Mechanobehaviour in dolichofacial and brachyfacial adolescents.

OBJECTIVES: To test whether mechanobehaviour (temporomandibular joint (TMJ) loads, jaw muscle use) was different between facial types and correlated with ramus height (Condylion-Gonion, mm). SETTING AND SAMPLE POPULATION: University of Missouri-Kansas City (UMKC) Orthodontic Clinic. Ten dolichofacial and ten brachyfacial adolescents (Sella-Nasion-Gonion-Gnathion (SN-GoGn) angles ≥37° and ≤27°, respectively) consented to participate. MATERIALS AND METHODS: Numerical models calculated TMJ loads for a range of static biting based on subjects' three-dimensional anatomy. Subjects were trained to record jaw muscle electromyography (EMG) over 2 days and 2 nights in their natural environments. Laboratory EMG/bite-force calibrations determined subject-specific EMG for 20 N bite-force (T20Nave ). Jaw muscle use via duty factors (DF=muscle activity duration/total recording time, %) was determined from day and night recordings for muscle-specific thresholds from ≥5% to ≥80%T20Nave . ANOVA and Tukey's HSD post hoc tests assessed for group differences in mechanobehaviour (TMJ loads, DFs). Regression modelling correlated subjects' normalized TMJ loads, DFs and ramus height. RESULTS: Dolichofacial compared to brachyfacial subjects produced significantly higher (P<.05) TMJ loads, where ipsilateral loads were ≥20% larger for some biting angles, but had significantly less (all P<.05) masseter (day, night) and temporalis (night) DFs. Regression analysis showed a significant relationship amongst normalized TMJ loads, masseter DF and ramus height (R2 =.49). CONCLUSIONS: Mechanobehaviour showed significant differences between facial types and was correlated with ramus height.

Effect of length post and remaining root tissue on fracture resistance of fibre posts relined with resin composite.

To investigate the influence of post length and amount of remaining root tissue on the fracture resistance of roots restored with fibre posts relined with resin composite. Ninety upper canine teeth were divided into nine groups (n = 10). The post spaces were prepared resulting in different lengths, as follows: group 2/3, preparations with lengths of 10 mm; group 1/2, preparations with lengths of 7·5 mm; and group 1/3, preparations with lengths of 5 mm. Each group was divided into 3 subgroups according to amount of remaining root tooth tissue (2, 1 mm or 0·5 mm of thick root). Fibre posts relined with resin composite were cemented, and all teeth were restored with metal crowns. The samples were submitted to the fracture resistance test in a universal testing machine, at an angle of 135° and speed of 0·5 mm min(-1) . Failure modes were observed and the data of fracture resistance were submitted to the anova and Tukey's (α = 0·05). No statistically significant difference in fracture resistance was found among different post lengths (P > 0·05). Remaining dentin thickness of 2 and 1 mm did not differ statistically in fracture resistance (P > 0·05), which was higher than of 0·5 mm dentin thickness (P < 0·05). A prevalence of repairable failure was observed in all groups. It can be concluded that the length of fibre post relined with resin composite did not influence fracture resistance, but thickness was an important factor for the restoration of endodontically treated teeth.

Delay of constant light-induced persistent vaginal estrus by 24-hour time cues in rats.

The normal ovarian cycle of female rats is typically replaced by persistent estrus when these animals are housed under constant light. Evidence presented here shows that the maintenance of periodicity in the environment can at least delay (if not prevent) the photic induction of persistent vaginal estrus. Female rats in constant light were exposed to vaginal smearing at random times or at the same time every day. In another experiment, female rats were exposed to either constant bright light, constant dim light, or a 24-hour photic cycle of bright and dim light. The onset of persistent vaginal estrus was delayed in rats exposed to 24-hour time cues even though the light intensities were the same as or greater than those for the aperiodic control groups. The results suggest that the absence of 24-hour time cues in constant light contributes to the induction of persistent estrus.

Human non-24-hour sleep-wake cycles in an everyday environment.

A sighted college student maintained a sleep-wake cycle longer than 24 hr in his everyday environment for more than half of nearly four years. The range of sleep-wake periods and the amount and regularity of sleep are consistent with those found in time-free environments. Episodes of 24 hr periodicity suggest that social cues or obligations are effective entraining agents. He reported more sleep difficulties while on a 24 hr than a non-24-hr schedule.

Respiratory disease in tungsten carbide production workers.

We carried out a medical and environmental survey to evaluate respiratory disease at two tungsten carbide (TC) production plants. The study population of 290 subjects (19.2 percent of the total work force) was chosen to focus on those with the greatest potential exposures to cobalt, a binding agent which is probably the cause of interstitial fibrosis and airways disease in TC workers. We found peak air concentrations of cobalt exceeding 500 micrograms/m3 during many major steps in TC production. Nine subjects at plant A and two at plant B had interstitial infiltrates. Two of these nine from plant A had restriction (total lung capacity less than 80 percent of predicted). A lung biopsy specimen in one showed interstitial fibrosis. Two nonsmokers at plant A and one nonsmoker at plant B had obstructive defects. These results suggest that interstitial and obstructive lung disease occur in TC workers in association with elevated peak air concentrations of cobalt.

Lateral sinus thrombosis associated with otitis media and mastoiditis in children.

Lateral sinus thrombosis (LST) is an infrequent complication of otitis media and mastoiditis in the antibiotic era. A recent case of LST in a 7-year-old boy, the third such case at our institutions in the past 5 years, prompted a review of the modern day English literature concerning LST in pediatric patients. Our goal was to highlight the clinical findings suggestive of LST in the antibiotic era as well as to analyze retrospectively the diagnostic and therapeutic modalities of greatest benefit based on the outcomes reported in the reviewed studies.

Imaging of lymphoma manifestations in the extracranial head and neck region.

CT and MRI are the most efficient imaging techniques for diagnosing lymphomas while Gallium-67 scintigraphy is used to assess treatment results. In this review, the imaging aspects of lymphoma are addressed according to anatomical subregions, from the orbit to the trachea, Waldeyer's ring being the most common site, in the head and neck. Lymphomas of this region are not easily distinguished from the more common squamous cell carcinomas; however, multiple extranodal sites, the presence of many non-necrotic lymph nodes and a large nasopharyngeal mass without significant bone destruction should alert one to the possibility of lymphoma.

Malignant tumors of the paranasal sinuses: radiologic, clinical, and histopathologic evaluation of 200 cases.

Malignant tumors of the paranasal sinuses are often found to be greatly advanced by the time a clinical or radiologic diagnosis is established. Therefore, the overall cure rate is low, even when surgery and radiation therapy are combined. The clinical manifestations and pathologic findings are analyzed in 200 cases to illustrate the wide spectrum of these tumors as to their type, specific location, and the extent to which they can spread within the sinuses and to adjacent anatomic areas. The various radiologic modalities, including conventional x-ray films, angiography, and conventional and computed tomography are presented. Their relative merit in the diagnosis and staging of these tumors is evaluated.

Phase-contrast imaging of the parotid region.

Standard T1- and T2-weighted spin-echo acquisitions were compared with T1- and T2-weighted phase-contrast techniques in a series of 10 consecutive patients with parotid masses to assess the role of phase-contrast methods in the evaluation of lesions in the parotid fossa. Greater tissue-lesion contrast was obtained with phase-contrast methods in nine of 10 cases, allowing improved lesion visualization; however, an increase in lesion detectability was not observed in this series. Standard MR imaging methods are sufficient for imaging the parotid region in most cases, but can be quite time-consuming. Recommended screening of the parotid fossa that optimizes tissue-lesion contrast, lesion detectability, and imaging time is performed by combining a standard T1-weighted acquisition with a T1- or T2-weighted phase-contrast acquisition. Selection of a T1- or T2-weighted phase-contrast acquisition is determined by the T1 characteristics of the lesion.

Imaging of cysts and odontogenic tumors of the jaw. Definition and classification.

For the evaluation of jaw cysts and odontogenic tumors, the radiologic examinations include conventional films, computed tomographic (CT) scans, and magnetic resonance (MR) images. The indications for these radiologic methods are discussed along with the radiologic findings for the various cysts and tumors described. The differential diagnosis of these lesions is also included in the discussion.

Inflammatory disorders of the paraorbital sinuses and their complications.

This article discusses paranasal sinus infection and mucoceles that affect the orbital cavity. The radiologic findings demonstrated by plain films and computerized tomography (CT) are described. Special emphasis is placed on CT, as it represents the primary modality in assessing orbital complications.

CT and MR imaging evaluation of neck infections with clinical correlations.

Infection of the neck is a common clinical problem in all age groups, especially children and young adults. The clinical symptoms and signs are often suggestive of the diagnosis. Imaging studies including CT and MR imaging are frequently required to confirm the diagnosis but more importantly to localize the infectious process and search for and delineate an abscess cavity. Ultrasound has also been used in the evaluation of superficial neck infections, especially to determine fluid accumulation. Conventional films consisting of an anteroposterior and lateral view were the examination before the introduction of CT in 1972. Conventional films can still be used for a preliminary survey, especially of the retropharyngeal space when there is a question of a retropharyngeal phlegmon or abscess.

Neurogenic tumors of the neck.

Neurogenic tumors of the neck occur in children and adults. Important parameters to aid in the differential diagnosis are age at presentation, location, and a history of NF or multiple endocrine neoplasia. Schwannoma is the most common solitary neurogenic tumor in the neck and is usually seen in patients between 20 and 50 years of age. The plexiform neurofibroma and multiple localized neurofibromas are characteristic of NF1. MPNSTs are uncommon aggressive lesions that can arise de novo in patients with NF (10% to 30%) and postirradiation. Neuroblastic tumors consist of neuroblastoma, ganglioneuroblastoma, and ganglioneuroma. These tumors typically arise in the chest and abdomen but occasionally present as a primary neck mass. A neck mass with a histologic diagnosis of neuroblastoma is, however, more commonly metastatic from an abdominal neuroblastoma.

The thyroid and parathyroid glands. CT and MR imaging and correlation with pathology and clinical findings.

Thyroid imaging approach is based on the preliminary clinical evaluation. Lesions that are smaller than 2 cm should be assessed with US, which is capable of discriminating masses as small as 2 mm and distinguishing solid from cystic nodules. US-guided FNAB provides tissue for cytologic examination of thyroid nodules. CT and MR imaging are indicated for larger tumors (greater than 3 cm diameter) that extend outside the gland to adjoining structures, including the mediastinum, and retropharyngeal region. Metastatic lymph nodes in the neck and invasion of the aerodigestive tract are also in the realm of CT and MR imaging. Thyroid nodules are categorized on scintigraphy as hot or cold nodules. Hot nodules are rarely malignant, whereas cold nodules have an incidence of 10% to 20% of malignancy. Calcifications (amorphous, globular, nodular, and linear) occur in adenomas and carcinomas and have no differential diagnostic features except for psammomatous calcifications, which are a pathognomonic finding in papillary carcinomas and a small percentage of medullary carcinomas. Papillary carcinoma is the most common malignant tumor (80%) followed by follicular (20% to 25%); medullary (5%); undifferentiated; anaplastic carcinomas (< 5%); lymphoma (5%); and metastases. Lymph node metastases are common in papillary carcinoma, 50% at presentation, and less common in follicular carcinomas. The metastatic nodes in papillary carcinoma may enhance markedly (hypervascular); show increased signal intensity on T1-weighted images (increased thyroglobulin content or hemorrhage); and reveal punctate calcifications. Localized invasion of the larynx, trachea, and esophagus occurs predominantly in papillary and follicular carcinomas; the incidence is less than 5%. Ectopic thyroid tissue may be encountered in the tongue (foramen cecum); along the midline between posterior tongue and isthmus of thyroid gland; lateral neck; mediastinum; and oral cavity. Goiter and malignant tumors, notably papillary carcinoma, may develop in ectopic thyroid tissue. Carcinomas may also arise in thyroglossal duct cysts, which develop from duct remnants between the foramen cecum and thyroid isthmus. Infectious disease of the thyroid gland is not common and the CT and MR imaging findings are similar as described under neck infection. Other types of inflammatory disorders including Hashimoto's thyroiditis, granulomatous thyroiditis, and Riedel's struma display no specific imaging features. Imaging studies may, however, be indicated to confirm a suspected clinical diagnosis and assess compromise of the airway (Riedel's struma). HPT is a clinical diagnosis in which hypercalcemia is the most important finding. Parathyroid hyperplasia, adenoma, and carcinoma represent underlying lesions. To relieve the patient's symptoms surgical extirpation is indicated. The surgical success rate without imaging is 95%. The indications for imaging studies vary but it is generally agreed that reoperation after a previous failed surgical attempt and suspicion of an ectopic parathyroid adenoma should be investigated by imaging. These consist of US, nuclear medicine studies, CT and MR imaging. US and technetium sestamibi scanning have the highest accuracy rate for localizing an adenomatous gland at and near the thyroid gland. Ectopic adenomas, particularly if they are located in the mediastinum, are preferrably investigated with CT and MR imaging with gadolinium and fat suppression. Carcinomas and parathyroid cysts are optimally evaluated by CT and MR imaging. On MR imaging adenomas are low in signal intensity on T1-weighted images, high in signal intensity on T2-weighted images, and enhance post introduction of gadolinium.

Pseudotumor of the orbit. Clinical, pathologic, and radiologic evaluation.

Pseudotumor, Graves' disease, and lymphoproliferative disease are the most common ophthalmologic disease entities requiring evaluation by CT and MR imaging. A history of acute onset, pain, swelling, proptosis, and response to steroids are the classical findings. The radiologic findings are categorized according to location into dacryoadenitis, myositis, and sclerouveitis, with and without associated infiltrations. The inflammatory infiltrate, which is composed of polymorphic leukocytes, lymphocytes, and plasma cells interspersed with a variable amount of fibrovascular tissue, may be diffuse or localized. The preferred radiologic method used for assessment of pseudotumor is CT. MR imaging, however, is indicated for evaluation of the Tolosa-Hunt syndrome, which is characterized by an inflammatory infiltrate in the orbital apex and cavernous sinus leading to cranial nerve involvement with ophthalmoplegia. The clinical and radiologic constellation of findings allows a definitive diagnosis in most cases.

Imaging of benign and malignant soft tissue tumors of the neck.

Soft tissue tumors of the neck are a heterogeneous group of neoplasms arising from adipose, muscular, and fibrous tissue. With the exception of lymphomas, they account for only a small fraction of neck masses. Nevertheless, accurate diagnosis is important since the behavior of these neoplasms differs markedly from each other and from other head and neck masses. Noninvasive imaging, usually with CT and MR imaging, plays an important role in diagnostic evaluation and treatment planning for these tumors. In some cases, imaging features may be suggestive of a single entity. In most cases, imaging is needed to assess the location and extent of the tumor prior to biopsy or excision. This article discusses imaging techniques used for such assessment, the imaging features that help to separate these neoplasms from other head and neck tumors, and the behavior and imaging features of each of the more common benign and malignant soft tissue tumors that occur in the neck.

Abnormally large frontal sinus. II. Nomenclature, pathology, and symptoms.

Based on a review of the literature and analysis of six new cases, three categories of enlarged, aerated sinuses are defined, namely: hypersinus, pneumosinus dilatans, and pneumocele. The information gained by our study of the area variation of the frontal sinuses in a normal population (part I of this paper) was utilized to define the term hypersinus. In this condition there is generalized enlargement of the sinus beyond the upper limit of normal in an asymptomatic patient. The principal difference between pneumosinus dilatans and a pneumocele is the presence of bony thinning or erosion in the latter entity. The clinical findings and the possible etiologies of these conditions are discussed.

Radiologic evaluation of the jugular foramen. Anatomy, vascular variants, anomalies, and tumors.

The jugular foramen varies considerably in size and shape, along with the jugular vein. The foramen is traversed by several vessels and nerves. CT, in various section planes, demonstrates the bone anatomy optimally, whereas MR (including MR angiography) reveals the vascular and soft tissue structures to best advantage. A diverse group of vascular anomalies originate in the foramen and adjacent carotid canal that must be differentiated from tumors. The most common tumor within the jugular foramen is the hypervascular glomus jugulare tumor followed by neurogenic tumors, predominantly the schwannoma. Less common lesions comprise meningioma, hemangiopericytoma, chondrosarcoma, and plasmacytoma. Metastases and malignant tumors arising in adjacent anatomic structures (nasopharynx, parotid, and temporal bone), in advanced stages, may spread to the jugular foramen. Endolymphatic sac tumors arise at the posterior medial aspect of the petrous bone and frequently extend to the jugular foramen. Irregular lytic bone destruction, with enlargement and hypervascularity, demonstrated by CT and MR imaging, are characteristic for glomus jugulare tumors. Benign tumors, most commonly the jugular foramen schwannoma, display an enlarged jugular foramen with well-defined bone margins.

Chondrosarcoma of the skull base.

Chondrosarcomas are relatively rare tumors of the skull base. This article surveys the clinical and pathologic features of these lesions. In recent years there have been remarkable advances in both the imaging and treatment of these lesions. Both CT scanning and MR imaging are usually necessary for the complete evaluation of these tumors because of the involvement of both soft tissue and bony structures at the skull base. New surgical techniques and the use of high-energy proton beam irradiation have improved the prognosis for patients with these lesions.

Imaging evaluation of the optic nerve and visual pathway including cranial nerves affecting the visual pathway.

The radiologic investigation of the optic pathways has an integral part in the diagnostic evaluation of diverse lesions, such as inflammatory disease, vascular disorders, and benign and malignant tumors that afflict the optic pathways. These radiologic methods consist principally of computed tomography and magnetic resonance imaging, and, in vascular lesions, magnetic resonance angiography and conventional angiography.