Bone morphology after delayed tooth replantation - case series.

The purpose of this report was to describe the morphological changes in the alveolar bone after delayed replantation of avulsed teeth using three dimensional cone-beam computed tomography in 11 during the time period 2003-2012. The radiographic observations revealed the following: Delayed replantation results in ankylosis-related replacement root resorption; the resorption is delayed or arrested around the cervical area superior to the alveolar crest. The buccal bone is reduced in thickness but not the palatal bone. The buccal bone resorption of the alveolar crest progresses approximately to the root canal space of the ankylosed root. Delayed replantation does not completely maintain the bone volume. The buccal profile of alveolar bone in the maxillary anterior region is depending on teeth with viable periodontal ligament.

Illusion caused by vibration of muscle spindles reveals an involvement of muscle spindle inputs in regulating isometric contraction of masseter muscles.

Spindle Ia afferents may be differentially involved in voluntary isometric contraction, depending on the pattern of synaptic connections in spindle reflex pathways. We investigated how isometric contraction of masseter muscles is regulated through the activity of their muscle spindles that contain the largest number of intrafusal fibers among skeletal muscle spindles by examining the effects of vibration of muscle spindles on the voluntary isometric contraction. Subjects were instructed to hold the jaw at resting position by counteracting ramp loads applied on lower molar teeth. In response to the increasing-ramp load, the root mean square (RMS) of masseter EMG activity almost linearly increased under no vibration, while displaying a steep linear increase followed by a slower increase under vibration. The regression line of the relationship between the load and RMS was significantly steeper under vibration than under no vibration, suggesting that the subjects overestimated the ramp load and excessively counteracted it as reflected in the emergence of bite pressure. In response to the decreasing-ramp load applied following the increasing one, the RMS hardly decreased under vibration unlike under no vibration, leading to a generation of bite pressure even after the offset of the negative-ramp load until the vibration was ceased. Thus the subjects overestimated the increasing rate of the load while underestimating the decreasing rate of the load, due to the vibration-induced illusion of jaw opening. These observations suggest that spindle Ia/II inputs play crucial roles both in estimating the load and in controlling the isometric contraction of masseter muscles in the jaw-closed position.