Sp.imp.procedures./ orthodontic assistant training

NEUTRAL ZONE IMPRESSION
TECHNIQUE
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

INTRODUCTION

AimsAims
To determine the space within which the
denture can be sited without being subjected to
excessive displacing forces from the
surrounding musculature.

The portion of the oral cavity that is or may be
occupied by the maxillary and / or mandibular
denture (s).www.indiandentalacademy.com

Neutral ZoneNeutral Zone
That area in the mouth, where, duringThat area in the mouth, where, during
functions thefunctions the forcesforces of the tongueof the tongue
pressingpressing outwardoutward areare neutralizedneutralized by theby the
forcesforces of the cheeks and lips pressingof the cheeks and lips pressing
inwardinward..
 Hence a possible zone of equilibrium

IndicationsIndications
Past denture looseness due
to powerful lower lip activity.
Non-replacement of missing
teeth leading to tongue /
cheeks / lips partially
occupying the usual denture
space.
Enlarged tongue,
Abnormal anatomy,
Inability to wear a lower
denture

To achieve optimum success in complete denture
prosthesis, the dentures should be both retentive and
stable.
“The retention of denture is dependent on the
accuracy of impression and fit of the denture base to
the tissues”.
“The stability of a denture dependent on occlusion,
tooth position, flange form, and contours “.
Tooth position , flange form, and contours are
developed by the neutral zone procedures.

How to record a neutral zone:How to record a neutral zone:

.Various materials used to locate neutral zone.
.Locating the neutral zone for lower arch and
upper arch.
. Locating the plane of occlusion.

Recommended movementsRecommended movements
Suck
Swallow
‘ooh’
‘ah’

Technique – the trays are adjusted to eliminate
overextension and create stable trays.
Color -coded impression procedure- Two impression
pastes of contrasting colors are used, the purpose is to
locate areas of tissue displacement.
The impression tray and two zinc oxide and eugenol
pastes should be of three different colors.

Lower and upper secondary impression
Relief of pressure areas
Correcting lower impression

Border seal.
Tissues at rest – overextended
Extreme movements- underextended
Technique used- CLOSED MOUTH TECHNIQUE
Two advantages- 1.the desire to obtain a more
accurate functional molding of the borders.
2. by having the patient close gently and swallow,
there is more even distribution of pressure and
impression material with less likelihood of excessive
pressure in one area or the other.

Plaster matrices constructed around records.
Matrices guide in arranging & waxing teeth &
polished surfaces in optimum denture space.

After wax trial is completed, external impressions are
obtained using ZOE paste / light – bodied elastomer.

conclusion
The influence of tooth position and flange contour on
denture stability is equal to or greater than that of
any other factor. We should not insist that teeth be
placed over the crest of the ridge, buccal or lingual to
the ridge. Teeth should be placed as dictated by the
musculature, and this will vary for different patients.
Positioning artificial teeth in the neutral zone
achieves two objectives.

First the teeth will not interfere with the normal
muscle function and second, the forces exerted by the
musculature against the dentures are more favourable
for stability and retention.

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