Is There a Governing Role of Osteocytes in Bone Tissue Regeneration?

PURPOSE OF REVIEW: Bone regeneration plays an important role in contemporary clinical treatment. Bone tissue engineering should result in successful bone regeneration to restore congenital or acquired bone defects in the human skeleton. Osteocytes are thought to have a governing role in bone remodeling by regulating osteoclast and osteoblast activity, and thus bone loss and formation. In this review, we address the so far largely unknown role osteocytes may play in bone tissue regeneration. RECENT FINDINGS: Osteocytes release biochemical signaling molecules involved in bone remodeling such as prostaglandins, nitric oxide, Wnts, and insulin-like growth factor-1 (IGF-1). Treatment of mesenchymal stem cells in bone tissue engineering with prostaglandins (e.g., PGE2, PGI2, PGF2α), nitric oxide, IGF-1, or Wnts (e.g., Wnt3a) improves osteogenesis. This review provides an overview of the functions of osteocytes in bone tissue, their interaction with other bone cells, and their role in bone remodeling. We postulate that osteocytes may have a pivotal role in bone regeneration as well, and consequently that the bone regeneration process may be improved effectively and rapidly if osteocytes are optimally used and stimulated.

Evaluation of a new biphasic calcium phosphate for maxillary sinus floor elevation: Micro-CT and histomorphometrical analyses.

OBJECTIVES: Synthetic biphasic calcium phosphate (BCP) with a hydroxyapatite/ß-tricalcium phosphate (HA/ß-TCP) ratio of 60/40 (BCP60/40) is successfully used as alternative for autologous bone in patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement. A high percentage of HA in BCP60/40 may hamper efficient scaffold remodeling. Osteogenesis and neovascularization are pivotal in effective bone regeneration. We aimed to investigate whether differences exist in osteogenic and/or vasculogenic potential of BCP60/40 and BCP20/80 in patients undergoing MSFE. MATERIALS AND METHODS: Twenty patients undergoing MSFE were treated with BCP60/40 (n = 10) or BCP20/80 (n = 10). Bone and graft volumes were determined by micro-computed tomography and histomorphometrical analysis of biopsies of the augmented region. Osteoid volumes, number of osteoclasts, and blood vessels were determined by histomorphometrical analysis. The biopsies were taken 6.5 months (26 weeks) postoperatively prior to dental implant placement. RESULTS: Bone and osteoid volumes were 9.7% and 0.8% higher at the most cranial side of the BCP20/80 biopsies compared to the BCP60/40 biopsies. Graft volumes, number of osteoclasts, and blood vessels were similar in both groups. CONCLUSIONS: BCP20/80 showed enhanced osteogenic potential in patients undergoing MSFE compared to BCP60/40, due to either a faster bone remodeling rate or an earlier start of bone formation in BCP20/80-treated patients, suggesting that a higher TCP content positively contributes to the bone remodeling rate. Therefore, BCP20/80 might perform better, at least in the short term, as a scaffold for bone augmentation in the MSFE model than BCP60/40 as more bone is formed, and more osteoid is deposited at the cranial side in BCP20/80-treated patients compared to BCP60/40-treated patients. However, catch-up of BCP60/40 in the long term cannot be ruled out.

Dental floss as a possible risk for the development of peri-implant disease: an observational study of 10 cases.

AIM: To report on a possible relationship between the use of dental floss or superfloss and the development of peri-implantitis. MATERIALS AND METHODS: Ten patients with progressive peri-implantitis with an intensive oral hygiene protocol, which consisted of extensive professional supra- and submucosal cleaning, and not responding to this therapy were scheduled for examination. Plaque and bleeding indices and probing depth measurements were assessed, and radiographic examination was performed every two years. RESULTS: In all ten cases, remnants of dental floss were found around the neck and coronal part of a dental implant. After careful removal of these floss remnants and implant cleansing, a significant improvement in the peri-implant conditions in nine of ten cases was noted. In one case, peri-implant probing depth decreased substantially. However, bleeding on probing was still present. In vitro testing yielded that the application of various types of dental floss on the exposed rough implant surfaces may easily lead to tearing of floss fibers. This may result in the deposition of floss remnants on rough implant surfaces, which, in turn, may lead to the development of plaque-related peri-implant inflammation and, subsequently, bone loss. CONCLUSION: In case of exposed rough surfaces of the dental implant, the peri-implant conditions may be jeopardized by the application of dental floss, and hence, the utilization of interproximal brushes or toothpicks may be preferred for daily home care practices.

10-year survival rate and the incidence of peri-implant disease of 374 titanium dental implants with a SLA surface: a prospective cohort study in 177 fully and partially edentulous patients.

PURPOSE: This prospective cohort study evaluates the 10-year survival and incidence of peri-implant disease at implant and patient level of sandblasted, large grid, and acid-etched titanium dental implants (Straumann, soft tissue level, SLA surface) in fully and partially edentulous patients. MATERIAL AND METHODS: Patients who had dental implant surgery in the period between November 1997 and June 2001, with a follow-up of at least 10 years, were investigated for clinical and radiological examination. Among the 506 inserted dental implants in 250 patients, 10-year data regarding the outcome of implants were available for 374 dental implants in 177 patients. In the current study, peri-implantitis was defined as advanced bone loss (≧1.5 mm. postloading) in combination with bleeding on probing. RESULTS: At 10-year follow-up, only one implant was lost (0.3%) 2 months after implant surgery due to insufficient osseointegration. The average bone loss at 10 year postloading was 0.52 mm. Advanced bone loss at 10-year follow-up was present in 35 dental implants (9.8%). Seven percent of the observed dental implants showed bleeding on probing in combination with advanced bone loss and 4.2% when setting the threshold for advanced bone loss at 2.0 mm. Advanced bone loss without bleeding on probing was present in 2.8% of all implants. CONCLUSION: In this prospective study, the 10-year survival rate at implant and patient level was 99.7% and 99.4%, respectively. Peri-implantitis was present in 7% of the observed dental implants according to the above-mentioned definition of peri-implantitis. This study shows that SLA implants offer predictable long-term results as support in the treatment of fully and partially edentulous patients.

A novel approach revealing the effect of a collagenous membrane on osteoconduction in maxillary sinus floor elevation with ß-tricalcium phosphate.

Calcium phosphates are used in maxillary sinus floor elevation (MSFE) procedures to increase bone height prior to dental implant placement. Whether a collagenous barrier membrane coverage of the lateral window affects bone formation within a bone substitute augmentation is currently an important matter of debate, since its benefit has not been irrefutably proven. Therefore, in this clinical study twelve patients underwent an MSFE procedure with ß-tricalcium phosphate (ß-TCP). The lateral window was either left uncovered, or covered with a resorbable collagenous barrier membrane. After a 6-months healing period, bone biopsies were retrieved during implant placement. Consecutive 1 mm regions of interest of these biopsies were assessed for bone formation, resorption parameters, as well as bone architecture using histology, histomorphometry and micro-computed tomography. Comparable outcomes between the groups with and without membrane were observed regarding osteoconduction rate, bone and graft volume, osteoclast number and structural parameters of newly formed bone per region of interest. However, osteoid volume in grafted maxillary sinus floors without membrane was significantly higher than with membrane. In conclusion, our results - obtained with a novel method employed using 1 mm regions of interest - demonstrate that the clinical application of a bioresorbable collagenous barrier membrane covering the lateral window, after an MSFE procedure with ß-TCP, was not beneficial for bone regeneration and even decreased osteoid production which might lead to diminished bone formation in the long run.

Long-Term Safety of Bone Regeneration Using Autologous Stromal Vascular Fraction and Calcium Phosphate Ceramics: A 10-Year Prospective Cohort Study.

This prospective cohort study aimed to assess long-term safety, dental implant survival, and clinical and radiological outcomes after maxillary sinus floor elevation (MSFE; lateral window technique) using freshly isolated autologous stromal vascular fraction (SVF) combined with calcium phosphate ceramics. All 10 patients previously participating in a phase I trial were included in a 10-year follow-up. They received either ß-tricalcium phosphate (ß-TCP; n = 5) or biphasic calcium phosphate (BCP; n = 5) with SVF-supplementation on one side (study). Bilaterally treated patients (6 of 10; 3 ß-TCP, 3 BCP) received only calcium phosphate on the opposite side (control). Clinical and radiological assessments were performed on 44 dental implants at 1-month pre-MSFE, and 0.5- to 10-year post-MSFE. Implants were placed 6 months post-MSFE. No adverse events or pathology was reported during a 10-year follow-up. Forty-three dental implants (98%) remained functional. Control and study sides showed similar peri-implant soft-tissue quality, sulcus bleeding index, probing depth, plaque index, keratinized mucosa width, as well as marginal bone loss (0-6 mm), graft height loss (0-6 mm), and graft volume reduction. Peri-implantitis was observed around 6 implants (control: 4; study: 2) in 3 patients. This study is the first to demonstrate the 10-year safety of SVF-supplementation in MSFE for jawbone reconstruction. SVF-supplementation showed enhanced bone regeneration in the short term (previous study) and led to no abnormalities clinically and radiologically in the long term.

Bone vitality and vascularization of mandibular and maxillary bone grafts in maxillary sinus floor elevation: A retrospective cohort study.

OBJECTIVES: Mandibular retromolar (predominantly cortical) and maxillary tuberosity (predominantly cancellous) bone grafts are used in patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement. The aim of this retrospective cohort study was to investigate whether differences exist in bone formation and vascularization after grafting with either bone source in patients undergoing MSFE. METHODS: Fifteen patients undergoing MSFE were treated with retromolar (n = 9) or tuberosity (n = 6) bone grafts. Biopsies were taken 4 months postoperatively prior to dental implant placement, and histomorphometrically analyzed to quantify bone and osteoid area, number of total, apoptotic, and receptor activator of nuclear factor-κB ligand (RANKL)-positive osteocytes, small and large-sized blood vessels, and osteoclasts. The grafted area was divided in three regions (caudal-cranial): RI, RII, and RIII. RESULTS: Bone volume was 40% (RII, RIII) higher and osteoid volume 10% (RII) lower in retromolar compared to tuberosity-grafted areas. Total osteocyte number and number of RANKL-positive osteocytes were 23% (RII) and 90% (RI, RII) lower, but osteoclast number was higher (retromolar: 12, tuberosity: 0) in retromolar-grafted areas. The total number of blood vessels was 80% (RI) to 60% (RIII) lower, while the percentage of large-sized blood vessels was 86% (RI) to 25% (RIII) higher in retromolar-grafted areas. Number of osteocyte lacunae and apoptotic osteocytes were similar in both bone grafts used. CONCLUSIONS: Compared to the retromolar bone, tuberosity bone showed increased bone vitality and vascularization in patients undergoing MSFE, likely due to faster bone remodeling or earlier start of new bone formation. Therefore, tuberosity bone grafts might perform better in enhancing bone regeneration.

Regional differences in microarchitecture and mineralization of the atrophic edentulous mandible: A microcomputed tomography study.

OBJECTIVE: The aim of the present study was to assess mineralization and trabecular microarchitecture in atrophic edentulous mandibles and to identify regional differences and relations with the extent of resorption. METHODS: Cortical and trabecular bone volumes in anterior, premolar and molar regions of 10 edentulous cadaveric mandibles (5 males and 5 females; mean age ± SD: 85.4 ± 8.3 years) were assessed by microcomputed tomography. Mandibular height and Cawood & Howell classes were recorded. Concerning trabecular volumes, bone mineral density (BMD), bone volume fraction, trabecular tissue volume fraction, connectivity density, trabecular number, trabecular thickness, trabecular separation, degree of anisotropy, and structural model index were measured; concerning cortical volumes porosity, BMD and cortical thickness were measured. RESULTS: In molar regions, the bone volume fraction and trabecular number were lower, whereas trabecular separation, degree of anisotropy and cortical BMD were higher compared to anterior regions. In premolar regions, mandibular height correlated negatively with trabecular number (Spearman's correlation r = 0.73, p = 0.017) and connectivity density (Spearman's correlation r = 0.82, p = 0.004), and correlated positively with trabecular separation (Spearman's correlation r = - 0.65, p = 0.04). Cortical BMD was higher at bucco-inferior cortex of molar and inferior border of premolar region and lower at anterior cranial buccal and lingual surface. CONCLUSIONS: In the premolar region, increased resorption coincides with local impairment of trabecular bone quality. Cortical bone BMD is higher in areas with highest strains and lower in areas with most mandibular resorption. Trabecular bone volume and quality is superior in the anterior region of the edentulous mandible, which might explain improved primary stability of dental implants in this region.

Tissue Level Changes after Maxillary Sinus Floor Elevation with Three Types of Calcium Phosphate Ceramics: A Radiological Study with a 5-Year Follow-Up.

This study evaluates the radiological changes in tissue height after maxillary sinus floor elevation (MSFE) using three types of calcium phosphate ceramics over a period of up to 5 years after dental implant placement. In 163 patients, MSFE was performed. Three groups of patients were distinguished and treated based on the type of calcium phosphate ceramic used and radiologically evaluated: 40 patients with ß-tricalcium phosphate (ß-TCP), 76 patients with biphasic calcium phosphate (BCP) 20% hydroxyapatite (HA)-80% ß-TCP, and 47 patients with BCP 60% HA-40% ß-TCP. Radiological measurements were performed on panoramic radiographs at several time points up to 5 years after dental implant placement. After MSFE, a slow decrease in tissue height measured over time was seen in all three study groups. Resorption of the grafted bone substitutes was more prominent in ß-TCP than in BCP ceramics with an HA component (60/40 and 20/80). Loss of tissue height after 5 years was lowest in BCP 60/40 and highest in ß-TCP. This radiological study shows a predictable and comparable behavior of the slow decrease in tissue height over time for all three types of calcium phosphate ceramics used in MSFE. The fraction of HA in calcium phosphate ceramics and dental implant loading seems to be beneficial for tissue height maintenance after MSFE.

Long-term changes in graft height after maxillary sinus floor elevation with different grafting materials: radiographic evaluation with a minimum follow-up of 4.5 years.

OBJECTIVE: To compare the vertical dimensional changes with regard to graft height in a long-term follow-up in patients treated with two different grafting materials used in maxillary sinus floor elevation procedures. MATERIAL AND METHODS: Twenty consecutive patients were included. One group was grafted with autogenous bone from the mandible (chin area), and the other group was augmented with a 100% beta-tricalcium phosphate (beta-TCP). During a 4- to 5-year period, in each patient, at least five panoramic radiographs were made. These panoramic radiographs were used for morphometric measurements, at three different locations. The three locations were the first bone to implant contact at the distal side of the second most posterior implant (L1), halfway between this implant and the most posterior implant (L2) and the site 5 mm distal to the most posterior implant (L3). The measured vertical bone heights were evaluated to assess whether there was loss of height and, if so, whether the reduction in graft height occurred in an initial healing period or whether it was an ongoing process during the whole study period. RESULTS: There is a statistically significant reduction of vertical bone height in time at all locations (P<0.001). The mean decrease of the total vertical height during the whole study period at the three different locations did not differ significantly for and between both grafting groups. Repeated measures analysis of variance showed that at location L1, the reduction in millimeters per month decreased in time (P=0.001). There was no difference between the grafting groups (P=0.958). Similar results were found on L2 (P=0.005). For L3, there also appeared to be a statistically significant difference in reduction in time in millimeters per month (P=0.004). There was no statistically significant difference in height reduction between locations L1, L2 and L3 for vertical bone height and graft height, respectively. CONCLUSIONS: Both beta-TCP and mandibular bone grafts resulted in radiographic reduction of the vertical height over the 5-year period following maxillary sinus floor elevation. After an initial height reduction in the first 1.5 year, subsequent changes were minimal. No significant differences were observed between the two types of grafting material. There was no statistically significant difference in reduction between the three locations for vertical bone height and graft height, respectively.

Wound dehiscences following pre-implant bone augmentation with autogenous iliac crest bone grafts: A retrospective cohort study.

PURPOSE: To evaluate possible risk factors associated with wound dehiscences following pre-implant alveolar bone augmentation with autologous anterior iliac crest bone grafts covered with resorbable collagen membranes or human demineralised bone laminae. MATERIALS AND METHODS: Data of 161 patients who underwent bone augmentation prior to the insertion of dental implants were analysed. The preoperative dental status, locations of alveolar bone augmentation sites and location of wound dehiscences were recorded. Gender, age, smoking, alcohol exposure, and dental and medical histories were reviewed. Information was also collected on the surgeons, augmentation technique, application of a collagen membrane, fixation screw type and suture material. Univariate logistic regression analysis was used to evaluate pre- and perioperative variables as predictors of dehiscences. RESULTS: A total of 42 (26.1%) of the 161 augmented patients developed a wound dehiscence following surgery. Most commonly affected sites were the anterior maxilla, followed by the anterior mandible. Males developed wound dehiscences with higher probability than females (odds ratio female = 0.444; P = 0.025; 95% CI: 0.214 to 0.903). Furthermore, marginal associations (P < 0.10) are found for smoking and an anterior location of the augmentation. Smokers were found to have higher probability of a wound dehiscence (odds ratio 2.089; P = 0.064; 95% CI: 0.957 to 4.500) compared to non-smokers. A posterior location of the augmentation was associated with lower probability of a wound dehiscence (odds ratio 0.188; P = 0.076; 95% CI: 0.035 to 0.802) compared to an anterior location. CONCLUSIONS: Based on this study population, smoking in males seems to be the most important risk factor for the development of wound dehiscences after pre-implant alveolar bone augmentation procedures.

Bone Tissue Regeneration in the Oral and Maxillofacial Region: A Review on the Application of Stem Cells and New Strategies to Improve Vascularization.

Bone tissue engineering techniques are a promising alternative for the use of autologous bone grafts to reconstruct bone defects in the oral and maxillofacial region. However, for successful bone regeneration, adequate vascularization is a prerequisite. This review presents and discusses the application of stem cells and new strategies to improve vascularization, which may lead to feasible clinical applications. Multiple sources of stem cells have been investigated for bone tissue engineering. The stromal vascular fraction (SVF) of human adipose tissue is considered a promising single source for a heterogeneous population of essential cells with, amongst others, osteogenic and angiogenic potential. Enhanced vascularization of tissue-engineered grafts can be achieved by different mechanisms: vascular ingrowth directed from the surrounding host tissue to the implanted graft, vice versa, or concomitantly. Vascular ingrowth into the implanted graft can be enhanced by (i) optimizing the material properties of scaffolds and (ii) their bioactivation by incorporation of growth factors or cell seeding. Vascular ingrowth directed from the implanted graft towards the host tissue can be achieved by incorporating the graft with either (i) preformed microvascular networks or (ii) microvascular fragments (MF). The latter may have stimulating actions on both vascular ingrowth and outgrowth, since they contain angiogenic stem cells like SVF, as well as vascularized matrix fragments. Both adipose tissue-derived SVF and MF are cell sources with clinical feasibility due to their large quantities that can be harvested and applied in a one-step surgical procedure. During the past years, important advancements of stem cell application and vascularization in bone tissue regeneration have been made. The development of engineered in vitro 3D models mimicking the bone defect environment would facilitate new strategies in bone tissue engineering. Successful clinical application requires innovative future investigations enhancing vascularization.

Anatomical and surgical findings and complications in 100 consecutive maxillary sinus floor elevation procedures.

PURPOSE: To investigate the prevalence of anatomical and surgical findings and complications in maxillary sinus floor elevation surgery, and to describe the clinical implications. PATIENTS AND METHODS: One hundred consecutive patients scheduled for maxillary sinus floor elevation were included. The patients consisted of 36 men (36%) and 64 women (64%), with a mean age of 50 years (range, 17 to 73 years). In 18 patients, a bilateral procedure was performed. Patients were treated with a top hinge door in the lateral maxillary sinus wall, as described by Tatum (Dent Clin North Am 30:207, 1986). In bilateral cases, only the first site treated was evaluated. RESULTS: In most cases, an anatomical or surgical finding forced a deviation from Tatum's standard procedure. A thin or thick lateral maxillary sinus wall was found in 78% and 4% of patients, respectively. In 6%, a strong convexity of the lateral sinus wall called for an alternative method of releasing the trapdoor. The same method was used in 4% of cases involving a narrow sinus. The sinus floor elevation procedure was hindered by septa in 48%. In regard to complications, the most common complication, a perforation of the Schneiderian membrane, occurred in 11% of patients. In 2%, visualization of the trapdoor preparation was compromised because of hemorrhages. The initial incision design, ie, slightly palatal, was responsible for a local dehiscence in 3%. CONCLUSION: To avoid unnecessary surgical complications, detailed knowledge and timely identification of the anatomic structures inherent to the maxillary sinus are required.

Blood Vessel Formation and Bone Regeneration Potential of the Stromal Vascular Fraction Seeded on a Calcium Phosphate Scaffold in the Human Maxillary Sinus Floor Elevation Model.

Bone substitutes are used as alternatives for autologous bone grafts in patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement. However, bone substitutes lack osteoinductive and angiogenic potential. Addition of adipose stem cells (ASCs) may stimulate osteogenesis and osteoinduction, as well as angiogenesis. We aimed to evaluate the vascularization in relation to bone formation potential of the ASC-containing stromal vascular fraction (SVF) of adipose tissue, seeded on two types of calcium phosphate carriers, within the human MSFE model, in a phase I study. Autologous SVF was obtained from ten patients and seeded on ß-tricalcium phosphate (n = 5) or biphasic calcium phosphate carriers (n = 5), and used for MSFE in a one-step surgical procedure. After six months, biopsies were obtained during dental implant placement, and the quantification of the number of blood vessels was performed using histomorphometric analysis and immunohistochemical stainings for blood vessel markers, i.e., CD34 and alpha-smooth muscle actin. Bone percentages seemed to correlate with blood vessel formation and were higher in study versus control biopsies in the cranial area, in particular in ß-tricalcium phosphate-treated patients. This study shows the safety, feasibility, and efficiency of the use of ASCs in the human MSFE, and indicates a pro-angiogenic effect of SVF.

Bone Regeneration Using the Freshly Isolated Autologous Stromal Vascular Fraction of Adipose Tissue in Combination With Calcium Phosphate Ceramics.

: In patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement, bone substitutes are currently evaluated as alternatives for autologous bone. However, bone substitutes have only osteoconductive properties and lack osteoinductive potential. Therefore, this phase I study evaluated the potential additive effect on bone regeneration by the addition of freshly isolated, autologous but heterologous stromal vascular fraction (SVF), which is highly enriched with adipose stromal/stem cells when compared with native adipose tissue. From 10 patients, SVF was procured using automatic processing, seeded on either ß-tricalcium phosphate (n = 5) or biphasic calcium phosphate carriers (n = 5), and used for MSFE in a one-step surgical procedure. Primary objectives were feasibility and safety. The secondary objective was efficacy, evaluated by using biopsies of the augmented area taken 6 months postoperatively, concomitant with dental implant placement. Biopsies were assessed for bone, graft, and osteoid volumes. No adverse effects were reported during the procedure or follow-up (≥3 years). Bone and osteoid percentages were higher in study biopsies (SVF supplemented) than in control biopsies (ceramic only on contralateral side), in particular in ß-tricalcium phosphate-treated patients. Paired analysis on the six bilaterally treated patients revealed markedly higher bone and osteoid volumes using microcomputed tomography or histomorphometric evaluations, demonstrating an additive effect of SVF supplementation, independent of the bone substitute. This study demonstrated for the first time the feasibility, safety, and potential efficacy of SVF seeded on bone substitutes for MSFE, providing the first step toward a novel treatment concept that might offer broad potential for SVF-based regenerative medicine applications. SIGNIFICANCE: This is the first-in-human study using freshly isolated, autologous adipose stem cell preparations (the stromal vascular fraction [SVF] of adipose tissue) applied in a one-step surgical procedure with calcium phosphate ceramics (CaP) to increase maxillary bone height for dental implantations. All 10 patients received CaP plus SVF on one side, whereas bilaterally treated patients (6 of 10) received CaP only on the opposite side. This allowed intrapatient evaluation of the potential added value of SVF supplementation, assessed in biopsies obtained after 6 months. Feasibility, safety, and potential efficacy of SVF for bone regeneration were demonstrated, showing high potential for this novel concept.

Short (15 minutes) bone morphogenetic protein-2 treatment stimulates osteogenic differentiation of human adipose stem cells seeded on calcium phosphate scaffolds in vitro.

A one-step concept for bone regeneration has been postulated in which human adipose stem cells (hASCs) are harvested, triggered to differentiate, seeded on carriers, and implanted in the same operative procedure. Toward this goal it was investigated whether short (minutes) incubation with bone morphogenetic protein-2 (BMP-2) suffices to trigger osteogenic differentiation of hASCs seeded on calcium phosphate carriers. hASCs were treated with or without BMP-2 (10 ng/mL) for 15 min, and seeded on ß-tricalcium phosphate granules (ß-TCP; sized <0.7 mm or >0.7 mm) or biphasic calcium phosphate (BCP; 60%/40% or 20%/80% hydroxyapatite/ß-TCP). Attachment was determined after 10-30 min. Proliferation (DNA content) and osteogenic differentiation (alkaline phosphatase activity, gene expression) were analyzed up to 3 weeks of culture. hASC attachment to the different scaffolds was similar, and unaffected by BMP-2. It stimulated gene expression of the osteogenic markers core binding factor alpha 1, collagen-1, osteonectin, and osteocalcin in hASCs seeded on BCP and ß-TCP. Downregulation of osteopontin expression by BMP-2 was seen in BCP-seeded cells only. BMP-2 treatment inhibited expression of the adipogenic marker peroxisome proliferator-activated receptor gamma. In conclusion, 15 min BMP-2 preincubation of hASCs seeded on BCP/ß-TCP scaffolds had a long-lasting stimulating effect on osteogenic differentiation in vitro. These results strongly support a one-step clinical concept for bone regeneration.

Human maxillary sinus floor elevation as a model for bone regeneration enabling the application of one-step surgical procedures.

Bone loss in the oral and maxillofacial region caused by trauma, tumors, congenital disorders, or degenerative diseases is a health care problem worldwide. To restore (reconstruct) these bone defects, human or animal bone grafts or alloplastic (synthetic) materials have been used. However, several disadvantages are associated with bone graft transplantation, such as limited bone volume, donor-site morbidity, surgical and immune rejection risks, and lack of osseo-integration. Bone tissue engineering is emerging as a valid alternative to treat bone defects allowing the regeneration of lost bony tissue, thereby recovering its functionality. During the last decades, the increasing aged population worldwide has also raised the prevalence of maxillary atrophy. Maxillary sinus floor elevation (MSFE) has become a standard surgical procedure to overcome the reduced amount of bone, thus enabling the placement of dental implants. MSFE aims to increase the bone height in the posterior maxilla, by elevating the Schneiderian membrane and placing the graft material into the surgically created space in the maxillary sinus floor. Importantly, oral bone regeneration during MSFE offers a unique human clinical model in which new cell-based bone tissue engineering applications might be investigated, since biopsies can be taken after MSFE before a dental implant placement and analyzed at the cellular level. New approaches in oral bone regeneration are focusing on cells, growth factors, and biomaterials. Recently, adipose tissue has become interesting as an abundant source of mesenchymal stem cells, which might be applied immediately after isolation to the patient allowing a one-step surgical procedure, thereby avoiding expensive cell culture procedures and another surgical operation. In this new cell-based tissue engineering approach, stem cells are combined with an osteoconductive scaffold and growth factors, and applied immediately to the patient. In this review, MSFE is discussed as a valid model to test bone tissue engineering approaches, such as the one-step surgical procedure. This procedure might be applied in other regenerative medicine applications as well.

Fractures of the iliac crest after split-thickness bone grafting for preprosthetic surgery: report of 3 cases and review of the literature.

PURPOSE: In this study fractures of the iliac crest after split-thickness bone grafting in a patient population treated for preprosthetic reasons were evaluated. PATIENTS AND METHODS: In a retrospective patient population of 146 patients, during a 5-year period (1998 to 2002), 3 avulsion fractures of the iliac crest were noticed. All fractures were postsurgical, occurring as late fractures. A review of the literature regarding etiology, clinical characteristics, and results of treatment is given. RESULTS: In all 3 cases treatment was conservative, consisting of a period of bed rest followed by progressive ambulation. Further recovery was uneventful. CONCLUSIONS: According to this patient population and the literature, late fracture of the iliac crest after split-thickness bone grafting is an uncommon complication. We recommend a harvesting and grafting technique at an appropriate distance from the iliac spine with an oscillating saw. Treatment of an iliac crest fracture is almost always conservative.

Histomorphometry of human sinus floor augmentation using a porous beta-tricalcium phosphate: a prospective study.

Tricalcium phosphate (TCP) has been historically a well-accepted material for bone augmentation. We examined the use of a porous beta-TCP (100%) in a split mouth model for sinus floor augmentation. Five patients were treated bilaterally, receiving 1-2 mm-sized beta-TCP particles (Cerasorb) on one side (test side) and autologous chin bone particles on the other (control) side. Four other patients were treated with a unilateral sinus floor augmentation using 100% beta-TCP (no controls). Biopsies of the augmented sites were taken at 6 months. Histomorphometry measurements were carried out in order to quantify bone augmentation at test and control sides. The average bone volume (BV) formed in the augmented sinus at the control side was 41% (32-56%) and 17% (9-27%) in the test side when all nine patients were included (statistically significant, P=0.04). When only the five bilateral patients were included, mean BV of the test side was 19% (13-27%), which was also significantly different from the control side (P=0.009). Osteoid formation tended to be higher in the test side biopsies (1.3%) than in the controls (0.3%) (marginally significant, P=0.1), indicating ongoing bone formation in the TCP material. The amount of lamellar bone at the test side was less than half the amount in the control side, indicating that remodelling had only recently started in the TCP-augmented side. The resorption surface, however, did not differ significantly between the two sides. These histological results indicate that Cerasorb is an acceptable bone substitute material for augmentation of the maxillary sinus. Due to the osteoconductive, but not osteoinductive properties of this material, the rate of bone formation is somewhat delayed in comparison to autologous bone.