Impression materials or prostheses can be contaminated with oral microflora and provide a significant source for cross-contamination. A study of such contamination was carried out using an approach different from that of infection control, which has often been investigated in previous studies. The study focused on microorganisms known to cause local and systemic diseases and which are normally found in the oral flora. The persistence of Streptococcus mutans (S. mutans), Escherichia coli (E. coli), Staphylococcus aureus and Candida albicans (C. albicans) on zinc-oxide eugenol, silicone rubber, irreversible hydrocolloid and polyether-rubber was investigated using 99mTc-labelled microorganisms. Ten specimens from each of the four impression materials were prepared as discs of 3 mm in height and 10 mm in diameter. After the specimens had been placed into a suspension of 99mTc-labelled microorganisms, remaining radioactivity was counted in a gamma counter. According to own findings, S. mutans was the most, and E. coli the least persistent on the specimen surfaces. The number of microorganisms removed after washing was less than the amount remaining on the surfaces. C. albicans was removed most easily from all impression surfaces that bore persistent microorganisms after washing. Other microorganisms showed various degrees of persistence according to the impression material.
An attempt was made to quantify the location of oral lesions. Panoramic radiographs of non-odonto-genic cysts (13 globulomaxillary cysts, 8 median maxillary cysts, 8 nasopalatine cysts, 5 nasoalveolar cysts and 11 simple bone cysts) and odontogenic cysts (37 radicular cysts, 13 radicular granulomas, 68 dentigerous cysts and 40 odontogenic keratocysts) were examined. Metrical data (integers) were obtained from a conversion table and the abscissa values (to the first decimal place) were obtained from the centroid of the cysts. Differential diagnosis among these lesions revealed the following : 1. In the maxilla, it was possible to differentiate median maxillary cysts and nasopalatine cysts from globulomaxillary cysts, nasoalveolar cysts, radicular cysts, radicular granulomas, dentigerous cysts and odontogenic keratocysts. 2. In the mandible, it was difficult to differentiate simple bone cysts, radicular cysts, radicular granulomas, dentigerous cysts and odontogenic keratocysts from one another. The present findings revealed that data on lesion location can be changed into metrical data for differential diagnosis of cysts.
The sagittal split-ramus osteotomy (SSRO) technique has gained widespread acceptance, for it can be easily adapted to correct a wide variety of mandibular abnormalities. However, in spite of its many advantages, numerous investigators have reported postoperative relapse following mandibular advancement surgery. SSRO was performed on four patients with deficiency of mandibular growth which had led to characteristic protrusion of the maxilla. In three of the four cases, postoperative skeletal relapse occurred, which was corrected by postoperative orthodontic treatment.
Linear measurements of passive mandibular border positions and angular measurements of passive opening were recorded in a group of patients with craniomandibular disorders. The relationships between signs and symptoms of craniomandibular disorders and abnormal capacity of movement were studied. There was significant association of some signs and symptoms related to the temporomandibular joint and abnormal vertical and horizontal excursions. On the other hand, there was only one relationship between occlusal factors and abnormal passive mandibular border positions.
Clinical cases of cysts of the jaw treated in the Department of Oral Surgery of our university during the 10 y between 1980 and 1989 were studied clinically. Patients with radicular cyst, dentigerous cyst, odontogenic keratocyst and postoperative maxillary cyst, which were found at relatively high frequencies, were further analyzed with regard to age, sex and anatomical distribution. A diagnosis of cyst was established in 1, 444 patients during the above period, and 1, 234 (85.5%) of them had cysts of the jaw. According to a pathological classification by Ishikawa's method, these patients included 509 (41.2%) with radicular cyst, 259 (27.0%) with dentigerous cyst, 95 (7.7%) with odontogenic keratocyst and 267 (21.6%) with postoperative maxillary cyst. The pattern of age distribution in cases of radicular cyst, odontogenic keratocyst and postoperative maxillary cyst was similar to that found in previous studies. Among patients with dentigerous cyst, those aged under 20 y accounted for about 60%. Radicular cyst occurred most frequently in the maxillary lateral incisors, dentigerous cyst in the mandibular wisdom teeth, and odontogenic keratocyst in the region between the mandibular molar and the ramus of the mandible.
MRL/l strain mice, which possess a lymphoproliferative gene inducing swelling of systemic lymph nodes, develop a SLE (systemic lupus erythematosus) -like syndrome at around 8 w of age. MRL/n mice, which carry 99.6 % of the genes of MRL/1 mice, lack the gene for lymphoproliferation and exhibit only a slight degree of lymph node swelling late in life. This study investigated whether the salivary immune response caused by Streptococcus mutans (S. mutans) infection prevented dental caries in MRL/l and MRL/n mice after 8 w of age. A total of 10 MRL/l mice and 10 MRL/n mice were fed a commercial pellet diet without sucrose until 74 d of age, and then fed Diet 2000 containing 56 % sucrose ad libitum from 75 to 130 d of age. On d 75, both strains of mice were inoculated with S. mutans JC-2 for 7 d. At 130 d of age, saliva samples were collected and caries scores were assessed. The results obtained suggested that the salivary immune response was one of the most important factors regulating caries occurrence.
In an attempt to gain a better understanding of temporomandibular joint (TMJ) sounds, we recorded joint sounds from 14 non-orthodontically treated dental students, analyzed the acoustic characteristics of the TMJ sounds, and correlated the sound characteristics with axiographic features, morphologic observations of X-ray images and clinical history. The group with a low peak frequency (<500Hz) of the opening click had a shorter history of subjective joint sound, a longer distance between the opening and closing curves, and a low rate of TMJ transformation. For the closing click, the history of subjective joint sounds tended to be longer when the duration of the wave was short. Acoustic analysis of TMJ sounds could be an aid to the differential diagnosis of temporomandibular disorders, although it is difficult to deduce the clinical history and internal deformities of the TMJ based solely on acoustic characteristics.