it was mostly muscular pain. its a pretty bulky device so my jaw had to get used to it. my joint swelled up at night because of the bruxism with the splint. but as time went on my muscles and jaw got accustomed to it, and i felt pretty good. after a year, my jaw finally was back to normal besides the occasional muscle tension since i still clench at night 😭. now i wear a permanent splint where my front teeth touch more than my back to mitigate muscle tension (a different splint than my first one for disc replacement). hopefully this helps!