Kooji Hanada

Masticatory function in patients with mandibular prognathism before and after orthognathic surgery.

Masticatory function was analyzed in 54 patients with mandibular prognathism before or after orthognathic treatment and in 40 adults with normal occlusion. Masticatory efficiency was evaluated spectrophotometrically by measuring the amount of adenosine triphosphate eluted from masticated adenosine triphosphate granules. Occlusal contact was evaluated by calculating the number and area of occlusal contacts from the illuminated images of a silicone record of the occlusion that was stored in the image analysis system with the aid of a charge-coupled device camera. The mean masticatory efficiency of the preoperative group was approximately half that of the control group. The value for the postoperative group was slightly higher than that for the preoperative group, but there was no statistical difference between the two groups. Likewise, the number and area of occlusal contacts in the preoperative group were also approximately half or less as compared with those of the control group, and they did not show significant changes postoperatively. Statistically, there were correlations between the masticatory efficiency and the number and area of occlusal contacts. The results indicate that although the occlusal relationship of the upper and lower teeth were greatly improved by orthognathic treatment, the postoperative occlusion is not tight enough and may need further adjustment at the end of the treatment.

Responses of calcitonin gene-related peptide-immunopositive nerve fibres in the periodontal ligament of rat molars to experimental tooth movement

Nerve fibres showing CGRP-immunoreactivity were exclusively distributed around blood vessels in the periodontal ligament of normal teeth. The CGRP-positive nerves as well as the vessels were more dense during tooth movement and reached a maximum density and intensity of immunoreaction after 3 days. After that, the immunoreactive nerves gradually disappeared, and returned to the control level by the 7th day. Some of the CGRP-nerves were adjacent to bone resorptive lacunae at 3 days when active remodelling of alveolar bone was taking place. These findings suggest that the distribution of CGRP-positive nerves is dynamically changed around the blood vessels in the periodontal ligament during tooth movement, and that CGRP might affect the regulation of blood flow in the ligament. CGRP is possibly involved in the tissue remodelling, directly or indirectly, in addition to its function as a neurotransmitter.

Tongue and jaw muscle activities during chewing and swallowing in freely behaving rabbits

To study the function of the tongue and the coordination among jaw, tongue, and hyoid muscles during chewing and swallowing, we recorded the electromyographic activities from the masseter (Mas), digastric (Dig), mylohyoid (Myl), thyrohyoid (Thy), genioglossus (Gg) and styloglossus (Sg) muscles as well as jaw movement trajectories in the freely behaving rabbit. Three phases were identified in the chewing cycle (fast- and slow-closing and opening phases). The Gg (main tongue protruder) was active synchronously with the Dig during opening. The Sg (tongue retractor) showed two peaks in each cycle, one in the opening phase and the other in the closing phase. The latter may have a role in retracting the tongue during jaw closing. The co-contraction of the antagonists (i.e. Gg and Sg) during opening may contribute to shape the tongue to be appropriate to gather the foodstuff. In the swallowing cycle, five phases were identified, two in the closing phase and three in the opening phase. Regression analysis revealed that swallowing cycles had a longer cycle duration than that of the chewing cycles due to an extra phase (a pause) inserted in the opening phase, where there was a small co-activation in the jaw opening and closing muscles. The findings suggest that the swallowing center affects masticatory center in the central nervous system, and may also support the view that the masticatory burst timing begins with the Dig activities in the middle of the opening phase.

Down-Regulation of Gap Junctional Intercellular Communication Between Osteoblastic MC3T3-E1 Cells by Basic Fibroblast Growth Factor and a Phorbol Ester (12-O-Tetradecanoylphorbol-13-Acetate)

To address the relation between osteoblast growth and cell‐to‐cell communication, we examined the effects of basic fibroblast growth factor (bFGF) and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), both potent stimulators of osteoblastic proliferation, on gap junctional intercellular communication between osteoblastic MC3T3‐E1 cells. The level of intercellular communication was estimated by a photobleaching method. TPA inhibited the degree of intercellular communication in two different time‐dependent manners. The early (<1 h) inhibition by TPA was consistent with an increase in the phosphorylation of connexin 43 (Cx43). The later inhibition was caused by reduction in the total amount of Cx43 on the plasma membrane, due to the decrease in the level of Cx43 transcripts. These qualitative and quantitative modulations by TPA were inhibited by a selective inhibitor of protein kinase C, GF109203X. bFGF also attenuated the gap junctional intercellular communication. However, short exposure (<5 h) to bFGF did not affect the communication. The fact that the growth factor immediately stimulated the phosphorylation of Cx43 indicates that the phosphorylation site(s) affected by bFGF was not involved in the inhibition of communication. The decrease in the intercellular communication level was detected by the longer exposure (>8 h) to bFGF and paralleled the decline in the Cx‐mRNA level. This inhibitory effect of bFGF was abolished by the addition of a tyrosine kinase inhibitor, herbimycin A. Thus, gap junctional intercellular communication between osteoblasts was down‐regulated by osteoblastic mitogens through different mechanisms of the modulation of Cx43.

Nonsurgical Treatment of Adult Open Bite Using Edgewise Appliance Combined with High-Pull Headgear and Class III Elastics

This case report describes the effect of a combination of high-pull headgear and Class III elastics on the nonsurgical treatment of an adult open bite. The 19-year 1-month-old Japanese female presented with the anterior open bite of 4.0 mm and mild crowding. She had a skeletal Class II but a Class III molar relationship due to a severe proclination of the mandibular dental arch. Unilateral congenital missing premolars caused a discrepancy between the facial and dental midline. After extraction of two premolars and the impacted mandibular third molars, nonsurgical therapy was performed using the standard edgewise appliance combined with a high-pull headgear and Class III elastics. The successful treatment outcome and stability of the final occlusion indicates that a combination of high-pull headgear and Class III elastics is one of the effective devices in the nonsurgical treatment of open bite and, is especially helpful in uprighting the mandibular dental arch.

Three-dimensional analysis of facial morphology before and after orthognathic surgery

A method for three-dimensional analysis of the facial hard- and soft-tissue morphologies is described. The soft-tissue analysis consisted of calculating three-dimensional values of reference points on the face by perspective transformation of their values in two pairs of photographs, taken simultaneously, from the right and left sides of the face. The shape of the mandible was analyzed three-dimensionally by the simultaneously taken frontal and lateral cephalograms. The hard- and soft-tissue changes were analyzed with the method in 28 patients in whom mandibular prognathism had been corrected by orthognathic surgery. The magnitude of the surgically-produced soft tissue volumetric changes in the anterior mandibular region was proportional to the posterior movement of the mandible. Asymmetry of the face also improved in response to correction of lateral deviation of the mandible and a close correlation between the directional indices of asymmetry of the hard and soft tissues was observed. Thus, the method was found to be quite useful for the analysis of facial morphology in jaw deformity.

The effects of surgical-orthodontic correction of skeletal class III malocclusion on mandibular movement

The effects of surgical-orthodontic treatment on mandibular movement were studied using the mandibular kinesiograph in 30 patients with skeletal class III malocclusion that was corrected by the sagittal split osteotomy (27 patients), a combination of the sagittal split osteotomy and body ostectomy (2 patients), or the sagittal split osteotomy and a posterior alveolar osteotomy of the maxilla (1 patient). Postoperatively, the mean maximum anterior and posterior excursions of the mandible increased significantly from 4.1 to 6.7 mm and from 0.6 to 2.6 mm, respectively. The lateral excursion to the right and left sides also showed significant increases from 4.8 to 7 mm and from 5.5 to 7 mm, respectively, after surgery. In analysis of the habitual and rapid opening and closing movements of the mandible, marked impairment was not observed in most patients except for crossing and discrepancy in the tracings of the habitual opening and closing movements in the sagittal plane observed in 11 patients. These findings were observed in only one patient postoperatively. The results indicate that the surgical orthodontic correction of skeletal class III malocclusion has favorable effects on the function of the mandible.

Satisfaction of patients following surgical-orthodontic correction of skeletal Class III malocclusions.

To assess whether patients were satisfied with the results of treatment, questionnaires were sent to 65 patients who had undergone either the extraoral curved oblique osteotomy or the sagittal split osteotomy for correction of skeletal Class III malocclusions. Seventy-eight per cent of the patients answered that they were satisfied with the results in regard to their chief problems and 75% had improved masticatory function. A favorable change in appearance was recognized by 33 patients, whereas 30 patients noticed no major changes. Factors affecting satisfaction with the results are discussed.

Role of stromal cells in osteoclast differentiation in bone marrow

Abstract. Bone marrow stromal cells have been considered to play an important role in osteoclast differentiation. However, the interaction of these cells in vivo has not been clearly demonstrated. To clarify this, we examined the distribution of alkaline phosphatase (ALPase) and tartrate-resistant acid phosphatase (TRAPase) activities as markers of osteoblastic and osteoclastic cells, respectively. Rat tibiae were fixed and embedded in Technovit 8100 or paraffin. ALPase and TRAPase activities were detected simultaneously on a plastic section by the azo-dye method. ALPase activity was detected on the plasma membranes of osteoblasts and some bone marrow fibroblastic stromal cells. These ALPase-positive cells were connected to each other by cytoplasmic processes, forming a cellular network in bone marrow. The ALPase activity of fibroblastic stromal cells tended to be stronger in those cells close to the bone surface than in the cells in the center of bone marrow. Reticular fibers in bone marrow were found to form a network. The ALPase-positive fibroblastic stromal cells may be reticular cells, because the localization of those cells was in accord with the localization of reticular fibers. The TRAPase-positive mononuclear cells and osteoclasts were mostly observed to be associated with the intensely ALPase-positive fibroblastic stromal cells. Immunoreactivity of osteoclast differentiation factor (ODF) was found in the fibroblastic stromal cells. These findings suggest that the network of ALPase-positive fibroblastic stromal cells in bone marrow serves as a guide for the migration of osteoclast precursor cells toward the bone surface, and may control the differentiation and activity of osteoclasts.

Changes in type I, II, and X collagen immunoreactivity of the mandibular condylar cartilage in a naturally aging rat model

The effect of aging on type I, II, and X collagen in the mandibular condyle was histologically and immunohistochemically assessed in 1−, 4−, 9−, and 16-month-old rats. Hypertrophic chondrocytes, observed in the 4-month-old rat, were absent in the 9-month-old. In 9- and 16-month-old rats, a mineralizing front ran parallel to the surface of the condyle, and the calcified cartilage was thicker than in the younger rats. Type I collagen was observed from the fibrous layer to the upper maturative cell layer in the 1- and 4-month-old rats. In the 9-month-old, the type I collagen-positive area extended to the whole cartilaginous region. In the 16-month-old, type I collagen took on an archlike configuration around the lacunae. Intense type II collagen reactivity in the maturative and hypertrophic cell layers of the 1-month-old rat was only slightly changed in the 4-month-old. In the 9-month-old rat, immunoreaction was detected from the proliferative cell layer; this extended to the whole cartilage in the 16-month-old. Type X collagen was localized in the hypertrophic cell layer in the 1-month-old and had expanded over the maturative cell layer in the 4-month-old rat. It was detected beneath the proliferative cell layer in the 16-month-old. Type X collagen was always observed in the area immediately above the mineralizing front of the cartilage matrix. Thus, our study indicated that mandibular condylar cartilage becomes fibrocartilage-like tissue with advancing age and that type X collagen may play a pivotal role in the progression of the mineralized front.