A patient presents with bitewing radiographs showing an open contact between premolars #20 and #21 following mesial and distal restorations. The patient reports food impaction between these teeth. What is the most likely cause?

Correct answer: D. Poor contour and adaptation of the matrix band

• A. INCORRECT — While improper wedging can affect contact tightness, the primary cause of open contacts in composite/amalgam restorations is poor matrix adaptation and contour.
• B. INCORRECT — A matrix band that is too thick would cause the contact to be tighter, not open. The cause of an open contact is failure to establish proper approximal contour.
• C. INCORRECT — Self-cleaning mechanism refers to the natural food-clearing action of the cheeks and tongue. While relevant to oral hygiene, it is not a cause of an open contact.
• D. CORRECT — Poor contour and improper adaptation of the matrix band during restoration placement is the primary cause of open contacts. If the matrix is not properly burnished/adapted against the adjacent tooth and contoured appropriately, the restoration will harden with an open contact point.