ENDODONTICS

Question 1

Briefly describe the chemical reaction of MTA and what are its ideal characteristics?

Answer 1

o Chemical reaction:
 MTA + Sterile water = Slurry form
 Ions (Ca dominates) reacts with PO4 ions to form HA
 Firm binding of MTA to surrounding dentine

Characteristics:
Superior sealing → Homogenous interfacial layer of HA with dentine (> amalgam, IRM and GIC)
Biocompatible → Minimal cytotoxicity and pulp irritation
Bioactivity → Promotes regeneration and remineralisation of hard tissues (PDL, cementum and bone-like material)
Clinical applications:

Question 2

Which of the following is true regarding MTA vs Biodentine?
A) Biodentine is the gold standard bioceramic in endodontics
B) MTA has easier handling qualities than biodentine
C) MTA creates a thicker interfacial layer
D) Biodentine creates a more homogenous interfacial layer

Answer 2

C is true

A) False - MTA is the gold standard
B) False - MTA has difficult handling qualities
D) False - MTA has more homogenous interfacial layer

Question 3

What is the application process of sodium hypochlorite vs EDTA?

Answer 3

Sodium hypochlorite
o Apply 2-5mL between each instrument
o Rinse after instrumentation complete to remove chelating agent

EDTA
Application: Apply 5-10mL after instrumentation complete for 1 minute (DO NOT exceed 10mins) → Rinse off with NaOCl

Question 4

CaOH and Chlorhexidine
- What type of microbes are they effective against
- What are their indications

Answer 4

CaOH
- Effective against gram negative anaerobes
- Indications
> Primary root canal infection
> Liner material
> Ext inflammatory root resorption

Chlorhexidine
- Effective against gram + anaerobes
- Indications: persistent root canal treatments/retreatment

Question 5

What are the components of ledermix and odontopaste? What is the duration of the medication?

Answer 5

Ledermix
• Components:
o Tetracycline antibiotic = Demeclocycline
o Corticosteroid = Triamcinolone acetonide
• Duration of medication = 3 – 7 days

Odontopaste
• Components:
o Clindamycin antibiotic
o Corticosteroid = Triamcinolone acetonide
• Duration of medication = 3 – 7 days

Question 6

List 10 factors to consider when referring to endodontist.

Answer 6

• Patient considerations
o ASA Class
o Anxious/Uncooperative
o Small mouth opening
o Gag reflex
o Severe pain or swelling

• Clinician factors
o Lack of appropriate instruments
o Lack of experience in difficult case
o Unable to localise pain and therefore definitive diagnosis

• Tooth factors
o Radiographic difficulties – difficulty obtaining/interpreting radiographs (e.g. area of superimposition)
o Position in arch
 2nd or 3rd molar
 Extreme inclination
 Extreme rotation
o Crown morphology
 Full coverage restoration
 Bridger abutment
 Deviation from normal root form (e.g. taurodontism, microdens, fusion)
 Significant loss of tooth structure
o Canal/Root morphology
 Significant canal curvature (e.g. S shaped)
 Open apex >1.5mm in diameter
 Canal divides in middle or apical third
 Specific teeth
• Mandibular premolar or anterior with two roots
• Maxillary premolar with three roots
 Large roots
 Long roots >25mm
 Canals not visible on x-ray
 Extensive apical resorption
 Internal or external resorption

• Trauma history
o Complicated crown fracture of mature or immature teeth
o Horizontal root fractures
o Subluxation
o Avulsions

• Endodontic history
o Previous access with complications (e.g. perforation, ledge, separated instrument)

• Periodontal history
o Concurrent severe periodontal disease
o Cracked teeth with periodontal complications
o Endo-perio lesions

Question 7

List 5 reasons for post treatment endodontic disease.

Answer 7

 Iatrogenic procedure errors/complications
• Perforations, ledges, transportations
• Fractured files
• Untreated canals
 Poor chemo mechanical and obturation techniques
• Inadequate canal debridement
• Inadequate root filling
 Coronal leakage
• Fractured restoration
• Retained cotton pellets
• Delay in placement of permanent restoration

Question 8

Factors that influence success of endodontics - preoperative, intraoperative and postoperative?

Answer 8

Preoperative
Age: ↑ Age = ↓ Healing rate
Symptoms
Presence of periapical lesion and size: ↑ Size = ↓ Prognosis
Tooth factors: canal morphology, isthmus
Pulpal status: Vital > necrotic
Systemic health

Intraoperative
Tooth factors: 
- Iatrogenic damage
- Loss of structure in access
- Apical enlargement
- Excessive tapering
Mechanical and chemical debridement 
Correct taper 
Rubber dam
Medicaments
Irrigation
Quality of root filling
Number of treatment sessions
Complications

Postoperative
Tooth factors: 
Loss of coronal seal
Position of tooth and functioning 
Quality of root filling
Restoration type

Question 9

What tooth factors would make you consider referral to endodontist?

Answer 9

o Radiographic difficulties – difficulty obtaining/interpreting radiographs (e.g. area of superimposition)
o Position in arch
 2nd or 3rd molar
 Extreme inclination
 Extreme rotation
o Crown morphology
 Full coverage restoration
 Bridge abutment
 Deviation from normal root form (e.g. taurodontism, microdens, fusion)
 Significant loss of tooth structure
o Canal/Root morphology
 Significant canal curvature (e.g. S shaped)
 Open apex >1.5mm in diameter
 Canal divides in middle or apical third
 Specific teeth
• Mandibular premolar or anterior with two roots
• Maxillary premolar with three roots
 Large roots
 Long roots >25mm
 Canals not visible on x-ray
 Extensive apical resorption
 Internal or external resorption

Other considerations:
- Previous treatment
- Endo-perio lesion
- Hx of trauma

Question 10

When should surgical endodontics be carried out?

Answer 10

• Endodontic surgery: only appropriate when lesions of endodontic origin have not healed following orthograde RCT
o Inability to fully debride infected root canal – e.g. severe root curvature, blockages (fractured instrument etc)
o Some perforations which inhibit optimal disinfection and sealing of the canal from an orthograde approach
o Non healing (refractory) lesions
o Persistent symptomatic cases

Question 11

Why are NiTi files preferred?

Answer 11

o Flexible = Prevents overpreparation and transportation
o Permits greater taper
o Predictable shape during obturation

Question 12

Mechanism of external inflammatory root resorption?

Answer 12

1. Mechanical injury/bacterial contamination
2. Macrophages from intact PDL remove debris = Resorption cavity and intermediate cementum layer penetrated with exposure of dentinal tubules and infected pulp
3. Bacteria colonise pulp and release toxins → Travel through tubules to PDL
4. Osteoclasts stimulated on root surface = Inflammatory root resorption