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A theoretical investigation is carried out for double-electron excitation processes of ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ induced by proton and antiproton impact at the enegy of 1.5 MeV. Excitation cross sections to the 2${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}^{\mathit{e}}$, 2s2p $^{1}$${\mathit{P}}^{\mathit{o}}$, and 2${\mathit{p}}^{2}$ $^{1}$${\mathit{D}}^{\mathit{e}}$ states are calculated by using the plane-wave Born approximation, the distorted-wave Born approximation, and the close-coupling method. Wave functions of ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ are generated employing the hyperspherical coordinate method. It is shown that the low-lying continuum 1skp $^{1}$${\mathit{P}}^{\mathit{o}}$ is identified as an important intermediate state in the double-electron excitation process to the 2${\mathit{p}}^{2}$ $^{1}$${\mathit{D}}^{\mathit{e}}$ state. We have also evaluated the ejected-electron spectra from the 2s2p $^{1}$${\mathit{P}}^{\mathit{o}}$ shape-resonance state. It is found that its spectral shape is close to the observed line profile of the photodetachment of ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ since the excitation mechanism to this state is mostly dominated by the optically allowed transition at the projectile energy concerned here.

Tissue response to a readily consolidating material prepared by mixing α-tricalcium phosphate (α-TCP) powder with a glycolic acid dextran solution and to this consolidating material combined with particulate hydroxylapatite (HA) was studied after implantation in the subperiosteal space of the mandible in rabbits. Active new bone formation comparable to that seen on HA implants was observed around the two compounds. The newly formed bone was in direct contact with the HA as well as the readily consolidated material and little adverse effect resulting from the glycolic acid and dextran was observed. Because the readily consolidating material was firm and could be countoured into any shape during the process of consolidation, it may be quite useful as a bone substitute and as an adherent for HA particles for reconstructive bone surgery, overcoming the disadvantages inherent to the particulate form of HA.

Bone change in the temporomandibular joint (TMJ) in 540 patients with TMJ disorders was studied radiographically in relation to the loss of premolar and/or molar support.The incidence of bone change (erosion or deformity) which was observed in 49. 404 of the patients was higher in female patients and showed a tendency to increase in older pati-ents. The bone change was noted in the symptomatic side in 72.3%, in the asymptcmatic side in 13.5% and bilaterally in 14.2% with an increase of bilateral involvement in older patients. The joint pain and the limited range of motion of the mandible were seen significantly higher in patients with bone change at the initial examination. The bone change was observed in 56.4% of patients with loss of premohr and/or molar support which was significantly higher than 40.4% of the patients without loss. The number of patients with loss of premolar and/or molar support and the incidence of bone change seen in these patients increased with age.The results indicate that the loss of premolar and/or molar support is one of the factors leading to bone change in TMJ

An 18-year-old man with unilateral hypertrophy of the masseter muscle is reported. The patient complained of a painless swelling on the left side of the face. On palpation, there was an evident asymmetry of the masseter muscles and remarkable hypertrophy of the left masseter muscle associated with deformity, and lateral deviation of the mandible was revealed by CT scans.The lower and inner portion of the left masseter muscle was resected and the expanded portion of the lateral cortical plate was trimmed away by an intraoral approach. There was no complication except slight paresthesia of the left cheek skin. Postoperative CT scans showed that the asymmetry of the face and the mandible was greatly improved. The patient was satisfied with the result of surgical correction.

The results of replantation of 29 teeth are described. Maxillary incisors constituted 85% of 27 permanent teeth. The period between avulsion and replantation ranged from within an hour to 86 days, but the actual extraoral period was within 5 hours in all but one case. Nineteen of the 27 permanent teeth were functioning for 7 months to 6 years and 7 months postoperatively. Root resorption was the cause of tooth loss in five cases. The incidence of root resorption seemed to increase with the increase of the extraoral period, but it was not affected by the period between avulsion and replantation, the condition of supporting tissues, the degree of root formation, and the type and period of splinting, indicating multiple factors involved in determining the prognosis of replanted teeth. In conclusion, every effort should be made to preserve avulsed teeth even in unfavorable conditions.

Summary An unusual case of malignant paraganglioma that manifested itself as pain in the temporomandibular joint and trismus and later manifested itself as a rapidly growing neck mass is described. Computed tomography revealed a huge mass with upward and downward extension in the infratemporal fossa. Radiotheraphy was completely ineffective. At autopsy, a malignant paraganglioma with multiple metastases was found, but the site of origin could not be determined because of the size and extent. One hundred and ninety-one cases of paraganglioma of the head and neck published in the Japanese literature were analyzed with regard to their site, clinical, radiographic and microscopic features as well as treatment and results.

Summary A huge chondrosarcoma of the mandible (80 × 95 × 100 mm in size) with extension into the infratemporal fossa is described. The tumour was successfully treated by surgical removal and postoperative irradiation. A survey of the Japanese literature revealed 23 cases of chondrosarcoma with involvement of the mandible. The tumours occurred equally in males and females whose mean age was 38 years. The molar region was the site of predilection. The most common symptom was swelling and it was accompanied by pain in 7 cases and paraesthesia in 5 cases. Radiographically, the lesions were quite variable and with the exception of 3 cases in which information was not available, they consisted of a combination of irregular radiopacity and radiolucency in 9 cases, whereas the predominant feature was radiopacity in 6 cases and radiolucency in 4 cases. There was no radiographical abnormality in 2 cases. Root resorption of adjacent teeth was noted in 3 of 6 cases where information existed. Computed tomography was thought to be quite valuable in determining the nature and extent of the tumour. Although an elevation of serum alkaline phosphatase was observed in our case, results of laboratory tests were mostly of no diagnostic significance. Surgical removal was employed in 22 cases alone or in conjunction with irradiation and/or chemotherapy. Of 14 cases on whom information was available, local recurrence occurred in 6 cases in which radiotherapy was not given and distant metastasis in 2 of 10 cases on whom information was available. Of 20 patients on whom information was available on the postoperative course, 7 patients died 5 months to 6 years after the primary treatment.

Summary An unusual case with an aggressive destructive granulomatous lesion of the maxilla is reported. Although the possibility of infection and neoplasm could be ruled out, a definite diagnosis could not be established even repeated biopsies which showed the lesion to be a non-specific inflammatory process. Since Wegener's granulomatosis was most unlikely, the patient was treated by radiotherapy which caused rapid remission of the lesion with not sign of recurrence after 4 years. The clinical and histological findings as well as the responsiveness to the treatment were most indicative of idiopathic midline destructive disease. Effective management of lethal midline granuloma of unknown aetiology is discussed.

An application of a palatal island flap to reconstruction of a defect following excision of a palatal tumor in two cases is reported. The first case was a 55-year-old man with a malignant tumor of salivary gland origin on the right side of the soft palate. An excision of the tumor resulted in formation of a large defect approximately 30mm in diameter with communication to the nasal cavity. The defect was closed by posterior rotation of a mucoperiosteal island flap which was elevated from the anterior portion of the ipsilateral palate, The postoperative course was uncomplicated, but slight velar dysfunction remained postoperatively due to scar contraction of the flap. In the second case, an oronasal fistula of 9× 5mm in size developed following excision of a pleomorphic adenoma in the posterior portion of the right hard palate. The fistula was successfully closed by a mucoperiosteal palatal flap elevated from the contralateral side without leaving functional disturbance.In conclusion, the flap was found to be useful for reconstruction of palatal defects of varing sizes an locations because of good blood supply, extensive mobility, technical easiness and least aesthetic disturbance.

Clinical and radiographic findings of 16 teeth (17 roots) displaced into the maxillary sinus and their treatment were studied.Patients from 10 to 39 years of age constituted 87.5 per cent of the population with a peak in the third decade, and there was no sex prevalence. The maxillary first molars mostly affected by severe caries were involved in all cases but one with the highest incidence of displacement of the palatal root. Radiographically the floor of the maxillary sinus was located very close to the roots of the maxillary premolars and molars in 75 per cent of cases. Evidence of maxillary sinuitis was noted in 14 cases. The period from displacement to removal or spontaneous discharge was within a week in 7 cases, a week to 2 weeks in 2 cases and over 2 weeks in 6 cases. The displaced roots were removed from the tooth sockets in 7 cases and by an approach via the canine fossa in 7 cases. A root was spontaneously discharged from the socket. With the exception of 3 cases, all roots were found or thought to be present inside the sinus cavity.In conclusion utmost care should be taken not to dislodge the root during extraction when the floor of the maxillary sinus is located in its close proximity and the earliest removal was recommended on dislodgement into the maxillary sinus to prevent the development of complications.

Tissue response to preformed tricalcium phosphate (TCP) blocks prepared from alpha-tricalcium phosphate (alpha-TCP) powder by hydration and hardening at 80 degrees C was studied by implanting them subperiosteally on the buccal aspect of the mandible in rabbits. X-ray diffraction of the alpha-TCP powder showed a typical pattern of TCP, whereas a mixed pattern of TCP and hydroxylapatite was obtained after hydration and hardening. The radiographic findings at 4 weeks showed a tendency to bony union of the TCP block with the underlying bone. Microscopically, new bone that was being formed extensively from the underlying bone surface and filling the space between the block and bone at 4 weeks gradually changed into lamellar bone. There was no evidence of resorption of the TCP block throughout the experiment. The tissue response was essentially consistent with that to hydroxylapatite particles studied under similar conditions in our laboratory. It was concluded that the hydration and hardening of alpha-TCP powder may provide an implant block with a desirable contour that does not interfere with bone formation.

A case of melanotic neuroectodermal tumour of infancy (MNTI) with rapid recurrence is described, together with a survey of 16 reported recurrent cases. The recurrent lesion was successfully treated by wide excision of the maxilla. The recurrent tumour had two lesions of different natures, one consisting of a lobular mass indistinguishable from the primary tumour but located remote from the original site and the other showing diffuse infiltration of tumour cells deep in the medulla of the maxilla. A survey of the recurrent cases indicated that, although incomplete removal of the primary tumour, dissemination of tumour cells during surgery and a multicentric origin could be the causes of a recurrence, the presence of a silent lesion which may express an aggressive growth on stimulation may also explain the complex behaviour of the tumour.

The efficacy of using gelatin as an adherent of particulate hydroxylapitite was studied by implanting preformed blocks of a hydroxylapatite-gelatin mixture subperiosteally on the buccal aspect of the mandible in rabbits. The rabbits were killed at 1, 2, 4, 12, and 24 weeks after implantation. After radiographic examination, excised specimens were decalcified and examined microscopically. The radiographic findings in the hydroxylapatite-gelatin group were essentially consistent with those of the hydroxylapatite group, except that in the hydroxylapatite group migration of particles was seen in some specimens. Microscopically the majority of the gelatin was unidentifiable at 1 week and there was no evidence of a rejection response. The degree of new bone formation and tissue response in hydroxylapatite-gelatin mixture group was essentially the same as in the hydroxylapatite group. The results indicate that gelatin is an excellent adherent for particulate hydroxylapatite, enabling easy handling and proper placement of the material with no inhibitory effect on new bone formation.

A rare case of spontaneous regeneration of the mandibular condyle following hemimandibulectomy by disarticulation is described.