NEWER GINGIVAL RETRACTION MATERIALS: A REVIEW

INTRODUCTION:

During various procedures like impression or luting of the restorations, multiple challenges can surface. Moisture control plays a pivotal role for any dental procedure- direct or indirect. This is achievable only in case of effective isolation techniques. Numerous problems are faced in operative dentistry. These can range from the limiting influence of all the associated muscles to other hindrances manifested due to limited vision and isolation, which can be a result from of crevicular fluid, saliva and gingival bleeding during tooth preparation to receive a restoration. 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. Gingival retraction is aimed at accessibility of the impression material beyond the abutment margins and also to provide enough space for the impression material to be thick enough. This is because thickness of material has been found to affect its tear resistance. The present clinical condition will dictate the gingival retraction technique being used. Hemorrhage and its magnitude may incline towards a specific retraction technique.

NEED FOR GINGIVAL RETRACTION

• 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.

• Helps in obtaining the perfect die with accurate margins, which helps in margin placement and contouring of the restoration.

• Helps in blending of the restoration with the unprepared tooth surface.

• Helps in placement and finishing of the margins on the prepared tooth.

• During cementation it helps in easy removal of cement without tissue damage.

• It helps the dentist in visually assessing the marginal fit and any caries if present.

• In situations when it is necessary to extend the restoration below the gingival margin to enhance retention.

• 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

METHODS FOR GINGIVAL RETRACTION:

Method which is used most commonly for retraction of gingival is retraction cord (can be combined with different chemical solutions and gels with astringent or hemostatic action). Other commonly used methods include electrosurgical units, soft tissue diode lasers and retraction pastes. A combination of these techniques can also be used. Although gingival cord is more readily used, but it can damage the delicate epithelial lining of the sulcus and underlying connective tissues.^9,10

Hence, focus is being shifted to newer methods for gingival retraction. Some of them include:

EXPASYL:

• Expasyl (Kerr Corporation, Orange, CA) is a clay- like material that is dispensed from a syringe apparatus through a narrow needle-like tip.

• It is available in vials and dispensed directly into the sulcus with a heavy-duty delivery gun loaded with a syringe. Expasyl has no chemical or setting reaction. It does not go through an expansion phase.

• The material is left in place for up to 2 min and is then rinsed off with an air/water syringe. The sulcus is then ready for the impression. The material contains aluminum chloride, a potent hemostatic agent. Hence, no violation occurs to the gingival complex.

• Gingival recession is also not encountered. After removal of Expasyl, sulcus is clean which reduces artifacts during making of digital CAD/CAM impressions. It provides the best outcome of chemical choices available.

DISADVANTAGES:

More expensive

Inhibits set of polyvinyl siloxane and polyether impressions

Less effective with very subgingival margins.

MAGIC FOAM CORD:

• Magic foam cord is a new non-hemostatic method.

• It is a vinyl polysiloxane material designed for retraction of the gingiva.

• The material is syringed around the margins of tooth preparation and pressure is maintained using a cap.

The material expands, and after 5 min, impression can be made. The material expands (160%) after 5 min

MATRIX IMPRESSION SYSTEM:

Matrix impression system is a new system in which impression procedure includes three steps:

• First, a matrix of polyether occlusal registration elastomeric material is done over the prepared tooth.

• The retraction cord is removed and a definitive impression is recorded in the matrix using a high viscosity elastomeric impression material.

• After the matrix impression is positioned, medium viscosity elastomeric material is loaded in an impression tray and is seated over the matrix and remaining teeth to create impression of the entire arch.

The design of the matrix also forces the high viscosity impression material along the preparations and into the sulcus. The matrix impression system uses three impression materials of different viscosities.

ADVANTAGES:

1. Eliminates chances of tearing of the sulcus

2. Cleans blood and debris from the sulcus area

3. Delivers impression material in the gingival sulcus slowly and with more accuracy and speed

4. Holds the sulcus open for an increased time.

DISADVANTAGES:

Increased chairside time.

MEROCEL STRIPS:

• Merocel is a new retraction material to displace gingiva with no tissue injury before making impression.

• Merocel retractions strips are synthetic material, which are specifically chemically extracted from a polymer hydroxylate polyvinyl acetate that creates a net-like strip without debris or free fragments.

• Placement of Merocel retraction technique does not require use of local anesthesia.

• Merocel retraction strip provides very excellent gingival retraction when compared to conventional retraction cord.

• The porous and sponge-like microstructure of Merocel produces a dry field for the impression to accurately capture the details. The absence of fibers decreases the risk of postoperative problems.

GINGITRAC:

• Gingitrac is a paste system that uses a syringe to apply the paste around the margins.

• The syringe is preloaded with the paste.

• The paste contains aluminum sulfate as an astringent. If necessary, a hemostatic agent can be applied before its use.

• The cap is first filled with the paste and then placed over the tooth for 5 min. The paste is applied with a syringe in the sulcus.

• For impressions of more than one tooth, a plastic tray is used to carry a firm paste matrix over which the Gingitrac paste is syringed.

• The tray is then positioned and removed after 3-5 min. For both single and multiple tooth preparations, retraction of gingiva is by pressure application. The paste is removed prior to impression making.

STAY PUT:

• Stay put combines the advantages of both an impregnated and braided cord with the adaptability of an ultrafine copper filament. Aluminum chloride hexahydrate is used for impregnation. Nonimpregnated stay put cord is also available which can be impregnated with hemostatic agent as needed.

• The pliable core is so effective that the cord is not only easy to place in the sulcus but it stays there.

G-CUFF:

• It is a disposable plastic collar launched by Canadian company, named Stomatotech, for the purpose of retraction of gingiva.

• It is first inserted on the apical end of the abutment after which the abutment should be engaged to the implant.

• The plastic collar is found between the apical part of the abutment and the gingival soft tissue.

• The plastic collar should be drawn out and then removed permanently after retrieving the impression from the mouth.

LASER:

• Use of lasers is adjunctive in fixed prosthodontics. The laser produces minimal damage of collateral tissue when laser energy of the correct wavelength is used.

• Neodymium: yttrium-aluminum-garnet lasers are not used as their use can result in loss of bone.

• Erbium: yttrium-aluminum-garnet (Er: YAG) lasers are fairly safe to use as they penetrate soft tissues minimally. CO2 lasers are used around implants. The primary chromophore for CO2 lasers is H2O. These lasers take in less energy close to metal implant surfaces, producing less temperature increases (<3°C) and less collateral damages. The soft-tissue structure is not altered by these lasers.

CONCLUSION:

• Finish line exposure in fixed prosthodontics is no longer difficult. Various advanced materials are available for gingival retraction. Using these materials, we can definitely improve the quality of impressions in fixed prosthodontics. Furthermore, the procedure can be relatively painless, quick, and atraumatic. The selection of material has to be carefully done by the operator. Since gingival retraction is an integral part of clinical practice, the clinician should make an effort to utilize different methods and products available for retraction of gingival tissues in various clinical scenarios. Sometimes a combination of methods may be needed, and some things may work for one clinician and not for another. The effort put into the appropriate retraction of gingival tissues pays off in terms of longevity of restorations, better margins and aesthetics.