Efthimia K. Basdra

Effect of protein kinase inhibitors on the stretch-elicited c-Fos and c-Jun up-regulation in human PDL osteoblast-like cells

Osteoblastic cells transduce signals of mechanical loading that plays a key role in maintaining bone formation. In an attempt to elucidate the biochemical events associated with the conversion of mechanical stress to biological outcome, we examined cultured human periodontal ligament (hPDL) osteoblastic cells exposed to continuous stretch, in terms of cellular parameters correlating known signaling cascades to the initial phase of osteoblast‐specific transcriptional control. Time‐course experiments revealed that mechanical stretch‐loaded hPDL cells exhibit a very rapid and relatively sustained increase in the abundance of the immediate‐early gene products, c‐Fos and c‐Jun, components of the activator protein‐1 (AP‐1) transcription factor. Moreover, this increase in protein levels was accompanied by hyperphosphorylation and thereby potentiation of c‐Jun, the principal modulator of AP‐1 activity. Importantly, these inductive effects were partly or completely abolished by pre‐incubating the cells with SB 203580, PD 098059, and the novel compound Y‐27632, inhibitors of p38 mitogen‐activated protein kinase (MAPK), MAPK kinase (MEK), and Rho‐associated protein kinase (RhoK), respectively. These results consolidate AP‐1 as the pivotal downstream effector in the early response of hPDL cells to continuous mechanical stretching, via the coordinate stimulation of de novo synthesis and post‐translational regulation of AP‐1 proteins. This “integrating” function of AP‐1 is mediated through a mechanotransduction circuit that incorporates elements of well‐defined upstream signaling protein kinase systems. J. Cell. Physiol. 190: 313–321, 2002.

Mesiodentes: Inzidenz, morphologie, ätiologie

ZusammenfassungTrotz zahlreicher Veröffentlichungen über klinische, radiologische und chirurgische Aspekte in der Therapie von Mesiodentes bleibt die Frage nach der Ätiologie dieser Zähne weitgehend unbeantwortet. Ziel dieser Studie war daher, ursächliche Faktoren bei unseren Patienten mit Mesiodentes zu eruieren. Die Untersuchung beinhaltete 30 Patienten mit insgesamt 45 Mesiodentes. Bei 31% der Patienten lag eine familiäre Disposition vor, so daß der Vererbung eine maßgebliche Rolle bei der Entstehung von Mesiodentes zugemessen werden muß. Die Ergebnisse legen weiterhin die Vermutung nahe, daß ein ätiologischer Zusammenhang zwischen dem Auftreten von Mesiodentes und anderen Zahn- und Kieferanomalien wie Hyperdontie, Hypodontie und Spaltbildung besteht. Zuletzt sprechen sowohl die Gemination des Milchschneidezahnes auf der Seite des Mesiodens bei einem unserer Patienten als auch die mesiodistalen Breitenvergleiche der mittleren Schneidezähne dafür, daß der Theorie der Dichotomie des Zahnsäckchens bei der Entstehung von Mesiodentes den Vorzug gegenüber der Theorie einer Überaktivität der Zahnleiste gegeben werden muß.SummaryThere are many publications in the literature focusing on clinical, radiological and surgical aspects of the treatment of mesiodentes. However, the etiology of this dental anomaly remains widely unclear. The purpose of this study was to evaluate etiologic factors for mesiodentes in a collective comprising 30 patients with a total of 45 mesiodentes. Thirty-one percent of the patients showed a familial disposition, pointing to inheritance as a key factor in the development of mesiodentes. Our results further support the hypothesis of related etiologic factors for several dental and craniofacial anomalies, such as hyperdontia, hypodontia and cleft lip and palate. Finally, we report the gemination of a deciduous incisor on the same side as a mesiodens. We also found differences in the mesiodistal width of central incisors depending on unilateral or bilateral occurrence of mesiodentes. Both these findings support the dichotomy theory of the split in the tooth bud inducing the development of mesiodentes, a theory we favor over that of local hyperactivity of the dental lamina.

Mechanical stress induces DNA synthesis in PDL fibroblasts by a mechanism unrelated to autocrine growth factor action

Periodontal regeneration is thought to require the proliferation of stress‐sensitive periodontal ligament (PDL) fibroblast cells. The influence of physiological amounts of mechanical stretching on the DNA synthesis potential of human PDL fibroblasts was examined by means of an established, simple in vitro system of stretch application. A significant increase in the relative levels of incorporation of tritiated thymidine was observed in cultures stretched for 1–6 h. Neutralising antibodies for platelet‐derived growth factor (PDGF) and transforming growth factor‐beta (TGF‐β) did not blunt the DNA synthesis induction. This mitogenic response to stretch appears to be independent of an autocrine mechanism involving growth factors in general, because stretch‐conditioned medium, when transferred to non‐stretched fibroblasts, did not mimic the mitogenic effect of stretch.

Rab and rho GTPases are involved in specific response of periodontal ligament fibroblasts to mechanical stretching

To investigate the contribution of ras-related signalling molecules to the mechanotransduction process, stretch-sensing human periodontal ligament (PDL) fibroblasts were isolated and cultured in dishes with a flexible bottom. The cells were stimulated by stretching the bottom of the dishes and membrane fractions were prepared and analysed at the level of mapping small GTP-binding proteins by high resolution two-dimensional gel electrophoresis followed by renaturing transfer and an [alpha-32P]GTP-overlay procedure. This analysis revealed that mechanically-stretched PDL fibroblasts exhibit complete down-regulation of rhoA and induction of rab6, rab17 and a putative member of the rab3 subfamily in a cell type-specific manner.

[The etiology of canine tooth impaction--a space analysis].

ZusammenfassungZiel dieser Untersuchung ist es festzustellen, inwieweit ein Platzüberschuß als ätiologischer Faktor für die Impaktierung der Oberkieferenckzähne, unter besonderer Berücksichtigung der Rolle der seitlichen Schneidezähne, in Betracht gezogen werden muß. Zur Klärung dieser Frage wurden sowohl die Anfangs- und Abschlußmodelle von 63 Patienten mit 84 impaktierten Eckzähnen als auch die Fernröntgenseitenbeilder von 116 Patienten mit 144 verlagerten Eckzähnen vermessen. Die Ergebnisse dieser Studie zeigen: Die palatinale Verlagerung Überwog mit 84,5% deutlich gegenüber der verstibulären Retention mit 15,5%. Ein Platzmangel konnte lediglich bei 18% deer Patienten mit palatinaler Verlagerung im Gegensatz zu 46% bei vestibulärer Impaktierung festgestellt werden. Hypoplastische seitliche Schneidezähne traten in 35% der Fälle mit palatinaler Verlagerung, edoch bei keinem Patienten mit vestibulärer Retentiion auf. Die kephalometrische Analyse zeigte ebenfalls einen unterschiedlichen Gesichtsschädelaufbau bei palatinaler und vestibulärer Verlagerung. Während 80% der Patienten mit palatinaler impaktierung einen horizontalen achstumtyp aufwiesen, wurde ein solcher nur in 23% der Fälle mit vestibulärer Retention gefunden.SummaryThe aim of this study was to examine to what extent excess space must be taken into consideration as an etiological factor in upper canine impaction with special attention paid to the role of the adjacent laterals. To clarify this question the pre- and post-treatment models of 63 patients with a total of 84 impacted cuspids were measured and the cephalograms of 116 patients havign 144 impacted cuspids were analyzed. The results of this study revealed: 85.5% of the cuspids were palataly impacted while 15.5% were labially impacted. An arch deficiency was found in only 18% of the palatally impacted cuspids, whereas there was an arch-length deficiency in 46% of the buccally impacted. In 35% of the cases there was a correlation between peg shaped laterals and palatal impaction, however, such was not present in te patients with vesbibular retention. Finally the cephalometric data revealed horizontal growth characteristics in 80% of the palatally impacted canines as opposed to 23% in those labially impacted.The aim of this study was to examine to what extent excess space must be taken into consideration as an etiological factor in upper canine impaction with special attention paid to the role of the adjacent laterals. To clarify this question the pre- and post-treatment models of 63 patients with a total of 84 impacted cuspids were measured and the cephalograms of 116 patients having 144 impacted cuspids were analyzed. The results of this study revealed: 84.5% of the cuspids were palatally impacted while 15.5% were labially impacted. An arch deficiency was found in only 18% of the palatally impacted cuspids, whereas there was an arch-length deficiency in 46% of the buccally impacted. In 35% of the cases there was a correlation between peg shaped laterals and palatal impaction, however, such was not present in the patients with vestibular retention. Finally the cephalometric data revealed horizontal growth characteristics in 80% of the palatally impacted canines as opposed to 23% in those labially impacted.

Extraction of maxillary second molars in the treatment of Class II malocclusion

The results of treatment following the extraction of maxillary second molars for Class II correction were evaluated. Records (cephalograms, orthopantomograms, and models) of 32 patients treated with maxillary second molar extraction were analyzed. Cephalograms taken before and after treatment were traced and 18 variables were compared. Changes in the axial inclination of the erupted third molars relative to the occlusal plane were measured on the orthopantomograms. The form and the position (eruption in occlusion, rotations) of the maxillary third molars were evaluated on the models. The average treatment time was 26 months. The results of this study show significant changes of the angles SNA, SNB, ANB, 1/4:SN, and the distances 1-NPog, and 1-APog, as well as significant effects on the soft tissue profile. In 19 cases examined 4 years postretention, all maxillary third molars had erupted into occlusion with a mesial contact point and acceptable mesiodistal axial inclination.

Mechanical loading triggers specific biochemical responses in mandibular condylar chondrocytes.

The effect of mechanical loading on the phosphorylation state of condylar cartilage proteins was investigated by high resolution electrophoretic analysis of 32P-labelled proteins from mechanically stimulated rat mandibular condylar chondrocytes. Specific dephosphorylation (and/or loss) of an acidic, 35-36 kDa protein(s) and of proteins overlapping with members of the ras superfamily of small GTP-binding proteins was observed. These responses may constitute part of a mechanically induced transduction system which establishes the differentiated phenotype.

Factors Influencing Changes in Maxillary Arch Dimensions in Unilateral Cleft Lip and Palate Patients until Six Months of Age

OBJECTIVE The objectives of the present study were (1) to investigate whether growth increments until 6 months of age are influenced by particular factors, (2) to analyze whether anterior cleft reduction is dependent on the extent of the cleft width at birth, and (3) to examine the correlation between maxillary measurements at birth and the anterior cleft width at 6 months of age. DESIGN The study design was prospective and longitudinal. SETTING Heidelberg University Hospital Interdisciplinary Cleft/Craniofacial Center. PATIENTS AND METHOD The longitudinal records of 34 patients (24 male and 10 female) with complete unilateral cleft lip, alveolar ridge, and hard and soft palate were included in this study. All patients were treated with the same protocol. All participants were assessed at 0 and 6 months of age. Maxillary plaster casts of the patients were analyzed using a computer-controlled three-dimensional digitizing system. MAIN OUTCOME MEASURE Maxillary models were measured and compared to putative factors influencing growth. RESULTS No statistically significant differences were found between maxillary growth changes and increases in weight and length. Similarly, there was no significant interaction between the extent of the alveolar cleft width at birth and its reduction prior to lip closure. In contrast, significant differences of maxillary growth increments could be found between male and female patients. Stepwise regression analysis demonstrated a correlation between maxillary measurements at birth and growth increments. CONCLUSION The results of the study indicate that gender plays a certain role in growth changes within the first 6 months of age.

Mechanische Dehnung von Desmodontalfibroblasten — eine Untersuchung zur zytoskelettalen Beteiligung

ZusammenfassungZur Untersuchung der molekularen Mechanismen, ausgelöst durch orthodontische Zahnbewegungen, wurden Desmodontalfibroblasten isoliert und in Kulturschalen mit flexiblen Böden angezüchtet. Die Zellen wurden über den flexiblen Boden der Kulturschalen stimuliert und das Gesamtzellextrakt mittels Natrium-Dodecyl-Sulfat-Polyacrylamid-Gel-Elektrophorese (SDS-PAGE) analysiert, transferiert auf eine Nitrozellulosemembran und immungeblotted mit spezifischen Antikörpern gegen Vimentin sowie α- und β-Tubulin. Es ergaben sich keine auffälligen Veränderungen im Expressionsprofil der Hauptkomponenten des Zytoskeletts. Darüber hinaus ließ eine Immunfluoreszenz gegen die gleichen Proteine keine auffälligen Veränderungen in der topographischen Organisation von gedehnten und ungedehnten Zellkulturen erkennen.SummaryTo investigate molecular aspects of the mechanism(s) involved in orthodontic tooth movement, periodontal ligament fibroblasts (PDL) were isolated and grown on culture dishes with a flexible bottom. The cells were stimulated by stretching the bottom of the culture dishes and whole cell extracts were prepared and subjected to sodium dodecyl sulfate polyacrylamide (SDS-PAGE) electrophoresis, electrotransfered to nitrocellulose membrane and immunoprobed with antibodies specific for vimentin and α- and β-tubulin. No apparent alterations in the expression profile of the above mentioned major cytoskeletal elements were evident after mechanical stretching. Moreover, immunofluorescence against the same proteins revealed no changes in their topographical organisation between stretched and unstretched cell cultures.

Extraction therapy in patients with class II/2 malocclusion

The aim of this study was to analyze the dynamic development of Class II, Division 2 malocclusion with reference to the untreated patients from the Belfast Growth Study. As a second step, the influences of premolar extraction in all 4 quadrants and of maxillary second molar extraction in the upper jaw in Class II/2 patients were examined, focusing on the cephalometric variables in comparison to those of the untreated patients from the Belfast study. The longitudinal cephalometric values of 20 patients in each group were compared.In addition, the possibility of thirds molar eruption was evaluated in the extraction patients from the panoramic radiographs. The overbite based on study models at the beginning and end of treatment was calculated. Furthermore, renewed spacing after premolar extraction was assessed.The results derived from cephalometric analysis demonstrated that profile flattening was also observed in untreated Class II/2 patients during the growth period. Comparison of these data with those obtained from the extraction groups revealed a significantly marked recession of the upper lip after premolar extraction. In contrast, only slightly increased flattening after maxillary second molar extracton was observed compared with the untreated patients of the control group. Whereas the interincisal angle was reduced to a value approximating that of untreated Class I patients after maxillary second molar extraction, only a small decrease was recorded after premolar extraction.From our point of view, the claim that premolar extraction facilitates third molar eruption should be seen in an extremely critical light and should not contribute to the decision in favor of extraction. In addition, there is a problem of renewed spacing in the extraction area after premolar extraction.ZusammenfassungGegenstand der Arbeit war, am Beispiel der uns zur Verfügung gestellten Belfaster Wachstumsstudie unbehandelter Patienten, die dynamische Entwicklung der Angle-Klasse II/2 zu analysieren. In einem zweiten Schritt wurden die Einflüsse der Prämolarenextraktion in allen vier Quadranten bzw. der Siebenerextraktion im Oberkiefer bei Klasse-II/2-Patienten auf die kephalometrischen Variablen untersucht und mit denen der unbehandelten Belfaster Patienten verglichen. Die longitudinalen fernröntgenologischen Befunde von jeweils 20 Patienten wurden gegenübergestellt. Zusätzlich wurden bei den Extraktionspatienten anhand der Orthopathomogramme die Durchbruchsmöglichkeit der Weisheitszätzlich wurden bei den Extraktionspatienten anhand der Orthopantomogramme die Durchbruchsmöglichkeit der Weisheitszähne beurteilt sowie anhand der Kiefermodelle der vertikale Überbiß bei Behandlungsbeginn und-abschluß bestimmt. Weiterhin wurde eine erneute Lückenbildung nach Prämolarenextraktion abgeklärt.Die Ergebnisse der kephalometrischen Analyse zeigten, da\ eine Abflachung des Profils auch bei den unbehandelten Klasse-II/2-Patienten während des Wachstums beobachtet werden kann. Der Vergleich dieser Messungen mit denen der Extraktionsgruppen ergab, daß die Oberlippe nach Prämolarenextraktion signifikant stärker zurückwich. Hingegen kam es nach Siebenerextraktion zu geringfügig größeren Abflachung im Vergleich zur unbehandelten Kontrolgrppe. Während der Interinzisalwinkel nach Siebenerextraktion auf einen Wert verringert werden konnte, der nahezu dem unbehadelter Klassel-Patienten entspricht, wurde nach Prämolarenextraktion lediglich eine geringe Reduktion beobachtet.Das Argument, daß Prämolarenextraktionen die Durchbruchsmöglichkeiten der Weischeitszähne verbessern, muß aus unserer Sicht äußerst kritisch betrachtet werden und sollte daher nicht zur Extraktionsentscheidung beitragen. Nach Prämolarenextraktion stellt sich zudem das Problem einer erneuten Lückenbildung im Extraktionsbereich.