ENDODONTICS Flashcards
Which law is this statement associated with
“ the floor of the pulp chamber is always located in the centre of the tooth at the level of the CEJ”
A. Law of Centrality B. Law of Concentricity C. Law of the CEJ D. Law of Symmetry E. Law of Orifice Location F. Law of Colour
A - correct
What is the law of concentricity
Walls of the pulp chamber are always concentric to the external surface of the tooth at the level of the CEJ
Which of these is incorrect in relation to the law of colour;
A. the floor of the pulp chamber is always darker than surrounding dentinal walls
B. the colour difference creates a distinct junction where the walls and floor of the pulp chamber meet
C. the developmental root fusion lines are darker than the floor
D. reparative dentine/calcifications are darker than the pulp chamber floor
D - is incorrect
The reparative dentine and calcifications appear lighter than the pulp chamber floor
What are the 3 points in the laws of orifice location
- ofirices are always at the junction of walls and floor
- orifices are located at the angles of the wall-floor junction
- orifices lay at the terminus of developmental root fusion lines (if present)
Define the Anatomic and Radiographic apex
Anatomic - the tip of the root determined morphologically
Radiographic - the tip or the end of the root as determined radiographically
What file is this?
Stainless Steel
Tightly spiralled cutting edges
Tip is cutting
Cutting occurs when pushed, pulled or rotated
Cross-section is square (can also be diamond, triangular)
A. H-file
B. K-file
C. Barbed broach
D. C-file
B- correct
Which of these characteristics is incorrect for a H-file
A. aggressive relative to K file
B. Stainless steel
C. Cutting occurs in pulling and pushing motion
D. Round cross-section
C - cutting only occurs on the pulling stroke
What is the difference between a C+ and a C-pilot file
C+ files have a pyramid shaped cutting tip
C-pilot files have a non-cutting tip
Both are stainless steel and square in cross section
Which statement is most correct regarding endodontic files?
A. K files are used in the coronal and middle section of mechanical cleaning and shaping in the crown-down technique
B. Flexofiles are similar to K-files except they have a non-aggressive tip and increased flexibility
C. Barbed broaches are not effective in removing necrotic tissue debris from the root canal
D. H-files are utilised in the apical zone when hand-filing in a crown-down technique
B is correct
A - this is actually the function of H files
C - Barb broaches are very effective in this function
D - this is actually the function of K-files
What are the benefits of the crown-down technique in root canal therapy
- Reducing procedural error
- Improves access of instruments and irrigation to apical 1/3
- Reduces apical extrusion of debris
- Creates a canal escapeway for debris to flow coronally
Define; Transportation Perforation Ledge Zip
Transportation - removal of structure outside the curve of the root canal in the apical 1/2 due to the files tendency to restore a linear shape
–> can lead to a ledge OR perforation
Perforation - mechanical or pathologic communication between the canal system and periodontium/external root surface
Ledge - artificial irregularity impeding instrument access to the apex
Zip - tear drop shaped widening of apical foramen that has been formed during instrumentation of a curved canal. The file has transported through the apical foramen to the outer wall of the tooth
A tooth has one canal orifice, two root canals and one apical foramen
What is it’s Weine Classification?
Weine Type II
The other types
Type I - one orifice, one canal, one apical foramen
Type III - two orifices, two canals, two apical foramina
Type IV - one orifice, one canal, two apical foramina
Which of the statements is incorrect
A. Mandibular lateral incisors can present with Type I, II and III canal forms
B. Maxillary 1st molars have 3 roots and 4 canals 50% of the time
C. Maxillary second pre-molars typically have a Type I canal form in 48% of cases
D. Maxillary central incisors can have 3 pulp horns in a young patient
B - Maxillary 1st molars have 3 roots and 4 canals 95% of the time
When is it ideal to obturate - what are 5 key things we are looking for before we fill a root canal system
- When adeqaute biomechanical preparation hasbeen completed and confirmed (apical stop, clean/tapered walls)
- When the tooth is asymptomatic
- When the canals can be dried –> no exudate/fluid still present from periodontal tissues
- When the draining sinus and/or swelling has resolved (if it was initially present)
- When the tooth has normal mobility
What are the two most common sealer materials?
ZOE-based (zinc-oxide eugenol) and AH26/plus
What are four routes of root canal infection
Dentinal Tubules - any cause of dentine exposure where bacteria can invade tubules
Direct Pulp Exposure - the most obvious and common route
Periodontal Disease - only when the periodontal pocket reaches the apical foramen
Anachoresis - circulating blood or lymph reaching an area of damaged tissues
Which of the following is an example of a intra-radicular infection
A. acute apical abscess
B. initial infection where the bacteria invade and colonise pulp tissue –> necrosis
C. apical actinomycosis from peri-radicular surgery
B
A & C are examples of extra-radicular infections
What are the most common micro-organisms in primary endodontic infections?
Gram -ve
Dialister, Prophyromonas, Tannerella, Prevotella
What is the most common bacterial species that is found in root-canal treated teeth
E. faecalis
What patterns of colonisation do microbes have in the root canal system and what effects does this have on treatment
Planktonic (unnatached) - these are easy to access and eliminate
Aggregates/Coaggregates - adhered to the walls (biofilm)
Clogged in Lateral Canals/Isthmuses (biofilm)
- biofilm is difficult to eliminate and requires chemical, mechanical cleaning, irrigation, medicaments etc.
Which of the following is correct regarding electrical pulp testing
A. A-delta and C-fibres are stimulated
B. The numbers (1-80) of the EPT is important for severity
C. EPT should be performed on the roots of the teeth
D. EPT could give a false +ve due to poor isolation or contacting soft tissue
D is correct
A - only A-delta are stimulated
B - the numbers are just relative to this patient, the test utliamtely only give a yes/no
C - should be performed on the mid buccal of a sound crown
Briefly discuss how hot and cold cause a pain response in the tooth?
Short, sharp cold pain = vitality
Hydrodynamic mechanism:
Contraction of fluids –> outward flow –> deforming the A-delta fibre –> stimulation and pain
In the case of an acute advanced pulpitis there are no A-delta fibres, in this case the cold decreases intrapulpal pressure and relieves pain from C-delta fibres (for a short period)
Hot response:
Delayed = normal
Immediate/no response = abnormal
A normal tooth has to reach a certain temperature prior to pain from heat - response is delayed
A tooth with an inflamed pulp already has increased pressure and so the applicaiton will cause immediate pain
A necrotic pulp will have no response to hot or cold
Which of the following is correct regarding root canal treatment
A. for every mm lost in WL the chance of failure increases 14%
B. The goal is to be at the radiographic apex
C. in a 2% taper the file increases 0.2mm in size every 1mm from the tip
D. The purpose of recapitulation is to pass through and keep the apical foramen open
A
B. goal is to be 1mm from apex
C. taper increases by 0.02mm
D. this is referring to ‘apical patency’. Recapitulation is to keep the apical area clean and patent, without compromising the seal.
When would you want to be more than 1mm from the radiographic apex?
In cases where;
The apex is slightly open
There is root resorption
There is a lateral canal exit
Explain the importance of the file taper and goal of working up 3 files sizes in relation to bacterial penetration of canals
Coronal-middle zones of a root canal will be easily irrigated throughout the RCT process and therefore undergo sufficient chemical preperation to reduce microbial load
The apical zone is much harder to access and its imperative to then ensure the apical zone is cleared of bacteria, so this portion relies more heavily on the mechanical removal
Studies have show bacteria can penetrate up to 300microns (0.3mm) into the dentine - our goal is to remove around 150 microns (0.15mm)
A 15K file with a 2% taper will be 0.15mm at its tip
Each mm from the tip will increase this by 0.02 e.g. 1mm up will be 0.17
If a 15k file binds tightly 1mm from the apex this means in this zone the width is 0.15mm and there is at least 0.15mm of dentine we need to remove to clear the bacteria so we would need to widen this to at least 0.30-0.35
This is done by increasing working size to a K30-K35
What are the two positive features of NaOCl in endodontics
- dissolves organic tissue
2. antimicrobial effects
