A biodifferential system of face-bow mechanics

A review of the literature, both scientific and commercial, did not demonstrate the separation of the inner and outer bows into a biodifferential interchangeable system. The prime design idea, to separate the inner and outer bows, increased versatility and yielded a multiple appliance with a greater range of use and safety. The joint couple systems could be adapted to fulfill the criteria cited in the literature during preliminary treatment (deciduous dentition), partial treatment, full-banded treatment, and retention. The biodifferential design was compatible with most mechanical orthodontic appliances and systems currently used. The three joint designs presented and the three inner bow lock devices fulfilled the parameters expected from the normal use of the present face-bow in necessary strength, stability, and use. Further, the use of a joint couple between the inner and outer bows expanded the versatility of the face-bow into a biodifferential system and allowed for an easily manageable and orderly change of forces, vectors, sizes, and shapes requiring little chair time and minimum instruction to the patient. The inner bow could be used as an intraoral appliance for bumpers, shields, and oral screens. These easily made, preformed, interlocking parts could be marked or color coded as to type and size and keyed, grooved, and designed to prevent inverted interlocking of parts. The inner bow could be tied in, as an aid in patient cooperation, or the inner and outer bows could be pinned or ligated together to prevent separation. One of the most important factors of the biodifferential system is protection of the patient from severe trauma to the eyes, face, and mouth due to misuse or accident, as has occurred in the one-piece face-bow. The biodifferential system fulfills the five criteria of the investigation: (1) a system of interchangeable, interlocking joint parts, (2) safety and dependability, (3) easy changes in force, vectors, and moments, (4) enhanced patient cooperation, and (5) oral hygiene.