Search PubMed⌕ Search

Biomedical subjects

D S Carlson

Publications and source records attributed to D S Carlson.

At least 37 records · Page 2Linked to original sources
PubMed1992

Influence of asymmetric occlusal relationships and decreased maxillary width on the growth of the facial skeleton in the guinea pig.

The purpose of this study was to evaluate the effect of muscle function and occlusal form on mandibular growth in guinea pigs. We hypothesized that restriction of maxillary width and asymmetric function of the mandible would lead to mandibular asymmetry. The hard palate of 12 animals was exposed at the age of ten days, and cyanocrylate was used to close the midpalatal suture in order to restrict transverse maxillary growth. The right incisors and right molars were ground obliquely at the time of surgery and every two weeks thereafter until the animals were sacrificed 4, 8 and 12 weeks later (four animals in each time group). Six age-matched animals served as controls. Dorsoversal x-rays were taken at sacrifice, followed by the removal of small biopsies from six different sites of the maxillomandibular skeleton for biochemical studies, which will be reported separately. Relative to controls, the treated animals exhibited a narrow maxilla and asymmetry in the height of the ramus and in the length of the mandible from the mental foramen to the angular process. The maximum width between the angular processes of the mandible was extremely narrow, as was the condylar neck especially on the right side. It was concluded that abnormal masticatory muscle function caused by occlusal deviation led to a narrowing and a slight asymmetry of the mandible in the growing guinea pig.

Aging↗
PubMed1992

Uranium in vitro bioassay action level used to screen workers for chronic inhalation intakes of uranium mill tailings.

A uranium in vitro bioassay (urinalysis) action level was derived for use at the Department of Energy's Uranium Mill Tailings Remedial Action Project sites to identify chronic inhalation intakes of uranium mill tailings causing 0.5 mSv (50 mrem) annual effective dose equivalent. All radionuclides in the 238U decay chain that contribute 1% or more to the annual effective dose equivalent from an inhalation intake of uranium mill tailings were included in the derivation of the urinalysis action level. Using a chronic inhalation intake model, the uranium urinalysis action level for a 24-h urine sample, collected on a quarterly schedule, was calculated to be 1.5 micrograms.

Humans↗
PubMed1990

Occlusal force and craniofacial biomechanics during growth in rhesus monkeys.

The masticatory muscles in 132 anesthetized male and female rhesus monkeys ranging in age from juvenile to adult were unilaterally stimulated. Muscle forces and speeds were measured with a bite force transducer positioned at the incisors, premolars, and molars during twitch and tetanic contractions. Lateral cephalographs of all animals were used to estimate the orientation and mechanical advantage of the masticatory muscles. Results showed that maximal occlusal forces increased at a greater rate than body weight during growth. However, maximal occlusal forces increased isometrically relative to mandibular length. Mean forces at the incisors ranged from 70.3 newtons (n) in juveniles up to 139.9 n in adult males. Forces at the molars were 2-2.5 times greater than at the incisors. Time-to-peak tension decreased with increasing body size from 44.1 msec in juveniles to 37.4 msec in adult females to 31.0 msec in adult males. Regression analysis showed that adult males have faster muscles than adult females or juveniles even when corrected for body size. Temporalis and masseter orientation was found to change little throughout growth. The mechanical advantage of the masseter and temporalis muscles for producing occlusal forces on the distal molars improved between juveniles and adults, which is contrary to findings of Oyen et al. (Growth 43:174-187, 1979). Among adults, females had a greater mechanical advantage of the masseter muscles than males.

Analysis of Variance↗
PubMed1990

Coronoid process elongation in rhesus monkeys (Macaca mulatta) after experimentally induced mandibular hypomobility. A cephalometric and histologic study.

The present study provided an experimental model that allowed a cephalometric and histologic analysis of craniofacial growth in monkeys with induced translatory impairment of the mandibular condyle. Cauterization was performed anterior to the joint in nine experimental rhesus monkeys, while eight animals served as control subjects. The experimental procedure produced mandibular hypomobility in six animals, in three by means of temporomandibular joint ankylosis and in three by means of dense scar tissue formation anterior to the joint. In the remaining three experimental animals no restriction of mandibular mobility was created. Mandibular hypomobility was found to induce elongation of the coronoid process and was also associated with bone deposition in the gonial region. In contrast, normal remodeling of the gonial region was found in the experimental animals with normal range of movements and in the control animals.

Animals↗
PubMed1990

Electromyography of the suprahyoid musculature following mandibular advancement with and without rigid fixation.

The purpose of this investigation was to determine if the activity of the suprahyoid musculature changes following advancement of the mandible and the use of rigid or nonrigid fixation. Ten monkeys underwent mandibular advancement; six underwent 6 weeks of maxillomandibular fixation (MMF), and four had rigid fixation without MMF. Electromyography (EMG) of the suprahyoid musculature was performed preoperatively, and at 3, 7, and 10 weeks postoperatively. The results of this study fail to demonstrate an increase in suprahyoid EMG activity following mandibular advancement. Furthermore, there were no differences between the groups with different types of fixation.

Analysis of Variance↗
PubMed1990

Histochemical analysis of the masseter and temporalis muscles in macaca mulatta after mandibular advancement using rigid or nonrigid fixation.

This study compared the histochemical characteristics of the temporalis and masseter muscles in monkeys who underwent mandibular advancement with and without immobilization of the mandible. The results showed, when compared with controls, that the animals who underwent maxillomandibular fixation (MMF) following advancement of the mandible had significant atrophy in both temporalis and masseter muscles. In contrast, much less myoatrophy was noted in the animals who underwent rigid internal fixation and no MMF following advancement of the mandible.

Analysis of Variance↗
PubMed1990

The effect of bite-opening appliances on mandibular rotational growth and remodeling in the rhesus monkey (Macaca mulatta).

Previous experimental studies that have used a bite-block cemented to the maxillary dental arch have shown that the direction of growth of the maxillary complex is redirected in a superior and anterior direction for approximately 12 weeks but reassumes a normal inferior and anterior direction after that time. The purposes of this study were (1) to examine the effect of increased vertical dimension and altered mandibular posture on growth of the mandible and (2) to determine whether or not an alteration in chronic mandibular position alters mandibular intramatrix rotation. Eleven Macaca mulatta monkeys wore 15 mm vertical bite-opening appliances for 24 or 48 weeks. Nine untreated animals were used as controls. All animals received tantalum bone implants to facilitate cephalometric analysis. Serial lateral radiographs of the mandible were traced and superimposed on bone implants for each animal to determine overall changes in mandibular shape (gonial angle) and the location of bone remodeling. During normal growth, the gonial angle closed an average of 0.1 degrees over a 48-week period. In the experimental animals, the gonial angle opened 6.4 degrees (p less than 0.005) as a result of remodeling during the period that mandibular posture was altered. Once normal mandibular posture was restored, this process was reversed; the gonial angle once again became more acute over time, and remodeling along the body and ramus of the mandible was similar to that observed in control animals. These results suggest that mandibular growth and remodeling can be influenced by altered mandibular vertical posture.

Animals↗
PubMed1990

Adaptation of the lateral pterygoid and superficial masseter muscles to mandibular protrusion in the rat.

It has been suggested that protrusion of the mandible results in an alteration of the functional activity of the lateral pterygoid muscle. If this is true, however, it is unclear whether this altered muscle function is a transient phenomenon with no long-term effect or whether it results in structural and functional adaptation of the involved musculature. The purpose of this study was to determine whether or not physiologic and metabolic changes take place within two jaw-protruder muscles--the lateral pterygoid muscle and the superficial masseter muscle--in rats after treatment with a protrusive appliance. Thirty 45-day-old male Sprague-Dawley rats were divided equally into experimental and control groups. The experimental animals wore bonded protrusive-type appliances for 2 weeks. Histochemical analysis of muscle fiber types and in vivo whole-muscle contractile-property analysis were used to evaluate structural and functional muscle adaptations. Mandibular length was slightly but significantly greater in the experimental group, indicating that the protrusive appliance had the expected positive effect on mandibular growth. Histochemically, the lateral pterygoid muscle in the experimental group exhibited a significantly greater area occupied by type I fibers at the expense of type IIb fibers. The superficial masseter muscle exhibited a significantly greater percentage of areas for both type IIa and type IIb fibers in the experimental group. Contraction time (TPT) increased in both muscles; that is, the muscles became slower. The histochemical and contractile-properties data indicate that the protrusive appliance caused the lateral pterygoid muscle to become more active with respect to tonic (postural) activity, whereas the superficial masseter muscle became more active phasically.

Adaptation, Physiological↗
PubMed1990

Aggregation of proteoglycans in cephalic, epiphyseal and articular cartilages in growing sheep.

The purpose of this study was to determine whether there are age and site related differences in proteoglycan aggregation in craniofacial and epiphyseal cartilages from neonatal and two-month-old lambs. Proteoglycans were extracted using a dissociative extraction method, and aggregates and monomers separated with molecular sieving. Only a small proportion of the proteoglycans were isolated as aggregates in the articular and mandibular condylar cartilage of the neonatal animals, while in the nasal septal, epiphyseal and synchondrosal cartilages of the same animals the portion of proteoglycans isolated as aggregates, was 3 to 6 times as high. During the first 2 months of postnatal development the proportion of proteoglycans isolated as aggregates tripled in the articular and mandibular condylar cartilages, it decreased substantially in the anterior and posterior nasal septum, while it decreased slightly in the other cartilages. These observations indicate that there are age and site related differences in the extent of proteoglycans isolated as aggregates in cephalic, epiphyseal and articular cartilages.

Aging↗
PubMed1989

Collagenolytic and phosphatase activity in the rat mandible after functional protrusion.

The effect of chronic mandibular protrusion on the collagenolytic and phosphatase activity of several mandibular bone sites and the condylar cartilage was evaluated. Ninety-three male Sprague-Dawley rats were equally divided into two experimental and one control group. One experimental group wore a protrusive appliance for 2 weeks, the other for 4 weeks. All animals were killed at 59 days of age. Collagenolytic, alkaline and cid phosphatase activities were determined in the condylar cartilage, the subchondral bone and condylar neck, and in the gonial angle and coronoid process. In the cartilage and subchondral bone, the protrusive appliance caused a reduction in collagenolytic and alkaline phosphatase activity. In the condylar neck, it caused a large increase in collagenolytic activity and a decrease in alkaline phosphatase activity in both experimental groups. In the gonial angle and coronoid process, the appliance increased the collagenolytic activity only in the 2-week group. In the 4-week group, the alkaline phosphatase and collagenolytic activities were not different from the activities in those tissues in the control animals. Thus a protrusive appliance induced quantitative changes in enzyme activities in condylar cartilage and mandibular bone. The increase in collagenolytic activity (representing increased bone resorption) occurred typically in areas of muscle attachment and might have been the result of the neuromuscular changes induced by the protrusive appliance. The recovery to normal values of collagenolytic activity in the coronoid process and gonial angle of the 4-week group suggests that at these sites the muscles (and subperiosteal bone) might have adapted to their new biomechanical environment after the longer period of appliance wear.

Acid Phosphatase↗
PubMed1989

Short-term stability and muscle adaptation after mandibular advancement surgery with and without suprahyoid myotomy in juvenile Macaca mulatta.

The purpose of this study was to examine the short-term adaptations that occur within the mandible and anterior digastric muscle complex after mandibular advancement with and without suprahyoid myotomy in 20 juvenile rhesus monkeys. The results showed that the animals that did not undergo myotomy experienced relapse equivalent to 13% of the surgical advancement. Those animals that underwent a myotomy of the digastric muscle complex showed complete stability of the surgical lengthening of the mandible. Both groups of animals grew normally after the fixation period when compared to age-matched control animals. Analysis of adaptations within the digastric muscle complex was performed with the use of radiopaque muscle and tendon markers. The results showed an immediate lengthening of the entire digastric muscle complex with mandibular advancement surgery in the group that underwent advancement without myotomy. Further analysis showed that most lengthening in these animals occurred at the connective tissue interfaces of the complex--at the muscle-bone and muscle-tendon interfaces. No significant changes in sarcomere or fiber length were found in the group that did not undergo myotomy, although there was a significant shortening of muscle fibres resulting from loss of serial sarcomeres in the myotomy group. Comparison of histochemical characteristics of the anterior digastric muscle before and after surgery revealed the following findings: (1) there were no significant differences in percentage of composition between control and experimental muscles; (2) despite fixation of the jaws and myotomy, there was no evidence of atrophy of the anterior digastric muscle at any experimental interval; and (3) the type I fibers of the anterior digastric muscle underwent significant stretch-induced hypertrophy after lengthening. The results of this study support the hypothesis that tension produced by stretching of the connective tissues associated with the digastric muscle complex can contribute to postsurgical relapse of the surgically advanced mandible. However, no adverse effect on future growth of the mandible was observed from stretching the digastric muscle complex by mandibular advancement surgery in juvenile subjects.

Adaptation, Physiological↗
PubMed1989

Stability of midface augmentation: an experimental study of musculoskeletal interaction and fixation methods.

This study examined stability of vertical midface augmentation when different methods to alleviate potentially distracting muscles were used. Eighteen adult monkeys underwent Le Fort I osteotomy with interpositional bone grafts. One group had wire fixation of the maxilla and bone graft. A second group underwent a similar procedure with the addition of myotomies of the masseter and temporalis muscles. A third group wore a bite-opening appliance before downgrafting. A fourth group underwent downgrafting with rigid internal fixation. Serial cephalograms with the aid of bone markers were used to assess postsurgical change. The results showed that the animals who underwent rigid fixation had the most stable results, followed by the myotomy and bite-opening appliance groups. The animals who underwent wire fixation with no supplemental procedures had gross relapse, resulting in an average retention of only 15% of the surgical change by 12 weeks.

Adaptation, Physiological↗
PubMed1989

The effects of mandibular immobilization on the masticatory system. A review.

It is clear from this review that mandibular immobilization is not as benign a procedure as once thought. Detrimental effects on several tissues within the masticatory apparatus have been observed following mandibular immobilization. Atrophy of the muscles of mastication, degenerative changes within the mandibular condyle, and decreases in range of passive bite opening are all consistent findings following several weeks of mandibular immobilization. The use of fixation procedures which avoid the use of mandibular immobilization (i.e., rigid internal fixation) has been shown to minimize these problems. As with any procedure, however, the risks and benefits of rigid internal fixation must be weighed against the time-honored standard (i.e., maxillomandibular fixation). It is hoped that future research and clinical experience will direct the surgeon to select whichever technique is in the best interest of the patient.

Fracture Fixation, Internal↗
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

Histochemical characteristics of masseter and temporalis muscles after 5 weeks of maxillomandibular fixation--an investigation in Macaca mulatta.

This study describes the histochemical characteristics and cross-sectional areas of the superficial masseter and temporalis muscles in juvenile rhesus monkeys after 5 weeks of maxillomandibular fixation. Four juvenile male Macaca mulatta underwent mandibular surgery and 5 weeks of maxillomandibular fixation as part of a study of temporomandibular joint (TMJ) adaptations after condylar replacement. Immediately before the time the animals were killed (5 weeks postsurgically), biopsies of the masseter and temporalis muscles were obtained and submitted to histochemical analysis and calculation of muscle-fiber areas. The data were compared to histochemistry from 12 juvenile control Macaca mulatta. Significant decreases in mean cross-sectional area were exhibited in both type I (p less than 0.05) and type II (p less than 0.01) fibers in all muscles when compared to controls (n = 12). The ratio of type I to type II fibers, however, remained constant during maxillomandibular fixation in masseter and temporalis muscle samples, indicating no change in relative types of fibers. We conclude from this experimental investigation that (1) significant atrophy occurs in the temporalis and masseter muscles after 5 weeks of maxillomandibular fixation, and (2) this atrophy occurs in both type I and type II fibers, indicating that overall recruitment of the muscle (and not just of one fiber type of motor unit) was affected during fixation.

Adenosine Triphosphatases↗
PubMed1988

A comparison of stimulated bite force after mandibular advancement using rigid and nonrigid fixation.

This study evaluated maximum stimulated molar bite force following advancement of the mandible in 17 adult Macaca mulatta using rigid and nonrigid fixation techniques. Cephalometric analysis was also performed to determine the amount of proximal segment rotation. Analysis of the bite force showed the animals whose mandibles were advanced using rigid fixation to have significantly greater bite force at six weeks postsurgery when compared to those animals who underwent mandibular advancement and six weeks of maxillomandibular fixation. By the ninth postoperative week, there was no longer any significant difference between the two groups, indicating a rapid recovery of muscle function in the animals whose mandibles were immobilized following advancement. Both groups, however, had significant decreases in bite force at 12 weeks postsurgery when compared to preoperative values. Neither group had a significant amount of proximal segment rotation from the surgery.

Animals↗
PubMed1988

Adaptation of the suprahyoid muscle complex to large mandibular advancements.

The purpose of this study was to provide quantitative data concerning the changes and adaptations that take place within the suprahyoid complex to larger mandibular advancements. Mandibular advancement of 6.5 mm was performed on 12 adult rhesus monkeys. Six underwent maxillomandibular fixation (MMF) using the dentition, six underwent MMF using the dentition plus skeletal suspension wires. Mandibular position and changes in the length of the various anatomic regions of the suprahyoid complex were evaluated cephalometrically with the aid of radiopaque bone, muscle, and tendon markers implanted preoperatively. Relapse of the mandible in the dental MMF animals was 27% of the advancement, whereas there was none in the dental plus skeletal MMF group. Results of adaptations within the suprahyoid complex showed that 1) the suprahyoid complex was elongated slightly less than the mandible, and 2) the major adaptations (lengthening) occurred at the muscle-bone interface, the muscle-tendon interface, and within the belly of the anterior digastric muscle. On the basis of these results, it was concluded that adaptations within the suprahyoid complex to mandibular lengthening occur first at the connective tissue attachments of the muscle, and then within the muscle belly itself. The methods of dealing with the potentially distracting forces from the stretch within the suprahyoid complex are discussed.

Adaptation, Physiological↗