Pros Flashcards
Discussion of Relining complete dentures (6mins)
Procedure - selecting correct material - prescription
- Reasoning
Reline : When fitting surface is inadequate ( not retentive or underextended) but denture is otherwise okay
Rebase: When you want to keep occlusal surface but change fitting surface and polished surface (old/broken)
- Method
~ Check all occlusal relations are acceptable
~ Remove undercuts from denture fitting surface using acrylic bur
~ Adjust borders for under or over extention with green stick ( Ant and post)
~ Apply adhesive to fitting surface
~ Insert impression material ( Light body PVS) into the fitting surface of the denture and seat in pt mouth
~ Take a functional impression while pt biting down - Take lower imp with denture in situ
- Take bite reg if OVD is not obvious
- Send to lab for reline
- Precription
~ Please pur impression in 100% dental stone using denture imp provided. Please mount upper to lower cast and create a self-cure PMMA reline to change the fitting surface - Replace post dam
( Please remove and replace denture base in case of a rebase)
( See doc for more info about relining and rebasing)
Lower CoCr Design
Lower CoCr design / 6 mins
Design a cobalt chrome partial denture for the lower arch and fill in the lab sheet by both drawing and writing the prescription. Assume that the teeth are of sound prognosis, the dentition is free of caries and the oral hygiene is optimal.
Write instructions for a dental laboratory to enable the trial stage of a cast allow RPD base for the lower arch only
Kennedy class II mod I
- Support - Occlusal rests
~ 34m, 44m/d , 47m
Retention
~ 47; Occlusally approaching ring clasps (engaging lingual undercuts)
~ 34m ; gingivally approaching clasp with bracing from plate
~ 44 gingivally approaching clasp (needs composite)
- Indirect retention
~ 43 cingulum rest or 44d - Reciprocation
~ all clasps has reciprocal components eaither from plate or reciprocating clasp arms - Undercuts - all clasps drawn to engage undercuts , modification on 44
~ major connector ; lingual bar
~ Tooth modification- Composite on 44 buccal
guideplanes
Tooth prep for occlusal rests
Denture Design with examiner
Identify the type of articulator , reciprocation and bracing
- Type of articulator ; average value
Other types ; simple hinge , semi-adjustable , fully adjustable - Prescription supplied
~ position of all occlusal rest seats
~ 4 i-bar clasps
~ two occlusally approaching and 2 ring clasps
~ midpalatal bar and lingual bar - Areas providing reciprocation
~ Any part of the denture that is opposite to a clasp arm , resist lateral movement of teeth from clasps forces
~ Indicate all 8 areas - Areas providing reciprocation
~ Resistance to lateral movements of the dentures
~ what stops the denture from moving side to side
~ Achieved with clasps , plates , major connectors and flanges - Clasp depth is 0.25 for CoCr and rest seat depth is 1.5-2mm
Complete denture faults
C/C fractured , dentures are provided
Please identify 6 faults with this denture and how to rectify these?
- Anterior flange missing
- remove undercuts , build flange with greenstick then reline
- Rebase if not possible or remake
- Midline diastema
1. if want to keep physical aspects of denture but change aesthetics only
~ replica dentures with correct tooth position at trial stage
2. Remake if other problems - Underexteded posteriorly at tuberosities
1. Reline if this is the only problem
2. Remake - Locked occlusion
~ Remake with replica technique and use cuspless teeth - BAse plate too thin
~ Rebase using high impact resin - Tori
~ relief clinically if only problem or ask for tin-foil relief
~ if too thin then rebase or remake ( with tin foil) and ensure lab waxes undercuts - Tooth position is wrong
~ Remake - Occlusal table too long ( too many posterior teeth over tuberosities)
~ Selective grinding
~ remove posterior teeth
~ Remake
Give some problems with dentures that are related to the denture itself
- Impression surface
~ Cause - poor impression (lack of adhesion to tray, lack of post dam , distorted imp)
~ Solutions - Reline/Rebase/Remake / add post dam - Occlusal surface
~ Causes
1. pre-mature occlusal contact
2. centric occlusion and relation not coincident
3. high lower occlusal plane restricting the tongue
4. Locked occlusion
~ Solutions
Remake , adjust if against natural teeth or go back to tooth trial
- Polished surface
~ Causes
1. over-extension
2. under extension
3. teeth not in neutral zone
~ Solutions
1. remove overextension with bur and PIP
2. add greenstick to underextension and reline / remake
3. Replace teeth ( take neutral zone impression) / remake
- Loose denture and poor denture bearing foundations use cuspless teeth to reduce interference
Give some problems with dentures that are related to the denture wearer?
- Poor neuromuscular control ( Stroke and Parkinson’s)
- Poor denture bearing foundations
~ anterior flabby ridge
use perforated tray with light body silicone
~ atrophic mandibular ridge
use the admix technique ( 3 imp compound and 7 greenstick)
~ high frenal attachments
Provide relief
~ Bony prominence
Provide relief on cast before processing
~ Xerostomia
Why would a denture keep fracturing?
- Denture base too thin
- Under extended or missing flanges
- Stress on denture due to large frenal notch , midline diastema
- Lack of adequate relief
- Poor fit
- Tooth wear
- Previous repairs
- lack of balanced occlusion
How could you prevent a denture from fractures?
- Inclusion of a metal palate
- Use high impact resin or -polycarbonates for thin underextended flanges or open-faced denture for denture base materials
How would you repair a fractured denture?
- Midline fractures?
Secure the twi fragments with sticky wax and send to lab to repair using light cured PMMA
- Multiple fragments?
1. take imp with large denture fragments with alginate and send to lab if possible
- Remake
- Fractured or missing teeth
Impression of the opposing dentition , bite registeration and send to lab to repair with self cure acrylic resin
Setting teeth 12 mins station
Set upper 4 anterior teetg for tooth trial
- Tooth trial
~ Check denture extension, support, retention ( trial denture will be looser than actual denture)
~ Check stability and occlusion
~ Check speech , aesthetics
~ Mark post dam on cast - Check incisor height, width , canine to canine width , choose shade and mould
- Check the teeth from the side that they are not protruding or retruding
Surveying , 6 mins
Components , undercut gauges and material of clasp to use for each undercut
- Surveying helps analyse and mark undercuts to utilise them for denture retention
- Area below maximum contour is known as undercuts (area below maximum bulbosity)
- denture may be displaced in various directions but a common PD is at 90 degrees to the occlusal plane
- Use ruler to ensure cast is horizontal to occlusal plane
- Use analysing rod to inspect undercuts
- Tripoding
- Survey abutments using graphite marker
- Adjust surveyor platform by using analysing rod to block out undercuts (PI) - make sure previous undercuts are eliminated by achieving parallelism with rod
- Tripod again due to change of PI , then survey
- Use gauge (0.25 for CoCr) , to mark where gauge contacts the tooth surface
Complete dentures - Primary imps and lab card (6mins)
Select tray for edentulous lower primary impression. Select handle and place in correct place.
What position would you stand in and what material would you use
Fill in lab card
- Tray selection ; edentulous , blue , shallower
- Material :
~ Alginate ; cheaper
~ Impression compound - Position
~ 7 O’Clock for lowers
~ Behind pt for upper - Lab card
Please pour impressions in 50/50 dental stone and plaster , pleade construct lower special tray in light cure PMMA with spacer ( 2mm for alginate) , non perforated, finger rests and intra-oral handle
Please return trays with casts - include date, disinfection, and details
CoCr Partial Trial on Cast (6mins)
Check metal framework against prescription and find faults
- Faults with metal framework casting :
- Errors in casting ;
~ CoCr bubbles making surface rough , due to trapped air bubbles on wax
~ Prevent by using a wetting agent to coat wax pattern then a vacuum mix vibrated into the casting
~ Water droplets on waz pattern which remain when investing and cause nodules
~ Prevent by using correct thickness of investment mix and correct powder/water ratio and then a vacuum mix vibrated into the casting ring
~ Overheating the investment mould leading to decomposing and weakening of the surface resulting in loss of surface detail on casting
~ no sandblasting of mould , sprues remaining
- Faults between drawing and writing on prescription
~ Support ; Missing rests , no posterior stop (posterior of free end saddle ends further anteriorly than desirable)
~ Retention ;ring clasp around the wrong way (check survey lines)
~ Connection ; sublingual bar instead of lingual bar
~ No labial relief as asked
Complete denture Jaw reg
What equipment would you need
What important lines and featured would you use
What are the reference lines
- Equipment
~ Fox’s occlusal plane to set occlusal plane
~ Willis bite gauge ; measure OVD, RVD , FWS - Lines/features
~ High smile line
why?
^ allows waxing of teeth in correct height and alignment ( not showing too much gum)
how?
^ get pt to smile and mark upper lip level
~ Centre line/midline
why?
^ to orientate central incisor making the block symmetrical
how?
^ using nasal septum, labial frenum , or existing upper lower anteriors
~ Canine line
why?
^ to set canine position and provide size measurements for tooth selection
how?
^ measured using vertical line from inner canthus of eye
- Reference lines
1. ala-tragus line
2. inter-pupillary line
Used to ensure anterior and posterior occlusal plane is level
