Effects of Chitosan as a Novel Obturation Material for Pulpectomized Teeth on Periapical Inflammation, Periodontal Ligament Widening, and Hard Tissue Resorption: A Preliminary Exploratory Study on Dogs.

Objectives: This preliminary animal study was conducted to assess the effects of chitosan as a novel obturation material for pulpectomized teeth on periapical inflammation, periodontal ligament (PDL) widening, and hard tissue resorption. Materials and Methods: Forty premolar root canals in two mature dogs were obturated with zinc oxide eugenol (ZOE) and an experimental 3% chitosan paste (n=20 in each group). The teeth were then restored with amalgam. After 28 days, the dogs were sacrificed, and histopathological assessment was performed. The amount of resorbed obturation material, degree of inflammatory response, degree of PDL widening, and the number of bone/cementum/dentin resorption defects were recorded under ×40 and ×200 magnifications. Data were analyzed using the Mann-Whitney U test, one-sample Wilcoxon signed-rank test, and Fisher's exact test (α=0.05). Results: Bone, cementum, and dentin resorption were seen in 6, 10, and 1 chitosan-obturated canals and 14, 15, and 0 ZOE-obturated canals, respectively. Only the bone resorption defects were significantly fewer in the chitosan group (P=0.026). Mild, moderate, and severe inflammation were observed in 17, 3, and 0 chitosan-obturated canals, and 7, 9, and 4 ZOE-filled canals, respectively (P=0.004). Mild, moderate, and severe PDL widening were seen around 15, 5, and 0 chitosan-filled canals and 7, 12, and 1 ZOE-filled canals, respectively (P=0.025). Conclusion: The 3% chitosan was superior to ZOE in terms of causing less inflammation and PDL widening. It also decreased bone resorption and acted similar to ZOE in terms of dentin and cementum resorption.

Preclinical in vivo assessment of a cell-free multi-layered scaffold prepared by 3D printing and electrospinning for small-diameter blood vessel tissue engineering in a canine model.

Tissue-engineered vascular grafts (TEVGs) are promising alternatives to existing prosthetic grafts. The objective of this study is to evaluate the clinical feasibility of a novel multi-layered small-diameter vascular graft that has a hierarchical structure. Vascular grafts with elaborately designed composition and architecture were prepared by 3D printing and electrospinning and were implanted into the femoral artery of 5 dogs. The patency of the grafts was assessed using Doppler ultrasonography. After 6 months, the grafts were retrieved and histological and SEM examinations were conducted. During implantation, the grafts exhibited resistance to kinking and no blood seepage thanks to the helical structure of the innermost and outermost layers. The grafts showed a high patency rate and remodelling ability. At 6 months post-implantation, the lumen was endothelialized and middle layers were regenerated by infiltration of smooth muscle cells (SMCs) and deposition of extracellular matrix (ECM). These results suggest that the multi-layered vascular graft may be a promising candidate for small-diameter blood vessel tissue engineering in clinical practice.

In vivo assessment of bone repair by an injectable nanocomposite scaffold for local co-delivery of autologous platelet-rich plasma and calcitonin in a rat model.

BACKGROUND: Gellan gum is obtained from the bacterium Sphingomonas elodea and is a polysaccharide with carboxylic acid functional groups. The goal of this project was to investigate the osteoinductive effect of local administration of calcitonin through an injectable scaffold of gellan gum containing salmon calcitonin loaded in silsesquioxane nanoparticles, hydroxyapatite, and platelets rich plasma. METHODS: The femur of rats was defected by creating a 2 × 5 mm2 hole using an electric drill. The defect was filled with an injectable hydrogel scaffold composed of gellan gum enriched with salmon calcitonin loaded in silsesquioxane nanoparticles, hydroxyapatite, platelets rich plasma, and then the radiologic images were taken. Bone densitometry and the histologic studies were carried out by Hematoxylin & Eosin test. Biochemical analysis was done to measure the serum alkaline phosphatase (ALP), calcium, and calcitonin concentration. RESULTS: Healing of the bone defects and bone densitometry in the treated group by calcitonin-loaded scaffold was significantly higher (p < 0.05) and bone formation occupied 75% of the defect was greater than in other groups. Serum ALP and calcium levels in the scaffold-loaded calcitonin group were more than in the other groups (p < 0.05). The osteogenic marker genes also increased significantly (p < 0.05) with free calcitonin and the scaffold. CONCLUSIONS: Gellan gum-based scaffold loaded with calcitonin may be considered a promising local treatment to progress bone formation in repairing skeletal injuries.

Histological assessment of the local effect of different concentrations of aminoguanidine hydrochloride on bone healing in rats.

BACKGROUND: Nitric oxide (NO) has several functions in bone healing and affects bone metabolism. Selective inducible NO synthase (iNOS) inhibitors can be used to assess the efficacy of NO for healing of bone defects. This study sought to assess the local effect of different concentrations of aminoguanidine hydrochloride (AG), a selective iNOS inhibitor, on bone healing in rats. MATERIALS AND METHODS: In this animal experimental study, 72 rats were divided into six groups of control, placebo, 5% AG, 10% AG, 15% AG, and 20% AG. A bone defect measuring 5 mm × 5 mm was created in the femur. The defect remained empty in the control group. In the placebo group, neutral gel was placed in the bone defect, and in the remaining four AG groups, different concentrations of AG were applied to the defects. Bone healing was assessed histologically. The healing score in the six groups was analyzed by the Kruskal-Wallis test. A P < 0.05 was considered statistically significant. RESULTS: The healing score in 20%, 15%, 10%, and 5% AG groups was significantly higher than that in the neutral gel and control groups (P < 0.01). Among the four groups of AG, 20% concentration showed better results, but the difference was not significant. CONCLUSION: Four concentrations of AG caused greater bone healing compared to the other two groups. Selective iNOS inhibitors such as AG can be used to promote local bone healing.

Calcitonin-loaded octamaleimic acid-silsesquioxane nanoparticles in hydrogel scaffold support osteoinductivity in bone regeneration.

Novel osteoinductive scaffolds fabricated using the benefits of tissue engineering techniques accompanied by utilizing drugs can accelerate bone regeneration. The purpose of this study was to load salmon calcitonin (sCT) in octamaleimic acid-silsesquioxane (OMA-POSS) nanoparticles and enrich the hydrogel scaffold based on hydroxyapatite, Gelrite® and platelet-rich plasma (PRP) for use in bone tissue engineering. The loading efficiency, release percentage, particle size and zeta potential of the nanoparticles were evaluated. The proliferation of seeded MG-63 osteoblast cells on the designed scaffold, its cytotoxicity and osteo-conductivity were studied by alkaline phosphatase measurement and Alizarin red staining. The expression of cellular osteogenic markers such as collagen 1 (COL1A1), osteocalcin (BGLAP) and osteopontin (SPP1) was examined using reverse transcription polymerase chain reaction. The results revealed that the particle size of the nanoparticles varied between 94.2 and 199.2 nm and their negative surface charge increased after drug conjugation. The osteoblast cell proliferation and calcium granule production in the optimum formulation were significantly higher in comparison with the control group (p < 0.05). Osteogenic markers increased significantly after a specific number of days of cell culture compared to the control group (p < 0.05). The results also showed the potential of the designed scaffold in bone tissue engineering.

In-vivo evaluation of a partially resorbable poly l-lactic acid/ braided bioactive glass fibers reinforced composite for load bearing fracture fixation.

Our previous studies have been focused on the design, optimization and manufacture of a partially resorbable composite bone plate consisting of a poly l-lactic acid matrix reinforced with braided fabrics bioactive glass fibers (PLLA/BG). In the present study, the response of the composite samples, the degradation rate, the inflammatory response, fibrous capsule formation and tissue-implant bonding to the in-vivo environment were assessed via implantation in the rabbit subcutaneous tissue. Despite the presence of both enzymatic degradation and hydrolysis processes within the body, the rate of the molecular weight loss as an indicator of degradation did not show a significant difference with the in-vitro conditions. It was predicted that strength loss would show the same trend since it was a consequence of molecular chain disruption and the loss of molecular weight. Inexistence of chronic inflammation, as confirmed by our previous results on the controlled degradation rate, also showed the maintenance of the physiological pH in the peripheral environment of the implant. Moreover, lack of the fibrous capsule tissue around the implant indicated that the implant was bioactive. In addition, given the composition of the bioactive glass fibers, that could be bonded to soft and hard tissues, tissue bonding with the PLLA/BG composite samples was also observed, thereby confirming the bioactivity and biocompatibility of the proposed bone plate.

Polyhedral Oligomeric Silsesquioxane /Platelets Rich Plasma/Gelrite-Based Hydrogel Scaffold for Bone Tissue Engineering.

BACKGROUND: Polyhedral oligomeric silsesquioxane (POSS) is a monomer with silicon structure and an internal nanometric cage. OBJECTIVE: The purpose of this study was to provide an injectable hydrogel that could be easily located in open or closed bone fractures and injuries, and also to reduce the possible risks of infections caused by bone graft either as an allograft or an autograft. METHODS: Various formulations of temperature sensitive hydrogels containing hydroxyapatite, Gelrite, POSS and platelets rich plasma (PRP), such as the co-gelling agent and cell growth enhancer, were prepared. The hydrogels were characterized for their injectability, gelation time, phase transition temperature and viscosity. Other physical properties of the optimized formulation including compressive stress, compressive strain and Young's modulus as mechanical properties, as well as storage and loss modulus, swelling ratio, biodegradation behavior and cell toxicity as rheometrical parameters were studied on human osteoblast MG-63 cells. Alizarin red tests were conducted to study the qualitative and quantitative osteogenic capability of the designed scaffold, and the cell adhesion to the scaffold was visualized by scanning electron microscopy. RESULTS: The results demonstrated that the hydrogel scaffold mechanical force and injectability were 3.34±0.44 Mpa and 12.57 N, respectively. Moreover, the scaffold showed higher calcium granules production in alizarin red staining compared to the control group. The proliferation of the cells in G4.5H1P0.03PRP10 formulation was significantly higher than in other formulations (p<0.05). CONCLUSION: The optimized Gelrite/Hydroxyapatite/POSS/PRP hydrogel scaffold has useful impacts on osteoblasts activity, and may be beneficial for local drug delivery in complications including a break or bone loss.

Nano-Biphasic Calcium Phosphate Ceramic for the Repair of Bone Defects.

Calcium phosphate bioceramics has recently experienced increased interest in bone reconstruction. Mimicking of natural structure of bone, like the use of nanomaterials, is an attractive approach for generating scaffolds for bone regeneration. The aim of present study was to evaluate the effect of nanonization on the biphasic calcium phosphate (BCP) ceramic in the repair of bone cavities in the canine mandible. A commercial BCP was dry-milled in a high energy planetary ball mill with zirconia balls and container. Three holes (8 mm in diameter) were outlined to the depth of cortical bone of mandibular angle of 5 dogs bilaterally. The first hole (positive control group A, n = 10) was filled in with commercial BCP material. The second hole was loaded with the nanonized BCP (experimental group C, n = 10) and the third one was left untreated (negative control group B, n = 10). The defects were allowed to regenerate for 8 weeks. New bone formation was greater in groups A and C than in B. No difference was seen between group A and group C (P = 0.676). The residual bone material in group C (19.34 ±â€Š8.03) was as much as one-half of that in group A (38.69 ±â€Š7.90%) (P = 0.000). The negative control group B presented the highest amount of soft tissue within the bone defects. The least percentage of marrow space was found in the positive control group (13.23 ±â€Š13.52). Our results depicted that the rate of resorption increased significantly after nanonization even though the nano-sized BCP failed to make a superior regeneration than the ordinary BCP.

Selective nitric oxide synthase inhibitor promotes bone healing.

BACKGROUND: Nitric oxide (NO) has many functions in wound healing and bone metabolism. This study sought to assess the local effect of aminoguanidine (AG), a selective inducible NO synthase (iNOS) inhibitor, on the rate of bone healing. MATERIALS AND METHODS: This experimental interventional study was conducted on 36 rats, which were randomly divided into three groups of control, placebo, and AG. Bone defects measuring 5 mm × 5 mm were created in the femur. In control group, bone defects remained empty. A placebo gel was applied to defects in the placebo group. AG gel was placed in bone defects in AG group. New bone formation and healing were assessed using histological and histomorphometric analyses. The healing score and the percentage of new bone formation (total bone mass, immature bone, and mature bone) were compared among the three groups using the Kruskal-Wallis test and analysis of variance, respectively. A P < 0.05 was statistically significant. RESULTS: The mean healing score in AG group (3.17 ± 0.577) was significantly higher than that in control (2.67 ± 0.49) and the placebo (2.58 ± 0.515) groups (P = 0.036). The percentage of new mature (lamellar) bone in AG group (22.06 ± 1.90) was significantly higher than that in control (20.94 ± 2.03) and the placebo (20.53 ± 1.20) groups (P = 0.008). CONCLUSION: The rate of bone healing was faster in the AG compared to the other two groups. Local application of selective iNOS inhibitors like AG may be efficient as an adjunct in the clinical setting where local bone formation is required.