What is a potential implant issue when fitting a bar overdenture?

A potential issue when fitting a bar overdenture is a non-passive fit of the bar. This condition occurs when the bar does not accurately and comfortably align with the implants. A non-passive fit can lead to complications such as stress on the implants, which may result in bone loss or implant failure over time. Proper passive fit is critical for the longevity of the implants and the function of the overdenture, ensuring that forces are evenly distributed during function.

While the other options may present challenges in dental implantology or overdenture fitting, they do not specifically relate to the mechanical fit of the bar. Excessive dental plaque, for instance, is a periodontal concern that affects oral hygiene rather than the structural integrity of the overdenture fit. Insufficient bone density relates to the surgical planning and potential stability of the implants, while incorrect shade selection is more of an aesthetic issue irrelevant to the mechanics governing how the overdenture interacts with the implants.