Removeable Prosthodontics

Question 1

IO exam with dentures in situ

Answer 1

RETENTION :
CD - push on incisal edges of anterior teeth & see if denture drops
PD - check clasp engagement
STABILITY :
CD/PD - press unilaterally on posterior teeth & check for drop on opposite side
SUPPORT :
CD / PD - press on occlusal surfaces of teeth & check if denture sinks or if it causes pt discomfort
OVD :
CD/PD - take multiple readings using willis bite gauge & calculate an average
OCCLUSION :
CD - check for balanced occlusion
PD - conforms to current occlusion
LATERAL GUIDANCE :
CD / PD - canine / group function
AESTHETICS :
CD / PD- smile line, incisal show, curve of spee, buccal corridor, nasio labial angle & previous natural teeth shade & form

Question 2

CoCr as denture base

Answer 2

strength - greater
comfort - thinner skeleton as stronger, less bone resorption & tissue change under denture, greater support, minimal palatal coverage, greater temp conductivity
retention - can incorporate clasps, more accurate fit improves retention
construction accuracy - greater as metal prevents warpage during processing
addition - difficult to make additions only suitable for those with good long term abutments
repair - difficult & costly to accurately solder any clasps
cleanability - OH easier as CoCr less porous
cost - greater

Question 3

acrylic as denture base

Answer 3

strength - lower
comfort - lower as increased thickness to compensate for lower impact strength, more palatal coverage (for support) and less temp conductivity
retention - can be good with appropriate case selection, dependent on border seal & accurate fit, can incorporate stainless steel clasps
construction accuracy - reduced
addition - easier to modify & add teeth
cleanability - less due to porous nature of acrylic
cost - lower

Question 4

imp technique for kennedy class I & II

Answer 4

2 stage imp technique can be used:
initial imp of just the free end saddle region using putty PVS / compound then an alginate or light body PVS is taken of the entire arch over this
ensure adequate border moulding

Question 5

key for lower imps

Answer 5

ensure pt displaces tongue L / R / out of mouth so FoM is captured and the full depth of the lingual sulcus
this improves denture stability as well as influencing connector choice by capturing depth of the FoM
same in special trays; this is a functional imp

Question 6

what to check in imp (5)

Answer 6

1. full coverage of denture bearing area
2. no encroachment of impression material on tongue space
3. presence of rolled borders with no drags
4. absence of voids, drags, tears
5. mechanical retention of impression material through the tray perforations

Question 7

when to ask for occlusal wax rims

Answer 7

1. if ICP cannot be achieved
2. if casts cannot be hand articulated

Question 8

direct retention in cocr

Answer 8

resistance to vertical displacement of denture:
- provided by clasps, guide planes, path of insertion & precision attachments
- cocr clap 15mm in length will engage 0.25mm undercut
- minimise clasp number, a tripod of clasps is sufficient, aim for largest triangle
- consider RPI system for free end saddle designs

Question 9

indirect retention in cocr

Answer 9

resistance to rotational displacement of denture:
- provided by major connector, minor connectors, rest seats, saddles & denture base
- identify clasp axis around which the denture can rotate by envisioning a line between 2 clasps on opposite sides
- indirect retention is then achieved by drawing a line perpendicular to this & placing a component on the opposite end

Question 10

reciprocation in cocr

Answer 10

an opposing force to the clasp to make the clasp passive
provided by opposing clasp arm or the connector

Question 11

key when designing cocr denture

Answer 11

design must be finalised prior to master impressions so all conns, perio etc must be carried out & under control & rest seats, guide planes & undercut regions can be incorporated into indirect restorations

Question 12

RPI system

Answer 12

proximal plate
mesial rest seat
gingivally approaching I bar clasp

Question 13

types of upper major connectors (4)

Answer 13

1. full palatal coverage
2. mid palatal strap
3. horseshoe design
4. ring design

Question 14

types of lower major connectors (4)

Answer 14

1. lingual bar - MUST have 8mm clearance from FoM to gingival margin
2. dental bar
3. lingual plate
4. kennedy bar design

Question 15

when assessing special tray

Answer 15

retract lips to check for any over / underextension of special tray flanges
must be relieved around the frenulum attachment areas & short of the sulcus by 2mm (to achieve good rolled border)
for lower dentures overextension is likely if the special tray displaces with tongue movement

Question 16

how to correct over / underextension of special tray

Answer 16

over - acrylic trimmer
under - addition of green stick

Question 17

what to check on occlusal wax rims (record blocks)

Answer 17

• rims should not be rocking on casts
• major faults require new imps & a remake
• stability; rocking can be caused by excess plaster on cast, poor trimming of cast, poor mucosal coverage & flange overextension
• poor retention as a result of over / under extension & an inaccurate fit
• good mucosal coverage is necessary for support

Question 18

how to adjust occlusal rims

Answer 18

UPPER:
1. adjust buccal / labial thickness; aim for 90 degree nasio labial angle
2. adjust any over / underextenions & relieve frenulum areas; used heated wax knife to remove & add wax as necessary
3. orientate posterior occlusal plane parallel to ala tragus line & the incisal plane parallel to the inter pupillary line; a foxes bite plane or a wooden spatula can be used
4. remove wax from palatal aspect as it can often be bulky
5. at rest 2mm of wax should display
LOWER
1. assess lower record block in mouth
2. adjust buccal / labial thickness & remove wax from lingual as this is often bulky (improves tongue space & phonetics)
3. correct over / under extensions, relieve frenulum areas, cut back heels on upper and lower rims until there is an even bilateral occlusion intraorally

ask pt to close in ICP with both rims in place and check if reference teeth are separated; trim premature contacts until the reference teeth contact as before

Question 19

reorganised v conformative approach

Answer 19

REORGANISED - used when increasing OVD / when no index teeth present, this involved recording occlusion in RCP
CONFORMATIVE - when denture conforming to pt existing occlusion, 2 or more contacting teeth must be present so that ICP is achievable; occlusion recorded in ICP

Question 20

marking lines on rims for jaw reg

Answer 20

if conformative approach record OVD & ensure it is the same when record blocks removed, adjust occlusal surface of lower block accordingly
if reorganised approach, make sure 4-5mm of FWS available
centreline should be in line with philtrum of lip & canine line should be from inner canthus of eye to outer part of nostrils (nares)
for kennedy class I and II cut locating notches into wax edentulous areas
conformative = ICP & reorganised = RCP closure make sure pt can do this
record using bite reg paste or by softening wax rims and getting pt to close
confirm shade & mould
for acrylic go to wax tooth trial and for cocr go to framework try in

Question 21

metal framework try in - what to examine on articulated working models

Answer 21

1. adaptation
2. presence of sharp edges
3. that clasps are engaging undercuts
4. for any lab induced defects on denture bearing areas
5. path of insertion

Question 22

PD metal framework try in

Answer 22

1. insert & check that it seats fully; ask pt how it feels & check for blanching
2. check accuracy of fit of components
3. stability - should not rock
4. support - rest seats must not interfere with occlusion (adjustments may require lab remake with new 2ndary imps
5. retention - clasp arms must be engaging undercuts (check relative to cast & survey lines), use finger pressure to activate passive clasp
6. assess occlusion
7. assess aesthetics - esp of gingivally approaching clasps
8. if both U & L try in both at same time
9. send to lab & continue to metal wax jaw reg

Question 23

how to get pt to close in RCP

Answer 23

ask pt to curl their tongue to the back of their throat and close
practice this multiple times
used in reorganised approach

Question 24

metal frame work jaw reg

Answer 24

same as for bite reg but in this case there is now wax on the metal framework
carry out same procedure then send to lab for tooth trial

Question 25

what to check on articulated working models prior to tooth trial (5)

Answer 25

1. adaptation
2. flange extensions
3. denture bearing areas of the cast are free from lab induced defects
4. balanced occlusion present (for many missing units)
5. position of the denture teeth buccolingual compared to natural teeth

Question 26

what to check at tooth trial / try in stage of partial denture

Answer 26

1. insert each denture individually & assess. blanching can be caused by inaccurate setting of teeth / jaw reg or denture may not seat if undercuts inadequately blocked out during acrylic processing; pressure indicating paste can be used to identify areas of discomfort
2. stability & retention - should not be rocking,
3. correct any over or underextensions (acrylic trimmer used in final fit)
4. insert both dentures & assess
5. vertical - OVD should remain unchanged (if conformative approach)
6. occlusal - incisal plane parallel to interpupillary line, posterior occlusal plane parallel to alar-tragus line, plane of mandible; tongue should rest on lingual aspect of lower teeth
7. aesthetics of teeth and wax / acrylic gingivae; check papillae, incisal show, tooth position, shade, gingival position & contouring
8. speech - phonetics test
9. check occlusion with articulating paper
10. show pt & confirm they are happy with feel, function & aesthetics then send to lab for finish for delivery or give to pt with instructions

Question 27

denture advice to give pt

Answer 27

1. take denture out at night time & leave in bowl of water
2. clean after every meal with lukewarm water soap & soft brush; consider cleaning agents but read manufacturer’s instructions carefully
3. retention & general feel will improve with time as neuromuscular system adapts
4. begin with soft diet
5. if denture causes irritation return to previous set but wear for 24h prior to appt so clinician can see traumatised areas

Question 28

primary imps for CD

Answer 28

• edentulous trays are non perforated so material is pushed up into the sulci
• can be over extended in resorbed ridges so adjust with acrylic trimmer
• materials of choice inc; alginate, medium body silicone, polyether. ensure adequate border moulding
• for lower denture; paramount that pt displaces tongue L R & out of mouth so FoM & full depth of lingual sulcus is captured
• make sure to mark post dam & flange extensions with indelible pencil

Question 29

what to check for in primary imp of CD

Answer 29

• full coverage of denture bearing areas
• no encroachment of impression material on tongue space
• presence of post dam
• adequate flange depth
• presence of rolled borders with no drags
• absence of drags, voids, tears

Question 30

master imps of CD

Answer 30

• try in special tray & check extension
• retract lips to assess for any under / over extension of flanges, must be relieved around the frenulum attachment areas & short of sulcus by 2mm to achieve good rolled border
• over extension of lower tray is likely if tray displaces with tongue movement
• consider border moulding the tray flanges, retromolar pad, lingual pouch with greenstick
• functional imp needed for lower
• if facebow being requested; ask for 2 wax rims (1 for jaw reg & 1 for facebow recording)

Question 31

when to consider taking facebow (2)

Answer 31

1. if upper complete opposing natural dentition
2. if implant retained denture

Question 32

jaw reg on CD

Answer 32

• assess on casts; should not be rocking
• stability - poor mucosal coverage & flange over extension / retention - poor due to over / under extension, inaccurate fit & incorrect post dam / support - good mucosal coverage & post dam necessary
• adjust under / over extension, relieve frenulum areas & adjust buccal / labial thickness; use heated wax knife & aim for 90-100 degree nasiolabial angle
• posterior occlusal plane parallel to ala tragus & incisal plane parallel to inter pupillary line, 2mm of wax should be on display
• remove wax from palatal aspect as often bulky
• consider lingual wax removal to improve tongue space
• for reorganised approach ensure 4-5mm FWS
• mark post dam on upper occlusal; identified by asking pt to say ahh and marking vibrating line
• mark centre line, canine line & smile line on upper & centre line on lower
• cut notches into wax rims & take bite reg using registration paste
• reconfirm shade with pt, disinfect rims & send to lab for tooth trial

Question 33

tooth trial / denture fit of CD

Answer 33

same as for PD
pressure indicating paste used to identify areas of discomfort
modify using acrylic trimmer
recheck all the lines

Question 34

indications for copy dentures (4)

Answer 34

1. pt has requested spare denture set & is satisfied with current
2. staining of current denture teeth & not other issues
3. worn teeth / overclosure & no other issues
4. # baseplate or denture teeth in an otherwise functional denture

Question 35

1 step in copy denture technique

Answer 35

record OVD, RVD, FWS & decide whether OVD requires changing & if so consider articulating study casts using a facebow

Question 36

stock tray method of copy dentures

Answer 36

1. select stock tray larger than size of denture
2. load with heavy body putty & seat denture occlusal surface into loaded tray - place some putty in palate of denture to get better impression
3. once set, cut wedge shaped location grooves in external borders - this allows lab to bring two trays together correctly
4. keeping denture in place insert heavy body putty into the fit surface and on to the back of the 2nd stock tray & place over the denture fit surface
5. once set, separate stock trays & remove dentures. disinfect & send to lab
6. get lab to pour up casts & construct wax try in confirming shade & mould with pt
7. assess wax try in - should be adequate retention, stability & support, measure OVD & check FWS
8. take a light/medium body silicone wash impression using fit surface as a master tray & mark post dam on cast
9. disinfect wax rims & send to lab. if changes made request a wax tooth trial otherwise rims can be processed for denture fit

Question 37

risks of immediate denture

Answer 37

1. suboptimal immediate denture fit as 2ndary imps not routinely taken
2. denture fit may worsen with time as socket heals & bone remodels (new denture required 3-6mths later)
3. unaesthetic appearance in high smile line cases as a result of gingival recession after healing

Question 38

denture advice for immediate denture

Answer 38

• wear for 24h including during sleep to protect the blood clot formed
• thereafter remove at night & store in glass of water
• wash denture daily & after meals with warm soapy water & soft brush
• consider denture cleaner but follow manufacturer’s instructions

Question 39

process of immediate denture making for multiple teeth

Answer 39

1. upper & lower alginate imps with medium body PVS bite reg (light body if only for 1 tooth)
2. request special trays & wax rims
3. take 2ndary imp & jaw reg then take a shade
4. cast & fabricate wax try in then send for processing if satisfactory
5. xla should be booked on expected date for denture delivery
6. ensure haemostasis achieved prior to fitting denture then check retention, stability, support, occlusion & guidance
7. make adjustments as necessary (try not to over adjust fit surface as there will be inflammation following xla), confirm pt satisfied & give denture advice
8. review as necessary
9. for only 1 tooth replacement following primary imps go straight to delivery

Question 40

when adding a tooth to a denture ask for

Answer 40

ask lab to shade match to the remaining denture teeth

Question 41

process of addition of tooth to denture

Answer 41

take alginate imps with denture in situ (U+L) then send to lab (both imps and pt denture) then proceed with xla on day denture is due back

Question 42

risks of adding tooth to existing denture

Answer 42

1. point of addition will be slightly weaker & prone to breakage
2. denture may not fit satisfactorily
3. possible unaesthetic appearance in high smile line cases
4. limitation
5. pt will not have their denture for a short period of time

Question 43

why fit denture on day of xla

Answer 43

allows better gum contouring & control of bleeding

Question 44

indications of over dentures (4)

Answer 44

RCT treated teeth with significant toothwear
MH precludes xla
preservation of bone necessary
over implant abutment

Question 45

requirements prior to overdenture (3)

Answer 45

1. satisfactory RCT on retained teeth well obturated within 2mm of apex & good coronal seal
2. adequate interocclusal space
3. retained tooth periodontally stable

Question 46

+/- of over denture

Answer 46

+ maintains bone around teeth
+ good transition psychologically for pts going from teeth to no teeth
- optimal OH required
- can require XLA if becomes carious or periodontally involved & new denture will then be required

Question 47

process for overdenture

Answer 47

perform retained root prep & ensure good coronal seal
follow steps for partial denture construction
confirm pt happy with aesthetics, function, feel & review after 1 wk