What is the most common cause of gagging (gag reflex stimulation) in complete denture wearers?

The most common mechanical cause of gagging in maxillary complete denture patients is overextension of the posterior border of the denture into the soft palate or beyond the vibrating line (the junction of movable and non-movable palatal tissue at the distal extent of the posterior palatal seal). When the denture extends too far posteriorly, it contacts the highly sensitive soft palate tissues, which are richly innervated with sensory receptors, triggering the gag reflex (pharyngeal reflex mediated by CN IX and X). Management includes trimming the posterior border to the correct vibrating line position. Psychological gagging (psychogenic) also occurs and is more challenging to manage. The mandibular denture rarely causes gagging as it does not contact the soft palate.