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lec 6 Flashcards

1
Q

negative likeness or copy in reverse of the surface of an object.

A

Ø Impression

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2
Q

positive replica of denture foundation tissues.

A

Ø Cast

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3
Q

OBJECTIVES OF IMPRESSION TAKING (5)

A

1) Preservation of the alveolar ridge
2) Retention
3) Stability
4) Support
5) Esthetics

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4
Q

Based on THEORIES OF IMPRESSION:

A
  • Pressure theory
  • Minimal pressure theory
  • Selective pressure theory
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5
Q

Based on the POSITION OF THE MOUTH while making the impression:

A
  • Open mouth
  • Closed mouth
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6
Q

Based on the METHOD OF MANIPULATION FOR BORDER MOLDING:

A
  • Hand manipulation
  • Functional movements
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7
Q
  • Was proposed on the assumption that tissues recorded under functional pressure (mastication) provided better support and retention for the denture.
A

PRESSURE THEORY (MUCOCOMPRESSIVE OR DEFINITE PRESSURE)

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8
Q
  • Heavy bodied material (Impression compound)
A

PRESSURE THEORY (MUCOCOMPRESSIVE OR DEFINITE PRESSURE)

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9
Q

Better retention and support during occlusal functions like mastication

A

PRESSURE THEORY (MUCOCOMPRESSIVE OR DEFINITE PRESSURE)

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10
Q

o Excess pressure could lead to increased alveolar bone resorption – loose denture.
o Excess pressure result in transient ischemia
o Dentures which fit during mastication tend to rebound when the tissue resume to their normal resting state.
o Pressure on sharp spiny ridges or other bony areas often resulted in pain.

A

PRESSURE THEORY (MUCOCOMPRESSIVE OR DEFINITE PRESSURE)

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11
Q
  • Interfacial surface tension was the only significant way of retaining complete denture. Retention is achieved through accurate tissue adaptation.
A

MINIMAL PRESSURE THEORY (MUCOSTATIC OR NONPRESSURE OR PASSIVE TECHNIQUE)

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12
Q
  • Covers firmly attached mucosa – shorter flanges.
A

MINIMAL PRESSURE THEORY (MUCOSTATIC OR NONPRESSURE OR PASSIVE TECHNIQUE

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13
Q
  • Equal transmission of pressure to all part.
A

MINIMAL PRESSURE THEORY (MUCOSTATIC OR NONPRESSURE OR PASSIVE TECHNIQUE)

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14
Q

Tissue health and preservation.

A

MINIMAL PRESSURE THEORY (MUCOSTATIC OR NONPRESSURE OR PASSIVE TECHNIQUE)

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15
Q

Give disadvantages of Minimal Pressure Theory

A
  • Disadvantages:
    o Shorter flanges prevent the wider distribution of masticatory stresses
    o Reduced coverage, reduced retention
    o Lack of border molding reduces effective peripheral seal therefore reduced retention
    o Short denture borders provoke irritation to the tongue
    o Shorter flanges reduce support for the face which affects the esthetics
    o Shorter flanges, less lateral stability
    o Patients with poor residual ridge were difficult to treat.
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16
Q
  • Combines the principles of both pressure and minimal pressure techniques.
A

SELECTIVE PRESSURE THEORY

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17
Q
  • Zones of basal seat: (3)
A

a) Primary stress bearing area
b) Secondary stress bearing area
c) Relief areas

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18
Q
  • Advocates maximum extension within the comfort and functional limits of the surrounding muscle and tissue
A

SELECTIVE PRESSURE THEORY

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19
Q

o Considers the physiologic functions of the tissues of the basal seat and therefore appears more sound and appealing.

A

SELECTIVE PRESSURE THEORY

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20
Q

o Some feel that it is impossible to record areas with varying pressure.
o Since some areas are still recorded under functional load, the denture still faces the potential danger of rebounding and loosing retention.

A

SELECTIVE PRESSURE THEORY

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21
Q

CLASSIFICATION OF IMPRESSION MATERIAL
Based on ELASTICITY:

A

Ø Rigid – ZOE impression paste, impression compound, impression plaster
Ø Elastic – alginate, elastomeric impression material.

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22
Q

CLASSIFICATION OF IMPRESSION MATERIAL
Based on its PROSTHODONTIC USE:

A

Ø Preliminary impression material
Ø Final impression material

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23
Q

Modelling Compound (3)

A
  1. Impression compound
  2. Tray compound
  3. Stick compound
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24
Q

à Used both for preliminary impression material as well as final impression material.

A

Alginate

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25
FINAL IMPRESSION MATERIAL (5)
1. Alginate 2. Rubber base 3. Zinc oxide eugenol paste 4. Impression plaster 5. Waxes
26
à A device used to carry, confine, and control impression material while making an impression.
IMPRESSION TRAY
27
CLASSIFICATION OF IMPRESSION TRAYS Based on FABRICATION:
1) Stock tray 2) Custom tray
28
Based PRESENCE OF RETENTIVE HOLES:
1) Perforated 2) Nonperforated
29
Based on USE:
1) Dentulous trays 2) Edentulous trays 3) Combination trays (RPD)
30
* A negative likeness made for the purpose of diagnosis, treatment planning, fabrication of custom tray.
PRELIMINARY IMPRESSION (PRIMARY IMPRESSION)
31
flabby ridges, severe undercut ridges.
o Alginate
32
preferred material, contraindicated for hypermobile ridges.
o Impression compound
33
poured immediately (prevents syneresis) / covered in moist gauze and enclosed in a sealed bag.
Ø Alginate
34
poured immediately for greater accuracy.
Compound
35
Disinfection: ?
Ø Rinsed in a running water and sprayed with disinfecting solution.
36
à Used for diagnosis, treatment planning, and fabrication of impression tray.
PRELIMINARY CAST
37
POURING TECHNIQUE:
1. Nonboxing method 2. Boxing method 3. Pumice-plaster method
38
à Designed to provide more pressure in the primary stress bearing areas and little or minimal pressure in the non-stress bearing or relief areas by constructing the tray with wax spacer.
FABRICATING CUSTOM TRAY
39
Ø_________ – tray extension Ø______– denture base extension
Blue Red
40
à Reduction or elimination of undesirable pressure or force from a specific region under denture base.
RELIEF
41
à Creation of space in an impression tray for the impression material.
RELIEF
42
first recommended by Roy Mac Gregory in the region of incisive papilla and midpalatine raphe.
Ø Tin foil
43
in thickness of 0.9 mm advocated by Neil and to be adapted all over except PPS area.
Ø Casting wax
44
used as spacer when shellac is used for custom tray fabrication.
Ø Nonasbestos ring liner (wet) used
45
used as spacer when acrylic resin is used for custom tray fabrication.
Ø Base-plate wax
46
* The shaping of border areas of an impression tray by functional or manual manipulation of the tissue adjacent to the borders to duplicate the contour and size of the vestibule.
BORDER MOLDING (MUSCLE TRIMMING/ PERIPHERAL TRACING)
47
* Determining the extension of a prosthesis by using tissue function or manual manipulation of the tissues to shape the border areas of an impression material.
BORDER MOLDING (MUSCLE TRIMMING/ PERIPHERAL TRACING)
48
 Mold the borders in harmony with the natural functional movements of daily life.
1. Functional method
49
 which simulates the muscle action  Digital(finger) manipulation of the cheeks and lips.
2. Manual or digital manipulation
50
 Combination of digital and functional movements.
3. Combination
51
molds the labial and buccal borders
 Smiling, whistling and puckering motion
52
buccal frenum and buccal borders
 Sucking motion
53
lingual border
 Licking the lips and other tongue movements
54
lingual border and floor of the mouth
 Swallowing motion
55
OTHER FUNCTIONAL MOVEMENTS (2)
 Occluding  Opening and closing and side to side movements of the jaw
56
COMBINATION A. __________________– most common B. __________________ – requires occlusion rim or teeth
Open mouth technique Closed mouth technique
57
MAXILLARY BOLDER MOLDING (4)
A. Buccal Flange  Extend cheek outward, downward, & inward  Open wide & move from side to side  Pucker & smile B. Buccal Frenum  Elevate cheek & pull outward, downward, & inward  Move backward & forward  Pucker & smile C. Anterior Region  Elevate lip & extend outward, downward & inward  Pucker & smile  Massage upper lip with a lateral motion D. Posterior Limit
58
BORDER MOLDING WITH STICK COMPOUND (5)
A. Heating – heating over a flame to soften. B. Placing – flowed along the border of the required segment. C. Tempering – tempered in warm water making it more comfortable for the patient B C A Border molding with stick compound. D. Inserting – inserted carefully in the mouth after retracting the lip and cheek. E. Trimming - excess material on the inside of the tray is trimmed away.
59
MANDIBULAR BOLDER MOLDING (5)
A. Buccal Frenum  Lift cheek outward, upward, inward, backward & forward  Pucker & smile B. Masseter Region & Retromolar Pad  Pull cheek buccally (ensures not trapped under tray)  Cheek upward &inward  Ask pt. to close while resisting closure with figure rests C. Labial Flange  Lower lip outward, upward & inward D. Anterior Lingual Flange  Protrude tongue  Push tongue against front part of palate  Push tongue against thumb in lower incisor area E. Molar Lingual Flange  Protrude tongue OR make ‘K’ sound  Push tongue against thumb in lower incisor area  Swallow
60
If the retention is adequate, you are ready to CUT BACK the compound. What is cut back?
 Scrape away a thin layer of compound from the border molded periphery.
61
PURPOSE OF VENT HOLE/ SCAPE HOLES:
à To permit proper seating of the loaded master impression tray while making the final impression. à To relieve the pressure over the incisive papilla and the rugae/ reduce the build-up of hydrostatic pressure and facilitate the escape of the material. à To prevent entrapment of air bubbles in the impression.
62
 Apply a _______________ and permit it to dry. Note that adhesive is applied 2-3mm onto the external border of the tray.
thin layer of tray adhesive
63
 An elastic, free flowing, light body ____________________ is recommended for most maxillary impressions.
polysulfide impression material
64
. It should have hydrophilic properties and adequate viscosity to reduce the probability of gagging.
 Polyvinylsiloxane impression
65
mix impression material according to the manufacturer’s instruction.
 Mixing
66
material is spread out evenly to all parts of the tray. The material must be free flowing and not viscous as this can affect the pressure exerted on the tissues and the seating of the tray.
 Loading
67
CRITERIA FOR GOOD IMPRESSION:
1. Smooth well-defined peripheries. 2. Maximum extension. 3. Even pressure distribution (there should be no areas where the underlying tray or compound shows through). 4. There should be intimate tissue contact.
68
IMPRESSION TECHNIQUE FOR HYPERMOBILE RIDGES
WINDOW TRAY IMPRESSION TECHNIQUE
69
most often seen anteriorly and may be particularly prominent in patients with combination syndrome. It is advisable to remove these mobile tissues because the underlying bony ridge is usually knife edged. These tissues act as a cushion and rarely impinge upon the interocclusal space.
 Mobile tissues

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