Endodontics Flashcards
When should an RCT be followed up?
- clinical and radiographic follow-up at least 1 year after treatment
- further follow up for up to 4 years
When is RCT retreatment indicated?
- persistent periapical pathology following RCT
- new periapical pathology associated with a root-filled tooth
- new restoration for tooth planned and radiographic assessment shows inadequate root canal filling or periapical radiolucency
What can be seen radiographically in the presence of a persistent periapical pathology following RCT?
No radiographic signs of bony healing after 4 years
What is considered new periapical pathology associated with a root-filled tooth?
- initial healing but a new radiolucency develops some time later.
- Root canal system has become infected subsequent to previous treatment
What are the estimated success rates of primary and secondary RCT?
Primary 83%
Secondary 80%
What are three main prognostic factors for RCT pretreatment?
1) pre-operative periapical lesion
2) apical extent of coronal restoration
3) quality of coronal restoration
What does the term “healed” indicate with RCT?
- clinically - no signs/symptoms
- radiological - no residual radiolucency or scarring after surgery
What does the term “healing” indicate with RCT?
- clinical - no signs/symptoms
- radiological - reduced radiolucency in follow up <4yrs
What does the term “asymptomatic function” indicate with RCT?
- clinical - no signs/symptoms combined with no or persistent radiolucency, reduced in size or unchanged
What does the term “persistent/recurrent/emerged disease” indicate with RCT?
- clinical - with or without symptoms
- radiological - new, increased, unchanged or reduced after >4yrs
What guidelines are there in the prevention of post-treatment disease regarding quality of RCT?
- rubber dam isolation
- proximity of preparation to AC
- sufficient taper of preparation
- adequate irrigation and placement of interappointment medicament
- correct extension of obturation without extrusion
- adequate coronal seal to prevent re-infection
What are the four indications for root canal retreatment?
1) previous treatment failed - signs of inflammation/infection
2) persistent symptoms, sinus tract (chronic abscess), swelling, pain
3) failure of previous treatment due to technical reasons
4) existing pathology and new restoration planned for tooth
What are four different types of periapical pathology?
1) intraradicular microbes
2) extraradicular microbes
3) foreign body reaction
4) true cyst
What are five examples of microbial causes of post-treatment disease?
1) intraradicular microbes - either persistent or secondary to major cause of endo failure
2) extraradicular microbes
3) radicular cyst
4) cracked teeth, vertical root fracture
5) coronal leakage
What are two examples of non-microbial causes of post-treatment disease?
1) cholesterol crystals
2) foreign body reactions in periapical tissues
What are the two causes of intraradicular infection root canal treated teeth?
1) persisting infection - inadequate isolation/disinfection during RCT
2) new/secondary infection through leakage
Do radiographs indicate the biological status of the root canal?
no
What are “persistent bacteria”?
those that remain in the root canal system after root canal disinfection and interappointment dressing
What type of bacteria is commonly considered a “persistent bacteria”?
Gram positive bacteria - appears to be more resistant to antimicrobial treatment and has the ability to adapt to harsh environmental conditions in instrumented canals
How many species of bacteria usually exist in “apparently well treated canals”?
1-5 species
How many species of bacteria usually exist in “inadequately treated” canals?
10-20 species, similar to untreated canals
What are the microbes commonly found in retreatment cases? 6
1) E faecalis
2) streptococcus
3) lactobacillus
4) actinomycetes
5) propionobacterium
6) candida albicans
What are three possible origins of microbes in retreatment cases?
1) contamination during initial treatment
2) leaving a tooth on open drainage
3) coronal leakage post-treatment
What forms can bacterial colonies exist in extraradicularly?
- biofilms on external root surface
- inside periapical granulomas
- establish periradicular infection e.g. acute apical abscess
What is a radicular cyst?
- most common odontogenic cyst of inflammatory origin
What does a radicular cyst arise from?
epithelial cell rests in the PDL
What are the two types of radicular cyst?
- true cyst
- pocket cyst
What is a true cyst?
lesion enclosed by an epithelial lining
What is a pocket cyst?
epithelial sac communicates with the root canal system
What kind of cyst will heal following RCT?
a pocket cyst will normally heal following endodontic treatment whereas a true cyst won’t
What are cholesterol crystals formed of?
from dying cells during chronic inflammation
What are four examples of things that can cause a foreign body reaction (non-microbial cause of post treatment disease)?
- gutta percha
- sealers
- paper points
- cotton pellets
What radiographic techniques can be used to detect apical periodontitis and which is highly sensitive?
- panoramic radiographs 0.28
- periapical radiographs 0.55
- CBCT 1.00 (very high sensitivity)
Accessing a root canal treated tooth through an existing crown risks what?
higher risk of perforation due to reduced visibility and tooth alignment may be altered by the crown
When should a pre-existing crown be removed for re-treatment and what are the advantages?
- when a crown is defective/caries
- to allow assessment of remaining tooth structure
- to improve visibility and access to canals
- avoid perforation risk
What does sectioning involve?
- take sectional putty impression first
- section crown into two halves taking care not to cut through core, then remove with excavator
What kind of bur should be used to section a porcelain crown?
diamond bur
What kind of bur should be used to section a metal crown?
tungsten carbide
What is the WAMkey technique for removing a metal or MCC?
1) estimation of access point
2) incision of crown
3) horizontal extension of cavity
4) shaping of cavity
5) insertion of WAMkey instrument
6) slight rotation movement of shaft
What are two examples of crown removers?
1) crown tapper
2) KaVo Coronaflex
What are the two main techniques of post removal?
- post removal with ultrasonic energy
- post removal with post pulling devices
What kind of ultrasonics are used for post removal using ultrasonic energy?
Piezoelectric ultrasonics - 30-40kHz
tips for post removal have a blunt end
How do you remove a screw type active post?
-remove core material from around post with high speed burs and ultrasonics
- use wrench supplied by manufacturer for insertion
- ultrasonics can aid process by breaking up cement
How do you remove a cast post and core?
- usually involves removal of coronal restoration
- may require cutback of core using tungsten carbide bur prior to ultrasonics
- if post extremely well fitting then removal can be very difficult
What are four examples of post pulling devices?
1) Egglers post pulling device
2) Ruddle post pulling kit
3) Massarann Kit
4) ivory miniature post puller
What makes a post more difficult to retrieve?
adhesive resin cements
What is used to remove a quartz fibre post?
RTD quartz fibre post removal kit
What four techniques can be used for the removal of gutta percha?
1) rotary endodontic files
2) ultrasonics
3) heat
4) solvents
How is GP removed using PTG?
1) measure estimated WL for radiograph
2) depending on diameter select either F2 or F3, length 21mm
3) rpm to 600
4) use in coronal 2/3 - work from F3-F2-F1 if required
5) go down in 1mm increments checking EAL until WL and patency achieved
6) if apical section underprepared/not obdurated negotiate with size 10 file, establish WL and patency and complete prep using normal PTG sequence at 300rpm (S1, S2 etc)
What is the Hedstrom files and solvent approach to removing GP?
- traditional technique
- files are SS therefore less flexible, not effective in narrow, curved canals
- useful if a single cone obturation or poorly compacted GP
- engage loose GP with file and pull to remove
- do not engage canal wall
Are solvents required for retreatment with rotary NiTi instruments?
no definitive answer
What are 5 types of solvent?
1) chloroform
2) turpentine
3) DMS IV (Eugenol)
4) Endosolv R (resin)
5) Endosolv E (eugenol)
How can heat be used to remove GP?
- softens and removes GO
- useful when removing coronal GP for post placement
- remaining GP soft and requires vertical compaction
What are the two types of carrier-based GP removal?
1) thermafil
2) guttacore
What is thermafil?
- carrier based GP removal
- plastic carrier covered in alpha phase GP
- plastic sprue difficult to remove esp in underprepared canals
- care must be taken as very easy to deflect and perforate
What is guttacore?
- carrier based GP removal
- carrier made of cross-linked GP
- allows easier removal in re-treatment cases
What are silver points?
- technique for removal of RCT filling
- care not to cut coronal end
- remove with Stieglitz forceps or gently trough with fine ultrasonic tip
- when micro leakage occurs, cement fails and cone corrodes
Why are endodontic pastes mainly banned now?
- technique for removal of RCT filling
- shrinkage and poor seal made of toxic materials
- often contain paraformaldehyde which is mutagenic, carcinogenic
- endomethasone
- resorcinol-formalin (Red Russian) - sets very hard, not radiopaque, difficult to remove and often discolours tooth pink/red
