A novel implantation model for evaluation of bone healing response to dental implants: the goat iliac crest.

OBJECTIVES: Despite the availability of numerous animal models for testing the biological performance of dental and orthopedic implants, the selection of a suitable model is complex. This paper presents a new model for objective and standardized evaluation of bone responses to implants using the iliac crest in goats. MATERIAL AND METHODS: The feasibility of the iliac crest model regarding anatomy and implant positioning was determined using two cadaveric specimens and the bone structure was evaluated and compared with that of the goat femoral condyle. Additionally, the validity of the model was tested by performing an in vivo study. RESULTS: By means of a rather simple, safe, fast and reproducible surgical procedure, the iliac crest in goats could be approached and allowed the implantation of maximally five dental implants per iliac crest. Because of the bilateral implantation possibility, statistical comparisons between groups on either side of the goat could be performed, resulting in a high statistical power, and hence a reduction in the number of animals required to obtain significant data. CONCLUSIONS: In terms of surgical approach, anatomy and implant positioning, the iliac crest is the preferred model over the femoral condyle model. The iliac crest implantation model is suitable for evaluation of the osteogenic response to bone implant materials and represents a justified and deliberate alternative to the already existing animal models.

Effects of implant geometry, surface properties, and TGF-beta1 on peri-implant bone response: an experimental study in goats.

OBJECTIVES: Despite the high success rates in implantology, the desire to use oral implants in more challenging clinical situations drives the need for continuing refinements in implant design and surface properties. In the present study, the effect of implant geometry on implant bone response was evaluated using two geometrically different implant types, i.e. screw type (St) and push-in type(Pi). Furthermore, the potential beneficial effect of an electrosprayed calcium phosphate (CaP) coating, either or not enriched with the osteoinductive growth factor TGF-beta1, on the osteogenic response was examined. MATERIAL AND METHODS: A total of 54 implants, divided into six groups (n=9), were inserted into the femoral condyles of nine goats. After an implantation period of 12 weeks, retrieved specimens were evaluated histologically and histomorphometrically. Measurements were statistically evaluated using SPSS 14.0 and analyzed using a linear regression model. RESULTS: With respect to implant design, St-implants showed an overall superior biological healing response compared with Pi-implants. Considering surface properties, the deposition of an electrosprayed CaP (2-3 microm) coating onto implants significantly increased the amount of bone-implant contact for both implant types. Additional enrichment of the CaP coating with the osteoinductive growth factor TGF-beta1 did not significantly affect peri-implant bone response. CONCLUSIONS: The results of this study indicate that a substantial improvement of the osteogenic response to titanium implants can be achieved by the deposition of an electrosprayed CaP coating. The enrichment of the coating with 1 microg TGF-beta1 has only a marginal effect.

Cleft palate cells can regenerate a palatal mucosa in vitro.

Cleft palate repair leaves full-thickness mucosal defects on the palate. Healing might be improved by implantation of a mucosal substitute. However, the genetic and phenotypic deviations of cleft palate cells may hamper tissue engineering. The aim of this study was to construct mucosal substitutes from cleft palate cells, and to compare these with substitutes from normal palatal cells, and with native palatal mucosa. Biopsies from the palatal mucosa of eight children with cleft palate and eight age-matched control individuals were taken. Three biopsies of both groups were processed for (immuno)histochemistry; 5 were used to culture mucosal substitutes. Histology showed that the substitutes from cleft-palate and non-cleft-palate cells were comparable, but the number of cell layers was less than in native palatal mucosa. All epithelial layers in native palatal mucosa and mucosal substitutes expressed the cytokeratins 5, 10, and 16, and the proliferation marker Ki67. Heparan sulphate and decorin were present in the basal membrane and the underlying connective tissue, respectively. We conclude that mucosal cells from children with cleft palate can regenerate an oral mucosa in vitro.

Orthotopic bone formation in titanium fiber mesh loaded with platelet-rich plasma and placed in segmental defects.

The effect of platelet-rich plasma (PRP) on bone formation was investigated in a rabbit segmental radial defect model. The purpose of the study was to evaluate the bone inductive properties of PRP with titanium fiber mesh and autologous bone chips in a 15-mm rabbit radial defect model. Eighteen New Zealand white rabbits were divided into three groups: I, PRP with autologous bone (PRP-Ti-Bone); II, autologous bone (Ti-Bone); III, control group (Ti). The implants were placed in the radial defect for 12 weeks. After sacrifice, all specimens were harvested for histological, histomorphometrical and radiographic analysis. Histomorphometrical analysis showed that bone formation was higher in the implants with PRP (PRP-Ti-Bone: 37+/-8%) than in those without PRP (Ti-bone: 25+/-6% and Ti: 25+/-5%) after 12 weeks of implantation. It was concluded that PRP has a stimulatory effect on bone formation in titanium fiber mesh filled with autologous bone graft in segmental bone defects. Titanium fiber mesh was also shown to be an excellent scaffold material for the application of autologous bone grafts with or without PRP.

Closing capacity of cranial bone defects using porous calcium phosphate cement implants in a rabbit animal model.

Calcium phosphate (Ca-P) cement is a well established material for bone repair. The bone biological properties of Ca-P cement can even be further improved by creating porosity in the material. The current study aimed on the evaluation of the osteoconductive behavior of porous Ca-P cement. Therefore, circular defects (6, 9, and 15 mm in diameter) were created in the cranium of 3 months old rabbits and filled with porous Ca-P cement implants. The total porosity of implants was calculated to be 71, 74 and 74% respectively and the average pore diameter was 150 microm. In addition, empty control defects were prepared. After 12 weeks implantation time the animals were sacrificed and radiographic, histological, and histomorphometrical evaluation was performed. The Critical Size Defect (CSD) of this species at this location for an implantation time of 12 weeks was confirmed to be 15 mm. Bone was observed to be present over and through almost all porous Ca-P cement implants. Only, in one out of eight animals with a 15 mm implant complete bone bridging of the defect did not occur. The size of the defect was found not to affect the total percentage of bone formation in the cement; (17 +/- 7)%, (18 +/- 6)% and (17 +/- 3)% for respectively 6, 9, and 15 mm diameter implants. We concluded that porous Ca-P cement is an excellent osteoconductive material in non weight bearing situations and complete bridging of a critical sized skull defect occurs in this rabbit model after 12 weeks of implantation.

Influence of RGD-loaded titanium implants on bone formation in vivo.

Little is known about the ability of peptide-coated surfaces to influence cell responses in vivo. Many studies have demonstrated that peptide-modified surfaces influence cell responses in vitro. Integrins, which bind specifically short peptide sequences, are responsible for these cell responses. In this way, information can be transmitted to the nucleus through several cytoplasmic signaling pathways. The peptide sequence Arg-Gly-Asp (RGD peptide) plays an important role in osteoblast adhesion. The present study was designed to investigate new bone formation in a porous titanium (Ti) fiber mesh implant, which was coated with cyclic RGD peptide. The RGD-Ti implants were inserted into the cranium of a rabbit and were compared with porous titanium fiber mesh disks without RGD sequence (Ti) and with an open control defect. Histologic and histomorphometric examinations were performed 2, 4, and 8 weeks postoperatively. A significant increase in bone formation, or bone ingrowth, was seen in the RGD-Ti group compared with the Ti group after 4 and 8 weeks. All control defects stayed open in all three periods. It was concluded that the use of cyclic RGD peptide in combination with titanium fiber mesh has a positive effect on bone formation in vivo in a rabbit animal model.

Controlled release of rhBMP-2 loaded poly(dl-lactic-co-glycolic acid)/calcium phosphate cement composites in vivo.

The release kinetics of recombinant human bone morphogenetic protein-2 (rhBMP-2) loaded poly(dl-lactic-co-glycolic acid)/calcium phosphate cement (PLGA/Ca-P cement) composites were studied in vivo. RhBMP-2 was radiolabeled with (131)I and entrapped within PLGA microparticles or adsorbed onto the microparticle surface. PLGA microparticles were prepared of high molecular weight (HMW) PLGA (weight average molecular weight [M(w)] 49,100+/-1700) or low molecular weight (LMW) PLGA (M(w) 5,900+/-300) and used for preparation of 30:70 wt.% PLGA/Ca-P cement composite discs. Release of 131I-rhBMP-2 loaded composites was assessed by scintigraphic imaging according to a 2(2) two-level full factorial design in the rat ectopic model during four weeks. In vivo release kinetics varied among formulations. All formulations showed slow release without initial burst, and displayed a linear release from 3 to 28 days. Release of LMW entrapped rhBMP-2 composites (1.7+/-0.3%/day) was significantly faster than release from other formulations (p<0.01). After 28 days, retention within the composites was 65+/-5%, 75+/-4%, 50+/-4% and 70+/-6% of the initial rhBMP-2 for HMW entrapped, HMW adsorbed, LMW entrapped and LMW adsorbed rhBMP-2 composites, respectively. Release from the composite was probably slowed down by an interaction of rhBMP-2 and Ca-P cement after rhBMP-2 release from PLGA microparticles. We conclude that PLGA/Ca-P cement composites can be considered as sustained slow release vehicles and that the release and retention of rhBMP-2 can be modified according to the desired profile to a limited extent.

Bone formation in calcium-phosphate-coated titanium mesh.

The osteogenic activity of porous titanium fiber mesh and calcium phosphate (Ca-P)-coated titanium fiber mesh loaded with cultured syngeneic osteogenic cells was compared in a syngeneic rat ectopic assay model. In 30 syngeneic rats, (Ca-P)-coated and non-coated porous titanium implants were subcutaneously placed either without or loaded with cultured rat bone marrow (RBM) cells. Fluorochrome bone markers were injected at 2, 4, and 6 weeks. The rats were sacrificed, and the implants were retrieved at 2, 4, and 8 weeks post-operatively. Histological analysis demonstrated that none of the (Ca-P)-coated and non-coated meshes alone supported bone formation at any time period. In RBM-loaded implants, bone formation started at 2 weeks. At 4 weeks, bone formation increased. However, at 8 weeks bone formation was absent in the non-coated titanium implants, while it had remained in the (Ca-P)-coated titanium implants. Also, in (Ca-P)-coated implants more bone was formed than in non-coated samples. In general, osteogenesis was characterized by the occurrence of multiple spheres in the porosity of the mesh. The accumulation sequence of the fluorochrome markers showed that the newly formed bone was deposited in a centrifugal manner starting at the center of a pore. Our results show that the combination of Ti-mesh with RBM cells can indeed generate bone formation. Further, our results confirm that a thin Ca-P coating can have a beneficial effect on the bone-generating properties of a scaffold material.

Influence of rhBMP-2 on rat bone marrow stromal cells cultured on titanium fiber mesh.

Titanium (Ti) fiber mesh is a candidate scaffold material for the creation of bone graft substitutes (BGS). Two densities (3.54 x 10(4) cells/cm(2) [LD or low density] and 3.54 x 10(5) cells/cm(2) [HD or high density]) of rat bone marrow stromal cells were seeded on Ti-fiber mesh discs. Cells were cultured for up to 16 days, 7 days of which the cells were in the presence of various concentrations of rhBMP-2 (0, 10, 100, and 1,000 ng/mL) in order to evaluate osteogenic expression. Scanning electron microscopy (SEM), light microscopy (LM), energy dispersive spectroscopy (EDS), DNA and calcium (Ca) content measurements, and x-ray diffraction (XRD) analysis were performed. SEM and EDS evaluation showed that a confluent layer of cells was present on top of the meshes together with collagen bundles and calcified globular accretions. Light microscopical evaluation showed a densely stained layer in the upper part of the mesh. SEM and Ca content measurement showed that calcification starts at 8 days. In addition, it was demonstrated that DNA content peaked at 8 days. LM, SEM, and Ca content evaluation revealed positive effects of increasing the cell seeding density, the rhBMP-2 concentration and the culture time on mineralization. Increasing the cell seeding density also showed a positive effect on DNA content. No effects of rhBMP-2 concentration were seen on DNA content. Finally, XRD revealed that the deposited matrix contained a precipitate of a stable calcium phosphate phase. We conclude that (1) titanium fiber mesh sustains excellent osteogenic expression in vitro, (2) increasing the cell seeding density has a positive effect on osteogenic expression in titanium mesh in vitro, and (3) in high density specimens, rhBMP-2 concentrations of 100 ng/mL and 1,000 ng/mL stimulate extracellular matrix calcification in a dose-responsive manner.

A model for monitoring nerve blood flow during expansion by laser Doppler flowmetry in the rabbit.

A new model is described for monitoring nerve blood flow during expansion by laser Doppler flowmetry. Rabbit sciatic nerve is gradually expanded with a custom-made spherical expander, while nerve blood flow is monitored by laser Doppler flow output. This model provides a valid method of controlling nerve blood flow during expansion.

Peripheral nerve elongation by laser Doppler flowmetry controlled expansion: functional and neurophysiological aspects.

A new method for elongation of peripheral nerves with preservation of function is presented. Nerve blood flow during experimental nerve expansion of rabbit sciatic nerve is controlled by laser Doppler flowmetry in order to avoid nerve ischemia. Using this method, nerve function in relation to gait remained intact in 72.5% of the animals and recovered within 3 weeks in the others. Disturbances in toe-spread reflex recovered completely in all animals after 3 weeks. Significant nerve elongation up to 40% is possible with preservation of function when nerve blood flow is controlled by laser Doppler flowmetry.

The oncological implications of immediate breast reconstruction.

AIMS: The timing of breast reconstruction following mastectomy has been an area of contention. The purpose of this study was to report the oncologic safety of mastectomy and immediate breast reconstruction, primarily with a tissue expander. METHODS: We offered 54 patients (58 reconstructions) an immediate breast reconstruction after a modified radical mastectomy was done for invasive breast cancer. RESULTS: Fifty-eight mastectomies were done for an invasive cancer. Thirteen out of 54 women suffered relapse of their cancer and nine patients died of their disease during the follow-up period. Only in one patient a local recurrence was detected at an early stage and treated without removal of the prosthesis. Disease free survival for all patients was 93% at 5 years. CONCLUSION: Immediate breast reconstruction after mastectomy is an oncologically safe approach and represents a clear improvement in the quality of life for patients with breast cancer. Thus this procedure can safely be offered to appropriately selected women.

Bone formation in CaP-coated and noncoated titanium fiber mesh.

The osteogenic activity of calcium phosphate (CaP)-coated and noncoated porous titanium (Ti) fiber mesh loaded with cultured syngeneic osteogenic cells after prolonged in situ culturing was compared in a syngeneic rat ectopic assay model. Rat bone marrow (RBM) cells were loaded onto the CaP-coated and noncoated Ti scaffolds using either a droplet or a suspension loading method. After loading, the RBM cells were cultured for 8 days in vitro. Thereafter, implants were subcutaneously placed in 39 syngeneic rats. The rats were euthanized and the implants retrieved at 2, 4, and 8 weeks postoperatively. Further, in the 8 week group fluorochrome bone markers were injected at 2, 4, and 6 weeks. Histological analysis demonstrated that only the CaP-coated meshes supported bone formation. The amount of newly formed bone varied between single and multiple spheres to filling a significant part of the mesh porosity. In the newly formed bone, osteocytes embedded in a mineralized matrix could be observed clearly. On the other hand, in the noncoated titanium implants, abundant deposition of calcium-containing material was seen. This deposit lacked a bonelike tissue organization. Further analysis revealed that the cell-loading method did not influence the final amount of bone formation. In CaP-coated implants the accumulation sequence of the fluorochrome markers showed that bone formation started on the mesh fibers. In conclusion, our results prove that the combination of a thin CaP coating, Ti-mesh, and RBM cells can indeed generate ectopic bone formation after prolonged in vitro culturing. No effect of the loading method was observed on the final amount of bone.

Survey of analgesia regimens in burns centres in the UK.

A survey of the analgesia regimens used in burns units throughout the UK was performed. Continuous intravenous opiate infusions remain the mainstay for providing pain relief in patients in severe pain as a result of burn injuries. Other methods include: patient-controlled analgesia in appropriate patients, bolus doses of opiates combined with Entonox for control of peaks of pain and a wide variety of oral analgesics for less painful burn injuries.

The popliteal pterygium syndrome: an analysis of two families.

The popliteal pterygium syndrome is characterized by multiple anomalies of the face, genito-urinary system and extremities with autosomal dominant inheritance with variable expression. Also sporadic cases probably based upon spontaneous mutation can be recognized. The plastic, orthopaedic, and maxillofacial surgeon should be aware of the variable nature of the syndrome and should consult a medical geneticist. A coordinated team approach appears to be most adequate for diagnosis, counselling and treatment.

Cleft palate repair: Furlow versus von Langenbeck.

The Furlow cleft palate repair using a double opposing Z-plasty appears to be very promising. In order to detect advantages and disadvantages concerning the technique as well as speech- and hearing results, the Furlow palatoplasty was compared with the classical von Langenbeck technique. Data analysis from 10 children in both groups revealed that the Furlow technique proved to be superior to the von Langenbeck technique as far as speech sound is concerned: at a mean age of 3.5 years, nasality and nasal escape were absent in almost all cases. However, there were no significant differences between the techniques in respect of articulatory skills, language comprehension, language production as well as hearing. Technically, the Furlow technique is more difficult to perform, particularly in wide clefts.

The use of silicone occlusive sheeting (Sil-K) and silicone occlusive gel (Epiderm) in the prevention of hypertrophic scar formation.

The development of hypertrophic scars and keloids is an unsolved problem in the process of wound healing. For this reason, a successful treatment to prevent excessive scar formation still has not been found. Over the last decade, however, a promising new treatment has been introduced. Silicone materials have proved to reduce the amount of scar tissue and are believed even to prevent hypertrophic scar and keloid formation. In this study, the prophylactic effect of a silicone occlusive sheeting (Sil-K, Degania, Israel) and a silicone occlusive gel (Epiderm, Inamed B.V., The Netherlands) was investigated in a bilateral breast-reduction scar model in which the nontreated scars were supported by nonocclusive Micropore (3M, The Netherlands). The inframammary scars of 129 female patients with a mean age of 31 years ( 14 to 69 years) were studied up to 1 year after the operation. The width and height were measured, and B-scan ultrasound, laser-Doppler flowmetry, and color measurements were used as objective indicators to distinguish between normal and exuberant scars. Three months following the operation, 64.3 percent of the patients developed a hypertrophic scar, which was reduced to 56.6 percent after 6 months and down to 35.3 percent after 1 year. No keloids were seen. Patients with an easily tanning skin, nonsmokers, and patients with an allergy showed more hypertrophic scar formation. Neither Sil-K, used in 68 patients, nor Epiderm, used in 61 patients, could prevent the formation of hypertrophic scars. If both groups were taken together, the scars treated with silicone materials even developed significantly more hypertrophy compared with the Micropore-applicated scars.

Preoperative injection using a diluted anesthetic/adrenaline solution significantly reduces blood loss in reduction mammaplasty.

Breast reductions are very common operations in the plastic surgical practice. The cosmetic results are generally satisfactory but are often accompanied with large volumes of blood lost. In this study, the reduction of blood loss together with other positive and negative effects of a preoperatively diluted anesthetic/adrenaline solution was tested. A group of 41 female patients treated with the infiltration solution was compared with a group of 29 female patients treated without the solution. No statistical differences were found in age at operation, weight, length, Quetelet index, amount of tissue resected, preoperative hemoglobin and hematocrit, postoperative drainage, duration of operation, and the viability of the skin flaps (p > 0.05). Blood loss was significantly less in the adrenaline-treated group measured in several ways (p < 0.0001). There were more adrenaline-treated patients with less hospitalization time compared with the nontreated group (p = 0.0858). In conclusion, diluted anesthetic/adrenaline solution significantly reduces blood loss in reduction mammaplasty without any adverse effects.

Ectopic bone formation in titanium mesh loaded with bone morphogenetic protein and coated with calcium phosphate.

The osteoinductive properties of porous titanium fiber mesh, with or without a calcium phosphate coating and loaded with recombinant human bone morphogenic protein-2 (rhBMP-2) or rhBMP-2 and native bovine BMP (S-300) were investigated in a rat ectopic assay model. A total of 112 calcium phosphate-coated and 112 noncoated porous titanium implants, either loaded with rhBMP-2 and S-300 or loaded with rhBMP-2 alone, were subcutaneously placed in 56 Wistar-King rats. The rats were killed 5, 10, 20, and 40 days postoperatively, and the implants were retrieved. Histologic analysis demonstrated that all growth factor and carrier combinations induced ectopic cartilage and bone formation at 5 and 10 days, respectively. At 20 days, bone formation increased and was characterized by trabecular bone and bone marrow-like tissue. At 40 days, more lamellar bone and hemopoietic bone marrow-like tissue were present. At both times, more bone had been formed in calcium phosphate-coated implants than in noncoated samples. Further, in rhBMP-2 and S-300-loaded specimens, bone formation was higher than in rhBMP-2 only-loaded specimens. In rhBMP-2 only-loaded specimens, bone formation was mainly localized inside the mesh material, whereas in specimens loaded with both rhBMP-2 and S-300, the bone was localized inside and surrounding the titanium mesh. The histological findings were confirmed by calcium content and alkaline phosphatase activity measurements. In addition, all specimens showed osteocalcin expression as early as 5 days postoperatively. Our results show that the combination of titanium mesh with BMPs can induce ectopic bone formation and that this bone formation seems to be similar to "enchondral" ossification. In addition, a thin calcium phosphate coating can have a beneficial effect on the bone-inducing properties of a scaffold material. Finally, rhBMP-2 and native BMP act synergistically in ectopic bone induction.

Peripheral nerve elongation by laser Doppler flowmetry-monitored expansion: an experimental basis for future application in the management of peripheral nerve defects.

Nerve grafting often fails to achieve optimal functional results and is always associated with donor-site morbidity. Peripheral nerve elongation by the use of a tissue expander may provide a useful adjunct in the management of segmental nerve loss. In the present study, rabbit sciatic nerve (n = 40) was elongated by expansion while nerve blood flow was monitored by laser Doppler flowmetry. Elongation was possible up to 40 percent with preservation of clinical nerve function. Nerve conduction velocity of the expanded nerves decreased in a linear relation to elongation. The reduction in nerve conduction velocity may be secondary to the observed widening of the nodes of Ranvier and altered membrane properties after remyelination. Demyelination and remyelination of whole internodes and axonal degeneration occurred only sporadically. Thus laser Doppler flowmetry-monitored expansion provides a safe method for elongation of intact rabbit sciatic nerve while nerve function and axonal continuity are preserved. Further studies are needed before clinical use is considered. This technique may represent a favorable alternative to nerve grafting for the treatment of peripheral nerve defects.