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

A retrospective study of advancement genioplasty.

This study examined the immediate and postsurgical changes in the hard and soft tissues of the chin after advancement genioplasty by means of oblique osteotomy of the mandibular symphysis. Twenty-three patients who had undergone this procedure were evaluated cephalometrically for up to 6 months after surgery. The results indicated that the position of the genial segment is stable after advancement. There was a good correlation between the amount of hard versus soft tissue change with surgery in the horizontal direction but a poor correlation in the vertical plane. There was, however, a great amount of variability from one patient to the next in most of the variables examined. Follow-up results were generally very stable.

Adolescent↗

PubMed1989

A study of the utility of measuring mandibular mobility by means of the interincisal dimension.

The purpose of this investigation was to determine the reliability of using the interincisal dimension as a measure of mandibular range of motion. Thirty patients who underwent mandibular advancement and 15 patients who underwent mandibular setback were included in this study. Preoperatively, a lateral cephalogram in centric relation and a second cephalogram with the mandible at maximum voluntary gape were obtained. Immediately following surgery, another centric relation cephalogram was obtained. A composite tracing of the two preoperative tracings was made to show how the mandible changed in position from the closed-mouth to the open-mouth radiographs. The proximal segment (ramus) of the postoperative cephalogram was then superimposed on the open-mouth mandibular ramus, and the distal segment of the postoperative mandible was drawn. This composite produced a tracing of what the postoperative maximal gape cephalogram would be if the same amount of condylar rotation and translation as in the preoperative tracing had occurred. The preoperative interincisal dimension was recorded on the composite tracings (factoring in any overbite or openbite) as was the would-be postoperative interincisal dimension. These measures were compared using the paired t test and Pearson's correlations to determine if there were any significant differences between them. The results showed that the interincisal dimension is a fairly reliable measure of mandibular mobility even when the length of the mandible is altered with surgery.

Cephalometry↗

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

Extracorporeal shock wave lithotripsy in a renal transplant patient.

We report a case of nephrolithiasis in a transplanted kidney that was treated successfully with extracorporeal shock wave lithotripsy. The patient experienced transient partial obstruction after lithotripsy and, thus, intense monitoring of the transplant patient is necessary.

Adolescent↗

PubMed1989

Traumatic asphyxia: report of a case.

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Adult↗

PubMed1989

Immunohistochemical localisation of tissue plasminogen activator in human brain tumours.

The distribution of tissue plasminogen activator (t-PA) has been studied in a series of 38 human brain tumours and two specimens of cerebral cortex, using the monoclonal antibody ESP6. t-PA was localised in vascular endothelium in the majority of tumours and both the cortical specimens, confirmed by double staining with Ulex europaeus lectin (Uel) and Factor 8-related antigen. Nineteen out of 22 high grade astrocytomas showed strong endothelial staining whereas staining was weak or absent in the four low grade astrocytomas studied. No consistent relationship was found between the pattern of staining and tumour grade in the other tumours, although strong staining of the three metastatic lesions with Uel was observed. Among the astroglial tumours only one glioblastoma showed any tumour cell staining for t-PA, which raises questions concerning the origin of t-PA producing cells derived from human gliomas in vitro. Studies of t-PA in brain tumours should take account of this vascular localisation before concluding that the activity is derived from neoplastic cells.

Brain Neoplasms↗

PubMed1989

Immunochromatographic measurement of phenobarbital in whole blood with a non-instrumented assay.

We tested the precision and accuracy of the AccuLevel Phenobarbital Test, which reports whole-blood (fingerstick) results in plasma equivalent values, and compared these values with plasma results obtained using established methods. We conclude that the assay is precise, reliable, accurate for single tests, and is appropriate for use in offices, outpatient settings, and emergency rooms.

Chromatography↗

PubMed1989

Role of inhalation challenge testing in the diagnosis of isocyanate-induced asthma.

Results of isocyanate challenge tests performed on 63 workers referred with a diagnosis of probable isocyanate asthma between 1974 and 1988 were reviewed. Thirty (48 percent) had an acute episode of asthma with a greater than 20 percent decline in FEV1 following subirritant exposure to isocyanates. No difference in the frequency or type of respiratory complaints between isocyanate reactors and nonreactors was found. No differences in lung function results were present when comparing smoking and ex-smoking reactors and nonreactors. In never-smokers with complaints consistent with isocyanate-induced asthma, the presence of obstructive lung disease increased the likelihood that isocyanate-induced asthma was present. Bronchial responsiveness to methacholine occurred in nearly all isocyanate reactors but predicted isocyanate-induced asthma in only 68 percent of the workers. In nearly all cases of challenge-confirmed toluene diisocyanate (TDI)-induced asthma, a 15-min exposure to 20 ppb of the commercial TDI mixture (80:20 2,4:2,6) provoked asthma. Conversely, in the absence of an asthmatic response following exposure to this dose for this duration, a second exposure at this concentration for a longer time would be reasonable to confirm the absence of isocyanate-induced asthma. Among workers employed in the production of polyurethane foam and confirmed to have TDI-induced asthma by inhalation challenge to the different TDI isomers, there appeared to be increased airway reactivity to the 2,6 isomer. This may have relevance to the frequency and intensity of respiratory symptoms that workers with TDI-induced asthma develop in differing industrial settings.

Adult↗

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↗

PubMed1989

Diagnosis and treatment planning for the surgical-orthodontic patient.

Contemporary orthognathic surgery has made it possible to reposition either or both jaws in one piece or as segmental osteotomies. This has provided the patient, who has a severe dentofacial problem, with the option of having all components of their malocclusion and facial aesthetic concerns addressed. The close collaboration between the orthodontist and the surgeon provides a comprehensive diagnosis and treatment plan to be generated. The goal of the presurgical phase of orthodontics is to remove the dental compensations and allow optimum surgical correction of the jaw discrepancy. A short phase of orthodontic treatment postoperatively is usually necessary to detail the final occlusion. A systematic approach to diagnosis and treatment planning is discussed in the context of the problem-oriented approach. The application of this approach is illustrated in a case report of the combined orthodontic-surgical treatment of a patient who benefited from a two-jaw surgical procedure with pre- and postoperative orthodontic treatment. The principles of presurgical orthodontic treatment are discussed and should avoid any counterproductive tooth movements that can be part of the surgical correction. Tooth movements done as part of the postoperative treatment should avoid compromising the surgical outcome. Illustrations of the cephalometric prediction tracing and its application to the diagnosis and treatment plan of the patient discussed in the case report is an important aspect in providing the dentofacial patient with a representation of the expected treatment outcome.

Cephalometry↗

PubMed1988

Influenza activity in Canada.

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Canada↗

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↗