Calcium sulphate as a bone substitute for various osseous defects in conjunction with apicectomy

Immediate implant placement and simultaneous bone grafting with bone cement in extraction sockets: A systematic review

Background

The placement of immediate dental implants intrinsically displays crestal gaps, which may compromise implant osseointegration. Several grafting materials have been used to overcome this issue. Of the available materials, the use of bone cement is relatively new in oral implantology. This study aimed to examine the available literature on the utilization of bone cements in immediate placement of dental implants and assess its potential in oral implantology.

Objectives

To synthesize evidence for appraising the impact of bone cements on implant stability and bone-to-implant contact (BIC) of dental implants placed immediately after extraction in humans and animals after 3 months of healing from tooth extraction.

Methods

A systematic search was conducted in PubMed, Medline, and ScienceDirect for relevant studies published from inception to September 2021 using relevant search terms. Of the 1624 studies, 4 were selected for this systematic review.

Results

Three of the four studies concluded that bone cements enhanced implant stability and/or BIC with better quality and/or quantity of bone surrounding the immediate dental implant. The conclusion drawn by one article remained indecisive. Meta-analysis could not be performed owing to the presence of substantial heterogeneity.

Conclusion

Bone cement is a promising treatment alternative as it augments implant stability and/or BIC in immediate dental implants. Nonetheless, further prospective human clinical trials are required to establish its clinical effectiveness and arrive at a definitive conclusion to recommend its clinical use.

The use of guided tissue regeneration in endodontic Microsurgery: Setting a threshold

Aim

We aimed to compare the radiographic outcomes of conventional and regenerative approaches in endodontic microsurgery (EMS) and set a critical defect size for healing in conventional and regenerative therapies.

Methodology

The study evaluated 53 root canal-treated teeth (33 patients) with periapical lesions. Among them, 19 teeth (35.8 %) were treated with regenerative treatment, whereas 34 teeth (64.1 %) were managed with the conventional approach. Conventional and regenerative approaches were performed by endodontic and periodontic residents under consultants' supervision. Healing was evaluated after a minimum period of 6 months by comparing pre- and post-operative cone-beam computed tomography (CBCT) findings. The radiographic interpretation was conducted by a single examiner who was not participating in the surgeries and was blind on the type of treatment prior to CBCT evaluation. New healing criteria were proposed owing to the limitations on the present criteria in evaluating endodontic surgery after regenerative treatment. Critical measurements were calculated for each approach based on periapical lesion dimensions.

Results

The regenerative approach presented significantly better healing than conventional treatment (mean, 1.21 and 1.59, respectively; p = 0.047). Based on the critical-point calculations, the conventional approach was effective in lesions of up to 3 mm depth and height, whereas the regenerative approach resulted in better healing rates in lesions with 3-9 mm depth and 3-6 mm height.

Conclusions

Performing the regenerative approach in EMS resulted in better healing rates than those of the conventional approach. The conventional approach is recommended for small periapical lesions, whereas the first had better results in larger lesions.

Clinical outcomes of endodontic microsurgery in complicated cases with large or through-and-through lesions: a retrospective longitudinal study

OBJECTIVES

To investigate the clinical outcomes of endodontic microsurgery in complicated cases presenting with large or through-and-through lesions.

MATERIALS AND METHODS

We retrospectively collected and analyzed preoperative, intraoperative, and follow-up data from 143 complicated cases that underwent endodontic microsurgery. Clinical outcomes were assessed in terms of tooth survival and surgery success. Cox regression analysis was used to evaluate the survival rate and identify associated risk factors. Additionally, the success rate was compared across different postoperative periods, and potential factors contributing to surgical failure were identified through binary logistic regression.

RESULTS

The overall survival and success rates were 93.0% and 91.7%, respectively. The Cox regression model identified four risk factors affecting tooth survival, including apicoectomy of four teeth (HR = 35.488; P = 0.0002), an open apex observed on preoperative radiographs (HR = 6.300; P = 0.025), the performance of guided tissue regeneration technique (HR = 8.846; P = 0.028), and a palatal surgical approach (HR = 8.685; P = 0.030). The success rate demonstrated an initial increase in the early postoperative period (from 0.5 to 2 years; P = 5.8124e-30), followed by stabilization (from 2 to 9 years; P = 0.298). Surgery success rate significantly declined when apicoectomy involved four teeth (OR = 109.412; P = 0.002).

CONCLUSIONS

Endodontic microsurgery demonstrates satisfactory outcomes in complicated cases, maintaining a stable success rate after two years. However, tooth survival and surgery success are significantly compromised when apicoectomy involves four teeth. Factors such as guided tissue regeneration, an open apex, and the palatal surgical approach are associated with an increased risk of tooth extraction.

CLINICAL RELEVANCE

Despite achieving acceptable outcomes in complicated cases, endodontic microsurgery is adversely affected by the apicoectomy of four teeth.

Efficacy of mixture of injectable-platelet-rich fibrin and type-1 collagen particles on the closure of through-and-through periapical bone defects: A randomized controlled trial

AIM

To determine the efficacy of a combination of injectable-platelet-rich fibrin and type-1 collagen particles on the healing of through-and-through periapical bone defect and subsequent closure of bony window.

METHODOLOGY

The clinical trial was registered in ClinicalTrials.gov (NCT04391725). Thirty-eight individuals with radiographic evidence of periapical radiolucency in maxillary anterior teeth and confirmed loss of palatal cortical plates in cone beam computed tomographic imaging were randomly assigned to either the experimental group (n = 19) or the control group (n = 19). A mixture of i-PRF and collagen as a graft was applied to the defect in adjunct to periapical surgery in the experimental group. No guided bone regeneration procedures were used in the control group. The healing was evaluated using Molven's (2D) and modified PENN 3D (3D) criteria. Percentage reduction of the buccal and palatal bony window area, and complete closure of through-and-through periapical bony window (tunnel defect) were assessed using Radiant Diacom viewer software (Version 4.0.2). The reduction in the periapical lesion area and volume was measured using Corel DRAW and ITK Snap software.

RESULTS

Thirty-four participants (18 and 16 in the experimental and control groups respectively) reported for follow-up at 12 months. There was 96.9% and 97.96% reduction of buccal bony window area in the experimental and control groups respectively. Similarly, palatal window showed 99.03% and 100% reduction in the experimental and control groups respectively. No significant difference in both buccal and palatal window reduction was noticed between the groups. A total of 14 cases (seven in the experimental group and seven in the control group) showed complete closure of through-and-through bony window. No significant difference in clinical, 2D and 3D radiographic healing, percentage reduction in area and volume was observed between the experimental and control groups (p > .05). Neither the area nor the volume of lesion, and the size of buccal or palatal window had significant effect on healing of through-and-through defects.

CONCLUSION

Endodontic microsurgery results in high success rate in large periapical lesions with through-and-through communication with more than 80% reduction in volume of lesion and size of both buccal and palatal window after 1 year. A mixture of type-1 collagen particles and i-PRF, adjunct to periapical micro-surgery did not improve the healing in through-and-through periapical defects.

Present status and future directions - Managing perforations

Root perforations are severe complications and are associated with compromised endodontic treatment outcomes, especially when bacterial infection is allowed to establish. Perforations may occur due to pathological processes or treatment consequences. Various dental materials have been proposed over the years for perforation repair with varying degrees of success. The use of bioactive materials, such as mineral trioxide aggregate (MTA) and other calcium-silicate cements, promotes a favourable environment for regeneration and has been used successfully for perforation repair. This is in contrast to materials used previously that often led to unpredictable outcomes. With the increasing range of new bioactive endodontic materials available, the number of potential materials being used for repair of root perforations is growing. Though promising to date, there is little evidence to support the use of most of these new materials. The aim of this narrative review is to provide the background, clinical techniques and outcome of nonsurgical and surgical perforation repair.

Guided Tissue Regeneration in Surgical Endodontic Treatment: Case Report and Literature Review

Background/Aim: Guided tissue regeneration is widely used in endodontic surgery. The aim is to aid in the healing process and bone regeneration and provide more successful and predictable outcomes.

Case report: This case report describes the successful treatment of an endodontic-periodontal lesion (with primary endodontic involvement), including root canal retreatment and endodontic surgery with the use of GTR (collagen absorbable membrane-xenogeneic bone graft). CBCT examination was used to aid in diagnosis and in the follow-up examination after two years to provide additional confirmation of the healing process. An extensive literature review was undertaken focusing on clinical studies that assessing the added benefit of GTR in surgical endodontics. The clinical and radiographic examinations showed uneventful healing and the reconstruction of the buccal plate and periapical area. The patient remained asymptomatic throughout the entire two years period after surgical intervention. A literature review concluded that lesion type, lesion size and the selection of the biomaterial are important factors that influence the outcome of GTR in comparison control groups. A favorable outcome was found in cases of large periapical lesions (>10mm), through-through lesions and with the use of an absorbable membrane, with or without a bone graft.

Conclusions: GTR is thought to provide an added benefit in bone regeneration and the healing process in specific cases. The outcomes in the case report are consistent with the conclusions of literature review.

Analysis of the Osteogenic Effects of Biomaterials Using Numerical Simulation

We describe the development of an optimization algorithm for determining the effects of different properties of implanted biomaterials on bone growth, based on the finite element method and bone self-optimization theory. The rate of osteogenesis and the bone density distribution of the implanted biomaterials were quantitatively analyzed. Using the proposed algorithm, a femur with implanted biodegradable biomaterials was simulated, and the osteogenic effects of different materials were measured. Simulation experiments mainly considered variations in the elastic modulus (20–3000 MPa) and degradation period (10, 20, and 30 days) for the implanted biodegradable biomaterials. Based on our algorithm, the osteogenic effects of the materials were optimal when the elastic modulus was 1000 MPa and the degradation period was 20 days. The simulation results for the metaphyseal bone of the left femur were compared with micro-CT images from rats with defective femurs, which demonstrated the effectiveness of the algorithm. The proposed method was effective for optimization of the bone structure and is expected to have applications in matching appropriate bones and biomaterials. These results provide important insights into the development of implanted biomaterials for both clinical medicine and materials science.

Synchronization of calcium sulphate cement degradation and new bone formation is improved by external mechanical regulation

A major challenge faced in the bone materials of weight-bearing without internal fixture support is the mismatch of material degradation and new bone formation, leading to weakening or even failure of the overall bony structure. This study demonstrated in the rat femur model that calcium sulphate cement degradation and new bone formation could be better synchronized by external mechanical force. An ascending force in line with calcium sulphate cement degradation could achieve bone healing in 37 days with ultimate load to failure of 87.00 ± 7.30 N, similar to that of intact femur (80.46 ± 2.79 N, p = 0.369). In contrast, the healing process under either a constant force or no force illustrated significant residual defect volumes of 1.47 ± 0.44 and 4.08 ± 0.89 mm(3) (p < 0.001), and weaker ultimate loads to failure of 69.56 ± 4.74 and 59.17 ± 7.48 N, respectively (p < 0.001). Our results suggest that the mechanical regulation approach deserves further investigation and may potentially offer a clinical strategy to improve synchronization.

A new dimension in endo surgery: Micro endo surgery

There is an immense difference between tradizional Endodontic Surgery and Micro-Endo Surgery. Microsurgical techniques made possible and accessible results,that were unimaginable before. Under microscopic control,the operative techniques reached continous changes,allowing a better precision and quality standards. The dramatic evolution from Endo Surgery to Micro-Endo Surgery has enlarged the horizon of therapeutic options. Illumination and magnification through the Microscope has fundamentally and radically changed the way endo surgery can be performed.

Mechanical force enhanced bony formation in defect implanted with calcium sulphate cement

To improve the osteogenic property of bone repairing materials and to accelerate bone healing are major tasks in bone biomaterials research. The objective of this study was to investigate if the mechanical force could be used to accelerate bone formation in a bony defect in vivo. The calcium sulfate cement was implanted into the left distal femoral epiphyses surgically in 16 rats. The half of rats were subjected to external mechanical force via treadmill exercise, the exercise started at day 7 postoperatively for 30 consecutive days and at a constant speed 8 m·min⁻¹ for 45 min·day⁻¹, while the rest served as a control. The rats were scanned four times longitudinally after surgery using microcomputed tomography and newly formed bone was evaluated. After sacrificing, the femurs had biomechanical test of three-point bending and histological analysis. The results showed that bone healing under mechanical force were better than the control with residual defect areas of 0.64±0.19 mm² and 1.78±0.39 mm² (P<0.001), and the ultimate loads to failure under mechanical force were 69.56±4.74 N, stronger than the control with ultimate loads to failure of 59.17±7.48 N (P=0.039). This suggests that the mechanical force might be used to improve new bone formation and potentially offer a clinical strategy to accelerate bone healing.

Biologic response of local hemostatic agents used in endodontic microsurgery

Appropriate use of local hemostatic agent is one of the important factors on the prognosis of endodontic microsurgery. However, most investigations to date focus on the hemostatic efficacy of the agents, whereas their biologic characteristics have not received enough attention. The purpose of this paper was to review the biologic response of local hemostatic agents, and to provide clinical guidelines on their use during endodontic microsurgery. Electronic database (PUBMED) was screened to search related studies from 1980 to 2013, and 8 clinical studies and 18 animal studies were identified. Among the materials used in these studies, most widely-investigated and used materials, epinephrine, ferric sulfate (FS) and calcium sulfate (CS), were thoroughly discussed. Influence of these materials on local tissue and systemic condition, such as inflammatory and foreign body reaction, local ischemia, dyspigmentation, delayed or enhanced bone and soft tissue healing, and potential cardiovascular complications were assessed. Additionally, biological property of their carrier materials, cotton pellet and absorbable collagen, were also discussed. Clinicians should be aware of the biologic properties of local hemostatic agents and their carrier materials, and should pay attention to the potential complications when using them in endodontic microsurgery.

Integration of a novel injectable nano calcium sulfate/alginate scaffold and BMP2 gene-modified mesenchymal stem cells for bone regeneration

The repair of craniofacial bone defects is surgically challenging due to the complex anatomical structure of the craniofacial skeleton. Current strategies for bone tissue engineering using a preformed scaffold have not resulted in the expected clinical regeneration due to difficulty in seeding cells into the deep internal space of scaffold, and the inability to inject them in minimally invasive surgeries. In this study, we used the osteoconductive and mechanical properties of nano-scale calcium sulfate (nCS) and the biocompatibility of alginate to develop the injectable nCS/alginate (nCS/A) paste, and characterized the effect of this nCS/A paste loaded with bone morphogenetic protein 2 (BMP2) gene-modified rat mesenchymal stem cells (MSCs) on bone and blood vessel growth. Our results showed that the nCS/A paste was injectable under small injection forces. The mechanical properties of the nCS/A paste were increased with an increased proportion of alginate. MSCs maintained their viability after the injection, and MSCs and BMP2 gene-modified MSCs in the injectable pastes remained viable, osteodifferentiated, and yielded high alkaline phosphatase activity. By testing the ability of this injectable paste and BMP2-gene-modified MSCs for the repair of critical-sized calvarial bone defects in a rat model, we found that BMP2-gene-modified MSCs in nCS/A (nCS/A+M/B2) showed robust osteogenic activity, which resulted in consistent bone bridging of the bone defects. The vessel density in nCS/A+M/B2 was significantly higher than that in the groups of blank control, nCS/A alone, and nCS/A mixed with MSCs (nCS/A+M). These results indicate that BMP2 promotes MSCs-mediated bone formation and vascularization in nCS/A paste. Overall, the results demonstrated that the combination of injectable nCS/A paste and BMP2-gene-modified MSCs is a new and effective strategy for the repair of bone defects.

Aesthetic and functional management of a patient with Cornelia de Lange syndrome

Cornelia de Lange syndrome is a syndrome of multiple congenital anomalies. The genetic and molecular bases of these lesions are not clear. It is divided into three types based on the severity of the anomaly. Dental findings revealed contracted maxilla, malaligned teeth, multiple impacted and missing teeth. This article describes the successful management of upper central incisor with lateral opening in the apical third on the mesial surface of the root along with aesthetic and functional rehabilitation.

Effect of guided tissue regeneration on the outcome of surgical endodontic treatment: a systematic review and meta-analysis

INTRODUCTION

The use of guided tissue regeneration (GTR) techniques has been proposed as an adjunct to endodontic surgery in order to promote bone healing. Studies assessing the added benefits of GTR for the outcome of endodontic surgery are significantly variable in their treatment protocols, follow-up periods, and inclusion criteria, thus generating inconsistent and confusing results. The aim of this study was to evaluate the influence of GTR on the outcome of surgical endodontic treatment by means of a systematic review of the literature and meta-analysis.

METHODS

An exhaustive literature search combined with strict inclusion and exclusion criteria was undertaken to identify clinical studies that assessed the added benefit of GTR in endodontic surgery.

RESULTS

A trend of better outcome was found when GTR was used compared to control cases, but the results were not statistically significant. Lesion size, lesion type, and membrane type were identified as factors significantly affecting the outcome of GTR versus control cases. GTR techniques favorably affected the outcome of surgical endodontic treatments in cases of large periapical lesions and through-and-through lesions. A favorable outcome was found when using a resorbable membrane over using a nonresorbable membrane or graft alone.

CONCLUSIONS

GTR techniques may improve the outcome of bone regeneration after surgical endodontic treatments of teeth with certain lesions. Additional large-scale prospective clinical studies are needed to further evaluate possible benefits of GTR techniques in endodontic surgery.

Use of a matrix for apexification procedure with mineral trioxide aggregate

This articles describes a technique for placement of a matrix barrier prior to use of mineral trioxide aggregate (MTA) as an artificial root-end barrier. The technique also demonstrates the use of a delivery system utilizing large-bore needles for the predictable and precise placement of the barrier materials at the apex of the tooth.

Alveolar bone regeneration around immediate implants using an injectable nHAC/CSH loaded with autogenic blood-acquired mesenchymal progenitor cells: an experimental study in the dog mandible

BACKGROUND

Lack of osseointegration between a dental implant and the walls of the alveolar bone is a common problem in immediate implantation. Injectable tissue-engineered bone (ITB) may be an effective and minimally invasive solution to the problem. In this study, an injectable bone cement, nHAC/CSH, which consists of nano-hydroxyapatite/collagen (nHAC) and calcium sulfate hemihydrate (CaSO4 .½H2 O; CSH) was investigated as a tissue-engineered scaffold material with blood-acquired mesenchymal progenitor cells (BMPC) as seeding cells.

PURPOSE

The aim of the study was to assess the new bone formation around immediate dental implants using nHAC/CSH loaded with dog blood-acquired mesenchymal progenitor cells (dBMPC) in a canine model.

MATERIALS AND METHODS

dBMPC were first isolated from peripheral blood of healthy adult dogs. Alizarin red and oil red O staining were then used to evaluate the potential of dBMPC to differentiate into bi-lineage mesenchymal tissues in vitro. Four healthy mongrel dogs were used in this study. The alveolar bone defects around immediate implants of dogs were created. Each defect was randomly assigned to one of the following three groups: (1) the ITB group (dBMPC+nHAC/CSH); (2) injectable bone cement nHAC/CSH; or (3) no materials (controls). Methylene blue staining was used to examine the bone formation after 3 months.

RESULTS

Studies in vitro revealed that dBMPC could be induced to osteoblasts and adipocytes. The ITB group (dBMPC+nHAC/CSH) showed significantly more bone-implant contact and bone density than either nHAC/CSH or control groups in the areas with peri-implant defects 3 months after implantation.

CONCLUSION

The results indicate that the ITB composed of nHAC/CSH and dBMPC may represent a useful strategy for the clinical reconstruction of bone defects around immediate implantation. However, further investigation is needed involving the use of human BMPC as well as possible use of stem cells.

The use of regenerative techniques in apical surgery: A literature review

Apical surgery has become a standard of care for tooth maintenance if conventional endodontic retreatment is not possible or associated with risks. However, in certain situations, the outcome of apical surgery may be compromised due to the extent or location of the periapical or periradicular lesions. The present review article including clinical and experimental studies reports and discusses the outcome of regenerative techniques (RT) in conjunction with apical surgery, with regard to the type of periradicular lesions:

APICAL LESIONS

The majority of studies have shown no benefit for healing in test sites treated with RT compared to control sites treated without RT. The use of a radio-opaque bone filler/substitute may even compound the radiographic interpretation of periapical healing. Currently, the use of RT for lesions <10 mm limited to the apical area is not warranted.

THROUGH-AND-THROUGH LESIONS

All reviewed studies demonstrated a better outcome for test sites with RT compared to the control sites without RT; hence the use of RT for treatment of tunnel lesions in apical surgery is recommended.

APICO-MARGINAL LESIONS

All clinical studies assessed cohorts without controls, and, therefore, no firm conclusion about the benefit of RT for treatment of apico-marginal lesions in conjunction with apical surgery can be drawn. However, the experimental animal studies have shown that healing of teeth with apico-marginal lesions appears to benefit from RT.

Improvement on the performance of bone regeneration of calcium sulfate hemihydrate by adding mineralized collagen

Comparative investigations of bone regeneration performance for calcium sulfate hemihydrate (CaSO(4).(1/2)H(2)O; CSH) only and CSH with mineralized collagen are reported in this article. The mineralized collagen is the nanohydroxyapatite/collagen (nHAC). The investigations included biocompatibility in vitro and performance of bone repair in vivo. Quantitative and qualitative biocompatibility assays with bone stromal stem cells were performed. A critical box-shaped defect model in the mandible of the rabbit was used to evaluate the bone-remodeling ability of CSH and nHAC/CSH. Results in vitro indicated that the nHAC/CSH significantly improved bioactivity compared with that of CSH, especially in promoting cell adhesion. Further, a higher bone remodeling activity was observed around nHAC/CSH composite than the CSH, especially at the early stage of remodeling. This result means that nHAC/CSH could cause an earlier accelerator and better osseointegration for bone repair than CSH only.

Augmentation of screw fixation with injectable calcium sulfate bone cement in ovariectomized rats

The objective of this study was to determine the effect of augmenting screw fixation with an injectable calcium sulfate cement (CSC) in the osteoporotic bone of ovariectomized rats. The influence of the calcium sulfate (CS) on bone remodeling and screw anchorage in osteoporotic cancellous bone was systematically investigated using histomorphometric and biomechanical analyses. The femoral condyles of 55 Sprague-Dawley ovariectomized rats were implanted with screw augmented with CS, while the contralateral limb received a nonaugmented screw. At time intervals of 2, 4, 8, 12, and 16 weeks, 11 rats were euthanized. Six pair-matched samples were used for histological analysis, while five pair-matched samples were preserved for biomechanical testing. Histomorphometric data showed that CS augmented screws activated cancellous bone formation, evidenced by a statistically higher (p < 0.05) percentage of osteoid surface at 2, 4, and 8 weeks and a higher rate of bone mineral apposition at 12 weeks compared with nonaugmented screws. The amount of the bone-screw contact at 2, 8, and 12 weeks and of bone ingrowth on the threads at 4 and 8 weeks was greater in the CS group than in the nonaugmented group (p < 0.05), although these parameters increased concomitantly with time for both groups. The CS was resorbed completely at 8 weeks without stimulating fibrous encapsulation on the screw surface. Also, the cement significantly increased the screw pull-out force and the energy to failure at 2, 4, 8, and 12 weeks after implantation, when compared with the control group (p < 0.05). These results imply that augmentation of screw fixation with CS may have the potential to decrease the risk of implant failure in osteoporotic bone.

Marine derived polysaccharides for biomedical applications: chemical modification approaches

Polysaccharide-based biomaterials are an emerging class in several biomedical fields such as tissue regeneration, particularly for cartilage, drug delivery devices and gelentrapment systems for the immobilization of cells. Important properties of the polysaccharides include controllable biological activity, biodegradability, and their ability to form hydrogels. Most of the polysaccharides used derive from natural sources; particularly, alginate and chitin, two polysaccharides which have an extensive history of use in medicine, pharmacy and basic sciences, and can be easily extracted from marine plants (algae kelp) and crab shells, respectively. The recent rediscovery of poly-saccharidebased materials is also attributable to new synthetic routes for their chemical modification, with the aim of promoting new biological activities and/or to modify the final properties of the biomaterials for specific purposes. These synthetic strategies also involve the combination of polysaccharides with other polymers. A review of the more recent research in the field of chemical modification of alginate, chitin and its derivative chitosan is presented. Moreover, we report as case studies the results of our recent work concerning various different approaches and applications of polysaccharide-based biomaterials, such as the realization of novel composites based on calcium sulphate blended with alginate and with a chemically modified chitosan, the synthesis of novel alginate-poly(ethylene glycol) copolymers and the development of a family of materials based on alginate and acrylic polymers of potential interest as drug delivery systems.

Evaluation of surgical cavities filled with three types of calcium sulfate

The aim of this study was to evaluate histologically, three types of calcium sulfate - Merck (Brazil), Surgiplaster (Italy) and Capset (USA) - in surgically created defects on rabbit femurs. Twenty male New Zealand rabbits were used. Two surgical bone defects (5 mm diameter x 8 mm depth) were created on each distal epiphysis using a #3 Dentoflex trephine bur. Defects were filled with: group 1 - di-hydrated calcium sulfate (Merck); group 2 - Capset (Lifecore-USA); group 3 - Surgiplaster (Classimport-Italy); group 4 - control (blood clot). The animals were sacrificed 30, 60, 90 and 180 days postoperatively. Semi-serial 6-mm-thick sections were obtained, stained with hematoxylin and eosin and examined under light microscopy. Bone defects treated with calcium sulfate exhibited new bone formation regardless of the product trademark.

Development of a new calcium sulphate-based composite using alginate and chemically modified chitosan for bone regeneration

In this work we developed a novel calcium sulphate-based composite in which the hemihydrate calcium sulphate (CHS) can be encapsulated in a polymeric biodegradable and biocompatible matrix, in order to retain the structural integrity and decrease the bioresorption rate in bone regeneration applications. Two polymers were employed to realize this system: chitosan (Ch) and sodium alginate (Alg), both already widely used in biotechnological and biomedical applications. Chitosan was modified in order to obtain a water soluble polymer, the N-succinylchitosan (sCh). The reaction was performed with succinic anhydride in presence of pyridine and confirmed by FT-IR and NMR analyses. Finely ground Alg and sCh powders were mixed in different compositions with CHS and by adding water to the powder mixture it was obtained a mouldable paste that sets in few hours. Thermogravimetric analyses coupled with solvent extraction performed on the composite proved the alginate crosslinking in the presence of CHS. Mechanical studies carried out on composites of different compositions demonstrated that the blend of the two polymeric components causes a substantial synergistic reinforcement of composites. The presence of carboxylic groups on sCh chain in addition to those of alginate could enhance the chelating power of polysaccharide mixture. The results obtained with morphological analyses (SEM) further confirmed the hypotesis of the synergistic effect between alginate and N-succinylchitosan in presence of calcium sulphate. In vitro cytotoxicity tests proved that the developed system was not cytotoxic.

A Novel Injectable Poly(ɛ-caprolactone)/Calcium Sulfate System for Bone Regeneration: Synthesis and Characterization

A novel poly(epsilon-caprolactone)/calcium sulfate system was prepared and characterized in order to enhance calcium sulfate (gypsum) performance as bone graft substitute overcoming its brittleness and fast resorption rate. A poly(epsilon-caprolactone) (PCL) photo-crosslinkable derivative (PCLf) was synthesized by reaction of a low molecular weight PCL diol with methacryloyl chloride and confirmed by FT-IR and 1H NMR analyses. An injectable and easy mouldable mixture of PCLf and calcium sulfate hemi-hydrate (PCLf/CHS) was obtained. Thermal analyses and solvent extraction proved the occurrence of PCLf photo-crosslinking, even in the presence of CHS, in a time suitable for clinical applications. Swelling studies demonstrated that the encapsulation of the inorganic filler increases network hydrophilicity making it more permeable to water. Scanning electron microscopy, performed on crosslinked PCLf/CHS and on the same material after incubation in a PBS solution, showed the feasibility to obtain, in situ, gypsum entrapped into a degradable polymeric network. In vitro cytotoxicity tests, performed according to ISO 10993-5, proved that the developed system was not cytotoxic supporting its potential use in tissue engineering as a new, injectable, photocurable bone graft material. SEM micrograph of calcium sulfate di-hydrate (gypsum) entrapped in the PCL network.

Dual growth factor delivery and controlled scaffold degradation enhance in vivo bone formation by transplanted bone marrow stromal cells

Supraphysiological concentrations of exogenous growth factors are typically required to obtain bone regeneration, and it is unclear why lower levels are not effective. We hypothesized that delivery of bone progenitor cells along with appropriate combinations of growth factors and scaffold characteristics would allow physiological doses of proteins to be used for therapeutic bone regeneration. We tested this hypothesis by measuring bone formation by rat bone marrow stromal cells (BMSCs) transplanted ectopically in SCID mice using alginate hydrogels. The alginate was gamma-irradiated to vary the degradation rate and then covalently modified with RGD-containing peptides to control cell behavior. In the same delivery vehicle, we incorporated bone morphogenetic protein-2 (BMP2) and transforming growth factor-beta3 (TGF-beta3), either individually or in combination. Individual delivery of BMP2 or TGF-beta3 resulted in negligible bone tissue formation up to 22 weeks, regardless of the implant degradation rate. In contrast, when growth factors were delivered together from readily degradable hydrogels, there was significant bone formation by the transplanted BMSCs as early as 6 weeks after implantation. Furthermore, bone formation, which appeared to occur by endochondral ossification, was achieved with the dual growth factor condition at protein concentrations that were more than an order of magnitude less than those reported previously to be necessary for bone formation. These data demonstrate that appropriate combinations of soluble and biomaterial-mediated regulatory signals in cell-based tissue engineering systems can result in both more efficient and more effective tissue regeneration.