4.2 Complete Denture

8/3/2019 4.2 Complete Denture

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Conventional Definitive Impression Technique:

Disinfect Spl. Trays & rinse in water.

Check tray is:- adequately extended antero-posteriorly & bucco-lingually.

- not interfering function of peri-denture soft tissues.

- has correct overextension (using pressure-relief paste).

Correct under-extension (adding green-stick / other material).

Apply tracing compound to the posterior aspect of the upper

tray to produce a posterior seal.

The tracing compound should extend uninterrupted from oneborder of the tray to the other to create a post dam.

In the lower tray, the compound should be added to displace

the retro-molar pad sufficient to give a posterior seal.


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Load the tray with the material.

Technique is same for the primary impression.

Upon setting, remove from mouth.Check for accuracy and form.

Disinfect procedure (hypochlorite 1,000 ppm).

Indicate the extent of the peripheral roll to bepreserved on the master cast.

Creation of the peripheral seal is essential.

Peripheral seal depends upon:

- correct outline / record of PPS tissues.

- PPS tissue reproduction in master cast .


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Definitive impression with well-defined area for the placement of carding wax

prior to boxing the impression, thereby preserving the functional width and

depth of the sulci.


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Selective Pressure Impression Techniques:

Support problems overcome by relieving master cast but;

- But in specific cases, modified impression proceduresused B/C of perceived support problems including:

- displaceable upper anterior (flabby) ridge.

- fibrous (unemployed) posterior mandibular ridge.

- flat lower ridge covered with atrophic mucosa.Several variations of impression techniques exist to deal

with the above.

General Steps for Definitive / Secondary / final Imp:

Fabricate special trays.Adjust special / custom trays.

After peripheral moulding, do specific modifications to the

trays / impression techniques.


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Impression Technique for Displaceable (Flabby) Anterior

Maxillary Ridge:

Achieve seal with peripheral functional border moulding.Record impression of maxilla in ZOE or a medium-bodied

PVS) impression material.

ZOE not recommended in a patient with a dry mouth.

On setting, the impression is removed from the mouth.

Draw the extent of the displaceable tissue on the

impression surface.

This area, and the equivalent area of the tray, are thenremoved, using a scalpel and acrylic bur.

This modification renders tray no longer retentive.


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Fibrous (Unemployed) Posterior Mandibular Ridge:

Recognized by the presence of a thin, mobile thread-like

ridge which is essentially fibrous in nature.A Staged sequence impression technique is used for this

situation.

Custom tray checked for peripheral extension.

Tray loaded with tracing compound (greenstick).Impression of the denture-bearing area recorded.

Using the heated spoon-end of a Le Cron carver:

- remove greenstick relating to crestal tissues.

Perforate tray in this region.Downward finger pressure of the modified impression, in

the mouth, should elicit no discomfort.

Record definitive impression in light-bodied PVS.

Treat impression as for a conventionally made impression.


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Flat Mandibular Ridge Covered With Atrophic Mucosa:

Equate to Atwood's Ridge Clases V & VI.

Atrophic & / or non-keratinized tissue folds seen on ridge.The impression philosophy is that a viscous admix of cake

imp. compo & stick compo removes any soft tissue folds

& smoothes them over the mandibular bone.

Discomfort arising from the 'atrophic sandwich', i.e creasedmucosa b/w CD base & mandibular bone is reduced.

Prepare the impression medium as admix of 3 parts by wt.

of (red) imp. compo & 7 parts by wt. of stick compo.

Admix made in hot water by kneading using vaselinedgloved fingers.

Make lower impression (Working time of admix is 12

minutes) by moulding the peri-tray tissues to achieve

good peripheral border recording.


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On removal, impression is chilled in water & then re-

inserted.

The operator presses on the stub handles of the tray onthe premolar region & reciprocates with thumbs on the

inferior body of the mandible:

- ideally no discomfort will be felt by the patient in the

area pressed by the operator's thumbs!Any discomfort in the DBA may be treated by adjusting the

offending area of the impression with a heated wax

knife and re-inserting as required until no further

discomfort is felt.Alternatively, painful area is relieved on the master cast.

Admix technique gives a reliable guide to the load-bearing

potential of patient's DBA when making definitive imp.


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Definitive impression made with Admix Method (MC Cord & Tyson)


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Template (Replica Denture Tray) Impression Technique:

Used when replacing existing CDs by copy method.

Replication of the form of polished surfaces of CDs

help the patient's adaptation to new dentures.

Fabricate mould of CD to obtain its acrylic replica.

Final imp. recorded in acrylic replica of CD

(template).


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Functional impression Techniques

used where problems of stability exist:

- poor muscle adaptation and /or imbalance or

- because of problems of available denture space).

- also useful in patients having recently suffered from stroke.

Two variations are commonly used for functional impressions.

- Local areas of modification

CDs exhibiting looseness, not primarily from retention problemsbut because of localized areas of poor functional adaptation.

In these cases, use a thin mix of a resilient lining material (e.gVisco-Gel, or Peripheral Seal).

The mixed material is added to the fitting surface of the denture.

Patient instructed to wear the denture for one hour.

After one hour of functional moulding CD removed from mouth.

Conventional relining process completed.


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Reline and rebase techniques (including secondary

template impressions)

Conventional reline impression is taken or a:- secondary impression for the template technique.

They are both definitive impressions.

Must consider the same degree of attention as standard

impression techniques.The denture, or its replica, to be relined is modified:

Establish peripheries /peripheral seal.

Undercuts are removed from fit surface of CD:

to ensure that master cast is not damaged onremoval of the dent


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ZOE or Elastomer (PS / PVS / PE) imp used.

Before recording the definitive impression, there is merit

in placing tracing compound as spacing on the denturein the region corresponding to the ridges of the canine

areas (But no OVD Raising).

Perforate maxillary spl. Tray in in the midline of the rugae

to prevent any possibility of imperfections in theimpression, e.g air bubbles.

Also important is good communications with the

laboratory (Good rapport b/w Lab).Conventional techniques, however, do little to inform the

technician on the customizing of upper record rims.


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Problems associated with denture space/neutral zone

This technique is well documented and has been referred

to as the neutral zone technique oranthropoidal pouch

technique.

We prefer to use the term denture form impression

technique. It is designed for patients with poor track

records of lower denture stability, a large tongue or

other anatomical anomaly.

The clinical stages are standard up to and including the

registration visit. After this, the upper denture is set up

conventionally to the prescribed occlusal vertical

dimension (OVD). Opposing the upper set-up is a resin

base with three vertical stops joined by a wire bent in a

sinusoidal manner. The stops must contact the upper

teeth at the selected OVD.


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4.2 Complete Denture

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