Endodontics Flashcards
1
Q
What guidelines are used for RCT quality assurance?
A
European Society of Endodontology’s Quality Guidelines.
2
Q
When should a patient be reviewed after RCT?
A
- CLINICAL and RADIOGRAPHIC follow up at least 1 year after treatment.
- Further follow up for up to 4 years.
3
Q
4 indications for root canal retreatment?
A
- Persistent periapical pathology following root canal treatment (persistent symptoms, sinus tract, swelling, pain).
- New periapical pathology associated with a root-filled tooth.
- A new restoration is planned for a tooth and radiographic assessment shows an inadequate root canal filling and/or a periapical radiolucency.
- Failure of previous treatment (ex. due to technical errors, signs of inflammation/ infection).
4
Q
What were the Ng studies? What did the find (%)?
A
- Systematic review of 17 studies, 1961 - 2005.
- Secondary RCT has a 77% SUCCESS RATE.
5
Q
3 prognostic factors of retreatment according to Ng study?
A
o Pre-operative periapical lesion.
o Apical extent of root canal filling.
o Quality of coronal restoration.
6
Q
Healed?
A
- Clinically: no signs/symptoms.
- Radiological: No residual radiolucency or scarring after surgery.
7
Q
Healing?
A
- Clinically: no signs or symptoms.
- Radiological: reduced radiolucency in follow up <4 years.
8
Q
Asymptomatic function?
A
- Clinically: no signs or symptoms.
- Radiological: no or persistent radiolucency, reduced in size or unchanged.
9
Q
Persistent/ recurrent/ emerged disease?
A
- Clinically: with or without symptoms.
- Radiological: new, increased, unchanged or reduced after >4 years.
10
Q
Prevention of post treatment disease (6)?
A
- Rubber dam isolation.
- Proximity of preparation to the constriction.
- Sufficient taper of preparation.
- Adequate irrigation and placement of inter appointment medicament.
- Correct extension of root canal obturation without extrusion.
- Adequate coronal seal to prevent re-infection.
11
Q
Persistent periapical pathology following root canal treatment?
A
no radiographic signs of bony healing after 4 years.
12
Q
new periapical pathology associated with a root filled tooth
A
- Initial healing but a new radiolucency develops some time later.
- Root canal system has become infected (by coronal leakage) subsequent to previous treatment.
13
Q
Toronto study?
A
- Friedman.
- Primary treatment –> 81 success.
- Retreatment –> no PA 89-100%, PA 56-84%.
14
Q
Treatment outcomes - Ng et al 2011
A
Success based on periapical health:
- Primary RCT 83%.
- Secondary/ Retreatment RCT 80%.
15
Q
5 microbial causes of post-treatment disease?
A
- Intraradicular microbes.
- Extraradicular infection (microbes have invaded host defense mechanism and established themselves in periapical tissues).
- True/ Radicular cyst (cavity which has walled itself off from the root canal system).
- Cracked teeth, vertical root fracture.
- Coronal leakage
16
Q
Intraradicular microbes as a microbial cause of post-treatment disease (2)?
A
Intraradicular infections, either:
- Persistent: microbes were not removed during initial treatment.
- Secondary: microbes entered root canal system via coronal leakage.
17
Q
2 non microbial causes of post-treatment
A
- Foreign body reactions in periapical tissues (to extrusion of RCT material).
- Cholesterol crystals
18
Q
2 types of intraradicular infections in root canal treated teeth?
A
- Persisting infection: inadequate isolation/ disinfection during treatment.
- New secondary infection through leakage.
19
Q
What is a shortcoming of radiographs for assessing root canal treatments?
A
Radiographs do not indicate the BIOLOGICAL STATUS of the root canal.
20
Q
What are radiographically poor root canal fillings often associated with?
A
Periapical radiolucencies.
21
Q
What is a shortcoming of rotary files?
A
- Instrumentation can be done very quickly HOWEVER must ensure ADEQUATE DISINFECTION has occurred.
22
Q
Define persistent bacteria?
A
Bacteria that remain in the root canal system after root canal disinfection and interappointment dressing.
23
Q
What bacterial type is more likely to be persistent bacteria?
A
GRAM POSITIVE bacteria appear to be more resistant to antimicrobial treatment.
- Ability to adapt to harsh environmental conditions in instrumented and medicated root canals.
24
Q
Do persistent bacteria always cause infection?
A
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 to access to periapical tissues and thus nutrients.
25
How many bacterial species are expected in well-treated canals?
1-5 species.
26
How many bacterial species are expected in canals with inadequate treatment?
10-20 species, similar to untreated canals.
27
6 pathogens likely to be found in re-treated root canals?
- 9 times more likely to harbor **E facaelis**.
- **Candida albicans** in 18%.
- **Streptococcus**
- **lactobacillus**
- **actinomyces**
- **propionibacterium**
28
How is an apical abscess formed?
- In most cases apical periodontitis inflammatory lesions succeed in preventing microorganisms from invading the periapical tissues.
- Occasionally they can overcome this defence barrier and establish an extraradicular infection (ex. acute apical abscess).
29
2 things extraradicular bacterial colonies can do?
- Can form biofilms on the external root surface.
- Can exist inside periapical granulomas (actinomyces, propionibacterium proprionicum).
30
2 types of bacteria that may exist in periapical granulomas?
- Actinomyces.
- Propionibacterium propionicum.
31
What forms radicular cysts?
- Most common odontogenic cyst of INFLAMMATORY origin.
- Arises from EPITHELIAL CELL RESTS in PDL.
32
What is a true cyst?
- Lesion enclosed by epithelial lining.
- NO communication between cyst lumen and root canal system.
- Therefore will not heal after RCT and may thus require surgical intervention.
33
What is a pocket cyst?
- Epethilial sac lumen communicates with root canal system.
- Therefore will normally heal following RCT.
34
What did Heling et al find in their study 'endodontic failure caused by inadequate restorative procedures: review and treatment recommendations'
1. Prognosis can be improved by sealing the canal and minimizing leakage of oral fluids and bacteria.
2. Place definitive restoration as soon after root canal treatment as possible.
35
What has a clear correlation to periapical health?
Studies show a CLEAR CORRELATION between the TECHNICAL QUALITY OF ROOT CANAL FILLINGS apparent on RADIOGRAPHS and periapical health.
- Quality of coronal restoration also impacts success rate.
36
How our cholesterol crystals formed? How do they appear on histopathological slides?
- From DYING CELLS during chronic inflammation.
- Show as CLEFTS on histopathological slides.
37
4 materials that can cause a foreign body reaction?
- Gutta percha.
- Sealers.
- Paper points.
- Cotton pellets.
38
Why do paper points and cotton pellets cause foreign body reaction?
contain CELLULOSE and body does not have ability to break it down.
39
4 treatment options after assessing a tooth that require retreatment?
- Do nothing.
- Extract.
- Retreatment.
- Surgical retreatment.
40
10 things to things to check in radiographs/ CBCT?
* Caries
* Defective restorations
* Periodontal health
* Quality of obturation
* Existence of missed canals or procedural errors
* Periapical pathology
* Perforations
* Fractures
* Resorptions
* Canal anatomy
41
Sensitivity of DPT vs PA vs CBCT?
- DPT 0.28.
- PA 0.55
- CBCT 1
42
6 questions to consider when planning retreatment?
- is it a strategic tooth?
- How much remaining coronal tooth structure?
- what is the periodontal support?
- Is periapical disease present?
- Are there aesthetics issues?
- Are there technical difficulties as shown radiographically?
43
Steps to retreating teeth with DIRECT restorations?
1. Remove any existing caries.
2. Reduce any unsupported cusps.
3. Ensure sufficient remaining tooth structure to place definitive restoration.
4. Ensure tooth can be isolated under rubber dam.
44
2 ways to ensure a tooth can be isolated under rubber dam?
1. Orthodontic band/ GI.
2. Electrocautery, crown lengthening procedures.
45
Considerations when retreating a tooth with an INDIRECT restoration?
1. Assess quality of restoration
- Integrity of coronal seal, no recurrent caries or marginal deficiencies then retreat THROUGH indirect restoration.
46
What did Iqbal find in his study 'factors associated with the periapical status of restored, endodontically treated teeth'?
Crown margins of poor quality affected adversely the overall periapical status of root filled teeth.
47
2 reasons why accessing through a crown causes a higher risk of perforation?
- Visibility reduced.
- Tooth alignment may be altered by the crown.
48
2 occasions when we remove crowns prior to retreatment?
- When the crown is defective/ caries.
- If any potential difficulties are noted through the pre-treatment radiograph.
49
3 pros of removing crowns prior to retreatment?
* 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 or in older patients where pulp chamber depth is small.
50
What teeth are often rotated and artificially corrected with crowns?
Upper premolars
51
3 steps to sectioning a crown?
- Take a sectional impression in putty.
- Section the crown into 2 halves taking care not to cut through the core.
- Remove the two parts with an EXCAVATOR.
52
What bur is used to cut through a porcelain crown?
diamond bur.
53
What bur is used to cut through a metal crown?
tungsten carbide.
54
How to use a WAMKEY?
1. cut an oval shaped cavity in buccal wall of the crown in a depth slightly beyond midway into the occlusal surface of the tooth.
2. Insert WAMKEY and ROTATE it.
- Works well if crown has not been cemented with an ADHESIVE cement.
55
What are WAMKEYS used for?
Crown removal.
56
Downside of crown tapper?
Works really well in deficient margins.
Difficult to use if margins are intact.
57
Name 2 crown removers?
- Crown tapper.
- KaVo coronaflex.
58
What must the patient always be warned of when a post is to be removed?
ALWAYS ADVISE RISK OF ROOT FRACTURE!!!!!!!!
59
What must you do prior to attempting to remove a post?
Assess post type and length/ width on a pre-treatment radiograph.
- Parallel/ tapered, active/passive, metal/quartz fibre.
60
2 main techniques for post removal?
- Ultrasonic energy.
- Post pulling devices.
61
What is an important consideration when using ultrasonics to remove a post?
ALWAYS BLOW AIR/ WATER COOLANT.
- Ultrasonic tip generates a lot of heat, which can be transmitted through the core and post into the periapical tissues and cause BONY NECROSIS.
62
What are the ultrasonics used for removal of posts called? What is their shape?
- Piezoelectric ultrasonics (vibrations 30-40 kHz).
- Tips for post removal have a blunt end.
63
2 reasons why screw type active posts are no longer used?
- Wedging forces in root can result in root fracture.
- Do not provide a good seal within the root canal system.
64
3 steps to removing screw type active posts?
1. Remove core material from around post using high speed burs and ultrasonics.
2. Ultrasonics can help break up cement (and post may then unscrew).
3. Use WRENCH supplied by manufacturer.
65
Removing CAST post and core (3)
- Usually involves removal of coronal restoration
- May require cut back of core using tungsten carbide bur prior to using ultrasonics.
- If post is extremely well fitting removal can be very difficult especially in oval shaped canals.
66
Which post pulling device is useful when a fractured post is present in the canal?
Massarann kit.
67
4 examples of post pulling devices?
- Egglers post pulling device.
- Ivory miniature post puller.
- Ruddle post pulling kit.
- Massarann kit.
68
Downfall of all post pulling devices?
Require post to be loose.
69
What type of cement should be used when cementing posts?
DO NOT use ADHESIVE RESIN CEMENTS routinely to cement posts as it makes them difficult to remove.
- Do not use routinely with metal posts unless compromised retention.
- May lead to periapical surgery or XLA.
70
What can be used to remove Quartz fibre posts?
RTD fibre post removal kit.
1. Pin drill puts pilot hole into the quartz fibre post.
2. Second creates a CHANNEL through the post.
3. Pizzo size 2 used to remove remaining quartz fibre.
71
Important consideration about thermafill carrier based system?
Obturator has central plastic sprue covered in gutta pecha which can be very challenging to remove.
72
4 different types of root canal filling materials?
- Gutta percha.
- Carrier based systems (thermafil, guttacore).
- Silver points.
- Endodontic pastes.
73
Name an example of endodontic pastes?
Resorcinol.
74
4 techniques to remove gutta percha?
1. **Rotary endodontic files** (protaper D, PTG endo instruments).
2. **Ultrasonics** (used to remove extra gutta percha from pulp chamber in retreatment cases)
3. **Heat** (to remove gutta percha in post and core preparation).
4. **Solvents** (adjunct when carrying out retreatment as they can help soften the gutta percha).
75
What would you ideally use during retreatment cases?
Root canal retreatments ideally require the use of magnification to ensure all material has been removed from the root canal system.
76
2 downsides of rotary protaper retreatment files?
- Not very flexible.
- D1 has partially cutting tip, thus easy to cause LEDGES and PERFORATIONS.
77
5 steps to retreatment using PTG to remove GP?
1. Measure estimated WL from radiograph.
2. Depending on canal diameter select either F2 or F3 finishing file, length 21mm (shorter file is less flexible, rigidity needed to cut through GP).
3. Set rpm to 600.
4. Use in coronal 2/3rds of canal, work from F3 - F2 - F1 if required.
5. Then go down in 1mm increments checking with EAL until WL and patency have been achieved.
78
What to do in retreatment cases if the apical part of the canal is underprepared/ not obturated?
If apical part is underprepared/ not obturated:
1. Negotiate with size 10 file.
2. Establish WL/ patency.
3. Complete preparation using normal PTG sequence at 300 rpm (S1, S2 etc).
78
What is a more traditional technique of removing gutta percha for retreatment?
Hedstrom files and solvent.
79
In which canals do hedstrom files and solvent work well (2)? In which not?
Bad
- NOT effective in NARROW, CURVED canals (files made from SS therefore less flexible).
Good
- SINGLE CONE obturation.
- POORLY COMPACTED GP.
80
How are Hedstrom files used to remove GP?
- Engage the loose GP with the Hedstrom file, rotate and pull to remove.
- Do not engage the canal wall (can cause ledging).
81
In what cases should solvents to remove GP NOT be used.
- Never use solvents to remove GP when preparing a tooth for a POST SPACE.
- No control how far the solvent will permeate into the root canal system, could compromise apical seal.
82
5 types of solvents.
- Chloroform (no longer used).
- Turpentine
- DMS IV (eugenol).
- Endosolv R (resin).
- Endosolv E (eugenol).
83
Is solvent necessary?
No definitive answer as to whether a solvent is essential for retreatment with rotary NiTi instruments.
84
Use of ultrasonics to remove GP (2)?
- Useful to remove GP from the pulp chamber and entrance into the canals.
- Fine tips can be used to remove remaining tags of GP (using magnification).
85
Heat to remove GP (3)?
- Softens and removes GP.
- Useful when removing CORONAL GP for post placement.
- Remaining GP will be soft and requires vertical compaction.
86
What is thermafil? What is a downside?
- Carrier based gutta percha.
- Plastic carrier covered in GP.
- Plastic sprue is difficult to remove especially in underpreppared canals.
87
How can thermafil be removed (2)?
- Hedstrom files and solvent.
- Protaper D files.
- Care must be taken as very easy to deflect and perforate.
88
What is guttacore?
- Carrier-based gutta percha.
- Carrier is made from cross-linked GP. This allows for easier removal in retreatment cases.
89
2 downsides of silverpoints?
- Fail to adhere to sound biological principles.
- When microleakage occurs, the cement fails and the cone corrodes.
90
How are silver points removed (2)
- Care not to cut coronal end.
- Remove with **Stieglitz forceps**.
- Gently trough around with fine ultrasonic tip.
91
3 downsides of endodontic pastes?
- Shrinkage.
- Poor seal
- Made from toxic materials (mutogenic, carcinogenic).
92
3 ingredients in endodontic pastes?
- **Paraformaldehyde**: mutagenic, carcinogenic, neurotoxic.
- **Endomethasone**.
- **Resorcinol-formalin (red russian**: sets very hard, not radiopaque, very difficult to remove, tooth often discolored pinky-red.
93
What serious complication endodontic pastes cause?
NERVE PARAESTHESIA on extrusion.
94
4 aims of endodontic treatment?
- Access, clean and disinfect the root canal system.
- Reduce the number of microorganisms (those in planktonic suspension, in biofilm attached to canal walls, in inaccessible areas like apical delta and isthmuses).
- Remove necrotic tissue.
- Seal the system to prevent reinfection.
95
5 causes of persistent periapical radiolucencies in endodontically treated teeth?
- Intraradicular infection.
- Extraradicular infection.
- Foreign body reaction.
- true cyst.
- Fibrous scar tissue.
96
How can you differentiate between the different types of periradicular lesions?
- Clinically, periradicular lesions CANNOT be differentially
diagnosed as cystic or non-cystic based on conventional
radiographs.
- Only possible through HISTPATHOLOGY.
97
2 types of cysts?
- True cyst: cavities completely enclosed in an epithelial lining.
- Pocket/bay cyst: epithelium-lined cavities that are open to the root canal.
98
What did Nair et al find when they tested 256 periapical lesions histopathologically?
15% cysts.
99
4 indications for periradicular surgery
- **Failure of previous endodontic treatment if retreatment is NOT possible/ will not correct the problem** (ex. GP extrusion, post crown without obturation below post).
- **Anatomical deviations which prevent complete cleaning and obturation by an orthograde approach** (tortuous, curved roots, canal calcification).
- **Procedural errors** (ledges, blocks, perforations, file breakages, overfills).
- **Exploratory surgery** (identification of root fractures).
100
5 contraindications to periradicular surgery?
- **Anatomical factors** (proximity to nerve bundles, thick cortical bone, difficult access ex. palatal roots upper molars).
- **Inadequate periodontal support**
- **Non restorable tooth**
- **Medical history** (blood disorders, MI, cancer treatment).
- **Skill and ability of surgeon**
101
What type of lens system is used in loupes? What magnification? Type of light? 3 disadvantages?
- Convergent lens system (greenough system).
- Fixed magnification up to 4.5x.
- Light not integral but provided by fibreoptic headlight.
- Disadvantages: Users eyes must converge, ocular muscles can tire causing eyestrain and fatigue, small movements of the head result in loss of visual field.
102
what is the triad of endodontic microsurgery?
- Magnification.
- Illumination.
- Instruments.
103
4 things that determine magnification?
- The power of the eyepiece.
- The focal length of the binoculars.
- The focal length of the objective lens.
- The magnification changer factor.
104
What is the magnification range of a microscope? What do we use for periradicular surgery?
- 3x-30x.
- Use 8-10x for periradicular surgery.
105
Low, midrange and high magnification. Values and uses?
- **Low x3 to x8**: Wider field, high focal depth. Orientation and alignment of instruments.
- **Midrange 10 to 16**: Moderate focal depth. WORKING magnification.
- **High 20 to 30**: Focal depth shallow, inspection of fine detail.
106
3 preoperative medications for periradicular surgery?
- **Anti-inflammatory agents**: Ibuprofen 600mg immediately before surgery. Inhibits cyclo-oxygenase, preventing the formation of inflammatoy mediators.
- **Antibacterial rinses**: 0.2% chlorhexidine night before, morning of, 30 minutes before appointment.
- **Diazepam**: 5mg diazepam if very nervous.
107
2 uses of anaesthesia for periradicular surgery?
- Prevents pain during surgery
- Obtains presurgical haemostasis
108
Lidocaine for periradicular surgery (5)?
- lidocaine 2% with 1:80000 epinephrine (ideally 1:50000).
- Causes activation of alpha receptors in arteriolar muscles, submucosa and periodontium.
- Maximum dose 5 cartridges.
- Rate 1/2mL per min.
- Little or no response from CNS.
109
Articaine for periradicular surgery (2)?
- The only amide LA that contains a thiophene ring and an additional ester ring
- Greater tissue diffusion
110
What is a semilunar flap? 4 disadvantages?
- Created by a single curved HORIZONTAL incision.
- Disruption of blood supply, poor wound healing, limited surgical access, scarring.
- NOT USED IN MODERN ENDODONTICS.
111
What is a mucoperiosteal flap?
Includes mucosa, connective tissue and periosteum.
112
What is an intrasulcular design flap?
A mucoperiosteal flap where the horizontal incision involves the papillae and sulcular epithelium.
113
What is the flap usually used for periapical surgery called?
Papilla based incision.
114
What is a papilla based incision (4 steps)?
1. A shallow first incision at the base of the papilla.
2. Second incision folowing the contour of the first incision directed to the CRESTAL BONE --> Creates a **SPLIT THICKNESS FLAP** in the area of the papilla.
3. Intrasulcular incision in the cervical area of the tooth.
4. 1 or 2 relieving incisions.
115
2 advantages and 1 disadvantage of a papilla based incision?
1. Prevents gingival recession.
2. Heals quickly.
3. 2 sutures per papilla - time consuming suturing.
116
What type of blades are used during periradicular surgery?
- Relieving incisions: 15 or 15c.
- Papilla incisions: mini blades.
117
4 steps to flap elevation?
1. A sharp, small elevator is placed at the junction pf the horizontal and vertical incisions, with the CONCAVE surface against bone.
2. Place elevator beneath gingivae at LINE ANGLE.
3. Reflect APICALLY with a slow, firm motion to prevent TEARING.
4. Reflect periosteum completely to prevent bleeding, diminish pain and inflammation and speed up healing.
118
4 reasons to elevate the periosteum when raising a flap?
- Prevent bleeding.
- Diminish pain.
- Diminish inflammation.
- Speed up healing.
119
What elevator is used for periradicular surgery?
Prichard periosteal 4.5mm or 5.5mm.
120
What retractors are used for periradicular surgery? Name an advantage?
- KIM-PECORA RETRACTORS.
- Serrated tips give better anchorage
121
Define osteotomy?
Removal of cortical plate to expose root end.
122
2 things to do when preparing for osteotomy?
1. Assess length, number and curvature of roots using preoperative radiograph.
2. Look at proximity of apices to apices of adjacent teeth, mental foramen, mandibular nerve and sinus space.
123
What is used to "clean out" the area during periradicular surgery? At what magnification?
- CURETTES are used to remove granulation tissue, foreign bodies and bone particles (x10 to x16).
124
How can we clean the LINGUAL aspect of a periradicular pathology?
- Lingual aspect may only be cleaned after root resection.
- Bleeding will stop when all tissue has been removed.
125
What is the process of removing the granulation tissue during periradicular surgery called? How should this be done? Name an instrument.
- CURETTAGE.
- Try to peel granulation tissue from bony crypt in one piece if possible - limits amount of bleeding in bony crypt.
- Curettage should be as CLEAN AND FAST as possible.
- KiS instruments (can change tips).
126
Hemostasis during periradicular surgery?
Hemostasis is directly related to removal of the inflammatory material.
127
Preoperative hemostasis?
LOCAL ANESTHESIA.
- Use topical.
- 2% Lidocaine with 1:80.000 epinephrine.
- Alpha adrenergic receptors in smooth muscles of arterioles.
- Maximum dose of 1:50,000 is 5 cartridges.
- Rate 1/2mL/ min.
- Delay initial incision 15 minutes.
128
4 intraoperative hemostatic agents?
- Epinephrine pellets.
- Ferric sulphate.
- Calcium sulphate.
- Others (ex. surgical wax, thrombin, gelfoam, surgicel, collagen).
129
How does ferric sulphate cause hemostasis?
Agglutination of blood proteins - forms a plug.
130
How does calcium sulphate cause hemostasis? What is another benefit?
- Mechanically blocks open vessels.
- Aids in bone regeneration as forms a scaffold for osteoblasts.
131
What is the most effective and economic product for intraoperative hemostasis?
Epinephrine pellets.
132
4 steps to intraoperative hemostasis using epinephrine pellets?
1. Remove root apex.
2. Place racellet/ epinephrine pellets into the base of the bony crypt one by one.
3. Press pellets for **2-4 minutes** (allows blood to clot).
4. Remove one by one leaving racellet in place until final irrigation (aka after root canal prep and fill).
133
How long do you leave in racellets for hemostasis?
2-4 minutes.
134
What do we aim to create during root resection/
An environment conducive to regeneration of periodontium, alveolar bone, PDL and cementum.
135
How is root resection completed?
1. 3mm is resected perpendicular to long axis of tooth, LOW MAGNIFICATION.
2. Examine at MEDIUM magnification for presence of PDL (use dye to ensure resection complete).
136
3 benefits of root end resection?
- Decreases dentine tubules peripheral microfiltration.
- Removed majority of lateral canals and ramifications.
- Avoids endo-perio communications.
137
What handpiece and bur is used for root end resection?
- Impact air SURGICAL handpiece 45 degrees.
- LINDEMANN bur.
138
What can you use to ensure the entire depth of the root has been resected?
**1% methylene blue dye**
- stains PDL.
139
What do we do with the resected root surface (5)?
- Examine at HIGH magnification using the MICROMIRROR.
Examine for:
- Isthmus.
- C shaped canals.
- Canal fins.
- Apical microfractures.
- Leaky canals with partial seals and poor adapted GP.
140
3 traits of an ideal ultrasonic retrocavity preparation?
- Clean cavity.
- Parallel walls and centered along the long axis of the root canal filling.
- 3mm in depth.
141
under what magnification should ultrasonic retrocavity preparation be done?
- Carried out under medium magnification (10-16x).
- Inspected under high magnification (20-25x).
142
2 types of ultrasonic microtips?
- Piezo ultrasonic units.
- KiS tips.
143
What are ultrasonic microtips coated with (2)?
- White diamond OR zirconium nitride.
- Cuts fast, use with irrigation, leaves a rough surface.
144
5 advantages of ultrasonic microtips.
- Better access.
- Ultrasonic cleaning.
- Preparations follow canal anatomy.
- Isthmus preparation.
- Parallel walls - superior retention.
145
What do we inspect ultrasonic root end preparation for?
- Look for remnants of gutta percha.
- Re condense GP at base of preparation.
146
What is a historical material used for a root end filling? 4 disadvantages?
AMALGAM.
Poor clinical performance:
- Sets slowly, not biocompatible (free mercury, copper, zinc), leakage, corrosion.
147
Success and failure rates of amalgam as a root end filling?
- Success rates 57.7%
- Failure rates 42.3%
148
2 types of zinc oxide eugenol cements that can be used as root end filling materials?
- Intermediate restorative material (IRM).
- Super ethoxybenzoic acid.
149
Components of intermediate restorative material (IRM)? 2 advantages?
- Zinc oxide eugenol cement.
- Addition of polymethacrylate to powder.
- Better biocompatibility and higher success rates than amalgam.
150
Components of super ethoxybenzoic acid? 2 advantages and 2 disadvantages?
- Addition of quartz or aluminum oxide.
- Advantages: Well tolerated by tissues, good seal.
- Disadvantages: No capacity to regenerate cementum, difficult to manipulate.
151
6 components of MTA? What form is it found in?
- Tricalcium silicate.
- Tricalcium aluminate.
- Tricalcium oxide.
- Silicate oxide.
- Bismuth oxide.
- Iron (absent in white MTA)
- Hydration of powder forms a COLLOIDAL GEL.
152
6 characteristics/ advantages of MTA as a root canal end filling?
- Sets in 3 hours.
- Hydrophilic.
- Stimulates cementogenesis.
- Best biocompatibility.
- Best sealing ability.
- Best dimensional stability.
- Radiopaque.
- High pH.
153
Success rates of MTA as a root end filling material?
- 84% after 1 year.
- 92% after 2 years.
154
Placement technique of MTA as root canal filling?
1. Protect bone crypt.
2. Mix powder with sterile water to putty consistency.
3. Carry to root end with an MTA gun or Dovgan carrier.
4. Use micropluggers/ burnishers to lightly condense material.
5. Wipe off excess with a small moist cotton pellet.
155
What type of healing do we want by suturing? What type of suture is used? 2 disadvantages and 1 advantage?
- PRIMARY INTENTION healing.
- MONOFILAMENT suture.
- Disadvantage: Difficult to handle and knot.
- Advantage: less contamination.
156
What MATERIAL is used for suturing after periradicular surgery? What size of suture?
PROLENE
- 5-0: flaps with SULCULAR incisions and FREE GINGIVA.
- 6-0/ 7-0: PAPILLAE based incisions.
157
What type of knot is required for suturing following periradicular surgery? Why?
SURGEONS KNOT
- Double overhand.
- Single overhand in opposite direction.
- Prevents SLIPPAGE when using monofilaments.
158
5 steps to suturing following periradicular surgery?
1. Replace flap in correct position.
2. Press a damp gauze with finger pressure for 5-10 minutes.
3. Place first suture at FREE END of flap.
4. Use interrupted sutures.
5. Remove sutures after 48 hours- 4 days.
159
6 potential complications or periapical surgery?
- Post operative pain.
- Swelling
- Paraesthesia.
- Serious infection.
- Lacerations.
- Maxillary sinus perforation.
160
Advice given to patient for post-operative pain (2)?
- Anti inflammatory agents before pain begins (ibuprofen 600mg every 8 hours).
- Continue with pain medication for 48 hours.
161
Advice given to patient for post-operative swelling (3)?
- Comes up 2 DAYS AFTER the procedure and lasts 24 HOURS before disappearing.
- Can be alleviated with intermittent application of COLD DRESSING (20 minutes on 20 minutes off for the first 8 hours).
- Slows the blood flow and stimulates intravascular clotting.
162
What causes post operative ecchymosis? Where does it occur? Advice to patient?
- Caused by EXTRAVASATION and BREAKDOWN of blood in the subcutaneous tissues.
- Often occurs DISTAL from surgical site.
- Reassure patient, SELF-LIMITTING and resolves within 2 WEEKS.
163
What is paraesthesia? 5 causes? What do we advise patient?
- The abnormal sensation of burning, pricking, itching or numbness.
Caused by:
- Impingement.
- Handling.
- Laceration.
- Severance of a nerve.
- Transient caused by inflammatory swelling.
- Normal sensation returns in 4 WEEKS.
164
Treatment of serious infection following periradicular pathology?
- rarely occurs.
- Treated with ANTIBIOTICS if signs of PYREXIA and LYMPHADENOPATHY.
165
Avoiding lacerations as a complication of periradicular surgery?
- Apply vaseline to lips.
- Avoid careless elevation of flap.
166
Treating maxillary sinus perforation as a complication of periradicular surgery? 2 advice given to patient?
- Suturing of flap is sufficient.
- No nose blowing.
- Recommend anticongestant.
167
What did fabbro et al 2008 conclude regarding surgical vs non surgical endodontic retreatment for periradicular lesions (2)?
- The initial advantage of surgical over non surgical appears to disappear if the follow up is prolonged to 4 years.
- Surgery can isolate but not completely eliminate endodontic bacteria.
168
What did torabinejad conclude regarding outcomes of nonsurgical retreatment and endodontic surgery?
Non surgical retreatment offers a more favorable long-term outcome.
169
What did tsesis 2009 find regarding the outcome of surgical endodontic treatment performed by traditional vs modern techniques?
- Success rate traditional: 60%.
- Success rate modern (microscope): 91.6%.
170
Define root resorption?
- A physiological or pathological event mainly occurring due to the action of ACTIVATED CLAST CELLS.
- Characterized by the transitory or progressive loss of CEMENTUM or CEMENTUM/DENTINE.
171
What is onset of resorption associated with? (2)
- Significant necrosis of cementoblasts?
- And/or injury to the PDL.
172
What are the 2 phases required for root resorption?
1. Injury.
2. Stimulation.
173
What does injury cause when it comes to root resorption?
- Injury is related to NON-MINERALIZED PRECEMENTUM or PREDENTINE.
- Cementoblasts are destroyed directly or become necrotic as a result of compromised blood supply to PDL or pulp.
174
3 causes of injury to the root that lead to root resorption?
1. **Mechanical** - trauma, surgical procedures, excessive pressure (impacted teeth, cysts, orthodontics).
2. **Infections** - of root canal or PDL.
3. **Chemical** - bleaching agents (30% hydrogen peroxide -used for internal bleaching in the past).
175
What causes STIMULATION of root resorption (2)? What type or resorption does it cause?
- Infection.
- Pressure.
- Without a constant stimulus, the process is SELF LIMITING (**TRANSIENT RESORPTION**).
176
6 systemic and endocrine diseases that can result in root resorption?
- Hypo and hyper thyroidism.
- Calcinosis.
- Gauchers syndrome.
- Turner syndrome.
- Pagets disease.
- Herpes zoster.
This occurs BILATERALLY at the ROOT APEX.
177
4 causes of root resorption?
- Injury.
- Stimulation.
- Systemic and endocrine diseases.
- Idiopathic. (no local or systemic factors).
178
What is the mechanism of root resorption? (3)
- Damage causes a chemotactic process which attracts activated cells (odontoclasts/ osteoclasts).
- These colonise the damaged surfaces and initiate the resorptive process.
- The cells are located in depressions known as **Howships lacunae**.
179
Where are osteoblasts and osteoclasts responsible for root resorption located?
In depressions known as **Howships lacunae**.
180
What system plays a role in root resorption?
The receptor-ligand system RANKL/RANK/OPG
181
What are the RANKL/RANK/OPG? What do they regulate?
- Proteins of the TNF (tumor necrosis factor) family.
- Regulate physiological and pathological resorption of mineralized tissues.
182
What do the RANKL/RANK/OPG proteins control?
- Control OSTEOCLAST FUNCTION.
- Regulate COMMUNICATION between BONE CELLS, VASCULAR and IMMUNE CELLS.
183
What cells carry the RANK receptor (2)?
- Osteoclast precursor cells.
- Dendritic cells.
184
What does the binding of RANKL to RANK induce?
Induces fusion of osteoclast precursor cells into multinucleated cells.
185
How does an odontoclast cause root resorption?
- Under the RUFFLE BORDER the odontoclast secretes ENZYMES to effect DECALCIFICATION.
- The enzymes can dissolve both ORGANIC and INORGANIC components of mineralized tissue.
186
What is the most common cause of root resorption according to Fuss et al?
PULP INFECTION
187
6 causes of root resorption based on STIMULATION FACTORS according to Fuss et al.
- Pulp infection.
- Periodontal infection.
- Orthodontic pressure.
- Ankylosis.
- Tumor.
- Impacted pressure.
188
What usually causes extrnal inflammatory root resorption?
- Usually a result of TRAUMA (intrusion, lateral luxation, avulsion).
189
What does external inflammatory root resorption affect? How does it progress (4)?
- Affects the external root surface.
- Damage to non-mineralized cementum.
- Allows exposure of DENTINE to ODONTOCLASTIC activity.
- Progresses due to MICROBIAL stimulation from the INFECTED, NECROTIC PULP.
190
How is external inflammatory root resorption diagnosed?
Based on radiographic and CBCT interpretation.
191
What is the treatment for external inflammatory root resorption (3)?
- Removal of necrotic pulp as soon as signs of EIR.
- Use CALCIUM HYDROXIDE as an interappointment dressing.
- In many cases the resorption is too advanced to treat.
192
What is used as an inter appointment dressing for external inflammatory root resorption?
calcium hydroxide.
193
Where does external cervical resorption occur (3)?
- Originates on EXTERNAL ROOT SURFACE but can invade root dentine in any direction.
- Develops immediately APICAL to the EPITHELIAL ATTACHMENT in the CERVICAL REGION.
- Thus would feel a PALPABLE DEFECT with the probe beneath the gingiva.
194
How does invasive cervical resorption occur?
- Occurs when loss of protective non-mineralized layer at CEJ (developmental, physical/chemical trauma).
- Microbial stimulation from gingival sulcus.
195
4 predisposing factors to invasive cervical resorption?
- Orthodontics
- Trauma
- Surgery
- Intracoronal bleaching
196
What can invasive cervical resorption be misdiagnosed as?
Can be misdiagnosed as a form of INTERNAL RESORPTION but it is a PERIODONTALLY DERIVED FORM OF ERR.
197
5 clinical features of invasive cervical resorption?
- Asymptomatic.
- Tooth may look PINK.
- POSITIVE sensibility test.
- Tooth will be vital as pulp is protected until late in the process by a layer of dentine and predentine.
- Eventually the lesion will perforate the canal wall resulting in canal infection and necrosis.
198
Who created the clinical classification for invasive cervical resorption?
Heithersay 1999
199
Clinical classification of invasive cervical resorption?
Heithersay 1999
- Class I: Small with shallow penetration.
- Class II: Close to coronal pulp, no radicular extension.
- Class III: Deeper but not beyond coronal third.
- Class IV: extensive beyond coronal third.
200
Radiographic features of invasive cervical resorption?
- Radiolucent area which can be confused with internal root resoprtion.
- Use PARALLAX and CBCT for further information.
201
How to radiographically differentiate between internal vs invasive cervical resorption?
- Will see outline of pulp canal in invasive cervical resorption (not seen in internal root resorption).
202
1. Protect soft tissues with **glycerol**.
2. Remove granulation tissue from defect using **90% trichloracetic acid**.
3. (RCT if communication with pulp canal).
4. Smooth over margins of tooth and restore with GI or composite or biodentine.
203
Where does internal root resorption originate and what does it affect?
- Originates in and affects the root canal wall.
204
What causes internal root resorption (2)?
- Follows damage to odontoblastic layer and predentine by trauma and pulpal inflammation due to infection.
- Aetiology still unknown, usually as a result of TRAUMA.
205
How does internal root resorption progress?
- To continue the pulp tissue apical to the lesion must have a viable blood supply.
- Eventually pulp will become NECROTIC and resorption will STOP.
206
Clinical appearance of internal root resorption? (1)
- Extensive resorption can result in pink discoloration of the crown which may be confused with ICR.
207
What is the prevalence of internal root resorption?
0.01-1%.
208
Treatment for internal root resorption (3)?
- Root canal treatment if tooth can be saved.
- Lesion difficult to clean (due to bleeding) and obturate (due to shape).
- Must use THERMOPLASTIC techniques.
209
What happens if internal root resorption is left untreated? (2)
- If untreated, the resorption will progress and cause perforation.
- Clast cells can obtain nutrients from surrounding periapical tissues to keep the process going.
210
How can orthodontics cause root resorption?
- APICAL root resorption due to injury originating from PRESSURE applied to the roots during tooth movement.
211
2 clinical features of teeth with orthodontic root resorption?
- Teeth asymptomatic.
- Pulp vital unless pressure is such that apical blood supply is disturbed.
212
2 radiographic features of teeth with orthodontic root resorption?
- Shortened roots.
- No sign of radiolucency in the bone.
213
Which impacted teeth are usually the cause of impacted tooth root resorption (2)?
- Maxillary canines and mandibular 3rd molars.
214
What are tumors responsible for root resorption (4)?
Those that are slow growing:
- Cysts
- Ameloblastomas
- Giant cell tumors
- Fibre-osseous lesions.
215
Clinical features of teeth with root resorption due to impacted tooth/ tumour pressure (2)?
- Asymptomatic.
- Vital (unless impacted tooth/ tumor is located near the apical foramen disrupting the blood supply).
216
Radiographic features of teeth with root resorption due to impacted tooth/ tumour pressure (1)?
- No radiolucent areas as no infection.
217
Treatment for teeth with root resorption due to impacted tooth/ tumour pressure?
Surgery to remove the stimulation factor.
218
How does replacement root resorption occur (4)?
- Severe traumatic injuries (ex. intrusion, avulsion with delayed reimplantation).
- Injury to root canal is large and healing with cementum is not possible.
- Bone comes into contact with the root surface thus OSTEOCLASTS ARE IN DIRECT CONTACT WITH MINERALISED DENTINE.
- Therefore resorption can occur without further stimulation and BONE IS LAID DOWN INSTEAD OF DENTINE.
219
3 clinical features of replacement resorption?
- Teeth lack physiological mobility.
- `sound metallic to percussion.
- Sometimes infraocclusion.
220
1 clinical feature of replacement resorption?
- Bone fills the resorption lacunae thus NO RADIOLUCENCY.
221
Treatment for replacement resorption (3)?
- As no stimulation factor to remove, no predictable treatment.
- PREVENTION is better by minimizing the damage to PDL.
- A FUNCTIONAL SPLINT should be placed for 7-10 days and root canal treatment to prevent pulpal infection and root resorption.
222
Ankylosis vs replacement resorption?
- Ankylosis: no loss of root dentine and cementum, merely fusion or close proximity of the root and bone.
- Replacement resorption: dentine and cementum are lost and replaced with bone.
223
3 ways in which rotary files can fracture?
- Torsional stress.
- Cyclical fatigue.
- Both factors combined together.
224
Torsional stress?
- Happens when a TIP bind against a canal wall.
- The coronal part of the file rotates --> the ELASTIC LIMIT of the metal is exceeded --> PLASTIC DEFORMATION --> FRACTURE.
225
Cyclic fatigue?
Repeated cycles of tension and compression happen during bending.
226
9 factors contributing to file breakage?
- File size and taper.
- Type of alloy (SS vs NiTi).
- Manufacturing process of NiTi files.
- Less experienced operator.
- Inadequate access and glide path.
- Anatomy (merging/dividing canals, abrupt curvature, s-shape, isthmus etc).
- Apical pressure
- High speed
- Repeated use
227
File breakage - BIGGER files?
- More vulnerable to CYCLIC FATIGUE but more resistant to TORSIONAL STRESS.
227
File breakage - FINE files?
- More vulnerable to TORSIONAL STRESS (high torque) but more resistant to CYCLIC FATIGUE.
228
FAVORABLE prognosis for separated instruments (4)?
- No periapical periodontitis.
- Instrument separated in the APICAL ONE THIRD of the root.
- Able to retrieve non-surgically or surgically if apical pathology is present.
- Defect restorable with apical surgery.
229
QUESTIONABLE prognosis for separated instruments (3)?
- Instrument fracture in mid/ coronal third of root canal.
- Patient asymptomatic.
- No periapical periodontitis.
230
UNFAVORABLE prognosis for separated instruments (3)?
- Patient symptomatic OR
- Lesion persists requiring extensive procedures to retrieve instrument that would compromise long term tooth survival.
- Surgical treatment is not an option.
231
Influence of canal infection - irreversible pulpitis (4)?
- Canal MINIMALLY INFECTED.
- NO apical pathology.
tx:
- Remove or bypass if possible.
- If not possible the retained fragment should NOT influence prognosis.
232
Influence of canal infection - infected canals (4)?
- **End of instrumentation** --> canals disinfected, embed fragment in filling material if cannot be removed.
- **Early** --> canal beyond instrument cannot be cleaned and this may be responsible for failure --> attempt REMOVAL or BYPASS if possible.
233
What does bypass mean?
Insert small size 10 file alongside the instrument and reaching working length.
234
You fractured an instrument and it can be bypassed.
Continue canal preparation and obturation, DO NOT ACTIVELY ATTEMPT REMOVAL.
235
You fractured an instrument. It cannot be bypassed and is located in the apical third.
REMOVAL NOT PRACTICAL WITHOUT RISK OF DAMAGE.
236
You fractured an instrument. It cannot be bypassed and is located in the middle/coronal third.
- If straight line access NOT possible --> DO NOT ATTEMPT REMOVAL.
- If straight line access POSSIBLE --> CONSIDER ATTEMPT REMOVAL (after risk vs benefit analysis).
237
Factors affecting prognosis of a tooth with a broken instrument when considering attempt at removal (4).
1. Periapical lesion.
2. Stage of canal preparation.
3. Potential weakening of root.
4. Perforation/ procedural risks.
238
What % of fractured files were removed according to Suter?
- 87% of files removed
239
What % of fractured files failed to be removed according to Suter? Why? (2)
13% failure due to:
- perforation (mostly in apical 1/3).
- incomplete removal.
240
3 factors influencing successful removal of fractured files according to Patel?
1. Position of the file in relation to the root curvature.
2. Depth within the canal (affects ability to achieve straight line access).
3. Whether the file is visible using a microscope.
241
5 risks of removal of fractured instruments?
- Excessive removal of radicular dentine which may predispose the root to fracture.
- Ledging.
- Perforation.
- Limited application in narrow and curved canals.
- Possibility of extrusion of the fractured files into the periapical tissues.
242
when is the highest risk of iatrogenic damage when retrieving a fractured file?
The more apically position, the higher the risk of iatrogenic damage.
243
4 techniques (name) for removal of fractured files?
1. Mechanical.
2. Ultrasonics.
3. Tube techniques.
4. Other.
244
Issues of a tooth with a broken instrument when considering attempt at removal (5).
- Root length, curvature, dentine thickness.
- Technique of removal.
- Length of fragment.
- Presence/ absence of PA radiolucency.
- Stage of canal preparation when fracture occured.
245
3 mechanical mathods of removing fractured files?
1. **HEDSTORM FILES**- Insert 2 HEDSTROM files around instrument and rotate to remove (only work if instrument in the CORONAL part of a very WIDE canal).
2. Gripping devices **fine haemostat** or **stieglitz forceps**.
3. **Excavators**.
246
How are ultrasonics used to remove fractured files (2)?
- Create straight line access to the file.
- Trephine around the file (anti-clockwise) to expose its coronal part an loosen it off.
247
Tube systems for removal of fractured files? (3)
- IRS: instrument removal system.
- Core drills used to create straight line access.
- Tube system with little recess and plunger which allows retrieval of instrument.
248
What is a modern/ easy system for removing fracture instruments from root canals?
BTR pen. (Broken tool removal pen)
249
4 other methods of removing fractured instruments from root canals that are no longer recommended?
- Masseran kit.
- Cancellier kit.
- Altered needles.
- Using a glue.
250
2 things that give a more FAVORABLE prognosis to a tooth in which a fractured instrument cannot be removed?
- Pulp VITAL and NOT INFECTED.
- Instrument fractured at ADVANCED STAGES OF PREPARATION.
251
What does prognosis of a tooth with a fractured instrument depend on?
the presence of PREOPERATIVE PERIRADICULAR PERIODONTITIS.
252
4 pieces of information that must be given to a patient if a file fractures?
- LEGALLY the patient has to be informed about the complication.
- Possible consequences (broken instrument is not always a direct cause of treatment failure).
- Influence on success rate.
- Complications which might occur.
- Further treatment.
253
What is a ledge? Where is it common?
- An iatrogenically created irregularity in the canal that impedes access of the instruments to the apex.
- Common on the OUTER SIDE of curved canals.
254
8 causes of ledging?
- 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.
254
6 steps to managing ledges?
1. Establish the length at which the ledge is present.
2. Coronal flare up to F2-F3 working **1-2mm shorter than the ledge**. Use a small irrigation needle to irrigate between files & recapitulate.
3. Use passive ultrasonic irrigation (PUI) with a chelator and NaOCL.
4. Probe with a pre-bent size 8 ss file coated in chelator paste, use the SHORTEST file available (21mm).
- At the level of the ledge, use "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.
5. Repeat with size 10, 15 and 20 files until ledge is removed.
6. Use pre-bent hand ProTaper files to complete preparation, use of rotary files may not be possible.
255
2 things that can be used to p re bend hand SS or hand pro taper files?
- Endobender.
- Tweezers
256
What is done when the ledge cannot be bypassed?
- If ledge CANNOT be bypassed AND patient has no symptoms:
1. Prepare to ledge + copious irrigation.
2. Dress with non setting calcium hydroxide.
3. Obturate using a THERMOPLASTIC technique.
- Inform patient of guarded prognosis and review clinical symptoms and bony healing.
257
3 ways of PREVENTING ledging?
- Create a REPRODUCIBLE GLIDE PATH.
- Very narrow/ curved canals: coronal pre-flaring may be necessary (up to S2) before the full working length can be used.
- Copious irrigation using gauge 30 needle + recapitulation.
258
What is canal blockage?
- A blockage of a previously patent canal that prevents access and complete disinfection in the most apical part of the root canal.
259
3 things that a canal blockage may contain?
- Compacted dentinal mud (likley infected).
- Residual pulp tissue
- Remnants of filling materials.
260
4 causes of canal blockage>
- Apical patency is not confirmed and secured when WL is measured with EAL.
- Pulpal tissue is packed and solidified in apical constriction by instruments during instrumentation.
- Instrumentation not accompanied by irrigation and recapitulation.
- Instruments are not cleaned before their insertion in the canal.
261
Differentiate between canal blockage vs ledge formation?
TACTILE SENSATION
- Canal blockage: small instrument reaches a solid but PENETRABLE wall.
- When a ledge is present, the instrument hits a completely SOLID wall.
262
How do you recognize a canal blockage has occurred?
- Instruments or GP cones no longer able to reach full WL.
- In previous RCT teeth: short obturation with no visible root canal apical to the root filling can be a sign of blockage.
263
3 things a radiographic appearance of a short obturation with no visible root canal apical to the root filling could suggest?
- Canal blockage.
- Calcification.
- Artefact due to superimposition.
264
7 steps to removing a blockage?
1. Establish the length at which the ledge is present.
2. Coronal flare up to F2-F3 working **1-2mm shorter than the ledge**. Use a small irrigation needle to irrigate between files & recapitulate.
3. Use passive ultrasonic irrigation (PUI) with a chelator and NaOCL.
4. Probe with a pre-bent size 8 ss file coated in chelator paste.
- Detect a weak "sticky spot" in the mass of debris. Use file in watch winding motion and small in and out stokes until it reaches working length.
5. DO NOT remove file but turn in 2-3 times clockwise at full WL.
6. Remove and irrigate.
7. Repeat with size 10 and 15 files until blockage is removed.
265
Prognosis of teeth with canal blockage? (4).
- If recognized and corrected, NO EFFECT.
- When it cannot be corrected, it may have negative effect on Tx outcome particularly in infected cases.
- If pre existing AP is present/ developed after tx: consider periradicular surgery.
- If not symptoms or AP: regular monitoring indicated.
266
4 ways to prevent canal blockages?
- Copious irrigation as soon as the pulp chamber roof is removed.
- In narrow and curved canals, coronal pre-flaring before full WL is established.
- Use a small pre-bent k file (6-8) to establish WL using EAL. File should be introduced passively through the apical constriction (0.5mm is enough) remove the collagen stump and confirm canal patency.
- Recapitulation during irrigation using the smallest file (6-8) passively not to damage the apical constriction.
267
Define canal transporation?
- Removal of canal wall on the OUTSIDE CURVE in the apical half of the canal due to the tendency of ss files to restore themselves to their original linear shape during canal preparation may lead to ledge formation and possible perforation.
268
7 causes of canal transportation?
- Insufficiently designed access cavities.
- Canal curvature (greater curvature and smaller radius, unseen curves).
- Instrumentation technique using ss files (using straight files, size larger than 15 - inflexible).
- Leaving rotary files in the same position.
- Forcing a file into the canal.
- Insufficient irrigation.
- Clinical experience.
269
What endodontic instruments can cause canal transportation?
Independent of alloy, ALL endodontic instruments tend to straighten themselves inside a curved root canal and this leads to an ASYMMETRICAL DENTINE REMOVAL:
- A file is pressed against the outer side of the canal when working in the apical 1/3rd.
- A file is pressed against the inner side of the canal when working in the mid and coronal 1/3rd.
270
What instruments are less likely to cause canal transportation?
New CONTROLLED MEMORY protaper gold instruments.
271
Why is damage to the apical constriction a problem?
Risk of debris extrusion.
272
What is zip formation and why is it bad?
- Elliptical shape at the apical endpoint.
- Negative impact on the apical seal.
273
What is elbow formation and why is it bad?
- Narrow point at the maximum curvature.
- insufficient taper of the preparation.
274
What is strip perforation?
- Along the inner side of the curvature in the mid and coronal 1/3rd.
275
10 potential consequences of canal transporation?
- Damage to the apical constriction.
- Zip formation.
- Elbow formation.
- Perforation.
- Strip perforation.
- Ledging
- Inadequately cleaned canals.
- Difficulty achieving apical seal.
- Over reduction of sound dentine thus reduced fracture resistance.
- Destruction of the integrity of the root.
276
5 ways to prevent canal transporation in curved canals?
- Use pre bent flexible files to create a REPRODUCIBLE GLIDE PATH (8,10 + proglider).
- Avoid putting pressure on the outside wall in apical third and inner wall in coronal/mid third.
- never keep a rotary file in the same position for more than 1s.
- dont force files down the canal.
- Use adequate irrigation+ recapitulate.
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