Primary implant stability after maxillary sinus augmentation with autogenous mesenchymal stem cells: a biomechanical evaluation in rabbits.

OBJECTIVES: To mechanically evaluate the effect of transplantation of precultured preosteoblasts derived from autogenic adult mesenchymal stem cells (aMSC) for experimental sinus floor augmentation on primary dental implant stability in comparison with conventional augmentation procedures in rabbits. MATERIAL AND METHODS: After experimental sinus floor augmentation with a synthetic bone substitute, autogenous bone transplantation or osteoblast precursor cells, the primary stability of implants inserted in the edentulous part of the upper jaw of New Zealand White Rabbits was examined. Mechanical evaluation was performed by determination of insertion torque values (Osseocare(™) ), percussion testing (Periotest(™) ), resonance frequency analysis (Osstell(™) and scanning laser Doppler vibrometer) and measurement of extraction forces. RESULTS: Evaluation of mechanical properties with percussion testing and resonance frequency analysis with Osstell(™) revealed slightly higher primary stability of the stem cell group whereas the scanning laser Doppler vibrometer and measurement of pull-out forces showed no significant difference to the bone substitute group. Transplantation of autogenous bone graft resulted in the highest primary implant stability. CONCLUSIONS: The three examination modalities proved suitable for the determination of primary implant stability. The experimental maxillary sinus floor augmentation with precultured osteoblast precursor cells from autogenic stems cells clearly enhanced the primary stability of implants compared with the unaugmented sinus and lead to comparable primary mechanical properties to bone substitutes in rabbits. In comparison with the autogenous bone graft stability enhancement by stem cell transplantation declined.

Primary osteoplasty using calvarian bone in patients with cleft lip, alveolus and palate.

PURPOSE: The results of primary bone grafting in terms of initial cleft width, existence or absence of a lateral incisor and scar formation in the donor area are compared. METHODS: After primary osteoplasty with calvarian bone at an average age of 24 months (4-56 months) radiographic assessment was carried out in 31 patients with 40 alveolar clefts. The bone formation in the grafted area was assessed using dental radiographs taken at 66 months on average (13-114 months) after primary bone grafting. According to the Abyholm classification patients were assigned to 4 groups (indices I-IV) with indices I and II being rated as a success. RESULTS: We observed success (indices I and II) in 76% and poor results (index IV) in 14%. The causes for the poor results were an alveolar cleft width of 11-12 mm in three cases, an extraction of a decayed deciduous tooth 17 months after bone grafting in one case and a traumatic transplant loss in another case. The non-existence of a lateral incisor and a broad cleft are related to poor results. CONCLUSION: Based on the results presented, primary bone grafting using calvarial bone seems to be a promising alternative in bridging narrow alveolar defects. This method allows early intervention at an age in which children do not recognize themselves as cleft patients. The preservation of the deciduous teeth is equally important regarding their functional stimulus for bone development.

Conditioning of myocutaneous flaps.

PURPOSE: The improvement of the ischaemic tolerance of myocutaneous flaps is of clinical importance and hence the subject of numerous investigations. METHODS: In an attempt to increase the ischaemic tolerance, 20 myocutaneous flaps (rectus abdominis muscle) in pigs were elevated and perfused with various, established solutions prior to the onset of ischaemia. The flaps were elevated, utilizing the superior epigastric vessels as the pedicle. Ten flaps were flushed with the University of Wisconsin solution, five with the Euro-Collins solution and the last five with a Ringer-Lactate solution, prior to the 6h long, normothermic ischaemia. On the day of operation, the first, third, fifth, seventh and tenth postoperative day clinical examinations and thermography were performed as well as biopsies. Additionally, on the tenth postoperative day, the rate of necrosis was determined morphometrically as the average of three measurements. RESULTS: Ten days after surgery, the flaps pretreated with the University of Wisconsin solution displayed a vital surface area of 89%, the Euro-Collins solution 23% and the Ringer-Lactate solution 14%. Histologically, muscle tissue proved to be more susceptible to ischaemia than skin. CONCLUSION: Regarding the rectus abdominis flap in a pig model, the University of Wisconsin solution proved superior in the prevention of ischaemic injury compared with the Euro-Collins solution and Ringer Lactate. In accordance with the literature, muscle tissue proved to be more susceptible to ischaemia than skin in our study.

The biosurgical wound debridement: experimental investigation of efficiency and practicability.

The use of maggot therapy is experiencing a revival in the treatment of problem wounds. Although this alternative therapy is ancient, little scientific research has been aimed at standardizing this therapy. The purpose of our investigation was to determine the debridement efficiency of this therapy, i.e., to compare the use of freely crawling maggots with maggots in a Biobag and to estimate the amount of maggots needed for debridement. We designed an artificial wound model and investigated the rate of decomposition of porcine tissue. Two application alternatives were compared, each being carried out either for 3 or for 4 days, (1) maggots that were allowed to crawl freely over the substrate and (2) maggots confined to a Biobag with no direct contact with the wound. We found that a single maggot was capable of debriding approximately 0.15 g of dead tissue per day. Assuming an absolute difference of <0.05 g per day and maggot as clinically irrelevant, the debridement efficiency of free maggots appears to be similar to those in a Biobag. We were able to determine for the first time the average debriding ability of maggots and thus provide the clinician with data that may help to optimize the maggot therapy by facilitating more exact approximations of the number of maggots needed. Furthermore, the result that the maggots in the Biobag are equal to free maggots in their debriding efficiency will promote its use, especially with respect to the time saved for changing of the dressings. Also, we were able to show that no direct contact is necessary between the maggots and the wound surface, proving that the mechanical crawling effect appears to be neglectable. Because significantly more tissue was metabolized after 4 than after 3 days, application intervals of 4 days appear more appropriate than those of 3 days.

Cervical soft tissue imaging using a mobile CBCT scanner with a flat panel detector in comparison with corresponding CT and MRI data sets.

OBJECTIVE: The aim of this study was to evaluate soft tissue image quality of a mobile cone-beam computed tomography (CBCT) scanner with an integrated flat-panel detector. STUDY DESIGN: Eight fresh human cadavers were used in this study. For evaluation of soft tissue visualization, CBCT data sets and corresponding computed tomography (CT) and magnetic resonance imaging (MRI) data sets were acquired. Evaluation was performed with the help of 10 defined cervical anatomical structures. RESULTS: The statistical analysis of the scoring results of 3 examiners revealed the CBCT images to be of inferior quality regarding the visualization of most of the predefined structures. Visualization without a significant difference was found regarding the demarcation of the vertebral bodies and the pyramidal cartilages, the arteriosclerosis of the carotids (compared with CT), and the laryngeal skeleton (compared with MRI). Regarding arteriosclerosis of the carotids compared with MRI, CBCT proved to be superior. CONCLUSIONS: The integration of a flat-panel detector improves soft tissue visualization using a mobile CBCT scanner.