My experience is I got a Hawley retainer to relieve a deep bite, which caused my lower teeth to push against my upper front teeth, causing them to just begin to flare out, resulting in about a 1 mm gap. The retainer functioned as a bite plate where my lower bicuspids would hit before my lower teeth could reach my uppers. Also, the ortho put 2 small wire prongs on the wire on each side of my front teeth with pushed them back together. I wore the retainer 23/7 for a few weeks then just waking hours for about 4 months. Worked beautifully, now I can hold my mouth comfortably in good position, though I still have a deep bite. 5 years later the gap remains closed. I have near perfect dentition otherwise, never had braces.