Y3 L3 Anatomy and access for posterior teeth Flashcards
Describe the maxillary first premolar.
- Usually 2 canals with 2 roots
- Vertucci’s type 1 in each root
- Sometimes 1 root with 2 canals, 2 foaramen
If a maxillary first premolar has 3 roots how will they be positioned?
- 2 buccal
- 1 palatal
Describe the maxillary second premolar.
- Majority have 1 root with 1 canal but there can be a lot of variation
What is the access cavity shape for maxillary premolars?
Ovoid
Describe the mandibular first premolar.
- Commonly 1 canal with 1 foramen
- Some begin with 1 canal with 2 foramina (branching canal, Vertucci’s type V)
Describe the mandibular second premolar.
- 97% have 1 canal with 1 foramen
- 12% of these have a branching canal which re joins at the apex
Describe the access cavity for mandibular premolars.
- Ovoid
- Crown is asymmetric, larger buccal cusp = sloped occlusal surface
- Be careful not to undermine the small lingual cusp
- Penetrate depth of 3-4mm (left of first image), then reorientate yourself to be more in line with the long axis of the tooth (green line)
What are the average canal lengths for the premolars?
- U4: 20.6mm
- U5: 21.5mm
- L4: 21.6mm
- L5: 22.3mm
Describe the maxillary first molar.
- Approx 21mm long (20.8mm)
- Majority have 3 roots (1 palatal, mesiobuccal and distobuccal)
- Majority have 4 canals: 2 mesiobuccal canals
Which canal is often missed in the maxillary first molar?
- MB2
- The second mesiobuccal canal
- Draw an imaginary line between palatal orifice and MB1, MB2 will be located mesial to that line
- Mesiobuccal root is figure of 8 shape
What percentage of maxillary first molars have 2 canals in the MB root?
- Some say 60%
- A more recent study quoted 90% (go with this figure)
Describe the maxillary second molar.
- Much more variable in shape and configuration of canals
- Approximate length: 20mm
- Most common is 3 canals in 3 roots
- 2nd: 4 canals in 3 roots
- 3rd: 2 buccal roots fusing apically, 3 canals
- 4th: 1 buccal, 1 palatal
- 5th: conical root with 1 single canal
- 6th: 4 roots with 4 canals
Describe the access cavity for maxillary first molars.
- Trapezoid shape
- Wider base bucally, smaller palatally
- More mesially positioned
Describe the access cavity for maxillary second molars.
- More triangular
- Base facing buccally
- Point facing palatally
Describe the mandibular first molar.
- Average length of 21mm
- Most commonly 2 roots with 3 canals
- 2 canals in mesial root and 1 canal in distal root
- 30-40% of the time there are 2 distal canals
- Roots curve distally
Describe the mandibular second molar.
- Average length of 20mm
- Similair to mandibular first molar but slightly shorter
- Roots very close to ID nerve: carefull irrigation
- Most common to find 1 mesial canal (40% have 2) in 1 mesial root and 1 distal canal in 1 distal root
- 13% have C-shaped distal canals difficult mechanical cleaning
- 9% have a conical shaped root
Describe the access cavity shape for mandibular molars.
6: triangular shape with base facing mesially and the point/apex distal
7: larger mesially
What are the laws of orifice location?
- Law of colour change: floor of chamber is much darker
- Law of symmetry: applies to all posterior teeth except maxillary molars. If you draw an imaginary line mesio-distally, the orifices are situated at equal distances in each root
- Law of orifice location 1&2: orifices are found at interface between the wall and floor, and are found between the developmental fusion lines
Canal orifices are…
Failure to achieve straight line access increases the risk of what procedural errors?
