retraction of gingiva and isolation when used for cervical or subgingival restorations. Wedges placed inter-proximally physically depress the gingival for retraction, and can protect the gingiva during preparation of the tooth. - Chemo-mechanical methods This method employs the retraction cord with use of a chemical or a medicament. A wide variety of materials have been used in conjunction with gingival cords. The cords may be preimpregnated with these chemicals or plain retraction cords may be soaked in them before placement. The main function of all these chemical agents is to arrest haemorrhage and decrease the leaking of crevicular fluid, while the cord physically displaces the gingival tissues. They can be vasoconstrictors that cause contraction of the blood vessels, AstringentsTM that contract the gingival tissue or chemicals that cease bleeding by haemostatis and coagulation. Some products are available in gel or liquid formulation, which can be directly syringed into the gingival sulcus for arrest of bleeding and crevicular fluid. This can be followed by placement of the cord. The chemicals used for this purpose can be classified according to their mode of action. Epinephrine has been the most popularly used chemical with which retraction cords were impregnated, although its use for this purpose has decreased overtime. It is most commonly used as 8% racemic epinephrine, but other concentrations have also been used. Retraction cords are either dipped in epinephrine or come pre-impregnated. Because of the high vascularity of the gingival tissue, the systemic effects exerted by epinephrine have been a tissues have been lacerated. The systemic effect of epinephrine has been described as ‘epinephrine reaction’ or ‘epinephrine syndrome’ and is associated with the use of epinephrine-soaked retraction cords. This is characterized by tachycardia, increased blood pressure, nervousness, anxiety, increased respiration and post-operative depression. One study indicated that there was almost 50 times more epinephrine in 1 inch of retraction cord as in 1 cartridge of 1:100,000 epinephrine. This is a clear indication of how cautiously epinephrine impregnated cords must be used in patients with significant cardiovascular history. Some of the effect exerted by epinephrine can be avoided by using in diluted form and for the minimum amount of time needed for retraction. Some studies have even demonstrated that there is no significant difference in degree of retraction while using plain and epinephrine impregnated cord. Ferric sulfate (15.5−20%) is commonly employed as a coagulant while performing associated gingival displacement. The problems associated with using ferric sulfate is the removal of smear layer if placed for more than 10 minutes. This can cause sensitivity in patients after the procedure. Also, ferric sulfate can form a residue on the tooth surface, which interferes with the impression setting and can also discolour the dentine, due to its high iron content. Furthermore, if a composite restoration is planned, the residue can interfere with the bonding of composite to the tooth. If ferric sulfate is to be used with the retraction cords, the sulcus should be washed out after removal of the cord and prior to impression-taking. Another agent used for haemostasis is 20−25% aluminum chloride. It has been found to be least irritating to the gingival tissues but also results in the removal of the smear layer and dentine etching. Aluminum sulfate is considered to be the safest astringent because it does not have any significant systematic effect, but they are also less effective at controlling haemorrhage and crevicular exudates. They have limited use in gingival retraction methods. Zinc chloride (bitartrate) and silver nitrate both physically causing haemostasis and precipitation of protein on the mucosal surface, resulting in coagulation. Zinc chloride is available in 8% and 40% concentrations but its use has been associated with soft-tissue injury and hence is no longer recommended. Studies have described ophthalmic or nasal decongestants as potential vasoconstrictive and haemostatic agents used in conjunction with retraction cords due to their active components, like tetrahyrozoline or oxymetazoline, which are sympathomimetic amines. These are mild compounds with local vasoconstriction and minimal systemic effects. One study described them to be safer than 25% aluminum chloride for epithelial cells. These medicaments are still not approved for clinical use as gingival haemostatic agents. - Surgical retraction – Lasers Lasers’ properties largely depend on their wave- length and waveform characteristics. The commonly used diode lasers have a wavelength of 980 nanometers (nm). Neodymium: yttriumaluminum-garnet (Nd:YAG) lasers have a wavelength of 1064 nm. They cause less bleeding and hence the gingival retraction is minimal. Tissue shrinkage is less through scarring, which helps to preserve gingival margin heights. Visualizing the action of laser beams are difficult, owing to the plume of coolant water. Therefore, there is potential for attached gingiva to be obliterated when lasers are used for retraction purposes, since clinicians receive virtually no tactile feedback. - Electrosurgery An electrosurgery unit may be used for tissue removal before impression making. However, electrosurgery is not recommended as the concentrated electrical current at the tip of electrodes can generate heat, which may cause osseous or mucosal necrosis and also there is a potential for gingival recession after treatment. GINGIVAL RETRACTION MATERIALS Gingival retraction materials can be broadly classified into three groups based on the method of application: gingival hemostatic agents, gingival retraction cord/caps and gingival retraction paste/gels of the material. - Gingival Hemostatic Agents Astringents and vasoconstrictors are commonly used for presoaking retraction cords. Astringents exert their action topically on the injured mucosal surface, whereas the hemostatic effect of vasoactive molecules is accomplished through a direct vascular action. Aluminum chloride has been found to be least irritating, and it may be left in the sulcus for up to 15 minutes without causing any permanent damage. Aluminum chloride is solid in a stable acidic buffer resulting in an etched dentine. Aluminum chloride and zinc chloride in high concentrations are caustic to gingival tissues and thus are not recommended. Ferric sulfate acts as a clotting agent, and often, when the string is removed, the clot is pulled out with it, and hemorrhage begins. Also, ferric sulfate does not cause actual shrinkage of the tissues. Alum acts mainly as an astringent and is considered to be safe and moderately effective as a tissue-displacing agent. - Gingival Retraction Cord/Caps Epinephrine is very commonly used along with gingival retraction cords to effectively control bleeding. The sulcus bleeding is said to be better controlled with this than astringent containing cord. Epinephrine-impregnated retraction cord contains 8 percent racemic epinephrine. It has been shown that epinephrine produces a syndrome of undesirable side effects that may include tachycardia, increased respiratory rate, hypertension, nervousness, and feelings of weakness in the extremities, frank apprehension, and post-operative depression. Tissue injury may also occur on introducing cords impregnated with epinephrine. Therefore, recommendations have been made to either limit or avoid use of such epinephrine impregnated retraction cords. In a recent study, the authors could not find any clear advantage of using cords impregnated with epinephrine. Pure cotton cords on the other side do not sufficiently reduce the crevicular fluid flow. - Gingival Retraction Paste/Gels Expasyl is a universally accepted and widely used gingival retraction paste. It is composed of three materials: Aluminum chloride, Kaolin and Excipicent. The product is supplied in reusable capsules. The consistency of Expasyl is especially formulated not to damage the healthy periodontium; the phenomena of gingival recession or bone resorption are thus avoided. Gingival retraction is obtained by a single application of Expasyl in the sulcus. On contact with crevicular fluid, this material provides mild displacement of the gingiva within two minutes. Expasyl, easily visible owing to its colour, is simply eliminated by an air and water spray, and a dry and widely opened sulcus is then obtained. It is painless when used on a healthy periodontium. Absence of bleeding or oozing allows achieving a perfectly dry sulcus. Atraumatic gingival tissue management for impression making provides greater patient comfort during and after impression making. During restorative procedures, it is incumbent upon clinicians to consider the advantages and limitations of each method in individual case and patient, and to strive for minimally invasive methods that optimize the procedural site for impression making and restoration placement.