Relationship between masticatory function and frailty in community-dwelling Japanese elderly

BACKGROUND

Frailty likely results in impaired functioning, and frail individuals requiring long-term care have recently attracted the attention of researchers. In the oral health field, the number of elderly individuals who require intervention for retaining occlusion has been increasing, as has the number of remaining teeth and required prosthetic treatment. Additionally, the number of elderly with reduced masticatory function has also been increasing, and frailty is a suspected factor.

AIMS

The aim of this study is to clarify the relationship between frailty and masticatory function decline.

DESIGN

A cross-sectional study.

METHODS

A total of 747 participants (total mean age 73.6 ± 5.8 years old) underwent a comprehensive examination at the Tokyo Metropolitan Institute of Gerontology. Three masticatory functions were evaluated: maximum occlusal force, mixing ability, and self-reported chewing ability. Frailty was determined using all 25 questions of the Basic checklist developed by the Japanese Ministry of Health, Labour and Welfare, following the method reported by Satake et al. RESULTS: Binomial logistic analysis clarified the relationship between frailty and evaluation of each of the three masticatory functions. Significant correlations of pre-frailty or frailty with maximum occlusal force, mixing ability, and subjective chewing ability were observed.

CONCLUSION

All three masticatory functions (maximum occlusal force, mixing ability, and self-reported chewing ability) were associated with pre-frailty or frailty in community-dwelling Japanese elderly.

A 2-year longitudinal study of the relationship between masticatory function and progression to frailty or pre-frailty among community-dwelling Japanese aged 65 and older

BACKGROUND

An association has recently been reported between frailty and reduced masticatory function; however, the causal relationship remains unclear.

OBJECTIVE

The aim of this study was to clarify the relationship between masticatory function and frailty progression.

METHODS

Among 6699 individuals aged 65 and older (mean age 72.8 ± 5.2 years) who were invited to participate in comprehensive medical check-ups, 418 who underwent examinations at the Tokyo Metropolitan Institute of Gerontology in both 2013 and 2015 and who met inclusion criteria were included in this study. Frailty was determined with the Kihon Checklist developed by the Japanese Ministry of Health, Labour and Welfare. The following three masticatory functions were evaluated: occlusal force, mixing ability and subjective chewing ability. The following confounding factors were investigated: age, sex, grip strength, comfortable walking speed, Mini-Mental State Examination (MMSE) score, Self-Rating Depression Scale (SDS) score, skeletal mass index (SMI), number of medications taken and number of remaining teeth. Statistical analysis was performed with binomial logistic regression analysis.

RESULTS

Logistic regression analysis revealed that comfortable walking speed, SDS score, MMSE score and masticatory function were significantly related to progression to frailty or pre-frailty. Of the three masticatory function items evaluated, mixing ability and subjective chewing ability were related to frailty progression.

CONCLUSION

Our results confirm that masticatory function was associated with the progression to pre-frailty or frailty among community-dwelling individuals 65 years and older over the 2-year period of this longitudinal study. Of the masticatory function items evaluated, mixing ability and subjective chewing ability were associated with frailty progression.

Oral hypofunction in the older population: Position paper of the Japanese Society of Gerodontology in 2016

BACKGROUND

There is growing international interest in identifying the effects of ageing on oral health and on appropriate strategies for managing oral disorders. The Japanese Society of Gerodontology (JSG), as the official representative of researchers and clinicians interested in geriatric dentistry in Japan, makes several recommendations on the concept of "oral hypofunction."

AIMS

This study proposes diagnostic criteria and management strategies to reduce the risk of oral hypofunction among older people.

CONCEPTUAL FRAMEWORK

We define oral hypofunction as a presentation of 7 oral signs or symptoms: oral uncleanness; oral dryness; decline in occlusal force; decline in motor function of tongue and lips; decline in tongue pressure; decline in chewing function; and decline in swallowing function. The criteria of each symptom were determined based on the data of previous studies, and oral hypofunction was diagnosed if the criteria for 3 or more signs or symptoms were met.

CONCLUSIONS

We recommend that more evidence should be gathered from clinical studies and trials to clarify our diagnostic criteria and management strategies.

Identification of patterns of factors preceding severe or life-threatening asthma exacerbations in a nationwide study

BACKGROUND

Reducing near-fatal asthma exacerbations is a critical problem in asthma management.

OBJECTIVES

To determine patterns of factors preceding asthma exacerbations in a real-world setting.

METHODS

In a nationwide prospective study of 190 patients who had experienced near-fatal asthma exacerbation, cluster analysis was performed using asthma symptoms over the 2-week period before admission.

RESULTS

Three distinct clusters of symptoms were defined employing the self-reporting of a visual analogue scale. Cluster A (42.1%): rapid worsening within 7.4 hours from moderate attack to admission, young to middle-aged patients with low Body mass index and tendency to depression who had stopped anti-asthma medications, smoked, and hypersensitive to environmental triggers and furred pets. Cluster B (40.0%): fairly rapid worsening within 48 hours, mostly middle-aged and older, relatively good inhaled corticosteroid (ICS) or ICS/long-acting beta-agonist (LABA) compliance, and low perception of dyspnea. Cluster C (17.9%): slow worsening over 10 days before admission, high perception of dyspnea, smokers, and chronic daily mild-moderate symptoms. There were no differences in overuse of short-acting beta-agonists, baseline asthma severity, or outcomes after admission for patients in these 3 clusters.

CONCLUSION

To reduce severe or life-threatening asthma exacerbation, personalized asthma management plans should be considered for each cluster. Improvement of ICS and ICS/LABA compliance and cessation of smoking are important in cluster A. To compensate for low perception of dyspnea, asthma monitoring of peak expiratory flow rate and/or exhaled nitric oxide would be useful for patients in cluster B. Avoidance of environmental triggers, increase usual therapy, or new anti-type 2 response-targeted therapies should be considered for cluster C.

Surface morphology of silicone soft relining material after mechanical and chemical cleaning

PURPOSE

The objective was to investigate the influence of chemical and mechanical cleaning on the surface morphology of a silicone soft relining material.

METHODS

Three plate-shaped specimens were prepared for each group (Control, Hard and Soft) by laminating a 1.5-mm-thick silicone soft relining material. The Control group specimens were stored in water, and the Hard and Soft group specimens were cleaned with hard and soft bristle denture brushes, respectively. Abrasion testing with a toothbrush and immersion testing with an enzyme-containing peroxide denture cleanser were performed, simulating a period of approximately 4 months. The arithmetic mean roughness (Sa) and maximum height of the cross-section (Sz) were measured before and after abrasion and immersion testing.

RESULTS

Sa was 4.9±0.9, 22.1±4.2 and 44.2±4.0μm in the Control, Soft and Hard groups, respectively. Sz was 257.5±31.7, 392.0±23.8 and 452.2±41.9μm in the Control, Soft and Hard groups, respectively. After abrasion testing, Sa and Sz differed significantly between the Soft and Control groups and between the Hard and Control groups. Sa was 2.2±1.2μm before and after immersion, and Sz was 142.1±81.4μm before and after immersion. No significant difference was noted in either Sa or Sz in the Control specimens before or after immersion.

CONCLUSIONS

Surfaces cleaned using a soft bristle brush were less likely to roughen than those cleaned with a hard bristle brush under the conditions of this study. Additionally, chemical cleaning using the enzyme+neutral peroxide denture cleanser did not roughen the surface of the silicone soft relining material.

Influence of the mechanical properties of resilient denture liners on the retention of overdenture attachments

STATEMENT OF PROBLEM

Information is lacking about the selection criteria for silicone resilient denture liners applied as a matrix material for attachments on overdentures.

PURPOSE

The purpose of this in vitro study was to investigate the mechanical properties of silicone resilient denture liners and their influence on the initial retention force of overdenture attachments and the reduction in retention force over time.

MATERIAL AND METHODS

Nine types of silicone resilient denture liner were injected and fixed to the matrix section of an experimental denture base. They were then fitted to an epoxy resin model that simulated the residual ridge with a patrix ball attachment (n=10). The retention force of the denture was measured with a digital force gauge, and the maximum force of traction (N) was regarded as the initial retention force. The retention force reduction (N) after repeated insertion and removal (n=5) was calculated by subtracting the retention force after 3348 cycles (3-year simulated insertion and removal) from the initial retention force. The intaglio of the matrix was observed with a scanning electron microscope (SEM) before and after the 3348 cycles. Four mechanical properties (hardness, strain-in-compression, tensile strength, and arithmetic mean roughness) of the resilient denture liners were measured. One-way ANOVA of the initial retention force of each lining material was performed, followed by the Scheffe test (α=.05). Pearson correlation analysis was used (α=.05) to analyze correlations of the initial retention force with the retention force reduction after insertion and removal and the mechanical properties of each material. Multiple regression analysis with the stepwise method extracted the initial retention force and the retention force reduction as dependent variables, and the resilient denture liner mechanical properties as explanatory variables (α=.05).

RESULTS

The initial retention force of the resilient denture liners was 1.3 to 5.4 N. Multiple comparisons showed significant differences in some groups (P<.05). The retention force reduction of the resilient denture liners was 0.2 to 1.9 N. Multiple regression analysis with the stepwise method extracted hardness and strain-in-compression as explanatory variables for the initial retention force and the retention force reduction.

CONCLUSIONS

Within the limitations of this in vitro study, hardness was found to influence the initial retention force of the overdenture, and strain-in-compression influenced the retention force reduction in the 3-year simulation.

Regulation of Perfusion Pressure during Cardiopulmonary bypass using Sevoflurane

In hypothermic cardiopulmonary bypass (CPB), various vasodilators are used to control the perfusion pressure. These agents, however, often decrease the pressure excessively, and the low perfusion pressure may persist until the end of CPB. In this study we evaluate the safety and characteristics of the regulation of perfusion pressure during CPB using a volatile anesthetic, sevoflurane which has an extremely low partition coefficient. Twenty adult patients who underwent cardiac surgery were studied. Sevoflurane was applied by a vaporizer inserted into the oxygenator gas supply line. Pump flows were fixed at 2.4 L/min/m2 during the hypothermic period. Sevoflurane concentration was adjusted to keep mean arterial pressure (MAP) between 40 and 70 mmHg during CPB. Hemodynamic and metabolic parameters were measured and compared to the group we previously treated with chlorpromazine. In all cases, MAP could be maintained adequately. In the sevoflurane group, systemic vascular resistance indices (SVRI) during the rewarming period and at the end of CPB were higher, and doses of norepinephrine needed at the end of CPB were significantly lower than in the chlorpromazine group. The regulation of perfusion pressure during CPB using sevoflurane was safe and could easily maintain adequate SVRI.

Biodistribution of N-lsopropyl-p-lodoamphetamine in the Rat Brain

The biodistribution of N-isopropyl-p-iodoamphetamine (IMP) was studied in the rat brain.131 l-labelled IMP was injected intravenously in awake animals. Activities in the brain of Sprague-Dawley rats were 2.68–3.22 (% dose/g) in the cortex and 0.59–0.66 (% dose/g) in the white matter at 1 min p. i. Activities in the cortex were slightly increased at 60 min p. i., while activities in the white matter increased markedly at 60 min and 6 h p. i. Therefore, the cerebral cortex-to-white matter ratio decreased from 5 to 1 within 60 min after injection. Autoradiograms of the rat brain at 1–10 min p. i. showed high contrasts. Activities were high in the cortex and low in the white matter, but homogeneous at 60 min – 6 h. IMP seems to be a useful agent for cerebral perfusion imaging in the early phase after injection. Knowledge of biodistribution of this agent is considered to be indispensable for the interpretation of images.

Effect of chewing or compressing food on autonomic nervous activity in older adults

OBJECTIVE

To determine if autonomic nervous activity increases in older people during mastication and how this activity is related to the softness of food. We hypothesised that the coefficient of variation of R-R intervals (CVRR), high-frequency (HF) power, low-frequency (LF) power, LF/HF ratio and total power increase during chewing foods within the range of softness from moderate food to extremely soft food in older adults.

MATERIALS AND METHODS

Participants were 20 older volunteers (71-90 year old). CVRR and HF on the electrocardiogram (ECG) were used as indices of parasympathetic nervous activity. LF and the LF/HF ratio on the ECG were used as indices of sympathetic nervous activity. Total power, reflecting the level of autonomic nervous activity, was also measured. Participants were asked to chew gum with three different degrees of softness, or to compress extremely soft gum between their palate and tongue.

RESULTS

There were significant differences in HF between at resting and all chewing/compressing conditions, but no significant differences relating to food softness. There were significant differences in total power between at resting and all chewing/compressing conditions, but no significant differences relating to food softness. There were no significant differences in LF, LF/HF and CVRR among all conditions.

CONCLUSION

Autonomic nervous activity, especially parasympathetic activity in older adults, increased during chewing and compressing food when compared to activity while at rest. Within the range of food's softness from moderate to extreme soft, food's softness had no measurable effect on autonomic nervous activity.

Psychological stress-relieving effects of chewing - Relationship between masticatory function-related factors and stress-relieving effects

PURPOSE

The objective of the present study was to investigate the relationship between masticatory function-related factors (masticatory performance, occlusal contact area, maximum bite force, number of chewing strokes, and muscle activity) and the stress-relieving effects of chewing.

METHODS

A total of 28 healthy male subjects were instructed to rest or chew for 10min after 30min of stress loading with arithmetic calculations. Their stress state was assessed by measuring salivary cortisol levels. Saliva was collected at three time points: before stress loading, immediately after stress loading, and 10min after stress loading. Compared to resting, chewing produced a significantly greater reduction in the rate of change in salivary cortisol levels 10min after stress loading.

RESULTS

A negative correlation was observed between the rate of decrease in salivary cortisol levels and the number of chewing strokes. No significant correlation was observed between the rate of decrease in salivary cortisol levels and other measurement items.

CONCLUSION

In healthy dentulous people, the number of chewing strokes has been shown to be a masticatory function-related factor that affects stress relief from chewing, suggesting the possibility that more appropriate chewing would produce a greater effect psychological stress relief.

Efficacy and safety of rebamipide liquid for chemoradiotherapy-induced oral mucositis in patients with head and neck cancer: a multicenter, randomized, double-blind, placebo-controlled, parallel-group phase II study

BACKGROUND

Recent preclinical and phase I studies have reported that rebamipide decreased the severity of chemoradiotherapy-induced oral mucositis in patients with oral cancer. This placebo-controlled randomized phase II study assessed the clinical benefit of rebamipide in reducing the incidence of severe chemoradiotherapy-induced oral mucositis in patients with head and neck cancer (HNC).

METHODS

Patients aged 20-75 years with HNC who were scheduled to receive chemoradiotherapy were enrolled. Patients were randomized to receive rebamipide 2% liquid, rebamipide 4% liquid, or placebo. The primary endpoint was the incidence of grade ≥ 3 oral mucositis determined by clinical examination and assessed by central review according to the Common Terminology Criteria of Adverse Events version 3.0. Secondary endpoints were the time to onset of grade ≥ 3 oral mucositis and the incidence of functional impairment (grade ≥ 3) based on the evaluation by the Oral Mucositis Evaluation Committee.

RESULTS

From April 2014 to August 2015, 97 patients with HNC were enrolled, of whom 94 received treatment. The incidence of grade ≥ 3 oral mucositis was 29% and 25% in the rebamipide 2% and 4% groups, respectively, compared with 39% in the placebo group. The proportion of patients who did not develop grade ≥ 3 oral mucositis by day 50 of treatment was 57.9% in the placebo group, whereas the proportion was 68.0% in the rebamipide 2% group and 71.3% in the rebamipide 4% group. The incidences of adverse events potentially related to the study drug were 16%, 26%, and 13% in the placebo, rebamipide 2%, and rebamipide 4% groups, respectively. There was no significant difference in treatment compliance among the groups.

CONCLUSIONS

The present phase II study suggests that mouth washing with rebamipide may be effective and safe for patients with HNC receiving chemoradiotherapy, and 4% liquid is the optimal dose of rebamipide.

TRIAL REGISTRATION

ClinicalTrials.gov under the identifier NCT02085460 (the date of trial registration: March 11, 2014).

Inhibition of denture plaque by TiO2 coating on denture base resins in the mouth

STATEMENT OF PROBLEM

Information is lacking about antiadhesion effect of titanium dioxide (TiO₂) coating on denture base resins in the mouth.

PURPOSE

The purpose of this clinical study was to investigate the antiadhesion effect of TiO₂ coating on denture base resins.

MATERIAL AND METHODS

Ten healthy dentate participants (mean 27 ±2 years of age) participated in this study. Disks and palatal appliances were made with denture base resin. They were divided into 2 groups: a TiO₂-coated group and an uncoated group. A primer and a top coat containing TiO₂ were applied to the surfaces of the resin by means of an air spray. In the denture plaque staining test, resin disks were fixed to the retainer, placed in each participant's mouth for 3 days, and stained with a dental plaque-disclosing solution. The staining rate was calculated. The resin disks and palatal appliances were used to measure the total number of microbes. The resin specimens were placed in each participant's mouth for either 3 or 7 days and swabbed to count the total number of microbes. The chewing gum adherence test was performed both subjectively and objectively. Subjectively, each participant wearing a palatal appliance rated adherence using a visual analog scale. The objective test was performed with a chewing gum adhesion test. The staining rate, the total number of microbes, and the visual analog scale values were statistically analyzed using the Wilcoxon signed rank test, and the adhesive force was statistically analyzed using a Student t test.

RESULTS

In the denture plaque staining test, the measurement of microbes, and the resin chewing gum adherence test results, significant differences were observed between the TiO₂-coated groups and the uncoated groups.

CONCLUSIONS

TiO₂ coating of the denture base acrylic resin inhibited the adhesion of microbes, denture plaque, and highly adhesive food.

Microwave-assisted hydrolysis of biomass over activated carbon supported polyoxometalates

Activated carbon supported polyoxometalates (AC-POMs) were used for acceleration of hydrolysis of biomass under microwave irradiation.

Diabetic peripheral neuropathy and prevalence of erectile dysfunction in Japanese patients aged <65 years with type 2 diabetes mellitus: The Dogo Study

Only limited epidemiological evidence exists regarding the relationship between diabetic neuropathy and erectile dysfunction (ED) among Japanese patients with type 2 diabetes mellitus. To investigate the relationship between diabetic neuropathy and ED among Japanese patients with type 2 diabetes mellitus, a multicenter cross-sectional study was conducted in 287 male Japanese patients with type 2 diabetes mellitus, age (19-65 years). Diabetic neuropathy was diagnosed if the patients showed two or more of the following three characteristics: neuropathic symptoms, decreased or disappeared Achilles tendon reflex and/or abnormal vibration perception. ED, moderate to severe ED, and severe ED were defined as present when a subject had a Sexual Health Inventory for Men score <22, <12 and <8, respectively. The prevalence values of diabetic neuropathy and severe ED were 47.0 and 39.0%, respectively. Diabetic neuropathy was independently positively associated with severe ED, but not ED and moderate ED: the adjusted odds ratio was 1.90 (95% confidence interval: 1.08-3.38). No relationships were found between diabetic retinopathy or diabetic nephropathy and ED. Diabetic neuropathy is positively associated with severe erectile dysfunction among Japanese type 2 diabetes mellitus patients aged <65 years.

Influence of early clinical exposure for undergraduate students on self-perception of different aspects of geriatric dental care: Pilot study between two colleges from Japan and India

Objective:

The objective of this study is to identify the influence of early clinical exposure for undergraduate students on self-perception of different aspects of geriatric dental care.

Materials and Methods:

We have selected two different colleges from Japan and India, namely, Tokyo Dental College (TDC), Tokyo, and Government Dental College (GDC), Nagpur, respectively. The GDC students exposed to patients in a 3^rd year and TDC in the 5^th year of course. Survey of 74 undergraduate students GDC and 95 of TDC was conducted. The questionnaire was developed based on to the 50 points undergraduate curriculum by European College of Gerodontology. The questionnaire categorized into four parts; Part I (15 questions) on aging and medicine, Part II (15 questions) on communication skills, Part III (15 questions) on diagnosis/treatment, and Part IV (5 questions) on need of more training in Gerodontology. Their own-perception on self-knowledge and competency was scored on 4 level scale as 3, 2, 1, and 0 for response yes, rather yes, rather no, and no, respectively. Average scores were calculated and presented.

Results:

The differences of the opinions as per students’ perception level were found to be slightly more affirmative in GDC students (1.9 for the 4^th year and 2 for the 5^th year) than TDC students (1.1 for 5^th grade and 1.5 for 6^th grade). Both clinical and didactic hours should be increased in curriculum according to the TDC (89%) and GDC (79%) students. Separate gerodontology subject is suggested from TDC (76%) to GDC (81%) students.

Conclusion:

Average scores about own-perception of knowledge and competency about aging, medicine, and communication skills were almost same in both GDC and TDC students. With early clinical exposure, GDC students appear have better self-perception regarding the different aspects of the geriatric dental care including subject knowledge, communications, diagnosis, and treatment planning than TDC students with late clinical exposure.

Dynamic helical CT-guided needle localization of non-palpable and mammographically occult breast lesions: Case reports

Dynamic helical CT-guided needle localization of non-palpable and mammographically occult breast lesions is described. Dynamic helical CT-technique enabled fast volume scanning of the whole breast during the early contrast enhancement phase, which provided sufficient contrast to localize the target lesions. The procedures were successfully completed without complications.

Follow-up Study on Intra-Aneurysmal Embolization for Unruptured Cerebral Aneurysms

We describe follow-up clinical and angiographical results in patients with unruptured cerebral aneurysms treated with IDC or GDC. In 28 patients who underwent intra-aneurysmal occlusion for unruptured aneurysms, there were no permanent neurological deficits in the periprocedural period, while three transient neurological deficits were observed.

On the angiograms obtained immediately after the procedure, complete aneurysmal occlusion was achieved in three patients (10.7%), a small neck remnant was detected in two cases (7.1%), a body filling in 12 cases (42.9%) and both of them were detected in 11 patients (39.3%). On the follow up angiograms (median angiographical follow-up period 15.6 months), 46.4% of incompletely obliterated aneurysms showed aneurysmal recanalization, and a incompletely embolized aneurysm ruptured 15 months after initial embolization.

Detachable platinum coil embolization is a safe treatment for unruptured aneurysms with a lower incidence of peri-procedural morbidity, wheareas follow-up results are less satisfactory in cases involving incompletely obliterated lesions. With this limitation in mind, patients need to be very carefully chosen for GDC embolization and strict follow-up angiography is mandatory when a complete embolization is not achieved.

Severe or life-threatening asthma exacerbation: patient heterogeneity identified by cluster analysis

BACKGROUND

Severe or life-threatening asthma exacerbation is one of the worst outcomes of asthma because of the risk of death. To date, few studies have explored the potential heterogeneity of this condition.

OBJECTIVES

To examine the clinical characteristics and heterogeneity of patients with severe or life-threatening asthma exacerbation.

METHODS

This was a multicentre, prospective study of patients with severe or life-threatening asthma exacerbation and pulse oxygen saturation < 90% who were admitted to 17 institutions across Japan. Cluster analysis was performed using variables from patient- and physician-orientated structured questionnaires.

RESULTS

Analysis of data from 175 patients with severe or life-threatening asthma exacerbation revealed five distinct clusters. Cluster 1 (n = 27) was younger-onset asthma with severe symptoms at baseline, including limitation of activities, a higher frequency of treatment with oral corticosteroids and short-acting beta-agonists, and a higher frequency of asthma hospitalizations in the past year. Cluster 2 (n = 35) was predominantly composed of elderly females, with the highest frequency of comorbid, chronic hyperplastic rhinosinusitis/nasal polyposis, and a long disease duration. Cluster 3 (n = 40) was allergic asthma without inhaled corticosteroid use at baseline. Patients in this cluster had a higher frequency of atopy, including allergic rhinitis and furred pet hypersensitivity, and a better prognosis during hospitalization compared with the other clusters. Cluster 4 (n = 34) was characterized by elderly males with concomitant chronic obstructive pulmonary disease (COPD). Although cluster 5 (n = 39) had very mild symptoms at baseline according to the patient questionnaires, 41% had previously been hospitalized for asthma.

CONCLUSIONS & CLINICAL RELEVANCE

This study demonstrated that significant heterogeneity exists among patients with severe or life-threatening asthma exacerbation. Differences were observed in the severity of asthma symptoms and use of inhaled corticosteroids at baseline, and the presence of comorbid COPD. These findings may contribute to a deeper understanding and better management of this patient population.

Comparison of Adhesive Resistance to Chewing Gum among Denture Base Acrylic Resin, Cobalt-Chromium Alloy, and Zirconia

The purpose of this study was to compare the adhesiveness of chewing gum to acrylic resin, cobalt-chromium alloy, and zirconia. Test specimens were fabricated using acrylic resin (resin), cobalt-chromium alloy (Co-Cr), and Ceria stabilized tetragonal zirconia polycrystal-based nanostructured zirconia/alumina composite (zirconia). Specimens of each material were attached to the upper and lower terminals of a digital force gauge. The operator masticated chewing gum, wiped off any saliva, and placed the gum on the lower specimen. The gum was compressed to a thickness of 1 mm between the upper and lower specimens. Thereafter, traction was applied to the upper specimen at a cross-head speed of 100 mm/min under 3 different conditions (dry, wet with distilled water, and wet with artificial saliva) to determine the maximum adhesive strength of the chewing gum. The statistical analysis was performed using the Bonferroni test after a one-way analysis of variance (α=0.05). Under dry conditions, adhesive force was 14.8±6.8 N for resin, 14.0±4.8 N for Co-Cr, and 4.3±2.3 N for zirconia. Significant differences were noted between resin and zirconia, and between Co-Cr and zirconia. When distilled water was applied to the specimen surface, the adhesive strength was 16.8±1.7 N for resin, 8.3±2.1 N for Co-Cr, and 2.7±0.8 N for zirconia. Significant differences were noted between resin and Co-Cr, resin and zirconia, and Co-Cr and zirconia. When artificial saliva was applied to the specimen surface, the adhesive force was 18.5±2.8 N for resin, 5.3±0.8 N for Co-Cr, and 3.0±1.7 N for zirconia. Significant differences were noted between resin and Co-Cr, and resin and zirconia. Chewing gum adhered less strongly to zirconia than to acrylic resin or cobalt-chromium alloy.

Anti-infective control in human bronchiolar epithelial cells by mucin phenotypic changes following uptake of N-acetyl-L-cysteine

PURPOSE

Aspiration pneumonia is infection of the respiratory tract resulting from accumulation of sputum in the larynx. N-acetyl-L-cysteine (NAC) might regulate mucin (MUC) expression and activate inherent anti-infective system in bronchiolar epithelial cells after cellular uptake, and therefore, serve as the preventative agent for chronic lung disease including aspiration pneumonia. The purpose of this in vitro study was to evaluate the effect of uptake of NAC by human bronchiolar epithelial cells on bacterial infection and regulations of mucin expression in association with cellular redox status under co-culture with a representative pathogen for hospital- and community-acquired pneumonia, Streptococcus pneumoniae.

MATERIALS AND METHODS

Human bronchiolar epithelial cells preincubated with or without 20 mM NAC for 3 h were co-cultured with or without bacteria for 8 h and evaluated with respect to cellular redox balance, expressions of various types of MUC, proinflammatory cytokines and mediators, and bacterial infection state by biochemical, genetic, and immunofluorescent assays.

RESULTS

Markedly increased intracellular reactive oxygen species and oxidized glutathione levels plus increased release and expression of proinflammatory cytokines and mediators were observed in cells co-cultured with bacteria. These bacteria-induced cellular redox disturbance and proinflammatory events were prevented and alleviated by pretreatment with NAC. Cells co-cultured with bacteria did not increase expression of anti-infective membranous MUC4 but exhibited increases in gel-forming MUC5AC expression and bacterial infection. However, NAC-pretreated cells avoided bacterial infection along with enhancement of MUC4, but not MUC5AC, expression.

CONCLUSION

Uptake of NAC by human bronchiolar epithelial cells prevented bacterial infection and upregulated membranous, but not gel-forming, MUC expression along with the increase in intracellular antioxidant level under co-culture conditions with S. pneumoniae.