pros need to know 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 tip of mesiobuccal cusp of upper 1st molar on each side
what is the neutral zone?
a specific area where the function of the musculature will not unseat the denture and where forces generated by the tonque are neutralised by the forces generated by the lips and cheeks
how is denture stability achieved?
- by making sure the peripheries of denture are extended to the right depth
- by making sure the occlusion is balanced
what is the occlusal rim?
a wax structure with occluding surfaces attached to denture bases
what is an occlusal rim used for?
- used for recording the relation of the maxilla to the mandible
- positioning the teeth
which articulator is preferred for use?
fixed condylar articulator
why are non arcon articulators inaccurate?
- condylar inclination changes as articulator is open
- can lead to inaccuracies when a protrusive record is being used to determine articulator settings
why would you need to rebase and reline a denture?
- bone resorption
- multiple denture fractures
- denture base deterioration
what features should be present on maxillary definitive impressions?
- tuberosity
- hamular notch
- extension anterior to the vibrating line for post dam
- functional depth and width of sulcus to create a food peripheral seal and ensure hard palate and residual ridge are functional for primary support
what features should be present on a mandibular definitive impression?
- coverage of pear-shaped pad and buccal shelf
- retro-molar pad and extension into the lingual pouch should occur
- functional width and depth of the sulcus
- ensure there is area of primary support of buccal shelf and retromolar pad
what general features should be present on definitive impressions?
- ensure denture bearing areas are covered
- ensure there is good functional sulcus present
- ensure there is good surface detail with no air blows
what indicates the posterior border of the maxillary denture?
- post dam- sits 1-2mm anterior of vibrating line
where should a maxillary denture sit in order to creat a good posterior seal?
- at the level of the hamular notch-located between distal surface of tuberosity and hamular process of medial pterygoid plate of maxilla
what impression materials are used for primary impressions?
impression compound
alginate
describe the 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
what impression materials are used for master impressions?
- silicone
- polyether/impregum
- alginate
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 a 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 Watt and Macgregor’s Biometric guide?
- one of the methods of designing complete dentures
- it uses the remnat of the lingual gingival margin in the bucco-lingual placement of prosthetic teeth
what material would you use in a special tray with a 3mm spacer?
alginate
how big should the spacers be in special trays for use of silicone/polyether impression material?
2mm for upper
0.5-1mm for lower
what is the purpose of stops to the space prescribed in the canine and post dam regions of upper trays?
to allow correction of the posterior borders of the tray and will perform space for the impression material
where should stops be placed to the space provided on lower trays in order to allow preformed space for the impression material?
- retromolar pad
- ridge of the canine areas
why is silicone not used for primary impressions?
- dimensionally stable and hydrophobic- can cause small defects and blows
- very messy and technique sensitive
what muscles lie adjacent to the retro-molar pad?
- laterally- buccinator
- posteriorly- temporalis tendon
- medially- superior constrictor and pterygomandibular raphe
when applying Watt and Macgregor’s biometric guides, what anatomical feature is used as the fixed reference point?
- the positional relation to the central incisors which are 8-10mm anterior to the incisive papilla
*
what is the average horizontal bone loss for the fixed reference point in central incisors?
6.3mm
what is the average horizontal bone loss for the fixed reference point in canines?
8.5mm
what is the average horizontal bone loss for the fixed reference point in premolars?
10mm
what is the average horizontal bone loss for the fixed reference point in molars?
12.8mm
what information should be recorded on to a record block?
- the OVD
- the centre line
- the occlusal plane
- high lip line
- canine line
- arch form
name 2 thermal properties of acrylic dentures
low thermal conductivity
high softening temperature of the acrylic
why is low thermal conductivity in acrylic dentures important?
because the denture base would not be able to transmit heat that well to the palate
patient less sensitive to the temperature of fluid/food
advise patient to be careful to not scald the back of their throat
why is high softening temperature of acrylic dentures important?
tolerant to hot food and drinks
must tell patient not to clean denture with boiling water
what provides retention for dentures?
accurate fit - as little space as possible between denture base and mucosa
border seal- extending flanges to the depth of functional sulcus and incorporation of post dam
what anatomical features healp identify where the posterior border should be placed for the upper denture?
hanular notch
vibrating line
palatine fovea
what impression materials would you use for an edentulous pt on the mandibular arch?
primary- alginate/impression compund
definitive- alginate/polyether/silicone
what are the signs and symptoms of denture induced stomatitis?
inflamed mucosa, particularly under upper denture
burning sensation
discomfort
bad taste
explain 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 - Depressed Bone level
what is the primary support area for maxillary dentures
hard palate
what is the secondary support area for maxillary dentures
ridge crest
what are two areas in a maxillary denture that may require relief
midline suture
incisive papilla
lingual frenum
what part of the maxilla does not contribute support
denture border
what are the primary support areas in lower dentures
buccal shelf and pear shaped pad
what are the secondary support areas in lower dentures
ridge crest and genial tubercles
what areas may need relief in lower dentures
lingual ridge incline and mylohyoid ridge
what areas of lower mucosa do not contribute to denture support
labial ridge incline
define retention in Pros
the resistance to displacement of the denture away form the ridge
define stability in pros
ability for the denture to resist displacement by dunctional stresses
what materials can be used to modify trays
soft red wax
greenstick - small additions to tray best
putty - hard to use
impression compound
label from left to right and explain
labial sulcus - overextension causes denture to look bulky
incisive papilla - may need to relieve here due to underlying nerves , indicates where teeth have been
buccal frenum - in premolar area, connects to cheek
palatine raphe - midline of denture, tissue tight
tuberosity - most distal extension of maxilla
vibrating line - junction of hard and soft palate
palatine foveae - dimples in soft palate behind vibrating line
hamular notch - junction of maxilla to hamular process, overextension causes ulceration
buccal sulcus - overextension loses muscle balance, under-extended loses peripheral seal and makes unretentive
palatine rugae - lumps in palate
labial frenum - muscle attachment to midline, may need relieved
label from left to right and explain
labial sulcus
lingual frenum - attachment to tongue
buccal sulcus - overextension loses muscle balance, under-extended loses peripheral seal and makes unretentive
retromolar pad - most distal extension of mandible, rest denture as far back as possible here
buccal shelf - primary support area, make sure denture extended as far back as this
lingual sulcus - mylohyoid ridge here and may cause discomfort
buccal frenum
labial frenum
what should the extension of master impressions be and why
2mm short of sulcus depth to allow border moulding
what thickness of spacer is required for alginate
3mm
what thickness of spacer is required for silicone elastomers
2mm
what stage is not required for replica dentures
registraion
what is FWS and what is the ideal space
FWS = RVD - OVD
2-4mm
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
- minimum pressure is applied to the tissues to record at rest
what are the steps of jaw reg
- adjust upper bloc for retention
- adjust 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 shade and mould
UPPER CORRECT BEFORE LOWER
what do you assess for patients current denture
L - lip support, nasiolabial angle 90 degrees
I - Incisal Level
M - midline, use middle of nose
B - buccal corridor, space in corners of mouth, taper towards back
O - occlusal plane, interpupillary line and ala-tragus 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 for dentures
- reduce porosity
- easier for deflasking to be carried out
why do you keep dentures moist
- prevent denture becoming brittle
- prevent warping/altered shape
when would you use impression compound
primary impressions on edentulous patients
why is alginate more suitable than silicone for 3mm spacing
- alginate is mucostatic
- silicone is mucocompressive and likely to tear and not effective if undercuts present
what is another name for master impressions
secondary impressions
definitive impressions
what part of the mandible affects maxillary impressions
coronoid notch
what provides retention for dentures
accurate fit - little space between denture base and mucosa
border seal - extending flanges to depth of functional sulcus and incorporation of post dam
what are records required for mounting casts on a semi adjustable or average value articulator
face bow
inter occlusal record on the retruded axis
what is the value of the sagittal condylar guidance which can be used in an articulator
30 degrees
what is the terminal hinge axis
when the condyles of the mandible are in their most superior and posterior position in the glenoid fossa
why is the retruded contact position important
it is the initial point of tooth contact during mandibular closure
it is used as a reference point for mounting casts on an articulator
