This paper describes the use of cold-curing dental acrylics (used on non-anesthetized psittacines) to help abnormally growing beaks grow normal again.
Anyway--see how the rhinotheca is deviated to the bird's right? and because the gnathotheca has nothing to wear against, it is overgrown.
To treat this bird, you would trim both rhino- and gnathotheca, score the rhampotheca on the gnathotheca (to give the acrylic something to grip) and apply layers of acryllic to the gnathotheca rhampotheca (being careful to keep the bird's tongue away!). Then when it's dry, you shape the acrylic so it's higher on the bird's right and create a "groove" in the middle of the gnathotheca (where the rhinotheca sits in normal birds)--this forces the rhinotheca tip to slide into a more normal position, lining up with the gnathotheca.
After 6 weeks the acrylic usually falls off (or just pry it off) and voila! A more functionally (but not perfectly) aligned beak!
(Dental Composite for Use in Psittacine Species.
Journal of Exotic Pet Medicine, Vol 19, No 4 (October), 2010: pp 290 –297)