Endodontics Flashcards
Pathological Resorption: 52 - 94 Management of complex cases: 95 - 140 Retreatment Procedures: 141 -175
Endodontic material
Types of stainless-steel files
Files:
1. K file – have a square cross section
2. Flexofile – have a triangular cross section
3. Hedstroem file
4. Barbed broaches – only used for removing pulpal tissue when present, not suitable for use in narrow, curved canals
Most canal treatments are started with hand instruments followed by the completion by rotary instruments.
Hand instruments are especially useful at the early phases of instrumentation to establish a glide path, prior to using rotary instruments.
In anatomically challenging cases an in treating instrumentation complications, hand instruments may be the only solution.
Flexofiles
Used for most instrumentation:
preparation of a glide path – defined as a smooth, patent passage from the coronal orifice of the canal to the radiographic terminus (apical constriction). A successful glide path is an uninterrupted passage that can be reproduced when small-size files are used in sequence in the canal.
Apical gauging – apical gauging implies measuring/assessing the apical diameter of the canal, where the instrument fits snuggly and resist further apical movements. This ensures apical terminus of the prepared canal. Ni-Ti instruments are preferred for gauging because of their flexibility. They are inserted straight in and straight out, without any rotation. This is done after preparation of root canal. They have a nonaggressive tip (batt tip)
Hedstroem files – very stiff files, can only be used in up and down motion, file cuts when moved in the coronal direction. Today only used in retreatment cases to help remove gutta-percha or an overfilling of the root canal.
Interappointment medicaments:
Use of non-setting calcium hydroxide paste in endodontics, non-setting paste, powder mixed with sterile water.
Aims –
1. To reduce and prevent multiplication of microorganisms that remain following careful cleaning and shaping.
2. Prevent reinfection through coronal or apical leakage
Calcium hydroxide uses –
1. Inter-appointment intracanal medicament
2. Pulp capping
3. Apexification
4. During treatment of root perforations, root fractures, root resorption and dental trauma.
5. Root canal sealer
The European society of endodontology’s quality guidelines suggest that when we carry out root canal treatment, we are obliged to do a clinical and radiographic follow-up at least:
- 1 year after treatment
- Further follow-up for up to 4 years – if bony healing is not complete according to Strinberg Acta Odontol Scand 1956: 14: 1-175
When is root canal retreatment indicated:
- Persistent periapical pathology following root canal treatment
No radiographic signs of bony healing after 4 years - 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 after previous treatment. - A new restoration is planned for a tooth and radiographic assessment shows an inadequate root canal filling and/or a periapical radiolucency.
The Toronto study is a publication on the treatment outcome in endodontics shows the following for initial treatment.
Primary treatment
- Without periradicular periodontitis = 92%
- With periradicular periodontitis = 74%
- Overall = 81%
The Toronto study then later went to do a publication: treatment outcome in endodontics: the Toronto study—phases 3 and 4: orthograde retreatment.
Retreatment
- Without periradicular periodontitis = 89-100%
- With apical periodontitis = 56-84%
A study done by Ng et al. 2011: a prospective study of the factors affecting outcomes of nonsurgical root canal treatment: part 1: periapical health.
The conclusion from this study was that success was based on periapical health
- Primary RCT 83%
- Secondary RCT 80%
A systematic review done by Ng: outcome of secondary root canal treatment: a systematic review of the literature.
17 studies were included ranging from 1961-2005, the overall success rate was found to be 77%
The studies had three prognostic factors; these three factors all determine the success rate of secondary root canal treatment.
- Pre-operative periapical lesions
- Apical extent of root canal filling
- Quality of coronal restoration
The terms to describe the outcome of RCT is no longer success or failure, they are the following.
Healed
- Clinically – no signs/symptoms
- Radiological – no residual radiolucency, or scarring after surgery
Healing
- Clinical – no signs or symptoms
- Radiological – reduced radiolucency in follow-up < 4 years
Asymptomatic function
- Clinical – no signs or symptoms combined with no or persistent radiolucency, reduced in size or unchanged.
Persistent/recurrent/emerged disease
- Clinical – with or without symptoms
- Radiological – new, increased, unchanged or reduced after >4 years
Prevention of post-treatment disease
Guidelines on the quality of root canal treatment
- Rubber dam isolation
- Proximity of preparation to apical constriction
- Sufficient taper of preparation – allowing for adequate irrigation and disinfection of the root canal. This will also allow enough space for interappointment medicament if required (non-setting calcium hydroxide)
- Correct extension of root canal obturation without extrusion
- Adequate coronal seal to prevent re-infection
Indications for root canal retreatment
- Previous treatment has failed
Signs of inflammation or infection - Persistent symptoms, sinus tract (chronic abscess), swelling, pain.
- Failure of previous treatment because of technical reasons
- Existing pathology and new restoration planned for tooth.
A = radiograph of mandibular with inadequate root filling and asymptomatic apical periodontitis.
B = the tooth has been retreated conservatively through the crown.
C = complete periapical repair is evident at the 6-month control.
This image shows 4 potential areas where microbes can be post treatment.
- Intraradicular microbes: if the preparation of the canal is not at its correct length, then microbes will persist at the constriction and spread.
- Extraradicular microbes: this is when microbes have invaded the host response system and established themselves in the periapical tissues.
- Foreign body reaction to extruded gutta- percha.
- True cyst which is cavity that has walled itself off from the root canal system.
Causes of post-treatment disease
Microbial causes
- Intraradicular microbes: Intraradicular infections, either persistent or secondary are the major causes of endodontic treatment failure.
Persistent = where the microbes were not removed during the initial treatment
Secondary = where the microbes have entered the root canal system via coronal leakage
- Extraradicular microbes
- Radicular cyst
- Cracked teeth, vertical root facture = allowing microbes to enter the root canal system
- Coronal leakage
Non-microbial causes
- Cholesterol crystals in the periapical tissues
- Foreign body reactions in the periapical tissues
Intraocular infections in root canal treated teeth can be classified in two groups
- Persisting infection: inadequate isolation/disinfection during treatment
- New secondary infection through leakage
Radiographically you can see if a poor root canal filling has been placed, and often associated with periapical radiolucency, it is worth to note that radiographs do not indicate the biological status of the root canal.
Persistent bacteria
- Those that remain in the root canal system after root canal disinfection and interappointment dressing gram positive bacteria appear to be more resistant to antimicrobial treatment and can adapt to harsh environmental conditions in instrumented and medicated root canals.
However, they do not always maintain an infectious process
- Residual bacteria may die after obturation
- Residual bacteria may be present in insufficient numbers and virulence
- They may be located in areas where they have no access to periapical tissues
In canals that are apparently well treated tend to have – 1-5 species
In canals with inadequate treatment tend to have 10-20 species like untreated canals.
In retreatment cases nine times more likely to harbour Enterococcus Faecalis, candida in 18%
Common microbes associated with retreatment cases:
- Enterococcus faecalis
- Streptococcus
- Lactobacillus
- Actinomyces
- Propionibacterium
- Candida albicans
The possible origins of these microbes:
- Contamination during initial treatment
- Leaving a tooth on open drainage
- Coronal leakage post-treatment
In most cases apical periodontitis inflammatory lesions succeed in preventing microorganisms from invading the periapical tissues.
The inflammatory response would be the bodies response to supress this infection from reaching the periapical tissues.
Occasionally the microorganisms can overcome the inflammatory defence barrier and establish an?
Extraradicular infection e.g., acute apical abscess.
Bacterial colonies can also form biofilms on the external root surface and bacterial colonies can exist inside periapical granulomas.
What is a radicular cyst?
Is the most common odontogenic cyst of inflammatory origin, arising from epithelial cell rests in periodontal ligament.
A radicular cyst can develop into a true cyst or a pocket cyst. what are the differences?
True cyst: lesion enclosed by epithelial lining.
Pocket cyst: epithelial sac communicates with root canal system.
- A pocket cyst will normally heal following endodontic treatment whereas a true cyst wont.
Endodontic failure caused by inadequate restorative procedures: review and treatment recommendations, Healing et al. J prosthet dent; 87: 674-8 – reviewed literature 1969-99 41 papers concluding:
Prognosis can be improved by sealing the canal and minimizing leakage of oral fluids and bacteria – do it as soon after root canal treatment as possible.
Cholesterol crystals are from ?
dying cells during chronic inflammation
Foreign body reaction include:
- Gutta-percha
- Sealers
- Paper points
- Cotton pellets – contain cellulose and the body has no way of breaking it.
A patient coming in for retreatment for root canal, a clinical assessment has to be made, this includes the following.
- Patient history
- Examination
- Special investigations as required
- Radiographic examination
- CBCT
- Diagnosis
- Treatment plan
Do nothing
Extract tooth
Retreatment
Surgical retreatment
When we look at a radiograph and CBCT for evaluation of retreatment the following is looked for:
- Caries
- Defective restorations
- Periodontal health
- Quality of obturation
- Existence of missed canals or procedural errors
- Periapical pathology
- Perforations
- Fractures
- Resorptions
- Canal anatomy
when Planning retreatment what should we be considering?
- Is it a strategic tooth? If it is a lone standing molar, then maybe it’s not worth the time and cost to retreat.
- How much remaining coronal tooth structure is remaining? So that tooth can be restored once the complex procedure is complete.
- What is periodontal support?
- Is periapical disease present?
- Are there aesthetics issues
- Are there technical difficulties as shown radiographically?
Techniques to retreating root canals
1. Gain access to root canal system
Crown removal
Post removal
2. Removal of root canal filling material
Gutta percha
Carrier based systems
Silver points
Pastes
Treatment with direct restorations, what are the stages to get access to the canals?
- Remove any existing caries
- Reduce any unsupported cusps
- Ensure sufficient remaining tooth structure to place definitive restoration
- Ensure tooth can be isolated under rubber dam
Orthodontic band/GI
Electrocautery, crown lengthening procedures
Teeth with indirect restorations, assess quality of restoration
1. Crowns, bridges, inlays, onlays, post cores
2. Integrity of coronal seal – no recurrent caries or marginal deficiencies
Access through existing crowns pose a risk, why?
- A higher risk of perforation
- Visibility reduced
- Tooth alignment may be altered by the crown
Important to carefully assess the pre-treatment radiograph, if any potential difficulties remove the crown.
Removing crowns, what are the benefits when trying to gain access to the canals?
- When the crown is defective/caries
- Allows assessment of remaining tooth structure
- Visibility and access to root canals improved
- Avoids risk of perforation when searching for canals – especially if tooth alignment has been altered by the crown
Removing a crown by sectioning, what are the procedures for this?
- Take a sectional impression first in putty
- Section the crown into two halves taking care not to cut through the core, then remove with an excavator
- Use a diamond bur for porcelain and tungsten carbide for metal
what is a wamkey used for?
a technique used to remove a crown.
Post removal can be complicated, the technique is dependent on the type of post, what should we ensure we do before we remove any posts ?
what are the types of posts/core/cement used?
what must you assess on a radiograph when undergoing post removal?
what techniques are available to remove posts?
Technique should minimize risk of root fracture: always important to advise patient that root fracture may be a complication of attempted post removal
Depends on type of post and core and cement: parallel/tapered. Active/passive, metal/quartz fibre
Always assess post type and length/width on a pre-treatment radiograph
2 main techniques:
- Post removal with ultrasonic energy
- Post removal with post pulling devices
Removing cast post core
1. Usually involves removal of coronal restoration
2. May require cut back of core using tungsten carbide bur prior to using ultrasonics
3. If post is extremely well fitted removal can be very difficult especially in oval shaped canals.
Techniques used to remove gutta percha
- Rotary endodontic files
Protaper D files for retreatment – used at 600 rpm 4Ncm
PTG endo instruments
- Ultrasonics
- Heat
- Solvents
Removal of GP using PTG
1. Measure estimated WL for radiograph
2. Depending on canal diameter select either an F2 or F3 finishing file, length 21mm
3. Set rpm to 600
4. Use in coronal 2/3s of canal – work from F3-F2-F1 if required
5. Then go down 1mm increments checking with EAL until WL and patency have been achieved
6. If apical part of the canal is underprepared/not obturated, negotiate with size 10 file, establish WL and complete preparation using normal PTG sequence at 300 rpm
Types of stainless-steel files
Files:
- K file – have a square cross section
- Flexofile – have a triangular cross section
- Hedstroem file
- Barbed broaches – only used for removing pulpal tissue when present, not suitable for use in narrow, curved canals
Most canal treatments are started with hand instruments followed by the completion by rotary instruments.
Hand instruments are especially useful at the early phases of instrumentation to establish a glide path, prior to using rotary instruments.
In anatomically challenging cases an in treating instrumentation complications, hand instruments may be the only solution.
Flexofiles
Used for most instrumentation:
preparation of a glide path – defined as a smooth, patent passage from the coronal orifice of the canal to the radiographic terminus (apical constriction). A successful glide path is an uninterrupted passage that can be reproduced when small-size files are used in sequence in the canal.
Apical gauging – apical gauging implies measuring/assessing the apical diameter of the canal, where the instrument fits snuggly and resist further apical movements. This ensures apical terminus of the prepared canal. Ni-Ti instruments are preferred for gauging because of their flexibility. They are inserted straight in and straight out, without any rotation. This is done after preparation of root canal. They have a nonaggressive tip (batt tip)
Hedstroem files – very stiff files, can only be used in up and down motion, file cuts when moved in the coronal direction. Today only used in retreatment cases to help remove gutta-percha or an overfilling of the root canal.
Interappointment medicaments:
Use of non-setting calcium hydroxide paste in endodontics, non-setting paste, powder mixed with sterile water.
Aims –
1. To reduce and prevent multiplication of microorganisms that remain following careful cleaning and shaping.
2. Prevent reinfection through coronal or apical leakage
Calcium hydroxide uses –
- Inter-appointment intracanal medicament
- Pulp capping
- Apexification
- During treatment of root perforations, root fractures, root resorption and dental trauma.
- Root canal sealer
A physiological or pathological event mainly occurring due to the action of activated clast cells.
Characterised by the transitory or progressive loss of cementum or cementum/dentine. Onset is associated with significant necrosis of cementoblasts and/or injury to the periodontal ligament – this is the definition of what?
Resorption
Resorption occurs mainly due to the activation of which cells?
Clasts cells
The onset of resorption usually begins with what?
Significant necrosis of cementoblasts and/or injury to the periodontal ligament.
Two phases are required for resorption what are they?
Injury and stimulation
- Injury is related to non-mineralized precemtum or predentine
- Cementoblasts are destroyed directly or become necrotic as a result of compromised blood supply to PDL or Pulp
There are three main causes of injuries that result in resorption what are they?
- Mechanical
- Trauma
- Surgical procedures
- Excessive pressure (impacted teeth, cysts tumours, orthodontic treatment) - Infections of root canal or PDL
- Chemical – bleaching agents (30% hydrogen peroxide)
What type of stimulation results in resorption?
- Infection
- Pressure
- Without a constant stimulus the process is self-limiting (transient resorption)
There are some systemic and endocrine diseases that may result in tooth resorption, what are they?
- Hypo and hyperthyroidism
- Calcinosis - a condition in which calcium salts are deposited in the skin and subcutaneous tissue.
- Gaucher’s syndrome - the result of a build-up of certain fatty substances in certain organs, particularly your spleen and liver.
- Turner syndrome – female only, developmental problems
- Pagets disease – disrupts normal cycle of bone renewal, causing bone to become weak and deformed.
- Herpes zoster – shingles
What is the mechanism for resorption?
- Damage causes chemotactic process
- Area of damage attracts activated cells
- Activated cells odontoclasts/osteoclasts
- Activated cells colonise the damaged surfaces and initiate the resorptive process
- The cells are located in depressions known as howship lacunae
When an osteoblasts detects some form of damage what does it release?
They release RANKL
What to the RANKL bind on to?
They bind on to the RANKL receptors on the nearby monocytes (precursor osteoclast) on the surface
What does the binding of the RANKL do the monocyte?
RANKL induces the monocytes to fuse together to form a multinucleated osteoclast cell. RANKL helps the osteoclast cell to mature and activate so they can start resorbing
What enzymes do osteoclasts cells release to resorb the bone?
Secrete lysosomal enzymes (collagenase)
The osteoclasts drills pits in to the bone known as what?
Howship’s Lacunae
Osteoclast also produce hydrochloric acid which dissolves what to produce what?
Hydrochloric acid dissolves to hydroxyapatite to produce calcium and phosphate ions
o keep the bone resorption under control, the osteoblasts also secrete?
Osteoprotegrin
What is the purpose of osteoprotegrin?
Osteoprotegrin binds to RANKL and prevents its from activating the RANK receptors on the monocyte. Slowing down the activation of osteoclasts
Once osteoclasts have completed there job they commit suicide by?
Apoptosis
Following bone resorption osteoblasts migrate to site of resorption (lacunae) and secrete?
Osteoid seam, which is made of collagen to fill in the lacunae created by the osteoclasts.
Calcium and phosphate deposit on the seam creating what?
Hydroxyapatite
this image shows the Heithersay 1999 clinical classification of cervical resorption. What do each class indicate.
Class 1 - small with shadow penetration
Class 2 – close to coronal pulp, no radicular extensions
Class 3 – deeper but not beyond coronal third
Class 4- extensive beyond coronal third
What would you see in a radiographic feature that discriminates internal root resorption.
With internal root resorption on a radiograph you would not expect to see the outlines of the pulp canal. With invasive cervical resorption, you would see resorption inside, but because you can see the outline of the pulp, this determines that it is invasive cervical resorption.
Oval, round lesions any site along root canal usually symmetrical, what type of resorption is going on?
Internal root resorption
this radiograph is an example of what type of resorption?
Orthodontic pressure root resorption
Who proposed this algorithm to manage the fracture of NiTi instruments?
Washes et al
Which author determined that the position of the file in relation to the root curvature influences the successful removal of the file?
Bobby Patel.
What are the mechanical techniques to remove the fractured file?
- H file (s)
- Gripping devices: fine haemostat or Stieglitz forceps
- Excavators
The removal of a fractured file using the hedstroem file technique is only possible if?
The file is located coronally with a wide canal
What are these?
Ultrasonics
How does the tube system work?
Straight line access is required for this system to work
- Trephine with ultrasonic
- Position the microtube
- Engage and remove
broken tool remover uses lasso mechanism to get file out
What is a ledge?
An iatrogenically created irregularity (platform = very firm stop) in the canal, that impedes access of the instruments to the apex.
What are the causes of ledge formation?
- Inadequate access cavity
- Incorrect assessment of canal curvature
- Failure to pre-bend ss files
- Using larger, stiffer ss instruments
- Failure to use instruments in a sequential manner
- Cutting on inward rather than outward stroke
- By-passing a fractured instrument
- Negotiation of calcified canal
What are the management of ledges?
- Establish the depth at which the ledge is present
- Coronal flaring up to f2-f3 working 1-2 mm shorter, use a small irrigation needle (gauge 30-purple) to irrigate between files + recapitulation
- PUI with chelator and NaOCL
- Probe with a pre-bent 08 ss file (coated in a chelator paste).
- Use the shortest file available which the level of the ledge in watch-winding and a gentle picking motion.
- If possible to bypass do not remove the file but use short vertical strokes with a gentle anti-curvature pressure to change the shape of the ledge.
- Keep the tip of the file apical to the ledge at all times.
- Repeat with size 10, 15 and 20 files until ledge removed
- Use pre-bent hand ProTaper files to complete preparation
A = radiograph of mandibular with inadequate root filling and asymptomatic apical periodontitis.
B = the tooth has been retreated conservatively through the crown.
C = complete periapical repair is evident at the 6-month control.
This image shows 4 potential areas where microbes can be post treatment.
- Intraradicular microbes: if the preparation of the canal is not at its correct length, then microbes will persist at the constriction and spread.
- Extraradicular microbes: this is when microbes have invaded the host response system and established themselves in the periapical tissues.
- Foreign body reaction to extruded gutta- percha.
- True cyst which is cavity that has walled itself off from the root canal system.
A radicular cyst can develop into a true cyst or a pocket cyst?
True cyst: lesion enclosed by epithelial lining.
Pocket cyst: epithelial sac communicates with root canal system.
- A pocket cyst will normally heal following endodontic treatment whereas a true cyst wont.
