RPD OSCE Flashcards by Olivia Russell

what are saddles?

the teeth being replaced by RPD

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what is seen in a patient with Kennedy Class I ?

bilateral free end saddle

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what is seen in a patient with Kennedy Class II?

Unilateral free end saddle

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what is seen in a patient with Kennedy Class III ?

bounded saddle

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what is seen in a patient with Kennedy Class IV ?

anterior bounded saddle that crosses the midline

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if there are multiple saddles, what saddle is the Kennedy Classification score based on?

the MOST POSTERIOR saddle

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what is support defined as in relation to RPD design?

the resistance of the denture to occlusally directed load

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what is seen in a patient with Craddock Class 1?

tooth borne support

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what is seen in a patient with Craddock Class 2?

mucosa borne support

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what is seen in a patient with Craddock Class 3?

combination of tooth and mucosa borne support

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what is retention defined as in relation to RPD design?

the resistance of the denture to vertical displacement/lifting away from the tissues

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What are the different methods of providing retention to an RPD?

clasps
soft tissue undercuts
path of insertion
adhesion

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what is indirect retention defined as in relation to RPD design?

the resistance of the denture to rotational displacement

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what is indirect retention provided by?

rests! (not clasps)

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what is reciprocation defined as in relation to RPD design?

reciprocation prevents a clasp arm moving a clasped tooth

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what are the undercut gauges used when surveying for clasps?

25mm
50mm
75mm

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There is an undercut of 0.25mm, what material would the clasp be made of?

Cobalt Chromium

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There is an undercut of 0.5mm, what material would the clasp be made of?

wrought gold

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There is an undercut of 0.75mm, what material would the clasp be made of?

stainless steel

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What method of support is better, tooth borne or mucosa borne? WHY?

TOOTH BORNE

transmits load via periodontal ligament, more natural for patient
more comfortable for patient
protects soft tissue from trauma

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Why are the problems with Mucosal Support?

Must cover as large an area as possible or there will be REDUCTION OF OCCLUSAL TABLE
Allows the denture base to move slightly which can cause TRAUMA TO ADJACENT GINGIVAL MARGINS

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What load of support can a healthy tooth carry? (potentially)

A healthy tooth can potentially carry its own load plus one and a half similar teeth

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What teeth are best for providing support?

1st = molars
2nd = canines
3rd = premolars

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What teeth should be avoided when looking to provide support?

The incisors

- lower incisors are weakest (smallest root)

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How should rests be positioned?

Rests positioned so that they transfer load through the long axis of the tooth to prevent tilting

Why shouldn’t the denture base be positioned within 3mm of the gingival margin?

Soft tissue is compressible, this will place pressure at the gingival margin

Where does mucosal support mainly come from in a maxillary denture?

Hard palate

Where does mucosal support come from in a Mandibular denture?

- Tends to come from the buccal shelf (on right and left area) - Edentulous area may gain support from pear shaped pad

Why is having support from the alveolar bone bad?

Alveolar bone RESORBS

What are the tooth supportive components used in RPD design?

RESTS

Where is an Occlusal Rest located?

On the occlusal surface of the tooth

Where is a Cingulum rest located?

on the cingulum of the cingulum of the anterior teeth

What type of rests can be used on purely acrylic dentures? Why is this tricky?

Wrought stainless steel | - causes a low base strength

Why are small rests NOT recommended?

They apply large forces per unit area… | - Large rests direct the force down the long axis of the tooth

Why are incisal rests not commonly used?

Poor aesthetics | Usually interferes with occlusion

Where are cingulum rests most commonly located?

On maxillary and mandibular canines | - Unless prominent cingulum is present A REST PREPARATION IS REQUIRED

What material type denture base is preferred? Why?

Metal framework base > PMMA (acrylic resin) base | - metal framework rigid and strong

What is the root to crown ratio for lower central and lateral incisors?

1.0

What is the root to crown ratio for lower canines?

1.7

What is the root to crown ratio for lower 1st & 2nd premolars?

1.25

What is the root to crown ratio for lower molars?

2.7

What is the root to crown ratio for upper central incisors?

1.3

What is the root to crown ratio for upper lateral incisors?

1.1

What is the root to crown ratio for upper canines?

1.7

What is the root to crown ratio for upper 1st and 2nd premolars?

1.4

What is the root to crown ratio for upper molars?

2.7

Where is the ‘default’ position to place a rest for a bounded saddle?

immediately adjacent to the saddle area.

Where is the ‘default’ position for a rest in a free ended saddle?

The rests should be placed on the opposite side of the tooth adjacent to the saddle area (eg. mesial of tooth)

Why can preparing a rest seat potentially be problematic?

- destruction of tooth surface | - exposure of dentine

What is a clasp ?

A metal arm that when in position contacts the tooth and prevents removal of the denture base

Where must the clasp be located in order to be successful?

Below the bulbous part of the tooth (in an undercut)

What are the different types of clasps known as?

- occlusally approaching (clasps approach undercut from occlusal surface) - gingivally approaching (clasps approach undercut from gingival margin)

What is an example of a gingivally approaching clasp?

I-Bar Clasp

What are examples of occlusally approaching clasps?

- self reciprocating clasps | - single arm clasp (with reciprocal arm)

What is the ideal pattern of retention?

Triangular (as big as possible)

What pattern of retention is provided by 2 claps?

straight line retention

what is meant by CONNECTORS?

A term used to describe the rigid part of a RPD that unites all the components - minor connectors - major connectors

What are the guidelines a major connector should follow?

- be rigid - avoid covering gingival margins - cover as little tissue has possible

What is the default connector for a lower RPD?

Lingual bar if possible

There is less than 8mm of lingual space on the lower arch, what connector will be used?

Lingual plate design

How thick should a lingual bar be to maintain rigidity?

2mm

What connector design is desirable for a craddock class 2 denture? (mucosa borne)

Plate design

What is the common choice connector design for a craddock class 1? (tooth borne)

Bar design

What is the purpose of the RPI clasp system?

Stress relieving system | - prevents torking/rotation/tilting of the last standing abutment tooth

What length should a CoCr clasp be?

15mm