ASSOCIATIONS BETWEEN SCREENING FOR FUNCTIONAL JAW DISTURBANCES AND PATIENT REPORTED OUTCOMES ON JAW LIMITATIONS AND ORAL BEHAVIORS.

OBJECTIVES: Temporomandibular disorders (TMDs) is a collective term for pain and functional disturbances related to the jaw muscles and the temporomandibular joint. In contrast to screening for orofacial pain, knowledge is limited on the association between patient-reported outcomes and screening for joint-related functional jaw disturbances. Therefore, our aim was to evaluate the association between a screening question for functional jaw disturbances, and disease-specific outcome measures for functional jaw limitations and oral behaviors. METHODS: This study included 299 individuals (201 women; 20-69 years, median 37.0) in a general population sample from Västerbotten, Northern Sweden in 2014. A single screening question for functional jaw disturbances "Does your jaw lock or become stuck once a week or more?" was used to categorize individuals as cases or controls. Patient-reported outcomes on functional jaw disturbances were assessed with the 20-item jaw functional limitation scale (JFLS-20) and oral behaviors with the 21-item Oral Behaviors Checklist (OBC-21). RESULTS: The strongest predictive probability to have a positive screening outcome was functional jaw limitations related to mobility (AUCboot=0.78, 95 CI:0.71-0.86, P < .001), followed by limitations related to communication (AUCboot = 0.74, 95 CI:0.63-0.80, P < .001) and mastication (AUCboot = 0.73, 95 CI:0.66-0.81, P < .001). The frequency of oral behaviors was not significantly associated with a positive screening outcome (AUCboot = 0.65, 95 CI:0.55-0.72, P = .223). CONCLUSIONS: Self-reported functional limitations, but not oral behaviors, are strongly associated with a single screening question for frequent functional jaw disturbances. This finding provides support for incorporating a question on jaw catching/locking once a week or more in screening instruments for TMDs.

The Longitudinal Relationship between Jaw Catching/Locking and Pain.

Orofacial pain and joint-related dysfunction can negatively affect daily jaw function. A common cause for limitations in jaw movements is joint-related dysfunction such as various forms of catching and locking. However, knowledge is limited regarding the development and natural course of joint-related jaw dysfunction and its relationship to the onset and course of orofacial pain. Therefore, the aim was to evaluate the incidence, prevalence, and gender differences in jaw catching/locking over time and in relation to orofacial pain in the general population. Data from 3 validated screening questions on orofacial pain and jaw catching/locking were collected from all routine dental checkups in the Public Dental Health Services in Västerbotten, Sweden, from 2010 to 2017. Logistic generalized estimating equation was used to account for repeated observations and Poisson regression for incidence analysis. In total, 180,308 individuals (aged 5-104 y) were screened in 525,707 dental checkups. In 2010, based on 37,647 individuals, the prevalence of self-reported catching/locking was higher in women than in men (3.2% vs. 1.5%; odds ratio, 2.11; 95% confidence interval [CI], 1.83-2.43), and this relationship and magnitude remained similar throughout the study period. The annual incidence rate was 1.1% in women and 0.5% in men. Women were at a higher risk than men for reporting both first onset (incidence rate ratio [IRR], 2.29; 95% CI, 2.11-2.49) and persistent (IRR, 2.31; 95% CI, 2.04-2.63) catching/locking. For the onset subcohort (n = 135,801), an independent onset of orofacial pain or jaw catching/locking exclusively was reported by 84.1%, whereas a concurrent onset was reported by 13.4%. Our findings of higher incidence, prevalence, and persistence in women than in men indicate that the gender differences seen for orofacial pain are evident also for jaw catching/locking. The findings also suggest independent onset of self-reported catching/locking and orofacial pain, which reinforces the pathophysiological differences between these conditions.

The Global Need for Easy and Valid Assessment Tools for Orofacial Pain.

The World Health Organization recently adopted a historic resolution (WHA74.5) on the urgent need for global oral health improvement. This resolution is particularly relevant in the perspective of the high prevalence of untreated oral diseases. However, one important aspect has been mentioned only in passing, namely that poor oral health often leads to orofacial pain, which is the most common reason for emergency dental visits worldwide. Therefore, an evidence-based decision-making process on oral health should include data related to orofacial pain complaints. To that end, the availability of reliable and valid assessment tools of orofacial pain and related treatment outcomes is essential. INfORM (International Network for Orofacial Pain and Related Disorders Methodology) of the International Association for Dental Research has been one of the driving forces behind the development and implementation of comprehensive sets of tools for such assessments. However, as a prerequisite for the desired global implementation, reliable and valid tools that are also brief, easy to translate, and culturally adaptable need to be further developed and tested. Some of the groundwork to facilitate this process has already been carried out. In addition, a working group within INfORM has developed a short clinical assessment tool for orofacial pain diagnostics that is near completion and will soon be ready for dissemination. Ultimately, reliable and valid orofacial pain assessment is a necessary step toward the development and implementation of appropriate "best buy" interventions that address this major driver of need for oral health care worldwide.

RECOMMENDATIONS FOR USE AND SCORING OF ORAL HEALTH IMPACT PROFILE VERSIONS.

BACKGROUND: OHIP's original seven-domain structure does not fit empirical data, but a psychometrically sound and clinically more plausible structure with the four OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact has emerged. Consequently, use and scoring of available OHIP versions need to be revisited. AIM: We assessed how well the overall construct OHRQoL and its four dimensions were measured with several OHIP versions (20, 19, 14, and 5 items) to derive recommendations which instruments should be used and how to score them. METHODS: Data came from the "Dimensions of OHRQoL Project" and used the project's learning sample (5,173 prosthodontic patients and general population subjects with 49-item OHIP data). We computed correlations among OHIP versions' summary scores. Correlations between OHRQoL dimensions, on one hand, and OHIP versions' domain scores or OHIP-5's items, on the other hand, were also computed. OHIP use and scoring recommendations were derived for psychometrically solid but also practical OHRQoL assessment. RESULTS: Summary scores of 5-, 14-, 19- and 49-item versions correlated highly (r = 0.91-0.98), suggesting similar OHRQoL construct measurement across versions. The OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact were best measured by the OHIP domain scores for Physical Disability, Physical Pain, Psychological Discomfort, and Handicap, respectively. CONCLUSION: Recommendations were derived which OHIP should be preferably used and how OHIP versions should be scored to capture the overall construct and the dimensions of OHRQoL. Psychometrically solid and practical OHRQoL assessment in all settings across all oral health conditions can be achieved with the 5-item OHIP.

The impact of gender of the examiner on orofacial pain perception and pain reporting among healthy volunteers.

OBJECTIVES: Pain on palpation of jaw muscles is a commonly used diagnostic criterion when examining patients with orofacial pain. It is not known, however, if pain reports are affected by the gender of the examiner. Our aim was to investigate if pressure pain threshold (PPT), pressure pain tolerance (PTol), and pain intensity assessed over the masseter muscles in healthy individuals are affected by the gender of the examiner. MATERIALS AND METHODS: Healthy, pain-free individuals were recruited on a voluntary basis. PPT and PTol were assessed using pressure algometry. At the PTol level, participants also rated pain intensity on a 0-10 numeric rating scale. Assessments of PPT and PTol were conducted with six repeated measurements performed twice, separately by one female and one male examiner, on each participant. RESULTS: In total, 84 participants (43 women; median age 24, IQR 6) were included. With a female examiner, women reported higher pain intensity than men (Mann Whitney U, p = 0.005). In the multivariable analysis, significantly higher PTol was predicted by male examiner. Also, a higher ratio between PTol and reported pain intensity was predicted by male examiner. CONCLUSIONS: The gender of the examiner influences pain reporting and perception in an experimental setting. This effect on pain perception related to gender of the examiner is probably related to normative gender behaviors rather than to biological alterations within the examined individual. CLINICAL RELEVANCE: In clinical and experimental settings, gender of the examiner may affect not only pain perception but also pain reporting, with potential implications for diagnostics in patients with pain.

Pharmacological treatment of oro-facial pain - health technology assessment including a systematic review with network meta-analysis.

This health technology assessment evaluated the efficacy of pharmacological treatment in patients with oro-facial pain. Randomised controlled trials were included if they reported pharmacological treatment in patients ≥18 years with chronic (≥3 months) oro-facial pain. Patients were divided into subgroups: TMD-muscle [temporomandibular disorders (TMD) mainly associated with myalgia]; TMD-joint (TMD mainly associated with temporomandibular joint pain); and burning mouth syndrome (BMS). The primary outcome was pain intensity reduction after pharmacological treatment. The scientific quality of the evidence was rated according to GRADE. An electronic search in PubMed, Cochrane Library, and EMBASE from database inception to 1 March 2017 combined with a handsearch identified 1552 articles. After screening of abstracts, 178 articles were reviewed in full text and 57 studies met the inclusion criteria. After risk of bias assessment, 41 articles remained: 15 studies on 790 patients classified as TMD-joint, nine on 375 patients classified as TMD-muscle and 17 on 868 patients with BMS. Of these, eight studies on TMD-muscle, and five on BMS were included in separate network meta-analysis. The narrative synthesis suggests that NSAIDs as well as corticosteroid and hyaluronate injections are effective treatments for TMD-joint pain. The network meta-analysis showed that clonazepam and capsaicin reduced pain intensity in BMS, and the muscle relaxant cyclobenzaprine, for the TMD-muscle group. In conclusion, based on a limited number of studies, evidence provided with network meta-analysis showed that clonazepam and capsaicin are effective in treatment of BMS and that the muscle relaxant cyclobenzaprine has a positive treatment effect for TMD-muscle pain.

Effects on jaw function shortly after whiplash trauma.

Normal jaw function involves muscles and joints of both jaw and neck. A whiplash trauma may disturb the integrated jaw-neck sensory-motor function and thereby impair chewing ability; however, it is not known if such impairment is present shortly after a neck trauma or develops over time. The aim was to evaluate jaw function after a recent whiplash trauma. Eighty cases (47 women) were examined within 1 month after a whiplash trauma and compared to 80 controls (47 women) without neck trauma. Participants completed the Jaw disability checklist (JDC) and Neck Disability Index (NDI) questionnaires and performed a 5-minute chewing test. Elicited fatigue and pain during chewing were noted, and group differences were evaluated with Fisher's exact test and Mann-Whitney U-test. Compared to controls, cases had higher JDC (P < .0001) and NDI scores (15% vs 2%, P < .0001), and reported more fatigue (53% vs 31%, P = .006) and pain (30% vs 10%, P = .003) during the chewing test. Cases also had a shorter onset time for fatigue and pain (both P = .001) Furthermore, cases reporting symptoms during chewing had higher JDC and NDI scores compared to cases not reporting symptoms (both P = .01). Symptoms mainly occurred in the trigeminal area for both groups, but also in spinal areas more often for cases than for controls. Taken together, the results indicate that jaw-neck sensory-motor function is impaired already within 1 month after a whiplash trauma. The association between neck disability and jaw impairment underlines the close functional relationship between the regions, and stresses the importance of multidisciplinary assessment.

Outcome of three screening questions for temporomandibular disorders (3Q/TMD) on clinical decision-making.

Patients with temporomandibular disorders (TMD) seem to go undetected and not adequately managed within dentistry. To identify these patients, three screening questions (3Q/TMD) have been introduced within dentistry in parts of Sweden. It is not known whether 3Q/TMD affects the clinical decision-making for these patients. The aim of this study was to evaluate the outcome of 3Q/TMD on the clinical decision-making and to analyse whether gender, age and the fee system the individual was assigned to were related to prescribed TMD treatment. This cohort study was carried out within the Public Dental Health service in Västerbotten, Sweden. As part of the routine dental check-up, a health declaration including 3Q/TMD was completed. The study population was randomly selected based on their 3Q/TMD answers. In total, 300 individuals with an affirmative answer to any of the 3Q/TMD, and 500 individuals with all negative answers were selected. The 3Q/TMD includes questions on weekly jaw-face-temple pain (Q1), pain on function (Q2) and catching/locking of the jaw (Q3). The 3Q/TMD was analysed in relation to prescribed treatment assessed from dental records. There was significantly more treatment performed or recommended for 3Q-positives (21·5%), compared to 3Q-negatives (2·2%) (P < 0·001). The odds ratio for TMD-related treatment for 3Q-positives versus 3Q-negatives was 12·1 (95% CI: 6·3-23·4). Although affirmative answers to the 3Q/TMD was related to TMD treatment, the majority of individuals with a screen positive still did not, according to dental records, receive assessment or treatment. Further studies are needed to better understand the clinical decision-making process for patients with TMD.

Validity of three screening questions (3Q/TMD) in relation to the DC/TMD.

Temporomandibular disorders (TMD) are common but seem to be largely undetected within general dental care. To improve dentists' awareness of these symptoms, three screening questions (3Q/TMD) have been introduced. Our aim was to validate 3Q/TMD in relation to the diagnostic criteria for TMD (DC/TMD), while taking into account the severity level of the symptoms. The study population consisted of 7831 individuals 20-69 years old, who had their routine dental check-up at the Public Dental Health Service in Västerbotten, Sweden. All patients answered a health declaration, including the 3Q/TMD regarding frequent temporomandibular pain, pain on movement and catching/locking of the jaw. All 3Q-positives (at least one affirmative) were invited for examination in randomised order. For each 3Q-positive, a matched 3Q-negative was invited. In total, 152 3Q-positives and 148 3Q-negatives participated. At examination, participants answered 3Q/TMD a second time, before they were examined and diagnosed according to DC/TMD. To determine symptom's severity, the Graded Chronic Pain Scale and Jaw Functional Limitation Scale-20 (JFLS-20) were used. In total, 74% of 3Q-positives and 16% of 3Q-negatives met the criteria for DC/TMD pain or dysfunction (disc displacements with reduction and degenerative joint disorder were excluded). Fifty-five per cent of 3Q-positives had a TMD diagnosis and CPI score ≥3 or a JFLS-20 score ≥5, compared to 4% of 3Q-negatives. The results show that the 3Q/TMD is an applicable, cost-effective and valid tool for screening a general adult population to recognise patients in need of further TMD examination and management.

Pain and Disability in the Jaw and Neck Region following Whiplash Trauma.

The relationship between whiplash trauma and chronic orofacial pain is unclear, especially with regard to the time elapsed from trauma to development of orofacial pain. The aim was to analyze prevalence of jaw pain and disability, as well as the relationship between pain and disability in the jaw and neck regions in the early nonchronic stage after whiplash trauma. In this case-control study, 70 individuals (40 women, 30 men, mean age 35.5 y) who visited an emergency department with neck pain following a car accident were examined within 3 wk of trauma (group 1) and compared with 70 individuals (42 women, 28 men, mean age 33.8 y), who declined to attend a clinical examination but agreed to fill in questionnaires (group 2). The 2 case groups were compared with a matched control group of 70 individuals (42 women, 28 men, mean age 37.6 y) without a history of neck trauma. All participants completed questionnaires regarding jaw pain and dysfunction, rating pain intensity in jaw and neck regions on the Numerical Rating Scale, the Neck Disability Index, and Jaw Disability Checklist. Compared with controls, individuals with a recent whiplash trauma reported more jaw pain and dysfunction. Furthermore, there was a moderate positive correlation between jaw and neck pain ratings for group 1 (r = 0.61, P < 0.0001) and group 2 (r = 0.59, P < 0.0001). In the logistic regression analysis, cases showed higher odds ratios (range, 6.1 to 40.8) for jaw and neck pain and disability compared with controls. Taken together, the results show that individuals with a recent whiplash trauma report more jaw pain and disability compared with controls without a history of neck trauma. Furthermore, the correlation between jaw and neck pain intensity implies that intensity of neck pain in the acute stage after whiplash trauma might be a possible risk factor also for development of chronic orofacial pain.

Temporomandibular pain and jaw dysfunction at different ages covering the lifespan--A population based study.

BACKGROUND: Temporomandibular pain and jaw dysfunction can have a negative effect on daily life, but these conditions are not well recognized in the health care systems. The general aim was to examine the cross-sectional prevalence of frequent temporomandibular pain and jaw dysfunction in men and women across the lifespan. METHODS: The analysis was based on data from 137,718 individuals (mean age 35 years, SD 22.7) who answered three questions (3Q/TMD) included in the digital health declaration in the Public Dental Health care in the county of Västerbotten, Sweden; Q1: 'Do you have pain in your temple, face, jaw or jaw joint once a week or more?'; Q2: 'Does it hurt once a week or more when you open your mouth or chew?'; and Q3: 'Does your jaw lock or become stuck once a week or more?' RESULTS: The prevalence of frequent temporomandibular pain (Q1) was 5.2% among women and 1.8% among men (p < 0.0001). The prevalence of frequent pain on jaw movement (Q2) was 2.5% among women and 0.9% among men (p < 0.0001). The prevalence of frequent locking of the jaw (Q3) was 2.7% among women and 1.2% among men (p < 0.0001). CONCLUSIONS: The study shows that the cross-sectional prevalence of temporomandibular pain and jaw dysfunction varies during the lifespan. For men and women, respectively, symptoms increase during adolescence, peak in middle age and then gradually diminish. The prevalence of these symptoms is significantly higher among women except from the first and last decades of a 100-year lifespan.

Jaw-opening accuracy is not affected by masseter muscle vibration in healthy men.

There is a functional integration between the jaw and neck regions with head extension-flexion movements during jaw-opening/closing tasks. We recently reported that trigeminal nociceptive input by injection of hypertonic saline into the masseter muscle altered this integrated jaw-neck function during jaw-opening/closing tasks. Thus, in jaw-opening to a predefined position, the head-neck component increased during pain. Previous studies have indicated that muscle spindle stimulation by vibration of the masseter muscle may influence jaw movement amplitudes, but the possible effect on the integrated jaw-neck function is unknown. The aim of this study was to investigate the effect of masseter muscle vibration on jaw-head movements during a continuous jaw-opening/closing task to a target position. Sixteen healthy men performed two trials without vibration (Control) and two trials with bilateral masseter muscle vibration (Vibration). Movements of the mandible and the head were registered with a wireless three-dimensional optoelectronic recording system. Differences in jaw-opening and head movement amplitudes between Control and Vibration, as well as achievement of the predefined jaw-opening target position, were analysed with Wilcoxon's matched pairs test. No significant group effects from vibration were found for jaw or head movement amplitudes, or in the achievement of the target jaw-opening position. A covariation between the jaw and head movement amplitudes was observed. The results imply a high stability for the jaw motor system in a target jaw-opening task and that this task was achieved with the head-neck and jaw working as an integrated system.

Prevalence of whiplash trauma in TMD patients: a systematic review.

The purpose of this systematic review was to describe the prevalence of whiplash trauma in patients with temporomandibular disorders (TMDs) and to describe clinical signs and symptoms in comorbid TMD/whiplash compared with TMD localised to the facial region. A systematic literature search of the PubMed, Cochrane Library and Bandolier databases was carried out for articles published from 1 January 1966 to 31 December 2012. The systematic search identified 129 articles. After the initial screening of abstracts, 32 articles were reviewed in full text applying inclusion and exclusion criteria. Six studies on the prevalence of neck trauma in patients with TMD met the inclusion criteria and were included in the review. Two of the authors evaluated the methodological quality of the included studies. The reported prevalence of whiplash trauma ranged from 8·4% to 70% (median 35%) in TMD populations, compared with 1·7-13% in the non-TMD control groups. Compared with patients with TMD localised to the facial region, TMD patients with a history of whiplash trauma reported more TMD symptoms, such as limited jaw opening and more TMD pain, and also more headaches and stress symptoms. In conclusion, the prevalence of whiplash trauma is higher in patients with TMD compared with non-TMD controls. Furthermore, patients with comorbid TMD/whiplash present with more jaw pain and more severe jaw dysfunction compared with TMD patients without a history of head-neck trauma. These results suggest that whiplash trauma might be an initiating and/or aggravating factor as well as a comorbid condition for TMD.

Experimental masseter muscle pain alters jaw-neck motor strategy.

BACKGROUND: A functional integration between the jaw and neck regions has been demonstrated during normal jaw function. The effect of masseter muscle pain on this integrated motor behaviour in man is unknown. The aim of this study was to investigate the effect of induced masseter muscle pain on jaw-neck movements during a continuous jaw opening-closing task. METHODS: Sixteen healthy men performed continuous jaw opening-closing movements to a target position, defined as 75% of the maximum jaw opening. Each subject performed two trials without pain (controls) and two trials with masseter muscle pain, induced with hypertonic saline as a single injection. Simultaneous movements of the mandible and the head were registered with a wireless optoelectronic three-dimensional recording system. Differences in movement amplitudes between trials were analysed with Friedman's test and corrected Wilcoxon matched pairs test. RESULTS: The head movement amplitudes were significantly larger during masseter muscle pain trials compared with control. Jaw movement amplitudes did not differ significantly between any of the trials after corrected Wilcoxon tests. The ratio between head and jaw movement amplitudes was significantly larger during the first pain trial compared with control. CONCLUSIONS: Experimental masseter muscle pain in humans affected integrated jaw-neck movements by increasing the neck component during continuous jaw opening-closing tasks. The findings indicate that pain can alter the strategy for jaw-neck motor control, which further underlines the functional integration between the jaw and neck regions. This altered strategy may have consequences for development of musculoskeletal pain in the jaw and neck regions.

Head immobilization can impair jaw function.

Findings that jaw-opening/-closing relies on both mandibular and head movements suggest that jaw and neck muscles are jointly activated in jaw function. This study tested the hypothesis that rhythmic jaw activities involve an active repositioning of the head, and that head fixation can impair jaw function. Concomitant mandibular and head-neck movements were recorded during rhythmic jaw activities in 12 healthy adults, with and without fixation of the head. In four participants, the movement recording was combined with simultaneous registration of myoelectric activity in jaw and neck muscles. The results showed neck muscle activity during jaw opening with and without head fixation. Notably, head fixation led to reduced mandibular movements and shorter duration of jaw-opening/-closing cycles. The findings suggest recruitment of neck muscles in jaw activities, and that head fixation can impair jaw function. The results underline the jaw and neck neuromuscular relationship in jaw function.

Endurance during chewing in whiplash-associated disorders and TMD.

We have previously shown an association between neck injury and disturbed jaw function. This study tested the hypothesis of a relationship between neck injury and impaired endurance during chewing. Fifty patients with whiplash-associated disorders (WAD) were compared with 50 temporomandibular disorders (TMD) patients and 50 healthy subjects. Endurance was evaluated during unilateral chewing of gum for 5 min when participants reported fatigue and pain. Whereas all healthy subjects completed the task, 1/4 of the TMD and a majority of the WAD patients discontinued the task. A majority of the WAD patients also reported fatigue and pain. These findings suggest an association between neck injury and reduced functional capacity of the jaw motor system. From the results, we propose that routine examination of WAD patients should include jaw function and that an endurance test as described in this study could also be a useful tool for non-dental professionals.

Head movements during chewing: relation to size and texture of bolus.

Coordinated mandibular and head-neck movements during jaw opening-closing activities suggest a close functional linkage between the jaw and the neck regions. The present study investigated whether size and texture of bolus can influence head-neck behavior during chewing. Using an optoelectronic 3-D recording technique, we analyzed concomitant mandibular and head-neck movements in 12 healthy adults chewing small (3 g) and large (9 g) boluses of chewing gum and Optosil. The main finding was a head extension during chewing, the amount of which was related mainly to bolus size. Furthermore, each chewing cycle was accompanied not only by mandibular movements, but also by head extension-flexion movements. Larger head movement amplitudes were correlated with larger size and, to some extent, also with harder texture of the bolus. The results suggest that head-neck behavior during chewing is modulated in response to changes in jaw sensory-motor input.

Disturbed jaw behavior in whiplash-associated disorders during rhythmic jaw movements.

As shown previously, "functional jaw movements" are the result of coordinated activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints. In this study, the effect of neck trauma on natural jaw function was evaluated in 12 individuals suffering from whiplash-associated disorders (WAD). Spatiotemporal characteristics of mandibular and concomitant head movements were evaluated for three different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Compared with healthy subjects, the WAD group showed smaller magnitude and altered coordination pattern (a change in temporal relations) of mandibular and head movements. In conclusion, these results show that neck trauma can derange integrated jaw and neck behavior, and underline the functional coupling between the jaw and head-neck motor systems.

Co-ordinated mandibular and head-neck movements during rhythmic jaw activities in man.

Recent observations in man of concomitant mandibular and head movements during single maximal jaw-opening/-closing tasks suggest a close functional relationship between the mandibular and the head-neck motor systems. This study was aimed at further testing of the hypothesis of a functional integration between the human jaw and neck regions. Spatiotemporal characteristics of mandibular and associated head movements were evaluated for 3 different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Mandibular and head-neck movements were simultaneously recorded in 12 healthy young adults, by means of a wireless opto-electronic system for 3-D movement recordings, with retro-reflective markers attached to the lower (mandible) and upper (head) incisors. The results showed that rhythmic mandibular movements were paralleled by head movements. An initial change in head position (head extension) was seen at the start of the first jaw-movement cycle, and this adjusted head position was retained during the following cycles. In addition to this prevailing head extension, the maximal jaw-opening/-closing cycles were paralleled by head extension-flexion movements, and in general the start of these head movements preceded the start of the mandibular movements. The results support the idea of a functional relationship between the temporomandibular and the cranio-cervical neuromuscular systems. We therefore suggest a new concept for human jaw function, in which "functional jaw movements" are the result of activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints.

Wireless optoelectronic recordings of mandibular and associated head-neck movements in man: a methodological study.

Human mandibular movements in space are the result of combined motions of the mandible and the head-neck. They can be simultaneously monitored by an optoelectronic recording technique via markers at different locations on the mandible and on the head. Markers can be attached to the teeth or to the facial skin. Mandibular movements relative to the head can be calculated by one- or three-dimensional (1D and 3D, respectively) mathematical compensation for head movements. The present study analysed mandibular and associated head movements during maximal jaw opening-closing tasks in 10 healthy subjects using a wireless 3D optoelectronic movement recording system. The study aimed to: (i) estimate the soft tissue related displacement of skin-attached markers at different locations on the face; (ii) compare 1D with 3D mathematical compensation for associated head movements; (iii) evaluate the influence of marker location on the recorded head and mandibular movement amplitudes; and (iv) compare skin-attached markers with teeth-attached markers with regard to temporal estimates of recorded mandibular and head movements. Markers were attached to the upper and lower incisors and to the skin of the forehead, nose-bridge, nose-tip and chin. Soft tissue related displacement of skin-attached markers varied between locations. The displacement for the chin marker was larger than that of other markers. The least displacement was found for the nose-bridge marker. However, relative to mandibular and head movements, respectively, the displacement of the chin marker was of the same order as that of the nose-bridge marker. The temporal estimates were not significantly affected by displacement of the skin-attached markers. Markers at different locations on the head and the mandible registered different amplitudes. The mandibular movement patterns calculated by 1D and 3D compensation were not comparable. It is concluded that markers attached to the chin and the nose-bridge can be reliably used in temporal analyses of mandibular and head movements during maximal jaw opening-closing. With certain limitations, they are acceptable for spatial analyses. Selection of method of marker attachment, marker location, and method of compensation for associated head movements should be based on the aim of the study.