Denture choice and design Flashcards
What is an overdenture/onlay or overlay denture?
Denture used where the natural crown for AB teeth is not complete
What are transitional dentures?
When you want to make a denture but you know some teeth need extracting within the expected lifetime of the denture
What are immediate dentures and immediate addition dentures?
This is a new denture placed in mouth immediately after a tooth is extracted
Immediate addition - where a patients existing denture has an extra tooth added and is fitted imm after extraction
What are temporary dentures
A denture used for a short time before permanent denture is made
What is a diagnostic denture
tests if patient can tolerate something new (commonly a change in kaw relationship or change in tooth position) or to see if pt can tolerate a denture at all
What are obturators
a denture that has an extra piece of acrylic that blocks a hole in the palate (specialist skills needed)
2 materials that dentures are made of
Acrylic and CoCr
What factors do you need to consider when choosing which type of denture?
Time available - acrylics quicker (can make them fit if impression incorrect)
Yours and technicians skills - CoCr more difficult
Costs - to you and pt (time and money)
Pts choice and expectations - pts preferences guided by dentist
Pts prev denture experience - which denture has worked for them before, how is current denture regarding support, retention, stability
Outline of steps for CoCr RPD design
- Survey cast - choose/limit POI - consider natural or artificial GPs
- S (saddle areas)
- S (support - tooth and mucosa)
- R (retention - direct and indirect)
- R (reciprocation)
- C (connectors - major and minor)
CHECK ALL CLASPS RECIPROCATED AND EVERYTHING CONNECTS
How can guide planes and POI be utilised when designing dentures?
Choose POI = diff to path of common displacement (right angles to occlusal surface)
Survey cast
Identify favourable and un-favourable undercuts
Identify natural and artificial guide planes
Art GP - flatten contours of AB teeth using burs = parallel sides = limit POI = more retentive, aesthetics of ant teeth (black tri.), function
S - saddle
What is Kennedy Class I
Bilateral free end saddles
S - saddle
What is Kennedy Class II
Unilateral free end saddles
S - saddle
What is Kennedy Class III
Bounded saddles
S - saddle
What is Kennedy Class IV
Anterior bounded saddle that crosses midline
What is a modification in kennedy classification
Main classification is allocated using most posterior saddle and then however many other saddles there are determines the number of modifications
S - support
What are the key features of rests used for support?
Rest on each end of a saddle
Distribute them evenly around the arch - table with 4 legs
Rest on teeth that healthy
Ensure no occlusal interference - enough space and clearance - PREPARATIONS
R - retention (direct)
What is used for direct retention
List the parts of the assembly of this
Clasps
System:
-Rests (occlusal)
-Clasp arm (tapered and thinner at the end)
-Reciprocal arm (same length throughout and thicker)
-Minor connector
What does a reciprocal arm do?
Prevents unwanted tooth mvmt
How do clasps and reciprocal arms work
Sit passive in undercut and terminal third only engages undercut on AB teeth when denture removed as resists movement
Reciprocal arm engages with tooth throughout and does not move
What are the different types of clasps
Occlusally approaching - circumferential
Gingivally approaching - anterior teeth
Ring - (recip wraps buccal to lingual)
Lateral
How do you choose no of clasps and where to place them
One disadvantage
Depends on teeth missing and pattern of tooth loss
Adjacent to the saddles and spread evenly around arch
2 clasps needed - diagonally opposites sides of arch to spread out
Increases risk of caries
R - retention (indirect)
What is indirect retention and what is used
Rests added
Usually for free-end saddles
-Aim to prevent the FW rotating around an axis which is formed across the AB teeth that are clasped
-Denture rests on teeth or mucosa can resists rotation
What are the different types of rests?
Occlusal
Cingulum
R - reciprocation
What can be used to provide reciprocation for clasp assemblies for posterior teeth and what can be used for anterior teeth?
Plate/arm for posterior teeth
Plate with rest/rest only for anterior teeth
C - connectors (major)
Different types of upper major connector - which is most commonly used
Palatal strap
Palatal plate
Anterioposterior bar
Palatal horseshoe
Combo of chrome and acrylic
Most common:
Anteroposterior bar - relives some of the palate for improved taste
Different types of lower major connectors and most commonly used and why?
Lingual bar
Sublingual bar
Dental bar
Lingual plate
Most common:
Lingual bar - frees gingival margin for comfort and health purposes compared to plates - need enough sulcus space - 8mm
How do you plan for tooth position in CoCr metal dentures?
Which teeth do we usually do this for?
Plan ahead - decide where teeth are going to go before making metal framework
Tooth try-in before master impression - set teeth in wax bases on primary cast and let pt see in mouth
Jaw registration - articulate primary casts first
Only for teeth that pt can see in mirror (upper anteriors)
Can you adjust or tri/polish a CoCr metal framework?
Strong metal alloy so used in thin sections - not enough thickness for major adjustments (thus any errors in impressions or jaw reg poses problems)
Difficult to trim and polish chairside:-
-trimming - maybe with diamond bur
-polishing - softer bur needed for finishing
-FW may overheat w use of burs
-any sharp edges due to trimming may cause trauma
What needs to be done properly in order to make an accurate framework?
Articulate casts properly - to design occlusal scheme, rests and denture teeth
Block out undercuts properly - on master casts so that fw seats in the mouth first time
Survey properly - ensure natural tooth undercuts present for clasps
Take accurate master impressions - must not distort
Cast master impressions accurately - may affect rests and fit of fw
What needs to be assessed to ensure fw is correct?
- Is it same as design
- Are features placed correctly e.g. clasps in undercuts and major connectors in correct position (not too low or high in sulcus)
- Damage during polishing or over polishing - distort clasps or teeth change in shape
- How strong is the fw - too thin/bends easily? Porosity (lead to fracture)?
What metal is CoCr alloy free of to avoid allergy
Nickel
Beryllium
If you cant save the whole tooth but you save what can and use a denture to replace the missing parts of the tooth e.g. if natural tooth cannot be restored to full size (using crown or composite) - what is this called?
Why would you want to keep tooth?
Overdenture, overlay/onlay denture
If you want to retain bone
What is an overdenture? What kind of situations are they useful for?
Why would you want to keep or use roots as the abutment?
What can be used on the AB teeth?
Partial or complete dentures that completely covers at least one tooth or root - ‘overdenture abutment’
Useful for teeth that cannot be restored to cull crown height but want to keep tooth to retain bone
Root provides denture support and sometimes retention (only if gold coping with precision attachment involved)
‘Domed’ root face (w or w/o RCT). Metal copings can be used but needs RCT. Short crowns can be used.
Indications for overdentures
Very few teeth in arch (especially upper)
Extreme tooth wear (restorations not possible)
Hypodontia cases (teeth small or mis-shaped)
Cleft palate cases (tooth position compromised)
Transition to complete dentures (can extract roots later after got used to wearing complete denture)
Advantages of overdentures
Support - eff use of small number of teeth
Preserves alveolar bone
Stability - better than complete dentures
Retention - excellent with precision attachments
Proprioception - preserved PDL
Appearance - can be improved (tooth shape and position)
Masticatory efficiency - better than complete dentures
Psychological - pt not rendered edentulous
Disadvantages of overdentures
Complex treatment required - if RCTs needed (unsuccessful RCT then XLA needed), rubber dam placement difficult
Increased risk of caries and perio disease - can pt keep teeth and overdenture clean to increase longevity of potential ABs
Soft tissue support - where tooth or root remains –> flange becomes bulky = issues anteriorally (POI needs careful consideration if bony undercuts present - follow direction of bone)
Time and cost - use of precision attachments
Transitional denture definition
Acrylic partial to which teeth are added over a period of time until it becomes a complete denture
What do you need to consider when choosing material of denture? (Acrylic vs CoCr)
How long do you want denture to last?
Will things change sig over next few months e.g. bone remodelling (happens due to time)? future tooth loss (acrylic)? natural teeth changing shape due to restorative tx?
Advantages of acrylic dentures
Easy to modify - remove or add acrylic
Quicker to make - compared to CoCr FW
No metal components needed - (unless clasping teeth) –> pts may not like metal sensation, allergies or aesthetics so acrylic is best
Cheaper to make - BUT may not last as long as metals
Ideal for temporary dentures - lower costs, quicker to make, easier modifications before definitive denture is made
Advantages of CoCr dentures
Improved stability and comfort - tooth support possible
Better retention - clasps on CoCr more efficient, POI can be limited through guide planes, rests provide indirect retention
Lightweight - stronger, so thinner sections so less bulky (best for lower dentures due to tongue space)
Hygienic designs - connectors that avoid gingival margins –> preserve perio health
Better thermal conductivity - pt aware of temp sensation etc
Less likely to break - major connector rigid (BUT clasps can break easily)
Reduces chances of denture stomatitis - due to framework design and major connector choice
