Lower Jaw Position Research Articles

Influence of oral motor tasks on postural muscle activity during dynamic reactive balance.

Jaw clenching improves dynamic reactive balance on an oscillating platform during forward acceleration and is associated with decreased mean sway speed of different body regions. It is suggested that jaw clenching as a concurrent muscle activity facilitates human motor excitability, increasing the neural drive to distal muscles. The underlying mechanism behind this phenomenon was studied based on leg and trunk muscle activity (iEMG) and co-contraction ratio (CCR). Forty-eight physically active and healthy adults were assigned to three groups, performing three oral motor tasks (jaw clenching, tongue pressing against the palate or habitual lower jaw position) during a dynamic one-legged stance reactive balance task on an oscillating platform. The iEMG and CCR of posture-relevant muscles and muscle pairs were analysed during platform forward acceleration. Tongue pressing caused an adjustment of co-contraction patterns of distal muscle groups based on changes in biomechanical coupling between the head and trunk during static balancing at the beginning of the experiment. Neither iEMG nor CCR measurement helped detect a general neuromuscular effect of jaw clenching on the dynamic reactive balance. The findings might indicate the existence of robust fixed patterns of rapid postural responses during the important initial phases of balance recovery.

Analysis of hardware methods of treatment of patients with temporomandibular joint dysfunction

Objective. To conduct a comparative analysis of effectiveness of treatment of patients with dysfunction of temporomandibular joint (DTMJ) using hardware methods of treatment with occlusive mouthguards of various types. Materials and methods. 99 patients (88 females and 11 males aged 41,2 ± 10,7) with different combinations of revealed and confirmed signs of DTMJ were examined from 2013 to 2023. According to the personal clinical picture, complaints revealed, aetiology and pathogenesis of the disease all the patients of the comparison group and 2 main groups (99 patients) were administered individual complex treatment for DTMJ. The treatment was aimed at the elimination of pain, relief of masticatory muscles spasm, improvement of the extent of opening of mouth, correction of the lower jaw position, occlusive interference elimination and restoration of height of the lower third of the face. While carrying out the hardware treatment, occlusive mouthguards of 3 types were made based on the jaw model of the patients. The models were got from the silicone imprints of the jaw. Results. MR images of temporomandibular joints of the 99 patients showed that ventral dislocation of articular disk occurred most frequently (in 88 patients). Less frequently (4 % of cases) it was combined with dislocation of the disk laterally. Rarely distal dislocation of the articular disk occurred – 1,9 % of cases (2 patients). Study of the results of the appliance of different types of occlusive mouthguards demonstrates the necessity to work out the types of occlusive devices allowing decompression of temporomandibular joint elements, centering lower jaw position and orthodontic elimination of dentofacial abnormalities and deformities which lead to occlusive interference. Conclusions. Analysis of occlusive devices used in the diagnosis and treatment of patients with DTMJ shows that the most effective devices are those that successfully combine elements of splints with a narrower purpose.

Optimizing Orthognathic Surgery: Leveraging the Average Skull as a Dynamic Template for Surgical Simulation and Planning in 30 Patient Cases.

Virtual planning has revolutionized orthognathic surgery (OGS), marking a significant advancement in the field. This study aims to showcase the practical application of our established 3D average skull template as a guiding framework for surgical planning, and to share valuable insights from our clinical experience. We enrolled 30 consecutive Taiwanese patients (18 females and 12 males) who underwent two-jaw orthognathic surgery with surgical simulation, utilizing the average skull template for planning. Results indicate the method's applicability and precision. By adhering to the surgical plan, post-operative outcomes closely aligned with the average skull template, showing negligible deviations of less than 2 mm. Moreover, patients expressed high satisfaction with post-surgery facial changes, with the chin appearance receiving the highest satisfaction scores, while the lowest scores were attributed to nose appearance. Notably, the substantial change in lower jaw position post-mandibular setback surgery contributed to increased satisfaction with the chin position. In conclusion, this study does not seek to replace established surgical planning methods, but underscores that utilizing an average skull as a surgical design template provides a viable, accurate, and efficient option for OGS patients.

Two-phase rehabilitation of patients with a forced position of the lower jaw: a clinical case

Relevance. Malocclusion correction in children very frequently requires several orthodontic appliances throughout the entire treatment period. The high prevalence of dental abnormalities in childhood determines the issue's relevance.Clinical cases' description. The article presents summaries from the records of the patients who presented for orthodontic care with malocclusion complicated by the forced position of the lower jaw. The authors implemented a two-phase orthodontic treatment protocol and achieved acceptable aesthetic and functional results.Conclusion. Laboratory-made plates with occlusal pads in the first phase of treatment of patients with mixed dentition contributes to the normalization of the lower jaw position and the alignment of the occlusal plane. In the second phase of orthodontic treatment, a standard silicone aligner allows for the improvement of dental arch relationship in the vertical, sagittal and transversal planes, normalization of dental arch form, and the correction of displaced teeth.

CONCEPTUAL APPROACH TO DIAGNOSING AND TREATING DENTOALVEOLAR TRANSVERSAL DIVERGENT OCCLUSION

The results of clinical, photometric, morphometric, radiological and functional studies were employed to develop an advanced methodology for treating patients with dentoalveolar transversal divergent occlusion. The dentoalveolar type of transversal divergent occlusion has been identified as being both an independent nosological issue and can be combined with other issues and deformations affecting dentoalveolar arches. The developed concept for comprehensive rehabilitation of patients with dentoalveolar transversal divergent occlusion complicated by dentition issues has a following algorithm: counseling, diagnosis, splint treatment using a distracting splint, previously completed orthodontic treatment, splint treatment using a stabilizing splint, final orthodontic treatment, aesthetic and functional prosthetics. Comprehensive rehabilitation offered to patients with dentoalveolar transversal divergent occlusion is aimed at improving the jaw bones position and the occlusion. Thus, it creates multiple fissure-tubercle dentition contacts; stabilizes the lower jaw position; improves position of intra-articular structures. The comprehensive rehabilitation enable eliminating functional disorders, muscle excessive tension and pain symptom. In general, the face profile as well as the occlusal plane horizontal position is improved.

The time course of first formant movement in normal and loud speech

Louder speech tends to be slower than typical speech. For some vowels (viz., low and lax ones), louder speech may also be associated with higher first formant frequencies (F1s) at vowel midpoint. Possibly, increased duration allows speakers more time to reach a lower jaw position, thus a higher value of F1, in loud speech. In earlier work, we found that some loudness differences appeared at 25% and 75% of vowel durations, i.e., they were seen for much of the vowel. The current study presents data from 11 German-speaking women producing naturally elicited typical and loud speech. Target words included high, low, tense, and lax vowels with surrounding consonantal place controlled. We will present full vowel trajectories, i.e., from preceding to following consonants, to assess the time course of F1 differences across vowel types and loudness conditions. F1 will also be considered within normalized time intervals to control for durational differences between conditions. We expect that F1 formant trajectories will show minimal loudness differences throughout the vowel for high tense vowels, but time-varying differences will be more apparent for low and lax vowels, and appear rather early in the vowel.

Comparative analysis of the effectiveness of the use of various orthodontic appliances in the correction of malocclusion of the II class in children and adolescents

This study is dedicated to a comparative analysis of effectiveness of using orthodontic appliances when treating class II malocclusion in children and adolescents. It was shown that treatment with the Invisalign system with a change of the lower jaw position is the most effective method for correcting class II malocclusion in growing patients. Using Invisalign aligners showed not only the best efficacy according to teleroentgenograms. but also made the treatment process comfortable for patients at all its stages. Moreover, higher level of compliance was demonstrated with treatment using the Invisalign system compared to the Twin-block appliance.

Algorithm for treatment of patients with class II malocclusion rejecting orthognathic surgery

Orthodontic treatment of 60 patients with class II malocclusion at the age of 18 to 44 years, using the bracket system, FFTA and orthodontic miniscrews was performed. In order to assess the results of treatment, cone-beam computed tomography were obtained at the beginning and at the end of treatment. As a result of the treatment normalization of lower jaw position, dental position and occlusion were achieved, the lower incisors protrusion was eliminated and the facial profile was improved, reliably confirmed by lateral cephalograms. The proposed treatment algorithm proved to be effective for stable correction of skeletal class II malocclusion in patients rejecting orthognathic surgery.

Functional Aesthetics in Implantology and Reconstructive Dentistry: Analysis and Transfer of Referenced Individual Patient Information With the PlaneSystem®

The goal of every dental treatment should be a sustainable and functional care which is adapted to the individual movement patterns. In this context, a structured and anatomically accurate functional analysis can contribute to the correct muscular and skeletal adjustment of patients in order to develop the correct treatment strategy, which then guarantees a permanently stable reconstruction. The individual and whole-body analysis as well as the dental history of the patient and the correct transfer into the articulator play an important role. How accurately can the dental technician judge the actual situation of the patient? How realistic are planes, chewing patterns, jaw joint movements and closing angles represented in the articulator compared to the oral situation? Innovative aspects such as the reference to the natural head position (NHP), the exact determination of the anatomical centre and the correct three-dimensional transfer into the articulator are decisive factors which influence the success of the treatment. This article focuses on the realistic, correctly positioned transfer of the casts and other anatomical parameters into the analogue or virtual articulator. The development of the function-analytical method is presented using the PlaneSystem®. The detection of patient-specific details using the analogue method (e.g. head posture, facial proportions, physiognomic landmark, cast analysis, cast orientation, movement recording, joint mechanics, lower jaw position in physiological, unmanipulated centric) as well as the digital procedure (e.g. facial scan, three-dimensional analysis, photo documentation) and their transfer into the articulator form the basis. The occlusal plane and asymmetries are measured individually for each patient and transferred into the articulator in the same way as the vertical dimension of the occlusion (VDO) and the alignment of the lower jaw. All collected information can finally be integrated into a digital workflow so that reference can be made to purely virtual solutions. In the following, the necessity out of which the systematics developed as well as the individual development stages are described. Furthermore, the potential is illustrated in that the use of this method offers to the prosthetic working team.

Simultaneous, radiation-free registration of the dentoalveolar position and the face by combining 3D photography with a portable scanner and impression-taking

ObjectivesSimultaneous, radiation-free registration of the teeth and the upper and lower jaw positions in relation to the extraoral soft tissue could improve treatment planning and documentation. The purpose of this study is to describe a workflow to solve this form of registration and surface acquisition with a mobile device.MethodsFacial scans of ten healthy participants were taken using a blue-light LED 3D scanner (Artec® Space Spider; Artec® Group; Luxembourg). An impression of the maxillary dentoalveolar arch was taken simultaneously to the 3D photo using a modified impression tray with two different extraoral registration geometries (sphere vs. cross). Following, an impression of the mandibular dentoalveolar arch was taken once. Both impressions were scanned with the 3D scanner. All resulting standard tesselation language (.stl) files of the geometries were compared to the original, virtual .stl files and the root mean square errors (RMSE) were calculated for each surface (Artec Studio 13 Professional × 64; Artec® Group; Luxembourg) to determine which geometry serves as a better reference for intra-extraoral registration.ResultsThe RMSE between the original geometries and the scanned counterfeits were statistically lower for spherical geometries (p < 0.008). Once scanned and aligned, both geometries enabled an alignment of the intra- and extraoral scan. However, the spherical geometries showed virtually better results without significance (p = 0.70).ConclusionsThe presented study provides a radiation-free solution for simultaneous dentoalveolar correlations in relation to the extraoral soft tissue. Spherical geometries achieved more precise and easier intra-extraoral alignments using the applied mobile 3D scanner and workflow.

Coordinative movement of articulators in bilabial stop /p/*

Speech articulators are coordinated for the purpose of segmental constriction in terms of a task. In particular, vertical jaw movements repeatedly contribute to consonantal as well as vocalic constriction. The current study explores vertical jaw movements in conjunction with bilabial constriction in bilabial stop /p/ in the context /a/-to-/a/. Revisiting kinematic data of /p/ collected using the electromagenetic midsagittal articulometer (EMMA) method from seven (four female and three male) speakers of Seoul Korean, we examined maximum vertical jaw position, its relative timing with respect to the upper and lower lips, and lip aperture minima. The results of those dependent variables are recapitulated in terms of linguistic (different word boundaries) and paralinguistic (different speech rates) factors as follows. Firstly, maximum jaw height was lower in the across-word boundary condition (across-word &lt; within-word), but it did not differ as a function of different speech rates (comfortable = fast). Secondly, more reduction in the lip aperture (LA) gesture occurred in fast rate, while word-boundary effects were absent. Thirdly, jaw raising was still in progress after the lips’ positional extrema were achieved in the within-word condition, while the former was completed before the latter in the across-word condition. Lastly, relative temporal lags between the jaw and the lips (UL and LL) were more synchronous in fast rate, compared to comfortable rate. When these results are considered together, it is possible to posit that speakers are not tolerant of lenition to the extent that it is potentially realized as a labial approximant in either word-boundary condition while jaw height still manifested lower jaw position in the across-word boundary condition. Early termination of vertical jaw maxima before vertical lower lip maxima across-word condition may be partly responsible for the spatial reduction of jaw raising movements. This may come about as a consequence of an excessive number of factors (e.g., upper lip height (UH), lower lip height (LH), jaw angle (JA)) for the representation of a vector with two degrees of freedom (x, y) engaged in a gesture-based task (e.g., lip aperture (LA)). In the task-dynamic application toolkit, the jaw angle parameter can be assigned numerical values for greater weight in the across-word boundary condition, which in turn gives rise to lower jaw position. Speech rate-dependent spatial reduction in lip aperture may be able to be resolved by means of manipulating activation time of an active tract variable in the gestural score level.

Coordinative movement of articulators in bilabial stop /p/*

Speech articulators are coordinated for the purpose of segmental constriction in terms of a task. In particular, vertical jaw movements repeatedly contribute to consonantal as well as vocalic constriction. The current study explores vertical jaw movements in conjunction with bilabial constriction in bilabial stop /p/ in the context /a/-to-/a/. Revisiting kinematic data of /p/ collected using the electromagenetic midsagittal articulometer (EMMA) method from seven (four female and three male) speakers of Seoul Korean, we examined maximum vertical jaw position, its relative timing with respect to the upper and lower lips, and lip aperture minima. The results of those dependent variables are recapitulated in terms of linguistic (different word boundaries) and paralinguistic (different speech rates) factors as follows. Firstly, maximum jaw height was lower in the across-word boundary condition (across-word &lt; within-word), but it did not differ as a function of different speech rates (comfortable = fast). Secondly, more reduction in the lip aperture (LA) gesture occurred in fast rate, while word-boundary effects were absent. Thirdly, jaw raising was still in progress after the lips’ positional extrema were achieved in the within-word condition, while the former was completed before the latter in the across-word condition. Lastly, relative temporal lags between the jaw and the lips (UL and LL) were more synchronous in fast rate, compared to comfortable rate. When these results are considered together, it is possible to posit that speakers are not tolerant of lenition to the extent that it is potentially realized as a labial approximant in either word-boundary condition while jaw height still manifested lower jaw position in the across-word boundary condition. Early termination of vertical jaw maxima before vertical lower lip maxima across-word condition may be partly responsible for the spatial reduction of jaw raising movements. This may come about as a consequence of an excessive number of factors (e.g., upper lip height (UH), lower lip height (LH), jaw angle (JA)) for the representation of a vector with two degrees of freedom (x, y) engaged in a gesture-based task (e.g., lip aperture (LA)). In the task-dynamic application toolkit, the jaw angle parameter can be assigned numerical values for greater weight in the across-word boundary condition, which in turn gives rise to lower jaw position. Speech rate-dependent spatial reduction in lip aperture may be able to be resolved by means of manipulating activation time of an active tract variable in the gestural score level.

Strength improvements through occlusal splints? The effects of different lower jaw positions on maximal isometric force production and performance in different jumping types.

ObjectiveThe influence of the jaw position on postural control, body posture, walking and running pattern has been reported in the literature. All these movements have in common that a relatively small, but well controlled muscle activation is required. The induced effects on motor output through changed jaw positions have been small. Therefore, it has been questioned if it could still be observed in maximal muscle activation.MethodTwenty-three healthy, mid age recreational runners (mean age = 34.0 ± 10.3 years) participated in this study. Three different jump tests (squat jump, counter movement jump, and drop jumps from four different heights) and three maximal strength tests (trunk flexion and extension, leg press of the right and left leg) were conducted. Four different dental occlusion conditions and an additional familiarization condition were tested. Subjects performed the tests on different days for which the four occlusion conditions were randomly changed.ResultsNo familiarization effect was found. Occlusion conditions with a relaxation position and with a myocentric condylar position showed significantly higher values for several tests compared to the neutral condition and the maximal occlusion position. Significance was found in the squat jump, countermovement jump, the drop jump from 32cm and 40cm, trunk extension, leg press force and rate of force development. The effect due to the splint conditions is an improvement between 3% and 12% (min and max). No influence of the jaw position on symmetry or balance between extension and flexion muscle was found.ConclusionAn influence of occlusion splints on rate of force development (RFD) and maximal strength tests could be confirmed. A small, but consistent increase in the performance parameters could be measured. The influence of the occlusion condition is most likely small compared to other influences as for example training status, age, gender and circadian rhythm.

Patient's Psychological Response to Twin-block Therapy

ABSTRACT Aims and objectives To determine the psychological response of the patient to twin-block therapy. To design and formulate a questionnaire to patient on twin-block therapy in the orthodontic clinic and the result will be evaluated. Materials and methods A total of 14 patients within the age group of 12 to 14 years on twin-block therapy for treatment of skeletal class II malocclusion with a mandibular deficiency in the Department of Orthodontics were selected. A questionnaire was formulated at the end of twin-block therapy. The completed questionnaire was analyzed and the patient responses to the different aspects of twin-block treatment were recorded. Results Of the 14 patients, 12 patients liked wearing the appliance. All the patients wore it comfortably full time. About 3 out of 14 had pain, 1 had ulcer, 9 14 had difficulty in eating, 6 patients had altered taste, and 3 had altered speech. A total of 13 patients observed improvement in lower jaw position. A total of 13 patients considered recommending the appliance to families and friends. Conclusion The response of the patient to twin-block appliance was positive. The twin block appears to be well accepted by the patients despite their age. Clinical significance Patient compliance directly affects the treatment outcome of the appliance. How to cite this article Thirumurthi AS, Felicita AS, Jain RK. Patient's Psychological Response to Twin-block Therapy. World J Dent 2017;8(4):327-330.

Influence of the Lower Jaw Position on the Running Pattern.

IntroductionThe effects of manipulated dental occlusion on body posture has been investigated quite often and discussed controversially in the literature. Far less attention has been paid to the influence of dental occlusion position on human movement. If human movement was analysed, it was mostly while walking and not while running. This study was therefore designed to identify the effect of lower jaw positions on running behaviour according to different dental occlusion positions.MethodsTwenty healthy young recreational runners (mean age = 33.9±5.8 years) participated in this study. Kinematic data were collected using an eight-camera Vicon motion capture system (VICON Motion Systems, Oxford, UK). Subjects were consecutively prepared with four different dental occlusion conditions in random order and performed five running trials per test condition on a level walkway with their preferred running shoes. Vector based pattern recognition methods, in particular cluster analysis and support vector machines (SVM) were used for movement pattern identification.ResultsSubjects exhibited unique movement patterns leading to 18 clusters for the 20 subjects. No overall classification of the splint condition could be observed. Within individual subjects different running patterns could be identified for the four splint conditions. The splint conditions lead to a more symmetrical running pattern than the control condition.DiscussionThe influence of an occlusal splint on running pattern can be confirmed in this study. Wearing a splint increases the symmetry of the running pattern. A more symmetrical running pattern might help to reduce the risk of injuries or help in performance. The change of the movement pattern between the neutral condition and any of the three splint conditions was significant within subjects but not across subjects. Therefore the dental splint has a measureable influence on the running pattern of subjects, however subjects individuality has to be considered when choosing the optimal splint condition for a specific subject.

Does a Temporary Leg Length Discrepancy have an Influence on Upper Body Posture and Lower Jaw Position in Competitive Athletes?

The purpose of this study was to examine the linkage between the musculoskeletal and the craniomandibular system in competitive athletes. Therefore the upper body posture and lower jaw position were investigated while a temporarily induced leg length discrepancy (LLD) during standing was induced. In this study 34 competitive athletes (2 women/32 men) who had no signs of temporomandibular dysfunction according to their own statements were investigated. The measurement of the upper part of the body posture was performed with a three-dimensional back scanner. Afterwards the condylar position was registered by using a homologated and approved electronic registration device. In order to induce the leg length discrepancy, wooden panels measuring 1 and 3 cm thickness were placed unilaterally under one foot. The statistical analysis of the three-dimensional back measurement was carried out using the Friedman and Wilcoxon matched pairs tests with Bonferroni-Holm correction. The results showed in comparisons of the lateral trunk a decline (p ≤ 0.05), of the height of the shoulder girdle (p ≤ 0.05) and, in every pair comparison, of the height of the pelvis area significant correlations between the body posture and the experimentally induced leg length discrepancy. The biggest changes can be observed in the area of the height of the pelvis in the transverse plane. The alterations in statics can be found at the ipsilateral as well as the contralateral side of the body, whereby changes are dependent of the parameter. Moreover, the position of the left condyle in space changes significantly (p ≤ 0.05). The results illustrate functional correlations of the musculoskeletal system through muscular, neurological and fascia based processes. Furthermore, they show that athletes who have a distinctive supporting and postural musculature possess a good body demeanor as well as a fast musculoskeletal compensation by way of the sensorimotor system correspondent to the heightened side of the body. The theory of the ascendant chain spanning from limb to shoulder girdle and further to mandibular condyles can be demonstrated. Athletes with strong postural muscles can quickly compensate through the use of the somatic nervous system.

경부 통증 유무에 따른 심부 경부 굴곡근의 근력과 지구력 비교

The purpose of this study was to investigate the strength and endurance of the deep neck flexor muscles in individuals with work-related neck pain. Subjects consisted of two groups: twenty industrial workers with neck pain and twenty age-matched healthy subjects. To evaluate the strength and endurance of deep cervical flexors, maximum voluntary contractile strength (MVCS) and a sustained time at sub-maximal voluntary contractile strength (SMVCS) (80% and 50% of MVCS) were measured using a pressure biofeedback unit and a stop watch in supine. The MVCS of deep neck flexor muscles was 29.67±4.56 in neck pain group and 54.27±6.78㎜Hg in normal group. The sustained time at 80% SMVCS was 12.42±2.64 seconds and 55.12±12.76 seconds in the groups with and without neck pain. The sustained time at 50% SMVCS was 25.40±5.88 seconds and 109.70±31.50 seconds in the groups with and without neck pain. The difference of the lower jaw position was 16.75±3.57㎜ and 23.03±2.51㎜. The MVCS, endurance at the two sub-maximal levels and the difference of the lower jaw position were significantly greater in the group without neck pain than with neck pain (p＜0.05). The findings indicate that the maximal strength and endurance of the deep neck flexors were decreased in the workers with neck pain compared to those without neck pain. Therefore, it is necessary to include strengthening and endurance exercises of the deep neck flexor muscles in therapeutic program of work-related musculoskeletal disorders involving neck pain.

P434 Pulse transit time as a measure of arousal in patients with obstructive sleep apnea hypopnea syndrome

measurement of some angles and distances with computer software. Results: Thirty-four Caucasians, thirty-eight Asians. Age (50 ± 11 vs 49 ± 10; p = 0.97), BMI (29.6 ± 2.9 vs 25.7 ± 2.1; p < 0.0001), AHI (25.7 ± 27.0 vs 43.6 ± 16.7; p = 0.0015),ANBangle: relation between upper and lower jaw (6.5 ± 3.0 vs 8.3 ± 2.9; p = 0.0072),NGnHangle: lower jaw position (119.2 ± 7.5 vs 123.4 ± 8.1; p = 0.04). Conclusions: Jaw relation (ANB) and jaw position (NGnH) were significantly different between Caucasian and Asian. The micrognathia, retrognathia or small retro-positioned jaw are characteristic findings in Asian patients rather than Caucasian. Digital photography can be used to assess anatomic structure of patients with OSA.

Interarticulator cohesion within coronal consonant production

If more than one articulator is involved in the execution of a phonetic task, then the individual articulators have to be temporally coordinated with each other in a lawful manner. The present study aims at analyzing tongue-jaw cohesion in the temporal domain for the German coronal consonants [s, f, t, d, n, l], i.e., consonants produced with the same set of articulators--the tongue blade and the jaw--but differing in manner of articulation. The stability of obtained interaction patterns is evaluated by varying the degree of vocal effort: comfortable and loud. Tongue and jaw movements of five speakers of German were recorded by means of electromagnetic midsagittal articulography (EMMA) during [aCa] sequences. The results indicate that (1) tongue-jaw coordination varies with manner of articulation, i.e., a later onset and offset of the jaw target for the stops compared to the fricatives, the nasal and the lateral; (2) the obtained patterns are stable across vocal effort conditions; (3) the sibilants are produced with smaller standard deviations for latencies and target positions; and (4) adjustments to the lower jaw positions during the surrounding vowels in loud speech occur during the closing and opening movement intervals and not the consonantal target phases.

Effects of vibration stimulus on lower-jaw-position sensation in patients with cerebral palsy during inhalation of laughing gas

To clarify the effects of a vibration stimulus applied during sedation with nitrous oxide (hereafter referred to as laughing gas) on the ability of muscles attached to the lower jaw to sense lower-jaw position and on the sensation of muscle spindles attached to the lower jaw in patients with cerebral palsy (CP) using healthy adult subjects without functional abnormalities of the jaws and oral cavities as control subjects (hereafter referred to as healthy subjects). Experiments were performed under the following conditions: for each subject, before the application of the vibration stimulus (referred to as S pre ) and after the application of the vibration stimulus (S post ); before the inhalation of laughing gas (LG) and oxygen (air-inhalation condition: referred to as without LG inhalation) and during the inhalation of LG and oxygen (inhalation condition of LG and oxygen under LG-induced sedation: referred to as during LG inhalation). Subjects in the experiments were eight CP patients and eight healthy people as controls. The ability to discriminate lower-jaw position was estimated by asking the subjects to determine whether the diameter of a test stick was larger or smaller than that of a reference stick after performing the following tasks: a) holding a reference stick between the central teeth of their upper and lower jaws for 5 s, and b) replacing the reference stick with a test stick and holding it at the same position for 5 s, and the test stick was then removed. The following findings were obtained. 1) In comparing the ability of healthy subjects to discriminate between S pre and S post during LG inhalation using different test sticks, when the test stick diameter was 9.5 mm (smaller than the reference stick diameter), the rate of mis-estimation (RME) for Spost was significantly larger than that for Spre ( P < 0.05). No significant differences were observed for any other test sticks. 2) In comparing the ability of CP patients to discriminate between S pre and S post during LG inhalation using different test sticks, when the test stick diameter was 9.5 mm (smaller than the reference stick diameter), the RME for S post was significantly smaller than that for S pre ( P < 0.05). No significant differences were observed for any other test sticks. These results suggest the following: the combination of LG for sedation with vibration stimulus further inhibits neuronal functions at the upper level of the central nervous system in CP patients, compared with cases in which each variable is applied separately, and the combination also inhibits the sustained increase in muscle tonus, which is characteristic of CP patients. LG reduces the activity of γ-motor neurons via the upper level of the central nervous system. In addition, tonic vibration reflex (TVR) develops due to the vibration stimulus, which increases the threshold value of sensitive muscle sensation and decreases the activity of γ-motor neurons, and furthermore decreases the activity of muscle spindles attached to the lower jaw. Consequently, a tendency toward increased ability to discriminate lower-jaw position is observed.