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BDS2 Prosthodontics (removable) > Setting teeth > Flashcards

Setting teeth Flashcards

1
Q

What is the aim of setting teeth

A

The aim when setting artificial teeth for partial dentures is to have the teeth set in a position that will complement the existing teeth, thus restoring the arch, aesthetics and function.

If these aims can be accomplished it will greatly improve patient self-confidence and protect their ‘denture privacy’

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2
Q

Is there any difference between setting teeth for cobolt chrome or a PMMA base?

A

no
n.b. Although for cobalt chromium bases the scheme for mechanical retention for the PMMA to metal base must be considered. (post or mesh depending on available space)

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3
Q

What different materials can artificial teeth take?

A

acrylic

porcelain

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4
Q

what is the most popular material for artificial teeth for RPDs

A

Polymethyl methacrylate acrylic (PMMA) resin

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5
Q

Properties of plastic/acrylic teeth

A
  • Chemical bond with the denture base
  • Natural appearance and feel-silent in function
  • Tough
  • Soft-low abrasion resistance
  • Easily trimmed and polished/customised
  • Cold flow under pressure
  • Insoluble in mouth fluids-some dimensional change
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6
Q

Properties of porcelain teeth

A
  • Mechanical attachment with the denture base. (silane coupling agent)
  • Natural appearance-possible noise in function
  • Brittle
  • Friable -grinding removes surface glaze
  • Hard-high resistance to abrasion
  • Inert in mouth fluids-no dimensional change
  • High heat distortion-no permanent deformation under forces of mastication
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7
Q

Properties of modified acrylic/composite/polymers

A
  • Chemical bond with the denture base.
  • Partial bonding - recommended mechanical and / or bonding agent (4-meta)
  • Higher abrasion resistance
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8
Q

An example of software to help you choose teeth moulds and shade guides?

A

enigma

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9
Q

What things do you have to do when setting teeth

A
  • choosing the material of artificial teeth
  • choose an appropriate tooth mould (size)
  • customise artificial teeth/ adjustments (shade)
  • set teeth considering aesthetics and function
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10
Q

What information do we need from the tooth mould chart?

A
  • shape of tooth (square, ovoid, tapered)
  • length of anterior teeth
  • height of central incisor
  • width of central incisor
  • function and design
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11
Q

How do acrylic teeth bond to the denture base

A

chemically

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12
Q

How do porcelain teeth bond to the denture base

A

mechanically

via a metal retention pin incorporated within the tooth on anterior teeth

via a hollowed area that will fill with the denture base on posterior teeth

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13
Q

what is setting teeth often dictated by

A

the arrangement and position of the remaining natural teeth

teeth cannot be set without considering blocking out for the insertion of the denture (?)

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14
Q

What is a common reason for compromise when setting teeth

A

tooth loss may also involve tooth drifting and change in available space to set the artificial teeth

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15
Q

What are the 3 types of tooth shape?

A

tapered
ovoid
square

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16
Q

how can we accomodate for the fact that partical dentures frequently require customising

A

choosing a larger mould

17
Q

why should you not adjust the tooth mould from the incisal tip/cervical margin

A

can affect the shade

18
Q

where should you adjust the tooth mould from

A

the ridge lap

19
Q

How can debonding occur

A

during the preparation of artificial teeth when setting the teeth for trial

The more the ridge lap is reduced the less bonding area is available.
The ‘softer’ bonding area if reduced in area can affect the bond with the ‘enamel’ layer having a harder surface.

20
Q

how does the ridge lap differ in material from the rest of the artificial tooth

A

Artificial teeth comprise of at least two layers of material; the ridge lap is made up of a more heavily cross-linked acrylic, specifically to bond with the denture base.

21
Q

How do you prevent tooth de-bonding for heat cured dentures (adhesive failure)

A

Grind teeth with DIAMOND cutters to produce a rougher abraded surface (micro-abrasion)
No wax or grease on the tooth surface – use detergent when boiling out (removing the wax from the flask)
Ensure no residue of mould seal on the tooth surface.

22
Q

How do you prevent tooth de-bonding for self cured dentures (cohesive failure)

A

Grind teeth with DIAMOND cutters to produce a rougher abraded surface (micro-abrasion)
No wax or grease on the tooth surface – use detergent when boiling out (removing the wax from the flask)
Ensure no residue of mould seal on the tooth surface.
Add a drop of monomer to the tooth surface and allow to soak into the tooth before addition the self cure PMMA

23
Q

When removing tooth surface, what views should we look at the teeth with

A
  • frontal
  • sagittal
  • occlusal
24
Q

what can we use to ensure teeth are placed correctly in the arch

A

survey lines

25
Q

why is it not advisable to have large areas blocked out

A

creates ‘dead spaces’ resulting in food impaction

26
Q

How can we check occlusion

A
  • the wear facets on the natural teeth should be checked
  • the artificial teeth must conform to the existing tooth surface wear
  • the natural tooth guidance is followed by the artificial teeth
  • check tooth guidance using the canines or groups of teeth e.g. premolars
27
Q

What happens after teeth have been customised?

A

they can be attached to the trial base plate with modelling wax

28
Q

What is a trial denture

A

The denture base for the trial denture stage (and occlusal rim stage) is a temporary base that will be discarded at the processing stage of denture production.

29
Q

What is a trial denture made of

A

Rigid base with wax saddle

Light-cured acrylic or shellac

A trial to establish tooth position/finishing lines may be used for cobalt chromium then teeth are positioned onto the Co Cr base once constructed for trial.

30
Q

How do you provide symmetry to the appearance

A

Set the teeth to the long axis of the corresponding tooth.

Contact points should also correspond to the natural dentition

31
Q

Why do posterior teeth sometimes not conform to the classical arrangement of teeth?

A

The position and occlusion is dictated by the natural teeth. The denture teeth should not be set in contradiction to this guide.

Teeth are set according to the edentulous saddle tooth space.

It is acceptable for example that a premolar is set in a space previously occupied by a molar.

32
Q

Where should the final adjustment of tooth length happen?

A

at chairside

BDS2 Prosthodontics (removable) (9 decks)

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