What is the most common cause of vertical root fracture occurring during root canal treatment?

Correct answer: A. Excessive force during lateral condensation of gutta-percha

• A. CORRECT. LATERAL CONDENSATION generates high wedging stresses inside the canal. A spreader driven with excessive force — particularly into a canal already thinned by over-instrumentation, or into a root with a thin, oval cross-section such as a mandibular incisor or the mesial root of a lower molar — can crack the root longitudinally. The fracture may not become apparent for months or years.
• B. Sodium hypochlorite has no mechanical wedging action; its risks are chemical (hypochlorite accident) rather than structural.
• C. Coronal flaring removes dentine and can weaken a root over time, but the acute fracture event is associated with obturation forces.
• D. A clamp acts on the crown and, correctly placed, does not generate the intracanal wedging force that splits a root.

Note: Preserve dentine. Excessive coronal flaring, aggressive post space preparation and heavy condensation forces compound one another — and post placement is the other major contributor to vertical root fracture.