Pros Flashcards
things to consider when designing a denture & denture prescription sheet
kennedy class
I = bilateral free end saddle
II = unilateral free end saddle
III = unilateral bounded saddle
IV = anterior bounded saddle crossing midline
most posterior gives classification then the rest are modifications
craddock class
tooth supported = teeth provide hard tissue resistance to occlusal loading
mucosa supported = large coverage provides resistance to occlusal loading
tooth & mucosa = reduced no of teeth & large edentulous area
support = resistance of denture to occlusally directed load. rests provide support for the denture from vertical opposing forces & prevent movement of RPD towards the mucosa; mesial, distal, occlusal, cingulum
retention = clasps. resistance of denture lifting away from tissues (vertical dislodging forces). direct = vertical & indirect = rotational. gingivally approaching is i bar clasp, occlusally approaching is a single arm, circumferential with reciprocal arm or ring clasp. material = cocr 0.25mm, gold 0.5mm, SS 0.75mm
indirect retention = RPI system for free end saddles. mesial occlusal rest, proximal plate adjacent to saddle ( guided surface of 2-3mm & undercut to permit movement), gingivally approaching I bar clasp located on greatest prominence of tooth contour
major connector, minor connector, rests, saddle areas & denture base
major connector choice -
maxilla - anterior palatal strap / bar, mid palatal strap, horseshoe, full palatal coverage
mandible - lingual bar (8mm clearance; 3mm gingival margin, 4mm for bar & 1mm above FoM), sublingual bar or lingual plate
complete denture jaw reg; equipment, lines, features & reference lines
fox’s occlusal guide plane - used to set occlusal plane
willis bite gauge - measures OVD, RVD, FWS
high smile line - allows waxing of teeth in correct height & alignment so not showing too much gum. get pt to smile & mark lip level
centre line - to orientate central incisors making block symmetrical
canine line - to set canine position & also provide size measurements for tooth selection. measured using vertical line from inner canthus of the eye
reference lines - used to ensure anterior & posterior occlusal plane is level; ala tragus line & interpupillary line
CoCr trial on cast; check metal framework against prescription & find faults
faults with metal framework casting inc:
- errors in casting; CoCr bubbles making surface rough; due to air bubbles trapped on wax pattern investing
- errors in design; too close to gingival margin, undercuts not blocked out
faults with prescription between drawing & writing:
- support; rests missing, no posterior stop i.e. posterior of free end saddle ends further anteriorly than desired
- retention; ring clasp around wrong way; are they ineffective? check cast for survey lines
- connector; sublingual bar instead of lingual bar - sublingual bar actually lays on the FoM and there is no 1mm functional depth as is with the lingual bar
- check for indirect retention & appropriate reciprocation for clasps
- no labial relief as asked
complete dentures - primary imps & lab card
select tray for edentulous lower imp, place in correct place, where would you stand & what material would you use. write stage on lab card
edentulous trays (blue shallow one)
primary imp in alginate with impression compound
stand at 7o’clock for lower imp
please pour casts in 50/50 dental stone/plaster & construct lower special tray in light cure PMMA with
1-2mm spacer (1mm for PVS & 2mm for alginate) non perforated with finger rests & IO handle. please return trays with casts
surveying - components, undercut gauges & material of each clasp to use in undercut
mount cast & tripod draw 3 lines with analysing rod & pencil
pencil rod - mark survey line of all abutment teeth & soft tissue undercut
do not overmark (in common path of displacement)
determine whether the cast needs to be tilted i.e. when undercuts unfavourable - change path of insertion to highlight undercuts in this path (mainly for soft tissue)
if cast needs to be tilted, re tripod with red marker then mark new survey line with red rod
in common path of displacement (path of insertion & removal if altered), find appropriate location for clasps with undercut gauges (normally buccal of upper molars & lingual of lower molars)
mark clasp positions with pencil
0.25mm cocr
0.5mm gold
0.75mm ss
what is reciprocation & bracing
reciprocation is provided by any part of the denture that is directly opposite a clasp arm; resists lateral movement of teeth from forces of clasps / retentive component during insertion
bracing is the resistance to lateral movements
complete denture faults - 8 common faults & how to rectify
- anterior flange missing - remove undercuts, build flange with greenstick & reline, rebase if not possible or remake if necessary
- midline diastema - if want to keep physical aspects of denture but change aesthetic only;
- replica (2 stage putty & denture, vaseline to separate)
- wax replica used for functional imp & jaw reg
- ask lab to close diastema at tooth trial stage
- remake if other problems - underextended posteriorly at tuberosities
- reline; if functionally good & this is the only issue
- remake if everything bad - locked occlusion - remake with replica technique & use cuspless teeth
- base plate too thin - rebase thicker or rebase using high impact resin or remake
- tori - relieve clinically if only problem or ask for tin foil relief, if too thin or other problems rebase or remake and ensure lab waxes undercuts
- tooth position wrong - remake
- occlusal table too long i.e. too many posterior teeth over the tuberosities - remove posterior teeth / grind down or remake
reline vs rebase
reline = replacement of denture fitting surface
- relining satisfactory for mandibular denture but will increase thickness of upper denture making it heavier & less retentive
- amount of thickness is directly related to the choice of impression material
- the more viscous the impression material the greater the thickness of the reline
- therefore use low viscosity light body PVS
rebase = replacement of whole denture base
reline mandibular dentures
rebase maxillary dentures
adjust peripheral borders of denture as necessary; to correct over trim the denture or correct under extension add greenstick or imp material
general denture faults
problems with denture:
1. impression surface
cause - poor imp (lack of post dam, poor adhesion to tray), damage to cast
solution - reline / rebase, remake, add post dam using reline
2. occlusal surface
cause - premature occlusal contact, centric occlusion / relation not coincident, high lower occlusal plane restricting the tongue, locked occlusion
solutions - cuspless teeth, selective grinding, re recording centric occlusion, remake
3. polished surface
cause - overextension, underextension (depth +/- width), not in neutral zone
solutions - remove overextension esp lower lingual use pressure indicating paste to allow fraenal & flange relief, add greenstick to underextension, remake if extensive
problems with denture wearer:
1. poor neuromuscular control i.e. parkinson’s, stroke
2. unstable foundations
- anterior flabby ridge; solution = perforated trays & light body PVS imp or special tray with surgical window, take a wash & cut it out & light body PVS
- atrophic lower ridge solution = admix technique (3 parts imp compound 7 greenstick)
- high fraenal attachments solution = provide relief
- palatine tori solution = relief of area on cast prior to processing
3. xerostomia
denture fracture faults
fracture prone features
- thin, under extended +/- absent flanges (open faced)
- previous repairs
- stress concentrators e.g. large fraenal notch, midline diastema, foreign particles
- poor fit
- lack of adequate relief
- toothwear
prevention
- inclusion of metal plate
- use of an alternative denture base material such as high impact acrylic resin for thin underextended flanges or open faced denture
repair
- for simple midline 2 fragments secured in position with sticky wax & additional reinforcement e.g. wooden sticks across line of # then sent to lab. light cure PMMA normally used due to easier processing technique but is weaker than heat cure PMMA
- if denture in multiple fragments may be necessary to reposition the larger of the fragments IO and to take an in situ overall imp in alginate; if not possible the remake
- for repair of #/missing teeth an imp of the opposing dentition +/- denture is required to ascertain the correct occlusal relationship
what to check in tooth trial
check denture extension, support, retention (trial denture will be looser than actual one), stability, occlusion (balanced & articulation), speech, aesthetics (mould, shade, gingivae position), mark post dam on cast
reline complete denture; procedure, selecting correct material & prescription
relines = when fitting surface inadequate but denture otherwise okay i.e. occlusal planes, OVD, profile acceptable but fitting surface underextended, not supportive / stable or retentive
rebase = when you want to keep occlusal surface but change fitting & polished surface
- check all occlusal relationships are stable & appropriate
- remove undercuts from denture fit surface using acrylic bur
- adjust border for under/over extension using greenstick
- apply adhesive to fit surface of denture to be relined
- insert imp material i.e. light body PVS into fit surface & seat the denture
- functional imp; ask pt to bite together so imp taken in OVD
- take lower imp with denture in situ (gold standard but may not be required)
- take bite reg if OVD not obvious
- when set remove imp & send denture for reline
prescription to say - please pour imp in 100% dental stone using denture imp provided. please mount upper to cast & create self cure PMMA reline to change imp surface
