An adult case of skeletal open bite with a large lower anterior facial height.

Control of the height of posterior dentoalveolar regions is of great importance for the correction of skeletal open bite. Traditionally, second premolar extraction facilitates the closure of open bite by inducing a counterclockwise mandibular rotation without molar intrusion. This article reports treatment for a 24-year six-month-old female patient with an open bite and large anterior facial height. She complained of occlusal disturbances and difficulty of lip closure because of the open bite. Overjet and overbite were +3.0 mm and -3.0 mm, respectively. To correct open bite and crowding, the bilateral extraction of the maxillary and mandibular second premolars plus multibracket appliances for mesial movement of the molars was selected as the treatment plan. After a two-year treatment, an acceptable occlusion was achieved, the lower anterior facial height was decreased, and the lips showed less tension in a lip closure. An acceptable occlusion was maintained without recurrence of the open bite during a three-year retention period, indicating a long-term stability of the occlusion. The results of this treatment indicated that the correction of open bite with no or less molar intrusion or incisor extrusion is of great importance for achieving stable occlusion and avoiding the relapse of open bite.

Administration of MK-801 decreases c-Fos expression in the trigeminal sensory nuclear complex but increases it in the midbrain during experimental movement of rat molars.

Various studies reported c-Fos expression in the neurons in the trigeminal sensory nuclear complex (TSNC) following experimental tooth movement, which implies pain transmission to the central nervous system. Meanwhile, MK-801, a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptors, was shown to markedly reduce the expression of c-Fos in the trigeminal subnucleus caudalis (Vc) following noxious stimulation but to enhance c-Fos expression markedly in other brain regions, i.e., the neocortex, dorsal raphe and thalamic nuclei. In the present study, we examined the nature of c-Fos expression in the brainstem including the TSNC and midbrain following administration of MK-801 and/or experimental movement of the rat molars. Twelve hours after the beginning of experimental tooth movement, c-Fos was expressed bilaterally in the superficial laminae of Vc (Vc I/II), dorsomedial areas of the trigeminal subnucleus oralis (Vodm) and rostro-dorsomedial areas of the trigeminal subnucleus oralis (Vor) with the ipsilaterally dominant distribution, but hardly in the periaqueductal gray (PAG), dorsal raphe nucleus (DR) and Edinger-Westphal nucleus (EW). Intraperitoneal administration of MK-801 (0.03, 0.3 and 3.0 mg/kg) prior to the onset of experimental tooth movement reduced c-Fos in the TSNC (Vc I/II, Vodm and Vor) but increased it in the nucleus raphe magnus (NRM), ventrolateral PAG (vl PAG), DR and EW. These results highly emphasize that during experimental tooth movement, a blockade of NMDA receptors induces neuronal suppression in the TSNC but increases neuronal activity in the descending antinociceptive system including the NRM, vl PAG, DR and EW.

Expression of c-Fos-like immunoreactive neurons in the supratrigeminal region in the rat following noxious stimulation of the orofacial tissues.

This study was conducted to investigate immunohistochemically the expression of c-Fos in neurons around the trigeminal motor nucleus following application of mechanical force to a tooth, a mechanical pinch to the tongue, and paraformaldehyde injection into the periodontal ligament and masseter muscle. Following the application of all of these stimuli except pinching the tongue, a small number of c-Fos-like immunoreactive (Fos-LI) neurons were found in the ipsilateral supratrigeminal region. c-Fos expression was also detected in numerous neurons in the superficial laminae of the subnucleus caudalis in all experimental animals. Induction of c-Fos in the subnucleus caudalis and the supratrigeminal region indicates that Fos-LI neurons in the supratrigeminal region are involved in the processing of intraoral nociceptive signals.

Impulsive compression influences the viscous behavior of porcine temporomandibular joint disc.

Traumatic joint injury is known to produce osteoarthritic degeneration in the temporomandibular joint (TMJ). However, little information, is available on its possible effect on the dynamic viscoelastic behavior of the disc. In the present study, impulsive compression was applied to the disc as a model for traumatic joint injury. This was tested in 32 porcine discs. Prior to a dynamic tensile test, impulsive compression with strain rates of 0.01, 0.1 and 1 s(-1) to a final strain of 30% was applied to these discs. Tensile stress was applied in the antero-posterior direction with a wide range of frequencies (0.1-100 Hz). The dynamic E-moduli increased as the loading frequency increased. The dynamic viscosity and elasticity decreased with an increase of strain rate, although the effect on viscosity was greater than on elasticity. The results suggest that strain rate and subsequent peak stress of impulsive compression affect primarily the dynamic viscosity of the disc, and that impulsive compression at high strain rates reduces the resistance of the TMJ disc to stress, resulting in permanent disc deformation and perforation.