I think that for davening it would be proper to take them out (however in your case of only wearing it at night it may be different). davening is compared to approaching a king and one would never wear retainers (if they were remoavable) when approaching a king so kal vechomer (even the more so) Hakadosh Baruch Hu. However, stam simple brachos may be different. If you eat with retainers then it would seem fine to keep them in (as long as words of bracha can be said correctly) – this is different from davening as it’s a “thank you” to Hashem as opposed to an official meeting/conversation. However, if you don’t eat with retainers then why not take it out for the bracha – you might as well + it wouldn’t be respectful to take them out for eating but not for blessing Hashem.
These are just some of my thoughts… for practical application of halacha, however, CONSULT YOUR RAV OR LOCAL POSEK to answer specific questions. Hatzlachah!