Occlusal disharmonies modulate central catecholaminergic activity in the rat

Association of the Number of Teeth With Physical Function and Length of Hospital Stay After Hip Fracture Surgery: A Prospective Observational Study at a Tertiary Hospital in Japan

OBJECTIVES

Although lower-extremity muscle strength is associated with physical function, there are challenges in assessing the muscle strength of patients after hip surgery due to pain or limited cognitive function. The number of teeth is a characteristic that can be easily examined. Although the relationship between the number of teeth and physical function has been reported in recent years, there are no reports examining the relationship with prognosis in patients with hip fractures. Therefore, this study aimed to investigate the relationship between the number of teeth and physical function and length of hospital stay after hip fracture surgery and to evaluate the predictive efficacy of the number of teeth on postoperative prognosis.

METHODS

This prospective cohort study was conducted in a tertiary clinical care facility. Patients aged ≥65 years who underwent hip surgery were included. A total of 101 patients (mean age: 85.1±8.0 years) were included. The factor analyzed was the number of teeth at admission. Patients were divided into two groups according to the number of teeth: those with ≥20 and those with ≤19 teeth. The outcomes were knee extension muscle strength-to-weight ratio at two weeks postoperatively and the length of hospital stay. A multiple regression analysis was performed to determine the association between the two groups.

RESULTS

Of 101 patients, 79 (78.2%) had ≤19 teeth, whereas 22 (21.8%) had ≥20 teeth. The mean muscle strength-to-weight ratio and length of hospital stay were 0.26±0.11 kgf/kg and 57.5±31.4 days, respectively. Multiple regression analysis revealed that the number of teeth was significantly associated with the muscle strength-to-weight ratio (β=-0.26, p=0.04) but not with the duration of hospitalization (β=0.17, p=0.09).

CONCLUSIONS

We suggest that assessment of the number of teeth at admission may be a useful predictor of patient physical function.

Malocclusion of Molar Teeth Is Associated with Activities of Daily Living Loss and Delirium in Elderly Critically Ill Older Patients

A single-center retrospective cohort study examined the association between molar malocclusion status at ICU admission and loss of activities of daily living (ADL) at hospital discharge among acutely ill patients. Patients were assigned to the bilateral occlusion group or malocclusion group (N = 227 and 93, respectively). The following data were collected from electronic medical records: age, sex, Clinical Frailty Scale (CFS) on admission, Acute Physiology and Chronic Health Evaluation (APACHE) Ⅱ score, confirmed diagnosis (neurological disorders or others), CFS at hospital discharge, and occlusion condition. Patients who were frail at admission (CFS > 5) were excluded from analysis, and ADL loss was defined as CFS > 5 at hospital discharge. Multivariate analysis showed malocclusion was independently associated with ADL loss [OR, 2.03; 95% CI, 1.13-3.64; p = 0.02]. For those aged 65 and older, malocclusion was significantly associated with both ADL loss [OR, 3.25; 95% CI, 1.44-7.32; p < 0.01] and the incidence of delirium [OR, 2.61; 95% CI, 1.14-5.95; p = 0.02]. Malocclusion on ICU admission was associated with ADL loss in critically ill patients, and was associated with ADL loss and the incidence of delirium in the elderly. Poor oral health was a poor prognostic factor among critically ill patients.

Bruxism, Related Factors and Oral Health-Related Quality of Life Among Vietnamese Medical Students

Although bruxism is a common issue with a high prevalence, there has been a lack of epidemiological data about bruxism in Vietnam. This cross-sectional study aimed to determine the prevalence and associated factors of bruxism and its impact on oral health-related quality of life among Vietnamese medical students. Bruxism was assessed by the Bruxism Assessment Questionnaire. Temporomandibular disorders were clinically examined followed by the Diagnostic Criteria for Temporomandibular Disorders Axis I. Perceived stress, educational stress, and oral health-related quality of life were assessed using the Vietnamese version of Perceived Stress Scale 10, the Vietnamese version of the Educational Stress Scale for Adolescents, and the Vietnamese version of the 14-item Oral Health Impact Profile, respectively. The prevalence of bruxism, sleep bruxism, awake bruxism, and both conditions in Vietnamese medical students were 51.2%, 38.2%, 23.4%, and 10.4% respectively. Stress, temporomandibular joint pain, masticatory muscle pain, and tooth attrition were associated with the presence of bruxism. Vietnamese medical students were negatively affected by bruxism in terms of oral health-related quality of life.

Dental occlusion as one cause of tinnitus

There is large support in literature linking tinnitus to dental occlusion and temporomandibular joint disorders (TMD). However, there is no model to explain such a link. This hypothesis explains how the fusimotor system of the muscles innervated by the trigeminal motor nucleus is affected by inadequacies in the occlusion of the teeth that cause changes in posture and movement of the mandible. Reptile to mammal evolution shows that stomatognathic structures underwent changes related to mastication. Among several changes, there was the appearance of a new articulation between the mandible and skull: the temporomandibular joint. The bones of the old reptile joint, quadrate-articular, have detached from the mandible and are part of the middle ear bone chain. The former becomes the incus and the latter the malleus. This bone change also carried the tensor tympani and its trigeminal motor innervation. Inadequate occlusal contacts give rise to an adapted function of the mandible and the most common compensatory muscular response is hypertonia involving all mandibular muscles, including the tensor tympani. A fundamental clinical feature that demonstrates the involvement of the trigeminal fusimotor system is the characteristic pain by palpation, but no pain on the mandibular movement. Muscle pain is always felt in the dermatome innervated by the mandibular branch of the trigeminal nerve, which carries the motor fibers, reported as tightening, similar to cramp, and has regular behavior in intensity, duration and frequency. In addition, the patient has increased musculature volume, detected by palpation of certain anatomical landmarks, but with loss of functional efficiency. The neuromotor control of the mandibular movements is poor and when asked to make lateral jaw movement touching the teeth, it is common to observe that the patient moves the lips, eyes, and even turns the head in the same direction as the movement. There is also difficulty eating hard foods and talking fast. Tongue biting while chewing is frequent, meaning that these non-physiological events surpass protective reflex circuits. The report of ear pain, tinnitus, blocked ear sensation and sudden hearing loss is common in such patients, compatible with the tonic contraction of the tensor tympani. The fusimotor system hypothesis is able to explain all events related to the symptoms and helps to establish a correct diagnosis for certain types of hearing disorders.

Novel stress increases hypothalamic-pituitary-adrenal activity in mice with a raised bite

BACKGROUND AND OBJECTIVE

In humans, occlusal disharmony may cause various physical complaints, including head and neck ache, stiffness in the shoulder and neck, and arthrosis of the temporomandibular joints. Occlusal disharmony induced by raising the bite in rodents, increases plasma corticosterone levels, which leads to morphologic changes in the hippocampus and altered hippocampus-related behavior. The paraventricular nucleus (PVN) of the hypothalamus regulates the hypothalamic-pituitary-adrenal system. Chronically stressed animals exposed to a novel stress exhibit higher adrenocorticotropic hormone levels than naive control animals. We hypothesized that there would be different response of the corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) to a novel acute stress with occlusal disharmony.

DESIGN

In order to investigate how exposure of mice with occlusal disharmony to a novel acute stress (restraint stress) affects the PVN, we induced occlusal disharmony by raising the vertical dimension of the bite (bite-raised condition) and examined the expression of corticotrophin releasing hormone (CRH) mRNA and arginine vasopressin (AVP) mRNA in mouse PVN.

RESULTS

CRH mRNA expression was increased in the PVN of the bite-raised group 90min after the bite-raising procedure, but the expression was recovered to the control level at 14days. AVP mRNA expression in the PVN was normal at 90min, and increased significantly 14days after the bite-raising procedure. Exposure to restraint stress in the bite-raised mice induced a significant increase in CRH mRNA expression in the PVN.

CONCLUSIONS

The bite-raising procedure induced a rapid CRH mRNA response and a slower AVP mRNA response in the parvocellular PVN of the hypothalamus. Exposure to a novel stress following the bite-raising procedure further reinforced the CRH stress response. Thus, occlusal disharmony, such as that induced by raising the bite, may be a risk factor for hypersensitivity to a novel stress.

Oral Implant-Prostheses: New Teeth for a Brighter Brain

Several studies have demonstrated that chewing can be regarded as a preventive measure for cognitive impairment, whereas masticatory deficiency, associated with soft-diet feeding, is a risk factor for the development of dementia. At present the link between orofacial sensorimotor activity and cognitive functions is unknown. In subjects with unilateral molar loss we have shown asymmetries in both pupil size and masticatory muscles electromyographic (EMG) activity during clenching: the molar less side was characterized by a lower EMG activity and a smaller pupil. Since implant-prostheses, greatly reduced both the asymmetry in EMG activity and in pupil's size, trigeminal unbalance, leading to unbalance in the activity of the Locus Coeruleus (LC), may be responsible for the pupil's asymmetry. According to the findings obtained in animal models, we propose that the different activity of the right and left LC may induce an asymmetry in brain activity, thus leading to cognitive impairment. According to this hypothesis, prostheses improved the performance in a complex sensorimotor task and increased the mydriasis associated with haptic tasks. In conclusion, the present study indicates that the implant-prosthesis therapy, which reduces the unbalance of trigeminal proprioceptive afferents and the asymmetry in pupil's size, may improve arousal, boosting performance in a complex sensorimotor task.

Trial of oral metoclopramide on diurnal bruxism of brain injury

Bruxism is a diurnal or nocturnal parafunctional activity that includes tooth clenching, bracing, gnashing, and grinding. The dopaminergic system seems to be the key pathophysiology of bruxism and diminution of dopaminergic transmission at the prefrontal cortex seems to induce it. We report two patients with diurnal bruxism in whom a bilateral frontal lobe injury resulted from hemorrhagic stroke or traumatic brain injury. These patients' bruxism was refractory to bromocriptine but responded to low-dose metoclopramide therapy. We propose that administering low doses of metoclopramide is possibly a sound method for treating bruxism in a brain injury patient with frontal lobe hypoperfusion on positron emission tomography imaging.

Lesions of the ventral ascending noradrenergic bundles decrease the stress response to occlusal disharmony in rats

Occlusal disharmony induced by placing an acryl cap on the lower incisors of rats is perceived as chronic stress. This chronic stress activates corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN), resulting in stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. The ventral ascending noradrenergic bundles (V-NAB) from the brainstem innervate the PVN. To investigate the relationship between the response of the HPA axis and the V-NAB, we examined changes in extracellular noradrenaline (NA) in the PVN and plasma corticosterone, the final output of the HPA axis, following occlusal disharmony in rats injected with 6-hydroxydopamine (6-OHDA), a specific catecholamine neurotoxin. 6-OHDA microinjection into the V-NAB reduced the magnitude of the responses of extracellular NA in the PVN and the plasma corticosterone to occlusal disharmony. Our results suggest that V-NAB to the PVN are involved in occlusal disharmony-induced activation of the HPA axis.

Masticatory function and cognitive function

Recent studies have suggest that masticatory (chewing) function is useful for maintaining neurocognitive function in the elderly. For example, a reduced ability to masticate, such as that resulting from toothlessness or soft-diet feeding, causes learning and memory deficits in aged animals and pathologic changes in the hippocampus. In addition, occlusal disharmony impairs hippocampal memory processes via chronic stress, and induces similar hippocampal pathology. Chewing, however, rescues stress-induced suppression of long-term potentiation in the hippocampus and the stress-induced impairment of hippocampal-dependent learning. These findings strongly suggest a link between mastication and neurocognitive function.

Associated conditions and clinical significance of awake bruxism

BACKGROUND

Awake bruxism is defined as an oral parafunctional activity that includes clenching and grinding of teeth during wakefulness. Confirming the possible related anatomy and the clinical significance of awake bruxism in geriatric hospitals is the aim of this study.

METHODS

We analyzed the medical records of 503 patients who were admitted to hospital from April to June 2008. After the recognition of bruxism, the clinical, brain imaging studies and statistical parametric mapping (SPM) of brain single photon emission computed tomography were performed.

RESULTS

In each disease group, five of 125 Alzheimer's disease (AD) patients (4.0%), three of 11 frontotemporal dementia (FTD) patients (27.3%), seven of 230 stroke patients (including two patients related to citalopram, 3.0%), one of 45 Parkinson's disease patients (2.2%) and four of 17 hydrocephalus patients (23.5%) had bruxism. Even though awake bruxism occurred early after stroke onset, it occurred late after AD and FTD onset. This occurred in a far advanced stage of AD, while it occurred in a moderately advanced stage of FTD. SPM analysis in AD and FTD patients with awake bruxism revealed significant hypoperfusion in frontotemporal and other subcortical structures. Surface electromyography recordings from the masseter muscle showed rhythmic regular motor activity at a rate of 1-2/s.

CONCLUSION

This study suggests that awake bruxism is encountered not infrequently in various diseases in geriatric hospitals. It is frequently observed in FTD and normal pressure hydrocephalus, which characteristically shows frontal lobe dysfunction. These facts and SPM analysis show that awake bruxism can be regarded as a frontal neurological sign of various neurological disorders.

Occlusion and brain function: mastication as a prevention of cognitive dysfunction

Research in animals and humans has shown that mastication maintains cognitive function in the hippocampus, a brain area important for learning and memory. Reduced mastication, an epidemiological risk factor for the development of dementia in humans, attenuates spatial memory and causes hippocampal neurons to deteriorate morphologically and functionally, especially in aged animals. Active mastication rescues the stress-attenuated hippocampal memory process in animals and attenuates the perception of stress in humans by suppressing endocrinological and autonomic stress responses. Active mastication further improves the performance of sustained cognitive tasks by increasing the activation of the hippocampus and the prefrontal cortex, the brain regions that are essential for cognitive processing. Abnormal mastication caused by experimental occlusal disharmony in animals produces chronic stress, which in turn suppresses spatial learning ability. The negative correlation between mastication and corticosteroids has raised the hypothesis that the suppression of the hypothalamic-pituitary-adrenal (HPA) axis by masticatory stimulation contributes, in part, to preserving cognitive functions associated with mastication. In the present review, we examine research pertaining to the mastication-induced amelioration of deficits in cognitive function, its possible relationship with the HPA axis, and the neuronal mechanisms that may be involved in this process in the hippocampus.

Stomatognathic adaptive motor syndrome is the correct diagnosis for temporomandibular disorders

Temporomandibular disorder is a generic and inadequate conception to be used as a diagnosis. It fails to express the etiology or the pathophysiology and it is mainly associated with the anatomical site. Moreover, the clinical condition presents a mandibular motor problem and not a joint problem. The hypothesis presents the new diagnosis stomatognathic motor adaptive syndrome, which comprehend a motor response and the adaptive processes it induces. Inadequate occlusal contacts cause the mandible to shift in order to reach an ideal intercuspal position. The condylar displacements are proportional to such movements. Temporomandibular joint (TMJ) receptors respond to the capsular mechanical stress and the information reaches the trigeminal sensory nuclei. The mandibular modified position seems to be relevant information and may interfere with catecholaminergic neurotransmission in basal ganglia. The main motor responses comprise increased jaw muscle tone, decreased velocity of movements and incoordination. The overload of muscle function will produce adaptive responses on many stomatognathic structures. The muscle adaptive responses are hypertonia, pain, fatigue and weakness. Temporomandibular joint presents tissue modification, disc alteration and cracking noise. Periodontium show increased periodontal membrane, bone height loss and gingival recession. Teeth manifest increased wear facets, abfraction and non-accidental fractures. The periodontal and teeth adaptive processes are usually identified as occlusal trauma. The altered stomatognathic functions will show loss of velocity during mastication and speech. Fatigue, weakness in jaw muscle and difficulties to chew hard food are related to hypertonia. Incoordination between stomatognathic muscles groups is found, causing involuntary tongue/cheek biting and lateral jaw movements on speech. Otologic complaints, as aural fullness and tinnitus, are related to the tensor tympani muscle, innervated by the trigeminal nerve.

Occlusal disharmony increases stress response in rats

Repeated or chronic stress is known to produce structural and functional changes in the rat brain, and in particular, alter the response of the hypothalamic -- pituitary -- adrenal (HPA) axis to subsequent new stress. Occlusal disharmony via placement of acryl cap on the lower incisors of rats is perceived as chronic stress. To determine the response of the HPA axis to subsequent new stress in rats with occlusal disharmony, we measured plasma corticosterone levels in these rats after subjecting them to new stress. Plasma corticosterone levels in rats with and without incisal cap increased and reached a peak 30 min after exposure to the new stress. However, a later decrease in plasma corticosterone levels from peak levels was found in rats with incisal cap compared with rats without incisal cap. This finding suggests that occlusal disharmony alters the response of the HPA axis to subsequent new stress.

The bite-raised condition in aged SAMP8 mice reduces the expression of glucocorticoid receptors in the dorsal and ventral hippocampus

In the present study, we examined whether the effects induced by the bite-raised condition on glucocorticoid receptor (GR) expression differ between the dorsal and ventral hippocampus in SAMP8 mice. In the bite-raised condition, the number of GR-immunoreactive cells was significantly decreased in both the dorsal and ventral CA1 and dentate gyrus (DG) subfields of the hippocampus compared to control mice, as revealed by immunohistochemical analysis. The decrease in the number of GR-immunoreactive cells tended to be greater in the dorsal hippocampus than in the ventral hippocampus. Only in the DG subfield was there a significant difference in the number of GR-immunoreactive cells between the dorsal and ventral hippocampus. These findings suggest that in aged SAMP8 mice, the bite-raised condition decreases the number of GR-immunoreactive cells in both the dorsal and ventral hippocampus.

Urinary levels of catecholamines among individuals with and without sleep bruxism

INTRODUCTION

Sleep bruxism (SB) is characterized by repetitive and coordinated mandible movements and non-functional teeth contacts during sleep time. Although the etiology of SB is controversial, the literature converges on its multifactorial origin. Occlusal factors, smoking, alcoholism, drug usage, stress, and anxiety have been described as SB trigger factors. Recent studies on this topic discussed the role of neurotransmitters on the development of SB.

OBJECTIVE

Thus, the purpose of this study was to detect and quantify the urinary levels of catecholamines, specifically of adrenaline, noradrenaline and dopamine, in subjects with SB and in control individuals.

MATERIALS AND METHODS

Urine from individuals with SB (n = 20) and without SB (n = 20) was subjected to liquid chromatography. The catecholamine data were compared by Mann-Whitney's test (p </= 0.05).

RESULTS

Our analysis showed higher levels of catecholamines in subjects with SB (adrenaline = 111.4 microg/24 h; noradrenaline = 261,5 microg/24 h; dopamine = 479.5 microg/24 h) than in control subjects (adrenaline = 35,0 microg/24 h; noradrenaline = 148,7 microg/24 h; dopamine = 201,7 microg/24 h). Statistical differences were found for the three catecholamines tested.

CONCLUSION

It was concluded that individuals with SB have higher levels of urinary catecholamines.

Malocclusion induces chronic stress

We examined the effect of occlusal disharmony in senescence-accelerated (SAMP8) mice on plasma corticosterone levels, spatial learning in the water maze, fos induction, hippocampal neuron number, expression of glucocorticoid receptors (GR) and glucocorticoid receptor messenger ribonucleic acid (GRmRNA) in hippocampus and inhibitor of glucocorticoid (metyrapone). Bite-raised aged mice had significantly greater plasma corticosterone levels than age-matched control mice as well as impaired spatial memory and decreased Fos induction and a number of neurons in hippocampus. GR and GRmRNA expressions were significantly decreased in aged bite-raised mice compared with age-matched control mice. Pretreatment with metyrapone inhibited not only the bite-raised induced increase in plasma corticosterone levels, but also the reduction in the number of hippocampal neurons and impaired spatial learning. These datas suggest that the bite-raised condition may enhance the aging process in hippocampus, thereby leading to impairment of spatial memory by stress.

Duration-dependent effects of the bite-raised condition on hippocampal function in SAMP8 mice

We evaluated the effect of the duration of occlusal disharmony induced chronic stress on hippocampal function by examining spatial memory in the Morris water maze and on the number of hippocampal neurons in aged senescence-accelerated prone (SAMP8) mice. The bite of SAMP8 mice was raised 0.1 mm using dental adhesive. Groups of mice were tested in the Morris water maze 8, 11, or 22 d after raising the bite. The results indicated that the longer the duration of the bite-raised condition, the greater the impairment in spatial learning ability and the greater the decrease in the number of neurons in the hippocampal CA3 subfield. Thus, behavioral and morphologic deficits induced by the bite-raised condition in aged SAMP8 mice are influenced by the duration of the occlusal disharmony.

Enhanced sympathetic cardiac modulation in bruxism patients

Sleep bruxism, an oral parafunction including teeth clenching and grinding, might be related to increased stress. To evaluate sympathetic cardiac activity in bruxism patients, we monitored cardiac autonomic modulation using spectral analysis of heart rate variability and compared results to those of age-matched healthy volunteers. In bruxism patients, sympathetic cardiac activity was higher than in volunteers. The increased sympathetic tone suggests increased stress and might be related to occlusal disharmonies.

A proposed mechanism for diurnal/nocturnal bruxism: hypersensitivity of presynaptic dopamine receptors in the frontal lobe

There are many reports in the literature concerning nocturnal bruxism, however, diurnal (non-sleep)/nocturnal bruxism is rarely mentioned. We report three patients with diurnal/nocturnal bruxism. They differed from the usual features of nocturnal bruxism in hypoperfusion of the left frontal lobe, a poor response to l-dopa or bromocriptine therapy and a favourable response to metoclopramide. Hypersensitive presynaptic dopamine receptors may be the underlying pathology responsible for this type of bruxism. Regional differences in dopamine receptor pharmacology may explain the perplexing relationship of bruxism to both hyper- and hypo-dopaminergic states.

Occlusal disharmony affects plasma corticosterone and hypothalamic noradrenaline release in rats

Few neuro-endocrinological studies have examined the relationship between occlusal disharmony and stress. To determine the effect of occlusal disharmony on the central nervous system, we measured plasma corticosterone and extracellular noradrenaline in the vicinity of the hypothalamic paraventricular nucleus in rats both with and without incisal caps. After the caps were set, plasma corticosterone and extracellular noradrenaline levels gradually increased, reaching a peak at 8.5 and 6.5 hours, respectively, after which they decreased. Furthermore, plasma corticosterone and extracellular noradrenaline levels increased in a circadian fashion around the onset of the dark phase in rats without caps, but not in rats with caps. These results suggest that occlusal disharmony causes chronic stress in the rat.