Free- way space

1. 1 Free Free- -way space way space Prepared by Prepared by Dr. Mohammed Alruby Dr. Mohammed Alruby Free Free- -way space way space Dr. Mohammed Alruby Dr. Mohammed Alruby

2. 2 Freeway space: = is the inter-occlusal space (vertical distance) between maxillary and mandibular teeth when the mandible is in natural or physiologic rest position under the reciprocal coordination of elevator and depressor masticatory muscles. = McNamara, stated that; the rest position of the mandible is influenced by the activity of elevator muscles through stimuli from peripheral receptor such as those located in TMJ, periodontal ligament, gingiva, tongue, palate = the freeway space is negatively correlated with ALFH and positively correlated with PLFH (ramus height) = freeway space increase in deep bite cases Peterchonchak 1987: Definition: natural rest position of the mandible, suspended by reciprocal coordination of elevator and depressor muscles with upper and lower teeth separated. =He takes S N ----- Mp angle to describe the face into: a-Low angle; short face b-High angle: long face = He make another study and increase the sample of subjects and his aim is directed to; a-Compare freeway space FWS with cephalometric parameter b-Compare FWS with angle classification Results: a-Angle classification not correlated to FWS b-FWS has inverse correlation to S N---- MP angle Fuggi 1977: Demonstrate that transcutaneous electrical nerve stimulation TENS produce deconditioning of musculature by reducing muscle spindle feedback N: B: the muscle relaxation that result from TENS: induce proprioceptive disfacilitation of the fifth motor nerve and is not a fatigue phenomenon because of increased electo-myographic activity of the musculature. FWS types: ( Jakleson 1978) 1-Adaptive FWS: the inner occlusal space that exist when patient is instructed voluntary to allow the jaw to relax 2-True FWS: jaw position after induced muscular relaxation by transcutaneous electrical nerve stimulation (TENS) N: B; when need to measure FWS we must put the patient in rest position, normal FWS 3mm at canine region Methods for measuring freeway space: 1-Direct intraoral method: by using caliper in patient mouth at canine region 2-Direct extraoral method: two marks on face, nose and chin on sagittal plane and measure the difference between the rest and occlusion 3-Indirect extraoral: two cephalometric radiograph, one in rest and other in occlusion Free Free- -way space way space Dr. Mohammed Alruby Dr. Mohammed Alruby

3. 3 Methods for rest position: 1-Phonetic method: repeat letter m or ward Mississippi and the mandible present in rest position after 1 to 2 seconds after exercise 2-Command method: after swallowing 3-Non command method: examine patient when he has not aware Methods for measuring true FWS: 1-TENS: transcutaneous electrical nerve stimulation: that made deconditioning of the muscles by eliminating the proprioceptive sensory input from the existing malocclusion TENS, is applied to the motor division of the 5th cranial nerve Mode of action of TENS: a-Reduce the muscle spindle feed back b-Block the 5th cranial motor nerve fibers c-Inhibition of upper motor neuron on the motor nucleus of trigeminal nerve deactivation of the gamma motor neuron drive to the muscle spindle ==Results of TENS: reduce the elevator muscle stretch reflex and thus reducing the resting EMG activity of masticatory muscles ==True FWS is larger than adaptive FWS 1.8: 2.9 respectively according to Konchack There is a significant correlation between adaptive freeway space and Sn-Mp angle also ALFH ==Normal FWS; 2 – 4mm == <2mm: open bite == >4mm: deep bite 2-Bite plate: traditional method: = It can be used as a valuable diagnostic tool in measurement of correct vertical dimension and true freeway space. Also in diagnosis and treatment disorder and bruxism = For measuring: put bite plate in patient mouth for sufficient time to allow eliminate the sensory input for the malocclusion, then move it and the orthodontist can measure the FWS by instruct the patient to relax the mandible When the amount of freeway space is larger than normal, there is great chance for correction of deep bite by guiding the vertical alveolar development Free Free- -way space way space Dr. Mohammed Alruby Dr. Mohammed Alruby