Prosthodontics Flashcards
What is meant by the term “saddle” in RPDs?
the teeth being replaced
What is a Kennedy Class I?
Bilateral free end saddles
What is a Kennedy Class II?
Unilateral free end saddle
What is a Kennedy Class III?
Bounded saddle
What is a Kennedy Class IV?
Anterior bounded saddle that crosses the midline
How do you determine what Kennedy Class an arch falls under if there is multiple saddle areas?
Most posterior saddle determines Kennedy Classification
What is meant by the term “support” in RPDs?
the resistance of the denture to occlusally directed load
What support classification is used in RPDs?
Craddocks Classifications
- Class 1 = tooth borne
- Class 2 = mucosa borne
- Class 3 = tooth & mucosa borne
What is meant by the term “retention” in RPDs?
resistance of the denture to vertical displacement (lifting away from tissues)
What are some methods of retention used in RPD design?
- clasps
- soft tissue undercuts
- adhesion (eg maxillary plates over hard palate)
- path of insertion
- precision attachments/implants
What is meant by the term “indirect retention” in RPDs?
Resistance of a denture to rotational displacement
What is meant by the term “reciprocation” in RPDs?
Prevention of a clasp arm moving the clasped tooth (eg tilting/tipping)
What is meant by the term “major connector” in RPDs?
Part of denture that connects all the components together
What is meant by the term “minor connector” in RPDs?
Connects rests, clasps and bracing arms to major connector
What connector design is this?
Palatal strap
What connector design is this?
plate design
What can you use to record the inter-occlusal record during a jaw-reg?
- bite registration paste (usually polyvinyl siloxane)
- wax wafer
Why is bite registration paste sometimes a better option for recording inter-occlusal record compared to wax wafer technique?
Wax wafer can sometimes prop occlusion open
What area of a treatment plan does construction of RPDs fall under?
Reconstructive phase
What are the clinical stages in RPD construction?
- primary impressions
- mount & survey study casts
- design denture
- tooth prep if required
- master impressions
- jaw registration
- tooth trial
- delivery
- review
What can be involved in “mouth preparation” prior to creation of RPD?
- pre-prosthetic surgery
- periodontal treatment
- orthodontic treatment
- tooth preparation
- fixed pros
- endodontics
ETC
When preparing pt mouth for a new RPD, what may be involved as a part of pre-prosthetic surgery?
- remove retained roots/unerupted teeth
- remove any pathology
- reduction of bony prominences
- eliminate prominent frenal attachments
Why is tooth preparation sometimes required before taking master impressions?
- provide rest seats
- establish guide surfaces
- create undercuts / retentive areas
Why might rest seats need to be prepared?
- prevent interference with occlusion
- reduce prominence of the rest
- produce favourable tooth surface for support
How deep should rest seats ideally be?
Deep enough to allow a rest of at least 1mm thick
What are guide planes?
2 or more parallel axial surfaces on abutment teeth, which limit the path of insertion of a denture
What are the pros of guide planes?
- increased stability
- reciprocation
- prevention of clasp formation
- improved appearance
How can undercuts/retentive areas be created on abutment teeth?
- addition of composite
- tooth surface reduction
Give a brand name of PVS:
Extrude
In which patients is polyether unsuitable to use for impression taking?
Pt with severe undercuts
- polyether sets rigidly
Give example of a brand name of polyether material?
Impregum
In which patients is impression compound a good option to use for impressions?
Edentulous pts
List the procedural steps involved at the master impression stage of RPD production:
- try in special tray & trim peripheries if overextended
- modify peripheries with greenstick
- modify free end saddles with green stick
- apply adhesive & use alginate/polyether/PVS for impression
- border mould when impression seated
- disinfect & place in sealed back
What has likely happened if you receive framework trial from lab, the framework fits the cast BUT does not fit the patient?
impression error
What is the technique used to create a cobalt chromium RPD base?
LOST WAX TECHNIQUE
- base design created on cast in wax
- cast placed in mould & put into furnace
- wax melts away and is replaced by molten CoCr
- mould allowed to cool & is removed
- metal base casting is now sandblasted with aluminium
At what temperature does Cobalt Chromium alloy melt at?
1400 degrees celcius
WHY must we record the occlusion in the production of RPDs?
Must know the position of the teeth in relation to each other as:
- try to keep occlusion same for pt after denture fitted
- facilitates denture design (eg heavy contacts noted)
- ensure loading forces are directed in the correct direction
What can be used to record the OVD?
- Willis bite gauge
- Dividers
What problems may cause record block to be displaced when trying it in?
- overextension into peripheries
- too much lip support
When reference points/lines are important to note at jaw reg stage?
- midline
- canine line
- inter-pupillary line to guide incisal plane
- ala-tragus line
- smile line
- incisal level
What materials can artificial teeth for RPDs be composed of?
- acrylic
- porcelain
How do acrylic / porcelain teeth on an RPD differ from each other?
Acrylic
- chemical bond with denture base
- silent during function
- easily trimmed/customised
- low abrasion resistance
Porcelain
- mechanical attachment with the denture base
- natural appearance
- noisy in function
- brittle
- high abrasion resistance
What instructions might you provide to the patient at the RPD delivery stage?
- how to insert/remove denture
- denture cleaning instructions
- wear instructions (eg take out overnight)
- OHI of remaining teeth
What information/warnings may you give to the patient at RPD delivery stage?
- excess saliva initially
- speech difficulties
- eating discomfort initially
- soreness, continue to wear denture if possible so at rv appt we can see where to reduce acrylic
Pt comes back to see you for a RPD review appointment, they complain that they are experiencing pain over the entire denture bearing area, what is likely to be the problem?
None/not enough free way space
- pt may also complain of discomfort in MoM and TMJ
Pt comes back to see you for a RPD review appointment, they complain that the denture becomes displaced easily when talking & protruding tongue, what is likely the problem?
Overextension into lingual sulcus
Why is tooth support better than mucosal support for RPDs?
Tooth support
- transmits load via PDL
- feels more like natural dentition
- more comfortable
- protects soft tissues from trauma
Mucosa support
- may cause reduction of occlusal table
- allows denture base to move around
Describe the method of an RPD achieving mechanical retention:
Engaging tooth undercuts via
- clasps
- guide surfaces
Describe the method of an RPD achieving physical retention:
Via existing forces of:
- adhesion = surface forces of saliva on denture & mucosa
- cohesion = forces within saliva, viscosity
- atmospheric pressure
Determined by closeness of adaptation to tissues
Describe the method of an RPD achieving muscular retention:
Dependent on the patients muscular control
What is the difference between direct and indirect retention of an RPD?
Direct = resistance to vertical displacement of denture
Indirect = resistance to rotational displacement of denture
What type of clasp is pictured here?
Gingivally approaching I-bar clasp
What is the ideal “pattern of retention” ?
Triangular pattern of retention
What makes a bar connector superior to a plate connector?
Less mucosal coverage with bar connection
What should the minimum thickness of a lingual bar be?
2mm thick
Name the mandibular connectors listed here:
- Lingual bar
- Lingual plate
- Dental bar
- Sublingual bar
- Labial bar (uncommon)
Where should a lingual bar be positioned in relation to the gingival margin?
At least 3mm below gingival margin
How much space is usually require on lingual mandibular surface for use of a lingual bar connector in RPD design?
8mm
- sits 3mm from gingival margin
- bar 4mm thick
- 1mm clearance to FoM
When is an RPI system typically used?
Free-end saddle designs to prevent stress on the last abutment tooth
What effects are associated with edentulism?
- loss of masticatory function
- appearance issues
- self esteem issues
- general health effects
- poorer quality of life
- speech problems
What clinical effects are observed as a result of edentulism?
- ridge resorption
- soft tissues changes to lip & chin
- reduction in face height
Why might complete dentures not be a good option for parkinsons patients?
complete dentures require good neuro-muscular control
What denture history is relevant to obtain when a pt attends your practise requiring new ones?
- age of current dentures
- what age did they start wearing dentures
- how many denture sets have they had
- what they like/dislike about their current dentures
- how long have they had their current set of dentures
What medical history may cause complete dentures to be contraindicated?
- neuromuscular problems
- strokes
- dementia
- epilepsy
- polypharmacy may cause dry mouth
A diabetic patient wears complete dentures, what condition are they more at risk of developing?
candida infections
