Endodontics · patient case question
Retreatment will require re-establishing straight-line access. What is the principal ADVANTAGE of straight-line access?
Patient case: Full-mouth series in a patient with several root-treated teeth
Patient: Male, 52 years old
Chief Complaint: New patient examination. Intermittent vague discomfort in the upper right quadrant.
Background: Several root canal treatments completed at different times by different clinicians.
Current Findings: A full-mouth radiographic series has been taken. On the periapical below, one root-filled tooth shows an obturation that stops well short of the radiographic apex, with a small periapical radiolucency (arrow).
Show answer and explanation
Correct answer: C. Instruments can reach the apical third of curved canals
- A. Irrigation is indispensable regardless of access. Sodium hypochlorite dissolves tissue and kills bacteria in regions no file ever touches.
- B. Straight-line access necessarily REMOVES more tooth structure. That is its acknowledged trade-off, not its advantage.
- C. CORRECT. Straight-line access removes the coronal interferences — overhanging dentine, unroofed pulp horns, the cervical bulge — so files enter the canal without deflection. The instrument then follows the canal's own curvature rather than being restrained at the orifice, which is what allows the apical third of a curved canal to be reached and shaped. It also reduces ledging, transportation and instrument separation.
- D. Access design does not change how many canals exist. Good access makes them easier to FIND, but the number is fixed by the anatomy.
Note: Straight-line access: reduces ledging, removes unsupported dentine, unroofs the pulp horns, and gives adequate access to the apical third. Its one disadvantage: more tooth structure is removed.