What is the most common cause of failure of root canal treatment?

• Intracanal microrganisms
• Missed canals
• Inaccessible canals due to perforations
• Ledges
• Fractured files/silver points

Management of fractured instruments

• Inform the patient
• Take radiographs to document situation
• If visible and in coronal canal it may be removable
• If in middle bypass using small files
• If at apex accept or bypass
• Prognosis depends on when file fractured

Causes of fractured instruments

• Cyclic fatigue is The file rotates freely but undergoes tension and compression until fatigue occurs
• Torsional failure is when the file becomes locked in the canal but continues to rotate

How to avoid fracturing files

• Always establish a good glide path-slide size 10
• Lubricate canal with irrigants
• Watch for loaded files
• Attend rotary courses to get used to systems

Symptoms of hypochlorite accident

• Pain whilst irrigating
• Burning pain
• Instantaneous swelling may spread
• Bleeding from the canal
• Patient may taste irrigant if in sinus
• Anaesthesia or paresthesia

Treatment of hypochlorite accident

• Irrigate with saline
• Pain control via local anaesthesia and analgesics (NSAIDs preferable 600mg ibuprofen 4 times a day 1-2 days)
• Cold compresses
• After one day irrigation with warm water to encourage blood supply to increase
• Recall 1 day, 3 days, 1 week (since incident)

Why are perforations a problem?

• Removes further hard tissue which means the fracture resistance of the tooth is decreased
• Creates a defect which bacteria in the gingival sulcus can colonise and cause periodontal disease
• Creates another portal of exit for bacterial products
• Creates a defect which allows the diffusion of fluid back into the canal to supply nutrients to bacteria
• Creates a defect that means sodium hypochlorite can enter the tissues and potentially cause a hypochlorite accident

How to avoid perforation

• Magnification 3X loupes minimum & light
• Preop assessment- using bur next to PA
• Use orifice openers with non cutting tips
• Microdebriders size 10 06 taper or 04 taper (file on a stick)

Treatment of pulpally involved cracked teeth

• Check for periodontal defects
• Access of canals
• Visualise fracture
• Visualise extent
• The crown margin must be able to be placed well below the fracture line
• The lower second molars are the most commonly cracked teeth as this tooth is closest to TMJ and W shaped fissure pattern

Prevention of cracked tooth syndrome

• Patients have teeth together for 10 mins a day in normal function!
• Those that have cracked tooth syndrome usually have a parafunctional habit
• Identify patients at risk
• Assess quality and number of previous restorations
• Provide education (stress and diet) cuspal coverage and or splint therapy

General Dental