A newly delivered maxillary complete denture is retentive at rest but repeatedly dislodges when the patient speaks or opens wide. The most likely cause is:

A maxillary denture that dislodges with function usually has overextended borders or flanges (e.g., into the hamular notch, buccal frena, or across the vibrating line) that movable tissues displace, breaking the peripheral seal.Other options: Saliva does not dislodge a well-fitting denture; an adequate posterior palatal seal improves retention; thinness alone does not cause functional dislodgement.Key exam takeaway: Retentive at rest but loose in function = overextended/over-contoured borders; identify and relieve the overextension.