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BDS2 CDS Prosthodontics Removable > Setting teeth for RPD > Flashcards

Setting teeth for RPD Flashcards

1
Q

aim when for setting teeth for RPD

A

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.

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2
Q

impact on patient if aim of setting teeth achieved

A

will greatly improve patient self-confidence and protect their ‘denture privacy’

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3
Q

point to remember when setting teeth for CoCr base

A

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)

CoCr is setting directly over free end saddles – can impact
- May need to reduce the acrylic teeth to accommodate

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4
Q

how can artificial teeth be selected to look natural?

A

Not set to perfect, slightly irregular, shade and tone varies to hide false teeth

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5
Q

2 types of artificial teeth material

A

acrylic and procelain

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6
Q

most popular artificial teeth material

A

acrylic

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7
Q

what are tooth cards used for

A

to choose shade of acrylic artificial teeth

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8
Q

properties of plastic acrylic teeth

A

Chemical bond with the denture base
- Only processed 50% and then rest when finalising so better bond

Natural appearance

Silent in function

tough
- 5 year durance

Soft-low abrasion resistance

Easily trimmed and polished/customised

Cold flow under pressure

Insoluble in mouth fluids-some dimensional change

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9
Q

bonding of acrylic teeth

A

teeth bond chemically with the PMMA denture based – this is an important

consideration but attention must be paid to the removal of the tooth bond layer (cross-lining).

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10
Q

what do acrylic teeth look like

A

natural

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11
Q

advantage of acrylic teeth being easily trimmed

A

can be customised

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12
Q

are acrylic teeth hard wearing?

A

only best quality

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13
Q

properties of porcelain teeth

A

Mechanical attachment with the denture base. (silane coupling agent)
- No chemical bond at all
Anterior teeth – metal pin on back, mechanical retention
Posterior – hollow area
Natural Appearance

Make noise when bite potentially

Brittle

Friable
- grinding removes surface glaze

Hard-high resistance to abrasion
- Wear down opposing dentition

Inert in mouth fluids-no dimensional change

High heat distortion
- no permanent deformation under forces of mastication

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14
Q

how are anterior porcelain teeth attached?

A

mechanically attached, by metal pins in anterior teeth

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15
Q

how are posterior porcelain teeth attached

A

mechanically attached, by holes (diatorics) manufactured into posterior teeth.

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16
Q

can porcelain teeth be easily customised?

A

no - cannot trim the ridge lap area or polished surface which therefore normally precludes their use.

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17
Q

is porcelain hard wearing

A

yes - very

in some cases would not be recommended for occlusion opposing natural teeth because of this hardness.

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18
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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19
Q

what are mould charts used for

A

to select mould or shape of tooth

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20
Q

how to choose mould/shape of tooth from mould chart

A

copy what the patient already has

technician may override choice if they see a problem with your chosen mould

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21
Q

where should shade selection be carried out

A

in clinic

under natural light - hard to match under unnatural light

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22
Q

advantage and disadvantage of better designed acyclic teeth

A

more expensive

but more natural looking – see mamelons through incisor tip

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23
Q

3 common tooth shapes

A

square
ovoid
tapered

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24
Q

4 bits of information from the tooth/mould chart

A

square, ovoid and tapered are most commonly used shapes

length of anterior teeth - two dimensional

  • length of canine to canine
  • length of central incisor

width of central incisor

25
Q

what must be considered when selecting tooth mould

A

angulation guidance of cusps

high cusps – impact on contact, unstable denture during function

higher cuspal angle – can be better for mastication for molars

26
Q

what often dictates where teeth are set when making a partial denture

A

the arrangement and position of remaining natural teeth

firstly, re-establish midline (central incisor) and compromise around that

27
Q

why understanding the material that is used to make RPDs is important

A

impact clinical decision

  • communicate well with other team members
  • good knowledge can ensure you are comfortable with treatment plan
28
Q

why may you need to compromise when setting teeth

A

available space
(e.g. accomodate central and lateral in smaller space than naturally be)

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

29
Q

why would a larger mould be chosen for a tooth

A

to allow customisation

30
Q

what can customisation effect

A

the denture base and tooth bond

31
Q

where should artificial teeth be trimmed from

A

remove from the ridge lap
- Trim from the back

Removal from the length of the tooth, i.e. the cervical margin or the incisal tip can affect the shade.

32
Q

why shouldn’t tooth be trimmed from incisal edge

A

too thin, tooth becomes thick and square looking

33
Q

how much tooth should be trimmed

A

small bit at a time till fits the mucosa

34
Q

what effect does removing tooth have on the bond

A

The more reduced the less chemical bond with denture base – more veneer like

Easily broken off

Too much trimming can look unnatural

35
Q

what is the ridge lap in artificial teeth made of

A

more heavily cross linked acrylic

36
Q

why would a tooth need reduced/trimmed

A

to fit a pronounced ridge or if a CoCr base being used

37
Q

the more the ridge lap is reduced….

A

‘softer’ bonding area if reduced in area can affect the bond with the ‘enamel’ layer having a harder surface.

38
Q

how to prevent de-bonding in heat cured dentures

A

Trim teeth with diamond cutters
- Produce a rougher, abraded surface (micro-abrasion)

Use a post for retention when space is limited for PMMA
- Ensure no wax or grease on teeth surface
- Use detergent when boiling out
- Remove as creates a barrier – less sticky
No mould seal residue present when processing

39
Q

how to prevent de-bonding in self-cured dentures

A

Try to avoid heavy contact on the denture teeth – cuspal interference
- Not fully processed – soft
Cold cure
- Not fully set – easy to adapt (used for CoCr)

No wax or grease
- Use detergent when boiling out (removing wax from the flask)

No mould seal

Add a drop of monomer onto tooth surface and allow to soak in before acrylic (self cure PMMA)

40
Q

where to look when considering removing tooth surface

A

in 3 dimensions (occlusal, frontal and sagittal view)

accommodate the dental arch firstly

41
Q

what can overlap do

A

disguise falseness

42
Q

how should teeth sit in correspondence with arch

A

in line with arch

survey line determines the extension of the flange

43
Q

what does the survey line determine

A

the extension of the flange

44
Q

why is not advisable to have large areas blocked out

A

therefore creating ‘dead spaces’ and resulting food impaction.
- Don’t want acrylic to enter the undercut

45
Q

how far should tooth protrude in sagittal view

A

not too far, should blend into surrounding teeth

be careful as neck of tooth can protrude when incisal tip isn’t

46
Q

what will articulator show

A

lateral excursion

check guidance - important when setting teeth

47
Q

what should be checked in relation to guidance

A

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 if teeth are going to collide with lower incisors
  • Glides over, no premature contact (can break off)
48
Q

when is the denture base used

A

for the trail denture stage (and occlusal rim stage)

49
Q

what is the denture base

A

trial, temporary base which is discarded at the processing stage of denture production

50
Q

types of denture base

A

rigid base with wax saddle

light cured, acylic or shellac

51
Q

CoCr trial uses

A

lines which teeth are positioned to once CoCr base constructed for trial
- trial done in wax to see if any problems arise before making CoCr

52
Q

what cast is used for the trial

A

duplicate cast or master cast

  • trial should have positive fit
  • clasps can be incorporated if required
53
Q

why is light cure material not the best idea for tooth trial

A

wax can stick

54
Q

how to provide symmetry to the appearance

A

set teeth to long axis

slight angulation maybe to correspond so symmetry maintained (mirror image of arch)

contact points should also correspond to natural dentition

55
Q

what compromise/improvisation may be necessary for setting posterior teeth

A

May not conform to the classical arrangement of teeth
- Depends on the available space
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.
Needs to follow the natural tooth guidance

56
Q

where should the final adjustment of tooth length be

A

at chair-side if the denture is not tooth supported - some movement might be expected

57
Q

why is it an advantage for the dentist to set teeth at chair-side

A

less time, less visits

lab may leave incisal tip longer
- so dentist can match ideally chairside

58
Q

how can the flange effect the position of the denture

A

fills space

nothing else may fit there

BDS2 CDS Prosthodontics Removable (10 decks)

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