The occurrence of accidental ingestion/aspiration and preventive measures were investigated at Tokyo Dental College Chiba Hospital. In addition, the characteristics of accidents at our hospital were analyzed by surveying the awareness of accidental ingestion/ aspiration to utilize the data for prevention. Accidental ingestion accounted for about 30% of accidents that occurred at our hospital in fiscal 2008, but all ingested items were naturally excreted, and no accidental aspiration occurred. Accidental ingestion most frequently occurred when dental restorations were removed. Inlays and crowns were most frequently ingested, and dentists with 5 to less than 10 years of clinical experience tended to be involved in these accidents. According to the results of the questionnaire, Clinical Report 95Bull Tokyo Dent Coll (2010) 51(2): 95-101 96

Human mesenchymal stem cells (hMSCs) are multipotent cells, and have been expanded and differentiated into several kinds of mesodermal tissue in vitro. In order to promote bone repair, enhancement of the proliferation and differentiation of hMSCs into osteoblasts in vitro is recommended prior to therapeutic delivery. However, for clinical applications, it is still unclear which method is more advanced for tissue engineering: to transplant undifferentiated cells or partially differentiated stem cells. Therefore, the present study aimed to investigate how osteogenic differentiation medium (ODM) affects hMSCs cultured in a 3D scaffold using a radial-flow bioreactor (RFB) besides cell growth medium (GM). To produce precultured sheets, the hMSCs were first seeded onto type 1 collagen sheets and incubated for 12 h, after which they were placed in the RFB for scaffold fabrication. The culture medium was circulated at 3 mL/min and the cells dynamically cultured for 1 week at 37 °C. Static cultivation in a culture dish was also carried out. Cell proliferations were evaluated by histological analysis and DNA-based cell count. Alkaline phosphatase (ALP) activity, immunocytochemical analysis with BMP-2, and osteopontin on the hMSCs in the collagen scaffold were performed. After 14 days of ODM culture, a significant increase in cell number and a higher density of cell distribution in the scaffold were observed after both static and dynamic cultivation compared to GM culture. A significant increase in ALP activity after 14 days of ODM was recognized in dynamic cultivation compared with that of static cultivation. Cells that BMP-2 expressed were frequently observed after 14 days in dynamic culture compared with other conditions, and the expression of osteopontin was confirmed in dynamic cultivation after both 7 days and 14 days. The results of this study revealed that both the proliferation and bone differentiation of hMSCs in 3D culture by RFB were accelerated by culture in osteogenic differentiation medium, suggesting an advantageous future clinical applications for RFB cell culture and cell transplantation for tissue engineering.

This study investigated the optical properties and flexural strength of translucent TZP layered with high-translucent PSZ using resin cement of various shades. Zirconia specimens (translucent TZP; Zpex and high-translucent PSZ; ZpexSmile) were 13 mm in diameter, layered at thickness ratios of 0.3/0.7, 0.5/0.5, and 0.7/0.3 mm (ZpexSmile/Zpex), and then luted using resin cement of 3 shades. Monolithic specimens of both were used as controls. CIE L*a*b* color coordinates and translucency parameter (TP) were evaluated as optical properties. Biaxial flexural strength was also determined as a mechanical evaluation. The a* and b* values of layered specimens varied depending on the shade of cement. TP values were not affected by shade of cement and thickness ratio. The biaxial flexural strength was intermediate value between both monolithic specimens. The layering method of zirconia with various translucencies using resin cement of different shades can improve color expression while maintaining clinically sufficient flexural strength.

Many types of interdental instrument, such as dental floss and interdental brushes, can be purchased easily and sell in large numbers. Many studies have compared the effects of such instruments. Few studies have investigated their relationship with regions of residual plaque, however. The purpose of this study was to compare rates of plaque removal from the mesial and distal surfaces of the bilateral maxillary and mandibular premolars and molars among 3 types of interdental instrument: finger-winding-dental floss, holder-type dental floss, and an interdental brush. Prior to the experiment, the artificial teeth in a jaw model were removed for application of artificial plaque. The teeth were then replaced and the model attached to a phantom. An operator brushed the teeth in a posture close to that adopted in actual tooth brushing with each type of instrument, after which the plaque removal rate was compared among them. The rate of plaque removal using finger-winding floss was the highest, although this type of instrument is less easy to hold than the others. The rate with a handle-equipped interdental instrument showed a decrease in some regions, although it is easy to hold. The results of this study suggest that the type of interdental instrument used should differ depending on the region to be cleaned.

No abstract

The purpose of this study was to investigate the influence of anteroposterior postural change on electromyography (EMG) activity in the lateral pterygoid muscle. Subjects consisted of 7 patients attending this hospital for close examination. The inferior heads of the lateral pterygoid and masseter muscles were chosen as evaluation sites. For the EMG recordings, the test movement was opening and closing of the mouth; postural conditions were the upright and supine positions. The mean value of EMG activity in the inferior head of the lateral pterygoid muscle was calculated. During mouth-opening in 5 out of the 7 patients, and during mouth-closing in 2 out of the 7 patients, mean value of EMG activity differed significantly with body position. Mean value of EMG activity was reduced in the supine position. The results revealed that anteroposterior postural change affected mean value of EMG activity in this muscle.

We used porous sapphire dental implants made of alumina clinically for 4 years 1 month, commencing September, 1984 until September, 1988. Subjects consisted of 18 men and 42 women 20-71 years old (mean age: 35 years). Sixty-five implants were inserted in 60 patients. Of these, 20 were clinical cases of an implant connected with natural teeth and 45 were free-standing cases. We conducted a follow-up study on these patients over a 23-year period. One implant in 1 patient had to be removed because of postoperative infection and 8 implants in 7 patients had to be removed because of fracturing or detachment of the porous-part. This paper reports 3 cases where implants remained in place for 21-23 years. These cases have all shown good long-term clinical progress.

The purpose of the present study was to investigate the relationship between mastication and head posture using foods with different degrees of hardness. A total of 12 healthy, dentulous volunteers participated in the study. Each participant was required to chew two types of gummy candy with two levels of hardness while sitting upright. Measurements were conducted using an optoelectric jaw-tracking system with 6 degrees of freedom (Gnatho-Hexagraph II JM-2000 ® ). The horizontal plane perpendicular to the direction of gravitational force served as the reference plane. Analysis of the gradient of the Frankfurt plane (head posture) and pitching of the head during masticatory movement was conducted. The influence of the type of test food on these parameters was evaluated during mastication. During stable mastication, the gradient of the Frankfurt plane was 4.66 degrees on average, close to the horizontal plane. The time course of the Frankfurt plane gradient revealed a tendency toward dorsal flexion during the first to middle phases of mastication, and a tendency toward ventral flexion during the middle to last phases, regardless of the hardness of the test food. The participants were divided into two groups based on change in head posture during chewing. The results showed while there was no change in head posture in the group with marked pitching of the head, head posture did change in the group with little pitching.