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Prostho > 5. Impressions > Flashcards

5. Impressions Flashcards

1
Q

Define impression

A
  • A negative likeness or copy in reverse of the surface of an object
  • an imprint of the teeth and
    adjacent structures for use in dentistry
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2
Q

Aim of every impression?

A

to obtain a cast (positive) by pouring plaster into the impression (negative) that mimics the oral tissues

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3
Q

Can you get a good cast from a bad impression?

A

no

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4
Q

Impressions: tissues must be in good condition, both underlying bone and gingiva because…? (2)

A
  • For stability reasons.

- For easiness of impression taking

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5
Q

How long does bone take to heal completely after extraction?

A

6-9 months

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6
Q

What happens to bone after extraction? (2)

A
  • new bone created into extraction socket

- alveolar ridge has to be remodeled so it is stable over time

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7
Q

A prosthesis wont fit if the treatment for a complete denture occurs before…

A

6-9 months and bone remodeling

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8
Q

What are the options if a complete denture has to be done before 9 months? (4)

A
  • Carry out an immediate complete denture
  • Carry out an interim complete denture
  • Use a previous removable partial denture
  • Carry out a final complete denture right after soft tissue healing
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9
Q

Before 9 months of healing, what occurs for an immediate complete denture? disadvantages? (4)

A
  • Impressions taken before extraction, and remaining teeth are removed from cast.
  • This denture is worn for 9 months.
  • Afterwards, a final prosthesis is done.
  • Disadvantage: cost of two dentures.
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10
Q

Before 9 months of healing, what occurs for an interim complete denture? disadvantages (4)

A
  • Impressions taken right after soft tissues have healed (2-4 weeks).
  • This denture is worn for 9 months.
  • Afterwards, a final prosthesis is done.
  • Disadvantage: cost of two dentures.
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11
Q

Before 9 months of healing, what occurs for using a previous removable partial denture? (3)

A

• Convert it into an interim complete denture after
teeth extraction.
• Wear it for 9 months.
• Do a final complete denture after that.

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12
Q

Before 9 months of healing, what occurs for carrying out a final complete denture right after soft tissue healing?

A

-reline it 9 months afterwards

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13
Q

In case the patient hasn’t got teeth and he/she lost

them more than 9 months ago: (2)

A
  • The complete denture can be carried out right away.

* Condition of the supporting mucosa has to be previously assessed.

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14
Q

What can you find when assessing the mucosa for dentures?

A
  • Prosthetic candidiasis
  • Epulis fissuratum (connective tissue hyperplasia)
  • Traumatic ulcers.
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15
Q

How do we treat prosthetic candidiasis?

A

500.000 IU (5 ml) of Mycostatin 2-4 times a day for 2 weeks

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16
Q

How do we treat epulis fissuartum?

A

Surgical treatment and wait one month until complete healing

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17
Q

How do we treat traumatic ulcers? (2)

A
  • Due to former denture.

- Remove denture for a week, and then take impressions

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18
Q

What are the different types of impressions? (2)

A

• Anatomical impressions. • Functional impressions.

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19
Q

Whats another name for anatomic impressions? (2)

A
  • mucostatic

- non-pressure

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20
Q

What material is an anatomical impressions preformed with?

A

alginate

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21
Q

What do anatomical impressions reproduce?

A
  • the mucosa at rest, not under functional load
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22
Q

Describe what happens during anatomic impressions regarding load and muscles (3)

A
  • No functional load over supporting tissues during impression (mastication, deglutition…)
  • No perioral muscle activity
  • Minimal deformation due to the pressure done by
    the impression material
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23
Q

What allows a denture to stay put when the mouth is open? (2)

A
  • Base fit (adhesion and cohesion)

- Adequate extension of denture base

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24
Q

Should there be contact between dentures when the mouth is open?

A

no

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25
Q

What allows a denture to stay put when the mouth is closed?

A

balanced articulation

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26
Q

Why is alginate a good material for anatomic impressions? (2)

A
  • Alginate doesn’t exert pressure upon the tissues. - Flows well up to surrounding tissues.
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27
Q

What impression trays do we use for anatomical impressions?

A

Standard dentate

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28
Q

Anatomic impressions: Why do we get overextended impressions? (2)

A
  • Alginate flows further away than in functional conditions.

- Bottom of the vestibule is reached, as opposed to functional impressions

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29
Q

What are the indications for anatomical impressions? (2)

A

Good prognosis dentures:
• Wide alveolar ridges (Crespi class I & II) » retention.
• Homogenous and firm attached gingiva.

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30
Q

Where is the denture bases extended to in the cast?

A

mucogingival junction

corrected in mouth of patient

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31
Q

Whats another name for functional impressions?

A

Mucodynamic impression

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32
Q

Define functional impression:

A

seek the reproduction of the tissues at function, not at rest

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33
Q

Functional impression denture base?

A

must not extend to the area where muscles move the mucosa

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34
Q

What does a functional impression capture? (2)

A
  • Functional area of orofacial muscles by performing movements while taking the impression.
  • Orofacial muscles mark off the limits of the denture base.
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35
Q

Types of functional impressions? (3)

A
  • without pressure
  • with pressure
  • with selective pressure
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36
Q

What is a functional impression without pressure? (3)

A
  • The best type of functional impressions.

* Only minimal deformation of tissues due to the pressure done by the impression material

37
Q

What material do we use for a functional impression without pressure? (2)

A

zinquenolic paste or light body silicone

38
Q

What is a functional impressions with pressure? (2)

A

• The final impression is taken with a record base
with artificial teeth mounted on it.
• It records the mucosa under occlusal load.

39
Q

Why is a functional impression with pressure a bad idea? (2)

A
  • Mucosa may suffer a bedsore (decubitus ulcer).

- Denture may lose retention, because tight mucosa will try to throw it out at rest.

40
Q

What is a functional impressions with selective pressure (2)

A
  • Exert more pressure at the areas that can bear it better while biting.
  • It is achieved by the Boucher’s technique, preparing custom trays specially.
41
Q

Why is a functional impression with selective pressure a bad idea? (2)

A
  • Mucosa may suffer a bedsore (decubitus ulcer).

- Denture may lose retention, because tight mucosa will try to throw it out at rest.

42
Q

Objective of a function impression? (2)

A
  1. To exactly determine the limits of the denture

2. Achieve a good border seal of the denture.

43
Q

How is the limit of the denture in a function impression achieved? advantages? (3)

A
  • Achieved by modeling the functional edge of the denture and moving the mobile tissues during the impression.
  • Usually possible to obtain bases extended 1-2 mm more than with mucostatic impressions.
  • It enhances support, retention and stability
44
Q

How do you achieve a good border seal with a functional impression? (3)

A
  • The edge of the denture will extend up to the bottom of the vestibule of the functionally modeled impression (and therefore, of the cast).
  • The edge will fit the mobile mucosa, thus improving border seal.
  • This will also enhance retention and stability.
45
Q

How are functional impressions made? (4)

A
  • With custom trays with its borders functionally modeled (generally with godiva).
  • Godiva is a thermoplastic rigid impression material.
  • Impression material with good creeping capability, like zinquenolic paste or addition silicone.
  • When taking the impression, we make the patient move his/her orofacial muscles, so border structures move.
46
Q

Where should the denture be extended to in a functional impression? (4)

A
  • Achieve maximum extension of the denture.
  • Extension should be within the limits marked off by function of orofacial muscles.
  • Extension up to mobile mucosa.
  • Health of supporting tissues and surrounding structures must be preserved
47
Q

Indications for functional impressions? (4)

A

• In bad prognosis dentures:
- Size and shape of residual ridges (Crespi class III and IV), specially at the mandible.
- Soft and mobile attached gingiva.
• Higher base extension partially compensates this problems

48
Q

What materials are used for impressions? (4)

A
  • Alginate.
  • Low melting point godiva.
  • Zinquenolic paste.
  • Light-body addition silicone
49
Q

Alginate properties? (5)

A
  • Irreversible hydrocolloid.
  • Good elesticity.
  • Bad dimensional stability.
  • Impression must be cast before 10 minutes.
  • most widely used for complete dentures
50
Q

Low melting point godiva properties? (4)

A
  • Melts at 45-50C.
  • Used in bars.
  • Applied at the border of custom trays to functionalize impressions and improve border seal.
  • Heated with an alcohol or gas lamp, then immersed in 50C water before carried into the mouth.
51
Q

Zinquenolic paste properties? (5)

A
  • Paste-to-paste zinc oxide eugenol (ZOE).
  • Very accurate impression material.
  • Good creeping capability.
  • Rigid, so it can get fractured if there are undercuts.
  • It is used with custom trays without separator and without adhesive
52
Q

Light body addition silicone properties? (3)

A
  • Very elastic, so it performs well if there are undercuts.
  • Good dimensional stability.
  • It is used with custom trays with separator (2mm) and adhesive.
53
Q

Common impression instruments? (4)

A
  • Mouth mirror.
  • Gauzes (to dry the palate). - Suction.
  • Air syringe.
54
Q

Impression trays for impressions? (2)

A
  • Standard trays: stainless steel. Rim-lock retention system.
  • Acrylic custom trays
55
Q

Custom trays previously a _________ must be taken (4 words)

A

standard tray alginate impression

56
Q

Custom trays for functional impressions use… (2)?

A

zinquenolic paste or addition silicone

57
Q

Separators for Custom trays for functional impressions? (2)

A
  • No separator: for zinquenolic paste.

- 2 mm separator: for silicones.

58
Q

Minimum thickness for custom tray?

A

2mm (tough and rigid)

59
Q

Do custom trays have to be heat resistant? why?

A

yes to withstand heat from godiva

60
Q

Custom trays and handles must not…

A

interfere with lip movements

61
Q

Customs trays must be made with..? Specifically? (3)

A

biocompatible material:

  • Acrylic resin (best option b/c tougher)
  • Truwax®
62
Q

Where should the patients mouth be for impressions?

A

At the height of the elbow of the dentist

63
Q

Should we smooth the surface of alginate with a wet finger?

A

no

64
Q

How thick should the impression material be?

A

5-6mm

65
Q

How do we take impressions of nausea-easy patients?

A

topical anaesthetic over the palate

66
Q

Silicone impressions need adhesive. true or false?

A

true

67
Q

Can you put some alginate with your finger when taking an impression? why?

A

Yes if there are areas difficult to access

68
Q

How do you insert a tray for impressions? (3)

A

◦ Vertically.
◦ Upper tray: from back to front.
◦ Lower: from front to back.

69
Q

Where should the tray be in relation to the teeth when taking an impression?

A

5mm ahead of the teeth

70
Q

Should alginate be seen behind the tray when taking impressions?

A

yes

71
Q

Should the patient raise their tongue when taking impressions?

A

yes

72
Q

How do we detach the tray when taking impressions? (4)

A
  • Firmly.
  • Vertically.
  • No lateral movements.
  • With a singe movement
73
Q

Why do we reject impressions? (5)

A 
- Perforated (tray is seen
through)
-  Bubbles.
- Drags.
- Undefined areas. 
- Not enough extension.
74
Q

Impression management? (4)

A
  • Plaster wash (not for zinquenolic paste and
    silicone impressions).
  • Gentle drying.
75
Q

When should impression casting? (5)

A
  • Alginate: before 10 min after being taken.
  • Zinquenolic paste and silicones don’t require immediate casting.
  • Trimming of unsupported areas of the impression or areas that would touch the resting surface.
  • from deeper areas to shallower areas
  • moisture chamber for 45-60 mins
76
Q

FUNCTIONAL IMPRESSION PROCEDURE custom tray preparation? (3)

A
  • Acrylic resin.
  • Without separator for zinquenolic paste.
  • With 2 mm separator for silicone
77
Q

FUNCTIONAL IMPRESSION PROCEDURE tray fitting? (2)

A
  • Trimming of tray edges: up to functional line.

* Check that under orofacial muscle activity tray is not detached

78
Q

FUNCTIONAL IMPRESSION PROCEDURE What must be done during the upper tray try in? (4)

A
  • Pull lips and cheek.
  • Perform lateral mandibular movements to check
    space for coronoid process.
  • Open mouth to check space for hamular
    notches.
  • Say letters A, K, G for vibrating line
79
Q

FUNCTIONAL IMPRESSION PROCEDURE What must be done during the lower tray try in? (3)

A
  • Pull lips and cheek.
  • Move tongue up, forth and laterally.
  • Open the mouth to check space for
    pterygomandibular ligament.
80
Q

FUNCTIONAL IMPRESSION PROCEDURE Modelling of tray borders? (3)

A
  • With low melting point godiva.
  • Same manouvers as when checking the tray.
  • Sector by sector.
81
Q

FUNCTIONAL IMPRESSION PROCEDURE what do we use for the final impression? (2)

A

• Zinquenolic paste or light body silicone

82
Q

FUNCTIONAL IMPRESSION PROCEDURE final impression and pressure? movements?

A
  • Press until no more impression material pours out of the holes (mild to no pressure)
  • Make functional movements again
83
Q

FUNCTIONAL IMPRESSION PROCEDURE how long does it take to set completely?

A

5-6min

84
Q

Functional impression objective: (2)

A
  • To record the tissues without pressure.

- Find the borders of the mobile mucosa

85
Q

Functional impression deepest point?

A

deepest point of the vestibule is where mucosa starts moving while in function.

86
Q

Functional impression ideal extension?

A

Base plates will extent up to bottom of vestibule of the cast

87
Q

When do we get the final extension of the record base for anatomical impressions? (2)

A
  • limit of record base is drawn in the cast

- final extension is at the occlusion tim try in appointment

88
Q

Do functional impressions have border seals?

A

Have a good border seal

Prostho (17 decks)

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