Molars are the largest teeth, positioned at the back of the jaws, designed for grinding and crushing food. The root system anchors these teeth to the jawbone beneath the gums. Unlike front teeth, molars are multi-rooted, but the exact number of roots varies. The number of roots a molar possesses is determined by its location, specifically whether it resides in the upper or lower jaw.
Root Structure of Lower Molars
Lower (mandibular) molars typically possess two distinct roots in over ninety percent of cases. These are the mesial root (closer to the front) and the distal root (toward the back). The roots are positioned one behind the other and are flattened from front to back.
Although there are usually only two roots, the internal anatomy includes multiple root canals. The mesial root almost always contains two separate canals, while the distal root most frequently houses a single canal. This common arrangement means a typical lower molar has three root canals.
Variations occur, such as a third root, known as a radix entomolaris, which may be present on the lingual side. This extra root can complicate treatment. Less commonly, the two roots may be fused, or the entire root system may have a single, C-shaped canal structure.
Root Structure of Upper Molars
Upper (maxillary) molars typically have three distinct roots, a structure found in the majority of these teeth. These roots are named the mesiobuccal, the distobuccal, and the palatal root.
The two buccal roots face the cheek, while the single palatal root faces the roof of the mouth. The palatal root is often the largest and longest, frequently exhibiting a noticeable curvature. This robust root provides substantial anchorage.
The complex root system often contains four root canals. The palatal and distobuccal roots usually contain one canal each. The mesiobuccal root commonly contains a second canal, often called the MB2 canal, which is small and challenging to locate.
Variations include the fusion of two or more roots, or the presence of an extra fourth or fifth root. This complex and divergent anatomy is a significant factor in treatment planning due to the roots’ close proximity to the maxillary sinus.
Clinical Importance of Molar Roots
The number and morphology of molar roots have direct implications for dental treatment, particularly in endodontics and oral surgery. The presence of multiple, separate roots (two lower, three upper) is the primary source of anatomical complexity. While root divergence provides stability, it makes surgical removal, or extraction, more challenging.
During extraction, the dentist must navigate the roots’ separation, sometimes requiring the tooth to be sectioned into individual parts for safe removal. In endodontics (root canal treatment), the challenge is magnified by the number of canals and their curved pathways. A molar with multiple roots and canals requires careful exploration to ensure all infection is removed.
A major reason for root canal failure is the failure to locate and clean all canals, such as the elusive MB2 canal in the upper molar. Furthermore, the curvature of individual roots increases the risk of procedural complications. Navigating a curved canal requires specialized techniques to prevent damage.
The success of preserving a molar is closely tied to a dentist’s ability to accurately identify all roots and canals. Modern imaging technology, such as Cone-Beam Computed Tomography (CBCT), is often used to map this complex three-dimensional anatomy. This precise mapping is frequently the difference between successful treatment and tooth loss.