Restoration of the Endodontically treated tooth Flashcards
What you include in your clinical assessment of a RCT tooth
Coronal seal - restorations/crowns. Leakage? Caries?
Amount of remaining tooth structure- ferrule
Is the tooth restorable? Can you isolate it with rubber dam?
Swelling
Sinus
TTP
Buccal sulcus - tender to palpation?
Mobility
Increased pocketing – periodontal disease and root fractures
What would you look for in your radio graphic assessment of RCT tooth
Root filling - length, quality of obturation e.g. voids
Unfilled/missed root canals
Shape of canal
Patency - fracture instruments, posts, sclerosis
Bone support – mild, moderate, severe
Crown to root ratio (1:1.5)
Pathology - periapical radiolucency – healing?, resorption, perforations
If in your radiograpghic assessment of a RCT tooth you identify inadequate root fillings what would you do
should be re-treated before restoration
What are the Problems after RCT/re-RCT
Amount of remaining tooth structure - externally and internally
Lack or no ferrule
Wide post holes e.g. re-RCT
Endodontic complications - fractured instruments, perforations, short/long root fillings
What are the properties of a RCT tooth like to a normal tooth
Q. Are teeth brittle after RCT?
A. “Teeth do not become more brittle after endodontic treatment” (Sedgley CM & Messer HH JOE 18:332 1992)
Q. Are root treated teeth more prone to fracture?
A. “a root filled tooth with minimal loss of dentine is no more likely to fracture than a vital tooth”
(Stokes AN International Endodontic Journal 20:1 1987)
Q. After RCT are teeth as hard as non-root treated teeth?
A. “dentine hardness is not altered after endodontic treatment”
(Lewinstein I & Grajower R JOE 7 421 1981)
Q. Does dehydration affect the hardness of a RCT tooth?
A. “dehydration does not appear to weaken dentine structure in terms of strength or toughness”
(Huang TJG Schilder H& Nathanson D JOE 18:209 1992)
What is Coronal microleakage and why is it important
Ingress of oral micro-organisms into the root canal system
Important cause of RCT failure
Significant in multi-rooted teeth
When should a tooth me re-root treated and how
Root filled teeth unrestored for 3 months or longer should generally be re-root canal treated
Trim GP to the AC and place RMGI over pulp floor and root canal openings
Lining should not be too thick, allowing remainder of pulp chamber for retention and restoration
When would you place a Core build –up with crown or Post crown
Anterior teeth with marginal ridges destroyed (post core crowns)
What is a post/core
After getting a root canal, if the tooth has not much tooth structure remaining to support a follow-up dental crown work, the post-core may be needed
It is a little screw that gains intraradicular support for a definitive restoration
Core provides retention for crown
Post retains the core
Posts do not strengthen or reinforce teeth
Preparation of the root canal for a post, weakens the tooth
What are the components of a post and core
Post - placed in the root canal
Core - is what the prosthesis is cemented to e.g. crown or bridge abutment
What are the guidelines for post placement
Tooth type
-Incisors and canines, post unnecessary if sufficient coronal dentine is present
-Avoid in mandibular incisors due to thin/tapering/ narrow mesiodistal roots
-Premolars, small pulp chambers and tapering roots. Thin in mesiodistal cross-section and proximal invaginations. If a post is to be placed then place in the widest root canal. Avoid in curved canals to avoid perforations!
Root filling length
-4-5mm root filling apically
Post width
-No more than 1/3 of root width at narrowest point and 1 mm of remaining circumferential coronal dentine
Sufficient alveolar bone support, at least half of post length into the root
Minimum 1:1 post length/crown length ratio
Ferrule
At least 1.5mm height and width of remaining coronal dentine
What is a ferrule and what does it do
Dentine collar. Encirclement of 1- 2 mm of vertical axial tooth structure within walls of a crown
Prevents tooth fracture
If crown margin is not placed onto solid tooth, root fracture significantly increased
Orthodontic extrusion or crown lengthening may be necessary to achieve this
What is the ideal post
Parallel sided
-Avoids ‘wedging’
-More retentive than tapered
Non-threaded (Passive)
-Smooth surface incorporates less stress to remaining tooth than threaded (Active)
Cement Retained
-Less retentive than threaded posts but cement acts as buffer between masticatory forces and post/tooth
What are the classifications of posts
Manufacture – pre-formed/prefabricated or custom made
Material – cast metal, steel, zirconia, carbon/glass fibre
Shape – parallel sided or tapered
What are prefabricated posts
Only 1 visit required
No impressions and laboratory visit required
Chairside core build-up
Post and core are different materials
Immediate preparation of core
Large selection of designs and materials
What are the types of prefabricated posts
A: Tapered Smooth
B: Tapered Serrated
C: Tapered Threaded
D: Parallel Smooth
E: Parallel Serrated
F: Parallel Threaded
What are custom posts and how they made
Cast from direct pattern fabricated in patients mouth e.g. Duralay
Indirect pattern can be fabricated in the lab e.g. impression of the post hole and wax-up of post and core in lab (most common method)
Unified post and core e.g. made one piece, the same material
2 visits required – impressions and fit. Temporisation between visits and lab stage required. Risk of contamination of the root canal between visits.
Cast post made in Type IV heat hardened gold
What can the post materials be
Metal - cast gold, stainless steel, brass, titanium
Ceramics - alumina, zirconia
Fibre - glass, quartz, carbon
What are the advantages and disadvantages of the post materials used
Metal
-Poor aesthetics, root fracture, corrosion, nickel sensitivity. Radiopaque on radiographs
Ceramics
- High flexural strength and fracture toughness. Favourable aesthetics. Difficult retrievability and root fracture common
Fibre
- Flexible, similar properties to dentine. Aesthetic, retrievable, bond to dentine with DBA’s. Radiolucent on radiographs
What is a core build up
Internal part of tooth is built-up with restorative material to replace the lost tooth tissue
The core is prepared. It provides retention and resistance for definitive restorations (so that it can successfully support a dental crown)
What materials are used for a core build up
Composite
– most commonly used core material. Tooth coloured so good aesthetics. Bonds to the tooth structure. Technique sensitive, so moisture control required. Used with fibre posts
Amalgam
- tend to avoid as retention is required. Poor aesthetics. Core cannot be prepared straightaway – need 24hrs to set. Avoid pinned amalgams.
Glass ionomer
- not really used as it absorbs water and core expands in size
Problems with post crowns
Perforation
Core fracture
Root fracture or crack
Post fracture
How is post perforation managed
Repair – internal or external (periradicular surgery)
Extraction
How can you remove a post
Ultra-sonics
Masseran Kit
Eggler
Moskito Forceps
