partial dentures system of design Flashcards
what are some alternative treatments to partial dentures
- no active treatment
- fixed prosthesis, either conventional or resin bonded
- implant retained prosthesis
why is it important for the clinicians to be the one to design the denture
we have seen the patient, know their story and what they expect
condition of the teeth, oral health
we have assessed current dentures and occlusion
have a more complete understanding of alternatives and can give clear cost information
what are the key principles to partial denture design
replace lost tissue and teeth, restore function, speech and aesthetics
minimise damage to adjacent teeth, restorations and tissues
designed with periodontal health in mind
what is the systematic approach to denture design
0 - case assessment
1 - classification of support for each saddle
2a - choose the denture base material
2b - connect saddles together
3 - choose the path of insertion and delineate undercuts
4 - resistant of movement away from the teeth
5 - indirect retention
6 - resistance of movement toward the teeth and tissues
7 - resistance to horizontal movement
8 - simplification
how are saddles connected together
connectors. literally.
what is surveying
choose the path of insertion and delineate undercuts
what is retention
resistance of movement away from the teeth
what is support
resistance of movement toward the teeth and tissues
what is bracing or reciprocation
resisting horizontal movement
label the partial denture and provide a short description of their function
from the top down
- major connector (lingual bar) to connect the parts
- cingulum rest (support and indirect retention)
- acrylic tooth restoring natural tooth
- pink acrylic restoring lost mucosa and bone
- occlusal rest for support
- ring clasp for retention
what is a saddle
an area of oral mucosa where teeth are being replaced
how are edentulous saddles classified for partial dentures
Craddock classification based on how the saddle is loaded. Kennedy classification based on the location of the saddles.
describe the craddock classifications
Class 1 - tooth borne
class II - mucosa borne
class III - tooth and mucosa borne
class IV - implant borne
class V - implant and mucosa borne
describe the Kennedy classifications
class I - bilateral free end saddle
class II - unilateral free end saddle
class III - single bounded saddle not crossing the midline
class IV - single bounded saddle crossing the midline
Kennedy class I
Kennedy class 2
Kennedy class III
Kennedy class IV
what is the difference between Kennedy class III and IV
III is not crossing the midline but IV does cross the midline
which saddle should be used to define the main Kennedy classifications
the most posterior saddle
what is the solution if there is more than 1 edentulous saddle
modifications are used to refine the basic classification, but the most posterior saddle will be used to define the main Kennedy classification
can you have a modification for all saddle classes
not class IV
what are the options for denture base material
acrylic
cobalt chrome
polyether ether ketone
flexible
gold
what are the two types of connectors
major connectors which connect all the components
minor connectors which connect rests, clasps and bracing arms
what are the common mandibular major connectors
acrylic plate, lingual bar, lingual plate
acrylic plate
lingual bar
lingual plate
mid palatal bar
anterior palatal bar
how to choose the path of insertion and delineate undercuts
surveying casts
surveyor or digital surveying
choose retentive elements
path of insertion and removal of the denture
retention means…
resistance of the denture to vertical displacement lifting away from the tissues
what are some common methods of retention
clasps
soft tissue undercuts
adhesion
friction
path of insertion
precision attachments and implants
how is indirect retention achieved
by one or more indirect retainers that reduce the tendency for a denture base to move in an occlusal direction or rotate about the fulcrum line
describe how the indirect retention occurs in this picture
incisal rest X transfers, but the fulcrum line AB to AC. as D rises on the new fulcrum, clasps act indirectly to resist this movement, the further C is away from AB the more effective the indirect retention will be
what are the two methods of rests to support the partial denture
occlusal and cingulum rests
what happens if there is inadequate denture support
It will sink into the tissues and traumatise them
what can be done if there is insufficient occlusal space for a rest
prepare rest seats with a drill
what is the horizontal movement that must be resisted in a partial denture
bracing of forward, backward and lateral dislodging forces
what does reciprocation prevent
clasp arms moving the clasped tooth
what do reciprocal arms do
prevent the tooth movement and engage the undercut
why should partial dentures be kept simple
complex designs have complex failures and problems
patient prefers simple
meet the demands of economic viability of working within health services
which saddle support is the least damaging
tooth borne
what is a clasp
something resting on the tooth to reduce the tendency for the denture to move
what are the functions of occlusal rests for partial removable denture
- provide vertical support for the partial denture
- maintain components in their planned positions
- maintain established occlusal relationships by preventing settling of the denture
- prevent impingement of the soft tissues
- directs and distributes occlusal loads to abutment teeth
what shape should occlusal rests be
rounded triangular shape with the apex toward the centre of the occlusal surface
why do the clasps have to cover both sides of the tooth ie wrap around it
the tooth would move otherwise
basic sequence of design
saddles
support
retention
bracing and reciprocation
connector
indirect retention
review of completed design
what does RPD design need to satisfy
the four principles shown to promote continued oral health
- effective support
- clearance of gingival margins
- simplicity
- rigid connector
why is the movement potential less for a tooth supported prosthesis
the functional loading is provided by the teeth
what is the residual ridge
remaining alveolar bone and overlying connective tissue covered with mucosa
how are tooth supported partial dentures retained and stabilised
by a clasp at each edentulous space
what is a requirement for clasps
they need to flex sufficiently during placement and removal of the denture to pass over the height of the contour of the teeth
describe the pros and cons of acrylic denture bases
pros
- affordable
- easy to repair
cons
- likely to break and crack
- stain
describe the pros and cons of cobalt chrome denture bases
pros
- strong and durable
- lighter and thinner than acrylic so more comfortable to wear
- less likely to stain
- more resistant to temperature changes
cons
- more expensive
- harder to adjust
what are the pros of cobalt chrome partial dentures
- custom designed for gums and bite
- can be made smaller to uncover more of the palate
- help prevent neighbouring teeth from moving out of position
- better for your overall oral hygiene
