12 Restoration of RCT and Periodontally Weakened Teeth 2009

8/12/2019 12 Restoration of RCT and Periodontally Weakened Teeth 2009

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Restoration of ndodonticallyTreated Teeth

Donna N. Deines, DDS, MSFixed Prosthodontics

Sources: Shillingburg et. al.Rosenstielet. al.

Post-Core (Dowel or Dowel-Core)

A post which fits within the canal and retains thecore, which replaces the missing coronal toothstructure.

Does not reinforce endodontically treated teeth. RCT should be gutta percha

Cast Post-Core / Custom Dowel

Custom cast post-core (dowel) Pre-fabricated Post-Core Treatment Planning: Assure Restorability

Remove all caries (before RCT) Assess adequate tooth structure. Determine periodontal health / lack of mobility Determine need for crown lengthening or

extrusion.

Treatment Planning: Restorability

Caries extent to bone level - consider C:R aftercrown lengthening

Evaluate bite-wing radiograph as well as PA Option for FPD or implant replacement

Role of tooth in restorative treatment

Usefulness for effective occlusion Abutment for prosthesis Esthetics Could the tooth be more effectively be replaced?

FPD or implant

Treatment Planning:Determine success of endodontic treatment

Asymptomatic Well-filled

Good apical seal No evidence of pathology


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Poor RCT Fill or Apical Seal:Re-treatment

Treatment Planning

Long-standing temporary filling Recurrent caries Non-restorability Contamination of RCT Re-treatment

Evidence of Pathology

Fractured root Periapical lesion Draining fistula Pain, mobility Isolated deep pocket

Root Resorption Considerations for Anterior Teeth

Intact moderate-size anterior: Bleach and composite resin Porcelain laminate veneer (fx tooth, discoloration) No post will weaken tooth

Anterior Teeth

Extensive coronal destruction Post-core necessary to provide crown retention Resists horizontal dislodging forces

Posterior Teeth

Greater loading vertical fracture Cuspal coverage always recommended .

Full crown with high fracture risk

Large circumference : post not necessary for lateralresistance just retention of core.

Pulp chamber retention / pre-fabricated post / pin-retention dependent on tooth structure.

Amalgam or composite resin

Molars

If a post is needed:

Palatal root of maxillary molars Distal root of mandibular molars (Buccal roots of maxillary and mesial roots of

mandibular molars small, concavities, curvature)


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Premolars

Use post/core only if roots are long, bulky, straight Use post if abutment / lateral stress / height:CEJ

diameter is great. Minimum 2mm axial wall covered by crown (ferrule

effect).

General ConsiderationsCast or Prefab PC / Pin/pulp chamber retention Thickness of tooth

structure surroundingcanal

Bulk / height of remainingcoronal tooth structure

Diameter / morphology ofroot

Bone support Role in final restorative

plan

General considerations :

RCT tooth as abutment for 1-pontic FPD RCT generally not indicated for free-end

RPD abutment. (esp. premolars)

Preparation of clinical crown

Conserve tooth structure Smooth sharp angles in cast post preps to minimize

cementation stress & casting accuracy.

Ferrule Effect Ferrule Effect

Encirclement of vertical axial wall to protectagainst fracture by counteracting spreadingforces generated by the post. Crown margin must be placed on solid tooth structure

or risk root fracture.

Ferrule Effect Anti-rotation

Pins, keyways, or remaining tooth structure. Peripheral distribution of retention and resistance

features of core enhance resistance of restoration.

Anti-rotation features


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Anti-rotation features

2 posts;Oval shape of pulpchamber;remaining toothstructure .

Canal Preparation

Rubber dam isolation: asepsis; protection Remove gutta percha and prepare canal in separate

procedures. Ideal time to make post space is immediately after

obturation.

Post-Core Considerations

Make post-core separately from final preparation. Marginal adaptation and fit Facilitates replacement of crown Facilitates FPD abutment preparation

Retention form of posts: geometry

Serrated Smooth - Threaded

Embedment: Post LengthRetention: 2/3 length of root (embedded in bone) andat least the length of clinical crown

Post Length

Post Embedment

Fracture resistanceFracture resistance ::Post length should extend to at least the distanceof which the root is supported in bone.

Threaded post / inadequate lengthof post fractured root

Post Embedment

Leave 4-5 mm apical seal Without endangering root thickness

1/3 diameter of root at its narrowest 1 mm surround of sound dentin at mid-root and beyond


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A cylindrical post with near perforationof mesial aspect of distal canal

Forces are directed outward along length of post Root fractures often caused by;

Too short a post Too large diameter

Safe removal of gutta percha

Peeso reamer Round bur

TwistdrillHeat Carrier - yes

Cutting instruments NO!

Perforations can be caused by anycutting instrument

Perforation of palatal root maxillary molar

Improper angulation from access preparation. Facial curvature hidden on radiograph.

Remove little if any additional dentinbeyond what is needed to perform the RCT

General guidelines for post design:

Conserve: remove little if any additional dentinbeyond what is needed to perform the RCT

Retain a minimum of 4-5 mm gutta-percha apically.

An adequate ferrule of minimum 2 mm verticalheight and 1 mm dentin thickness. Use a post designed to incorporate mechanical

features that resist rotational forces. Post length: place the post to extend apical to the

crest of the bone at least = height of clinical crown.

Modification of a cylindrical post


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Modification of post space by adding corematerial or casting to cylindrical post

Cast Post-Core Advantages:

Preservation of tooth structure(post fits space)

Anti-rotation properties Core retention (inherent part of

post)

Disadvantages: # of appointments necessary Decreased retention of tapering

design Wedging effect on root ????(If no flat root face vertical stop)

Cylindrical Pre-fabricated Post-Core

Advantages:

Increased retention w/in root Ease of placement

Disadvantages: Enlargement of canal for

post at apex for fit Core retention to post can

be problem Potential for rotation

Cast post-core using cylindrical serrated post Technique: Pre-fabricated Post-Core

1. Measure canal length2. Remove gutta percha (heat carrier)3. Enlarge canal (Peeso reamer)4. Drill post hole (twist-drill)

Pre-fabricated Post-Core

Fit the post; correct length; x-ray Note post #11 is not fully seated due to coronal contact

Place anti-rotation features, if necessary(grooves, pins)

Vlock Post Retentive Head

Active threaded design or Passive serrated design(threaded design root fracture)

Post Cementation

Etch; wash; dry (air and paper points) Coat post with cement Spin cement into canal with Lentulo spiral (ZnPO4) Seat using slow, finger pressure only

Pre-fabricated Post Composite Core


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Pre-Fabricated Post Composite Core

Resin must presentcontrast in posterior teeth.

Retentive headrequires resin core.

Pre-fabricated Post Amalgam Core

Place matrix band and condense amalgam;Leave slightly out of occlusion.

Cast Post-Core: Preparation

Internal walls must diverge (noundercut).No sharp internal angles.

Cast Post-Core: Pattern

Plastic post pattern fitted to lubricated canal withDuralay resin.

Coronal portion added w/ second mix of resin. Resin core shaped to crown preparation.

Cast Post-Core: pattern cast in gold

Resin pattern is invested and cast (type III gold). Vent is cut with inverted cone bur. Cementation complete crown preparation.

Provisional restoration for cast post-core

Internal wireor temporarypost Provisional crown

matrix combinesacrylic resin withpost.

Post Materials Cast metal (Type III gold; Au-Pd) Stainless steel Titanium

Ceramic / zirconium Fiber (carbon / quartz) / composite

Cast metal core to pre-fab post Pressed ceramic to ceramic post

Metal Dowel darkened root

Root discoloration oftencaused by internal debris,corrosion or microleakage.

Translucent posts: Ceramic / Composite Resin


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Ceramic post composite coreResin cementation of post

Ceramic Post - Composite CoreTranslucent post-core with all-ceramic crown

Reinforced Composite Resin Post

Modulus of elasticity same as dentin Post will not cause root fracture Fatigue causes fiber / composite breakdown and post

fracture Use only when well-supported by sound tooth

structure and lack of heavy lateral forces.

Inadequate post depth & retentionDissimilar metals - corrosion

Brass post amalgam core -corrosion

Short post in facial canal. Amalgam condensed into lingual canal(fractured).

Cast post-core:Retention / resistance from both canals.

(long post facial / short lingual)Contiguous metal structure resistsfracture.

Orthodontic and periodontal adjuncts torestoring damaged teeth

Regaining interproximal space Extrusion

Crown lengthening with osseouscorrection Root resection

Long-standing carious lesion on proximalsurface: migration of adjacent tooth

Orthodontic movement to create space


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Orthodontic movement

Core restoration placedand prepared for fullcrown.

Acrylic provisional crownis cemented.

Elastic orthodonticseparator is placed.


0.6 mm ligature wirewrapped aroundcontact and tightened.

Check / tighten at 1-week intervals

Adjust occlusion Add contact to

provisional crown


Adjust occlusion as

tooth is tipped. Surgical crown

lengthening mayalso be necessary.

Full crown is placed .

Extensive loss of tooth structure

Tooth structure lost to level of alveolar crestdoes not allow ferrule effect of crown toprotect from root fracture.

Surgical crown lengthening

Crown lengthening: osseous re-contour andapical re-positioning of flap (3 mm apical tocrown margin).

Deep cervical margin and bone resorption resultin un-esthetic difference in gingival height.

Can be due to deep fracture, caries, and crownlengthening surgery.

Orthodontic Extrusion

Normal anatomic C:R for CI is 11:14 Crown lengthening for 3 mm apical fracture

leaves unstable and unesthetic 14:11. Extrusion / crown lengthening 11:11 - more

esthetic and stable .


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Orthodontic Extrusion

Endodontics and post-core Arch wire with mid-facial loop and embedded

pin in provisional crown Elastic from pin to loop Movement of 1.0 1.5 mm / week

How much movement is necessary?

Distance the destruction extends apical to thealveolar crest

The biologic width of 2.0 mm 1.0 mm for sulcus apical to crown margin

Amount of extrusion desired 3mmBracket placed 3mm apical to center of post-core/provisional;

Arch wire placed in brackets .

Incisal lengthadjusted as toothmoves coronally.

#10 extruded foradequate ferrule withpost-core.Bone travels with root unesthetic gingival line(low).

Eruption of tooth and crestal bone

The descended level of gingiva and bone makesclinical crown shorter.

(The alveolar crest descends with the tooth.) Osseous re-contouring to level of adjacent tooth

allows equal length of clinical crown.

Facial tissuerecontouring withperiodontal surgery

Extract or Restore #13?Unfortunate clinical scenario -Patient desires FPD replacement of #13.

Over-reduction and over-convergence of MF wall#12 pulp exposure necessitates RCT. Near exposure on mesial #14 later needed RCT.

Improper angulation of access preparation nearperforation of mesial concavity.

Mesial perforation of root #12


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Preparations for Periodontally Weakened Teeth

Shoulder finish line extended onto rootsurface requires excessive axial reduction:possible pulpal involvement and weakeningof entire tooth

Conservative treatment:Prepare for metal-ceramic toCEJ;Long bevel or light chamfer metal collar

Furcation Flutes

Preparation finish line intersects with the vertical flutes inthe root trunk.

Axial surface of tooth preparation occlusal to the inversionof the gingival finish line must have a vertical concavity orflute, as will the crown. Like seating groove must parallel path of insertion .

The anatomic facial groove should merge with thevertical concavity extending from the furcation flute

The facial convexity should not be replicated in the restoration.

Root Resection Eradicate areas of tooth which cause

problems in hygiene maintenance. Salvage teeth with endodontic

problems. Must not have excessive bone loss. Furcationmust be in coronal 1/3 and

well separated roots. Must be treatable w/ endo.

DF and MF Root Resection on Maxillary Molars Mesial / Distal Root Resection onMandibular Molars

Mesial root resection #30


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Cast post-core distal root and FPD #29-30 Metal framework and metal ceramicFPD #29-#30

Facial and palatal root resectionson maxillary molars

Documents

12 Restoration of RCT and Periodontally Weakened Teeth 2009