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Yr 3 Restorative - biomaterials and CSL > Extensive amalgam > Flashcards

Extensive amalgam Flashcards

1
Q

Why do we restore cavities?

A
  • to restore the integrity of the tooth surface
  • to restore the function of the tooth
  • to restore the aesthetics of the tooth
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2
Q

What is an extensive amalgam restoration?

A

= involves rebuilding of cusps and the provision of auxiliary retention (use extra aids for retention)

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3
Q

When are extensive amalgam restorations indicated?

A

= to postpone the placement of cast restorations (less invasive, expensive and time)

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4
Q

What is the average survival time for routine amalgam fillings?

A

10 - 20 years (this is the same for well made extensive amalgam restorations)

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5
Q

How is amalgam retained in a cavity?

A

Undercuts (macro-mechanical retention)

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6
Q

When a cusp has been lost how do we retain an amalgam restoration?

A

There are different routes for amalgam to come out = need extra retention measures

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7
Q

What is retention form?

A

The features of the cavity preventing withdrawal of the restoration in the long axis of the preparation

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8
Q

What is resistance form?

A

The features preventing dislodgement of the restoration under all other forms of loading

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9
Q

What is Auxiliary retention?

A

Supplementary retention required for extensive restorations

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10
Q

What are the different types of Auxiliary retention?

A

Cavity design features

(Dentine) Pins

Adhesives

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11
Q

Which cavity design features can be used so that each part of the cavity is independently retentive?

A

Boxes

Axial grooves

Slots

Pits

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12
Q

What is a slot?

A

A long ditch just inside ADJ = approx 1 mm wide

(pic = occlusal view)

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13
Q

What is an axial groove?

A

Groove just along base of cavity along axial walls = retention from coming out of the side

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14
Q

What is the depth and width of slots and pits?

A

Depth = no greater than 1 mm

Width = little more than the diameter of the instruments used to prepare them

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15
Q

What type of internal form do they have?

A

Sharp internal form = increases stresses within the tooth and material = necessary to provide resistance form

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16
Q

What is the evidence of pins?

A

Lab tests = consistently perform well

Unfortunately the studies do not replicate the clinical situation (quite a lot of damage to a tooth and dangerous in the wrong instance)

17
Q

What are the 3 different types of pin?

A

Cemeneted pins

Friction grip pins

Self-threading pins (most retentive)

18
Q

How do you know how many pins to use?

A
  • 1 pin per missing cusp
  • 1 pin per missing line angle (i.e. mesiobuccal line = those that make up the 3D structure of the tooth)
  • 1 pin per missing proximal surface
19
Q

What is needed for a pin to be placed?

A

Sufficient bulk of HEALTHY dentine (remove caries first)… for self threaded pins:

  • between 1-2 mm inside DEJ/CEJ
  • 2 mm depth into dentine
  • 2 mm depth into amalgam
  • 2 mm from opposing tooth
20
Q

Which diameter pins are more retentive?

A

Larger diameter

21
Q

Why should pins be used with caution?

A
  • They weaken both tooth structure and the restoration
  • Failures in studies = due to fracture
  • 1971 study concluded all pins other than cemented pins caused stresses within the surrounding tooth structure = cracks in dentine and enamel
  • Incorrectly placed pins can perforate into the pulp and periodontal tissues (infection) -> generally placed in the direction of the long axis of the tooth
  • pins placed too close to the pulp will cause post-operative sensitivity
  • pins placed buccally or lingually will be superimposed on the pulp chamber and their angulation in the pulp/periodontal direction cannot be seen radiographically
22
Q

Adhesives containng which materials are used in extensive amalgam restorations?

A
  1. 4META (AmalgamBond)
  2. MDP = Methyacryloyloxydecyl dihydrogen phosphate (Panavia)
23
Q

What are the advantages of using adhesives in extensive amalgam restorations?

A
  • Increase retention
  • Conserve sound tooth structure (no pins or slots needed)
24
Q

What evidence is there for use of adhesives?

A

No evidence reporting a difference in survival between bonded and non bonded amalgam restorations (therefore important to be mindful of the additional costs that may be incurred)

25
Q

In which two ways can restorations fail?

A
  1. New disease (i.e. secondary/recurrent caries)
  2. Technical failure (e.g. fracture, loss of filling etc.)
26
Q

List 4 thing that can cause technical failure:

A
  • Defective contact point = traps food
  • Overhanging restorations = plaque build up = periodontal disease
  • Non retentive cavity
  • Fractured restoration
27
Q

When are teeth susceptible to new pulp problems?

A
  • Heavily restored teeth = liable to pulpal inflammation
  • > pulpal necrosis (sinus develops)

N.b. pulpal necrosis of heavily restored teeth can result from the original disease or the operative procedure used to restore it

28
Q

Where can you get caries on an extensive amalgam restored tooth?

A
  • New disease around existing restoration (secondary/ recurrent caries)
  • At another site on the same tooth
29
Q

What is replacement of a restoration?

A

The complete removal of restoration together with base or lining materials

30
Q

What can replacement of a defective extensive amalgam restoration lead to?

A
  • Inadvertantly removal of sound tooth tissues
  • increase cavity size
  • risk of damage to the dental pulp
  • development of clinical symptoms
31
Q

What is repair of a restoration?

A

Only the defective area of the restoration is removed and replaced

32
Q

What are the advantages of repair over replacement?

A

Repair is…

  • conservative
  • quicker
  • cheaper
  • less traumatic to the patient and the tooth
  • local anaesthesia may not be required
33
Q

There is an absence of any high level reliable evidence on whether repair or replacement is better so the clinician should base their decisions on…

A
  • clinical experience
  • individual circumstances
  • in conjunction with the patients’ preferences where appropriate
34
Q

What is the difference between post and pins?

A

Posts are used more in the interior of teeth (where the tooth is root canal treated = extends into the root)

35
Q

What distance should there be between the base of the pin and the cusps of the opposing tooth?

A

6mm

Yr 3 Restorative - biomaterials and CSL (16 decks)

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