Endodontic Access

Question 1

Describe the basic principles of endodontic access

Answer 1

• Sound knowledge of tooth and root anatomy
• Parallel pre-operative radiograph
• Prepare access before placing rubber dam
• Good illumination and magnification
• Locate the major pulp horn
• Copious irrigation and note colour changes

Question 2

Describe 2 objectives for all access cavity preparations

Answer 2

1. Allow unimpeded entry of instruments into root canals (straight line access)
2. Allow sealing of cavity between visits

Question 3

Name 4 important features of access cavities

Answer 3

1. Site
2. Size
3. Shape
4. Depth

Question 4

Describe the average root length and number of canals in maxillary central incisor

Answer 4

23mm with 1 canal

Question 5

Name 2 features of maxillary central incisors

Answer 5

1. Access starting at cingulum and extending towards incisal edge
2. Triangular shape to encompass pulp horns

Question 6

Describe the average root length and number of canals in maxillary lateral incisor

Answer 6

22mm with 1 canal

Question 7

Describe a key features of maxillary lateral incisor

Answer 7

Apical 3-4mm has palatal curvature

Question 8

Describe the average root length and number of canals in maxillary canine

Answer 8

26mm with 1 canal

Question 9

Describe 1 key feature of maxillary canine

Answer 9

Rounder access cavity than incisors (no need to flare access cavity as 1 pulp horn)

Question 10

Describe the average root length and number of canals in maxillary 1st premolar

Answer 10

21 mm with 1 (5%), 2 (90% - B,P) or 3 (5% - MB,DB,P) canals

Question 11

Describe 2 key features of maxillary 1st premolar

Answer 11

1. Access centre of occlusal central grove

2. Widen access B-P to locate root canal entrance

Question 12

Describe the average root length and number of canals in maxillary 2nd premolar

Answer 12

21mm with 1 (75%) or 2 (25% - B,P) canals

Question 13

Describe 1 feature of the maxillary 2nd premolar

Answer 13

If only 1 root canal should be centred and oval in shape (B-P) to encompass pulp horns

Question 14

Describe the average root length and number of canals in maxillary 1st molar

Answer 14

• 22mm (P longer than MB and DB)

- 3 (40% - MB,DB,P) or 4 (60% - MB1,MB2,DB,P) canals

Question 15

Describe 3 features of maxillary 1st molars

Answer 15

1. Rhomboid access cavity outline
2. Distal aspect on mesial aspect of transverse ridge
3. MB2 located between MB1 and P

Question 16

Describe the average root length and number of canals in maxillary 2nd molar

Answer 16

• 20mm (P longer than MB and DB)

- 3 (60% - MB,DB,P) or 4 (40% - MB1,MB2,DB,P) canals

Question 17

Describe 3 features of maxillary 2nd molar

Answer 17

1. Lower incidence of MB2
2. DB root canal closer to centre of tooth
3. Increased likelihood of fusion of canals (B-P)

Question 18

Describe the average root length and number of canals in mandibular incisors

Answer 18

21mm with 1 (60%) or 2 (40% - B,L) canals

Question 19

Describe 2 features of mandibular incisors

Answer 19

1. Starts at base of cingulum

2. Should extend to nearly to incisal edge to confirm presence or absence of 2nd canal

Question 20

Describe the average root length and number of canals in mandibular canines

Answer 20

24mm with 1 (90%) or 2 (10% - B,L) canals

Question 21

Describe 1 feature of mandibular canines

Answer 21

Starts at the base of the cingulum

Question 22

Describe the average root length and number of canals in mandibular 1st premolars

Answer 22

22mm with 1 (75%) or 2 (25% - B,L) canals

Question 23

Describe 2 features of mandibular 1st premolars

Answer 23

1. Starts in central occlusal groove

2. Access is oval bucco-lingually in shape

Question 24

Describe the average root length and number of canals in mandibular 2nd premolars

Answer 24

22mm with 1 (90%) or 2 (10% - B,L) canals

Question 25

Describe 2 features of mandibular 2nd premolars

Answer 25

1. Starts in central occlusal groove | 2. Access is oval bucco-lingually in shape

Question 26

Describe the average root length and number of canals in mandibular 1st molars

Answer 26

21mm with 3 (65% - ML,MB,D) or 4 (35% - ML,MB,DL,DB) canals

Question 27

Describe 2 features of mandibular 1st molars

Answer 27

1. Mesial root canal orifices found below respective cusp tips 2. If distal root canal orifice not centred then inc likelihood of 2nd canal

Question 28

Describe the average root length and number of canals in mandibular 2nd molars

Answer 28

20mm with 3 (90% - MB,ML,D) or 2 (10% - M,D) canals

Question 29

Describe 1 feature of mandibular 2nd molars

Answer 29

Increased incidence of fused root canals

Question 30

Describe isolation during endodontic treatment

Answer 30

- Rubber dam is mandatory - Prevents infection of the root canal - Protects the patient from irrigants - Access cavity cut before placing rubber dam

Question 31

Name 2 ways magnification can be achieved during endodontic treatment

Answer 31

1. Loupes | 2. Microscopes

Question 32

Name 2 burs used for accessing canals

Answer 32

1. Straight diamond fissure bur gains access through enamel | 2. Size 6 round bur to remove dentine and locate relevant canals

Question 33

What is the apical constriction?

Answer 33

Narrowest part of the root canal system lying around 0.5-1mm short of the apical foramen

Question 34

Name 5 contributing factors to working length determination

Answer 34

1. Previous radiographs 2. Average values 3. Diagnostic working length radiographs 4. Electronic apex locators 5. Tactile sensation

Question 35

Describe how to estimate working length from pre-operative radiographs

Answer 35

- EWL from pre-operative radiographs and average root length - Use size 10 SS K files until reached EWL - Take WL radiograph or use electronic apex locator to determine WL

Question 36

Name 2 problems when taking radiographs during endodontics

Answer 36

1. Estimating root canal lengths 2. Film placement when instruments, rubber dam and clamps in position 3. Identification and separation of canals

Question 37

What holder is used for taking endodontic x-rays?

Answer 37

Endo ray holder

Question 38

Name 2 ways to identify and separate canals during endodontic x-rays

Answer 38

1. Use different sizes of flies with different numbers of rubber stops in each canal 2. Take 2 radiographs using different horizontal x-ray tube-head positions (parallax technique)

Question 39

Describe electronic apex locators

Answer 39

- Optimum is cemento-dentinal junction with precise position variable - Modern locators better than tactile or radiographic techniques - Accuracy 90-100% for 0.5-1mm from apex respectively - Still need radiographs in combined approach

Question 40

Name 5 clinical tips when using electronic apex locators

Answer 40

1. Remove metallic restorations from access cavity 2. File should be large enough to contact walls of root canal system 3. Apex / 0 reading is most accurate 4. Re-check WL with EAL after coronal 2/3 shaping 5. Detects perforations