After my braces can I use both?

Okay so im getting braces but after I get two teeth pulled out to make room. The orthodontist said I need to wear retainers after-wards (18mths to 2yrs is the length i have to wear my braces) but after my braces will that show 10 teeth because mine now only show 8. Or can I wear both retainers and palet expanders ?