Par 2 - Obturation Materials Flashcards
(87 cards)
1
Q
Who is the “Father of Endodontics”?
A
Dr. Grossman
2
Q
Manufacturers can control what aspects of obturation materials…?
A
- content/composition
- toxicity
- physical properties
3
Q
Clinician’s choice of obturation materials should be based on what…?
A
- meeting standards–ADA, ISO, ANSI
- compatibility w/ pt’s medical history
- match instrumentation & obturation techniques
4
Q
What are the 2 basic groups of obturation materials?
A
core materials & sealers
5
Q
Does the core chemically bond to tooth structure? Does the sealer?
A
- Core is not chemically bonded to the tooth structure.
- The sealer may or may not bond to the tooth structure.
6
Q
What is an example of a natural polymer for core materials? An example of a synthetic polymer? Metal core material?
A
- Natural polymer: gutta percha
- Synthetic polymer: Resilon
- Metal: silver points (obsolete)
7
Q
What is the main characteristic of gutta percha that makes it so useful?
A
Thermoplasticity (flexible when heated!)
- Also when it cools, it is not brittle.
8
Q
What is the main characteristic of gutta percha that makes it so useful?
A
Thermoplasticity (flexible when heated!)
- Also when it cools, it is not brittle.
9
Q
What is gutta percha made of?
A
natural latex produced from the sap of a Taban tree (native to SE Asia)
10
Q
T/F? Gutta percha is bio-inert, resilient, & is a good electrical insulator.
A
TRUE.
11
Q
Chemically, gutta percha is a polymer of what?
A
isoprene (trans-1,4-polyisoprene)
- regular structure, able to crystallize, ~60% crystalline, hard, rigid, high MP)
- Natural rubber is cis-polyisoprene (less symmetrical, less packing, soft, highly flexible, low MP)
12
Q
What are the 2 conformations of Gutta Percha?
A
alpha & beta phases
13
Q
Which phase is due to very slow cooling? Which one is due to fast (normal) cooling?
A
Very slow cooling –> alpha phase
Fast (normal) cooling –> beta phase
14
Q
What is alpha phase conformation used for? What is beta phase conformation used for?
A
a-phase: warm gutta percha technique
B-phase: dental gutta percha; the form you normally use
15
Q
At what temp is the phase transition from beta to alpha phase?
A
115 F (46 C)
16
Q
At what temp is the amorphous phase reached?
A
130-140 F (54-60 C)
17
Q
At what temp does gutta percha soften? Melts?
A
Softens at 60-65 C.
Melts at 100 C.
(cannot be heat sterilized)
18
Q
Which phase is denser?
A
Alpha phase (has better thermoplastic characteristics)
19
Q
What are the important composition components of gutta percha?
A
~20% gutta percha
~60-75% ZnO
20
Q
What is the purpose of metal sulfates in gutta percha?
A
For radiopacity
- had extra notes that said ZnO gives gutta percha its radiopaque characteristic too…
21
Q
What is the purpose of waxes or resins for gutta percha?
A
plasticizer
22
Q
Gutta percha dissolves in what?
A
chloroform, xylene, halothane
- able to remove from root canals for post; re-tx
- alternative obturation technique
23
Q
What solvents does gutta percha absorb?
A
acetone or alcohol (causes gutta percha to swell)
24
Q
What property of gutta percha compromises apical seal?
A
1-2% shrinkage when cooled or after removal from solvent
25
How should you disinfect gutta percha?
sodium hypochlorite (bleach)
26
What happens when you expose gutta percha to light, high temp, or air?
Gutta percha will be oxidized & become brittle!
| Refrigeration extends shelf life.
27
T/F? Gutta percha by itself can provide a seal.
FALSE. When used without sealer, gutta percha does NOT provide a seal.
28
What are some negative aspects of gutta percha?
Gutta percha shrinks when it cools down and has no chemical adhesion to either sealer or canal wall. Therefore, gutta percha alone does not have a hermetically seal. It does NOT have antibacterial properties (but is bacteriostatic.)
29
What has more toxicity--gutta percha or sealer?
Sealer is more toxic. Gutta percha is more biocompatible.
30
What is the main advantage of Resilon over gutta percha?
Adhesion.
Resilon bonds to Epiphany sealer, which bonds to the canal wall through primer. The system creates a 'monoblock.'
31
What is the Epiphany Primer?
Self-etch primer (contains sulfonic acid)
32
What is Epiphany Root Canal Sealant?
A dual-cure methacrylate-based sealer similar to resin composite.
33
What is the most important characteristic of sealers?
impermeable fluid tight seal & maintains seal overtime
34
Sealers should adhere to what?
dentin of canal walls & core material
| other imp. qualities: adequate adhesive strength & insoluble in tissue fluids
35
What does ISO cover for dental root canal sealing materials?
- Handling characteristics (flow, working time, setting time)
- Performance (film thickness, dimensional change, solubility, radiopacity)
36
Flow requirement?
No less than 20mm
37
Working time requirements?
According to manufacturer OR Not less than 90% if set in less than 30min
38
Setting time requirements?
30 min to 72 hrs
39
Film thickness requirements?
No more than 50 microns
40
Solubility requirements?
Cannot exceed 3% mass fraction
41
Radiopacity requirements?
No less than the radiopacity of 3 mm aluminum
42
Shrinkage requirements?
Cannot exceed 1% in shrinkage or in expansion
43
Types of sealers?
1) zinc oxide eugenol-based
2) calcium hydroxide-based
3) glass ionomer
4) resin-based (ex. epoxy [AH], methacrylate)--we use this one
NEW TYPES
5) MTA-based
6) Bioceramic (calcium silicate)
7) Silicone-based
44
What is the 'gold standard' sealer?
zinc oxide eugenol (due to its long clinical history; most widely used)
45
What are the ingredients of ZOE-based sealers?
- Powder: 42% zinc oxide (ZnO)--main ingredient
| - Liquid: 100% eugenol
46
What does stabellite resin do for ZOE-based sealers?
It increases the adhesive quality & decreases solubility.
47
What does barium sulfate do for ZOE-based sealers?
Added for radiopacity.
48
What is bismuth subcarbonate & sodium borate do for ZOE-based sealers?
Control working & setting times.
49
Humidity & body temp does what to setting time of ZOE-based sealers? What about long & vigorous mixing? Smaller ZnO particles?
- Humidity & body temp decreases setting time.
- Long & vigorous mixing decreases setting time.
- Smaller ZnO particles increase setting time.
50
T/F? Free eugenol (released from the setting rxn of ZOE-based sealers) decreases as the setting process continues.
TRUE. The free eugenol is the main reason for the cytotoxicity of freshly mixed, unset sealer--can also retard composite curing.
51
What does Zn eugenolate do?
Can block pain through prostaglandin
52
T/F? ZOE-based sealers have some antibacterial properties.
TRUE.
53
Do calcium hydroxide-based sealers have antimicrobial effects?
Yes, it creates a highly alkaline (high pH) environ., which has antimicrobial effects.
54
How does calcium hydroxide affect long term sealing?
To be effective, calcium hydroxide has to dissociate, which results in high solubility. Therefore, longterm sealing properties are compromised.
55
Describe the bond between glass-ionomer sealers and dentin.
Hydrophilic & chemical bond
56
What are disadvantages of glass-ionomer sealers?
short working time & difficulty of retreatment bc of its high hardness & low solubility
57
Advantages & disadvantages of resin-based sealers?
Advantages: long working time but rapid setting time; good adhesion to core materials & dentin
Disadvantages: polymerization shrinkage
58
What type of resin-based sealers do we use in clinic?
epoxy-amine (the AH series--AH 26, AH Plus)
59
What are the ingredients for epoxy-based sealer, AH 26?
Powder: bismuth oxide, methanamine
Resin: epoxy resin
60
What does AH 26 release during the setting rxn?
formaldehyde, which can cause post-op sensitivity
*formaldehyde = genotoxic susbtance, so use AH series w/ caution
61
T/F? AH 26 is indicated as a root canal sealing and filling material, meaning that it can be used with or without core material.
TRUE.
62
T/F? AH 26 is easy to remove.
FALSE. It cannot be removed w/ conventional solvents.
63
What are advantages of AH Plus over AH 26?
No formaldehyde release & removable w/ solvent
64
What does MTA stand for in MTA-based sealers? What are these sealers good for?
mineral trioxide aggregate; material of choice in cases of vital pulp therapy (pulp capping, partial pulpotomy) or to seal pathways of communication betw root canal system & external root surface (perforation, apexification, or retrograde filling)
- aiming to replace calcium hydroxide in tx of pulpal & periodontal healing complications
65
What are the major components of MTA-based sealers?
They are calcium silicate-based, & the major components of the powder component are tricalcium silicate & dicalcium silicate.
66
What happens when MTA-based sealers react w/ water?
They produce calcium hydroxide, which is released in solution & induces formation of hydroxyapatite structures in simulated body fluid.
67
What is unique to MTA-based sealers?
They stimulate mineralization & apatite-like crystalline deposits along the canal walls.
68
What type of sealer is EndoSequence BC Sealer?
Calcium phosphate silicate bioceramic
| *note that hydroxyapatite is co-precipitated to reinforce the set cement--due to this, they are osseo-conductive.
69
What type of cones do you use w/ EndoSequence BC sealers?
use w/ ActiV GP cones to strengthen root (inc in vitro fracture resistance)
70
What are limitations/challenges of bonding/adhesive materials in the root canal?
1. dentin: coronal vs pulpal vs radicular
2. unfavorable geometry of root canal
3. adhesive procedures can be compromised
4. curing mode (light, dual, self-cure?)
5. irrigation solution & other chemicals
71
T/F? Increased number of tubules in apical region of dentin.
FALSE. REDUCED number of dentinal tubules in apical region.
| - this means resin tag density is less, too.
72
Why is good adhesion to radicular dentin more difficult to achieve?
There is different collagen cross-linking in radicular dentin.
73
Why is the coronal dentin better/easier to bond to?
Because of the Hybrid layer will form easier with the Coronal dentin (because of the intertubular dentin)
74
Why do root canals have unfavorable geometry for bonding?
They have very high C-factors! (bonded to unbonded surfaces)
75
What are some issues with self-cure or dual-cure materials?
They may not be compatible w/ self-etching adhesive bc of the acidic component.
76
Why do hydrogen peroxide and sodium hypochlorite irrigating solutions affect bonding materials? And how do we solve this issue?
They leave an oxygen-rich layer behind on dentin surface. Oxygen inhibits polymerization of resin & thus compromises the bonding.
Solution: final rinse w/ EDTA can reverse the effect of NaOCl.
77
What effect does chloroform have on bonding materials? What about eugenol?
Chloroform reduces adhesion.
Eugenol can inhibit polymerization (affecting bonding & setting of composites.)
78
*The most important property of root canal sealers for successful endodontic therapy is a...?
long lasting apical seal
79
*Dental gutta percha contains how much zinc oxide and how much gutta percha?
~70% zinc oxide
| ~20% gutta percha
80
*The gold standard Grossman's sealer is...?
Zinc oxide eugenol-based sealer
81
*Conditions for improving bond strength through the use of adhesives in canal obturation include...?
elimination of sodium hypochlorite as a final rinse prior to bonding
- final rinse w/ EDTA
82
*Coronal seal placement is essential to...?
prevent contamination of obturated system
83
*Decreased composite bond strength has been reported with sealers containing...?
eugenol
84
* A molar tooth with no excess tooth destruction, other than an endodontic access, are best restored with which of the following?
a. Polyalkenoate core to full contour
b. Bonded composite core to full occlusion
c. A core with an additional cuspal coverage restoration
d. Post with Class I amalgam core
c. A core with an additional cuspal coverage restoration
85
* Which of the following offers the most practical restoration of an endodontic access through a well-fitting ceramo-metal posterior crown?
a. Secondary intention post and amalgam core in existing crown
b. Bonded composite core in existing crown
c. Removal of the existing crown and replacement with an onlay to provide cuspal coverage
d. Replace the entire crown
b. Bonded composite core in existing crown
86
T/F? A disadvantage of AH Plus is that its shrinkage is higher than standard value.
TRUE.
87
*What is the most significant limitation of glass ionomer?
low mechanical properties
