Maxillary and Mandibular Root Morphology in Endodontics

Maxillary Molars

The Maxillary First Molar is characterized by high variability. It typically possesses three roots ($97.7%$). While $40%$ of these teeth have three canals, $60%$ possess four canals. A critical clinical consideration is the MB2 canal (the second mesiobuccal canal), which is present in a significant number of cases—up to $70%$ when viewed via CBCT.

The Maxillary Second Molar often exhibits root fusion, which can complicate treatment. While three roots are most common ($74%$), configurations with two roots ($15%$) or even a single fused root ($2\text{--}6\%$) are observed. Canal numbers are also variable, with three canals being the most frequent ($\approx 59\%$).

Mandibular Teeth: Complexity and Classification

Mandibular teeth often present unique challenges, such as ribbon-shaped roots and C-shaped canal configurations, which require specific clinical approaches.

Mandibular Anterior Teeth

The Mandibular Central Incisor is primarily single-rooted ($99.92%$) with an average length of $20.8\text{ mm}$. Its canal morphology is best understood through the Vertucci classification:

• Type I ($70%$): A single canal from pulp to foramen.
• Type II ($25\text{--}27\%$): Two separate canals that join into one before reaching the apex.
• Type III ($3%$): A single canal that divides and then rejoins.
• Type IV ($5\text{--}15\%$): Two distinct canals that exit through two separate foramina.

The Mandibular Lateral Incisor is similar but shows a higher prevalence of Type IV morphology ($15%$) compared to the central incisor.

Mandibular Premolars and Canines

The Mandibular Canine has an average length of $25.0\text{ mm}$ and an ovoid access. A significant morphological variation is the ribbon-shaped root, which can mimic the appearance of two separate canals until the dentin fin is removed during instrumentation.

The Mandibular First Premolar is mostly single-rooted ($94%$) and single-canaled ($71.3%$), though approximately $27.9%$ of cases present with two canals.

Mandibular Molars

The Mandibular First Molar typically has two roots ($87%$), though a third root, known as radix entomolaris, occurs in approximately $12%$ of the population. Clinicians should be aware of the middle mesial canal, which is present in $1\text{--}15\%$ of these teeth.

The Mandibular Second Molar is highly variable due to the presence of C-shaped canals. These occur when the mesial and distal roots fuse, creating a continuous, crescent-shaped canal space rather than distinct round canals.

Clinical Tip: The MB2 and Middle Mesial Canals When treating maxillary first molars, always search for the MB2 canal using a systematic approach. For mandibular first molars, if a middle mesial canal is suspected, use an ultrasonic tip under magnification to trough the dentin along the developmental groove between the mesial orifices.

Summary of Morphological Data

The following tables summarize the average lengths and canal prevalence for key teeth.

Maxillary Teeth Summary

Mandibular Teeth Summary

Exam Note: Vertucci vs. Weine Classifications Be careful not to confuse the two systems. A "Type III" in the Weine classification describes different anatomy than a "Type III" in the Vertucci classification. Always verify which system is being used when reviewing literature.