Cushion Type Research Articles

A web-based survey of denture adhesive use among denture wearers 40 years of age and older

The purpose of this study was to clarify the usage and understanding of denture adhesives among 1,825 denture wearers, aged 40 years and older in Japan, using a web-based survey. The NTTCom Online survey (a closed investigation) was conducted over a period of 4 days using a 13-item questionnaire about denture adhesives. Results showed that 67.1% of the respondents were satisfied with their dentures; 81.5% of respondents knew about denture adhesive, but only 347 (19.0%) had used the product. Products used by the 347 denture wearers included cream type (79.7%), cushion type (16.2%), and powder type (3.2%). The most common reason for the selection of a particular type was "Saw the product" (59.9%), followed by "Saw an advertisement" (19.3%), and "Explanation at a dental clinic" (8.4%). The response of "Ill-fitting denture" significantly affected the response of "Use of denture adhesives" (chi-square test; P < 0.001). Moreover, the sensitivity (0.56) was lower than the specificity (0.75). These findings show that denture adhesives were not always necessary for those with ill-fitting dentures.

Dynamic behavior of laterally loaded caisson foundations based on different cushion types: an experimental and theoretical study

Bridge foundations located in deep water are usually subjected to horizontal dynamic loads and moments which may be caused by the wind, waves, earthquake, and the possibility of boat crashing or vehicle braking. Caisson foundations based on gravel or sand cushions are a new type of deep-water foundation for bridges, suitable for meizoseismal areas. In this paper, harmonic horizontal excitation tests for the study of the lateral dynamic response of caisson foundations based on cushion layers are described. Different lateral loads and two different cushion types are considered. The results show that the lateral dynamic responses of caisson foundations based on sand and gravel cushions both show strong nonlinear characteristics, and the resonant frequency of the foundation decreases with the increase of the excitation force. The dynamic displacement of a foundation based on a sand cushion is far less than that based on a gravel cushion, and the rate of decrease of the resonant frequency of a foundation based on a gravel cushion is faster than that of a foundation based on a sand cushion under the same conditions. Under dynamic loading the gravel cushion can more effectively dissipate vibration energy and isolate the vibration, than the sand cushion can. A simplified nonlinear analysis method is proposed to simulate the lateral dynamic response of caisson foundations, and the predicted response shows a reasonable match with the results observed in laboratory tests. Scaling laws have also been applied in this small-scale vibration model test to predict the dynamic behavior of the prototype foundation.

Influence of Wheelchair Cushions Fabricated by Therapists on Stability, Comfort, and Functionality

“Ease of comfort” and “functionality” are important factors that have been cited to improve wheelchair seating. The ability to maintain balance and posture while seated in a wheelchair improves stability, comfort, and functionality and is a prerequisite for daily activities. In this study, the authors used a sitting position measuring device to scientifically verify differences in sitting posture, comfort, and functionality depending on the presence or absence of cushions and the type of cushion in elderly individuals who used wheelchairs. Results suggested that a cushion fabricated by a therapist was more useful than a commercially available air cushion. While a commercially available air cushion was the most suitable, the therapist’s self-made cushion could be expected to demonstrate the same or better applicability than an air cushion.

Wheelchair Seating: Peak Pressure Distribution in Young versus Elderly Healthy Controls

Background: People may use a wheelchair when they need assistance with mobility. Some users have to remain seated in their wheelchair for most of their awake time and for a lot of activities. The need for a well fitted and supportive wheelchair is important and, for those who use the wheelchair for many hours, peak pressure distribution is of interest to prevent pressure ulcers and discomfort. Aim: To describe how high local peak pressures may be distributed over risk areas for pressure ulcers in different wheelchair settings. Methods: Two groups of healthy adults were recruited (40 elderly and 30 younger individuals). Two standard models of manual wheelchairs were used together with two types of wheelchair cushions. Results: The elderly group had a higher peak pressure over the ischial tuberosity and increased posterior pelvic rotation in the shaped seat cushion. Both groups had higher peak pressure over the trochanter in the shaped seat cushion. Peak pressure was also higher over the coccyx for the elderly in the shaped seat cushion compared with the plain cushion; this was lower for the younger group. Discussion: The results indicate that age might influence the important physical prerequisites when fitting a wheelchair to an individual.

Experimental Study on Rockfall Impact Force Applied to Frame Shed Tunnels

A model experiment is performed to test the rockfall impact force applied to frame shed tunnels under the protection of different types of cushions embedded on tunnel roof slabs. The changing rule of impact force induced by rockfall is analyzed according to different impact energies and types of cushions embedded on shed tunnels. An enlargement coefficient reflecting the relationship between average impact force and maximum impact force is presented using experimental data and theoretical analysis. The improved method for calculating rockfall impact force can consider the many factors that affect this phenomenon. For a particular rockfall impact energy, the rockfall impact force with different types of cushion properties is affected by the cushion property function f∼(h,E,μ,γ). A large f value equates to the minimal discreteness of the expansion coefficient of rockfall impact force under different types of cushion, and vice versa.

Off loading wheelchair cushion provides best case reduction in tissue deformation as indicated by MRI

Off-loading or the Orthotic approach to wheelchair seating has been used successfully to provide seating that optimizes tissue protection at the ischial tuberosities (ITs), sacrum and greater trochanters. Recent publications indicate the significance of preventing tissue compression to reduce ulcer formation. Comparative Magnetic Resonance Imaging (MRI) of individuals seated on two cushion types provides direct evidence of tissue unloading resulting in the reduction in tissue compression. Measurement of tissue compression in MRI images provides the cumulative impact of compression and shear resulting in ultimate tissue thickness documented here. In this study's application of MRI to off-loading cushions (OLC), an alternate form of tissue protection was observed. Instead of incorporating immersion and envelopment, loads were transferred from high-risk areas, such as bony prominences, to lower risk soft tissues. This method shows both shearing and compression of load bearing tissues in seated individuals with the OLC in place. Tissue thickness measurements determined by MRI analysis indicate that the OLC provides greater reduction in tissue deformation than the air cell cushion (ACC). Deformation of tissues loaded by the OLC is not significantly different from the deformations seen with the ACC. This research represents the first reported use of MRI to document the comparative off-loading capabilities of two cushions and the resultant tissue compression and ulceration risk. While MRI analysis may not be incorporated in daily cushion prescription, this paper proposes a methodology in which MRI analysis of tissue deformation on comparative cushions allows the determination of best-case cushion selection for reduction of ischial pressure ulcer (PU) risk.

Pressure Mapping of a Standard Hospital Recliner and Select Cushions With Healthy Adults: A Comparative Study.

The aim of the study was to compare the degree of pressure created when healthy adult volunteers sat on a hospital recliner chair in various positions and on various cushions. Comparative cross-sectional study. Thirty-four healthy subjects were recruited from the community, an urban city in a rural area of Eastern North Carolina. Interface pressure measurements were taken by the investigators for each subject sitting on a standard hospital recliner under each of the following conditions: no cushion, foam cushion, nonadjustable air cushion, nonadjustable air/foam cushion, and adjustable air cushion. Subject positions, upright sitting and reclined, were randomly selected. Analyses consisted of data visualizations by investigators and univariate statistics. For each surface, mean pressure, peak pressure, and Pressure Area Index (PAI) were obtained and compared. Inferences were drawn from a repeated-measures analysis-of-covariance model. Subject position was not associated with any of the measures for each surface after adjusting for other variables (average pressure P = .1094, maximum/peak pressure P = .1318, PAI P = .4336). Subject weight, the type of surface, and their interaction do impact the results (average pressure, maximum/peak pressure, and PAI, P < .0001). The foam cushion had the highest mean and average interface pressures and the lowest PAI. The nonadjustable air and air/foam cushions performed most similarly to each other, showing lowest mean and average interface pressures and the highest PAI. Position of a hospital recliner chair in the 2 positions studied had no association with interface pressure outcomes; therefore, other methods of pressure redistribution need to be utilized by clinicians. Based on the results of this study, clinicians may need to reevaluate the type of cushion used in the acute hospital setting, as a standard foam cushion was found to increase interface pressures when compared to other cushions and a standard hospital recliner.

An MRI investigation of the effects of user anatomy and wheelchair cushion type on tissue deformation

Aim of the studyTissue deformation is recognized as an important risk factor for pressure injuries. This study investigated the effects of anatomy and wheelchair cushion type on tissue deformation. Materials and methodsDirect 3-dimensional tissue deformation response was measured for six participants sitting on six different wheelchair cushions using MR imaging. Two participants had a traumatic spinal cord injury (SCI) within one year of the assessment, two sustained traumatic SCI at least 13 years prior, and two were without SCI. Tissue deformation was quantified using the difference in volume of tissue beneath the ischial tuberosity (IT) between unloaded and loaded (sitting) conditions. ResultsThe participants with SCI tended to have less muscle tissue volume beneath their ITs while sitting compared to participants without SCI. Reductions in muscle and fat volumes in the loaded conditions varied depending on both cushion and participant. Higher interface pressures tended to be associated with lower unloaded tissue thicknesses. ConclusionThe study showed no single cushion type tested produced the lowest amount of tissue deformation across all participants. Individual anatomy and cushion type affect deformation response of tissue and related pressure injury risk.

Model proposal for steel cushions for use in Reinforced Concrete frames

The purpose of this paper is to propose an analytical model for a new type of steel cushion for use in Reinforced Concrete (RC) frames. Theoretically, steel cushions were installed in the RC frame between a beam and chevron-type bracing elements to dissipate a considerable amount of energy during earthquake events. The cyclic shear behaviours of the steel cushions were experimentally determined by performing quasi-static tests. The results of these tests served as the main basis for a simplified hysteretic model that was proposed for the steel cushions. An analytical model was developed for an RC frame that represents low-rise structures. The analytical models of the steel cushions and the RC frame were superimposed. The effectiveness of the steel cushions was numerically assessed by performing a nonlinear static analysis of the frame instrumented with the steel cushion. The results of the numerical analysis indicate that the steel cushions contribute to the energy dissipation and damping properties of the RC frame. The strength of the instrumented frame was significantly higher than the strength of the bare frame. The proposed model is effective and practical for representing the contribution of the steel cushion to the total behaviour of the RC frame.

Comparing the interface pressure redistribution after applying three different types of cushions: differences according to cushion type.

[Purpose] The purpose of this study was to compare the interface pressure redistribution when sitting after applying three different types of cushions and on a firm surface in individuals in their 20s and those older than 60 years old. [Subjects and Methods] Healthy 100 elderly (60 years and older) subjects and 111 college students participated in this study. Interface pressure redistribution while sitting on a firm surface or honeycomb, air, and memory foam cushions, examined in that order. [Results] For all groups, significant differences were found in the total pressure mean among sitting states. When the hip and thigh interface pressure among sitting states were compared within each group, significant differences were found in the mean right hip pressure, mean left hip pressure, peak right hip pressure, peak left hip pressure, right hip pressure ratio, and left hip pressure ratio. [Conclusion] Our data indicated that the type of cushion should be considered and fit for individuals when recommending appropriate interface pressure redistribution cushions.

Comparing the interface pressure redistribution of three different types of cushions: differences according to age groups and cushion preferences.

[Purpose] The purpose of this study was to analyze the change in interface pressure redistribution of three different types of cushions sat on by individuals in their 20s and older than 60 years old. [Subjects and Methods] One hundred and eleven college students and 100 persons than 60 years old were recruited. Sitting pressure redistribution was measured while subjects sat without cushions or on honeycomb, air, and memory foam cushions in that order. Subsequently, the cushion preference was measured. After obtaining all measurements, the mean total pressure and each quadrant’s mean and peak pressure were analyzed. [Results] The mean hip and the peak pressures were low in the group of females aged 60 years or older, and the highest in the group of males in their 20s. The hip pressure ratio was low in the groups of females in their 20s and 60 years or older, whereas the thigh pressure ratio was high in the same groups. The analysis of cushion preference showed that the groups of males (42.0%) and females (40.0%) in their 20s mostly preferred air cushion. The men (55.1%) and women (50.0%) aged 20 years or older selected honeycomb and air cushions as the first and third preferred cushions with a high response rate. [Conclusion] Our results indicate that gender and age should be considered when recommending appropriate pressure redistribution cushions.

長周期地震動を受ける超高層免震建物における衝突緩衝材による応答低減効果に関する検討

As a provision for excessive inputs, effect of cushions installed in a seismically isolated high-rise structure was studied. Results were as follows; 1) Though optimum parameters for various types of cushions were different on their restoring characteristics, effects of them were similar. 2) Common appropriate parameters against 3 kinds of inputs considered can be found. 3) Required force of cushions was not more than 5 % of the building weight. 4) Energy absorption of cushions was slightly effective. 5) The effect of cushions could be seen as increasing of 7-8 or 10-odd% of damping factor of seismic isolation layer.

Effects on sitting pressure distribution during the application of different cushions and anterior height wedges.

[Purpose] The purpose of this study was to investigate interface pressure redistribution in healthy volunteers when applying different cushions and anterior wedge heights. [Subjects and Methods] This study included 36 healthy individuals in their 20s. The peak and mean pressures were measured by applying different cushions and anterior wedge heights. The results were analyzed by using a one-way analysis of variance and post-hoc analysis. [Results] The peak and mean pressures were statistically significant based on the cushion types and anterior wedge height. The peak pressure was at its highest and lowest when sitting on a 6-cm anterior wedge and a foam cushion, respectively. The mean pressure was greatest when sitting on a 6-cm anterior wedge of a firm surface and smallest when sitting on a 5 cm foam cushion. [Conclusion] This study shows that the most effective method for pressure redistribution was sitting on a 5 cm foam cushion without an anterior wedge.

The influence of the number and the type of magnetic attachment on the retention of mandibular mini implant overdenture.

PURPOSEThe aim of this study was to compare the retention of mini implant overdenture by the number, the type of magnetic attachment, and the directions of applied dislodging force.MATERIALS AND METHODSThe experimental groups were designed by the number and type of magnetic attachment. Twenty samples were tested with Magden implants. Each attachment was composed of the magnet assembly in overdenture sample and the abutment keeper in a mandibular model. Dislodging forces were applied to the overdenture samples (50.0 mm/min) in 3 directions. The loading was repeated 10 times in each direction. The values of dislodging force were analyzed statistically using SPSS at 95% level of confidence.RESULTSThe retentive force of group 2 was greater than that of group 1 in both types of attachment in every direction (P < .05). Oblique retentive force of flat type magnetic attachment was higher than that of cushion type attachment in both groups (P < .05). In group 1, oblique retentive force showed the highest and anterior-posterior retentive force showed the lowest value in both attachment types (P < .05). In group 2, both types of attachment showed the lowest retentive force with anteriorposterior direction of dislodging force (P <.05).CONCLUSIONProper retentive properties for implant overdenture were obtained, regardless of the number and type of magnetic attachment. In both types of magnetic attachment, the greater retentive force was attained with more implants. Oblique retentive force of flat type magnetic attachment was greater than that of cushion type. Among all subgroups, anterior-posterior retentive force was the lowest among three different directions of dislodging force.

The effect of cushion properties on skin temperature and humidity at the body-support interface

ABSTRACTThe purpose of this study is to explore the effects of various cushions on skin temperature and moisture at the body–seat interface during a 2-hour period of continuous sitting. Seventy-eight participants were randomly assigned to sit on one of the three types of wheelchair cushions for unrelieved sitting for over 2 hours. Skin temperature and relative humidity (RH) were measured under the subjects’ ischial tuberosities and thighs bilaterally with digital temperature and humidity sensors. Data were collected before sitting and at 15-minute intervals thereafter. Participants sitting on foam–fluid hybrid cushions showed significantly lower skin temperatures than those sitting on air-filled and foam cushions (p < 0.05), but RH did not differ significantly among the cushions (p = 0.97). The three cushions produced a similar increasing trend in RH over time and RH reached a plateau during the 2-hour sitting period. To select the appropriate wheelchair cushion, the microclimate (heat and moisture control) between the body–seat interface should be considered as well as pressure distribution. In comparison with foam–fluid hybrid cushions, the air-filled rubber and foam cushions tended to increase skin temperature by several degrees after prolonged sitting. However, cushion materials did not have significant differences in moisture accumulations.

Misuse of booster cushions among children and adults in Shanghai—an observational and attitude study during buckling up

ABSTRACTObjective: Traffic crashes are one of the leading causes of fatalities among Chinese children. Booster cushion usage in China is low, and there are no studies showing how a population with limited experience handles booster cushions during buckling up. The purpose of this study was to evaluate the handling of and explore the attitudes toward booster cushions among children, parents, and grandparents in Shanghai.Methods: An observational study including a convenience sample of 254 children aged 4–12 years was conducted in 2 passenger cars at a shopping center in Shanghai. Parents, grandparents, or the children themselves buckled up the child on 2 types of booster cushions, a 2-stage integrated booster cushion (IBC) and an aftermarket booster cushion (BC). The test participants were observed during buckling up, first without and then with instructions. The test leaders conducted structured interviews.Results: Ninety-eight percent of the uninstructed participants failed to buckle up without identified misuse on the aftermarket booster cushion and 31% of those uninstructed on the integrated booster cushion. The majority of misuse was severe, including placing the belt behind the arm and the lap belt routing above the guiding loops. Instruction reduced misuse to 58% (BC) and 12% (IBC), respectively, and, in particular, severe misuse. Some misuse was related to limited knowledge of how to buckle up on the booster cushion, and some misuse was intentional in order to reduce discomfort.The participants, both children and adults, reported that they preferred the IBC due to good comfort and convenience. Safety was reported as the main reason for adults using booster cushions in general, whereas children reported comfort as the most important motivation.Conclusions: Education is needed to ensure frequent and correct use of booster cushions in China and to raise safety awareness among children and adults. Furthermore, it is important that the booster cushions offer intuitively correct usage to a population with limited experience of booster cushions.This is the first study published on the handling of and attitude toward booster cushions after child restraints laws were introduced in Shanghai 2014.

ETFE 필름의 2축 인장특성 및 텐션방식 막구조물의 응력완화 거동에 관한 실험적 연구

Until recently, almost all ETFE film structures that have been erected is the cushion type because there are problems at lower allowable strength under elastic range and viscosity behaviour such as creep and relaxation of ETFE films under long-term stresses. But the number of tension type structures is currently increasing. This paper proposes the stretch fabrication of ETFE film to verify the applicability of ETFE films to tensile membrane structures. First of all, to investigate the possibility of application on tensile membrane structures, the stretch fabrication test is carried out, and it is verified that it is possible to increase the yield strength of the film membrane structures. After simulating the experiment also carries out an analytical investigation, and the effectiveness of the elasto-plastic analysis considering the viscous behavior of the film is investigated. Finally, post-aging tension measurement is conducted at the experimental facilities, and the viscosity behavior resulting from relaxation is investigated with respect to tensile membrane structures.

Wheelchair seating: A study on the healthy elderly

Background: Many frail elderly and disabled persons have to use a manual wheelchair to remain mobile and active. Apart from a well-fitted wheelchair, an appropriate wheelchair cushion is considered crucial for postural support and to prevent complications.Aim: To examined the effect of two types of seat cushions in two types of wheelchairs with regard to pelvic rotation, respiratory function, and interface pressure.Material and methods: Forty healthy elderly between 67 and 85 years of age participated. Two types of commonly used manual wheelchairs and two types of seat cushions were tested. Interface pressure, pelvic position, and respiratory function were measured using a sensor array mat, a study-specific inclinometer, and a spirometer.Results: Differences in interface pressure and pelvic rotation between cushions were found in both wheelchairs. Compared with sitting on a standard cushion, sitting on the positioning cushion increased peak pressure. The posterior pelvic tilt increased with the positioning cushion in the Etac Cross wheelchair and for both cushions in the Etac Cross wheelchair compared with the HD Balance wheelchair. No difference was observed in respiratory function.Conclusions: This study highlights the importance of a thorough evaluation of the effects of wheelchair interventions, especially for the elderly and disabled.

Effects of different seat cushions on interface pressure distribution: a pilot study.

[Purpose] The purpose of this study was to evaluate pressure redistribution on the supporting area of healthy volunteers when using different cushions. [Subjects and Methods] Twenty healthy individuals ranging in age from 19–23 years old and 20 older adults age 60 or above participated in the study. All participants lived in urban communities in South Korea. Group differences according to gender, age, and cushion types were analyzed with one-way analysis of variance and post-hoc analysis. [Results] Statistically significant differences in peak pressure and mean pressure were identified between age, gender, and cushion types. Peak pressure and mean pressure were higher on firm surfaces and on the air cushion than other cushion types. The pressure ratio was lower when an air cushion was used in the buttock area and was higher when it was used under the thighs compared to that in other conditions. [Conclusion] This study showed that interface pressure can be distributed differently depending on what cushions are used. Therefore, when using seat cushions, individuals should seek advice to help them choose the appropriate cushion for their needs.

A seakeeping analysis method for a high-speed partial air cushion supported catamaran (PACSCAT)

The partial air cushion supported catamaran (PACSCAT) is a type of air cushion assisted catamaran with planing demihulls. Both the air cushion and the demihulls can strongly affect the seakeeping performance. Although there exist some methods for analyzing the seakeeping of other air cushion supported vessels considering the effects of both the air cushion and demihulls, they can take considerable computational time. In this paper, an efficient numerical method is presented, which is formed by combining the 2.5D theory for solving hydrodynamics of demihulls with simplified wave-equation for solving aerodynamics of pressurized air to analysis the seakeeping performance of the high-speed PACSCAT. In the method, the cushion pressure is determined by using adiabatic gas law together with boundary conditions including the craft motion, free surface elevation, fan flows and air leakage. Two models are proposed for air leakage: constant leakage area and varying leakage area linearly related to ship motions and free surface elevation. The results obtained by the newly formulated method are compared with the experimental data, showing that the numerical results have reasonable agreements with experimental ones.