some concept stuff Flashcards
(21 cards)
why do we have to classify? For Kennedy
- give clues to treatment and design problems of a particular case
- location and number of edentulous spans
- allow us to think about the type of support required: tooth, mucosa or tooth and mucosa
- can facilitate discussion between dentists
definition of surveying
is a diagnostic procedure of locating, delineating and appraising the contour and position of teeth and alveolar bone prior to designing a removable prosthesis
defn of guide plane
Glossary of Prosthodontic Terms 1977
guide planes are 2 or more vertically parallel surfaces of abutment teeth oriented so as to direct the path of placement and removal of RPDs
they may occur naturally or more commonly, need to be prepared
fxn of guide planes
- provide one path of placement and removal of the restoration (hence eliminating detrimental strain to abutment teeth and framework components during placement and removal)
- ensure the intended actions of reciprocal, stabilizing and retentive components (retention against dislodgement will work when the dislodging force is directed other than parallel to the path of removal)
- eliminate gross food traps between abutment teeth and components of denture
4 factors that determine path of insertion
1) GUIDE PLANES
- determines the direct path of insertion and withdrawal
- provide frictional retention
2) RETENTIVE AREAS
- need to try to balance the number of retentive undercuts on abutment teeth for both sides
3) INTERFERENCES
- look out for teeth with high survey lines because we cant be placing our wires so high
- avoid large soft and hard tissue undercuts because when we block these out then large gaps will be between dentures and tissues which causes poor retention
4) ESTHETICS
- if replacing anterior teeth, a more vertical path of placement is often necessary so that neither the artificial teeth nor adjacent natural teeth will have to be modified excessively
disadvantage of having a vertical path of insertion/ removal that coincides with path of displacement
is that the denture comes out easily when eating sticky foods
and so retention will depend entirely on clasps
defn of rest
a rigid extension of a fixed or removable partial denture which contacts a tooth or teeth to dissipate vertical or horizontal forces (ie supports the denture)
defn of direct retainers and what are some examples
is a clasp or other retentive device applied to an abutment tooth for the purpose of holding a RPD in position
examples of direct retainers
- clasps
- guide planes
- soft tissue undercuts (which the flange engages)
- fitting surface of denture base (retain by cohesion and adhesion)
- muscular control
why do we need reciprocation (what is the rationale for it)
during insertion and removal of prosthesis, damaging lateral forces may be applied to the teeth by clasps as they move over the maximum curvature of the crown
so each force exerted on a tooth by a clasp arm must be offset by an equal and opposite force that is provided by reciprocal arms
what is an indirect retainer and the function of it
it is when free end saddles are going to be dislodged, they rotate about fulcrum lines and this movement can be countered by placement of indirect retainers
indirect retainers assist direct retainers in preventing the displacement of the denture bases by functioning through lever action on the opposite side of the fulcrum line
where should we place indirect retainers
as far as possible from the distal extension base
in a prepared rest seat on a tooth capable of supporting its function
defn of connector
- major vs minor
connector: a part of a RPD which unites its components
major: part of a RPD that connects components on one side of the arch to components on the other side
minor: connecting link between major connector or the base of a removable partial denture
and the other units of the prosthesis like clasps, indirect retainers and occlusal rests
what are the 3 surfaces of a denture
1) FITTING surface
- in contact with underlying mucosa and neighbouring teeth
2) OCCLUSAL surface
- surface which makes contact with corresponding denture/ dentition
3) POLISHED surface
- in contact with lips, cheeks, tongue
what is the approach to denture design
OSCARR (elaborate on each in different flashcards)
1) outline saddle
2) support
3) connect
and
4) retain
5) reciprocate
what are our considerations for the outline saddle?
occlusal table
- we want to reduce the area of the occlusal table to reduce force to underlying tissues during mastication
- can have narrower posterior teeth
base extension
- we want maximum possible area covered by base, in order to distribute functional forces over a larger area
design of polished surface
- must be shaped correctly so muscular forces can enhance stability and retention
- denture placed in neutral zone
defn of neutral zone
space between tongue and cheeks where opposing muscular forces are in balance
defn of support and components which provide it
resistance of a denture to displacement by functional stress in a tissue ward or vertical direction
components:
- rests
- denture base and flanges
- major connectors
defn of bracing, rationale and the components of RPD which provide bracing
defn:
- resistance to horizontal components of masticatory forces which tend to displace denture in antero posterior and lateral directions
- only occurs when the denture is fully seated
components:
- flanges, connectors
- rigid bracing arm of clasp and plates
what is the bracig component specific to a distal extension saddle case
- distal extension saddle is special because it is capable of being displaced posteriorly and of rotating in the horizontal plane
- posterior movement of distal extension saddle is prevented by coverage of pear shaped pad and by minor connector which contacts the mesiolingual surface of the premolar tooth
what are possible damaging effects of rpd
1) damage to gingiva
because of enhanced plaque retention, food impaction at gaps, poor support
2) denture caries
enhanced plaque retention and poor OH
3) leverage on abutment teeth
excessive load on weak abutment tooth, or poor designs of clasps
4) accelerated bone resorption
due to increased OVD or under extended flanges for support
5) inflammation of mucosa covered by denture
can be due to localised pressure or candida infection
defn of fulcrum line
an axis passing through the rests of the most posterior abutments
