Hi hteller!

Great question.

830.0 = Closed dislocation of jaw

So for a "right displacing disc without reduction", this following code/description seems like it would describe that particular condition better:
524.63 - Temporomandibular joint disorders, articular disc disorder (reducing or non-reducing)

As for the limited mouth opening, "trismus" (reduced opening of the jaws caused by spasm of the muscles of mastication, or may generally refer to all causes of limited mouth opening) is coded as:
781.0 = Abnormal involuntary movements


Here is more detail on closed and open locks as shown in the ICD coding book:

Dislocation (articulation) (closed) (displacement) (simple) (subluxation) 839.8

jaw (cartilage) (meniscus) (closed) 830.0
open 830.1
recurrent 524.69

mandible (closed) 830.0
open 830.1

maxilla (inferior) (closed) 830.0
open 830.1

symphysis
jaw (closed) 830.0
open 830.1
mandibular (closed) 830.0
open 830.1
pubis (closed) 839.69
open 839.79

temporomandibular (joint) (closed) 830.0
open 830.1
recurrent 524.69


Hope this helps, please let us know if you have any further questions!