Effect of Vinyl Acetate, Glass Fibers Contents, and Buffer Space on EVA's Mechanical Property and Shock Absorption Ability.

OBJECTIVES: The aim of the study was to evaluate the mechanical properties and impact absorption capacity of prototype materials comprising ethylene vinyl acetate (EVA) of different hardness reinforced using different amounts of glass fibers (GFs), considering a buffer space. MATERIALS AND METHODS: Six prototype materials were made by adding E-GFs (5 and 10 wt%) to EVA with vinyl acetate (VA) contents of 9.4 wt% ("hard" or HA) and 27.5 wt% ("soft" or SO). Durometer hardness and tensile strength tests were performed to evaluate the mechanical properties of the materials. Moreover, an impact test was conducted using a customized pendulum impact tester to assess the impact absorption capacity (with or without a buffer space) of the specimens. RESULTS: The mechanical properties of the prototypes, namely, durometer hardness, Young's modulus, and tensile strength, were significantly higher in the HA group than in the SO group, regardless of the presence or added amount of GFs. The addition of GFs, particularly in a large amount (10 wt%), significantly increased these values. In terms of the impact absorption capacity, the original hardness of the EVA material, that is, its VA content, had a more substantial effect than the presence or absence of GFs and the added amount of GFs. Interestingly, the HA specimens with the buffer space exhibited significantly higher impact absorption capacities than the SO specimens. Meanwhile, the SO specimens without the buffer space exhibited significantly higher impact absorption capacities than the HA specimens. Moreover, regardless of the sample material and impact distance, the buffer space significantly improved impact absorption. In particular, with the buffer space, the impact absorption capacity increased with the added amount of GFs. CONCLUSION: The basic mechanical properties, including durometer hardness, Young's modulus, and tensile strength, of the EVA prototype were significantly increased by reducing the amount of VA regardless of the presence or added amount of GFs. Adding GFs, particularly in large amounts, significantly increased the values of aforementioned mechanical properties. Impact absorption was significantly affected by the hardness of the original EVA material and enhanced by the addition of the buffer space. The HA specimen had a high shock absorption capacity with the buffer space, and the SO specimen had a high shock absorption capacity without the buffer space. With the buffer space, impact absorption improved with the amount of added GFs.

Improving light-cured intermediate resin for hard and space mouthguard using a glass fiber.

BACKGROUND/AIMS: A light-cured intermediate material is useful for fabricating a hard insert and a buffer space mouthguard (H&SMG). However, it requires improvement in its mechanical properties and shock-absorbing capacity. The aim of this study was to evaluate the mechanical properties of two prototype light-cured intermediate materials reinforced with glass fibers, and the impact absorption capacity and durability of H&SMGs made with the prototype intermediate materials. MATERIALS AND METHODS: Two prototype materials containing long and microlength glass fibers in a light-cured intermediate material, Innerframe LC®, for H&SMG, were fabricated and tested. A three-point bending test was performed for evaluation of the mechanical properties. In addition, a shock absorption test was conducted using a customized pendulum impact testing machine to evaluate the H&SMGs' impact absorption capacity and durability. RESULTS: Long and microlength glass fibers significantly improved flexural modulus and strength. H&SMGs made with these two glass fiber-containing materials had high impact absorption capacity against both low and high impact forces, while the mouthguards made with long glass fiber materials had the best results. CONCLUSION: Long and microlength glass fibers with the prototype materials improved the mechanical properties of Innerframe LC® and the impact absorption capacity and durability of H&SMGs. H&SMGs made with the long glass fiber prototype materials had the best performance.

Jaw-Clenching Intensity Effects on Masseter Oxygen Dynamics and Fatigue: A NIRS Oximetry Study.

The purpose of this study was to clarify the effects of jaw-clenching intensity on masseter muscle oxygen dynamics during clenching and recovery and masseter muscle fatigue using the spatially resolved method of near-infrared spectroscopy. Pulse rate, mean power frequency from electromyography in the masseter and visual analogue scale for masseter fatigue were also examined as related items. The 25% and 50% maximum voluntary contractions were determined using electromyography before the experiment and used as visual feedback on the screen. Twenty-three healthy adult male subjects volunteered for this study. Clenching decreased oxygen and oxygenated haemoglobin, and increased deoxygenated haemoglobin in the masseter muscle. The higher the intensity of clenching, the more prominent the effect. The oxygen dynamics tended to return to normal after clenching, but the change was slower with higher clenching intensity. Pulse rate increased with clenching, and the increment was more prominent with higher clenching intensity. Clenching caused a shift of mean power frequency to a lower range, an increase in subjective fatigue, an early appearance of a breakpoint appearance time and a prolongation of a 1/2 recovery time. All of these effects were more evident with increasing clenching intensity. In conclusion, clenching intensity influenced the oxygen dynamics of the masseter muscle and fatigue state during clenching and recovery. The higher the intensity, the greater the impact.

The effect of light-cured resin with a glass fiber net as an intermediate material for Hard & Space mouthguard.

BACKGROUND/AIMS: Despite the use of conventional mouthguards, preventable sports-related dental injuries continue to occur. The authors have developed a two-layered ethylene polyvinyl acetate (EVA) mouthguard with a hard polyethylene terephthalate (PET) insert and a buffer space (H&SMG). However, adapting the PET onto the EVA layer requires skill. A light-cured Splint Resin (SRLC) and a glass fiber net (NET) reinforcement appear to resolve this issue. The aim of this study was to investigate whether SRLC with NET could replace PET and find a more practical application for NET. MATERIALS AND METHODS: A pendulum impact testing machine and a dental model with strain gages were used. Six types of mouthguards were made: one with two laminated EVA blanks (LAM-MG), a three-layer type with a PET insert and an intermediate space (PET-H&SMG), a H&SMG with SRLC insert (LC-H&SMG), and three other types with differential NET-SRLC reinforcement; NET on the outer surface of SRLC, NET on the inner surface of SRLC, and NET on both the outer and inner surfaces. Five mouthguards of each type were fabricated and tested ten times with impact distances of 15 and 30 cm. Forty more impacts were applied to all H&SMGs to confirm the durability of the hard inner layer. RESULTS: All H&SMGs showed significant strain reduction compared to the LAM-MG. PET-H&SMG and the four types of LC-H&SMG exhibited an equally slight strain (approximately 95% shock absorbing ability) in all conditions. During the test against the smaller impact, all H&SMGs showed no cracks. When tested against the stronger impact, only the LC-H&SMG with the reinforced inner surface, the double NET-reinforced LC-H&SMG, and the PET-H&SMG remained intact. CONCLUSION: The NET-reinforced SRLC can replace PET as an intermediate mouthguard material. The NET application, at least on the internal surface, is indispensable for the LC-H&SMG reinforcement.

Effect of Mastication Muscle Activity on Prefrontal Cortex NIRS Measurement: A Pilot Study.

Changes in NIRS signals are related to changes in local cerebral blood flow or oxy-Hb concentration. On the other hand, recent studies have revealed the effect of chewing gum on cognitive performance, stress control etc. which accompanied brain activity in the prefrontal cortex (PFC). However, these relationships are still controversial. To evaluate the chewing effect on PFC, NIRS seems to be a suitable method of imaging such results. When measuring NIRS on PFC, blood volume in superficial tissues (scalp, skin, muscle) might have some affect. The aim of the present study was to clarify the effect of the anterior temporal muscle on NIRS signals during gum chewing. Eight healthy volunteers participated. Two-channel NIRS (HOT-1000, NeU, Japan), which can distinguish total-Hb concentrations in deep tissue and superficial tissue layers, was used. In addition to a conventional optode separation distance of 3.0 cm, Hot 1000 has a short distance of 1.0 cm (NEAR channel) to measure NIRS signals that originate exclusively from surface tissues. NIRS probes were placed at Fp1 and Fp2 in the normal probe setting. The headset was displaced to the left in order to allow the left probe to be placed over the left anterior temporal muscle. In the normal setting, the superficial signal curve shows no notable change; however, the neural (calculated and defined in HOT-1000) and deep curves show an increase during the gum chewing task. At the deviated setting, all three signals show marked changes during the task. Total-Hb concentration in the deviated probe setting is significantly large (p < 0.05) than that of in the normal probe setting. When using gum chewing as a task, it would be better to consider a probe position carefully so that the influence of muscle activity on NIRS signal can be distinguished.

PFC Blood Oxygenation Changes in Four Different Cognitive Tasks.

Aging often results in a decline in cognitive function, related to alterations in the prefrontal cortex (PFC) activation. Maintenance of this function in an aging society is an important issue. Some practices/drills, moderate exercise, mastication, and a cognitive task itself could enhance cognitive function. In this validation study, before evaluating the effects of some drills on the elderly, we examined the neural substrate of blood oxygenation changes by the use of four cognitive tasks and fNIRS. Seven healthy volunteers (mean age 25.3 years) participated in this study. Each task session was designed in a block manner; 4 periods of rests (30 s) and 3 blocks of four tasks (30 s). The tasks used were: a computerized Stroop test, a Wisconsin Card Sorting Test, a Sternberg working memory paradigm, and a semantic verbal fluency task. The findings of the study are that all four tasks activated PFC to some extent, without laterality except for the verbal fluency task. The results confirm that NIRS is suitable for measurement of blood oxygenation changes in frontal brain areas that are associated with all four cognitive tasks.

Successful Treatment for Chronic Hepatitis C-Autoimmune Hepatitis Overlap Syndrome due to Daclatasvir and Asunaprevir.

Persistent hepatitis C virus (HCV) infection may induce autoimmune diseases and chronic hepatitis C is sometimes accompanied by autoimmune hepatitis (AIH). However, we are worried about the treatment for chronic hepatitis C-AIH overlap syndrome because interferon-based antiviral therapies may enhance autoimmunity and immunosuppressive corticosteroid administration may promote viral replication. Here, we report a patient having chronic hepatitis C-AIH overlap syndrome treated with the direct-acting antivirals (DAA), daclatasvir and asunaprevir. A 50-year-old man was referred to our hospital because of positive anti-HCV antibody and liver dysfunction at a health checkup. Blood tests showed increased immunoglobulin G (IgG) and a high titer of antinuclear antibody (ANA) in addition to elevated serum alanine aminotransferase (ALT) and HCV-RNA. Infiltration of lymphocytes and plasma cells in Glisson's capsule and severe interface hepatitis were observed in biopsied specimen, which fulfilled the criteria of AIH. We first started oral corticosteroid administration, and serum ALT levels decreased once but elevated again. We commenced daclatasvir and asunaprevir (60 and 200 mg/day, respectively) and serum HCV-RNA became negative after 6 weeks. Adverse effects were not found during the DAA treatment, and serum ALT, IgG, and ANA were significantly decreased. Corticosteroid could be tapered and stopped, but no recurrence occurred. DAA treatment appears to be effective and safe for the patients with chronic hepatitis C-AIH overlap syndrome.

Vonoprazan-Based Regimen Is More Useful than PPI-Based One as a First-Line Helicobacter pylori Eradication: A Randomized Controlled Trial.

Background. A new agent, potassium-competitive acid blocker vonoprazan (VPZ) has potent acid-inhibitory effects and may offer advantages over conventional H. pylori eradication therapies. We aimed to compare the eradication rate between VPZ-based treatment and PPI-based one. Methods. This randomized controlled trial was designed to assign 141 patients with H. pylori-positive gastritis to VPZ group (VPZ 20 mg, amoxicillin 750 mg, and clarithromycin 200 or 400 mg twice daily for 7 days) or PPI group (rabeprazole 20 mg or lansoprazole 30 mg, amoxicillin 750 mg, and clarithromycin 200 or 400 mg twice daily for 7 days). Primary endpoints were eradication rates and adverse events. Results. Seventy of 72 patients in VPZ group and 63 of 69 patients in PPI group completed the treatment after 7 days. The eradication rate was significantly higher in VPZ group than PPI group by intention-to-treat analysis (95.8% versus 69.6%, P = 0.00003, 95% confidence interval [CI] 88.3-99.1% versus 57.3-80.1%) and per-protocol analysis (95.7% versus 71.4%, P = 0.0002, 95% CI 88.0-99.1% versus 58.7-82.1%). The incidence of adverse events was not different between the groups (26.3% in VPZ group versus 37.7% in PPI group, P = 0.15). Conclusion. VPZ-based regimen is more useful than that PPI-based regimen as a first-line H. pylori eradication therapy.

[Survey of gemcitabine treatment for advanced pancreatic cancer in 20 hospitals of Nagano Prefecture].

To establish an effective therapy for pancreatic cancer, we made a retrospective survey of gemcitabine treatment performed at 20 hospitals in Nagano Prefecture. We analyzed data of 106 patients (64 men and 42 women, median age 66 years (33-83 years old)), half of whom had stage IV disease. Gemcitabine was administered for 3 consecutive weeks with one week rest in 57 patients, biweekly in 30 patients, initially for 3 weeks with 1 week rest and switched to biweekly schedule to 15 patients, and with another regimen to 4 patients. Analysis of the results of gemcitabine treatment between the 3 weeks with 1-week-rest regimen and the biweekly regimen revealed no differences between regimens in growth inhibition and symptom alleviation. However, we found less occurrence of blood toxicity in the biweekly regimen (40%) than in the 3 weeks with 1 week-rest regimen (59%). Median survival time for the biweekly regime was 9.7 months, only slightly longer than that of the 3 weeks with 1-week-rest regimen (8.5 months). The present study showed that a biweekly regimen for gemcitabine administration may be equivalent to the standard regime of 3 weeks with 1-week-rest regimen. Moreover, the biweekly regimen has advantages over the 3 weeks with 1-week rest regimen both economically and in terms of convenience for outpatient treatment. Therefore, the present results should be confirmed in future prospective studies, with the hope of developing a new standard treatment regimen for pancreatic cancer.

[Clinical problems in gemcitabine treatment for unresectable pancreatic cancer in the elderly--a multicentric retrospective study of 53 cases].

In Gemcitabine treatment, elderly patients with unresectable pancreatic cancer are more likely to suffer from haematological and non-haematological adverse effects than non-elderly patients. Forty percent of the elderly patients were dropped from the initial protocol due to the adverse effects, mainly because of non-haematological events or symptoms. To avoid adverse effects, the administration schedule for Gemcitabine tended to be less often and at a lower dose for elderly patients among members of the Nagano Pancreatic Cancer Study Group. However, the fact that some cases showed a limited effect from this administration schedule albeit without adverse effect, might suggest that the frequency of ordinary administration schedule should be maintained, although the Gemcitabine dose could be decreased in unresectable pancreatic cancer patients in poor condition.

Hemorrhagic rectal ulcer caused by a deformity of the coccyx complicated by normal delivery.

A 25-year-old woman delivered her first-born child weighing 3400 g by full-term normal delivery. Bloody stool developed 3 days after delivery. Colonoscopic examination revealed two linear ulcers parallel to the anal column on the posterior side of the rectal ampulla about 5 cm from the anal ring. Coagulated blood was detected at the ulcer bottom, suggesting the site of hemorrhage. Bowel rest in the absence of oral intake resulted in the disappearance of bloody stool. Three days later colonoscopic examination revealed improvement in the ulcer. There was no sign of constipation. A lateral pelvic radiograph showed that the apex of the coccyx was flexed anteriorly. The parturient canal may have physically pressed the rectum against the apex of the coccyx during delivery, causing mucosal injury. Only a few studies have reported the complication of a rectal ulcer due to injury during delivery. Furthermore, none of the previous studies has reported a rectal ulcer caused by deformity of the coccyx.