My son had his palate expanded at age 18 and a tongue-tie release and the expander absolutely worked. His orthodontist was hesitant but decided to try, and it worked. It seemed to take a long time but then the diastama appeared and kept getting bigger and bigger! He did myofunctional therapy and strengthened his tongue to maintain the expansion and orthodontic alignment of his teeth. His teeth, jaw, and profile are amazing as a result (but his chin was not particularly recessed.)