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DMD2 sem 2 > Impression and Tissue Management > Flashcards

Impression and Tissue Management Flashcards

1
Q

Why are impressions taken?

A

Restorations that can fit exactly are:

More efficient and faster working

Aid periodontal prophylaxis and prevent caries

Are aesthetic

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2
Q

What is the aim of an impression?

A

Produce a dimensionally stable “negative” that can serve as the mould for a model or be scanned

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3
Q

What are the objectives of a definitive secondary impression?

A

Exact duplication of the prepared and uncut tooth beyond the preparation to allow evaluation of location and configuration of finishing line

Duplicate other teeth and soft tissue to permit proper articulation of the cast and controuing the restoration

Must be free of bubbles specially at finishing line and prepared surface

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4
Q

What are the prerequisites of a impression/scanning?

A

Tissue management

Gingival tissue displacement if needed

Saliva control

Adequate impression/scanning technique

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5
Q

What can of tissue management needs to be done for impression/scanning?

A

Careful preparation (Hard tissue/soft tissue)

Atraumatic procedure

Well-contoured provisional restoration

Adequate oral hygiene

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6
Q

What should the tooth preparation look like for adequate tissue management?

A

Supragingival margins is possible

Minimally subgingival or intracrevicular if not possible to be supragingival

Well-defined, smooth and continuous margins

Well-finished and tidy preparation

Atraumatic to gingival tissues

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7
Q

What is the maximal subgingival depth allowed if preparation is subgingival?

A

Maximum around 0.7mm

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8
Q

Why are subgingival margins such a bad idea?

A

Defective margins

Inaccurate fit

Roughness of the tooth-restoration interface

Improper crown contour

Violation of the connective tissue attachment

Greater pathogenicity of the subgingival dental plaque

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9
Q

Why is the gingiva displaced for a crown prep?

A

Enlargement of the gingival sulcus

Tissue deflection horizontally and vertically to displace the margin and root surface. (Finishing line for the restoration and development of adequate emergence profile)

Control of gingival bleeding and exudate

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10
Q

What are the methods of gingival displacement?

A

Mechanical displacement:

Retraction cord

Copper band

Surgical widening:

Electrosurgery

Laser

Chemicals:

Astringent (Aluminum chloride, ferric sulfate)

Adrenaline (Transient ischaemia and epithelial tissue shrinkage)

Combined:

Retraction cord + Chemical

Expasyl (Kerr)

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11
Q

How does the copper band work?

A

It is placed around the tooth within the gingival sulcus thus spreading the sulcus outwards

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12
Q

How does the retraction cord work?

A

Cord is packed into the sulcus stretching the circumferential periodontal fibers 0.3 - 0.4mm

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13
Q

What are the types of retraction cords?

A

Braided

Twisted

Knitted

Medicated and nonmedicated

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14
Q

How is a retraction cord placed?

A

Using a cord packers (Can be serated or non-serrated)

Using 2 instruments it is pushed in

Leave the cords in place 3 to 5 minutes.

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15
Q

How many cords are placed into the gingival sulcus?

A

Can be a single or double cord

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16
Q

What is the function of the double cord?

A

Primary cord is important for vertical retraction and secondary cord for horizontal displacement

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17
Q

What are the indications for a single cord?

A

Shallow sulcus

Thin periodontium

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18
Q

What are the indications of double cord?

A

Thick periodontium

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19
Q

What are the advantages and disadvantages of single cord?

A

Advantages:

Least traumatic

Little potential for gingival recession

Disadvantages:

Haemorrhage and exudate

20
Q

What are the advantages and disadvantages of using double cord?

A

Advantages:

Control of bleeding

Excellent lateral displacement

Disadvantages:

Time consuming

Potentially traumatic

Least predictable gingival response

21
Q

How is surgical widening done?

A

Remove the inner epithelial lining to get better access to the finish line and control haemorrhage

22
Q

What should practitioners be careful of when using surgical widening?

A

Risk of permanent damage to gingiva (recession)

Avoid for thin gingiva

23
Q

What are the methods of surgical widening?

A

Electrosurgery and laser

24
Q

What are the advantages and disadvantages of surgical widening with electrosurgery?

A

Advantages:

Lower cost than lasers

Electrosurgery cuts extremely rapidly when compared to a diode laser

When on the proper setting homeostasis is almost immediate

After curring the wound is nearly painless

25
Q

What are the disadvantages of surgical widening with electrosurgery?

A

Contraindicated in patients with any electrical device

You must anaesthetize patients

Burning smell

Risk of overcutting

Because of high heat production while cutting, electrosurgery should not be used around implants

26
Q

What are the advantages of surgical widening with laser?

A

Minimal LA needed

Does not harm dental tissue

Can be used around implants

Can be used around full metal, PFM crowns, amalgam or gold alloy restorations

27
Q

What are the disadvantages of surgical widening with laser?

A

Cost

Cuts much slower than electrosurgery

Cutting large pieces of soft tissue is time consuming

Danger of laser beam

28
Q

What are the issues with chemical displacement?

A

Causing transient ischaemia

Shrinkage of gingival tissues

Reduce flow of gingival fluids

Adrenaline can cause tachycardia so other medications are preferred

29
Q

What are some examples of chemical displacement agents?

A

Aluminum chloride

Aluminum sulfate

Potassium sulfate

Ferric chloride

Ferric sulfate

30
Q

What combination is commonly used for tissue retraction?

A

Retraction chord + astringents

31
Q

What is contained in expasyl?

A

Combination of aluminum chloride and kaolin

32
Q

What is contained in traxodent?

A

Aluminum chloride paste

33
Q

How is saliva control achieved?

A

Absorbents block salivary ducts (eg cotton rolls and absorbing cards)

Saliva evacuator

LA (Controls blood and saliva)

Anticholinergic meds

34
Q

How must gingival tissues be treated to achieve a good impression? Why is this important?

A

Gingival health must be achieved before embarking on definitive impressions

If gingiva isn’t healthy it is impossible to prepare a predictable intracrevicular margin.

Impressions are difficult due to uncontrollable haemorrhage

As soon as periodontal resolution occurs there will be recession

35
Q

What materials are used for impressions?

A

Monophase (medium body) = polyether

Multiphase (heavy body and light body) = Polyvinyl siloxane

36
Q

What are the important keys to correct impression technique?

A

Adequate manipulation of the material

Proper thickness of the material

Proper pressure applying during impression making

37
Q

What is the purpose of an intraoral custom tray try in?

A

Check for clearance and comfort

To adjust if required

38
Q

How long must the adhesive be applied to impression tray before the impression?

A

15 minutes

39
Q

What are the steps to gingival displacement with retraction cord and astringent?

A

Isolate prepared teeth

Cut sufficient cord length

Soak cord in astringent

Loop the cord around the tooth and gently insert it into the sulcus

Avoid overpacking

Dry the teeth (do not dessicate)

Evaluation (Visualize all the margins of the preparation, no soft tissue folding on the cord)

40
Q

How is impression material mixed?

A

If using “cartridge” system extrude a little impression material at first ensuring an even mix of material and no blockage in the cartridge

Addition silicone: base and catalyst are mixed

41
Q

How much base and catalyst should be used for addition silicone?

A

Equal amounts of base and catalyst

42
Q

How should the tray be loaded?

A

Load tray such that impression material is slightly below the lip of the tray

Apply light body material around the prep and load the tray with heavy body material

Light bodied material should be applied intraorally after 10 - 15 seconds of removing cord and assessing gingival tissues

Inject the material slowly around the preparation margins. The tip shold follow the material and continue in one direction staying close to the sulcus

Once the sulcus is filled continue over the rest of the tooth

Gently air blow the material

43
Q

How should tray be inserted?

A

Position the tray first into the mouth

Clear lips from the tray

Using one continuous motion seat tray until resistance stops

44
Q

How should the tray be removed?

A

Hold the tray in the mouth until the impresison is set and remove in one fluid movement

Optimum removal of impression tray for upper jaw is to loosen tray on opposing side

Optimum removal of impression from lower jaw is loosening tray on prep side.

Finger and air stream should be used together to loosen impression

45
Q

What should be inspected after taking an impression?

A

All gingival margins should be clear and defined

Uniform layer of material

Detailed with accurate occlusal surfaces

Distal surfaces of molars are captured

46
Q

What should not be present on a successful impression?

A

No bubbles, voids, thin walls, shifts, or double imprints that compomise dental anatomy.

DMD2 sem 2 (97 decks)

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