Back to Access Cavities
MaxillaryTriangular
Maxillary First Molar
Maxillary First Molar - Axial View showing triangular/rhomboidal access with MB1, MB2, DB, and palatal canal orifices
Average Length21.0 mm
Root Development10 years
Universal #3, 14
FDI #16, 26
Access Cavity Design
ShapeTriangular/Rhomboidal
OrientationVertices at MB, DB, and P; extend mesially for MB2
Entry PointCentral pit, mesial two-thirds of occlusal surface
Landmarks
- Central pit
- MB-DB-P triangle
Do Not Invade
- Mesial marginal ridge
- Oblique ridge
Canal Anatomy
Configurations
4 canals (MB1, MB2, DB, P)~70%
3 canals (MB, DB, P)~30%
Canal Positions
MB1Mesiobuccal 1
Slightly distal to MB cusp tip
DBDistobuccal
Distal and slightly palatal to MB1, in line with buccal groove
PPalatal
Distal to mesiopalatal cusp tip - largest canal
MB2Mesiobuccal 273.8% (CBCT), 71-82% (with microscope)
2 mm palatal and 1-2 mm mesial from MB1
Clinical Tips
🔧
Technique
Rule of 2: MB2 is 2 mm palatal and 2 mm from MB1
🔧
Technique
Champagne/Bubble Test: NaOCl effervesces at orifice with organic tissue
🔧
Technique
Use ultrasonic diamond tips (E2D, E6D) for troughing MB-MB2 isthmus
💡
Tip
Dental microscope increases MB2 detection from 17% to 82%
⚠️
Warning
Always direct ultrasonics away from furcation
Anatomical Variations
MB2 Canal
73.8% (CBCT worldwide)Second canal in mesiobuccal root, often calcified in older patients
Access Modification: Convert triangular to rhomboidal shape by extending mesiobuccally