Apatite implantation into the jaw bones of adult dogs was carried out histologically to check the biocompatibility. At 5 days, the bone matrix formation began on the surface of tne apatite. In the 10-day specimen, the area of bone formation on the surface of the apatite was enlarged and at the same time the calcification began. TEM observation of this condition revealed the differentiation of the osteoblast around the surface of the apatite, followed by the formation of collagen fibers and osteoid with many small round deposits of bone crystals and matrix vesicles in an isolated from. A thin layer without the collagen fibers was observed on the surface of the apatite. In such areas, the plate-shaped crystals began to deposit directly on the surface of the apatite. In the area where the bone formation was rapid at 10 days, gradually the isolated crystal deposits became larger by the further deposition of crystals in the longitudinal direction to the surrounding collagen fibers and fused with each other, and fused further with the crystal layer without the collagen fibers on the surface of the apatite. Finally, a wide calcified layer was formed on the apatite. Subsequently, the crystals on and around the apatite grew gradually and exhibited a condition similar to that of the normal mature bone at 30 days.
Forty-two autopsy cases of squamous cell carcinoma of the mobile portion (anterior 2/3) of the tongue was reviewed clinicopathologically and the causes of the failure were studied retrospectively. Thirteen primary lesions (31.0%), even of the T3, T4 stage, were controlled by radiation therapy alone or with chemotherapy, and the effectiveness of the radiation therapy was evaluated. The recurrent tumor, frequently developing from regional lymph node metastases, was resistant to the theray and tended to manifest continuous and diffuse extention, forming a bullky neck tumor. The management of the neck tumor was the most important problem. Rupture of the neck vessels (7.1%) was one of the most serious complications. The incidence of the metastases was higher than that reported in literature. The metastases to the lymph nodes below the level of the clavicle were seen in 42.9% and the hematogenous metastases occurred in 61.9%. Pulmonary infection was the most common complication, being the main direct cause of death in the cachetic state. Five hundred and eighty-four autopsy cases of squamous cell carcinoma of the mobile portion and the base of the tongue collected from the Annual of Pathological Autopsy Cases in Japan were also analyzed.
The objective of this investigation is to identify the effects of the marginal fitness of the crowns on the gingival tissues. Ten porcelain-fused-to-gold crowns with different degrees of overhangs were cemented in three clinical cases. The crown contours and their marginal fitness were measured intra-orally with an electronic device. The severity of the gingival inflammation was assessed on the marginal gingivae at the midpoint of the labial aspect of these crowns by (1) a newly developed instrument which can measure the consistency and the volume pulse of the gingivae, (2) by the gingival fluid meter“Periotron®”and (3) by clinical examinations. Based on the results of these experiments, the following conclusions can be made: 1. Subgingival restoration with properly placed and well-fitted margins will not affect the marginal gingivae. 2. The crown margins should not be extended too deeply into the gingival crevice. 3. The overhanging restoration caused deleterious effects on the gingivae, and those effects still remained after the removal of the overhangs. 4. Proper oral hygiene instructions are indispensable for the maintenance of healthy gingivae of the crowned teeth.
The effects of selenium utilization on the safety of the silver amalgam were studied in the cultured L cells and mice. (1) Silver-tin spherical alloy was triturated with mercury. The amalgam pieces were immersed immediately in the culture medium, being rolled for 3 or 4 days. In terms of 51Cr release assay and microscopic observation, the amalgam-immersed medium, the final concentration being 1.0g amalgam in 1ml medium, showed severe cytotoxicity, which was counteracted dose-dependently by the simultaneous administration of 12.5-100. μM of sodium selenite. (2) The cytotoxicity of the amalgam was suppressed markedly by incorpor a ting 0.2wt% of selenium into the alloy. The selenium content below 0.1wt% or above 0.4wt% in the alloy was not sufficient for attenuating the amalgam cytotoxicity. (3) The amalgam-immersed medium made from 0.2wt% selenium-containing alloy was injected intraperitoneally into the male ddY mice for 7 days, totaling 1.3g per gram of body weight. In mice receiving selenium-lacking amalgam, the behavior was inactive, the body weight did not increase and the proximal tubules of the kidneys were damaged whereas with the selenium-containing amalgam, the behavior was active, the body weight increased and the renal tissues were not impaired. The hepatocytes were damaged in the mice receiving amalgam, which contained or lacked selenium. (4) The toxicity of the silver amalgam was decreased markedly in the cultured L cells and mice when selenium was added to the alloy.
Hydroxyapatite ceremic has an excellent biocompatibility. However, there is required some improvement in respect to the mechanical characteristics of hydroxyapatite ceramic. In order to improve the mechanical characteristics of hydroxyapatite ceramic, this study is on the method of forming a composite structure of hydroxyapatite ceramic adhered to the metals by glass. Experimental proceaures were as follows: a) Bonding strength of the metals with 4 types of glasses adhered to them. b) Bonding strength of the metals by the addition to the glass of 5% (wt%) of Sn or Ba. c) Bonding strength of hydroxyapatite ceramics by the addition to the glass of 5% (wt%) of Sn or Ba. d) Bonding strength of hydroxyapatite ceramic and metals by the addition to the glass of wt% Ba. 5% (wt%) e) Study of adherence mechanism by S. E. M. and E. P. M. A. The results obtained showed that the bonding strength between the glass, which was produced in this study, and the Ti, Co-Cr-Ti alloy was good. Especially, the bonding strength between the Co-Cr-Ti alloy and the hydroxy-apatite by the addition to the glass of 5% (wt%) of Ba was shown to be from 308.5 kg/cm2 to 420 kg/cm2 in the pull out test.
The purpose of this study is to reveal the activities of the neck muscles closely related to the head posture maintenance during various mandibular movements. The sternocleidomastoid, the trapezius and the masseter muscles of six subjects were investigated electromyographically with surface electrodes. Among the neck muscles which were measured, only the activity of the sternocleidomastoid was recognized in the mandibular retruded position without clenching. However, during voluntary maximal clenching in the various mandibular positions and during maximal jaw-opening, the sternocleidomastoid and trapezius were both active. The degree of activity was greater in the former. The occlusal forces and electromyographic activities were recorded simultaneously. The activities of the sternocleidomastoid hardly increased even if the occlusal forces increased. However, when the occlusal force reached the maximum, the activities were rapidly strengthened. During unilateral mastication, the ipsilateral sternocleidomastoid activity was rhythmic in concern with the mandibular masticatory movement in all subjects. The contralateral side activity was also rhythmic in some subjects. It is concluded that the sternocleidomastoid and the trapezius are related to the mandibular movements and are in harmony with the masticatory muscles.