BDS 3 Sem 2 > Fix Pros > Flashcards

Fix Pros Flashcards

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1
Q

What are the aims of fixed prosthodontics?

A

It ranges from restoration of a single tooth to rehabilitation of the entire occlusion.

The main aims are:

  1. Restore biological health
  2. Restore function
  3. Restore aesthetics
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2
Q

What are the two categories of restorations?

A
  1. Direct - activated in mouth
  2. Indirect - prepared in labs or milling machines (think outside mouth and cemented in)
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3
Q

What are the two types of indirect restorations?

A
  1. Intra-coronal - inlays or onlays
  2. Extra-coronal - crowns or veneers
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4
Q

Why would you choose a intra-coronal restoration rather than a direct material?

A
  1. Need for stronger material
  2. Difficulty with getting appropriate contact with direct restoration
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5
Q

What is the difference between the cavity preperation for a direct restoration vs indirect intra-coronal restoration?

A

Cavity prep can not have undercuts

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6
Q

What are the functions of a crown?

A
  1. Reproduces the morphology of the damaged coronal portion
  2. Restore function
  3. Protect remaining tooth structure
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7
Q

What are the indications for crowns?

A
  1. Protection of weak tooth structure
  2. To re-establish the occlusion
  3. Modification of tooth shape
  4. Replacement of missing tooth structure
  5. As retainers
  6. Aesthetics
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8
Q

What are the contraindications for crowns?

A
  1. Poor oral hygiene and active dental disease
  2. Cost
  3. Patient’s age - young patients who have large pulp chambers which may be exposed
  4. Excessive removal of tooth structure
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9
Q

What are some of the considerations for a crown selection

A
  1. Occlusion
  2. Endodontic status/vitality
  3. Other teeth requiring treatment
  4. Future of tooth
  5. Future dentition
  6. Restorability of tooth/teeth
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10
Q

What are the parts of a dental bridge?

A
  1. Abutment - a tooth that serves to support or retain the bridge
  2. Pontic - an artificial tooth/teeth on a prosthesis that replaces a missing natural tooth
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11
Q

What are the indications for a veneer?

A
  1. Diastema closure
  2. Alter shape, contour, position
  3. Alter tooth color
  4. Mask tooth surface anomalies
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12
Q

What are primary functions of a post?

A
  1. Retain the core
  2. Stabilise the core
  3. Obturation of the post canal
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13
Q

What are the general checks before commencing fixed pros.

A
  1. There a control of active disease - periodontal, caries, occlusal
  2. Ensure the patient can maintain good oral health
  3. Occlusal analysis
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14
Q

WHat are the 5 key principles of crown prep?

A
  1. Preservation of tooth structure - preserve remaining tooth structure
  2. Retention and resistance form
  3. Structural durability - enough thickness of the crown material so it doesn’t fail - each material requires different thickness
  4. Marginal integrity - utilise finish lnes - bevels, chamfers, shoulders - remember bad margin = caries, gingivitis and perio - to recreate the appropriate finish design - use the right bur! easy peasy (remember to just use half of the bur so you dont create undermined enamel) - burs come in different sizes, so the size of the bur will dictate the width of the finish line
  5. Preservation of periodontium - dont fuck up the periodontium - put your margins supragingival ideally
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15
Q

What is retention and resistance form?

A
  1. Retention prevents removal of the restoration along the path of insertion
  2. Resistance prevents dislodgement of the restoration by forces in an apical or oblique direction (rocking)
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16
Q

How do we achieve appropriate retention and resistance form in crown prep?

A
  1. Appropriate taper - the more parallel the walls are - the more resistance you have - combined angle of 6 degrees is optimal (3 degrees deviation at the crownal part comparing to the base of the tooth on each side, 3+3=6)
  2. MORE SURFACE AREA - think big teeth retain crowns better - more crown height and width
  3. Path of insertion - NO UNDERCUTS, NO NEIGHBOURING TEETH TILTING
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17
Q

How many visits usually does a standard crown prep and insertion take?

A

Usually - 3 visits

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18
Q

What happens during the first visit of indirect restoration process?

A

Visit 1: Examination, construction of study models, shade selection, finalisation of treatment plan and consent

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19
Q

What happens during the second visit of indirect restoration process?

A

Visit 2: Putty key, confirmation of shade selection, crown prep, secondary impression, provisional restoration

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20
Q

What happens during the third visit of indirect restoration process?

A

Visit 3: removal of provisional and insertion of final crown

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21
Q

What are your options in terms of temporary crown?

A
  1. Custom made temporary crowns using protemp4 for example
  2. Preformed crowns - select appropriate size and Bob is your uncle
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22
Q

What are the desirable properties of a cement?

A
  1. Adhesion to enamel and dentine
  2. Adhesion to corwn
  3. Biocompatability
  4. Adequate compressive strength
  5. Thin film thickness
  6. Rapid setting time
  7. Insoluble in oral fluids
  8. Transparent colour
  9. Anticariogenic
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23
Q

Why do we use alloys rather than pure metals?

A

Alloys have superior physical and mechanical properties in the oral environment vs pure metals

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24
Q

What are some of the desirable clinical properties of dental alloys?

A
  1. Grain size - polishibiltiy
  2. Phase structure
  3. Yield strength - how is it to bend
  4. Hardness - to resist occlusal forces
  5. Elastic modulus - stiffness or rigidity of the alloy
  6. Colour
  7. Corrosion - IT BETTER NOT DO THIS
  8. Porcelain-bonding properties
  9. Ease of casting
  10. Cost
  11. Ease of soldering or joining
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25
What are the three classifications of dental alloys by composition?
1. High Noble Alloys - noble metal content of above 60% and gold of above 40% 2. Noble Alloy - Noble metal content of below 25% with no gold required 3. Base metal - Noble metal content well below 25% with no gold required
26
What are the properties of high noble alloys?
1. Good biocompatibility 2. Good adhesion between alloy and ceramic 3. Good casting accurate for margins 4. Less creep at high temperature 5. Good physical properties 6. Firing temperature close to ceramica 7. More costly than Noble and base metal alloys
27
What are the properties of base metal alloys?
1. Cheaper than noble alloys 2. Better strength than Noble Alloys 3. More chemically reactive 4. Hypersensitivity potential 5. Higher shrinkage on cooling 6. Thicker oxide layer so adhesion to ceramics may be weaker if not processed correctly
28
What are the requirements for metal-ceramic systems?
1. High melting range of the alloy than the ceramic to resist sintering temperature 2. Low fusing temperature of the ceramic 3. Strong bond to porcelain 4. Adequate stiffness and strength of the alloy to provide good support for the ceramic layer 5. High sag resistance (no change in shape) 6. No discoloration of porcelain 7. Compatible coefficients of thermal expansion of the ceramic and metal - make sure that the materials do not expand or constrict too much
29
What are the 3 systems in high noble metal alloys? And what are their advantages and disadvantages?
1. Gold-Platinum-Paladium - easy to adjust and finish but is VERY EXPENSIVE comperative to others 2. Gold-Paladium-Silver - a bit harder but can change colour 3. Gold-paladium - great properties overall but costs a lot
30
What are the 3 systems in noble metal alloys? And what are their advantages and disadvantages?
1. Palladium-Silver - strong but can be discolorised 2. Palladium-Copper-Gallium - very hard material but has bat adherence to porcelain 3. Palladium-Gallium - idk
31
What are the 3 systems used in base metal alloys?
1. Nickel-Chromium - lower cost but remeber nickel allergy 2. Cobalt-Chromium - good for dentures but the finishing of the material kinda shit 3. Titanium - great biocompatibility but very hard to cast
32
Why do we like to use ceramic?
1. Very stable material 2. Good strength 3. They are thermal and electrical insulators 4. Good biocompatibility 5. Great aesthetic properties 6. Holds shape well
33
What are the contraindications for all-ceramic prostheses?
1. Sever bruxism 2. Extensive wear of tooth structure 3. Excessive bite-force capability 4. A previous history of all-ceramic inlay or crown fractures
34
What is the main aspect we use to classify ceramics?
Composition of the ceramic
35
What are the three main compositions of the dental ceramics?
1. Glass Ceramics - main component is Silica 2. Glass ceramics reinforced with fillers - Silica plus some major filler - example is an Emax crown 3. Polycrystalline ceramics - zirconium oxide matrix
36
What are the three main types of ceramic fabrication?
1. Powder liquid - sintering process of painting material and than putting it into the furnace 2. Slip-Cast All-Ceramic Materials - using refractory molds 3. Heat-Pressed All-Ceramic Materials - heat-pressing
37
What is one of the most important propertie of a ceramic material?
It is the optical propertied of the material - the translucency that is similar to enamel
38
What are the three methods of toughening of a ceramic material?
1. Crystaline reinforcement - the design of crystals is altered 2. Glaze application - glaze applied and when heat up the glaze is able to "tighten" the crown 3. Transformation toughening - certain material can tranfer due to temperature change in the furnace - example zirconia
39
What are the usual thickness of the metal coping thickness in a PBM crown?
1. 0.5mm for noble alloys (lower toughness = thicker metal needs to be applied) 2. 0.3 mm for base metals
40
What is the minimal thickness of the porcelain in the PBM crown?
Minimum is 0.7mm and optimal is 1mm Meaning that for a full PBM crown with porcelein on all surface - it needs to be minimum 1mm reduction on all surfaces (remember that minimum metal framework thickness if 0.3mm and minimal porcelaine thickness is 0.7mm thus 0.7 + 0.3)
41
What are the four mechanisms of metal ceramic bonding to the tooth?
1. Micromechanical bonsing - use air abrasion to create a clean 2. Compressive forces due to thermal coefficient of expansion - essentially the metal can make the porcelein more compressed due to greater changes in structure from the changes in temperature 3. Molecular bonding - any bonding between molecules 4. Chemical bonding through oxide layer - VERY CRITICAL
42
What are the disadvantages of metal ceramic crowns?
1. Destructive preparation 2. Expensive 3. Increased wear of opposing natural teeth and gold restorations 4. Still not as good looking as natural tooth 5. It can be brittle in areas of porcelain
43
What are some of the other crowns we can use instead of PBM?
1. Porcelain bonded to zirconium 2. Full contour zircona crowns 3. E.max crowns 4. Alumina crowns 5. Full gold crowns
44
What are some of the principles of crown preparation?
1. Conserve and protect hard and soft tissues 2. Maintain retention and resistance form 3. Structural durability - proper thickness 4. Margin integrity
45
What are the measurements for the prep of an anterior tooth
The labial: 1/3 (gingival) - 1.0 to 1.3 mm 2/3 (incisal) - 1.5 mm Proximal 0.5mm at gingival to 1.5 mm at incisal Lingual: Gingival cingulum wall - 0.5mm Concave surface - if metaland ceramic = 1.0mm, If metal only = 0.5mm to 0.8mm
46
What are the 4 major burs you use in PBM crown prep?
1. Technic 847 - tapered wall and flat end 2. L10 - thin bur 3. Komet 8877 - for shoulder 4. Horico 239 - pear shape bur (VERY AGGRESSIVE) 5. 8877 bur - for smoothness
47
What is the advantage of constructing a temporary crown first before doing a secondary impression?
1. Time may be essential 2. Will show you the undercuts
48
What are the functions of provisional restoration?
1. Pulpal protection 2. Positional stability 3. Restoring function 4. Restoring esthetics 5. Maintain periodontium 6. Protect underlying tooth structure
49
What are some of the options for a temporary crown?
1. Prefibricated - crown formers - could be metal for posteriors! 2. Custom made - using Protemp4
50
What is Protemp4?
It is a composite resin based material that produces no heat, is chemically cured and can create dimension stable crowns. Caution - please be careful when using on skin might be not a good idea
51
What are the steps of constructing of a temporary crown?
1. Take impression of tooth on study model or intra-orally before cutting preparation - use take one putty 2. Place 'Protemp4' in impression and seat on prepared tooth 3. Remove temp from tooth when resin has set to "rubbery" stage - remove with flat plastic 4. Trim with soflex disc 5. Assess the margins, polish and check contact 6. Check the crown on - cement the crown with temporary cement - preferably eugenol free temporary cement - most common is tempbond 7. Check occlusion but remember that the material might crack
52
What are the criteria for a satisfactory secondary impression?
1. Good recording of crown margins and adjacent cervical tooth/root surface 2. All surfaces and line angls of crown preparation 3. All retentive features 4. Adjacent teeth + 'emergence profile' which is the relationship of cervical tooth contrours and gingival tissues 5. Occlusal surfaces so can articulate upper and lower models 6. Edentulous ridge form for bridgework
53
What do we want to avoid in secondary impressions?
1. Air bubles 2. Absence of voids 3. Abscence of drag lines 4. No contact between teeth and tray
54
How do w achieve a satisfactory secondary impression for our crown prep?
1. Well defined and exposed crown margins 2. Gentle handling and retraction of marginal gingiva - use gingival retraction cord or electrosurgery 3. Remove all surface contaminants 4. Dry working field and moisture control
55
What are some of the things to consider in terms of gingival retraction cords?
1. Size 2. If they are impregnated with a haemostatic agents
56
What technique do we apply when we placing gingival retraction cords?
We use a double cord technique: 1. Primary cord - in order to create vertical displacmenet 2. Secondary cord - usually a one size larger cord - to create vaertical and lateral displacement
57
What are the 3 main types of impression materials?
1. Non-elastomeric materials - not elastic 2. Aqueous Elastomers - water + elastic 3. Non-Aqueous Elastomers - no water + elastic (need dry field)
58
How do polysulfieds set? What is it's advantages and disadvanatages?
They set by condensation reaction between sylfydryl groups with lead dioxide and sulfur. Water and heat accelerate the reaction. Advantages: good tear strength and low cost Disadvanatages: Poor dimensional stability and very bad odor
59
How do condensation silicones set? What is it's advntages and disadvantages?
It sets by a condensation reaction Advantages: very good stability and good tear strength Disadvantages: Alcohol as by product = bad odor
60
How do PolyVinyl Siloxanes (PVS) set? What is it's advantages and disadvantages?
It sets via cross-linking which is better than condensation. It is the most common material use in light and heavy body. Advantages: Super stable, odor neutral, great tear strength and elastic recovery - amazing delivry system via a gun (automix) or machine (pentamix) Disadvantages: chemical reaction reacted with latex, locking into undercuts and open membranes and is expensive as shit
61
How do Polyethers set? What is it's advantages and disadvantages?
It sets via cross-linking and is an excellent material in terms of dimensional stability because it does not have a bi-product int eh reaction Advantages: amazing ccuracy and very good shelf life Disadvantages: VERY STIFF VERY VERY STIFF do not use if you have undercuts again VERY STIFF VERY VERY STIFF, shorter working time than PVS silicones and sometimes it gets stuck to oral mucosa
62
What are the trays that we can use for secondary impressions?
1. Stock trays that fit most of people - S, M, L sizes - pretty standard 2. Special position tray - it is custom made, expensive but it is super accurate 3. Triple tray - amazing tray but expensive - dual sided, take bite registration aswell - great for gagging patients
63
What type of adhesive do we use on the tray?
Use PVS for PVS, use PE for PE - dont be an idiot
64
What type of technique in terms of viscosity do we use when constructing a secondary impression?
Dual Viscosity Technique 1. Ask DA to start loading heavy body 2. Remove secondary cord Discard 5 mm of light body on the tray, than inject around the margins of the tooth, entire tooth and adjacent teeth 3. Keep the tie below the surface to avoid air bubbles 4. Seat the tray 5. Allow to set for 5 minutes 6. Remove tray 7. Wash with water 8. Dry impression and assess 9. Send to the lab with instruction
65
What is the post of a post and core system?
1. Preserve remaining tooth structure 2. Protect remaining tooth structure 3. Preserve apical seal
66
What are the three main components of the restoration of endodontical teeth using post and core systems?
1. Dowel (post) - core retention 2. Core - replacement of the lost coronal structure 3. Coronal - restoration itself
67
What is the function of the dowel? What are types of dowels?
Function: 1. Give retention of the core 2. Distribute the stresses along the root 3. Use for obturation Classification: 1. According to material - metallic, combination and all non-metallic 2. According to attachment - 3 piece (all object separate), detached 3. According to method of construction - pre-fibricated or custom made
68
What are the characteristics of ideal post?
1. Post diameter - diameters should be just sufficient to resist bending but not too large to induce root fracture - wider is better for retention but too wide may result in fracture - recommendation if 1/3 of root diameter 2. Post length - RULES: 1. two thirds the length of the canal - good retention 2. half the length of the root supported by bone in case periodontally affected tooth 3. A minimum of 4-5 mm of GP should be left ' 3. Post material - withstand functional stresses and resists corrosion 4. Radio-opacity - needs to be clearly seen on radiographs 5. Bio-compatible 6. Retrievable 7. Can bond to tooth structure and dental materials 8. Consider crack factor 9. No interference with aesthetics
69
When is post necessary?
A post is required if there is insufficient sound coronal tooth structure remaining to provide stability and retention for the final restoration
70
What are contraindications for posts?
1. If core can be retained and supported without post 2. Non-restorable tooth 3. Short roots, thin roots and carious roots 4. Bends/blockages in root canals 5. Existing tooth pathology 6. Poor periodontal support
71
What are desirable properties for a core?
1. High strength 2. Dimensional stability 3. Ease of manipulation 4. Short setting time 5. Ability to bond to both tooth and dowel
72
What types of cores?
1. Direct - think composite resin cores 2. Indirect - cast metal for examples - mainly if you cant fit a pre-fabricated post
73
What is the "Ferrule Effect"?
Even is you have build up a core - a certain amount of tooth structure needs to remain in order to provide adequate resistance in order to reduce 'splitting' of the root.
74
What are some of the problems with post-retained restorations?
1. Loss of retention 2. Secondary caries 3. Root fracture 4. Post fracture 5. Post bending 6. Root resorption 7. Apical infection
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