Dental shade matching using a digital camera.

OBJECTIVES: Digital cameras could be substitutes for contact-type instruments in shade selection and overcome their drawbacks. The images taken show morphology and color texture of teeth. A new method was proposed to compare the color of shade tabs taken by a digital camera using appropriate color features. METHODS: Vita 3D-MASTER shade guide and Canon EOS 1100D digital camera were employed. Shade tab images were compared in two reference strategies. The color of tooth surface was presented by a content manually cropped out of the image. The content was divided into 10 × 2 blocks to encode the color distribution. Color features from commonly used color spaces were evaluated. The top n matches were selected when the least n shade distances between the shade tabs were attained. RESULTS: Using Sa*b* features, the top one accuracy was 0.87, where the feature S is defined in HSV color space, a* and b* features are defined in L*a*b* color space. This rate was higher than previous reports using contact-type instruments. The top three matching accuracy was 0.94. CONCLUSIONS: Sa*b* were suitable features for shade matching using a digital cameras in this study. Both the color and texture of the tooth surface could be presented by the proposed content-based descriptor. Clinical use of digital cameras in shade matching became possible. CLINICAL SIGNIFICANCE: This in vitro study proposed a method for shade matching using digital cameras through the comparisons of the color patterns on the shade tab surfaces. The method overcame some drawbacks from the devices such as colorimeters or spectrophotometers. The results supported the use of digital cameras in shade matching.

An intention driven hand functions task training robotic system.

A novel design of a hand functions task training robotic system was developed for the stroke rehabilitation. It detects the intention of hand opening or hand closing from the stroke person using the electromyography (EMG) signals measured from the hemiplegic side. This training system consists of an embedded controller and a robotic hand module. Each hand robot has 5 individual finger assemblies capable to drive 2 degrees of freedom (DOFs) of each finger at the same time. Powered by the linear actuator, the finger assembly achieves 55 degree range of motion (ROM) at the metacarpophalangeal (MCP) joint and 65 degree range of motion (ROM) at the proximal interphalangeal (PIP) joint. Each finger assembly can also be adjusted to fit for different finger length. With this task training system, stroke subject can open and close their impaired hand using their own intention to carry out some of the daily living tasks.

Extracellular matrix stability of primary mammalian chondrocytes and intervertebral disc cells cultured in alginate-based microbead hydrogels.

Three-dimensional alginate constructs are widely used as carrier systems for transplantable cells. In the present study, we evaluated the chondrogenic matrix stability of primary rat chondrocytes and intervertebral disc (IVD) cells cultured in three different alginate-based microbead matrices to determine the influence of microenvironment on the cellular and metabolic behaviors of chondrogenic cells confined in alginate microbeads. Cells entrapped in calcium, strontium, or barium ion gelled microbeads were monitored with the live/dead dual fluorescent cell viability assay kit and the 1,9-dimethylmethylene blue (DMB) assay designed to evaluate sulfated glycosaminoglycan (s-GAG) production. Expression of chondrogenic extracellular matrix (ECM) synthesis was further evaluated by semiquantitative RT-PCR of sox9, type II collagen, and aggrecan mRNAs. Results indicate that Ca and Sr alginate maintained significantly higher population of living cells compared to Ba alginate (p < 0.05). Production of s-GAG was similarly higher in Ca and Sr alginate microbead cultures compared to Ba alginate microbeads. Although there was no significant difference between strontium and calcium up to day 14 of culture, Sr alginate showed remarkably improved cellular and metabolic activities on long-term cultures, with chondrocytes expressing as much as 31% and 44% greater s-GAG compared to calcium and barium constructs, respectively, while IVD cells expressed 63% and 74% greater s-GAG compared to calcium and barium constructs, respectively, on day 28. These findings indicate that Sr alginate represent a significant improvement over Ca- and Ba alginate microbeads for the maintenance of chondrogenic phenotype of primary chondrocytes and IVD cells.

Aging and mfERG topography.

AIM: To study the effect of aging retina on the multifocal electroretinogram (mfERG). METHODS: A total of 18 young subjects (age 18-24 years) and 36 elderly subjects (aged 60-85 years) with intraocular lenses (IOLs) were recruited for this study. No subjects had significant eye diseases or media opacities. mfERG was measured in standard conditions using the VERIS system (version 4.1). There were three groups of 18 subjects: (1) 18-25 years, (2) 60-70 years, and (3) 75-85 years. mfERG responses were grouped into central, paracentral, and peripheral regions for analysis. The N1 amplitude, P1 amplitude, N1 latency, and P1 latency of the first-order responses were analysed. RESULTS: Age had no effect on P1 latency, N1 amplitude, and P1 amplitude; however, N1 latencies from central to peripheral regions were significantly longer for group 3 than for group 1. CONCLUSIONS: This study suggests that measured age-related decreases in mfERG responses are due to optical factors (decrease in retinal light levels, scatter) before the age of 70 years, but neural factors significantly affect mfERG topography after the age of 70 years.

The detection of small relative simulated field defects using multifocal VEPs.

INTRODUCTION: The multifocal visual-evoked potential (mfVEP) has been widely used in the study of diseases of the visual system. However, the sensitivity of the mfVEP in the objective detection of relative field defects has not been determined. This study investigates variations in mfVEP responses while simulating relative field defects by using different luminous transmission masks [neutral density (ND) filters] on the stimulus pattern. METHODS: Simulated relative field defects with four different luminous transmissions were obtained by using 0.2, 0.4, 0.6, and 0.8 ND filters, 5 degrees in size, at two different retinal eccentricities (10 and 16 degrees) on a standard mfVEP dartboard stimulus. Eleven normal subjects were recruited for mfVEP measurements. The response amplitudes and latencies of the N1 and P1 of the mfVEP, with and without small simulated relative field defects, were compared. RESULTS: The mfVEP amplitudes of N1 and P1 decreased substantially when 0.6 and 0.8 ND filters were introduced. The effects were similar at both the 10- and 16-degree eccentricities but there was no change in latency with simulated field defects at either location. CONCLUSIONS: The mfVEP can detect a simulated relative field defect 5 degrees in size starting with 0.6 log unit reduction in luminance at both 10-degree and 16-degree eccentricities. This illustrates that the sensitivity of the mfVEP measurement is nearly comparable with that of the Humphrey Visual Field Analyser.

Smoking cessation among Hong Kong Chinese smokers attending hospital as outpatients: impact of doctors' advice, successful quitting and intention to quit.

To identify factors affecting current smokers' intention to quit smoking and factors associated with successful quitting among ex-smokers in Hong Kong. A cross-sectional survey of Chinese patients attending medical and surgical Specialist Outpatient Clinics (SOPCs) of public hospitals in Hong Kong, using a structured questionnaire. Results of the 642 respondents, 21% were current smokers, 9% were ex-smokers and 69% were non-smokers. 74% of the smokers reportedly received quitting advice from doctors. Among the current smokers, past quitting attempts, receiving information from sources other than doctors, believing that doctor's advice was useful, believing that all smokers should quit smoking and a positive attitude towards quitting were associated with intention to quit. Among those who had attempted to quit, being older (aged 50 or above), being retired/unemployed and consuming more than 10 cigarettes per day were associated with successful quitting. We found that advice from doctors on quitting smoking did not have any impact on Chinese smokers quitting or future intention to quit and reflect the inadequacy of advice given by Hong Kong doctors. The predictors of intention to quit and successful quitting identified in the study could be used to design future smoking cessation services.

Effects of different degrees of cataract on the multifocal electroretinogram.

AIM: To study the effect of different degrees of nuclear cataract on the multifocal electroretinogram (mfERG). METHODS: mfERGs were recorded from 30 elderly subjects with very mild, mild, or moderate nuclear cataracts using a VERIS System (version 4.1). The subjects were divided into three groups (10 in each group) according to their degree of nuclear cataracts as classified according to the Lens Opacities Classification System III (LOCS III). No subjects had any significant eye disease or degenerative changes except for cataracts. The mfERG responses were grouped into six concentric rings for analysis. Both the N1 and P1 amplitudes and the latencies of N1 and P1 of first-order responses were used for analysis. RESULTS: Amplitudes of N1 and P1 from the central retina (14 degrees) were significantly reduced in patients with mild or moderate cataract when compared with subjects with very mild cataract. However, there was no significant reduction of N1 and P1 amplitudes in the para-central retina (14-40 degrees). There was no difference in the latencies of N1 and P1 in these three groups of subjects. CONCLUSIONS: The mfERG responses from the central retina (central 14 degrees) were affected by the severity of cataract, but responses from the paracentral retina (14-40 degrees) were not affected. This suggests that in interpreting the mfERG in subjects with mild or moderate cataract subjects some care should be taken as reduced amplitudes (N1 and P1) will be expected from the central retina.

The detection of small simulated field defects using multifocal VEPs.

INTRODUCTION: The multifocal visual-evoked potential (mfVEP) has been widely investigated in the study of diseases of the visual system. However, the sensitivity of the mfVEP in objective detection of field defects has not been determined. This study investigates the variation of the mfVEP responses whilst simulating field defects by using different sizes of mask on the stimulus pattern. METHODS: Simulated field defects of four different sizes (2, 3, 5, and 7 degrees) at two different eccentricities (10 and 16 degrees) were generated on a standard mfVEP dartboard stimulus using opaque masks. These masks were placed at the centre of each dartboard sector and the modified stimuli were used to elicit mfVEPs from 10 normal subjects. The response densities and latencies of N1, P1 of the mfVEP were compared, without and with small simulated field defects. RESULTS: The minimum size of simulated field defect causing significant response density reduction in P1 and N1 was 5 degrees at both retinal eccentricities. N1 showed similar reduction in response density at both retinal eccentricities, but P1 showed larger reduction at the 10-degree location than at the 16-degree location. There was no change in latencies with simulated field defect at either location. CONCLUSIONS: The mfVEP is only sensitive to a simulated field defect equal to or larger than 5 degrees in diameter, and mfVEP has greater sensitivity at 10-degree eccentricity than at 16-degree eccentricity.

Effect of inhaled preservatives on asthmatic subjects. II. Benzalkonium chloride.

Benzalkonium chloride has been used as a preservative in some antiasthma respirator solutions and is known to cause bronchoconstriction in asthmatic subjects. To increase understanding of how it causes bronchoconstriction, the characteristics of airway response in 28 asthmatic subjects were documented. Subjects inhaled histamine, in doses ranging from 0.03 to 7.8 mumol, or benzalkonium in doses ranging from 0.04 to 5.33 mumol on separate days. The dose of histamine or benzalkonium that caused a 20% fall in the 1-s forced expiratory volume (PD20FEV1) was measured. All subjects responded to histamine, with PD20FEV1 values in the range of 0.14 to 7.8 mumol and 17 responded to benzalkonium, with PD20FEV1 values in the range 0.35 to 5.55 mumol. Subjects who responded to benzalkonium were more sensitive to histamine (mean PD20FEV1 0.44 mumol) than subjects who did not respond (mean PD20FEV1 1.84 mumol) and, among the benzalkonium responders, there was a significant correlation between PD20FEV1 values for histamine and benzalkonium (r = 0.5, p less than 0.05). Inhalation of benzalkonium enhanced subsequent responses to histamine, causing a decrease in mean PD20FEV1 from 0.51 to 0.18 mumol histamine (p less than 0.001), but did not alter subsequent responses to benzalkonium. The response to benzalkonium reached a maximum 1 min after inhalation and was slow to recover, taking up to 60 min to return to baseline values. Response to benzalkonium was inhibited by 8 mg cromolyn sodium but not by 160 micrograms ipratropium bromide. The characteristics of the response to benzalkonium suggest a mechanism of action via release of mediators.