Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Prosthodontics > CSCD > Flashcards

CSCD Flashcards

1
Q

What factors may affect prognosis of dentures

A

-patient satisfaction and expectations (not too unrealistic)
-patient compliance
-previous denture wear
-patients being able to adjust
- ridge anatomy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

List examples of aspects that may appear in a treatment plan when making new dentures

A

-Increasing of decreasing OVD/ freeway space
-Fixing tooth wear
-Modifying under or overextensions
-improving the retention/ stability
-changing the tooth shade/ shape
-adjusting occlusal contacts
-adjusting incised level
-adjusting centre line
-adjusting incisal/ occlusal plane
-repairing broken ones
-making a copy for a spare set (due to often misplacing them etc.)
-better lip support

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Common complaints from denture wearers

A

-rubbing, soreness
-struggle talking
-struggle eating. Having to change diet. Weight loss
-looseness
-poor retention and stability
-appearance. self confidence, social withdrawal, depression
-broken
-odour
-white patches
-feel bulky
-bad taste
-food getting trapped
-ulcers
-fungal infection
-worn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What to ask in a denture history

A

How long they have had them for, age of dentures, how many sets thy have had, were they made at NDH, how successful previous ones were, how frequent replaced, how frequently they are worn, worn at night?, how often cleaned and with what, were current dentures initially fine, when they noticed problems
-when teeth were extracted (dentures will last longer if not soon after extractions as bone is still rapidly resorbing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the Cawed and Howell classification (class I - VI)

A

-classifies the from of the alveolar processes of edentulous ridges
Class I= dentate
Class II= immediately post extraction
Class III= well-rounded ridge form, adequate in height and width
Class IV= knife-edged ridge form, adequate in height, inadequate in width
Class V= flat ridge form, inadequate in height and width
Class VI= depressed ridge form , with some basilar loss evident

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Definition of retention and stability. And how to test it. What denture problems affect retention and stability

A

-Retention: ability to not vertically displace. Fingers at premolars on maxilla and pull down and should stay in place. (3-4mm is acceptable) Fingers at incisors and rotate back and forth to test the back seal.
-Good if well defined ridge. No under or over extensions. Good border seal at vibrating line. Thin Layer of saliva between denture and mucosa helps due to surface tension. So dry mouth affects it. Patients with good neuromuscular control. Undercuts

-Stability: ability to not horizontally displace. Fingers at premolars and rock and rotate. Poor stability due to fitting inaccuracies, not utilising all of denture-bearing areas, poorly defined ridge, under or over extensions

Under extensions= no seal
Over extensions= easily pops out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Age related oral changes

A

atrophy of bone causing tooth loss and loss of facial height, TMJ remodelling, reduced nerve and muscle function, salivary gland hypo function, cell dysfunction causing oral cancer,
-thicker cementum, PDL less cells, thinning of mucosa, reduced taste, tooth wear, smaller pulp, secondary dentine, sclerotic dentine, dead tracts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Requirements for edentulous impression materials

A

good accuracy, little porosity, minimal dimensional change, biocompatible, plastic then elastic so doesn’t change shape when removed, good wet ability, low Tg, ideal WT and ST, pleasant taste and smell, simple technique, can be disinfected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What factors increase oral candida infection. What medical conditions

A

-Xerostomia; saliva reduces adherence of c.albicans
-Low (acidic pH) favours colonisation of candida species. Low pH observed in denture plaque in patients with sucrose or glucose rich diets.
-Denture plaque (bacteria) may contribute to colonisation.
-Defects in cellular immune system predispose as T-cell and macrophage mediated activation of the immune system is critical. Malnutrition in association with high carbohydrate diets, iron, folate, B12 def), hypoedocrine states, diabetes, blood disorders e.g. leukemia, HIV
-disease of the diseased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How to advise patients to clean their dentures and reduce fungal infection

A

-Denture hygiene advice –soft nail brush and liquid soap or oxygenating cleaner.
-Soak in steradent or chlorhexidine and cold water for 10 mins twice a week.
-Cold water over night
-Leave dentures out at night
-Correction of denture faults
-Diet advice
-Antifungal – miconazole gel

Don’t use pastes that will scratch it (notch sensitive) + don’t use boiling water as it will be above glass transition temperature (deformation) and changes refractory index (looks white/bleached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a hydrocolloid. Give examples of impression materials. What is the properties

A

-water-based. A colloid with water. A sol when initially mixed, then forms a gel.
-colloid= heterogenous (particles in a liquid). 2 phases that cannot be readily differentiated.
-alginate and agar
-low viscosity, elastic, can go in undercuts, hydrophilic,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a true solution and suspension. Where does colloid sit here. What is an emulsion

A

-true: homogenous, solid completely dissolved in liquid
-suspension- heterogenous. Solid particles dispersed in liquid. Can be seen as particles are large
-colloid sits in between these

-emulsion= liquid dispersed in liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Name examples of impression materials that are elastic and non-elastic

A

-Elastic: agar, alginate, silicone, polyether
-Non-elastic: plaster, compound, ZOE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which is reversible and which is irreversible: agar or alginate.

A

-Agar= reversible hydrocolloid
-Alginate= irreversible hydrocolloid. Water and powder forms a solid mass which cannot be reversed. When form a gel, they cannot return to sol state.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is alginate made of and its reaction with water

A

-sodium alginate, calcium sulphate and other stuff
[-Alginic acid is insoluble in water so we take the sodium or potassium salts of alginic acid to make it soluble]
-when mixed with water, Soluble alginate reacts with calcium sulfate to produce calcium alginate gel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Advantages and disadvantages of impression compound

A

advantages= viscous so muco-compressive and well-extended into sulcus depth, ideal for primary impressions to make special tray, trimmed easily, easily added to and readapted, can be used in combination with other materials (TypeII), compatible with cast materials
-Disadvantages= handling is technique sensitive, sticky, cannot record undercuts, doesn’t record fine details, needs a water bath to soften, shrinkage of 1.5%, poor dimensional stability so cast should be poured within 1 hour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Advantages and disadvantages of zinc oxide eugenol

A

advantages= fluid so excellent surface detail, dimensionally stable, can be added to and readapted, muco-static (but tends to iron out tissues rather than compress them), adheres to dry surfaces, adheres well to compound
-Disadvantages= not used when slight undercut exists, only sets well when thin, doesn’t produce satisfactory impression at periphery unless well supported by accurately fitting special tray, non-toxic but some eugenol allergies causes burning, adheres to skin so Vaseline needed, presence of water and increased temperature reduces setting time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Pros and cons of alginate

A

Advantages: Cheap, easy to use, non-toxic, non-irritant, can be used in stock trays and special trays, records fine details, can record undercut areas, well controlled setting time
Disadvantages: dimensionally unstable (imbibition and syneresis) so needs to be cast quickly, surface reproducibility not as good as agar or elastomers, poor tear resistance and strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is a sol and a gel

A

sol= viscous liquid
gel= elastic solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

why might defects occur in impressions

A

Due to poor mixing, polymerization shrinkage, loss of condensation reaction by-product (water or alcohol), thermal contraction from mouth to room temp, absorption of water or disinfection over time, incomplete recovery of deformation because of viscoelastic behaviour, poor seating force or position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

are hydrocolloids and elastomers elastic or non-elastic

A

elastic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

name examples of elastomers

A

silicones, polyether, polysulfide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

which materials need perforations in the special tray: alginate, elastomers, ZOE

A

-Alginate must be perforated for mechanical retention
-elastomers and zinc oxide not perforated because thin layer and has good chemical adhesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is gypsum made of. Is there more expansion in stone or plaster. The differences. Requirements of gypsum

A

calcium sulphate dihydrate which is dried down to a calcium sulphate hemihydrate powder so water is added when needed. Used for models, casts, impression material, investment material
-0.3mm expansion for plaster. 0.2mm for stone. Stone has smaller particles, more regular, more dense, less porous.
-Requirements: minimal dimensional change on setting and over time for good accuracy, compatible with impression materials, color contrast so easy to read, easy to use, not costly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Definition of mucocompressive and mucostatic. And give examples of materials

A

-Mucocompressive= displace the tissues so are more viscous. Compound
-Mucostatic= the tissues displace it so are lower viscosity. Alginate, ZOE, silicone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Requirements for denture bases

A

natural appearance, easy processing, easy to clean, easy to repair, inexpensive, long shelf life, biocompatible, resistant to bacterial contamination, radio-opaque (8% BaSO4 so can see in x-rays if in airways), heat transfer (thermal diffusivity and conductivity to maintain health of soft tissues), accurate reproduction of surface detail, dimensional stability, good fit, resists distortion, no water or saliva absorption, corrosion resistant, adequate mechanical properties (strength, stiffness, hardness, toughness),

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is PMMA and what its used for

A

highly crosslinked poly-methyl-methacrylate with polymer chains of varying lengths and some residual monomer
-makes denture bases. acrylic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are the 5 consistencies of PMMA during mixing. At what stage do you want to be packing

A

sandy, stringy, dough, rubbery, stiff
-want to pack at dough stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

During heat curing of PMMA, what is the powder made of and what is the liquid made of

A

-Powder= beads of PMMA, initiator (benzoyl peroxide), pigments, dyes, optical pacifiers (TiO2/ZnO), plasticizers), synthetic fibers (nylon)
-Liquid= methyl methacrylate monomer, inhibitor (hydroquinone), crosslinking agent (diethylene glycol dimethacrylate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the difference with chemical cure, compared to heat cure

A

-an accelerator is added to the liquid
-cures at lower temperature. Self curing/ cold curing/ auto polymerisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are the 4 stages of polymerisation

A

Activation: activator reacts with benzyl peroxide initiator to form free radicals. (Low molecular weight compound converted to high in heat)
Initiation: free radicals react with monomers, as monomer C=C breaks
Propagation: reaction continues, more monomers added to the radical-monomers, chain grows, crosslinking
Termination: chain cannot grow anymore. Free radicals react with each other. Due to high viscosity/ impurities/ no more monomer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are the main stages of processing the wax dentures into acrylic

A

Wax-up, flasking, melt out the wax, packing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What issues can occur during acrylic processing of the dentures

A

porosity, warpage, distortion, fracture,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what temperatures are used for acrylic processing

A

70 degrees for 5-7 hours then 100 degrees for 2.5-3 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is contraction porosity, causes, how to avoid it

A

-porosity throughout whole denture. Incorrect shape due to polymerisation shrinkage (polymer more dense than monomer), insufficient material packed into flask, or inadequate flasking pressure
-avoided by ensuring these things don’t happen. Process under pressure using dough molding technique

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is granular porosity, how to avoid it

A

-porosity appears in thin sections of denture. Often look white and frosted.
-due to incorrect polymer: monomer ratio or failing to pack the flask at the dough stage so avoid these.

37
Q

What occurs if you pack in sandy stage

A

high fluidity so will flow out of flask, causing granular porosity

38
Q

What happens if you pack in a rubbery stage

A

too stiff and material will not flow, causing lack of denture details, moved or fractured teeth

39
Q

What is gaseous porosity, how to avoid it

A

Porosity in localised area, particularly in thicker parts. Caused by evaporation of monomer during processing
-avoid high processing temperatures

40
Q

Is porosity, deformation, strength, colour stability better or worse in heat or chemical cure

A

chemical cure= more porosity, more distortion, less strong, less colour stability

41
Q

Advantages and disadvantages or PMMA

A

pros= Excellent aesthetics, Easy and cheap to process, Low density
cons= Low strength and toughness
Susceptible to distortion
Prone to discoloration
Low thermal conductivity
Radiolucent

42
Q

Potential health effects of PMMA

A

-Inhalation: may cause respiratory tract irritation. Move person to fresh air, if effects occur consult a physician
-Skin: may cause skin irritation if absorbed through skin. Wash skin and seek medical attention if needed
-Eyes: may cause eye irritation. Flush eyes thoroughly with water for several minutes, remove contacts lenses
-Ingestion: may cause GI blockage. Seek medical attention, don’t induce committing unless directed to do so
Types of adverse reactions:
-toxic reactions, irritant contact dermatitis, allergic contact dermatitis, oral lichenoid reactions, anaphylactoid reactions, contact urticaria
-irritant contact dermatitis most common in lab due to regular contact with monomer so rubber gloves worn and barrier creams may help
-allergic contact dermatitis usually associated with release of residual monomer. So must ensure full cure of denture. Worse with cold-cure resins. May need to consider alternative material such as polycarbonate or nylon

43
Q

List all the lab and clinical stages of complete denture production

A
  1. Initially patient assessment
  2. Primary impressions
  3. Preliminary cast and special tray
  4. Major impressions
  5. Major cast and reg block production
  6. Registration
  7. Mount cast on articulator, set up of teeth
  8. Try-in and adjust where necessary
  9. Processed into acrylic
  10. Insert
  11. Review
44
Q

What are the requirements/ stages of preliminary impressions

A

-muco-compressive impression compound to record sulcus depths. 1.5 bricks.
-Correct stock tray (5mm around ridges).
-Softened in water bath at 55 degrees. Mould into rough shape of tray, soften in bath, put in tray with correct amount, soften again, then take impression.
-seat with correct pressure
- Border moulding with good tissue manipulation to get functional sulcus. If issues, place back in bath and redo, or pin flame certain areas. Seat from back the forwards
-Disinfect for 3 minutes.
- Complete prescription form for special trays to be made.

45
Q

Key requirements/ stages in preliminary casts production

A

-100g plaster, 50ml cold water. Correct consistency, viscosity, WT
-pour plaster onto impressions
-Keep tapping or use vibrating plate to get rid of bubbles and so it goes into all gaps, to prevent weakening or affecting anatomy
- Place on top of a mound of plaster and smoothen edges. Set for 20 mins.
-Place in warm water to remove the impression from the plaster. Trim excess and make everything smooth and parallel.

46
Q

Key requirements and stages in special tray production

A

-Outline key pencil markings on the cast- posterior border (roughly where the vibrating line is), depth of the sulcus cleared by 1-2mm (so room for greenstick later to record sulcus), going around frenal attachments, extending over tuberosities.
-Wax sheet is melted until floppy and then placed over model. It is closely adapted without making it too thin. [Wax is a 0.6cm spacer which leaves room for zinc oxide euganol] It is trimmed to the outlines.
-Visible light cured acrylic resin placed over the wax then trimmed to the same outlines.
-Handle is made at the incisive papilla at 45 degree angle.
-Put Vaseline on so that the oxygen doesn’t prevent setting. Light cured for 5 minutes.
-Take off model then spray with hot water to melt the wax and Vaseline away.
-Cure underside for further 30 seconds. Trim the tray with the handpiece and tungsten-carbide bur so not sharp edges

47
Q

Requirements/ stages of major impressions

A

-Special tray tried in mouth. Vibrating line (anterior to palatine fovea, where soft and hard meets) is marked with pencil on patient so that it transfers to tray. Tray is trimmed to this line. Trim to 2mm short of sulcus depth and around frenal attachments. To check if you have trimmed enough, try border moulding to see if it displaces the tray at all, and if it does then it is overextended so trim more.
-Border moulding with green stick: Maxillary= heat in Bunsen until gloopy, drip it from the 3 to 3 region of tray with correct thickness. Place in water bath then into patient’s mouth. Do the same for 3 to 8 regions on one side, and the other side. Pin flame uneven transitions. Then post dam region (bring into onto palate slightly). Pin flame the transitions, water bath, then mouth. Trim post dam excess.
Mandible= sulcus is less defined as maxilla, so less greenstick needed. R buccal, R lingual, L buccal, L lingual. Put at retro molar pad region if underextended. Don’t put in the lingual incisors region as it tends to be overextended here
-Trim excess green stick from fitting surface
-Impression taken using zinc oxide eugenol – base and catalyst pastes, equal lengths of both. Mix until smooth using spatula and pad. Once tacky load into tray. Thin layer of 0.6mm. Place in mouth, and border mould.
-Small air bubbles filled in with Kelly’s paste or a better options is with wax. Trim post dam region with scalpel.
[If green stick not sticking well, likely coz tray is still damp]
-Disinfect for 3 minutes

48
Q

Requirements stages of lab stage of reg block production (measurements and angles etc.)

A

-major cast made using dental stone
-Light cure acrylic is moulded around major cast. Trimmed to half way around the ridge and cutting out tuberosities. Crosses are scored on the ridge. Cured for 5 mins.
-Heat wax until floppy then fold over 1cm length way. Squash this into sulcus then mould the rest over the ridge. Trim just on the inside of the crosses made. Seal palatal edges with heated knife.
-Registration block placed on ridge, ensuring it won’t interfere with tongue or cheeks
-10 degrees anterior inclination of maxilla block. Vertical anterior inclination for mandibular block.
- using heated knife to adjust buccal widths= 5-6mm anterior, 7-8mm premolar, 9-10mm molar.
-use hot plate to adjust maxillary height= 22mm at front (from deepest part of sulcus), 20mm at back. Mandibular height= 18mm.
-45 degree in the hamular notch areas to prevent heals clashing.
-For refinement, pools of wax are created using heated knife and dripped over the model to seal and smoothen the edges. Pin flamed, wipe with wet cotton wool

49
Q

What are reg blocks used for. Describe what the neutral zone is

A

-used to record position of denture teeth by recording horizontal and vertical jaw relationships, occlusal plane, lip support
-prescribed positions should correspond to the neutral zone (area where the muscular forces of lips, cheeks, tongue are in equilibrium)

50
Q

Check list of things to assess during clinical registrations

A

Asses upper first. then once happy move onto lower
-check extensions and extensions around frenulum
-check stability and retention and comfort
-buccal corridors: 4-5 mm space
-Pressure cream to check any rubbing etc.
-labial/ buccal thickness. Lip support
-incisal level: at rest should be 2mm more than level of lip
-Fox’s plane to assess incisal plane (inter pupillary line) and occlusal plane (alar tragal line)
-10 degree incline of maxillary labially

-Measure resting vertical dimension with willis gauge, then take way 2-4mm to get the OVD and adjust the lower block accordingly
-assess even contacts
-lower parallel to upper
-adjust labial/ buccal thickness

-mark centre line, cuspid line (distal of alar), smile line. Match these on lower
-blue mousses: notches in blocks, layer of mousse on lower, bite together, squirt in notches. Wait until set
-disinfect
-select tooth size, shape, shade

51
Q

Requirements/ stages for articulating of the casts and setting in the teeth for before try in

A

-average value articulator, 30 degrees at condyles. Cast mounted on the articulator using plaster.
-Next to centre line, cavity of wax is removed. Knife is heated then mush up the wax. Position the central incisor so that is the correct angle, labial contour and incisal level. Insert upper teeth going posteriorly.
-For lowers, start with 6s which should be 1 cusp anterior to upper 6. It should be tipped distally and bucaly slightly. Then 7s.
-The molars should have a curve of spee and curve of monson. Then insert 5s. Then 1, 2, 3, 4. Note that the lower anterior are set just above the incisal plane due to overjet (2-3mm) and overbite (0.5-1mm).
-Ensure balanced occlusion and articulation.
-Neaten the wax and seal them in place then carve the gingival margins. Wipe with wet cotton wool. Ready for try in. If fine, then processed into acrylic

52
Q

definition of balanced occlusion and articulation

A

balanced occlusion (simultaneous contacts on posteriors when static) and articulation (when dynamic).

53
Q

Which teeth are left out or added for class II and class III when setting in teeth in reg blocks

A

-For class II= leave out lower 4s and/or lower 1s
-For class III= leave out upper 4s and/or add an extra lower central incisor

54
Q

What to assess during try-in

A

-Checking centreline, shape/ size/ position of teeth, lip support, buccal corridors, incisal and occlusal planes, balanced occlusion and articulation, overjet, overbite, OVD, freeway space, retention/ fit/ stability, extensions, speech, any movement during speech, occlusal contacts
-Use bur to trim any extensions or areas rubbing. Use pressure cream to identify
-Use articulating paper for ICP and excursive contacts. Get patient to close teeth and check if denture slides at all. Sliding means there are premature contacts that needs adjusting. Can use the bur to trim tooth, or if big adjustments then re-set teeth

55
Q

How to adjust bilateral increased OVD

A

at chairside, remove posterior lowers going anteriorly until correct OVD, then replace the wax in that area, re-register occlusion in mouth, lab re-articulates, resets lowers, then retried in mouth

56
Q

How to adjust bilateral decreased OVD

A

occlusion re-registered with wax sheet between teeth. Lab re-articulates lowers and resets teeth (reset the lowers if uppers correct, or reset upper and lowers if uppers incorrect)

57
Q

How to adjust unilateral increased OVD or decreased OVD. How its detected

A

-Unilateral increased OVD= -Detecting by putting a knife between the teeth and small twisting movements. Look for any displacement towards the tissues. This means there is unilateral occlusal error, where the side with no movement has the increased OVD
-Remove teeth from offending side that is increasing the OVD (premature contact) to allow the other side to occlude to correct OVD, Restore block, re-register, lab etc. )Or can place wax between non-contacting teeth and lab resets
-Lack of OVD= re=register correct OVD, rearticulate lower cast, reset lowers to the correct upper. Retried in mouth

58
Q

How to take a copy box impression of dentures

A
  1. Disinfect dentures for 3 minutes
  2. Each half of the box needs 8 scoops of alginate
  3. Measure 8 scoops into bowl. Measure 8 parts cold water (slightly more to allow a more runny consistency)
  4. Bottom part of box has no holes. Fill box with alginate
  5. Smear excess alginate onto teeth (to prevent air blows although not essential)
  6. Place into alginate in the centre. Seat in, where the top of the sulcus is roughly 1cm above the box edge. If touches the bottom need to start again
  7. Once set, trim with knife so it is flush with box, and want the alginate to go as close to the gingival margin without exposing the teeth
  8. For the posterior border part, follow the contour of the denture at the back
  9. Vasline the alginate surface
  10. Move onto the top half of the box, with the holes.
  11. Mix 8:8 water and alginate. Fill box
  12. Place alginate onto the fitting surface of the denture
  13. Push the boxes together, making sure they are firmly shut
    Then do the same for the other denture
59
Q

When to do copy impressions. why

A

-To copy successful elements of complete dentures and adjusting less favourable features. If significant changes needed, then conventional technique more appropriate.
-Indications=elderly patients with reduced adaptive capacity as don’t want to make extensive changes, previous satisfactory dentures so want minor adjustments, making a copy of immediate dentures while conventional dentures made, patient wanting a spare set in a care home, misplacing them due to dementia etc., denture discoloured, worn teeth

60
Q

What is the difference between simple and modified copy technique for copy dentures.

A
  1. Simple copy-=used if dentures can be hand articulated. Fit together accurately. If no adjustments needed or minor adjustments. Copy box impressions then try -in then wash impression stage
  2. modified=cannot be hand articulated
    -includes a registration stage
    Making changes such as Issue with occlusion, OVD, wear, interference
61
Q

What stages are involved in simple copy technique

A
  1. Patient assessment and treatment plan
  2. Copy box impression. Ask lab for try-in
  3. Lab pours casts and replicas - wax filled into mould through spur holes then acrylic. Articulate and set up teeth
  4. Try in to assess fit, OVD etc. Take wash impression to re-establish fit - layer of ZOE on fitting surface and get patient to close
  5. Lab make it into acrylic using lost wax technique- flask, pack, process and finish
  6. Insert
  7. Review after 1-2 weeks
62
Q

What stages differ in modified copy technique compared to simple copy

A

-Before copy box impression, perhaps modify base extensions with green stick if need be
-Ask lab for reg blocks rather than try-in.
-Registration stage, after lab pours cast and replicas, and before lab articulate and set up teeth. Reg blocks are wax replicas of existing dentures and allows you to remove or add wax where necessary.
-then ask for try-in, then do wash impressions etc.

63
Q

Explain the lost wax technique for complete dentures (4 stages)

A

-Flasking: a plaster cast mould of the wax denture is made
-Boiling out: the wax is melted when in a boiling out machine and then washed away with hot water jets
-Packing: heat cure acrylic is packed into the mould at dough stage. It is covered in plastic separating sheets, then placed in hydraulic bench press where pressure is slowly increased and excess acrylic squeezed out of mould.
-Curing: for 9 hours, temperature gradually increases to 100 degrees

64
Q

Why should acrylic be covered once packed during processing. Why is the acrylic not trimmed completely before putting back into press. Why is curing long and slow

A

-covering to prevent monomer evaporation and gaseous porosity
-Flash is trimmed around the periphery, leaving slightly over-filled to prevent contraction porosity, and placed back into the press for final closure
-long slow cure prevents gaseous porosity, ensuring monomer doesn’t evaporate

65
Q

What is the boiling point of monomer used for denture acrylic. Its relevance for processing

A

100.3 degrees. During curing, the cure is long and slow (9 hours) and the temperature gradually increases, only reaching 100 degrees for the last 2 hours to prevent excess monomer evaporating and causing gaseous porosity

66
Q

Why OVD increases when articulation and occlusion is assessed after de-flasking. What technique reduces risk of this happening

A

due to polymerisation shrinkage. Injecting packing process reduces this risk
-OVD is restored by using articulation paper and adjusting any high spots until there is balanced occlusion and balanced articulation

67
Q

Once de-flasked what processes are involved to clean, neaten and smoothen the dentures

A

-ultrasonic cleaners in a solution of Ty-solve liquid to remove plaster residue
-tungsten carbide bur used to remove flash, trim buccal flanges, adjust palatal thickness
-silicon polishing cylinder to smoothen
-air bubbles flicked away, sharp edges removed
-polished: pumice and brush to smoothen the dentures due to abrasive properties
-acrylic gloss for high shine, no roughness, easy to keep clean
-placed in detergent in the ultrasonic to clean off any polishing debris
-washed, disinfected

68
Q

What is involved in transfer injection moulding and what are its advantages.

A

-compensates for curing polymerisation shrinkage of acrylic. Holds flasks so tightly together so no increased OVD
-pressure is applied to the resin and is injected into the mould
-mechanically mixed so is a consistent mix, and limited monomer exposure to user
-little trimming and polishing required
-high impact acrylic so less prone to breakage
BUT costly so only used in private care

69
Q

Reason why a denture may break

A

-dropped= impact fracture
-gripping it too tightly =causing midline fracture
-stress fracture: perhaps due to poor fitting (due to alveolar resorption)
-uneven or excessive loading= causes tooth loss

70
Q

How to fix a simple fracture of a denture

A

-2 halves tacked together with sticky wax.
-Denture placed onto plaster or putty matrix (ensures accurate relocation to the cast later).
-Once set, the denture is removed from matrix and the fracture site is bevelled to increase surface area for new acrylic to bond better to and improve the colour match.
- Self-cure acrylic filled to slight excess onto the trimmed area
-cured in pressure pot for 5 mins at 1 bar pressure (prevents gaseous porosity) then trimmed and polished

71
Q

How to fix a denture with a lost tooth

A

(caused by excessive loading or if not all wax removed during processing)
-relocate tooth, or select a replacement if don’t have it, and wax the tooth into place
-make plaster/ putty matrix to allow accurate relocation. once set remove matrix, trim/ bevel acrylic, reassemble matrix and tooth onto denture
-apply self cure to slight excess, pressure pot for 5 mins to cure, trim then polish

72
Q

How to add an identity tag

A

-cut recessed area onto lingual or palatal molar region
-stainless steal chip cut slightly smaller than area and scribe patients details into it (name, DOB, hospital no.)
-embedded: edges bent inwards so no exposed sharp edges
-covered with self-cure acrylic
-cured for 5 mins in pressure pot
-trim and polish

73
Q

When relines and rebases required and why

A

-if a more permanent solution to the fracture is required, which will replace the whole of the fitting surface.
-relining: if loose, relined to replace fitting surface for a tighter fit of lower dentures
-rebasing: replacing fitting surface and base acrylic, of uppers. to prevent excessive thickness so the palatal thickness doesn’t increase too much

74
Q

Clinical and lab stages of rebasing

A

-clinical: remove undercuts, wash impression in fitting surface with closed mouth technique
-lab: stone cast poured onto wash impression. Matrix applied for easy relocation later. Remove impression material, remove matrix, remove periphery of denture and roughen fitting surface for good adhesion between the new and old. If upper then remove palate to prevent excessive thickness
-self-cure acrylic applied to fitting surface. Apply matrix then relocate onto cast
-cured trimmed polished

75
Q

What is an over denture. Its pros and cons

A

-A denture that gets support from one or more abutment teeth or implant, by completely enclosing them beneath its impression surface. Improves retention of denture

-Pros: Preserve roots so less resorption to preserve bone and don’t lose as much vertical height as conventional dentures would
-Maintaining alveolar ridge height increases stability and retention
-Roots can also be used for attachments to further improve retention
-Improved sensory feedback as PDL not destroyed

BUT: high degree of maintenance
-Potential for caries and perio disease
-Occassional difficulty with undercuts
-Ocassional fracture of acrylic due to being thinner

76
Q

What are the indications for using abutments and over dentures. And contra indications

A

Good for patients with hypodontia, severe tooth wear, cleft palate/ surgical defect, a single complete denture
Not ideal for extremes of age, severe debilitation (can’t maintain), poor cooperation, mental handicap, complex medical history affecting extractions, any condition which would need RCT

[want for abutments on upper, 2 on lower]

77
Q

What types of abutments are used for over dentures

A

-an abutment is a modified crown or root structure of a natural tooth
-types: doming, copings, precision attachments, stud attachments, locator attachments, magnets
-also implants can be used for implant supported over dentures

78
Q

What considerations need to be taken when selecting an abutment/ tooth. Requirements

A

-crown: root ratio. Want long roots (canines)
-no subginigval caries
-RCT possible
-symmetrically distributed in the arch
-at least 2 abutments required as 2 would cause rotation
-easy to clean
canines>premolars>molars>incisors

79
Q

What abutment requires the simplest prep. Which have a matrix and a matrix. Which are hard to clean and unfavourable due to lateral forces. Which have a ball on the end

A
  1. doming
  2. Locator attachments
  3. Simple and telescopic copings
  4. stud attachments
80
Q

Why implant supported over dentures may be used instead of regular. Requirements. Contraindications.

A

-If retention problems of conventional dentures, excessive loading of muscosa, psychological problems accepting dentures, trauma, diastema. Improves stability, retention, function
-Requirements: bone quality and quantity needs to be adequate
-Contraindications: unrealistic patient expectations, smoking (will contribute to peri-implantitis), poor general or local health, poor bone volume or quality, cost (£3500 - £4000), poor patient compliance/ co-operation/ maintenance, unfavorable anatomy

81
Q

What is osseointigration. What factors affect ability for osseoinigration

A

-direct structural and functional connection between ordered, living bone and the surface of a load carrying implant
-Factors for integration = biocompatibility, implant design, implant surface, state of host bed, surgical technique, loading conditions
-Implants have no PDL so are rigid and have no visco-elastic movement.

82
Q

What is peri-implantitis. Causes

A

-inflammatory process in soft tissues, and bone loss around an osseointegrated implant
-increased risk in patients who have a history of chronic periodontitis, poor plaque control skills, and no regular maintenance care after implant therapy. smoking and diabetes potential risk factors

83
Q

Explain the pick-up major impression technique for implant supported overdenture

A

-Need to consider implant abutments. Usually locator abutments in mandible. Gold or rose-gold
-Firstly, fit on impression copings on the abutments.
-Try in special tray and make any adjustments
-Once done greenstick, apply an adhesive to the tray because no mechanical or other adhesion.
-Load polyether (more rigid than silicone) into tray and seat over the ridge and copings.
-Border moulding.
-Trim excess with scalpel or scissors
-Seat coping back into impression and check they don’t move

84
Q

Common cause of denture displacing when talking

A

-overextension of buccal flanges
[-underextensions will cause it to fall at rest]

85
Q

is ZOE hydrophilic or hydrophobic

A

hydrophilic

86
Q

What muscles are at the retomolar region and the buccal sulcus

A

-posterior to retor molar =massseter
-buccal= buccinator

87
Q

treatment of a denture granuloma

A

Relieve the effected area and encourage the patient to leave the denture out

88
Q

the 3 types of denture stomatitis. Risk factors. Management

A

1/ Pin point hyperemia and diffuse inflammation.
2/ Diffuse erythema on most of the denture bearing area.
3/ Granular inflammation or inflammatory papillary hyperplasia

-Poor host defenses, dry mouth, Continuous denture wear, dental trauma, dental plaque and candida albicans.
-Management: Denture hygiene advice, Leave dentures out at night, Tissue conditioners, Correction of denture faults or Anti fungal (miconazole gel or fluconazole tablets).

89
Q

What happens to the vertical dimension during the heat curing of acrylic denture

A

The vertical dimension increases due to polymerization shrinkage
Injection molding technique reduces shrinkage

Prosthodontics (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions