Impact of providing in-home water service on the rates of infectious diseases: results from four communities in Western Alaska.

Approximately 20% of rural Alaskan homes lack in-home piped water; residents haul water to their homes. The limited quantity of water impacts the ability to meet basic hygiene needs. We assessed rates of infections impacted by water quality (waterborne, e.g. gastrointestinal infections) and quantity (water-washed, e.g. skin and respiratory infections) in communities transitioning to in-home piped water. Residents of four communities consented to a review of medical records 3 years before and after their community received piped water. We selected health encounters with ICD-9CM codes for respiratory, skin and gastrointestinal infections. We calculated annual illness episodes for each infection category after adjusting for age. We obtained 5,477 person-years of observation from 1032 individuals. There were 9,840 illness episodes with at least one ICD-9CM code of interest; 8,155 (83%) respiratory, 1,666 (17%) skin, 241 (2%) gastrointestinal. Water use increased from an average 1.5 gallons/capita/day (g/c/d) to 25.7 g/c/d. There were significant (P-value < 0.05) declines in respiratory (16, 95% confidence interval (CI): 11-21%), skin (20, 95%CI: 10-30%), and gastrointestinal infections (38, 95%CI: 13-55%). We demonstrated significant declines in respiratory, skin and gastrointestinal infections among individuals who received in-home piped water. This study reinforces the importance of adequate quantities of water for health.

Biogeographical Impacts of Dental, Oral, and Craniofacial Microbial Reservoirs.

The human mouth, or oral cavity, is at the crossroads of our external and internal environments, and it is increasingly evident that local colonization of dental, oral, and craniofacial (DOC) tissues and cells by bacteria and viruses may also have systemic effects across myriad diseases and disorders. Better understanding of this phenomenon will require a holistic understanding of host-microbial interactions in both spatiotemporal and biogeographical contexts while also considering person-, organ-, tissue-, cell-, and molecular-level variation. After the acute phase interaction with microbes, the establishment of site-specific reservoirs constitutes an important relationship to understand within the human body; however, despite a preliminary understanding of how viral reservoirs originate and persist across the human body, the landscape of single-cell and spatial multiomic tools has challenged our current understanding of what cells and niches can support microbial reservoirs. The lack of complete understanding impacts research into these relevant topics and implementing precision care for microbial-induced or microbial-influenced diseases. Here, via the lens of acute and chronic microbial infections of the DOC tissues, the goal of this review is to highlight and link the emerging spatiotemporal biogeography of host-viral interactomics at 3 levels: (1) DOC cell types in distinct tissues, (2) DOC-associated microbes, and (3) niche-specific DOC pathologies. Further, we will focus on the impact of postacute infectious syndromes such as long COVID, neurodegenerative disorders, and other underappreciated postviral conditions. We will provide hypotheses about how DOC tissues may play roles systemically in these conditions. Throughout, we will underscore how COVID-19 has catalyzed a new understanding of these biological questions, discuss future directions to study these phenomena, and highlight the utility of noninvasive oral biofluids in screening, monitoring, and intervening to prevent and/or ameliorate human infectious diseases.

A Roadmap for the Human Oral and Craniofacial Cell Atlas.

Oral and craniofacial tissues are uniquely adapted for continuous and intricate functioning, including breathing, feeding, and communication. To achieve these vital processes, this complex is supported by incredible tissue diversity, variously composed of epithelia, vessels, cartilage, bone, teeth, ligaments, and muscles, as well as mesenchymal, adipose, and peripheral nervous tissue. Recent single cell and spatial multiomics assays-specifically, genomics, epigenomics, transcriptomics, proteomics, and metabolomics-have annotated known and new cell types and cell states in human tissues and animal models, but these concepts remain limitedly explored in the human postnatal oral and craniofacial complex. Here, we highlight the collaborative and coordinated efforts of the newly established Oral and Craniofacial Bionetwork as part of the Human Cell Atlas, which aims to leverage single cell and spatial multiomics approaches to first understand the cellular and molecular makeup of human oral and craniofacial tissues in health and to then address common and rare diseases. These powerful assays have already revealed the cell types that support oral tissues, and they will unravel cell types and molecular networks utilized across development, maintenance, and aging as well as those affected in diseases of the craniofacial complex. This level of integration and cell annotation with partner laboratories across the globe will be critical for understanding how multiple variables, such as age, sex, race, and ancestry, influence these oral and craniofacial niches. Here, we 1) highlight these recent collaborative efforts to employ new single cell and spatial approaches to resolve our collective biology at a higher resolution in health and disease, 2) discuss the vision behind the Oral and Craniofacial Bionetwork, 3) outline the stakeholders who contribute to and will benefit from this network, and 4) outline directions for creating the first Human Oral and Craniofacial Cell Atlas.

Use of sport-related concussion information sources among parents of United States middle school children.

OBJECTIVE: Parents may use various information sources to obtain information about sport-related concussions (SRC). This study examined SRC-related information sources used by parents of United States middle school children (age: 10-15 years). METHODS: A panel of 1083 randomly selected U.S. residents, aged ≥18 years and identifying as parents of middle school children, completed an online questionnaire capturing parental and child characteristics, and utilization and perceived trustworthiness of various sources of SRC-related information. Multivariable logistic regression models identified factors associated with utilizing each source. Adjusted odds ratios (OR) with 95% confidence intervals (95%CIs) excluding 1.00 were deemed significant. RESULTS: Doctors/healthcare providers (49.9%) and other healthcare-related resources (e.g., Centers for Disease Control and Prevention, WebMD) (37.8%) were common SRC-related information sources; 64.0% of parents utilized ≥1 of these sources. Both sources were considered "very" or "extremely" trustworthy for SRC-related information among parents using these sources (doctors/healthcare providers: 89.8%; other healthcare-related resources: 70.9%). A 10-year increase in parental age was associated with higher odds of utilizing doctors/healthcare providers (adjusted odd ratio (ORadjusted) = 1.09, 95%CI: 1.02-1.16) and other healthcare-related resources (ORadjusted = 1.11, 95%CI: 1.03-1.19). The odds of utilizing doctors/healthcare providers (ORadjusted = 0.58, 95%CI: 0.40-0.84) and other healthcare-related resources (ORadjusted = 0.64, 95%CI: 0.44-0.93) were lower among parents whose middle school children had concussion histories versus the parents of children who did not have concussion histories. CONCLUSION: One-third of parents did not report using doctors/healthcare providers or other healthcare-related resources for SRC-related information. Factors associated with underutilization of these sources may be targets for future intervention. Continuing education for healthcare providers and educational opportunities for parents should highlight accurate and up-to-date SRC-related information.

Factors associated with concussion-symptom knowledge and attitudes toward concussion care seeking in a national survey of parents of middle-school children in the US.

BACKGROUND: Developing appropriate concussion prevention and management paradigms in middle school (MS) settings requires understanding parents' general levels of concussion-related knowledge and attitudes. This study examined factors associated with concussion-symptom knowledge and care-seeking attitudes among parents of MS children (aged 10-15 years). METHODS: A panel of 1224 randomly selected U.S. residents, aged ≥ 18 years and identifying as parents of MS children, completed an online questionnaire capturing parental and child characteristics. The parents' concussion-symptom knowledge was measured using 25 questions, with possible answers being "yes", "maybe", and "no". Correct answers earned 2 points, "maybe" answers earned 1 point, and incorrect answers earned 0 point (range: 0-50; higher scores = better knowledge). Concussion care-seeking attitudes were also collected using five 7-point scale items (range: 5-35; higher scores = more positive attitudes). Multivariable ordinal logistic regression models identified predictors of higher scores. Models met proportional odds assumptions. Adjusted odds ratios (aORs) with 95% confidence intervals (95%CIs) (excluding 1.00) were deemed statistically significant. RESULTS: Median scores were 39 (interquartile range: 32-44) for symptom knowledge and 32 (interquartile range: 28-35) for care-seeking attitude. In multivariable models, odds of better symptom knowledge were higher in women vs. men (aOR = 2.28; 95%CI: 1.71-3.05), white/non-Hispanics vs. other racial or ethnic groups (aOR = 1.88; 95%CI: 1.42-2.49), higher parental age (10-year-increase aOR = 1.47; 95%CI: 1.26-1.71), and greater competitiveness (10%-scale-increase aOR = 1.24; 95%CI: 1.13-1.36). Odds of more positive care-seeking attitudes were higher in white/non-Hispanics vs. other racial or ethnic groups (aOR = 1.45; 95%CI: 1.06-1.99) and in older parental age (10-year-increase aOR = 1.24; 95%CI: 1.05-1.47). CONCLUSION: Characteristics of middle school children's parents (e.g., sex, race or ethnicity, age) are associated with their concussion-symptom knowledge and care-seeking attitudes. Parents' variations in concussion knowledge and attitudes warrant tailored concussion education and prevention.

Approaching community priorities in youth sports injury prevention research.

BACKGROUND: Research in youth sports is often complex. As interest in youth sports injury prevention grows, scientists should consider community priorities beyond a specific research study. MAIN TEXT: This commentary discusses the authors' personal experiences researching concussion prevention in middle school sports, as the overarching community faced multiple challenges. These challenges included a series of weather-related emergencies that resulted in a shift in the community's priorities, multi-day school closures, and cancellations of sports activities and meetings. We discuss the importance of considering community priorities and providing support as scientists, colleagues, and members of the communities in which we conduct research. CONCLUSION: Scientists should consider the changing circumstances and dynamics surrounding community priorities in order to help drive their research-based decisions and ensure successful and respectful applications of research based on community values and priorities.

Flossing Is Associated with Improved Oral Health in Older Adults.

The effect of preventive oral habits is largely unexplored in older individuals. The purpose of this study was to evaluate the associations between home use of flossing and prevalence of periodontal disease and caries in older adults. Five-year incident tooth loss was also evaluated. Data on 686 individuals ≥65 y-old from the Piedmont 65+ Dental Study were examined including: 1) interproximal clinical attachment level (iCAL), 2) interproximal probing depth (iPD), 3) numbers of caries, and 4) missing teeth. Flossing behavior was evaluated according to the Periodontal Profile Class (PPC) system. Five-year follow-up data (n = 375) was evaluated for incident tooth loss. Dichotomous and categorical variables were analyzed using Pearson chi-square tests as well as covariate-adjusted Cochran-Mantel-Haenszel tests. Multiple linear regression compared clinical parameters based on flossing behavior. Elderly flossers had lower (mean, SE) %iCAL≥3 mm (38.2, 2.38 vs. 48.8, 1.56) and %iPD≥4 mm (8.70, 1.41 vs. 14.4, 0.93) compared to nonflossers (P ≤ 0.005). Flossers showed less coronal caries compared to nonflossers (P = 0.02). Baseline number of missing teeth (mean, SE) was 11.5 (0.35) in nonflossers compared to 8.6 (0.53) in flossers (P < 0.0001). Regular dental visitors had lower oral disease levels compared to episodic dental users. The majority of flossers classified into PPC-Stage I (health) whereas nonflossers classified as PPC-Stages V, VI, and VII (disease). At the 5-y follow-up visit, the average tooth loss for flossers was ~1 tooth compared to ~4 teeth lost for nonflossers (P < 0.0001). Among all teeth, molars showed the highest benefit (>40%) for flossing behavior (P = 0.0005). In conclusion, the extent of oral disease for older individuals was significantly less in flossers than in nonflossers. Flossers showed less periodontal disease, fewer dental caries, and loss of fewer teeth over a 5-y period. These findings further support flossing as an important oral hygiene behavior to prevent oral disease progression in older adults.

fMRI study of brain activity elicited by oral parafunctional movements.

Parafunctional masticatory activity, such as the tooth clenching and grinding that is associated with bruxism, is encountered by clinicians in many disciplines, including dentistry, neurology and psychiatry. Despite this, little is known about the neurological basis for these activities. To identify the brain network engaged in such complex oromotor activity, functional magnetic resonance imaging (fMRI) was used to elucidate the brain activation patterns of 20 individuals (10 males and 10 females, mean s.d. age of 26.3+/-4.1 years) with (parafunctional, PFx group, 5M/5F) and without (normal functional, NFx group, 5 M/5F) self-reported parafunctional grinding and clenching habits during clenching and grinding tasks. Subject group classification was based on: (i) self-reported history, (ii) clinical examination, (iii) evaluation of dental casts and (iv) positive responses to the temporomandibular disorder (TMD) History Questionnaire [Dworkinand LeResche, Journal of Craniomandibular Disorders, (1992) 6:301]. While subjects performed these oromotor tasks, each wore a custom-designed oral appliance minimizing head motion during imaging. Mean per cent signal changes showed significant between group differences in motor cortical (supplementary motor area, sensorimotor cortex and rolandic operculum) and subcortical (caudate) regions. Supplementary motor area data suggest that motor planning and initiation, particularly during the act of clenching, are less prominent in individuals with oromotor parafunctional behaviours. The overall extent of activated areas was reduced in subjects with self-reported parafunctional masticatory activity compared with the controls. This study's methodology and findings provide an initial step in understanding the neurological basis of parafunctional masticatory activities that are relevant for therapeutic research applications of temporomandibular joint and muscle disorders and associated comorbidities.

Transcriptomic profiling of tantalum metal implant osseointegration in osteopenic patients.

OBJECTIVES: The long-term success of dental implants is established by literature. Although clinically well defined, the complex genetic pathways underlying osseointegration have not yet been fully elucidated. Furthermore, patients with osteopenia/osteoporosis are considered to present as higher risk for implant failure. Porous tantalum trabecular metal (PTTM), an open-cell porous biomaterial, is suggested to present enhanced biocompatibility and osteoconductivity. The goal of this study was to evaluate the expression patterns of a panel of genes closely associated with osteogenesis and wound healing in osteopenic patients receiving either traditional titanium (Ti) or PTTM cylinders to assess the pathway of genes activation in the early phases of osseointegration. MATERIAL AND METHODS: Implant cylinders made of Ti and PTTM were placed in osteopenic volunteers. At 2- and 4 weeks of healing, one Ti and one PTTM cylinder were removed from each subject for RT-PCR analysis using osteogenesis PCR array. RESULTS: Compared to Ti, PTTM-associated bone displayed upregulation of bone matrix proteins, BMP/TGF tisuperfamily, soluble ligand and integrin receptors, growth factors, and collagen genes at one or both time points. Histologically, PTTM implants displayed more robust osteogenesis deposition and maturity when compared to Ti implants from the same patient. CONCLUSIONS: Our results indicate that PTTM properties could induce an earlier activation of genes associated with osteogenesis in osteopenic patients suggesting that PTTM implants may attenuate the relative risk of placing dental implants in this population.

Using opinion leaders to address intervention gaps in concussion prevention in youth sports: key concepts and foundational theory.

Behavioral interventions to increase disclosure and proper management of concussion in youth sports have unrealized potential when it comes to preventing concussion. Interventions have focused on changing individual athlete behavior and have fallen short of the potential for sustained systemic behavioral change. One potentially critical reason for this shortfall is that other key determinants of risk behaviors at all levels of the socio-ecological model (e.g. interpersonal, community, policy) are not addressed in extant programming. There is a critical need for theory-driven interventions that address concussion prevention and education at the community level and target sustainable culture change. The Popular Opinion Leader (POL) intervention, a multi-level intervention model previously successfully employed in multiple public health contexts, is theoretically well positioned to affect such change. POL is based on the Diffusion of Innovations framework and involves identifying, recruiting, and training well-respected and trusted individuals to personally endorse prevention and risk-reduction within their social networks. Critical behavioral changes related to concussion disclosure and management have been shown to diffuse to others if enough opinion leaders endorse and support the behaviors. This article summarizes the concepts and principles of POL and describes how it could be adapted for and implemented in youth sport settings. For optimal impact, POL needs to adapt to several factors unique to youth sports settings and culture. First, adult involvement may be important, given their direct involvement in the athlete's medical care. However, parents and coaches' opinions on injury care-seeking, competition, and safety may affect their perceptions of POL. Second, youth sports are structured settings both physically and socioculturally. Games and practices may provide opportunities for the informal interactions that are critical to the success of POL. However, youth sport setting membership is transient as players get older and move to other sport settings; POL approaches need to be self-sustaining despite this turnover. Moreover, stakeholder value placed on athlete development and competition, alongside safety, must be considered. Formative research is needed to ensure that POL principles are translated into the youth sport setting while maintaining fidelity to the concepts and principles that have made POL successful for other health outcomes.

Closing the Gap: Mouse Models to Study Adhesion in Secondary Palatogenesis.

Secondary palatogenesis occurs when the bilateral palatal shelves (PS), arising from maxillary prominences, fuse at the midline, forming the hard and soft palate. This embryonic phenomenon involves a complex array of morphogenetic events that require coordinated proliferation, apoptosis, migration, and adhesion in the PS epithelia and underlying mesenchyme. When the delicate process of craniofacial morphogenesis is disrupted, the result is orofacial clefting, including cleft lip and cleft palate (CL/P). Through human genetic and animal studies, there are now hundreds of known genetic alternations associated with orofacial clefts; so, it is not surprising that CL/P is among the most common of all birth defects. In recent years, in vitro cell-based assays, ex vivo palate cultures, and genetically engineered animal models have advanced our understanding of the developmental and cell biological pathways that contribute to palate closure. This is particularly true for the areas of PS patterning and growth as well as medial epithelial seam dissolution during palatal fusion. Here, we focus on epithelial cell-cell adhesion, a critical but understudied process in secondary palatogenesis, and provide a review of the available tools and mouse models to better understand this phenomenon.

Phase I/II study of combined granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor administration for the mobilization of hematopoietic progenitor cells.

PURPOSE: To study the toxicity and efficacy of combined granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) administration for mobilization of hematopoietic progenitor cells (HPCs). MATERIALS AND METHODS: Cohorts of a minimum of five patients each were treated subcutaneously as follows: G-CSF 5 micrograms/kg on days 1 to 12 and GM-CSF at .5, 1, or 5 micrograms/kg on days 7 to 12 (cohorts 1, 2, and 3); GM-CSF 5 micrograms/kg on days 1 to 12 and G-CSF 5 micrograms/kg on days 7 to 12 (cohort 4); and G-CSF and GM-CSF 5 micrograms/kg each on days 1 to 12 (cohort 5). Ten-liter aphereses were performed on days 1 (baseline, pre-CSF), 5, 7, 11, and 13. Colony assays for granulocyte-macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E) were performed on each harvest. RESULTS: The principal toxicities were myalgias, bone pain, fever, nausea, and mild thrombocytopenia, but none was dose-limiting. Four days of treatment with either G-CSF or GM-CSF resulted in dramatic and sustained increases in the numbers of CFU-GM per kilogram collected per harvest that represented 35.6 +/- 8.9- and 33.7 +/- 13.0-fold increases over baseline, respectively. This increment was attributable both to increased numbers of mononuclear cells collected per 10-L apheresis and to increased concentrations of progenitors within each collection. The administration of G-CSF to patients already receiving GM-CSF (cohort 4) caused the HPC content to surge to nearly 80-fold the baseline (P = .024); the reverse sequence, ie, the addition of GM-CSF to G-CSF, was less effective. The CFU-GM content of the baseline aphereses correlated with the maximal mobilization achieved (r = .74, P = .001). CONCLUSION: Combined G-CSF and GM-CSF administration effectively and predictably mobilizes HPCs and facilitates apheresis.

Cerebellar ablation and mastication in the guinea pig (Cavia porcellus).

The jaw movements of 3 subadult guinea pigs were recorded before and after cerebellar ablation with the aid of an optoelectronic tracking system. Despite overall ataxia of the animals' body and limbs, masticatory patterns were essentially normal. The major effects of cerebellar ablation upon Cavia mastication were a statistically significant (P < 0.01) increase in chew cycle duration and a decrease in chew duration variability.

Prolonged seizure suppression by a single implantable polymeric-TRH microdisk preparation.

Thyrotropin-releasing hormone (TRH; Protirelin) is an endogenous neuropeptide known to have anticonvulsant effects in several seizure models and in intractable epileptic patients. Like most neuropeptides, its duration of action may be limited by a lack of sustained site-specific bioavailability. To attempt to provide long-term delivery, we attached TRH to a biodegradable polyanhydride copolymer as a sustained-release carrier. Utilizing the rat kindling model of temporal lobe epilepsy, a single TRH microdisk implanted stereotaxically into the seizure focus (amygdala) significantly suppressed kindling expression when assessed by the number of stimulations required to reach each behavioral stage and to become fully kindled (8.63 +/- 0.92 vs. 16.17 +/- 1.37; Mean +/- S.E.M.). Two indices of seizure severity, afterdischarge duration (Mean +/- S.E.M., sec.) (stimulated amygdala [87.40 +/- 5.47 vs. 51.80 +/- 15.65] and unstimulated amygdala [89.60 +/- 5.55 vs. 48.67 +/- 15.8] and clonus duration (71.2 +/- 5.94 vs. 29.40 +/- 8.87; Mean +/- S.E.M., sec.), were also significantly reduced by a single polymeric-TRH implant. Fifty days after initiation of the study a significant reduction in clonus duration (53.90 +/- 3.27 vs. 40.09 +/- 4.14) still remained in the TRH-implanted groups. This report is the first to provide evidence in support of in situ microdisk pharmacotherapy for potential neuropeptide delivery in intractable epilepsy and possibly other neurological disorders.

Loci and characteristics of EMG silent periods during masticatory mandibular movements in rats.

Frontal plane mandibular movements and the associated superficial masseter EMG signals of six 39-day-old rats were simultaneously recorded and digitized at a rate of 1 kHz by the optoelectronic method in order to investigate the loci and attributes of masseteric silent periods during mastication of hard (pellets) and soft (slurry) food items. The marked silent periods, defined as cessations of EMG activity during the slow-close (SC) phase of single chewing cycles, were analyzed for their (1) onset and offset durations relative to physiological centric occlusion (PCO), (2) frontal vertical (FV) and frontal horizontal (FH) loci relative to PCO, and (3) FV and FH velocities and accelerations of masticatory mandibular movements in relation to PCO. The start (SSP) and end (ESP) of silent period loci relative to PCO moved superiorly as sequences of pellet mastication progressed. All silent period attributes during slurry consumption were significantly different (p less than or equal to 0.01) from pellet attributes: Slurry SSP and ESP loci were closer to PCO than were pellet loci; durations of silent period loci during pellet mastication were more variable than were slurry durations. FV distance and velocity values for pellets were greater than with pellets. Although FV velocities during both pellet and slurry mastication decreased at ESP relative to SSP values, their FH velocities at ESP actually increased relative to SSP velocities. Loci attributes of EMG silent periods appeared largely dependent on the consistency of the food item being masticated.

Effects of post-natal serotonin levels on craniofacial complex.

Although the role of serotonin (5-hydroxytryptamine or 5-HT) in pre-natal craniofacial growth and development has been studied, no research has been done on the effects of serotonin on post-natal craniofacial growth and development. The following experimental question was tested: What effect does increasing in vivo serotonin levels adjacent to trigeminal motoneurons have on post-natal craniofacial structures in young, actively growing rats? Forty male Sprague-Dawley rats were divided into 4 experimental groups (10% serotonin microspheres, 15% serotonin microspheres, blank microspheres, sham surgeries) and underwent stereotactic neurosurgery at post-natal day 35; 5 rats of each group were killed at 14 and 21 post-surgical days for data collection. Statistical analyses by mixed-model, 4 x 2 repeated-measures ANOVA, and post hoc Fisher LSD tests revealed significant (P < or = 0.05, 0.01) differences between groups and sides for muscle weight, cranial dimension, and TMJ dimension data. Data described here indicate that significant alterations of post-natal craniofacial structures can be caused by altered in vivo levels of serotonin adjacent to trigeminal motoneurons.

Human and macaque mastication: a quantitative study.

Significant differences exist between human and Macaca fascicularis patterns of mandibular movement during mastication. Macaque patterns display less asymmetry, more uniformity, and limited lateral excursions when compared to humans for mastication of the same food. Different anatomical structures between the two species offer explanations of the different patterns that were observed. Researchers should use caution when using macaques as models for human mastication.

Craniofacial and TMJ effects after glutamate and TRH microsphere implantation in proximity to trigeminal motoneurons of growing rats.

The sequelae of sustained, in vivo delivery of two important neurotransmitter substances, glutamate and thyrotropin-releasing hormone (TRH), upon craniofacial growth and development have previously not been investigated. Our purpose was to document and compare the relative effects of glutamate and TRH microspheres stereotactically placed in proximity to trigeminal motoneurons within the trigeminal motor nucleus. The following null hypotheses were tested: (1) TRH microspheres in proximity to trigeminal motoneurons have no significant effect upon the craniofacial skeleton, and (2) there are no significant differences between the relative effects of chronic, long-term delivery of glutamate and TRH upon the neuromusculoskeletal system of growing rats. Forty male Sprague-Dawley rats were divided into 4 experimental groups (glutamate microspheres, TRH microspheres, blank microspheres, sham surgeries) and underwent stereotactic neurosurgery at 35 days; 5 rats of each group were killed at 14 and 21 days for data collection. Histology revealed that implants were clustered in the pontine reticular formation, close to the ventrolateral tegmental nucleus. Both glutamate and TRH rats had implant-side deviation of their facial skeleton and snout regions; 4 x 2 ANOVA and post hoc t-tests revealed significant (P < or = 0.05, 0.01) differences between groups and sides for motoneuron count, muscle weight, and osteometric data. TRH rats also demonstrated larger implant-side TMJ discs and mandibular fossae in comparison with the other groups. The stated null hypotheses were therefore rejected.

Mandibular movement and muscle activity during mastication in the guinea pig (Cavia porcellus).

Optoelectronic analysis of mandibular movement and electromyography (EMG) of masticatory muscles in Cavia porcellus indicate bilateral, unilateral, and gnawing cycles. During bilateral and unilateral cycles, the mandibular tip moves forward, lateral, and down during the lingual phase of the power stroke to bring the teeth into occlusion. EMG activity is generally asymmetric, with the exception of activity of the temporalis muscle during bilateral cycles. During gnawing cycles, the mandible moves in an anteroposterior direction that is opposite that during bilateral and unilateral chew cycles. Bilateral and unilateral cycles of pellets were significantly longer than carrot. With the exception of the width of bilateral cycles, the magnitude of cycle width, length, and height during the mastication of carrots was greater than that during the mastication of pellets. Significant differences exist between EMG durations during mastication of pellets and carrots. The lateral pterygoid displays continuous activity during gnawing cycles. Significant differences also exist in the duration of EMG activity between the working and balancing side during all three cycle types. High level of activity of balancing side temporalis and anterior belly of digastric (ABD) during bilateral cycles occurs during rotation and depression of the mandible during the power stroke. The temporalis apparently provides a "braking" or compensatory role during closing and power strokes. Differences between Cavia masticatory patterns and those shown by Rattus and Mesocricetus are apparently due to differences in dental morphology, occlusal relationships, and, possibly, the poorly developed temporalis in Cavia. The large number and wide diversity of rodent groups afford students of mammalian mastication an opportunity to investigate and compare different masticatory specializations.

Characterization of brux-like movements in the laboratory rat by optoelectronic mandibular tracking and electromyographic techniques.

High-resolution optoelectronic mandibular tracking and fine-wire electromyographic (EMG) data from the anterior temporalis muscles of laboratory rats (Rattus norvegicus) were collected during mastication (chewing) and bruxing/thegosis (grinding sharpening of teeth) in order to test for task-related activity patterns of the anterior temporalis. Analyses of the collected data revealed that masticatory and bruxing/thegosis cycles displayed significantly different patterns of movement trajectories, displacement, duration, velocity, and acceleration in all three spatial dimensions (frontal vertical, frontal horizontal and sagittal horizontal). Activity patterns in the anterior temporalis during masticatory and bruxing/thegosis behaviours were also significantly different from each other. High-resolution analyses revealed that the masticatory cycle had both opening-burst and closing-burst phasic patterns of anterior temporalis activity while the bruxing/thegosis cycle displayed only opening-burst phasic patterns. The opening- and closing-burst attributes of anterior temporalis phasic activity patterns in relation to physiological centric occlusion also revealed significant differences between masticatory and bruxing/thegosis behaviours. These data demonstrate that the anterior temporalis muscle of the laboratory rat does indeed display task-related activity patterns depending upon the manifested oral behaviour. The task-related shifts of EMG patterns in the anterior temporalis between masticatory bruxing/thegosis behaviours in the same animal suggests a complex neurophysiological substrate that coordinates the three-dimensional expression of phasic activity patterns in the muscle. The radically different nature of masticatory and bruxing/thegosis cycles and their associated EMG patterns in the anterior temporalis suggest the possible existence of a bruxing/thegosis pattern generator in addition to the masticatory one. Careful, high-resolution analyses of these rat behaviours by combined optoelectronic/EMG techniques suggest that the rat model for human bruxism may prove useful in future studies.