Rattling bones in the open mouth may be due to joint misalignment. When the temporomandibular joint is structurally disturbed, such as a misaligned joint disc, it can cause the bones to rattle when the mouth is opened. However, in addition to this, the ringing of bones when opening the mouth may be a normal physiological response, or it may be related to masticatory muscle dysfunction, inflammatory diseases of the joints and osteoarthrosis.