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Dentistry Module 7 > Endodontics > Flashcards

Endodontics Flashcards

1
Q

What is the clinical and radiographic follow-up time period required after RCT?

A

At least 1 year after treatment

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2
Q

What are the three indications for root canal retreatment?

A
  1. Persistent periapical pathology following RCT
  2. New periapical pathology associated with a root-filled tooth
  3. A new restoration is planned for a tooth and radiographic assessment shows an inadequate root canal filling and/or a periapical radiolucency
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3
Q

According to the Toronto Study, what is the likelihood of a successful primary treatment outcome overall in Endodontics?

A

81%

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4
Q

What are the three main prognostic factors for outcome of secondary root canal treatment?

A
  1. Pre-operative periapical lesion
  2. Apical extent of root canal filling
  3. Quality of coronal restoration
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5
Q

What are the 5 types of microbial causes of post-treatment disease?

A
  1. Intraradicular microbes
  2. Extraradicular infection
  3. True cyst
  4. Cracked teeth, vertical root fracture
  5. Coronal leakage
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6
Q

What are Intraradicular microbes?

A

Microbes that are situated in the apical part of the root canal system in areas that are often inaccessible to instrumentation and therefore much more difficult to disinfect.

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7
Q

What is meant by extra-radicular infection?

A

Infection where microbes have evaded the host defence mechanism and established themselves in the periapical tissues

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8
Q

What are the two non-microbial casues of post-treatment disease?

A
  1. Cholesterol crystals
  2. Foreign body reactions in periapical tissues
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9
Q

What type of bacteria tends to be persistent and remain in the root canal system after root canal disinfection and inter-appointment dressing? Give an example.

A

Gram +ve bacteria, an example would be E Faecalis.

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10
Q

What chronic inflammatory lesion can develop from bacterial colonies forming biofilms on the external root surface of a tooth?

A

Periapical granuloma

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11
Q

What two types of bacteria are most commonly found to cause periapical granuloma?

A
  1. Actinomyces
  2. Propionibacterium propionicum
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12
Q

What is the most common Odontogenic cyst of inflammatory origin?

A

Radicular cyst

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13
Q

How do radicular cysts arise?

A

From epithelial rests in periodontal ligament

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14
Q

What are the two types of radicular cyst?

A

True cyst to a pocket cyst

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15
Q

Define a true cyst.

A

A lesion enclosed by epithelial lining

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16
Q

Define a pocket cyst.

A

An epithelial sac which communicates with the root canal system

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17
Q

Which cyst is less likely to heal following endodontic treatment- A true or pocket cyst?

A

A true cyst (It may require surgical intervention)

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18
Q

How are cholesterol crystals produced as a non-microbial cause of post-treatment failure?

A

Produced from dying cells during chronic inflammation

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19
Q

Give 4 examples of endo materials that could cause foreign body reactions.

A
  1. Gutta percha
  2. Sealers
  3. Paper points
  4. Cotton pellets
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20
Q

What is the advantage of using limited FOV CBCT in the detection of apical periodontitis?

A

This type of CBCT concentrates on just a few teeth therefore the radiation exposure is much reduced compared to normal CBCT.

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21
Q

What is the main risk of accessing the root canal through an existing crown? And why?

A

Perforation, usually due to lack of visibility or tooth alignment is altered by the crown.

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22
Q

What is an alternative treatment to accessing root canal through a crown, which will avoid risk of perforation?

A

Removal of crown before access

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23
Q

What warning should always be given to patients prior to post removal?

A

Risk of root fracture

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24
Q

What are the two main technqiues of post removal?

A
  1. Ultrasonic energy
  2. Post pulling devices
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25
Q

What type of cements make post removal more difficult? Potentially leading to periapical surgery or extraction of the tooth.

A

Adhesive resin cements (e.g. relyX, panavia etc.)

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26
Q

What are the 4 technqiues used to remove GP from root canal?

A
  1. Rotary endodontic files
  2. Ultrasonics
  3. Heat
  4. Solvents (as an adjunct to help soften GP)
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27
Q

Why should solvents never be used in retreatment cases if preparing the tooth for a post space?

A

Because you have no control over how far the solvent will permeate into the root canal system and it may compromise your apical seal.

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28
Q

Why does guttacore supersede theramfil as a carried based gutta percha for obturation?

A

It is made from cross-linked gp, this allows easier removal in retreatment cases.

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29
Q

Why are endodontic pastes no longer recommend in most countries?

A

Due to shrinkage and poor seal made from toxic materials. Often contains parafomaldehyde which is mutagenic and carcinogenic.

Can cause permanent nerve paresthesia.

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30
Q

State the 5 causes of persistent periapical radiolucencies in endodontically treated teeth.

A
  1. Intraradicular infection
  2. Extra radicular infection
  3. Foreign body reaction
  4. True cyst
  5. Fibrous scar tissue
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31
Q

True or false, periradicular lesions can be differentially diagnosed as cystic or non-cystic based on conventional radiographs.

A

False

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32
Q

What is the only possible way to differentially diagnose a periradicular lesion as cystic or non-cystic?

A

By histopathological investigation

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33
Q

What are the two categories of periradicular cyst?

A

True cyst and pocket cyst

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34
Q

Define a true cyst.

A

Cavities completely enclosed in an epithelial lining

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35
Q

Define a pocket cyst.

A

Epithelium-lined cavities that are open to the root canal

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36
Q

What are the 4 indications for periradicular surgery?

A
  1. Failure of previous endodontic treatment where re-treatment is not possible or will not correct the problem.
  2. Anatomical deviations which prevent complete cleaning and obturation
  3. Procedural errors (e.g. ledges,blocks, perforations)
  4. Exploratory surgery for identification of root fractures
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37
Q

What are 7 contraindications of periradicular surgery?

A
  1. Proximity to neurovascular bundle
  2. Thick cortical bone
  3. Difficult to access
  4. Inadequate periodontal support
  5. Non-restorable tooth
  6. Medical history (e.g. blood disorders, recent MI, cancer treatment)
  7. Poor skill and ability of surgeon
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38
Q

State the “triad of endodontic microsurgery”.

A
  1. Magnification
  2. Illumination
  3. Instruments
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39
Q

State 3 types of pre-operative medications patients are advised to take prior to periradicular surgery.

A
  1. Anti-inflammatory agents (ibuprofen 600mg immediately before surgery)
  2. Anti-bacterial rinses (0.2% Chlorohexidine the night before, morning of and 30 mins before appointment)
  3. Premedication (5mg diazepam if very nervous)
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40
Q

Why would in be in the patients best interest to take 600mg ibuprofen immediately before surgery?

A

Because ibuprofen inhibits cyclo-oxygenase, preventing the formation of inflammatory mediators (reduce post op pain)

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41
Q

What are the two main purposes of anaesthesia during periradicular surgery?

A
  1. Prevents pain during surgery
  2. Obtains presurgical haemostasis
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42
Q

In flap design, what are the 6 rules to follow to allow a safe procedure and good wound healing?

A
  1. Flap must never cross bony defect
  2. Relieving incisions should be over concave bone surfaces not conveys bone eminences
  3. End of vertical incision at gingival crest should finish at the mesial or distal line angles and curve so that the incision meets the free gingival margin 90 degrees to gingival contour
  4. The base of flap must as wide as its free edge
  5. The periosteum must be raised with the flap
  6. The retraction must rest on bone and not soft tissue
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43
Q

What are the two types of flap design that can be used for periradicular surgery?

A
  1. full mucoperiosteal flap
  2. Papilla based incison
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44
Q

What is the advantage of a papilla based incision flap design?

A

Prevents gingival recession

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45
Q

Define an osteotomy.

A

Removal of cortical plate to expose root end.

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46
Q

What is used as a preoperative measure to ensure haemostasis?

A

Local anaesthetic

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47
Q

What is used most commonly as an intra-operative topical haemostatic agent?

A

Epinephrine pellets

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48
Q

Describe the process of resectioning a root end.

A

3mm is resected perpendicular to long axis of tooth at low magnification.

49
Q

Describe the 4 steps to using ultrasonic in root end preparation.

A
  1. Carried out under medium magnification
  2. Correctly select tip and position at apex
  3. Apical preparation is prepared with copious amounts of coolant to a depth of 3mm
  4. Prepared cavity is inspected with a micro mirror at high magnification
50
Q

What are the disadvantages of using amalgam as a sealing material in periradicular surgery?

A
  1. Sets slowly
  2. Cytotoxic (mercury, cooper, zinc)
  3. Leakage
  4. Corrosion and staining
51
Q

Name two zinc oxide euganol cements that could be used as sealing materials for periradicular surgery.

A
  1. Intermediate restorative material (IRM)
  2. Super ethocybenzoic acid
52
Q

Which material supersedes other materials as a sealing material for periradicular surgery, due to its biocompatibility, sealing ability and dimensional stability?

A

MTA

53
Q

What are the complications that can arise from periradicular surgery? And which the patient should be informed of prior to commencing treatment.

A
  1. Post-operative pain
  2. swelling
  3. Ecchymosis (bruising)
  4. Parasthesia
  5. serious infection
  6. Lacerations
  7. Maxillary sinus perforations
54
Q

Why is it advantageous to apply intermittent application of cold dressing to an area of swelling after surgery? Give two reasons.

A
  1. Slows the blood flow
  2. Stimulates intra vascular clotting
55
Q

What causes ecchymosis (brushing)?

A

Extravasation and breakdown of blood in the subcutaneous tissues

56
Q

How long should it take normal sensation to return after a transient period of paraesthesia?

A

4 weeks

57
Q

Define,

‘a physiological and pathological event mainly occurring due to the action of activated clast cells, and characterised by the transitory or progressive loss of cementum or cementum/dentine’

A

Resorption

58
Q

What is the onset of resorption associated with?

A

Significant necrosis of cementoblasts and/or injury to the PDL

59
Q

During resorption, how are cementoblasts destroyed?

A

Directly or become necrotic as a result of comprimised blood supply to PDL or pulp

60
Q

What are the two phases required for resorption to occur?

A

Injury and stimulation

61
Q

Why is constant stimulation required in the resorption process?

A

Without constant stimulation the resorption process is transient and self-limiting, so it will stop and healing will occur.

62
Q

The resorption process is highly complex. The activated cells (odontoclasts/ odontoblasts) initiate resorption and are located in depressions. What are these depressions known as?

A

Howships lacunae

63
Q

What role does the receptor ligand system RANKL/RANK/OPG have in the resorption process?

A

They control osteoclastic function and regulate communication between bone, vascular and immune cells.

64
Q

What is the most common cause of resorption?

A

Pulp infection

65
Q

Name 6 stimulation factors that can cause resorption of mineralised tooth tissue?

A
  1. Pulp infection
  2. Periodontal infection
  3. Orthodontic pressure
  4. Ankyloses
  5. Tumour
  6. Impacted pressure
66
Q

What is usually the cause of external inflammatory root resorption?

A

Trauma

67
Q

How is external inflammatory root resorption diagnosed?

A

Based on radiographic and CBCT interpretation

68
Q

What are the treatment options for external inflammatory root resorption?

A

Removal of necrotic pulp + Use of calcium hydroxide as an interapppointment medicament

OR

Extraction, resorption may be too advanced to treat.

69
Q

How does invasive cervical resorption occur?

A

When there is loss of protective non-mineralised layer at CEJ of tooth. This can be developmental, physical/chemical trauma.

70
Q

What are predisposing factors to invasive cervical resorption?

A
  • orthodontics
  • trauma
  • surgery
  • intracoronal bleaching
71
Q

Is invasive cervical resorption a type of external resorption or internal resorption?

A

External, however it is periodontally derived.

72
Q

What are the two main clinical signs of cervical resorption?

A
  1. Pinkish discolouration
  2. Obvious palpable defect extending sub gingivally upon probing
73
Q

what radiographic feature allows you to differentiate internal root resorption with cervical resorption?

A

Cervical: outline of pulp canal running through the middle of the radiolucent lesion

Internal: no outline of pulp canal through middle of radiolucent lesion

74
Q

What are the treatment options for invasive cervical resorption?

A
  1. Remove granulation tissue from defect using trichloracetic acid before restoring with GI, composite or bio dentine.
  2. RCT if communication with pulp canal
75
Q

Damage to what structures initiates internal root resorption?

A

Odontoblastic layer and predentine

76
Q

For internal resorption to continue, what are the conditions required within the pulp tissue apical to the lesion?

A

Mist still have a viable blood supply

77
Q

What are the treatment options for internal root resorption?

A
  1. RCT
  2. Extraction
78
Q

What specific technique for obturating is required during RCT of a canal with internal root resorption?

A

Thermoplastic techniques to obturate to specific shape of lesion

79
Q

What are clinical signs of replacement resorption?

A
  • Teeth lacking mobility
  • metallic percussive sound
  • can be infra-occluded
80
Q

What is the difference between replacement resorption and ankylosis?

A

In ankylosis, there is no loss of root dentine ad cementum, merely fusion or close proximity of the root and bone.

In replacement resorption, dentine and cementum are lost and replaced with bone.

81
Q

What are the two different ways in which files can fracture?

A

Torsional stress and cyclic fatigue

82
Q

What is meant by torsional stress?

A

Torsional stress is what happens when a tip binds against a canal wall and the coronal part of the file rotates; elastic limit of the metal is exceeded which increases plastic deformation which leads to fracture.

83
Q

What is meant by cyclic fatigue?

A

When repeated cycles of tension and compression happen during bending which can lead to fracture.

84
Q

What files are more vulnerable to torsional stress but more resistant to cyclic fatigue?

A

Fine, flexible files.

85
Q

What is considered a favourable prognosis in the instance of a compromised tooth due to fractured instrument in root canal?

A
  1. No periapical periodontitis
  2. Separated instruments in apical 1/3rd of the root
  3. Able to retrieve instrument
  4. Defect correctable with apical surgery
86
Q

What is considered a questionable prognosis in the instance of a compromised tooth due to fractured instrument in root canal?

A
  1. Instruments fractured in the coronal or mid portion of the canal and cannot be removed
  2. Patient asymptomatic
  3. No periapical periodontitis
87
Q

What is considered an unfavourable prognosis in the instance of a compromised tooth due to fractured instrument in root canal?

A
  1. The patient is symptomatic
  2. lesion persists requiring extensive procedures in order to retrieve instrument that would ultimately compromise long term survival of the tooth and surgical treatment is not an option
88
Q

What is the influence of a tooth with irreversible pulpitis on success of retrieving a separated instrument from the root canal?

A

If possible, remove or by-pass instrument.

If not possible, the retained fragment should not influence prognosis.

89
Q

If you are at the end stages of instrumenting a root canal, the canals have been disinfected and unfortunately the file breaks, what is the best management of this?

A
  1. Attempt to remove if straightforward
  2. Embed fragment in filling material if it cannot be removed
90
Q

If you are at the early stages of instrumenting a root canal, where the canals haven’t been fully disinfected and unfortunately the file breaks, what does this mean for the prognosis of the tooth? And what is the best management of this?

A

The canal beyond instrument cannot be cleaned and this may be directly responsible for failure

Management: attempt removal or bypass if possible

91
Q

What does it mean to bypass an instrument?

A

Involves inserting a small size 10 file alongisde the instrument and reach WL

92
Q

If a fractured instrument can be bypassed what should the rest of treatment involve?

A

Continue canal prep and obturation. Do not actively attempt to remove file.

93
Q

What are the 4 factors affecting prognosis of a tooth that has a fractured instrument in root canal?

A
  1. Periapical lesion
  2. Stage of canal preparation
  3. Potential weakening of root
  4. Perforation/procedural risks
94
Q

What are the three main factors influencing successful removal of fractured instrument from root canal?

A
  1. position of the file in relation to the root curvature
  2. Depth within the canal
  3. whether the file is visible using microscope
95
Q

What are the 5 main risks of removal of fractured instruments from root canals?

A
  1. Excessive removal of radicular dentine which may predispose the root to fracture
  2. Ledging
  3. Perforation
  4. Limited application in narrow and curved canals
  5. Possibility of extrusion of the fractured file
96
Q

What are the 3 techniques of removal of fractured instrument from root canal?

A
  1. Mechanical
  2. Ultrasonics
  3. Tube techniques
97
Q

Name 3 mechanical techniques that can be used to remove fractured files.

A
  1. Hedstrom file(s)
  2. Gripping devices (fine forceps)
  3. Excavators
98
Q

What is the most popular technique for removal of fractured files from root canals?

A

Ultrasonic

99
Q

What is the ultrasonic technique used to retrieve a fractured file from a root canal?

A
  1. Create straight line access to file
    1. Trephine around the file in anti-clockwise direction
    2. This will allow to to be loosened off and removed
100
Q

What is the tube system for retrieval of file from root canal system?

A
  1. Trephine around file with ultrasonic
  2. Position micro tube
  3. Engage and remove
101
Q

What is required for the tube system of retrieval to be effective?

A

Good straight line access

102
Q

What is the most modern type of technqiue commonly used for retrieval of a fractured file in a root canal?

A

Use of BTR pen, very fine lasso at end of needle which is placed around instrument, tightened and then removed alongside instrument.

103
Q

If a file fractured in a root canal, what is your legal obligation?

A

Inform the patient about the complication that has occurred, tell them:
1. possible consequences
2. Influence on success rates
3. Complications which might occur
4. Further treatment

104
Q

What is a ledge?

A

An iatrogenically created irregularity in the canal, that impedes access of the instruments to the apex.

105
Q

Where are ledge formations common?

A

On outer side of curved canals

106
Q

Name 8 causes of ledge formation within a root canal.

A
  1. Inadequate access cavity
  2. Incorrect assessment of canal curvature
  3. Failure to pre-bend ss files
  4. Using larger, stiffer ss instruments
  5. Failure to use instruments in a sequential manner
  6. Cutting on inward rather than outward stroke
  7. By-passing a fractured instrument
  8. Negotiation of calcified canal
107
Q

What is the management of ledge formation?

A
  1. establish depth a which ledge is present
  2. Coronal flaring up to F2-3 working 1-2 mm shorter
  3. Passive ultrasonic irrigation with a chelator and NaOCl
  4. Probe with pre-bent 08 ss file in watch winding and picking motions.
  5. Repeat with size 10,15 and 20 until ledge is removed
  6. Use pre-bent hand protaper files to complete preparation
108
Q

What should you do if a ledge formation has been created in a root canal and cannot be by-passed, and the patient has no symptoms?

A
  1. Prepare to ledge using copious irrigation
  2. Dress with non-setting calcium hydroxide
  3. Use a Thermoplastic technqiue for Obturation
109
Q

How are ledges prevented?

A

By creating a reproducible glide path

110
Q

How can you attempt to prevent ledge formation in very narrow or curved root canals?

A

Coronal pre-flaring may be necessary (up to S2) before full WL can be used

111
Q

What are 4 causes of root canal blockage?

A
  1. Apical patency is not confirmed and secured when WL is measured using EAL
  2. During instrumentation, pulpal tissue is packed and solidified in the apical constriction by use of instruments
  3. Instrumentation is not accompanied by copious irrigation and recapitulation
  4. Instruments are not cleaned before their insertion in the canal
112
Q

How do you tell the difference between a canal blockage and a ledge formation?

A

When a canal is blocked, there is a characteristic tactile sensation when a very small file is reaching an almost solid but penetrable “wall”, whereas when a ledge is present, the instrument hits a completely solid “wall”

113
Q

What is the management of canal blockage?

A
  1. establish depth a which blockage is present
  2. Coronal flaring up to S2 working 1-2 mm shorter
  3. Passive ultrasonic irrigation with a chelator and NaOCl
  4. Probe with pre-bent 08 ss file in watch winding and picking motions. Irrigate.
  5. Repeat with size 10,15 and 20 until ledge is removed
114
Q

When might canal blockage have a negative effect of to outcome?

A

In infected canal cases, where there is pre-existing apical periodontitis.

115
Q

What is a canal transportation?

A

Removal of canal wall structure on the outside curve in the apical half of the canal

116
Q

How does canal transportation tend to occur?

A

Tendency of ss files to restore themselves to their original linear shape during canal preparation

117
Q

What some additional consequences of canal transportation?

A
  1. Damage to the apical constriction (risk of debris extrusion)
  2. Zip formation (elliptical shape at apical endpoint)
  3. Elbow formation (narrow point at max curvature)
  4. Perforation on apical 1/3rd
  5. Strip perforation along inner side of curvature in mid/coronal 1/3rd
  6. Ledging
118
Q

What are 4 main consequences of canal transportation?

A
  1. Inadequately cleaned canals, harbouring debris and microorganisms
  2. Difficulty achieving apical seal
  3. Over-reduction of sound dentine which may leaf to reduced fracture resistance
  4. Destruction of the integrity of the root
119
Q

How can canal transportation be prevented?

A
  1. Use pre-bent flexible files to create reproducible glide path
  2. Avoid putting pressure on the outside wall of the root canal when working in the apical 3rd and into the inside wall when working in the coronal and mid 3rd
  3. Never keep a rotary file in Sam position for more than 1 second
  4. Don’t force the files down the canal
  5. Use adequate irrigation

Dentistry Module 7 (14 decks)

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