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Mandibular Trapezoidal

# Mandibular Second Molar

[Previous tooth Mandibular First Molar FDI 36 · 46](https://endo-guide.app/access-cavities/mand-first-molar)

![Three-canal mandibular molar access — mesiobuccal, mesiolingual and distal orifices](https://endo-guide.app/images/access-cavities/atlas/mandibular-molar-3canal.webp)

Three-canal mandibular molar access — mesiobuccal, mesiolingual and distal orifices

 Average Length 19.8 mm

 Root Development 14-15 years

 Universal # 18, 31

 FDI # 37, 47

### Access Cavity Design

Shape Trapezoidal

OrientationCompact trapezoidal; similar to first molar but smaller and more mesially positioned

Entry PointMesial two-thirds of occlusal surface

Landmarks

- Mesial pit as primary reference
- Orifice pattern more compact than first molar

Do Not Invade

- Mesial marginal ridge
- Lingual wall (especially thin in C-shaped variants)

### Canal Anatomy

#### Configurations

2 roots, 3 canals60-80%

2 roots, 2 canals~13%

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

Radix Entomolaris (extra distolingual root)1.4-2% (lower than first molar)

#### Canal Positions

 MB Mesiobuccal

May appear as single oval with ML in fused roots

 ML Mesiolingual

May be fused with MB

 D Distal

Typically single canal

 C C-Shaped

Continuous ribbon-shaped orifice from MB to D

#### Danger Zones

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

### Clinical Tips

Tip

C-shaped appearance: Ribbon-shaped orifice connecting MB to D (180 degree arch) — pathognomonic finding

Technique

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

Technique

Thermoplasticized GP (warm vertical or carrier-based) mandatory for C-shaped obturation — lateral compaction inadequate

### 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%

### Other teeth in the atlas

Maxillary

[Maxillary Central Incisor](https://endo-guide.app/access-cavities/max-central-incisor)[Maxillary Lateral Incisor](https://endo-guide.app/access-cavities/max-lateral-incisor)[Maxillary Canine](https://endo-guide.app/access-cavities/max-canine)[Maxillary First Premolar](https://endo-guide.app/access-cavities/max-first-premolar)[Maxillary Second Premolar](https://endo-guide.app/access-cavities/max-second-premolar)[Maxillary First Molar](https://endo-guide.app/access-cavities/max-first-molar)[Maxillary Second Molar](https://endo-guide.app/access-cavities/max-second-molar)

Mandibular

[Mandibular Central Incisor](https://endo-guide.app/access-cavities/mand-central-incisor)[Mandibular Lateral Incisor](https://endo-guide.app/access-cavities/mand-lateral-incisor)[Mandibular Canine](https://endo-guide.app/access-cavities/mand-canine)[Mandibular First Premolar](https://endo-guide.app/access-cavities/mand-first-premolar)[Mandibular Second Premolar](https://endo-guide.app/access-cavities/mand-second-premolar)[Mandibular First Molar](https://endo-guide.app/access-cavities/mand-first-molar)

For Educational Purposes Only

Access cavity designs based on established endodontic principles. Always refer to current literature and clinical guidelines.

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