Posts and Core Flashcards
1
Q
Moisture Content of ETT
A
- moisture levels between ETT and vital teeth are not different
- dehydration alone doesn’t account for changes in physical properties
2
Q
Flexibility of ETT
A
- less flexible compared to vital teeth
2. endo tx alone affects stiffness only by 5%
3
Q
Proprioception of ETT
A
- ETT requires 57% higher pressure to initiate a pressoreceptive response
- ETT have pain threshold levels that are more than 2X as high as those of vital teeth
- RESULT: failures due to patients not being aware of applied force
4
Q
Classic Physical Properties of ETT
A
- hardness, load to fracture, toughness, strength (compressive, shear, tensile)
- no definitive conclusions due to considerable variation amount the various studies
5
Q
Structural Integrity of ETT
A
higher occurrence of fracture
6
Q
To crown or not to crown an ETT?
A
- due to extensive loss of tooth structure, full coverage restoration usually indicated
- EXCEPTION: anterior ETT with very conservative access
7
Q
Endodontic Posts
A
- pin usually made of metal that is fitted into prepared root canal of a natural tooth
- provides retention and resistance for the restoration when combined with an artificial crown or core
8
Q
Purpose of Endodontic Posts
A
- decreases fracture resistance of ETT (EXCEPTION…ETT with thin root canal walls due to over-instrumentation)
- MAIN PURPOSE: provide retention of the core
- RESULT: if the core can be retained without a post, a post isn’t necessary (more than 50% of tooth structure remains)
9
Q
Desirable features of endodontic posts
A
- should not cause root fracture
- retentive in the root
- retain core material
- provide adequate coronal seal
- esthetic
- radiopaque
- biocompatible
10
Q
Fabrication methods of posts
A
- pre-fab
2. custom
11
Q
Design of posts
A
- tapered: less retentive
- parallel sided: more retentive
- threaded
12
Q
Fit of posts
A
- passive
2. active: more retentive, but cause fractures
13
Q
Material of posts
A
- metallic (stainless steel, titanium, gold)
2. non-metallic (glass fiber reinforced, quartz fiber reinforced, carbon fiber reinforced)
14
Q
Advantages of pre-fab posts
A
- post and core completion in one appointment
- tooth can be immediately provisionalized
- can be more esthetic
15
Q
Disadvantages of pre-fab posts
A
- separate core material necessary
2. available sized may not match canal shape
16
Q
Pre-fab post technique
A
- ETT with temporary material
- temporary material removed
- size-associated drill is used to re-shaped canal to proper length and width
- post is tried in, shortened, and cemented
- core build-up made with composite resin, prepared to resemble complete tooth prep
17
Q
Features of custom cast post/cores
A
- post and core are one piece
- customized to canal shape
- needs two appointments
- Indications: loss of significant tooth structure, canal has circular shape
- expensive!!
18
Q
Custom cast post/cores technique
A
- pre-fab plastic pattern
- pattern resin-powder and liquid
- monomer applied to plastic pattern
- resin applied to plastic pattern
- coronal resin is added to form core
- resin prepared to resemble a complete crown prep
- post/core resin pattern removed and sent to lab
19
Q
Post length
A
- general guidelines: 2/3 to 3/4 of root canal length
- must have at least 4 mm of apical seal, ideally 5 mm
- long roots: as long as possible while retaining 5 mm of apical seal
- molars: post should not extend more than 7 mm apical to root canal orifice
- anterior and premolars: extend half way the root portion that is embedded into bone
20
Q
Post diameter
A
- general guidelines: shouldn’t exceed 1/3 of root diameter
- post size should be between 0.6 mm-1.2mm depending on tooth size
- primary roots, D roots of mandibular molars, P roots of maxillary molars (need to have more than 1 mm of dentin around post)
- IMPORTANT: protects tooth from perforation, increases fracture resistance
21
Q
What should be considered with the post diameter?
A
- root size and curvature
- place post into D root of mandibular molars
- place palatal root of maxillary molars
22
Q
Biological Width
A
- distance between crestal bone and deepest point of sulcus
- 2 mm in most patient
- SHOULD not be violated
23
Q
Ferrule Effect
A
- band of metal that surrounds tooth, which greatly increased fracture resistance
- ideally need 2 mm of circumferential tooth structure
- MORE IMPORTANT THAN POST LENGTH
- remaining coronal tooth structure is the most important factor for good long term prognosis
24
Q
What if the ferrule is less than 2 mm?
A
- sub-gingival margin placement (DON’T violate biological width)
- crown lengthening
- orthodontic extrusion
- tooth extraction
25
Complications of restoring ETT
1. post loosening
2. root fracture and root perforation
3. caries and periodontal disease
26
Desirable features of core materials
1. high compressive strength
2. dimensional stability
3. easy to use
4. short setting time
5. ability to bond to both post and tooth
6. esthetic when applicable
27
Types of core materials
1. composite resin core
2. amalgam core
3. cast core
28
Composite resin core
1. bond to teeth
2. short setting time
3. easy to use
4. relatively strong
5. tooth can be prepared for crown the same day
29
Amalgam core advantages
1. very strong
2. easy to use
3. material with longest history of success
30
Amalgam core disadvantages
1. crown prep cannot be complete the same day
2. environmental concerns
3. corrosion potential
4. discoloration of dentin or gingiva
31
Summary
1. purpose of post is to retain artificial core
2. post space prep should be conservative (AT LEAST 1 mm of radicular dentin around the post)
3. always maintain adequate apical seal (IDEALLY 5 mm, minimum 4 mm)
4. remaining coronal tooth structure is most important for success (2 mm ferrule and 2 mm biological width)
32
Restoring ETT Summary
1. Ferrule: at least 2 mm long
2. BWD: at least 3 mm (sulcus=1 mm, BW=2 mm)
Total: at least 5 mm from bone to most coronal area
Proposed finish line: margins must be in sound tooth structure
