Setting teeth for RPD

Question 1

What is the aim when setting artificial teeth for partial dentures?

Answer 1

set teeth in a position to compliment the existing teeth therefore restoring the arch, aesthetics and function

Question 2

How does setting teeth for a Co/Cr base or a PMMA base differ?

Answer 2

no difference

Question 3

What are the 2 options for the mechanical retention of PMMA to the Co/Cr base?

Answer 3

post or mesh - depends on available space

Question 4

What are the different possible materials for artificial teeth?

Answer 4

acrylic / PMMA (most popular) or porcelain

Question 5

How do posterior tooth moulds for partial dentures differ to posterior tooth moulds for complete dentures?

Answer 5

posterior tooth moulds for partial dentures are generally larger / wider than that for complete dentures

Question 6

How are acrylic teeth bonded to the denture base?

Answer 6

chemical bond

Question 7

How are porcelain teeth bonded to the denture base?

Answer 7

mechanical attachment with denture base (silane coupling agent)

Question 8

How are anterior porcelain teeth mechanically bonded to the denture base?

Answer 8

using a metal retention pin incorporated within the anterior tooth

Question 9

How are posterior porcelain teeth mechanically bonded to the denture base?

Answer 9

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

Question 10

What are the properties of acrylic teeth?

Answer 10

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

Question 11

What are the properties of porcelain teeth?

Answer 11

• mechanical attachment to denture base
• 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)

Question 12

What are the properties of modified acrylic / composite / polymer artificial teeth?

Answer 12

• chemical bond to denture base
• partial bonding - recommended mechanical and / or bonding agent
• higher abrasion resistance

Question 13

How artificial teeth chosen for the patient?

Answer 13

using mould charts and shade guides provided by the tooth manufacturers

Question 14

What does mould mean?

Answer 14

shape and size

Question 15

What is the aim when choosing a mould and shade for the artificial teeth?

Answer 15

conform to natural dentition

Question 16

What external factors must be considered when trying to match the shade of the natural dentition?

Answer 16

lighting - check with natural lighting and the dental light

Question 17

What are the features of more natural-looking acrylic teeth that come at a higher cost?

Answer 17

• darker necks
• canines darker
• internal mamelons
• blue / white opalescence and fluorescence
• demineralisation points

Question 18

What information is provided on a tooth / mould chart?

Answer 18

• shape of tooth (square, ovoid, tapered)
• length of anterior teeth
• height of central incisor
• width of central incisor

Question 19

What is described by the occlusal tooth form?

Answer 19

cuspal angles

Question 20

Why is occlusal tooth form important?

Answer 20

for denture stability (cuspal angles)

Question 21

What cuspal angle should you chose if denture stability is a concern?

Answer 21

a low cusp angle (high cusp angle would cause denture to tilt in function esp during lateral excursions)

Question 22

What cusp angle would you chose for complete dentures?

Answer 22

more flat cusps / cusp angle

Question 23

What cusps are a good option if there are no denture stability concerns?

Answer 23

large cusps (high cusp angle) - easier for patient to break down food during mastication

Question 24

How does the space available on the edentulous saddle compare to the width of the same remaining teeth?

Answer 24

space available on the edentulous saddle is smaller than the width of the remaining teeth due to drifting

Question 25

When are adjustments (customisation) to the tooth mould made?

Answer 25

during setting of teeth for RPDs

Question 26

From what aspect of the artificial tooth should adjustments to the tooth mould be made?

Answer 26

from the ridge lap

Question 27

Why are adjustments to the tooth mould made at the ridge lap?

Answer 27

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

Question 28

What 2 layers of material are artificial teeth comprised of?

Answer 28

'enamel' layer and ridge lap

Question 29

What is the ridge lap layer made of?

Answer 29

a more heavily cross-linked acrylic which specifically bonds with the denture base (chemical bond)

Question 30

What is the risk of reducing the ridge lap?

Answer 30

de-bonding and reduced bond with the 'enamel'

Question 31

Why may the ridge lap require trimming?

Answer 31

to fit a more pronounced ridge / retention area of metal framework

Question 32

What angles should you check to see the 3D view of the set teeth?

Answer 32

frontal (width and length of tooth), sagittal (labial projection), occlusal (conform with natural arch)

Question 33

What determines the extension of the flange?

Answer 33

the survey lines - do not exceed (unless intending to change path of insertion and eliminate undercut)

Question 34

What does the sagittal view during teeth setting show?

Answer 34

the emergence profile (ensure tooth is not protruding beyond natural teeth)

Question 35

In what way may the artificial teeth not match the adjacent natural teeth?

Answer 35

not proportional in size, gingival margins not aligned, tooth angles / axes not in harmony

Question 36

What is a possible solution for an upper saddle with too small of a space for upper teeth?

Answer 36

could use a lower tooth e.g. lower incisor to fill unconventional upper lateral gap

Question 37

How can gaps due to soft tissue / tooth undercuts between the denture saddle and natural dentition be resolved?

Answer 37

- accept this as a compromise - alter path of insertion to mitigate gaps

Question 38

What should you check with regards to wear facets on natural teeth?

Answer 38

ensure artificial teeth conform to existing tooth surface wear

Question 39

How can you ensure the artificial teeth follow the natural tooth guidance?

Answer 39

use articulator / in situ get patient to do left and right lateral excursions. Check tooth guidance using canines of groups of teeth e.g. premolars. Ensure no heavy contacts

Question 40

What does a the denture base for the trial denture stage and occlusal rim stage comprise of?

Answer 40

a rigid base with wax saddle (will be discarded after)

Question 41

What 2 materials can a trial denture base be made out of?

Answer 41

light-cured acrylic or shellac

Question 42

What are the advantageous properties of shellac?

Answer 42

light, great adaptation to palate, stable in mouth

Question 43

What is a disadvantageous property of shellac?

Answer 43

thermoplastic (heats up and can distort) - need to be aware of time in patient's mouth

Question 44

How are the customised teeth attached to the trial base (light-cure acrylic / shellac)?

Answer 44

using modelling wax

Question 45

How can you ensure the denture provides symmetry to the dentition?

Answer 45

- set teeth to long axis of adjacent tooth - contact points should correspond to natural dentition

Question 46

What improvisation can be done if a 1st molar saddle is too small to fit an artificial 6?

Answer 46

use a premolar tooth instead - still conforms to natural tooth guidance so acceptable

Question 47

Why is it advantageous for the dentist to be able to set teeth / make minor adjustments to the wax trial at chairside?

Answer 47

saves time instead of sending to technician and scheduling another appointment

Question 48

Example of a minor adjustment of the wax trial that a dentist should be able to do chairside

Answer 48

fine adjustment of tooth length e.g. bringing tooth down slightly