#D3/S2/W1
#Endo

Tooth is never compromised

• options are
• restorable
  • excellent
  • good
  • fair
  • borderline
• end stage (unrestorable)

Permanent Coronal Restorative Step

Myth vs Reality

• RCT teeth are not brittle
• survival of root canal treated teeth is dependant on remaining amount of tooth

Aim

• manage coronal aspect of pulp space to maintain tooth as integral member of dental arch and oral environment

Objective of permanent coronal restorative step

• preserve RC filling to prevent coronal leakage - heal AP
• replace lost tooth substance - function
• protect and reinforce remaining tooth - tooth survival
• provide appropriate aesthetics - appearance

Risk management

• overall survival at 4 years following root canal filling is 96%
• depends on
  • endo prognosis
  • marginal perio prognosis
  • structural prognosis
  • strategic prognosis

Principles of Root Canal Material

Post/core system

• core
  • aids in replacing lost dentine inside an anatomical or prosthetic crown
  • not supported by dentine
• post
  • aids in replacing pulp space and is supported by dentine
  • connects unsupported core to surrounding dentine
  • may be direct or indirect
  • direct post may include direct placement prefabricated post DPPP
    • provides added stability to post core
    • aids in stress distribution to tooth
• together post and core work synergistically and interdependently with the remaining tooth to support both the remaining tooth substance and the prosthetic restoration
• Prosthetic crown
  • overlays anatomical crown
  • essentially replaces enamel with cusp coverage
  • may be direct or indirect

Survival of root canal treated tooth

• complex geometry of tooth and periodontium
• remaining anisotropic tooth structure
• post/core system
• crown, occlusal forces
• periodontal structures (marginal and apical)

Coronal and apical seal continuum - heal AP

• quality of restoration and root canal filling is more important than the type of restoration (including post) for healing apical periodontitis

Replace lost tooth substance - function

• occlusal management
• cusp management
• interproximal contact area

Protect and reinforce remaining tooth - tooth survival

• ensure anatomical crown protected by changing the stressed placed on anatomical crown
• protect cusps with appropriate cusp overlay to minimise cusp flexure
  • the more coronal tooth substance the less flexure
  • cusp flexure results in caries, cracked cusp, crack or split
• ensure stress distribution through crown of tooth
  • coronal stressed accumulate and are distributed through CEJ, known as
    • peripheral rim
    • peri cervical dentine
  • 
  • compression dome effect
    • distribution of compressive forced through enamel and or cornw
    • absorbed by cervical margin (pericervical dentine/ peripheral rim theory)
• importance of peri-cervical dentine
  • area roughly 4mm above alveolar bone crest and 6mm below
    • supports coronal compression of bio dome
    • acts as medium to aid in transmission of forces between occlusal aspect and roots
    • critical factor in regards to long term survival of tooth and optimum tooth function
• partial cover restoration relies mainly on compression dome complex
  • tangential forces are created into axial forces through the dentine into cervical rim
  • may be direct or indirect cusp coverage restoration
• full coverage indirect restoration
  • more pericervical dentine the better the tooth can absorb and redirect occlusal forces creating occlusal compressive axial not oblique forces
  • if an indirect full crown is present, the supragingival dentine is the ferrule
• Crown to root ratio
  • anatomic ratio - clinical average crown:root 1:2
  • clinical ratio - amount of alveolar support clinical crown to clinical root intra-alveolar 1:1.4
  • Restorative ratio - amount of unsupported core to supported post ratio, prefer about 1:1 + apical GP
  • 
  • 
• DPPP or indirect post
  • width
  • 
• no correlation between crowned root canal treated teeth and vertical root fracture

Provide appropriate aesthetics - appearance

• composite very aesthetic

Implementation of Restorative principles during RCT

Differential diagnosis

• informs risk assessment prognosis in 4 dimensions
• structural - amount of tooth
• endodontic - pulpal/periapical
• strategic - stability/deterioration
• Marginal periodontal - supporting
• 
• 
• 
• 
• Case classification part 1
  • skill experience
  • equipment available
  • instruments available
  • materials available
• case classification part 2
  • tooth risk based prognosis for each tooth
• part 3
  • summary
    • straightforward
    • advanced
    • complex
• prognosis guides treatment plan - defined by risk
  • excellent
  • good
  • fair
  • borderline
  • extraction

Risk assessment prognosis

• guides treatment plan
• **Structural assessment
  • preferred minimum
    • tooth remaining supragingival is 30% tooth substance
    • cervical rim - 2mm wide and 2mm high 2/3 around tooth
  • ideal amount
    • supragingival dentine wall more than 1/2 occlusal height, 2mm wide, 2/3 around the tooth
  • what material?
    • conserve as much cervical tooth as possible
    • partial coverage direct/indirect
      • inlay - no cusp
      • onlay - 1 or more cusp
      • overlay - all cusp
    • full coverage - indirect
  • therefore permanent coronal restoration related to
    • amount of supragingival tooth
    • need for cusp coverage
    • patient risk factors
    • terminal/catastrophic failure of tooth not more prevalent in any cusp coverage group
  • When to place DPPP
    • when 2mm thick cusp wall is less than half the height of the anatomical crown and at least 2/3 around the tooth
    • restorative core:post ratio minimum 1:1 and need apical gp
    • 
  • Choosing DPPP
    • outcome for diverse choice of DPPP is minimised when suitable supragingival coronal dentine is present
    • bonded direct placement prefabricated fibre posts do not reinforce tooth restoration complex
    • bonding of fibre DPPPP still remains a challenge
    • DPPP fibre posts may degrade in contact with fluid
  • cusps should be covered - direct or indirect
    • adjacent to lost marginal ridge
    • if a marginal ridge is less than 2mm wide
    • if height of cusp excess twice the width at the base of the cusp
    • direct cusp coverage should be at least 2mm thick
• Endodontic assessment
  • use direct resto during disease control phase while reviewing PA healing
• Strategic assessment
  • note any pre-existing fractures - coronal, radicular
  • avoid tooth fracture or restoration fracture - material synergy - direct post core restoration function initially independently of a cusp coverage indirect restoration
  • post core system may be required to support an indirect restoration in the future
  • place indirect restoration as the crown
    • may be deterioration of the direct coronal restoration or colour changes after 2 to 3 years
    • indirect for functional or aesthetic reasons
    • may need to improve interproximal contact or embrasure with indirect restoration
• Marginal Periodontal Assessment
  • after RCT ideally want 2/3 of root embedded in bone, may be an issue with crown lengthening
  • what about DME? does supracrustal tissue attachment matter?
    • after 12 months with resin and GIC subgingival restoration, no further periodontal bone loss with no progressive clinical attachment loss and negligible inflammation

Treatment plan

• details anticipated outcome
• patient centred