Restoration of the endodontically restored tooth Flashcards
What should you be looking for in your clinical assessment?
- Is the coronal seal adequate, restorations/crowns/leakage/caries
- How much remaining tooth structure is there
- Is tooth restorable and can you isolate with rubber dam
- Swelling
- Sinus
- TTP
- Buccal sulcus tender to palpation
- Mobility
- Increased pocketing (periodontal disease and root fracture)
What is included on radiographic assessment?
- Root filling (length, quality of obturation e.g. any voids)
- Unfilled or missed root canals
- Shape of canal
- Patency (fractured instruments, posts, sclerosis)
- Bone support (mild, moderate, severe)
- Crown to root ratio
- Any pathology (perforations, radiolucency)
What are some problems after RCT/re-RCT?
- Amount of remaining tooth structure can be little so determines what restoration type can do
- Lack or no ferrule
- Wide post holes with re-RCT
- Endodontic complications like fractured instruments, perforation, short/long root fillings
Are teeth brittle after RCT?
- No
Are root treated teeth more prone to fracture?
- A RCT with minimal loss of dentine no more likely to fracture than vital tooth
After RCT are teeth as hard as non-root treated teeth?
- Dentine hardness not altered
Does dehydration affect the hardness of RCT tooth?
- Dehydration does not appear to weaken dentine structure in terms of strength or toughness
What is coronal microleakage?
- Ingress of oral micro-organisms into root canal system
What can coronal microleakage cause?
- Important cause of RCT failure
- Root filled teeth unrestored for 3 months or longer they should be generally be re-root canal treated
What should you do to reduce coronal microleakage?
- Trim GP to AC
- Place RMGI over pulp floor and root canal openings
- Don’t have lining too thick, allows remainder of pulp chamber for retention and restoration
What can you do if anterior tooth has intact marginal ridges?
- Composite restoration
- Veneer
What can you do if anterior teeth with intact marginal ridges and discoloured crown?
- Bleaching
- Veneer
- Crown
What to do with anterior teeth with marginal ridges destroyed or post core crowns?
- Core build up with crown
- Post crown
What is a post/core?
- Gains intraradicular support for definitive restoration
- Post placed in root canal
- Core what prosthesis is cemented to e.g. crown or bridge abutment
- Core provides retention for crown
- Post retains the core
- Post don’t strengthen or reinforce teeth
- Preparation of root canal for post weakens the tooth
What is the root filling length of post placement?
- 4-5mm root filling apically
What teeth can be used for post placement?
- Incisors and canines but it is not needed if sufficient coronal dentine present
- Premolars (place in widest root canal)
Why should you not place post in mandibular incisors?
- They have thin/tapering/narrow mesiodistal roots
What should you be careful of if placing post in premolars?
- Have small pulp chambers and tapering roots
- Thin in mesiodistal cross-section and proximal invaginations
- Place in widest root canal
- Avoid curved canals to avoid perforations
What is the post width?
- No more than 1/3 root width at narrowest point
- 1mm remaining circumferential coronal dentine
What is the minimum post length/ crown length ration?
1:1
Is sufficient alveolar bone support needed for post placement?
- Yes
- Need at least half of post length into root
What is the ferrule measurements needed for post placement?
- At least 1.5mm height and width of remaining coronal dentine
What is a ferrule?
- Dentine collar
- Encirclement of 1-2mm of vertical axial tooth structure within walls of a crown
- Prevents tooth fracture
What can happen if a crown margin not placed onto solid tooth?
- Root fracture significantly increased
- Ferrule helps prevent this
- Orthodontic extrusion or crown lengthening might be needed to be done
What are the components of an ideal post?
- Parallel sided
- Non-threaded (passive)
- Cement retained
Why is a parallel sided post good?
- Avoids wedging
- More retentive than tapered
Why is a non-threaded (passive) post good?
- Smooth surface incorporates less stress to remaining tooth than threaded (Active)
Why is cement retained a good post?
- Less retentive than threaded posts
- But cement acts as buffer between masticatory forces and post/tooth
How can posts be classified?
Manufacture
- Pre-formed/prefabricated
- Custom made
Material
- Cast metal
- Steel
- Zirconia
- Carbon/glass fibre
Shape
- Parallel
- Tapered
What are the different types of prefabricated posts?
A: Tapered Smooth
B: Tapered Serrated
C: Tapered Threaded
D: Parallel Smooth
E: Parallel Serrated
F: Parallel Threaded
Benefit of prefabricated posts?
- Only 1 visit required
- No impressions and lab visit required
- Chairside core build up so immediate prep of core
- Large selection of designs and materials
What are custom posts?
- Cast from direct pattern fabricated in patients mouth e.g. Duralay
- Indirect pattern fabricated in lab
- Post and core unified and one material
- Type IV heat hardened gold
Disadvantage of custom posts?
- 2 visits required for impressions and fit
- Temporisation between visits and lab stage needed
- Risk of contamination of root canal between visits
What are some metal post materials?
- Cast gold
- Stainless steel
- Titanium
What are some advantages and disadvantages of metal post materials?
- Poor aesthetics
- Root fracture
- Corrosion
- Nickel sensitivity
- Radiopaque on radiographs
What are some ceramic post materials?
- Alumina
- Zirconia
What are the advantages and disadvantages of ceramic post materials?
- High flexural strength
- High fracture toughness
- Favourable aesthetics
- Difficult retrievability and root fracture common
What are some fibre post materials?
- Glass
- Quartz
- Carbon
What are some advantages and disadvantages of fibre post materials?
- Flexible
- Similar properties to dentine
- Aesthetic
- Retrievable
- Bond to dentine with DBA
- Radiolucent on radiographs
Advantages and disadvantages of tapered prefab post ?
- Conservative
- High strength
- High stiffness
- Less retentive than parallel or threaded
What is the recommended use and precaution of tapered prefab?
- Use in small circular canals
- Avoid excessively flared canals
Advantages and disadvantages of Parallel prefab?
- High strength
- Good retention
- Comprehensive system
- Precious metal post expesnive
- Corrosion of SS
- Less conservative
What is the recommended use and and precaution of Parallel prefab?
- Use in small circular canals
- Have care during prep
Advantages and disadvantages of Threaded post?
- High retention
- Stresses generated in canal may cause fracture
What is the recommended use and precaution of Threaded post?
- Use Only when max retention essential
- Care to avoid fracture during seating
Advantages and disadvantages of Custom cast post and core?
- High strength
- Better than prefab
- Less stiff than wrought
- Mulitple apts
- Complex
What is the recommended use and precautions of Custom cast post and core?
- Use in eliptical or flared canals (non circular or extreme taper)
What is the recommended use and precautions of Custom cast post and core?
- Use in elliptical or flared canals (non circular or extreme taper)
- Care to remove nodules before insertion
What is a core build up?
- Internal part of tooth built up with restorative material to replace lost tooth tissue
- Core is prepared
- Provides retention and resistance for permanent restorations
What are some different core materials?
- Composite
- Amalgam
- Glass ionomer
Why is composite the most used core material?
- Tooth coloured so good aesthetics
- Bonds to tooth structure
- Used with fibre posts
- But is technique sensitive so moisture control required
Why is amalgam not tend to be used for core material?
- Retention is required so healthy tooth tissue drilled away
- Poor aesthetics
- Core can’t be prepared straightaway as need 24hrs to set
Why is glass ionomer not really used for core materials?
- Absorbs water and core expands in size
What is Nayyar Core?
- Root treatment removed from root canals
- Amalgam packed into root canals and tooth built up which provides retention for amalgam
- Can’t be prepared for 24hrs until amalgam sets
What is anti rotation notch/groove?
- If sufficient coronal structure present rotation is prevented by vertical coronal wall
- If coronal dentin absent then small vertical groove in canal serves as anti rotational element
- Located in bulkiest area of root , usually lingual
What is the lab prescription?
- Please construct cast post and core
- Para post (colour)
- Core 6 degree taper
- Please leave 2mm space in occlusion for crown
- Enclosed registration/ opposing impression/ shade
What to do at Try in?
- Check post space for temp bond
- Irrigate chlorhexidine 0.2%
- Dry paper points
- Ensure fits around prep
- Do you have enough occlusal clearance?
What to do to get correct fit?
- Careful not to fill post pace with cement as may prevent it seating
- Firm apical pressure
- Get rid of excess
- Can ask lab for provisional acrylic crown
- Make sure non excess around when taking crown imp/ fitting MCC
- Practice fit sequence
What are some problems with Posts?
- Perforation
- Core fracture
- Root fracture or crack
- Post fracture
How to manage post perforation?
- Repair internal or external (periradicular surgery)
- Extraction
What to do if post fracture?
- Post removal using
- Ultra-sonics
- Masseran Kit
- Eggler
- Moskito forceps (screw retained)
What are the stastitics of Post failure?
- 60% due to restorative reasons
- 32% due to periodontal problems
- 8% due to endodontic reasons
How much GP should you leave when placing a post?
- 3-5mm GP in apical third
- Solid GP plug
