#D3/S2/W1
#Endo
AIm of access cavity

• provide access to root canal system

issues that result from good access

• root perforation
• ledge formation
• instrument breakage
• inadequate cleaning of root canal system
• incorrect shape of completed canal preparation

Issue with access

• most common
  • making it too small
• most critical
  • wrong place -> may lead to perforation

Steps of access

• case assessment
• tooth iso
• change gloves
• open RCT kit
• initial prep
• place interim restoration
• re-access tooth

Pre-operative assessment

• preop radiogrpah PA or CBCT
• consider
  • size of chamber
  • angulation
  • long axis of tooth and roots
  • anatomical landmarks
  • roof of pulpchamber at gingival margin
  • floor of chamber at alveolar crest
• remove caries, defective restoration and assess fracture prior to access cavity prep
• 

Isolation

• best to isolate multiple teeth for better orientation
• use caulking agent to seal dental dam (poli-grip)

Interim restoration

function of provisional restoration

• prevent contamination either from lateral or occlusal areas
• provide structural support to the tooth to prevent fracture

temporary restoration

• create seal for canals in access cavity and usually made in an interim restoration
• seal medication between visits

Interim

• GIC generally not used for marginal ridge, does not have good shear strength
• use SS band if marginal ridge is missing
• SS band is difficult to place when opposite marginal ridge is intact, use composite resin with appropriate cusp overlay

Re access

access cavity outline form

• how large?
  • traditional access occupies about 1/3 of access surface to avoid perforation or missing canals
• may have to be extended to allow straight line access resulting in an unstrained instrument approach to the apical foramen
• compromise straight line access for incisors (dont include incisal edge)

importance of straight line access

• permits access to apical third of root canal
• ensure maximum debridement
• prevent instrument flexure and separation
• provide smooth freeway for consistent and passive placement of instruments into canal orifice

Lower molar and premolar

• straightline access may be difficult, will need to remove lingual shelf of dentine
  • access initially perpendicular to enamel with high speed bur
  • when through enamel 2 bur widths straight up perpendicular to long axis of the tooth
• 

Pulp Calcification

• secondary dentine is white
• mantle dentine is grey
• tertiary dentine is brown with central white dot of canal

Access to pay attention to

Maxilla

• central - triangle and remove palatal shoulder

• lateral - oval to triangular depending on pulp horns and removal palatal shoulder

• canine - oval but check for pulp horns, remove palatal shoulder
  

• premolar - oval
  

  • 1st premolar
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2nd premolar
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• Maxillary molar - rhomboid/trapezoid toward mesial of occlusal to avoid oblique ridge
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• transverse ridge - buccal and lingual triangular ridge join
• oblique ridge - prominent ridge connect MP and DB cusp
• may need to encroach oblique ridge
  
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Mandibular teeth

Central

• oval or triangular if pulp horns
• not through incisal edge unless severely worn or difficult to restore and remove lingual shoulder to access lingual canal
• younger patient with pulp horns may be triangular
• as pulp recedes only need oval shape access

Lateral

• same as central

Canine

• same as central

Premolar

• round to oval to expose canal variation
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Molar

• mesial slightly to buccal
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Convenience form

• removes impediments to provide access to canal orifice - locate canals
• remove pulp chamber roof and overhanging dentine
• remove coronal pulp contents that may
  • contaminate RC prep
  • cause coronal discolouration
• step 2 of root canal freeway
• provide direct access to apical foramen
• allow effective cleaning and shaping of RC system
• adequate obturation of root canal system
• 

Mandibular molar

• 15% have mid-mesial canal
• C shaped canals in mandibular molar teeth (variation)
• extra MB root - radix paramolaris
• extra DL root - radix entomolaris

Summary rules for access

• the tooth will be devitalised anyways, water not necessary on drill and without can improve visiblity
• Through enamel use .010 bur for anterior and premolars.
• Use .014 for molars
• Through dentine when can’t see bur tip use
  .009 or .010 pulp bur for anterior and premolars. Use .014 for molars – water not necessary
• Use diamond and water for porcelain
• Know outline form access shapes to remove pulp horns roof of coronal pulp chamber and locate canals – create notches
• Know canal variations
• Know invaginations of roots
• Prepare adequate temporary and interim restoration