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PubMedDate not supplied

Indicators of mandibular dental crowding in the mixed dentition.

PURPOSE: Dental crowding occurring in the anterior part of the mandible in the early mixed dentition has been a subject of increasing concern for child patients, their parents, and the pediatric dentist. The aim of this study was to evaluate indicators of crowding found at the primary dentition, which may lead to the future manifestation of crowding at the anterior part of the mandibular arch in the early mixed dentition. METHODS: Skeletal and dental morphological characteristics at the stage of primary dentition were compared between two groups, using dental casts and cephalograms of 23 subjects. These two groups had been formed by evaluating the degree of crowding at 9 years of age (12 normal and 11 crowded cases). RESULTS: The size of several teeth in the crowding group was significantly greater than that found in the normal group. For the cephalometric measurements, a statistically significant difference was found only in the cranial base dimension (S-SE). The stepwise discriminant analysis showed that the mesiodistal size of the maxillary primary canine, the maxillary and mandibular dental arch lengths, and the posterior cranial base length (S-Ba) were effective discriminators in separating the two groups. CONCLUSIONS: It is concluded that larger primary tooth size is the chief indicator in the development of dental crowding. However, the maxillary and mandibular dental arch lengths and the cranial base dimensions, especially that of the posterior cranial base length in the primary dentition, should also be considered as indicators when attempting to predict dental crowding in the early mixed dentition.

Case-Control Studies↗
PubMed2006

Effect of the lower third molars on the lower dental arch crowding.

Increasing lower dental arch crowding with the age is a recognized clinical problem, and one that has become more apparent in recent years as more adults retain their teeth longer. One of the theories is that the erupting third molars push anterior teeth forward and cause their crowding. On the other hand, a number of studies found no correlation between lower third molars and lower incisor crowding. Because of all these contrasting findings this study was started to re-evaluate correlation between third molars presence and lower dental arch crowding. The study group consisted of 91 subjects with an average age 21.01+/-4.13 years. The individual, quantitative and cast-based analytical registration of crowding was based on the measurements of mesiodistal width of teeth and related to the length of the appropriate segment of the lower dental arch. No statistically significant third molar presence-specific differences were recorded in the lower dental arch crowding between the groups with erupted, unerupted and agenesis of third molars. Although differences between the groups were not statistically significant, some tendency for crowding in the anterior part of lower dental arch was more expressed in the groups with the presence (erupted 0.57 mm and unerupted 0.74 mm) of third molars, than with agenesis (surplus space 0.03 mm). Nevertheless, the present study do not provide enough evidence to incriminate third molars as being the only or even major etiologic factor in the late lower dental arch crowding.

Adolescent↗
PubMed1986

The relationship of dental crowding to tooth size, dental arch width, and arch depth.

This study was undertaken to answer the question, "Are there any differences in the mesiodistal tooth diameters, dental arch width and dental arch depth between the crowded and noncrowded dentitions?" The materials submitted for study consisted of the Orthoscan intraoral occlusograms of 89 subjects with well-aligned dentition and those of 74 subjects with gross dental crowding. The tooth size and arch dimensions were measured from these intraoral occlusograms. The data were subjected to statistical treatment for comparison of noncrowded and crowded groups. The findings in this study lead to the following conclusions: The mesiodistal tooth diameters of the crowded group were significantly larger than those of the noncrowded group. The dental arch widths of the crowded group were significantly smaller than those of the noncrowded group. No substantial or significant difference in dental arch depth between the crowded and noncrowded subjects could be noted. From these findings it seems that tooth size and dental arch width are determining factors in the formation of dental crowding. Clinically, these results suggest that in the treatment of dental crowding, extraction of teeth and/or expansion of dental arches should be considered depending on what is the main causative factor.

Adolescent↗
PubMed1995

Current controversies in late incisor crowding.

Although the terminology is mildly controversial, late incisor crowding (tertiary crowding, late secondary crowding, post-adolescent crowding) is widely regarded as a normal maturation event which is likely to affect most individuals to some extent. Disagreement arises when attempts are made to quantify the change and to predict the timing of the crowding. Most young adults experience some degree of loss of incisor alignment, usually near the anticipated emergence time for the third molars, and almost characteristically it is the lower anterior teeth which best demonstrate the phenomenon. Unfortunately, the physiological crowding changes are frequently confused with orthodontic treatment relapse. Greater controversy surrounds the aetiology of the undesirable crowding changes and despite many attempts we are still not in the enlightened position of explaining, predicting or preventing the problem (except by permanent retention). It is illogical to assume a single cause as the beguilingly simple observation of crowding belies the complexity of possible interacting factors. Perhaps it is a capricious combination of: tooth size and arch form; facial growth pattern (differential soft tissue and skeletal maturation); continuing late growth rotations; cumulative effects of resting, functional and parafunctional soft tissue pressures; lack of compensating attrition; and an ill-defined, mesially acting force emanating from the back of the dental arch. Many theories have attempted to resolve the mystery of the mesially acting force, including: pressure from erupting third molars; an inherent mesial migration; continuing mesial and occlusal dental drifting; maturation and contraction of periodontal soft tissues (particularly the transseptal fibres); the anterior component of occlusal forces; and the lower anterior arch contracting influence of the incisor overbite.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Rat cortical morphology following crowded-enriched living conditions.

This experiment studied cerebral cortical morphology in rats living in a crowded-enriched condition. Three groups of 60-day-old, male Long-Evans rats were divided accordingly: 12 rats, 3 per small cage (32 X 20 X 20 cm), standard colony condition; 12 rats in a single, large, enrichment cage with "toys" (70 X 70 X 45 cm), enriched condition; and 36 rats in a large, single, enrichment cage with "toys", crowded-enriched condition. Matched toys for the two enriched cages were changed twice a week at the time of cage cleaning. Measurements on 20-micron, transverse brain sections showed that in both the crowded-enriched and enriched groups the thickness of the medial occipital cortex increased by 4 to 6% compared with the cortex from animals in the standard colony condition. In addition, the crowded-enriched group demonstrated a 4% (P less than 0.05) increase in thickness in area 39 in the left hemisphere compared with the standard control. However, the thickness in area 39 in the crowded group was not significantly different from that of the enriched area 39. These results indicate that the cortex increases in thickness as much with "crowding" and enrichment as with enrichment alone. We hypothesize that diversion through interaction with "toys" mitigates the stress of crowded conditions.

Animals↗
PubMed1985

Crowding pregnant mice affects attack and threat behavior of male offspring.

Attack and threat behavior of adult male offspring of female mice crowded during the final third of pregnancy was investigated. In 5-min test pairings with an anosmic "standard opponent" which had 50 microliter of male mouse urine applied to its fur, the prenatally stressed group of males showed significantly less attack behavior; attack latency was longer and number of attacks, bites, amount of time spent attacking, and composite aggression scores were all lower, compared with the control group. Similarly, less threat behavior was observed in offspring from crowded dams; there were lower frequencies of tail rattles, rough grooms, and upright threats. Additionally, proportionally fewer males in the prenatally stressed group attacked or displayed threats. A second experiment was designed to investigate the effects of exogenous androgen on the aggressiveness of males from crowded mice: testosterone propionate administration (500 micrograms/animal/day, for 5 days prior to testing) abolished differences both in the proportion of males from crowded mice that fought and also apparently abolished differences in intensities of attack and threat behavior between groups. However, trends toward reduced aggression in prenatally crowded males remained. More detailed analysis of these responses, based only on animals that displayed aggression, revealed significantly reduced intensity of aggression in offspring from females crowded during pregnancy, indicating that testosterone propionate therapy did not completely restore this behavior. In order to reduce postnatal effects due to possible differences in mothering, all offspring were fostered to untreated mothers at birth. The results are discussed in terms of in utero exposure of male fetuses of crowded dams to stress-liberated adrenal steroids of maternal origin, and the possible consequences for the endocrine integrity of these offspring.

Aggression↗
PubMed2004

Emergency department crowding and thrombolysis delays in acute myocardial infarction.

STUDY OBJECTIVE: We estimate the effect of emergency department (ED) crowding on door-to-needle time for patients given intravenous thrombolysis for suspected acute myocardial infarction. METHODS: This was a retrospective observational study of patients thrombolyzed in the ED for suspected acute myocardial infarction in 1998 to 2000 in 25 community and teaching hospital EDs in Ontario. EDs located close together and sharing a common ambulance diversion system were grouped into networks consisting of 2 to 5 hospitals each. At patient registration in an ED, the ambulance diversion status of all EDs in the network was determined. Network crowding was calculated as the percentage of EDs that were diverting ambulances on patient registration, categorized as none (0%), moderate (<60%), and high (> or =60%). Door-to-needle time was defined as time from ED registration to drug administration. Multivariable quantile regression and logistic regression were carried out; covariates included age, sex, ECG characteristics, previous acute myocardial infarction, vital signs, time of presentation, and hospital type. RESULTS: A total of 3,452 thrombolysis patients were included: mean age was 62.9 years, and 73% were male patients. Overall median door-to-needle time was 43 minutes (interquartile ratio 27 to 80). Median door-to-needle time was 40, 45, and 47 minutes in conditions of none, moderate, and high network crowding, respectively ( P <.001). The adjusted odds ratios for door-to-needle time delay (>30 minutes) and major delay (>60 minutes) were 1.32 (95% confidence interval [CI] 0.98 to 1.79) and 1.40 (95% CI 1.12 to 1.75), respectively, for high network crowding compared with none, and 1.21 (95% CI 0.89 to 1.63) and 1.06 (95% CI 0.86 to 1.29), respectively, for moderate crowding compared with none. In multivariate analyses, moderate and high crowding conditions were associated with increased median door-to-needle time (3.0 minutes [95% CI 0.1 to 6.0] and 5.8 minutes [95% CI 2.7 to 9.0], respectively). CONCLUSION: ED crowding is associated with increased door-to-needle times for patients with suspected acute myocardial infarction and may represent a barrier to improving cardiac care in EDs.

Aged↗
PubMed2004

Immobilization and cold stress affect sympatho-adrenomedullary system and pituitary-adrenocortical axis of rats exposed to long-term isolation and crowding.

Changes in plasma levels of noradrenaline (NA), adrenaline (A), adrenocorticotropic hormone (ACTH) and corticosterone (CORT), as well as in cytosol glucocorticoid receptor (GR) and heat shock protein 70 (Hsp 70) in hippocampus of adult rat males exposed to two long-term types of psychosocial stress, both under basal conditions and in response to immobilization and cold as heterotypic additional stressor were studied. Long-term isolation produced a significant elevation of basal plasma ACTH and CORT levels, but did not affect that of NA and A, while long-term crowding conditions did not elevate the basal plasma levels of these hormones. Long-term isolation of rats exposed to 2 h of immobilization or cold led to a significant elevation of plasma NA, A and CORT in comparison with the controls. Long-term crowding conditions and exposure of animals to immobilization or cold also resulted in an increased plasma NA, A and CORT levels, but to a lesser extent in comparison with the long-term isolation. At the same time, plasma ACTH was significantly more elevated in long-term crowded than in long-term isolated rats. Both kinds of long-term psychosocial stresses (isolation and crowding) had similar but less pronounced effects on cytosol GR and Hsp 70 concentrations in hippocampus comparing to acute immobilization and cold stress. It seems that long-term psychosocial stresses attenuate the effects of an additional stress on hippocampal GR and Hsp 70 concentrations. These data suggest that individual housing of rats appear to act as a stronger stressor than crowding conditions. When the animals suffering a long-term isolation were exposed to either acute immobilization or cold, a stronger activation of the sympatho-adrenomedullary system (SAS) was recorded in comparison with that found in the long-term crowded group subjected to short-term immobilization or cold. No significant differences in the activity of hypotalamo-pituitary-adrenal (HPA) axis were observed between long-term isolated and long-term crowded rats.

Adrenal Cortex↗
PubMed1991

Emergency departments and crowding in United States teaching hospitals.

STUDY OBJECTIVES: To assess the extent and distribution of hospital and emergency department crowding nationally. DESIGN: The research design consisted of a mailed questionnaire disseminated in the fall of 1988 to the member institutions of the National Association of Public Hospitals (NAPH) and the Council of Teaching Hospitals (COTH). TYPE OF PARTICIPANTS: Study participants included hospital administrators and ED directors from 239 of the non-Veterans Administration, general acute care, US members of COTH and NAPH. MEASUREMENTS: Key measures of hospital and ED crowding including mean ED holding times for floor and ICU beds. MAIN RESULTS: Three fourths of responding hospitals reported increases in ED visits over the preceding three years. Mean ED holding times for admitted patients were 3.5 hours (median, 2.0 hours) for a floor bed and 2.9 hours (median, 1.5 hours) for an ICU bed. Half of all hospitals noted maximum waits for floor and ICU beds of ten hours or more and seven hours or more, respectively. Measures taken by hospitals to manage crowding during August 1988 included restricting access to some types of patients (mean, 3.6 days), actively transferring patients to other hospitals (mean, 2.2 days), transfer refusal (mean, 2.8 days), and total ambulance diversion (mean, 1.6 days). CONCLUSIONS: Our study strongly suggests that ED crowding is not an isolated phenomenon; ED crowding and its attendant problems appear to affect hospitals with similar adverse effects regardless of ownership. Although our results suggest that ED crowding is concentrated in metropolitan areas and in a smaller subset of hospitals, we found instances of crowding among hospitals nationwide.

Bed Occupancy↗
PubMed1976

The experience of crowding: a two-factor theory.

It was proposed that the experience of crowding occurs in a two-step process: First, the individual becomes aroused by violations of his personal space, and then he attributes the cause of this arousal to other people in his environment. Based on this model it was predicted that violations of personal space rather than simple density is the spatial variable associated with crowding. Further, it was predicted that the experience of crowding can be alleviated if the individual is distracted from making the attribution that his arousal is caused by other people. In order to test these prediction, interaction distance (close and far) and density (high and low) were varied separately. In addition, for half of the conditions, pictures (attribution inhibitors) were placed on the walls of the experimental room, and in the other half, the walls were bare. Subjects worked on two tasks and were then questioned about their experience of crowding. The results showed that interaction distance was more closely related to crowding than was density and that the addition of pictures reduced the experience of crowding only in the close interaction conditions. The results were interpreted as supporting the attribution analysis of crowding.

Arousal↗
PubMed1986

Pituitary gonadal function in adult male rats subjected to crowding.

The effect of crowding on the pituitary-gonadal axis was studied in adult male rats. Crowding reduced body weight gain, did not alter relative adrenal weight and increased relative testis weight. Neither basal levels of corticosterone nor its response to acute stress were altered by crowding. Likewise, LH secretion was similar in control and crowded rats. Prolactin levels tended to be lower in crowded than control rats, but they did not reach statistical significance. In contrast, impaired testosterone secretion was observed in crowded rats, at least in part due to reduced Leydig cell responsiveness to gonadotropin release. In addition, some mechanisms other than pituitary-adrenal hyperactivity might be responsible for reduced testosterone secretion during crowding.

Adrenal Glands↗
PubMedDate not supplied

Household crowding and reproductive behavior.

Ethological studies suggest that animal populations that live in crowded conditions display a number of behaviors that tend to limit the size of the population, such as aberrant forms of sexual behavior, small litter sizes, a higher incidence of spontaneous abortion, ineffectual maternal care, and even cannibalism of their young. Studies of household crowding in North America cities have produced only modest and selective evidence that crowding has similar effects among humans. In this paper, we examine the effect of household crowding on marital sexual relations, on desire for additional children, and on fetal and child loss in Bangkok, Thailand, a city with a much wider range of household crowding than is typically found in North America. In spite of the wider range, and higher mean level of crowding, we find that both the objective and subjective dimensions of crowding have only modest selective effects on sexual and reproductive behavior.

Adult↗
PubMed2003

Effect of cyclooxygenase inhibitors on the CRH-induced pituitary-adrenocortical activity during crowding stress.

The aim of the present study was to determine the effect of social stress and significance of prostaglandins (PG) generated by constitutive and inducible cyclooxygenase (COX-1 and COX-2) in the stimulation of hypothalamic-pituitary-adrenal (HPA) axis by corticotropin releasing hormone (CRH) under basal and social crowding stress conditions. The stressed rats were crowded in groups of 24 to a cage for 3 or 7 days, whereas the control animals were haused in groups of 7 to a cage of the same size. The activity of HPA axis was determined by measuring plasma ACTH and serum corticosterone levels 1 h after i.p. CRH administration. Inhibitors of COX-1, piroxicam (0.2, 2.0, and 5.0 mg/kg), and COX-2, compound NS-398 (0.2 and 2.0 mg/kg), were administered i.p. 15 min prior to CRH (0.1 microg/kg i.p.) to control or crowded rats. The obtained results indicate that social stress for 3 and 7 days markedly intensifies the stimulatory action of CRH on ACTH secretion. Neither piroxicam nor NS-398 induce any significant effect on the CRH-elicited ACTH and corticosterone secretion in non-stressed or crowded rats. Therefore, PG generated by COX-1 or COX-2 do not participate to a significant extent in the stimulation of HPA axis by CRH under either basal conditions or during crowding stress. These results also indicate that the stimulatory action of CRH on ACTH secretion is not only completely resistant to desensitization but is sensitized during social crowding stress. The results contrast with a significant involvement of PG in the vasopressin-induced stimulation of HPA response during crowding stress.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Molecular crowding reduces to a similar extent the diffusion of small solutes and macromolecules: measurement by fluorescence correlation spectroscopy.

Aqueous environments in living cells are crowded, with up to >50 wt% small and macromolecule-size solutes. We investigated quantitatively one important consequence of molecular crowding--reduced diffusion of biologically important solutes. Fluorescence correlation spectroscopy (FCS) was used to measure the diffusion of a series of fluorescent small solutes and macromolecules. In water, diffusion coefficients (D(o)w) were (in cm2/s x 10(-8)): rhodamine green (270), albumin (52), dextrans (75, 10 kDa; 10, 500 kDa), double-stranded DNAs (96, 20 bp; 10, 1 kb; 3.4, 4.5 kb) and polystyrene nanospheres (5.4, 20 nm diameter; 2.3, 100 nm). Aqueous-phase diffusion (Dw) in solutions crowded with Ficoll-70 (0-60 wt%) was reduced by up to 650-fold in an exponential manner: Dw = D(o)w exp (-[C]/[C]exp), where [C]exp is the concentration (in wt%) of crowding agent reducing D(o)w by 63%. FCS data for all solutes and Ficoll-70 concentrations fitted well to a model of single-component, simple (non-anomalous) diffusion. Interestingly [C]exp were nearly identical (11+/-2 wt%, SD) for diffusion of the very different types of macromolecules in Ficoll-70 solutions. However, [C]exp was dependent on the nature of the crowding agent: for example, [C]exp for diffusion of rhodamine green was 30 wt% for glycerol and 16 wt% for 500 kDa dextran. Our results indicate that molecular crowding can greatly reduce aqueous-phase diffusion of biologically important macromolecules, and demonstrate a previously unrecognized insensitivity of crowding effects on the size and characteristics of the diffusing species.

Diffusion↗
PubMed2000

No correlation between primary mandibular anterior crowding and vertical craniofacial configuration or lower incisor inclination.

The aim of the present study was to evaluate the correlation between primary mandibular anterior crowding and vertical craniofacial configuration or sagittal lower incisor inclination. The collective comprised 100 consecutive patients (50 males, 50 females) subject to 4 selection criteria: mandibular anterior crowding > or = 1.0 mm, no previous orthodontic therapy, completely preserved deciduous canines and molars, and lateral cephalograms of good diagnostic quality before initiation of orthodontic treatment. Study casts of all patients were used to measure the mesiodistal width of the incisors and deciduous canines as well as the anterior arch circumference. The difference between the 2 represented the amount of crowding. On all cephalograms 16 parameters of vertical craniofacial configuration and 9 parameters of lower incisor inclination were measured. For error evaluation all measurements were repeated independently on 10 randomly selected study casts and cephalograms. This error amounted for the combined tooth width to 0.51% +/- 0.81, for arch circumference to 0.03% +/- 0.68, and for all cephalometric parameters to 0.38% +/- 4.81. For all parameters, arithmetic means, standard deviations and ranges were calculated. Further, correlation coefficients were calculated between anterior crowding and all 25 cephalometric parameters. The arithmetic mean of crowding was m = 2.0 +/- 1.3 mm with a range of 1.0 to 6.6 mm. The values of all cephalometric parameters were close to well accepted norms in the literature. The correlation coefficients between crowding and all cephalometric parameters varied from r = 0.0 to 0.3. According to this study there is no correlation between primary mandibular anterior crowding and vertical craniofacial configuration or sagittal lower incisor inclination.

Cephalometry↗
PubMed2004

A quantitative approach for measuring crowding in the dental arch: Fourier descriptors.

Dental crowding is defined as a discrepancy between tooth size and jaw size that results in a misalignment of the tooth row. Proposed reasons for crowding include excessively large teeth, small jaws, and a combination of both. Nevertheless, the parameters that would allow the prediction of crowding have not been identified. This study compared the shape of crowded and uncrowded dental arches, matched for size and sex. The application of elliptical Fourier functions (EFFs) provided an accurate numeric description of the dental arch form. Dental casts from the Nihon University School of Dentistry at Matsudo, Chiba, Japan, were studied. Group I, the control group, consisted of 118 dental cast pairs (49 female, 69 male, aged 20.40 +/- 1.68 years [mean +/- SD]) with little or no crowding. Group II, which exhibited crowding, consisted of 78 dental cast pairs (64 female, 14 male, aged 19.67 +/- 4.95 years). From photographs, a set of 24 homologous points describing the tooth row was identified. These points were then fitted with EFFs. Each maxillary and mandibular outline was subsequently standardized for size by scaling the bounded area to a constant 10,000 mm(2). These "shape only" data were used to assess differences between arches in the 2 groups. By multivariate analysis of variance, statistically significant shape differences between groups I and II were obtained for both arches. Patients with crowding exhibited more variability than did the controls. This variability was illustrated with canonical axes derived from discriminant function analysis.

Adolescent↗
PubMed1986

The importance of peer group ("crowd") affiliation in adolescence.

Many researchers have speculated about the role peer groups play in adolescent development, but few have examined teenagers' own perspective on the importance of group affiliations. The two studies reported here, involving 1,300 7th to 12th graders in three Midwestern U.S. communities, assessed teenagers' valuation of belonging to a "crowd" as well as the reasons they cited to support or oppose crowd affiliation. The importance of crowd affiliation declined across age. Younger adolescents generally favored membership, emphasizing the crowd's ability to provide emotional or instrumental support, foster friendships and facilitate social interaction. Older respondents expressed dissatisfaction with the conformity demands of crowds and felt their established friendship networks obviated the need for peer group ties. The importance of crowd affiliation was not related to the strength of respondents' sense of identity but did vary significantly with their willingness to conform to peers and the centrality of their position in peer groups or the type of crowd to which they belonged. Findings emphasized that adolescent peer groups can serve multiple functions, whose salience shifts with age.

Adolescent↗
PubMed2002

Molecular crowding regulates the structural switch of the DNA G-quadruplex.

Almost all biochemical reactions in vitro have been investigated through numerous experiments conducted in dilute solutions containing low concentrations of solutes. However, biomacromolecules such as nucleic acids, proteins, and polysaccharides are designed to function and/or form their native structures in a living cell containing high concentrations of biomacromolecules, substrates, cofactors, salts, and so on. In the present study, we have demonstrated quantitatively the effect of molecular crowding on structures and stabilities of the G-quadruplex of d(G(4)T(4)G(4)). Molecular crowding with poly(ethylene glycol) (PEG) induced a structural transition from the antiparallel to the parallel G-quadruplex of d(G(4)T(4)G(4)), while molecular crowding with polycations did not alter the structure of the antiparallel G-quadruplex. The binding constants of putrescine, one of the polycations, for d(G(4)T(4)G(4)) in the absence and presence of Na(+) are calculated to be 277 and 2.5 M(-)(1), respectively. This indicates that the polycations coordinate to d(G(4)T(4)G(4)) with electrostatic interactions. The thermodynamic parameters of the antiparallel G-quadruplex formation under the crowding and noncrowding conditions induced by putrescine were also estimated. The stability of the antiparallel G-quadruplex decreased (-DeltaG degrees (25) decreased from 28 to 22 kcal mol(-)(1)) with molecular crowding by putrescine. Also, enthalpy and entropy changes in the structural formation under crowding and noncrowding conditions clearly showed that destabilization was entropy-driven. These quantitative parameters indicated that both the volume excluded by PEG and chemical interactions such as electrostatic interaction with solute polycations are critical for determining how molecular crowding affects the structure and stability of highly ordered DNA structures.

Animals↗