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Biomedical subjects

C S Stohler

Publications and source records attributed to C S Stohler.

At least 37 records · Page 2Linked to original sources
PubMed1997

Media hype: musculus sphenomandibularis.

The report of an allegedly so far unknown craniomandibular muscle ('the sphenomandibularis') in 1996 by Dunn and co-workers provoked much comment in journals and newspapers. The authors' hypothesized role of the 'm. sphenomandibularis' in temporomandibular disorders and headaches created hopes and expectations. The present article examines whether two detailed descriptions by Ramalho and co-workers [1978, in Portuguese], and by Zenker [1954, 1955, and 1956, in German] deal with the very same muscle. From the comparison of these descriptions it becomes evident that the 'm. sphenomandibularis' is not a new muscle, but corresponds to the 'medial portion' [Zenker], or 'deep portion' [Ramalho et al.] of the temporalis muscle. Further directed search identified descriptions of the muscle in question back into the 19th century.

Classification↗
PubMed1997

Pain descriptors characteristic of persistent facial pain.

The McGill Pain Questionnaire is an instrument that is widely used to assess the multidimensional experience of pain. Although it was introduced more than 20 years ago, limited information is available about its use in patients suffering from persistent facial pain. The aim of this study was to investigate the response patterns of persistent facial pain patients to the McGill Pain Questionnaire, to correlate these patterns with patients' beliefs about the seriousness of the condition, and to compare the findings with data reported from other painful conditions. The study sample consisted of 200 consecutive female patients referred to a tertiary care facial pain clinic. The Pain Rating Index scores of the McGill Pain Questionnaire subscales and the total number of words chosen by these patients closely matched the summary scores reported by Wilkie et al, who pooled data from seven pain conditions (cancer, chronic back, mixed chronic, acute/postoperative, labor/gynecological, dental, and experimentally induced) in their meta-analysis. On the other hand, when the data collected in this study were compared with those from specific clinical subsets, such as cancer patients, chronic back pain patients, or dental patients, differences in McGill Pain Questionnaire scores could be identified. Differences were also found in the choice of specific pain descriptors. More than 20% of the facial pain patients selected "radiating" and "pressing"; this was not the case for those suffering from other pain conditions. Facial pain patients who felt that their condition was more serious or different from what the treatment providers had told them had a greater likelihood of choosing specific word categories of the McGill Pain Questionnaire.

Adolescent↗
PubMed1996

The effect of experimental jaw muscle pain on postural muscle activity.

The purpose of this study was to examine whether tonic muscle pain of an intensity at least as great as that reported by the majority of chronic muscle pain patients causes an increase in postural electromyographic activity of the affected musculature. Twenty young adults volunteered for experiments, knowing that they involved experimental pain. We chose a controlled, two-period crossover and repeated measures design involving four experimental conditions: (1) baseline 1, (2) tonic experimental muscle pain, (3) sham pain, and (4) baseline 2. Subjects were randomly assigned to one of two sequential orders that differed with respect to whether tonic pain preceded sham pain or vice versa. At the within-subject level, the condition (baseline 1, sham pain, tonic pain, baseline 2) had a statistically significant effect on mean rms electromyographic activity at all four recording sites. We found that postural activities at all four recording sites, left/right masseter and left/right anterior temporalis were statistically different from baseline 1 and 2 during tonic pain (P < 0.004, s.; P < 0.024, s.). However, postural activities during tonic pain and sham pain were not significantly different from each other (P < 0.493, n.s.). We concluded that our data do not support the hyperactivity model which assumes a re-enforcing link between pain and muscle hyperactivity.

Adult↗
PubMed1996

Jaw muscle pain and its effect on gothic arch tracings.

Perceived changes in occlusion and decreased range of motion are often expressed by patients with masticatory muscle pain. The adverse loading of craniomandibular tissues that results from an inadequate maxillomandibular relationship in combination with the coexisting dysfunction is widely regarded as the cause of pain. This study was designed to test whether pain can cause significant changes in position of the mandible and therefore form the basis for any perceived changes in the maxillomandibular relationship. A second objective was to determine whether pain can cause changes in the mandibular range of motion. Five subjects who rated pain intensity on a visual analog scale were used in a single-blind, randomized, repeated-measures study design. Tonic muscle pain was induced by infusion of 5% hypertonic saline solution into the central portion of the superficial masseter muscle. Isotonic saline solution was used as a control, with subjects blinded to the type of substance given. The effect of pain on the position of the apex of the gothic arch tracing, the direction of the lateral mandibular border movements, and the mandibular range of motion was studied in a horizontal plane with minimal occlusal separation. Pain significantly affected the position of the apex of the gothic arch tracing in anterior (F = 11.46, p = 0.03) and transverse (F = 35.0, p = 0.004) directions. Similarly, pain affected the orientation of the mandibular lateral border movements (F = 12.44, p = 0.02) and their magnitude (F = 14.97, p = 0.01). All pain-induced effects proved to be reversible. The observed effect of pain can explain the perceived change of bite that is frequently noted by patients with orofacial pain. This study provided evidence of an alternative causal relationship between pain and changes in occlusal relationship and questions occlusal therapy as treatment, directed toward the elimination of the underlying cause in patients with masticatory muscle pain.

Adult↗
PubMed1995

Three-dimensional unilateral method for the bilateral measurement of condylar movements.

Using a unilateral optoelectronic tracking system (JAWS-3D), a method was developed for the simultaneous measurement of the three-dimensional kinematics of both ipsilateral and contralateral human condyles, the latter being represented by virtual points beyond the field of vision of the camera system during the actual recording. The method leaves the subject's head unrestrained while measuring the movements of two sets of three light-emitting diodes rigidly attached to the upper and lower teeth. The Tait-Bryan angles method was employed for calculating the jaw rotations in three dimensions. Movements were referenced to both a skeletal and a dental coordinate system. The worst-case static measurement errors were 0.24 mm for a 20 mm translation and 0.71 degrees for a 35 degrees rotation. The mean dynamic measurement errors were 9.73 microns s-1 at a constant linear velocity of 200 microns s-1 and 0.73 degrees s-1 at a constant angular velocity of 149 degrees s-1. The utility of the method was demonstrated in a subject who was asked to open and close the mouth in a cyclic fashion.

Humans↗
PubMed1993

A closed-loop system for maintaining constant experimental muscle pain in man.

Reliable experimental models are needed to help improve our knowledge of how the central nervous system adapts to function in the presence of muscle pain in man. We developed a microprocessor-based control system for maintaining a constant level of experimental muscle pain. Pain was induced in the relaxed right masseter of healthy young adults by using an infusion pump to inject an algesic 0.15 mL bolus of 5% hypertonic saline over 15 s. Subjects supplied feedback on their present pain intensity (PPI) via a 10 cm long electronic visual-analog scale (VAS) and a 0.07 Hz zero-order hold. The adaptive controller identified the system dynamic response and proportional-integral-derivative (PID) controller parameters from the subject's initial response to the bolus (pain rise and fall time constants and peak amplitude) as well as his/her response to a 90 s constant infusion. Finally, using the pain feedback the adaptive PID controller was successfully used to adjust the infusion rate to maintain PPI in five out of seven healthy adults at a mean (SD) 4.8(0.9) PPI level with respect to the 5.0 PPI setpoint for periods up to 15 min (when the experiment was arbitrarily terminated). The infusion rate required to maintain the given level of masseter pain was found to increase by approximately 3 to 5%/minute.

Adult↗
PubMed1992

Determining the force absorption quotient for restorative materials used in implant occlusal surfaces.

It has been hypothesized that the type of material used to form the occlusal surface of restorations retained by dental implants may impart a "dampening effect" to the bone-implant interface. This study compared the force transmitted to human bone by gold, porcelain, and resin occlusal surfaces in a simulated implant occlusal rehabilitation. A Branemark self-tapping implant was placed in a human cadaver mandible with a stacked three element strain gauge cemented to the lingual cortical plate. An Instron testing machine was used to apply an axial force, through a peanut sample, to a restoration that contained interchangeable occlusal surfaces. Applied force was divided by recorded microstrain at the bone-strain gauge junction to derive a calculated ratio, or force absorption quotient. No statistically significant difference of the force absorption quotient between the occlusal surfaces of gold, porcelain, and resin was observed.

Absorption↗
PubMed1992

Prosthetic rehabilitation in temporomandibular disorder and orofacial pain patients. Clinical problem solving.

Good clinical decision making represents an integral part of quality care. A definition of the dental problem and its significance from a dental point of view, in combination with a good working hypothesis of the nature of the concurrent TMD condition are prerequisites of any successful clinical problem solving. It is hoped that, with time, we will be in a position to call upon hard data on the probability and utility of successful outcome for each treatment alternative. This will bring the needed structure and scientific validity to a terribly complex albeit clinically important problem.

Decision Trees↗
PubMed1991

Predicting foodstuff from jaw dynamics during masticatory crushing in man.

In previous in vitro experiments using an Instron instrument, each test food was found to have characteristic textural properties. In vivo experiments were now made (1) to determine the degree to which variations in the vertical jaw movements during the crushing phase of mastication can be explained by the inherent properties of the foodstuff being chewed, and (2) to establish the degree to which the foodstuff being chewed can be identified by certain features of the jaw dynamics. Five adults were used for chewing tasks with standardized pieces of beef, carrot or peanut. Each subject made two trials with each foodstuff. The movement of the lower incisal point was monitored; features of movement associated with jaw closing in the first chewing cycle were considered. Five of these features were not suitable to categorize the various test foods. Each of the remaining 4, however, was able to distinguish either one food from the 2 others (2 cases), or one from another (2 cases). Pattern recognition techniques based upon principal component analysis could differentiate jaw closing patterns associated with chewing beef from those involving peanut or carrot. The extent to which peanut could be distinguished from carrot was not as predictable as the categorization of peanut or carrot versus beef. Cross-correlation of in vitro force-time breakage characteristics and the jaw movement data showed that on average 52% of the variation in the vertical jaw movement during crushing of food could be explained by the inherent properties of the food.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The pain-adaptation model: a discussion of the relationship between chronic musculoskeletal pain and motor activity.

Articles describing motor function in five chronic musculoskeletal pain conditions (temporomandibular disorders, muscle tension headache, fibromyalgia, chronic lower back pain, and postexercise muscle soreness) were reviewed. It was concluded that the data do not support the commonly held view that the pain of these conditions is maintained by some form of tonic muscular hyperactivity. Instead, it seems clear that in these conditions the activity of agonist muscles is often reduced by pain, even when this does not arise from the muscle itself. On the other hand, pain causes small increases in the level of activity of the antagonist. As a consequence of these changes, force production and the range and velocity of movement of the affected body part are often reduced. To explain how such changes in the behaviour come about, we propose a neurophysiological model based on the phasic modulation of excitatory and inhibitory interneurons supplied by high-threshold sensory afferents. We suggest that the "dysfunction" that is characteristic of several types of chronic musculoskeletal pain is a normal protective adaptation and is not a cause of pain.

Adaptation, Physiological↗
PubMed1990

Changes in resistance to mouth opening induced by depolarizing and non-depolarizing neuromuscular relaxants.

Mouth opening was measured in 43 children anaesthetized with isoflurane and paralysed with vecuronium or suxamethonium. Measurements of mouth opening were made for up to 10 min after loss of the adductor pollicis twitch and cessation of muscle fasciculations. In 22 patients receiving suxamethonium, a significant (P less than 0.001) reduction in mean mouth opening occurred in the 60 s after loss of twitch and cessation of fasciculations. Mouth opening reductions could last for up to 10 min after the loss of twitch, beyond the return of the twitch. One patient experienced "masseter spasm"; he did not develop malignant hyperpyrexia during 2.5 h of isoflurane anaesthesia. Patients receiving vecuronium showed a significant (P less than 0.0006) increase in mouth opening. In 20 subjects, mouth opening was generated with a small (1.67 N) and a larger (4.32 N) force. Proportionally equal reductions in mouth opening were obtained with either force after suxamethonium administration. Relatively equal increases with either force followed vecuronium administration. Isolated masseter spasm is not pathognomonic for malignant hyperpyrexia. If the diagnosis of malignant hyperpyrexia is contemplated, signs of hypermetabolism, such as increases in end-tidal carbon dioxide concentration during constant minute ventilation, should be sought.

Analysis of Variance↗
PubMed1990

Cervical muscle myoelectric response to acute experimental sternocleidomastoid pain.

A method is presented for investigating the response of passive and active muscle to experimentally induced deep muscle pain. Ten healthy adult males performed multiple, submaximal isometric neck flexion tasks before and after pain had been induced in the sternocleidomastoid (SCM) muscle by injecting 5 ml of a hypertonic (5%) saline solution. A similar volume of isotonic saline was injected into the contralateral muscle as a control. Cervical myoelectric signal (MES) root-mean-square (RMS) response to each injection was recorded from eight neck muscles over 8 minutes. The subject rated perceived pain at regular intervals using a visual analog scale (VAS). Sternocleidomastoid pain, which reached a mean of 36 mm on the 100-mm VAS 2 minutes after the injection, resulted in significantly increased (1-2 microV, P less than 0.05) RMS MES in the otherwise relaxed SCM muscle during the first 2 minutes. This was followed by a gradual return to control values after 5 minutes. A similar trend in MES was found for the active SCM muscle during a 10% maximum voluntary contraction (MVC) isometric neck flexion effort. Thus, acute deep muscle pain caused subtle, yet systematic, changes in motor output in both the relaxed and active painful muscle, and its synergists and antagonists.

Acute Disease↗
PubMed1990

Textural properties of food used in studies of mastication.

Foods are known to influence jaw elevator muscle activity in chewing. With the long-range goal of gaining insight into force control and modeling muscle recruitment, these initial experiments were performed to determine the textural properties of commonly used test food. Experiments were carried out by means of a standard Instron instrument, equipped with a compression cell. A stylus with 45-degree cuspal angulation and an opposing copper-plated lower arch was used for approximation of the natural situation. The breakage force characteristics of a single peanut, a carrot cube, beefstick, and monkey chow were determined. The peanut demonstrated the steepest and beefstick the least steep force build-up, with breaking forces of 104 N (Newtons) for monkey chow, 66 N for the carrot, and 52 N for the peanut. No clear breakage point was found with beefstick; the force build-up showed an initial plateau at 25 N, which was followed by a significantly steeper force increase to peak. We conclude that each of the test foods commonly used in studies of mastication had particular breakage characteristics in terms of its force-time curve.

Analysis of Variance↗
PubMed1990

Force-time breakage characteristics of food during simulated initial phase of mastication.

With the long range goal of gaining an insight into force control and muscle recruitment, it seems necessary to understand the task given to the masticatory apparatus. The purpose of this study was to characterize food breakage properties, and to study the influence of different compression speeds and occlusal morphologies on the categorized food properties. Experiments were carried out by means of a standard Instron instrument, modified with a switching relay. A stylus with 45 degree angulation and an opposing copperplated lower arch of either human or Macaca fascicularis were used for approximation of the natural situation. Crosshead speeds of 2 and 5 cm/min were selected. For future application, monkey chow was chosen as the testfood. Six parameters were defined to categorize food properties, which were initial breakage force (IBF), initial force buildup (IFB), maximum breakage force (MBF), breakage point (BP), temporal location of MBF (TL), and total compression time (TCT). The results showed that the force-time breakage characteristics of monkey chow were affected by different compression speeds in some aspects. However, this was not the case for the alteration of occlusal morphology.

Animal Feed↗
PubMed1989

Differing effect of agonist and antagonist muscle relaxants on cat jaw muscles.

Mouth closure and an increased resistance to mouth opening follow succinylcholine administration in humans. To elucidate the effects of succinylcholine on masticatory muscle function, mouth opening in the cat, produced by a constant test force, was measured during steady state halothane anesthesia. After baseline measurements, either succinylcholine (0.3 mg.kg-1 of body weight) or vecuronium (0.1 mg.kg-1 of body weight) was infused intravenously, and mouth opening measurements were repeated for up to 30 min. Concomitantly, muscle relaxant effect was quantified by measurement of the neurally-evoked tibialis anterior muscle response. All animals given succinylcholine displayed active jaw closure, which was followed by an increased resistance to mouth opening. This increased resistance was present after cessation of fasciculations and during complete twitch suppression. It lasted beyond the time at which the limb muscle twitch had fully recovered. Vecuronium administration was associated with a decreased resistance to mouth opening without a closing action. The initial jaw closure and the subsequently increased resistance to mouth opening after succinylcholine administration during halothane anesthesia in the cat are comparable with mouth opening changes after succinylcholine administration during inhalation anesthesia in humans. The cat may serve as an animal model for study of the mechanisms involved in responses of jaw muscles to succinylcholine with use of techniques inappropriate in humans.

Animals↗
PubMed1988

The effects of pain from the mandibular joint and muscles on masticatory motor behaviour in man.

Habitual chewing of a coherent bolus was studied in 12 dentate subjects with painful mandibular-joint disorders and 12 healthy, dentate controls. Bilateral electromyograms of jaw elevators, and jaw movement, were recorded for three complete masticatory sequences. Computer analysis was used to classify chewing movements as continuous or discontinuous. Root-mean-square (r.m.s.), myoelectric signal amplitudes were computed for each of four jaw elevators. Although discontinuous chewing cycles were significantly more frequent in painful function (p = 0.001), they also occurred in pain-free function, a finding which reduces their diagnostic significance. During painless and painful function, r.m.s. activities did not differ statistically when elevators acted as agonists on both the dominant and non-dominant chewing side (p greater than 0.1). When used as antagonists, such as during jaw opening, the elevators had greater mean peak activities during painful than painless function (p = 0.0001). Variability in maximum gape was greater during painful than painless function (p = 0.001), but peak maximum gapes in complete masticatory sequences were not affected by pain, and neither were minimum interocclusal gapes. More frequent reshaping and repositioning of the bolus in the presence of pain could explain these differences between painful and pain-free function.

Electromyography↗
PubMed1988

Increased masticatory muscle stiffness during limb muscle flaccidity associated with succinylcholine administration.

The resistance of mouth opening to a constant force of 1.7 N was measured in 44 pediatric subjects anesthetized with enflurane and paralyzed with succinylcholine or vecuronium. Measurements were made during a deep level of anesthesia before relaxant administration, immediately after the loss of the adductor pollicis muscle twitch and 45 s later. In 22 patients receiving succinylcholine, there was a significant reduction in mean mouth opening (from 16.9 +/- 2.8 to 12.6 +/- 4.3 to 13.0 +/- 4.3 mm; P less than 0.0005) and an increase in jaw stiffness (from 102.3 +/- 21.9 to 154.5 +/- 77.4 to 150.5 +/- 77.0 Nm/degree; P less than 0.02) immediately after disappearance of the evoked thenar muscle twitch, as well as 45 s later. In six patients receiving succinylcholine, measurements were continued at 1 min intervals; mouth opening reduction and jaw stiffness increase lasted up to 10 min and extended beyond the return of visible twitch. One patient had a reduction of mouth opening from 20 to less than 1 mm; his corresponding jaw stiffness changed from 83.4 to 3335.4 Nm/degree. This patient, considered by us to have masseter spasm, required several attempts at tracheal intubation due to an increased resistance to mouth opening, as did one other patient. Patients receiving vecuronium showed a significant (P less than 0.02) increase of mouth opening 45 s following loss of twitch (from 19.8 +/- 3.6 to 20.9 +/- 4.1 mm; jaw stiffness changed from 87.0 +/- 15.3 to 83.0 +/- 17.2 Nm/degree). Anesthesia and surgery proceeded normally; in most patients, in excess of 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗