Shock absorption and dispersion capability of a novel five-layer mouthguard sheet material

There is a growing need for a mouthguard sheet material with higher shock absorption and dispersion capacity than those obtained by conventional materials. A five-layer mouthguard sheet material was previously developed using laminated ethylene vinyl acetate and polyolefin copolymer resin. In this study, the shock absorption capacity and dispersion capability of the new sheet material were investigated and compared with those of other materials. Impact testing for the new sheet material showed that the force required to displace the sheet by 1 mm was significantly higher at all thicknesses (p<0.001), whereas the puncture energy and displacement were significantly lower than those for ethylene vinyl acetate (p<0.05). The five-layer mouthguard sheet material successfully absorbed and resisted shock. Therefore, the sheet material potentially increases resistance to applied deformation in teeth and alveolar bone and maintains structure. The five-layer sheet material could expand the range of mouthguard products and help prevent oral trauma.

Quantitative text analysis of the mechanisms of tooth injury: Analysis of accidents in five sports that occurred in 15 years under school control

BACKGROUND/AIM

Dental trauma may occur in school settings and it can impact patients' quality of life. Analysis of the occurrences of dental trauma is essential in identifying preventive methods. There are numerous reports of such accidents but most are quantitative analyses with limited data. The aim of this study was to extract information on the mechanisms of injuries that leads to prevention by performing a qualitative analysis of the occurrence of dental trauma.

MATERIAL AND METHODS

After screening 7684 cases of dental injuries that occured in schools and were reported to the Japan Sports Council between 2005 and 2020, 533 detailed descriptions of injuries that occurred during sports were included. Quantitative text analysis was performed on the target data by performing statistical analysis, extracting frequently used words, and creating a co-occurrence network. Injury mechanisms were evaluated based on appearance of words.

RESULTS

Dental injuries occurred frequently in five sports included in the survey. They were in order of decreasing frequency: baseball, basketball, soccer, volleyball, and rugby. Males were injured more often in all sports other than volleyball. The number of accidents increased in all sports among high school students. The frequent word list and co-occurrence network were different for each sport. This allowed typical accident occurrence mechanisms to be extracted for these five sports.

CONCLUSIONS

Typical accident occurrence mechanisms were extracted from quantitative text analysis targeting free texts on the occurrence of accidents for five sports. Quantitative text analysis is useful for the evaluation of accident cases, which may aid in accident prevention.

Continuous Oral Administration of Sonicated P. gingivalis Delays Rat Skeletal Muscle Healing Post-Treadmill Training

BACKGROUND

A delay in muscle repair interferes with the effect of training or exercise; therefore, it is important to identify the factors that delay muscle repair. P. gingivalis, one of the most common periodontal disease pathogens, has the potential to inhibit muscle repair after training, as inferred from a previous study. To assess the expression of satellite cells in this in vivo study, we evaluated the relationship between P. gingivalis and muscle regeneration after training.

METHODS

A total of 20 male Wistar rats (eight weeks in age) were randomly divided into two groups: one orally administered sonicated P. gingivalis four times per week for six weeks (PG group) and one given no treatment (NT group). After four weeks of training using a treadmill, the gastrocnemius was evaluated using histology of the cross-sectional area (CSA) of myotubes and immunohistochemistry of the expression of skeletal muscle satellite cells. In addition, an endurance test was performed a day before euthanization.

RESULTS

The CSA and expression of Pax7+/MyoD- and Pax7+/MyoD+ cells were not significantly different between the groups. However, the expression of Pax7-/MyoD+ cells and running time until exhaustion were significantly lower in the PG group.

CONCLUSIONS

Infection with P. gingivalis likely interferes with muscle repair after training.

Case Report: Psychoacoustic Analysis of a Clarinet Performance With a Custom-Made Soft Lip Shield Worn to Prevent Mucosal Erosion of Lower Lip

Introduction

Wind instrument players sometimes suffer from erosion of the mucous membrane of the lip. This is caused by the action and pressure of the mouthpiece of the wind instrument against teeth. To address this problem, a lip shield is fitted over the dental arch to prevent direct contact between the lips and teeth. However, there are a few studies on the influence of the lip shield on the acoustics of wind instruments. The purpose of this study was to analyze the psychoacoustics of a clarinet performance with the player wearing a custom-made soft lip shield to prevent mucosal erosion of the lower lip.

Case Description

A lip shield was custom-made with a soft thermoplastic material for a female clarinetist who complained of mucosal erosion and pain of the lower lip. The psychoacoustics of her musical performance played in different dynamics, fortissimo, mezzo forte and pianissimo were analyzed, including loudness and sharpness. A self-evaluation questionnaire with items rated on a 10-point scale was administered. After wearing the lip shield, the patient reported that the mucosal erosion and pain of her lower lip when playing clarinet resolved. The lip shield had little effect on the loudness. There was a slight decrease in sharpness when the lip shield was worn compared to when it was not, describing the reduction of high frequencies. Furthermore, fewer variations in sharpness between the tones were observed.

Conclusion

The results suggest that lip shields made of soft materials can eliminate mucosal erosion and pain of the lower lip while having little effect on performance, although, a slight change in timbre is possible.

Useful design of custom-made mouthguard for athletes undergoing orthodontic treatment with brackets and wires

Background/purpose

Custom-made mouthguards (MGs) are strongly recommended for athletes during sports activities to prevent dental injuries. Athletes undergoing orthodontic treatment and wearing brackets require specially designed MGs for better protection and to create more space that will not hinder the planned orthodontic tooth movement. The purpose of this study was to fabricate effective, specially designed, custom-made MGs for patients or athletes with ongoing orthodontic treatment and to evaluate the shock absorption abilities of these MGs by an in vitro comparison of three different designs.

Materials and methods

Three different types of specially designed, double-layered MGs, (i) creating inter bracket space inside the MG, (ii) embedding silicon wax inside the MG, and (iii) creating a buffer space with additional hard insertion, were fabricated from a simulated bracket attached model. Impact test was performed using a free-falling object on a vertical rod, and the strain-gauge system was used to assess the strain on the dentition with the MGs for the comparison of the shock absorption abilities of the three types. Analysis of variance at a significance level of 5% and multiple comparisons were performed for statistical analysis.

Results

The strains on the dentition with the MG creating buffer space with hard insertion were significantly lower than those with the other two types of MG (P < 0.001).

Conclusion

Insertion of a hard material and ensuring buffer space between the MG and the teeth and/or appliance was more effective than other methods of fabricating custom-made MGs to prevent sports-related traumatic dental injuries in athletes undergoing orthodontic treatment.

Effectiveness of computer-assisted learning in sports dentistry: studies over a multiple-year period and at two universities

INTRODUCTION

Insufficient educational resources on sports dentistry result in varying lecture implementations across dental schools, which cause knowledge gaps amongst students. Thus, a new interactive sports dentistry-related computer-assisted learning (CAL) module was created to facilitate dental school undergraduate students' education. This study compared the CAL module's learning effectiveness with conventional video lectures (VL) and assessed its effectiveness when used over several years at a university, and examined its validation in different university contexts, and students' perceptions.

MATERIALS AND METHODS

Participants were 305 fifth-year students. Students from a university in Tokyo participated for 3 years and those from a university in Saitama for 1 year. In each year, the students were divided into two groups-CAL and VL. They studied their assigned modules in 20-min lessons. A written test was administered to determine their knowledge acquisition levels, along with a questionnaire.

RESULTS

Two hundred sixty-two consenting participants were included in the statistical analysis. The CAL groups' test scores at both schools were significantly higher than the VL groups' every year (p < .001). Furthermore, test results from all years revealed no gender differences or repetition of the school years at either school. Most students at both universities evaluated the CAL module as excellent.

CONCLUSION

The interactive CAL module generated consistently strong results over multiple years, during which it was used by a diverse group of students at two universities. The students highly rated the module's learning process as well as its contents.

Antibacterial effect of a disinfectant spray for sports mouthguards on Streptococcus sobrinus

BACKGROUND

Mouthguard (MG) disinfectant sprays are available for maintaining MG hygiene. The effect of these sprays against Streptococcus sobrinus is still unknown. The purpose of this study was to evaluate the antibacterial effect of an MG disinfectant spray against S. sobrinus using the modified ISO 22196 standard.

MATERIALS AND METHODS

In this in vitro study, we used the following treatment groups for antibacterial testing: MG spray-1 (left in spray for 30 s), MG spray-2 (60 s), and control (n = 4). All analyses were performed at a statistically significant level (P = 0.05) using JMP^® 14.

RESULTS

The log colony-forming units of the MG spray-2 group were significantly lower than those of the other groups. The antibacterial activity of MG spray-2 against S. sobrinus was >2.1.

CONCLUSION

We confirmed the antibacterial effect of the MG spray against S. sobrinus, and it was influenced by the treatment duration, with the optimum effect at a longer duration.

Air Permeability, Shock Absorption Ability, and Flexural Strength of 3D-Printed Perforated ABS Polymer Sheets with 3D-Knitted Fabric Cushioning for Sports Face Guard Applications

Sports face guards (FGs) are devices that protect athletes from maxillofacial injury or ensure rapid return to play following orofacial damage. Conventional FGs are uncomfortable to wear owing to stuffiness caused by poor ventilation and often slip off due to increase in weight due to absorption of moisture from perspiration, lowering players’ performance. Herein, combinations of 3D-printed perforated acrylonitrile butadiene styrene (ABS) polymer sheets and 3D-knitted fabrics with honeycomb structures as cushioning materials were investigated to balance better wearing feel and mechanical properties. The flexural strength, weight, and shock absorption ability of, and air flow rate through, the ABS sheets with five different perforation patterns were evaluated and compared with those of conventional FG materials comprising a combination of polycaprolactone sheets for the medical splint and polychloroprene rubber for the cushioning material. The ABS sheets having 10% open area and 2.52 mm round holes, combined with knitted fabric cushioning, exhibited the requisite shock absorbing, higher air permeability, and lower weight properties than the conventional materials. Our results suggest that FGs fabricated using combinations of 3D-printed perforated ABS polymer sheets and 3D-knitted fabrics with honeycomb structures may impart enhanced wearing comfort for athletes.

Use of the fiberglass reinforcement method in thermoplastic mouthguard materials to improve flexural properties for enhancement of functionality

The purpose of this study was to evaluate the application of fiberglass reinforcement method in thermoplastic mouthguard materials to improve flexural properties and adhesive strength. Commonly used two types of commercial mouth guard materials (ethylene-vinyl acetate copolymer-based and polyolefin-based) were reinforced with glass fiber clothes by two-step hot press. Flexural strength and adhesive strength with each base material were examine via three-point bending test and delamination test, respectively. Ethylene-vinyl acetate copolymer-based fiberglass-reinforced material has significantly greater adhesive strength with base material and improvement of flexural properties compared with polyolefin-based material. These results suggest that flexural properties of both conventional commercial mouthguard materials were improved when the glass-fiber-reinforced method was applied to reinforce mouthguard materials, and more, ethylene-vinyl acetate copolymer was more desirable for the base material.

Thickness change and deformation of custom-made mouthguards after two years of use by Bangladeshi field hockey players

BACKGROUND/AIM

Sports mouthguards are effective devices that prevent dental trauma in sports activities. Players should change mouthguards on a regular basis because of thickness reduction and shape deformation. However, there is no guidance regarding the best timing to change mouthguards. The aims of this study were to analyze the thickness change and deformation of mouthguards after 2 years of use in Bangladesh field hockey players and to consider appropriate evaluation criteria.

MATERIAL AND METHODS

Fifty-seven field hockey players belonging to the Bangladesh Sports Education Institute participated in this study. Participants were provided with double-layered mouthguards made of polyolefin-based material using a vacuum-forming machine. Mouthguards were fabricated using 2-mm-thick sheet as the first layer and 3-mm-thick sheet as the second layer. Players used the mouthguards for 2 years. Before and after using the mouthguards, the thicknesses of nine areas were measured. In addition, the lengths of five areas were used to analyze shape deformation.

RESULTS

After 2 years, the thicknesses of all measured areas had significantly reduced, and the lengths had significantly increased. Thickness reduction of the posterior-occlusal and anterior-incisal areas and deformation of the posterior-buccal and posterior-palatal areas were significantly larger than those in other measured areas.

CONCLUSIONS

Mouthguards should be changed on a regular basis to minimize thickness reduction and deformation. Occlusal and incisal thickness and length of the buccal-posterior area and the palatal-posterior area are factors to be considered in establishing guidelines regarding the timing of mouthguard change.

Application of Glass Fiber and Carbon Fiber-Reinforced Thermoplastics in Face Guards

Face guards (FGs) are protectors that allow for the rapid and safe return of athletes who are to play after sustaining traumatic facial injuries and orbital fractures. Current FGs require significant thickness to achieve sufficient shock absorption abilities. However, their weight and thickness render the FGs uncomfortable and reduce the field of vision of the athlete, thus hindering their performance. Therefore, thin and lightweight FGs are required. We fabricated FGs using commercial glass fiber-reinforced thermoplastic (GFRTP) and carbon fiber-reinforced thermoplastic (CFRTP) resins to achieve these requirements and investigated their shock absorption abilities through impact testing. The results showed that an FG composed of CFRTP is thinner and lighter than a conventional FG and has sufficient shock absorption ability. The fabrication method of an FG comprising CFRTP is similar to the conventional method. FGs composed of commercial FRTPs exhibit adequate shock absorption abilities and are thinner and lower in weight as compared to conventional FGs.

Fabrication technique of obturator-type sports mouthguard for a patient who had undergone maxillectomy and its speech intelligibility assessment:A case report

PURPOSE

Wearing a sports mouthguard is not only recommended in collision sports, such as American football, boxing, and rugby football, but also in low-contact sports, such as basketball, handball, and soccer. It is recommended to remove oral prosthetic devices while playing sports to avoid the risk of fracturing the device. However, players with maxillectomy must wear obturator-type prosthetic devices for speech, breathing, and deglutition even while playing sports. Therefore, there is a need for an oral appliance to prevent dental injury while playing sports without the risk of fracturing the device for players who have undergone maxillectomy.In this case, we fabricated and proposed overlay-type and obturator-type customized sports mouthguards for a patient who had undergone maxillectomy and assessments of satisfaction, speech intelligibility, nasopharyngeal closure function, and swallowing function while playing soccer.

RESULTS

The patient was only satisfied with the obturator-type mouthguard, and the results of the speech intelligibility, nasopharyngeal closure function, and swallowing tests using the obturator-type mouthguard showed no differences compared to those associated with the previously used prosthetic device.

CONCLUSIONS

This case may help highlight the importance of providing obturator-type mouthguards for players who have undergone maxillectomy to prevent dental injury and physical and mental discomfort.

The influence of temperature on sheet lamination process when fabricating mouthguard on dental thermoforming machine

Laminated custom-made mouthguards tend to delaminate with use; this is a problem in clinical use. Insufficient bonding strength causes delamination, and bonding strength is strongly affected by heating temperature during lamination. The present study aimed to evaluate the influence of heating temperature on the sheet lamination process. Seven mouthguard sheet products were laminated together at different heating temperatures. To evaluate the bonding strength, a delamination test (n = 6) was performed, and the fracture patterns were inspected visually. To evaluate the shock absorption capability, a falling impact test (n = 5) was performed, and the specimen thicknesses were measured. All recorded values were analyzed using two-way analysis of variance and Tukey's Honest Significant Difference Test (P < 0.05). The present study confirmed that bonding strength was dependent on heating temperature: In ethylene-vinyl acetate copolymer products, the bonding strength was almost constant at 130°C and above, and it was constant at 110°C and above in polyolefin products. The thickness of every specimen decreased and, in some specimens, the shock absorption capability decreased with increasing heating temperature. The present study concludes that the heating temperature during the sheet lamination process when laminated custom-made mouthguards are fabricated may not be less than 120°C in ethylene-vinyl acetate copolymer products and 110°C in polyolefin products.

Interactive effect of rehydration with diluted sports drink and water gargling on salivary flow, pH, and buffering capacity during ergometer exercise in young adult volunteers

The present study was conducted to investigate the influence of rehydration with diluted sports drink and water gargling on salivary flow, pH and buffering capacity during exercise. Nineteen participants performed a 30-min bicycle ergometer exercise at 80% of maximal heart rate while consuming a sports drink, followed by gargling with water, or no gargling, immediately after the exercise (Exp. 1). The same experiment was then conducted on 9 participants who drank 1.5-fold diluted sports drink (Exp. 2-A) and 10 who drank 2-fold diluted sports drink (Exp. 2-B). Paraffin-stimulated whole saliva samples were collected for 3 min before, during and after exercise, and salivary parameters were examined using a hand-held pH meter. Statistical significance was assessed using multi-factor ANOVA and Turkey-Kramer test (P < 0.05). The decrease in salivary pH was significantly suppressed after water gargling in Exp. 1 (P < 0.01) and Exp. 2-A (P < 0.001). Dilution of the sports drink had an interactive effect with water gargling in Exp. 2-B (P < 0.01). These results suggest that gargling with water suppresses the decrease of salivary pH resulting from sports drink rehydration during ergometer exercise, but that this effect may be lost if athletes consume sports drink that has been diluted 2-fold with water.

Establishment of experimental models to evaluate the effectiveness of dental trauma splints

The purpose was to describe a novel simple experimental model of injured teeth for developing dental trauma splints (DTS), and to test various splints by combining use of this model and the Periotest^® device. Rubber O-rings and spring washers were used to simulate and modify injured tooth mobility. Splinting effects were assessed among three kinds of DTS, including a composite splint and two wire-composite splints (1: rectangular orthodontic wire 0.533×0.635 mm, 2: cobalt-chromium alloy wire Φ0.9 mm). The Periotest values were measured three times for each tooth before and after splint insertion. The splinting effect was defined as the change in tooth mobility. Splinting effects significantly increased in the order wire-composite splint 1<wire-composite splint 2<composite splint (p<0.05). This model system could evaluate the effects of DTS including the differences among various splint methods, which showed reasonable reproducibility of dental trauma situations depending on severity in clinical usage.

Evaluation of the flexural properties of a new temporary splint material for use in dental trauma splints

The present study evaluated the flexural properties of a new temporary splint material, G-Fix, for use in dental trauma splints in comparison with other resin materials. Four types of resin materials were considered in the present study: MI Flow II, light-cured composite resin (MI); G-Fix, light-cured resin for splinting teeth (GF); Super-Bond C&B, adhesive resin cement (SB); and Unifast III, self-cured methyl-methacrylate resin (UF). The flexural properties of these four materials were tested according to ISO 4049. The flexural strength significantly increased in the order of UF (64.9 MPa) < SB (76.5 MPa) < GF (94.3 MPa) < MI (161.2 MPa). The elastic modulus significantly increased in the order of UF (2.11 GPa) ≒ SB (2.23 GPa) < GF (2.62 GPa) < MI (7.39 GPa). A splint made of GF may be more flexible than a composite splint, which is categorized as a rigid splint.

Erratum to: Application of addition-cured silicone denture relining materials to adjust mouthguards

The purposes of this study were to examine the shock absorption capability of addition-cured silicone denture relining materials and the bonding strength of addition-cured silicone denture relining materials and a commercial mouthguard material to determine its applicability to mouthguard adjustment. Two addition-cured silicone denture relining materials were selected as test materials. The impact test was applied by a free-falling steel ball. On the other hand, bonding strength was determined by a delamination test. After prepared surface treatments using acrylic resin on MG sheet surface, 2 types of addition-cured silicone denture relining materials were glued to MG surface. The peak intensity, the time to peak intensity from the onset of the transmitted force and bonding strength were statistically analyzed using ANOVA and Tukey's honest significant difference post hoc test (p<0.05). These results suggest that the silicone denture relining materials could be clinically applicable as a mouthguard adjustment material.

Suitable design of mouthguard for sports-active person with spaced dentition

AIM

Custom-made mouthguard (MG) is popularly used by sports-active persons or athletes having either normo-occlussion or malocclusion to prevent dental injury. For sports-active person with malocclusion, specially designed mouthguard is often required. The purpose of this study was to make a suitable design custom-made mouthguard for sports-active person with spaced dentition by the shock absorption capability.

MATERIALS AND METHODS

Two different types of double layered mouthguards were made from a model of a sports-active person having spaced dentition with polyolefin sheets. One type was made by filling the interproximal spaces of the spaced dentition and the other type, which was devoid of interproximal space covering, without mouthguard materials (keeping space). The impact tests were carried out by a free-falling object via testing machine and a vertical rod. The strains of the dentition with mouthguard were measured by means of strain gage system to compare between two different designs of mouthguard. Unpaired t-test was carried out as statistical analysis.

RESULT

The strains of the dentition with mouthguard by filling the interproximal spaces were significantly low compared with the mouthguard by keeping spaces (P < 0.05).

CONCLUSION

For sports-active person with spaced dentition, it is important for reducing injury risks that the mouthguard covered the teeth and filled or embedded interproximal space certainly.

Combined analysis of shock absorption capability and force dispersion effect of mouthguard materials with different impact objects

The aims of the present study were to investigate the shock absorption capability and force dispersion effect of mouthguard (MG) materials using load cell and film sensors. Two kinds of MG materials, ethylene vinyl acetate and polyolefin, were chosen for this study. When impact forces of approximately 5,000 N were applied on the MG materials using a round flat-nosed rod and a bluntly pointed rod, peak intensities were measured using the load cell sensor while peak stresses and impressed stress distribution areas were measured using the film sensor. Combined analysis using both load cell and film sensors clearly showed the shock absorption properties and force dispersion effects of different MG materials with different impact object shapes. Therefore, impact analysis involving a combined use of these sensor systems was useful and reliable in assessing the shock absorption capability and force dispersion effect of MG materials.

Long-term survivors of advanced esophageal cancer without surgical treatment: a multicenter questionnaire survey in Kyushu, Japan

Since the introduction of recent improvements in adjuvant therapy for esophageal cancer, some patients have demonstrated good prognosis. In the present study, we analyzed 3- and 5-year survivors of advanced esophageal cancer who did not undergo any surgical treatment. Between 1990 and 1998, 831 patients were admitted to 14 university hospitals and one cancer center associated with the membership of the Kyushu study group for adjuvant therapy of esophageal cancer. Twelve (1.4%) of the patients were 3-year survivors and 13 (1.6%) were 5-year survivors. The reasons for non-operation were refusal (eight patients), tumor-related factors (11 patients), and host-related factors (six patients). With a single exception, all patients had locally advanced tumors. Almost all long-term survivors had fewer than five lymph node metastases, in regions limited to the neck and/or mediastinum. Radiation therapy was combined with chemotherapy for 16 of the 25 patients, and chemotherapy-based cisplatin was used for 15 of these 16 patients. Fifteen of the patients remain alive; 10 died seven of them from esophageal cancer. Chemoradiation therapy was effective for some patients with locally advanced esophageal cancer, particularly in the absence of or with few lymph node metastases. To improve the prognosis of patients with advanced esophageal cancer who, for various causes, cannot undergo surgical treatment, a new protocol for adjuvant therapy is required.

[Relation between teeth clenching and grip force production characteristics]

This study investigated the possible contributing effect of oral motor function on maximal and explosive grip force production characteristics. Fourteen healthy male subjects (age 22.5 +/- 2.1 years) were asked to exert maximal explosive grip strength with their dominant hands under the following four conditions: 1. Teeth clenching before and during grip strength exertion (C-C), 2. Teeth clenching before grip strength exertion and mandibular resting position during grip strength exertion (C-R), 3. Mandibular resting position before grip strength exertion and teeth clenching during grip strength exertion (R-C), and 4. Mandibular resting position before and during grip strength exertion (R-R). Maximal force (maxF), average force for every 0.1 s (aveF), maximal rate of force development (maxRFD) and time required to reach 90% of maxF (T 90% max) were analyzed for 1 s from the onset of grip force production. MaxF under C-C and R-C were significantly greater than that under R-R by 12.1% and 12.3%, respectively. AveF under C-C was significantly greater by 10.0-41.2% than that under R-R for all ten periods. AveF under C-R was significantly larger by 9.8-19.0% than that under R-R conditions from 0 to 0.4 s. Compared with under R-R conditions, maxRFD under C-C and C-R increased by 15.8% and 8.5%, respectively, and T 90% max under C-C, C-R and R-C decreased by 22.3%, 12.3% and 12.8%, respectively. These findings suggest that oral motor functions such as teeth clenching may influence not only maximal grip strength generation but also the rapidity of grip force production.

Pain palliation by percutaneous acetabular osteoplasty for metastatic hepatocellular carcinoma

A 68-year-old man with hepatocellular carcinoma and known skeletal metastasis developed right hip pain and gait disturbance due to an osteolytic metastasis in the right acetabulum. This was treated initially with chemoembolization and radiation therapy. When these procedures proved unsuccessful percutaneous injection of acrylic bone cement into the acetabulum was undertaken. Immediately after this procedure, he obtained sufficient pain relief and improved walking ability, which continued for 3 months until he died of hepatic insufficiency.

The position of the opposite flat applicator changes the SAR and thermal distributions of the RF capacitive intracavitary hyperthermia

The variations of the specific absorption rate (SAR) and thermal distribution in the JSHO QA phantoms were investigated by radiofrequency (RF) capacitive intracavitary hyperthermia (ICHT) applicator (AP-T01, Omron Electric Co., Kyoto, Japan) with the changing position of the opposite flat applicator (15-cm in diameter). The thermal distribution was observed with the thermographic camera and the normalized SAR distribution was calculated with the thermal data that were measured with the thermocouple thermometers. The SAR and thermal distributions of AP-T01 significantly varied with the position of the opposite flat applicator. The slope of the normalized SAR became gradual towards the side of the flat applicator. During the operating of a high flow rate (1500 ml/min) cooling system, the region between AP-T01 and the flat applicator was widely and rather homogeneously heated, except the hot spot around the end of AP-T01. This hot spot may be due to the imbalance of cooling of AP-T01 and the warming-up of the electrode. These results suggest that the RF capacitive ICHT using AP-T01 may be clinically effective on the deep-seated tumours in the direction of either the end wall, such as cervical cancers, or the upper wall, such as prostatic cancers and the mediastinal metastatic lymph nodes, if an improvement of the cooling system is achieved.

The size and distance of the opposite flat applicator change the SAR and thermal distributions of RF capacitive intracavitary hyperthermia

The variations of the specific absorption rate (SAR) and thermal distributions in the JSHO QA phantom were investigated by using the radiofrequency (RF) capacitive intracavitary hyperthermia (ICHT) applicator (AP-T01, Omron Electric Co., Kyoto, Japan) and the opposite flat applicators of different sizes (AP-75E: 7.5 cm in diameter, AP-100E: 10 cm in diameter, and AP-150E: 15 cm in diameter). The influences of the distance between both applicators were also investigated. Heating of the region between both applicators became weaker with the increase in size of the opposite flat applicator, and it became stronger with the decrease of the distance between both applicators. Heating near the flat applicator became weaker with the increase in size of the flat applicators, and it showed no apparent difference with the increase of the distance between both applicators. The normalized SAR values between AP-T01 and the opposite flat applicator became smaller and its slope became steeper with the increase in size of the opposite flat applicator and in the distance between both applicators. These results suggest that the variability of the specific absorption rate (SAR) and thermal distributions of the region between both applicators may show the potentiality of usefulness for heating the tumours of various sizes, shapes and location.

Radiotherapy for adrenal gland metastasis from lung cancer: report of three cases

Adrenal gland metastasis is often observed during the clinical course of patients with lung cancer. However, treatment of adrenal gland metastasis is seldom considered because of the systemic spread of the disease. Treatment with curative intent is very rare, but palliative treatment may sometimes be considered when symptoms such as flank pain are observed. Three cases of adrenal gland metastasis were reported. Two of them received surgery for lung cancer and developed a sole metastasis of the adrenal gland. Case 1 developed a sole left adrenal gland metastasis with left flank pain 14 months after surgery for large cell carcinoma of the lung. Curative radiotherapy after intra-arterial chemotherapy was given. A good response was obtained, and he has been alive for 2 years and 9 months. Case 2 developed a right adrenal gland metastasis after radiotherapy for brain metastasis, after having received right upper lobectomy because of SCLC. The increase in the size of the right adrenal gland led us to treat the lesion before symptoms developed. Radiotherapy was given on an outpatient basis. Case 3, who was previously treated with chemoradiotherapy for SCLC, developed brain, liver, and bilateral adrenal gland metastasis. Huge adrenal gland metastases displaced the pancreas and caused severe pain with the increase in serum amylase level. Concurrent radiotherapy with systemic chemotherapy was given and remarkable shrinkage of the adrenal gland metastases was obtained together with pain relief. Cases 2 and 3 died after 8 and 4 months, respectively. In some cases, radiotherapy for adrenal gland metastasis is a good palliative therapy even in the advanced stage patients. Radiotherapy can sometimes curatively treat adrenal metastasis from NSCLC, as in our Case 1, in which adrenalectomy appeared difficult at the time of recurrence.

A case of follicular thyroid cancer with tracheal stenosis responded to external radiation therapy

We report the case of a 70-year-old man with follicular carcinoma of the thyroid who complained of worsening dyspnea and was successfully treated by external radiation therapy. The total dose given was 61 Gy in 28 fractions. This case suggests that external radiation therapy is effective for the management of differentiated thyroid cancer with critical stenosis of the trachea that is inoperable and difficult to treat with radioiodine.

Effectiveness of RF capacitive hyperthermia combined with radiotherapy for stages III and IV oro-hypopharyngeal cancers: a non-randomized comparison between thermoradiotherapy and radiotherapy

Seventy-two patients with Stages III and IV (TNM, UICC, 1987) squamous-cell carcinoma of the oropharynx and hypopharynx (oro-hypopharyngeal cancer) were treated with external irradiation, or irradiation plus 13.56 MHz radiofrequency (RF) capacitive hyperthermia from 1989 to 1995. This study compared initial response, histological effect and 5-year survival rate of thermoradiotherapy (TRT) group with those of radiotherapy alone (RT) group. In the TRT group, 15 patients were treated definitively, and 18 patients preoperatively. In the RT group, 15 patients were treated definitively, and 24 patients preoperatively. With definitive irradiation, the complete response rate of the primary lesions was 73% in the TRT group and 27% in the RT group (p = 0.009) and the complete response rate of the metastatic lymph nodes was 80% in the TRT group and 27% in the RT group (p = 0.005). With preoperative irradiation, the pathological CR (No residual cancerous cells) rate of the primary lesions was 56% in the TRT group and 8% in the RT group (p = 0.01), and the pathological CR rate of the lymph nodes was 72% in the TRT group and 21% in the RT group (p = 0.001). The 5-year survival rates with definitive irradiation were 47.6% in the TRT group and 18.7% in the RT group (p = 0.025). Thus TRT was more effective than RT for advanced oro-hypopharyngeal cancer.

Osseous primitive neuroectodermal tumor--a case report

PNET and Ewing sarcoma are pathologically distinct entities with very similar clinical and radiological characteristics. Immunohistochemical studies are needed to distinguish PNET from Ewing sarcoma, with the former being characterized by neural differentiation. We present the case of a 17-year-old man with immunohistochemically confirmed PNET in the cervical vertebrae.

Intrapancreatic accessory spleen: case report

We report a rare case of intrapancreatic accessory spleen which radiologically mimicked a pancreatic hypervascular tumor. The diagnosis of an intrapancreatic accessory spleen should be considered when a pancreatic mass has the CT densities and/or MR signal intensities similar to those of the spleen, with and without contrast medium.

[MR imaging appearances of schwannoma: correlation with pathological findings]

Peripheral schwannomas are nerve sheath neoplasms that consist of focal proliferation of Schwann cells. We reviewed the MRI findings in 17 patients with pathologically proved peripheral schwannomas. When compared with the signal intensity of muscle, that of the mass was isointense or hyperintense on T1-weighted images and hyperintense in all 17 tumors on T2-weighted images. All of the masses showed heterogeneous enhancement following the intravenous injection of Gd-DTPA on T1-weighted images. On T1-weighted images, hyperintensity was observed in the tumors that contained predominantly hypercellular Antoni type A tissue, while isointensity was observed in the tumors that contained predominantly hypocellular Antoni type B tissue. Relatively high signal intensity seen on T2-weighted images and Gd-DTPA enhanced T1-weighted images was observed in the tumors that contained predominantly Antoni type B tissue when compared with the signal intensity of tumors that contained predominantly Antoni type A tissue. A capsule was pathologically identified in 15 of 17 tumors. MRI correctly identified the presence of a capsule in 11 of 15 tumors and the absence of a capsule in one of 2 tumors. Thus the diagnostic accuracy was 71% (12/17). The cause of 4 false negative results appeared to be a hemorrhage or cystic change around the peripheral portion of the tumor, and it appeared to be a chemical artifact in one false positive result. Thus the appearance of MRI may suggest the cellular type of schwannoma, Antoni type A or B. However, prediction of the presence or absence of tumor capsule may be relatively difficult with MRI.

[A case of advanced esophageal cancer successfully treated by concurrent use of radiotherapy and low-dose CDDP and continuous infusion of 5-FU]

A 75-year-old male patient with advanced esophageal cancer was treated by radiotherapy and chemotherapy. External radiotherapy was performed by the field in field method. A total dose of 60 Gy was used in the small field (7 x 5 cm) (2.4 Gy/f and 25 f/5 wks) and a total dose of 45 Gy in the large field (14 x 6 cm) (1.8 Gy/f, 25 f/5 wks). Concurrent chemotherapy was performed at the 2nd and 5th weeks of the radiation therapy. In this chemotherapy of CDDP plus 5-FU, CDDP (25 mg/day) was given on days 1,3 and 5 of the week and 5-FU (500 mg/day) was given for 5 days by continuous infusion for the same week. By this treatment, a complete response (CR) was obtained, and no serious side effects were observed. After 1 year and 6 months, he is alive with no evidence of recurrence.

A case of pulmonary pseudolymphoma: five years' roentgenographic observation

A patient with pulmonary pseudolymphoma whose chest X-ray shadows could be observed for over five years is reported. A 73-year-old man was admitted to our hospital in March 1993, because of abnormal shadows on a chest X-ray film. There was a solitary mass in the left upper lung field and infiltrate in the right middle and lower lung fields. These shadows had been observed on a chest X-ray film in 1988, and had been gradually growing for more than five years. Transbronchial lung biopsy (TBLB) of the left upper lobe mass resulted in a histological diagnosis of pulmonary pseudolymphoma. The shadows showed no change during the next nine months after his discharge. These findings are suggestive of the natural history of pulmonary pseudolymphoma. It seems that the process involved in this case was benign rather than malignant.

Case report: hepatocellular carcinoma diagnosed radiologically, treated by transcatheter arterial embolization and limited-field radiotherapy

Even though the resection rate for hepatocellular carcinoma (HCC) has risen recently, many patients cannot be treated surgically because of the advanced stage of the tumour and/or coexisting cirrhosis. An alternative therapeutic approach for some of these patients is transcatheter arterial embolization (TAE) which has become very common in Japan. However, it is not a curative measure, and an additional therapy is required to eradicate the residual disease. In this communication, we report a case in which a patient with HCC has been successfully treated by TAE followed by limited-field radiotherapy. The results suggest that this is a very promising therapeutic approach for HCC and that the potential of limited-field radiotherapy for HCC with or without TAE also needs to be explored.

Suppression of rabbit VX-2 subcutaneous tumor growth by gadolinium neutron capture therapy

VX-2 tumors growing in hind legs of New Zealand White rabbits (n = 4) were exposed to thermal neutrons for 40 min (2.1 x 10(12) neutrons cm-2) while one of two hind leg tumors of each rabbit was infused continuously with meglumine gadopentetate through a branch of the left femoral artery. The contralateral (uninfused) tumors served as controls. Although no differential distribution of gadolinium was achieved between the tumor and its adjacent normal tissue, the gadolinium concentration in the infused tumor was approximately 5-6 fold higher than that in the contralateral tumor. Growth of gadolinium-infused tumors was significantly inhibited compared to that of control tumors (P < 0.05) between the 16th and 23rd days after treatment.

Linac-based small-field radiotherapy for brain tumors

Small-field radiotherapy based on a 6-MeV linac and a conventional head mold is investigated as an alternative to radiosurgery with stereotactic frames. The system requires no additional device and allows fractionated treatment. The dose distributions obtained are comparable to those reported with a Gamma Unit. Overall positioning errors are within 2 mm. Using this approach, seven patients with brain tumors who could not have been treated otherwise, underwent fractionated radiotherapy with total accumulated doses ranging from 70 to 108 Gy. The treatment was tolerated well with no acute toxicity or adverse effect encountered during the follow-up period of 8-14 months. All of the patients remained free from disease progression in the treated volumes. Although the follow-up is brief, the preliminary results suggest that this is a simple and inexpensive but effective system for the treatment of small intracranial malignancies.