Access

Question 1

What shapes should access cavities be on each tooth?

Answer 1

Incisors:
-Triangle with point located gingivally. Should be located as close to the CEJ as possible

Premolars:
-Oval shaped at the area of the occlusal table co-inciding with the centre of the CEJ

Upper molars:
Triangle shape on the mesio-buccal cusp with point facing palatally

Lower molars :
Rectangular shaped on occlusal surface

Question 2

What should you check for in a pre-operative radiograph?

Answer 2

• Both crown and root tips captured
• Tilting
• Sufficient tooth structure for longevity after treatment

Question 3

What is the outline form? What bur would you use to achieve it?

Answer 3

Project the internal anatomy of the tooth to the external surface (basically gain initial access + remove all caries)
-Bur: High speed 169L or tapered diamond or beaver

Question 4

What is the convenience for? What bur would you use to achieve it?

Answer 4

• Allow accurate preparation and filling of root canals (basically permits straight line, unobstructed access to canals)
• Slow speed 3/4 shank round 3 tungsten carbide

Question 5

How can you tell if a pulp stone is present? How can it be removed?

Answer 5

Floor of mouth has dark grey-ish hue

-Remove by ultrasonic or cutting around outline with fine diamond and lifting up

Question 6

What is a cavity toilet? How can it be created?

Answer 6

• When all pulp, caries and debris is removed from the cavity the cavity toilet is created
• Done by slow speed tungsten carbide, irrigation, spoon excavators

Question 7

How do you locate the MB2 canal?

Answer 7

Draw line from MB to P canal, MB2 will sit somewhere mesial of this line, usually closer to MB1

Question 8

What are the laws that govern the location of the canals?

Answer 8

CEJ laws

• Law of CEJ: CEJ is most consistent, repeatable landmark for locating position of pulp chamber
• Law of concentricity: Walls of pulp chamber are always concentric to external contour at level of CEJ
• Law of centrality: Floor of pulp chamber is always located at centre of tooth at level of CEJ

Maxillary molar not included laws

• Orifices of canals will always lie equidistant from a line drawn through centre of tooth mesio-distally
• Orifices of canals always lie perpendicular to line drawn through centre of tooth mesio-distally

Generic laws:

• Orifices of canals always located at junction between wall and floor
• Orifices of canals located at terminus of root developmental fusion lines

Question 9

Why should you take a radiograph right before accessing?

Answer 9

To see if anyone has touched the tooth before you have (if you don’t and a previous operator perforated, it becomes your perforation!)