Dominik Kraus

Matrix metalloproteinase 20 (MMP20) is a member of the family of matrix metalloproteinases. Under normal conditions the expression of MMP20 is restricted to ameloblasts and odontoblasts. In order to identify a possible expression of MMP20 under pathological conditions, we investigated three major human tumor entities, i.e. colon, breast and lung tumors, on the mRNA and protein level. Real-time RT-PCR and immunocytochemical analyses of established human tumor cell lines were employed for our study; immunohistochemical analysis was performed on both primary tumors and normal control tissues. MMP20 was identified on both the mRNA and the protein level in breast MCF-7, colon HT-29, and lung A549 cell lines. MMP20 was also detected in primary tumor tissue by immunohistochemistry. MMP20 is a new potential candidate for tumor diagnosis or therapy.

The objective of this study was to examine a new blue light diode laser system (445 nm) for dental soft tissue surgery on cellular level. An in vitro cell culture model was established to evaluate the effects of the 445-nm diode laser in comparison to an established infrared diode laser (IR). Monolayer cell cultures were irradiated and wound healing was morphometrically measured. Fluorescence staining was used for proof of potential DNA double-strand breaks as well as cytoskeleton alterations. Cellular live/dead discrimination was performed and temperature development during laser irradiation was measured with a thermographic infrared camera. A characteristic zone formation was detected after irradiation with both wavelengths. Despite a larger wound area after irradiation with 445 nm, due to its higher temperature development, this laser system showed a faster wound healing in comparison to the IR laser. No increase of devitalized cells was documented with higher distances between laser tip and cell layer and thus without thermal interaction. Neither cytoskeleton alteration nor DNA double-strand breaks could be recorded after irradiation in non-contact mode. The blue diode laser system demonstrated an excellent direct thermal coupling to cells and tissues without side effects even by reduced power settings. The blue diode laser seems to be a promising technology for clinical application due to high absorption of blue light without major side effects in adjacent tissues even by reduced power settings.

Due to the high intensities of USP laser radiation, the interaction with matter is always attended with a plasma formation. Therefore the surrounding tissue can be influenced by heat generation and additional light emission from the UV up to the near and mid infrared. In dentistry it is of importance that the treatment of bone and soft tissues, i.e. oral mucosa, with a USP laser should not cause any kind of morphological changes on the cell level leading to a delayed wound healing or cell mutation. HaCaT keratinocyte cells were used for epidermal (soft tissue) and MG-63 osteoblast-like cells for hard tissue (bone) modelling. Cell growing was realized on glas cover slips. Irradiation was carried out with a USP Nd:YVO4 laser having a center wavelength at 1064 nm. Based on the pulse duration of 8 ps and a pulse repetition rate of 500 kHz the laser emits an average power of 9 W. For efficiency testing of cell removal on glas cover slips, 1, 5, 25, 50 and 75 repetitions of the scanning pattern (scan loops) were used. Heat distribution during laser irradiation was measured with an infrared camera system. Subsequently haematoxylin staining and SEM investigations were used to analyse the morphological changes. Differences of cell removal efficiency were observed with repetitions ≤25. Irradiated areas with repetitions ≥50 were cell-free. Additionally, repetitions ≥25 showed side effects for both cell lines. Cell destruction in both cell lines could be verified using the haematoxylin staining and the SEM pictures.

Background: Because of the infrequence of salivary gland tumours and their complex histopathological diagnosis it is still difficult to exactly predict their clinical course by means of recurrence, malignant progression and metastasis. In order to define new proliferation associated genes, purpose of this study was to investigate the expression of human α-defensins (DEFA) 1/3 and 4 in different tumour entities of the salivary glands with respect to malignancy. Methods: Tissue of salivary glands (n=10), pleomorphic adenomas (n=10), cystadenolymphomas (n=10), adenocarcinomas (n=10), adenoidcystic carcinomas (n=10), and mucoepidermoid carcinomas (n=10) was obtained during routine surgical procedures. RNA was extracted according to standard protocols. Transcript levels of DEFA 1/3 and 4 were analyzed by quantitative realtime PCR and compared with healthy salivary gland tissue. Additionally, the proteins encoded by DEFA 1/3 and DEFA 4 were visualized in paraffin-embedded tissue sections by immunohistochemical staining. Results: Human α-defensins are traceable in healthy as well as in pathological altered salivary gland tissue. In comparison with healthy tissue, the gene expression of DEFA 1/3 and 4 was significantly (p<0.05) increased in all tumours – except for a significant decrease of DEFA 4 gene expression in pleomorphic adenomas and a similar transcript level for DEFA 1/3 compared to healthy salivary glands. Conclusions: A decreased gene expression of DEFA 1/3 and 4 might protect pleomorphic adenomas from malignant transformation into adenocarcinomas. A similar expression pattern of DEFA-1/3 and -4 in cystadenolymphomas and inflamed salivary glands underlines a potential importance of immunological reactions during the formation of Warthin’s tumour.

The aim of this study was to examine the wear behavior of conical crowns with electroplated gold copings that are used to connect implants and teeth to a removable denture. Gold alloy and zirconium dioxide ceramic crowns were compared. Fifteen crowns each were milled for two groups: gold alloy and zirconium dioxide. Each specimen had a 2-degree taper. The electroplated coping was established by direct electroforming. The retentive forces and the correlating distance during insertion and separation were measured after 10,000 wear cycles were applied. The wear testing was separated into a start phase, an initial wear phase, and the long-term wear period. The retention force value and the force-distance integral of the first 0.3 mm of each cycle were calculated. The changes in retention force and integral did not differ significantly between both groups in the start and the initial wear phase. No differences were seen in force development during the long-term wear period. Only the force-distance integral showed a significant difference: the median values of the gold crowns increased slightly, and they decreased slightly for the zirconia crowns. The median force values never fell below 6 N for gold and 4 N for zirconia. Within the limitations of this study, the tested conical crowns showed clinically acceptable retentive properties. As with other retentive elements for dentures, the specimens tested showed the greatest amount of change in retentive forces during the first 2,000 cycles. The development of retention force in both groups was not significantly different. However, the zirconia specimens showed reduced variability, which is preferable in clinical practice.