prosthodontics Flashcards
what is the vibrating line?
junction between the hard palate and soft palate
what is the occlusal plane?
horizontal surface occupied by upper teeth
extends from tip of mesioincisal edge of upper central incisor to of mesiobuccal cusp of upper 1st molar on each side
what is the neutral zone?
specific area where the function of musculature will not unseat the denture
where forces generated by tongue are neutralised by forces generated by lips and cheeks
how is denture stability achieved?
make sure peripheries of denture are extended to the right depth
by making sure occlusion is balanced
what is the occlusal rim?
a wax structure with occluding surfaces attached to denture base
what is an occlusal rim used for?
recording relation of maxilla to mandible
positioning of the teeth
what features should be present on maxillary definitive impressions?
tuberosity
hamular notch
extension anterior to vibrating line for post dam
functional depth and width of sulcus
what features should be present on a mandibular definitive impression?
coverage of pear-shaped pad and buccal shelf
retro-molar pad and extension into lingual pouch
functional width and depth of sulcus
ensure area of primary support of buccal shelf and retromolar pad
where should a maxillary denture sit in order to create a good posterior seal?
at level of hamular notch
located between distal surface of tuberosity and hamular process of medial pterygoid plate of maxilla
describe use of impression compound for primary impressions
non-elastic material which records poorer surface detail
expensive and can be messy
good for primary due to high mucocompressive viscosity
describe the use of alginate for primary impressions
elastic material- will flow into undercuts
can record surface detail for primarys
describe the use of silicone for master impressions
dimensionally stable
can be made into a variety of consistencies which means it accurately records surface detail
describe the use of polyether/impregum for master impressions
dimensionally stable
can be made into variety of consistencies which means it accurately records surface detail
describe the use of alginate for master impressions
elastic- can flow into undercuts if they are present
what is the purpose of stops to the space prescribed in the canine and post dam regions of upper trays?
to allow correction of posterior borders of trays and will perform space for impression material
where should stops be placed to the space provided on lower trays in order to allow preformed space for impression material?
retromolar pad
ridge of canine areas
why is silicone not used for primary inpressions?
dimensionally stable and hydrophobic- can cause small defects and blows
very messy and technique sensitive
what information should be recorded on to a record block?
the OVD
centre line
occlusal plane
high lip line
canine line
arch form
what provides accurate fit for dentures?
accurate fit- as little space as possible between denture base and mucosa
border seal- extending flanges to depth of functional sulcus and incorporation of post dam
what anatomical features help identify where the posterior border should be placed for the upper denture?
hamular notch
vibrating line
palatine fovea
explain the cawood and howell classification
1- before extraction
2- after extraction
3- high well rounded ridge
4- knife edge shaped ridge
5- low well rounded ridge
6- depression bone level
what is the primary support area for maxillary dentures?
hard palate
what is the secondary support area for maxillary dentures?
ridge crest
name areas in a maxillary denture that may require relief
midline suture
incisive papilla
lingual frenum
what are the primary support areas in lower dentures?
buccal shelf and pear shaped pad
what are the secondary areas of support in lower dentures?
ridge crest and genial tubercles
what areas may need relief in lower dentures?
lingual ridge incline and mylohyoid ridge
define ‘retention’
the resistance to displacement forces e.g. gravity, speech and mastication
define ‘stability’
the ability of the denture to resist displacement by functional stresses
what materials can be used to modify trays?
soft red wax
green stick
putty
impression compound
what should the extension of master impressions be?
2mm short of sulcus depth to allow border moulding
what impression material is used for masters on replica dentures?
light body silicone
what material is used to make special trays?
light cured acrylic resin
define ‘mucocompression’
pressure is applied to the mucosa so that the shape of the tissues under load is recorded
define ‘mucostasis’
the minimum pressure applied to the tissues to record at rest
what are the steps of jaw registration?
adjust upper and lower block for retention
adjust upper block for occlusal planes
lower tooth position and horizontal jaw relationship
measure vertical dimension and establish face height
select shape and mould
what do you asses for patient’s current denture?
LIMBO
Lip support, nasiolabial angle 90 degrees
Incisal level
Midline
Buccal corridor- space in corners of mouth, taper towards back
Occlusal plane, interpupillary line and ala-traguc line
how do you record the bite?
jaw registration paste- jetbite
soft wax and patient bites onto it
what is the role of mould liners?
reduce porisity
easier for deflasking to be carried out
name the stages of complete denture design
primary impressions
primary casts and special trays
master impressions
master casts and record blocks
jaw registration
mount casts and set up
try in
finish denture
denture delivery
review
what are the laboratory stages of complete dentures?
primary casts and special trays
master casts and record blocks
mount casts and set up
process/finish denture
what are the transfer lines used when making dentures?
high smile line
centre line
canine line
residual alveolar line
alveolar contour line
rim profile
why do we mark the residual alveolar line?
so that the teeth are set in such a way above the the lower residual ridges that the contacts are on this line
why do we mark the alveolar contour line?
if the teeth are set on a slope then the denture may be displaced during function
what would you write in master impression stage of a complete denture lab sheet?
please pour cast of primary impression in 50:50 plaster/stone
construct upper and lower custom trays in light cured PMMA, non-perforated with upper 2mm spacing and lower 1mm spacing , intra oral handles and finger stops
what would you write in jaw registration stage of a complete denture lab sheet?
please pour casts of master impressions in 100% dental stone and construct wax rims for jaw registration. return rims on casts
what would you write in tooth trail stage of a complete denture lab sheet?
please mount casts in registration and set teeth for wax trial
return wax trial dentures on mounted casts
what would you write in delivery stage of a complete denture lab sheet?
please finish denture in heat cured PMMA and return on casts
what are the stages of denture delivery?
feel for lumps/bumps with gloved finger
remove any excess acrylic with acrylic bur in straight hand piece
check fit, retention, stability, aesthetics, speech, occlusal contacts
ask pt what they think
what instructions do you give to the pt when delivering a denture?
may take a while to get used to- if uncomfortable just wear for a few hours per day
may cause increased salivation and impede speech- this will stop eventually
chew on both sides of the mouth
rinse denture with water after every meal
clean denture twice a day
remove when sleeping
clean over sink with water- never use boiling water
brush with toothbrush and unperfumed soap e.g. washing up liquid
be careful not to distort the clasps
soak in denture cleanser once daily according to manufacturers instructions
avoid solutions with sodium hypochlorite e.g. milton
rinse after soaking
soak overnight in water
use adhesives according to manufacturers instructions
what is the purpose of surveying?
to determine guide planes and mark survey lines for fabrication of RPD
determines undercuts
why do we mark the high smile line?
to get an idea of how much tooth will show when smiling
why do we mark the high centre line?
so that the midline of the patient’s teeth matches their face
why do we mark the canine line?
marks which tooth size should be used
why do we mark the rim profile?
to ensure adequate lip support
How long do you steep cobalt chrome dentures for
no more than 10 minutes or they will corrode
