Hydrodynamic Interactions, Hidden Order, and Emergent Collective Behavior in an Active Bacterial Suspension.

Spontaneous self-organization (clustering) in magnetically oriented bacteria arises from attractive pairwise hydrodynamics, which are directly determined through experiment and corroborated by a simple analytical model. Lossless compression algorithms are used to identify the onset of many-body self-organization as a function of experimental tuning parameters. Cluster growth is governed by the interplay between hydrodynamic attraction and magnetic dipole repulsion, leading to logarithmic time dependence of the cluster size. The dynamics of these complex, far-from-equilibrium structures are relevant to broader phenomena in condensed matter, statistical mechanics, and biology.

Tuning bacterial hydrodynamics with magnetic fields.

Magnetotactic bacteria are a group of motile prokaryotes that synthesize chains of lipid-bound, magnetic nanoparticles called magnetosomes. This study exploits their innate magnetism to investigate previously unexplored facets of bacterial hydrodynamics at surfaces. Through use of weak, uniform, external magnetic fields and local, micromagnetic surface patterns, the relative strength of hydrodynamic, magnetic, and flagellar force components is tuned through magnetic control of the bacteria's orientation. The resulting swimming behaviors provide a means to experimentally determine hydrodynamic parameters and offer a high degree of control over large numbers of living microscopic entities. The implications of this controlled motion for studies of bacterial motility near surfaces and for micro- and nanotechnology are discussed.

Characteristics of adult dentally fearful individuals. A cross-cultural study.

This cross-cultural study investigated adult dental fear patients in three countries. A joint intake interview questionnaire and a dental anxiety scale explored the level, background and concomitant factors of dental anxiety among patients at the Universities of Tel Aviv (Israel), Goteborg (Sweden), and Pittsburgh (USA). It was shown that patients at all three sites were quite similar with regard to age, sex, level of dental anxiety (DAS) and avoidance time. Negative emotions were common, with more negative everyday life effects among Swedish patients. Regardless of country, most patients stated that they had always been fearful, but environmental etiologic factors were frequently reported. Swedish patients more often reported both direct and indirect learning patterns than Israeli patients. Patients' motivation for treatment was high, while the belief in getting fear reduction was clearly lower. The most common reason for Israeli patients to seek treatment was a personal decision to try to cope with the situation, while for Swedish patients it was pain. Israeli and US patients preferred more 'active' modes of treatment such as behavioral management therapies, while Swedish patients equally preferred active and more 'passive' treatment approaches such as general anesthesia. Preference for dentist attributes were similar among groups and underlined the strong emphasis that fearful individuals place upon dentists' behaviors and their performance of dentistry.

The craniofacial morphology of bruxers versus nonbruxers.

The purpose of this investigation was to test for an association between the craniofacial morphologies of bruxers and nonbruxers. The sample for this retrospective descriptive comparative study consisted of 28 Caucasian dental school subjects. Sixteen were bruxers and 12 were nonbruxers. The determination of bruxism was based on a six-item questionnaire as well as objective measures of the severity of tooth wear as analyzed from dental casts. Craniofacial morphology was determined directly using anthropometric spreading calipers. Craniofacial measurements included glabella-opiscranion, euryon-euryon, nasion-gnathion, zygoma-zygoma, and gonion-gonion. From these measurements, the following indices were calculated: cephalic (Gla-Op/Eu-Eu), facial (Na-Gla/Zy-Zy), gonial (Zy-Zy/Go-Go), and gonial height (Na-Gla/Go-Go). This study found no differences in the craniofacial morphologies of bruxers and nonbruxers, nor was there a difference in overbite. There was, however, a statistically significant difference in the bizygomatic (Zy-Zy) and cranial (Eu-Eu) widths of bruxers compared with nonbruxers.

Dental splint prescription patterns: a survey.

A random sample of U.S. dentists was surveyed with a mailed questionnaire to determine the number of splints that they fabricated over the preceding year for bruxers, patients with myofascial pain-dysfunction syndrome and patients with TM joint pain. The results indicate that a significant number of dentists treat these disorders with dental splints. Estimates are provided for the dental profession's yearly splint output for each disorder.

Stress, anticipatory stress, and psychologic measures related to sleep bruxism.

This study examined (1) the relationships between electromyographic-measured nocturnal bruxism, self-reported stress, and several personality variables, and (2) the relationship between belief in a stress-bruxism relationship and self-reported stress. One hundred adult bruxers completed a battery of personality questionnaires, indicated whether they believed in a stress-bruxism relationship, presented for a dental examination, and had dental impressions taken. Subsequently, electromyographic measurements of bruxing frequency and duration were recorded for fifteen consecutive nights. Prior to each night's measurements, subjects indicated their levels of stress for the immediately preceding 24 hours. No overall relationship was established between electromyographic measures and the personality variables nor between electromyographic measures and self-reported stress. Correlations between electromyographic measures and self-reported stress were statistically significant for eight individual subjects. Further, subjects with high levels of stress reported more anxiety, irritability, and depression, and less denial. Subjects who believed in a stress-bruxism relationship reported greater stress.

The dentofacial morphology of bruxers versus non-bruxers.

The dentofacial morphology of 35 bruxers was compared with that of 28 non-bruxers. Direct head and facial measurements were made using anthropometric spreading calipers. Cephalic (head width vs. head length), facial (face height vs. face width), and "gonial" (gonial width vs. zygomatic width) indices were calculated, then headform and facial type were determined for all subjects. The findings demonstrated no difference in the dentofacial morphology between bruxers and non-bruxers (Chi square, P < or = 0.05). The predominant craniofacial type and dental morphology of both bruxers and non-bruxers were: dolichocephalic headform, euryprosopic facial type, and Angle Class I dental occlusion.

Reliability and validity of instrumentation used to record nocturnal clenching and/or grinding.

Nocturnal clenching and grinding can be recorded with a portable electromyograph unit and a standard cassette tape recorder, which registers the clenching episodes on a cassette tape. The information can then be coded by a new instrument, called a Pulse Identifier, that subsequently transfers the data to a polygraph chart recorder. This study evaluated the reliability and validity of the Pulse Identifier when interfaced with other instruments that measure nocturnal clenching/grinding. A known number of clenching incidents over a baseline period of time were evaluated by three "blind" scores. The results demonstrated an interscorer reliability coefficient of 0.99 and a validity coefficient of 0.99.

Reliability and validity of a transverse horizontal axis location instrument.

Previous studies have demonstrated a relatively accurate location of the transverse horizontal axis (THA) with several different instrument systems. This study statistically evaluated the reliability and validity of an instrument used to locate a known THA on a mannequin. Three experienced prosthodontists were the subjects. Each operator used 15 mm of interincisal arc to locate the THA. The mandibular stylus was aligned by the investigator with the known horizontal axis. The vertical microdot flags were positioned so the stylus was over a known coordinate and were repositioned so the operator could attempt to locate the axis. The known coordinates were varied with each of four trials. Subjects No. 1 and 3 demonstrated the best coefficient of reliability, 0.25. The 95% confidence interval for linear deviation from the known was 0.44 +/- 0.10 mm on the right side and 0.97 +/- 0.10 mm on the left side. These confidence intervals did not include zero. A statistically better result was achieved on the right side compared with the left side (F1,3 = 131.24, p = 0.0014). The results of this study indicate that a random error factor of 0.3 to 1.2 mm can be expected when this instrument system is used clinically.

Pharmacologic desensitization for dental phobias: clinical observations.

The elimination of the extreme fear reported by dental phobic patients traditionally involves psychologic interventions such as systematic desensitization. Observations resulting from a conscious sedation approach, as outlined in two case histories, suggest that a desensitization phenomena is occurring. This pharmacologic desensitization appears to mimic elements of systematic desensitization. Optimal management of fearful patients may sometimes require conjunctive support from both dental behavioral scientists and dental anesthesiologists.

Methodological considerations concerning the use of Bruxcore Plates to evaluate nocturnal bruxism.

The purpose of this study was to evaluate the Bruxcore Plate (BP) as a dependent measure of nocturnal bruxing activity. As part of a bruxism treatment study, we evaluated 100 nocturnal bruxers for bruxing activity before, during, and immediately after treatment and again at a six-month recall. The first 40 subjects wore both a BP and an EMG (electromyographic) unit for every night of each 14-night evaluation period (baseline; post-treatment; six-month recall). During the treatment period, these subjects wore the EMG unit but no Bruxcore Plates. Another 40 subjects wore the EMG unit and never used Bruxcore Plates. We evaluated a 20-subject no-treatment control group by two methods. Ten control subjects were evaluated with the EMG unit and the BP and another ten with the EMG unit alone. We hypothesized that the BP would not measure the same construct as an accepted EMG measure of bruxing activity, and that the BP would effect changes in EMG measured nocturnal bruxing activity. The results supported the conclusions that the BP did not measure the same construct as the EMG measure, and that the BP did effect changes in nocturnal bruxing activity. Correlations of BP scores with EMG data for equivalent measurement periods were low or non-existent. For the control group and the massed practice (negative practice) treatment group, there were significant interaction effects for EMG-measured bruxing episodes per hour for BP vs. no-BP Groups, with respect to measurement periods (time). Interpretation of these results indicated that BP evaluation of nocturnal bruxing activity was confounded with measurable treatment effects.

A comparison of different treatments for nocturnal bruxism.

One hundred bruxers were evaluated for bruxing activity before, during, and after treatment with a portable electromyograph (EMG). A six-month post-treatment follow-up of bruxing activity was obtained. Experimental treatment groups consisted of diurnal biofeedback, nocturnal biofeedback, massed negative practice, and splint therapy. A no-treatment control group was included. The comparative efficacy of treatments was determined by analyses of variance. Both EMG-measured frequency of bruxing episodes and duration of bruxing activity decreased significantly for nocturnal biofeedback and splint therapy treatments but not for massed negative practice, diurnal biofeedback (relaxation), or the no-treatment control group. The two-week treatment effects were transient, and bruxing activity generally returned to baseline levels when treatment was withdrawn. These findings are consistent with the findings of previous researchers with regard to nocturnal biofeedback and splint therapy but differ from previous findings for massed negative practice therapy.