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BDS5 > OSCE DOC - Pros > Flashcards

OSCE DOC - Pros Flashcards

1
Q

When would you attempt a reline of a complete denture?

A

Relines: when fitting surface inadequate but denture otherwise okay
- i.e. occlusal planes, OVD, profile are acceptable but fitting surface underextended, not supportive / stable or retentive

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2
Q

Explain the method and materials used for a reline of a complete upper denture?

A
  • Check all occlusal relationships are acceptable and appropriate
  • Remove undercuts from denture fitting surface using acrylic bur
  • Adjust border from under / over extension with green stick
  • Apply adhesive to fitting surface of the denture to be relined
  • Insert impression material (light body PVS) into the fitting surface and seat the denture
  • Functional impression- ask the patient to bite together so the impression is taken in OVD
  • Take a lower impression with the denture in situ (gold standard but may not be required)
  • Take a bite registration if OVD is not obvious
  • When set, remove the impression and send the denture for reline
    • please pour impression in 100% dental stone using denture impression provided. Please mount upper to cast and create a self-cure PMMA reline to change the impression surface
  • (my reline notes?)
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3
Q

Lower Co/Cr Denture Design (6 mins)- 22 marks
Design a cobalt chrome partial denture for the lower arch and fill in the lab sheet by both drawing and writing the prescription. Assume that the teeth are of sound prognosis, the dentition is free of caries and the oral hygiene is optimal.
On the sheet provided, write instructions for a dental laboratory prescription to enable the trial stage of a cast alloy removable partial denture base for the lower arch only.
The laboratory prescription should contain a drawing of the design with supporting written description.
Mounted casts surveyed in the common path of displacement are provided to assist you.
Please design a lower CoCr denture- Kennedy Class II mod 1
Teeth present- 34, 33, 32, 31, 41, 42, 43, 44, 47

A

Identifies the saddle areas to be restored
Saddle areas correctly identified and retentive element (mesh, etc.) clearly shown
2 marks

Support:
Occlusal rests:
- 34m
- 44m / d
- 47m
4 marks

Retention:
47:
- occlusally approaching ring clasps (engaging lingual undercuts)
- or
- 47 three-armed clasp
- or
- 47 occlusally approaching clasp with bracing from plate (1 mark)
Mesial gingivally approaching clasp 34 (with plate reciprocation / bracing) (1 mark)
Gingivally approaching clasp 44 (needs composite) (1 mark)
All clasps have reciprocating element- either from plate or reciprocating clasp arm (2 marks)
Undercuts
All clasps drawn to engage undercut
Need to mention modification 44
2 marks

Indirect retention
Cingulum rests 43 or 44d
1 mark

Tooth modification
44 buccal cervical composite addition
Occlusal rests (at least 47m +/- 34, 44)

Guideplanes
2 marks for identifying 2

Connector:
Lingual bar (2 marks)
Lingual plate (1 mark)

Notes:
Look at survey lines and occlusion
Draw retentive elements on saddles
Remember reciprocation
Don’t complicate the design- there is more than one way to make a denture, as long as you are sensible you should be okay

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4
Q

What are the four different kennedy classifications?

A

I- bilateral free-end saddles
II- unilateral free-end saddles
III- unilateral bounded saddle
IV- anterior bounded saddle only

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5
Q

What are the different craddock classifications?

A

Class I
- Tooth
- Bounded saddles <4 teeth, occlusal and cingulum rests
- Teeth provide hard tissue resistance to occlusal loading
Class II
- Mucosa
- Free end saddles, RPI systems, utilised when no suitable teeth available
- Large coverage provides resistance to occlusal loading
Class III
- Tooth and mucosa
- Bounded saddles >4 teeth
- Combination of hard tissue and large coverage when there are reduced number of teeth and large edentulous saddles. Free end saddles must have tooth and mucosa borne support.

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6
Q

Define support?

A
  • Resistance to occlusally directed load
  • Use of hard tissue or large surface coverage
  • Rests (NB can prepare rest seats)
  • Mesial or distal occlusal, Cingulum
  • Onlay, overlay, ledge, ring
  • Immediately adjacent to bounded saddles
  • Mesially to free end saddles
  • Consider opposing arch- is there space for rests?
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7
Q

Define retention and give some examples of it?

A

Resistance of denture to lifting away of the tissues
Mechanical
- Clasps- composite can be added- close to base, adjacent to abutment teeth
- Guide surfaces- close to base and parallel to path of insertion
- Precision attachments
Muscular
- Patient’s muscular control
- Relates to polished surface of denture
Physical
- Adhesion (surface forces of saliva on denture and mucosa)
- Cohesion (forces within saliva, viscosity)
- Atmospheric pressure (resistance to displacing forces)
- Due to closeness of adaptation, amount of area covered, peripheral seal
Direct
- Resistance to vertical displacement of denture
Indirect
- Resistance to rotational displacement of denture
- To place components so as to resist rocking of denture around direct retainers
- Not needed if three clasps present- provide stability in free end saddles and very long bounded saddles
- If two clasps- place a supporting element to the opposite side of the clasp axis than the origin of the displacing force (90 degrees to the clasp axis and as far away as possible)

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8
Q

What size of undercut must be present for;
- CoCr
- Gold
- SS

A
  • 0.25mm CoCr
  • 0.5mm Gold
  • 0.75mm SS
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9
Q

How long must a CoCr retentive Occlusally approaching arm be to engage an undercut?

A

15mm in length to engage a 0.25mm undercut

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10
Q

Give some examples of upper major connectors?

A
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11
Q

Give some examples of lower major connectors?

A
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12
Q

How much clearance is required for a lingual bar?

A

Lingual bar (8mm space- 3mm gingival margin, 4mm bar, 1mm depth FOM),

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13
Q

What is reciprocation?

A

Reciprocation is what stops the tooth moving when the clasp is active

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14
Q

What is bracing?

A

*Bracing is what stops the denture moving side to side
Can be achieved with clasps, plates, major connectors, flanges

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15
Q

Define indirect retention?

A

resistance to rotational displacement around the clasp axis

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16
Q

Label the anatomy of this maxilla?

A
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17
Q

Label the areas of the mandible?

A
18
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Anterior flange missing:

How would you go about fixing this fault?

A

Remove undercuts, build flange with greenstick and reline
Rebase if not possible or remake if necessary

19
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Midline diastema

How would you go about fixing this fault?

A

If want to keep physical aspects of denture, but change aesthetic only
- Replica (2 stage putty around denture, Vaseline to separate)
- Wax replica used for functional impression and jaw registration
- Ask lab to close diastema for tooth trial stage
Remake if other problems

20
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Underextended at the tuberocities

How would you go about fixing this fault?

A

Reline- if functionally good and only problem is the retention
Remake- if everything bad

21
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Locked occlusion

How would you go about fixing this fault?

A

Remake with replica technique and use cuspless teeth

22
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Base plate is too thin

How would you go about fixing this fault?

A

Rebase thicker or rebase using high impact resin

23
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Tori

How would you go about fixing this fault?

A

Relieve clinically if only problem or ask for tin-foil relief
If too thin or other problems- rebase or remake and ensure lab waxes undercuts

24
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Tooth position wrong

How would you go about fixing this fault?

A

Remake

25
Q

Complete Denture Faults (6 mins)

C/C (fractured?) denture provided.
Please identify 6 faults with this denture and how to rectify these.

  • Occlusal table to long

How would you go about fixing this fault?

A

I.e., too many posterior teeth over the tuberosities
Remove posterior teeth / grind down- or remake

26
Q

Explain what the difference between reline and rebase are and when arch you would use for each?

A

Reline
Replacement of a denture fitting surface
Note of caution- relining is satisfactory for a mandibular denture but will increase the thickness of an upper denture- making it heavier and less retentive
The amount of thickness is directly related to the choice of impression material- the more viscous the impression material, the greater the thickness of the reline; use low viscosity light body PVS

Rebase
Replacement of the whole denture base

*Reline mandibular dentures and rebase maxillary dentures

27
Q

General Denture Faults
Problems with denture:
What are possible causes of damage to the Impression surface and solutions?

A
  • Cause- poor impression (impression distorted, lack of post dam, poor adhesion to tray), damage to cast, warped denture base
  • Solutions- reline / rebase, remake, add post dam (using reline procedure or chairside technique)
28
Q

General Denture Faults
Problems with denture:
What are possible causes of damage to the occlusal surface and solutions?

A
  • Cause- premature occlusal contact; centric occlusion / relation not coincident; high lower occlusal plane restricting the tongue; locked occlusion
  • Solutions- spot grid; remove teeth and keep bases; generally remake; adjust if against natural teeth, if cuspless teeth, no overbite; adjust teeth

*With looseness and poor denture bearing foundations, can use cuspless teeth to reduce interferences, take care with peripheries to ensure not overextended, and use a soft lining to reduce discomfort *

29
Q

General Denture Faults
Problems with denture:
What are possible causes of damage to the polished surface and solutions?

A
  • Cause- overextension; underextended (depth and / or width); teeth not in neutral zone
  • Solutions- remove overextension (especially lingual lower, use pressure indicating paste, allow fraenal relief and flange); add greenstick to underextension and reline, remake if extensive; replace teeth (neutral zone impression), remake
30
Q

What are some possible problems that patients can have that makes it hard for them to wear and retain a denture.

A

Poor neuromuscular control, e.g., stroke, Parkinson’s
Poor denture bearing foundations
- Anterior flabby ridge- solution- perforated trays and light body PVS impression (or special tray with surgical window and take a wash and cut it out and light body PVS)
- gag reflex
- Atrophic mandibular ridge- solution- admix technique (3 parts impression compound, 7 parts greenstick)
- High fraenal attachments- solution- provide relief
- Bony prominence, e.g., palatine tori- solution- relief of area on cast before processing
- Xerostomia

31
Q

What are some possible causes for denture fracture?

A

Denture Fracture Causes
* Underextended
* Poor fit
* Inadequate relief
* trauma
* Tooth wear/bruxism
* Stress concentrators
* Soft linings
* Porosities

32
Q

If a patient is high risk of fracturing their denture, what can be done to prevent this from happening?

A

Metal baseplate
High impact acrylic

33
Q

If a patient turns up with a fractured denture how would you treat them?

A
  • For simple midline fracture, two fragments are secured in position with sticky wax and additional reinforcement, e.g., wooden sticks across the line of fracture; sent to the lab- light cure PMMA is normally used because of its easier processing technique but is weaker than heat cured PMMA
  • If denture fractured into multiple fragments, it may be necessary to reposition the larger of the fragments intraorally and to take an in situ overall impression in alginate; if not possible- remake
  • For repair of fractured or missing teeth, an impression of the opposing dentition and / or the denture is required to ascertain the correct occlusal relationship + bite reg?
34
Q

A patient is coming in for a tooth trail of upper and lower completes. Explain what you would check and do during this appointment?

A
  • Check denture extension, support, retention (trial denture will be looser than actual denture)
  • Check stability and occlusion (balanced occlusion and articulation)
  • Check speech, aesthetics (tooth mould, shade, gingivae position)
    * Mark post dam on cast
35
Q

Surveying (6 mins)
Components. Undercut gauges and material of clasp to use for each undercut.
Survery a cast for a CoCr partial denture.

A
  • Mount cast and tripod:
  • Draw three lines with analysing rod and pencil (mark as PD)
  • Analysing rod- to analyse abutment teeth and soft tissue undercuts
  • Pencil rod- mark survey line of all abutment teeth and soft tissue undercut (do not overmark- in the common path of displacement)
  • Determine whether the cast needs to be tilted
  • I.e., when undercuts favourable
  • Change the path of insertion to highlight undercuts in this path (mainly for soft tissues)
  • If cast needs to be tilted- re-tripod with red marker, then mark new survey line with red rod
  • Another set of lines (mark as PI)
  • Find clasp location
  • In the common path of displacement (path of insertion and removal if altered), find appropriate location for clasps with undercut gauges (normally buccal of upper molars and lingual of lower molars)
  • Mark the clasp positions with pencil
  • 0.25mm- CoCr
  • 0.5mm- wrought gold
  • 0.75mm- wrought SS
36
Q

CoCr Partial Trial on Cast (6 mins)
Check metal framework against prescription and find faults.
Faults with metal framework casting (could include):

A
  • Errors in casting- CoCr bubbles making surface rough- due to air bubbles trapped on wax pattern investing
  • Errors in design- too close to gingival margin, undercuts not blocked out
37
Q

CoCr Partial Trial on Cast (6 mins)
Faults with support, retention and connector?

A

Support- rests are missing, no posterior stop (i.e., posterior of free end saddle ends further anteriorly than desirable)
Retention- ring clasp around the wrong way (are there any ineffective clasps? Check the cast for survey lines)
Connector- sublingual bar instead of lingual bar on prescription (sublingual bar looks almost identical to lingual bar- the sublingual bar actually lays on the floor of mouth and there is no 1mm from the functional depth as is with the lingual bar)
Also check for- indirect retention, appropriate reciprocation for clasps

38
Q

Complete Denture Jaw Registration (extra Q)
Equipment. Lines / features. Reference lines.
Equipment:

What is this equipment used for?

  • Fox’s occlusal plane guide
  • Willis bite gauge
A

Fox’s occlusal plane guide- used to set occlusal plane
Willis bite gauge- used to measure OVD, FWS, RVD

39
Q

Complete Denture Jaw Registration (extra Q)
Equipment. Lines / features. Reference lines.
Equipment:

What lines are marked during this stage and how is this done?

A

High smile line
- Why- allows waxing of teeth in correct height and alignment (not showing too much gum)
- How- getting patient to smile and marking lip level

Centre line / midline
- Why- to orientate central incisors making the block symmetrical
- How- using nasal septum, labial frenum, existing upper / lower anteriors

Canine line
- Why- to set canine position; also provides size measurements for tooth selection
- How- measured using vertical line from inner canthus of eye

40
Q

What 2 reference lines does the foxes bite plane use to make sure the occlusal plane is level?

A

Used to ensure anterior and posterior occlusal plane is level
- ala-tragus line
- interpupillary line

BDS5 (22 decks)

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