In class II restorations, which of the following is NOT considered a probable cause of periodontal problems?

In class II restorations, ensuring optimal contour and margin placement is vital for maintaining periodontal health. Overextension of the lining in the cavity typically refers to the dental material being placed beyond the intended area of the preparation, which primarily affects the restoration's quality and longevity rather than causing direct periodontal problems.

On the other hand, a flat marginal ridge can lead to food impaction, which may compromise the gingival health. A cervical wall that is too deeply apical can also contribute to periodontal issues as it may create an environment that is difficult to clean. Similarly, a faulty or improper contour can create areas that trap plaque and food debris, promoting gingival inflammation. Therefore, while all the other choices relate directly to factors that could lead to periodontal problems, overextension of the lining does not directly contribute to these issues in the same way.