Variance Of Hue Research Articles

Physical frailty and oral health as risk factors for low bone density in community-dwelling residents

This study aimed to explore the association between bone mineral density and physical frailty including nutrition, muscle mass, and oral function. We included participants aged 35–80 years and examined their bone mineral density, serum albumin level, body composition, and variance of hue (VOH) of two-colored gum. We also used the geriatric oral health assessment index (GOHAI). These data were used to calculate the geriatric nutritional risk index (GNRI) and skeletal muscle index (SMI). Multinomial logistic regression was performed to assess the relationship between GNRI, SMI, VOH, GOHAI, and bone mineral density after adjusting for comorbidities, including hypertension, diabetes mellitus, and previous bone fracture. We included 228 participants and classified their bone mineral density as normal, osteopenic, or osteoporotic. Older age (odds ratio (OR) 1.15, 95% confidence interval (CI) [1.08, 1.23]), low GNRI (OR 0.90, 95% CI [0.83, 0.98]), low SMI (OR 0.43, 95% CI [0.27, 0.68]), and high VOH (OR 1.08, 95% CI [1.01, 1.17]) were significantly associated with osteoporosis. Older age (OR 1.08, 95% CI [1.04, 1.11]) and low GNRI (OR 0.93, 95% CI [0.87, 0.99]) were significantly associated with osteopenia. GNRI, SMI, and VOH were significantly associated with osteoporosis among male participants. Although the multinomial logistic regression analysis indicated that GNRI, SMI, VOH, and GOHAI were not significantly associated with osteoporosis or osteopenia among female participants, the demographic distribution showed that older age, low GNRI, and low SMI were significantly associated with bone mineral density decline. Physical frailty, including nutritional decline, muscle mass loss, and poor oral status, is associated with low bone density. This easy-to-use tool can be used to detect osteoporosis early and to prevent osteoporosis and osteoporosis-related fractures.

Comparative evaluation of masticatory efficiency, clinical performance, and patient satisfaction of single implant-retained mandibular overdenture versus conventional complete denture: A prospective in vivo study.

The aim of this within-subject prospective clinical study was to investigate the scope of single implant mandibular overdenture by assessing its masticatory efficiency, clinical performance, and patient satisfaction compared to conventional complete dentures. Prospective In Vivo Study. This prospective in vivo study was conducted in the Department of Prosthodontics and Crown and Bridge, Christian Dental College, Ludhiana. A total of 12 completely edentulous patients received a single implant in the mandibular anterior midline region. After the healing period, the conventional maxillary and mandibular dentures were fabricated. 15 days post insertion of the conventional dentures, patients were evaluated for masticatory efficiency, clinical performance including retention and stability, and patient satisfaction. To evaluate the masticatory efficiency blue raspberry and original pink "Hubba Bubba tape gum" were used as a test food. Colorimetric analysis was done to assess variance of hue. To assess clinical performance, retention, and stability of the mandibular denture was recorded using a digital force gauge and was tabulated as per CU-modified Kapur's criteria. OHIP-14 index was used to assess patient satisfaction. After evaluation of the parameters of conventional dentures, the denture was converted into an implant-retained mandibular denture by chairside conversion with locator attachments. 15 days post-implant loading, parameters of the implant retained mandibular overdenture were assessed again followed by statistical analysis. The masticatory efficiency was assessed using a paired t-test. The patient satisfaction was sequentially assessed with Wilcoxon signed rank test and thereafter paired t-test was used to compare between conventional complete denture and overdenture. Clinical performance was assessed using the Wilcoxon signed rank test. The masticatory efficiency of single implant mandibular overdenture was higher than that of conventional complete dentures. The clinical performance of the overdenture was higher than that of the conventional denture. Stability being a time-dependent parameter might need longer follow-ups for further conclusions. Patient satisfaction with single implant retained overdenture was significantly higher than conventional complete dentures. Single implant mandibular overdenture has improved masticatory efficiency, clinical performance, and patient satisfaction compared to conventional complete dentures.

Digital oral health biomarkers for early detection of cognitive decline

BackgroundOral health could influence cognitive function by stimulating brain activity and blood flow. The quantified oral status from oral inflammation, frailty and masticatory performance were rarely applied to the cognitive function screening. We aimed to adopt non-invasive digital biomarkers to quantify oral health and employ machine learning algorithms to detect cognitive decline in the community.MethodsWe conducted a prospective case-control study to recruit 196 participants between 50 and 80 years old from Puzi Hospital (Chiayi County, Taiwan) between December 01, 2021, and December 31, 2022, including 163 with normal cognitive function and 33 with cognitive decline. Demographics, daily interactions, electronically stored medical records, masticatory ability, plaque index, oral diadochokinesis (ODK), periodontal status, and digital oral health indicators were collected. Cognitive function was classified, and confirmed mild cognitive impairment diagnoses were used for sensitivity analysis.ResultsThe cognitive decline group significantly differed in ODK rate (P = 0.003) and acidity from SILL-Ha (P = 0.04). Younger age, increased social interactions, fewer cariogenic bacteria, high leukocytes, and high buffering capacity led to lower risk of cognitive decline. Patients with slow ODK, high plaque index, variance of hue (VOH) from bicolor chewing gum, and acidity had increased risk of cognitive decline. The prediction model area under the curve was 0.86 and was 0.99 for the sensitivity analysis.ConclusionsA digital oral health biomarker approach is feasible for tracing cognitive function. When maintaining oral hygiene and oral health, cognitive status can be assessed simultaneously and early monitoring of cognitive status can prevent disease burden in the future.

Assessment of masticatory function in the differential diagnosis of Stage IV periodontitis: A pilot diagnostic accuracy study.

After diagnosis of periodontitis is made, detection of Stage IV cases is critical for appropriate management that may call for interdisciplinary care. This study aims to identify and assess the accuracy of a simple screening approach for practice and surveillance of Stage IV periodontitis. Masticatory function assessments by both validated self-reported masticatory dysfunction questionnaire and dual-color chewing gum mixing ability test (index test) were conducted in 214 consecutive patients, followed by a full-mouth periodontal examination. Periodontal diagnosis was based on the 2017 World Workshop classification of periodontal diseases (reference standard). Multivariate logistic regression and area under the receiver operating characteristic curve (AUROC) analyses were performed. Overall, the individual patient-reported masticatory dysfunction questions showed low to moderate accuracy for predicting Stage IV periodontitis. The objective measures of masticatory function by calculating the variance of hue from the chewing gum test performed better with an AUROC of 0.840. A diagnostic approach based on age, self-report of altered food type intake, and chewing gum test results exhibited excellent performance for predicting Stage IV periodontitis (sensitivity: 89.7%; specificity:76.3%; AUROC:0.912). Once the presence of periodontitis has been established, a simple diagnostic approach that does not require specialized workforce, complex, or lengthy assessment allows identification of patients with Stage IV periodontitis. This is important as these patients require specific case work up and interdisciplinary care pathways. Additional studies are required to validate the findings in multiple populations.

Comparing Masticatory Performance of Maxillary Mini Dental Implant Overdentures, Complete Removable Dentures and Dentate Subjects.

Background: Mini dental implant (MDI) overdenture rehabilitation for the edentulous maxilla is a valuable, less invasive and affordable treatment alternative for complete removable dentures (CRD). However, comparative quantification of masticatory performance in different oral conditions are scarce. Purpose: This study compares objective masticatory performance of dentate groups, maxillary CRD and MDI overdentures and subjective masticatory performance in maxillary CRD and MDI overdentures. Materials and Methods: Four groups were defined, age 20+ dentate dental students (DS), age 50+ complete dentate subjects (DP), age 50+ maxillary CRD or MDI overdentures/dentate mandible. Objective masticatory performance was evaluated by measuring circular Variance of Hue (VOH) or the mixture degree of two-color chewing gum (Hue-check View Gum® Test). Additionally, subjective masticatory comparison was investigated in the CRD and MDI groups, with a visual analogue scale (VAS) for different food consistencies and the Oral Health Related Quality of Life (OHRQL) OHIP-14 questionnaire. Results: The mean VOH was 0.11 (SD 0.50, range 0.05–0.27) for the dentate dental 20+ students, 0.13 (SD 0.08, range 0.03–0.31) for the 50+ dentate group (p = 0.774), 0.41 (SD 0.41, range 0.14–0.76) for the CRD group and 0.39 (SD 0.18, range 0.07–0.76) for the MDI group (p = 0.725). Based on the VAS scores, no improvement was found between the CRD and the MDI overdenture group (p > 0.050). The mean OHIP-14 total score was 12.10 (SD 15.87, range 0–56) for CRD, while the MDI group (p = 0.039) saw a significant improvement to 2.85 (SD 2.85, range 0–15). Conclusion: Comparable results in objective masticatory performance were registered in dentate 20+ and 50+ subjects with a remarkable inferior outcome for the CRD and MDI group. Compared to CRD, MDI overdentures revealed no substantial improvement in subjective and objective masticatory performance. However, for MDI a significant increase in OHRQL was apparent.

Assessment of masticatory function in older individuals with bimaxillary implant-supported fixed prostheses or with a natural dentition: A case-control study

Statement of problemA clinical assessment of the masticatory performance of edentulous people treated with bimaxillary implant-supported fixed prostheses is lacking. PurposeThe purpose of this case-control study was to compare the masticatory performance of edentulous people treated with bimaxillary implant-supported fixed prostheses to that of those with a natural dentition by using a simplified comminution test with hard viscoelastic test food and a mixing ability test. Material and methodsThirty-six participants were recruited and divided into 2 equal groups (n=18) based on their dental status. The experimental group (7 women, mean ±standard deviation age=69.8 ±7.5 years) had bimaxillary implant-supported fixed prostheses, and the control group (9 women, mean ±standard deviation age=68.3 ±5.6 years) had a natural dentition. A hard viscoelastic food comminution test and a mixing ability test with 2-colored chewing gum were performed in both groups. The number and total area of the particles during the comminution test and the variance of hue during the mixing ability test were measured. The data were analyzed with the parametric (paired t test) and nonparametric (Mann-Whitney U) tests to assess differences between the groups (α=.05). ResultsThe experimental group exhibited significantly fewer pieces in the food comminution test than the control group (P=.001). The experimental group also showed significantly higher variance of hue values than the control group (P<.001). ConclusionsPatients treated with bimaxillary implant-supported prostheses had reduced masticatory performance in comparison to those with a natural dentition, despite having been provided with satisfactory and well-functioning prostheses.

Prosthetic rehabilitation status, dental prosthesis functionality and masticatory function in nursing home residents.

To evaluate the association of masticatory function with prosthetic rehabilitation status and dental prosthesis functionality in nursing home residents. Prosthetic rehabilitation status and dental prosthesis functionality may adversely affect mastication of older people, and this relationship is underestimated in nursing home residents. This cross-sectional study included 179 nursing home residents who used dental prostheses [mean (SD) age: 78.9 (9.0) years]. Masticatory function data were determined by assessing (a) masticatory performance using two-colour chewing gum, and (b) swallowing thresholds by counting the number of peanut chewing cycles. Older adults were categorised as: (1) using dental prostheses in both jaws (n=100) and (2) partially dentate using removable partial dental prostheses (RPDPs) or complete dentures (CDs) in only one jaw (n=41), or (3) edentulous using CD in only one jaw (n=38). Stability, retention, occlusion, vertical dimension and defects were considered in assessing dental prosthesis functionality. Greater variance of hue (VOH) of the chewing gum and lower swallowing thresholds (worse masticatory function) was associated with edentulous using CD in only one jaw. Older adults wearing dental prostheses with poor occlusion and vertical dimensions presented worse masticatory function. Dental prosthesis stability was associated with lower VOH values. Higher number of chewing cycles while eating peanuts was associated with non-broken dental prosthesis use. Edentulous participants using CD in only one jaw and non-functional dental prosthesis use negatively affect the masticatory function of nursing home residents.

Comparison of smartphone-camera and conventional flatbed scanner images for analytical evaluation of chewing function.

The two-colour mixing test is a quick method to assess chewing function (CF). The use of smartphone cameras for acquiring images may help in further simplifying the process. This study evaluated the reliability of smartphone-camera images of chewing gums to assess CF. Five test samples of a bicoloured chewing gum were produced by a single fully dentate adult volunteer. The specimens were flattened to 1-mm thick wafers. The two sides of the wafers were digitised with a conventional flatbed scanner (control) and were photographed 20 times using 8 different smartphones. The images were assessed optoelectronically to obtain the variance of hue (VoH) and subjectively by visual assessment (SA) using a categorical scale (SA1-SA5). Spearman's correlation and regression models were used for statistical analyses. The intra-group variability for SA1-SA3 was <1% for all smartphones, but significantly higher than controls for SA4 and SA5 (smartphone: SA4=5.57%; SA5=8.76%; control: SA4=2.5%; SA5=0.79%). VoH was progressively lower from SA1 to SA5 for all imaging devices (r>-.97; P<.001). VoH comparisons between control and smartphone images revealed significant differences for the individual SA categories, and however, the magnitude of differences was small and non-significant when the full range of SA levels were considered. The linear mixed model regression showed significant effects for all the smartphones (P<.001) and SA levels (P<.001) in relation to the flatbed scanner values. Smartphone cameras may be used to evaluate colour mixture for a bolus-kneading test, however, the precision is lower with higher degrees of colour mixing.

Quantitative Evaluation of Masticatory Performance with Two-Color Mixing Ability Test: Development of a New Digital Method.

To develop a new digital method for color-mixing analysis and to evaluate the validity of this method for quantifying masticatory performance. Specimens of red-green (RG) chewing gum were prepared as a bicolor test food. A total of 300 specimens were masticated by 20 healthy volunteers for different numbers of mastication cycles (from 1 to 25). The boluses were flattened and scanned, and the digital images were analyzed using ImageJ software. Two parameters (spatial and value) of color mixing were measured, and multiple regression analysis was performed to estimate the number of mastication cycles. The estimated number of mastication cycles that the healthy reference cohort needed to achieve a certain degree of color mixing was proposed as the mastication index (MI). The validity of this method was assessed using Pearson correlation between the MI and concurrent measurements with ViewGum software (variance of hue) within a group of 10 healthy subjects and 10 complete denture wearers. Independent samples t test showed a significant difference in MI between healthy subjects and denture wearers (P < .001). A significant correlation was observed between the MI and ViewGum outcomes (r = -0.95, P < .001). The new proposed method proved to be valid and has the potential for evaluating masticatory performance in both research and clinical settings.

Stabilizing Removable Partial Dentures by Immediate or Delayed Loading of Mini-implants: Chewing Efficiency in a Randomized Controlled Clinical Trial.

The aim of this investigation was to compare the chewing efficiency after immediate and delayed loading of mini-implants that served as supplementary support for removable partial dentures (RPDs). In this four-center randomized trial, patients who had RPDs in arches with unfavorable tooth distributions, ie, no canine and at most two posterior teeth in one or both quadrants, received strategic mini-implants with ball abutments. The mini-implants in group A were loaded immediately either by housings with O-rings (insertion torque ≥ 35 Ncm) or by soft relining material (insertion torque < 35 Ncm). In group B, the RPDs were only hollowed over the balls. After 4 months, the soft relined RPDs and all RPDs of group B received the housings. Masticatory efficiency was evaluated with a validated mixing ability test of two-colored chewing gum before surgery and 14 days, 4 months (before housing pickup), 4.5 months, and 12 months after surgery. The circular variance of hue was the measure of mixing. From 76 participants with 79 RPDs, 38 each were randomly allocated to group A or B. In group A, the housings in six participants were picked up immediately, and the remaining RPDs were primarily soft relined. There was a significant group difference only after 4 months. The mixing ability was better after immediate loading than after delayed loading (P < .0001). In group B, the chewing efficiency was notably deteriorated after the RPDs were hollowed over the ball abutments. However, immediately after all housings were picked up, the chewing efficiency in both groups was substantially improved, and the variance of hue values after 1 year were very similar in the groups. The chewing performance can be improved by inserting supplementary mini-implants under existing RPDs with unfavorable tooth support. This improvement occurred faster by immediate loading than by delayed loading.

The effects of prosthetic status and dementia on the chewing efficiency of seniors in nursing homes.

The oral health of seniors in nursing homes is compromised. Furthermore, reduced chewing efficiency is described to be associated with reduced cognition. However, studies investigating how prosthetic status affects the chewing efficiency of nursing home residents are not available. To evaluate associations between prosthetic status, dementia and chewing efficiency of seniors in nursing homes. This study was performed in ninenursing homes. In addition to assessing the general and medical data of the participants, a dental examination was assessed and the severity of dementia was evaluated by use of the Clinical Dementia Rating (CDR). Furthermore, chewing efficiency was assessed by use of a two-colour mixing ability test. Descriptive and bivariate statistics, as well as linear regression models with the dependent variable chewing efficiency and possible confounders, were used to analyse data at P<.05. Complete target variables of 146 participants were analysed. The mean (SD) chewing efficiency of the study sample, as expressed by the variance of hue, was .590(.250). The type of prosthesis used (P<.001), the number of occluding tooth pairs (P<.001) and the presence of dementia (P=.002) were the main variables significantly affecting chewing efficiency. The condition of removable dentures also had an effect (P=.016). Multivariate testing predominantly confirmed these associations. The chewing efficiency of seniors in nursing homes is somewhat compromised. Beyond dental aspects, suffering from dementia seems to reduce the chewing efficiency. Further interventional/longitudinal studies are, however, encouraged to verify this outcome.

Changes in masticatory performance of edentulous patients treated with single-implant mandibular overdentures and conventional complete dentures.

The aim of this study was to test the effect of a single-implant mandibular overdenture (SIMO), compared with conventional complete denture (CD), on masticatory performance measured by the mixing ability of a two-coloured chewing gum. A sample of edentulous subjects was randomly assigned to the SIMO (n=15) and CD (n=19) groups. Patients in both groups received a set of new complete dentures, and the SIMO group received a single implant in the symphyseal region of the mandible (Straumann® Standard Plus SLActive®) and an eliptical matrix and ball attachment for denture retention. Masticatory tests were performed using a two-colour chewing gum (Vivident Fruitswing, Perfetti van Melle, Turkey) for 20 and 50 chewing cycles. Colour-mixing ability was assessed by electronic colourimetric analysis (ViewGum©, Dhal Software, Greece), expressed by the variance of hue. Tests were performed at baseline and at the 6- and 12-month follow-ups. Multilevel linear regression was used to model the changes in masticatory performance. Groups were similar at baseline for 20 and 50 cycles (P>0.05). A significant linear effect was observed on time points for 20 and 50 cycles (P<0.001). No difference was observed between treatment groups factor (P>0.05). However, the way masticatory performance varied according to time points differed in the CD and SIMO groups for 20 cycles (P=0.048). Masticatory performance improved significantly after 12months, irrespective to the insertion of a single implant to retain a mandibular overdenture. Moreover, results suggest that SIMO treatment may perform better than CD in the shorter follow-up period.

Validation of a purpose-built chewing gum and smartphone application to evaluate chewing efficiency.

To validate a purpose-built two-coloured chewing gum (Hue-Check Gum® ), and to test the accuracy of a custom-built smartphone application for a colour-mixing ability test to assess chewing function. Fully dentate participants (28D-group) and edentulous participants with implant overdentures (IOD-group) were recruited. They chewed a Hue-Check Gum® for 5, 10, 20, 30 and 50 chewing cycles, respectively. Maximum voluntary bite force (MBF) was assessed with a digital gauge. The specimens were analysed according to their colour mixture (variance of hue, VOH) with a validated software (VOH_scan) and a newly developed smartphone application (VOH_app). Participants segregated by dental state were significantly different regarding the number of occluding pairs of teeth, age and MBF. VOH_scan showed a negative logarithmic association with the number of chewing cycles, and VOH could be predicted from chewing cycles, MBF and gender. The clearest discrimination between the IOD and the 28D groups was observed for n=20 chewing cycles; at this point, VOH was distinguishably different with a P-value<0.0001. The VOH_app was a very good predictor for VOH_scan with 0.80<pseudo-R2 <0.83, depending on light exposure and measuring distance. There was, however, a systematic error in the accuracy of the app for inadequately chewed specimens. The use of the two-coloured chewing gum would provide a fast, simple and inexpensive method for the assessment of masticatory performance, which could be used in geriatric wards or in private practices without the requirement of specialised equipment or trained staff.

Masticatory efficiency of implant‐supported removable partial dental prostheses in patients with free fibula flap reconstructed mandibles: A split‐mouth, observational study

The aim of this split-mouth study was to evaluate the masticatory efficiency in patients with segmentally reconstructed mandibles using free fibula flaps, with and without stabilizing osteosynthesis material in-situ during implant placement for rehabilitation with implant-supported removable partial dental prostheses (ISRPDPs). Ten participants (n=10; ♀=2, ♂=8; mean age=38.1years) consented to participate in this study. The participants' normal side (Side N) of the mandible served as the control side, for comparing the masticatory efficiency of the segmentally reconstructed and rehabilitated side (Side R). Masticatory efficiency was evaluated using the two-colored chewing gum test, measured as subjective assessment (SA) and electronically evaluated variance of hue (VOH). Data were checked for normal distribution and statistically analyzed with the level of significance set to p<0.05. Thirty-four tissue-level implants were placed in reconstructed mandibles of 10 participants. There was no significant difference observed in the masticatory efficiencies between Side N and Side R, in both subjective and electronic assessments. No implant loss was observed after a post-rehabilitated mean follow-up period of 42.7months, revealing an implant survival rate of 100%. In patients with surgically reconstructed mandibles, a normal masticatory function can be successfully achieved with a rehabilitation of the reconstructed side with implant-supported removable partial dental prostheses. Implant-supported prostheses should be actively advocated in patients with reconstructive surgeries to restore their masticatory function, extend their food choices, and improve their overall oral health-related quality of life.

Visual perception of surface wetness

We can visually recognize a variety of surface state. Just a quick look is sufficient to find the bath floor is dry, the road in front is slippery, the window glass is frosty, or the ornament is dusty. If a given surface state perception relies on the analysis of diagnostic image features, an effective strategy to reveal those features and the associated visual processing is to find a stimulus transformation that alters the apparent surface state. Here we report an image transformation that makes dry objects look wet. This wet filter consists of two operations: (1) Tone-remapping with an accelerating nonlinear function that renders the intensity histogram positively skewed: (2) color saturation enhancement. In an experimental test, we applied the wet filter to a variety of natural textures of the McGill Calibrated Colour Image Database. The results of a wetness rating experiment showed that the wet-filtered images were perceived as wetter than the original images. In addition, the perceived wetness depended on the variance of hue. The wet-filter was less effective for images with a small variance of hue. Optically, wetting a surface tends to increases the specular reflection. In addition, as the incoming light scatters repeatedly within the surface liquid layer, the light going out from the surface tends to be darker and more saturated. The effects of these optical changes can be simulated by the two wet-filter operations. However, positively skewed luminance histogram and high chromatic saturation may be caused by other factors - for instance, the visual scene may happen to include highly saturated glossy objects. This is presumably why hue variation matters. If the same image transformation simultaneously occurs in many different objects, the brain infers that the change likely has the same cause, such as water shower in the present case. Meeting abstract presented at VSS 2015. Language: en

A novel colourimetric technique to assess chewing function using two-coloured specimens: Validation and application

ObjectivesChewing efficiency may be evaluated using cohesive specimen, especially in elderly or dysphagic patients. The aim of this study was to evaluate three two-coloured chewing gums for a colour-mixing ability test and to validate a new purpose built software (ViewGum©). MethodsDentate participants (dentate-group) and edentulous patients with mandibular two-implant overdentures (IOD-group) were recruited. First, the dentate-group chewed three different types of two-coloured gum (gum1–gum3) for 5, 10, 20, 30 and 50 chewing cycles. Subsequently the number of chewing cycles with the highest intra- and inter-rater agreement was determined visually by applying a scale (SA) and opto-electronically (ViewGum©, Bland–Altman analysis). The ViewGum© software determines semi-automatically the variance of hue (VOH); inadequate mixing presents with larger VOH than complete mixing. Secondly, the dentate-group and the IOD-group were compared. ResultsThe dentate-group comprised 20 participants (10 female, 30.3±6.7 years); the IOD-group 15 participants (10 female, 74.6±8.3 years). Intra-rater and inter-rater agreement (SA) was very high at 20 chewing cycles (95.00–98.75%). Gums 1–3 showed different colour-mixing characteristics as a function of chewing cycles, gum1 showed a logarithmic association; gum2 and gum3 demonstrated more linear behaviours. However, the number of chewing cycles could be predicted in all specimens from VOH (all p<0.0001, mixed linear regression models). Both analyses proved discriminative to the dental state. ConclusionViewGum© proved to be a reliable and discriminative tool to opto-electronically assess chewing efficiency, given an elastic specimen is chewed for 20 cycles and could be recommended for the evaluation of chewing efficiency in a clinical and research setting. Clinical SignificanceChewing is a complex function of the oro-facial structures and the central nervous system. The application of the proposed assessments of the chewing function in geriatrics or special care dentistry could help visualising oro-functional or dental comorbidities in dysphagic patients or those suffering from protein-energy malnutrition.

Minimizing eyestrain on a liquid crystal display considering gaze direction and visual field of view

Recently, it has become necessary to evaluate the performance of display devices in terms of human factors. To meet this requirement, several studies have been conducted to measure the eyestrain of users watching display devices. However, these studies were limited in that they did not consider precise human visual information. Therefore, a new eyestrain measurement method is proposed that uses a liquid crystal display (LCD) to measure a user’s gaze direction and visual field of view. Our study is different in the following four ways. First, a user’s gaze position is estimated using an eyeglass-type eye-image capturing device. Second, we propose a new eye foveation model based on a wavelet transform, considering the gaze position and the gaze detection error of a user. Third, three video adjustment factors—variance of hue (VH), edge, and motion information—are extracted from the displayed images in which the eye foveation models are applied. Fourth, the relationship between eyestrain and three video adjustment factors is investigated. Experimental results show that the decrement of the VH value in a display induces a decrease in eyestrain. In addition, increased edge and motion components induce a reduction in eyestrain.

Memory Representation of Object Colours

Memory colours, ie colours recalled in association with familiar objects, impose a powerful constraint on colour appraisal of images of natural scenes. The purpose of this study is to specify the memory representation of one particular object colour. To this end, the colour of a banana was manipulated by varying hue-angle and saturation in the CIELUV colour space. Subjects' task was to rate the similarity in colour of the resulting banana samples displayed on the screen to the typical ripe banana stored in their mind. In order to examine the dependence of memory colour on texture information and context, three ways of presentation were used: original (banana among other fruit), isolated (the same banana against a homogenous gray background), and contour (silhouette of the banana with its average colour against the gray background). The relationships between the similarity judgments and chromaticity coordinates of the manipulated banana-represented points in the CIELUV colour space is described by a bivariate normal distribution with four parameters: two means and two variances of the Gaussians on the hue and saturation dimensions. For all three types of presentation, the variance of hue is significantly smaller than the variance of saturation; this suggests that memory description of hue is more precise than that of saturation. The data show systematic differences in the hue of memory colour between the original, isolated, and contour presentations of the banana. A model describing the hue shift in terms of illuminant and surface information content in the images is discussed.