The impact of a total hip replacement on jaw position,upper body posture and body sway

Objectives:

The purpose of this study was to examine whether, and to what extent, a total hip replacement can influence the position and the movement of the jaw, the upper body posture and body sway.

Methods:

Twenty test subjects (6 females, 14 males) participated in this study pre- and post-total hip replacement, in addition to a healthy control group of 20 subjects (5 females, 15 males). The measurements were conducted by means of an ultrasound system to measure jaw condyle position and movement of the lower jaw, a three-dimensional back scan to analyze upper back posture, and a static and dynamic force plate to measure body sway. For statistical analysis the Wilcoxon-Matched-Pairs-Test or Man–Whitney-U-Test, including a Bonferroni–Holm correction, respectively, was used.

Results:

After surgery, the mean values of the left and right jaw condyles of the test group moved posterior, and the left condyle position was located more caudally. There were no significant differences concerning the jaw position between the two groups. There was little change in upper body posture in both groups. The test group had a more anteriorly inclined thoracic spine and a less pronounced lumbar lordosis. During static body sway measurements, increased fluctuations in the test group after surgery could be seen.

Conclusion:

Differences between both groups in the pre- and post-surgical condition could be detected. These differences were more prominent when the measured body segments were more distally located with respect to the hip region.     

The different effects of intraoral vertical ramus osteotomy (IVRO) and sagittal split ramus osteotomy (SSRO) on mandibular border movement

Objectives: This study investigated the different effects of intraoral vertical ramus osteotomy (IVRO) and sagittal split ramus osteotomy (SSRO) on mandibular border movement.

Methods: The participants included 22 patients receiving IVRO and 22 patients receiving SSRO who were treated at Okayama University Hospital. Their mandibular border movement was evaluated in three dimensions with 6° of freedom using an optical recording system.

Results: A strong correlation between condylar and lower incisor movement was observed during maximum jaw protrusion and laterotrusion. Significant improvements in condylar and lower incisor movement were detected after orthognathic surgery during maximum jaw protrusion and laterotrusion in the IVRO group and during maximum jaw protrusion in the SSRO group.

Discussion: IVRO likely achieves greater improvement in jaw movement than SSRO. Therefore, the application of IVRO could be considered in the treatment of patients with jaw deformities featuring temporomandibular joint problems.     

Alternative technique to transfer jaw relations for custom mandibular advancement devices: A case report

Background: Oral appliance therapy for obstructive sleep apnea can be helpful in mild and moderate cases. This clinical report evaluates the efficacy of a protocol that predicts an optimal jaw position and describes the response of a young OSA patient to treatment.

Clinical Presentation: A 27-year-old woman was diagnosed with moderate OSA and had an apnea–hypopnea index (AHI) of 25.8/hr. In order to fabricate a custom device, an alternative procedure to determine the optimal protrusion and vertical positioning of the jaw was applied. After a follow-up period of 14 months, her apnea-hypopnea index (AHI) significantly decreased from 25.8 to 1.0 per hr with the appliance. The total number of respiratory events decreased from 211 to 8.

Conclusion: Improved polysomnographic parameters showed that the oral device was efficient in treatment. The advantages of the device in this study are that it is comfortable, economical, and simple to fabricate.     

Non-apneic snoring and the orthodontist: radiographic pharyngeal dimension changes with supine posture and mandibular protrusion

Abstract

Objective: To evaluate the radiographic changes that occur in the pharynx and surrounding structures with alteration of posture from the upright to the supine position and the effect that mandibular protrusion whilst supine has on these dimensions.

Design: Prospective cephalometric study.

Setting: University Dental Hospital and School.

Subjects and method: This prospective study involved 35 consecutively referred adults with proven non-apneic snoring. Lateral skull radiographs were obtained with the subjects upright in occlusion, supine in occlusion and supine with the mandible protruded to the maximum comfortable position. Radiographs were traced and digitized, and the pharyngeal dimensional changes and hyoid position were examined. Males and females were examined separately.

Results: Radiographic pharyngeal dimensions were changed with altered posture, resulting in significant reductions in the minimum post-palatal (p<0.01) and post-lingual (p<0.05) airway measurements in the supine position. Mandibular protrusion whilst in the supine position produced increases in the functioning space for the tongue.

Conclusion: A supine posture results in significant reductions in pharyngeal airway measurements of non-apneic snorers. Mandibular protrusion whilst in the supine position produces an increase in the functioning space for the tongue.     

The effect of supervised exercise on localized TMD pain and TMD pain associated with generalized pain

Objectives: To evaluate the effect of a supervised exercise program in patients with localized/regional temporomandibular disorder (TMD) pain and with TMD associated with generalized pain.

Material and methods: Consecutively referred patients with localized/regional TMD pain (n?=?56; 46 women and 10 men, mean age 44 years) and TMD associated with generalized pain (n?=?21; 21 women, mean age 41 years) participated. Patients underwent a 10-session structured supervised exercise program over 10–20 weeks that included relaxation, and coordination and resistance training of the jaw and neck/shoulders. The outcomes were jaw pain intensity on the Numerical Rating Scale, endurance time for jaw opening and protrusion against resistance and chewing, and effect of pain on daily activities.

Results: After the exercise program, a reduction in jaw pain was reported by the local (p?=?.001) and general (p?=?.011) pain groups. There were no significant differences in jaw pain intensity between the groups, before (p?=?.062) or after treatment (p?=?.121). Endurance time increased for both groups for jaw opening/protrusion (both p?<?.001) and chewing (both p?=?.002). The effect of jaw pain on daily activities decreased after exercise compared to baseline for both the local (p?<?.001) and general (p?=?.008) pain groups.

Conclusions: Supervised exercise can reduce TMD pain and increase capacity in patients with TMD. The results suggest that activation of the jaw motor system with exercise has a positive effect in patients with localized/regional TMD pain and TMD associated with generalized pain.     

Clenching and Grinding: Effect on Masseter and Sternocleidomastoid Electromyographic Activity in Healthy Subjects

Abstract

This study compares the effect of clenching and grinding on masseter and sternocleidomastoid electromyographic (EMG) activity during different jaw posture tasks in the sagittal plane. The study included 34 healthy subjects with natural dentition, Class I bilateral molar Angle relationship, and absence of posterior occlusal contacts during mandibular protrusion. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the right masseter and sternocleidomastoid muscles. EMG activity was recorded while the subjects were in standing position, during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge protrusive contact position; C. maximal clenching in the edge-to-edge protrusive contact position; D. grinding from edge-to-edge protrusive contact position to intercuspal position; E. grinding from retrusive contact position to intercuspal position. EMG activities in tasks B, C, D, and E were significantly lower than in task A in both muscles (mixed model with unstructured covariance matrix). EMG activity among tasks B, C, D, and E did not show significant differences in both muscles, except between tasks D and E in the masseter muscle. A higher effect was observed on the masseter than on the sternocleidomastoid muscle to avoid excessive muscular activity during clenching and grinding. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.     

Altered electromyographic responses to emotional and pain information in awake bruxers: case–control study

Objectives

This study aims to investigate how emotional information and pain-related information affect the activity of the masticatory muscles in participants with awake bruxism and controls.

Material and methods

Different videos and texts, with positive, negative, and neutral valence or related to pain, were presented to a sample of university students, while their electromyographic (EMG) activity around the masseter muscle and their skin conductance were recorded. Two groups were selected, with 24 subjects each: one group of subjects with definitive awake bruxism (confirmed by posterior EMG activity) who also suffered from moderate jaw discomfort, and another group of subjects without bruxism.

Results

The results demonstrated that the subjects with definitive awake bruxism displayed greater muscular activity when presented videos and texts with negative valence, especially when related to pain, than the non-bruxist group.

Conclusions

This study supports the idea that persons with bruxism who also suffer moderate levels of jaw discomfort present greater bruxism activity when watching pain-related stimuli, and to a lesser extent when watching negative stimuli.

Clinical relevance

The increased muscular activity induced by negative and pain-related information might contribute to pain exacerbation and perpetuation in persons with bruxism who suffer from discomfort.

     

Following the Money at the NIDCR

Abstract

This study was designed to determine the effect of the occlusal scheme on masseter EMG activity at different jaw posture tasks. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance, and 15 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right masseter muscles. EMG activity was recorded during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge lateral contact position; C. maximal clenching in the edge-to-edge lateral contact position; D. grinding from edge-to-edge lateral contact position to intercuspal position. EMG activity in tasks B, C, and D was lower than in task A (mixed model with unstructured covariance matrix). EMG activity was not significantly different with canine guidance or group function. EMG activity recorded on the nonworking side was higher than the working side during task C, and no different between tasks B or D. On the nonworking side, EMG activity in task B was significantly lower than C and D, and similar between task C and D. On the working side, EMG activity was significantly higher in task D than C and B, and in task B significantly higher than task C. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.     

Natural mediotrusive contact: does it affect the masticatory and neck EMG activity during tooth grinding?

Objectives: There is scarce knowledge regarding the influence of a natural mediotrusive contact on mandibular and cervical muscular activity. The purpose of this study was to analyze the EMG activity of the anterior temporalis (AT) and sternocleidomastoid (SCM) muscles during awake grinding in healthy subjects with or without a natural mediotrusive occlusal contact.

Method: Fifteen subjects with natural mediotrusive occlusal contact (Group 1) and 15 subjects without natural mediotrusive occlusal contact (Group 2) participated. Bilateral surface EMG activity of AT and SCM muscles was recorded during unilateral eccentric or concentric tooth grinding tasks. EMG activity was normalized against the activity recorded during maximal voluntary clenching in intercuspal position (IP) for AT muscles and during maximal intentional isometric head-neck rotation to each side, for SCM muscles.

Results: EMG activity of AT and SCM muscles showed no statistical difference between groups. EMG activity of AT muscle was higher in the working side (WS) than in the non-WS (NWS) in Group 1 during concentric grinding (0.492 vs 0.331, p?=?0.047), whereas no difference was observed in Group 2. EMG activity of SCM was similar between working and NWSs in both groups and tasks. Asymmetry indexes (AIs) were not significantly different between groups.

Discussion: These findings in healthy subjects support the assumption that during awake tooth grinding, central nerve control predominates over peripheral inputs, and reinforce the idea of a functional link between the motor-neuron pools that control jaw and neck muscles.     

Craniofacial features of patients with sickle cell anemia and sickle cell trait

Objective:To identify the craniofacial characteristics of patients with sickle cell trait (SCT) and sickle cell anemia (SCA) and to compare these measurements with those of nonaffected subjects.Materials and Methods:Clinically normal patients and those with SCT and SCA were evaluated in this study. The patients were divided into three groups: normal (control), SCA, and SCT (n  =  with 15 in each group). Inclusion criteria were SCA or SCT verified by laboratory methods and no treatment with fixed orthodontics or facial orthopedics. Lateral cephalometric radiographs were carried out and were used to obtain angular and linear measurements of anatomic structures displayed. All markings and measurements were performed by a single examiner.Results:The average ANB was increased in groups with SCA (5.47 ± 2.0°) and SCT (3.80 ± 1.4°), indicating a tendency to Class II. The mean SNA angle was 83.0 ± 3.8° and 82.1±3.5° for SCA and SCT, indicating a proper positioning of the jaw from the skull base. There was an interaction between the group and sex factors for the variable SN-GoGn; measures were higher for men in the SCA group.Conclusion:Patients with SCA and SCT exhibited characteristics of Class II skeletal pattern because of mandibular retrusion. Most patients showed no compensatory maxillary expansion, which was determined by the normal jaw length and absence of maxillary protrusion.     

On the Perception of Jaw Position and Bite Force by Subjects with Craniomandibular Disorders

This study investigated the sense of jaw position and the sense of bite force in subjects with symptoms of temporomandibular joint (TMJ) disorders. The results were compared with those of control experiments on symptom-free subjects. It was shown that: 1. Some subjects with signs of TMJ disorders showed deviant matching behavior when matching the magnitude of jaw separations to an imagined standard but not when matching to the remembered size of a standard gauge of 4.75 mm. These subjects also showed considerable fluctuation in their match. Moreover, values of imprecision of jaw position matches were greater in subjects with TMJ symptoms than in symptom-free subjects.

2. Some subjects with TMJ symptoms showed deviant matching behavior when matching to a 2-N and a 10-N but not to a 50-N standard. These subjects were also variable in their match.

3. Bruxism and nail biting correlated with these findings. Certain clinical implications are discussed.

     

Influence of dental occlusion on postural control and plantar pressure distribution

Objective: The number of studies investigating correlations between the temporomandibular system and body posture, postural control or plantar pressure distribution is continuously increasing. If a connection can be found, it is often of minor influence or for only a single parameter. However, small subject groups are critical. This study was conducted to define correlations between dental parameters, postural control and plantar pressure distribution in healthy males.

Methods: In this study, 87 male subjects with an average age of 25.23 ± 3.5 years (ranging from 18 to 35 years) were examined. Dental casts of the subjects were analyzed. Postural control and plantar pressure distribution were recorded by a force platform. Possible orthodontic and orthopedic factors of influence were determined by either an anamnesis or a questionnaire. All tests performed were randomized and repeated three times each for intercuspal position (ICP) and blocked occlusion (BO). For a statistical analysis of the results, non-parametric tests (Wilcoxon-Matched-Pairs-Test, Kruskall-Wallis-Test) were used. A revision of the results via Bonferroni-Holm correction was considered.

Results: ICP increases body sway in the frontal (p ≤ 0.01) and sagittal planes (p ≤ 0.03) compared to BO, whereas all other 29 correlations were independent of the occlusion position. For both of the ICP or BO cases, Angle-class, midline-displacement, crossbite, or orthodontic therapy were found to have no influence on postural control or plantar pressure distribution (p > 0.05). However, the contact time of the left foot decreased (p ≤ 0.001) while detecting the plantar pressure distribution in each position.

Conclusions: Persistent dental parameters have no effect on postural sway. In addition, postural control and plantar pressure distribution have been found to be independent postural criteria.     

Effect of food hardness on chewing behavior in children

Objective

To investigate the effects of food hardness on chewing behavior in children compared with adults.

Materials and methods

Healthy children (3–17 years) were equally divided into five groups based on their dental eruption stages. Each participant ate soft and hard viscoelastic test food models (3 each), while the three-dimensional jaw movements and electromyographic (EMG) activity of the bilateral masseter muscles were recorded. The data from the children were compared with a control group of healthy adults (18–35 years). The data were analyzed with nonparametric tests.

Results

There was no significant difference in the number of chewing cycles and the duration of the chewing sequence between children groups and adults. Children with primary dentition (3–5 years) showed shorter lateral jaw movement and higher muscle activity at the end of the chewing sequence, compared with adults. Further, children’s age-groups (3–14 years) failed to adapt their jaw muscle activity to food hardness. However, at the late-permanent dentition stage (15–17 years), children were capable of performing adult-like chewing behavior.

Conclusions

Overall, it seems that children as young as 3-year-old are quite competent in performing basic chewing function similar to adults. Yet, there are differences in the anticipation or adaption of jaw muscle activity and jaw kinematics to food hardness.

Clinical relevance

The study may have clinical implication in the diagnosis and management of children with chewing impairment associated with dental malocclusions and other orofacial dysfunctions.

     

Impact of pain-related temporomandibular disorders on jaw functional limitation,psychological distress and quality of life in postoperative class III East Asian patients

Objectives

This cross-sectional study determined the prevalence of painful TMD and its impact on jaw function, psychological status and oral health-related quality of life (OHRQoL) in postoperative Chinese patients. It also assessed factors influencing OHRQoL of these patients.

Materials and methods

Subjects were recruited from the National Dental Centre Singapore dentofacial deformity registry. Invitations to participate in the study were sent to patients who sought treatment from March 2011 to November 2017. Patients who consented were directed to an online link to complete a series of questionnaires based on the Diagnostic Criteria for TMD (DC-TMD) and the orthognathic quality of life questionnaire (OQLQ).

Results

The subjects (n = 99) had a mean age of 25.2 ± 6.0 years and postoperative time of 29.4 ± 22.7 months. 18.2% were found to suffer from pain-related TMD postorthognathic surgery and these patients (n = 18) had significantly higher median JFLS-8 score than those without TMD pain (p = 0.008). Time since surgery was significantly associated with OHRQoL (p = 0.00000026).

Conclusions

Prevalence of painful TMD and psychological distress was low while prevalence of jaw functional limitation was moderately high in postoperative class III Chinese patients.

Clinical relevance

Painful TMD impacted jaw function especially when subjects open wide enough to drink, yawn, talk and smile but had no significant consequence on psychological status and OHRQoL.

     

Alteration in mandibular posture by vibration of posterior fibres of the temporalis muscle

Introduction : Vibration causes reflex muscle shortening because of excitation of muscle spindle primary afferents. Although this is subordinate to voluntary control, responses have been demonstrated in jaw elevator and (unexpectedly) in jaw depressor muscles. Forward posturing of the mandible is a common habit. The only part of the perioral musculoskeletal system that actively retrudes the mandible is the posterior part of the temporalis muscle. This study set out to investigate the effect of vibration of this area on the horizontal position of the mandible during a jaw registration procedure.
Method : In a randomized cross-over study, the posterior fibres of both left and right temporales of 17 subjects were vibrated synchronously at 180 Hz. Interocclusal wax jaw registrations were recorded for each subject with and without vibration applied. Position of the mandible was assessed by mounting pairs of casts using these registrations and measuring their position relative to intercuspal position.
Results : In 17 subjects, the effects of vibration on mandibular posture were: no change in one; protrusion in two; and retrusion in 14. A sign test returned a value of P  < 0·01.
Discussion : Reasons for the protrusion seen in two subjects are discussed. These may be anatomical or methodological. However, vibration of the posterior part of the temporalis muscle retruded the mandible in a significant majority of cases.     

Patterns of cervical and masticatory impairment in subgroups of people with temporomandibular disorders–an explorative approach based on factor analysis

Objectives: To identify clinical patterns of impairment affecting the cervical spine and masticatory systems in different subcategories of temporomandibular disorder (TMD) by an explorative data-driven approach.

Methods: For this observational study, 144 subjects were subdivided according to Research Diagnostic Criteria for TMDs into: Healthy controls, temporomandibular joint (TMJ) signs without symptoms, TMJ affected, temporomandibular muscles affected, or TMJ and muscles affected. Factor analysis and linear regression were applied to cervical spine and masticatory data to identify and characterize clinical patterns in subgroups.

Results: Factor analysis identified five clinical dimensions, which explained 59% of all variance: Mechanosensitivity, cervical movement, cervical and masticatory dysfunction, jaw movement, and upper cervical movement. Regression analysis identified different clinical dimensions in each TMD subgroup.

Conclusion: Distinct clinical patterns of cervical spine and masticatory function were found among subgroups of TMD, which has clinical implications for therapeutic management.     

An Investigation into the Changes in Airway Dimension and the Efficacy of Mandibular Advancement Appliances in Subjects with Obstructive Sleep Apnoea

Abstract

This prospective clinical study evaluates a group of 37 male Caucasians with obstructive sleep apnoea for changes in airway dimension and the efficacy associated with the use of mandibular advancement splints. Lateral skull radiographs were obtained with the subjects—upright in occlusion, supine in occlusion, and supine in protrusion. Each radiograph was traced and digitized, and changes in mandibular position, airway dimensions, and hyoid were examined. Subjects were invited to complete pre- and post-treatment questionnaires, and interviewed following fitting of a removable Herbst mandibular advancement splint.

Significant changes were recorded in the airway dimensions in response to both a change in position, from upright to supine, and in response to mandibular advancement. A compliance rate of 76 per cent was achieved with no reported serious complications associated with the use of mandibular advancement devices.     

Jaw clenching effects in relation to two extreme occlusal features: patterns of diagnoses in a TMD patient population

Objective:

The aim of this investigation was to compare the pattern of temporomandibular disorder (TMD) diagnoses in clenching patients with different occlusal features, the null hypothesis being that no between-group differences exist.

Materials and methods:

Two groups of subjects receiving a jaw clenching diagnosis and having large overjet or anterior open bite (Group A; N?=?45, 75·5% females, mean age: 38·1±15·9 years) or normal occlusion (Group B; N?=?69, 71% females, mean age: 34·6±13·8 years) were recruited among a TMD patient population and were given Research Diagnostic Criteria for TMD (RDC/TMD) axis I diagnoses, namely, group I muscle disorders, group II disc displacements, and group III arthralgia/osteoarthritis/osteoarthrosis.

Major findings:

The distribution of RDC/TMD single and combined group diagnoses was significantly different between the two groups (P<0·05), with Group A subjects showing a higher prevalence of multiple diagnoses (60% versus 43·3%), as well as a higher prevalence of combined RDC/TMD axis I group II and III diagnoses (37·8% versus 20·2%). All TMD signs and symptoms were more frequent in the patients with large overjet or anterior open bite with respect to the patients with normal occlusion.

Conclusion:

In a TMD patient population, jaw clenching may have different consequences in subjects with large overjet or anterior open bite with respect to subjects featuring normal occlusion.     

TMJ symptoms reduce chewing amplitude and velocity,and increase variability

Objective: The null hypothesis was that mandibular amplitude, velocity, and variability during gum chewing are not altered in subjects with temporomandibular joint (TMJ) internal derangements (ID).

Methods: Thirty symptomatic subjects with confirmed ID consented to chew gum on their left and right sides while being tracked by an incisor-point jaw tracker. A gender and age matched control group (p > 0.67) volunteered to be likewise recorded. Student’s t-test compared the ID group’s mean values to the control group.

Results: The control group opened wider (p < 0.05) and chewed faster (p < 0.05) than the ID group. The mean cycle time of the ID group (0.929 s) was longer than the control group (0.751 s; p < 0.05) and more variable (p < 0.05).

Discussion: The ID group exhibited reduced amplitude and velocity but increased variability during chewing. The null hypothesis was rejected. Further study of adaptation to ID by patients should be pursued.