1
Q
Open Margins are the only form of marginal issue which are NOT SEALED.
What are 5 possible causes?
A
- Poor impression
- Improperly trimmed of die
- Incomplete casting
- Over-polished casting
- Fit surface defect → Crown not fully seated
2
Q
How is excess cement moved following cementation with:
- Resin Cements?
- Any other Cements?
A
- Remove BEFORE SETTING
- Remove after set (3-in-1 wash and pick away)
3
Q
If upon crown cementation we have NOT maintained an accurate occlusion, what 3 outcomes could this result in?
A
- Over-eruption of teeth
- Tilting or drifting of teeth
- Working or Non-working side interferences produced
4
Q
What are the functional cusps in:
- Upper teeth?
- Lower teeth?
A
- Palatal
- Buccal
5
Q
What 4 things do we check in a seated crown before cementation? (detail)
A
- PROXIMAL CONTACTS (with Floss)
- Too tight = Mark with articulation paper between adjacent teeth and trim with rubber wheel on mandrel in straight handpiece
- Too loose = Send back to labs (Gold solder or Ceramic additions)
- MARGINAL FIT (with Straight Probe)
Ideally sealed with no openings (100µm opening = borderline acceptable)
Marginal seal on gold crowns can be improved by burnishing…
- AESTHETICS
- OCCLUSION (LAST)
- Shimstocks on pair of occlusing teeth (compare with crown in and out) - Light contacts anterior, Tight contacts posterior
- Dry and use GHM foil in Miller’s forcepts to identify high spots in ICP (remove with flame-shape diamond bur)
- Mark excursive contacts and remove non-working side interferences
6
Q
What is meant by the “Dual Cord Technique”?
What are the advantages (1) and disadvantages (2) of its use?
A
TWO Impregnated Retraction Cords used:
- Smaller/Thinner - Placed 1st and REMAINS in sulcus during impression
- Larger/Thicker - Placed 2nd and REMOVED before impression
A: Small cord prevents gingival cuff recoiling
D: Increased inflammation & Tissue damage
7
Q
In the Re-organised approach, a splint is used to test patient tolerance of what 3 main changes?
A
- RCP = ICP
- Increased OVD
- Steepness of canine ramps (does this produce canine guidance with posterior disclusion on lateral movement?)
8
Q
What are 5 causes of crowns not being able to be fully seated on tooth prep?
A
- Fit surface defects (e.g. nodules/casting blebs/bubbles)
- Proximal contacts - Tight
- Marginal fit - Over/Under extended
- No Die Spacer - Varnish layer applied to allow for cementation space, if not applied sandblast die before seating
- Impression distortion
9
Q
What are 3 types of Adhesive/”Irretrevable” Luting Cements?
What are 5 of their uses?
A
- Resin: Composite
- Resin: Compomer
- RMGIC
- Crowns
- Bridges (“Resin-Bonded”)
- Inlay/Onlay
- Veneer
- Prefabricated Non-Metal Posts
10
Q
What is a Pantograph?
In what type of Guidance does it transfer information from splint to articulated casts?
What are 2 advantages & 1 disadvantage to its use?
A
Pantograph = Jaw recorder
Transfers information as: POSTERIOR GUIDANCE
Advantages:
- Less chair time
- Less risk of error (clinic-lab interface, more steps involved in transfering as Anterior Guidance)
Disadvantages:
- Expensive!
11
Q
All Elastomer Impression materials exist as 2 pastes, in what 4 ways can they be supplied?
Which 2 avoid incomplete mixing and therefore the incorperation of air bubbles?
A
- Separate Tubes (Base and Catalyst)
- 2 Putty Tubs or 1 Putty with Catalyst Paste
- Double Barrel Cartridge Gun
- Pouches for machine mix (PentaMix)
The last 2 options avoid human error (incorperation of air bubbles on mixing)
12
Q
What is a “Triple Tray”?
What 3 things does it take an impression of?
What are 2 disadvantages/limitations to its use?
A
Type of impression tray (can be full arch or sectioned)
Takes an impression of:
- Prepared tooth
- Opposing teeth
- Occlusion (replacing need for a Bite Reg)
LIMITATIONS:
- Less accuracy
- Dynamic articulation and guidance movements of the whole arch are not replicaed
13
Q
Why do we require soft tissue management for tooth prep margins at or below the gingival crevice? (3)
A
- Physical Barrier
- Moisture control: Prevent bleeding (Haemostasis)
- Improve impression accuracy (Impression material can reach entire margin) → Improved restoration fit
14
Q
What is the main shade guide used on clinic?
What are 4 disadvantages of using shade guides?
A
Vita Lumin
- Restrictive colours
- Block ceramic colour (no translucency or surface textures)
- No commercial shade guide is identical
- Lab ceramic may be different to restorative ceramic
15
Q
What are the 2 main aspects of tooth preparation that affect a crown’s retention and resistance?
A
- Taper (increased R when taper is reduced)
- Tooth length (best when longer)
16
Q
What are the options for treating worn teeth in:
- Removable Pros? (1)
- Fixed Pros? (3)
A
REMOVABLE PROS:
- RPD (Onlay, Overlay or Over denture)
- N.B. Fixed tooth build up done alongside*
FIXED PROS:
- Crowns
- Composite Build-ups
- Adhesive Shims (metal or composite)
17
Q
What are 3 contraindications for Electrosurgery? (STM)
A
- Cardiac pacemaker
- Topical anaesthetics
- Flammable Aerosols
18
Q
What is the difference between a Full and Partial Gold Crown?
What are 4 indications for each?
A
Full Gold Crown covers ENTIRE tooth crown whereas Partial Gold Crown only gives cuspal coverage
FULL GOLD CROWN
- Maximum retention needed (achieved by encompassing entire tooth)
- Preservation of tooth structure
- Minimum aesthetic demands
- Caries/retoration on all axial walls
PARTIAL GOLD CROWN
- Only cuspal coverage required
- Preservation of tooth structure
- Moderate aesthetic demand
- Part of axial walls intact (buccal cusps intact)
19
Q
What are the 2 main classifications of Luting cements? When are they both indicated?
(Give examples of each)
A
- NON-ADHESIVE - Retentive Prep (Zinc Phosphate, Zinc Polycarboxylate and GIC)
- ADHESIVE - UNRetentive Prep, Micromechanical bonding (Resin: Composite or Compomer and RMGIC)
20
Q
What is the 2 STAGE “INJECTION MOULDING” technique for tooth-prep impressions?
When might this technique be preferred?
A
- Impression taken of arch BEFORE tooth-prep with Heavy-bodied Silicone
- Hole drilled through impression into area of tooth prep
- AFTER tooth-prep, impression reseated and Light-bodied Silicone syringed into channel
Useful in issues with Moisture control (e.g. lower posteriors)
21
Q
Anterior Guidance can be on ANY teeth - Ideally anterior.
In what 2 (incisal) occlusal relationships does anterior guidance only exist on posterior teeth?
A
- Class 2 div. 1
- Class 3
22
Q
What are the only type/category of Impression materials used in fixed pros? WHY?
Name 4 materials that belong within this category…
- Which 2 are Hydrophobic?
- Which 2 undergo Addition Polymerisation?
A
ELASTOMERS
(Vs. Hydrocolloids..
- Good Dimentional Stability
- High Strength
- Better Tear Resistance
- More accurate replica of teeth and supporting tissues
- Addition Silicone [Hydrophobic, Addition] - Most commonly used
- Condensation Silicone [Hydrophobic, Condensation]
- PolyEther [Hydrophilic, Addition]
- PolySulphide [Hydrophilic, Condensation]
23
Q
What type of luting cements are Zinc Phosphate and Zinc Polycarboxylate?
What are 4 indications for their use?
What are their advantages (4) and disadvantages (4)?
A
Both = Non-Adhesive (Retentive prep needed)
Use:
- Metal/Ceramo-Metal or Ceramic crowns with retentive preps
- Posts (Zinc Phosphate 1st line use)
- Fixed Partial Ceramo-Metal Dentures
- Multiple cementations
ADVANTAGES:
- Low film thickness (25µm)
- High compressive strength
- Resistant to water dissolution
- Longest track record!
DISADVANTAGES:
- Low tensile strength (retentive prep needed)
- No adhesion to tooth/material
- Properties heavily reliant on Power/Liquid Ratio (technique sensitive)
- Not acid dissolution resistant
24
Q
Over and Under Extended Margins both lead to Ledge formation, what are the possible cause of both?
(HINT: 2 causes are same)
A
BOTH:
- Poor impression
- Improperly trimmed die
OVER-EXTENDED: Surplus untrimmed wax/ceramic
UNDER-EXTENDED: Difficulty identifying finishing line (margin) or Over-polished
25
At what 4 stages in crowns might we need soft tissue retraction?
1. Crown preparation
2. Impressions
3. Provisional crown construction
4. Tooth try-in and Cementation
26
What are 4 scenarios when a crown should be placed?
1. Weakened tooth (e.g. Toothwear, Endo, Large restorations) → Preserved remaining tooth structure
2. Aesthetics (e.g. discolouration following endo)
3. Abutment for fixed/removable partial dentures
4. Alteration of the occlusal plane (e.g. hypodontia cases without full eruption of teeth)
27
What is meant by the "Biological Width"?
Where should the crown margin prep be in relation to this point?
The width between the gingival sulcus and alevolar bone crest (2.04mm)
Marginal finishing line/prep should NOT be placed within 2mm from the alveolar crest (within Biological width) - Ideally it should be SUPRA-gingivally
28
What modifications can be made to a Stock Tray if:
1. Impression of last standing molar not caught fully on impression?
2. Px arch is wider than the Stock Tray?
1. Extend Stock Tray distally to form "post dam" with Acrylic, Greenstick or Putty
2. Heat stock tray (flame-free heater) and bend outwards
29
What is the best form of Surgical Soft Tissue Management?
How is it carried out?
ELECTROSURGERY (Vs. Rotary Curettage or Crown Lengthening)
* LA and moisture control
* High frequency electrical current set up (electrical circuit completed by passive electrode place placed under Px shoulder but NOT in direct contact with skin)
* Light, sweeping strokes (7mm/sec) used to cut soft tissues (NOT BONE - Crown Lengthening)
* 10 sec between strokes to allow tissue cooling (avoid necrosis)
* POI
30
What are 3 instances we would want a bite registration in crown prep?
1. Crown prep of last tooth in arch
2. Multiple crown preps
3. Mulitple crown preps in ANTERIOR
31
Should crown try-in and cementation be done with LA?
NO - We want proprioceptive Px feedback for fit and occlusion
32
What are the 2 methods of using Impregnated Retraction Cords?
# * LA and Moisture Control
* Choose cord thickness and cut to length of tooth circumference
* Place in Dappens pot of Astringent solution (e.g. 15% Ferric Sulphate) for 3 mins
* Remove and place on tissue to remove excess solution
* Pack into gingival sulcus with flat plastic ("back on itself") - Avoid excessive trauma
METHOD 1:
Leave cord for 4 mins → Remove → Wash and Dry → Syringe impression material in sulcus and around tooth "Mr Whippy" → Take impression
METHOD 2:
LEAVE cord in sulcus (ensure none above gingical margin) → Wash and Dry (...as above)
33
What 3 things do you check with a crown on the die before try-in or cementation?
1. Proximal Contacts
2. Marginal defects (4)
3. Crown fit surface defects (e.g. bubbles/nodules) - Preventing full seating
34
What is a chemo-mechanical STM alternative to retraction cord? How is it used?
What are its Advantages (2) and Disadvantages (2)?
Retraction Paste - Physical displacement and may be medicated (e.g. with Aluminium Chloride)
Squeezed into sulcus → Left for 2 mins → Washed, rinsed and dried → Impression taken
A: Quicker and Easier to use
D: Technique sensitive and sub-optimal results
35
All luting cements are resistant to water dissolution, except:
GIC (sensitive to moisture and only resistant once fully set)
36
What are the 3 disadvantages of using Impregnated Retraction Cord for soft tissue management (STM)?
1. Systemic effects
2. Trauma → Inflammation and Necrosis
3. Gingival Staining
37
What are the 2 main methods for increasing coronal space for restoration placement?
Which is 1st line/preferred and why?
1. Dahl Principle
2. Crown Lengthening
Dhal Priniple prefered as less invasive and painful
38
What is the 2 PHASE, 2 STAGE technique for taking impressions of a crown-prep?
1. Impression of arch taken BEFORE tooth-prep with Heavy-bodied Silicone
2. After tooth-prep, Light-bodied Silicone syringed onto prep tooth in "Mr Whippy" motion
3. Original impression reseated onto arch
39
What are 5 bite registration materials?
Which do we use on clinic?
1. Futar D (used on clinic!)
2. Polyvinyldimethylsiloxane (addition cure silicone)
3. Beauty Wax
4. Pink Wax *(not recommended in fixed pros)*
5. DuraLay
40
What are dental crowns?
What are the 5 main types (based on material)?
"Rigid restoration which covers part or whole external aspect of a tooth"
1. Full Gold Crown
2. Partial Gold Crown
3. All Ceramic Crown
4. Ceramo-Metal Crown
5. Composite Crown
41
What are 3 contra-indications for a Full-Ceramic Crown?
1. Not enough tooth tissue to allow sufficient prep (2mm)
2. Tooth with increased pulp chamber (e.g. Paeds)
3. Abrasion risks to opposing teeth (e.g. Bruxists)
42
What are 4 top tips when taking a shade match?
What is meant by Value and Hue Contrast Effect?
* Do early in appt when enamel wet
* Take in Natural/Colour-Corrected Lighting (5500 K)
* Remove any bright lipstic/makeup (accounts for Value and Hue Contrast Effect)
* Note down different colours for different areas (including translucency and surface appearance)
Value Contrast Effect = Darker background, Lighter tooth appears
Hue Contrast Effect = Tooth appears to take on tints of backgrounds complimentary colour (e.g. red → green or blue → orange)
43
What is "Group Function"?
(Hint: What is the alternative type of guidance?)
GF = Alternative to Canine Guidance (e.g. root filled canine makes it too weak)
Lateral working side guidance is therefore under next teeth back: Premolars or (rarely) Molars
*N.B. Canine Guidance is prefered due to 3 reasons of canine use... (particularly as premolars/molars closer to massater muscle, more forces applied)*
44
Name one instance we wouldnt have to use a bite registration in crown prep?
"Bounded Preparation" (crowned tooth is between 2 natural teeth with stable occlusions)
45
What are the 3 methods of tooth-prep Impressions with Addition Silicone?
Outline in detail the preferred (quickest) method...
1. 2 PHASE, 1/SINGLE STAGE (PREFERRED)
2. 2 PHASE, 2 STAGE
3. 2 STAGE INJECTION MOULDING
* Light-bodied silicone syringed around crown-prep tooth in "Mr Whippy" motion (Record Fine Detail)
* Tray filled with Medium/Heavy-Bodied silicone (Bulk)
* Seated in mouth - Impression taken in one stage (similar set time in both materials)
46
During Crown Try-In, what are the 4 main marginal fit errors?
Which is caused by over-waxing during pre-investment pattern stage?
1. Over-Extended
2. Under-Extended
3. Over Contoured (Thick) *- Caused by OVER WAXING*
4. Open Margin
47
What are the 5 disadvantages of Crown Lengthening?
* Discomfort
* Finish line on root surface cementum → Bonding issues
* Furcation Involvement → Cleaning issue
* Increased Crown:Root ratio
* Time needed for PO healing (longer as more invasive, bone removal rather than just gingival)
48
How does the name and width of finishing lines differ between:
1. Gold Crowns?
2. Porcelain/Ceramic Crowns?
1. "Chamfer" finishing lines = 0.5mm width
2. "Shoulder" finishing lines = 1mm width
49
What are the 3 Non-Adhesive/"Retrieveable" Luting Cements?
What are 4 uses?
1. Zinc Phosphate *- 1st line for posts*
2. Zinc Polycarboxylate
3. GIC
* Crowns
* Retentive Onlays
* Cast Custom-Made POSTS
* Pre-fabricated POSTS
50
How do we prepare the following restorations for cementation?
1. Metal
2. Indirect Composite
3. Glass Ceramic
4. Ceramic (Zirconia and Procera) - Retentive or Un-retentive prep
1. Sandblast fit surface (50 microns aluminium oxide)
2. HF (Hydrofluoric) acid-etch
3. HF acid-etch and Silane Treatment
4. Retentive prep = No treatment (Non-Adhesive cement used)
Un-retentive prep = Monobond Primer to remove proteins (and Adhesive Cement used)
51
What 3 astringents might be added to Impregnated Retraction Cords?
Which is used in clinics?
How long is the retraction cord soaked in solution?
1. Ferric Sulphate (15%) - Used on clinic!
2. Alum
3. Aluminium Sulphate or Chloride
Soaked for 3 mins then excess removed on tissue before insertion
52
What are 3 indications for use of a:
1. All Ceramic Crown?
2. Ceramo-Metal Crown?
*N.B. One indication is the same for both*
**ALL CERAMIC CROWN**
* Caries/restoration on all axial walls
* MAXIMUM aesthetic demand (Ant. teeth)
* Moderate strength required
**CERAMO-METAL CROWN**
* Caries/restoration on all axial walls
* HIGH aesthetic demand
* MAXIMUM strength required
53
What is meant by:
1. ANTERIOR
2. POSTERIOR
Guidance?
ANTERIOR GUIDANCE
Movement/Guidance under the influcence of ALL _teeth_ (influenced by tooth-to-tooth contact and therefore affected by steepness of cuspal inclines)
POSTERIOR GUIDANCE
Movement/Guidance at the level of the _condyles_ (under the influence of TMJ and MOM)
*Mainly in edentulous patients or severely worn dentition*
54
Ideal Occlusion = Mutually Protected Occlusion with Canine Guidance
Explain the 2 terms...
MUTUALLY PROTECTED OCCLUSION
* Multiple even contacts on all teeth in RCP/ICP (lighter contacts on anterior and tighter on posterior) - Where anterior teeth protect posterior and VV
* RCP = ICP
* Lateral movement: CANINE GUIDANCE
* Protrusive movement: Even contacts on all anterior teeth and complete disclusion of posterior teeth
CANINE GUIDANCE
Lateral movement → Only canines contact working side, with complete disclusion of all other teeth (posterior disclusion)
55
What is the definition of ICP?
(2 on Posselts diagram)
Position in which there is maximum tooth-to-tooth contact between upper and lower arches
*Most people can adjust to small changes in ICP but larger changes must be tested before proceeding with tooth prep...*
56
When is electrosurgery used/justified? (2)
1. When retraction cord alone is not feasable
2. Gingivectomy
57
Which luting cement is best for a high caries risk Px and why?
GIC - Fluoride release
58
Which luting cement is indicated for use in Ceramic, Zirconia or Composite Crowns/Inlays/Onlays/Veneers?
Resin Cements (Composite or Compomer)
*(But NOT RMGIC)*
59
In terms of crown prep, what is meant by:
1. Retention?
2. Resistance?
What can be added to increase both of these?
1. RETENTION = Prevention of removal along the POI or long axis of tooth preparation *(As taper increases, Resistance decreases)*
2. RESISTANCE = Prevention of removal by forces directed in apical or oblique directions, and prevents movement under occlusal forces
Increased by: Auxillary features (Slots & Grooves)
*Also increased by: Reduced taper and longer tooth lengths*
60
How does crown finish and polishing differ between:
1. Metal (Gold) Crown? (4)
2. Ceramo-Metal or All-Ceramic Crown? (4)
1. METAL
* Finishing burs
* Soflex discs (interproximally)
* Rubber Abrasive Points
* White Stone
2. CERAMIC
* Composite burs
* Soflex discs
* Rubber Abrasive Points
* Polish = Rubber Cup with Diamond Paste
*ALTERNATIVELY: Reglaze*
61
Why is Electrosurgery preferred over Rotary Curettage or Crown Lengtehing for STM?
(List disadvangtages for both techniques)
Rotary Curettage = Less effective
* Trauma and Haemorrhage
* Increased risk of periodontal destruction
Crown Lengthening = More invasive (gingiva AND BONE removal)
* Discomfort
* Prolongued healing needed
* Increased crown:root ratio
* Furcation involvement → Impaired cleaning
* Root surface cementum margin → Impaired bonding
62
What should be completed BEFORE Crown Preparation commences? (6)
* Periapical radiograph (up to date) *- rule out apical pathologies and assess any RCT*
* Tooth vitality testing
* Assess periodontal condition
* Assess core if present (add/replace as necessary)
* Occlusal plane assessment (using articulators)
* Diagnostic wax up if indicated (e.g. when planning multiple placements)
63
Canine Guidance: Why are canines best teeth for guiding occlusion? (3)
1. Longest roots (good crown:root ratio)
2. Palatal surface allows smooth guidance
3. Weaker forces applied - Due to position in front of masseter muscle
64
Only 3% Px have RCP = ICP
What is the difference in movement between RCP and ICP? How is this movement best visualised?
1.25mm (+/- 1mm) slide between RCP and ICP
Forward (protrusive) slide with possible lateral movement
Best visualised on: Mounted Study Cast
*Where movement is described in terms of horizontal (protrusion/retrusion) and vertical (occlusal space) components. E.g. "Large Horizontal and Small Vertical"*
65
Which 3 luting cements are able to form a bond (micromechanical) with the tooth?
1. GIC
2. RMGIC
3. Resin-based *(form bond with tooth AND restorative material)*
66
What are 3 materials that may be used to construct a Temporary Crown?
* PEMA
* Poly VINYL Ethyl Methacrylate
* PMMA
* Resins (Bis acryl composite)
67
What is it called if we record bite reg in:
1. RCP?
2. ICP?
Why would we do both?
1. **_R_**CP = **"**_R_**e-organised Approach"**
* Edentulous Px
* Unstable occlusion
* Large changes to dentate Px (e.g. large TSL/wear)
2. ICP = **"Conformative Approach"**
* Stable occlusion
68
What are the 5 main principles of tooth preparation?
1. Minimal tooth removal (conservative)
2. "Structurally Durable" - Enough removal to allow sufficient and equal restorative bulk
3. Retention & Resistance
4. Marginal Integrety - Well-sealed and well-defined, away from biological width
5. Preserve periodontal tissues (avoid encroaching on biological width)
69
What is the ideal direction of force when using Dhal Principle?
If the force is not _\_\_above\_\__ what will happen?
VERTICAL
If not:
* Pain
* Tooth movement → Tooth loss
70
What is the definition of RCP/CR?
(1 on Posselts Diagram)
"A _bilateral_, _unstrained_ position of the mandible in which the condylar disc assemply is in the most _superior_ and _anterior_ position in the Glenoid Fossa, and there is _pure hinge-axis_ for the _initial 20mm_ of incisal opening"
71
What is the difference between a Temporary and Provisional Crown?
Give 4 similar reasons for their use
TEMPORARY (Made at chairside) = Provide coverage of tooth preparation whilst a definitive crown is made in labs (Only lasts few weeks)
PROVISIONAL (Diagnostic) = Used to test changes in OVD, Shape, Size and Tolerance (MASS) (Expected to last a few months)
Both:
* Maintain occlusal relationship (avoid over-eruption or drifting)
* Maintain interdental space and contacts
* Maintain appearance
* Protect open dentinal tubules
72
What are the 4 options of trays for impressions?
1. Stock Tray - Most commonly used
2. "Modified Stock Tray" (E.g. Extend distally with acrylic, greenstick or putty OR widen arch width by heating and bending)
3. Custom Special Tray (Acrylic)
4. Triple Tray - Takes impression of prepared tooth, opposing arch and occlusion registration all in one
73
When is the "Re-organised Approach" used in tooth-wear cases? (2)
In what 2 ways is the occlusion altered?
1. Unstable occlusion
2. Multiple teeth require restoring
1. RCP = ICP
2. Increased OVD (not always done, depends if tooth-wear was accompanied by "Alveolar Compensation" → Normal FWS)
74
What are the ideal properties of an Impression material:
* Pre-impression taking?
* During impression taking?
* Upon removal?
* Post-impression taking (Storage and Labs)?
PRE-IMPRESSION:
* Easy mix
* Long working and Short setting time
DURING IMPRESSION:
* Biocompatible
* Good accuracy (captures fine details)
* Taste and Odor
* **"Snap Set"** - Rapid transition between set and unset state
REMOVAL:
* Good tear strength
* High elongation at break (good deformation recovery)
POST-IMPRESSION:
* Good dimentional stability in air
* Disinfected with loss of accuracy
* Can be cast up multiple times
* Compatible with gypsum in labs *(Addition silicone - free water in plaster/stone and unreacted Si-H → Hydrogen release and porosity)*
* Good lab reproduction detail (ADA Specification = 19:20)
75
What (occlusal) reduction is present on:
1. Gold (Full or Partial) Crowns?
2. Ceramo-Metal Crowns?
3. All Ceramic Crowns?
1. Gold = 1mm and 1.5mm on functional cusp
2. Ceramo-Metal = 1.5-2mm
3. All Ceramic = 2mm
76
What luting cement is first line choice in Posts? Why?
Zinc Phosphate (Non-Adhesive)
Due to POST EXPANSION SET
77
What are the 2 mechanical methods of STM?
Both aim to physically displace the gingivae - what are their disadvantages?
**Plain Retraction Cord**
* Sulcular haemorrhage (trauma)
**Copper Ring**
* Sulcular haemorrhage (trauma)
* Not effective
* Not accurate
78
What 2 luting cements can be used for Temprary Crowns?
Why are these used?
1. Zinc Oxide Eugenol
2. Zinc Oxide Non-Eugenol (e.g. if Composite restoration placed - Eugenol inhibits Composite set)
SOFT Cements which can be more easily removed
79
What are 3 outcomes if the marginal finishing line of a crown prep encroaches into the "biological width"?
1. Gingival inflammation
2. Loss of alveolar height
3. Periodontal pocket formation
80
What is the "Dhal Principle"?
What are the 2 types of tooth movement that occur? (Give their averages in mm for anterior teeth) Are these balanced?
Use of purposefully 'high' restorations on Tx teeth to open occlusion (increase OVD) and encourage other teeth to over-erupt and move into position
Re-occlusion can take 4-6 months
1. Tx teeth ⇒ Intrusion (1.05mm)
2. Other teeth ⇒ Over-eruption (1.47mm)
(Usually balanced but in 60% cases, Over-eruption is greater than Intrusion)
81
What are 5 Luting Cements? (including Temporary)
List in order of highest → lowest for:
1. Compressive Strength? *(we want this to be high)*
2. Solubility? *(we want this to be low)*
3. Cost? *(we want this to be low)*
* Resin-based
* GIC
* Zinc Phosphate
* Zinc Polycarboxylate
* ZOE/N-E
1. Resin → GIC → Zinc Phosphate → Zinc Polycarboxylate → ZOE
2. ZOE → Zinc Polycarboxylate → Zinc Phosphate → GIC → Resin
3. Resin → GIC → Zinc Polycarboxylate → Zinc Phosphate → ZOE
82
Why do we make putty matricies of teeth before crown prep? (2)
1. To guide our tooth preparation
2. Make temporary crowns
83
What:
1. MECANICAL (2)
2. CHEMO-MECHANICAL (2)
3. SURGICAL (3)
methods of soft tissue retraction can be used?
MECHANICAL:
* Plain Retraction Cord
* Copper Ring
CHEMO-MECHANICAL:
* Impregnated Retraction Cord (+/- Dual Cord Technique)
* Retraction Paste
SURGICAL:
* Rotary Curettage
* Electrosurgery
* Crown Lengthening
84
What is an alternative term for:
1. RCP?
2. ICP?
1. **_R_**CP = Centric **_R_**elation
2. ICP = Centric Occlusion
85
What is the only luting cement to be resistant to acid dissolution?
..Why?
Resin-based
*(They require ETCH-PRIME-BOND)*
86
What are the advantages (4) and disadvantages (4) to Resin-based Luting Cements?
**Advantages:**
* HIGHEST Compressive and Tensile Strength
* LEAST Soluble - Resistant to water dissolution
* Resistant to acid dissolution
* Molecular adhesion to tooth AND material (vs. just tooth in GIC and RMGIC)
**Disadvantages:**
* Polymerisation shrinkage
* Technique sensitive
* Highest cost
* Difficulty removing excess set cement (so excess to be removed pre-set)
87
When assessing colour match, what is meant by:
1. Hue?
2. Value?
3. Chroma?
4. Translucency?
1. HUE = Distinguishes between different colour families (based on wavelength of light reflected)
2. VALUE = Measure of lightness/darkness, where High value = Light & Low value = Dark *(best visualised in a black and white photo)*
3. CHROMA = Degree of colour saturation (colour intensity/vividness)
4. TRANSLUCENCY = How much light it permitted to pass through an object
88
Which 2 luting cements are not recommended for use with all-ceramic crowns/onlays/inlays/veneers?
(Both can be used with Metal or Ceramo-Metal)
* GIC
* RMGIC
89
What impression material is used to take an impression of:
1. Crown Prep?
2. Opposing teeth?
Why do we not use the same material for both? (3)
1. Addition Silicone
2. Alginate (Hydrocolloid)
Alginate not used on crown-prep tooth as:
* Less impression detail (vs. light-bodied silicone)
* Poor tear resistance - won't be able to accurately engage and replicate preparation
* Dimentionally unstable (Swell in water and shrink in air) - ADDITION SILICONE HAS BEST DS!
90
What is the difference between SOFT and HARD cements?
When would you give either based on whether the tooth was Symptomatic or Asymptomatic?
SOFT = _Symptomatic_ Tooth or Temp/Provision (E.g. ZOE)
HARD = _Asymptomatic_ Definitive restoration
91
What is an "Iwanson Guage" used for?
To test sufficient Occlusal reduction in Temporary/Provisional Crowns
BDS3
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