Identifying the biological properties of the cells residing within the periodontal ligament (PDL) will help in understanding the role that these cells play in the various functions of the periodontal ligament, and will improve the success of clinical procedures such as orthodontic tooth movement. For this purpose, fibroblasts isolated from human periodontium were cultured and characterized both histochemically and biochemically with respect to their putative osteoblast-like properties. Histochemically, cultured PDL fibroblasts showed an intense staining for alkaline phosphatase (ALP). Biochemically, the basal ALP activity increased in culture over time. ALP levels after stimulation with 1 alpha, 25-dihydroxyvitamin D3 were significantly higher than those of control cultures. Moreover, immunofluorescence against osteocalcin (a highly reliable osteoblastic marker) was strongly positive. Von Kossa staining of the cell cultures revealed the formation of mineral-like nodules. These results indicate that human PDL fibroblasts exhibit in vitro phenotypic characteristics consistent with osteoblast-like cells, thus suggesting that such cells have the potential to differentiate into osteoblasts and/or cementoblasts.

The aim of the present study was to investigate putative relationships between different malocclusions such as Class III and Class II division 1, and congenital tooth anomalies. Two-hundred Class III and 215 Class II division 1 patients were examined for the presence of any of the following congenital tooth anomalies: maxillary incisor hypodontia, maxillary canine impaction, transpositions, supernumerary teeth, and tooth agenesis. Their occurrence rates were then calculated as a percentage of the total sample and were compared for statistical differences. The results revealed no statistical difference (P > 0.05) in the occurrence rates of upper lateral incisor agenesis, peg-shaped laterals, impacted canines, or supernumerary teeth between the Class III and the Class II division 1 malocclusions. When the occurrence rate of all congenital tooth anomalies was compared between the two malocclusions, Class III subjects showed significantly higher rates (P < 0.05). Comparison with published surveys on general populations showed similar occurrence rates. It can be concluded that subjects with Class III and Class II division 1 malocclusions show patterns of congenital tooth anomalies similar to those observed in the general population. Congenital tooth anomalies may represent another criterion for the study of malocclusion, with respect to their origin and development.

Cell-matrix interactions and the ordered deposition of basement membrane (BM) components are of major importance for the maintenance of tissue homeostasis in complex epithelia. This aspect was studied in vitro in a coculture system designed as an oral mucosa model. As crucial epithelial features the kinetics of proliferation, expression of site-specific keratins as well as integrin patterns in correlation to synthesis of BM components were assessed by immunohistochemistry and in situ hybridization. Comparison with non-cornified gingiva as tissue of origin revealed different stages of epithelial development, eventually leading to complete reconstruction within a time frame of 1-3 weeks. First, the initial activated stage up to 1 week was characterized by (a) high keratinocyte proliferation, (b) extended expression of the basal cell-specific keratin K5 and (c) a patchy pattern of the differentiation-specific keratins K4 and K13. Second, after 2 weeks the improvement of histoarchitecture correlated to (a) predominant K5 expression in the basal and (b) extension of K4 and K13 within the suprabasal cell compartment, (c) high expression of integrins alpha3 beta1 and alpha6 beta4 including their ligand laminin-5 and (d) accumulating deposition of basement membrane components. Third, virtually complete tissue normalization at 3 weeks was indicated by (a) restriction of K5 to the basal cell area, (b) regular suprabasal localization of K4 and K13, (c) polarization of integrins to basal and parabasal cells and (d) linear codistribution of collagen IV, "classical" laminin (-1 or -10) and laminin-5 underneath the basal cells. Thus, these organotypic cocultures represent relevant equivalents for non-keratinized oral mucosa with typical gingival differentiation features and in addition suitable models for preclinical trials such as prospective dental material testing.

To establish a three-dimensional in vitro test system mimicking the physiological situation of the oral cavity, organotypic co-cultures consisting of primary gingival cells on a collagen matrix with fibroblasts were generated. The histomorphological development after 7 and 14 d revealed close similarity with the non-keratinized gingiva epithelium. Furthermore, as epithelial specific markers synthesis and localization of keratins as well as the deposition of basement membrane components were assessed on frozen sections by immunofluorescence and keratin expression by in situ hybridization. Primary keratinocytes in conventional culture strained positive for keratin K14 and the mucosal differentiation-specific keratins K4 and K13, while primary fibroblasts, isolated from the same tissue source, and also some keratinocytes, were positive for vimentin. In organotypic co-cultures the keratinocytes formed a multilayered epithelium within 14 d containing basal cells and flattened cells in the uppermost layers. Comparable to native non-keratinized gingiva keratin 14 gene expression was clearly detectable in the basal cell compartment but showed extending immunolocalization. In addition, particularly at the early stage (7 d), basally located keratinocytes were also vimentin positive. According to morphological differentiation K4 and K13 were detectable in suprabasal position a the RNA and protein level. The major basement membrane constituents collagen type IV and laminin increased with time revealing first an interrupted and later a fully extended staining underneath the basal cells. Maintenance of basal cell function was further demonstrated by cell proliferation (BrdU incorporation) which was initially high (7 d) but declined towards the later stages (14-21 d). The results demonstrate i) that this co-culture system leads to a stratified surface epithelium with morphological and biochemical characteristics of the non-keratinized gingiva epithelium and ii) that a state of physiological tissue balance was reached, thus rendering a suitable model for tissue compatibility studies.

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We employed topographical patterning to analyze early keratinocyte differentiation on top of microfabricated pillar arrays. Fibronectin immobilized on pillar "heads" yielded a nucleus-associated granular keratin 1 (K1) pattern in immortalized human gingival keratinocytes (IHGK) at pillar interspaces of 14 µm. Decreasing distances of 11and 8 µm revealed cytoplasmic extension of the early differentiation marker K1 on poly-(dimethylsiloxane) (PDMS) pillars. The most extensive cytoplasmic K1 protein distribution noted at the smallest pillar scale coincided with higher ratios of K1 mRNA gene transcription. These experiments suggest that early keratinocyte differentiation was governed by the topographical characteristics of the pillar pattern. Moreover, they form the basis to study cell functions such as differentiation in a defined topologically structured environment.

There 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.