Under what circumstances might an RPD need rebasing?

Rebasing an RPD becomes necessary primarily due to significant changes in the supporting oral tissues, which can compromise the fit of the denture. As patients age, or as their overall health changes, the shape and size of the structures in the mouth can alter, leading to issues such as resorption of alveolar bone. When these changes occur, the original framework of the RPD may no longer sit correctly against the tissues, causing discomfort, instability, and poor function. Rebasing involves replacing the entire denture base material to restore a proper fit over the altered areas, while preserving the original framework and any attachments.

The other options suggest reasons for making changes to the RPD that do not directly pertain to fit or function. Changing the color is a cosmetic preference that doesn’t necessarily affect how well the denture adheres to the gums. Simply breaking the denture prompts repair rather than rebasing, which is more extensive and involves reshaping the base to match new anatomical conditions. Regarding acclimatization, while it is common for patients to get used to wearing dentures, this does not necessitate rebasing unless there are fit issues arising from tissue changes. Thus, the most valid circumstance for rebasing an RPD is due to significant alterations