Susanna Marklund

Fibre Composition of Human Intrinsic Tongue Muscles

The muscle fibre composition of three human intrinsic tongue muscles, the longitudinalis, verticalis and transversus, was investigated in four anterior to posterior regions of the tongue using morphological and enzyme- and immunohistochemical techniques. All three muscles typically contained type I, IIA and IM/IIC fibres. Type I fibres expressed slow myosin heavy chain (MyHC), type II fibres fast MyHC, mainly fast A MyHC, whereas type IM/IIC coexpressed slow and fast MyHCs. Type II fibres were in the majority (60%), but regional differences in proportion and diameter of fibre types were obvious. The anterior region of the tongue contained a predominance of relatively small type II fibres (71%), in contrast to the posterior region which instead showed a majority of larger type I and type IM/IIC fibres (66%). In general, the fibre diameter was larger in the posterior region. This muscle fibre composition of the tongue differs from those of limb, orofacial and masticatory muscles, probably reflecting genotypic as well as phenotypic functional specialization in oral function. The predominance of type II fibres and the regional differences in fibre composition, together with intricate muscle structure, suggest generally fast and flexible actions in positioning and shaping the tongue, during vital tasks such as mastication, swallowing, respiration and speech.

Risk factors associated with incidence and persistence of signs and symptoms of temporomandibular disorders

Abstract Objective. To analyze whether gender, self-reported bruxism, and variations in dental occlusion predicted incidence and persistence of temporomandibular disorder (TMD) during a 2-year period. Material and methods. The study population comprised 280 dental students at Umeå University in Sweden. The study design was that of a case-control study within a 2-year prospective cohort. The investigation comprised a questionnaire and a clinical examination at enrolment and at 12 and 24 months. Cases (incidence) and controls (no incidence) were identified among those without signs and symptoms of TMD at the start of the study. Cases with 2-year persistence of signs and symptoms of TMD were those with such signs and symptoms at all three examinations. Clinical registrations of baseline variables were used as independent variables. Odds ratio estimates and 95% confidence intervals of the relative risks of being a case or control in relation to baseline registrations were calculated using logistic regression analyses. Results. The analyses revealed that self-reported bruxism and crossbite, respectively increased the risk of the 2-year cumulative incidence and duration of temporomandibular joint (TMJ) signs or symptoms. Female gender was related to an increased risk of developing and maintaining myofascial pain. Signs of mandibular instability increased the risk of maintained TMD signs and symptoms during the observation period. Conclusion. This 2-year prospective observational study indicated that self-reported bruxism and variations in dental occlusion were linked to the incidence and persistence of TMJ signs and symptoms to a higher extent than to myofascial pain.

Incidence and prevalence of myofascial pain in the jaw-face region. A one-year prospective study on dental students.

Objective. The aims of this study were to examine the 1-year period prevalence, incidence, and course of myofascial pain in the jaw–face region, and to analyze whether female gender, dental occlusion, and oral parafunctions have any influence on these signs and symptoms. Material and methods. The study population comprised 308 dental students examined at the start of their dentistry course and re-examined after 1 year. Case histories were collected using a questionnaire. The clinical examination included palpation sites of muscles, a submaximal clenching test, measurements of maximal mandibular mobility, and classification of morphological and functional dental occlusion. Results. The 1-year period prevalence of frequent myofascial symptoms was 19%. The incidence of myofascial pain, according to the Research Diagnostic Criteria for TemporoMandibular Disorders (RDC/TMD), was 4%. The female students presented an almost 4-fold incidence rate of myofascial symptoms compared to the male students. Non-symptomatic subjects were found predominantly among men, among those unaware of bruxism with bilateral contact in the retruded contact position (RCP), and among those with a stable intercuspal position (ICP). Variations in morphological occlusion did not show any relation to myofascial symptoms, nor did contact patterns in eccentric positions. Conclusions. Female dental students were more prone to developing frequent myofascial pain and to perceiving local muscle soreness than were male students during a 1-year period. Both self-reported bruxism and registered mandibular instability in ICP showed association with the 1-year period prevalence of myofascial signs and symptoms in the jaw–face region.

Reciprocal influence on the incidence of symptoms in trigeminally and spinally innervated areas

Temporomandibular disorders (TMD), headaches, and spinal pain show co‐morbidity and may therefore influence each other. The hypothesis tested is that the presence of any of these conditions will increase the risk of onset of new symptoms within a 2‐year period. The study population comprised 280 dental students, who were examined three times at 12‐month intervals. The incidence was calculated for a 2‐year period, based on subjects without the defined symptom at baseline. Each participant was classified into five different case‐control groups, representing incidence cases or no incidence (controls) of: (1) nonpain TMD symptoms; (2) jaw pain; (3) headaches; (4) spinal pain; and (5) TMD pain. Presence of headaches and of spinal pain and signs and symptoms of TMD at baseline were used as independent variables in logistic regression analyses, controlling for age and sex. Incidence cases with TMD pain reported spinal pain at baseline significantly more often than the controls, and were mostly women. Incidence cases with headaches and incidence cases with jaw pain significantly more often had signs of TMD and reported spinal pain at baseline, compared to controls. Incidence cases with nonpain TMD symptoms or spinal pain significantly more often presented with signs of TMD at baseline. Our findings show that pain and dysfunction in trigeminally innervated areas and pain in spinally innervated areas mutually predict the onset of new symptoms in dental students, indicating common pathophysiological mechanisms and individual vulnerability. This may be of importance in risk assessment and treatment planning of individuals with musculoskeletal pain.

Incidence and prevalence of temporomandibular joint pain and dysfunction. A one-year prospective study of university students.

Objective. The aims of this study were to investigate the incidence and recovery of temporomandibular joint (TMJ) pain and dysfunction during a 1-year period, and to examine factors associated with TMJ signs and symptoms. Material and Methods. The study population comprised 371 dental students examined at the start of education, out of which 308 were re-examined after 1 year. Case histories were collected with the aid of a questionnaire. The clinical examination involved TMJ mobility, TMJ pain, TMJ sounds, morphological and functional dental occlusion. Results. The 1-year incidence of TMJ signs and/or symptoms was 12%, with no statistically significant difference between men and women. Reported TMJ sounds (10%) and clinically registered TMJ pain (8%) reached the highest incidence rates. Approximately a quarter of those who had TMJ signs and/or symptoms at baseline had recovered at follow-up. Subjects with a non-symptomatic TMJ were significantly more often found among men and among those with bilateral contacts in centric relation, a normal transverse inter-maxillary relationship, and a stabile mandibular position in centric occlusion. Conclusion. The 1-year incidence of TMJ pain and/or dysfunction was high among 1st-year university students. The persistence of signs and symptoms during the observation period was related to gender, while incidence and disappearance of symptoms were not. Dental occlusion was not rejected as a possible concurrent factor in relation to TMJ pain and/or dysfunction among university students.

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

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.

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.

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.