Polymeric Nanocomposite Hydrogel Scaffolds in Craniofacial Bone Regeneration: A Comprehensive Review.

Nanocomposite biomaterials combine a biopolymeric matrix structure with nanoscale fillers. These bioactive and easily resorbable nanocomposites have been broadly divided into three groups, namely natural, synthetic or composite, based on the polymeric origin. Preparing such nanocomposite structures in the form of hydrogels can create a three-dimensional natural hydrophilic atmosphere pivotal for cell survival and new tissue formation. Thus, hydrogel-based cell distribution and drug administration have evolved as possible options for bone tissue engineering and regeneration. In this context, nanogels or nanohydrogels, created by cross-linking three-dimensional polymer networks, either physically or chemically, with high biocompatibility and mechanical properties were introduced as promising drug delivery systems. The present review highlights the potential of hydrogels and nanopolymers in the field of craniofacial tissue engineering and bone regeneration.

Evaluation of socket healing in irradiated rats after diode laser exposure (histological and morphometric studies).

OBJECTIVE: The purpose of this study is to evaluate the effect of low-level laser therapy (LLLT) in enhancing bone repair in irradiated sockets of albino rats. DESIGN: Thirty male Swiss Albino rats ranging from 120 to 150 g were used in this study. The animals were subjected 6 gray gamma radiations. Three days post irradiation, right and left mandibular first molars were extracted. The sockets of the left sides were irradiated by (GaAIAs) diode laser device immediately after extraction, while the sockets of the right side were not exposed to the laser and served as control. The rats were randomly assigned into three groups (10 rats each) according to the date of sacrifice, 3, 7 and 10 days into groups I, II and III, respectively. The two sides of each mandible were separated. Each group was further subdivided into subgroups A and B (10 specimens each), where A represents the right side of the mandible and B represents the left side. The specimens were stained with hematoxylin and eosin, and Masson's trichrome. RESULTS: LLLT accelerated bone healing, while, radiotherapy induced delay of bone healing along the three experimental groups. This acceleration was assessed histologically by the presence of mature collagen fibre bundles and early new bone formation in the lased groups. Histomorphometric analysis revealed an increase in the area percentage of bone trabeculae in the lased sockets compared to the control ones in group II. This increase was statistically significant (p = 0.0274). The increase in the area percentage of bone trabeculae between the lased and control sockets of group III was statistically insignificant (p = 0.1903). CONCLUSIONS: In a rat model application of LLLT with a GaAIAs diode laser device can enhance bone healing and mineralisation in sockets subjected to gamma radiation.

Prophylactic effect of green tea and Nigella sativa extracts against fenitrothion-induced toxicity in rat parotid gland.

OBJECTIVE: The aim of the present study was to compare between two antioxidant treatments in prevention of fenitrothion induced toxicity on rat parotid salivary gland. DESIGN: Forty adult male Wistar rats with an average weight of 120-150 g were randomised into 4 groups, control (group I), fenitrothion administration (group II), fenitrothion administration 1h after green tea extract or Nigella sativa oil extract administration (groups III and IV respectively). The rats were then sacrificed after 28 days. The submandibular salivary glands were examined histologically, immunohistochemically and ultrastructurally. RESULTS: Histopathologically the fenitrothion group showed sign of acini degeneration represented by loss of normal architecture (amalgamation). The nuclei of the acinar cells revealed different sizes and shape (polymorphism). The acini relatively preserved their shape in both prophylactic groups (III and IV). Histomorphometric analysis showed significant increase in the optical density of caspase-3 cleaved activity in all experimental groups (p=0.0001). A significant difference was observed between both prophylactic experimental groups III and IV (p=0.0039). Ultrastructurally, the nuclei of serous acini in group II appeared pyknotic with segregation of chromatin. Condensation of the chromatin at the periphery of the nucleus was observed in the nuclei of group III, Clumping of the chromatin with darkly stained pyknotic nucleus was detected in group IV. CONCLUSIONS: In a rat model the administration of natural antioxidants could be of beneficial effect on prevention of cytotoxicity induced by organophosphorous compounds. However, green tea showed more promising results than that of Nigella sativa.

Ultrastructural and histomorphometric alterations of rat jaw bones after experimental induction of lathyrism.

OBJECTIVE: The aim of this study was to investigate the effect of beta-aminopropionitrile (beta-APN), present in Lathyrus sativus (L. sativus) seeds consumed in drought prone areas, on the maxillary and mandibular bones of rats. DESIGN: Eighteen rats were used; they were divided into experimental group (12 rats) and a control group (6 rats). In the experimental group, lathyrism was induced by a once daily subcutaneous administration of beta-APN at a dose of 5mg in 0.4ml distilled water per 100g of body weight for 40 days. The specimens were examined histologically, histomorphometrically and ultrastructurally. RESULTS: Histopathological examination of lathyritic rats showed that both mandible and maxillae were significantly affected. Irregular bone trabeculae with wide medullary cavities and abundant marrow spaces were observed. Focal resorptive areas lined with osteoclasts were also present. Histomorphometric analysis showed a decrease in the area percentage of bone in lathyritic rats as compared to the control. This decrease was statistically significant only in the mandible (p=0.018). Moreover, a significant increase in the number of osteoclasts (p=0.014, 0.012) and resorptive bays (p=0.013, 0.002) was detected in the maxillae and mandible of the experimental group, respectively. Ultrastructurally, there was a significant difference in the microarchitecture of the collagen fibres in lathyritic rats compared to the control. The collagen fibres in the lathyritic group appeared disorganized, fewer in number and more spaced. CONCLUSIONS: This study provided evidence for lathyritic disturbances in bone architecture. These disturbances are likely to affect mineralization and bone strength as well.