RPDs Flashcards
What is Kennedy class 1?
Bilateral free end saddles
What is Kennedy class 2?
Unilateral free end saddles
What is Kennedy class 3?
Bounded saddle that doesn’t cross the mid line
What is Kennedy class 4?
Bounded saddle that crosses the mid line
What is a mod in Kennedy classification?
A bounded saddle, in addition to the saddle that indicates the classification.
NB: there is no such thing as a class 4 mod 1
What is an abutment?
A tooth that serves as support to the denture
What is a Pontic?
suspended component on a fixed partial denture that replaces the missing natural tooth
What is the residual ridge?
portion of alveolar bone and its soft tissue covering that remains after tooth loss/ extraction
What type of impression tray is preferable?
perforated
aids retention when tray is being removed
What is dental plaster?
- has large irregular particles
- heated in an open vessel with air readily available
What is gypsum?
- used for making dental casts
What is dental stone?
- small, regular particles
- heated in an autoclave
What is improved dental stone?
- compact smooth particles
- heated with added chemicals (calcium and magnesium)
What is a wax wafer?
- thin piece of wax a patient bites on to demonstrate the occlusion
What is an ARCON articulator?
- articulated condyle articulator
- anatomically similar to the TMJ
What is a non-ARCON articulator?
- doesn’t replicate the movement of the TMJ
- simple hinge movement
- can still show the occlusal relationship, but not how the teeth come together naturally
What is the design process order?
- saddles (yellow)
- support (red)
- retention (green)
- indirect retention (purple)
- reciprocation (blue)
- connectors (black)
- review
What is Craddock class 1?
- tooth borne support
- abutment teeth on both sides of the saddle
- no more than three teeth wide
What is Craddock class 2?
- mucosa borne support
- edentulous patients
What is Craddock class 3?
- mixed support
- free end saddles
- large saddles
What makes an ideal abutment tooth?
- suitable undercut
- space for a rest ie no heavy occlusal contacts
What is a gingivally approaching clasp?
- approaches undercut from the gingival margin
- does not cross the maximum bulbosity of the tooth
- used primarily on narrower teeth ie anteriors
What is a occlusal approaching clasp?
- approaches undercut from the occlusal surface
- crosses the maximum bulbosity of the tooth
- used primarily on molars
What is a ring clasp?
- self reciprocating occlusally approaching clasp
What is the recommended pattern of retention?
-triangular
Do rests work better on metal or acrylic bases?
metal as they are an integral part of the framework whereas on acrylic bases they need to be added and have potential to weaken base
What is the default position for a rest?
- abutment teeth, on the nearest surface to saddle
What is an RPI?
- a stress relieving clasp
- rest system used in free end saddles
- rests are placed on the mesial surface of the abutment tooth to reduce torque
- a post is used as reciprocation
- a gingivally approaching clasp is used
Why should rests extend to the midline of the tooth?
- to ensure force is transferred down the long axis of the tooth
What risks are associated with rest seats?
- dentine exposure
- sensitivity
- destruction of sound tooth tissue
- loss of occlusal stop when denture not in place
What benefits are associated with occlusal rests?
- prevent movement of RPD towards mucosa
- prevent over eruption of unopposed teeth
- distribute occlusal load
- indirect retention
- determines axis of rotation
What is indirect retention?
- resistance to rotational displacement
- key in free end saddles
- eg rests, connectors, saddles
What is retention?
- resistance to vertical displacement
What is reciprocation?
- prevents the forces from the clasp moving the tooth
What is bracing?
- resistance to lateral movement
What is key to ensuring good oral hygiene with a denture?
- clear margins where possible
- reduce the dark triangles by altering path of displacement
- OR ensuring gaps are big enough to allow salivary flow
When is a plate connector preferable?
- less tooth borne support
- Craddock class 2 or 3
What is the default mandibular connector?
- lingual bar
What are the disadvantages of a plate connector?
- more mucosal coverage
- may cover gingival margins
What are the disadvantages of a bar connector?
- thicker so patients may not tolerate well
What is closed saddle design?
- no space between saddle and abutment tooth
- better retention
- more mucosal coverage which may irritate
What is open saddle design?
- space between saddle and abutment tooth
- allows for saliva to flow through
- less retentive
What does RPI stand for?
(mesial) Rest
Proximal guide plate
I bar clasp
What are the phases in a restorative treatment plan?
immediate - treat pain , acute infection etc
initial - hygienic and preparatory - establish oral health, BPE, diet caries etc
reconstructive - restorations, implants, RPDs
maintenance - is treatment working / ptc coping ?
What is the benefit of preparing rest seats?
- prevents interference with the opposing occlusion
- proper loading
What is a guide surface?
- abutment tooth prepared to allow for parallel surfaces which allows the RPD to be inserted on the path of insertion
What is tray spacing?
- required for special trays
- additional space for material on top of initial impression
- alginate = 3mm
- silicone = 3mm
When are master impressions taken?
- once denture design is complete
- all tooth preparation and restorative steps are complete
How are trays altered on clinic?
- slow speed handpiece
- greenstick compound or wax can be added to the peripheries
What is polyvinylsiloxane?
- synthetic polymer
- addition silicon
- light / medium / heavy bodied
- requires adhesive
- eg EXTRUDE
What is polyether?
- synthetic elastomer
- sets rigidly, do not use in severe undercuts
- eg PENTAMIX
What is alginate?
- irreversible hydrocolloid
- casts used be poured ASAP to prevent distortion of impression
What stone should CoCr dentures be poured in?
improved stone
What stone should acrylic dentures be poured in?
100% dental stone
How can the framework be trialed?
- framework only
- framework with record blocks
- framework with wax tooth trial
What sulcus depth is required for a gingivally approaching clasp?
7mm
What is the minimum length for a CoCr clasp?
15mm
What is the minimum length for a stainless steel clasp?
7mm
What depth of undercut is required for a CoCr clasp?
0.25mm
What depth of undercut is required for a stainless steel clasp?
0.75mm
What depth of undercut is required for a gold clasp?
0.5mm
What depth of clearance is required for a lingual bar?
- 10mm
- 4mm from margin, 4mm for the bar, 2mm for clearance
What is a diastema?
- space between 2 teeth
How is the OVD or RVD recorded?
- two dot method on chin and nose, using dividers to measure distance
- willis bit gauge, using fixed arm placed under nose and sliding arm under chin
What is the OVD?
- occlusal vertical dimension
- teeth closed together
What is the RVD?
- resting vertical distance
- lips closed together
- jaw relaxed
- space between posterior teeth
What is the ala tragus line?
- tragus to corner of the nose
- parallel to the occlusal plane
What is the dentofacial midline?
- usually coincides with the space between the central incisors
What is the inter pupillary line?
- horizontal line between pupils
- parallel to upper incisal plane
What is ICP?
- intercuspation
- where is it comfortable for the patient to bite
What are the pros of acrylic teeth?
- chemically bond to base
- natural appearance
- silent function
- easy to adjust
What are the cons of acrylic teeth?
- low abrasion resistance
- soluble in saliva over time
- dimensional change over time
What are the pros of porcelain teeth?
- natural appearance
- inert in saliva
- high heat distortion
What are the cons of porcelain teeth?
- noisy function
- brittle
- mechanical attachment to base is more likely to fail
What is overbite?
- vertical misalignment
- upper teeth excessively overlap the lowers when posterior teeth close together
What is overjet ?
- horizontal misalignment
- horizontal separation of more than 2mm between uppers and lowers when posterior teeth are closed
What is ridge lap?
- section of artificial tooth that heavily overlaps with the base to ensure strength
What is freeway space?
- difference between the OVD and RVD
- space between teeth at rest
- usually between 2-4mm
When is it important to do a primary registration?
- when there aren’t enough teeth present to hand articulate the casts
Why should incisal rests be avoided?
- poor aesthetics
- interfere with the occlusion
What is the purpose of jaw registration?
- to ensure both height and position of teeth are recorded
What is the secondary registration?
- done after design and master impressions
- used to ensure no errors in complex cases
What is the retro molar pad?
- cushioned mass of tissue on the alveolar process of the mandible distal to the last molar
What is appointment 1 in RPD?
- patient assessment, examination and history
- take primary impressions
- casts are poured up and special tray made
What is appointment 2 in RPD?
- primary jaw registration if teeth cannot be hadn’t articulated *
- denture design created
- NB : this step is not require if casts can be hadn’t articulated
What is appointment 3 in RPD?
- tooth prep
- master casts taken with special trays
What is appointment 4 in RPD?
- framework trial
What is appointment 5/6 in RPD?
- jaw registration with record blocks on framework (if required)
OR - framework trial and wax tooth trial (selected tooth shade and mould at the previous appointment)
What is appointment 7 in RPD?
- delivery of the finished denture
Give an overview of the appointment schedule of a denture.
- Patient assessment, exam and history, primary impressions taken.
(2. Primary jaw registration if casts cannot be hand articulated.) - Tooth prep and master impressions taken in special trays.
- Framework trial.
(5. Framework trial with record blocks if required.) - Framework trial with wax tooth trial.
- Delivery of the completed denture.
- Review.
What are the effects of tooth loss?
- psychological
- loss of masticatory function
- loss of speech, some sounds are impacted by the loss of teeth (especially anteriors)
- loss of alveolar bone, PDLs and associated soft tissues
What are some contradictions to using an RPD?
- epilepsy (must be a fixed appliance)
- arthritis or neuromuscular problems may affect the ability to insert or remove denture, or the retention of the ridge/muscle tone
- xerostomia, can be drug induced, affects adhesion of the denture to the mucosa
- osteoporosis, bisphosphonates can induce osteonecrosis of the mandible
What are some complications associated with RPDs?
- denture stomatitis, occurs when denture is worn through the night, or not cleaned regularly
- mucosal irritation
- damage to soft tissues
- plaque retentive factor
What pathogen causes denture stomatitis?
- Candida albicans
Why are mounted study casts important?
- allow you to see the occlusal relationship between the jaws
- to see if any components would interfere with the occlusion
What is the purpose of surveying?
- to identify the path of insertion
- in turn, this identifies undercuts that can be used or retention or require blocked out
What do you use the analysing rod for?
- to survey the cast
What do you use the graphite marker for?
- to record the undercuts identified with the analysing rod
How do you tripod a cast?
- use the analysing rod and a pencil
- one line on the posterior wall, two on the anterior arch
Why do you tripod the cast?
- to reorientate the cast if needs be to the horizontal occlusal plane
What issues does graphite present when surveying?
- due to graphite being slightly flexible it can record artificial undercuts, therefor it is not a true, accurate representation
How can teeth be modified to assist with denture design?
- composite build up if the undercut is not deep enough
- rest seats if there are heavy occlusal contacts
What are the steps of surveying?
- ensure the occlusal plane is horizontal using steel rule
- assess the path of insertion/removal and undercuts using the analysing rod
- if happy with the path of insertion, tripod the cast using the analysing rod
- use a chiselled graphite marker to record any soft adn hard tissue undercuts
- use the undercut gauge to determine which undercut are suitable for retentive clasps
