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K A Schlegel

Publications and source records attributed to K A Schlegel.

16 recordsLinked to original sources
PubMed2006

Evaluation of substitutes for bone: comparison of microradiographic and histological assessments.

We created defects of standard size in the frontal bones of adult pigs and filled them with four different materials. On six occasions (at 1, 2, 4, 8, 12, and 26 weeks), samples were harvested, and evaluated by computing microradiographic images. We examined the specimens histologically as controls. After insertion of anorganic materials, microradiographic evaluation was easy and precise, and there were no significant differences between them and the histological controls (p=0.2). A quantitative evaluation of chemically sterilised bone by computer was not possible for more than 4 weeks.

Animals↗
PubMed2006

Expression of interleukin 1-beta, transforming growth factor beta-1, and vascular endothelial growth factor in soft tissue over the implant before uncovering.

BACKGROUND: Overexpression of inflammatory cytokines interleukin 1-beta (IL-1beta), transforming growth factor beta-1 (TGF-beta1), and vascular endothelial growth factor (VEGF) may cause healing impairment following implant insertion, jeopardizing success especially in patients previously irradiated. Limited data is available regarding expression pattern of inflammatory cytokines in peri-implant soft tissue caused by the surgical intervention itself. STUDY DESIGN: This study examined 21 patients receiving dental implants. Biopsies of peri-implant tissue were harvested at re-entry 4 months after initial surgery. Eight patients underwent probing of untreated mucosa. Three groups were created (group 1: regular peri-implant mucosa; group 2: patients with irradiated peri-implant mucosa, radiation treatment due to oral squamous cell cancer; group 3: control). Immunohistochemical staining was performed for TGFss1, IL-1ss, and VEGF. RESULTS: Following the placement of dental implants (group 1 vs group 3) a significant increase (P > .05) in TGF-beta1, IL-1beta, and VEGF expression in the peri-implant mucosa was demonstrated. No alteration of this distinct pattern was found for previously irradiated tissue (group 1 vs. group 2). CONCLUSIONS: The study highlights the fundamental involvement of TGF-beta1, IL-1beta, and VEGF during the regeneration of peri-implant soft tissue structures. The use of extended interim solutions may be one clinical implication of these prolonged tissue remodeling processes.

Adolescent↗
PubMed2005

Effect of betaTCP filled polyetheretherketone on osteoblast cell proliferation in vitro.

Non-resorbable thermoplastic polymers have become more important for reconstructive surgery due to their excellent chemical and physical properties. Polyetheretherketone-beta-tricalcium phosphate (betaTCP-PEEK) composites were developed as alternative materials for load-bearing applications. This study presents the effect of polyetheretherketone (PEEK) specimens incorporated with 5, 10, 20 and 40 wt% beta-tricalcium phosphate (betaTCP) and processed by injection molding on cultivated osteoblast cells. Normal human osteoblast (NHOst) cells were seeded onto polymer discs to evaluate cell viability and proliferation after 24, 72 and 120 h of cultivation by employing the WST-1 assay. Standard tissue culture plastic was used as a control. The osteoblast cells were found to be viable in all PEEK groups, while the cell proliferation was progressively inhibited due to the incorporated beta-tricalcium phosphate. BetaTCP-PEEK showed concentration independent decrease of cell proliferation compared to the unfilled PEEK and the control group. In summary, this study confirms the non-toxic nature of pure PEEK, whereas this could not definitely be verified for betaTCP-PEEK as a composite material in chosen concentrations of beta-tricalcium phosphate in vitro.

Benzophenones↗
PubMed2005

Onlay augmentation versus sinuslift procedure in the treatment of the severely resorbed maxilla: a 5-year comparative longitudinal study.

Augmentation procedures in the severely resorbed maxilla are standard techniques in preprosthetic surgery. Aim of the present study was to compare onlay bone grafting and sinus floor elevation with autogenous bone grafts in edentulous patients in terms of bone resorption of the posterior alveolar crest and implant survival in a 5-year longitudinal study. A total of 100 patients (53 female and 47 male patients) requiring augmentation using autogenous bone due to a severely resorbed maxillae were evaluated. The degree of resorption and bone quality were preoperatively estimated in panoramic radiographs according to Lekholm and Zarb. The overall 5-year success rate of implants placed after augmentation procedures in the posterior maxilla was 93.1%. Following onlay augmentations 215 out of 235 implant insertions were successful, i.e. a success rate of 91.5% was achieved. In the sinuslift group, 330 out 349 implants remained successful, i.e. a success rate of 94.6% was found. The difference between both groups was statistically significant at the end of the evaluation period. Bone resorption, measured as loss of total bone height in panoramic radiographs, was initially more pronounced following onlay augmentations (>20% after 12 months of observation). The degree of resorption decreased in the further course of the study. Lower resorption rates and a higher overall success rate were demonstrated for the sinus lift group.

Adult↗
PubMed2005

Expression of bone matrix proteins during de novo bone formation using a bovine collagen and platelet-rich plasma (prp)--an immunohistochemical analysis.

This animal study (domestic pig) examined the bone formation after filling defined defects with autogenous bone or a collagen lyophilisat in combination with Platelet-rich-plasma (PRP) by evaluating bone matrix proteins. Six groups, both materials with and without PRP in two concentrations (+ 1, + 2) were compared to untreated bone by means of immunohistochemistry at 2, 4, 12 and 26 weeks. BMP-2 expression was increased at 2 weeks in the collagen + 1 group and after 4 weeks in the collagen + 1 and + 2 group. Collagen-I expression was increased at 2 weeks in all collagen groups. After 4 weeks raised levels were observed after adding the higher concentrated PRP to bone and the collagen material. Osteocalcin expression was enhanced at 2 weeks in all collagen groups and the autogenous bone + PRP1 group, after 4 weeks in the bone and collagen + 2 groups. At 12 weeks higher values were observed after adding higher concentrated PRP to bone. Osteonectin and especially osteopontin were confirmed to be effective markers of early bone formation in all specimens. The described setting allows to combine established techniques (microradiography, light microscopy) with approaches to explore the underlying biology (immunohistochemistry) on the same specimen.

Animals↗
PubMed2004

[Experimental pilot study on surface activation of implants with liposomal vectors].

BACKGROUND: Surface coating with mitogenic or morphogenic proteins can improve the healing of bone adjacent to implants and increase the bone-implant interface. Clinical surveys have shown liposome-mediated gene transfer to be a promising and safe new therapeutic method. The aim of our study was to evaluate an experimental model of new approaches for topical treatment of the implant surface and of periimplant defects by using DNA liposomes encoding for BMP-2 (bone morphogenetic protein). MATERIAL AND METHODS: A total of 27 implants (3.5 x 14 mm) were placed in critically sized defects of the frontal skull bone of adult pigs (n=3). The bottom of the implant was placed in the base of the defect which guaranteed primary stability, whereas the superior part of the implant (10 mm) represented an implant in a defect area. Liposomes containing DNA encoding for BMP-2 and GFP (green fluorescence protein) were used. In a first trial GFP-DNA liposomes on a collagen matrix were directly applied to the periimplant defect. In a second stage, the surface of the implants was encoded with BMP-2 DNA liposomes. Subsequently, these implants were inserted in the manner described. The resulting bone samples were prepared for immunohistochemical staining. Staining for GFP was performed in the area of the defect and for BMP-2 on the bone-implant interface. RESULTS: Immunohistochemical staining on day 3 postoperatively revealed an increased GFP expression in the periimplant defect. Therefore, the effectiveness of the liposomal vector was verified for the chosen animal model. On the surface of the implants encoded with BMP-2 DNA liposomes an increased BMP-2 expression was found. Thus, the liposomal vector system was validated also for BMP-2 DNA transfer in the chosen animal model. Further, the established system allows a sustainable and delayed release of BMP-2 in the area of the bone-implant interface. CONCLUSIONS: As a result of the study we were able to collect data concerning the influence of implant surface conditioning on the bone-implant interface and on therapeutically relevant options for the treatment of periimplant defects. These approaches are currently being evaluated in a long-term study.

Animals↗
PubMed2004

[Applying an osteoinductive protein complex for regeneration of osseous defects].

INTRODUCTION: Growth factors are still not commercially available for routine clinical use. One possibility might be the application of Colloss, which is supposed to have osteoinductive properties. Therefore, it was the aim of the following animal experimental study to compare Colloss with autogenous bone and to investigate its osteoproductive potential. MATERIAL AND METHODS: In 24 pigs clinically relevant defects were created in the forehead area. Defects were filled with autogenous bone and Colloss. One defect was left unfilled and served as control. After 2, 4, 12 and 26 weeks, six animals were sacrificed and microradiography, light microscopy and immunohistochemistry were carried out using BMP-2 and osteocalcin as antibodies. RESULTS: After 2 weeks the defects filled with the bovine protein complex showed a mineralization of 52.6% +/-4.03 compared to autogenous bone (38% +/-9.9; p=0.068) and the control defect (30% +/-2.94; p=0.05). After 4 weeks the results became assimilated. Light microscopy revealed especially after 2 weeks an enhanced de novo bone formation in the Colloss-group. This was also evident in an early expression maximum of BMP-2 after 2 weeks. Autogenous bone and the control defect showed a later expression maximum. CONCLUSION: Colloss showed an acceleration of bone regeneration in the early phase. Nevertheless, after 26 weeks the results were comparable with the autogenous bone group.

Animals↗
PubMed2004

De novo bone formation using bovine collagen and platelet-rich plasma.

In order to regenerate critical-size bone defects, a variety of bone substitutes is used in addition to autogenous bone. The regenerative capacity of these bone substitutes is usually compared to the efficacy of autogenous bone known as the "golden standard". Different cytokines influence the regeneration process because of their morphogenic or mitogenic properties. Platelet-rich plasma (PRP), a platelet concentrate, is characterised by having a positive effect on wound healing, reducing bone graft resorption and increasing the density of bone transplants. This experiment was commenced with a view to studying the osseous defect regeneration after placing various combinations of "filler materials" in experimentally created defects in the forehead of adult pigs. Regeneration by means of grafted autogenous bone (Group 1) or a bovine collagen based medical device (Group 4) alone and combined with PRP in two concentrations (Groups 2, 3, 5 and 6) was evaluated by means of microradiography and light microscopy after 2, 4 and 12 weeks. The microradiographic and light microscopic findings showed that autogenous bone in combination with PRP (Groups 2 and 3) had a significant accelerating effect on early bone regeneration (2 weeks). This effect was not evident when PRP was added to the bovine collagen (Groups 5 and 6). When using the collagen alone, significantly higher mineralisation values were achieved after 2 and 4 weeks than when using autogenous bone alone. After a 12-week observation period, the existing differences between the healing processes in the various groups were more or less levelled out. In summary, the results of the study indicate that clinically autogenous bone, as expected, is the ideal defect filler. Combining autogenous bone with PRP did not provide significantly better results. The findings in the groups treated with bovine collagen indicate that its local application mimics the effect of autogenous bone and amplifies bone regeneration when comparing with the control defect.

Animals↗
PubMed2003

[In vitro effect of taurolidine on squamous cell carcinoma in the oral cavity].

Taurolidine (Taurolin) is a derivative of the amino acid taurine, successfully used in the treatment of peritonitis. In vitro and in vivo studies have shown that taurolidine inhibits cell proliferation and induces apoptosis in a variety of tumor cell lines. At present there are no published studies on the use of taurolidine in the treatment of squamous cell carcinoma. Our aim was to examine the inhibition of cell proliferation and induction of apoptosis in cell lines SCC 4 and SCC 15 treated with taurolidine in concentrations of 0.01%, 0.1%, and 0.5%. Analogue to the present investigations on adenocarcinoma cell lines, we used toxic antiseptic povidone iodine in the same concentration as for the reference group. Untreated cells were used as a control group. The cells were incubated with taurolidine or povidone iodine once for 2 h at 37 degrees C in 5% CO(2). Cell proliferation was assessed using WST-1 labeling kit after 3, 24, 48, 72, and 96 h. The additional measurement of cell apoptosis was examined using ELISA(PLUS) cell death detection kit and performed after 0, 24, and 48 h. The findings showed a significant inhibition of cell proliferation and induction of apoptosis in taurolidine-treated cells SCC 4 and SCC 15 in contrast to the reference group treated with povidone iodine or the untreated control group.

Antineoplastic Agents↗
PubMed2003

[Osseous defect regeneration using autogenous bone alone or combined with Biogran or Algipore with and without added thrombocytes. A microradiologic evaluation].

In addition to autogenous bone, a variety of bone substitute materials is used to regenerate bony defects. The aim of the study was to evaluate the reossification of critical size defects in the os frontale of adult pigs ( n=16) with microradiography. The defects were filled randomly with autogenous bone or the bone substitute materials Algipore and Biogran each combined with a defined quantity of autogenous bone. Additionally, platelet-rich plasma (PRP) was added in defined quantities (0.5 ml) in two different concentrations (4-fold and 6.5-fold). At 2, 4, 12, and 26 weeks four animals were sacrificed and the osseous regeneration documented by quantitative evaluation of the microradiographic findings. Microradiographic results in the autogenous bone group showed an earlier PRP concentration-dependent mineralization. Over the whole observation period the peak value of autogenous bone as filler alone could not be reached in both PRP groups. Using Algipore, no accelerated effect of mineralization however could be observed. In our study, Biogran proved to be a defect filler only partially suitable for bony defect healing, no matter whether PRP was added or not.

Alginates↗
PubMed2002

Degradation characteristics of alpha and beta tri-calcium-phosphate (TCP) in minipigs.

In seven Goettingen minipigs 3.5--4.7-ml cancellous bone defects were created in the area of the tibial head on both sides. The defects were filled with alpha-TCP or beta-TCP (tricalciumphosphate). ITI implants (Straumann, Freiburg, Germany) of 3.2 x 12-mm length were inserted into the underlying ceramic substitutes. Two additional pigs were used as control. Within the periods of observation (4, 16, 20, 28, 46, 68, and 86 weeks) fluorescent dyes were applied. Nondecalcified thin-sliced sections were examined by means of light and fluorescence microscopy. In addition microangiography and microradiography were performed. Bony regeneration occurred basally and on the sides of the defect according the angiogenetic reossification pattern. Resorption was due to a hydrolytic and cellular degradation process. After 46 weeks histomorphological evaluation showed an incomplete osseointegration of the simultaneously implanted dental implants. The bone contact surface ratio was lower than 25%. After 86 weeks 95--97% of both alpha- and beta-TCP were resorbed. Ceramic residuals stayed within the newly formed trabeculae thus resisting further degradation until remodeling occurred. Both alpha- and beta-TCP show a comparable degradation process. At the 86-week postoperative point only small residuals of the ceramic can be found. These residuals stay within the newly formed trabeculae, which show a functional orientation. In comparison control defects showed only sparse reossification. The beta-TCP material shows an accelerated degradation mode and has an optimal reactivity with the surrounding tissues. According to the results of this animal experiment both materials can be classified as bone-rebuilding materials.

Animals↗
PubMed2002

[Implantology in oromaxillofacial surgery].

Since the last 30 years endosseous implants are a well established treatment technique in maxillofacial surgery. Implants are used in the rehabilitation of patients having lost parts of maxilla or mandible due to tumor surgery, or which due to radiotherapy have problems tolerating mucosa-borne dentures. The implant borne prosthesis will aid to regain live quality to those patients. Improvement of live quality is also the result when epithetic reconstructions of soft tissue defects in the face are stabilized by extraoral implants. Aim of the paper is to give an overview on important implant related pathophysiological osseous healing patterns, discuss methods to influence these processes, to show correction possibilities for the bony bed and highlight their indications as well as to inform about clinical experiences with endosseous implants.

Dental Implantation, Endosseous↗
PubMed2002

Soft tissue findings above submerged titanium implants--a histological and spectroscopic study.

The aim of this study was to check the titanium level within the muco-periosteal flaps covering submerged titanium implants. The investigated material included 38 biopsies taken after 2.4-18 months (mean: 5.9) after implant insertion. Due to the evident time delay between implantation and taking the biopsy any influence of the implantation trauma itself was excluded. The implants came from the following producers: HaTi (Matthys, Switzerland), ITI (Straumann, Switzerland) and Branemark (Nobelbiocare. Sweden). The surface areas of these implants differ in size and structure. A comparison between the titanium impregnation of the investigated biopsies did not demonstrate any remarkable influence of the surface differences. This can be explained by the fact that only the top diameter and not the implant surface as a whole was the contact area with the excised tissue. Titanium in the biopsies was analysed in terms of its effect histologically and regarding the titanium quantity by spectrophotometry. Even the highest titanium contamination was without a negative effect on the muco-periosteal cover flaps. A correlation between time delay between implantation and biopsy or of the titanium amount and tissue reactions was not demonstrable. In summary, the results again highlighted the biological acceptance of titanium.

Biocompatible Materials↗
PubMed2000

Clinical and histological findings in guided bone regeneration (GBR) around titanium dental implants with autogeneous bone chips using a new resorbable membrane.

The aim of this study was to test the value of a polydioxanon-membrane (PDS(R), Ethicon, Norderstedt, Germany) in combination with autogenous bone as a spacer for guided bone regeneration of denuded implant surfaces in comparison to simple augmentation. Altogether, in 8 Beagle dogs of 12 months, the three mandibular premolars were extracted on both sides and, after an uneventful healing of the extraction sockets in each mandibular site, two seize defined bone defects were produced. The defects were 7 mm long, had a vertical extension of 7 mm, and were 7 mm deep. These also included, therefore, the resection of the lingual cortical bone wall. In the center of all these 32 bone defects, Brânemark fixtures with a diameter of 3 mm and a length of 10 mm were implanted. Every implant was primarily stable due to the fixation in the native bone under the created defects. In each mandible site, one bone defect was filled with autologous bone resulting from the previous defect preparation. Half of the defects were covered with a PDS membrane, and the other half were covered only by the relocation of the mucoperiosteal flap. During the observation period of 90-180 days, continuous clinical and radiological controls were executed. Aside from the observed clinical healing problems in the test sites, such as exposure of the membranes and serious inflammatory reactions, the histological and radiological results of the control group regarding bone regeneration were superior to these of the test group, which were valid also for the subgroups with or without autologous bone fillings.

Animals↗
PubMed1996

Endosseous dental implants in orthodontic therapy.

This paper presents cases in which endosseous titanium implants are used in orthodontic treatment as an alternative method of providing anchorage, as well as solving prosthodontic problems, and shows that such an approach can be successful.

Anodontia↗