Healthy bone is bombarded with many different mechanical strain derived signals during normal daily activities. One of these signals is present as a direct connective tissue strain on the cells. However, there is also the presence of an electrically charged streaming potential during this straining. The electrical potential is created from the movement of charged fluid through the small bone porosities. To date, little focus has been applied to elucidating the possible synergistic effects of these two stimulants. The aim of this project was to evaluate the effects of mechanical strain and indirect electrical stimulation upon the development of bone forming osteoblast cells and any possible synergistic effects of the two stimulants. This aim was achieved by using a novel device, designed and developed with the capability of creating a cell substrate surface strain along with an exogenous electrical stimulant individually or at the same time. Proliferation and differentiation were determined as a measure of cellular development. The indirect electrical stimulation was achieved through the use of a pulsed electromagnetic field (PEMF) while the mechanical strain was produced from dynamic stretching of a deformable cell substrate. Strain and strain rate were modelled from recent studies proposing that relatively high frequency, low strain osteogenic mechanical stimulants are more indicative of what healthy bone would be experiencing during normal activities. The PEMF signal mimicked a clinically available bone growth stimulator signal. Results showed a PEMF stimulus on monolayers of SaOS-2 and MG-63 osteoblast-like cells leads to a depression in proliferation. A concomitant increase in alkaline phosphatase production was also observed for the SaOS-2 cultures, but not for the MG-63 cell line. It was hypothesised that this was due to the MG-63's lack of phenotypic maturity compared to the SaOS-2 cells. Mechanical strain of the cell substrate alone, at a relatively high frequency (5Hz) but small strain, did not significantly effect either cell proliferation or differentiation for the MG-63 cells. However, when the electrical and mechanical stimulants were combined a significant increase in cellular differentiation occurred with MG-63 cultures, revealing a possible synergistic effect of these two stimulants on the development of bone cells.

Die vorliegende Arbeit fasst 4 Studien zusammen, die konservative Behandlungsstrategien und Folgeerscheinungen an Kiefergelenken mit bestehender Diskusverlagerung (DV) ohne Reposition evaluieren. Studie 1 beurteilt die Therapie mit Äquilibrierungsschienen in Form einer Anwendungsbeobachtung. Die Schmerzsymptomatik und die Kieferöffnungsweite werden über einen Beobachtungszeitraum von 13 Monaten positiv beeinflusst. Studie 2 zeigt als randomisierte, kontrollierte Doppelblindstudie, dass sich die Symptomatik der DV ohne Reposition sowie der aktivierten Arthrose während eines Beobachtungszeitraums von 4 Monaten signifikant verbessert, unabhängig von der durchgeführten Therapie bzw. der Behandlung mit einem Placebogerät. Somit erzielt die Pulsierende Signaltherapie keinen spezifischen therapeutischen Effekt. Die Studie 3 beurteilt die Kaueffektivität bei vorliegender DV ohne Reposition im Vergleich zu einer Kontrollgruppe. Die Kaueffektivität nimmt in Abhängigkeit von der Dauer des Krankheitsbildes deutlich zu, erreicht jedoch nicht die Effizienz der gesunden Vergleichsgruppe. Die Studie 4 stellt eine MRT-gestützte Nachuntersuchung von Patienten mit DV ohne Reposition dar. Das Krankheitsbild geht mit deutlichen degenerativen Veränderungen der Gelenkstrukturen einher, die sich aber über einen Beobachtungszeitraum von ca. 2 Jahren hinweg nicht signifikant verändern. Entzündungszeichen nehmen jedoch signifikant ab und die Translationsbewegung der Kondylen verbessert sich. Die DV ohne Reposition kann somit als Krankheitsbild mit morphologischen Veränderungen und funktionellen Beeinträchtigungen gewertet werden, dessen subjektive Beschwerden sich auch ohne Intervention verbessern. Morphologische Veränderungen unterliegen sich selbst limitierenden Adaptationsmechanismen. / This work presents four studies dealing with disk displacement without reduction, its treatment and long-term effects. Study 1 evaluates the treatment effects of stabilization splints. The study has a prospective follow-up design. Thirteen months after the baseline examination pain relieves and mouth opening reached a significant larger extend. Study 2 is randomised controlled and double blinded and evaluates pulsed electromagnetic fields (PEMF) as a new conservative treatment method. After a period of 4 months the pain relieves significantly and mouth opening is significantly larger in patients with anterior disk displacement or activated arthrosis, independent to active or mock treatment. PST has no specific effect on disk displacement without reduction or activated arthrosis. Study 3 tests the chewing efficiency of patients with disk displacement without reduction in comparison to a control trial. The chewing efficiency improves according to the time since onset of the disorder but is nevertheless reduced compared to a control group without TMJ-disorders. Study 4 is a MRI-controlled study, evaluating morphologic changements. Over an average time of 2 years no significant ongoing of degenerative changements accur, only high signal areas disappear and the translation of the condyle improves significantly. Anterior disk displacement is therefore a TMJ-disorder accompanied by limitation of joint function and degenerative changements of joint structures, which improve without treatment and can be interpreted as a self limiting adaptative process.