How to close 36 and 46 extraction spaces

I have a 16-year-old boy who had his lower 1st molars extracted abroad. He seems to have normal OB and OJ. His anterior teeth start to drift back to the extraction spaces, leaving gaps between his front teeth. My plan is to move the 37 and 47 forward to close the extraction spaces. Maintain current anterior OB and OJ. I am using elastic chains and see very little results for 3 months. Any advice would be highly appreciated!