#D3/S2/W12
#Endo

Primary endo treatment

• clear diagnosis of endodontic disease
• point along contiuum of pulp irritation leading to pulpal necrosis and extension into periapical tissues

secondary endodontic treatment / retreatment

• assessment of chaos

Causes of primary treatment failure

RCT usually fails when treatment falls short of accepted standards
failure to control an intracana lbacterial infection

• aseptic technique
• coronal leakage (caries/restorations)
• missed canals
• inadequately cleaned canals
• procedural errors (blockage, ledge, transportation, perforation)
• inadequate obturation
  persistence of disease in well treated teeth
• persisting intracanal infection (inaccessible anatomy)
• extra radicualr infection
• radicular cyst
• foreign body reaction

Retreatment case selection

Diagnosis

• can the reason for failure of the primary RCT be identified and corrected
• take CBCT
• identify additional untreated canals
• identify previous treatment complications
• exclude longitudinal tooth fracture

ROOT FRACTURE

detecting VRF in root filled teeth

• magnification
• transillumination
• isolated deep probing both sides of root
• probing + sinus tract (can be multiple)
• widened PDL along axial root wall
• bone loss pattern: vertical/crestal, lateral, frucation, J shaped, halo
• CBCT
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  Periodontal assessment
• assess for attachment apparatus damage
  restorative assessment
• eliminate pathways for bacterial ingress
• detect and assess cracks
• assess amount of remaining tooth structure
• restorative plan

Feasability of coronal access

• posts can generally be removed
• consider amount of tooth structure likely to remain after disassembly
• time/cost of dismantling and reconstruction

assess radicualr damage

• stiff instruments to straighten
• over preparation of outer wall (apically) and inner wall (middle)
• compromised cleaning and filling
• ledging, perforation, weakening
• procedural errors that alter RC morphology will affect prognosis for endo retreat
  • Gorni and gagliani 2004
  • RC altered 47% healed
  • RC respected 87% healed

Assess ability to negotiate canals

• calficiation
• blockage
• ledging
• fractured instruments

Outcomes

The toronto study (de Chevigny et al 2008)

• 4-6 year recall following NS retreatment of 229 teeth performed by supervised endo residents
• presence of pre op AP had important influence on outcome
• without ap 93% healed
• with AP 80% healed

Contemporary retreat techniques (he et al 2017)

• microscope, rotary niti, ultrasonic, irrigant activation
• 2 year recall following NS restreatment by endo resident
• 90.4% success
• during retreatment, negotiating entire canal length to patency doubled odds of success

Teeth exhibit high survival rates following endo retreatment

• Salehrabi et al 2010
• Ng et al 2011
• 4-5 year survival rate 89-95%

Disassembly techniques

Crown to remove or not

• if has defective margins of shows leakage/caries -> remove it
• PA and bitewing
• if accessing through crown, undertake internal assessment
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Removal deep core material

• magnification and illumination
• remove core material peripherally using HS burs, identify restorative dentine interface
• coarse ultrasonic tip to shatter thinned material at pulp chamber floor/orifices

Post removal

• piezon units with specialised tips at high power
• most posts can be safely removed
• negligible risk of root fracture
• can generate high temperatures
• prefabricated alloy posts
  • adequate access outline, shorten post, remove surrounding core material
  • fine US to remove bulk cemeent and open anatomic spaces
  • coarse US to vibrate post back/forth, counterclockwise
• cast postcore
  • remove surrounding core material HS burs
  • fine US to trephine and remove bulk cement
  • corase US to vibrate back forth counter clockwise
• Bonded fibre reinforced posts
  • carbon fibre, glass, quartz fibres in composite matrix bonded into canal
  • higher difficulty, requires microscope
  • drilled out as far as possible using fine hS carbide burs
  • US top to disintegrate apical part

Gutta percha removal

• preferable to avoid/minimse use of solvents
  • liquefied infected GP compacts into canal irregularities, hinders cleaning and can extrude
  • retreatment without sovlent leaves canal walls and tubules cleaner
• depends on characteristics of root filling
• quality of condensation
  • poorly compacted - bypass and engaged
    • bypass with find hand file, glide path
    • engage with hedstrom file
    • routine rotary/recip niti protocol
    • braiding technique
  • well compacted - may require solvent
    • no space available for instrument insertion
    • remove as much GP as possible by mechanical means before using solvent
    • Thermomechanical removal of coronal GP first, then apical GP removal with solvent if needed
• length of obturation
  • under extended - ledge may be present, use solvent to help avoid further ledging
  • overextended - carefully bypass and retrieve GP cone intact, avoid solvent
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Thermal injury through heat transfer using ultrasonics

• root surface temp increase > 10 degrees -> necrosis of PDL and bone
• can occur within 5 minutes
• recommended protocol
  • continuous water spray and suction, activate US for 15 second intervals
  • if removal attemp reach 10min, allow 2 min rest
  • refrigerant spray to cool post