4 pdf - Dr zhala - Muhadharaty

Impression of complete denture

Complete Denture Impressions

impression

: Record –ve form of tissue of oral cavity that make

up basal seal of denture.

•Most important step in complete denture
•Primary impression ….diagnostic ….tray
•Final impression…..final detail….master cast.

• Primary impression

: an impression of the edentulous mouth

which is made for purpose of producing a diagnostic cast upon
which custom tray will be fabricated.

• Final impression

: final detain…used for construction of master

cast ….upon which denture fabricated.

Objectives of C.D impression:

•Retention

: resist removal in direction opposite direction of its

insertion.
•What will happen to movable soft ridge…..in impression? Effect on
retention.

•Stability

: resist horizontal movement (quality final impression, flow

ability )…lack stability….gross soft tissue …bone change…

• Support

: vertical…basal seat…. Snow shoe.

• Esthetic

: good impression…good esthetic (border thickness ..lip

facial contour).

• Preservation of the residual ridge

: occlusion..interocclusal

distance…centric relation…impression technique…impression
materials.

Classification

dep.on theories of imp

A. passive-minimal

B. functional-pressure
C. selective pressure

dep.on the position of the mouth while making the impression

A. open mouth
B. closed mouth

dep.on the tray type

                                      A.stock tray
                                      B. custom tray
                                          1.close fit
                                          2.spaced

dep.on the manipulation for border molding

Hand manipulation
Functional movement

Theories of impression:

The

forces

directed to the tissue during impression is directly

influenced by:
• The

viscosity

and

flow

of the impression material used.

• Type of impression

tray

made

• Force

extended upon the tray when the impression is being

made.

Passive or Mucostatic

• use oversized tray
• record tissue at rest and jaws in normal relaxed condition
• no border mold
• Retention is achieved through accurate tissue adaptation.(poor retention stability)
• poor peripheral seal
• short denture flange so less resistance to lat. forces

Advantages

Health and preservation of the tissue

Disadvantages

• Reduce  coverage ….poor stress distribution
• Short flange…. irritation of tongue less lateral stability
• Lack border molding …..space….Food beneath the denture
• Flowable material used

Pressure or Functional

Under pressure resemble under mastication

Heavy material like impression compound used

•use close fit tray
•imp.comp …special tray with occlusion rim
•record tissue at pressure
•Close mouth technique

•border are molded
•Good peripheral seal
•Better retention and support
•rapid R.R resorption
•Tissue ischemia
•Pressure on sharp spiny ridge

Selective pressure:

Combines both pressure non pressure techniques.
Basal seal area are divided into
•Primary stress bearing area
•Secondary stress bearing area
•Relief area
This is achieved by design of sp.tray in which non stress bearing area are relieved and
stress on stress bearing area.

Advantages

Physiological function of tissue of basal seats

Disadvantages

Some recorded impossible to record area with varying pressure.
Excess pressure …bone lose

Selective Pressure

1-Cobination of both

Open mouth:

•Imp. Tray held by

dentist

while pt. mouth is open

•Limit tissue

recorded ,……when mouth open limit the extend of imp. Material ….

peripheral border.
•Allows better

observation

of the tray position and flow of material while lip cheeks

are border molded.
•Muscle movement

easier

•When mand. Literally or protruded …there will b e

clearance

between ramus and

mand. For good record.

Closed mouth:

•When mouth closed

tissue more relaxed

…good extension of material to recorded.

•Tongue

confined …cannot move …

material flow

to recorded

mylohyoid

ridge easier

•Occlusal rim

on tray to allow pt. to close on it.

•Pt. will do borer molding by (closing sucking grimcing swallowing)..

active molding

•Pressure by pt. during record….will be transmitted to denture …so once stress

release

tissue will rebound

this will effect denture seal

Primary imp.

•Alginate

…perforated tray

•Compound

….plain tray

Position of dental chair….

•Lower…pt. mouth with level of operator shoulder….dentist in front right side
•Upper…pt. mouth with level of operator elbow…chair tilted back little. dentist right
little behind.

Selection of stock tray:

• Oversize providing

3mm space

flange should not impinge on frenal.

Selection of lower tray:

• Calipers

to measure arch width .(for lower tip of caliper on lingual

aspect of ridge right left below retromolar pads.

• Pt. asked to rise tongue to check

tongue space.

Selection of the upper tray:

•Tip of caliper on buccal vestibule in tuberosity region….then on tray.
•2-3 mm space for material

Sequence of making impression :

upper

lower?

•Discomfort…anaxiety…reflex.
•Salivation when foreign body in mouth ….activation

Primary imp….compound:

adv.

Cost

easy

use…dimensional

stability

…….

disadv

viscosity

…

displace

tissue

. Not accurate

Soften

in water bath …kneaded

rolled

into ball on tray using tumb…spread adapt over

tray …approximate ridge contour.

Center

the tray using labial frenum as guide.

Apply pressure on molar

region then hold by finger

border molder

moving lips

cheeks…poured with plaster within 30 min

Mandibular imp.

•Same principle as maxillary imp. material rolled and rope shape
placed on tray …during border molding tongue moved for lingual
borders.

Final imp.

Border molding :

•Is the process by which the shape of the borders of the tray is made to
conform accurately to the contoured of the labial buccal vestibules
before making the final impression ….

also referred muscle trimming

•Done by manipulating tissue against moldable impression material that
are properly supported and controlled by the tray

It is the only way to get ideal peripheral seal and cover the available
area of support.

Varity of materials have been used for border molding:

• Molding compound wax
• Auto polymerizing acrylic resin
• Elastomeric materials
• Heavy body putty type silicone
• Polyether.

General considerations:

• The custom tray should be stable and borders are

2mm

short.

• Uniform

thickness 2mm

• Handle

should not interfere with lip or movements

• Molding compound should be done for each area separately not all at

once .

• Control bulk and temperature of the molding compound.

• Too much pressure

…thin overextended flanges …while too

little pressure…excessively thick borders

• Tray should be

dried

before u put compound …better stick

• Also before reheating compound should be

dried

• Each section

molded separately

Movement for border molding:

Maxillary

• Labial border:

upper lip elevated then extended outward downward

and inward.

• Buccal border:

cheek is elevated and then pulled outward downward

and inward.

• Buccal frenum

is recorded by pulling the cheek backward and

forward.

• The disto-buccal region

is recorded by pulling the cheek outward

downward inward fallowed by opening of the mouth widely and
moving the mandible from side to side.(when mouth widely
open coronoid process will come close to distal portion of max.
buccal sulcus.

• Thick flange

will cause will

interfere and pain

• Posterior palatal seal

area is molded by asking pt. To say ah

while refining area