Prosthodontics Flashcards
which denture reconstruction technique would be appropriate to give pt replacements dentures they can tolerate
replica dentures
other than replacement dentures, state 2 tx methods which can be used to improve retention and stability in loose complete dentures
relining
rebasing
what is the technique for replica dentures
- upper large dentate trays, vaseline and putty in the original denture
- capture impression of the occlusal surface, mould to 2mm of edge
- place vaseline and notches for removal and replacement
- capture impression with putty of the fitting surface of the denture tray, outer surface down
- ensure flanges of denture captures
- smooth edges and wait for set
- light bodies silicone for jaw registration
old dentures can be modified with greenstick before replica taken
what is relining a denture
adding a new base material tot issue of surface of existing denture in sufficient quantity to fill space which exists between original denture and altered tissue contour
improves stability and retention
usually chair side
3 types of relines and when done
temporary - tissue conditioning, post-immediate, after implant surgery
soft - parafunctional habits
permanent - peripheral seal problems, correction of errors after masters, immediate/post-immediate after lots of temporary relines
materials used for relines
heat-cured acrylic
self-cured acrylic [coe comfort]
heat-cured silicone
self-cured silicone
what is the technique for rebasing a denture
- undercuts removed
- wash impression taken using denture in closed mouth technique
- impression poured in stone with overcast
- denture removed to reveal new working model
- post dam carved
- remove fitting surface + palate
- denture placed back on overcast, gap between denture and model is filled with wax
- overcast removed as served purpose of maintaining denture position and OVD
- palate added back in wax
- flasked using Dundee injection method, wax removed and acrylic injected
- trimmed and polished
describe the 3 important features of complete dentures you would check in try-in stage
- retention and stability
- base extensions
- lip support
- incisal level
- midline
- buccal corridor
- occlusal planes
- position of teeth
- vertical dimension, FWS
- even contact in occlusion
- speech
- aesthetics
53 y/o presents with loose dentures and palate denture bearing area red.
which organsim is likely
Candida albicans
3 most likely contributing local factors to denture stomatitis
ill-fitting dentures, poor denture hygiene, wearing dentures overnight, reduced salivary flow, denture material
define support in RPD and what components do this
resistance to vertical movement of denture towards tissue via occlusal directed load
rest seats, abutments, connectors
define retention in RPD and what components do this
resistance to displacement of denture away from the tissue
clasps, minor connector
give types of connectors for maxilla and mandible
palatal bar/ring
mid palatal strap
plate
horseshoe
lingual bar
sublingual bar
plate
what is the advantage of lingual bars
minimal coverage of the gingival tissues and teeth
allows for better cleaning and salivary flow
reduced bulk in CoCr
how do you achieve retention in complete upper denture
post-dam
palatal coverage
adequate extension into buccal sulcus
adhesion-cohesion with acrylic
peripheral seal
neutral zone
biometric principles - where are denture teeth located on
upper - slightly buccal to ridge crest
lower - on the ridge crest
what is a shortened dental arch
reduced number of teeth in the dental arches, with reduced or absent molars/premolars
must be at least 20 teeth
do not replace them
generally 3-5 teeth each quadrant
why is the shortened dental arch acceptable
enough occluding pairs necessary for function, speech and aesthetics
indications for shortened dental arch
pt unwilling for complete dentures
good OH, no perio
extensive tooth loss
good prognosis remaining teeth
pt preference/motivation
medically compromised
contraindications for shortened dental arch
pathological tooth wear
poor prognosis remaining teeth
parafunctional habits
young pt
periodontitis
malocclusion
how could you extend a shortened dental arch
bridges
RPD
implant
5 requirements of occlusal stability
1 - stable occlusal contact all all teeth in centric relation/ICP
2 - anterior guidance in harmony with envelope of function
3 - all posterior teeth disclude in mandibular protrusive movement
4 - all posterior teeth disclude on non working side on lateral movement/excursion
5 - all posterior teeth disclude on working side on lateral movement/excursion
signs of occlusal trauma
mobility, pain, wear facets, fractured teeth, widening PDL, scalloping, pronounced linea alba, NCTSL
what are the ideal properties of a denture base
Dimensionally accurate, high softening temperature, high hardness/abrasion resistance, thermal expansion equal to abutment teeth, low density, high thermal conductivity, biocompatible, high YM, high elastic limit, high fatigue strength, inexpensive
what are the constituents of PMMA
- Powder = PMMA beads, benzoyl peroxide initiator, pigments, fillers
Liquid = MMA monomer, hydroquinone inhibitor, cross-linking agent ethylene glycol dimethacrylate, plasticisers
give 4 faults of denture base production and how they can occur
contraction porosity = too much monomer, insufficient pressure, insufficient excess material
gaseous porosity = monomer boiling in bulkier parts of denture
granularity = not enough monomer
crazing = internal stresses due to fast cooling rate
advantages as CoCr as a denture base
high YM - rigid
high strength
high impact resistance
high thermal conductivity
thin, lightweight
high softening temperature
corrosion resistant
excellent retention
disadvantages of CoCr as a denture base
cost
difficult to add teeth to
aesthetics
what undercuts are required for CoCr, SS + Au clasps
0.25mm CoCr
0.5mm SS
0.75mm Au
ideal properties of an impression material
high surface reproduction/ accuracy
high tear strength
100% elastic recovery
biocompatible
no dimensional change
ease of use
name 2 non-elastic impression materials
impression compound
impression paste [ZOE]
name 4 elastomers
polyether [impregum]
silicone;
- addition silicone [PVS]
- condensation silicone [lab putty]
polysulphide
name 2 hydrocolloids
alginate
agar
what are the constituents of alginate
sodium alginate
calcium sulphate
trisodium phosphate
filler
what is the setting reaction of alginate
sodium alginate + calcium sulphate
=
calcium alginate + sodium sulphate
2 advantages of alginate
ok accuracy
easy to use
acceptable taste/smell
no toxic
cheap
2 disadvantages of alginate
poor tear strength
sensitive to environmental factors e.g. temperature
needs stored properly
limited shelf life
uses of alginate
primary impressions
master impressions
study model impressions
3 advantages of elastomeric impression materials over alginate
better accuracy
better tear strength
better surface detail reproduction
better shelf life as doesn’t dry out
what does RPI stand for
rest on mesial surface
proximal plate on distal surface
I-bar, gingival approaching
RPI MOA
rest mesially acts as an axis of rotation
as proximal plate and I-bar rotates downwards and medially [respectively], around the axis of rotation during occlusal load
the I-bar and proximal plate disengage from tooth/undercuts
potential traumatic torque avoided
what are the measurements required for a lingual bar in RPD
3-4mm from gingival margin, height 4mm minimum of bar, clearance 3mm from floor of mouth
>7/8mm needed
aetiology of denture stomatitis
growth of bacteria e.g. Candida albicans
primarily denture bearing area
poor denture hygiene, wearing dentures overnight, smoking, immunocompromised, HIV, inhaler use
how is denture stomatitis managed
denture hygiene instructions
tissue conditioner
manage predisposing factors
OHI
antifungals - miconazole to fitting surface
how do you restore freeway space in very worn dentures
temporary relines
rebase
occlusal pivots
restore occlusal surface with auto-polymerising acrylic resin
what problem can occur with a complete upper denture occluding with partial lower
combination syndrome resulting in a flabby ridge
why does combination syndrome occur
bone loss maxillary ridge, hypertrophy of tuberosities and papillary hyperplasia in hard palate
extrusion of mandibular anterior teeth which occlude with force against the anterior ridge
causes bone to resorb with loose alveolar tissue
how to manage combination syndrome
reduce trauma = maximise coverage on denture bearing area [short post dam]
optimise load = use over denture abutments to reduce alvoelar resorption
stability = optimise border seal, effective post dam
ensure good posterior support
try to regularise occlusal plane
reduce incisor teeth length??
define Kennedy class 1
bilateral free end saddle
define Kennedy class 2
unilateral free end saddle
define Kennedy class 3
bilateral bounded saddles
define Kennedy class 4
anterior bounded saddle crossing midline
define Kennedy class 2 mod 1
unilateral free end saddle with 1 bounded saddle
how to take impression with flabby ridge/combination syndrome
mucostatic impression so tissues are recorded at rest
2 stage impression with medium body then cut out impression material and make hole in tray over flabby ridge and take 2nd impression with light body
OR
window technique with relief holes cut in special tray to allow flow of material and leave tissues undisplaced
use low viscosity impression material
what is a system of design used for designing PD
outline saddle areas
support
retention
stability
reciprocation
connector
give 2 maxillary connectors with adv and disadvantages
plate/strap =
- thin
- BUT palate covered
bar =
- less coverage
- BUT thicker
give 2 mandibular connectors with adv and disadvantages
lingual bar =
- gingiva clear
- less well tolerated
lingual plate =
- well tolerated as thin
- hard to keep clean
define stability in in RPD and how it is done
resistance to horizontal/lateral movement of denture
reciprocal arms of clasps
define indirect retention in RPD
resistance to rotational displacement
e.g. rest seats opposite fulcrum line
what is the difference between a soft lining and tissue conditioner
soft lining used to improve retention, fit, cushioning
conditioner used in unhealthy/ulcerated mucosa to aid healing
dissipates forces but good short term option
what is a functional impression
can be used with tissue conditioner
material applied and pt wears denture for 24hrs with movement and normal function
this impression is sent to lab for reline
how to check retention clinically of complete denture
pull on premolars, push on anteriors to check post dam
pull away lips to see if denture remains in situ
ask pt to speak, chew etc
what problem can an incorrect OVD give
pain, movement of denture, instability, TMD aggravation, angular chieilitis,
muscle strain and fatigue
overclosed appearance
reduced lip support
cannot function properly - speaking, chewing, swallowing
where should the post dam be
just anterior to the vibrating line - junction between soft and hard palate
what is the distal extension of a lower complete denture
2/3 of the retromolar pads
why is the buccal shelf used for support
stable anatomy, not as prone to resorption, large surface area, adjacent to buccinator muscle for support, less muscles action impact
what anatomical features help set the incisors
1mm anterior to incisive papilla
what 4 things make up shade
value, hue, chroma, translucency
give average horizontal bone loss for
incisors, canines, premolars, molars
incisors 6mm
canine 9mm
premolars 10mm
molars 13mm
adv of immediate dentures
maintain soft tissue, prevent collapse
haemorrhage control
transition help
uses existing occlusion
pt aesthetics and psychology
maintain muscle tone
allow continuation of function, speech and aesthetics
disadvantages of immediate dentures
fit poor as resorption
may require relining/rebase
only temporary measure which will need replaced
no trial stage
need to pay for 2 dentures in short time span
write a prescription for special trays for U+L complete dentures
please construct upper and lower special trays in light cured acrylic
non-perforated
upper 2 mm spacer and EO handle
lower 1mm spacer IO handle, finger rest premolar region
