Pathways of the Pulp Flashcards
Fluid movement within dentinal tubules can stimulate sharp, quickly reversible dental pain. What nerve fibers are responsible for this sensation?
Chapter 1: Diagnosis
A-delta nerve fibers
What nerve fibers produce an intense, slow, dull pain that can manifest as referred pain?
Chapter 1: Diagnosis
pulpal C fibers
What is the definition of spatial resolution?
Chapter 2: Radiographic Interpretation
the ability to display two objects that are close to each other as two separate entities
What is the definition of contrast resolution?
Chapter 2: Radiographic Interpretation
The ability to differentiate between areas on the image based on density
Endodontics require high-contrast resolution
What are the advantages of CBCT over multidector CT?
Chapter 2: Radiographic Interpretation
Faster, low-dose, low-cost, high-contrast images
High resolution isotropic images
What is a voxel?
Chapter 2: Radiographic Interpretation
cuboidal elements that constitute a 3D volume unlike pixels which are 2D
MDCT obtain pixels while CBCT obtains voxels
Does CBCT have lower or higher kV and mA exposure parameters than MDCT?
Chapter 2: Radiographic Interpretation
Lower
True or false: the smaller the voxel size the higher the spatial resolution
Chapter 2: Radiographic Interpretation
True
What is the maximum voxel size that should be used for endodontic imaging?
Chapter 2: Radiographic Interpretation
0.2mm
What percent mineral content loss is needed for radiolucent regions to be visualized on conventional radiographs?
Chapter 2: Radiographic Interpretation
30-40%
Planar based radiographs overestimate or underestimate success of endodontic treatment as compared to CBCT?
Chapter 2: Radiographic Interpretation
Overestimate success of endodontic treatment
What three characteristics must be present for a diagnosis of Medication Related Osteonecrosis of the Jaws (MRONJ)? (American
Association of Oral and Maxillofacial Surgeons: Position paper
on Bisphosphonate-Related Osteonecrosis of the Jaw)
Chapter 3: Case Selection and Treatment Planning
- Current or previous treatment with an antiresorptive drug
such as a bisphosphonate or an antiangiogenic drug (e.g.,
sunitinib [Sutent], sorafenib [Nexavar], bevacizumab
(Avastin), or sirolimus (Rapamune) - Exposed, necrotic bone in the maxillofacial region that has
persisted for more than 8 weeks - No history of radiation therapy to the jaws
What factors increase the risk of developing osteonecrosis of the jaw while recieving bisphosphanotes?
Chapter 3: Case Selection and Treatment Planning
history of taking bisphosphonates, especially intravenous (IV) formulations
previous history of cancer
history of a traumatic dental procedure
hx of chronic corticosteroid use
hx of diabetes
human only: hx of smoking, patient more than 65 years old
Which of the following is most correct regarding development of bisphosphonate-associated osteonecrosis?
A. The maxilla is more commonly affected than the mandible
B. 40% of cases are preceded by a dental procedure
C. patients with skeletal multiple myeloma and metastatic carcinoma recieving IV bisphosphonates comprise 94% of published MRONJ cases.
D. Patients less than 65 years old are at an increased risk
Chapter 3: Case Selection and Treatment Planning
C. patients with skeletal multiple myeloma and metastatic carcinoma recieving IV bisphosphonates comprise 94% of published MRONJ cases.
A. The mandible is more commonly affected than the maxilla (2:1 ratio)
B. 60% of cases are preceded by a dental procedure
D. Patients > 65 yro are at an increased risk
In what percent of cases are accessory canals found in the apical third of the root, the middle third and the cervical third?
Chapter 5: Tooth Morphology, Isolation and Access
Apical third 74%
Middle third 11%
Cervical third 15%
What is the definition of elastic limit in regards to endodontic instruments?
Ch 8
Maximal strain that allows a file to return to original dimensions
If you have a K file size #25 file with #.02 taper,
what mm distance is from D1 to D16 in the image, and what size in mm is the tip of the file?
What is the diameter at D16?
Distance: 0.32 mm
Tip: 0.25mm
Diameter: 0.57mm
What is the flute surface of an endodontic file?
Ch 8
Groove in the working surface that collects soft tissue and dentin from the walls, collects the dentin
What is the leading edge of an endodontic file?
What is the rake angle?
Leading edge: Surface with greatest diameter that follows the groove as it rotates – cuts the dentin
Rake angle: The angle formed by the leading edge and radius of file – Positive supposedly cuts; Negative supposedly scrapes
What is the helix angle of an endodontic file?
CH 8
The angle the cutting-edge forms with the long axis of file. Defines the type of file and how it is used
Define the order and direction of shaping the canal with each technique:
Step-back
Step-down
Crown-down
Ch 8
Step-back: Apical to coronal direction, taper canal
Step-down: Coronal pre-flaring before cleaning apically, WL before pre-flare
Crown-down: Coronal pre-flaring before cleaning apically, WL after pre-flare
What is the minimum concentration of NaOCl needed for pulp dissolution?
Ch 8
1 %
Which of the following properties of bleach leads to oxidizing pulpal tissue?
A. Saponification reaction
B. Neutralization reaction
C. Hypochlorous acid formation
D. Solvent action
Ch 8
C. Hypochlorous acid formation
Saponification reaction: Acts as an organic and fat solvent. Reduces the surface tension of the remaining solution.
Neutralization reaction: Neutralizes amino acids by forming water and salt. The pH is reduced.
Hypochlorous acid formation: Chlorine dissolves in water and it is in contact with organic matter: it forms hypochlorous acid. It is a weak acid that acts as an oxidizer.
Solvent action: Sodium hypochlorite also acts as a solvent, releasing chlorine that combines with protein amino groups (NH) to form chloramines (chloramination reaction). Chloramines impede cell metabolism and inhibits essential bacterial enzymes
What property of bleach makes it antimicrobial?
Ch8
High pH (>11)
The high pH interferes in cytoplasmic membrane integrity due to irreversible enzymatic inhibition, biosynthetic alterations in cellular metabolism, and phospholipid degradation observed in lipidic peroxidation.
What is the MOA of EDTA?
Ch 8
MOA: demineralizing chelating agent
Which of the following matches the material type and mechanism of action for GuttaFlow2 as a sealant?
A. Salicylate, Chelation
B. Silicone, Polymerization
C. Tricalcium silicate, Hydration
D. Salicylate, Ionomer formation
Ch 8
B. Silicone, Polymerization
Polymer formation by radical polymerization: Generation of a free radical monomer units results in polymers formation by the successive addition of free-radical building blocks
What is the term used to describe the histologic appearance of the coronal portion of young pulp odontoblasts?
Chp 13
The odontoblasts have a tall columnar form varying in height with nuclei staggered and not all at same level –> palisading
Appear 3-5 cells in thickness but only 1 layer
What are the layers of Dentin-Pulp Complex?
Dentin –> predentin –> odontoblast layer –> cell-poor zone –> cell-rich zone –> pulp proper
Ch 13
Are there more dentinal tubules per unit area in the root or the crown?
Ch 13
The crown
During cavity preparation what junctions in dentin are disrupted increasing dentin permeability?
Ch 13
Tight junctions
How are accessory canals formed?
By the entrapment of periodontal vessels in Hertwig’s epithelial root sheath during mineralization.
What is the most prominent cell in the pulp proper?
Ch 13
Fibroblast
Odontoblasts mainly synthesize what type of collagen?
ch 13
Type 1
What immune cells are found normally within dental pulp?
Ch 13
macrophages
dendritic cells
T lymphocytes
What type of immune cell is often found in inflamed pulp?
Ch 13
Mast cells
What is the rate of oxygen consumption of dental pulp?
Ch 13
3.2 ± 0.2 ml/min/100 g of pulp tissue
What dental materials have been shown to depress the metabolic activity of pulpal cells?
Ch 13
Eugenol
Zinc oxide and eugenol
Calcium hydroxide
silver amalgam
What primary proteogylcans are present during active primary dentinogenesis and then following eruption?
Ch 13
Dentinogenesis: Chondroitin sulfate
Tooth eruption: Hyaluronic acid
What types of collagen are present in the pulp proper?
Ch 13
Type I: thick striated fibrils thoughout pulp tissue
Type III: found in most unmineralized connective tissues
Where are Type I and Type II collagen found?
Ch 13
Type I: skin, tendon, bone, dentin, pulp
Type II: Cartilage
Where are Types IV and VII collagen found?
Ch 13
basement membranes
Where is Type V collagen found?
Ch 13
Interstitial tissues
Odontoblasts and osteoblasts synthesize what type of collagen?
Ch 13
Type 1
Fibroblasts synthesize types I, III, V, VII
Large collagen fibers are more numberous in the radicular or coronal pulp?
Ch 13
Radicular
Why pulpectomy procedures should engage pulp witha barbed broach in region of apex to remove tissue intact
What are apical deltas?
Apical deltas are multiple accessory canals that branch out from the main canal at or near the root apex.
What are furcation canals and how are they formed?
Furcation canals are accessory canals that are present in the bifurcation or trifurcation of multirooted teeth. These channels form as a result of the entrapment of periodontal vessels during the fusion of the diaphragm, which becomes the pulp chamber floor.
How are furcation lesions formed?
They are formed by pulp inflammation that communicates with the periodontium via furcation canals. Can be present without periodontal disease.
What are the functions of afferent neurons in the pulp?
Ch 13
conduct sensory impulses
What are the functions of autonomic or efferent neurons in the pulp?
Ch 13
Provide neurogenic modulation of the microcirculation, inflammatory reactions, perhaps regulate dentinogenesis
What is the path of symphathetic innervation of teeth from central to peripheral?
Ch 13
Superior cervical ganglion
Internal carotid nerve
Trigeminal nerve
Maxillary and mandibular division of trigeminal nerve
What type of A fibers compose 90% of dental pulp A fibers?
Ch 13
A-delta fibers
Function: Pain, temperature, touch
What are the characteristics and functions of A-delta fibers?
Ch 13
Myelinated
Function: pain, temperature, touch
Compose 90% of dental pulp A fibers
Located in periphery of pulp and penetrate the inner part of dentin
What are the characteristics and functions of C fibers?
Ch 13
Unmyelinated
Function: pain
Located in deeper part of pulp proper
What are the pain characteristics and stimulation thresholds of A-delta and C fibers respectively?
Ch 13
A-delta: sharp and pricking, stimulation threshold relatively low
C fibers: burning and aching, less bearable than A-delta fiber sensations, stimulation threshold realtively high, usually associated with tissue injury
What is the resting pulpal blood flow?
Ch 13
0.15 to 0.60 ml/min/g tissue
What is the consensus regarding the presence or absence of lymphatics in dental pulp?
Ch 13
Lymphatics have not consistently been demonstrated to be present in dental pulp
What inflammatory cytokines are elevated in inflamed pulp?
Ch 13
IL-1 and TNF-alpha
What is the definition of primary dentin?
Ch 13
The regular tubular dentin formed before eruption including mantle dentin
What is the definition of secondary dentin?
Ch 13
Regular circumferential dentin formed after tooth eruption
its tubules remain continuous with that of primary dentin
secondary dentin responsible for decreasing pulp width throughout life of tooth
What is the definition of tertiary dentin?
Ch 13
Irregular dentin that is formed in response to abnormal to abnormal stimuli such as excess wear, cavity preparation, restorative material, caries
What is the name of focal tertiary dentin formed by the original odontoblasts that made secondary dentin?
Ch 13
Reactionary dentin
What are the three anatomic and histological landmarks in the apical region of the root?
The apical constriction, the cementodentinal junction, and the apical foramen
What is the cementodentinal junction (CDJ)?
Histologically - where the cementum and dentin meet in the root canal. It is NOT synonymous with the apical foramen or apical constriction.
What is the name of the tertiary dentin that forms if the original odontoblasts are destroyed?
Ch 13
Reparative dentin
Tubules not continuous with those of secondary dentin, more irregular, less tubular
What can cause destruction of primary odontoblasts?
ch 13
Cutting cavity preparations dry
Bacterial products like LPS from deep carious lesions
mechanical exposure of pulps
What is the apical foramen (AF)?
The circumference or rounded edge, like a funnel or crater that differentiates the termination of the cemental canal from the exterior surface of the root.
What can one use to flare the canal orifice coronally?
Gates glidden burs or rotary nickel titanium (NiTi) orifice openers
The final position of the incisal wall of the access cavity is determined by what two factors?
- Complete removal of the pulp horns
- Straight line access
In humans pulp calcifications are present in what percent of all teeth?
Ch 13
At least 50%
What are the main age related changes to dentin?
Ch 13
increase in peritubular dentin
increased dentinal sclerosis
increased dead tracts
dead tracts: dentinal tubules with absent odontoblast processes
What are the reported overall success rates for orthograde root canal therapy for teeth diagnosed with irreversible pulpitis and teeth diagnosed with infected, necrotic pulps respectively?
Ch 8
Irreversible pulpitis: 95%
Necrotic, infected pulps: 85%
What is considered the minimum radicular wall thickness for root canal therapy?
Ch 8
0.3mm
How far do irrigants progress from the tip of the needle when using passive needle irrigation?
Ch 8
1mm
What is a radial land?
Ch 8
Feature between trailing and cutting file edge that forms a larger contact area with the radicular wall
Thought to reduce tendency of file to thread into canal, less efficient compared to triangular cross sections
Triangular point of cutting edge is cut off at the top to make it flat
A, B and C demonstrate what types of rake angles?
Ch 8
A. negative
B. Neutral
C. Positive
What is the standard taper of ISO files?
Ch 8
0.32mm over 16mm of cutting blades
0.02mm increase in diameter per millimeter of flute length
What are Gates Glidden drills and Peeso burs made out of?
Ch 8
Stainless steel
What is pseudoelasticity?
Describes the ability of NiTi files to return to their original shape after being deformed
Are K-files and NiTi files produced by milling or twisting?
Ch 8
K-files twisting
NiTi milling
What kind of files are A and B?
Ch 8
A. K-files (twisting)
B. Hedstrom file (grinding)
What is reaming vs filing motions?
Reaming is rotating the file while filing is an “in and out” motion
reaming generally causes less transportation
Failure in files occurs at half the number of rotations in a clockwise or counterclockwise rotation?
Ch 8
counterclockwise
What is the difference between reamers and K-files?
Ch 8
Reamers have fewer cutting flutes per mm of the working surface
More appropriate for twisting motion
H-files have positive, negative or neutral rake angles?
Ch 8
Positive
What kind of file is this?
Ch 8
Gates Glidden
What is the diameter range of Gates Glidden files sizes 1-6?
0.5 - 1.5mm
Gates Glidden drills should be used at what rpm?
750 - 1500 rpm
Group II rotary files lack what features which improves cutting efficiency?
Radial lands
What type of root canal shaping system has been associated with a higher incidence of preparation errors and reduced radicular wall thickness?
Ch 8
Ultrasonic devices
What is the champagne bubble test?
When you allow sodium hypochlorite (bleach) to remain in the pulp chamber to help locate a calcified root canal orifice—> tiny bubbles will appear in the solution, indicating the position of the orifice
What are problems that can occur when tooth angulations are not considered during access development?
Mistaken identity of an already identified canal, failure to locate a canal or extra canals, excessive gouging of crown, instrument separation during attempts to locate an orifice, failure to debride all pulp tissue from the chamber
What were the four factors that influenced the success of a non surgical RCT based off of a meta-analysis?
- The absence of a periapical lesion
- Root canal obturation containing no radiographic voids
- Obturation to within 2 mm of the radiographic apex
- An adequate coronal restoration
Combination of what two techniques has been shown to be most accurate for determining working length?
Ch 8
Electronic apex locators + radiographs
A, B, C, and D show what most common preparation errors?
Ch 8
A. Apical zip
B. Ledge
C. Apical zip with perforation
D. Ledge with perforation
What is the crown down root canal preparation approach?
Ch 8
Large instrument inserted until passive resistance met, then smaller files are used to progress more apically until terminus is reached
What is the step-back root canal preparation approach?
Ch 8
Working lengths decrease in stepwise manner with increasing instrument size
What does obturation do?
Reduces coronal leakage and bacterial contamination, seals the apex from the periapical tissue fluids, and entombs the remaining irritants in the canal.
When is obturation contraindicated?
Presence of exudation from the canal, or when you cannot full dry the canal.
How is removal of the smear layer generally accomplished?
By irrigating the canal with 17% disodium EDTA and 5.25% bleach
EDTA removes the inorganic material, and bleach or NaOCl removes the remaining organic components
What are the radiographic criteria for evaluating obturation?
Length, taper, density, adequate GP and sealer removal, and adequate provisional or definitive restoration
What are the mechanical and chemical objectives of irrigation?
Ch 8
1.) Flush out debris
2.) Lubricate the canal
3.) Dissolve organic and inorganic tissue
4.) Prevent formation of a smear layer during instrumentation or dissolve it once it forms
What is the external diameter of a 27 gauge injection needle?
Ch 8
0.42mm
What type of irrigation needle tips lead to maximum shear stress concentrated on the wall facing the outlet?
Ch 8
Side-vented
Double side-vented
What are the benefits of using irrigants in root canal treatment?
Ch 8
Removal of particulate debris and wetting of the canal walls
Destruction of microorganisms
Dissolution of organic debris
Opening of dentinal tubules by removal of smear layer
Disinfection and cleaning of areas inaccessible to endodontic instruments
What is the irrigant of choice in endodontics?
Ch 8
Sodium hypochlorite
What is the active component of sodium hypochlorite?
Ch 8
hypochlorous acid
Increasing the temperature of low-concentration NaOCl solution improves which of their characteristics?
Ch 8
Immediate tissue dissolving capacity
Remove organic debris from dentin shavings more efficiently
However- no clinical studies at this point to support the use of heated NaOCl
Low concentrations of NaOCl can be effective for canal irrigation when used at what volume and frequency?
Ch 8
Higher volume
More frequent intervals
What ion in bleach is responsible for its dissolving and antibacterial capacity and how quickly is it consumed?
Ch 8
Chlorine ion
Within 2 minutes
When do sealers exhibit toxicity?
When they are freshly mixed. Their toxicity is greatly reduced once they have set.
What types of bacteria and fungi is chlorhexidine effective against?
Gram-positive, Gram-negative bacteria
Yeasts
What is the substantivity reaction/property of chlorhexidine?
Ch 8
A concentration dependent reversible uptake/absorption of chlorhexidine onto the tooth surface that release of chlorhex into the environment for continued antimicrobial activity.
What sustance forms when chlorhexidine is mixed with NaOCl?
Ch 8
Parachloroaniline (PCA)
(4-chloroaniline)
What are the properties of an ideal sealer?
- Exhibits tackiness when mixed for good adhesion
- Establishes a hermetic seal
- Radiopaque, so that it can be seen on rads
- No shrinkage on setting
- No staining of tooth structure
- Bacteriostatic
- Exhibits a slow set
- Insoluble in tissue fluids
- Tissue tolerant - non irritating to periradicular tissue
- Soluble in a common solvent - for ease of removal
- Fine powder, to mix well with water
The precipitate formed by combination of NaOCl and CHX causes what effects in the canal?
Color changes
Formation of a possibly toxic insoluble precipitate that may interfere with the seal of the root obturation
What forms when CHX and EDTA are combined?
Ch 8
A white precipitate that is a salt
What is the definition of the smear layer? (American Association of Endodontists 2003)
Ch 8
A surface film of debris retained on dentin or another surface after instrumentation with either rotary instruments or endodontic files.
Consists of dentin particles, remnants of vital or necrotic pulp, bacterial components and retained irrigants
controversy regarding thoughts on if its removal either opens dentinal tubules to allow removal of bacteria or if it protects dentinal tubules
Only 1 in vivo study that found that use of EDTA sig incrased odds of success of retreatment
What does EDTA stand for?
Ch 8
Ethylenediamine Tetra-Acetic Acid
What benefits as an irrigant does EDTA provide?
Ch 8
It can chelate and remove the mineralized portion of the smear layer
What is the best method of obturation to distribute the sealer in the apical portion of the canal?
Trick question, there is no best method. However, lateral compaction results in better distribution of the sealer in midcoronal areas of the root canal system when compared to warm vertical compaction.
What is the MOA of EDTA’s chelating abilities?
Ch 8
Sequesters di and tricationic metal ions such as Ca2+ and Fe3+
After being bound by EDTA these metal ions remain in solution but exhibit diminished reactivity
Self-limiting
What is the antibacterial MOA of EDTA?
Ch 8
EDTA extracts bacterial surface proteins by combining with metal ions from the cell envelope which can eventually lead to cell death
Can also detach biofilms adhering to root canal walls
How long does it take for EDTA to remove the inorganic component of the smear layer?
Ch 8
< 1 minute
What are the pros and cons to zinc oxide and eugonol sealers?
Pros: Will absorb if extruded into periradicular tissues, soluble, antimicrobial
Cons: Slow setting time, shrink on setting, can stain teeth
What properties of NaOCl and EDTA are influenced the two are mixed?
Ch 8
NaOCl loses its tissue dissolving capacity
EDTA retains its calcium-complexing ability
EDTA and NaOCl should be used separately
What are the pros and cons to glass ionomer sealers?
Pros: Good dentin-bonding properties
Cons: Minimal antimicrobial activity, difficult to remove if retreatment is required
Should EDTA be heated?
Ch 8
No!
When chelators are heated the calcium binding capacity decreases
What is the consensus regarding adding detergants/surfactants to irrigants?
Ch 8
Not needed b/c they do not enhance the ability of NaOCl to dissolve pulp tissue or the efficacy of common chelators to remove calcium or smear layer
What are the contents of MTAD and Tetraclean?
Ch 8
Doxycycline
Broad spectrum antibiotic
Citric Acid
Detergent
The two differ in concentrations of doxycyline (MTAD higher)
What are the advantages of MTAD and Tetraclean?
Ch 8
CAn remove both the smear layer and organic tissue from the infected root canal system
Recommended as a final rinse after normal chemomechanical preparation
Tetracyclines are effective against what type of bacteria and are bacteriostatic or bacteriocidal?
Ch 8
Effective againist Gram-positive and Gram- negative (more Gram-negative effect)
Bacteriostatic but in high concentrations may have bacteriocidal effect
What does the term monoblock mean?
The idealized scenario in which the canal space becomes perfectly filled with a gap-free, solid mass that consists of different materials and interfaces, with the purported advantages of simultaneously improving the seal and fracture resistance.
What are the two major categories of resin sealers?
Epoxy resin and methacrylate resin
What type of sealer is GuttaFlow?
Silicone sealer
What are Pathways’ general recommendations for when to use EDTA and NaOCl during the procedure?
Ch 8
Bleach used throughout procedure as the irrigant of choice
EDTA or other chelators used at end of procedure to remove smear layer
Final flush with NaOCl for 1 minute for maximum cleaning efficiency and to minimize dentin erosion
What is passive ultrasonic irrigation (PUI)?
Introduction of noncutting ultrasonically activated small file into canal with irrigant once the final apical size has been reached
What are the pros and cons to GuttaFlow?
Cons: Setting time is inconsistent
Pros: Fills canal irregularities, biocompatible, working time 15 minutes, cures in 25-30 minutes, may promote PDL stem cells into cementoblasts
What are the negative side effects of having paraformaldehyde in sealers?
Overextension can result in osteomyelitis, dysesthesia, and permanent toxic effects on periradicular tissues.
What is ultrasonic instrumentation (UI)?
Ch 8
Cutting file brought into contact with wall during irrigation –> can lead to uncontrolled cutting of root canal walls without effective disinfection
What is the main advantage of negative apical pressure systems?
Ch 8
Irrigation solutions will not extrude through apex
What instrument is shown and what is its function?
Ch 8
Safety irrigator
Delivers irrgant apically under positive pressure and evacuates solution through large needle at canal orifice creating a negative pressure system
Designed to limit risk of NaOCl accidents
What laser and wavelength are best suited to root canal treatment?
Ch 8
Er:YAG laser
wavelength 2940nm
Highest absorption in water and high affinity to hydroxyapatite
What are the two ways laser energy may be used to activate irrigant solutions?
Ch 8
Molecular level: photoactivated disinfection (PAD)
Bulk flow level: laser activated irrigation (LAI)
What method of laser energy activation is best removing the smear layer and dentin debris?
laser activated irrigation (LAI)
MOA: generates secondary cavitation effects with expansion and successive implosion of fluids
What antibacterial nanoparticles have been evaluated for endodontics?
Ch 8
Chitosan (CS-np)
Zinco oxide (ZnO-np)
Silver (Ag-np)
What are the 10 properties of an ideal obturation material?
- Easily manipulated with ample working time
- Dimensionally stable with shrinkage once inserted
- Seals the canal laterally and apically
- Nonirritating to the periapical tissues
- Impervious to moisture and nonporous
- Unaffected by tissue fluids
- Inhibits bacterial growth
- Radiopaque
- Does not discolor tooth structure
- Sterile
- Easily removed from the canal if necessary
What is the mechanism of action for bioactive glass in root canal disinfection?
Ch 8
maintains an alkaline environment over time and kills bacteria
MOA not pH related
What is the MOA of ozone for killing bacteria?
Ch 8
destruction of cell walls and cytoplasmic membranes by oxidant potential –> increased permeability –> immediate function cessation
What rates of manual and rotary instrument fracture are reported?
Ch 8
Manual file: 1-6%
Rotary: 0.4-5%
Does the presence of a retained instrument result in a significantly higher rate of RCT failure when done by specialists?
Ch 8
No
What is torsional fracture of rotary instruments?
Ch 8
Occurs when an instrument tip is locked into a canal while the shank continues to rotate and fractures the tip
What is flexural fracture of rotary instruments?
Occurs when the cyclic loading leads to metal fatigue
What is the most popular core material used for obturation and why?
Gutta-Percha. Advantages to GP are its plasticity, ease of manipulation, minimal toxicity, radiopacity, and ease of removal with heat or solvents.
How many flexural cycles can NiTi instruments withstand before they fracture?
Ch 8
several hundred
Which canal shaping technique reduces torsional loads and risk of fracture by preventing a large portion of the tapered rotating instrument from engaging root dentin (taper lock)?
Ch 8
crown-down technique
What is the definition of canal transportation?
Ch 8
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
What are the disadvantages to Gutta Percha?
Lack of adhesion to dentin, and when heated, it will shrink once it is cooled down.
GP is the trans-isomer form of polyisoprene or natural rubber. What are its two crystalline forms?
Alpha and Beta
The beta form is when it is unheated - a solid mass that is compactable
The alpha form occurs when it is heated, it becomes pliable and tacky and can flow under pressure
What is a disadvantage of lateral compaction?
The technique may not fill canal irregularities as the process does not produce a homogenous mass
What are the disadvantages to warm vertical compaction?
Slight risk of vertical root fracture, less length control compared to lateral compaction, and therefor potential for overextrusion of obturation materials into periradicular tissues
What are the advantages of warm vertical compaction?
Filling of canal irregularities and accessory canals
Continuous wave obturation uses what equipment?
System B unit, hand pluggers, and a master cone
Continuous wave compaction is a variation of lateral or warm vertical compaction?
Warm vertical compaction
What are the contents of Gutta Flow
gutta percha, polydimethylsiloxane sealer, and nanosilver preservative particles
The cell-poor zone of the pulp is often not apparent in what age of pulps?
Ch 13
Young pulps where dentin forms rapidly
Older pulps where reparative dentin is being produced
