Airway Phenotypes and Nocturnal Wearing of Dentures in Elders with Sleep Apnea.

The objective of this study was to examine to what extent the anatomic characteristics of the upper airway can influence the effect of nocturnal wearing of dentures on the sleep of edentulous elders with untreated sleep apnea. This study used the data from a randomized crossover clinical trial and an exploratory approach to address its objectives. Cone beam computed tomography scans of 65 edentulous individuals (female, n = 37; male, n = 28; mean ± SD age, 74.54 ± 6.42 y) with untreated obstructive sleep apnea (OSA) were used to identify anatomic variables. Polysomnography data were collected by means of one portable overnight recording. The respiratory variable values, including apnea-hypopnea index (AHI), with and without denture worn during sleep were used to calculate the change. Statistical analyses included multiple linear regressions, cluster analysis, and binary logistic regressions. A receiver operator characteristic curve was used to illustrate the accuracy of the statistical model. The regression model explained 15.8% (R2) of AHI change. An increase in the lateral dimension of the minimum cross-sectional area was associated with a decrease in AHI, oxygen desaturation index, and respiratory arousal index changes (P ≤ 0.041). Furthermore, an increase in the length of the hypopharynx was associated with an increase in AHI and oxygen desaturation index changes (P ≤ 0.027). An increase in the lateral dimension of the minimum cross-sectional area of the upper airway was associated with a decreased likelihood of being in the group having a worsened AHI (odds ratio = 0.85; 95% CI, 0.76 to 0.95; P = 0.006). An increase in the length of the oropharynx was associated with an increased likelihood of having increased AHI (odds ratio = 1.10; 95% CI, 1.01 to 1.20; P = 0.026). The nocturnal aggravation of respiratory variables in edentulous individuals with OSA who wear dentures at night can be linked to certain anatomic characteristics of the upper airway. Replication of these findings may open novel avenues for personalized advice regarding nocturnal wearing of dentures in edentulous individuals with OSA (ClinicalTrials.gov: NCT01868295).

Carious lesion management in children and adolescents by Australian dentists.

BACKGROUND: The management of carious lesions in children and adolescents can have lifelong implications for the patient. The aim of this study was to assess the decision-making process of dentists when managing carious lesions in children and adolescents. METHODS: Approximately, 11 000 dentists listed as members of the Australian Dental Association Inc. (ADA) and Australian and New Zealand Society of Paediatric Dentistry (ANZSPD) were emailed a link in April 2017 to a 19-question survey delivered by SurveyMonkey™. RESULTS: In this study, 887 responses were received. In 'enamel-limited' carious lesions, dentists intervened most frequently in primary tooth approximal (365, 41.1%), followed by permanent tooth occlusal (295, 33.3%) and approximal (244, 27.5%), and primary tooth occlusal (203, 22.9%) surface carious lesions. Age, university of graduation, practicing state, decade of graduation and frequency of treatment of children between 6 and 15 years were significant demographic factors influencing the restorative threshold. CONCLUSIONS: Australian dentists reported significant variation in their management of approximal and occlusal carious lesions in both primary and permanent teeth. A substantial proportion of respondents would intervene surgically on non-cavitated enamel-limited lesions.

Effect of exogenous retinoic acid on tooth movement and periodontium healing following tooth extraction in a rat model.

OBJECTIVES: To evaluate the effect of isotretinoin on orthodontic tooth movement (OTM) and wound healing following exodontia. SETTING AND SAMPLE POPULATION: Sixteen 40-day-old male Wistar rats were divided into two groups: (a) OTM and (b) tooth extraction (TE) of the upper 1st molar and OTM. The experimental animals were treated with isotretinoin (7.5 mg/kg) and the control animals with oil solution for 37 days. MATERIALS AND METHODS: The OTM and bone volume were evaluated by the micro-CT and the periodontium healing was assessed by immunohistochemistry for VEGF-C, COX-2 and IL-1ß. RESULTS: The animals of both groups submitted to the TE showed a statistically significant decrease in the bone volume percentage and increase in OTM. No significant difference of OTM and bone volume was observed between the control and experimental group. However, the alveolar bone of the isotretinoin group revealed more medullary spaces with inflammatory, hematopoietic cells, blood vessels and intense immunolabeling for VEGF-C. This group also showed faster gingival regeneration. No significant difference was observed in the COX-2 and IL-1ß labelings following TE between both groups. CONCLUSION: The isotretinoin did not affect the OTM nor did it cause an alteration in maxillary bone volume. This exogenous acid may contribute to the acceleration of gingival healing.

Tooth Loss Increases the Risk of Diminished Cognitive Function: A Systematic Review and Meta-analysis.

Emerging evidence suggests that oral health is associated with cognitive function. This review aims to systematically assess this association in adult populations via prospective cohort study designs. Eligible study reports were identified by searching the MEDLINE (via Ovoid), EMBASE, PsycoINFO, and Cochrane Library databases. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated with a random effects model. From 1,251 identified articles, 10 were included in the systematic review and 8 in the meta-analysis. Random effects analysis showed, with statistically low heterogeneity, that individuals with suboptimal dentition (<20 teeth) were at a 20% higher risk for developing cognitive decline (HR = 1.26, 95% CI = 1.14 to 1.40) and dementia (HR = 1.22, 95% CI = 1.04 to 1.43) than those with optimal dentition (≥20 teeth). Studies on the association between periodontal disease and cognitive status showed conflicting results. Within the limits of the quality of published evidence, this meta-analysis lends further support to the hypothesis that tooth loss is associated with an increased risk of cognitive impairment and dementia. Knowledge Transfer Statement: Based on the published literature, the results of this study show that the risk for cognitive impairment and dementia increases with loss of teeth. This information adds to the evidence showing links between oral and general health and suggests that oral health strategies aimed to preserve teeth may be important in reducing risk of systemic disease.

Could transient hypoxia be associated with rhythmic masticatory muscle activity in sleep bruxism in the absence of sleep-disordered breathing? A preliminary report.

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth during sleep. Sleep bruxism activity is characterised by rhythmic masticatory muscle activity (RMMA). Many but not all RMMA episodes are associated with sleep arousal. The aim of this study was to evaluate whether transient oxygen saturation level change can be temporally associated with genesis of RMMA/SB. Sleep laboratory or home recordings data from 22 SB (tooth grinding history in the absence of reported sleep-disordered breathing) and healthy subjects were analysed. A total of 143 RMMA/SB episodes were classified in four categories: (i) no arousal + no body movement; (ii) arousal + no body movement; (iii) no arousal + body movement; (iv) arousal + body movement. Blood oxygen levels (SaO2 ) were assessed from finger oximetry signal at the baseline (before RMMA), and during RMMA. Significant variation in SaO2 over time (P = 0·001) was found after RMMA onset (+7 to +9 s). No difference between categories (P = 0·91) and no interaction between categories and SaO2 variation over time (P = 0·10) were observed. SaO2 of six of 22 subjects (27%) remained equal or slight increase after the RMMA/SB onset (+8 s) compared to baseline; 10 subjects (45%) slightly decreased (drop 0·01-1%) and the remaining (27%) decreased between 1% and 2%. These preliminary findings suggest that a subgroup of SB subjects had (i) a minor transient hypoxia potentially associated with the onset of RMMA episodes, and this (ii) independently of concomitant sleep arousal or body movements.

Animals with a schizophrenia-like phenotype are differentially sensitive to the motivational effects of cannabinoid agonists in conditioned place preference.

Cannabis is the most consumed illicit drug worldwide, but among patients with a diagnosis of schizophrenia, this consumption is higher suggesting that they are differentially sensitive to cannabis. We chose to study this problematic using a neurodevelopmental model of schizophrenia: neonatal ventral hippocampus lesions (NVHL). In a first study, we compared the locomotor response to novelty, a mild stress and two doses of amphetamine (0.75 and 1.5 mg/kg) in sham and NVHL rats at post-natal day 35 (PD35) or 56 (PD56). In a second study, we investigated the valence of the motivational effect of Delta-9-tetrahydrocannabinnol (THC, 0.5 mg/kg, i.p.) and the cannabinoid receptor agonist, WIN55,212-2 (WIN, 1 mg/kg, i.p.), using the conditioned place preference paradigm; we used a biased procedure that comprised 12 days of testing with 3 paired-conditioning. The effects of this dose of WIN were also measured on locomotor activity. Results confirmed that the adult NVHL animals displayed a stronger locomotor response to the two doses of amphetamine, but not to novelty and a mild stress. In adult NVHL, but not sham animals, WIN stimulated locomotor activity and produced a conditioned place aversion. At the dose tested, THC tended to produce an aversion in adult sham but not NVHL animals. Taken together these findings show that adult animals with a schizophrenia-like phenotype are differentially sensitive to the motivational effect of cannabinoids.

Comparison of ambulatory and polysomnographic recording of jaw muscle activity during sleep in normal subjects.

Clinicians and investigators need a simple and reliable recording device to diagnose or monitor sleep bruxism (SB). The aim of this study was to compare recordings made with an ambulatory electromyographic telemetry recorder (TEL-EMG) with those made with standard sleep laboratory polysomnography with synchronised audio-visual recording (PSG-AV). Eight volunteer subjects without current history of tooth grinding spent one night in a sleep laboratory. Simultaneous bilateral masseter EMG recordings were made with a TEL-EMG and standard PSG. All types of oromotor activity and rhythmic masseter muscle activity (RMMA), typical of SB, were independently scored by two individuals. Correlation and intra-class coefficient (ICC) were estimated for scores on each system. The TEL-EMG was highly sensitive to detect RMMA (0·988), but with low positive predictive value (0·231) because of a high rate of oromotor activity detection (e.g. swallowing and scratching). Almost 72% of false-positive oromotor activity scored with the TEL-EMG occurred during the transient wake period of sleep. A non-significant correlation between recording systems was found (r = 0·49). Because of the high frequency of wake periods during sleep, ICC was low (0·47), and the removal of the influence of wake periods improved the detection reliability of the TEL-EMG (ICC = 0·88). The TEL-EMG is sensitive to detect RMMA in normal subjects. However, it obtained a high rate of false-positive detections because of the presence of frequent oromotor activities and transient wake periods of sleep. New algorithms are needed to improve the validity of TEL-EMG recordings.

Perceived sleep quality among edentulous elders.

BACKGROUND: Anatomical changes associated with edentulism are thought to disturb seniors' sleep. OBJECTIVES: (1) To determine sleep quality and daytime sleepiness of edentulous elders. (2) To examine the association between oral health-related quality of life and sleep quality. METHODS: Data were collected at a 1-year follow-up from 173 healthy edentulous elders who had participated in a randomised controlled trial and randomly received two types of mandibular prosthesis. Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI, range 0-21), with higher scores indicating poorer sleep quality. The Epworth Sleepiness Scale (ESS) was used to measure the level of perceived daytime sleepiness, and scores ≥10 indicated sleepiness. RESULTS: The mean global PSQI and ESS scores were 4.7 ± 3.5 and 5.3 ± 3.9. There were no differences in sleep quality or sleepiness between those who wore their dentures at night and those who did not. Elders with frequent denture problems were sleepier during the day than those with fewer problems (p = 0.0034). General health (p = 0.02) and oral health-related quality of life (p = 0.001) are significant predictors of sleep quality. CONCLUSION: Healthy edentulous elders, independent of nocturnal wearing of their prosthesis, are good sleepers. Maintaining high oral health quality of life could contribute to better sleep.

Is oral health-related quality of life stable following rehabilitation with mandibular two-implant overdentures?

OBJECTIVES: The superiority of mandibular two-implant overdentures (IODs) over conventional complete dentures (CDs) in terms of quality of life is still questioned. Furthermore, the stability and magnitude of the treatment effect over time remain uncertain. This follow-up study aimed to determine the stability and magnitude of the effect of IODs on oral health-related quality of life (OHRQoL). MATERIAL AND METHODS: 172 participants (mean age 71 ± 4.5 years) randomly received CDs or IODs, both opposed by conventional maxillary dentures. OHRQoL was measured using the Oral Health Impact Profile (OHIP-20) at baseline, 1 and 2 years post-treatment. Repeated measures ANOVAs were conducted to assess the effects of time and treatment on the total OHIP and its individual domain scores. RESULTS: A statistically significant improvement in OHRQoL was seen for both treatment groups (P < 0.001). This improvement was maintained over the 2 year assessment. At both follow-ups, participants wearing IODs reported significantly better total OHIP scores than those wearing CDs (P < 0.001), with a 1.5 times larger magnitude of effect. In the CD group, baseline OHIP scores influenced the post-treatment scores (P < 0.001). This effect was not found in the IOD group. CONCLUSIONS: The effect of mandibular two-IODs on OHRQoL is stable over a 2-year period. The large magnitude of effect of this treatment supports its clinical significance.

Sleep bruxism and sleep arousal: an experimental challenge to assess the role of cyclic alternating pattern.

Rhythmic masticatory muscle activity (RMMA) is the characteristic electromyographic pattern of sleep bruxism (SB), a sleep-related motor disorder associated with sleep arousal. Sleep arousals are generally organised in a clustered mode known as the cyclic alternating pattern (CAP). CAP is the expression of sleep instability between sleep maintaining processes (phase A1) and stronger arousal processes (phases A2 and A3). This study aimed to investigate the role of sleep instability on RMMA/SB occurrence by analysing CAP and electroencephalographic (EEG) activities. The analysis was performed on the sleep recordings of 8 SB subjects and 8 controls who received sensory stimulations during sleep. Baseline and experimental nights were compared for sleep variables, CAP, and EEG spectral analyses using repeated measure ANOVAs. Overall, no differences in sleep variables and EEG spectra were found between SB subjects and controls. However, SB subjects had higher sleep instability (more phase A3) than controls (P= 0·05). The frequency of phase A3 was higher in the pre-REM sleep periods (P < 0·001), where peaks in RMMA/SB activity were also observed (P = 0·05). When sleep instability was experimentally increased by sensory stimuli, both groups showed an enhancement in EEG theta and alpha power (P = 0·04 and 0·02, respectively) and significant increases in sleep arousal and all CAP variables. No change in RMMA/SB index was found within either groups (RMMA/SB occurred in all SB subjects and only one control during the experimental night). These findings suggest that CAP phase A3 may act as a permissive window rather than a generator of RMMA/SB activity in predisposed individuals.

Better oral health related quality of life: type of prosthesis or psychological robustness?

UNLABELLED: Sense of coherence (SOC) is an individual-based coping characteristic and believed to influence a person's ability to adapt to life stressors, such as edentulism and using complete denture. Thus, SOC may mediate the effect of prosthetic treatment on quality of life. OBJECTIVES: 1. To simultaneously test the effect of type of treatment and sense of coherence on oral health related quality of life (OHRQoL) in edentate elders and to identify any interaction. 2. To report the level of sense of coherence among a sample of edentate elders. METHODS: Data were collected and analysed cross-sectionally at a 1-year follow-up from 173 edentulous elders who had randomly received mandibular-implant overdentures or conventional dentures, both opposed by new conventional maxillary dentures. The dependent outcome variable, oral health related quality of life, was measured using the Oral Health Impact Profile (OHIP-20). Independent variables included SOC and prosthesis type, as well as socio-demographic variables. SOC was evaluated using the 13-item likert scale of The Orientation to Life questionnaire. RESULTS: The group mean SOC score was 70.28 (SD=9.6). Married or coupled people had significantly higher SOC scores than those who were separated, single or divorced (p=0.04). General linear model analyses demonstrated that there was a statistically significant main effect for type of prosthesis, F(1.169)=0.71, p=0.008, with no interaction with SOC. CONCLUSION: The results of this study suggest that, in edentulous elders, SOC does not mediate the effect of the type of prosthetic treatment on oral health related quality of life.

[Molecular and genetic aspects of idiopathic scoliosis. Blood test for idiopathic scoliosis]. / Molekulare und genetische Aspekte der idiopathischen Skoliose. Bluttest bei idiopathischer Skoliose.

Spinal deformities, and particularly scoliosis, are the most frequent forms of orthopedic deformities in children and adolescents. About 1-6% of the population has scoliosis. This disorder leads to severe spinal deformities and predominantly affects adolescent girls.Although the multifactorial origin of adolescent idiopathic scoliosis (AIS) is broadly recognized, the genetic causes of AIS are still largely unknown. Our previous studies suggested a generalized dysfunction of melatonin transduction (the hormone that is primarily produced in the brain and epiphysis). In the meantime we have demonstrated that such a defect of signal transduction is caused by chemical alterations, which inactivate the function of the inhibitory G protein-coupled melatonin receptors. This discovery has led to the development of the first blood test to detect children without symptoms who are at risk of developing scoliosis. Since a single function (cellular reaction to melatonin) is determined, the unique advantage of this test is that it can be performed without knowledge of mutations in defective genes that could provoke the onset of AIS.

Oro-facial activities in sleep bruxism patients and in normal subjects: a controlled polygraphic and audio-video study.

To our knowledge, the large spectrum of sleep motor activities (SMA) present in the head and neck region has not yet been systematically estimated in normal and sleep bruxism (SB) subjects. We hypothesized that in the absence of audio-video signal recordings, normal and SB subjects would present a high level of SMA that might confound the scoring specificity of SB. A retrospective analysis of several SMA, including oro-facial activities (OFA) and rhythmic masticatory muscle activities (RMMA), was made from polygraphic and audio-video recordings of 21 normal subjects and 25 SB patients. Sleep motor activities were scored, blind to subject status, from the second night of sleep recordings. Discrimination of OFA included the following types of activities: lip sucking, head movements, chewing-like movements, swallowing, head rubbing and scratching, eye opening and blinking. These were differentiated from RMMA and tooth grinding. The frequency of SMA per hour of sleep was lower in normal subjects in comparison with SB patients (P < 0.001). Up to 85% of all SMA in normal subjects were related to OFA while 30% of SMA in SB patients were related to OFA scoring (P < 0.001). The frequency of RMMA was seven times higher in SB patients than in normal subjects (P < 0.001). Several SMA can be observed in normal and SB subjects. In the absence of audio-video signal recordings, the discrimination of various types of OFA is difficult to achieve and may lead to erroneous estimation of SB-related activities.

Topographical Fos induction within the ventral midbrain and projection sites following self-stimulation of the posterior mesencephalon.

Rats will readily perform an operant response to self-administer electrical stimulation to the posterior mesencephalon (PM). Previous results show that axons that support self-stimulation travel between the PM and the ventral tegmental area (VTA) and that their activation increases firing of VTA neurons. The present work sought to extend these findings by describing the distribution of ventral midbrain neurons affected by PM self-stimulation. In Experiment 1, ventral midbrain Fos-immunoreactivity (IR) was assessed in three groups of rats implanted with a monopolar electrode; two groups were trained to self-administer stimulation, but only one was allowed to self-stimulate on the test day, whereas the third was never trained or tested. Self-stimulation induced prominent Fos-IR that was differentially distributed within the VTA and substantia nigra (SN). Control rats showed only sparse labeling. In Experiment 2, ventral midbrain Fos-IR was assessed with three additional groups trained to self-administer PM stimulation and tested as follows: Group-1 was allowed to self-stimulate, Group-2 received stimulation at parameters that failed to support self-stimulation (deemed non-rewarding) "yoked" to the rate of responding of Group-1, and Group-3 received no stimulation. PM self-stimulation induced Fos-IR throughout the rostral-caudal VTA and within the SN reticulata. Non-rewarding stimulation induced sparse Fos-IR, comparable to no stimulation. Fos-IR specific to PM self-stimulation was also observed within the bed nucleus of the stria terminalis (BNST) and nucleus accumbens (NAS)-shell, but not within NAS-core, caudate putamen, medial prefrontal or orbital cortices. These findings are consistent with evidence that reward or positive reinforcement can be triggered by chemical and electrical stimulation over a large rostral-caudal extent of the VTA. They suggest that among ventral midbrain projection sites, the BNST and NAS-shell constitute important components of the circuitry implicated in reward. They provide additional support for the functional link between neurons that support PM and VTA self-stimulation, and offer topographical guidance to future attempts at their identification.

Favoring trauma as an etiological factor in denture stomatitis.

The etiology of denture stomatitis remains controversial. Trauma due to unstable dentures has been suggested as an etiological factor. Therefore, we tested the hypothesis that the prevalence of denture stomatitis is reduced when mandibular dentures are stabilized by implants. Data were collected at a one-year follow-up from 173 edentulous elders who had randomly received mandibular implant overdentures or conventional dentures. The diagnosis of denture stomatitis was determined according to the Newton classification. Elders wearing conventional dentures were almost 5 times more likely to have denture stomatitis than those wearing mandibular two-implant overdentures (P < 0.0001, Fisher's exact test). Adjusted odds ratios showed that only the type of the prosthesis (AOR = 4.54, 95% CI 2.20 to 9.40) and nocturnal wear (AOR = 3.03, 95% CI 1.24 to 7.40) predict the frequency of denture stomatitis. Thus, implant overdentures may reduce oral mucosal trauma and control denture stomatitis.

Identification of a sleep bruxism subgroup with a higher risk of pain.

Sleep bruxism research diagnostic criteria (SB-RDC) have been applied since 1996. This study was performed to validate these criteria and to challenge the hypothesis that pain is associated with lower frequencies of orofacial activities. Polygraphic recordings were made of 100 individuals presenting with a clinical diagnosis of sleep bruxism and 43 control individuals. TwoStep Cluster analyses (SPSS) were performed with sleep bruxism variables to reveal groupings among sleep bruxers and control individuals. Participants completed questionnaires during screening, diagnosis, and recording sessions. Cluster analysis identified three subgroups of sleep bruxers. Interestingly, 45 of the 46 sleep bruxers with values below SB-RDC were classified in the low-frequency cluster. These individuals were more likely to complain of pain and fatigue of masticatory muscles than were the higher-frequency sleep bruxers (odds ratios > 3.9, p < 0.01). Sleep bruxers were distributed among three heterogeneous groups. Sleep bruxers with low frequencies of orofacial activities were more at risk of reporting pain.

Sleep bruxism is associated to micro-arousals and an increase in cardiac sympathetic activity.

Sleep bruxism (SB) subjects show a higher incidence of rhythmic masticatory muscle activity (RMMA) than control subjects. RMMA is associated with sleep micro-arousals. This study aims to: (i) assess RMMA/SB episodes in relation to sleep cycles; (ii) establish if RMMA/SB and micro-arousals occur in relation to the slow wave activity (SWA) dynamics; (iii) analyze the association between RMMA/SB and autonomic cardiac activity across sleep cycles. Two nights of polygraphic recordings were made in three study groups (20 subjects each): moderate to high SB, low SB and control. RMMA episodes were considered to occur in clusters when several groups of RMMA or non-specific oromotor episodes were separated by less than 100 s. Correlations between sleep, RMMA/SB index and heart rate variability variables were assessed for the first four sleep cycles of each study group. Statistical analyses were done with SYSTAT and SPSS. It was observed that 75.8% of all RMMA/SB episodes occurred in clusters. Micro-arousal and SB indexes were highest during sleep cycles 2 and 3 (P < 0.001). Within each cycle, micro-arousal and RMMA/SB indexes showed an increase before each REM sleep (P

Quantitative polygraphic controlled study on efficacy and safety of oral splint devices in tooth-grinding subjects.

The efficacy of occlusal splints in diminishing muscle activity and tooth-grinding damage remains controversial. The objective of this study was to compare the efficacy and safety of an occlusal splint (OS) vs. a palatal control device (PCD). Nine subjects with sleep bruxism (SB) participated in this randomized study. Sleep laboratory recordings were made on the second night to establish baseline data. Patients then wore each of the splints in the sleep laboratory for recording nights three and four, two weeks apart, according to a crossover design. A statistically significant reduction in the number of SB episodes per hour (decrease of 41%, p = 0.05) and SB bursts per hour (decrease of 40%, p < 0.05) was observed with the two devices. Both oral devices also showed 50% fewer episodes with grinding noise (p = 0.06). No difference was observed between the devices. Moreover, no changes in respiratory variables were observed. Both devices reduced muscle activity associated with SB.

Involvement of the medial prefrontal cortex in two alternation tasks using different environments.

Spatial alternation performance in rats is usually evaluated with the T-Maze. The first aim of this study was to analyze the effect of a selective lesion of medial prefrontal cortex (mPFC) on performance in a T-maze. Second, we wanted to validate a new test using alternation in a water maze (AWM). The mPFC of 21 male Sprague-Dawley rats was lesioned bilaterally using in situ microinjection of ibotenic acid. Thirteen control rats received injections of the vehicle only. Results show that mPFC lesioned rats were significantly impaired in the T-Maze as well as in the AWM compared to controls. These results validate the AWM as a frontal cortex dependent task probing working memory and/or behavioral flexibility. We suggest that the AWM may be more powerful than the T-maze as an investigational tool, given that is can be easily compared to other water maze tasks that evaluate other (nonfrontal) cognitive modules.

Lower number of K-complexes and K-alphas in sleep bruxism: a controlled quantitative study.

OBJECTIVES: Although patients with sleep bruxism (SB) show a higher incidence of rhythmic masticatory muscle activity (RMMA) during sleep than matched normal controls, they are good sleepers. Sleep macrostructure (e.g. total sleep time, sleep latency, number of awakenings or sleep stage shifts and sleep stage duration) is similar between groups. Differences in sleep microstructure between SB patients and normals have been investigated only in few studies. The aim of the present study was to quantify number of microarousals, K-complexes, K-alphas, EEG spindles, and the density of slow wave activity, in both groups, in order to better understand the pathophysiology of SB. METHODS: Ten normal sleepers were matched for age and gender with 10 patients who exhibited frequent tooth-grinding during sleep. Using quantitative polysomnographic measures, we compared the above-mentioned sleep variables in both groups. Data are presented as indices for total sleep and for consecutive non-rapid eye movement (non-REM) episodes over non-REM to rapid eye movement (REM) cycles and per hour of sleep. RESULTS: SB patients showed 6 times more RMMA episodes per hour of sleep than normals (P<0.001), with a higher frequency in the second and third non-REM to REM cycles. SB patients presented 42.7% fewer K-complexes per hour of stage 2 sleep, but only normals showed a decline from the first to fourth non-REM episode. Only 24% of SB-RMMA episodes were associated with K-complexes in 60 s. The number of K-alphas was 61% lower in SB patients, no change across non-REM episodes was noted. While no difference in electroencephalographic (EEG) spindles or slow wave activity (SWA) was observed between groups, EEG spindles increased and SWA decreased linearly over consecutive non-REM to REM cycles. CONCLUSIONS: According to our observations, good sleep in SB patients is characterized by a low incidence of K-complexes or K-alphas and by the absence of any difference in other sleep microstructure variables or SWA.