Relationship between the unilateral TMJ osteoarthritis/osteoarthrosis,mandibular asymmetry and the EMG activity of the masticatory muscles: a retrospective study

Summary The purpose of this retrospective study was to investigate the relationship between the unilateral temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA), mandibular asymmetry and electromyographic (EMG) activity of the masticatory muscles. Twenty‐two Japanese women (aged 23·2 ± 5·4 years) and 10 Japanese men (aged 22·4 ± 2·8 years) exhibiting unilateral TMJ OA were included in this study. Two angular and seven linear measurements were obtained for the analysis of the skeletal hard tissues. The cephalometric measurement values (CV) were normalized using the CV ratio for the evaluation of the degree of mandibular asymmetry. The EMG was recorded during maximal voluntary clenching efforts for 10 s in the intercuspal position. The average values of integral EMG (iEMG) of three trials were normalized using the iEMG ratio for the evaluation of the functional balance of the masticatory muscles. The mandibular midline was shifted to the TMJ OA side with a median value of 9·85 mm. The CV ratio of the ramus height of the TMJ OA side was significantly smaller than that of the non‐OA side. For the masseter muscle, the iEMG ratio of the TMJ OA side was significantly larger than that of the non‐OA side (P < 0·05). These results suggest that unilateral TMJ OA is related to the dentofacial morphology, thus resulting in a mandibular midline shift to the affected side and it is associated with a masticatory muscle imbalance.     

山羊颞下颌关节腔内压测定及其意义

目的　研究山羊颞下颌关节上腔内压在5种运动状态下的变化规律。方法　采用Mingograf7型多道生理记录仪对15只健康成年雌性山羊颞下颌关节测量在休息位、小开口位、大开口位、咀嚼及侧向运动时关节内压的值。结果　在休息位时,颞下颌关节上腔内压为负值,开口过程中负压值下降,在咀嚼、侧向运动等周期性运动中,关节上腔内压处于负压与正压交替的周期性变化中。结论　关节上腔内压可用于反映颞下颌关节的功能运动状态。     

Occlusal‐supporting ability of individual maxillary and mandibular teeth

This study aimed to analyse occlusal force, area and pressure for individual maxillary and mandibular teeth by assessing their occlusal‐supporting abilities. Ninety‐nine subjects (49 men and 50 women; average age, 24·7 ± 3·4 years; range, 20–37 years) performed maximal voluntary clenching twice for 3 s in both the intercuspal position and the intercuspal position with sliding movement from edge‐to‐edge occlusion, with a pressure‐sensitive sheet placed between the maxillary and mandibular dental arch. Occlusal force, area and pressure of individual teeth were calculated by colour development in the pressure‐sensitive sheet with special analytical equipment and software. Occlusal contact condition of individual teeth was confirmed using the intra‐occlusal record. All data were analysed using unpaired Student's t‐test, Kruskal–Wallis test and Scheffe's test for multiple comparisons with a significance level of P < 0·05. The occlusal pressure in the intercuspal position with sliding movement from edge‐to‐edge occlusion was adopted as the representative occlusal‐supporting ability for each individual tooth, although there were, in part, statistically significant differences in the effects of laterality, performance and gender. Overall, the occlusal pressure increased gradually from the central incisor, peaked at the canine or first premolar and decreased sharply–and significantly (P < 0·01)–towards the second molar. We conclude that the occlusal pressure of individual teeth can be used as an indicator of occlusal‐supporting ability. This is therefore proposed as a possible suitable parameter for epidemiologic research, specifically for verifying the relationship between occlusal‐supporting ability and status of residual periodontal ligament support.     

Is the tongue position influenced by the palatal vault dimensions?

Summary The influence of the palatal vault dimensions on tongue position is here studied through evaluation of the in‐mouth air cavity (IMAC) volume when the mandible is in maximal intercuspal position. A sample of 35 women (mean age 21·2 ± 1·0) and 15 men (mean age 22·1 ± 0·9) was selected. The sagittal cross‐section area of the IMAC, which is modulated by the tongue position, was measured on lateral cephalograms. Dental casts were used to measure the palatal vault volume, which was defined by the occlusal plane, the hard palate and the posterior face of the second molars. Palatal vault volume allowed deduction of the IMAC volume through a rule of three procedure relating volume to area ratios. No IMAC could be calculated from cephalograms of 10 subjects who had the tongue stuck to the palate. For the 40 other subjects, the IMAC volume was 8·9 ± 4·8 mL. It was 2 mL larger in men (n = 14) than in women (n = 26) and was the largest in skeletal Class III and the smallest in skeletal Class II (P > 0·05). IMAC volume was strongly correlated with palatal vault height but neither with palatal width nor length. It was thus assumed that the height of the palatal vault could influence the most observed position of the tongue but this does not exclude a possible growth influence of the tongue on its surrounding skeletal structures.     

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.     

Association between oral habits and signs/symptoms of temporomandibular disorders in Flemish adolescent girls

The influence of oral habits on the development of signs and symptoms of temporomandibular disorders (TMD) and pain is unclear. The prevalence and nature of such oral habits may also vary geographically. The aim of the present study was to assess the prevalence of parafunctions in Flemish adolescent girls and to study the interrelationship with TMD. A group of 261 school girls (15–16 years of age) participated. A questionnaire used in a similar study ( Gavish et al., 2000 ) was translated and inquired for oral habits (chewing of gum, nails or foreign objects, eating of seeds, crushing of ice or food, continuous leaning on the arm, daytime or night‐time grinding or clenching, jaw play, unilateral chewing) and TMD symptoms (joint noises, catching or locking, joint or muscle pain, tension or fatigue in the muscles). A brief clinical examination was performed by a single examiner: active and passive maximal mouth opening, presence of joint sounds, palpation tenderness of the lateral poles of the joints and of the masseter and anterior temporalis muscles, extent of abrasion of the canines, tongue or cheek imprints. Statistical evaluation used Spearman correlation, chi‐squared analysis and multiple regression analysis. The intra‐examiner reproducibility was moderate to high (κ 0·6–0·8 – Spearman Correlation 0·99 for maximal mouth opening). The frequency of reported oral habits was high: leaning on the arm (98%), gum chewing (89%, mean duration 3 h day^?1), lip‐ (62·1%) and cheek‐biting (41%), ice‐crushing (30%). There was a significant (P < 0·0001) but weak (0·30) positive correlation between the number of oral habits and the number of symptoms. Internal derangements were significantly (P < 0·0001) but weakly (0·25) correlated with jaw play and other oral habits. There was no relation between tooth clenching and myogenous pain (χ², P=0·31, but only 27% power). Multiple regression analysis showed that the number of symptoms increased by 52% if the subject reported ‘jaw play’, by 24% if chewing gum more than 2 h day^?1, by 28% while cheek biting and by 25% if chewing unilaterally.     

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.     

Chewing movements altered in the presence of temporomandibular joint internal derangements

Aims:

The objectives were to find specific factors that are mathematically distinct between the chewing timings, movement pattern shapes, variability, and movement velocities of: (1) normal asymptomatic subjects and (2) a group of subjects with verified temporomandibular joint (TMJ) internal derangements.

Methodology:

Left- and right-sided chewing movement recordings of 28 subjects (34·5±14·0 years) were randomly selected from a large database of patients exhibiting verified unilateral or bilateral TMJ internal derangements. The chewing movements of an age- and gender-matched control group of 20 asymptomatic subjects (32·5±11·6 years, P>0·60) with verified normal TMJ function were also recorded. Means and standard deviations of the opening, closing, turning point, terminal chewing position, and velocity patterns were calculated. A two-tailed Student’s t-test with unequal variances was used to compare the parameters between the two groups (alpha?=?0·05).

Results:

The dysfunctional group functioned significantly slower and with greater variability than the control group. The vertical dimension was consistently smaller in the dysfunctional group (P<0·00001). The terminal chewing position was significantly less precise in the dysfunctional group (vertical: P<0·002 and lateral: P<0·037). The maximum lateral width was significantly less (P<0·0071), and the peak and the average velocities were significantly lower (P<0·00001 for both) in the dysfunctional group.

Conclusions:

This group of dysfunctional subjects exhibited significantly slower, smaller, and more variable chewing patterns than the control group. The functional pattern of mastication appears to be significantly altered in the presence of an internal derangement of the TMJ.     

Effects of soft tissue injury to the temporomandibular joint: report of 8 cases

Our aim was to describe the effects of soft tissue injury to the temporomandibular joint (TMJ), to analyse possible reasons for it, and to evaluate the results of treatment. Eight patients (12 joints) who developed disorders of the TMJ after trauma to the mandible without fracture of the condyle were treated in our department from 2009 to 2010. Magnetic resonance imaging (MRI) and computed tomography (CT) were used to check the condition of the joint. Five patients had their joints explored to relieve pain and improve mouth opening. MRI showed all 12 joints had displaced discs. CT showed that the surface of the condylar bone was “intact” immediately after injury but destroyed later in 8 joints. Exploration showed fibrous ankylosis in 5, osteoarthritis with intra-articular adhesions in 2, and internal derangement in 1. Four were treated by costochondral graft (CCG) with 7 symptomatic joints. The disc was repositioned in 1 case with 1 affected joint. The mean maximal incision opening at follow-up were significantly better than the one before treatment (mean 34 compared with 23 mm, p = 0.02). Pain in the TMJ was relieved by operation in all patients so treated. The other 3 patients (4 joints) had no treatment because their symptoms were minor and mouth opening was not restricted. Soft tissue injuries of the TMJ can potentially lead to internal derangement, osteoarthrosis, and possibly fibrous ankylosis, which should be considered during follow-up. Displacement of the disc and damage to the condylar cartilage seem to be the causes of these complications. Surgical management is effective in the short term.     

Effect of clenching level on mandibular displacement in Kennedy Class II partially edentulous patients

PURPOSE: Forceful clenching in the intercuspal position has the potential to cause significant mandibular displacement. Such a displacement can be expected to be exaggerated in patients without molar support. The appropriate clenching level for intercuspal position registration or evaluation in these patients has never been clarified. The aim of this study was to clarify the effect of clenching level and absence of posterior occlusal support on mandibular displacement. MATERIALS AND METHODS: Thirteen women with a unilateral edentulous area posterior to the first premolar were enrolled in this study. They were asked to perform intercuspal clenching at various occlusal force levels, and 3-D mandibular displacements were measured by an optoelectronic method. The effects of "clenching force level" and "side of molar tooth loss" on the displacements of the condylar and second molar points were analyzed. RESULTS: The mandible was elevated without substantial horizontal displacements during each clenching task. The effect of clenching level on vertical mandibular displacement was significant, with a clenching level > or = 50% of maximal voluntary contraction causing significantly greater elevations (P < .05). Clenching > or = 50% of maximal voluntary contraction caused consistent tipping of the mandible, with greater elevation on the edentulous side (P < .05). CONCLUSION: The clenching level should not surpass 50% of maximal voluntary contraction for registration or evaluation of intercuspal position in Kennedy Class II patients.     

Determination of daytime clenching events in subjects with and without self‐reported clenching

To confirm the validity of self‐awareness of daytime clenching, specific electromyogram (EMG) characteristics of clenching behaviour were determined using surface EMG recordings. Temporal muscle EMGs were recorded for 5 h in 13 subjects with self‐reported clenching (clenching group: 27·5 ± 3·8 years old) and 12 subjects without self‐reported clenching (control group: 28·6 ± 7·1 years old). All EMG data were recorded and stored on a portable EMG apparatus. The device was similar in size to a hearing aid, and suitable to record daytime EMG without restriction of daily activities. A clenching event was defined as muscle activity exceeding 10% of the maximum voluntary contraction. Furthermore, simultaneous voice recording was also performed to identify the corresponding EMG event as functional or parafunctional. The mean number of clenching events was 192·8 ± 228·8 and 24·8 ± 26·5 in the clenching and the control groups, respectively (P < 0·05, Mann–Whitney U‐test); the number of functional events was not significantly different between the groups. Because there was a significant difference in the number of clenching events between the groups, self‐reported daytime clenching is considered to be a reliable screening parameter for awake bruxism.     

Intraoral pH and temperature during sleep with and without mouth breathing

To measure and compare the intraoral pH and temperature of individuals during sleep with and without mouth breathing. Ten healthy participants [mean age = 25·8 (± 4·3)] wore a custom‐made appliance fitted with a pH probe and thermocouple for two sets of 48 h. Continuous pH and temperature measurements were taken from the palatal aspect of the upper central incisors. To simulate mouth breathing during sleep, participants wore a nose clip for two nights of the four, with the first group (n = 5) wearing the nose clip during the first night and the rest (n = 5) wearing the nose clip during the second night of sleep to balance any potential bias from the wearing sequence. Both qualitative and quantitative analyses were conducted. The mean intraoral pH during daytime was 7·3 (± 0·4) and during sleep was 7·0 (± 0·5). The mean intraoral pH during sleep with mouth breathing was 6·6 (± 0·5), which was statistically significant compared with the normal sleep condition (P < 0·01). The intraoral pH decreased slowly over the hours of sleep in all participants. When sleeping with forced mouth breathing, intraoral pH showed a greater fall over a longer period of time. The mean intraoral temperature was 33·1 °C (± 5·2) during daytime and 33·3 °C (± 6·1) during sleep, with no statistical significance between sleep with and without mouth breathing (P > 0·05). The results suggest that mouth breathing during sleep is related to a decrease in intraoral pH compared with normal breathing during sleep, and this has been proposed as a causal factor for dental erosion and caries.     

A new three-dimensional,print-on-demand temporomandibular prosthetic total joint replacement system: Preliminary outcomes

Purpose

The aim of this study is to present the preliminary clinical data on the OMX Temporomandibular Joint (TMJ) Prosthetic total joint replacement system.

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.     

Temporomandibular dysfunction post-craniotomy: Evaluation between pre- and post-operative status

ObjectiveTo identify risk factors associated with post-operative temporomandibular joint dysfunction after craniotomy.MethodsThe study sample included 24 patients, mean age of 37.3 ± 10 years; eligible for surgery for refractory epilepsy, evaluated according to RDC/TMD before and after surgery. The primary predictor was the time after the surgery. The primary outcome variable was maximal mouth opening. Other outcome variables were: disc displacement, bruxism, TMJ sound, TMJ pain, and pain associated to mandibular movements. Data analyses were performed using bivariate and multiple regression methods.ResultsThe maximal mouth opening was significantly reduced after surgery in all patients (p = 0.03). In the multiple regression model, time of evaluation and pre-operative bruxism were significantly (p < .05) associated with an increased risk for TMD post-surgery.ConclusionA significant correlation between surgery follow-up time and maximal opening mouth was found. Pre-operative bruxism was associated with increased risk for temporomandibular joint dysfunction after craniotomy.     

Influence of different narrative instructions to record the occlusal contact with silicone registration materials

This study examined the influence of narrative instructions on the occlusal contact area, occlusal contact point and masticatory muscle activities in normal subjects. Twelve healthy men and 12 healthy women with no more than one missing tooth per quadrant participated. Surface EMG was recorded from the masseter and temporal muscle. As a control measurement, intercuspal position was maintained to produce a habitual clenching record (NCR) while the occlusal contact area and occlusal contact point was recorded by means of silicone material. Subsequently, the occlusal contact area was recorded with the narrative instruction for minimum clenching record (MCR), light clenching record (LCR) and strong clenching record (HCR). While the EMG activity (%MVC) increased modestly from MCR to LCR (from 9·3 ± 2·0% to 11·5 ± 1·5%), the occlusal contact area increased rapidly (from 17·2 ± 11·3 mm² to 26·8 ± 15·6 mm²) (P < 0·05). Both EMG activity and occlusal contact area increased gradually from LCR to NCR (to 17·7 ± 2·0% and to 31·4 ± 14·2 mm², respectively). Finally, EMG activity still increased from NCR to HCR (to 44·5 ± 3·7%) (P < 0·05), but the occlusal contact area remained stable (to 36·8 ± 16·6 mm²). Occlusal contact points at left posterior, right posterior, anterior and total area were not significantly different between each task. This study showed that narrative instructions while recording the bite can result in largely stable occlusal contact area. An adequate narrative instruction may therefore contribute to taking a stable occlusal recording in natural dentition.     

Establishing better biological models to understand occlusion. I: TM joint anatomic relationships

Belief in and rejection of a relationship of occlusion and temporomandibular joint (TMJ) condyle–fossa position with normal and abnormal function are still contentious issues. Clinical opinions can be strong, but support in most published data (mostly univariate) is problematic. Distribution overlap, low sensitivity and specificity are a common basis to reject any useful prediction value. Notwithstanding, a relationship of form with function is a basic tenet of biology. These are multifactor problems, but the questions mostly have not been analysed as such. This review moves the question forward by focusing on TM joint anatomic organisation as the multifactor system it is expected to be in a closed system like a synovial joint. Multifactor analysis allows the data to speak for itself and reduces bias. Classification tree analysis revealed useful prediction values and usable clinical models which are illustrated, backed up by stepwise logistic regression. Explained variance, R², predicting normals from pooled TMJ patients was 32·6%, sensitivity 67·9%, specificity 85·7%; 37% versus disc displacement with reduction; and 28·8% versus disc displacement without reduction. Significant osseous organisational differences between TM joints with clicking and locking suggest that this is not necessarily a single disease continuum. However, a subset of joints with clicking contained characteristics of joints with locking that might contribute to symptom progression versus resistance. Moderately strong models confirm there is a relationship between TMJ osseous organisation and function, but it should not be overstated. More than one model of normals and of TM derangement organisation is revealed. The implications to clinical decision‐making are discussed.     

2例个体化人工关节用于颞下颌关节置换的初步效果评价

目的：采用CAD／CAM技术设计个体化人工全颞下颌关节，通过全关节置换，治疗严重颞下颌关节病，对其疗效进行初步评价。方法：2例女性颞下颌关节疾病患者，年龄分刖为53岁和60岁。术前经MRI等检查发现严重的关节盘及髁突病变，开口度分别为2．0cm和1．8cm，均表现有明显的关节疼痛。2例患者均采用TMJ Concepts公司的个体化人工颞下颌关节全关节置换术。结果：成功完成了2例3侧颞下颌关节的置换手术。未出现术后并发症。关节疼痛在术后2周后逐渐缓解。6个月后开口度分别为2．7cm和2．9cm。术后口颌功能改善良好。结论：人工全颞下颌关节置换治疗严重颞下颌关节骨关节病具有良好的效果，个体化设计可为人工关节发挥良好功能提供有效的保证．