Yes, research studies have found that people who wear a sleep apnea mask or commonly known as a CPAP mask can experience subtle structural facial changes from their time of wearing one. X-rays were conducted as part of the studies and confirmed that the facial structures of the participants of the study had changed. There was a reduction in the distinction of their upper and lower jaws, which also affected some teeth positioning.
The people who conducted this research did confirm that these changes in facial structuring should not put people off from using a CPAP mask as they are not noticeably different from looking at someone but only confirmed when X-rays were performed. However, people who are told to wear sleep apnea masks should be told about these possible side effects. People who already struggle with jaw or dental problems should be made aware of these facial structural changes as they could negatively impact their health and wellbeing more so.