What shapes should access cavities be on each tooth?
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
What should you check for in a pre-operative radiograph?
- Both crown and root tips captured
- Tilting
- Sufficient tooth structure for longevity after treatment
What is the outline form? What bur would you use to achieve it?
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
What is the convenience for? What bur would you use to achieve it?
- 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
How can you tell if a pulp stone is present? How can it be removed?
Floor of mouth has dark grey-ish hue
-Remove by ultrasonic or cutting around outline with fine diamond and lifting up
What is a cavity toilet? How can it be created?
- 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
How do you locate the MB2 canal?
Draw line from MB to P canal, MB2 will sit somewhere mesial of this line, usually closer to MB1
What are the laws that govern the location of the canals?
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
Why should you take a radiograph right before accessing?
To see if anyone has touched the tooth before you have (if you don’t and a previous operator perforated, it becomes your perforation!)
