Restoration of Endodontically Treated Teeth

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Restoration of Endodontically Treated Teeth

• Post and Core System

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Characteristics of endodontically treated teeth

• Tooth structure loss by
• Caries, trauma, erosion, abrasion, attrition.
• Previous restorations and recurrent caries under
  restorations.
• Endodontic treatment due to removal of coronal
  and intraradicular Dentine during access and root
  canal preparation.
• Micro cracks in remaining tooth structure
  produced by endodontic procedures.
• Weakened collagen intermolecular cross-links of
  Dentine ? lower shear strength.
• Dehydration non-vital teeth have less moisture
  content than vital teeth.
• Esthetics biochemically altered Dentine modifies
  light refraction through the tooth and modifies
  its appearance.
• The combined result of these changes are
  increased fracture susceptibility and decreased
  translucency.

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Treatment planning for non-vital teeth

• Pretreatment Evaluation
• Quality of the endodontic treatment
• Periodontal condition
• Restorative evaluation
• Strategic importance
• Anatomic position of the tooth
• The amount of remaining coronal tooth structure
• The functional load on the tooth
• esthetic evaluation

• Treatment plan
• Post
• Core
• Definitive restoration

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Treatment planning for non-vital teeth

• Pretreatment Evaluation
• Quality of the endodontic treatment
• The endodontic treatment should be properly done.
  
• Retreatment should be considered if tooth
  exhibits any clinical signs of inflammation, a
  periapical pathology exists, or inappropriate
  endodontic filling material was used ( silver
  pointes).
• Periodontal condition
• This is important for long-term success of teeth.
• Weak teeth should be extracted.
• A mutilated tooth in which the restorative
  treatment would violate the junctional
  epithelium or the attachment level (e.g.
  extensive caries, perforations, external root
  resorption) should be considered for crown-
  lengthening surgery or orthodontic extrusion.
  

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• Restorative evaluation
• Strategic importance
• does the final restoration depends on this tooth
  ? Are the adjacent teeth reliable? What about an
  implant ?
• Anatomic position of the tooth
• Anterior teeth
• They receive mainly angular forces ?
  reinforcement effect of posts is doubtful.
• If the tooth is intact except for the endodontic
  access opening ? etched resin in the access is
  sufficient.
• A post and core is only indicated when the tooth
  is weakened by the presence of large or multiple
  coronal restorations or they require form or/and
  color changes that cannot be affected by
  bleaching, resin bonding or laminate veneers.
• Mandibular incisors and maxillary lateral
  incisors ? usually require a post.
• Maxillary central incisors and canines ? crown
  preparation, the remaining tooth structure, is
  accomplished before deciding a post should be
  placed.

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• Posterior teeth
• They receive mainly vertical forces.
• When there is sufficient tooth structure to
  retain a core and crown ? posts are not needed.
• Teeth which dont have occlusal interdigitation
  or have an bucco-occlusal form that preclude
  interdigitation ( e.g. Mandibular 1st premolars
  with small poorly developed lingual cusps) , with
  sufficient coronal tooth structure, ? restoration
  of the access should be acceptable.
• Teeth which have interdigitation with opposing
  teeth ? full coverage crowns or onlays should be
  used as occlusal forces push the cusps apart.
• Maxillary premolars are subjected to angular and
  vertical forces ? if the clinical crown length gt
  its cervical width a post may be indicated.

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• The amount of remaining coronal tooth structure
• More than half ? conservative treatment with
  coronal restorations without posts.
• minimal ? post, core, and definitive
  restoration.
• The functional load on the tooth
• The post, core, and crown system is indicated,
  when more extensive protective and retentive
  features are required in the restoration
• Bruxism and heavy occlusion.
• Abutment teeth for long-span fixed bridges.
• Abutment teeth for free end removable partial
  denture.

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• esthetic evaluation
• Esthetic zone (Anterior teeth, premolars, and
  often 1st molar) requires
• Careful selection of restorative materials.
• Careful handling of the tissues.
• Timely endodontic intervention to prevent
  darkening of the root as it looses vitality.

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• Treatment plan (post and core)
• The purpose of a post is to provide retention for
  a core as both laboratory and clinical data fail
  to provide definitive support for the concept
  that posts strengthen endodontically treated
  teeth.
• If the walls of the root are thin owing to
  removal of internal root caries or
  over-instrumentation during post preparation then
  a post may strengthen the tooth.
• Reinforcement of a tooth by a post means moving
  the point of fracture from the gingival margin of
  the crown some distance up the root towards the
  root apex.
• The following characteristics should be
  determined prior to beginning the clinical
  procedures
• Post length
• Post diameter
• Type of post and core that will be used
  (prefabricated post and restorative material core
  or anatomically customized cast post and core)
• Root selection in multi-rooted teeth
• Core material and definitive restoration.

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• Post Length
• It is of more importance for retention than
  diameter.
• 4 - 5 mm of gutta-percha should be retained
  apically to ensure a good seal.
• posts should be extended to that length, or
  equivalent to the crown length, in all teeth
  except molars.
• With molars, posts should not be extended more
  than 7 mm from the orifice of root canal in the
  base of the pulp chamber. Extension beyond this
  length can lead to root perforation or only very
  thin areas of remaining tooth structure.
• Posts should extend 4 mm apical to the bone crest
  to decrease stress in dentine and in the posts.

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• Post Diameter
• It is important to resist distortion or permanent
  bending under functional forces.
• Ideally, after completion of endodontic
  treatment, the canal shouldnt be further
  enlarged. Rather, the post should be modified to
  fit the canal.
• Do not exceed one-third the root diameter.
• Optimal post diameter measurements have been
  determined to be
• Mandibular incisors ? 0.6 0.7 mm
• Maxillary central incisors, canines, and the
  palatal root of the maxillary 1st molar ? 1.0
  1.2 mm may even reach 1.7 mm.
• The rest of teeth ? 0.8 mm.
• Mesial roots of mandibular molars and the buccal
  roots of maxillary molars shouldnt be used for
  posts.
• Mandibular premolars with oval or ribbon shaped
  canals shouldnt be prepared further for a post ?
  the gap is filled with luting cement which add
  elasticity to it.
• Roots with remaining dentine thickness less than
  1mm are indicated For custom made posts.
• The amount of remaining intraradicular dentine
  after endodontic treatment
• Canines, maxillary incisors, and the palatal root
  of maxillary 1st molar gt 1mm.
• All other teeth lt 1mm.

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• N.B
• Craze Lines
• Craze lines in dentin are areas of
  weakness where further crack propagation may
  result in root fracture and tooth loss.
• The patient should be informed of their
  presence. If possible, avoid post placement in
  favor of a restorative material core.
• If a post is required, it should passively fit
  the canal, and the definitive restoration should
  entirely encompass the cracked area, whenever
  possible, by forming a ferrule.

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• Type of post
• Acc. to type of material
• Metallic.
• Non-metallic
• Carbon fiber posts composed of unidirectional
  carbon fibers in an epoxy matrix. Esthetic
  version contains quartz. It is smooth, rigid,
  highly radiopaque, and can be removed.
• Ceramic posts composed of zirconium dioxide. It
  is hard and can withstand high flexural stresses.
• Fiber-reinforced posts composed of woven
  polyethylene fiber ribbon that is coated with a
  dentine bonding agent and packed into the canal,
  when it is light cured. It is esthetic, smooth,
  less stiff, reduce incidence of root fracture,
  and less radiopaque.
• Excessive retention of zirconia (ceramic) posts
  may preclude conventional endodontic retreatment
  if cannot be removed atraumatically.
• Carbon fiber and Fiber-reinforced posts may not
  need to be as long as traditional posts. A 11
  ratio between the post and the crown is
  sufficient.

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• In laboratory tests metallic posts are more
  fracture resistant than carbon fiber posts.
• Most metal, carbon fiber, and ceramic posts
  chemically bond to resin cement.
• Stainless steel posts are more retentive to
  composite cores than carbon fiber posts.
• Carbon fiber and Fiber-reinforced posts have a
  lower modulus of elasticity than metal posts and
  are considered to have elasticity similar to
  dentine, this provide more force dissipation,
  reducing the risk of root fracture.
• Stainless steel contains nickel which may cause
  allergy. Non-metallic posts are highly
  biocompatible.
• Prefabricated Stainless steel posts may show
  corrosion. Custom-cast and non-metallic posts
  dont show corrosion.

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• Acc. to retention
• Active include many designs (e.g. threaded,
  split threaded). they produce high stresses which
  increase the potential for vertical fracture.
  They should be unscrewed one fourth of a turn
  after installation. Split threaded posts even
  produces higher stresses. Active posts are
  indicated in short canals.
• Passive it is cemented to the root canal using
  zinc phosphate, glass ionomer, or a resin cement.
  Resin modified glass ionomer is not indicated as
  hygroscopic expansion may cause root fracture.
  Low expansion formulations of resin modified
  glass ionomer can be used.
• Acc. to fabrication
• Pre-fabricated post
• tapered smooth, se , or threaded.
• parallel smooth, se , or threaded
• Custom-cast post
• indicated in
• Non-rounded root canals.
• Extremely divergent sidewalls of root canals.

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• Tapered smooth posts are the least retentive. And
  may cause wedging effect on the tooth.
• Tapered threaded posts are more retentive than
  parallel threaded.
• Parallel posts distribute stresses less evenly
  and cause apical stress concentration.
• Tapered posts cause post-core junction stress
  concentration and equal stress distribution
  between the cementoenamel junction and the apex.
  So , it should be considered for teeth that have
  thin apex.
• Tapered posts require no further canal
  preparation after endodontic treatment as it can
  be modified to fit into the canal. So, it can be
  used in thin fragile roots.
• Venting and surface roughness are important
  features which should be added to custom-cast
  posts.

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• Root selection in multi-rooted teeth
• posts are best placed in (the primary roots) in
  palatal roots of maxillary molars distal roots of
  mandibular molars, they are the. The buccal roots
  of maxillary molars and the mesial root of
  mandibular molars should be avoided if at all
  possible. If these roots must be used in addition
  to the primary roots, then the post length should
  be short (3 to 4 mm) and a small-diameter
  instrument should be used (no larger than a No. 2
  Peeso instrument, which is 1.0 mm in diameter).
• Use cast interlocking post
• It is two pieces, characterized by
  depressions parallel to the sidewalls of other
  canal. The distal post is put first then the
  other will interlock with it finally.

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Technical procedure for prefabricated posts
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Pattern construction of custom-cast post

• Direct method
• Material
• Wax.
• Self cure A.R.
• Plastic ready-made burn out post.
• Steps
• 1. Lubrication of root canal (die lubricant).
• 2. If direct wax pattern
• 1) Select a metallic sprue former
• - Fits loosely inside R.C.
• - Length gt than that of core.
• - Serrated using diamond stone or disc (to ensure
  good retention bet. wax sprue).
• 2) Softening of blue casting wax and insertion
  into the R.C.
• 3) Heating of sprue.
• 4) Wait till hardening of wax.
• 5) Add for any deficiencies until its removed
  with slight resistance snugly fit.
• 6) Core can be made of wax, followed by investing
  and casting.

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• 3. If direct A.R. pattern
• 1) Select a plastic dowel
• - Fits loosely inside R.C
• - Long.
• - Serrated (notched).
• 2) Mixing of A.R. and insertion into the R.C.
  before the dough stage.
• 3) Before complete curing, moisten the dowel with
  monomer and insert into R.C.
• 4) Also before complete curing, move the plastic
  dowel inward and outwards to prevent interlocking
  in any undercuts or roughness.
• 5) Add any modifications until its removed with
  slight resistance snugly fit.
• 6) Investing and casting.
• 4. Plastic ready made burnout post
• 1) Plastic posts supplied with its special drills
  (same size shape).
• 2) Prepare root canal.
• 3) Build up core with wax or acrylic resin.
• 4) Investing and casting.

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• Indirect method
• Steps
• 1. Impression
• - By light body elastomer applied by a syringe,
  starting from apex.
• - Insert an st.steel wire to 1- support imp.
  Material.
• 
  2- prevent imp. tearing during removal.
• - Use a (Cu band) or (tray) to complete
  impression procedures.
• - Remove the impression and evaluate it, then
  pour a stone cast.

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Thank you