Protrusive mandibular function, including maximum protrusive force and fatigue time, was investigated in 66 children displaying Class II Division 1 malocclusion. Thirty-two children were treated with the Clark Twin-block appliance and the other 34 children served as untreated controls. The observation period was 6 months. Cross-sectional data based on pretreatment records showed that maximum protrusive force ranged from 18.5 N to 160 N, with a mean of 80.3 +/- 30.7 N, Maximum protrusive force was significantly higher in males than in females (P < .001). The correlation between maximum protrusive force and chronologic age was low (r = 0.20) and did not reach significance. Maximum protrusive force in the group of children with disk displacement was not significantly different from that of the group without disk displacement. Comparison of pretreatment and 6-month records in the untreated control group revealed a significant increase in maximum protrusive force (P < .01) as a result of normal growth, while the measured change in the Twin-block-treated children did not reach significance. Fatiguing the protrusive muscles did not alter mandibular position in the Twin-block group after 6 months of treatment. The present study does not support the lateral pterygoid hypothesis, as there was no evidence of an increase in mandibular protrusive function after treatment with the Twin-block functional appliance.

Forty children displaying Class II Division 1 malocclusion were involved in a prospective magnetic resonance image investigation to evaluate the effects of Twin-block functional appliances on the temporomandibular joints. None of these children had clinical signs or symptoms of temporomandibular disorders. Nineteen children were treated with a Clark Twin-block appliance for 6 months; the other 21 children received no treatment and served as controls. Comparison between control and Clark Twin-block groups suggested that reduction of the condylar axial angle represents a feature of untreated Class II growth patterns, whereas axial angle stability with Clark Twin-block therapy may suggest alteration of condylar growth direction. Condyles that were positioned at the crest of the articular eminence by the Clark Twin-block at the beginning of treatment had reseated back into the glenoid fossa after 6 months. However, 75% of the condyles were more anteriorly positioned in successfully treated Clark Twin-block cases. There was no clear evidence of remodeling of the glenoid fossa at the eminence as a result of Clark Twin-block treatment. The initial prevalence of disk displacements for the combined groups was 7.5% anterior, 5% medial, and 12.5% for lateral disk displacement. Clark Twin-block therapy had neither positive nor negative effects on disk position, and there was no convincing evidence that the disk was recaptured.

Cadaver material was used in this study to correlate sequential sagittal and coronal T1-weighted magnetic resonance images against anatomic detail. Magnetic resonance imaging (MRI) was found to accurately represent soft tissues in normal and deranged joints. In contrast to previous reports, MRI was found to accurately represent the discal-retrodiscal junction and did not appear to give false positive findings for disc displacement. Magnetic resonance imaging provided good images of bony outline, particularly in coronal views. Difficulties in interpretation arose when different adjoining tissues produced the same MR image; the central tendon of the lateral pterygoid muscle can appear as an extension of the disc, imaging as a distorted and displaced disc. In anatomic sections, a medial hernia sac in the lower joint space was seen as a constant indicator of the medial component of disc displacement; however, this was not evident in sagittal and coronal T1-weighted images. Fibrocartilaginous remodeling of the articular surface projecting into a discal perforation presented the same image as normal discal tissue. Because discs are often thinned over the lateral pole, it is difficult to determine whether discal tissue is present between the articular surfaces when MRI is at its present resolution. Subcortical bone spaces may be misinterpreted as areas of avascular necrosis and osteochondritis dissecans. It is recommended that an imaging sequence of the TMJ include a midcondyle image and lateral, central, and medial sagittal images; however, the lateral sagittal image is the most difficult to interpret.

Confusion has existed as to whether the major insertion of the superior lateral pterygoid muscle is into the articular disc or the condyle. Five human cadaver joints were studied under the dissecting microscope. This allowed superior lateral pterygoid fibres to be selectively placed under tension to determine their point of insertion and to examine the integrity of the anterior joint capsule. All superior lateral pterygoid fibres gained either direct or indirect insertion to the condyle. A classification for the variation in insertion is suggested. The fibres of the anterior joint capsule extended from the anterior rim of the condyle to the roof of the infratemporal fossa but under the foot of the disc they blended with and became indistinguishable from disc fibres.

This paper proposes that a holistic view of an eLearning system within a given context is the most critical factor to achieving success, it is from a holistic perspective of eLearning that effective models can be designed, and it is in a holistic perspective of eLearning that true educational transformation can take place. A holistic perspective of eLearning supports the premise that the whole of the eLearning experience is greater than the sum of its parts. And it is through observing the qualities of the whole experience that the key parts of the eLearning system can be identified. A holistic approach is a systems-based perspective that recognizes the breadth and depth of the eLearning system. It seeks to identify and understand the interrelated, interactive, and interdependent elements within the system, and to anticipate and adjust to changes in the context where the system resides. Virginia Tech's holistic approach to eLearning focuses on six key elements: 1) the student, 2) learning, 3) faculty, 4) access, 5) costs, and 6) systems. The university's Institute for Distance and Distributed Learning which is responsible for providing leadership, coordination, management, and support to eLearning activities and initiatives connects to other university organizations and systems involved in the eLearning enterprise. Wherever possible it seeks to use existing links and connections to avoid redundancy and maximize resources. Where there are no effective connections, the Institute develops solutions and bridges between organizational systems and the eLearning system. It is through the connectivity within the eLearning system and between internal university systems and external systems that eLearning effectiveness is the greatest.