Biomedical subjects
Publications and source records attributed to C McNeill.
This article was prepared and submitted to members of the TMD academic community for their endorsement. A total of 120 people signed an endorsement; their names are available on request.
STATEMENT OF PROBLEM: Controversy continues in the area of epidemiology, etiology, diagnosis, and management of temporomandibular disorders (TMD). The field is replete with testimonials and clinical opinion, but it has been lacking in scientific foundation. PURPOSE: This article reviews the recent temporomandibular disorder and orofacial pain literature and summarizes the concepts published in the 1993 and 1996 American Academy of Orofacial Pain guidelines. Temporomandibular disorders rarely occur as single entities but rather as multiple problems with overlapping symptoms. CLINICAL SIGNIFICANCE: The multicausal nature of these problems and the number of conditions with similar signs and symptoms demand an effective differential diagnostic process. Diagnostic criteria are used from an operational standpoint to establish specific diagnoses based on a multiaxial diagnostic model. CONCLUSION: Because little is known about the natural course of the various classifications of temporomandibular disorders, and because most treatment approaches are reported to be equally effective, a conservative, noninvasive management program is endorsed. The emphasis is on a medical multidisciplinary model similar to ones used for other musculoskeletal disorders that involve the patient in the physical and behavioral management of his or her own problem. This article concludes that a majority of temporomandibular disorder patients achieve good relief of symptoms with noninvasive reversible therapy.
The reversible hearing loss in the nonoperated ear noted by patients after ear surgery remains unexplained. This study proposes that this hearing loss is caused by drill noise conducted to the nonoperated ear by vibrations of the intact skull. This noise exposure results in dysfunction of the outer hair cells, which may produce a temporary hearing loss. Estimations of outer hair cell function in the nonoperated ear were made by recording the change in amplitude of the distortion-product otoacoustic emissions before and during ear surgery. Reversible drill-related outer hair cell dysfunction was seen in 2 of 12 cases. The changes in outer hair cell function and their clinical implications are discussed.
Historically the field of temporomandibular disorders (TMD) has been based on testimonials, clinical opinion, and blind faith rather than on science. Reparative procedures to the joints, jaws, or occlusal surfaces of the teeth to develop idealized structural relationships that may be required for dental health and function are less likely to be required for the management of chronic musculoskeletal disorders. Because of the concerns of many people today regarding professional credibility and intellectual honesty, the need for a scientific foundation to support the various belief systems is of paramount importance. In fact, therapeutic approaches for TMD are undergoing a major evolution away from the traditional mechanistic dental concepts of the past to the more current biopsychosocial medical concepts that emphasize multidisciplinary approaches. Recent advances in the understanding of pain mechanisms and management of chronic pain have improved long-term treatment outcome. The emphasis is on treatment that involves the patient in the physical and behavioral management of their own problem. The majority of patients with TMD achieve good relief of their symptoms with noninvasive, conservative therapy.
The purpose of this study was to determine if there was a difference between the temporomandibular condylar movement patterns of a symptomatic adult population and those of an asymptomatic adult population. Thirty-five volunteers who were not seeking treatment for TMD underwent two different assessments for TMD signs and symptoms: (1) a self-administered questionnaire and (2) a clinical examination. Based on the information obtained from the questionnaires, subjects were divided into "reported-symptomatic" and "reported-asymptomatic" groups. Based on the investigator's clinically evaluation of the same subjects, subjects were divided into "clinically symptomatic" and "clinically asymptomatic" groups. To compare condylar movement patterns, both groups of subjects then had their mandibular border condylar movements measured bilaterally using a sagittal recording device during maximum opening, maximum protrusion, and maximum left and right excursion movements. The patterns were separated into two broad groups, "symmetric" and "asymmetric." Symmetric gliding movements were defined as uninterrupted bilaterally mirror-like patterns of each condyle with a difference between left and right total length excursion not exceeding 2 mm during opening in the sagittal plane or horizontal plane. Our results show that 63% of the subjects who reported clinically asymptomatic for TMD demonstrated asymmetric condylar movements. However, 100% of the patients (n = 5) who reported clinically symptomatic for TMD exhibited asymmetric condylar movements. This finding suggests that, while a very high percentage of TMD subjects will have asymmetric condylar movements, condylar movements alone are not necessarily diagnostic of TMD, and the sagittal recording device may alert the clinician to abnormal movements.
OBJECTIVE: To test the hypothesis that neuromuscular symptoms of patients with temporomandibular disorders that occur in the upper back and neck can be evaluated by recording the temperature patterns in the skin overlying the muscles. STUDY DESIGN: Liquid crystal contact thermography was evaluated on patients with temporomandibular disorders to demonstrate temperature changes in the muscles of the neck and upper back. The study consisted of 22 patients with temporomandibular disorders and 22 normal controls. RESULTS: The mean right-versus-left-side temperature difference of the control group was 0.13 degree C whereas the patient group showed a difference of 0.78 degree C. Of the 22 patients with temporomandibular disorders, 21 (95.5%) showed an increased temperature over the trapezius muscle on the symptomatic side. CONCLUSIONS: These findings indicate that thermography may be useful in the diagnosis of myofascial symptoms that may be associated with temporomandibular disorders.
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The masseter muscle was studied during postnatal development of the rabbit from the juvenile to adult stage in which the oral function was altered during maturation by modifying the diet to soft food. The muscle was assessed using phosphate magnetic resonance (31P NMR) spectroscopy with a single-turn copper surface coil to study potential changes in phosphate metabolism. The 31P NMR spectra consisted of five peaks related to unbound forms of inorganic phosphate (Pi), creatine phosphate (PCr), and three peaks related to the adenosine triphosphate (ATP). The masseter was assessed in one group of five rabbits at 8 weeks postnatally (juvenile) and after 4 months of this experimental group masticating on soft food. They were compared with a control group of five rabbits raised on a normal hard diet. The Pi/PCr ratio increased in the adult masseter much higher during twitching, tetany, and periodic contraction than in the juvenile regardless as to whether the adult animal had been raised from the juvenile period on soft or hard diet. There were relatively few differences between the experimental adult animals raised on a soft diet and the normal adult animals despite the soft diet animals demonstrating a significantly lower weight and smaller muscle mass. These findings suggest that chronic underuse of the masseter muscle by decreasing the masticatory loads has a minimal effect on the phosphate metabolism of the maturing masseter.
This work studies the dynamic metabolic changes of the rabbit masseter muscle during post-natal development. The composition and proportion of oxidative and glycolytic muscle fibers alter during maturation. The masseter muscle, as most muscles of the craniofacial region, exhibits unusual development in composition of isoforms of myosin. The effect of this unusual composition on the dynamic metabolic properties of the masseter muscle have not been assessed. The metabolism of the rabbit masseter muscle was studied by means of 31P-nuclear magnetic resonance (NMR) spectroscopy. Contraction was elicited by electrical stimulation of the muscle in the anesthetized animal. Five animals were studied at 8 weeks and 24 weeks so that both the juvenile and adult stages could be evaluated. The dynamic biochemical changes in the masseter muscle were studied by the analysis of NMR spectra. A single-turn surface coil (copper) was used, and the original signal was treated with Fourier transforms to obtain 31P spectra. The low signal-to-noise ratio required averaging 16 acquisitions (acquisition time = 400 msec, repetition rate = 1.8 sec) in 30 sec and then obtaining continuous spectra for 27 min. Each averaged spectrum demonstrated five peaks: inorganic phosphate (Pi), creatine phosphate (PCr), and three peaks related to adenosine triphosphate (ATP). The protocol involved recording an initial three-minute rest period, stimulating the muscle at 5 Hz for 3 min twice, separated by three-minute rest periods, and stimulating the muscle at 50 Hz twice for 3 min separated by rest periods. The Pi/PCr ratio increased significantly in the adult masseter during both 5-Hz stimulations, evoking twitching, and the first 50-Hz stimulation, evoking tetany (repeated ANOVA, P < 0.05). The resting pH (6.96 +/- 0.13) was significantly lowered during both twitching (6.85 +/- 0.10; P < 0.0038) and tetany (6.55 +/- 0.13; P < 0.0001), but only in the adult masseter muscle. These finding suggest that the adult masseter muscle possesses more glycolytic fibers as it modifies its metabolism during postnatal development.
The masseter muscles of six nonbruxing subjects (five men, one woman) and six bruxing subjects (four men, two women) were assessed during chewing by nuclear magnetic resonance spectroscopy (31P-NMR). The NMR spectra were collected on a GE Sigma 1.5T whole body magnet with a double-tuned 31P/1H surface coil. Two-minute trials of rest/chewing/rest were completed three times. Averaged spectra of inorganic phosphate, phosphocreatine, and three adenosine 5' triphosphate peaks were collected in each trial. Bruxing subjects had a lower concentration of total phosphate and phosphocreatine than nonbruxing (control) subjects at rest. Bruxing subjects increased their inorganic phosphate during chewing significantly less than control subjects. The pH levels during rest and during chewing were similar in both controls and bruxers. These preliminary results suggest that bruxing subjects exhibit an altered phosphate metabolism during rest and exhibit a different phosphate metabolism pattern during chewing as compared to nonbruxing subjects.
This anatomic study examines the attachment of the lateral pterygoid muscle to the capsule and disc of the temporomandibular joint. The anatomy of the temporomandibular joint and its surroundings, in particular the insertion of the superior head of the lateral pterygoid muscle, was studied by dissection and conventional histologic techniques. The material consisted of 16 cadaver specimens from individuals 60 years or older. The results showed that only a part of the superior head of the lateral pterygoid muscle is attached to the anterior portion of the capsule, which, in turn, is firmly attached to the disc, giving the impression that the muscle and the disc are directly connected. All specimens showed attachment of the superior head of the lateral pterygoid muscle to the anterior medial portion of the capsule, but they showed varying degrees of attachment to the lateral aspect of the temporomandibular joint capsule. The remaining part of the superior head of the lateral pterygoid muscle attached to the mandibular condyle. Serial sectioning in no instance showed direct insertion into the disc of the fibers of the superior head of the lateral pterygoid muscle.
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Dynamic biochemical changes in the masseter muscle were studied in 14 New Zealand adult male rabbits by 31P-nuclear magnetic resonance (NMR) spectroscopy. NMR spectra were obtained during rest and electrical stimulation of the muscle in the anaesthetized animal at 33 recording sessions. Electrical stimulation was applied by a pair of copper wires placed separately with hypodermic needles into the muscle. NMR spectra were acquired with a 2 x 3 cm, double-turn, copper transmit/receive coil. Sixteen spectra were averaged over 30 s to obtain averaged spectra continuously during a 30-min recording. The spectra were processed automatically using a non-linear 'least-squares' fitting program on the spectrometer. A Lorentzian line shape was assumed for the peaks, and values of peak height, area and chemical shifts were generated. Each averaged spectrum consisted of five peaks: inorganic phosphate (Pi), creatine phosphate (PCr), and three peaks related to ATP. Data were analysed as to absolute changes in Pi and PCr, in the ratio of Pi/PCr, and the shift of Pi to PCr to estimate pH. Several protocols were used in which ranges of frequency, intensity and duration of electrical stimulation were tested. The protocol for detailed studies involved stimulating the muscle twice at 5 Hz for 3 min separated by a 3-min rest period, then stimulating twice at 50 Hz for 3 min separated by a rest period. During contraction of the muscle, there was a significant increase in the Pi/PCr ratio (p < 0.05) as compared to the resting level. The ratio reached a plateau over a 3-min contraction using 5-Hz stimulation, then increased significantly more with the 50-Hz stimulation but decayed during the 3 min. Sustained stimulation with 50 Hz for 15-45 min evoked an initial sharp change in Pi/PCr, which then reached a steady plateau that remained over the entire stimulation. These findings indicate that the rabbit masseter muscle is relatively fatigue resistant in maintaining a steady-state equilibrium in the relation of Pi to PCr.
Twenty-three adult female patients were studied before and after injection of one temporomandibular joint to relieve pain. These patients had exhibited a persistent history of pain within their mandibular, neck, and somatic muscles, despite repeated treatment involving occlusal splints, physical therapy, and biofeedback. Patients were also screened for possible condylar degeneration using corrected tomograms. Initially, patients rated their pain on a linear scale from 0 to 10 and designated the site of the pain on a full-body-profile chart. The presence and location of the pain was determined by manual palpation using a rating scale of 0 to 10, and by the patients designating those regions perceived as painful by marking a full-body-profile chart. After this initial screening, subjects received an injection of 1% lidocaine (1:100,000) to the upper intracapsular space of one joint. The pain profile chart was completed by the patients 15 minutes after injection. Twenty of the 23 patients demonstrated a significant decrease in pain located in facial, head, and neck regions. These data suggest that injection of a local anesthetic to the temporomandibular joint will decrease pain for a short time in ipsilateral and contralateral regions of the head and neck.