Removable prosthodontics

Question 1

when setting teeth for a complete maxillary denture, what is meant by Watt and MacGregors biometric guides?

Answer 1

The biometric guide is one of the methods of designing complete dentures. It uses the remaining lingual gingival margin in the bucco-lingual placement of prosthetic teeth

Question 2

In removable prosthodontics, what is the average horizontal bone loss for the fixed reference point in the following maxillary tooth positions;
central incisors
canines 
premolar
molar

Answer 2

Central incisors 6.3mm
Canines 8.5mm
Premolars 10mm
Molars 12.8mm

Question 3

In removable prosthodontics, what is the minimum data that should be recorded onto the record block?

Answer 3

• OVD; the distance between the jaws with the teeth in occlusion
• centre line;
• occlusal plane; the central occlusal plane indicates where the incisal level of the tooth will be
• High lip line
• Canine line; line extended from the inner canthus of the eye
• Arch form (width-lip support)

Question 4

In removable prosthodontics, what is the minimum data that should be recorded onto the record block?

Answer 4

• OVD; the distance between the jaws with the teeth in occlusion
• centre line;
• occlusal plane; the central occlusal plane indicates where the incisal level of the tooth will be
• High lip line
• Canine line; line extended from the inner canthus of the eye
• Arch form (width-lip support)

Question 5

What are some general features that should be present on a definitive impression?

Answer 5

• ensure the denture bearing areas are covered
• ensure there is a good functional sulcus present
• ensure there is good surface detail with no air blows

Question 6

What features should be present on a maxillary definitive impression?

Answer 6

• coverage of maxillary tuberosity
• coverage of hamular notch
• extension anterior to the vibrating line for post dam
• functional depth and width of sulcus to create a good peripheral seal and ensure the hard palate and residual ridge are functional for primary support

Question 7

What features should be present on a mandibular definitive impression?

Answer 7

• coverage of pear shaped pad and buccal shelf
• retromolar pad and extension into the linual pouch should occur
• functional width and depth of the sulcus
• ensure there is an area of primary support of the buccal shelf and retromolar pad

Question 8

Kennedy class I

Answer 8

Bilateral free end saddle

Question 9

Kennedy class II

Answer 9

Unilateral free end saddle

Question 10

Kennedy class III

Answer 10

Bounded saddle

Question 11

Kennedy class IV

Answer 11

Anterior bounded saddle crossing midline

Question 12

Craddocks class I

Answer 12

Tooth borne

Question 13

Craddocks class II

Answer 13

Mucosal borne

Question 14

Craddocks class III

Answer 14

Combination of tooth and mucosal borne

Question 15

What indicates the posterior border of the maxillary denture?

Answer 15

• The post dam which should sit 1-2mm anterior of the vibrating
  line between the junction of the hard and soft palate.
• The maxillary denture should be at the level of the Hamular
  notch to produce a good posterior seal which is located
  between the distal surface of the tuberosity and the Hamular
  process of the medial pterygoid plate of the maxilla.

Question 16

What impression materials are used for primary and definitive impressions?

Answer 16

• Primary impressions:
  — Impression compound:
  i. Non elastic material which records poorer
  surface detail and this is why it isn’t used for
  definitive impressions. It isn’t cheap to use and
  can be messy.
  ii. It is good for primary impressions due to the
  high Mucocompressive viscosity
  — Alginate:
  i. Elastic material which means it will flow into
  undercuts and can record surface detail for
  primary impressions.
• Definitive impressions:
  — Silicone:
  i. It is dimensionally stable and can be made into
  a variety of consistencies which means it
  accurately record surface detail
  — Polyether/impregum:
  i. It is dimensionally stable and has very accurate
  recording of surface detail
  — Alginate:
  i. Can also be used for master impressions as if is
  elastic so can flow into undercuts if they are
  present.

Question 17

What two things are required for accurately mounting study casts on an
articulator?

Answer 17

• Jaw registration
• Occlusal rims:
  — Setting upper teeth to the wax rim and set lowers to
  uppers in RCP

Question 18

What is the relevance of freeway space in complete denture construction?

Answer 18

• The freeway space is the RVD – OVD which is ideally around 2-
  4mm
• If the freeway space is negative/reduced due to the increase in
  OVD it will cause the dentures to click
• If the teeth contact during speech there is not enough interocclusal
  space which means the OVD needs reduced to give
  more freeway space

Question 19

What types of custom tray and spacer is used?

Answer 19

• Alginate use for special trays should have 3mm spacer
• Silicone/polyether use for special trays should have 2mm for
  upper and 0.5-1mm spacers for lowers
• Upper trays should have stops to the space prescribed in the
  canine and post dam regions which will allow accurate
  correction of the posterior borders of the tray and will
  perform space for the impression material.
• Lower trays should have stops to the space prescribed on the
  retro-molar pad and on the ridge in the canine areas. This will
  allow preformed space for the impression material.

Question 20

What impression material is used for primary impressions and why is this
used prior to special trays?

Answer 20

• Usually alginate is used as it is an elastic materials so flows into
  undercut areas. It gives an accurate record of surface detail for
  impressions and is cheap and easy to use.

Question 21

Why is silicone not Used for primary impressions for dentures?

Answer 21

• Silicone is dimensionally stable and is hydrophobic so can
  cause small defects and blows. It is generally only used for
  master impressions and not for the production of special trays
  as it is very messy and technique sensitive.

Question 22

What 2 areas of primary support are on the maxilla?

Answer 22

• Hard palate and residual ridge

Question 23

Name 1 area of support on mandibular arch And what muscle lies adjacent to
this area?

Answer 23

• Retro-molar pad
• Muscles that lie next to it are:
  — Laterally buccinator
  — Posteriorly temporalis tendon
  — Medically superior constrictor and the
  pterygomandibular raphe

Question 24

What is gypsum?

Answer 24

• Gypsum plaster is calcium surface dihydrate which is used to
  cast a positive replica of an oral cavity.
• Type 1 plaster/impression plaster is used in making primary
  impressions of edentulous oral cavity in complete denture
  fabrication.
• Type III dental stone is an alpha form of calcium surface
  hemihydrate which is used to make master casts

Question 25

Describe Hanau’s quint?

Answer 25

- It is the inter relationship of 5 factors in order to maintain a
balanced occlusion:
— The saggital condylar guidance angle
— The inclination of the occlusal plane
— Compensating curves
— The cusp height
— The incisal guidance angle

Question 26

What anatomical areas are required for retention, support and relief?

Answer 26

• Retention:
  — Mandible – retro-mylohyoid space
  — Maxilla – tuberosity, peripheral seal
• Support:
  — Mandible - Retro-molar pad, residual ridge, buccal shelf
  — Maxilla – hard palate and residual ridge
• Relief:
  — Bony prominences (tori), high frenal attachments

Question 27

In partial dentures, name the appropriate materials for the following undercuts;

0. 75
1. 5
2. 25

Answer 27

0. 75 wrought ss
1. 5 gold
2. 25 Co/Cr