Access cavity and root canal preparation

Question 1

What are the 7 stages of root canal preparation?

Answer 1

1. Preparation of the tooth for root canal treatment
2. Access cavity preparation and canal orifice identification
3. Creating straight-line access
4. Initial negotiation
5. Coronal flaring
6. Working length determination
7. Apical preparation

Question 2

Why is a thorough clinical and radiographic assessment needed before performing any root canal treatment?

Answer 2

1. Determine the restorability of the tooth.
2. Pre-empt any possible difficulties of treatment
3. Consider suitable management of the tooth.

Question 3

What anatomy is important for root canal treatment?

Answer 3

look on notes

Question 4

What 10 things should you look at in a radiograph before root canal treatment?

Answer 4

1. Type of radiograph - is it suitable?
2. Teeth visible
3. Restorations
4. Caries
5. Position and size of the pulp chamber and its distance from the occlusal surface
6. Number of roots
7. Curvature of roots
8. Root canal morphology: is it visible throughout the root length? Are there any deviations? Can any lateral canals be visualised?
9. Presence of periapical radiolucency: location, estimated size.
10. Location of adjacent structures of note e.g. maxillary sinus, inferior alveolar canal.

Question 5

What 4 things must be checked/done following clinical and radiographic assessment for root canal treatment?

Answer 5

1. The periodontal status of the tooth must be stable.
2. Caries and defective restorations should be removed to prevent infected dentine and restorative materials entering the root canals.
3. Restorability must be assessed
4. Isolation of the tooth must be achievable

Question 6

If the tooth is restorable before root canal treatment what 2 things can be done?

Answer 6

1. Provisional restoration should be placed where required
   
   2. The tooth should be protected against fracture if necessary using an orthodontic band or copper ring (posterior teeth)

Question 7

What is an access cavity?

Answer 7

An opening created in the crown of the tooth which permits unimpeded access to the tooth’s pulp chamber and canal orifices.

Question 8

Give 6 main objectives of access cavity preparation.

Answer 8

1. Complete removal of the pulp chamber root to faciliate thorough disinfection of this space.
2. Allow direct access to and visualisation of the root canal orifices.
3. Produce a smooth walled preparation with no overhangs of dentine.
4. Create no damage to the pulp floor (in anterior teeth the pulp chamber merges into the root canal)
5. Facilitate the secrue placement of a temporary seal between visits.
6. Conserve as much sound tooth structure as possible.

Question 9

Prior to creating an access cavity what should the clincian have knowledge of in order to achieve these objectives?

Answer 9

1. A knowledge of basic tooth morphology and anatomy is essential.
2. The clinician should be aware of the number and location of canals likely to be present in every tooth.

Question 10

What is placed in the mouth prior to access cavity?

Answer 10

Rubber dam

Question 11

What clamps are used for upper molars?

Answer 11

12A or 13A.

Question 12

What are the 8 steps in access cavity preparation?

Answer 12

1. The outline of the access cavity is made with a tungsten carbide or diamond bur according to the anatomy of the specific tooth.
2. The bur is advanced toward the pulp horn of the largest canal until the pulp chamber roof is penetrated.
3. A safe-tipped endodontic access bur (EndoZ) is introduced into the pulp chamber and the entire roof of the pulp chamber is removed
4. The non-cutting tip is allowed to passively follow the contours of the pulp chamber floor.
5. A steel rose head bur in a slow hand-piece used in a pulling motion can be also used to remove the roof of the pulp chamber.
6. Remaining pulpal tissue and other debris is removed from the floor of the pulp chamber with an excavator.
7. The pulp chamber is flooded with sodium hypochlorite.
8. The canal orifices are located, if necessary, with the aid of a long pointed probe (DG16)

Question 13

Give 5 reasons why doing a root canal on a crowned tooth may be problematic.

Answer 13

The crown may mask the anatomical orientation of the underlying tooth

Vision may be limited by the cast restoration resulting in difficulty locating the canal orifices

Natural landmarks are no longer available with which the operator can orientate him/herself

Inadvertent perforations can result

Question 14

What is removed in order to achieve straight line access in a canal?

Answer 14

1. Coronal interferences including the complete removal of the roof of the pulp chamber.
2. So there is access to the coronal 2/3 of the canals.

Question 15

What burs are used to remove tertiary dentine to create straight line access in a canal?

Answer 15

Burs used to remove tertiary dentine left to right: standard length rose head bur, longer shank rose head bur, goose neck bur, long neck bur.

Question 16

How is access gained for a maxillary central incisior, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 16

1. Start access at cingulum and proceed towards the incisal edge.
2. Access cavity is triangular in shape to encompass the pulp horns
3. 1 canal
4. Average root length 23mm

Question 17

How is access gained for a maxillary lateral incisior, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 17

1. Start access at cingulum and proceed towards the incisal edge.
2. Access cavity is triangular in shape to encompass the pulp horns
3. 1 canal
4. Average root length 22mm

Question 18

How is access gained for a maxillary canine, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 18

1. Rounder access cavity than incisors
2. Only one pulp horn so no need for flared (triangular) access of incisors.
3. 1 canal
4. Average root length 26mm

Question 19

How is access gained for a maxillary first premolar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 19

1. Initial point of access centre of occlusal fissure
2. Access cavity is extended bucco-palatally to locate the canal orifices under the buccal and palatal cusp tips.
3. 1 canal 5%, 2 canals 90% (B,P), 3 canals 5% (MB, DB, P)
4. Average root length 21mm

Question 20

How is access gained for a maxillary second premolar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 20

1. Initial point of access centre of occlusal fissure
2. Access cavity is extended bucco-palatally to locate the canal orifices under the buccal and palatal cusp tips.
3. 1 canal 75%, 2 canals 25% (B,P)
4. Average root length 21mm

Question 21

How is access gained for a maxillary first molar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 21

1. Rhomboid access cavity shape
2. Distal aspect of the access cavity is on the mesial aspect of the transverse ridge.
3. Palatal canal is largest and initial penetration should be aimed toward this canal
4. 3 canals 40% (MB, DB, P), 4 canals 60% (MB, DB, P)
5. Average root length 22mm

Question 22

How is access gained for a maxillary second molar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 22

1. Rhomboid access cavity shape
2. Access cavity is narrower than first molar in a mesio-distal direction reflecting the close proximity of the canals to each other.
3. 3 canals 60% (MB, DB, P), 4 canals 40% (MB1, MB2, DB, P)
4. Average root length 20mm

Question 23

How is access gained for a mandibular central incisior, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 23

1. Starts at the base of the cingulum.
2. Access cavity is narrow mesio-distally and oval (bucco-lingually)
3. The cavity should be extended almost on to the incisal edge to aid location of a possible lingual canal
4. 1 canal 60&, 2 canals 40%
5. Average root length 21mm

Question 24

How is access gained for a mandibular canine, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 24

1. Starts at the base of the cingulum
2. Access cavity is oval with the incisal extension approaching the incisal edge and location of a possible lingual canal and the lingual extenstion must penetrate the cingulum.
3. 1 canal 90%, 2 canals 10% (B, L)
4. Average root length 24mm

Question 25

How is access gained for a mandibular first premolar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 25

1. Starts in centre of occlusal fissure 2. Access cavity is extended in bucco-lingual direction. 3. Access cavity is oval (bucco-lingually) in shape and located centrally when one canal present. 4. Extension of the cavity further buccally and lingually will be necessary when 2 canals present. 5. 1 canal 75%, 2 canals 25% (B, L) 6. Average root length 22mm

Question 26

How is access gained for a mandibular second premolar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 26

1. Initial point of access centre of occlusal fissure 2. Access cavity is extended bucco-palatally to locate the canal orifices under the buccal and palatal cusp tips. 3. 1 canal 90%, 2 canals 10% (B,L) 4. Average root length 22mm

Question 27

How is access gained for a mandibular first molar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 27

1. Mesial canal orifices are located below the mesial cusp tips. 2. Distal canal orifice is located closer to the centre of the tooth. 3. Access cavity outline is trapezoid or rhomboid in shape to encorporate pulp horns. 4. The distal canal will be centred on the mid-line of the tooth if there is only one present. 5. If a distal canal is ‘off centre’ there is likely to be another distal canal. 6. 3 canals 65% (MB, ML, D), 4 canals 35% (MB, ML, DB, DL) 7. Average root length 21mm

Question 28

How is access gained for a mandibular second molar, what shape is it, how many canals does the tooth have and what is the average root length of the tooth?

Answer 28

1. Mesial canal orifices are located below the mesial cusp tips. 2. Distal canal orifice is located closer to the centre of the tooth. 3. Access cavity outline is trapezoid or rhomboid in shape to encorporate pulp horns. 4. The distal canal will be centred on the mid-line of the tooth if there is only one present. 5. If a distal canal is ‘off centre’ there is likely to be another distal canal. 6. Access cavity for 2 canal variation will be narrow bucco-lingually and oval in shape 7. 3 canals 90% (MB, ML, D), 2 canals 10% (M, D) 8. Average root length 20mm

Question 29

What technique is used to complete the root canal and what does it involve?

Answer 29

Crown down technique: 1. Enlargement of coronal and middle third 2. Confirm working length 3. Prepare the apical third 4. Connect apical and middle third

Question 30

What are the 2 ways we prepare a canal for root canal treatment?

Answer 30

1. Mechanical Using a variety of instruments, both manual and machine driven. 1. Chemically Using antimicrobial irrigants and interappointment medicaments.

Question 31

What are 4 aims of mechanical preparation?

Answer 31

1. Remove pulpal debris and microbes 2. Provide a suitable shape for effective irrigation 3. Provide improved access for the placement of medicaments 4. Provide the optimal shape and resistance form for the root canal filling

Question 32

What are 6 aims of chemical preparation?

Answer 32

1. To flush out remnants of pulp tissue and debris created during mechanical instrumentation. 2. To dissolved residual pulp tissue 3. To kill microbes and remove microbial biofilm 4. To clean parts of the root canal system which are inaccessible to mechanical instrumentation 5. To act as a lubricant to prevent blockages during instrumentation 6. To remove the smear layer.

Question 33

What does initial negotiation consist of?

Answer 33

1. Once orifice located 2. Explore root canal with size 8 and 10 stainless steel flexofiles.

Question 34

What does coronal flaring consist of?

Answer 34

1. Once the root canals have been located. 2. The coronal half to 2/3 of the root canal is negotiated and instrumented. 3. This produces a tapered preparation, which is widest coronally.

Question 35

Give 5 aims of coronal flaring.

Answer 35

1. Removal of the bulk of infected coronal pulp tissue and dentine. 2. Less risk of forcing infected debris through to the periradicular tissues 3. Elimination of interferences in coronal third. 4. Early introduction of irrigant solution into apical portion. 5. Easier negotiation to working length.

Question 36

What burs are traditionally used to flare the coronal portion of the canal?

Answer 36

Gates glidden.

Question 37

What is the order of gates glidden and how far do you go down?

Answer 37

1. Size 2 - 1/3 of working length 2. Size 4 - 1/3 of working length 3. Size 3 - 1/3 of working length +1mm 4. Size 2 - 1/3 of working length +2mm

Question 38

What side of the gate glidden is used to flare?

Answer 38

The side cutting surface - NEVER the tip.

Question 39

What are 5 steps in coronal flaring?

Answer 39

1. Gates glidden 2,4,3 (+1mm) ,2 (+2mm) 2. If gates glidden number 2 does not make its way fairly easily use round head/diamond bur. 3. All gates glidden must start their rotation outside the canal. 4. File 8-10-15-20-25 passively (just to establish the patency of the coronal and middle third of the canal) 5. Irrigate after each file and instrument

Question 40

What size files should easily reach the apex with coronal flaring?

Answer 40

8 and 10.

Question 41

If you feel resistance when filing with a large size file what should you do?

Answer 41

1. Stop 2. Pass size 8 file again.

Question 42

What is the role of irrigation?

Answer 42

This prevents blockage of canals.

Question 43

Give 3 commonly used irrigating solutions.

Answer 43

* Sodium Hypochlorite (0.5% to 5.25%) Most commonly used Chlorhexidine Iodine potassium iodide

Question 44

How can EDTA be useful in coronal flaring?

Answer 44

1. Helps remove dentine. 2. Lubricating effect.

Question 45

Give 7 reasons why coronal flaring is important.

Answer 45

1. Enable unrestricted access to the apical portion of the root canal. 2. Straightening of the coronal portion of the canal. 3. Better tactile feedback for instrumentation apically. 4. Removal of the bulk of infected pulpal tissue and debris to prevent coronal microbes and debris from being introduced into the apical third of the canal. 5. Provide a resevoir for irrigant coronally 6. Minimise risk of creating apical blockages 7. Maintenance of working length during subsequent preparation.

Question 46

What is the working length?

Answer 46

Working length is the distance between a reference point on the crown of the tooth and the terminus of the roor canal that is normally identified with the apical constriction.

Question 47

What are 2 ways working length can be calculated?

Answer 47

1. The working length can be roughly determined from a parallel pre-operative radiograph, measured with a ruler. 2. The working length can be precisely determined by the use of the electronic apex locator.

Question 48

How does the electronic apex locator work? (5 steps)

Answer 48

1. The EAL creates a local electric current between the patient’s oral mucosa and the periodontal ligament at the end of the root canal. 2. The EAL is rested against the patient’s cheek via a hook and attached to a file via a clip which is inserted into the tooth. 3. The file is gradually moved apically until the file reaches the apical foramen. 4. When at the apical foramen you have reacehd your zero reading’. 5. On the display this will show either as APEX, red segment or 0 depending on the device.

Question 49

How can working length be confirmed?

Answer 49

By a radiograph made with an endodontic instrument:

Question 50

What can be done to identify which canal is which on a radiograph?

Answer 50

Use different sizes or types of instruments to help identify which canal is which.

Question 51

Give 5 reasons why the apex locator does not work properly.

Answer 51

1. When the file contacts metal (crown, amalgam, post) 2. When in there is a lot of pulp tissue in the canal (in some children for instance) 3. When the battery is low 4. When the tooth is not isolated well 5. When the apex is open.

Question 52

What size file and above can cause damage in maxillary premolars and molars’ anatomy?

Answer 52

25

Question 53

Give 2 main aims of apical preparation.

Answer 53

1. Apical enlargement To allow adequate space for the penetration and exchange of irrigants and placement of medication. 1. Creation of apical taper

Question 54

.