Fluid Control And Gingival Displacement
Describe various methods used for gingival retraction and add a note on the advantages of fluid control and tissue displacement.
Gingival Retraction Definition
Gingival retraction is a process of exposing margins when making impressions of prepared teeth.
Other names
Tissue dilation, tissue retraction, and tissue displacement.
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Advantages of Gingival Retraction
- Duplicating subgingival margins in impressions
- Copying the unprepared tooth surface to aid in evaluating the marginal finish line accurately
- Helps in the accuracy of wax pattern fabrication and location of the finish line
- Final restoration tends to have better marginal adaptation
- To alter the contour of the gingival tissue around the teeth or edentulous ridge.
Classification of Gingival Displacement
Generally classified as nonsurgical and surgical
Gingival Displacement Nonsurgical
- Mechanical: Retracted by mechanical methods
- Chemical: Dilation with the help of certain dilatants
- Mechanical–chemical: Retracted with a cord impregnated with a chemical for hemostasis.
Gingival Displacement Surgical
- Rotary
- Conventional (gingivoplasty, gingivectomy, and periodontal flap procedures)
- Electrosurgery
- Lasers (CO2, argon, diode, and Nd: YAG).
Gingival Retraction Mechanical methods
- Retraction by modified temporary crown or impression caps.
- Modified impression techniques
- Oversized copper bands with elastomeric impression materials
- Temporary acrylic coping
- Modified custom tray technique
- Matrix impression system.
- Mechanical retraction
- Gingival protectors
- Matrices and wedges/rubber dam
- Strips (hydroxylate polyvinyl acetate)/paste
- Syringed PVS/aluminium chloride.
- Mechanochemical methods
- Retracting with hemostatic agents
- Retracting with paste and hemostatic agent.
Mechanical methods
Impression techniques
Oversized copper bands
- Are placed on the prepared tooth and either impression compound or elastomeric impression material supported by acrylic with adhesive is used to make an impression of the prepared tooth which retracts the gingiva under pressure
- Time-consuming and can cause trauma to tissue.
Temporary acrylic coping
Acrylic coping is relieved by 1 mm and an adhesive is used followed by an elastomeric impression material.
Matrix Impression System (MIS)1
- Three impression procedures using three viscosities of impression materials
- Technique—A matrix fitting the tooth preparation is made using a semi-rigid elastomeric material before gingival retraction
- After gingival retraction, a definitive impression is made with the matrix using a high-viscosity elastomeric impression material
- Pick up with the matrix impression seated a stock tray filled with medium-viscosity elastomeric impression material is used to make the entire arch impression
- Advantage—The design of the matrix gently forces the high-viscosity impression material into the sulcus, which does not allow it to collapse as the medium-viscosity material in the stock tray is seated for the pick-up impression
- Disadvantage—Increased chair side time.
Modified custom tray Technique
- The custom tray is modified by intra-oral relining with auto-polymerising acrylic resin
- The relined custom tray is trimmed by 2 mm to obtain clearance for elastomeric impression material
- In the case of subgingival finish lines that area is only trimmed by 0.5 mm so that the elastomeric impression material is directed into the sulcus
- Advantages—Time-saving, accuracy, and retraction cord can be avoided.
Chemical methods
- Anti-sialogogues.
- Local anesthetics.
- Anticholinergics: Methantheline bromide (50 mg), propantheline bromide (15 mg), atropin, etc.
- Antihypertensives as clonidine hydrochloride (0.2 mg).
Chemical methods are done when mechanical methods cannot be achieved. Each of the drugs has side effects, which need to be critically evaluated.
Mechanical–Chemical Methods
This technique consists of using impregnated cords with chemicals.
Chemicals that are used are:
- Racemic epinephrine: Contraindicated in cardiac, hypertensive, and diabetic patients
- Aluminum potassium sulfate (least inflammation and little sulcus collapse after cord removal)
- Aluminum chloride and ferric sulfate (inhibits set of polyvinyl siloxane and polyether impressions)
- Phenylephrine hydrochloride
- Others as inert matrix polyvinyl-siloxane (generates hydrogen that causes expansion of material against sulcus walls)
- Injection of 15% aluminum chloride in Kaolin matrix (easy, no pain, no trauma but inhibits polyether and polyvinyl siloxane).
Armamentarium
- Saliva ejector.
- Mouth mirror.
- Explorer.
- Scissors.
- Cord packing instrument.
- Retraction cord.
- Hemodent liquid.
- Cotton pliers.
- Cotton rolls.
- Dappen dish.
- Cotton pellets.
- 2 × 2 gauze sponges.
Method of Gingival Retraction
- The prepared tooth area is dried and isolated with cotton rolls.
- A retraction cord of two-inch length is drawn out from the dispenser bottle held with sterile pliers and cut with scissors.
- The retraction cord is dipped in 25% aluminum chloride solution or 8% epinephrine.
- The excess amount of aluminum chloride is squeezed out with a gauze piece.
- The cord is made into a “u”, and looped around the prepared tooth. Only the end of the cord is to be touched.
- The cord is first secured in the mesial interproximal area and the distal interproximal area with a cord-packing instrument.
- After the cord is secured in the distal interproximal area, the cord is inserted from the mesiolingual to the distolingual corner. While tucking in the cord the tip of the packing instrument should be angled towards the area where the cord has been placed.
- Cut the excess amount of cord in the mesial interproximal area and complete the placement of the cord on the buccal side from the distal end to the mesial side until it overlaps the mesial. A minimum bulk of 0.2 mm sulcular width is essential to make an undistorted impression.
- After 5–10 minutes, the cord is gently removed with the sulcus around the prepared tooth exposed and hemostasis maintained.
- This is followed by the impression of the arch.
Double cord technique
Advantage — Declines the tendency of the gingival cuff to recoil and partially displace the impression material as it sets.
This is a technique in which a thin cord is placed initially and over which a large cord is placed. Thin cord remains during impression making. Hansen et al. observed that 98% of prosthodontists use cords of which 48% use a dual cord technique.
Surgical Tissue Dilation
Electrosurgery/Surgical diathermy
An electrosurgery unit is a high-frequency oscillator or radio transmitter that uses either a vacuum tube or a transmitter to deliver a high-frequency electric current of at least 1 Mega Hertz.
An electrosurgical unit consists of the oscillator, an active electrode, and a ground electrode for the safety of the patient.
Types of electrode
- Coagulating electrode: Controls hemorrhage
- Small wire-loop electrode: Used for sulcular enlargement
- Round electrode: Removes gingival tissue
- Large loop electrode: Is used to remove large amounts of tissue
- Straight electrode: By angling the working electrode at approximately 15–20 degrees and carrying the tip through the tissue, a small wedge of tissue can be removed. In anterior quadrants, the angle of the working electrode is positioned parallel to the long axis of the tooth.
Posner Electrode
With the AP 1 ½ electrode, the insulated portion of the electrode is directed around the tooth, removing the gingival sulcular epithelium. If less trough depth is desired, part of the tip is removed to create the desired depth at 0.5 mm, 0.75 mm, or 1.0 mm.
Types of current
- Monoterminal: Used for fulguration, removal of papillomas and fistulous tract
- Biterminal: For coagulation, removal of granulation tissue
- Unrectified damped current: Not used in dental treatments
- Fully-rectified full-wave modulated current: Good for gingival enlargement
- Fully-rectified filtered current: This is the best current source.
Posner Electrode Method
- Profound local anesthesia is given and a pleasant-smelling aromatic oil is applied on the vermilion border of upper lip.
- Plastic suction tips and plastic-mounted mouth mirrors are used. Odor is controlled by an outside ventilated oral evacuator system.
- Adequate power is set on the unit. The electrode is passed quickly over the tissue to be removed. Adequate time interval between each stroke needs to be followed.
- Fragments of tissue are removed with an alcohol-soaked sponge.
Posner Electrode Indications
- Minor tissue removal before impression procedures
- Removal of granulation or inflamed tissue around a given tooth
- For enlargement of the gingival sulcus in some cases
- Crown lengthening.
Posner Electrode Contraindications
- In cardiac pacemaker patients
- Not to use on thin attached gingiva.
Posner Electrode Rules
- Profound anesthesia.
- No metal instruments should be used.
- Proper grounding should be done.
- A fully-rectified filtered current should be used.
- The electrode should not make contact with any metal restorations in the patient’s mouth.
- A light stroke with a 5-second time interval between applications of the electrode.
- If the tip drags, the instrument is at too low a setting and the current should be increased.
- If sparking is visible the current level is set high and needs to be decreased.
- A cutting stroke should not be repeated within 5 seconds.
- The electrode must remain clean of tissue fragments.
- The sulcus should be swabbed with hydrogen peroxide before the displacement cord is placed.
- Maintaining the biological width after tissue healing.
- After the impression is made tincture of myrrh and benzoin is placed till healing completes in 5–10 days.
Rotary curettage/Gingettage
(Introduced by Amsterdam in 1954)
- This is a troughing technique to remove a limited amount of epithelial tissue in the sulcus while the chamfer finish line is prepared.
- This technique needs to be done on healthy, non-inflamed gingiva to avoid tissue shrinkage after healing the diseased tissue.
Rotary curettage Lasers
Diode lasers, such as neodymium: yttrium-aluminum-garnet (Nd-YAG), Erbium: yttrium-aluminum-garnet (Er: YAG) and CO2 laser are commonly used for gingival retraction around natural teeth.
Advantage
less bleeding (CO2 laser ), gingival recession, painless, and sterilizes sulcus.
Disadvantages
- Er: The YAG laser is not as good at hemostasis as the CO2 laser
- CO2 laser provides no tactile feedback hence, can damage junctional epithelium.
Advantages of Fluid Control and Tissue Management
- Patient comfort
- Safety for patient
- Good visibility while doing clinical procedures
- Clear the area of saliva and water, for better visibility.
Fluid control attained by:
- Rubber dam
- Cotton rolls
- High-volume vacuum
- Saliva ejector
- Svedopter
- Vac-ejector
- Moisture absorbing cords.
Rubber dam
Punch holes are made in the area of the preparation site of the rubber dam and clamped in position.
Fluid Control and Tissue Management Uses
- While removing old restorations
- While preparing onlay or inlay
- For endodontic procedures as a safety measure
- While using pin-retained restoration.
Fluid Control and Tissue Management Disadvantages
- Difficult to use while preparing crowns and FPD
- Reacts with polyvinyl siloxane impression materials.
Cotton rolls
- Absorbent cotton rolls are placed in the area where saliva pools (in the maxillary arch, a single cotton roll is used in the buccal vestibule and in the mandibular arch in the lingual sulcus).
Placement of cotton roll
- One or two cotton rolls are placed vertically against the horizontally placed cotton rolls or one single horse-shaped roll can be used.
Limitation
- The entire saliva and water-soaked roll needs to be removed each time.
High-volume vacuum
- Can be used as a retractor as well as for clearing saliva and water during preparation.
Saliva ejector
- Useful for maxillary arch along with cotton rolls
- Placed in the corner of the mouth opposite the quadrant being operated on with the patient’s head towards that side.
Svedopter/Speejector
- Svedopter consists of a metal saliva ejector with a tongue deflector. Effectively used in the mandibular arch. Effective fluid control along with cotton rolls. The patient is seated in an upright position.
Positioning
- Placed in the incisor region with the tubing under the patient’s arm.
Fluid Control and Tissue Management Disadvantages
- Access to the lingual aspect is limited
- Metal surfaces can cause tissue irritation
- Can cause gagging in some patients
- Cannot use in mandibular tori patients.
Vac-ejector
- Tongue control and high-volume evacuation along with a bite block. It aids in removing large volumes of fluid. Tongue deflectors and bite blocks are available in several sizes. The tongue deflectors are made of plastic.
Moisture absorbing cords
- Consists of pressed paper wafers covered on one side with a reflective foil. The wafer side is placed facing the tissues. Used along with cotton rolls to control saliva and retract cheek laterally.
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