Utilizing an additively manufactured Kois deprogrammer to record centric relation: A simplified workflow and delivery technique

A technique for fabricating an additively manufactured Kois deprogrammer is described from the initial patient data collection with an intraoral scanner to the 3D printing methods to fabricate the device. The incorporation of digital technologies for manufacturing a Kois deprogrammer provides new clinical and manufacturing tools, providing more efficient and less time-consuming design and manufacturing techniques than conventional techniques while maintaining conventional prosthodontic concepts.

Accuracy of digital and conventional systems in locating occlusal contacts: A clinical study

STATEMENT OF PROBLEM

The accuracy of methods used for locating occlusal contacts throughout the entire clinical procedure has been poorly studied.

PURPOSE

The purpose of this clinical study was to determine the reproducibility and criterion validity for different methods of locating occlusal contacts.

MATERIAL AND METHODS

Thirty-two adults with natural dentitions participated in this cross-sectional test-retest study. In total, occlusal contacts at maximum intercuspation were recorded by using 15 methods: silicone transillumination with Occlufast Rock (40, 50, 100, and 200 µm) and Occlufast CAD (40 and 50 µm); virtual occlusion (100, 200, 300, and 400 µm); articulating film (12-, 40-, 100-, and 200-µm-thick); and T-Scan III. Images of the occlusal records were scaled and calibrated spatially, and the occlusal contacts of the right posterior mandibular teeth were delimited by using the FIJI software program. Reproducibility was expressed as 95% confidence intervals (95% CI) of the percentage of agreement in the location of the occlusal contacts between images from the test sessions against retest sessions using the same method. Criterion validity was expressed as 95% CI of the percentage of agreement in the location of the occlusal contacts between images from the test sessions against images from Occlufast Rock (criterion standard).

RESULTS

Occlufast Rock achieved 85% to 95% agreement in the location of the occlusal contacts between the 2 sessions, whereas Occlufast CAD, 200-µm articulating film, and T-Scan offered 79% to 86%, 68% to 75%, and 65% to 75% agreement, respectively. The most valid method was Occlufast CAD (74% to 80%) followed by the 200-µm articulating film (57% to 63%), 400-µm virtual occlusion (53% to 62%), 100-µm articulating film (52% to 60%), and T-Scan (48% to 56%).

CONCLUSIONS

Conventional methods, such as 100- and 200-µm articulating film and digital methods, including 400 µm virtual occlusion and T-Scan, offer sufficient accuracy in locating the occlusal contacts. However, strategies are needed to improve accuracy.

Structural brain feature is associated with changes of masticatory performance in healthy elderly people: Evidence from longitudinal neuroimaging research over two years

BACKGROUND

Human neuroimaging studies have revealed the association between brain structure and masticatory function. However, the majority of the studies adopted a cross-sectional design, which hardly reveals the change in masticatory function and brain structure between different timepoints, and the dynamical association between changes in masticatory function and changes in brain structure has not been elucidated.

OBJECTIVE

With a longitudinal design, we assessed the association between changes in masticatory performance (MP) and regional brain volume.

METHODS

Twenty-two elderly participants received assessments of the number of missing teeth and MP (via colour-changeable chewing gum) when they entered the study (i.e. the initial stage, T0 ), approximately 6 months later (T0.5 ), and approximately 1-2 years later (T1 ). Difficulty of food intake was assessed using a questionnaire. The participants received magnetic resonance imaging (MRI) at T0 and T1 . The brain volume of the motor-related area was estimated using FreeSurfer for MRI data. The associations between different stages were analysed using Spearman's rho correlation coefficients.

RESULTS

(1) Individually, a smaller volume of right primary motor cortex at T0 was associated with increased MP from T0 to T1 , suggesting the brain's role in changing oral functions; (2) higher MP at T0 was associated with an increased volume of the left superior frontal cortex from T0 to T1 p, suggesting a potential effect on brain plasticity, and (3) increased difficulty to eat was associated with decrease MP but not brain volume of motor-related area.

CONCLUSIONS

The preliminary findings revealed a complicated pattern of structural brain features and masticatory function in elderly people, and either the hypothesis that the brain predisposes masticatory function or the hypothesis that mastication reshapes the brain is oversimplified.

Case Report: Modulation of Effective Connectivity in Brain Networks after Prosthodontic Tooth Loss Repair

INTRODUCTION. Recent neuroimaging studies suggest that dental loss replacements induce changes in neuroplasticity as well as in correlated connectivity between brain networks. However, as the typical temporal delay in detecting brain activity by neuroimaging cannot account for the influence one neural system exerts over another in a context of real activation (“effective” connectivity), it seems of interest to approach this dynamic aspect of brain networking in the time frame of milliseconds by exploiting electroencephalographic (EEG) data. MATERIAL AND METHODS. The present study describes one subject who received a new prosthodontic provisional implant in substitution for previous dental repairs. Two EEG sessions led with a portable device were recorded before and after positioning the new dental implant. By following MATLAB-EEGLAB processing supported by the plugins FIELDTRIP and SIFT, the independent component analysis (ICA) derived from EEG raw signals was rendered as current density fields and interpolated with the dipoles generated by each electrode for a dynamic study of the effective connectivity. One more recording session was undertaken six months after the placement of the final implant. RESULTS. Compared to the baseline, the new prosthodontic implant induced a novel modulation of the neuroplasticity in sensory-motor areas which was maintained following the definitive implant after six months, as revealed by changes in the effective connectivity from the basal strong enslavement of a single brain area over the others, to an equilibrate inter-related connectivity evenly distributed along the frontotemporal regions of both hemispheres. CONCLUSIONS. The rapid shift of the effective connectivity after positioning the new prosthodontic implant and its substantial stability after six months suggest the possibility that synaptic modifications, induced by novel sensory motor conditions, modulate the neuroplasticity and reshape the final dynamic frame of the interarea connectivity. Moreover, given the viability of the EEG practice, this approach could be of some interest in assessing the association between oral pathophysiology and neuronal networking.

Changes of neuroplasticity in cortical motor control of human masseter muscle related to orthodontic treatment

BACKGROUND

Orthodontic treatment is a common clinical method of malocclusion. Studies have found that neurons in the sensorimotor cortex of the brain undergo adaptive remodeling in response to changes in oral behavior or occlusion.

OBJECTIVE

To explore whether orthodontic treatment could be sufficient to cause neuroplastic changes in the corticomotor excitability of the masseter muscle.

METHODS

Fifteen Angle Class II malocclusion patients who were receiving orthodontic treatment participated in the study. Cortical excitability was assessed by electromyographic activity changes evoked by transcranial magnetic stimulation. Four orthodontic time points were recorded, including baseline, day 1, day 7, and day 30. Motor evoked potentials (MEPs) were recorded in the masseter muscle and the first dorsal interosseous muscle (FDI) serving as a control. The data were analysed by stimulus-response curves and corticomotor mapping. Statistical analyses involved repeated measures analysis of variance, two-way ANOVA, and Tukey's post hoc tests.

RESULTS

Motor evoked potentials (MEPs) of the masseter muscle were significantly decreased during orthodontic treatment compared with those of the baseline (p < .001). MEPs of the masseter muscle were dependent on session and stimulus intensity (p < .001), whereas MEPs of FDI were only dependent on stimulus intensity (p = .091). Finally, Tukey's post hoc tests demonstrated that MEPs of the masseter muscle on days 1 and 7, with 70%-90% stimulus intensities, were higher than those of baseline values (p < .001).

CONCLUSIONS

The present study suggested that orthodontic treatment can lead to neuroplastic changes in the corticomotor control of the masseter muscle, which may add to our understanding of the adaptive response of subjects to changes of oral environment during the orthodontic treatment.

Tactile sensation of natural teeth and dental implants in the somatosensory cortex

PURPOSE

This study aimed to investigate the cortical response characteristics evoked by natural teeth and implants.

METHODS

Five cats were subjected to intrinsic signal optical imaging to measure the cortical responses evoked by natural teeth and implants. The difference in tactile sensation between the implant and natural tooth was compared in detail at the cortical response level.

RESULTS

Some similarities were observed between the implants and natural teeth. The stimulating-response curves of the implants and natural teeth were generally S-curves, and both implants and natural teeth preferred labial-lingual direction stimulation. The implants and natural teeth differed in terms of their tactile sensitivity: implants were weaker than natural teeth in terms of both static and dynamic sensitivity. However, after saturation, there was no significant difference in tactile strength between implants and natural teeth.

CONCLUSIONS

Both natural teeth and implants are able to distinguish the tactile strength and stimulation direction. Although implants are less sensitive than the natural tooth, the maximal tactile function and directional preference of implants are similar to those of natural teeth.

Cognitive changes and neural correlates after oral rehabilitation procedures in older adults: a protocol for an interventional study

BACKGROUND

Epidemiological studies show an association between masticatory function and cognitive impairment. This has further strengthened the notion that tooth loss and impaired masticatory function may be risk factors for dementia and cognitive decline. Animal experiments have indicated a causal relationship and several possible mechanisms have been discussed. This evidence is, however, lacking in humans. Therefore, in the current interventional study, we aim to investigate the effect of rehabilitation of masticatory function on cognition in older adults.

METHODS

Eighty patients indicated for prosthodontic rehabilitation will be randomly assigned to an experimental or a control group. Participants will conduct neuropsychological assessments, masticatory performance tests, saliva tests, optional magnetic resonance imaging, and answer questionnaires on oral health impact profiles and hospital anxiety and depression scale before, 3 months, and 1 year after oral rehabilitation. The difference between the two groups is that the control group will be tested an additional time, (at an interval of about 3 months) before the onset of the oral rehabilitation procedure. The primary outcome is a change in measures of episodic memory performance.

DISCUSSION

Although tooth loss and masticatory function are widespread in older people, it is still an underexplored modifiable risk factor potentially contributing to the development of cognitive impairment. If rehabilitation of masticatory function shows positive effects on the neurocognitive function, this will have great implications on future health care for patients with impaired masticatory status. The present project may provide a new avenue for the prevention of cognitive decline in older individuals.

TRIAL REGISTRATION

The protocol for the study was retrospectively registered in ClinicalTrials.gov Identifier: NCT04458207, dated 02-07-2020.

Neurophysiological aspects of isotonic exercises in temporomandibular joint dysfunction syndrome

PURPOSE

The aim of the study was to investigate the electroneurophysiological aspects of volunteers with temporomandibular disorders before and after performing isotonic exercises for pain relief and self-care guidelines.

METHODS

The study was a parallel controlled randomized controlled trial under protocol 1,680,920. The inclusion criteria were age between 18 and 60 years, muscle temporomandibular dysfunction with or without limitation of mouth opening and self-reported pain with scores between 4 and 10. The individuals were randomized into experimental group and control. Twenty-three volunteers participated in the study, most of then were female. Control group had 11 and experimental group 12 individuals. Dropouts occurred in both groups, two in the experimental group and three in the control group. Since there were an intergroup imbalance the power density was analysed just in experimental group. Electroencephalographic recording was performed before and after the interventions, using the 32-channel apparatus, with sample frequency of 600 Hz and impedance of 5 kΩ. The data were processed through the MATLAB computer program. The individual records filtered off-line, using bandpass between 0.5 and 50 Hz. Epochs of 1,710 ms were created and the calculation of the absolute power density calculated by means of the fast Fourier transform. The statistical approach was inferential and quantitative.

RESULTS

The alpha power density analyzed presented a difference, but not significant, when compared in the two moments.

CONCLUSION

According to this study, isotonic exercises performed to reduce pain provided a small increase in alpha power density in the left temporal, parietal and occipital regions.

Effect of mandibular advancement device on plasticity in corticomotor control of tongue and jaw muscles

STUDY OBJECTIVES

This study aims to investigate if the use of a mandibular advancement device (MAD) is associated with neuroplasticity in corticomotor control of tongue and jaw muscles.

METHODS

Eighteen healthy individuals participated in a randomized crossover study with 3 conditions for 2 weeks each: baseline, wearing an oral appliance (OA: sham MAD) or MAD during sleep. The custom-made MAD was constructed by positioning the mandible to 50% of its maximal protrusion limit. Transcranial magnetic stimulation (TMS) was applied to elicit motor evoked potentials (MEPs). The MEPs were assessed by constructing stimulus-response curves at four stimulus intensities: 90%, 100%, 120%, and 160% of the motor threshold (MT) from the right tongue and right masseter, and the first dorsal interosseous muscles (FDI, control) at baseline, after the first and the second intervention.

RESULTS

There was a significant effect of condition and stimulus intensity both on the tongue and as well as on masseter MEPs (P < 0.01). Tongue and masseter MEPs were significantly higher at 120% and 160% following the MAD compared to the OA (P < 0.05). There were no effects of condition on FDI MEPs (P = 0.855).

CONCLUSIONS

The finding suggests that MAD induces neuroplasticity in the corticomotor pathway of the tongue and jaw muscles associated with the new jaw position. Further investigations are required in patients with obstructive sleep apnea (OSA) to see if this cortical neuroplasticity may contribute or perhaps predict treatment effects with MADs in OSA.

Effects of low occlusal loading on the neuromuscular behavioral development of cortically-elicited jaw movements in growing rats

The effect of altered occlusal force on masticatory-related neuromuscular control, which projects from the anterior part of the cortical masticatory area (A-CMA), during growth remains unclear. This study sought to evaluate the effect of occlusal hypofunction on neuromuscular development of jaw muscle activities and cortically-induced rhythmic jaw movements (RJMs) in growing rats. Sixty-four 2-week-old male albino Wistar rats were divided into the control (fed normal diet) and experimental (fed soft diet) groups soon after weaning. Electromyographic activity was recorded at 5, 7, 9, and 11 weeks from the right masseter and anterior digastric along with RJMs. We found a significantly longer onset latency and smaller peak-to-peak amplitude in the experimental group than that in the control group. The RJMs showed an increase in gape size and lateral excursion until up to 9 weeks in both groups. However, both the average gape size and lateral excursion were significantly smaller in the experimental group than that in the control group after 9 weeks. The jaw movement pattern also showed a significant decrease at the maximum opening period in the experimental group. Our findings indicate that inadequate occlusal function during growth alters neuromuscular control of masticatory behaviors and impairs the pattern of RJMs.

Does the Stomatognathic System Adapt to Changes in Occlusion? Best Evidence Consensus Statement

PURPOSE

The purpose of this Best Evidence Consensus Statement was to evaluate the existing literature on the stomatognathic system's ability to adapt to occlusal changes.

MATERIALS AND METHODS

The search term stomatognathic system was not useful as it resulted in over 400,000 results nor was the search term temporomandibular joint adaptation with 738 results due to the large number of references not related to the topic. The terms stomatognathic system adaptation to occlusal changes (186 results), teeth flexion (139 results), muscle adaptation to dental occlusion (278 results), and occlusal changes and neuroplasticity (11 results) provided the best selection of articles related to the topic. Limiting the above searches to systematic reviews and randomized controlled clinical trials resulted in multiple publications that were related to the question.9-13 Other literature reviews, data-based publications, and expert opinion resources have been included due to their relationship to the question.

RESULTS

From the extensive list of search results, 242 articles were determined to be potentially related to the focus question and were evaluated with 56 being included in this paper. It was determined that the stomatognathic system adapts to occlusal changes through the temporomandibular joint, muscles, teeth and bone. The dynamically modified periosteum on the articulator surfaces of the condyle and fossa has a unique load-bearing morphology with 3 subarticular layers of fibrocartilage that absorb and dissipate both peak (impact) and sustained loads. Adaptability of the TMJs and muscles can be documented through studies where artificially produced occlusal interferences were placed in patients and those study participants with normal temporomandibular joints (TMJs) adapted fairly well whereas those with a previous history of temporomandibular disorders (TMD) did not adapt as well.

CONCLUSIONS

Available evidence indicates patients generally adapt to the occlusal change inherent in orthodontic treatment, mandibular advancement surgery, and the use of mandibular advancement devices. The head and neck muscles also adapt to occlusal changes in patients without a history of TMD. The dentition adapts to changes through the bone and periodontal ligaments as well as the ability of teeth to undergo slight flexion under masticatory loading. This article is protected by copyright. All rights reserved.

The relation of poor mastication with cognition and dementia risk: a population-based longitudinal study

We investigated the effect of poor masticatory ability on cognitive trajectories and dementia risk in older adults. 544 cognitively intact adults aged ≥50 were followed for up to 22 years. Cognitive domains (verbal, spatial/fluid, memory, and perceptual speed) were assessed at baseline and follow-ups. Dementia was ascertained according to standard criteria. Masticatory ability was assessed using the Eichner Index and categorized according to the number of posterior occlusal zones: A (all four), B (3-1), and C (none).

At baseline, 147 (27.0%) participants were in Eichner category A, 169 (31.1%) in B and 228 (41.9%) in C. After the age of 65, participants in Eichner category B and C showed an accelerated decline in spatial/fluid abilities (β: -0.16, 95% CI: -0.30 to -0.03) and (β: -0.15, 95% CI: -0.28 to -0.02), respectively. Over the follow-up, 52 incident dementia cases were identified. Eichner categories B or C were not associated with an increased risk of dementia, compared to category A (Hazard Ratio [HR]: 0.83, 95% CI: 0.39 to 1.76 and HR: 0.63, 95% CI: 0.30 to 1.29, respectively).

Poor masticatory ability is associated with an accelerated cognitive decline in fluid/spatial abilities, however it was not related to a higher risk of dementia.

Tooth loss, cognitive impairment and chronic cerebral ischemia

BACKGROUND/PURPOSE

Vascular factor is an important risk factor in the process of cognitive impairment or dementia. Tooth loss could cause impairments of spatial learning and memory in mice, and nitric oxide (NO) and its synthase might be involved in the process. The objectives of this study were to investigate and compare the behavioral impairments between the Wistar rats with tooth loss and those with chronic ischemia and to determine the changes in nitric oxide (NO) and its synthases under those two conditions.

MATERIALS AND METHODS

The Morris water maze was used to test the spatial learning and memory abilities in the Wistar rats 8 weeks after the molar extraction procedure and the occlusion of 2 blood vessels to produce cerebral ischemia. The changes in NO and its synthases were evaluated using the Griess assay, Western blotting, and immunohistochemistry.

RESULTS

Similar impairments in the spatial learning and memory of Wistar rats were found after tooth loss and the induction of cerebral ischemia. The levels of NO and iNOS in the rat hippocampus increased, and the levels of eNOS decreased. Conclusion: For Wistar rats, the results of cognitive impairments related to tooth loss and those that occur due to chronic cerebral ischemia were statistically not significant and that NO, iNOS and eNOS in the hippocampus are involved in both cases.

Comparison of Cerebral Blood Flow Patterns in Patients with Phantom Bite Syndrome with Their Corresponding Clinical Features

BACKGROUND

Phantom bite syndrome (PBS) is characterized by an uncomfortable sensation during occlusion without any evident abnormality. A recent case-control study with single-photon emission computed tomography (SPECT) using ^99mTc-ethyl cysteinate dimer could not find the specific features of regional cerebral blood flow (rCBF), which might be due to the heterogeneity of PBS. We analyzed the brain images of PBS corresponding to the clinical features by studying PBS subgroups.

METHODS

This study contributes to elucidating the pathophysiology of PBS by evaluating regional brain perfusion on SPECT and its clinical features. We performed SPECT using ^99mTc-ethyl cysteinate dimer in 44 patients with PBS. The SPECT images were analyzed qualitatively and quantitatively.

RESULTS

Asymmetrical rCBF patterns were detected, corresponding to symptom laterality. Patients with PBS with right-side symptoms showed right-side-predominant rCBF asymmetry in the parietal region and left-side-predominant rCBF asymmetry in the thalamus, and vice versa. Moreover, the analysis of the association between rCBF and patient behaviors revealed that patients who blamed their dentists for their symptoms tended to have a symmetrical rCBF pattern.

CONCLUSION

Patients with PBS showed blood flow imbalance in the thalamus and parietal region corresponding to symptom laterality. There are two types of symmetrical and asymmetrical rCBF patterns in the pathophysiology of PBS despite similar clinical manifestations.

Tongue Force Training Induces Plasticity of the Lingual Motor Cortex in Young Adult and Aged Rats

Tongue exercise programs are used clinically for dysphagia in aged individuals and have been shown to improve lingual strength. However, the neural mechanisms of age-related decline in swallowing function and its association with lingual strength are not well understood. Using an established rat model of aging and tongue exercise, we hypothesized that the motor cortex of aged rats would have a smaller lingual motor map area than young adult rats and would increase in size as a function of tongue exercise. Over 8 weeks, rats either underwent a progressive resistance tongue exercise program (TE), learned the task but did not exercise (trained controls, TC), or were naïve untrained controls (UC). Cortical motor map areas for tongue and jaw were determined using intracortical microstimulation (ICMS). Rats in the TE and TC groups had a significantly larger motor cortex region for the tongue than the UC group. Lingual cortical motor area was not correlated with protrusive tongue force gains and did not differ significantly with age. These results suggest that learning a novel tongue force skill was sufficient to induce plasticity of the lingual motor cortex yet increasing tongue strength with progressive resistance exercise did not significantly expand the lingual motor area beyond the gains that occurred through the skilled learning component.

Chewing causes rapid changes in immunoreactive nerve patterns in rat molar teeth: Implications for dental proprioception and pain

OBJECTIVE

This study tests the hypothesis that normal use of teeth (chewing) causes changes in immunoreactive-(IR) patterns for endings of large Aβ and CGRP axons in rat molar cusps.

DESIGN

First, a new paradigm to test chewing in adult male rats was developed. Then IR patterns for large dental axons were analysed for a calcium-binding protein, parvalbumin (PV), heavy neurofilament protein-200 (NFP), and vesicle-release molecule synaptophysin (SYN) that all typify large dental axons and proprioceptors for comparison with endings of CGRP-IR neuropeptide axons. The behavior groups were: (1) daytime sleeping/fasting (Group:SF); (2) brief feeding after 8-11 h of daytime sleeping/fasting (Group:SF-C); (3) normal nocturnal feeding (Group:N); (4) nocturnal fasting (Group:NF); (5) brief feeding/chewing after nocturnal fasting (Group:NF-C).

RESULTS

Nerve endings with NFP-, PV-, or SYN-IR were lost or altered in pulp and dentin in all chewing groups. Other endings with CGRP-IR were near those with PV-, NFP- and SYN-IR at the pulp-dentin border and in dentin, and they also lost immunoreactivity in all chewing groups. The special beaded regions along the crown pulp/dentin borders lost neural labeling in all chewing groups. Nerves of molar roots and periodontal ligament were not changed.

CONCLUSIONS

Rapid neural reactions to chewing show extensive, reversible, non-nociceptive depletions of crown innervation. Those changes were rapid enough to occur during normal feeding followed by recovery during rest. The new dental paradigm related to chewing and fasting allows dissection of intradental proprioceptive-like mechanisms during normal tooth functions for comparison with nociceptive and mechanosensitive reactions after injury or inflammation.

Change of Cerebral Blood Flow After a Successful Pharmacological Treatment of Phantom Bite Syndrome: A Case Report

Background

“Phantom bite syndrome,” a persistent complaint of an uncomfortable bite sensation with no obvious occlusal abnormal finding, recently was suggested to be related with central nervous system dysfunction. Here, we report a case of phantom bite syndrome in which the occlusal discomfort was improved with mirtazapine and aripiprazole combination parallel with regional cerebral blood flow change.

Case report

A 60-year-old-female patient came to our clinic with the chief complaint of a “loosely bite” after dental treatment and various uncomfortable sensations of body sites. One year after the medication therapy, the prosthodontic retreatment was carried out successfully, and a good outcome was obtained for over 24 months so far. In addition, a subsequent change of regional cerebral blood flow was observed in single-photon emission computed tomography: the right and left asymmetry of cerebral blood flow in the frontal lobe has disappeared along with the improvement to the symptoms improvement.

Conclusions

This case suggests that some central nervous system dysfunction involving dopaminergic system might be related to the pathophysiology of phantom bite syndrome.

Does experienced pain affects local brain volumes? Insights from a clinical acute pain model

Background/Objective:To study pain-brain morphometry associations as a function of post-surgery stages (anesthesia, pain and analgesia) in an acute pain model. Method:Impacted mandible third molar were extracted. Before surgery, an anatomical T1 scan was obtained. Regional brain volumen and subcortical nuclei shapes were obtained. Statistical analyses were done using multiple regression, being pain scores the predictors and voxel volumes, subcortical nuclei volumes and subcortical nuclei shapes, the outcomes. Results:Pain was significantly larger at pain than at anesthesia and analgesia stages, and was higher during anesthesia than during analgesia. Pain intensity was related to grey matter in several cortical (Insula, Mid Frontal and Temporal Gyruses, Precuneus, Anterior Cingulate), and subcortical nuclei (Hippocampus, Thalamus, Putamen, Amygdala), depending of the post-surgical stage. A larger number of brain areas showed significance at pain that at anesthesia and analgesia stages. Conclusions:The relationships of regional brain volumes and subcortical nuclei shapes with pain scores seemed to be unsteady, as they changed with the patient's actual pain stage.

Alteration of occlusal vertical dimension induces signs of neuroplastic changes in corticomotor control of masseter muscles: Preliminary findings

PURPOSE

To investigate the effect of altering occlusal vertical dimension (OVD) in patients with severe attrition on corticomotor control of the masseter muscles as assessed by navigated transcranial magnetic stimulation (nTMS).

METHODS

Seven patients (58.6 ± 8.4 years) with decreased OVD due to severe attrition were given mandibular occlusal splints to alter the OVD with the instruction to wear during the whole awake time for a period of four weeks. Motor-evoked potentials (MEPs) and the motor cortex maps of the masseter muscles and first dorsal interosseous (FDI) muscles as control were recorded by nTMS at baseline and at least 4 weeks after the alteration of OVD. The stimulus-response curves of MEPs were analysed with two-way repeated-measures ANOVA, and the numerical rating scale scores, motor thresholds, onset latencies, motor cortex maps and centre of gravity (COG) were analysed with paired t tests.

RESULTS

There was a significant increase in the amplitude of the masseter muscle MEPs (P = 0.036), but no change in the motor cortex map areas (P = 0.111) four weeks after the alteration of OVD. Furthermore, there was no significant difference in either the amplitude of the FDI muscle MEPs (P = 0.466) or the motor cortex map areas (P = 0.230) before and after OVD alteration.

CONCLUSION

The results suggest that alteration of OVD in patients with severe attrition was associated with signs of neuroplastic changes in the corticomotor control of the masseter muscles. The results of the study may add to our understanding of the putative mechanisms related to cortical changes in response to OVD alterations.

Dental deafferentation and brain damage: A review and a hypothesis

In the last few decades, neurobiological and human brain imaging research have greatly advanced our understanding of brain mechanisms that support perception and memory, as well as their function in daily activities. Knowledge of the neurobiological mechanisms behind the deafferentation of stomatognathic systems has also expanded greatly in recent decades. In particular, current studies reveal that the peripheral deafferentations of stomatognathic systems may be projected globally into the central nervous system (CNS) and become an associated critical factor in triggering and aggravating neurodegenerative diseases. This review explores basic neurobiological mechanisms associated with the deafferentation of stomatognathic systems. Further included is a discussion on tooth loss and other dental deafferentation (DD) mechanisms, with a focus on dental and masticatory apparatuses associated with brain functions and which may underlie the changes observed in the aging brain. A new hypothesis is presented where DD and changes in the functionality of teeth and the masticatory apparatus may cause brain damage as a result of altered cerebral circulation and dysfunctional homeostasis. Furthermore, multiple recurrent reorganizations of the brain may be a triggering or contributing risk factor in the onset and progression of neurodegenerative conditions such as Alzheimer's disease (AD). A growing understanding of the association between DD and brain aging may lead to solutions in treating and preventing cognitive decline and neurodegenerative diseases.

Face sensorimotor cortex undergoes neuroplastic changes in a rat model of trigeminal neuropathic pain

Trigeminal nerve injury can result in neuropathic pain behavior and alterations in motor function, but it is unclear if such injury produces neuroplastic alterations in face sensorimotor cortex that could contribute to the alterations in motor function. Therefore, this study aimed to determine if trigeminal nerve injury in a rat neuropathic pain model induces neuroplastic changes in jaw and tongue motor representations in face sensorimotor cortex in association with facial nociceptive behavior. Right infraorbital nerve transection was performed in adult male Sprague-Dawley rats; sham-operated rats served as controls. Nociceptive behavior was assessed by testing facial mechanical sensitivity pre-operatively and post-operatively (1-28 days). Intracortical microstimulation was also applied post-operatively in a series of microelectrode penetrations to map jaw and tongue motor representations in the face sensorimotor cortex by analyzing anterior digastric and genioglossus electromyographic activities evoked by microstimulation at histologically verified sites in face primary somatosensory cortex (face-SI) as well as face primary motor cortex (face-MI). Compared to sham, infraorbital nerve injury induced a significant (2-way repeated-measures analysis of variance, P < 0.001) bilateral decrease in facial mechanical threshold that lasted up to 28 days post-operatively. Nerve injury also induced a significant bilateral decrease compared to sham (P < 0.05) in the number of anterior digastric and/or genioglossus sites in face-MI and in face-SI. These findings indicate that trigeminal nerve injury induces neuroplastic alterations in jaw and tongue motor representations in face sensorimotor cortex that are associated with facial nociceptive behavior and that may contribute to sensorimotor changes following trigeminal nerve injury.

Oro-facial impairment in stroke patients

Stroke is considered one of the leading causes of death and acquired disability with a peak prevalence over the age of 80 years. Stroke may cause debilitating neurological deficiencies that frequently result in sensory deficits, motor impairment, muscular atrophy, cognitive deficits and psychosocial impairment. Oro-facial impairment may occur due to the frequent involvement of the cranial nerves' cortical representation areas, central nervous system pathways or motoneuron pools. The aim of this narrative, non-systematic review was to discuss the implications of stroke on oro-facial functions and oral health-related quality of life (OHRQoL). Stroke patients demonstrate an impaired masticatory performance, possibly due to reduced tongue forces and disturbed oral sensitivity. Furthermore, facial asymmetry is common, but mostly discrete and lip restraining forces are reduced. Bite force is not different between the ipsi- and contra-lesional side. In contrast, the contra-lesional handgrip strength and tongue-palate contact during swallowing are significantly impaired. OHRQoL is significantly reduced mainly because of the functional impairment. It can be concluded that impaired chewing efficiency, dysphagia, facial asymmetry, reduced lip force and OHRQoL are quantifiable symptoms of oro-facial impairment following a stroke. In the absence of functional rehabilitation, these symptoms seem not to improve. Furthermore, stroke affects the upper limb and the masseter muscle differently, both, at a functional and a morphological level. The rehabilitation of stroke survivors should, therefore, also seek to improve the strength and co-ordination of the oro-facial musculature. This would in turn help improve OHRQoL and the masticatory function, subsequently preventing weight loss and malnutrition.

Orofacial motor functions in pediatric obstructive sleep apnea and implications for myofunctional therapy

OBJECTIVES

The purposes of this study were (1) to identify possible differences in muscular and orofacial functions between children with obstructive sleep apnea (OSA) and with primary snoring (PS); (2) to examine the standardized difference between normal values of myofunctional scores and those of subjects with OSA or PS; and (3) to identify the features associated with OSA.

METHODS

Participants were 39 children (mean age 8 ± 1.2 years) of which, 27 had a diagnosis of OSA and 12 had PS. All participants were examined by an otorhinolaryngologist and underwent overnight polysomnography. Orofacial characteristics were determined through a validated protocol of orofacial myofunctional evaluation with scores (OMES), surface electromyography of masticatory muscles, and measurements of maximal lip and tongue strength. Reference values in the OMES were included to quantify the standardized difference (effect size = ES) relative to the groups studied and in the regression analysis.

RESULTS

The OSA group had lower scores in breathing and deglutition, more unbalanced masticatory muscle activities than PS group (P < 0.05), but both groups had similar reductions in orofacial strength. OSA had a large ES (Cohen's d > 0.8) in all analysed OMES scores, while PS group showed small and medium differences in breathing and mastication scores, respectively. The mobility of the stomatognathic components score was the most important to contribute for group status (57%, P < 0.0001) in the regression analysis.

CONCLUSION

Children with tonsillar hypertrophy and OSA had relevant impairments in orofacial functions and lesser muscular coordination than children with PS.

Dental Occlusion and Ophthalmology: A Literature Review

Stomatognathic system is strictly correlated to other anatomical regions; many studies investigated relationship between temporomandibular joint and posture, several articles describe cranio-facial pain from dental causes, such as trigger points. Until now less interest has been given to connections between dental occlusion and ophthalmology, even if they are important and involving. Clinical experience in dental practice claims that mandibular latero-deviation is connected both to eye dominance and to defects of ocular convergence. The trigeminal nerve is the largest and most complex of the twelve cranial nerves. The trigeminal system represents the connection between somitic structures and those derived from the branchial arches, collecting the proprioception from both somitic structures and oculomotor muscles. The intermedius nucleus of the medulla is a small perihypoglossal brainstem nucleus, which acts to integrate information from the head and neck and relays it on to the nucleus of the solitary tract where autonomic responses are generated. This intriguing neurophysiological web led our research group to investigate anatomical and functional associations between dental occlusion and vision. In conclusion, nervous system and functional pathways strictly connect vision and dental occlusion, and in the future both dentists and oculists should be more and more aware of this correlation for a better diagnosis and therapy.