pros Flashcards
CoCr indications
greater strength
more hygienic design possible
acrylic indications
temporary denture
poor OH or likely to have denture additions
cheaper
inadequate support from remaining teeth alone (need mucosa support too)
kennedy classification
anatomical classification that describes the number and distribution of edentulous areas present
kennedy class I
bilateral free end saddle
kennedy class II
unilateral free end saddle
keneedy class III
unilateral bounded saddle
kennedy class IV
anterior bounded saddle
crossing the midline
craddock classification
simple classifciation based on support
craddock class I
tooth bearing
preferred - most comfotable, natural feeling (load transmitted via PDL)
craddock class II
mucosa bearing supporting
craddock class III
mixed - tooth and mucosa borne
support
definition
resistance to occlusal directed forces
prevents/resists movement and distributes load
support can be provided by
utilising hard tissues (teeth, bony undercuts) and large surface coverage (palate)
functions of rests
- Oppose movement of denture base towards tissue (support),
- help distribute/direct occlusal loads (down long axis of abutment tooth),
- provide anterior bracing,
- involved in reciprocation and indirect retention,
- determine axis of rotation for free-end saddle RPDs
how should rests be placed
Kennedy I/II - not immediately adjacent to saddles (free end)
Kennedy III/IV - immediately adjacent to saddles (bounded)
Craddock I - on tooth surface nearest base
Craddock III - on tooth surface not closest to base
rests
Components that provide mechanical support. Extension of the denture onto a tooth.
Described by the part of the tooth that they contact.
Rests in CoCr are rigid and strong and connect to base via connectors.
PMMA rests are flexible and have poor strength and are mechanically incorporated within the base and loads can cause stress
features f mucosal supported denture
As large an area as possible, base must be 3mm from gingival margin to adduct for soft tissue compressibility
every partial denture - Entirely mucosa-borne. Restores arch with contact points, wire stops prevent distal drift of most posterior teeth. Gingival margins not covered
retention
resistance to vertical displacement.
Mechanical, muscular, physical
direct retention
esistance to vertical displacement of denture. Clasps, guide planes, soft tissue undercuts, precision attachments
direct retention
esistance to vertical displacement of denture. Clasps, guide planes, soft tissue undercuts, precision attachments
indirect retention
resistance to rotation displacement of denture. Provided by placing components to resist rocking
ideal pattern of retention
Triangular, with one point on opposite side of the arch
retainers
Components that resist displacement of the denture
indirect retainers
Resist rotation about the clasp axis by acting on the opposite side to the displacing force.
fulcrum axis
Axis around which a tooth and Craddock III denture tends to rock when the saddles are loaded
mechanical retention
ways to provide
Clasps and guide planes
guide planes and how do they work
Retention through friction.
Supplementary direct retention.
Two or more parallel surfaces on abutment teeth used to limit the PoI and improve retention and stability
what do altered PoI provide
retention
what do clasps do
how to do they work
Provide retention by engaging the undercut of a tooth
If the clasp arm is seated below the undercut
clasp efficacy depends on
3
Material,
cross-sectional thickness and shape,
length
material and length for 0.25mm undercut
cast CoCr
at least 15mm
0.5mm undercut material
wrought gold
0.75mm undercut
wrought strainless steel
how is muscular rentention achieved
action of surrounding musculature on the shape of the polished surface. Involves patient’s muscular control and denture extension into sulcus
how is muscular rentention achieved
action of surrounding musculature on the shape of the polished surface. Involves patient’s muscular control and denture extension into sulcus
how is physical retention achieved
Existing forces of **adhesion, cohesion, surface tension, atmospheric pressure. **
Includes closeness of adaptation, extent of base and peripheral seal
how is indirect retention achieved
Extension of the base to provide a fulcrum of a class II lever, preventing rotation. Stability for free-end/very long bounded saddle
reciprocation
how to achieve
Movement/force of the opposing element to prevent pressure from the retentive clasp arm acting on the tooth (resistance to lateral movement).
Provided via reciprocating (non-retentive) clasp arm (or reciprocal connector) above maximum bulbosity of the tooth remaining in contact with the tooth, prevent horizontal tooth movement caused by action of clasp flexing.
RPI system
Stress reliving clasp system. Used in Craddock III and commonly for Kennedy I/II.
Used to reduce load on such teeth
Mesial rest, proximal guide plate, gingivally-approaching I-bar clasp
* As the saddle sinks into the denture bearing mucosa there is a rotation of the denture around the mesial rest
* Both the distal guide plate and the I bar rotate downwards and mesially and disengage from the tooth
* Potentially damaging torque avoided
Retention, indirect retention (via proximal plate and minor connector) and reciprocation (if gap between plate and connector is less than width of tooth)
major connectors
role
types
connect components on one side of the arch to the other
plate
bar
ring
space needed for lingual bar
8mm (3mm from gingival margin, 4 mm height of bar, 1mm clearance to Fom)
3 key anatomical features for complete dentures
Hamular notch
* area between distal surface of tuberosity and hauler process of medial pterygoid plate; ideal site for distal border,
* helps with post seal
Retromolar pad
* triangular pad of soft tissue at the posterior end of the lower edentulous ridge.
* Support
Retro-mylohyoid space
* space at distal end of lingual sulcus, posterior to mylohyoid.
* Aids in retention and stability
impression definition
reverse/negative form of the tissue
Cawood and Howell ridge classification
I. I - dentate;
II - post-extraction;
III - broad alveolar process;
IV - knife-edge;
V -flat ridge (no alveolar process);
VI - submerged ridge (loss of basal bone)
what is support in C/C
Resistance to vertical movement of denture (occlusal directed forces).
ways support is provided in upper C/C
2
hard palate, residual ridge
ways support provided in lower C/C
3
residual ridge, buccal shelf, retromolar pad
retention
reistance to displacmeent in a vertical direction
3 ways to get retention
Peripheral seal, contact area between denture and tissues,
denture extension,
close fit,
viscosity/volume of saliva** (adhesion cohesion)**
stability
Resistance to horizontal movement
ways to get stability
Stable/flat occlusal plane,
denture teeth in neutral zone,
correct denture extension.
neutral zone
Area where muscular displacing forces are in balance. Ideal tooth position where displacing forces of cheeks and lips are balanced with the opposing displacing forces of the tongue
6 ways to optimise retention and stablity of denture
Maximum extension of denture base,
close adaptation to mucosa,
teeth in neutral zone,
correct shape of polished surfaces,
good border seal,
balanced occlusion
alginate
5 properties
mucostatic,
cheap,
easy to use,
elastic,
poor tear resistance
impression compound
3 properties
non-elastic,
mucocompressive,
difficult to use
polyether (impregum)
3 properties
dimensionally stable
very accurate,
hydrophilic
occlusal stops
Allow accurate correction of posterior borders of tray by pre-forming impression material, improving peripheral seal
fucntion of border moulding
Full the functional sulcus (depth of sulcus during normal movement)
3 objectives of jaw registration
Determine occlusal plane and jaw relationship,
define shape of maxillary rim and position of lower teeth
select shade and mould of teeth
stages in jaw registration
measure RVD and OVD with willis bite gauge
adjust upper record block to anterior and posteiror occlusal plane and check buccal corridors
mark lip line, midline and canine line
establish face height but adjusting lower block to upper
identify lower tooth position
take bite registration
select appropriate tooth
assess during jaw reg
SOARE - Extension, retention, stability, occlusion, appearance.
LIMBO - lip line, incisive level, midline, buccal corridor, occlusion
Upper centrals 10mm anterior to incisive papilla, occlusal plane parallel to ala-tragus line
checks for delivery
Function, aesthetics, 3 denture surfaces, satisfactory occlusal contacts, extension, retention, stability, incisal plane orientation, occlusal plane orientation, OVD, porosity, undercut areas, sharp areas, comfort, looseness, appearance, speech, extension, retention, stability, occlusion, occlusal planes, OVD, FWS,
4 components of denture stomatitis (chronic pseudomembranous candidiasis)
Candidal infection, poor denture hygiene, night-time wear, high sugar intake, systemic factors (iron deficiency, steroid use, xerostomia).
Mx - denture hygiene, miconazole gel to fitting surface, systemic fluconazole if indicated
nystatin if on statins or warfarin
4 components of denture stomatitis (chronic pseudomembranous candidiasis)
Candidal infection, poor denture hygiene, night-time wear, high sugar intake, systemic factors (iron deficiency, steroid use, xerostomia).
Mx - denture hygiene, miconazole gel to fitting surface, systemic fluconazole if indicated
nystatin if on statins or warfarin
post dam helps in
Retention, stability
reasons for looseness
8
Tori, flabby ridge, high renal attachment, recent extractions, incorrect peripheral extension, teeth not in neutral zone, unbalanced articulation, hyposalivation
reasons for pain
12
Over-extension, blebs, residual monomer, poor fit, excessive post dam, retained roots, bruxism, premature occlusal contact, non-balanced occlusion, locked/wedged occlusion, rough fitting surface, errors in occlusion
eating problems
FWS, looseness, pain, chewing at side
speech problems
Incisors to palatal, incorrect OJ/OB, palatal PMMA too thick, lack of retention, reduced OVD
overdenture
what
adv
disadv
ideal abutments
Denture that derives support from one or more abutments or implants - seated over the top of these
Preserve alveolar bone around retainer tooth, improved support, retention and stability, preservation of proprioception via PDL, psychological benefit of maintaining natural teeth
RCT likely required, increased fracture risk, more maintenance required by patient and dentist, roots prone to caries, base may be required to be thinned to avoid excessive bulk in the region of the retained tooth
Canines > molars > premolars > incisors
Ideally bilateral and symmetrical with minimum of one tooth space between them; healthy attached gingiva, good perio support, no mobility
RPI system
Stress reliving clasp system. Used in Craddock III and commonly for Kennedy I/II.
Used to reduce load on such teeth
Mesial rest, proximal guide plate, gingivally-approaching I-bar clasp
* As the saddle sinks into the denture bearing mucosa there is a rotation of the denture around the mesial rest
* Both the distal guide plate and the I bar rotate downwards and mesially and disengage from the tooth
* Potentially damaging torque avoided
Retention, indirect retention (via proximal plate and minor connector) and reciprocation (if gap between plate and connector is less than width of tooth)
tx planning for RPD
History
Patient complaints
* Denture history
* How long have they had them? How they cope? How many had in last 5 years? Are they wearing their latest dentures?
* Full denture assessment form
Dental history
Medical history
Social history
Extra oral
Smile line
TMJD
Face height, commissures of lips
OVD and RVD
Intra oral
Soft tissues
Perio status
Restorations/caries – charting
Occlusion – index teeth
Aesthetics
paramount - assess need/desire/suitability/more tooth loss likely
tx planning for RPD
History
Patient complaints
* Denture history
* How long have they had them? How they cope? How many had in last 5 years? Are they wearing their latest dentures?
* Full denture assessment form
Dental history
Medical history
Social history
Extra oral
Smile line
TMJD
Face height, commissures of lips
OVD and RVD
Intra oral
Soft tissues
Perio status
Restorations/caries – charting
Occlusion – index teeth
Aesthetics
paramount - assess need/desire/suitability/more tooth loss likely
aims of partial denture design
3
- Replace lost teeth & tissues, restoring function , speech & aesthetics
- Minimize damage to adjacent teeth, restorations & tissues
- Designed with periodontal health in mind
designing partial dentures approach
case assessment - denture, OH, occlusion, risk factrs, index teeth
support - craddock and kennedy
denture base material - pt opinion and state of abutments
POI and undercuts - survey
retention - clasps
indirect retention - resistance to rotational movements around clasp fulcrum
bracing - flanges
simplification
systematic
designing partial dentures approach
case assessment - denture, OH, occlusion, risk factrs, index teeth
support - craddock and kennedy
denture base material - pt opinion and state of abutments
POI and undercuts - survey
retention - clasps
indirect retention - resistance to rotational movements around clasp fulcrum
bracing - flanges
simplification
systematic
CoCr denture base
thinner
stronger
more expensive
difficult to add to
better tolerated by pt
acrylic denture base
weaker
thicker
cheaper
easier to add to
less well tolerated
claps
Undercuts – need to be suitable depth
* Chrome 0.25mm
* Gold 0.5mm
* Stainless steel 0.7mm
Flexibility
* Longer the arm = more flexible
Aesthetics
* May need to compromise retention for aesthetics
Reciprocation
* Denture base or reciprocating arm
Minor connectors
Common clasp types
* I bar, occlusal approaching clasps
