Endodontics 1 Flashcards
1
Q
What are the aims of the root canal preparation?
A
- remove microbes and pulpal debris
- create sufficient space for irrigation and medication
- preserve integrity and location of apical canal anatomy
- avoid iatrogenic damage to canal anatomy
- facilitate canal filling
- avoid further irritation or infection to periapical tissues
- preserve sound root dentine to allow long term function of tooth
2
Q
What are the stages of a root canal treatment?
A
- pre operative diagnostic radiograph including estimated working length
- preparation of tooth for RCT
- access cavity and location of RC entrances
- create straight line access
- initial negotiation and coronal flaring
- chemical preparation
- corrected working length determination
- apical preparation
- obturation
3
Q
What information can we get from a pre-operative (diagnostic) radiograph?
A
- external morphology
- number of canals
- length, direction and degree of curvature
- branching, lateral canals
- position of pulp chanber in relation to external surface
- estimated working length
4
Q
What is the estimated working length?
A
length between the coronal referece point and the apical limit of the preparation
(apical limit of preparation should be 1mm short of the radiographic apex)
5
Q
What is the anatomical apex?
A
it is the endpoint of the root
6
Q
Why is the dentino-cemental junction considered the ideal end-point for the root canal preparation?
A
this is because it is considered to be the transition from endodontium to periodontium
this junction is strictly histological and impossible to locate clinically
7
Q
Numerous studies have shown that the foramen is generally not in the centre but may be situated on the lateral side of the root. True or fasle
A
true
8
Q
What is the apical constriction?
A
it is the narrowest part of the canal
(last few millimetres)
9
Q
What is the use of the anatomical landmark of the apical constriction
A
- assume periodontum starts here as we cannot clinically identify dentinocemental junction
- consider preparing or filling beyond this point overfilling/overinstrumentation
10
Q
The working length of a root canal preparation should be ____ from the radiographic apex. Why is this ?
A
2mm
accounts for foramen distance and radiographic image distortion
11
Q
It was thought for a long time that the dentinocemental junction/apical constriction are located at an average of 1mm from the radiographic apex hence the preparation to 1mm of the radiographic apex. Why is this technique no longer reliable?
A
- dentinocemental junction is rarely located at the apical constriction
- thickness of cementum varies greatly from one tooth to another and between patients
- thickness of cememtum changes with physiology; cementum thickness increases with ageing; and pathology (apical resorption related to the canal)
12
Q
The apical constriction is not always located 0.5-1mm from the radiographic apex. True or false
A
true
can be 3mm away from the radiographic apex
13
Q
How should you prep tooth for RCT?
A
- remove all caries or defective restorations; must be done before opening the pulp chamber
- place provisional restoration in broken down teeth for rubber dam application
14
Q
What is the benefit of using rubber dam for RCT?
A
- improve visibility
- prevent microbial (saliva) contamination
- soft tissue protection (lips and cheek)
- confine excess irrigant
- reduce risk of inhalation/ingestion of instruments/irrigants
- improved patient comfort
- reduce liability im medico-legal case
15
Q
How should you create your access cavities?
A
- remove the entire roof of the pulp chamber including pulp horns
- shape of access cavity is determined by number of canals and the location of the canals
16
Q
How many canals are present in the maxillar upper first molar? Name them
A
4
MB1
MB2
DB
palatal
17
Q
How can you tell have penetrated the roof of the pulp chamber when preparing the access cavity?
A
a sudden drop is felt
18
Q
What instrument is used to widen the access to create a smooth-walled preparation?
A
Endo Z bur
19
Q
What is the benefit of a widened access cavity?
A
- allows visualisation of the canal orifice
- allows unimpeded straight line accesss
20
Q
What is the benefit of using an endo-z bur to widen the access cavity?
A
- prevents perforation of the pulp floor
- damaging the pulp floor prevents access to the canals (debris blocking the canals
21
Q
State the characteristics of an endodontic explorer
A
- double ended
- long, sharp tips
22
Q
What is the purpose of the endodontic explorer?
A
used to check:
* accessibility of the orifice
* location of orifice
23
Q
What are the characteristics of a front surface mirror?
A
- reflective surface at the front of the glass
- does not produce double images as standard mirrors do
24
Q
What is the benefit of straight line access?
A
- reduces stress on instruments
- reduces chances of procedural errors
- simplified treatment by providing a clear path of insertion for instruments
25
List some ways in which straight line access can be reached
* removal of overhanging dentine - remove pulp horns
* remove any dentine lips
26
Gve examples of iatrogenic damage caused by root canal preparation
* ledge
* perforation
* strip perforation
* Zipping
dentine mud
27
What does zipping refer to in endodontics?
refers to transportation (movement away) away from the apical preparation due to the file straigening
The elbow then becomes the narrowest part of the canal which is where obturation reaches
28
List the preparation techniques for a RCT
* step back
* crown down
* double flare
* modified double flare
29
What are the phases of the double flare technique ?
* crown down- coronal 1/3 prepared
* apical enlargment- apical 1/3 prepared
* step back- apical preparation
30
What does the modified double flared technique entail?
* initial negotiation and coronal flaring using handfiles or gates glidden
* apical enlargment at WL until cutting clean dentine
* step back
31
What is the benefit of the crown down technique (preparation of the coronal 1/3)?
* removes infected pulpal tissue /debris
* prevents microbes from being introduced to apical area
* coronal obstructions removed
* straigtening of coronal section
* provides a resevoir for irrigant
* reduces risk of apical blockages
* working length maintained through subsequent preparation
* allows for better apical tactile feedback
32
List characteristics of gates glidden drills
* side cutting/non cutting tips
* there are six size shown by the number of bands on the side
* not flexible thus only used in straight part of cannal
* long shanks- prone to fractures at the neck
* aggressive- can easily remove dentine especially size 4s
33
What design features of the synrine prevents needle seperating during irrigation?
Luer-lock
34
What type of needles are used for irrigation?Why is this
27-30 G side vented needles
they prevent irrigant from being pushed through the apex
35
How far should you be able to insert your irrigant needle?
2-3mm of the working length
36
How does the irrigant reach the working length of the canal?
a small size 8/10 k-file can be used to agitate the irrigant to the working length
recaptulation essentially
37
List the characteristics of the ideal irrigant
* antimicrobial
* cheap
* dissolves pulpal tissue
* removes smear layer
* easy to use
* long shelf life
* low surface tension
* non staining
* non- cytotoxic
* compatible with dentine
* substantive
* tissue friendly
* non-toxic
* non- corrosive to instruments
38
Give characteteristic of NaOCl solution
* effective antimicrobial
* dissolves pulpal tissue and organic matter
* toxic
* not substantive
* discolours
* corrodes instrumets
* unpleasant odour
* ineffective in smear layer removal
39
What is a substantive antimicrobial agent?
this is one that is able to attach to hydroxyapatitite containing tissues and be released gradually
40
What gives the antimicrobial effect of NaOCl?
free chlorine iones break down bacterial proteins into amino acids
41
Why is regular replenishment and agitation of NaOCl required?
maintain Chlorine ions
agitation to maximise dissolution of organic debris
42
What is the concentration of NaOCl recommended?
0.5-3% usually recommended
43
Higher concentrations of NaOCl are effective against what microorganism?
E. faecalis
44
The volume of NaOCl uses is more critical than the concentration chosen. True or false
true
45
Whatare the symptoms of NaOCl accident?
* acute severe swelling and pain
* profuse bleeding from canal
* taste of chlorine and throat irritation
* bruising or ecchymosis of skin or mucosa
* longer term parasthesia or anaesthesia
46
How would you manage acute severe pain and swelling following a NaOCl accident?
* inform patient
* swelling may reduce
* provide analgesics and antibiotics
47
How would you manage profuse bleeding from the canal following a NaOCl accident?
* irrigate with saline
* dry
* apply temporary dressing
48
How would you manage taste of chlorine and throat irritation following a NaOCl accident?
patient to drink water and milk
49
How would you manage bruising or ecchymosis of skin or mucosa following a NaOCl accident?
* apply cold compress
* advise may take a week for bruising to subside
50
How would you manage longer term parasthesia or anaestheria following a NaOCl accident?
refer to hospital and inform patient
51
What should you do following a NaOCl accident in general?
recall 1- days and review symptoms
complete RCT when symptom free or refer to specialist
52
Taste of chlorine or throat irritation from NaOCl is an indication of ...
presence of NaOCl in the maxillary sinus
53
What is the potential benefit of CHX over NaOCl as an endo irrigant?
* extremely low level of tissue toxicity
* substantive antibacterial activity (binds to hydroxyapatite containing tissue)- last up to 12 hours
* more effective against G+ve such as E faecalis
54
What are the limitations of CHX as an irrigant?
* inability to dissolve organic matter (necrotic pulps)
* no action on the smear layer (minerals)
55
What does the smear layer contain?
Minerals
Organic matter (carbon containing compounds)
56
Why is EDTA able to remove the smear layer?
it reacts with the metal ions (minerals) contained in the smear layer e.g. calcium
57
What is the benefit of using EDTA as an irrigant?
it can help negotiate sclerotic canals
sclerotic canals - narrow due to deposition of tooth structure (hydroxyapaptite) so EDTA can bind
58
What are the limitations to using EDTA as an irrigant?
* if remains too long on the tooth it weakens the tooth and increases leakage (binding to Ca2+)
* it has no antibacterial effect
59
What is the benefit of a combination of EDTA and NaOCl?
* synergistic effect
* effective removal of the smear layer
60
Why is EDTA and NaOCl not used together?
this is because EDTA interacts with NaOC and this reduced the amount of chlorine ions available
this compromised the tissue dissolving and antibacterial abilities of NaOCl
61
How can EDTA and NaOCl be used?
* alternate use of NaOCl and EDTA
* copious amounts of NaOCl used to wash remnant of EDTA
*
62
What is the benefit of using Iodine as an irrigant?
E facecalis
C albicans
antiviral
63
State an advantage and disadvantage of using citric acid as an irrigant
* removes smear layer
* reacts with NaOCl so reduces available chrlorine
64
Define the smear layer
surface film of debris retained on dentine or other surfaces of instrumentation
consists of dentine particles, remnants of vital or necrotic pulp tissue, bacterial components and retained irrigant
65
What is the benefit of smear layer removal?
* ZOE (medicament) able to penetrate dentinal tubules
* may improve the seal and reduce leakage (affects the bond of sealers)
* may act as a barrier to irrigant penetration
66
State some advantages of leaving the smear layer
* slow bacterial invasion
* blocks dentinal tubules that are difficult to clean
* inhibitory effect on bacterial growth
67
What does patency filing refer to?
the use of a small file through the apical foramen during canal preparation to prevent blockage of the apical part of the canal by debris
68
What are the standard lengths of K files?
21mm
25mm
31mm
69
What is the length of the cutting blades of the handfiles?
16mm regardless of the legth of the file
70
Give examples of techniques used for instrument manipulation
* watch winding technique
* circumferential technique (push-pull)
* balanced force technique
71
When would the split-dam technique be used in endodontics ?
* when there is insufficient tooth structure
* presence of porcelain crown or veneers
72
How can you prevent leakages of irrigant when using the split dam technique?
* accurate positioning of the high vacuum suction tip
73
How can you estimate the depth of the pulp chamber?
using radiograph
74
What is a 2% taper?
this is when the diameter of the file increases by 0.02mm at each millimetre
75
What is the estimated height of the buccal cusp to the pulp chamber roof in mandibular and maxillary molars?
6mm
76
What is the estimated pulp chamber height in mandibular molars?
1.5mm
77
What is the estimated height of the pulp chambers in the maxillary molars?
2mm
78
What is the depth of seperation between the pulpal floor and the furcation in maxillary and mandibular molars?
3mm
79
Briefly describe the access of a maxillary anterior tooth
access starts at the cingulum and extends towards the incisal edge
Triangular shape to encompass the pulpal horns
80
How does an endo access cavity for a canine differ from an incisor?
rounder cavity access
no need to flare access as only one pulp horn
81
What should be removed when creating a canine access cavity?
the lingual shoulder
using SX or GG bur
82
What should you be aware of when creating access cavitues of mandibular incisors?
labio-lingual inclination of the tooth
83
What must you remove when creating an access cavity in a mandibular incisor?
lingual ledge
84
Give a brief example of complex morphology in mandibular premolars
canals can divide deep within the root
85
What are the 9 guidelines for the anatomy of the pulp chamber floor?
* law of centrality
* law of concentricity
* law of CEJ
* law of colour change
* 1st law of orifice location
* 2nd law of orifice location
* 3rd law of orifice location
* 1st law of symmetry
* 2nd law of symmetry
86
What is the law of centrality?
floor of the pulp champer is located in the centre of the tooth at CEJ level (unrelated to occclusal anatomy)
87
What is the law of concentricity?
walls of the pulp champer are concentric to the outer surface at the CEJ
88
What is the law of CEJ?
distance of the external surface to the wall chamber is the same throughtout the circumference of the tooth at the CEJ
89
How can you locate canal orifices using the law of colour change?
pulpal floor is darker, transparent
pulpal walls are brighter and opaque
90
The first law of orifice location refers to ...
orifices located at the wall to floor junction
91
The second law of orifices refers to ...
orifices at angles in floor to wall junction
92
The third law of orifice location refers to ...
orifices at terminus of roots developmental fusion lines
93
What do the 1st and 2nd law of symmetry state?
orifices are equidistant and perpendiculat to the M-D line drawn through the pulpal floor
if the canal is on the line then it is unlikely to find a 2nd canal in that root
94
What are the disadvantages of conservative access cavities?
* missed anatomy
* incomplete disinfection
* instrument fracture
* increase complexity of your case
95
What are the advantages of coronal flaring?
* eliminates cervical bulging
* reduces effect of canal curvature
* prevents working length changes
* better visualisation of canal
* cleansing and disinfection of coronal third before entering apical third
* early and increased irrigant volume
96
What should the passage of the endo files be guided by?
root canal walls
NOT access cavity walls
97
Where is the MB2 canal ususally located?
perpendicular from the DB canal
98
How can you radiographicall identify the MB2 canal?
a distal angled radiograph with a file in the MB1
If it is off centre, there may be an MB2
If MB2 and MB1 are close they may join
soak with NaOC 5.25% and look for bubbling
99
An endodontic explorer is also referred to as ...
DG16 probe
100
What is a micro-opener?
an explorer with the capability of a K-file
101
Califications of the canal occur from ____ to______.
coronal to apical
102
What are some tips for managing calcifications in canals?
* magnification and good lighting
* avoid damage to pulpal floor
* working dry (blow air into cavity) then wet cavity
* remove existing restorations if feasible
* use larger SS files or C+ file (stiffer and can push through)
* coronal flaring
* stop, close and next appointment
103
If you have reached the CEJ and you have not found your canals what should you do?
take a radiograph with a file/bur to check depth and angulation
104
Give examples of clinical conditions which may require a radiograph
* dental caries
* traumatised teeth
* tooth surface loss
* cracker/fractured teeth
* pulpitis
* periapical periodontitis
* root resorption
105
What are the aims of endodontic treatment?
* disinfection of teeth- caries removal, disinfection of root canal system
* sealing of teeth after root canal preparation to prevent reinfection
106
In order to seperate the MB1 and MB canals in maxillary molars, what technique would you use to take your radiographs?
mesial cone angulation
107
In order to achieve maximum seperation of the MB and ML canals in mandibular molars, what technique would you use to take your radiograph?
distal cone shift
108
What instrument is used to ensure GP points/obturation material is sufficiently packed into the canal orifices?
endodontic pluggers
Machtou pluggers
109
List the general principles for the crown down/ coronal -apical root canal preparation
1. access
2. coronal flaring
3. scouting
4. working length
5. glide path
6. apical preparation and finishing
110
What is coronal flaring?
opening the canal orifice and enlargening the coronal aspect of the root canal
111
What is scouting?
introducing the first small file to explore the coronal 2/3 of the canal
112
How is working length determined ?
apex locator
radiograph
113
What is a glide path?
this involves creating pilot channel/pathway to working length
114
Briefly describe the watch-winding technique
continuous clock-wise and anti-clockwise rotation with slight apical pressure, rapidly advances a fine file down root canal
115
What kind of hand file manipulation can Hedstom files be used for?
circumferential filing (push pull)
116
Hedstrom files should not be used for what hand filing technique?
watch winding
117
What are the main benefits of the NiTi files over the conventional stainless steel files?
super-elasticity
shape memory
118
What are the main rules of instrumentation for rotary instruments?
never exceed 10 seconds in a cana
limit to 3 insertions/pecks (brush don't peck?)
each peck should be 1-2mm
119
What is the protaper gold sequence for hand and rotary use?
* SX
* S1
* S2
* F1
* F2
* F3
120
What are functions of the scouting file?
* confirms straight line access
* verifies diameter of the canal
* reveals anatomy
121
What is the function of the optional SX file?
* allows flaring more coronally
122
What is the characteristic of the SX file?
shorter than other pro-taper files
19mm
123
What is the function of the S1 file
prepares the coronal 1/3 of the canal
124
What is the function of the S2 file?
enlarges and prepares the middle one-third
125
What is the function of the S1 and S2 shaping files ?
brushing (creates lateral space) allowing each instrument to passively feed deeper into the canal
126
What is the protaper gold filing sequence?
* scout
* glidepath
* shaping (shaping files)
* finishing (Finishing files)
127
What are the ideal properties of obturation materials?
* easily manipulated
* dimensionally stable (no shrinkage)
* seals apically and laterally
* non irritating to PA tissues
* impervious to moisture, non porous
* unaffected by tissue fluids (no corrosion/oxidation)
* inhibits bacterial growth
* radiopaque
* does not discolour the tooth
* sterile
* easily removed for retreatment
128
What technique is used for obturation following hand filing?
cold lateral condensation
129
What techniques are available for obturation when the canal has been prepared using the rotary file system?
* single cone (match GP cone with finishing rotary file)
* warm vertical condensation
* carrier-based system
130
What are the advantage of the single cone filling technique?
* easy
* quick
* good control of WL
* easily revised if necessary
* inexpensive
131
What are the disadvantages of the single cone technique?
* reliance on sealer
* inadequate fill
132
What is the chloro-percha technique ?
* GP placed in chloroform solvent for 30 seconds
* solvent adapted GP which may fill canal better
133
What is the risk of the chloro-percha technique?
shrinkage!
134
What are the advantages of the cold lateral compaction technique?
* gold standard
* long term success
* good control of WL
* easily revised if necessary
* easy to master
* inexpensive
135
What are the disadvantages of the cold lateral compaction technique?
* time consuming
* does not produce homogenous mass of GP
* not suitable for irregularly shaped canals
* too many accesory points; difficult to locate finger spreader and subsequent GP points
* wedging forceds
136
Briefly describe the cold lateral compaction technique
* coat root surface with sealer cement
* dip master GP point into sealer and insert it into canal to WL
* add accesory GP points by first creating a space with the finger spreader then quickly inserting the accessory GP point into the space created
* if there are any points (identified by finger spreader) add more GP
* sear off coronal part and pack down with machtou plugger
137
What is the initial apical file?
the first file which binds apically
138
What is the master apical file?
largest file which reaches WL
139
Ideally, the master apical file should be a number ...
20 file
140
What are the advantages of warm vertical compaction?
* homogenous mass of GP
* fills lateral and accessory anatomy
* quick
* can be revised if necessary
141
What are the disadvantages of warm vertical compaction?
* initial cost of equipment
* more skill to control WL
* sealer extrusion
142
What are the advantages of the carrier based system?
* fills lateral and accessory anatomy
* quick
* filling can be revised
143
What are the disadvantages of the carrier based system?
* initial cost of equipment
* more skill to control WL
* sealer extrusion
* failure to heat GP adequately may result in GP not sitting properly
* under-prepared root canals or incorrect angle of insertion can strip GP from its carrier
* difficult removal and post preparation
144
What is the purpose of the funnel shaped canal preparation created in a RCT?
* faciliates intracanal medicament e.g. CaOH between visits (antibacterial between visits)
* facilitates irrigation for disinfection
* disruption of the biofilm mechanically
145
What does a taper refer to?
it is an increase in file diameter at each millimetre along the working surface towards the file handle
146
Compare and contrast stainless steel files to rotary systems
Stainless steel files
* larger in diameter and thus more rigid
* this often presents a problem if the canal is not straight
Rotary Systems
* made of titanium
* more flexible so follows the anatomy of the canal
* allows the designer to go to a larger diameter while still maintaining the flexibility of the file
* more conservative
147
Describe the taper observed in protaper/rotary systems
they have a variable taper
at different levels, the taper changes (how much the diameter increases at each mm changes)
148
What are the advantages of using GOLD nickel titanium taper files?
there is an additional heat treatment done (which gives the gold colour) that increases the flexibility of the files
these files have resistance to cyclic fatigue
149
What is the benefit of creating a smooth glide path?
* enables a transition to larger files
* maintains the original anatomy whilst also reducing stress on larger shaping files
150
Why is pre-flaring the canal necessary?
to minimise the chance of permanently blocking the canal with a broken rotary instrument
151
What instruments can you use to create a glide path?
* hand files
* path files
* pro-glider
152
When using handfiles to secure a glidepath, they can be secured using up to a size __ file
size 20
153
When checking the patency of the canal you can go _____ beyond the apical foramen
0.5-1mm
154
In between files, what must you do ?
Irrigate
Recapitulate
Irrigate
(IRI)
155
You should never irrigate to working length. True or false
True
Hence why you measure your syringe
(recapitulation allows you to agitate you irrigant further into the canal)
156
What must you do to your files (rotary and hand) before they enter the canal?
* inspect them before and after they come out of the canal
* (additionally you can measure then before and after to ensure they have not broken)
* you should also clean your files
* check that there is no flattening or unwinding of files
157
How can you clean rotary files?
* wet gauze
* alcohol wipe
* sponge
File can be inserted into the sponge to clean superficial debris and then cleaned with wet gauze or alcohol wipe
158
Why are endodontic files single use?
* prions- cannot be removed after autoclaving
* to prevent fractures
159
What are the types of fatigues that a file can experience?
Metal/cyclic fatigue
Torque fatigue
160
What are the factors that contribute to cyclic fatigue?
* radius of curvature
* diameter
* taper
* number of cycles
* curvature
161
What factors contribute to torque failures?
* pressure
* suface area
* RPM
* lubrication
* curvature
162
The sequence for protaper hand and protaper gold files are the same. Outline the file sequence
1. Scouting
2. Glidepath
3. Shaping
4. Finishing
163
What are the uses of a scouting file?
* confirms straight line access
* verifies the diameter of the canal
* reveals the anatomy of the canal
* initiates the glide path
164
What is the function of the SX file?
* used to achieve a coronal flare so the canal can now happily contain more irrigation
165
What is the main characteristic of the SX file?
* 19mm file length
*
166
What are the functions of the S1 and S2 protaper files?
* S1 file prepared the coronal 1/3 of the canal
* S2 file enlarges and prepares the middle 1/3 of the canal
167
What is the benefit of using the brushing technique with rotary systems?
it is used to create lateral space allowing each instrument to passively feed deeper into the canal
168
When using an apex locator, when is a zero reading detected?
this is detected when the file exits the canal
169
How does a zero reading on an apex locator appear?
appears as a single red line
170
What is the size equivalent of an F1 finishing file?
20
171
What is the size equivalent of an F2 finishing file?
25
172
What is the size equivalent of an F3 finishing file ?
30
173
What is apical gauging?
this is a technique used to determine the size of the apical constriction and the taper of the apical portion closest to the foramen
174
Outline the full process of a RCT using rotary system
* pre-op radiograph for EWL, canal anatomy
* rubberdam/clamp after LA (caries free)
* scout using #10/ #8 files at (<2/3 of EWL) for straightline access
* SX for coronal flare
* Glidepath with #10, #15, #20 at 2/3rd of EWL then full EWL
* comfirm WL with apex locator, then WL radiograph, if withing 2mm of apex no need to repeat
* S1/S2 to WL, IRI, patency with #8/10 file
* F1 to complete apical prep, IRI, F1 GP cone
* Master cone F1 radiograph (with good tugback to confirm this is the master cone)
* IRI, penultimate flush with EDTA (flush as follows NaOCl, EDTA, NaOCl)- remember EDTA can weaken the root surface/enamel
* dry canals
* obturation of DRY canals; coat with sealer on paperpoint, then coat GP, use heater plugger to sear off GP at orifice level, compact with machtou plugger then sear off 1mm below orifice level
* post op radiograph
* review in 6 months to a year
175
When should you apically gauge?
only when there is no tugback with the mastercone
176
What types of sealers are used during obturation?
* ZOE
* CaOH
* Epoxy
* Silicone
* Resin
* GI
* RMGI
