Setting Teeth for RPD

Question 1

what is the aim when setting artificial teeth for partial dentures

Answer 1

to have the teeth set in a position that will complement the existing teeth
restore the arch, aesthetics and function

Question 2

what is the benefit of achieving the aims of setting artificial teeth for partial dentures

Answer 2

• improve patient self confidence

- protect denture privacy

Question 3

is there a difference when setting teeth for a CoCr base or a PMMA base?

Answer 3

no difference

although or CoCr bases the scheme for mechanical retention for the PMMA to metal base must be considered
(post or mesh depending on available space)

Question 4

what is involved in setting teeth for RPD

Answer 4

• choosing artificial teeth
• matching these to the natural teeth
• customising artificial teeth
• setting teeth to the exisiting dentition
• trial dentures

Question 5

what material are artificial teeth made out of

Answer 5

• acrylic (most popular)

- porcelain

Question 6

what are the properties of plastic / acrylic teeth

Answer 6

• chemical bond with the denture base
• natural appearance and silent in function
• tough
• soft (low abrasion resistance)
• easily trimmed and polished / customised
• cold flow under pressure
• insoluble in mouth fluids, some dimensional change

Question 7

what are the properties of porcelain

Answer 7

• mechanical attachment with the denture base (silance coupling agent, no chemical bond, anterior teeth have a metal pin for mechanical retention)
• natural appearance
• noise in function
• brittle
• friable (grinding removes surface glaze)
• hard (high resistance to abrasion but will wear down opposing dentition)
• inert in mouth fluids (no dimensional changes)
• high heat distortion (no permanent deformation under forces of mastication)
• nightmare to trim down

Question 8

what are the properties of modified acrylic / composite / polymers

Answer 8

• chemical bond with denture bond
• partial bonding - recommended mechanical and / or bonding agent (4-meta)
• higher abrasion resistance

Question 9

what is something that you must do in clinic that cannot be achieved in the lab

Answer 9

matching shade of the artificial teeth to the natural teeth
use natural light
difficult to match using a photograph

Question 10

what information should be taken from a tooth / mould chart

Answer 10

- shape of tooth 
> square
> ovoid
> tapered
- length of anterior teeth
- height of central incisor
- width of central incisor

Question 11

how do acrylic teeth bond to the denture base

Answer 11

chemical bond

Question 12

how do porcelain teeth bond to the denture base

Answer 12

mechanical bond provided by a metal retention pin incorporated within the tooth on anterior teeth
posterior teeth have a hallowed area that will fill with the denture base

Question 13

what happens when the space available on the edentulous saddle is smaller than the width of the remaining teeth

Answer 13

this will necessitate a compromise for setting teeth

Question 14

how should the tooth mould be adjusted

Answer 14

remove from the ridge lap
> removal from the length of the root ie the cervical margin or the incisal top can affect the shape
> trimming incisal edge can make it look square and unnnatural
> important to trim from the back

Question 15

the more the ridge lap is reduced, what happens

Answer 15

the less bonding area is available
the softer bonding area if reduced can affect the bond with the enamel layer having a harder surface
can be more easily broken off

Question 16

what can be done to prevent tooth de-bonding

Answer 16

• trim teeth with diamond cutters
• use a post for retention when space is limited for PMMA
• ensure no wax or grease on teeth surface
• no mould seal present when processing
• try to avoid heavy contact on the denture teeth (cuspal interference)
• no wax or grease
• no mould seal
• add a drop of monomer onto before acrylic

Question 17

why can holes be found in a denture base

Answer 17

to assist with retention

Question 18

is overlapping teeth in a denture always a bad thing

Answer 18

no
sometimes it isn’t when completing irregular work
overlapping can create a more natural looking denture when creating the dental arch

Question 19

what is correct with regards to setting a lateral

Answer 19

the lateral should be within the arch

the lateral should not overlap the central outside the arch

Question 20

what is correct in the emergence profile: sagittal view

Answer 20

the central is in line with the natural tooth

the central should not protrude beyond the natural tooth

Question 21

what is the occlusion: natural tooth guidance

Answer 21

• 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 the tooth guidance using the canine teeth or groups of teeth such as premolars

Question 22

what is the denture base like at the trial denture stage

Answer 22

a temporary base that will be discarded at the processing stage of denture production

• a rigid base with wax saddle
• light cured acrylic or shellac
• a trial to establish tooth positioning / finishing lines may be used for cobalt chromium then teeth are positioned onto the CoCr base once constructed for trial
• duplicate cast or master cast blocked out with plaster
• positive fit on cast
• clasps may be incorporated if required

Question 23

how can you provide symmetry to the appearance

Answer 23

• set teeth to the long axis of the corresponding tooth

- contact points should also correspond to the natural dentition

Question 24

what should be adjusted chairside

Answer 24

final adjustment of tooth length
if the denture is not tooth supported some movement is to be expected
can be an advantage to set teeth chairside