#D3/S2/W9
#Endo

Biology of the dental hard tissues and fractures

Myth vs fact

• fractures are not actually a point of weakness, rather a strategy of damage containment for tooth survival

How do teeth protect themselves

• resilent, can absorb energy before suffering complete failure
  • individual toot hstructure are brittle, but together can absorb and distribute energy before fracture
• have inbuilt mechanism to distribute and disperse forces and limit fracture propagation
  • enamel tufts and lamellae provide compliance allowing distortion of enamel, tufts provide stress shielding
• strctural integrity
  • biocomposite material - variable distribution of force
  • force distribution is not even - ansiotropic
  • fractures in teeth occur when biologic tolerance is exceeded
• stress can concentrate in different part of tooth
  • depending on where stress accumulate will determine outcome
  • can accumulate at
    • cervica lrim (NCTL, abfraction)
    • cusp tip (shovel shaped depression)
    • marginal ridge (fracture)
• fracture toughening in dentine to blunt fracture progression by deflection of fracture and distribution of stress concentration
  • 
• biomineralisation of dentine, preferable to retain pulp
  • teeth with RCT lower survival than teeth with vital puolp
  • teeth with vital pulp undergo continuing changes in mineralisation of dentine - biomineralisation
    • dentine can adapt to forces and age changes that are placed on tooth

Epidemiology of fracture

FOrces may

• be absorbed and distributed within tooth hard tissue
• result in wear of the tooth
• result in fatigue deformation and fracture
• affect pulp with traumatic hyperocclusion

Classification of fatigue fractures in teeth

Diagnostic nomenclature

• abfraction noncarious cervical lesion
• infraction
• cracked tooth
• fracture
• split tooth
• root fracture
• cracked tooth syndrome

Classify fatigue fractures based on origin

• fracture
  • broad term which means to break
  • used to define separation of hard tissue

Fatigue fractures due to stress accumulation

• enamel origin
  • enamel lamellae
  • craze line
  • crack (cracked tooth)
  • split
• dentine origin
  • cracked cusp
• cementum origin
  • vertical root fracture (root origin fracture)
  • cementodentinal tear

Acute Traumatic

• acute trauma induced crown fracture
• acute trauma induced crown - root fracture
• acute truama induced horizontal root fracture

Enamel Lamellae origin

• developmental defect
• developmental defects in surface of enamel that are visible to the naked eye
• enamel tufts and lamellae act to provide enamel compliance
• 

Craze or enamel infraction

• confined to enamel due to parafunciton or acute trauma
• 

Crack

• incomplete fracture beyond enamel
• extends usually longitudinally from enamel wall
• may or may not be symptomatic
• 
• may have associated probing defect
• 

Split

• through and through fracture
• complete separation of fragments
• begins in crown
• may be associated with periodontal probing defects
• may be longitudinal or oblique
• 

Cracked cusp

• begins in dentine under cusp
• extends laterally under one cusp extending no more than coronal 1/3 of root
• initially may be incomplete
• 
• crack becomes a split when the fracture extends through the furcation
• cracked cusp becomes a split when cracekd cusp extends beyond coronal 1/3

Usually only detect and manage coronal fractures when it becomes symptomatic

• cracked tooth syndrome
• perio defect
• tooth chipping evidence
• fracture progression
• evidence of pulpal necrosis and infection

Cracked tooth syndrome

• not a fracture type
• defined set of symptoms from vital pulp inside a tooth with a fracture in hard tissue
• may be due to cracked cusp, crack, split tooth
• how is pain felt
  • pressure change in fracture - bidirectional fluid movement in pulpodentine complex - hydrodynamic or transduction theory where odontoblastic processes have a mechanosensory role
  • direct stimulation of pulp by fracture
  • inflammation of pulp from microorganisms in fracture line
• 

Vertical root fracture

• root from RCT treated tooth is fractured
• begins in root
• rare without RCT
• 
• may have narrow isolated probing
• can confuse with endo probing, perforation, split, palatal groove
• J shaped radiolucency
• most occur 2-5 years after RCT
• many explanation
  • parafunction - the occlusion and force accumulation in the root. Inability of root filled tooth root to adapt to stress concentration with calcific change.
  • lack of coronal and cervical dentine allowing absorption of forces from direct crown limiting cusp flexure (crown helps absorb and distribute forces).
  • lack of binding effect (ferrule) limiting root flexure as well as stress distribution through the cervical of the tooth
  • method of obturation – use of SS spreader and not NiTi.
  • method of instrumentation: apical preparation size, flare, type of instrumentation
  • Width of direct post
  • type of post system
  • Over instrumentation of apical foramen causing apical crazing
  • Use of expanding amalgam in canals – Nayyar technique
  • Expanding root canal filling materials
  • Lack of proprioception of teeth with RCF
  • Loss of protective effect of pulp

Cementodentinal tear

• tear of surface cementum with resorption of overlying bone
• 

Clinical Management

treatment plan based on signs and symptoms

• differential diagnosis
  • informs risk assessment in 4 dimensions
• risk assessment prognosis
  • guide treatment plan
• treatment plan
  • details anticipated outcome

Differential diagnosis

• state of health of each tooth in 4 dimension
  • endodontic - pulpal periapical
  • strategic - stability/deterioration
  • marginal periodontal - supporting bone
  • structural - amount of tooth

Endo assessment and differential

• symptoms of CTS?
  • pain on off biting at a particualr angle
  • may respond to thermal change with allodynia and thermal hypersensitivity
    • pathognomic for coronal fatigue fracture with vital pulp normal or pulpitis
• is there pulpitis as well as classic CTS
  • thermal hypersensitivity and allodynia use pulp sensitivity test
• is there pulpal infection
  • all tooth is TTP vs CTS only one cusp responsive usually
  • no response to pulp sensibility

Strategic assessment

• bite sticks to locate fracture if CTS and vital pulp
• visual assessment (direct and indirect)
• PA radiograph may note shallow restoration in teeth with unusual pulp/periapical symptoms/signs
• fractures poorly detect in tooth on CBVT
• fracture needs to clear voxel size in width
• Voxel size = .08mm
• fracture must be atleast .15mm
• CBVT may display pattern of bone loss to indicated crack of split or VRF in tooth
• not all marginal bone loss is due to root fracture

Perio assessment

• bone loss extent

Structural assessmentt

• how much tooth remains
  • Risk assessment prognosis guides treatment plan
  • excellent
  • good
  • fair
  • borderline
  • extraction

Endodontic management

• if tooth has symptomatic CTS don't just place band or crown
  • 29% of symptomatic CTS required RCT after band placement (some had crowns placed)
  • as part of endo management need strategic assessment of extent of symptomatic coronal fracture before stabilise the cusps as fracture may be into pulp
• any fracture that extends into pulp as longitudinal crack = RCT
  • if not longitudinal coronal crack do not chase beyond gingival margin
• pulp infection or irreversible pulpitis = RCT
  • survival outcome does not change for pulp necrosis and infection
  • even 7mm probing results in 2-4 year survival
• remove resto and visual fracture
• remove fracture, is pulp exposed?
• ss if pulp not exposed and no irreversible pulpitis and restorable
• bands used for temporary restoration of teeth, not used for diagnosis

Strategic Management

• survival of RCT with longitudinal cracks
  • coronal cracks predictable treatmetn - 99% survival at 5 years
  • extension of fracture onto pulpal floor 88% survival at 5 years
• extract
  • if longitudinal fracture through furcation - split
  • if oblique fracture laterally beyond apical 1/3 - split
  • if any fracture involves a conical shaped root

Perio Management

• maintain when lateral coronal fragment of cracked cusp extends less than 1/3 into root and not involve furcation = split
• prognosis reduced when fracture associated with more than 5mm pocket
• asymptomatic coronal fracture - crack + vital pulp
  • if crack with 4-5mm probe and responsive to pulp sensitibility but not pulpitis treat with cusp coverage
• asymptomatic coronal fracture - crack + vital pulp
  • if crack and probing 4-5mm and responsive to pulp sensibility but not pulpitis treat with cusp coverage
  • no cusp coverage may result in fracture propagation

Structural management

• assess amount of remaining tooth after management of fracture especially if cusp lost
• usually place cusp overlay direct during disease control

Treatment Plan