Restoration of Endodontically Treated Teeth

Question 1

What does the clinical assessment of a tooth potentially requiring endodontic treatment include?

Answer 1

• potential for coronal seal
  
  • current restorations and crowns
  • leakage
  • caries
• amount of remaining tooth structure
  
  • ferrule
• restorability
  
  • isolation with rubber dam
• swelling
• sinus
• TTP
• buccal sulcus
  
  • TTP
• mobility
• increased pocketing
  
  • periodontal disease
  • root fractures

Question 2

What does the radiographic assessment of a tooth potentially requiring endodontic treatment include?

Answer 2

• root filling
  
  • length
  • quality of obturation (voids)
• unfilled/missing root canals
• shape of canal
• patency
  
  • fractured instruments
• bone support
  
  • mild
  • moderate
  • severe
• crown to root ration
  
  • 1:1.5
• pathology
  
  • periapical radiolucency
  • resorption
  • perforations

Question 3

For how long after completion of endodontic treatment should a tooth be monitored?

Answer 3

• 4 years

Question 4

What can happen as a result of re-treating inadequate root fillings?

Answer 4

• symptoms appear
  
  • due to disturbance of microorganisms
• must re-treat before restoration placed

Question 5

What problems can occur after RCT?

Answer 5

• little remaining tooth structure
  
  • internal and external
  • usually significant loss of dentine, structure undermined
  • functional and aesthetic restoration can be challenging
• lack or no ferrule
• wide post holes
  
  • on re-treatment
• endodontic complications
  
  • fractured instruments
  • perforations
  • short/long root fillings

Question 6

What is a ferrule?

Answer 6

• 1-2mm collar of dentine extending above the gingival level
• prevents tooth fracture
  • if crown margin not on solid tooth, risk significantly increased
  • braced at neck of tooth

Question 7

What are the properties of RCT teeth?

Answer 7

• prone to fracture due to lack of dentine
  
  • minimal access cavities rare in Scotland
• same hardness and brittleness as untreated teeth

Question 8

What is coronal microleakage?

Answer 8

• ingress of oral micro-organisms into the root canal system
  
  • infection, even though tooth non-vital, in PDL and bone
• important cause of RCT failure
• significant in multi-rooted teeth
• RCT teeth unrestored for >3 months should be re-RCT

Question 9

What can be done to prevent coronal microleakage?

Answer 9

• trim GP to the access cavity
• place RMGI over pulp floor and canal openings
  • not too thick
  • allows remainder of pulp chamber for retention of restoration

Question 10

What can be done to prevent coronal microleakage?

Answer 10

• trim GP to the access cavity
• place RMGI over pulp floor and canal openings
  • not too thick
  • allows remainder of pulp chamber for retention of restoration

Question 11

What are the restoration options for RCT anterior teeth?

Answer 11

• composite restoration
  
  • anterior teeth with intact marginal ridges
• veneer
  
  • anterior teeth with intact marginal ridges
  • anterior teeth with intact marginal ridges and discoloured crown
• bleaching
  
  • anterior teeth with intact marginal ridges and discoloured crown
• crown
  
  • anterior teeth with intact marginal ridges and discoloured crown
  • anterior teeth with marginal ridges destroyed (+ core build up)
• post crown
  
  • anterior teeth with marginal ridges destroyed

Question 12

What is a post/core?

Answer 12

• restoration gaining intra-radicular support for definitive restoration
• core
  
  • provides retention for crown/bridge
  • prosthesis cemented to core
• post
  
  • placed into canal
  • retains core
  • bonded to remaining tooth structure
  • do not strengthen teeth
  • preparation for post weakens tooth

Question 13

What are the guidelines for post placement?

Answer 13

• tooth type
  
  • incisors and canines
    - post necessary if sufficient coronal dentine present
  • mandibular incisors
    - avoid due to thin, tapering, narrow mesiodistal roots
  • premolars
    - small pulp chambers and tapering roots
    - thin in mesiodistal cross-section and proximal investigations
    - post to be placed in widest root canal
    - avoid placement in curved canals to avoid perforations
  • molars
    - avoid
    - commonly fail
    - easy to get wrong angulation
    - increased perforation risk
    - if no other option, use longest, straightest canal
• root filling length
  
  • 4-5mm apically
  • must maintain apical seal
• post width
  
  • no more than 1/3 root width at narrowest point
  • 1mm remaining circumferential coronal dentine
• alveolar boen support
  
  • sufficient
  • at least half post length into root
• 1:1 post length-crown length ratio
• ferrule
  
  • at least 1.5mm height and width of remaining coronal dentine

Question 14

What would be considered an ideal post?

Answer 14

• parallel sided
  
  • avoids wedging
  • more retentive than tapered
  • decreases fracture risk
• non-threaded
  
  • passive
  • smooth surface incorporates less stress to remaining tooth
• cement retained
  
  • less retentive than threaded
  • cement is a buffer between masticatory forces and post/tooth
  • usually glass ionomer cement

Question 15

What are the different ways to classify posts?

Answer 15

• manufacture
  
  • pre-formed/pre-fabricated
  • custom made
• material
  
  • cast metal
  • steel
  • zirconia
  • carbon/glass fibre
• shape
  
  • parallel sided or tapered

Question 16

What materials can be used to make posts?

Answer 16

• metal
  
  • poor aesthetics
  • root fracture
  • corrosion
  • nickel sensitivity
  • radiopaque on radiographs
    - cast gold
    - stainless steel
    - brass
    - titanium
• ceramics
  
  • high flexural strength and fracture toughness
  • favourable aesthetics
  • difficult retrievability
  • root fracture common
    - alumina
    - zirconia
• fibre
  
  • flexible, similar properties to dentine
  • aesthetic
  • retrievable
  • bond to dentine with DBAs
  • radiolucent on radiographs
    - glass
    - quartz
    - carbon

Question 17

What are the most common materials for posts?

Answer 17

• metal
• glass fibre

Question 18

What are pre-fabricated posts?

Answer 18

• pre-made posts
• only 1 visit required
  
  • no impressions or lab visit
• chairside core buildup
  
  • post and core different materials
  • immediate preparation of core

Question 19

What are custom posts?

Answer 19

• cast from direct pattern fabricated in patients mouth
  
  • duralay
• indirect pattern can be fabricated in lab
  
  • impression of post hole
  • wax up of post and core
  • most common method
• unified post and core
• 2 visits required
  
  • impression and fit
    - temporisation between visits
    - risk of contamination
• Type IV heat hardened gold

Question 20

What are the restoration options for posterior teeth after RCT?

Answer 20

• gold standard in cusp protection restoration
  
  • minimal standard prep
  • 2mm reduction over cusp

Question 21

What is a core build up?

Answer 21

• internal part of tooth is built up with restorative material
  
  • replaces lost tooth tissue
• core prepared
  
  • provides retention and resistance for definitive restorations

Question 22

What materials can be used for core-build up?

Answer 22

• composite
  
  • most common
  • good aesthetics
  • bonds to tooth structure
  • technique sensitive, moisture control required
  • used with fibre posts
  • Paracore and Corecem
• amalgam
  
  • avoided as retention is poor
  • poor aesthetic
  • core not prepared straight away, 24 hours to set
  • avoid pinned amalgams
• glass ionomer
  
  • not used as absorbs water
  • core expands in size
• SDR
  
  • bulk fill
  • colour not aesthetic
  • biodentine

Question 23

What is Nayyar core?

Answer 23

• root treatment removed from canals
  
  • 2-3mm coronal GP
• restorative material packed into root canals then tooth built up
  
  • provides retention
  • traditionally amalgam
  • now more commonly amalgam
    - challenging if re-treatment required

Question 24

What is ideal core design?

Answer 24

• creation of core as if crown prep on fresh tooth
• 6 degree taper
• length required
  • e.g. 2mm clearance for MCC
  • short cores do not retain crowns
    - results in rocking and rotation

Question 25

What kind of provisional restorations can be placed?

Answer 25

• provisional post core crown
  
  • temp-bond
• immediate denture
• dressing
  
  • poor aesthetics
  • prevents leakage
• Essex retainer

Question 26

What is involved in GP removal?

Answer 26

• placement oof dental dam
• softening of GP
  
  • using solvent or heat
• Gates-Glidden
  
  • minimum size 3 (0.9mm)
  • straight part of canal only
  • use working length and rubber stopper
  • creates path of least resistance for post
• leave 3-5mm GP in apical third
• check GP plug remains

Question 27

What is Para Post XP?

Answer 27

• kit for indirect posts and packing techniques
• components
  • provisional post
    - temporary restoration
  • para post drill
  • impression post
    - sent to lab

Question 28

What does post prep involve?

Answer 28

• preparation of post space
• placement and adjustment of impression post
• impression taken

Question 29

What is an anti-rotation notch/groove?

Answer 29

• small vertical groove in canal
  
  • located in bulkiest area of the root
  • requires sufficient coronal structure

Question 30

What does try in of post and core involve?

Answer 30

• check post space for remaining temporary bond
• irrigate with chlorhexidine 0.2%
• dry with paper points
• ensure fits around prep
• check for 2mm occlusal clearance

Question 31

What does fit of a post and core involve?

Answer 31

• protect airway and practice insertion
  
  • once cement is added only one shot at insertion
• do not fill post space with cement
  
  • may prevent proper seating
• use firm apical pressure
• remove excess cement
  
  • take impressions
  • fit crown
• place provisional acrylic crown

Question 32

What problems can occur with post crowns?

Answer 32

• perforation
  
  • repair internally or externally (periradicular surgery)
  • extraction
• core fracture
• root fracture or crack
  
  • indicated by repeated debonding
    - flexion on biting debonds cement
  • vertical most common on lateral and central incisors
• post fracture
  
  • post may remain in tooth
  • must be removed
    - endo-ultrasonic
    - masseran kit
    - eggler
    - moskito forceps (screw retained)

Question 33

What are the possible reasons for post failure?

Answer 33

• mostly restorative (60%)
• some periodontal (32%)
• some endodontic (8%)