Characterization of sounds emanating from the human temporomandibular joints

Stomatognathic adaptive motor syndrome is the correct diagnosis for temporomandibular disorders

Temporomandibular disorder is a generic and inadequate conception to be used as a diagnosis. It fails to express the etiology or the pathophysiology and it is mainly associated with the anatomical site. Moreover, the clinical condition presents a mandibular motor problem and not a joint problem. The hypothesis presents the new diagnosis stomatognathic motor adaptive syndrome, which comprehend a motor response and the adaptive processes it induces. Inadequate occlusal contacts cause the mandible to shift in order to reach an ideal intercuspal position. The condylar displacements are proportional to such movements. Temporomandibular joint (TMJ) receptors respond to the capsular mechanical stress and the information reaches the trigeminal sensory nuclei. The mandibular modified position seems to be relevant information and may interfere with catecholaminergic neurotransmission in basal ganglia. The main motor responses comprise increased jaw muscle tone, decreased velocity of movements and incoordination. The overload of muscle function will produce adaptive responses on many stomatognathic structures. The muscle adaptive responses are hypertonia, pain, fatigue and weakness. Temporomandibular joint presents tissue modification, disc alteration and cracking noise. Periodontium show increased periodontal membrane, bone height loss and gingival recession. Teeth manifest increased wear facets, abfraction and non-accidental fractures. The periodontal and teeth adaptive processes are usually identified as occlusal trauma. The altered stomatognathic functions will show loss of velocity during mastication and speech. Fatigue, weakness in jaw muscle and difficulties to chew hard food are related to hypertonia. Incoordination between stomatognathic muscles groups is found, causing involuntary tongue/cheek biting and lateral jaw movements on speech. Otologic complaints, as aural fullness and tinnitus, are related to the tensor tympani muscle, innervated by the trigeminal nerve.

An enhanced algorithm for knee joint sound classification using feature extraction based on time-frequency analysis

Vibroarthrographic (VAG) signals, generated by human knee movement, are non-stationary and multi-component in nature and their time-frequency distribution (TFD) provides a powerful means to analyze such signals. The objective of this paper is to improve the classification accuracy of the features, obtained from the TFD of normal and abnormal VAG signals, using segmentation by the dynamic time warping (DTW) and denoising algorithm by the singular value decomposition (SVD). VAG and knee angle signals, recorded simultaneously during one flexion and one extension of the knee, were segmented and normalized at 0.5 Hz by the DTW method. Also, the noise within the TFD of the segmented VAG signals was reduced by the SVD algorithm, and a back-propagation neural network (BPNN) was used to classify the normal and abnormal VAG signals. The characteristic parameters of VAG signals consist of the energy, energy spread, frequency and frequency spread parameter extracted by the TFD. A total of 1408 segments (normal 1031, abnormal 377) were used for training and evaluating the BPNN. As a result, the average classification accuracy was 91.4 (standard deviation +/-1.7) %. The proposed method showed good potential for the non-invasive diagnosis and monitoring of joint disorders such as osteoarthritis.

Oral processing assessed by M-mode ultrasound imaging varies with food attribute

Ultrasonic imaging was used to quantify oral movements made during the oral processing of foods while subjects assessed the intensity of the sensory attributes, thick, creamy, sweet and bitter. A series of four stimuli were prepared with high and low viscosities and high and low sweetness. Over five sessions, subjects (N=8) were asked to consume 5 ml spoonfuls of each of the stimuli while holding an ultrasound probe beneath their chin so as to produce a mid-line sagital image of the floor of the mouth and tongue. In the first session, subjects were asked to swallow the sample. In subsequent sessions, subjects were asked to rate one of the attributes, thickness, sweetness, creaminess or bitterness, in random order. The resulting video recordings were subjected to an image-processing algorithm to quantify the amount of intra-oral manipulation performed. The results demonstrated that oral movements varied with attribute, especially in the period during which the bulk of the food is typically processed and the following swallowing phase. The food's sweetness affected oral movements especially during the bulk phase, whereas the food's viscosity primarily affected movements during the following swallowing and clearance phases.

The dynamic range of TMJ sounds

It is of clinical interest to record the amplitudes of temporomandibular joint (TMJ) sounds. The aim was to test the hypothesis that sealing the meatus, when placing a microphone in the ear canal affects such recording by increasing the sound pressure level (SPL). Bilateral recordings of 249 TMJ clickings were made from three subjects, using sampling rates of 48 or 96 kHz and 24 bits A/D conversion, with and without the ear canals sealed by Silicone putty. The peak-to-peak equivalent sound pressure level (peSPL) was higher (P < 0.001) when the ear canal was sealed (range of mean differences was 8.3-24.9 dB peSPL). This means that the signal to noise ratio can be improved by sealing the meatus because the electronic noise level is not increased. Most important is that the dynamic range of the clicking sounds was 62 dB that is larger than the effective dynamic range of a 16 bits sound card. Future studies are needed to establish normative peSPL values. However, cards with at least 24 bits A/D conversion will be required, especially in patients with suspected disc displacement with reduction, where the difference in loudness between opening and closing clicking often is large.

The influence of mandibular movements on joint sounds in patients with temporomandibular disorders

STATEMENT OF PROBLEM

There are discrepancies among researchers concerning the reliability and use of temporomandibular joint sounds.

PURPOSE

This study examined the reliability of mandibular movements and sounds and determined the correlation between movements and sounds.

MATERIAL AND METHODS

The mandibular movements of 35 subjects diagnosed with temporomandibular disorders were recorded with 2 CCD cameras, and sounds were recorded bilaterally with Panasonic electret condenser microphones in the ear canal. Subjects performed 3 movements, each repeated 5 times.

RESULTS

Reliability of maximum movements across the 5 trials was good to excellent, with Intraclass Correlation Coefficients (ICC) between 0.76 and 0.91 for all movements except protrusion. Temporomandibular sound event counts were reliable for most movements, including vertical opening, protrusion, and right and left laterotrusion (ICCs between 0.41 and 0.81). Most subjects produced sound events either in 100% or in none of the trials. Reliability for sound events was better during protrusion (ICCs between 0.56 and 0.81) than vertical opening (ICCs 0.41 to 0.64). Subjects with sound events during vertical opening (followed by closing) were significantly more likely to have sound events during protrusion (followed immediately by vertical opening and closing) (P <.01).

CONCLUSION

Temporomandibular sound events are generally reliable and warrant study regarding their use in classifying and diagnosing patients with temporomandibular disorders. Condylar translation, which occurs during both vertical opening and protrusion, appears to have a strong influence on the production of temporomandibular sound events.

Subjective assessment of temporomandibular joint sounds

If it could be shown that the human ear was sufficiently sensitive to describe TMJ sounds, there would be no need to use sophisticated electronic equipment to analyse the sounds. To test this, the ability of normal listeners to distinguish the subtle changes in position, pitch, duration and latency present in TMJ sounds is measured using triangle tests to determine the just-noticeable differences. The results suggest that the human ear is a rather poor instrument for describing subtle differences in the position, duration and latency of TMJ sounds, but is capable of detecting small differences in frequency. It is therefore doubtful that the human ear can distinguish the reciprocal click associated with disc displacement with reduction from clicks due to defects of form on the basis of their relative position in the envelope of movement.

Validation of a recording protocol for assessing temporomandibular sounds and a method for assessing jaw position

Sounds are often produced by the temporomandibular joint (TMJ) during movement in both symptomatic and asymptomatic subjects. However, subjective methods of describing these sounds have been shown to have poor inter- and intra-observer reliability. In this study, a low cost system in which TMJ sounds were detected using the loudspeakers of lightweight in-ear headphones as microphones is evaluated. The sounds were recorded on tape and then analysed using a computer. Sounds were elicited by asking subjects to bring their teeth together with sufficient force to produce a tooth contact sound, then open their mouths as far as possible and then close again. Placing the microphones in the ears attenuated ambient sounds by 58%, thus providing a degree of immunity from ambient noise. Sampling was performed on the left microphone only at 3.4 kHz and from the left and right microphones together at 1.7 kHz for 60 TMJ sounds and 60 tooth contact sounds. Spectral analysis of sounds recorded at the two sample rates revealed no significant differences. Therefore, a sample rate of 1.7 kHz is adequate to resolve the frequency components present in the TMJ sounds. Although simply recording TMJ sounds does not give a direct measurement of the position of the mandible, using this protocol allows the length of the open close cycle to be determined. If the envelope of movement is assumed to approximate a sinusoid, then the direction of mandibular movement can be assumed to reverse at the half way point in the cycle. The accuracy of this assumption was calculated by comparing the mid-point of the cycle to the point of maximum gape in 129 cycles from nine subjects. The mean difference expressed as percentage of cycle length was 1.3 +/- 0.9%.