Dental composite resins are widely used in dental practice and are continually being developed in order to obtain better products. To gain full benefit from these materials, it is important for the clinician to understand their properties. The following is a review of the more common characteristics of composites in current use.
Histiocytosis X is a rare disorder with no particular predilection for race, age or sex. Since its discovery by Hand in 1893, the etiology has remained unknown, although viruses, bacteria and genetic factors have been implicated. Familial occurrence of this disease is very rare, and only a handful of such cases have been reported. The present study adds further evidence to support the influence of genetic factors in the etiology of histiocytosis X.
Quantitation of circulating immune complexes (CIC) was done in 45 patients with chronic periapical lesions. The levels were compared with those of age-matched healthy individuals. Both patients with chronic periapical granuloma and periapical cysts showed significantly higher levels of CIC than the controls. This observation indicates that the continuous presence of root canal antigens may cause elevated levels of circulating immune complexes. The possibility of chronic periapical lesions acting as foci of infection is discussed, and the importance of early treatment of these conditions is emphasized.
The effects of high-temperature sterilization methods (boiling, dry-heating, autoclaving and chemiclaving) on the properties of four types of stone cast were determined. SEM observations were made of the cast surface before and after sterilization. High-temperature sterilization affected the properties of the stone casts. Boiling, dry-heating and autoclaving were considered to be unacceptable methods for sterilizing stone casts before making prosthetic restorations.
Two cases of severely atrophic maxilla with poor palatal vault form treated by Kitayama's modified palatal vault osteotomy technique are described. The advantages of this osteotomy technique are outlined in comparison with other surgical methods.
Conventional plastic teeth (CV teeth) are inferior to porcelain teeth in maintaining an adequate esthetic appearance with wear and discoloration, and thus have a shorter period of durability. Recently, high-strength plastic teeth (HS teeth) have been developed and applied to overcome the wear problems of CV teeth. Since HS teeth made of hard resin are still susceptible to staining with pigments, it has been observed that the esthetics of removable partial dentures made from such plastic teeth are gradually impaired in many patients. To investigate the susceptibility of HS teeth to pigments, we conducted an in vitro study by immersing three types of artificial teeth in three coloring liquids. It was found that the HS teeth tended to be less susceptible to the test pigments than the CV teeth to various degrees. In contrast, they showed markedly stronger susceptibility to the pigments than porcelain teeth. For all three artificial tooth types, daily tooth cleaning with an ultrasonic vibrator had a tendency to reduce the coloration in comparison with their counterparts without ultrasonic cleaning.
The expression of ras-P21 protein and gene alteration of the K-ras gene were examined in 12 cases of pleomorphic adenoma of the salivary gland. The tumor cells in all 12 cases were strongly stained for ras-P21 protein by the indirect immunoperoxidase method, suggesting the enhanced expression of ras-P21 protein in pleomorphic adenomas. Analysis of the PCR products for the K-ras gene by temperature-gradient gel electrophoresis (TGGE) revealed that gene alterations such as point mutations occurred in 4 out of 12 pleomorphic adenoma tissues examined.
Several studies have shown that swinglock removable partial dentures are effective for stability of the abutment teeth and the surrounding tissues including alveolar bone. This efficacy has been thought to be due to the dynamic structure of the swinglock attachment. Individual biting force was measured to determine the physiological efficacy of teeth splints by use of the attachment. The results showed that individual biting forces with the swinglock removable partial denture were 10-25% higher than those without the denture. Furthermore, statistical analysis showed that the individual biting forces with the swinglock removable partial denture were significantly higher. The swinglock attachment can stabilize partially edentulous dentition by splinting all residual teeth. In addition, when physical forces are applied to the abutment teeth and the artificial teeth, this attachment can deliver and distribute the stress to the other abutment teeth and alveolar mucosa. The present findings suggest that the swinglock attachment augments the ability to withstand physical forces such as those occurring during biting and mastication.
An unusual case of regional odontodysplasia in an 8-year-old boy is presented. He was referred to our clinic because of failure of tooth eruption on the left side of the maxilla and frequent fever attacks. Treatment consisted of extraction of the affected teeth, and removal of inflamed tissue.