A bitewing shows an OPEN CONTACT between teeth #20 and #21 after recent restorations, and the patient reports persistent food impaction. What is the MOST likely cause?

Correct answer: C. Inadequate contouring and poor adaptation of the matrix band

• A. Band thickness contributes to the problem, but even a thick band produces a proper contact if it is burnished and a separation ring is used. The primary failure is contour and adaptation.
• B. There is no self-cleansing mechanism that compensates for an open contact; the complaint of food impaction demonstrates the opposite.
• C. CORRECT. An open or deficient proximal contact after a Class II restoration is almost always a MATRIX problem: the band was not adequately burnished or pre-contoured against the adjacent tooth, no separation ring was used to compensate for band thickness, or the wedge failed to adapt the band gingivally. The result is a flat, under-contoured proximal surface and an open contact — leading to food impaction, papillary inflammation, and eventually interproximal bone loss.
• D. Excessive wedging affects the gingival margin and can cause a ledge, but it does not open the contact — inadequate wedging and separation does.

Note: Fix it with a sectional matrix system plus a separation ring, pre-contoured bands, proper wedging, and burnishing the band against the adjacent tooth before placing material.