MandibularTrapezoidal

Mandibular Second Molar

Mandibular Second Molar - Axial View showing trapezoidal access with canal orifices

Average Length19.8 mm

Root Development15 years

Universal #18, 31

FDI #37, 47

Access Cavity Design

ShapeTrapezoidal

OrientationSimilar to first molar but smaller

Entry PointMesial two-thirds of occlusal surface

Canal Anatomy

Configurations

2 roots, 3 canals~79%

2 roots, 2 canals~13%

C-shaped anatomy0.6-45.5% (ethnic)

Canal Positions

MBMesiobuccal

May appear as single oval with ML in fused roots

MLMesiolingual

May be fused with MB

DDistal

Typically single canal

CC-Shaped

Continuous ribbon-shaped orifice from MB to D

Danger Zones

⚠Thin lingual wall in C-shaped canals - HIGH perforation risk

Clinical Tips

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Warning

C-shaped canal prevalence: Up to 45% in Korean population

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Tip

C-shaped appearance: Ribbon-shaped orifice connecting MB to D (180° arch)

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Technique

For C-shaped: Locate main canals first, then clean connecting isthmuses

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Warning

High perforation risk on thin lingual wall - use smaller taper files

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Technique

Thermoplasticized GP mandatory for C-shaped obturation

Anatomical Variations

C-Shaped Canal

0.6-45.5%

Single fused root with ribbon-shaped canal system

Access Modification: Expect continuous C-shaped or semicolon orifice, avoid over-extension

Ethnic Variation

Korean31.3-45.5%

Chinese0.6-41.27%

Burmese22.4%

Caucasian<5%