Restoration of the endodontically treated tooth Flashcards
When we clinically assess the tooth what do we want to look at
• Look at the coronal seal of the restoration or crown, is there any leakage or caries?
• Look at the amount of remaining tooth structure, how much ferrule is there?
Is the tooth restorable and can it be isolated with a rubber dam?
When doing the clinical assessment what things do we look at that indicate infection
• Is there any swellings
• Are there any sinuses
• Is there tenderness to percussion
• Is the buccal sulcus tender to palpation
• Is the tooth mobile
Is there increased pocketing due to periodontal disease and root fracture
What do we look at in a radiographic assessment in relation to the tooth
- What is the shape of the canal?
- Is bone support mild, moderate or severe
- What is the crown to root ratio?
What is the ideal crown to root ratio
○ Want height of the crown from the ACJ to the incisal edge/cusp
Want the root to be 1.5 times the length of the crown
When doing the radiographic assessment, what do we look at when critiquing the root treatment
○ Are there unfilled or missing root canals?
○ Are there any voids?
○ Is there fractured instruments?
○ Is there posts?
○ Is there root canal sclerosis?
○ Is there any pathologies such as periapical radiolucency
○ Is there any healing or resorption?
What should be done to inadequate root fillings
should be retreated before prosthodontics commences
What are other considerations in assessment
When was the RCT done? Is it healing or has it failed
• Was the treatment done under rubber dam and was hypochlorite irrigant used
Is the root filling short or long
What is coronal micro leakage
- This is the ingress of oral micro-organisms into the root canal system
- It is an importance cause of root canal treatment failure
When should a tooth be retreated after exposure
• If filled teeth is unrestored for 3 months or longer it should generally be re-rot treated as the GP is exposed to the mouth and so the root canal will be contaminated with bacteria as they have entered coronally
How important is coronal seal
• Technical quality of the coronal restoration is significantly more important for periodontal health than the technical quality of the RCT
What are problems after RCT/re-RCT
- Amount of remaining tooth structure both externally and internally
- The restoration type
- Lac or no ferrule
- Wide post holes
- Endodontic complications such as fractured instruments, perforations, short/long fillings
Are endodontic teeth more brittle
• Teeth do not become more brittle after endodontic treatment
Is an endodontic tooth more likely to fracture
• A root filled tooth with minimal loss of dentine is not more likely to fracture than a vital tooth
Is dentine hardness altered after endo tx
• Dentine hardness is not altered after endodontic treatment
Does dehydration of the tooth weaken dentine
• Dehydration does not appear to weaken dentine structure in terms of strength or toughness
What are the clinical choices
• Direct restoration - composite (glass ionomer) - class III or IV (glass ionomer tends to be used in class V cervical restorations) Indirect restoration - crown or post crown (veneer
What is the significance of marginal ridges
- If these are intact then you do a restoration, not crowns and post crowns
- When you lose a lot of the marginal ridge then you may need to go down the road of replacing them with crowns
What is the restoration for an anterior tooth with intact marginal ridge
can be given a direct restoration using composite
What is the restoration of anterior teeth with intact marginal ridges with our without a discoloured crown
direct restoration with composite, bleaching (think of bleaching both internally and externally before going down the route of indirect restorations)and or a veneer or a crown
What is the restoration for anterior teeth with marginal ridges destroyed
can opt for a core build up with a crown or a post crown
What is the function of a post/core
Gains intraradicular support for a definitive restoration
What does the core do
Core provides retention for crown
is what the prosthesis is cemented to e.g crown or bride abutment
What does the post do
- Post retains the core
- Posts DO NOT strength or reinforce teeth
placed in the root canal
Why can posts weaken teeth
• Prep of the root canal for a post weakens the tooth because you have to remove tooth structure in the inside to create space
What is the guidelines for posts in incisors and canines
§ the post is unnecessary if there is sufficient coronal dentine present
§ if there is extensive loss of coronal tooth tissue then the tooth will require a post as the pulp chamber and a single root canal are not adequate to retain a core
avoid in mandibular incisors
Why should posts be avoided in mandibular incisors
avoid in mandibular incisors due to thin/tapering/narrow mesiodistal roots
What are features of premolars
hey have small pulp chambers and tapering roots
§ They are thin in mesiodistal cross section and have proximal invaginations e.g the canine eminence region where there is a concavity
If a post is placed in a premolar where should it be placed
§ If a post is to be placed then it should be placed in the widest root canal
§ Avoid in curved canals to avoid perforations as the posts are straight
What should the length of the root filling be for a post
4-5mm root filling apically
What should the post width be
○ No more than 1/3 of root width at the narrowest point and 1mm of remaining circumferential coronal dentine
How much of the post length should be in the root
• Sufficient alveolar bone support is required and at least half of the post length should be into the root
What ratio of post length:crown length do we want
Want a minimum of 1:1 post length/crown length ratio
What is a ferrule
A ferrule is a dentine collar - it is an encirclement of 1-2mm of vertical axial tooth structure within walls of a crown
What is the benefit of a ferrule
It prevents tooth fracture
What is the risk of a crown margin is not placed on solid tooth
risk of root fracture is significantly increased
What may have to be done to achieve a ferrule
Orthodontic extrusion or crown lengthening may be necessary to achieve this
What is the ideal post
parallel sided
non threaded
cement retained
Why do we want a parallel sided post
○ Avoids ‘wedging’
More retentive than tapered
Why do we want a non threaded post
○ Passive
○ Smooth surface incorporates less stress to remaining tooth than threaded (active) as if it has grooves for example then it can transmit forces to the tooth
Why do we want a cement retained post
○ Less retentive than threaded posts but cement acts as a buffer between the masticatory forces and post/tooth
How can we classify posts
manufacture
material
shape
What is the manufacturer classifications
preformed/prefabricated or custom made
What are the material classifications
cast metal, steel, zirconia, carbon/glass fibre
What are the shape classifications
parallel sided or tapered
What are the benefits of prefabricated posts
- Only 1 visit is required
- No impressions and no fit visit required
- Chairside core build up
- Post and core are different materials
- Immediate preparation of core
- Large selection of designs and materials
What are custom posts
- Cast from direct pattern fabricated in patients mouth e.g duralay
- The indirect pattern can be fabricated in the lab by getting an impression of the post hole and waxing up the post and core in the lab
- Unified post and core e.g made one piece, the same material
What are the disadvantages of custom posts
• 2 visits are required - impression and fit
• Temporisation between visits and lab stage is required
• There is risk of contamination of the root canal between visits
The cast post is made in type IV heat hardened gold
What materials can posts be made of
cast gold, stainless steel, brass, titanium
What are the disadvantages of metal posts
○ Poor aesthetics as the metal could shine through the crown but now opaquer are put in the crown to try and stop this
○ Root fracture
○ Corrosion
○ Nickel sensitivity, radiopaque on radiographs
What are the ceramic posts made of
alumina, zirconia
What are the advantages of ceramic posts
○ High flexural strength and fracture toughness
○ Favourable aesthetics
What are the disadvantages of ceramic posts
○ Difficult retrievability and root fracture is common
What are the fibre posts made of
glass, quartz, carbon
What are the advantages of fibre posts
○ Flexible (more than ceramic), similar properties to dentine
○ Aesthetic
○ Retrievable - there are burs to drill them out in the event of fracture
Bond to dentine with dentine bonding agents
What are the disadvantages of fibre posts
○ Flexible (more than ceramic), similar properties to dentine
○ Aesthetic
○ Retrievable - there are burs to drill them out in the event of fracture
Bond to dentine with dentine bonding agents
What are the advantages of tapered prefab posts
conservative
high strength
high stiffness
What are the disadvantages of tapered prefab posts
less retentive than parallel or threaded
What are the advantages of parallel prefab posts
high strength
good retention
comprehensive system
What are the disadvantages of parallel prefab posts
precious metal
post expensive
corrosion of SS
less conservative
What are the advantages of threaded posts
high retention
What are the disadvantages of threaded posts
stresses generated in canal may cause fracture
What are the advantages of custom cast post and core
high strength better than prefab
Wha are the disadvantages of custom cast post and core
less stiff than wrought
multiple appointments complex
What is a core build up
• The internal part of the tooth is built up with restorative material to replace the lost tooth tissue so that the restoration can go on top of it and is held by the core
What are core build ups used more for
- Especially for molar access for RCT, may have not much tooth tissue left
- The core is prepared and it provides retention and resistance for permanent restorations
What are the core materials
composite
amalgam
glass ionomer
What are the features of composite as a core material
○ Most commonly used core material ○ Tooth coloured so good aesthetics ○ Bonds to the tooth structure ○ Technique sensitive so moisture control is required Used with fibre posts
What are the features of amalgam as a core material
○ Tends to be used for posterior teeth
○ Tend to avoid as retention is required (undercuts)
○ Poor aesthetics
○ Core cannot be prepared straight away - needs 24h to set
○ Avoid pinned amalgams
What are the features of glass ionomer as a core material
○ Not really used as it absorbs water and core expands in size meaning when it comes time to cement the restoration on, you cant get it on as it has expanded in size
Are there differences in the core materials
There are no significant differences in fracture and failure characteristics of composite, amalgam and cast gold as core material under a crown provided a 2mm ferrule exists on the margin of healthy tooth
What is a nayyar core
- After the tooth is root treated and its set, you go into the root canal and take out some GP and you pack down some amalgam into the root canal and this is built up in to the pulp chamber
- This provides retention for the amalgam as it is packed into the little nooks and crannies under the pulp chamber
- It cannot be crown prepared for 24h until the amalgam has set
What is the management for a post perforation
○ Repair
§ Can repair internally or externally (periradicular surgery)
○ Extraction
What should posts be avoided in
narrow root canals
What are common teeth that get post perforation
Common teeth that get perforated are premolars because they have particularly buccal root canals and they are very narrow
What is a core fracture
• If there is no ferrule then the core may break off from the root and you will see the crown with the core in it
What is root fracture
• This is when the post and core survive but the tooth doesn’t
Patient can complain of pain and you may see a deep pocket
What is post fracture
Sometimes the post is too short and sometimes its too narrow and if there are lots of lateral forces then the post will fracture off
How can posts be removed
• Ultra sonics
• Masseran kit
• Eggler
Moskito forceps (screw retained)
What is post crown failures due to
• 60% is due to restorative reasons such as caries around the crown margins
• 32% is due to periodontal problems such as a pre existing perio condition or a perio-endo lesion
8% is due to endodontic reasons
