Preformed Crowns

• What lasts longer? Stainless steel crowns, Amalgam, Composite or GIC restorations?

  Stainless Steel Crowns - 80% still in place after 5 years
• What are preformed metal crowns used for?

  ◦ No caries removal – Hall technique◦ Complete caries removal – Conventional technique◦ Following pulpotomy
• What material are preformed metal crowns made from?

  ▪ Stainless steel alloy including➢iron 65-74%➢chromium 17-19%➢nickel 3-9%
• What are the four different shapes of preformed metal crowns?

  ▪ Anatomical▪ Pre-contoured▪ Pre-trimmed▪ Crimped

  
• What are the advantages of preformed metal crowns?

  • High success rate
  • Strong and durable
  • Malleable
  • Cost-effective
  • Less technically demanding(Hall technique)
  • Single visit procedure
  • Predictable
  • No impressions
  • No lab work
• What are the disadvantages for preformed metal crowns?

  • Aesthetics
  • Allergies
  • More technically demanding (conventional technique)
  • Perceived as "difficult"
• What are indications for use of Preformed metal crowns?

  1) Molar with caries affecting multiple surfaces

  2) Rampant caries

  3) After Pulp therapy

  4) Developmental defects

  5) Restoration of worn/fractured teeth6) As a space maintainer abutment
• What are absolute contraindications for preformed metal crowns?

  Caries through floor of pulp chamber Sepsis Unsuccessful pulp therapy Close to exfoliation Known nickel allergy
• What are moderate contraindications for preformed metal crowns?

  Poorly motivated patient / parent Poor co-operation Multiple grossly carious teeth
• What is the aim of the Conventional Technique?

  To remove all infected carious tooth tissue and restore the tooth to function (Other techniques may be preferable for children due to the high risk of pulpal exposure and demanding nature of procedure for both child and clinician)
• What are the indications for use of the Conventional Technique?

  • primary molar with caries affecting multiple surfaces
  • Rampant caries
  • After pulp therapy
  • Developmental defects
  • Restoration of worn/fractured primary teeth
  • As a space maintainer abutment (NEED CHILD CO-OPERATION!)
• What equipment is used to fit preformed crowns?

  • set of preformed crowns
  • Burs - Short tapered diamond (eg. 633) Cylindrical diamond (eg. 541)
  • Crown scissors
  • Crimping pliers
  • Calipers
  • Crown / band remover
  • Floss
• What are the three steps for fitting preformed metal crowns?

  Preparation Adaptation Cementation
• What is procedure for caries removal?

  Prepare child Administer topical anaesthesia Administer LA Protect airway - rubber dam? Remove caries Ensure tooth is restorable Pulpotomy if necessary Restore with GIC
• How do you prep a tooth for a preformed metal crown?

  Occlusal reduction Reduce mesial & distal proximal surface Remove bulbosities / irregularities as necessary Round off sharp edges
• Describe how preformed metal crowns are adapted to the tooth.

  • Select a crown
  • use callipers to gauge interdental space
  • Try on tooth (lower - lingual to buccal)(upper - buccal to palatal)
  • Adjust crown as required
  • Contour - tooth shape
  • Trim - gingival margin
  • Crimp crown - at marginal edge
  • Try on tooth - aiming for tight fit
  • Remember: Trimming, contouring, crimping
• How is a preformed metal crown cemented?

  Dry tooth thoroughly Mix cement to 'clotted cream' consistency Load cement into crown Seat firmly Remove excess cement Check completed restoration

  
• What are some common problems in placing crowns?

  • CROWN WILL NOT SEAT, proximal ledge rather than knife edge finish, Solution: remove ledge (with tapered bur)
  • TOO LONG MESIO-DISTALLY, probable space loss due to tooth drift into carious site, Solution: reduce tooth buccally & lingually and choose a smaller crown OR adapt a crown by squeezing mesio-distally
• What is the Hall technique?

  A technique for managing carious primary molars with NO CARIES REMOVAL Dr Norna Hall
• How does the Hall Technique work?

  All these factors will cause a tooth to decay - Bacteria, diet, time and tooth surface

  The Hall Technique removes the tooth surface from the rest of the oral environment
• What are indications for using the Hall Crown Technique?

  • Child unable to accept conventional restoration
  • Bitewing radiographs available
  • No signs of infection - clinical / radiographic
  • Clear band of dentine
  • Class I - Non-cavitated if unable to accept sealant
  • Class I - Cavitated if unable to accept conventional restoration
  • Class II - Non-cavitated/Cavitated
• What are contraindications for using the Hall Crown Technique?

  • Irreversible pulpitis
  • Signs / symptoms of sepsis
  • Radiographic evidence of pupal involvement
  • Mobile tooth
  • Tooth close to exfoliation
  • Insufficient tooth tissue to retain crown
  • Poor co-operation - risk of endangering airway
  • Risk of IE Parent / child concerns about aesthetics
• Why are separators used?

  Where contact points between teeth are very tight Left in place for 3 days Creates space for crowns Small brightly coloured elastic bands

  
• What is the technique used when placing crowns using the Hall Technique?

  • Preparation is key
  • Ensure good understanding of child and carer
  • Allow child to handle crown
  • Get them to practice biting on CWR
  • Explain bitter taste of cement
  • Remove seps if used
  • Assess tooth shape
  • Protect the airway
  • Size the crown
  • Fill crown with luting cement |Seat crown and get child to bite down Remove excesscement

  
• Hall technique:

  • quick
  • easy to perform
  • easily tolerated: no la, prep, removal of decayed tissue
  • preferred by clinicians, children and parents
  • easy to teach
  • temp alteration of occ
  • requires careful selection
• What do we check for in a follow up after fitting a Hall Crown?

  GINGIVAL RESPONSE: No plaque accumulation if good adaptation

  FAILURE: Decementation, Occlusal wear / perforation, Signs of sepsis

  EXFOLIATION: This occurs normally