Root canal treatment is priced differently depending on which tooth is involved. The difference reflects anatomy, and the anatomy varies considerably from front to back.
Canal number rises toward the back
An upper front tooth typically contains a single canal in a single root, and it is relatively straight and accessible.
Premolars commonly have one or two, while molars usually have three or four, and additional canals are found in a meaningful proportion of cases.
Every canal must be located, cleaned, shaped and sealed individually, so the work scales with the number present rather than with the size of the tooth.
The shapes are more complex than a simple tube
Molar canals frequently curve, sometimes sharply, and they may divide and rejoin along their length or connect through small lateral branches.
Oval and ribbon-shaped cross-sections are common, meaning instruments contacting the walls in one direction may not reach the recesses at the sides.
Cleaning therefore relies heavily on irrigation reaching areas instruments cannot, and that requires time and careful technique. Solutions have to be exchanged repeatedly rather than left in place.
Access is physically harder
Molars sit at the back of the mouth where visibility is limited, instruments are harder to angle, and the patient must keep the mouth open for longer.
Isolation with a rubber dam is essential to keep the canal system free of saliva, and placing it well on a broken-down molar takes additional time.
Magnification and additional imaging are more often needed to locate canals that would be found readily in a front tooth.
What comes afterward differs too
A treated molar has lost structure to both decay and the access cavity, and it carries the heaviest chewing forces in the mouth.
Cuspal coverage is therefore often recommended to protect against fracture, adding a separate restorative cost to the endodontic one.
Front teeth frequently need only a filling in the access cavity, which is why the total cost gap is wider than the treatment fee alone suggests.
Where cases become more involved still
Retreating a previously treated tooth means removing existing filling material before the canals can be cleaned, which adds steps and risk.
Calcified canals, curved roots, existing posts or crowns and previous fractures all extend the work and may lead to referral to a specialist.
Whether treatment is appropriate at all, and whether the tooth is restorable afterward, are clinical judgements made from examination and radiographs.