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STRATEGIES OF RECONSTRUCTION OF RESTORATION OF ENDODONTICALLY TREATED TEETH

INTRODUCTION

  • Poorly made tooth restorations after post-endodontic treatment are one of the main causes of tooth loss.

  • Historically: metal post-and-core implants and prosthetic crowns.

  • nowadays: more conservative restoration techniques. thanks to adhesive dentistry

TEETH AFTER ENDODONTIC TREATMENT

  • Characteristics:

    • Reduced stiffness due to the loss of hard tissue

      • both in root and crown areas

      • → Biomechanical changes, which may lead → fracture.

    • Teeth exhibit dehydration over time.

    • Collagen in dentin undergoes degradation

    • → susceptibility to breakage.

FACTORS INFLUENCING MECHANICAL WEAKNESS

  • Factors that contribute to mechanical weakening after endodontic treatment:

    • Irrigation Agents: sodium hypochlorite and disodium edetate

    • Intracanal Materials: calcium hydroxide

    • Improper Instrumentation: Use of Gates Glidden, Largo Peeso drills, and rotary instruments

    • Preparation Techniques: Problems like :

      • excessive preparation of orifices towards furcation

      • use of a decalibrated contra-angle → vibrations + dangerous impacts

      • improper prep. using mirror → thinning of hard tissues

FACTORS DETERMINING CHOICE OF RECONSTRUCTION METHOD

1. Quantity of Remaining Hard Tissues of the Tooth Crown

  • Key factor in successful reconstruction is the quantity of remaining supragingival tissues:

    • Rim effect: Supragingival hard tissue encircles the tooth, crucial for strength. (esp. after rct)

    • Minimum required dimensions for predictable reconstruction:

      • 2 mm supragingival height in vertical dimension

      • 1 mm supragingival width in horizontal direction, especially on vestibular and palatal/lingual surfaces.

    • If insufficient hard tissue remains: Consider surgical crown lengthening or orthodontic extrusion.

2. Remaining Root Hard Tissues

  • Ideal Crown-to-Root Length Ratio:

    • 1:1 ratio = min. necessary for transfer of occlusal forces in healthy periodontium + balanced occlusion conditions.

  • Monitoring the thickness of root canal walls is essential, especially when considering endodontic retreatment or prosthetic re-restoration, as thin walls increase fracture risk.

ADDITIONAL FACTORS FOR CONSIDERATION

  • Number of preserved tooth tissues in both crown and root areas.

  • Type and function of the tooth group.

  • Occlusal conditions and morphology of the root and canal.

  • Quality of canal filling and potential for endodontic retreatment.

  • Periapical tissue condition and patient's oral hygiene status.

  • Marginal periodontal health, tooth position, and relation to opposing teeth should also be factored in.

  • Previous prosthetic work + prosthetic treatment plan, crown aesthetics, patient age, motivation, expectations, and financial limitations must also be considered.

CONTRAINDICATIONS TO TOOTH CROWN RECONSTRUCTION

  • Situations rendering crown reconstruction inappropriate include:

    • Poorly executed endodontic treatment.

    • Presence of root caries beneath the gingival margin.

    • Active periodontal disease or mobility of the tooth.

    • Root fractures extending below the apex.(longutudinal, oblique, transverse)

    • Unfavorable perforation location within the chamber or canal.

    • Shortened roots or incomplete root apex development.

    • Ongoing inflammation of periapical tissues.

    • Poor oral hygiene or uncooperative patients.

CLASSIFICATION OF TOOTH RESTORATION AFTER ENDODONTIC TREATMENT

Class 0: Reconstruction of Core with Composite

  • Treatment for:

    • Molars, premolars, or anterior teeth with minor crown destruction (>50% remaining tooth tissue)

    • molars w. large enough pulp chambers to allow sufficient adhesion + permanent retntion of composite core

  • No need for fiber post cementation due to sufficient tooth support.

    • no need to cement fiber post → lower risk of making mistake

  • Preferred material for core reconstruction: Composite resin.

Class 1: Fiberglass Insert

  • Indicated for:

    • Anterior/premolar with sig. tooth tissue destruction ( <50% remaining tissue, destruction of more than 50% of coronal part of hard tissue)

      • as: premolars more susceptible to lateral forces than molars during chewing

    • Molars with insufficient chamber anatomy to support “Anchoring” of composite core.

    • small tooth chamber surface

  • Core design aims to increase adhesion surface towards the root canal.

  • Recommended when more than 1/3 of coronal dentin present

Class 2: Fiberglass Post + Surgical Crown Lengthening/Orthodontic Extrusion

  • Appropriate when:

    • There is complete or partial loss of the rim.

  • molars need surgical crown lengthening

  • anterior/premolars need orthodontic extrusion in most cases

  • (additional procedures needed so post and core can obtain a rim → post + core fulfills its function)

    • disadvantages: delay in prosthetic treatment, patient discomfort, added costs, increased crown-to-root ratio, loss of tooth structure due to apical movement of the preparation margin

Class 3: Alternative Concept: Gold (or Silver-Palladium) Cast Insert

  • Recommended in unpredictable restoration scenarios where rim effect is absent but desired by patient.

  • missing rim + can’t do extension, but patient still wants to keep crown

  • withstands greater loads

  • if damaged, they break in a way that prevents the tooth from being preserved

  • disadvantages: longer visits, need additional visits, temp. crown needed, more costly, risk of bacterial contamination

Class 4: Extraction

  • Suggested when destruction of tooth structure does not permit predictable restoration, alternative options include prosthetic treatments like bridges or implants.

tooth restoration techniques

Glass fiber root + crown post

  • similar modulus of elasticity as dentin (uniform transfer + redistribution of stress to hard tissues)

    • metal + ceramic: very dif. modulus

  • quick procedure (put perm. crown on in one visit)

  • fastest permanent protection:

    • protect hard tissure from fracture

    • protects root canal system from infection

  • Indications: premolars and anterior teeth with significant loss (>50% hard tissue).

  • Selection:

    • Post should fill the canal adequately, but enter passively (enoufg space for cement between dentin + post)

    • leave 4-5mm of canal filling at apex → adequate sealing

    • post inserted to min ½ root length

    • post cemented min. 3mm below edge of alveolar process

    • post adheres well to apical part of canal filling (no free space between GP and post)

    • several posts in wide canal

    • completely cover post w. restorative material during final restoration

ADHESIVE PREPARATION OF HARD TISSUES of tooth + crown-root post

  • dentin prep.

    • clean dentin of GP + sealant

    • etch dentin if use 4th/5th bonding gen.

  • orthophosphoric acid etching

    • put into canal so in contact with all of canal dentin

    • rinse after 60sec w. syringe w. needle in canal

    • frain excess water w. paper points + gentle air stream

    • bonding: chemical bond activator, large application to dentin, blow, drain excess w. pp

    • if use self-etch: no etching procedure, apply bonding system 20sec, blow + lamp

  • prep of post

    • cover glass fiber post w. bonding system containg MDP molecule / silane OR sandblast it