Evaluation of fibrin, cyanoacrylate, and polyurethane-based tissue adhesives in sutureless vascular anastomosis: a comparative mechanical ex vivo study.

The stability of a microvascular anastomosis is an important prerequisite for successful tissue transfer. Advances in tissue adhesives are potentially opening new avenues for their use in sutureless microsurgical anastomosis, however they have not yet gained clinical acceptance. In this ex vivo study, a novel polyurethane-based adhesive (PA) was used in sutureless anastomoses and its stability compared with that of sutureless anastomoses performed with fibrin glue (FG) and a cyanoacrylate (CA). Stability was assessed using hydrostatic (15 per group) and mechanical tests (13 per group). A total of 84 chicken femoral arteries were used in this study. The time taken to create the PA and CA anastomoses was significantly faster when compared to the FG anastomoses (P < 0.001): 1.55 ± 0.14 min and 1.39 ± 0.06 min, respectively, compared to 2.03 ± 0.35 min. Both sustained significantly higher pressures (289.3 mmHg and 292.7 mmHg, respectively) than anastomoses using FG (137.3 mmHg) (P < 0.001). CA anastomoses (0.99 N; P < 0.001) and PA anastomoses (0.38 N; P = 0.009) could both withstand significantly higher longitudinal tensile forces compared to FG anastomoses (0.10 N). Considering the background of an in vitro study, the PA and CA anastomosis techniques were shown to be similar to each other and superior to FG, due to their stability and faster handling. These findings need to be validated and confirmed in further in vivo studies.

Perfusion of microvascular free flaps in head and neck reconstruction after prior neck dissection and irradiation.

Microvascular free flaps are frequently used for head and neck reconstruction after prior neck dissection (ND) and neck irradiation (RTX). The aim of this study was to investigate the influence of ND and RTX on flap perfusion as a critical factor for flap success. Overall, 392 patients reconstructed with a microvascular fasciocutaneous flap (FF) or perforator flap (PF) in the head and neck region between 2011 and 2020 were analysed retrospectively. Flap perfusion measured intraoperatively and postoperatively with the O2C tissue oxygen analysis system was compared between patients who had received neither ND nor RTX (controls), patients who had received ND but no RTX (ND group), and patients who had received both ND and RTX (ND+RTX group). Intraoperative and postoperative flap blood flow was decreased in FFs in ND group patients compared to controls (median 66.3 AU vs 86.0 AU, P = 0.023; median 73.5 AU vs 93.8 AU, P = 0.045, respectively). In the multivariable analysis, these differences showed a tendency to persist (P = 0.052 and P = 0.056). Flap success rates were similar in control patients, ND patients, and ND+RTX patients (98.7%, 94.0%, and 97.6%, respectively). Flap perfusion is not reduced in FFs and PFs in patients who have undergone ND or ND and RTX. This indicates that neck dissection and neck irradiation should not be contraindications for microvascular free flap reconstruction.

The primary stability of two dental implant systems in low-density bone.

Primary stability in low-density bone is crucial for the long-term success of implants. Tapered implants have shown particularly favourable properties under such conditions. The aim of this study was to compare the primary stability of tapered titanium and novel cylindrical zirconia dental implant systems in low-density bone. Fifty implants (25 tapered, 25 cylindrical) were placed in the anterior maxillary bone of cadavers meeting the criteria of low-density bone. The maximum insertion (ITV) and removal (RTV) torque values were recorded, and the implant stability quotients (ISQ) determined. To establish the isolated influence of cancellous bone on primary stability, the implantation procedure was performed in standardized low-density polyurethane foam bone blocks (cancellous bone model) using the same procedure. The primary stability parameters of both implant types showed significant positive correlations with bone density (Hounsfield units) and cortical thickness. In the cadaver, the cylindrical zirconia implants showed a significantly higher mean ISQ when compared to the tapered titanium implants (50.58 vs 37.26; P < 0.001). Pearson analysis showed significant positive correlations between ITV and ISQ (P = 0.016) and between RTV and ISQ (P = 0.035) for the cylindrical zirconia implants; no such correlations were observed for the tapered titanium implants. Within the limitations of this study, the results indicate that cylindrical zirconia implants represent a comparable viable treatment option to tapered titanium implants in terms of primary implant stability in low-density human bone.

Changes in the temporomandibular joint position depending on the sagittal osteotomy technique and extent of mandibular movement.

The bilateral sagittal split osteotomy (BSSO) and high oblique sagittal split osteotomy (HSSO) are common techniques for mandibular movement in orthognathic surgery. The aim of this study was to evaluate the influence of both techniques, as well as movement distances and directions, on the position of the temporomandibular joint (TMJ). A total of 80 mandibular movements were performed on 20 fresh human cadaver heads, four on each head. Pre- and postoperative cone beam computed tomography was used to plan the surgical procedure and analyse the TMJ. Reference measurements included the anterior, superior, and posterior joint spaces, intercondylar distances and angles in the axial and coronal planes, and the sagittal, coronal, and axial angulations of the proximal segment. Only minor differences were found between the BSSO and HSSO techniques, particularly in terms of the intercondylar angle in the axial plane (P < 0.03) and the condylar angle of the proximal segment in the sagittal plane (P < 0.011). Observed changes in the TMJ were mostly opposite when moving the mandible forwards and backwards and increased with increasing movement distance. BSSO and HSSO result in similar changes in TMJ position. The extent of the movement distance influences the position of the condyle more than the osteotomy technique.

Aesthetic aspects of adjacent maxillary single-crown implants-influence of zirconia and titanium as implant materials.

The purpose of this retrospective survey was to assess the esthetic aspects of adjacent zirconia and titanium implants in the anterior maxillary area. A total of 40 patients and 109 adjacent implants (17 patients with 47 titanium implants and 23 patients with 62 zirconia implants) was included. The primary aim of this survey was to assess the papillary fill (Jemt score). Additionally, further esthetic aspects were assessed. Papillae were fully present (Jemt score 3) around 39.1% of adjacent zirconia implants and 17.4% of adjacent titanium implants (p<0.01). The papilla deficit was significantly higher 1.64 mm (SD 1.35) around titanium compared to zirconia implants 0.92 mm (SD 0.94, p<0.01). The evaluation of the soft tissue recessions revealed no differences between implant materials, whereas titanium implants presented more visible implant shadows (p<0.01). Zirconia implants had more implants with papillae that filled the entire proximal space compared to titanium implants. Furthermore, titanium implants had a greater frequency of visible implant shadowing than the zirconia implants. Esthetic rules such as the interdental contact area and golden percentage rules did not differ significantly between the titanium and zirconia implants.

"Flipped OR": a modified didactical concept for a surgical clerkship in Oral and Maxillofacial Surgery.

The concept of the clerkship at the Department of Oral and Maxillofacial Surgery was modified into a modern and sustainable teaching model with a flipped classroom approach. The aim was to prove whether these changes increased the students' learning success. For the preparation of the clerkship, an e-learning module with 10 chapters was established. Students were supposed to access one chapter ahead of each day's seminar. A test to assess the gain in knowledge was undertaken before and after participation in the clerkship. An evaluation took place after the test. The results of the test after the clerkship were significantly higher than before (p<0.0001). The evaluation showed that the students were highly satisfied with the course in general, and the e-learning module specifically. In particular, the surgical videos helped them to better understand the operative steps. The clerkship at the Department of Oral and Maxillofacial Surgery was modified into a sustainable blended learning concept with a flipped classroom approach. With these developments, the "flipped operating room" was shown to be effective in improving knowledge and competence among undergraduate dental students.

Mechanism of action of Hic-5/androgen receptor activator 55, a LIM domain-containing nuclear receptor coactivator.

Hic-5/androgen receptor (AR) coactivator 55 (ARA55) is a group III LIM domain protein that functions as a nuclear receptor coactivator. In the present study, we examined the mechanism by which Hic-5/ARA55 potentiates glucocorticoid receptor (GR) transactivation in the A1-2 derivative of T47D breast cancer cells. Hic-5/ARA55 is an important component of GR-coactivator complexes in A1-2 cells because ablation of Hic-5/ARA55 expression by RNA interference-mediated silencing reduced GR transactivation. As shown by chromatin immunoprecipitation (ChIP) assays, Hic-5/ARA55 is recruited to glucocorticoid-responsive promoters of the mouse mammary tumor virus, c-fos, and p21 genes in response to glucocorticoid treatment. Results from sequential ChIPs established that Hic-5/ARA55 associates with GR-containing complexes at these promoters. We also used sequential ChIPs to examine Hic-5/ARA55 interactions with other well-characterized nuclear receptor coactivators and detected transcriptional intermediary factor 2, receptor-associated coactivator 3, cAMP response element binding protein-binding protein, and p300 within Hic-5/ARA55 complexes on the mouse mammary tumor virus promoter in hormone-treated cells. Ablation of Hic-5/ARA55 expression resulted in reduction of both transcriptional intermediary factor 2 and p300 recruitment to glucocorticoid-responsive promoters. Hic-5/ARA55 is also associated with the corepressor, nuclear receptor corepressor, on glucocorticoid-responsive promoters in cells not exposed to glucocorticoids. These results suggest that Hic-5/ARA55 is required for optimal GR-mediated gene expression possibly by providing a scaffold that organizes or stabilizes coactivator complexes at some hormone-responsive promoters.

Transcriptional activation by the sexual pheromone and wounding: a new gene family from Volvox encoding modular proteins with (hydroxy)proline-rich and metalloproteinase homology domains.

The green alga Volvox represents the simplest kind of multicellular organism: it is composed of only two cell types, somatic and reproductive, making it suitable as a model system. The sexual development of males and females of Volvox carteri is triggered by a sex-inducing pheromone at a concentration of < 10-16 M. Early biochemical responses to the pheromone involve structural modifications within the extracellular matrix (ECM). By differential screenings of cDNA libraries made from mRNAs of pheromone-treated Volvox, four novel genes were identified that encode four closely related Volvox metalloproteinases that we use to define a new protein family, the VMPs. The existence of several features common to matrix glycoproteins, such as signal peptides, a (hydroxy)proline content of 12-25%, and Ser(Pro)2-4 repeats, suggest an extracellular localization of the VMPs within the ECM. Synthesis of VMP cDNAs is triggered not only by the sex-inducing pheromone, but also by wounding, and is restricted to the somatic cell type. Sequence comparisons suggest that the VMPs are members of the MB clan of zinc-dependent matrix metalloproteinases, although the putative zinc binding site of all VMPs is QEXXHXXGXXH rather than HEXXHXXGXXH. The presence of glutamine instead of histidine in the zinc binding motif suggests a novel family, or even clan, of peptidases. Like the matrixin family of human collagenases, Volvox VMPs exhibit a modular structure: they possess a metalloproteinase homology domain and a (hydroxy)proline-rich domain, and one of them, VMP4, also has two additional domains. Metalloproteinases seem to be crucial for biochemical modifications of the ECM during development or after wounding in the lower eukaryote Volvox with only two cell types, just as in higher organisms.