#D3/S2/W6
#Endo

Important clinician questions

• how will the complication affect prognosis
• once complication has happened, how can the impact on prognosis be minimised
• how can the complication be avoided

Perforations

Why are they a problem

• create pathway for bacteria to reach periodontium and cause an inflammatory lesion
• can be difficult to disinfect and seal
• prognosis depends on control of bacterial infection at perforation site

Size

• larger (>3mm) more likely to have pathological changes in adjacent perio tissue
  • (Tsesis 2010, Mente 2014)
• more difficult to seal
  Time
• older more likely to have established infection
• immediate repair has best prognosis
  Location
• crestal
  • risk gingival epithelial downgrowth
  • pocket formation
  • bacterial ingress maintains inflammation
  • periodontal destruction
  • 

Study

Perforation repair principles

• disinfect perforation site
• seal perforation with a material that prevents bacterial leakage
• repair material should be biocompatible and encourage regeneration of periodontal tissues

Mineral trioxide aggregate

• hydrophillic powder mixed with sterile water
  • 75% portland cement, 20% bismuth oxide, 5% gypsum
• sets after 3 hours (Torabinejad 1995)
• calcium silicate cement (calcium crystals in an insoluble silicate matrix)
• release calcium hydroxide for >3month by surface hydrolysis
• promotes alkaline pH 11 -12 for >2month
• stimulate hard tissue formation
• superior sealing ability
  • forms mineralised interficial layer of hydroxyapatite crystals when placed against dentine
  • adaptation and seal better than amalgam, zoe/irm, gic
  • seal not affected by moisture or blood
  • 
• superior biocomptaibility
  • stimulated regeneration of cementum and PDL
  • biological seal

MTA disadvantage

• perforation with communicate with oral cavity/gingival sulcus
  • slow setting time - freshly mixed MTA can wash out
  • rough granular surface, promotes subgingival plaque formation
  • RMGIC preferred
• can discolour teeth when used in cervical zone
• cost 170 / gram
• difficult to handle

Other bioactive endodontic cements

• biodentine, bioaggregate, endosequence, theracal LC
• calcium silicated based material with common bioactive properties
  • release CaOH
  • form interficial layer
  • form apatie crystals on their surface in synthetic tissue fluid
• claim to have similar MTA properties without its drawback
• few studies to support, unknown long term efficacy
• use of MTA appears to give highest success rate

Furcation perforation repair

• non-surg approach with high mag
• decontaminate perforation site
  • debride dentine walls - fine pulp burs or ultrasonics under maginification
  • passive irrigation with sodium hypochlorite
• haemostasis - trichloroacetic acid TCA
• placement of mTA (protect canal orifices)

**Prevention of perforation

• intial radiographic assessment
  • angulation of tooth
  • location/depth of pulp chamber, measure distance from occlusal surface to pulp chamber floor
• during access
  • remove all restoration
  • cut access cavity to safe depth
  • aim for any visible chamber/canal space
  • expose a radiograph with a bur to check depth/direction
• identification
  • cbct

Middle third perforations

• misdirected posts
• strip perforation caused by endo files or gates glidden drills
• repaired via non-surgical approach
• prevention
  • dentine on furcation aspect of roots can be very thin
  • mean thickness of furcal wall in mesial root 0.7mm
  • when using rotary NiTi, be aware of taper
  • aim for mod taper 4% rather than larger taper 6%

Prevention of post space perforation

• distal canal of endodontically treated mandibular molars
  • residual dentine thickness furcal wall <0.5mm in 17% of cases
  • post space with # 4GG drill caused strip perf in 7% of cases
• post space should be limited to endodontically prepared canal
• safe post space prepartion
  • immediately after root filling
  • remove GP using heated instrument (+-# 2 gg drill = 0.7mm)
  • use post drills by hand if active cutting is required

Apical third perforations

• often impossible to regain access to apical canal
• surgery required when tehse cases do not respond to conventional RCT

Clinical outcomes of perforation repair

• clinical studies show fair-good prognosis for repair of perforations using MTA in absence of periodontal pocketing
  • healing rate 80-100%
• pocketing indicates poor prognosis
• prognosis reduced by
  • inexperience operator
  • post placement after perforation repair

Minimise impact on prognosis

• microscope required to adequately manage most perforations
• referral to endodontist is usually best
• if perforation detected
  • place cavit over area as temp seal
  • sound provisional restoraiton to prevent bacterial ingress
  • inform patient
  • refer patient and phone endo in advance to discuss

Fractured instruments

How common

• hand instrument 1.6%
• rotary niti 1.0%

Aetiology of instrument fracture

• Nickel titanium
  • torsional fracture
    • tip binds while shaft continues to rotate
    • deformation precedes fracture (unwinding)
    • usually due to excessive apical pressure or inadequate glide path
    • **prevention
      • adequate glide path prior to use
      • clean file flutes regularly using endo sponge
      • avoid excess apical pressure
      • discard files that show distortion or significantly curved canal
  • flexural fracture
    • cyclic fatigue occurs when file rotates in curved canal
    • work hardening and metal fatigue leads to initiation of surface cracks
    • file breaks suddenly without distortion
    • Prevention
      • use touch retract action
      • track file usage and discard after (up to) 4 uses
      • follow manufacturer guidelines for motor speed/torque settings
      • use heat treated NiTi files
  • double curvature produce greater stress
  • fatigue accumulates quickly and fracture may occur after very short time
  • no correlation between number of uses and frequency
  • single overloading event is most common mechanism
• see Root canal mechanical instrumentation 2, rotary canal preparation methods#Aetiology of NITi instrument fracture for rest of info

Does instrument fracture reduce prognosis

• 
• Fractured instruments are a problem when they prevent cleaning and hsaping of an infected root canal
• prognosis will depend on
  • presence of a PA lesion (indicates an infection) and
  • stage of canal preparation when breakage occurs (extent to which microbial control is compromised)
• Breakage before completion of instrumentation in an infected root canal has a high risk of persistent disease
• breakage in final stages of cleaning and shaping has best prognosis

Treatment planning following instrument fracture

• bypassing broken files
  • conserves tooth structure and still permits thorough cleaning and hsaping
  • file incorporated into root filling
  • 1 in 3 broken files could be bypassed
• Instrument removal - ultrasonic technique
  • must be able to see broken file (microscope)
  • modified GG drills used to create a staging platform
  • ultrasonic tips trough around and expose the coronal part of the file
  • ultrasonic tip wedged between file and canal wall to vibrate the file loose
  • direct vision and straight line access to broke file are essential
    • when coronal part of instrument lies in straight portion of the canal, safe removal was predictable
    • instruments located around the curve could not be safely removed and attempts led to major canal damage
  • platforming removes significant amount of tooth structure
    • root fracture resistance declines the more apical the fragment
• 

Loss of working length

Ledging and blockage

• instruments cant reach working length in a previously patent canal
• ledge
  • iatrogenic gouging of the outer wall in a curved canal
• blockage
  • compacted dentine mud, pulp tissue, foreign object (resto material)
• impact on prognosis
  • prognosis is reduced when root canal is infected and cant be fully instrumented
  • teeth with apical periodontitis
    • 
• Iatrogenic errors predisposing to ledging
  • inadequate straight line access
  • straight stainless steel files in curved canals
  • incorrect length determination (short)
  • false assessment of canal direction
• ledging with rotary NiTi
  • inadequate glide path
  • held stationary while rotating
• Bypassing blocks and ledges
  • pre enlarge coronal canal
  • precurved size #08 or #10 SS handfiles (21mm length)
  • circumferential picking action to locate a catch
  • advance file using watch-winding and short amplitude
  • in-out strokes (keep file tip apical to the block)
  • establish patency (electronic apex locator)
  • circumferential short amplitude strokes to open path for precurved # 15-20 hand files before trying rotary NiTi
  • precurve master GP cone+
• when unable to bypass blocks or ledges
  • prognosis depends on
    • presence of apical periodontitis
    • distance between blockage and root apex
    • stage of instrumentation when blockage occurred
  • if disease persists, options are apical surgery or extraction (or intentional replantation)