Gingival retraction permits completion of the preparation and cementation of the restoration. Helps the operator to make a complete impression of the preparation.
Importance of Finish Line Exposure
The gingival tissue must be healthy and free of inflammation before the fabrication of cast restorations. The finish line must be reproduced in the impression to ensure MARGINAL INTEGRITY.
Techniques for Gingival Retraction
Gingival retraction can be done with several ways, not just by using a physical material but also some chemico-mechanical ways in making that happen. Following are the few techniques to retract the gingival tissue.
- Copper Band
- Retraction Cord
- Rubber Dam
- 8% Racemic Epinephrine
- Aluminum Chloride
- Alum (Aluminum Potassium Sulphate)
- Aluminium Sulphate
- Ferric Sulphate
The mechanical and chemico-mechanical techniques are even a few other than these, though these are the commonly used techniques.
Mechanical Methods of Gingival Retraction
Used to carry the impression material as well as to displace the gingival to expose the finish line.
- Copper band is welded to form a tube corresponding to the size of the prepared tooth
- One end of the tube is trimmed to follow the outline of the gingival finish line
- Position and contour the tube over the prepared tooth
Tube is filled with modelling compound
- The filled tube is is seated carefully in place along the path of insertion of the tooth preparation
- Impression is made
Note: The disadvantage of this technique is that it can cause injury to the gingival tissues.
- Pressure packing the retraction cord into the gingival sulcus provides sufficient gingival retraction.
- Retraction cords should be made of absorbent materials like cotton.
- They are inserted into the gingival sulcus with special instruments.
Technique of using Retraction Cord
- The operating area should be dry
- Fluid control should be done with an evacuating device and the quadrant containing the prepared tooth is isolated with cotton rolls
- Retraction cord is drawn from the dispenser bottle and a piece of approximately 5cm is cut off
- The cord is twisted to make it tight and small
- The retraction cord should be dipped in 25% aluminium chloride solution in a dappen dish
- The cord is looped around the tooth and held tightly with the thumb and forefinger
- The cord is packed into the gingival sulcus starting from the mesial surface of the tooth
- Force should be applied in a mesial direction during cord placement so that the packed preceding segment does not get dislodged
- The cord should be stabilized near the distal end of the tooth
After 10 minutes,the cord should be removed slowly in order to avoid bleeding
- If active bleeding persists,a cord soaked in ferric sulphate should be placed in the sulcus and removed after 3 minutes
- The impression should be made only after cessation of bleeding
Note: Important points to consider
- The cord can be packed with special instruments like FISCHER PACKING INSTRUMENT or a DE PLASTIC INSTRUMENT IPPA.
- Occasionally it may be necessary to hold the cord with one instrument while packing with another.
- The instrument used for packing should be angled slightly towards the root to facilitate the sub-gingival placement of the cord.
- The instrument is inclined at an angle towards the tooth surface.If it is held parallel to the long axis of the tooth,the cord will rebounce.
- Excess cord is cut off near the inter-proximal area such that a slight overlap of the cord occurs in this region. If the overlap occurs on the facial and lingual surfaces, the gingival finish line in that area may not be replicated properly in the impression.
At least 2-3 mm of cord is left protruding outside the sulcus so that it can be grasped for easy removal.
- The retraction cord must be slightly moist before removal.
Removing dry cord from the crevice can injure the delicate epithelial lining of the gingival.
Chemico-Mechanical Methods of Gingival Retraction
Retraction cord soaked in a chemical will provide better gingival retraction compared to a plain retraction cord – principle behind the chemico-mechanical method of gingival retraction. It is a method of combining a chemical with pressure packing,which leads to enlargement of the gingival sulcus as well as control of fluids seeping from the sulcus.
NOTE: The most commonly used chemicals are already mentioned in the above flow chart. These chemicals are generally local vasoconstrictors which produce transient(temporary) gingival shrinkage.
Ideal Requirements for Chemicals used with Retraction Cord
- Should produce effective gingival displacement
- Should produce haemostasis
- Should not produce any irreversible damage to the gingival
- Should not have any systemic side effects
Contraindications for Epinephrine
Epinephrine is one of the most commonly used chemicals for retraction. Hence, knowing its contraindications is very important.
- CVS disease
- Known hypersensitivity to epinephrine
Surgical Methods of Gingival Retraction
Rotary Curettage / Gingettage
It is a troughing technique, wherein a portion of the epithelium within the sulcus is removed to expose the finish line.
It should be done only on healthy gingival tissue.
The following criteria should be fulfilled for gingettage:
Absence of bleeding upon probing from the gingival
The depth of the sulcus is less than 3mm
Presence of adequate keratinized gingiva
Technique of Gingettage
Usually done simultaneously along with finish line preparation.
- The torpedo diamond point is carefully extended into the gingival sulcus to half of its depth to remove a portion of the sulcular epithelium
- The hand piece should be run at low speed to improve the tactile sensation
- Abundant water should be sprayed during the procedure
- A retraction cord impregnated with aluminium chloride can be used to control bleeding
- Technique sensitive
- Can potentially damage the periodontium
- Electrosurgery denotes surgical reduction of sulcular epithelium using an electrode to produce gingival retraction.
- It is a high frequency radio transmitter that uses either a vaccum tube or a transisitor to deliver a high frequency electrical current of at least 1.0 MHz.
- The procedure is also called as SURGICAL DIATHERMY.
- In areas of inflamed gingival tissues
- In cases with gingival proliferation around the prepared finish lines
- Patients with cardiac pacemakers
- The use of topical anesthetics should be avoided when electrosurgery is to be used
- Sophisticated technique
- Can be done in cases with gingival inflammation
- Produces little to no bleeding
- Quick procedure
- Very technique sensitive
- Excess pressure may cause tissue damage
- Cannot be done in a dry field
Types of Current Used for Electro Surgery
- Unrectified, damped current
- Partially rectified, damped current
- Fully rectified current