The presence of two or three canals in this root has been reported in some population as in India, two canals were found in 5%. The palatal root is the longest and has the largest diameter in most cases, it contains one round canal from the orifice of the pulp chamber to the apex. The root canal system of the maxillary first molar is complex and has many variations among races due to that it has the highest rate of endodontic failure. Root fusion of this tooth was observed in about 0.9–3%. Despite this, in some populations these variations were observed: one, two, or four roots in the maxillary first molar. The maxillary first molar is the earliest permanent tooth that appears in the oral cavity and that makes it vulnerable to caries and furthers to the need of endodontic treatment. Type V: two or three canals without visible connection between them.
Type IV: a complete or incomplete isthmus between three or more canals Type III: very short complete isthmus between two canals Type II: two canals with a definite connection between them Type I: incomplete isthmus between two canals classified root canal shape and the presence of connections between canals into five types ( Figure 6): Root canal shape varies between round, oval, and C-shaped. For mandibular first molars, 80% of mesial roots have connection in the middle and apical third of the root. The prevalence of the isthmus was high in mesiobuccal root of maxillary first molars (about 30–50%) in the apical third of the root. The isthmus was found in 15% in maxillary anterior teeth, for maxillary premolars-it was identified in 16% at a 1-mm level of the apex and in 52% at a 6-mm level of the apex. In addition to describing root canal system, many authors studied the root canal shape and the presence of isthmus (which is a narrow ribbon-shaped communication between two root canals that contain pulp tissue). Root canal configurations according to (A) Beiris and (B) Al-Qudah. Type VIII (3-3): three canals run from the orifice to the apex. Type VII (1-2-1-2): one canal starts from the pulp chamber, then divides into two canals, again unites into one canal, and finally at the apex divides into two canals. Type VI (2-1-2): two canals run from the pulp chamber during its way they unite into one canal and then again split into two canals at the apex. Type V (1-2): one canal runs from the pulp chamber and splits into two canals when coming closer to the apex. Type IV (2-2): two canals run separately from the orifice to the apex. Type III (1-2-1): one canal runs from the pulp chamber, splits into two canals during its way, and then unites into one canal at the apex. Type II (2-1): two canals begin from the pulp chamber and join in one at the apex.
Type 1 (1-1): single canal runs from the orifice to the apex. The classification was as follows ( Figure 2): In 1984, Vertucci presented another classification for root canal configurations in maxillary first molars, and it has been commonly used in different studies. Weine’s classification of root canal configuration. Many techniques have been used to study the root canal system from clearing and radiographs to microcomputed tomography and cone-beam computed tomography scanning, which has the advantage of the high-quality three-dimensional slices. The root canals present different configurations between the teeth and among different populations. The root canal starts from the orifice in the pulp chamber and ends apically with an open orifice into the periodontium. Recent studies have demonstrated that root canal system is very complex due to splitting and union of canals during their way to the apex. Root canal system varies among the teeth, especially in molar teeth. The root canal contains the dental pulp, which occupies the internal cavity of the tooth. This knowledge helps the clinicians in endodontic treatment planning and decreases the percent of endodontic failure. The success of endodontic treatment depends on the precise knowledge of root and root canal anatomy and morphology, which is an important challenge due to the complexity of the root canal system and the anatomical variations.
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