| 摘要 |
An extraoral orthodontic appliance including a harness for mounting on the head and/or neck of a patient and connected to a conventional corrective tractive apparatus, such as a set of J-hooks, a face bow or a chin cup, by traction force devices (force modules) mounted on each side of the harness. The force modules incorporate force reels that are internally force-biased by inexpensive non-constant (cumulative) force, clock-type springs of large extension which can be adjusted to desired tractive force levels by winding and preset so as to apply a substantially constant tractive force during treatment periods, regardless of movement of the patient's head or jaw. Further, the force modules may include means to limit the extent to which the corrective tractive apparatus can be extended and retracted thereby protecting the patient from injury during placement and removal of the appliance or accidental uncontrolled retraction.
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