Biomedical subjects

Peter Kessler

Publications and source records attributed to Peter Kessler.

At least 19 recordsLinked to original sources

PubMed2006

Characterization of glycosomal RING finger proteins of trypanosomatids.

The glycosomes of trypanosomatids are essential organelles that are evolutionarily related to peroxisomes of other eukaryotes. The peroxisomal RING proteins-PEX2, PEX10 and PEX12-comprise a network of integral membrane proteins that function in the matrix protein import cycle. Here, we describe PEX10 and PEX12 in Trypanosoma brucei, Leishmania major, and Trypanosoma cruzi. We expressed GFP fusions of each T. brucei coding region in procyclic form T. brucei, where they localized to glycosomes and behaved as integral membrane proteins. Despite the weak transmembrane predictions for TbPEX12, protease protection assays demonstrated that both the N and C termini are cytosolic, similar to mammalian PEX12. GFP fusions of T. cruzi PEX10 and L. major PEX12 also localized to glycosomes in T. brucei indicating that glycosomal membrane protein targeting is conserved across trypanosomatids.

Amino Acid Sequence↗

PubMed2006

Dynamic periosteal elevation.

The osteoinductive potential of the periosteum can be stimulated by raising the periosteum using a type of distraction. This was tested and confirmed in an animal experiment in 6 Goettingen minipigs. A titanium mesh was implanted beneath the periosteum and then raised. Bone formed underneath the mesh, with rows of micro-pillars similar to those found after osteodistraction. The main advantages of dynamic periosteal elevation are that invasion and morbidity are minimal. Clinically it might be applicable in craniomaxillofacial surgery, in augmentation before implantation, and in reconstruction of the skull.

Animals↗

PubMed2006

Expression of ets-1 is not affected by N-ras or H-ras during oral oncogenesis.

PURPOSE: To determine whether ras-activated cascades lead to activation of ets-1 expression in sequential histological stages of oral oncogenesis in an experimental animal model. METHODS: Thirty-seven Syrian golden hamsters were divided into three experimental groups (A, B, C) and one control group. The hamsters' buccal pouches in experimental groups were treated with 0.5% 9, 10-dimethyl-1, 2-benzanthracene (DMBA) for 14 weeks and were excised at 10, 14, 19 weeks, respectively. The biopsies were classified pathologically (normal mucosa, hyperkeratosis, hyperplasia, dysplasia, early invasion, well and moderately differentiated carcinoma) and studied immunohistochemically. The two-tailed Student's t test was performed for each animal group and for each histological category. RESULTS: The ets-1 expression increased in early stages of oral tumor formation and invasion. The expression of N-ras gradually decreased during oral oncogenesis, as previously observed with H-ras. CONCLUSIONS: Neither N-ras nor H-ras affects ets-1 expression in contrast to other types of cancer in which N-ras and ets-1 are implicated in the same signalling pathway. Therefore, the existing pathway implicating these proteins might be somehow altered in oral cancer. It seems that ets-1 is a good prognostic marker for invasiveness and progression of oral cancer.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2006

Is there a need for autogenous blood donation in orthognathic surgery?

BACKGROUND: The present study sought to determine the frequency of blood transfusion and to evaluate the need for autogenous blood donations in patients undergoing bimaxillary orthognathic surgery. METHODS: According to an inclusion and exclusion protocol, 65 patients were selected for further analysis. Twenty-six patients donated a total of 45 units of autogenous blood; the remaining 39 patients did not. Medical records were reviewed retrospectively. RESULTS: Donors tended to have lower preoperative, intraoperative, and postoperative hemoglobin values, as well as lower hematocrit and leukocyte counts. Only the difference in mean preoperative leukocyte count, however, was statistically significant (donor: 6500/microl versus nondonor: 7400/microl; p = 0.021). The rate of transfusion was 2.5 percent for nondonors and 13 percent for donors of autogenous blood. Six donors had to be transfused a total of 8 units of autogenous blood, whereas only one of 39 nondonors received an allogenic blood transfusion. This difference turned out to be significant according to Fisher's exact test (p = 0.013). None of the donors received allogenic blood transfusion. CONCLUSIONS: In the authors' analysis, preoperative autogenous blood donation appears to be effective in reducing exposure to allogenic blood. Donors of autogenous blood, however, were transfused significantly more often than nondonors were. Neither intraoperative blood loss nor hematological values justify a preoperative donation of autogenous blood on a regular basis.

Adult↗

PubMed2006

Influence of platelet-rich plasma on a bioglass and autogenous bone in sinus augmentation. An explorative study.

Platelet-rich plasma (PRP) has been introduced to the field of oral and maxillofacial surgery for a decade, but its beneficial effects on maxillary sinus augmentation remain unclear. The aim of this study was to evaluate the short- and long-term effects of PRP on osseointegration following single-stage sinus augmentation in a randomized prospective animal study. The maxillary premolars of 24 minipigs were extracted bilaterally and allowed to heal for 2 months. Consecutively all animals underwent bilateral sinus floor elevation using autogenous bone, Biogran as well as a combination of the materials with PRP. Three dental implants (Ankylos, Dentsply Co., Mannheim, Germany) were installed in each sinus simultaneously. Four animals were sacrificed at each period of observation (1, 2, 8 and 12 months). Microradiographic images of the specimens were made for quantitative evaluation of the bone-implant contact (BIC) and light microscopic images were made for qualitative analysis. An increment of the BIC during the observation time could be seen over the observation time in all groups. Autogenous bone exhibited a level of BIC from 25.1 +/- 9.96% at 1 month to 55.1 +/- 13.10% at 12 months; on adding PRP, the BIC ranged from 28.4 +/- 4.64% to 52.5 +/- 17.06%. Biogran with and without PRP led to BIC levels from 16.3 +/- 4.64% to 37.6 +/- 16.40% and 21.7 +/- 4.33% to 46.6 +/- 19.37%, respectively. The results of this study did not show a significantly positive effect of PRP on the BIC following sinus augmentation in both groups.

Alveolar Ridge Augmentation↗

PubMed2006

Lack of beneficial effects of platelet-rich plasma on sinus augmentation using a fluorohydroxyapatite or autogenous bone: an explorative study.

BACKGROUND: Maxillary sinus augmentation is frequently necessary before placement of dental implants in the posterior maxilla. Besides autogenous bone graft, various bone substitutes have been used, with favourable results. Although platelet-rich plasma (PRP) has been used in the field of oral and maxillofacial surgery for years, its beneficial effects on osseous regeneration still remain unclear. The aim of this study was to evaluate the short and long time effects of PRP on single-stage sinus augmentation using autogenous bone or a fluorohydroxyapatite (Algipore) in a randomized prospective animal study. METHODS: After extraction of maxillary premolars of sixteen minipigs, the wounds were allowed to heal for 2 months. Then, sinus augmentations were performed bilaterally using one of the following grafting materials: autogenous bone and Algipore with or without PRP. Three dental implants (Ankylos) were installed in each sinus simultaneously. Four animals were euthanized at each period of observation (1, 2, 8 and 12 months). Implant-bearing specimens were sectioned bucco-lingually along the long axis of implants and undecalcified ground specimens were prepared. The bone-implant-contact (BIC) was measured by means of microradiographic examination. For histological evaluation, the specimens were stained with toluidin blue, and the percentage of the newly formed bone and the remaining bone substitute were evaluated. RESULTS: The grafting materials chosen showed increasing levels of BIC and newly formed bone throughout the period of observation in both PRP and non-PRP groups. Adding PRP resulted in lower BIC and newly formed bone compared with autogenous bone grafts or Algipore alone. However, a statistical significance was not found. The percentages of the remaining bone substitute in both the PRP and non-PRP groups were closely comparable in all observation periods. CONCLUSIONS: The application of PRP could not reveal significant beneficial effects on the BIC, the percentage of the newly formed bone and the remaining bone substitute in this study.

Animals↗

PubMed2005

Bioactivation of an anorganic bone matrix by P-15 peptide for the promotion of early bone formation.

This animal experiment compared the regenerative processes within defined bony defects of the porcine skull after delivery of routinely utilized bone graft materials: anorganic bone matrix (ABM) and an identical ABM carrying the cell binding peptide P-15. Particulated autogenous bone was used as a control group. The chosen porcine model guaranteed the transferability of the obtained results to clinical practice. A total observation period of 6 months was defined. The bone samples were examined microradiographically and histologically at 8 specific times. Sufficient osseointegration and osseoconduction could be demonstrated for both anorganic bone minerals. However, in the selected model significantly higher mineralization rates (p = 0.0286) were found in the microradiographic image at 12 weeks after application of the bioactive form. The histological examination confirmed this accelerating effect on bone formation starting at day 3. At the end of the study after 6 months, the mineralization values had equalized in both study groups. For the first time, the material was demonstrated to be suitable as a bone substitute material for the treatment of larger bony defects in a large animal model. The P-15 sequence accelerated the process of bone formation on the surface of the anorganic bone matrix as early as 3 days but was not traced over the whole term of the study.

Animals↗

PubMed2005

Hemoglobin value reduction and necessity of transfusion in bimaxillary orthognathic surgery.

PURPOSE: It has been the aim of the present clinical study to assess the reduction of the hemoglobin value and the frequency of blood transfusions during bimaxillary orthognathic surgery and to discuss the clinical consequences. PATIENTS AND METHODS: Fifty-six patients (31 female, 25 male; mean age, 28.6 +/- 13.0 years; range, 14 to 66 years) were operated on. Twenty-nine patients predeposited blood before surgery. As a threshold for intraoperative or postoperative transfusion, a hemoglobin value of 7.5 g/100 mL was chosen. RESULTS: Perioperatively, the hemoglobin values of the patients who predeposited blood decreased significantly after blood donation. The hemoglobin value reduced postoperatively by 2.6 +/- 1.4 g/100 mL in the non-donors and by 2.6 +/- 1.1 g/mL in the donors. None of the patients who did not predeposit blood received homologous blood transfusions intraoperatively or postoperatively. In the group of patients who predeposited blood, 3 were transfused intraoperatively. They received 1 or 2 units of autologous blood. CONCLUSION: The individual statistics of the department show that there was only a limited reduction of the intraoperative and postoperative hemoglobin values as a consequence of bimaxillary orthognathic surgery. The increased safety of homologous blood and the minimal transfusion rates support abandonment of routine predepositing of autologous blood and the acceptance of homologous blood in the rare case of transfusion in bimaxillary surgery.

Adolescent↗

PubMed2005

Bone regeneration in osseous defects using a resorbable nanoparticular hydroxyapatite.

PURPOSE: This animal study examined the de novo bone formation in bony defects following the insertion of autogenous bone alone versus an injectable nanoparticle hydroxyapatite alone and in combination with 25% autogenous bone. The regenerative potentials of the tested materials were compared with each other. MATERIALS AND METHODS: A model with biological similarity to humans with regard to bone regeneration was a prerequisite for the transferability of the results to clinical practice. Therefore, the adult domestic pig was the animal of choice. A total observation period of 6 months was selected. Microradiographic and histologic evaluation of the bone specimens was completed at 8 defined times. RESULTS: Microradiography indicated mineralization rates in the 2 bone substitute groups that were not significantly lower than those found in the autogenous bone group. Histologically, there was suitable osseointegration and osteoconduction of the used material. Complete resorption of the nanoparticle hydroxyapatite had taken place after 12 weeks. CONCLUSIONS: It can be concluded that the evaluated nanoparticular hydroxyapatite met the clinical requirements for a bone substitute material within the limits of this experimental setting. Due to its microstructure, complete resorption took place during the course of this study.

Absorbable Implants↗

PubMed2005

Stability of autogenous bone grafts after sinus lift procedures: a comparative study between anterior and posterior aspects of the iliac crest and an intraoral donor site.

BACKGROUND: Autologous bone is the standard material used for augmentations in oral-maxillofacial surgery. Depending on the origin of the graft, subsequent bone resorption may vary. STUDY DESIGN: This prospective study evaluated 57 patients receiving 2-stage sinus floor augmentations. Monocortical samples were taken at the site of bone harvesting, including the posterior (n = 28) and anterior pelvic (n = 15) and retromolar (n = 14) regions. At second-stage surgery, 6 months after the implant insertion, bone cores were harvested at the site of implant placement. All samples were analyzed by microradiography. RESULTS: Mean retromolar mineralization was 68.7% +/- 8.75%; 35.1% +/- 7.6% in the anterior and 30.7% +/- 9.5% in the posterior iliac crest. Areas augmented with grafts originating from the retromolar region showed a significant decrease to 53.0% +/- 5.15% (P = .001). A stable mineralization of 36.1% +/- 7.59% was found in sites where bone grafts from the anterior pelvic crest were used. Grafts from the posterior pelvis showed a slight increase to 34.5% +/- 6.5%. CONCLUSION: This prospective clinical study demonstrates the differences in mineralization depending on the origin of autogenous bone. Even after 6 months, these values could still be correlated to the transplants origin.

Alveolar Ridge Augmentation↗

PubMed2004

Reconstruction of skull bone defects using the hydroxyapatite cement with calvarial split transplants.

PURPOSE: We sought to present a new method for primary reconstruction of traumatic or tumor calvarial defects. PATIENTS AND METHODS: Forty-one patients underwent reconstruction of calvarial bone defects between October 1998 and December 2001. Among them were 19 patients who needed reconstruction of the calvaria due to traumatic bone loss. Five of these trauma cases had insufficient primary reconstruction of the calvaria. Tumor resection caused calvarial defects in 22 patients. For primary reconstruction of the skull bone defects, calvarial split grafts were used to cover the defect as accurately as possible. The monocortical layers of the calvaria were fixed with titanium miniplates. Irregular defects surrounding the transplanted regions were filled with hydroxyapatite cement. In one case of posttraumatic bone loss, hydroxyapatite cement alone was sufficient to reconstruct the defect. RESULTS: The follow-up of each patient was at least 6 months; the longest period was 38 months. Evaluated clinical and radiologic results are stable, showing no measurable side effects. CONCLUSION: Hydroxyapatite cement alone or in combination with calvarial split grafts gave clinically and aesthetically stable results in the reconstruction of skull bone defects. The cement can be used for many reconstruction possibilities in craniofacial surgery.

Adult↗

PubMed2004

Effects of platelet-rich plasma on bone healing in combination with autogenous bone and bone substitutes in critical-size defects. An animal experiment.

OBJECTIVES: An animal study was carried out to investigate the influence of platelet-rich plasma (PRP) on the regeneration of bony defects. MATERIAL AND METHODS: Critical-size defects in the forehead region of a mini-pig were filled with randomly distributed combinations of autogenous bone, tricalcium-phosphate granules (CeraSorb), bovine spongious blocks (BioOss) and a bovine bone inducing collagenous sponge (Colloss) with and without PRP in two preparations (Cusasan, 3i). The animals were killed after 2, 4 and 12 weeks. The specimens were evaluated microradiographically and immunohistologically. RESULTS: Autologous bone (38 +/- 9.9%) and Colloss (52.6 +/- 4.0%) showed the highest remineralization rates at 2 weeks. The initial high expression of BMP-2 in the Colloss-group gives evidence of an early initiation of bony regeneration. At 2 weeks PRP ad modum 3i was able to enhance bone healing significantly (P=0.028) only when applied in combination with autogenous bone (62.8 +/- 1.6%). Four weeks after surgery, both PRP preparations did no longer increase bony regeneration in the autogenous groups. The osteoconductive effect of Bio-Oss (38.7 +/- 5.5%) and CeraSorb (41+/-4.9%) was remarkable as well 4 weeks after surgery. Nevertheless, the addition of PRP hardly influenced bony regeneration, ceramic degradation or cytokine expression when bone substitutes were applied. At 12 weeks, the level of reossification had adjusted similarly in all groups. CONCLUSION: PRP did not add additional benefit when xenogenic bone substitutes were used. However, a significant effect on bone regeneration was found in the autogenous group initially when PRP is added.

Animals↗

PubMed2003

Lengthening of the reconstructed mandible using extraoral distraction devices: report of five cases.

Fibular and scapular osteocutaneous free-tissue transfer represents the workhorse procedure in the reconstruction of large oromandibular defects. However, transplanted bone segments for mandibular reconstruction may be too short for a correct interarch alignment, which is a prerequisite for further functional rehabilitation. Extraoral distraction osteogenesis was performed in the neomandible of five patients after tumor resection following neoadjuvant radiotherapy-chemotherapy. The neomandible was distracted bilaterally in two patients and unilaterally in three patients. Gradual distraction was applied at a rate of 0.5 mm twice a day after osteotomy in the region of vascularized fibular and scapular reconstruction. An average sagittal bone gain of 11 mm was achieved following active distraction. In three patients, the distraction procedure rendered good results with full compensation of the deficit; in one patient, the sagittal bone gain did not compensate for a lateral deviation of the mandible; and in another patient, the fixation pins loosened and had to be reaffixed. Osteodistraction is a treatment option in patients in whom vascularized bone grafts have been used for mandibular reconstruction, but due to contractures or lack of hard and soft tissues, no satisfactory interarch alignment could be achieved. Distraction procedures in irradiated and reconstructed neomandibles bear a higher risk of failure and complications than those in nonirradiated tissues. A correct and stable intermaxillary relation always has to be attempted in the first surgical approach, as osteodistraction cannot be suggested as a routine procedure in this special group of patients.

Bone Transplantation↗

PubMed2003

[Evaluation of quality of life of patients with oral squamous cell carcinoma. Comparison of two treatment protocols in a prospective study-first results].

BACKGROUND: The treatment of oral cancer has a strong impact on the quality of life. In recent years different therapeutic concepts have been developed, these include preoperative simultaneous "neoadjuvant" radiochemotherapy (RCT) and one-stage surgery with tumor ablation and reconstruction. When considering long-term survival, there is substantial evidence that evidenced modality treatment including neoadjuvant RCT is superior to the primary surgical approach with postoperative radiation. PATIENTS AND METHODS: This longitudinal study prospectively evaluates quality of life in two groups consisting of 53 neoadjuvant and primarily surgically treated patients with oral cancer, using the quality-of-life core questionnaire (QLQ-C30) and the head and neck cancer module (H and N 35) of the European Organization for Research and Treatment of Cancer (EORTC). RESULTS: Postoperatively both groups showed a marked reduction in quality of life. 1 year later quality of life had equalized between the two groups to such an extent that the quality of life scores had almost reached the preoperative level. Both groups showed specific impairments in the symptom scales. In the neoadjuvant therapy group however, global health and the emotional status were reduced to a greater degree than in the other group. CONCLUSION: Temporary limitations in quality of life can be expected after tumor treatment of oral cancer as presented here. Neoadjuvant therapy concept is more aggressive and might result in a longer disease-free survival, but the restriction in quality of life is more severe. Primary goal is the eradication of the tumor. Nevertheless preservation or reconstruction of a maximum of function is essential for a high level of quality of life.

Adult↗

PubMed2003

Er:YAG laser osteotomy directed by sensor controlled systems.

BACKGROUND: Great efforts have been taken in the past to develop laser systems suitable for bone cutting. Laser systems emitting light in the infrared spectrum (2.9, 3.0 microm) have been found to be ideal for efficient bone ablation with very little carbonization. AIM: To evaluate a new laser bone cutting system enabling the automatic detection of different tissue qualities by an integrated sensor to avoid damage to sensitive structures such as blood vessels or nerves. MATERIAL: An Erbium:YAG laser containing an integrated closed-loop control system, was constructed and tested on dissected bone. Process emissions such as resonance changes caused by the interaction of laser light and various tissue structures can be used for a controlled system. Sensor signals from a photodiode and a piezo-electric accelerometer were received and processed to guide the laser osteotomy. METHODS: Tests were performed on dissected bone specimens from rabbit femur (14) and minipig jaw (6). After laser application, the bone specimens were evaluated macroscopically and histologically. RESULTS: The specimens were evaluated histomorphometrically for the depth of cortical bone ablation when the closed-loop control system switched off the laser. Mean courses of 97.45% (pig) and 97.83% (rabbit) showed that the systems work with precision. CONCLUSION: After penetrating the cortical bone layer, the laser beam was promptly interrupted due to extreme changes of the signal character received by the sensor system. The in vitro tests of this new laser closed-loop control system were successful.

Aluminum Silicates↗

PubMed2003

Hydroxyapatite cement (BoneSource) for repair of critical sized calvarian defects--an experimental study.

AIM: In an experimental study the hydroxyapatite cement BoneSource was tested for the ability in relation to the defect size and for its resorption properties. MATERIAL AND METHODS: In an animal study, BoneSource was applied to repair bicortical defects of different sizes in frontal bones of six Goettingen minipigs. The area was evaluated radiographically and histologically 12, 18 and 40 weeks postoperatively. RESULTS: After 40 weeks approximately 90% of the hydroxyapatite cement had been resorbed and replaced with bone. After 12 weeks, approximately 30% had been degraded, and 40% after 18 weeks. In small bone defects, the mucosa of the frontal sinus lined the bone substitute (BoneSource). In the reconstruction of large areas, a membrane was used to stabilize the material. Despite this membranous support, BoneSource material prolapsed into the frontal sinus. DISCUSSION: Hydroxyapatite cement is for the repair of bone defects. It can be moulded to shape the reconstruction. Its use is limited by the defect size and the need for a dry bed. CONCLUSION: BoneSource is well suited to repair small defects with proven high biocompatibility. However, in large defects, the material is not sufficiently stable.

Animals↗

PubMed2003

Sinus floor augmentation with beta-tricalciumphosphate (beta-TCP): does platelet-rich plasma promote its osseous integration and degradation?

When dental implants are to be inserted, sinus floor augmentation is an effective treatment procedure to improve bone height in the posterior maxilla. In addition to autogenous bone material, allogenic materials, e.g. beta-tricalciumphosphate (beta-TCP), have been used successfully. The purpose of this study was to investigate whether the combination of beta-TCP with platelet-rich plasma (PRP) enhances bony regeneration and resorption of the tricalciumphosphate material. In a randomized prospective trial, 45 sinus floor elevations were performed in 39 patients. In 22 sites, PRP was added to the beta-TCP granules, while in 23 sites beta-TCP without PRP was used. Six months later, bone specimens were harvested from the augmented region during the implant insertion procedure. The formation of new bone was about 8-10% higher when PRP was applied. A faster degradation of the ceramic bone substitute was not observed. In conclusion, when PRP was added to beta-TCP, bone regeneration was supported to a small extent. However, the resorption of beta-TCP was not accelerated and foreign-body giant cells and soft tissue surrounding the beta-TCP granules were present.

Absorbable Implants↗

PubMed2003

Validation of in vivo assessment of facial soft-tissue volume changes and clinical application in midfacial distraction: a technical report.

The purpose of this study was to validate the assessment of visible volume changes of the facial soft tissue with an optical three-dimensional sensor and to introduce new parameters for the evaluation of the soft-tissue shape achieved from three-dimensional data of selected cases of midfacial distraction. Images of a truncated cone of known volume were assessed repeatedly with an optical three-dimensional sensor based on phase-measuring triangulation to calculate the volume. Two cubic centimeters of anesthetic solution was injected into the right malar region of 10 volunteers who gave their informed consent. Three-dimensional images were assessed before and immediately after the injections for the assessment of the visible volume change. In five patients who underwent midfacial distraction after a high quadrangular Le Fort I osteotomy, three-dimensional scans were acquired before and 6 and 24 months after the operation. The visible soft-tissue volume change in the malar-midfacial area and the mean distance of the accommodation vector that transformed the preoperative into the postoperative surface were calculated. The volume of the truncated cone was 235.26 +/- 1.01 cc, revealing a measurement uncertainty of 0.4 percent. The injections of anesthetic solution into the malar area resulted in an average visible volume change of 2.06 +/- 0.06 cc. The measurement uncertainty was 3 percent. In the five patients, the average distance of maxillary advancement was 6.7 +/- 2.3 mm after 6 months and 5.4 +/- 3.0 mm after 2 years. It was accompanied by a mean visible volume increase of 8.92 +/- 5.95 cc on the right side and 9.54 +/- 4.39 cc on the left side after 6 months and 3.54 +/- 3.70 cc and 4.80 +/- 3.47 cc, respectively, after 2 years. The mean distance of the accommodation vector was 4.41 +/- 1.94 mm on the right side and 4.74 +/- 1.32 mm on the left side after 6 months and 1.62 +/- 1.96 mm and 2.16 +/- 1.52 mm, respectively, after 2 years. The assessment of visible volume changes by optical three-dimensional images can be carried out with considerable accuracy. The determination of volume changes and accompanying accommodation vectors completes the cephalometric analysis during the follow-up of patients undergoing midfacial distraction. The new parameters will help to assess normative soft-tissue data on the basis of three-dimensional imaging with a view to an improved three-dimensional prediction of the operative outcome of orthognathic surgery.

Adolescent↗