CHAPTER 8 HIGH YIELD

What is the primary objective of cleaning and shaping regarding the apical foramen?

Maintain structural integrity and apical foramen

What is the primary objective of cleaning and shaping regarding soft and hard tissue?

Remove infected soft and hard tissue

What is the primary objective of cleaning and shaping regarding irrigants?

Provide access for disinfecting irrigants to the apical canal space

What is the primary objective of cleaning and shaping regarding canal shape?

Develop a continuously tapering cone

What is the primary objective of cleaning and shaping regarding irregularities?

Remove irregularities such as debris and pulp remnants

How is working length defined in endodontics?

Distance from a fixed coronal reference to the point where instrumentation or obturations ends

What is the standard distance of the working length from the radiographic apex?

Approximately 1 mm short

What is the desired termination point of root canal preparation for a vital tooth?

0.5 to 1 mm short of the radiographic apex

What imaging technique is necessary to separate superimposed files and structures?

Angled films or digital images

What rule determines canal position on angled radiographs or distal images based on the buccal object?

SLOB rule

What should the file do during the establishment of radiographic working length?

Bind at the estimated working length

How much length is subtracted from the estimated working length when there is no resorption?

1 mm

How much length is subtracted from the estimated working length when there is periapical bone resorption?

1.5 mm

How much length is subtracted from the estimated working length when there is bone and root apex resorption?

2 mm

Which device for working length determination is more accurate than radiographs but must always be confirmed with a radiograph?

Electronic Apex Locator

In which situations is an Electronic Apex Locator particularly useful?

Gag reflex, obstructions, or medical limitations

What factors make an Electronic Apex Locator inaccurate?

Metallic restorations, saliva, heavy bleeding, or open apices

Whom should you consult before using an Electronic Apex Locator in pacemaker patients?

Physician

What are the causes of working length loss?

Debris in apical third, apical patency loss, skipped file sizes, ledge or canal blockage, instrument separation, inadequate irrigation

What is the technique used to achieve apical patency?

Insert small hand files slightly beyond the foramen

What is the purpose of apical patency?

Prevent blockage and maintain working length

Does apical patency push bacteria beyond the apex?

No

Is apical patency associated with post-operative pain?

No

What is the thickness range of the smear layer on canal walls?

1 to 5 micrometers

Why must the smear layer be removed in necrotic pulps before obturation?

It is contaminated and can cause potential leakage

What are the components of the smear layer?

Organic and inorganic debris

What is the best technique to prevent canal obstruction during endodontic instrumentation?

Copious irrigation

How should an irrigating needle be positioned in the canal?

Not wedged into the canal to allow backflow of the solution

What is the concentration range of Sodium Hypochlorite used as an irrigant?

0.5 to 5.25 percent

Which irrigant is considered the gold standard in endodontics?

Sodium Hypochlorite

What are the main advantages of Sodium Hypochlorite?

Most effective in dissolving organic debris, bactericidal, lubricates

What is a major toxicity risk of Sodium Hypochlorite?

High toxicity if extruded beyond apex

What equipment must be used to prevent Sodium Hypochlorite extrusion?

Rubber dam

What concentration of Chlorhexidine is used as an endodontic irrigant?

2 percent

What are the main advantages of 2 percent Chlorhexidine?

Broad-spectrum antimicrobial, effective against E. faecalis, low toxicity, substantivity

Does Chlorhexidine remove the smear layer?

No

Does Chlorhexidine dissolve necrotic tissue?

No

When is Chlorhexidine used as an alternative to Sodium Hypochlorite?

If there is an allergy or sensitivity

What concentration of Hydrogen Peroxide is used for canal irrigation?

3 percent

What reaction does Hydrogen Peroxide undergo to provide mechanical debridement?

Effervescent reaction

Can Hydrogen Peroxide alone remove the smear layer completely?

No

What concentration of EDTA is used to chelate inorganic material?

17 percent

What is the primary action of EDTA in root canals?

Chelates inorganic material of the smear layer

What is MTAD used for as a final rinse alternative?

Removes smear layer and kills E. faecalis

Does warm Sodium Hypochlorite improve its effectiveness?

Yes

Is mixing Sodium Hypochlorite with Hydrogen Peroxide effective?

No

Is mixing Sodium Hypochlorite with Chlorhexidine recommended?

No

What is the recommended method to remove the smear layer created by instruments using EDTA and Sodium Hypochlorite?

Irrigation with 17 percent EDTA for 1 minute followed by a final rinse with NaOCl

What is the purpose of chelators used in endodontics?

Aid and simplify preparation for sclerotic canals after the apex has been reached with a fine instrument

Which tissues do chelators act upon?

Calcified tissues only

What are the components of Glycerin when used as a lubricant?

Alcohol-based

What are the characteristics of Glycerin as a lubricant?

Mild, nontoxic, cost-effective

What are the components of RC-Prep lubricant?

EDTA, urea peroxide, and glycol

What property does RC-Prep possess in addition to lubrication?

Antimicrobial property

What is the watch-winding or twiddling motion?

Reciprocating clockwise and counter-clockwise rotation of the instrument in an arch with light apical pressure

What is reaming in hand instrumentation?

Clockwise cutting rotation of the file in 180 to 360 degrees to plane walls and enlarge canal space

What is filing in hand instrumentation?

Placing the file into the canal and pressing it laterally while withdrawing along path of insertion

What is the turn-and-pull technique in filing?

Placing the file to binding point, rotating 90 degrees, and pulling along the canal wall

What is circumferential filing used for?

Canals that are larger and not round

Which walls are engaged during circumferential filing?

Mesial, distal, buccal, and lingual walls

What must be done to a filing instrument before using it in curved root canals?

Pre-curved

Which canal preparation techniques are categorized as apical to coronal?

Conventional, Step-back, Modified step back, Passive step back, Modified double back, Balanced force technique

Which canal preparation techniques are categorized as coronal to apical?

Step down technique, Crown down pressureless, Hybrid technique, Double flared technique

What is the standardized or conventional technique?

All files used at the same working length

What is the disadvantage of the standardized technique?

Limited control over canal taper and shape

What is the step-back technique designed to provide?

A tapering preparation

How does the step-back technique handle working length for larger files?

Reduces working length stepwise in 0.5 to 1.0 mm increments

What does the Initial Apical File represent?

First file to bind at working length, estimating apical diameter after coronal flaring

What does the Master Apical File represent?

Largest file that binds at corrected working length, defining apical prep size

Where does the step-back technique begin relative to the master apical file?

One file size larger than the master apical file with incremental shortening

How is the coronal portion prepared first in the step-down technique?

Using Gates-Glidden drills or greater taper rotary files

What file size is traditionally introduced with a watch-winding motion in the step-down technique until resistance?

Large file such as number 70

What are the advantages of the step-down technique?

Removes coronal interferences, minimizes apical transportation, enhances irrigant penetration

When is the working length established in the crown-down technique?

Later in the procedure

What are the benefits of the crown-down technique?

Better access to apical third and reduced debris extrusion

What is recapitulation?

Using the MAF or smaller file to re-enter the canal to corrected working length between instruments

What is the first principle of Ni-Ti rotary instrumentation regarding access?

Always prepare access into coronal and middle third first

What is the preferred technique for Ni-Ti rotary instrumentation?

Crown-down with passive rotary use

Why should Ni-Ti files never be forced?

Requires gentle, passive insertion to avoid torsional stress and breakage

When should a glide path be verified?

With small, non-precurved K-files to working length

When must hand files be used first in Ni-Ti instrumentation?

In difficult anatomy to prevent transportation and help maintain canal path

Why should you avoid file overuse in rotary instrumentation?

Prevents file deformation and separation

Can rotary files be used to bypass ledges?

Never; use hand files to establish safe path first

What does full-length engagement of rotary files cause?

Taper lock and fracture

How should motion be applied when using Ni-Ti rotary files?

Continuous, smooth motion in an in-and-out pecking motion with light apical pressure

What must be done constantly regarding length during rotary instrumentation?

Confirm and maintain working length precisely

Which canals are the hardest to instrument and most prone to loss of working length, transportation, and separation?

Small, curved canals

What does forcing files create in rotary instrumentation?

Torsional stress leading to untwisting or breaking

What happens if you over-prep toward the furcation?

Causes stripping perforation in the danger zone

What is the danger zone in root canal preparation?

Thin dentin area prone to stripping perforation

What should the walls of a properly cleaned and shaped canal look and feel like?

Glassy smooth

What indicates a successful cleaning and shaping procedure regarding debris?

No debris or irrigant visible under microscope or tactile sense

What tool fit is required for lateral compaction of gutta-percha?

Finger spreader should reach within 1 mm of working length

What tool fit is required for warm vertical compaction?

Plugger should reach within 5 mm of working length

What are the primary goals of intracanal medicaments?

Reduce interappointment pain, lower bacterial load, prevent regrowth, render canal contents inert

What is the pH nature of calcium hydroxide?

Alkaline pH

How does calcium hydroxide function as an antimicrobial agent?

Alkaline pH is bactericidal and dissolves necrotic tissue

In which type of pulps is calcium hydroxide most effective?

Necrotic pulps with bacterial contamination

Does calcium hydroxide provide proven benefit in vital pulp cases?

No

Does calcium hydroxide have a proven effect on pain reduction between appointments?

No