CP titanium is an appropriate material for the occulusal surface of artificial teeth. However, because of its low hardness, abrasion resistance must be improved in the occlusal contact region. We applied YAG laser nitriding to the occlusal surface to increase the strength and evaluated dimensional changes in the nitrided area. We found that cusps irradiated by the laser were evenly golden without macroscopic dimensional changes, and that many of the melted areas were surrounded by gold rings. Examination of the metal revealed dendrite-like structures in the surface layer, regions under the surface layer that had marked corrosion by the acid treatment, and needle or columnar crystals under the corroded areas. Compared with non-nitrided specimens, a very hard layer was present between the surface and the area 240μm below the surface, and the hardness was increased to a maximum of approximately 1, 063Hv. Analysis of the surface layer elements revealed virtually no nitrogen in the non-nitrided specimens, although there was approximately 4-10 weight percent nitrogen in the laser-nitrided specimens. Nitriding of the cusp area of CP titanium artificial teeth resulted in a mean change in the cusp height of ±11μm. Laser nitriding of artificial CP titanium teeth resulted in formation of a nitrided layer on the surface approximately 240μm thick. None the less, dimensional changes resulting from the nitriding treatment caused no clinical problems.
We performed histochemical and immunohistochemical investigations of changes in glycosaminoglycans(GAG)in the rat mandible at 3, 5, 15, 30 and 50 weeks of age. Mandibular GAG was also extracted for biochemical analysis. We found localization of hyaluronic acid(HA), chondoroitin sulphate(CD), dermatan sulphate(DS)and keratan sulphate(KS)in the articular condyle. Aging reduced the reaction to CD and increased the reaction to DS and KS. There was no clear change in HA in response to aging. Biochemical studies identified HA, CD and KS. CD, which is the main component of total GAG, decreased with age while HA and KS increased. The total amount of GAG in the dry tissue weight, as measured by the volume of uronic acid, decreased with age. These results indicate that the rat articular condyle loses elasticity with age and shows decreased buffering capacity to pressure.
Although changes in glycosaminoglycans(GAG)in the tissue around titanium(Ti)implants have been studied, little is known about the behavior of GAG on the titanium surface. We investigated adsorption of hyaluronic acid(HA), chondoroitin 4 sulfate(CS) and dermatan sulfate(DS)on calcium treated titanium(Ca-Ti)and non-treated titanium(non-Ti). While there was little GAG adsorption on non-Ti, it was much greater on Ca-Ti. CS and DS, both of which have a sulfuric acid group, presented greater absorption to both non-Ti and Ca-Ti compared with HA, which does not contain a sulfuric acid group. CS adsorption on Ti after HA adsorption, and DS adsorption on Ti after HA and CS adsorption were greater on Ca-Ti than on non-Ti. These results suggest that GAG adsorption increases through calcium(Ca)treatment of non-Ti. Ca treatment changes the charge state of non-Ti, making it more adsorptive of GAG.
We report a case where nitrous oxide-oxygen anesthesia(GO)was used to determine interocclusal relation for a patient with oral dyskinesia(OD)who required full dentures. The goal was to improve the OD through adjustment of the existing denture and to fabricate a new denture in centric occlusion. However, it was difficult to determine the interocculusal relation for the new denture owing to instability of jaw position caused by OD. The registration was not reproducible. We attempted to use nitrous oxide-oxygen anesthesia(GO)to relax muscle tension and control jaw motion to register interocclusal relation. Registration of occlusal relation was taken when the sedative effect was achieved ten minutes after the patient began inhaling 30% nitrous oxide gas. Registration was unaffected by OD. The new denture caused a decrease in OD. The OD of the mandible was observed using a Gnatho-Hexagraph which represents jaw movements in six degrees of freedom(GC Corp., Tokyo). Although mild OD was observed even after tne new denture was used, the severity was significantly decreased. In this case, GO produced a sedative effect that resulted in a relaxation of muscle tension that allowed control of jaw motion. This allowed fabrication of a better denture as a result of the reproducible interocclusal relationship.
Decorin, which is a small dermatan sulfate proteoglycan(PG), is distributed throughout the extracellular matrix of periodontal tissues. Little is known about the synthesis of decorin in inflammatory gingival tissue, although it is considered a regulator of tissue inflammation. The purpose of this study was to compare the expression of decorin mRNA between healthy and inflamed gingival tissue in the same person. Healthy and inflamed gingival tissues were obtained from a 74-year-old female with chronic adult periodontitis. Human gingival fibroblasts(Gin 1)in the stationary phase were also used as a control. Western blotting and reverse transcriptase-polymerase chain reaction(RT-PCR)were performed to determine decorin expression, and immunohistochemistry was used to localize its distribution. As a result, Western blot analysis demonstrated the presence of decorin core protein in both healthy and inflamed gingival tissued. Immunohistochemical observation using anti-decorin antibody detected positive stain only in the gingival connective tissue, not in the gingival epithelium. RT-PCR confirmed that both the tissues and the fibroblasts expressed decorin mRNA. However, the decorin mRNA level was significantly higher in the inflamed gingival tissue than in healthy gingiva, and was very low in the stationary cultured human gingival fibroblasts. These results indicate that the synthesis of decorin is increased in gingival tissue with chronic periodontal disease.
Adult periodontitis is a multifactorial disease with an etiology that is not well defined. Interleukin-1(IL-1)is major proinflammatory cytokine that is associated with several chronic inflammatory diseases, including adult periodontitis. To establish whether the IL-1 gene polymorphisms IL-1A-889, IL-1 B-511 and IL-1 B+3954 are associated with adult periodontitis, we performed a case-control study in 161 Japanese, aged 35-65 years. The IL-1 polymorphisms were detected by restriction fragment length analysis using Ncol, Aval and Taql digestion after polymerase chain reactions. IL-1 B+3954 gene polymorphisms(1/1 and 1/2 genotypes)were found to have a significant association with adult periodontitis(χ2=6.379 ; p=0.017). However, there were no significant differences between adult periodontitis patients and controls in IL-1 B-511 and IL-1 A-889 genotype and allele distributions. These findings suggest that there is a role for genetic factors associated with IL-1 B+3954 gene polymorphisms in susceptibility of Japanese to adult periodontitis.
Periodontitis is characterized by resorption of the alveolar bone, as well as the loss of soft tissue attachment to the tooth, which ultimately leads to tooth loss. Parathyroid hormone(PTH)plays a critical regulatory role in calcium metabolism and stimulates bone resorption indirectly. To establish whether a PTH gene polymorphism is associated with adult periodontitis, we conducted a case-control study of 150 Japanese subjects, aged 35-57 years. The subjects included 60 adult periodontitis patients and 90 control subjects. We analyzed a polymorphism that corresponds to a silent C→A transition located in exon 3 of the PTH gene. No significant differences were observed in the PTH genotype distribution in adult periodontitis patients versus control subjects. Nevertheless, a sensitivity analysis, based on the subjects having both a positive family history of adult periodontitis and being a non-smoker, suggests that significant associations exist in the frequency of PTH genotypes between adult periodontitis patients and control subjects(p=0.049). These findings suggest that a PTH gene polymorphism is associated with a susceptibility to adult periodontitis in individuals with predisposition to the disease.
We made a barium containing jelly(here after referred to as Ba-jelly)for use in video fluoroscopy(VF)of the elderly patients and measured its physical properties with a hardness testing device. A video fluoroscope was used to observe healthy adult subjects when they ingested and swallowed the Ba-jelly. Incorporating a greater amount of gelatin of barium increased the hardness of the Ba-jelly. We also found that the Ba-jelly was harder at 4℃ than at 24℃. Examination of mastication of Ba-jelly using VF was easier when it had a higher content of barium. However, it was easier for the subjects to ingest and swallow Ba-jelly of lower hardness. These results gave us valuable insights into the physical properties of Ba-jelly and how it can be used in VF of elderly subjects.
We evaluated ingestion and swallowing in healthy adults without somatognathic dysfunction using the Gnathohexagraph. The face bow of the Gnathohexagraph was Placeded on the mandibular anterior teeth and microphones were attached to the zygomatic bone and cricoid cartilage. The subjects were asked to ingest water and chew, jelly and fish cake(hereafter referred to as kamaboko)as common solid foods and barium containing jelly, hereafter referred to as Ba-jelly, as a test food. We observed jaw movements, muscle activities, occlusal sound and swallowing sound. During water ingestion and swallowing, a clear occlusal sound and a short swallowing sound were recorded once following a shoot, simple mouth opening and closure. With jelly and Ba-jelly, several chewing cycles were observed, followed by two occlusal sounds and a short swallowing sound. With kamaboko, complex chewing cycle was observed, followed by a few occlusal sounds and a long swallowing sound of small amplitude. We measured the time between the occlusal sound recorded at the end of chewing and occurrence of the swallowing sound(O-S lag). With water, the initial O-S lag was significant and had large variations that became somewhat stabilized after the fourth swallowing. Ingestion of kamaboko produced relatively stable results with a short O-S lag. Jelly and Ba-jelly produced larger O-S lags than kamaboko. The Ba-jelly produced a greater variation in results than did simple jelly. We would like to increase the number of subjects in order to better understand normal swallowing and injection evaluation can be established for ingestion and swallowing disorder using Gnathohexagraph.
Complete denture must have the proper morphology to restore or improve appearance and function. This requires fabrication of an occlusal rim with the correct maxillomandibular relation that is suitable for arrangement of the artificial teeth. However, current procedures require that the occlusal rim be modified several times in the patient's mouth, using considerable chair time. We reviewed how to properly establish the maxillomandibular relation for the edentulous patient and how to create the standard form of the occlusal rim for arrangement of the teeth. Further, we analyzed standard numeric values for the occlusal rim form. We found significant differences at the 5% level between men and women for the mean of each measured value of the posterior teeth and the maxillary anterior teeth. In the anterior region we found significant differences at the 5% level in the dispersion of the measured values from flange and from the crest of the ridge. However, neither the age of the patient at the time of denture fabrication or the number of yeas the patient had been edentulous had any significant effect on the measured values.
We examined the expected rate of correct answers(ERCA)for conventional A, K2, and X2 types of multiple-choice question formats, and the new XX type question format for which the number of correct answers is not specified. We determined how accurately the examinee's knowledge was evaluated for each type of question and investigated how changes in the format influenced the pass rate of the examinees. We found an increased correlation between the amount of knowledge and ERCA for the X2 type compared with the K2 and A types. We also found a good correlation between the amount of knowledge and ERCA for the X01 type. In theory, it was clear that a question of high identification coefficient could not be obtained simply by changing a question of the A or K2 type, for which the degree of difficulty of each choice was almost equal, to a question of the XX type. (J Osaka Dent Univ 2001 ; 35:133-140. )