If a denture falls down when smiling, what is the likely cause?

The situation described, where a denture falls out while smiling, suggests a primary issue with the retention of the denture during dynamic movements such as smiling. The thickness of the buccal notch and buccal flange can significantly affect how well a denture stays in place.

If the buccal notch and buccal flange are excessively thick, this can interfere with the fundamental anatomy of the mouth, leading to poor adaptation and a lack of necessary suction or fit against the oral tissues. An overly thick flange may prevent the denture from achieving the required stability and retention because it might not create an adequate seal or might not align correctly with the available support from the oral tissues.

Inadequate retention features might suggest that the design of the denture does not incorporate features intended to enhance grip or fit, but in the case of excessive thickness, it points towards a physical barrier to proper retention as well. Therefore, the condition of the buccal notch and flange is directly influencing the denture's ability to stay in place during functional movements, such as smiling.

Overall, addressing the thickness of these aspects during denture design and fitting can be crucial in preventing issues related to retention and functionality in the patient's daily activities.