The Journal of Osaka University Dental School最新文献

Localized wear tests have been performed on six resin composites using a recently developed three-body wear testing machine. After repeated loading to the composites, the worn surface was replicated. Then the wear values of the respective resin composites were determined from the surface area of the worn defect using an image-analyzer. In addition, the microstructure of the worn area was analyzed with a scanning electron microscope (SEM). This study revealed that a fine particle hybrid composite exhibited the greatest localized wear resistance of all resin composites investigated in this study. SEM of the microfilled resin composites showed some degradation between filler and matrix.

A case of myxoma, arising in the maxilla of a 28-year-old female, is presented. Relevant literature is discussed.

This paper evaluates the influence of the location of chewing on facial and jaw muscles' activity and mandibular movements. Ten subjects with complete dentition performed following chewing sequences; 1) right side chewing (unilateral location-unspecified chewing); 2) chewing on right molars; 3) chewing on right premolars; and 4) chewing on anterior teeth. Bilateral activities of upper lip, cheek, masseter (anterior, middle and posterior parts), and anterior bellies of digastrics were recorded by surface electromyography. Mandibular movements were simultaneously recorded by electrognathography. Chewing on anterior teeth showed smaller masseteric activity in posterior part, smaller envelope of motion, and lower velocity of both opening and closing than unilateral location-unspecified chewing and chewing on right molars. Chewing on premolars showed smaller envelope of motion than chewing on molars. No significant difference was found between unilateral location-unspecified chewing and chewing on premolars or molars.

The purpose of this paper was to compare generalized wear resistance of eleven proprietary posterior dental composites and one amalgam using a recently developed in vitro wear testing apparatus. Upon completion of the in vitro wear testing process the wear area of occlusal surface was replicated and the depth of enamel exposed at the cavity margin was measured by a traveling microscope. Based upon the results of this study it was demonstrated that there were significant differences amongst materials included in this study. Also this wear test not only reproduced the microstructure of worn oclusal surface, but also predicted wear rates which correlated somewhat well with clinical performances.

We developed a computer system for infection control education utilizing multimedia including video presentation. To evaluate the efficiency of the system, trial sessions were held among dental students attending final year of clinical courses. According to our results of comparison between pre and post assessment tests among these students, we concluded that this system has a great potential and advantages for achieving certain level of knowledge of infection control in limited amount of time.

Two different Mg-containing hydroxyapatites, H-MgAp and Mg-HAp, were synthesized at 80 degrees C and pH 7.4. For H-MgAp, the calcium solution was supplied in the first half of the synthesis period and the calcium solution containing magnesium was supplied in the second half. For Mg-HAp, the order of supply was reversed. The X-ray diffraction patterns of H-MgAp and Mg-HAp differed slightly from each other. The (002) reflection of both patterns shifted towards a higher angle. The chemical compositions, especially the Mg contents, of the two apatites were almost the same as each other; and the Mg contents were half of that of homogeneous MgHAp synthesized with continuous supply of Mg at the same concentration. However, their crystal shapes were quite different, with H-MgAp appearing plate-like and Mg-HAp needlelike. In a solubility experiment, Mg-HAp was more soluble than H-MgAp. These results suggest that two different heterogeneous Mg-containing hydroxyapatites may be formed: hydroxyapatite covered with Mg-containing hydroxyapatite, and Mg-containing hydroxyapatite covered with hydroxyapatite.

A case of adenoid cystic carcinoma (ACC) with polymorphous features and an unknown differential diagnosis was presented. It appeared, without any pain, in the right maxillary sinus of a 47 year-old man. A variety of histopathological patterns were found, including glandular, cribriform, tubular and solid ones. However, the typical features of ACC, such as cribriform pattern associated with pseudocyst and tubular formations were rather scarce. A single cell strand appearance, so-called "Indian file arrangement", and papillary cystic formation were also noted, which are often associated with polymorphous low-grade adenocarcinoma (PLGA). Immunohistochemistries of EMA, CEA and musclespecific actin showed also similar staining patterns to those of PLGA in some areas. Our case could not be regarded as PLGA; but this case with features of PLGA as well as those of ACC might suggest an entity of transitional type between ACC and PLGA.

Removable dental prosthesis with magnetic attachment was applied to a fifty-two-year old female with cerebral palsy. New magnetic attachments made of rare earth metal, a pair of Sm-Co magnets housed in a magnetic stainless steel keeper, were used as a safe and simple retention apparatus instead of the conventional cast metal or wire clasps for partial denture. The patient even with her severe physical disability could manipulate this denture without much difficulty.

This study investigated the retentive forces of rotational path clasping systems. Twelve rotational path removable partial dentures were applied in the clinical field and the retentive forces of the dentures were measured. The following results were obtained; 1. Retentive forces of the 12 dentures were varied from 187g to 1,380g. 2. As distances between abutment teeth increased from 10.9 mm to 27.7 mm, the retentive forces decreased accordingly (r = -0.56; p < 0.05). 3. As the inclination of the proximal surfaces was increased from 0 degrees to 50 degrees, the retentive forces showed a tendency to increase (r = +0.47). 4. Longer distances between abutment teeth as well as smaller inclination of proximal surface were present in three patients who answered that their dentures showed movement while eating. From these results, it became clear that the distance between abutment teeth and the inclination of the proximal surfaces greatly influenced the retention of the rotational path clasping system in the clinical field.

We have examined whether the adhesin of Porphyromonas gingivalis which aggregates Streptococcus oralis contributes to its fibrinogen-binding. Various properties of coaggregation between P. gingivalis and S. oralis were compared with those of fibrinogen-binding to P. gingivalis cells. The coaggregation activity was measured by a turbidimetric method and the fibrinogen-binding activity was determined by using 125I-fibrinogen. Both the activities showed maximum values in the pH range from 5.0 to 6.0 and they were inhibited by arginine and lysine. Heating treatment of P. gingivalis 381 cells at 75 degrees C abrogated the activities. However, treatment of P. gingivalis 381 cells with proteinase K considerably reduced the fibrinogen-binding activity but not the coaggregation activity. Metal ions such as Zn2+ and Cu2+ inhibited the coaggregation activity but enhanced the fibrinogen-binding activity. The results also indicated that P. gingivalis strains 381, ATCC 33277 and SU-3 showed relatively higher activities both in coaggregation and fibrinogen-binding, whereas P. gingivalis strains W83, 51 and 165 showing lower fibrinogen-binding activity than P. gingivalis 381 did not coaggregate with S. oralis ATCC 9811. These findings suggest that coadhesin of P. gingivalis with S. oralis is not be associated with its fibrinogen-binding.