Prosth: Sheeba Flashcards
1
Q
Goal of Tooth Preparation:
A
- Creat space for the restoration material
- create a path of insertion
- no undercuts
2
Q
Tooth preparaiton inculdes:
A
- Axial Walls
- buccal, lingual, mesial, distal
- Occlusal/incisal surface
- Finish line
- “preparation margin
- Funcitional Cusp Bevel
3
Q
Hand pieces when preping a tooth
A
- Turbine handpiece
- Gross tooth prep (40,000 RPM)
- very aggresive
- light strokes
- might give rough surface
- Electric handpiece
- Finishing and smoothing preparation
- 5000-10,000 RPM
4
Q
Burs for Tooth Prep
A
- Diamond Burs
- easy and fast preps
- micro roughness
- gives excellent crown retention
- more than one size an dshape
- each used for specific task
- Different abrasiveness
- color coded
- Carbide Burs
- remove deeps caries
- cutting boxes and grooves
- cut metal crowns
5
Q
Bur: Color coding scheme
A
- Yellow (504)
- super fine
- Red (514)
- Fine
- Blue (524)
- medium
- Green (534)
- coarse
- Black (544)
- super coarse
6
Q
Tapered Diamond Burs
A
- Different tip shape=different finish
- round end–Chamfer finish line
- flat end–Shoulder Finish Line
- fine end– Opening Proximal Contacts
7
Q
Football Diamond Burs
A
- reduce:
- occlusal surface of posterior teeth
- Lingual Fossa of Anterior teeth
8
Q
Wheel Diamond Burrs
A
- Reduce:
- occlusal surface of posterior teeth
- Lingual Fossa of anterior teeth
- same as Football diamond
9
Q
Preservation of Tooth structure
A
- balance b/w preservation and room for the restoration to achieve adequate restoration strength and satisfractory esthetics
- Over reduction might lead to=Poor prognosis
- pulpal exposure
- weakening of the tooth
10
Q
Guidelines for Preservation of Tooth Structure
A
- Use partial coverage restorations
- Avoid over tapering
- occlusal reduction should follow occlusal anatomy
- limit to the needed clearance
- Avoid unnecessary subgingival extensions of prep
11
Q
When are Subgingival Finish lines used:
A
- Esthetic reasons
- Hiding the margin in anterior tooth
- Subgingival caries or restoration
- can’t put the preparation margin on caries or direct restoration
- Short preparation
- subgingival extension to gain more height for resistance form
12
Q
Retention vs Resistance
A
- Retention:
- resistance to restoration in dislodgement along path of insertion
- Resistance:
- resistance to restoration in any direction other than path of insertion
- Retention and resistance
- are inseparable qualitites
- are not used interchangeably
13
Q
Factors affecting retention and resistance
A
- Total Occlusal Convergence Taper
- Length “preparation height
14
Q
Total Occlusal Convergence Taper
A
- seating VS resistance and and retention
- prep w/parallel axis walls=negative effect on seating the restoration due to hydraulic pressure build up
- Therefore SLIGHT TAPERING ALWAYS INDICATED
- Overtapering
- negative impact on retentions and resistance
- Recommended TOC
- 10-20 degrees
- prep w/parallel axis walls=negative effect on seating the restoration due to hydraulic pressure build up
- shorter the prep the less the TOC will be required to provide resistance and retention
15
Q
Path of insertion
A
- Prep with parallel axial walls
- best resistance and tape
- impossible to prepare without having undercuts
- Slight taper needed to:
- help seating of the crowns
- decrease hydraulic pressure
16
Q
Length Preparation Height
A
- Retention and resistance increase w/the increase occlusogingival height of the prep
- To achieve a adequate prep that provides good retention and resistance a ratio b/w occlusogingival hiegh and buccolingual width should be 4:10
- The loonger the prep
- more surface area to lute cement (interlock)
- provide excellent retention
- When occlusogingival height is not adequate
- added means rettention are added
- pins
- boxes
- grooves
- added means rettention are added
- Short preparations:
- TOC should be kep to minimal
17
Q
Structural Durability
A
- give enough bulk to the restoration to provide adequate strength
- only provided by tooth reduction
- inadequate space leads to
- bulky restoration or weak restoration
- AMount of reduction depends on the material being used
18
Q
Structural Durability: Occlusal Reduction
A
- Occlusal Clearance allows for strength on the restoration
- Occlusal surface is subjected to the highest stress
19
Q
Structural Durability: Functional Cusp Bevel
A
- Promides more room to increase the bulk of the restoration
- No functional cusp bevel leads to:
- weak restoration
- bulky restoration that opens the occlusion
20
Q
Structural Durability: Axial Wall reduction
A
- Needs specific bulk for maximum strength=1-1.5mm
- Axial wall reduction done with bur placed parallel to long axis
- automatically creates the finish line
- results in no undercut
- provides slight taper
- Lack of axial wall reduction leads to:
- overbulking the restoraiton
- weak restoration
21
Q
Marginal Integrity (marginal Adaptation)
A
- most important requirements for successful resotration
- Lack of marginal adaptation leads to:
- recurrent caries
- perio disease
- ultimately tooth loss
- Type of finish line plays a role in marginal adaptation
- Selecting finish line depends on:
- type of restoration
- tooth position
- practitioiners preference
22
Q
Marginal Integrity (marginal Adaptation): Finish Lines
A
- Type of restoration:
- Chamfer FL and Shoulder with Bevel FL
- metal margins
- Shoulder FL
- ceramic (porecelain) margins
- Chamfer FL and Shoulder with Bevel FL
- Tooth position:
- anterior teeth ceramic margins=esthetic reaons
- ceramic margins need shoulder FL
- most common finish line
- Chamfer and Shoulder
23
Q
Finish Lines: Chamfer vs Shoulder
advantages
disadvantages
indications
A
- Chamfer
- advantages:
- distinct margin
- adequate bulk
- easier to control
- disadvantage
- care needed to avoid unsupported lip of enamel
- Indication:
- cast metal restorations
- lingual margin of metal ceramic crowns
- advantages:
- Shoulder
- Advantages:
- bulk of restoration material
- Disadvantage:
- less conservative of tooth structure
- Indicaiton:
- facial margins of metal ceramic crowns
- Advantages:
24
Q
Marginal Integrity (marginal Adaptation): Chamfer Finish Line
A
- “classic” depth of reduction shoulud be 0.5mm
- Axial depth sutiable for metal margins
- prepared with tapered diamond w/round end
- Only half of the bur should be in the tooth\
- if whole bur is in the tooth=J-margin (enamel lip)
25
Q
End Cutting Bur
A
- aka Floor Bur
- 5000 RPM
- removes J margin
- corrects Chamfer FINish line
26
Q
Marginal Integrity (marginal Adaptation): Shoulder Finish Line
A
- Use tapered diamond w/flat end
- use w/ ceramic margins
- Regular shoulder vs Modified shoulder
- modified shoulder FL has more round axial gingival angle
- similar to deep chamfer
- modified shoulder FL has more round axial gingival angle
27
Q
Preservation of the periodontium: Biological Width
A
- location of the restoration margin could negatively affect the periodontal health of the tooth
- Finish line could be supragingival or subgingival
- Supragingival:preferred
- least impact on periodontal tissue
- Subgingival:
- greatest impact on periodontal heealth
- Supragingival:preferred
- Causes chronic periodontal inflammation
- infrabony pocket
- gingival recession
28
Q
Define Biological width
A
- distance b/w depth of the sulcus and crest of the alveolar bone
