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Biomedical subjects

D S Carlson

Publications and source records attributed to D S Carlson.

At least 55 records · Page 3Linked to original sources
PubMed1988

Maxillomandibular growth 2 years after mandibular advancement surgery with and without suprahyoid myotomy in juvenile Macaca mulatta.

There is conflict in the literature on whether continued and harmonious growth occurs after mandibular advancement in growing persons. The studies available are difficult to interpret because of the differing age ranges and the questionable growth potential inherent within the mandibular deficient patient. This study was performed to isolate the major question of interest to clinicians: Does the mandibular advancement surgical procedure inhibit future growth in a normally growing person? Six juvenile male Macaca mulatta monkeys were divided equally into two experimental groups. Group MAA had mandibular advancement surgery of approximately 4 mm. Group MAD had a similar surgical procedure with detachment of the suprahyoid musculature. All underwent 4 to 5 weeks of maxillomandibular fixation. Serial computerized cephalograms with the aid of bone markers were used to analyze the changes during a 2-year follow-up period. The postsurgical changes of the two experimental groups were compared statistically with control growth data on a large sample of normal Macaca mulatta animals available in our laboratory. The results showed the following. (1) There were significant short-term differences in the stability of the mandibular advancement between experimental groups. Group MAA (suprahyoid musculature attached) experienced significant relapse during the period of maxillomandibular fixation. Group MAD (suprahyoid musculature detached) experienced no relapse. (2) During the 2-year follow-up period after fixation, the rate and amount of mandibular growth in both experimental groups were not significantly different from age-matched controls or from each other. (3) At the end of the 2-year experimental period, the advanced mandibles were longer than the mandibles in age-matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Stability of the mandible following advancement: a comparison of three postsurgical fixation techniques.

This study examines short-term stability of the mandible following mandibular advancement surgery by means of three standard techniques of postsurgical fixation. Twenty-two adult female rhesus monkeys (Macaca mulatta) underwent sagittal ramus advancement osteotomy of approximately 4 to 6 mm. Six animals had dental maxillomandibular fixation alone. Six animals had dental plus skeletal maxillomandibular fixation with circummandibular wires connected to pyriform aperture wires. Ten animals had rigid internal fixation with bicortical bone screws between the proximal and distal segments without maxillomandibular fixation. Radiographic cephalograms with the aid of tantalum bone markers and dental amalgams were analyzed during the first 6 postoperative weeks to evaluate skeletal and dental stability. Rigid internal fixation and the use of dental plus skeletal maxillomandibular fixation were both equally effective in the prevention of postsurgical relapse. However, in the animals in which only dental maxillomandibular fixation was used, statistically significant changes (relapse) occurred when compared with either of the other groups.

Animals↗
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↗
PubMed1987

Histologic analysis of costochondral and sternoclavicular grafts in the TMJ of the juvenile monkey.

Variability in growth response of the mandible after replacement of the mandibular condyle with the costochondral junction of a rib (CCJ) is common. Other donor graft sites that are more similar to the mandibular condyle might be more suitable for mandibular condylar replacement. Previous studies have shown the histomorphologic and developmental similarities between the sternoclavicular joint (SCJ) and temporomandibular joint (TMJ). The purpose of this study was to evaluate histologically short-term adaptations within the TMJ after replacement of the mandibular condyle with the autogenous sternal head of the clavicle, and to compare these adaptations with autogenous CCJ and mandibular condyle (surgical control) transplants. Bilateral vertical ramus osteotomies were performed in 12 juvenile Macaca mulatta with the left condyle being immediately replaced and the right condyle removed and replaced with either the sternal head of the clavicle or costochondral junction of a rib. All grafts were stabilized with maxillomandibular fixation for five weeks. Two animals in each group were killed at five, 11, and 17 weeks postsurgery and prepared for histologic analysis. The results indicate that: 1) incorporation of all grafts into the recipient site occurred and all animals had good mandibular function and occlusion throughout the follow-up period; 2) the clavicular and mandibular condylar grafts were incorporated sooner than the CCJ grafts; 3) clavicular graft changes resembled those of the condylar grafts histologically while the costal grafts remained inert and unchanged; and 4) a new condylar process with cartilage similar to that of a normal mandibular condyle regenerated in the costal graft animals from cells presumably contributed by the periosteum of the mandibular ramus and TMJ capsule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Adaptation of the suprahyoid muscle complex to mandibular advancement surgery.

The suprahyoid musculature has been implicated as one of the major factors responsible for relapse after mandibular advancement surgery. Previous studies have also indicated that the muscle and connective tissues comprising the suprahyoid complex must adapt to increased length brought about by mandibular advancement for skeletal stability to be achieved. The purpose of this study was to provide quantitative data concerning the immediate changes and long-term adaptations that take place within the suprahyoid complex over a 2-year period after mandibular advancement. Mandibular advancement was performed on ten adult Macaca mulatta monkeys with and without suprahyoid myotomy (n = 5/group). Six animals were used as controls. Mandibular length and changes in the length of the various anatomic regions of the suprahyoid complex were evaluated radiographically with the aid of radiopaque bone, muscle, and tendon markers implanted preoperatively. The results for the nonmyotomy group showed that the suprahyoid complex was elongated approximately two thirds the amount of mandibular lengthening, the major immediate adaptations within the suprahyoid complex after the surgical procedure occurred at the muscle-bone interface and the muscle-tendon interface, the change in length at the muscle-tendon junction was maintained throughout the 2-year follow-up period, indicating that significant long-term adaptations took place primarily at that location, and no significant short-term changes or long-term adaptations were seen within the anterior digastric muscle or the intermediate digastric tendon. Within the myotomy group, it was found that the suprahyoid complex recoiled immediately after myotomy such that the anterior belly of the digastric muscle became separated from the advanced distal mandibular segment by more than twice the amount of mandibular lengthening, the anterior digastric muscle remained essentially at this posterior position throughout the 2-year follow-up period, and though not significant, there was a trend for a decrease in the length of the anterior digastric muscle belly. On the basis of these results, it was concluded that both short-term changes and long-term adaptations to lengthening of the suprahyoid complex as a result of mandibular lengthening occur primarily within the connective tissues comprising the muscle-tendon and muscle-bone interfaces, not within the muscle fibers themselves.

Adaptation, Physiological↗
PubMed1987

The effects of succinylcholine on mouth opening.

Mouth opening and the resistance to opening developed by the muscles of mastication were measured in 63 children anesthetized with halothane and relaxed with succinylcholine, pancuronium, or vecuronium. Measurement of mouth opening, induced by a constant test force, was made when each patient was deeply anesthetized, as judged by clinical parameters. Succinylcholine, vecuronium, or pancuronium was then administered. The mouth opening measurement was repeated immediately after the loss of limb muscle twitch response and 45 s following the loss of twitch response. For the 24 patients receiving succinylcholine, there was a significant reduction in mean mouth opening (P less than 0.0001) and a significant increase in jaw stiffness (P less than 0.0001) immediately after limb relaxation. Forty-five seconds after full limb relaxation was attained, the mean mouth opening was still reduced (P less than 0.0001) and the mean jaw stiffness was still increased (P less than 0.0003) in the succinylcholine group. Patients receiving either vecuronium or pancuronium did not show a significant change of mouth opening or jaw stiffness following limb relaxation. Three patients, who received succinylcholine, required several attempts at tracheal intubation due to increased resistance to mouth opening. Anesthesia and surgery proceeded in all patients. None of the patients developed malignant hyperthermia. In view of the fact that a reduction in mouth opening was a constant finding when succinylcholine was administered during halothane anesthesia, the assumption that isolated "masseter spasm" or jaw stiffness heralds malignant hyperthermia should be reconsidered.

Anesthesia, Inhalation↗
PubMed1987

Communicating leveled clinical expectations to nursing students.

Nurse educators agree on the need for objectives in the classroom situation and frequently communicate them in a written form. Written expectations for clinical, however, are rarely given to student nurses prior to their clinical experience. Clinical expectations are understood by instructors, but communicating them to students result in mixed interpretations. The article describes the development of a written method of communicating clinical expectations to solve this problem. This method correlates clinical expectations with classroom content and course objectives and levels the expectations in increasing complexity by using the nursing process as a framework. The written leveled expectations are distributed to student nurses on a weekly basis. Clinical experiences are enhanced for students and faculty who use this method.

Communication↗
PubMed1986

Histologic comparison of the costochondral, sternoclavicular, and temporomandibular joints during growth in Macaca mulatta.

The costochondral joint (CCJ) is commonly used to replace defective mandibular condyles in children for the restoration of normal temporomandibular (TMJ) growth and function. However, continued and harmonious growth following rib grafting is the exception rather than the rule. This may be due to the differences in the growth characteristics of the costal cartilage and the condyle. A joint that is similar both developmentally and structurally to the TMJ is the sternoclavicular joint (SCJ). The purpose f this study was to describe histologically the SCJ and CCJ during growth in Macaca mulatta and to compare the histomorphologic features with those of the TMJ. Costochondral and sternoclavicular joints were obtained from infant, juvenile, adolescent, and adult Macaca mulatta. The histologic sections were compared with mandibular condyles of the same ages available in our laboratory. The results indicate that the TMJ and SCJ are very similar morphologically throughout the growth period. The clavicular head contained layers of cartilage typical of the mandibular condyle, i.e., articular, prechondroblastic, chondroblastic, hypertrophic, and endochondral ossification layers, at each age during growth. Like those in the condyle, the hypertrophic cartilage cells were arranged in an apparently random, noncolumnar fashion. The CCJ, however, did not resemble the condyle but appeared to be more similar to the growth plate in a long bone epiphysis during growth. The results of this investigation indicate that the SCJ may be more suitable for mandibular condylar replacement than the CCJ.

Age Factors↗
PubMed1986

Occlusal force after mandibular advancement in adult rhesus monkeys.

Maxillofacial surgery not only alters facial appearance and occlusion but also affects the morphology, physiology, and biomechanics of the craniofacial skeleton and the muscles of mastication. This study was performed to evaluate one aspect of craniofacial function--maximum stimulated bite force (BF)--after mandibular advancement. BF in the molar region was measured with a transducer during muscle stimulation in 63 rhesus monkeys that had been divided into two groups: a control group of various ages and sexes (n = 50); and an experimental sample of 13 monkeys that had undergone mandibular advancement via C-osteotomy at least one year prior to BF measurement. Biomechanical analysis of lateral cephalograms was performed to estimate the amount of the change in BF in the experimental group that could be attributed to alteration of craniofacial form. Regression analysis demonstrated a significant relation between molar bite force and weight in control animals (r = 0.94). In the monkeys that underwent surgery, BF values were an average of 16.7% less than those found for the control animals relative to body weight. However, the biomechanical analyses suggested a smaller and less variable BF loss in the operated monkeys (11.6%). These results indicate a greater and more variable change in BF following mandibular advancement than would be predicted on the basis of biomechanical considerations.

Animals↗
PubMed1986

Response of the mandibular joint to loss of incisal function in the rat.

In a study of the rat mandibular joint (MJ), Simon [Acta anat. 97: 351-360 (1977)] suggested that reduction in condylar cartilage thickness noted in animals subjected to removal or trimming of incisors resulted from the lessening of joint reaction forces produced during incision. In order to explore this question further, the microanatomy of the MJ in 47-day-old rats whose incisors had been trimmed every other day was compared to that in control animals and in a third group fed a soft diet as a control for reduced joint reaction forces. Both the incisor-clipped and soft-diet groups exhibited reduced size and density of bony trabeculae underlying the condylar cartilage and diminished staining for alcian blue. The thickness of the prechondroblastic layer of the condylar cartilage was significantly (p less than or equal to 0.01) reduced relative to controls in both experimental groups on the superior aspect of the cartilage, but was reduced in the more posterior parts of the cartilage only in the incisor-clipped group. While not denying that joint reaction forces may affect MJ response, the reduced proliferative response noted in the posterior region of the condylar cartilage in incisor-clipped animals is perhaps best explained by a decrease in the frequency and extent of protrusion of the lower jaw due to a lack of incisal preparation of food items.

Animals↗
PubMed1986

Adaptations in the temporalis muscles of rabbits after masseter muscle removal.

Masseter muscles were surgically removed in six young female rabbits so that we could study adaptations of the superficial temporalis muscles (ST) to increased functional requirements. Eight weeks following surgery, we used morphological measurements, histochemistry, contractile properties in situ, and occlusal force in vivo to compare the muscles in the experimental animals and six control rabbits. Analysis of the results demonstrated a decrease in fatigability of ST after masseter myectomy. Incisal occlusal force decreased by 65% during the first two weeks, and no recovery was observed during the following six weeks. At eight weeks post-surgery, the mass, twitch tensions, and tetanic tensions of ST were not significantly different from those of the controls. An increase in the percent of the cross-sectional area composed of fast fatigue-resistant fibers, a slower time-to-peak twitch tension, and a decrease in fatigability suggest an increase in oxidative metabolism. Analysis of these results suggests that muscles used for highly repetitious activities with submaximal loadings adapt to increased functional requirements by increasing fatigue-resistant properties.

Adaptation, Physiological↗
PubMed1985

Cephalometric analysis of condylar adaptations to altered mandibular position in adult rhesus monkeys, Macaca mulatta.

Morphological adaptation to altered position of the mandible was investigated in 19 young adult rhesus monkeys (n = 10 experiment and 9 control). The experimental animals had a bite-splint cemented to the maxillary dentition which opened the bite interincisally by 15 mm and was worn continuously for 48 weeks. Lateral radiographic cephalograms were taken prior to the experiment and at 12-week intervals thereafter. Computerized cephalometry, facilitated by the use of radio-opaque bone markers, was used to assess changes in mandibular position and morphology. An immediate effect of the bite-splint was the clockwise rotation (opening) of the mandible and anterior translation of the condyle on the articular eminence, much as occurs normally during jaw depression. During the next 48 weeks, the mandible (1) rotated anti-clockwise (closed) due mainly to antero-superior displacement of the maxilla and intrusion of the mandibular dentition and (2) underwent a significant increase in length (p less than 0.05). These findings indicate that the mandibular condyle of young adult monkeys is capable of small, but biologically significant, compensatory growth after displacement.

Adaptation, Physiological↗
PubMed1985

Recovery of jaw muscle function following injection of a myotoxic agent (lidocaine-epinephrine).

Intramuscular injection of 2% lidocaine hydrochloride with epinephrine (1:100,000) bilaterally into the masseter muscles of growing rats resulted in a 30% to 40% decrease in maximal stimulated bite force at 3 days following injection. By 6 days postinjection, bite force had begun to increase, but significant differences from control bite force levels were still present 15 days postinjection. By 25 days postinjection, recovery to control values was complete. These data are consistent with previously documented fiber destruction and subsequent regeneration following exposure to this and other local anesthetic agents. It is suggested that local myotoxic effects produced by the administration of such drugs may result in a transient functional deficit in the injected muscle(s) that may persist for up to 2 weeks.

Animals↗
PubMed1984

Advancement genioplasty with and without soft tissue pedicle: An experimental investigation.

To determine whether maintaining a soft tissue pedicle to the genial segment decreases the amount of bone resorption following an advancement genioplasty, 12 rhesus monkeys (Macaca mulatta) underwent advancement genioplasty of 5-6 mm. The insertion of the digastric musculature and lingual soft tissues on the genial segment was maintained in six of the animals, and six had all soft tissues stripped. Cephalometric analysis of remodeling in the anterior part of the mandible indicated that the pedicled genial segments underwent significantly less resorption than the free graft segments (P less than 0.05). The results of this study indicate that soft tissue pedicles to the genial segments should be maintained during advancement genioplasty to minimize the amount of bone resorption in the post-operative period.

Animals↗
PubMed1983

Histological changes in the articular eminence and mandibular fossa during growth of the rhesus monkey (Macaca mulatta).

Unlike the mandibular condyle, the temporal component of the temporomandibular joint (TMJ) has been the object of relatively few investigations concerning its growth and remodeling. This report provides qualitative and quantitative documentation of microanatomical changes in the mandibular fossa and articular eminence during growth of the rhesus monkey (Macaca mulatta). The thickness of the fibrous articular tissue and the presence of cartilage cells in its deeper layers were examined histologically in 43 rhesus monkeys at five maturational levels (neonate, infant, juvenile, adolescent, and young adult). Absolute thickness of the articular tissue increased with maturational level in all areas studied, with the increase somewhat more pronounced on the posterior slope and crest of the articular eminence than in the roof of the mandibular fossa. Relative to condylar size, an increase in articular-layer thickness characterized the first three maturational levels, and was followed by a decrease during adolescent and young-adult stages. Articular tissue in the fossa roof constituted a steadily decreasing fraction of the total articular-tissue thickness with age, while relative thickness of the tissue on the posterior slope and crest of the eminence increased with age. These results parallel those obtained for the mandibular condyle, and they are best interpreted to indicate that forces delivered to the joint become directed more anteriorly with age. The overall pattern of topographical variation in articular-tissue thickness and cartilage-cell distribution suggests that greater loading of the lateral aspect of the TMJ, postulated in the human TMJ by various workers, may not be as pronounced in the monkey.

Animals↗
PubMed1983

Growth of the masseter muscle in rhesus monkeys (Macaca mulatta).

The growth of the masseter muscle in eight infant, juvenile, and adolescent female rhesus monkeys (M. mulatta) was examined over a 2.5 year period using serial radiographic cephalometric techniques with the aid of radiopaque muscle markers. The radiopaque markers, which are composed of small pieces of root canal broach inserted into the muscle belly, make it possible to determine longitudinal masseter muscle growth as well as migration of the masseter muscle relative to the mandible. It was found that the masseter muscle increased in length by 64% during the total growth period, most of which occurred between 6 and 18 months of age. Relative to the cranium, the masseter muscle grew markedly inferiorly and only slightly posteriorly. Relative to the mandible, the masseter migrated in a posterior and slightly superior direction, keeping pace with the ramus and condyle as they grew posteriorly and posterosuperiorly throughout the study period. It was concluded that: 1) radiopaque muscle markers are a valuable tool for analysis of muscle growth and alteration of muscle location; 2) the masseter muscle in the rhesus monkey undergoes elongation, probably due to addition of sarcomeres at the fiber-tendon junctions; and 3) posterior migration of the masseter muscle relative to the corpus of the mandible, probably due to the nature of its periosteal attachment, results in a stability of the anteroposterior position of the masseter muscle despite the anterior displacement of the mandible.

Aging↗
PubMed1983

Cephalometric analysis of adaptations after lengthening of the masseter muscle in adult rhesus monkeys, Macaca mulatta.

This relationship between the function of the muscles of mastication and craniofacial form was investigated in young adult monkeys by increasing the functional length of the elevator muscles of the mandible non-invasively by a bite-opening splint cemented to the maxillary dentition. The major adaptations to increased vertical dimensional were (1) marked superior and some anterior displacement of the maxillary complex, (2) dental intrusion and (3) rotation of the mandible. These alterations produced a shortening of the lengthened masseter muscle, i.e. a reduction in the amount of muscle stretch brought about by the appliance. Migration of the masseteric insertion along the ramus did not contribute significantly to the pattern of adaptation. The role of the masseter muscle in craniofacial adaptations to altered vertical dimension was determined by detaching and re-attaching the insertion of the masseter muscle in one group of experimental animals. The myotomized monkeys experienced significantly less anterior displacement of the maxilla than the non-myotomized monkeys, indicating that the surgery may have lessened some of the anteriorly-directed distracting forces of the lengthened masseter. Masseter myotomy alone was not sufficient to eliminate the vertically-directed distracting forces of the remainder of the mandibular elevator muscles brought about by increasing the vertical dimension of the lower face.

Adaptation, Physiological↗