Pathways Of The Pulp Chp 9 Cohen

Front 1

Hedstrom files

Back 1

Files that are milled from round, stainless steel blanks

Front 2

K-files

Back 2

Manufactured by twisting square or triangular metal blanks along their axis, producing partly horizontal cutting blades

Front 3

Gates Glidden Driils

Back 3

Work well for preenlargement of coronal canal areas. However, if misused--can dramatically reduce radicular wall thickness

Front 4

What is the diameter size of the tip of a size 1 GG?

Back 4

0.5mm

Front 5

What is the diameter size of the tip of a size 6 GG?

Back 5

1.5mm

Front 6

How does a GG cut?

Back 6

GG are side cutting instruments with safety tips; they can also be used to cut dentin as they are withdrawn from the canal

Front 7

What is the safest rpm to use a GG at?

Back 7

750-1500 rpm (**However, in real life we probably use them on a 4:1 slow speed, in some hands (mine) they can break in the canal at 750-1500 rpm)

Front 8

GG drills work best when used in electric gear reduction handpieces rather than with air motors

Back 8

True: ***Does this mean to use it on a reduction gear and a lightspeed handpiece? --you could, but clinically seems to do better in a 4:1 slow speed.

Front 9

How are Nickel Titanium Rotary Instruments manufactured?

Back 9

Either by:
1) a grinding process
2) laser etching

Front 10

What 2 properties of the NiTi alloy are of particular interest in endodontics:

Back 10

1. Superelasticity
2. High resistance to cyclic fatigue

Front 11

NiTi instruments have substantially reduced the incidence of several clinical problems, such as blocks, ledges, transportation, and perforation.
What is transportation?

Back 11

Transportation is the removal of canal wall structure on the outside curve in the apical half of the canal due to the tendency of files to restore themselves to their original linear shape during canal preparation; may lead to ledge formation and possible perforation

Front 12

What is the recommended working speed for LightSpeed instruments?

Back 12

1500-2000 rpm, with minimal torque

Front 13

What is annealing?

Back 13

a chemical process in which sterilization can restore the molecular structure of NiTi files, resulting in an increased resistance to fracture

Front 14

NiTi instruments can withstand several hundred flexural cycles before they fracture

Back 14

True

Front 15

What is the diameter at the tip of a GG drill?

Back 15

GGI: 0.5mm
GG2: 0.7mm
GG3: 0.9mm
GG4: 1.1mm
GG5: 1.3mm
GG6: 1.5mm
increases by 0.2mm between sizes

Front 16

What are the 4 factors governing the potential for NiTi rotary instrument fractures?

Back 16

1. Clinician's handling (most important)
2. Combination of torsional load, bending, and axial fatique
3. Root canal anatomy
4. Manufacturing quality

Front 17

What is the difference between lubrication and wetting?

Back 17

Lubricants are used during root canal instrumentation, particularly with rotary instruments, to enhance negotiation of the canal and to minimize friction and the rist of file separation
Wetting is a function of surface interactions of the model material with the impression. Wetting of impressions by gypsum or other materials is expressed quantitatively by the contact angle of the gypsum on the impression material. The larger the contact angle, the worse the wetting is and the more difficult it will be to pour a bubble-free impression with good detail reproduction. Surfactants act by reducing the contact angle of the gypsum on the impression material.

Front 18

Studies have shown that mechanical instrumentation alone cannot sufficiently disinfect root canals, regardless of whether stainless steel or NiTi instruments are used

Back 18

True

Front 19

It has also been found that irrigating alone, with no mechanical instrumentation cannot sufficiently disinfect root canals

Back 19

True

Front 20

What properties does the ideal irrigant have?

Back 20

1. Kills bacteria
2. Dissolves necrotic tissue
3. Lubricates the canal
4. Removes the smear layer
5. Does not irritate healthy tissues

Front 21

NaOCl is effective against endodontic microorganisms, including those difficult to eradicate from root canals (such as Enteroccus, Actinomyces, and Candida species
It also dissoves organic material, such as pulp tissue and collagen

Back 21

True

Front 22

NaOCl at lower concentrations (0.5-1%, bleach at full concentration is 5.25%) dissolve mainly necrotic tissue. Higher concentrations allow better tissue dissolution but dissolve both necrotic and vital tissue, which is not always a desirable effect.

Back 22

True

Front 23

Bleach is alkaline pH of 12-13

Back 23

True

Front 24

Chlorhexidine (CHX) is a broad spectrum antimicrobial agent effective against gram - and gram + bacteria

Back 24

It has a cationic molecular component that attaches to negatively charged cell membranes, causing cell lysis

Front 25

CHX shows no advantage over NaOCl

Back 25

True

Front 26

Iodine Potassium Iodide (IKI) kills a wide spectrum of microorganisms found in root canals

Back 26

Iodine acts as an oxidizing agent by reacting with free sulfhydryl groups of bacterial enzymes, cleaving disulfide bonds

Front 27

An obvious disadvantage of iodine is a possible allergic rxn in some patients

Back 27

True

Front 28

EDTA (Ethylenediamine Tetra-Acetic Acid) :

Back 28

Is a chelator that creates a stable calcium complex with dentin mud, smear layers, or calcific deposits along the canal walls
This may help to prevent apical blockage and aid in disinfection by improving access of solutions through removal of the smear layer

Front 29

Calcium binding results in the release of protons, and EDTA loses its efficiency in an acidic environment--thus the action of EDTA is thought to be self limiting

Back 29

True

Front 30

A comparison of bacterial growth inhibition showed that the antibacterial effects of EDTA were stronger than citric acid and 0.5% NaOCl but weaker than 2.5% NaOCl and 0.2% chlorhexidine

Back 30

EDTA exerts its stongest effect when used synergistically with NaOCl, although no disinfecting effect on colonized dentin could be demonstrated

Front 31

Chemical analysis indicated that chlorine, the active ingredient in NaOCl, is inactivated by EDTA

Back 31

Cohen says this

Front 32

What are the 5 benefits of using irrigants in root canal treatment?

Back 32

1. Removal of particulate debris and wetting of the canal walls
2. Destruction of micoorganisms
3. Dissolution of organic debris
4. Opening of dentin tubules by removal of the smear layer
5. Disinfection and cleaning of areas inaccessible to endodontic instruments

Front 33

What is the major biologic aim of endodontic therapy?

Back 33

To eliminate apical periodontitis

Front 34

What is apical periodontitis?

Back 34

An inflammatory disease, it can be classified on the basis of symptoms, etiology, histopathology, etc

Front 35

A classification system has been based on 4 factors for apical periodontits. What are these 4 factors?

Back 35

1. Distribution of inflammatory cells in the lesion
2. Whether epithelial cells are present or absent
3. Whether the lesion has been transformed into a cyst
4. The relationship of the cyst cavity to the root canal of the affected tooth

Front 36

Define Acute Apical Periodontitis

Back 36

An acute inflammation of the periodontium of endodontic origin, it is characterized by the presence of a distinct focus of neutrophils in the lesion

Front 37

What is primary vs. secondary acute apical periodontitis?

Back 37

Pimary (initial) periodontitis occurs when the inflammation is short-lived and starts in a healthy periodontium in response to irritants.
Secondary (exacerbating) periodontitis occurs when the acute response occurs in an already existing chronic apical periodontal lesion.
The secondary form is referred to as a flare-up , or Phoenix abscess

Front 38

What is Established Chronic apical periodontitis?

Back 38

Long-standing inflammation of the periodontium of endodontic origin
Characterized by granulomatous tissue predominately infiltrated with lymphocytes, plasma cells, and macrophages. These lesions may be epithelialized or non-epithelialized

Front 39

Periapical true cyst

Back 39

Apical inflammatory cyst with a distinct pathologic cavity completely enclosed in an epithelial lining so that no communication to the root canal exists

Front 40

Periapical pocket cyst

Back 40

Apical inflammatory cyst containing a saclike, epithelium-lined cavity that is open to and continuous with the root canal

Front 41

Mechanical debridement is shaping the canal to enlarge the canal to facilitate and allow the irrigants to clean and remove the infected dentin.

Back 41

Mechanical debridement does not "clean" the canal

Front 42

Thorough disinfection of the apical part of a root canal is essential, b/c this area is likely to contain intraradicular bacteria

Back 42

True

Front 43

What are the basic cleaning and shaping strategies for root canal preparation?

Back 43

1. Crown down: staring w/larger file, then using smaller
2. Step back: starting w/smaller file, then step back at end
3. Apical widening: Light Speed
4. Hybrid techniques

Front 44

What are the benefits of using a combination of instruments for endodontic therapy?

Back 44

1. Instruments can be used in a manner that promotes their individual strengths and avoids their weaknesses (most important)
2. Hand instruments secure a patent glide path
3. Tapered rotary instruments efficiently enlarge coronal canal areas
4. Less tapered instruments allow additional apical enlargement

Front 45

Volume of irrigant is a critical factor is disinfection

Back 45

The choice of an irrigation needle is also important (you want one to be near the apex (a mm or so away and not too much pressure)

Front 46

Different types of microorganisms, such as bacteria, yeasts and possibly viruses can infect the pulp and may lead to apical periodontitis

Back 46

True

Front 47

EDTA

Back 47

is a decalcifying, chelating agent used as a gel or a 17% buffered solution during instrumentation of root canals
It acts as a chelator with Ca ions and removes the dentinal debris produced on the root canal walls during preparation.
It thus opens the dentinal tubules, allowing better penetration of disinfectants

Front 48

How does NaOCl remove necrotic debris?

Back 48

Necrotic tissue and debris are dissolved by the breakdown of proteins into amino acids through free chlorine in NaOCl.
Since free chlorine is the important component, the NaOCl must be replinished frequently during preparation to compensate for lower concentrations and to constantly renew the fluid inside the root canal

Front 49

Dilution of NaOCl a 1:1 or 1:3 solution is 2.5% or 1% solution and both are suitable for clinical endodontic use

Back 49

The undiluted form is 5.25% and causes substantial necrosis of wound surface areas and may result in serious clinical side effects

Front 50

Higher concentrations of NaOCl are more aggressive toward living tissue and can cause severe injuries when forced into the periapical area

Back 50

Irrigation needles should never be wedged into canals during irrigation to avoid extrusion and serious damage to periapical tissues

Front 51

In one study, heating increased the antibacterial action of NaOCl

Back 51

Studies have shown that 1 minute at 116.6F (47C) is the cutoff exposure at which odotoblasts can still survive
However, higher temperatures may in fact be sufficient to kill osteoblasts and other host cells
Warming NaOCl to 122F (50C) or 140F (60C) increases collagen dissolution and disinfectiing potential, but it may also have severly detrimental effects on NiTi instruments, causing corrosion of the metal surface after immersion for 1 hour

Front 52

What is the smear layer?

Back 52

It consists of dentin shavings, cell debris, and pulp remnants. It can be described as having 2 separate layers; a loose superficial deposit and and attached stratum that extends into the dentinal tubules, forming occluding plugs

Front 53

The smear layer is a thin superficial layer

Back 53

1 to 5 um

Front 54

Since the smear layer consists of organic and inorganic components, alternating use of NaOCl and EDTA is most effective

Back 54

True

Front 55

Cleaning and shaping are important, interdependent steps in root canal therapy

Back 55

True