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PubMed1987

Periodontal status of secondary crowded mandibular incisors. Long-term results after orthodontic treatment.

The present study was undertaken to examine whether secondary crowded mandibular incisors experience more periodontal breakdown than aligned lower incisors long-term after orthodontic treatment. Patients from 19 to 35 years after active treatment were selected. 2 groups were established: 1 with crowded mandibular incisors and 1 with aligned incisors. The groups were matched according to age, time after treatment, gender and periodontal disease classification. A separate group with crowded and aligned incisors within the same individual was established. Accumulation of plaque, gingival inflammation, probing pocket depth and probing attachment level were registered at 6 locations around each incisor. Among the patients studied, the oral hygiene level was high. In both groups, the loss of connective tissue attachment was largely due to periodontal pocket formation in interproximal areas and gingival retraction in buccal and lingual areas. A small but statistically significant difference in probing attachment level was found between crowded and aligned interproximal areas within the same individual (P less than 0.05). No differences in accumulation of plaque or in gingival inflammation were found. No differences were found for any of the dependent variables between the groups with crowded and aligned incisors.

Adult↗
PubMed1989

Alveolar bone loss and crowding in adult periodontal patients.

The present study aimed to examine whether local crowding and tooth angulation in the mandibular incisor region led to alveolar bone loss in patients with moderate periodontal disease. The sample comprised 27 patients from the Department of Periodontology aged 29-57 yr. Mesiodistal tooth angulation and crowding, defined as an overlap of 2 mm or more, were assessed from dental casts. Alveolar bone loss was assessed from intraoral standardized paralleling radiographs by two methods, the absolute bone level (ABL), recorded from the cementoenamel junction, and the relative bone level (RBL), a new measure, expressing the bone level relative to the two adjacent interradicular crests. Contralateral sites were used as controls. A significant difference in bone level was found between crowded and non-crowded sites by both methods (-1.7 mm, P less than 0.001). This indicates that in periodontal patients local crowding and tooth angulation predisposes to increased bone loss. Analysis of the correlations between tooth angulations and the two measures of bone loss indicated that the RBL value is a more sensitive measure of localized bone loss.

Adult↗
PubMed1994

Macromolecular crowding and confinement in cells exposed to hypertonicity.

The nonideal properties of solutions containing high concentrations of macromolecules can result in enormous increases in the activity of the individual macromolecules. It has been proposed that molecular crowding and confinement occur in cells and are major determinants of the activity of the proteins and other intracellular macromolecules. This concept has important implications for cell volume regulation because, under crowded conditions, relatively small changes in concentration, consequent to alterations of water content, lead to large changes in macromolecular activity. This review considers several aspects of macromolecular crowding and confinement, including: 1) the physical chemical principles involved; 2) in vitro demonstrations of the effects; 3) relation to water activity; 4) estimates of the actual intracellular activity of water and macromolecules; 5) relation to osmotic regulation in various types of cells, including bacteria, red blood cells, and complex nucleated cells; and 6) the relation to inorganic ions and organic osmolytes in cells stressed by hypertonicity. We conclude that, while there is compelling evidence for important effects of molecular crowding in vitro and in red blood cells, the role of macromolecular crowding and confinement in osmotic regulation of more complex cells is an open question that deserves the extensive attention it is currently receiving.

Animals↗
PubMed2000

Macromolecular crowding as a cell volume sensor.

UNLABELLED: The non-ideal properties of solutions containing high concentrations of macromolecules can result in enormous increases in the activity of the individual macromolecules. There is considerable evidence that macromolecular crowding and confinement not only occur in cells, but that these are major determinants of the activity of the proteins and other intracellular macromolecules. This concept has important implications for cell volume regulation because, under crowded conditions, relatively small changes in concentration, consequent to alterations of water content, lead to large changes in macromolecular activity which could provide a mechanism by which cells sense changes in their volume. This brief review considers 1) direct demonstrations that introducing a high concentration of appropriate macromolecules into cells in vitro produced volume regulatory changes, 2) the physical chemical principles involved in the effects of crowding of macromolecules on their activity, 3) estimates of the actual intracellular activity of macromolecules, 4) a proposed model of how changes in macromolecular crowding could signal volume regulation in cells, and 5) brief consideration of the complexities introduced by interactions between macromolecules, water and cosolutes. CONCLUSIONS: The hypothesis that macromolecular crowding provides a mechanism by which cells sense changes in their volume is plausible and is supported by striking observations in red blood cell ghosts and perfused barnacle muscle cells. However, the signaling molecules involved have not been identified, the proposed model is not fully consistent with the experiments, experimental verification in intact cells is lacking, and numerous alternative or additional mechanisms are not excluded.

Cell Size↗
PubMed2006

Multiple diffusion mechanisms due to nanostructuring in crowded environments.

One of the key questions regarding intracellular diffusion is how the environment affects molecular mobility. Mostly, intracellular diffusion has been described as hindered, and the physical reasons for this behavior are: immobile barriers, molecular crowding, and binding interactions with immobile or mobile molecules. Using results from multi-photon fluorescence correlation spectroscopy, we describe how immobile barriers and crowding agents affect translational mobility. To study the hindrance produced by immobile barriers, we used sol-gels (silica nanostructures) that consist of a continuous solid phase and aqueous phase in which fluorescently tagged molecules diffuse. In the case of molecular crowding, translational mobility was assessed in increasing concentrations of 500 kDa dextran solutions. Diffusion of fluorescent tracers in both sol-gels and dextran solutions shows clear evidence of anomalous subdiffusion. In addition, data from the autocorrelation function were analyzed using the maximum entropy method as adapted to fluorescence correlation spectroscopy data and compared with the standard model that incorporates anomalous diffusion. The maximum entropy method revealed evidence of different diffusion mechanisms that had not been revealed using the anomalous diffusion model. These mechanisms likely correspond to nanostructuring in crowded environments and to the relative dimensions of the crowding agent with respect to the tracer molecule. Analysis with the maximum entropy method also revealed information about the degree of heterogeneity in the environment as reported by the behavior of diffusive molecules.

Biophysics↗
PubMed2004

On the relations between crowding and visual masking.

To study the question of which processes contribute to crowding and whether these are comparable to those of visual temporal masking, we varied the stimulus onset asynchrony (SOA) between target and flankers in a crowding setting. Monotonically increasing Type A masking functions observedfor small spacings and large eccentricities indicate that the integration of information from target and flankers underlies crowding. Decreasing masking functions obtained for large spacings and small eccentricities relate processes of crowding to those contributing to Type B masking. In addition, Type B masking was more frequent with letter-like nonletter flankers than with letter flankers, suggesting that Type B masking, just like crowding over large areas, is due to higher level interactions. The rapid decrease of the effects of interletter spacing and eccentricity with increasing SOA indicates that positional information is transient.

Fixation, Ocular↗
PubMed1999

The prevalence of crowding, attrition, midline discrepancies and premature tooth loss in the primary dentition of children in Jeddah, Saudi Arabia.

The aim of the present study is to evaluate the prevalence of crowding, attrition, midline discrepancies and premature loss of primary molars in primary dentition of children resident in Jeddah, Saudi Arabia. Five hundred and two (502) children aged 4-6 years old residing in the city of Jeddah, Saudi Arabia provide the data for the analysis. Crowding was found in 14.7% of the subjects crowding in the maxilla occurred in 27 (5.4%) of the children, and 67 (13.4%) in the mandible. Simultaneous crowding in maxilla and mandible was present in 20 (3.98%) of the subject. The prevalence of crowding was significantly higher in the mandible than the maxilla (P > 0.01) and higher in male (P < 0.05). Midline shift was present in 10% of the children with females showing a significantly higher prevalence than the males (P < 0.001). Attrition was present in 167 (33.3%) of the children. One hundred and sixty children (31.9%) had attrition in enamel, and only 7(1.4%) had attrition, which exposed the dentin. Thirty-one (6.2%) out of 502 children had 51 (0.5%) missing teeth out of total number of 10,040 teeth. Tooth #84 was most commonly lost tooth (P < .025). Overall premature loss of 1st primary molars was found to be significantly higher than 2nd primary molars (P < .001).

Chi-Square Distribution↗
PubMed2005

[Analyses of Pont Index of dental crowding patients and normal occlusion people].

OBJECTIVE: The research aimed to analyze the significance of Pont Index in the dental crowding. METHODS: Respectively selected 91 normal occlusion persons and 101 dental crowding patients, measured every item of Pont Index of these two sample groups, and compared the results. RESULTS: The premolar index and molar index of dental crowding patients were obviously bigger than that of normal occlusion, and there was apparent significant difference. There was no significant gender difference of Pont Index either in normal occlusion or dental crowding patients. Whereas there was significant gender difference of premolar arch width and molar arch width in normal occlusion. CONCLUSION: The occurrence of dental crowding is clearly related to Pont Index.

Bicuspid↗
PubMed2006

Don't bring me your tired, your poor: the crowded state of America's emergency departments.

If the time comes, people expect that the emergency department (ED) will have the resources necessary to treat them in a timely, high-quality manner. Increasingly, however, EDs may not be able to meet that expectation. Hospitals in urban areas with large populations, high population growth, and higher-than-average numbers of uninsured are particularly crowded: ambulances are often diverted to other hospitals and patients are frequently forced to "board" in the hallways (while they wait to be transferred to another facility or part of the hospital). This issue brief places EDs in the context of the U.S. health care system and its economics, discusses existing ED capacity and utilization, where crowding is happening and ways of measuring it, what is causing crowding in EDs, and the consequences of crowding. It highlights a number of potential ways to alleviate crowding at both the health system and the individual hospital level.

Demography↗
PubMedDate not supplied

Management of lower incisor crowding in the early mixed dentition.

This paper describes normal and problem development in lower incisor positioning and offers options for management of crowded cases. The following guidelines were recommended, (1) lower incisor crowding of 2 mm or less and with an intercanine width greater than 28mm will usually resolve spontaneously, (2) lower incisor crowding of 3-4 mm is best managed by discing of the primary dentition, (3) crowding assessment of 5-9 mm requires extraction of primary teeth with probable placement of a supportive lingual arch and, (4) crowding greater than 10 mm requires fixed appliance therapy and careful orthodontic management with attention to the severity of the malocclusion.

Cephalometry↗
PubMed1998

A longitudinal study of the development of crowded dental arch.

It is important to determine both where and when in the process of dental arch development crowding occurs. The authors investigated 81 children (boys/37, girls/44). These children were developing permanent dentition without early loss of deciduous or permanent teeth, which is considered to be one of the causes of malocclusion. Impressions were taken from subjects who had normal, spaced, or crowded permanent dental arch, and longitudinal casts made every two months from three years of age. In both the maxilla and the mandible, the transition to the crowded condition most often occurred (maxillary: 84.6%, mandibular: 64.5%) at the time of eruption. Crowding condition was also caused by the eruption of other teeth; however, this was rare. The maxillary and mandibular crowding mostly occurred (maxillary: 69.2%, mandibular: 77.4%) in the anterior teeth. It was seldom observed in the premolar and first molar regions.

Child↗
PubMed1999

Crowding in central and eccentric vision: the effects of contour interaction and attention.

PURPOSE: To quantify the crowding effect with eccentric stimuli and to determine the relative contribution of neural interaction and attention to crowding in central and eccentric vision. METHODS: Monocular visual acuity was measured with computer-generated tumbling E and Landolt C targets presented centrally or at 2 degrees in the right visual field. Crowding distractors were designed to cause increasing contour interaction or increasing need for focused attention. A four-alternative forced-choice method of constant stimuli was used. In experiment 2 the distance between the target and the distractors was varied. RESULTS: Data are presented in terms of normalized visual acuity. Crowding in central vision was minimal, mainly caused by contour interaction, and did not occur with distractors more than four stroke widths distant. Crowding in eccentric vision was far greater in magnitude and extent (occurring for distractors as far as 16 stroke widths distant) and was caused by contour interaction and attentional factors. CONCLUSIONS: The results indicate that eccentric vision differs quantitatively and qualitatively from central vision. The extent of contour interaction effects are consistent with the proposed size of cortical processing zones. The results are discussed with reference to current theories of preattentive and attentive tasks and with reference to subjects with low vision due to central scotoma who use an eccentric retinal locus for fixation.

Adult↗
PubMed1995

Crowding stress impairs the pituitary-adrenocortical responsiveness to the vasopressin but not corticotropin-releasing hormone stimulation.

To evaluate the effect of social crowding stress on the CRH and vasopressin-induced hypothalamic-pituitary-adrenocortical (HPA) response, both those neuropeptides were administered intracerebroventricularly and intraperitoneally to rats crowded for 3 days. Crowding stress did not affect the corticosterone response to CRH given by either route (1 micrograms i.c.v. or 2 micrograms/kg i.p.) but totally abolished or considerably diminished the response to vasopressin given i.p. (5 micrograms/kg) or i.c.v. (5 micrograms), respectively. Social crowding stress considerably impairs central vasopressin but does not change the CRH-system involved in the HPA stimulation.

Adrenocorticotropic Hormone↗
PubMed1984

Crowding or ACTH treatment of pregnant mice affects adult copulatory behavior of male offspring.

Sexual behavior of male offspring from female mice chronically crowded during Days 12-17 of pregnancy was investigated. In an 80-min test pairing with a sexually experienced female primed with estradiol and progesterone injections, males from crowded mothers displayed poorer copulation than controls: mount and intromission latencies were longer, number of mounts and intromissions lower, and ejaculations within the test period were abolished. Daily injections of 500 micrograms testosterone propionate improved copulatory vigor in offspring from crowded mothers. A second series of experiments investigated the effects of ACTH treatment of females during the same period of pregnancy. A low dose rate (1 IU injected daily) had little effect but male offspring from females injected daily with 8 IU displayed longer intromission latency and fewer mounts and intromissions than controls. Daily injections of 500 micrograms testosterone propionate improved copulatory vigor, although mount frequency remained depressed. The similarity of the effects on male offspring copulation of crowding their mothers during pregnancy or ACTH treatment during pregnancy suggest mediation by similar mechanisms, implicating involvement of maternal pituitary-adrenocortical secretions during pregnancy in the production of these behavioral deficits. Postnatal influences were minimized by fostering all litters at birth to untreated dams.

Adrenocorticotropic Hormone↗
PubMed1984

Effect of crowding on some physiological and behavioral variables in adult male rats.

The effect of two population densities on body weight gain, food and water intake and the weight of some organs and glands was studied in adult male rats. Behavioral reactivity to open field was also assessed. Crowded rats (10 animals per cage) showed lower body weight gain than control rats (3 per cage) throughout all the experimental period. Crowding decreased food intake and increased water intake. Any effect of crowding on the weight of thymus, liver and endocrine glands (except testes) was found. Open field defecation and activity were the same in control and crowded rats. Discrepancies from earlier works could likely be due to methodological differences and these are discussed in the text.

Animals↗
PubMed1986

Stress adaptation and adrenal activity in isolated and crowded rats.

Socially reared male control rats (Co) were compared with crowded reared rats (Cr) and isolated reared rats (I). We assayed the adaptation to moderate stress (activity and defecation rate in open-field test) and to intensive stress sensitivity to restraint ulcer), so as the basal adrenal activity measuring basal values of corticosterone (R.I.A.) and fresh weight of adrenal and thymus glands. Results show a great lack of adaptation to moderate and intensive stress in Cr and I reared rats which leads to a decrease of activity variables, an increase of defecation rates and a high sensitivity to restraint ulcers. The effect of crowding conditions show higher values than isolation. We also found, in isolated and crowded reared rats, an increase in the adrenal function with great values for the basal secretion of corticosterone and atrophy of the thymus gland, besides which, crowded reared animals showed adrenal hypertrophy.

Adrenal Glands↗
PubMed1981

Social crowding enhances aversiveness naloxone in rats.

If endorphins mediate various behavioural states including reactions to stress and social affect, then experimental manipulation of such states should alter the stimulus properties of opioid antagonists. The results of experiments in which the aversiveness of naloxone was increased by chronic environmental stress produced by rearing and maintaining male rats under conditions of severe social crowding, support this theoretical proposition. All rats acquired aversions to flavoured solutions that had been presented for 15 min immediately prior to a systemic injection of naloxone. The degree of the conditioned aversion was greater in rats maintained in crowded conditions. Transferring rats from crowded conditions to individual accommodation 3 weeks before the start of aversive conditioning did not attenuate the increased aversiveness of the antagonist. It is suggested that social interaction under conditions of chronic crowding induces a prolonged increase in the level of tonic activity in endorphinergic systems.

Animals↗
PubMed2006

The effect of crowding on access and quality in an academic ED.

BACKGROUND: Emergency department crowding has the potential to cause undesirable outcomes. We evaluated ED access and provider and patient assessments of quality. METHODS: This multimethod study, done in an urban academic ED, included descriptive analysis of administrative records, paired physician and nurse provider surveys, and pre- or postpatient surveys regarding expectations and experiences. Our outcomes were rates and characteristics of patients who left without being seen (LWBS), provider ratings of crowding/compromised care, and patient satisfaction. RESULTS: During data collection periods, 11743 patients registered, and 9% LWBS. Patients who LWBS tended to be younger than 45 years (relative risk [RR] = 1.7; 95% confidence interval [CI], 1.5-1.9), of nonurgent/stable triage acuity (RR = 3.1; 95% CI, 2.5-3.8), and without insurance (RR = 1.5; 95% CI, 1.3-1.7). Seventy-four percent of all patients had insurance, and 28% were private. Doctors and nurses had 81% agreement (kappa = 0.54) in their assessment of crowded conditions, which were temporally associated with LWBS rates (P < .01). In 47% of 57 shifts, at least 1 provider felt that crowding was compromising quality of care. Of 423 sequential ED waiting room patients approached, 310 (73%) enrolled and 174 (56%) of these completed phone follow-up. On average, patients felt that they should be seen within 1 hour but expected to wait for 2.1 hours. Patient's perceived that wait times on follow-up averaged 3.5 hours, 5+ hours for LWBS patients. Visit satisfaction was inversely related to patient's perceived wait times. CONCLUSIONS: We find that ED crowding increased LWBS rates and patient satisfaction. Systemwide changes in ED organization will be necessary for the ED to fulfill its role as a safety net provider and meet public health needs during disaster surge capacity.

Adult↗