Excluding the maxillary first molar, which tooth carries the highest risk of extruding sealer into the maxillary sinus?

Correct answer: D. Maxillary second premolar

• A. The maxillary canine has the LONGEST root and its apex lies well anterior and superior to the sinus, near the canine fossa.
• B. The maxillary central incisor apex lies near the nasal floor, not the sinus.
• C. Mandibular teeth have no anatomic relationship to the maxillary sinus; their apical risk structure is the inferior alveolar canal.
• D. CORRECT. Among the options given, the MAXILLARY SECOND PREMOLAR has apices that most closely approximate the floor of the maxillary sinus. The sinus floor typically extends from the premolar region back to the tuberosity, and the palatal recess can dip between the roots. In many patients only a thin cortical plate — sometimes nothing but mucosa — separates the premolar and molar apices from the antrum, allowing sealer, irrigant, or a fractured instrument to be pushed directly into the sinus.

Note: Sinus proximity order: maxillary second molar ≈ first molar > second premolar > first premolar. Establish an accurate working length and never over-instrument.