FLUID CONTROL AND GINGIVAL

DISPLACEMENT

INTRODUCTION Control of fluid and appropriate

displacement of gingiva are essential during tooth preparation to obtain accurate impressions ,and for cementation.

They enhance the operator visibility, increase patient comfort and aid in extracting optimum benefits from the impressions and cementation procedures.

FLUID CONTROL OBJECTIVES Primarily to remove fluids, isolate and

retract oral tissues. To enhance operator visibility and patient

comfort during tooth preparation. To prevent injury to patient oral tissues. To prevent aspiration of fluid along with

restorative debris.

Isolate specific areas of the oral cavity and ensure a dry operating field in preparation for impression and cementation procedures.

MethodsThe methods employed may perform the task of fluid control, isolation and retraction of oraltissues,singly or in combination.Fluid control methods: Two types1.Mechanical2.Chemical

Mechanical methods of fluid control

Rubber dam Cotton rolls Suction devices High volume suction Saliva ejector Svedopter

Rubber dam It is used to isolate the tooth during

restorative procedures. Some authors indicates its use during

preparation impression and cementation of indirect restoration.

When used with elastomeric impression materials,it should be lubricated and clamp removed.It should not be used with poly vinyl siloxane(addition silicones) as its polymerization will be inhibited

Cotton rolls Simplest method of fluid control and

isolation Used during impression and cementation

procedures. For isolating maxillary arch, single cotton roll

in the buccal vestibule adjacent to maxillary first molar where the parotid duct opens is sufficient.

For isolating the the mandibular arch, multiple cotton rolls are placed in the maxillary and mandibular mucobuccal fold.

Saliva ejector is usually placed in the lingual sulcus for fluid removal when ever cotton rolls are used for isolation.

An absorbent card may also placed buccally in conjunction with cotton rolls for isolation and fluid control.

High vacuum suction Used for fluid and saliva removal during

tooth preparation. It is powerful suction equipment used

with an assistant. It may also used to retract the lip

simultaneously.

Saliva Ejector(low vacuum suction)

Used for fluid removal during impression and cementation procedures.

May be used during tooth preparation in maxillary arch by placing it in the corner of the mouth opposite the side being prepared, with the patient’s head turned towards that side. It is not effective as high vaccum suction.

Can be used without any assistance.

Svedopter It is a flange type of saliva ejector made

of metal. Used for fluid removal and tongue

retraction during tooth preparation on mandibular arch,and isolation during impression and cementation.

Can be used with patient in an upright position,without assistance.

Disadvantages

Access to lingual surface of mandibular teeth may be limited

May injure the floor of the mouth if not used carefully, as it is made of metal. Cotton roll placed between the blade and mylohyoid ridge may reduce this problem.

Contraindicated in presence of mandibular tori.

Chemical methods of fluid control

Antisialogogues Local anaesthetics

Antisialogogues Drugs may be used to provide fluid control by

reducing salivary flow.This is especially beneficial during impression making.

Anticholinergic drugs-atropine,dicyclomine and propantheline may be used.They are given onehour before the dental procedures.

They are contraindicated in patients having

Hypersensitivity to drug,glaucoma,asthma,obstructive conditions of the gastrointestinal tract and congestive cardiac desorders.

Local anaesthetics In addition to pain control,local

anaesthetics also reduce salivary flow during impression making.

They act by blocking nerve impulse from the periodontal ligament that regulate salivary flow.

Clonidine ,an antihypertensive drug may also be used,it is safer than anticholinergics but should be used.It is safer than anticholinergics but should be used with caution other antihypertensives.

Drugs used for fluid control and their reccomended dosages are given below.

Drug DosageAtropine sulfate 0.4mgDicyclomine HCL 10-20mgPropantheline bromide 7.5 -15mgClonidine 0.2mg

GINGIVAL DISPLACEMENT Definition: The deflection of marginal

gingiva away from a tooth. Also called gingival retraction or tissue

dilatation. It is essential that gingiva in a healthy

state before tooth preparation.

ADVANTAGES1. To provide adequate reproduction of

finish line.2. To accurately duplicate sub gingival

margins.3. To provide best possible conditions for

the impression materials , fluid control4. To fabricate accurate restoration thereby

preventing periodontal diseases.

OBJECTIVES1. To expose the prepared finish line.2. To control the gingival crevicular fluid.3. To evaluate the depth and uniformity of the finish line.4. Allows the refinement of the finishline without

lacerations of soft tissue.5. Provide accesss for the impression materials to record

accurately the finished margins and a part of unprepared tooth beyond the finish line.

6. Helps to obtain accurate marginal fit which will reduce the marginal leakage and subsequent deterioration of the tooth.

Methods for gingival displacement

Mechanical1. Copper band2. Rubber dam3. Retraction cord4. Magic foams

Chemical1. Ferric sulphate2. Aluminium chloride3. Racemic

epinephrine Chemical-

mechanical

Mechanical Copper band It carries the impression materials and displaces the

gingiva. One end of the copper band is trimmed to follow the

contour of gingival margins. The top part is plugged with resin or compound. A vent is placed to allow escape of excessive impression materials. The tube is filled with impression materials and is seated parallel to the long axis of prepared tooth such that the contoured metal margins coincide with the free margins gently displacing them.

Though it is no longer used routinely ,it may be indicated with multiple abutments and

When full arch impression of multiple abutments have not recorded one /two teeth properly.

It can cause injury to the gingival and retraction is also minimal.

Rubber Dam• It is used when limited number of teeth in

one quadrant are being restored and when preparations donot have to extend sub gingivally

• Clamp should be avoided as rubber interfere with its setting.

Cotton threads Plain cotton threads have also been used

to produce mechanical gingival displacement.

The retraction achieved is purely physical without any heamostasis,very less and transient.

Retraction cord 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.

The technique for placement of the retraction cord is elaborated in chemical-mechanical methods of gingival retraction.

Chemicomechanical methods of gingival retraction(Retraction cord)

• A displacement /retraction cord is used for mechanically separating the tissue from the prepared margin and is impregnated with a chemical for astringent action and/or haemostasis as impressions are made. Cord displaces the gingival tissue both laterally and vertically.

Ideal requirements of cords• Dark in colour and never red.• Be made of absorbent materials.• Strong enough to resist placement and

should not snap.• I t should be available in different

diameters to accommodate the varying morphologies of the gingival sulcus.

Chemicals used• Cord is impregnated with the chemical or

cord may be dipped in specific chemical agents before packing into the gingiva.

• These cause a transient ischemia thereby shrinking the tissue, help control gingival fluids and provide haemostasis.

• The most commonly used chemical are ferric sulphate and aluminium chloride ,racemic epinephrine8% is also used though not commonly as it causes tachycardia.

Classification• Plain or impregnated• Lubricated or non lubricated• Twisted,braided or knitted• According to thickness-00,0,1,2Knitted cords are made of compressible interlocking chains which transport greater amount of chemical agent.

InstrumentInstrument used for packing the cord is called as ‘Fischer's cord packer.It should be thin enough to be placed in the gingival sulcus without damaging the tissues, and the angle of the instrument should allow packing of the cord all around the tooth. The tip may be serrated to enhance the grip of instrument concord.

Displacement techniquesTwo methods may be employed:1. Single cord technique.: one cord is placed in the

sulcus and the impression is made immediately following the retraction after removing the cord.

2. Double cord technique: Two cords are used ,one thin cord is packed deep into the sulcus and left there during impression making to provide haemostasis. The second cord is placed over the first cord to provide retraction and is removed immediately prior to impression making.

MethodSingle cord technique:• This is the most commonly used method• Indicated for making impression of one to

three teeth with healthy gingival tissues.• The operating field must be dry, isolated

with cotton rolls and fluid removed with saliva ejector.

• Cut appropriate length of cord to encircle the tooth 2 inches approximately.

• If impregnated ,moisten cord intraorally,or dip cord in appropriate chemical agent placed in a dappen dish

• From a ‘U’ shape and loop it around the prepared tooth so that cut ends are on the lingual side

• From the lingual side grasp the cut ends of the cord between the thump and forefinger and apply tension very slightly in an apical direction. This apical tension would result in the cord tucked in both the proximal and labial surfaces.

Double cord technique• The double cord technique is indicated

when making impressions of multiple prepared teeth and when tissue health is slightly compromised with more than normal bleeding anticipated.

• A small diameter cord is placed into the sulcus. The ends of this cord should be cut so that they exactly about against one another in the sulcus. Cord is left in the sulcus during impression making

Use the cord packing instrument to secure the cord in the proximal area first .Instrument should be angled towards the tooth.

Proceed to the lingual surface and facial surface beginning with the mesiolingual line angle.

Cut off the excess length of the cord protruding from the lingual sulcus leaving a small tag. This tag can be grasped for easy removal.

After 10 minutes ,moisten the cord with saline or sterile water and remove the cord slowly to avoid bleeding persists ferric sulphate chemical can be applied to the gingiva.

A second cord, soaked in the haemostatic agent of choice, is placed in the sulcus above the small diameter cord. The diameter of the second cord should be the maximum diameter that can be placed easily in the sulcus.

Eight to ten minutes after placement of the second cord, it is moistened, removed and impressions are made with the first cord in place.

After making the impression, the small diameter cord is moistened and removed from the sulcus

Magic foam This is a recent devolopment.It consist of

‘comprecop’-a hollow cotton and magicfoamcard-a poly vinyl siloxane material.

Prior to impression making a desired size of the comprecap is selectedMagic foamcord is injected around the preparation and inside the comprecap and is placed over the prepared tooth. Patient is instructed to gently bite to hold the comprecap.After about 3-4 minutes the comp recap is removed along with the magic formcord.

Advantage• Easy to use with less trauma. Disadvantage• Less retraction than cord• Haemostasis must be established prior to

retraction.

Chemical This is a recent development where

retraction achieved using only chemicals. This consist of an aluminium chloride

containing paste(Expasyl)which is indicated into the sulcus prior to impression making. The paste is left in the sulcus for 3-4 minutes to achieve the desired retraction .It is washed off and impression is made.

Advantage• Achieve good heamostasis• Disadvantage• Retraction is much less compared to

cord.

SURGICAL1. Rotary curettage(Gingettage)It is also called as ‘gingettage’.The concept of using rotary curettage was described by Amsterdam in1954.Rotary curettage is a troughing technique. Epithelial tissue in sulcus is removed by a rotary instrument while finish line is being created.

This technique is well suited for use with reversible hydrocolloid impression materials.Rotarycurettage must be done only on healthy gingiva to avoid tissue shrinkage. This technique can be used only when there is:

• Absence of bleeding upon probing.• Sulcus depth less than 3mm• Presence of adequate keratinized gingiva.

Technique Asupragingival finish line is first created

to complete the tooth preparation.A torpedo diamond is used to extended the finish line apically ,one-half to two thirds the depth of sulcus to produce a chamfer finish line.As only half the diamond is used to produce the chamfer, the other half will create a trough around the tooth removing a layer of epithelial tissue achieving the desired direction..

A retraction cord impregnated with aluminium chloride or alum is gently placed in the sulcus or a haemostatic agent is injected to control the haemorrhage.

After 4-8 minutes the cord is removed and sulcus is thoroughly impregnated with water and impression is made.

DisadvantageThis is poor tactile sensation while using diamonds which can leads to deepening of the sulcus. I t has potential for destruction of periodontium with in experienced.

Electro surgery: It produces controlled tissue destruction to

achieve a surgical resultMechanism• High density current from a small cutting

electrode produces a rapid rise of temperature at the point of contact with the tissue. The cells with the electrode are destroyed by this temperature rise.

• Unmodulated alternating current is recommended for gingival displacement.

Indications1. Gingival sulcus enlargement and

haemorrhage.2. Gingivectomy3. Crown lengthening.Contraindications4. Patients with electronic medical device –

cardiac pacemaker, insulin pump.5. Patients with delayed healing because of

debilitating disease of radiotherapy.6. Not used if attached gingiva is thin

3.Not to be used with metal instruments as contact with them can produce electric shock-better to use plastic mouth miror and saliva ejectors.It should not be used in presence of flammableagents,like topical anaesthetics such as ethylchloride or other aerosols,nitrous oxide analgesiaas electrosurgery can produce sparks during use.

Electrosurgical equipmentIt consist of the following:1.Unit-a high frequency oscillator or radiotransmitter that generates heat.2.Handpiece-holds the electrode3.Electrodes-basically like probes of different shapes that fit into the handpiece and are used for cutting or coagulation eg:coagulating,diamond loop,round loop,small straight and small loop.The small straight electrode is used for gingival displacement.

4.Grounding plate-Circuit is completed by placing a ground plate in the back or under the thigh of the patient. It is important to prevent burns.

Technique for gingival displacement: Width of the gingival sulcus is enlarged by

creating a trough around the finish line. The height of the sulcus should never be decreased.

There may gingival recession if not properly performed. Profound local anaesthesia necessary.The working electrode must be clean and without carbonization. Electrode must be used with very light pressure and quick, deft stroke. Debris inside the sulcus is removed with cotton soaked in hydrogen peroxide.

By angling the working electrode at approximately 15-20 degree and carrying the tip through the tissue until it rests against the tooth, a small wedge of tissue can be removed. In cases of thin gingiva the angle of the working electrode is changed to be more parallel to the long axis of the tooth.

It must be removed at a speed of 7mm/sec to prevent lateral heat penetration. No stroke should be immediately repeated. If it is necessary to retrace the path of a previous cut

At least 5 seconds should be allowed to elapse before repeating the strokes.The sequence of surgery should be ,lingual surface first, followed the by the facial surface, mesial surface and lastly the distal surface. This prevents the heat accumulation in the tissue.Most will cut best if it dries out; sterile water/saline is sprayed lightly. A high volume vacuum tip should be kept immediately adjacent to the cutting electrode at all times to remove the unpleasant odour that is generated.

Impression is made immediately following the procedure.

Proper technique can be summarized as follows:

1. Proper power setting2. Quick passes with the electrodes3. Adequate time intervals between

strokes.

3.Soft tissue lasersThis can be also used for gingival displacement similar to electro surgery.

SUMMARY Gingival displacement is an important

procedure for fabricating indirect restorations especially when sub gingival finish lines are used. Gingival displacement is relatively simple and effective when dealing with healthy gingival tissue and when margins are properly placed. The most common technique used for gingival displacement is the use of gingival retraction cord with haemostatic medicament. Retraction cords of appropriate diameter should be used.