Final Revision Flashcards
Which are the main components of an RPD?
saddles guide planes reciprocation type of prosthesis direct retainers: clasps artificial teeth minor connectors major connector/denture base rests
Clinical Indications of RPD:
- need for cross-arch stabilisation
- prophylaxis (TMJ)
- absence of adequate periodontal support (won’t support fixed prosthesis)
- long edentulous spans
- need to replace existing RPD
- failed fixed bridgework
- need for an immediate or temporary prosthesis
- financial limititations
- patient’s preference
- implants are contraindicated
- remaining teeth not suitable abutments for fixed bridge
- missing large number of teeth on both sides of the arch
Clinical Containdications of RPD:
- several unsuccessful previous attempts to provide satisfactory RPD
- non complaint patient/poor OH
- aesthetic demands impossible to satisfy
- patient expectations are non realistic
- implants placement may be possible with careful planning
- remaining teeth not suitable abutments for an RPD
- missing small number of teeth on one side of the arch
What is the treatment planning sequence?
- listen
- examine
- special tests
- evaluate
- discuss treatment
- reach agreement on treatment plan
What should be the No 1 priority when examining a new patient for the first time?
-screening for oral cancer and head & neck cancer
What is the treatment provision sequence?
- pain relief
- perio and endo treatment
- stabilization/temporization
- direct/indirect prostho & non-urgent endo
- prosthodontics
- maintenance
Anatomical features of maxilla?
Labial / buccal sulci Residual alveolar ridge Buccal shelf Labial / buccal frena Incisive papilla Rugae Labial / buccal lingual sulci Labial / buccal lingual frena Genial tubercles Retromylohyoid fossa Retromolar pad Palatine raphe (Palatine torus) Palatal gingival remnant Vibrating line / soft & hard palate junction (Mandibular tori) Mylohyoid ridge Fovea palatin Maxillary tuberosity Hamular notch
Labial / buccal sulci Labial / buccal frena Incisive papilla Rugae Residual alveolar ridge Palatine raphe (Palatine torus) Palatal gingival remnant Vibrating line / soft & hard palate junction Fovea palatin Maxillary tuberosity Hamular notch
Anatomical structures of mandible:
Labial / buccal sulci Residual alveolar ridge Buccal shelf Labial / buccal frena Incisive papilla Rugae Labial / buccal lingual sulci Labial / buccal lingual frena Genial tubercles Retromylohyoid fossa Retromolar pad Palatine raphe (Palatine torus) Palatal gingival remnant Vibrating line / soft & hard palate junction (Mandibular tori) Mylohyoid ridge Fovea palatin Maxillary tuberosity Hamular notch
Labial / buccal lingual sulci Labial / buccal lingual frena Genial tubercles (Mandibular tori) Residual alveolar ridge Buccal shelf Mylohyoid ridge Retromylohyoid fossa Retromolar pad
Why is it so important to know all anatomical features of an RPD?
- to avoid them
- to guide us on setting up the teeth
- to determine/limit denture extension
What biomechanical considerations do we need to have for an RPD?
forces applied to the tissues and to the RPD
Sequalae on using RPD:
damage to remaining teeth, periodontium, residual alveoar ridge
RPD design step by step:
- select POI
- mark teeth being replaced
- indicate positions and depth of undercuts
- plan: support, retention, stability
- join all components to major connector
- indirect retention
- direct retainers
- review
5 hazards in dental laboratory:
cross infection, fire, liquids, sharps and rotary instruments, eye injuries
Aims for preliminary jaw relationship registration:
- occlusion for diagnosis and treatment planning
- space for artificial denture teeth and other RPD components
What is MIP?
ICP
max intercuspal position
=teeth in max contact for an individual’s occlusion
-> best fit of teeth regardless of condylar position
What is RCP?
retruted contact position
=GUIDED occlusal relationship occuring at the most retruted position of condyles in the joint cavities
What is Retruted position?
same as RCP when there are no tooth contacts
What do we use to determine vertical dimension of occlusion?
wax bases and occlusal rims
Why do we need to establish a specific vertical dimension of occlusion first?
first OVD
after Jaw relationship
Surveying of primary casts for RPD design steps:
- preliminary visual assessment
- initial survey: Horizontal
- tilting the cast: Ant or Post -> avoid interferences, maximize retention and improve appearance
- final survey: ensure undercuts present both tilted and horizontal positions
- mark the tilt
Direct retention definition and example:
= prevents dislodging forces
ex: clasp (contains: reciprocal arm, minor connector, occlusal rest, retentive arm)
Indirect retention definition and example:
=resistance against rotational movement of a saddle away from the tissues around the major clasp axis
ex: (occlusal) rests
Tooth loss can be associated w/:
behaviour
What is risk analysis in relevance to RPD?
human error
Never make assumptions and always demonstrate to the patient
:)
Where to start if risks are involved?
yourself, dental team, patient, treatment outcome
What are the risks to the patient?
- direct injury
- direct trauma
- inhalation/swallowing small instruments
- treatment complications-> unsuccessful treatment outcome, damage to the remaining tissues, damage to the patient
What are the treatment complications specific to RPD?
- unretentive, unstable, poorly supported
- not well fitting
- not aesthetically acceptable
- patient unable to eat w/ the rpd
- technical complications
Damage to the remaining tissues:
bone, soft tissues, abutment teeth, non-abutment teeth
Damage to the patient:
swallowing/inhalation or rpd or components, tmj symptoms, allergic reaction, cross infection
SOS
General rules to avoid damage to remaining tissues by RPD?
- correct abutment tooth preps
- occlusal forces transferred to healthy periodontium
- only cover as little of tooth surfaces as possible
- avoid covering gingival margins and soft tissue as much as possible
- maintain 3mm distance b/w gingival margins and RPD components
- ensure retention, support, stability to minimize movement of RPD
- avoid creating food traps
- ensure occlusion is correct
- monitor regularly and modify
SOS
Common reasons for RPD failure:
failure to:
- undestand patient’s expectations
- communicate
- explain treatment options
- ensure patient what the treatment plan will involve
- treatment planning and treatment provision in correct order
specific to RPD:
- occlusion
- aesthetics
- RPD design
- RPD fabrication
Where can poor nutrition lead to?
- reduced immunity
- increased susceptibility to disease
- impaired physical and mental development
- reduced productivity
What are the short term effects of poor nutrition?
- stress
- tiredness
- capacity of work
What is good nutrition?
variety of foods from 5 groups each day
SOS
Components of masticatory system:
teeth
supporting tissues
jaws
TMJ
muscles involved directly/indirectly in mastication
vascular and nervous systems supplying these
What is the oral manifestation of vitamin A deficiency?
decreased salivary flow
dryness and keratosis of oral mucosa
decreased taste acuity
What is the oral manifestation of vitamin K deficiency?
increased blood blotting time following surgery
spontaneous bleeding of gingival tissues
What is the oral manifestation of Niacin deficiency?
filiform papillae exfoliation
red sore tongue
tongue and B mucosa burning sensation
What is the oral manifestation of Riboflavin deficiency?
angular cheilitis
red ‘plebby’ tongue
What is the oral manifestation of Folic Acid deficiency?
smooth red tongue
gingival inflammation
tongue and B mucosa erosions
What is the oral manifestation of vitamin C deficiency?
delayed healing
easily abraded tissues
What is the oral manifestation of Water deficiency?
dehydration of tissues
resulting in xerostomia
SOS
Masticatory ability defintion:
= individual’s own assessment of masticatory function
Masticatory efficiency defintion:
= time required to reduce food to a certain particle size
Patients w/ assymetric short dental arch:
unilateral chewing is prevalent
Masticatory performance definition:
=indicated by particle size and food distribution when chewed for a given # of strokes / time
Occlusal force measurements definition:
=measure functional forces when biting/chewing
Electromyography definition:
records muscle activity during chewing and maximal biting
What is a masticatory system?
=functional unit
-> functional and STRUCTURAL DISTURBANCE
ICP cases for Kennedy class IV:
avoid anterior contacts in ICP b/c in protrusion it will lose its stability
Non-ICP cases occlusal contact relationships for RPDs:
ensure its a non ICP case
wax bases and occlusal rims to establish OVD
the aim is to achieve a balanced occlusion
ICP cases occlusal contact relationships for RPDs:
post teeth provide simultaneous bilateral contacts
aim for canine guidance if there are concerns about stability of the RPD
you can ‘discover’ natural tooth contacts by guiding the mandible in RCP
Basic requirements for optimal occlusion:
- as many teeth as possible in ICP
- any slide from RP to ICP should be small and in a forward direction
- smooth, unrestricted movement in lateral excursions; any contact should be on the working side
- anterior tooth contacts bilaterally in protrusion
Cross arch stability definition:
=resistance against dislodging/rotational forces by teeth on opposite dental arch from edentulous space
Major connector definition:
=component of RPD connecting parts of it on one side of arch to those on the other side
-> provides cross arch stability to resist functional forces
Basic requirement of major connector?
rigidity
-ensures occlusal loads are evenly spread throughout the available supporting structures so smaller loads applied per surface area unit so less risk of damaging supporting structures
What happens if a major connector is flexible?
- damage to supporting tissues/structures
- patient discomfort
- ineffective RPD (eg: lack of retention, stability, support)
Basic design considerations of major connector:
- do not extend to moveable tissue (non-attached mucosa)
- avoid impinging on gingival tissues -> allow 3-4mm distance b/w major connector and gingival margins
- do not leave unnecessary ‘dead spaces’ of gingival margins
- avoid bony/soft tissue undercuts in placement/removal
- provide relief in areas of possible interference
- SOS consider possible rotation of free end saddle of RPDs
- biocompatible
- do not interfere w/ tongue movements
- do not substantially alter the natural contours of the lingual surface of the mandibular alveolar ridge and palatal vault
Mandibular major connectors:
lingual plate palatal bar lingual bar palatal strap sublingual bar palatal plate lingual bar w/ cingulum bar cingulum bar labial bar u-shaped connector
lingual plate lingual bar sublingual bar lingual bar w/ cingulum bar cingulum bar labial bar
Maxillary major connectors:
lingual plate palatal bar lingual bar palatal strap sublingual bar palatal plate lingual bar w/ cingulum bar cingulum bar labial bar u-shaped connector
palatal strap
palatal plate
palatal bar
u-shaped connector
Lingual bar properties:
- requires min 7-8mm height b/w lingual sulcus and gingival margins
- 3-4mm clearance to gingival margins for hygiene (below)
- 1st choice
- thicker inf. and tapered sup.
- trim and polish the inf border but not too much
- avoid impinging of soft tissues, especially in K class 1
Lingual bar ADV:
hygienic
aesthetics
rigid
avoids tongue movement interference
Lingual bar DISADV:
requires sufficient height
not easy to add teeth
doesn’t contribute to support or indirect retention
Lingual plate properties:
- LESS than 8 mm height b/w gingival margins and floor
- inf border placed more superiorly
- shouldn’t extent above the middle third of the teeth
- sup. part as thin as possible
- should incorporate cingulum rests on either end
- must follow teeth contours
Lingual plate ADV:
- can add teeth
- can be used to splint perio compromised teeth
- very rigid
- prevents food trapping
- contributes to support and retention
- comfortable
Lingual plate DISADV:
- challenging to ensure close fit
- may become visible
- covers wider area of teeth and soft tissues
- requires better OH
Sublingual bar properties:
- LESS than 8 mm b/w gingival margins and mouth floor
- more inf. and post. placement than Lingual bar
- when there is soft tissue undercut
Sublingual bar ADV:
aesthetic
more hygienic
Sublingual bar DISADV:
impression technique sensitive
not used when there is high frenulum / mandibular tori attachement
not easy to add teeth
does no contribute to support or indirect retention
Palatal strap properties:
Ant and post palatal strap properties:
Palatal strap:
Kennedy class 3 cases
rigid w/o being too bulky
shouldnt extend beyond occlusal rests
Ant and post palatal strap: very rigid all Kennedy classes thin as possible even when there is maxillary torus
Palatal strap ADV:
rigidity
midpalatal straps cause little tongue interference; acceptable by patients
Palatal strap DISADV:
ant straps interfere w/ tongue
difficult to cast and ensure close fit
post straps not well tolerated if extending too far posteriorly
Palatal plate properties:
covers more than half of palate requires close tissue adaptation thin as possible aim to replicate natural soft tissue contours of palate may be extended post w/ acrylic
Palatal plate ADV:
rigidity
support
well tolerated
easy to add teeth
Palatal plate DISADV:
increased weight
increased demands for indirect retention
extended tissue coverage
Minor connectors definition
=components that connect major connector to the clasp assembly, indirect retainers, occlusal and cingulum rests
-> transfer occlusal loads to abutment teeth and STABILIZE components
Minor connector location and properties:
location: embrasures, proximal surfaces
properties:
- should be rigid but not bulky
- reciprocation
- lingual embrasures need to make space for them in order to place the minor connectors on them to avoid tongue interference
Why are rest seat preps necessary?
- ensures V loading (better)
- avoid H loading
- avoid occlusal interference (teeth fracture)
- avoid rotation of base
occlusal rests on molars and premolars
cingulum rests on canines
RPD retention definition:
=RPD resistance to be displaced AWAY from supporting tissues
Which forces tend to displace an RPD from supporting tissues?
gravity
tongue
sticky food
Which is our primary concern?
retention
stability
support
support
-> if an RPD is poorly supported, occlusal forces acting across a fulcrum are conveyed to other parts of the RPD as displacement forces
Types of intracoronal RPD direct retainers:
precision attachements
semiprecision attachements
Types of extracoronal RPD direct retainers:
clasps
attachments
Disadvantages of Attachements:
- need to place crowns
- expensive
- increased difficulty
- increased maintenance needs
- require increased interarch space
- less hygienic (extracoronal)
Clasps definition:
=RPD components designed to provide mechanical retention through a flexible clasp arm, which engages an external surface of an abutment tooth in a cervical area to the greatest convexity of the tooth
-> direct retainers
Rest function and location:
=support
occlusal, incisal or cingulum rests
Proximal plate function and location:
stabilisation + determines path of insertion and removal
proximal surfaces. onto prepared guide planes
Clasp function and location:
middle third or above the survey line -> first 2/3: stabilization
gingival third, in measured undercut -> final 1/3: retention
Reciprocal arm function and location:
reciprocation
-middle third of the crown, opposite surface of the clasp
Important considerations of clasp design:
- depth of undercut
- exact position of termination of the clasp into the undercut
- flexibility
- visibility
- support
- protection of the abutment tooth
- risk of clasp fracture
SOS
What factors does flexibility depend on?
- length
- thickness
- shape (cross section)
- material
- fabrication method
Clasp length:
- gingivally approaching clasps longer than occlusal
- the longer the clasp, the more flexible
- stabilizing arm incorporated in acrylic so less flexible
- reduced flexibility w/ half round form lying in several planes (not a straight line)
SOS
Indirect retainer definition:
=RPD component which prevents vertical displacement of the distal extension denture base when it tries to move away from the tissues in pure rotation around the fulcrum line
Indirect retainers types:
auxiliary occlusal rests canine rests canine extension from occlusal rests on premolars palatal major connector modification areas cingulum bars or lingual plates
Denture base function:
supports artificial teeth
transfers occlusal forces to supporting tissues
aesthetics
stimulation of underlying tissues
Metal denture base ADV:
- biocompatible
- R to fracture
- thermal conductivity
- can be thinner
- rigid
- close tissue adaptation
- does not deform over time
Metal denture base DISADV:
- expensive
- increased weight
- adjustments, modifications and relining difficult/impossible
Considerations regarding the dentition prior to RPD provision:
dental charting perio condition endo condition occlusion occlusal plane interarch space amount of teeth 'showing'
Decision of extraction or restoring a tooth:
- strategic value of tooth
- amount of effort to restore/replace it
- rest of dentition condition
- objective criteria (ex: DPI)
- operator ability
- patient preference
- patient’s general condition
Dental Practiality Index ADV:
structural integrity perio state endo state local factors general factors
Dental Practiality Index:
0 1 2 4 6 >6
0 - no intervention 1 -simple treatment 2 -more complex treatment 4 -denture / bridge abutment 6 -treatment not generally considered practical >6 -implants
When should direct/indirect restorations be done?
prior to 2ry impressions
after RPD design
after the treatment plan is finalised
Interdigitation:
set up the RPD BEFORE the fabrication of opposing occlusal restorations to maintain occlusal anatomy of denture teeth
Types of preps on RPD abutments:
temporization perio treatment endo treatment direct restorations RPD preps prep for indirect restorations
Guide plane preps:
RECIPROCATION
3 mm height
remove > 0.5 mm of enamel
diamond bur
as far away from gingival margins as possible
direction of seating crown different to RPD POI
:)
Tooth & mucosa supported RPDs support is gained from:
depends on residual ridge
NOT from tooth or direct retention at the distal end
Indirect retention becomes more important
Support of a distal extension base:
- residual ridge
- RPD framework design
- total occlusal load applied
- impression technique
- accuracy of fit of denture base
- extent of residual ridge coverage by denture base
Ideal residual ridge:
- cortical bone covering dense cancellous bone w/ a broad, rounded crest and high vertical slopes
- firm, dense fibrous CT covering
Thinner loading bearing areas in:
mandible
Unfavourable residual ridge:
- mobile mucosa
- sharp ridge crest
- thin traumatized mucosa
SOS
Muco-static impression technique:
aim:
impression tray:
material of choice:
-no border moulding
aim: record soft tissues in their ‘anatomic form’
impression tray: spaced
material of choice: impression plaster
SOS
Muco-compressive impression technique:
aim:
impression tray:
material of choice:
-close fitting custom tray
aim: record soft tissues in their ‘functional form’
impression tray: viscous
material of choice: ZOE paste OR impression wax
SOS
Selective pressure impression technique:
aim:
impression tray:
material of choice:
-spacing of custom tray is different depending on location
aim: compress soft tissues only in main load bearing areas
impression tray: viscous
material of choice: ZOE paste
alternatively: impression wax, polyether
Custom made device definition:
=manufactured in accordance w/ a written prescription, under his responsibility, specific characteristics as to its design
Min requirement for Custom made device:
- device identification
- features extracted to define the particular device
- exclusive use by a particular patient
- ‘custom made device’ label
- conforms to all relevant essential requirements
- name of qualified person
- name and address of manufacturer
If you only provide a design sheet, what important info will you fail to convey?
POI
undercuts location for finishing clasps
exact major connector outline
flange extension
What other adjustments are needed at placement of RPD?
polished surfaces pink acrylic small inaccuracies expansion of plaster/acrylic occlusion again, before delivery
SOS
Interim prosthesis definition:
=a dental prosthesis designed to enhance aesthetics, stabilization and/or function for a limited period of time
What makes an RPD a temporary one?
- duration of use
- purpose of use
If a temporary RPD is used longer than initially intended the risks to the abutment teeth are:
lateral forces
excessive occlusal forces
caries
If a temporary RPD is used longer than initially intended the risks to periodontal tissues are:
denture bearing mucosa
periodontitis
residual alveolar ridge resorption
If a temporary RPD is used longer than initially intended the risks to the interim prosthesis are:
denture base fracture
artificial teeth fracture
If a temporary RPD is used longer than initially intended the risks to the patient are:
confidence loss
swallowing/inhalation of fractured part of interim RPD
develop habits
SOS
Provisional RPD to maintain space until definitive treatment is completed:
-adult patients: prevent migration of adjacent teeth or overeruption of opposing teeth
:)
SOS
Provisional RPD to assess and establish occlusal changes:
- most common: INCREASE in OVD
- fixed and removable options: RPD vs cast splint vs adhesive techniques
- overdenture vs overlay denture
:)
SOS
Never use a mucosa supported RPD to increase the OVD as a definitive treatment option
:)
SOS
Stability definition:
=prosthesis resistance to horizontal displacement
SOS
Interim restoration during treatment - typical time frame:
perio: 1-2
endo: 1/tooth
fixed: tooth/core built up
removable: 4-5 min
implant: 1-2
ortho: few months-few years
SOS
Temporary RPDs as training prostheses for perio patients:
- unless there are underlying medical conditions and/or aggressive periodontitis cases, these patients often are in denial of severity of their condition
- dental anxiety
- easier to accept RPD than CD
:)
What are the consequences of advanced residual ridge resorption on prostho treatment to replace the missing teeth?
advanced residual ridge resorption DOESNT MEAN loss of denture support
- ve impact on biomechanics of implant restoration
- reduced RPD support and stability
- increased RPD bulk
aim: maitain close denture base adaptation
SOS
Indications of relining tooth & mucosa supported RPD:
- SUPPORT FOR THE FREE END SADDLES
- food trapping
- discomfort
- denture not fitting well
- advance residual ridge resorption presence (space underneath the saddle)
How do we assess clinically for need for relining?
assess the occlusion, assess the rpd support in the free end saddles
