Foot strike patterns and running-related injuries among high school runners: a retrospective study.

BACKGROUND: There is a possible relationship between foot strike patterns and running-related injuries; however, this relationship among high school runners remains uninvestigated. Therefore, this retrospective cohort study examined this relationship among high school runners. METHODS: Overall, 123 male Japanese high school runners participated in this study and completed a questionnaire regarding their characteristics, running habits, and running-related injury histories. We filmed their habitual high-intensity training sessions from a lateral side. Participants' foot strike patterns were visually classified, and they were divided into the non-rearfoot strike (forefoot strike and midfoot strike) and rearfoot strike groups. An independent sample t-test or Welch's t-test was used to compare participant characteristics, running habits, the number of running-related injuries in the past 1 year, and the running speed at the filmed training sessions between both groups. A χ2 test was used to examine the relationship between running-related injury histories and foot strike patterns in both groups. RESULTS: The number of running-related injuries in the past 1 year was not significantly different between both groups; however, running-related injury incidence was significantly associated with non-rearfoot strike (P<0.05). Furthermore, non-rearfoot strike was significantly associated with a history of achillodynia (P<0.05). Other running-related injuries, such as medial tibial pain, lateral knee pain, and heel pain, were not significantly associated with foot strike patterns. CONCLUSIONS: Our study revealed that rearfoot strike runners did not have a higher risk of running-related injury compared to that of non-rearfoot strike runners, and that non-rearfoot strike was associated with achillodynia.

Evaluation of irradiation effects of near-infrared free-electron-laser of silver alloy for dental application.

In the application of lasers in dentistry, there is a delicate balance between the benefits gained from laser treatment and the heat-related damage arising from laser irradiation. Hence, it is necessary to understand the different processes associated with the irradiation of lasers on dental materials. To obtain insight for the development of a safe and general-purpose laser for dentistry, the present study examines the physical effects associated with the irradiation of a near-infrared free-electron laser (FEL) on the surface of a commonly used silver dental alloy. The irradiation experiments using a 2900-nm FEL confirmed the formation of a pit in the dental alloy. The pit was formed with one macro-pulse of FEL irradiation, therefore, suggesting the possibility of efficient material processing with an FEL. Additionally, there was only a slight increase in the silver alloy temperature (less than 0.9 °C) despite the long duration of FEL irradiation, thus inferring that fixed prostheses in the oral cavity can be processed by FEL without thermal damage to the surrounding tissue. These results indicate that dental hard tissues and dental materials in the oral cavity can be safely and efficiently processed by the irradiation of a laser, which has the high repetition rate of a femtosecond laser pulse with a wavelength around 2900 nm.

Development of MDP-based one-step self-etch adhesive--effect of additional 4-META on bonding performance.

We designed three experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based one-step (EX) adhesives consisting of MDP, urethane dimethacrylate, and triethylene glycol dimethacrylate adhesives with different water contents (98.4, 196.8, and 294.4 mg/g), and 4-methacryloyloxyethyl trimellitic anhydride (4-META) or 2-hydroxyethyl methacrylate (HEMA)-containing onestep adhesive. The effect of the amount of MDP-calcium (MDP-Ca) salt produced through demineralization of enamel and dentin on the bonding performance was examined. The efficacy of 4-META and HEMA was then discussed. When the amount of water in EX adhesive was increased, the production amount of MDP-Ca salt of enamel increased, but not the dentin. The enamel bond strength slightly increased with increasing the production amount of MDP-Ca salt, in contrast to the dentin. However, addition of 4-META in the EX adhesive (water content=98.4 mg/g) increased both bond strengths, although the production amounts of MDP-Ca salt significantly decreased. The 4-META enhances both bond strengths more effectively than the HEMA.

A selective medium for Rothia mucilaginosa and its distribution in oral cavities.

A selective medium for Rothia mucilaginosa (RMSM) was developed to examine the population of R. mucilaginosa in oral cavities. The growth recovery of R. mucilaginosa on RMSM was 85.1% relative to HI medium. R. mucilaginosa was detected at 3.4% of total bacteria from stimulated saliva of 8 subjects.

A novel selective medium for the isolation and distribution of Rothia dentocariosa in oral cavities.

Rothia dentocariosa is an indigenous microbial flora of dental plaque. To examine the bacterium population in oral cavities, a novel selective medium, designated RDSM, was developed for the isolation of R. dentocariosa. RDSM was prepared by adding 0.5 µg/ml of lincomycin, 10 µg/ml of colistin, and 40% sucrose to Heart Infusion (HI). Average growth recovery of R. dentocariosa on RDSM was 93.8% that of HI medium. Growth of other bacteria including Rothia mucilaginosa, Neisseria, Actinomyces, or streptococci was remarkably inhibited on the selective medium. Clinical efficacy was evaluated by the recovery of R. dentocariosa on RDSM from the stimulated saliva samples of 8 volunteers. R. dentocariosa was detected at 2.6 (range: 1.0-4.6) % to total bacteria of 8.0×10(7)CFU/ml on BHI in their oral cavities. The new selective medium, RDSM, was highly selective for R. dentocariosa and was useful for the isolation of R. dentocariosa from clinical samples.

[Aging effect of one bottle-type ceramic primer on bonding efficacy of resin cement].

PURPOSE: To understand the degradation mechanisms of commercially available one bottle-type ceramic primer, we prepared one bottle-type experimental ceramic primer consisting of gamma-methacryloxy-propyl-trimethoxysilane, gamma-MPTS, and 90% ethanol solution. The effects of aging of the experimental primer on the hydrolysis and condensation behavior of gamma -MPTS and on the bonding efficacy of gamma-MPTS at the interface between cement and ceramic were studied. METHODS: We used two lamina bond porcelain primers (LB), that had been aged for 20 months and newly purchased. Experimental primer was aged at 20 degrees C. After aging, we measured 29Si NMR spectrum of the gamma-MPTS and the shear bond strength of the cement to silane-treated ceramic by varying aging periods. RESULTS: When the LB was aged for 20 months, the mean bond strength decreased from 26 to 11 MPa. To understand the degradation mechanism in the bond strength, the effects of aging of experimental primer on molecular species of gamma-MPTS were examined. With prolonging its aging period, the methoxy group of the silicone functional portion in the gamma-MPTS hydrolyzed and the hydrolyzed gamma-MPTS species condensed together. The molecular weight of condensed gamma-MPTS species increased. On the other hand, when the dimer species of gamma-MPTS were produced, a maximum mean bond strength of 28 MPa was observed. Thereafter, the bond strength dropped down and leveled off at 16 MPa. CONCLUSION: When the LB was aged for 20 months, the bond strength dramatically decreased. This decrease in the mean bond strength was probably attributed to ester exchange reaction of the methoxyl group in the gamma-MPTS by the ethanol used as diluent solvent.