PRS03 - Lecture 9 - Partial Dentures Flashcards
What materials can be used for a partial denture framework? (6)
Acrylic
Co-Cr
Type IV gold alloy
Stainless steel (difficult to frabicate into framework)
Titanium (difficult to fabricate into framework)
Nylon (causes problems for remaining teeth)
What are the indications for an acrylic denture? (7)
Poor prognosis of teeth (i.e. require extractions or additions in the future)
Interim denture (i.e. immediate denture)
Rapid bone resorption
Young patient (growth and dentition still developing)
Allergies to metal
Aesthetic
No undercuts available for retention
What are the advantages and disadvantages of acrylic dentures? (5:4)
Advantages (5)
↑ Aesthetics
Cheap
Not invasive
Easily modified (i.e. repair, addition, re-line, re-base)
↓ Appointments
Disadvantages (4)
↓ Strength (fractures easily compared)
Restricted design (not retentive)
Requires more mucosa coverage (plaque/food retentive)
↑ staining
What are the advantages and disadvantages of a Co-Cr denture? (7:5)
Advantages (7)
↑ Strength (used in thin sections)
Better designs
Easier to clean
Smooth metal surface/better fit -> ↓ abrasion to underlying mucosa
Better thermal conductivity (know if your drinking hot or cold)
Easier to connect major and minor connectors
↓ Bulky major connectors
Disadvantages (5)
↓ Aesthetics (major connector does not blend + occlusal rest seats)
Expensive
Difficult to modify
Allergies to metals
Metallic taste
What is the function of clasps? (2)
Provide mechanical retention by engaging with undercuts
Thus, need to be flexible enough to insert or withdraw from undercuts without deforming or breaking
What different materials can be used for clasps? (4)
Gold alloy (type IV)
SS or wrought SS
Co-Cr alloy or wrought Co-Cr Nickel alloy (wiptam wire)
Acrylic (acetal resin i.e. dental D) - non flexible, cannot be altered and breaks easily however it is tooth coloured
What does the material you choose for clasps depend on? (9)
Abutment teeth (predominantly) - i.e. Co-Cr clasps amy be too rigid for periodontal involved teeth
Aesthetics
Cost
Ability of the material to be added onto framework
Flexibility
Positions
Length and thickness of the cross-section of clasp
Local anatomy structures - sulucus depth (difficult to use I bar next to buccal frenum), muscle attachments, undercuts
Patients choice
Compare the elastic modulus for materials used for clasps (5)
Gold alloy (type IV) – 100GN/M
SS wrought – 130 GN/M (depending on the alloy and manufacturing process)
SS cast- 200 GN/M
CoCr alloy (cast) – 250 GN/M
Acetal resin – 2.8 GN/M (hence bulky clasp)
When considering direct retention (clasps) when designing denture - what factors can improve aesthetics? (3)
Gingival approaching clasps (instead of occlusally approaching) if there is not anatomical interference
Place occlusally approaching clasps with the tip positioned in the mesio-buccal position (rather than disto buccal undercut) - this ensures the clasp arms is not so visible
Materials - use acetal resin or gold (instead of Co-Cr or Stainless steal (SS))
What materials can you use to record occlusion? (3)
Wax
Easy to use - quick, cheap, not messy
Can be re-heated and re-registered
↑ Coefficient of thermal expansion than other materials -> error on cooling
Dimensionally unstable
Hot -> burn patient
ZOE
Cheap
Easy to mix and apply
Flows well
Dimensionally stable
Records good surface detail
Needs to be in thin layers
Messy
Not pleasant for patients suffering from xerostomia
Silicone (medium body)
Easy to use
Records good surface detail
Dimensionally stable
Acceptable taste and odour
Expensive
What factors will reduce the number of clasps required for retaining the denture? (3)
Number of parallel guide planes
Size and number of saddles (especially free-end saddles)
Other rententive factors (i.e. flanges)
List problems a patient may complain about in the review stage - how would you resolve these? (15 - detailed)
Pain in soft tissues (ulceration) - over extention of flanges, rough edges, undercut not relieved -> adjust using pressure indicating paste
Pain on wearing after a while - wrong OVD/RVD, not enough FWS, patient may not be able to speak properly
Pain on eating - occlusal interference, lack of even contacts in ICP -> adjust with articulating paper
Painful teeth - occlusal interference and excessive force on abutment teeth due to poor design -> adjust with articulating paper or re-design
Pain on edentulous ridge - incorrect occlusion - identify using articulating paper to identify high spots and adjust
Appearance - colour, mould, amount of teeth showing anterioly (too much or too little), gaps (between denture and natural teeth) - ensure patiet is happy at try-in
Gagging - check palatal thickness, post extension, adaptation to tissues -> adjust
Looseness (unable to speak properly + food packing) - tighten clasp, check posterior border is extended adequately. frenal relief, flanges encroaching on muscle function, denture base closely adapted to tissues
Difficulty biting - check occlusion and if you have achieved ICP
Occlusion (not meeting anteriorly or posteriorly) - excessive OVD (-> trauma to underlying tissues, clenching, TMD, lack of lipseal) or underestimated OVD (-> dribbling, risk of angular chelitis, chin protrusion due to over closure of jaw, cheek biting, tongue biting) -> correct occlusion and advise patient to get used to denture before eating
Speech - check tooth position
Cheek biting - inccorect position of teeth, incorrect contour of buccal flange, cusps too sharp, loss of muscle tone (when patient doesnt have denture for a while)
Tongue biting - incorrect occlusal plane, incorrect tooth position, lack of muscle tone of the tongue due to not replacing teeth for a long time - > correct occlusion, advise patient to get use to denture before eating with it
Breaking - thin acrylic, trauma (dropping it), clasps (if place too deep into undercuts)
Collection of food in the buccal shelf area - poor contour of the flange -> recontour
