Rat Incisor Research Articles

Effect of sodium benzoate injections on the dentin biomineral ultrastructure of the lower incisor in white rats and its correction possibilities

Objective. To establish changes in the dentin biomineral ultrastructure of the lower incisor of white rats after a 60-day period of sodium benzoate (SB) injections and to substantiate the possibility of their correction with mexidol (MD) or thiotriazoline (TTZ). Materials and methods. 175 male rats weighing 200–210 g were used. SB was injected at a dose of 100 mg/kg/day, MD at a dose of 50 mg/kg/day, and TTZ at a dose of 117.4 mg/kg/day. The dentin biomineral ultrastructure of the lower incisor was studied by XRD analysis. Results. After a 60-day administration of SB, the crystallite sizes were larger than those in the control group from days 3 to 24 of readaptation by 6.06%, 7.88%, 6.58%, and 4.08%; the microtexturing coefficient (MC) from days 3 to 45 was lower by 8.23%, 6.53%, 8.12%, 6.77% and 4.90%. With the introduction of MD, dentin MC from days 10 to 45 exceeded the values of the control group by 2.75%, 3.31%, 3.64%, and 3.31%. With the introduction of TTZ, crystallite sizes from 3 to 15 days decreased by 3.87%, 5.23%, and 4.80%, and MC from 3 to 45 days increased by 2.76%, 3.43%, 3.83%, 4.09%, and 3.33%.Conclusion. SB injections to experimental animals is accompanied by destabilization of the dentin biomineral of the lower incisors. The introduction of MD or TTZ mitigates changes in the dentin biomineral ultrastructure. The use of TTZ was shown to be more effective.

MicroRNA-27a-5p Downregulates Expression of Proinflammatory Cytokines in Lipopolysaccharide-Stimulated Human Dental Pulp Cells via the NF-κB Signaling Pathway.

MicroRNA-27a-5p (miR-27a-5p) was significantly upregulated in dental pulp inflammation, yet its underlying mechanisms remain unclear. This study investigated the effect of miR-27a-5p on the expression of proinflammatory cytokines in human dental pulp cells (hDPCs) stimulated by lipopolysaccharide (LPS). LPS-stimulated hDPCs showed concurrent increases in the expression of miR-27a-5p and proinflammatory cytokines (IL-6, IL-8, and MCP1), and the increased expression was suppressed by NF-κB inhibitor BAY 11-0785. Transfection of the miR-27a-5p mimic downregulated the expression of proinflammatory cytokines, NF-κB activity, and the expression of NF-κB signaling activators (TAB1, IRAK4, RELA, and FSTL1) in LPS-stimulated hDPCs. Luciferase reporter assays revealed that miR-27a-5p bound directly to the 3'-UTR of TAB1. siTAB1 downregulated NF-κB activity and proinflammatory cytokine expression. Downregulation of proinflammatory cytokine expression, NF-κB activity, and NF-κB signaling activator expression (TAB1, IRAK4, and RELA) was also found in LPS-stimulated rat incisor pulp tissue explants following transfection with the miR-27a-5p mimic ex vivo. MiR-27a-5p, whose expression was induced by NF-κB signaling, negatively regulated the synthesis of proinflammatory cytokines via targeting NF-κB signaling. In particular, TAB1, a potent NF-κB activator, was targeted by miR-27a-5p. These results provide insights into the negative regulatory effects of miR-27a-5p, particularly those targeting the TAB1-NF-κB signaling pathway, on pulp inflammation.

Potential application of a combined extract of Channa striata and calcium hydroxide for inhibiting lymphocytes and interleukin-1β cells in the asymptomatic irreversible pulpitis of Wistar rats (Rattus norvegicus).

This study aimed to evaluate the effectiveness of combining Channa striata extract with calcium hydroxide (Ca(OH)2) in reducing lymphocyte counts and interleukin (IL)-1β levels in inflamed pulp teeth. A laboratory experimental setup with a posttest control group (CG) design was employed. Thirty-two rat incisor teeth were divided into four groups: a positive CG (100% Ca(OH)2), treatment 1 (25% C. striata extract + 75% Ca(OH)2), treatment 2 (50% C. striata extract + 50% Ca(OH)2), and treatment 3 (75% C. striata extract + 25% Ca(OH)2). These test materials were applied to Class 1 cavities extending to the pulp roof, with samples collected on days 1, 3, 5, and 7. Data were analyzed using analysis of variance and post hoc least significant difference tests. In all the groups, the highest levels of lymphocytes and IL-1β were observed on day 3, followed by a decline on days 5 and 7. The combination of C. striata extract with Ca(OH)2 significantly reduced inflammatory markers, particularly lymphocyte and IL-1β levels. The extract of C. striata holds significant potential as an innovative therapeutic approach for managing inflamed dental pulp.

“In Vivo Study on the Possible Desensitizing Role of Hydrocortisone versus Fluoride on the Dental Pulp of Albino Rat Incisor Subjected to Bleaching”

“In Vivo Study on the Possible Desensitizing Role of Hydrocortisone versus Fluoride on the Dental Pulp of Albino Rat Incisor Subjected to Bleaching”

Deciphering 3D periodontal fibroblast-macrophage crosstalk in bioactive nanoparticle-guided immunomodulation for treating traumatic dental avulsion

Prolonged extra-oral period in dental avulsion is often associated with loss of viability of Periodontal fibroblasts (PDLF) and increased risk of ankylosis. Root surface treatment with bioactive agents to reduce the risk of ankylosis can be a potential strategy. The objective of the study was to investigate the impact of an engineered chitosan nanoparticles (CSNP), photosensitizer Rose Bengal (RB) functionalized CSNP (CSRB) and sustained dexamethasone (CSDEX) releasing CSNP for application in management of delayed replantation of avulsed teeth. The 3D PDLF-macrophage (Mϕ) collagen model was developed and exposed to LPS, MCSF, RANKL with and without CSDEX/CSNP. Immunofluorescence and cytokine analysis was done at 2 and 7 days to assess cellular interactions. Maxillary right incisors in male Wistar rats were extracted, exposed to extraoral dry or LPS for 1 h and treated with or without CSDEX/CSRB for 1 min before replantation. Rats were euthanized after 21 days for micro-CT, TRAP, and immunofluorescence analysis. CSDEX/CSNP treatment in 3D model significantly reduced CD80, NFATc1, STAT6 and increased CD206 and periostin expression (p < 0.05). TNFα, MMP9 was downregulated and IL10, TGFβ1, MMP2 upregulated with CSDEX/CSNP (p < 0.05). CSDEX/CSRB in animal study significantly reduced resorption, ankylosis, TRAP activity and osteocalcin expression and increased periostin (p<0.05). CSDEX demonstrated higher anti-inflammatory activity by downregulating TNFα, while CSNP upregulated TGFβ1, periostin, and downregulated MMP9. The combination of matrix stabilization with CSRB with periostin upregulation and sustained releasing CSDEX showed potential for hampering root resorption and ankylosis in dental avulsion.

Quantity and diameter of dentinal tubules of human teeth and teeth of experimental animals according to scanning electron microscopy data

Insight into the interrelation between the structure and mechanical properties of dentin of a tooth is crucial for prevention and treatment of oral cavity diseases. The study of the structure of dental dentin is important for understanding the pathogenetic mechanisms of the spread of cariogenic microflora in progressive dental caries to the pulp and periodontium, as well as for the interpretation of the results of studies of dental dentin-adhesive materials. The in vitro research presented here involved the examination of coronal dentin in 46 intact teeth from rats, cats, dogs, and humans at various distances from the pulp chamber, with a focus on the quantity and diameter of dentinal tubules. The calculations were based on the analysis of 155 scanning electron microscope photographs of the enamel surface and pulp chamber wall. The researchers calculated the quantity and diameter of dentinal tubules per unit area, which they measured at various distances from the pulp chamber. It was found that dentinal tubules are the widest near the pulp chamber wall, where the average diameter ranged from 1.7 to 2.8 µm. The highest values were found in premolars of young humans and the lowest - in the incisors of rats. In the middle portion of the dentin, the diameter of dentinal tubules ranged from 1.0 to 13.3 µm, while at the periphery, it was 0.6–0.9 µm. The highest density of dentinal tubules per unit area was found closest to the pulp horn, and the lowest was in the enamel region. Near the pulp chamber wall, the average density of dentinal tubules ranged from 50 000 to 90 000/mm², in the middle of the dentin, it ranged from 37 000 to 50 000/mm², and at the periphery, it ranged from 10 000 to 25 000/mm². All examined teeth exhibited straight dentinal tubules, except for the rats’ incisors, which showed local irregularities. A comparison was made based on the quantity and width of dentinal tubules in the examined animals and humans.

Effects of obesity on the rat incisor enamel and dentine thickness, as well as on the hemimandible shape over generations

Obesity has several effects on the general body metabolism. However, little is known about the impact of obesity on the growth and shape of mineralized tissues like mandibles and teeth, as well as if it effects are passed down from generation to next. Therefore, in this study, we aimed to evaluate, over nine generations using the consanguineous mating (inbreeding), the effect of the obesity condition produced by the reduction in the number of rats per litter during the lactation period on the hemimandible shape, dentine, and enamel of the rat incisor. Litters were reduced to two males and two females after birth, and were consanguinity mated in adulthood for nine generations. For all evaluations performed in this investigation, only males were used. The control group was formed by a non-consanguineous litter containing eight males. The parameters evaluated were food consumption, body weight, Lee Index, and bone density of the hemimandible bone. Incisor enamel and dentine thickness were also evaluated. The hemimandible shape was evaluated using geometric morphometry. The results show a significant and progressive increase in food intake, Lee Index, body weight, hemimandible weight, and enamel thickness, and a decrease in dentine thickness. The linear measurements of the length of the ramus ascending hemimandibular segment were found to be shorter, while its height was increased. In contrast, the geometric morphometry shows that the general hemimandible shape changed over the consanguineous obesity generations. We conclude that over generations, obesity increases and maintains the parameters evaluated with significant changes in hemimandible shape as well as in the dimensions of enamel and dentine of incisors, suggesting that enamel and dentine could be used as phenotype biomarkers to detect changes in tooth and craniofacial development related to obesity effects.

Effect of ELVAX polymer subgingival implants with echistatin on extracted and reimplanted rats' teeth.

To investigate the effect of ELVAX polymer subgingival implants incorporated with echistatin peptide on incisor reimplanted tooth in rats. Forty-two male Wistars rats were divided into two groups: echistatin-treated rats (E) and control rats (C). The animals had their right maxillary incisors extracted and treated according to the International Association of Dental Traumatology replantation protocol. The extra-alveolar dry period was 30 and 60min, and the post-surgical experimental periods were 15, 60, and 90days. The samples were stained with H&E and analyzed for the presence of an inflammatory response, incidence of resorptions, and dental ankylosis. Results were statistically analyzed (p < 0.05). The presence of inflammatory resorption was significantly higher in group C at 30 and 60min extra-alveolar time, in the 15-day postoperative period as compared with the E group (p < 0.05). Dental ankylosis was significantly more prevalent in group E in 30min extra-alveolar time and 15days postoperative period (p < 0.05). However, in 60min extra-alveolar time and 60days postoperative period, dental ankylosis was more prevalent in C group (p < 0.05). The use of ELVAX subgingival implants with echistatin demonstrated therapeutic potential in preventing the experimental resorption process after replantation of maxillary incisors in rats.

MicroRNA-146b-5p Suppresses Pro-Inflammatory Mediator Synthesis via Targeting TRAF6, IRAK1, and RELA in Lipopolysaccharide-Stimulated Human Dental Pulp Cells.

MicroRNA-146b-5p (miR-146b-5p) is up-regulated during and to suppress the inflammation process, although mechanisms involved in the action of miR-146b-5p have not been fully elucidated. This study examined the anti-inflammation effects of miR-146b-5p in lipopolysaccharide (LPS)-stimulated human dental pulp cells (hDPCs). An increase in human miR-146b-5p (hsa-miR-146b-5p) expression following the mRNA expression of pro-inflammatory cytokines was observed in LPS-stimulated hDPCs. The expression of hsa-miR-146b-5p and pro-inflammatory cytokines was down-regulated by a nuclear factor-kappa B (NF-κB) inhibitor, and the expression of hsa-miR-146b-5p was also decreased by a JAK1/2 inhibitor. Enforced expression of hsa-miR-146b-5p abolished phosphorylation of NF-κB p65 and down-regulated the expression of pro-inflammatory cytokines and NF-κB signaling components, such as interleukin-1 receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6), and REL-associated protein involved in NF-κB (RELA). Expression of rat miR-146b-5p (rno-miR-146b-5p) and pro-inflammatory cytokine mRNA was also up-regulated in experimentally-induced rat pulpal inflammation in vivo, and rno-miR-146b-5p blocked the mRNA expression of pro-inflammatory mediators and NF-κB signaling components in LPS-stimulated ex vivo cultured rat incisor pulp tissues. These findings suggest that the synthesis of miR-146b-5p is controlled via an NF-κB/IL6/STAT3 signaling cascade, and in turn, miR-146b-5p down-regulates the expression of pro-inflammatory mediators by targeting TRAF6, IRAK1, and RELA in LPS-stimulated hDPCs.

Immunomodulatory Effect of Novel Electrospun Nanofibers Loaded with Doxycycline as an Adjuvant Treatment in Periodontitis.

The immunomodulatory effect of a novel biomaterial obtained through electrospinning, based on polylactic acid (PLA) and nano-hydroxyapatite (nano-HAP), loaded with doxycycline (doxy) was evaluated in an animal model. The treatment capabilities as a local non-surgical treatment of periodontitis was investigated on the lower incisors of Wistar rats, after the induction of localized periodontitis using the ligature technique. Following the induction of the disease, the non-surgical treatment of scaling and root planing was applied, in conjunction with the application of the new material. The results of the treatment were evaluated clinically, using the tooth mobility and gingival index scores, as well as histologically. The salivary concentrations of matrix metalloproteinase 8 (MMP-8) and plasmatic concentrations of interleukin 1 (IL-1), interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) were also monitored. Two weeks after the ligature application, the periodontal disease was successfully induced in rats. The application of the novel biomaterial obtained through electrospinning was proven to be more effective in improving the clinical parameters, while decreasing the salivary MMP-8 and plasmatic IL-1 and TNF-α concentrations, compared to the simple scaling and root planing. Thus, the novel electrospun biomaterial could be a strong candidate as an adjuvant to the non-surgical periodontal therapy.

The correlation between biotribological function and structural characteristics of bamboo rat teeth

Chinese bamboo rats consume a diet that consists mainly mechanically demanding bamboo. The ability of the rats to process food depends on the capacity of their teeth to resist wear during biting and chewing. The mechanisms of the bamboo rat teeth were determined by investigating and correlating the structure and tribological properties of the teeth. The rat's incisor has a cutting-edge cusp and outer enamel iron pigmentation, making the teeth harder, more resistant to acid attacks, and improving the resistance to cracking. Additionally, the incisor is designed to self-sharpen. The complex morphology at the macroscale, and the three-dimensional fabric body formed by densely packed rods and inter-rods at the microscale of molar enamel benefit molar rapid capture and effective breaking of bamboo, resisting the high stresses required to process bamboo without wear. The results of the structure–function relations of bamboo rat teeth in this study may provide new ideas for improving plant cutting and grinding tools.

The Role of Lead Toxicity on Eruption Rate of Hypofunctional Incisors in Albino Wistar Rats

OBJECTIVES This objective of this study was to evaluate the role of a heavy metal- lead acetate in the eruption rate of hypo functional incisors in albino Wistar rats. METHODOLOGY An experimental study was done in animal house of Post Graduate Medical Institute, Lahore since March 2019 to March 2020. 34 adult albino Wistar rats were randomly divided into two groups (n=17 for each group) i.e., control and lead acetate group. Right mandibular incisors were selected for this study. Selected incisors were marked 1mm above the level of gingival papillae. The incisors were cut above this mark to make it hypo-functional. The readings were measured by digital Vernier caliper. This was considered as day 0. Incisors length was measured at day 0, 3, 6, 12 and 15 and eruption was calculated. The data was analyzed using SPSS version 22. RESULTS Eruption rate was similar throughout the study except last follow up. At the end of this study eruption of incisors in albino Wistar rats in control was 03.30±0.72mm, in lead 02.43±1.19mm. At day 15, the difference between control and lead group was statistically significant (p-value 0.033). CONCLUSION These results reveal that besides other causes of delayed tooth eruption excessive lead intoxication are also acausative factor of delayed tooth eruption.

Effects of immunoglobulin Y-loaded amorphous calcium phosphate on dentinal tubules occlusion and antibacterial activity.

Aim: This study aimed to evaluate the effects of immunoglobulin Y (IgY)-loaded amorphous calcium phosphate (ACP) (IgY@ACP) on dentinal tubule occlusion and antibacterial activity. Methodology: IgY@ACP was synthesized based on a biomimetic mineralization strategy. The structure was examined by transmission electron microscopy and Fourier transform infrared spectroscopy. The IgY release property was assessed in vitro. The cell biocompatibility of IgY@ACP was evaluated by CCK-8. The dentin disks were prepared using healthy human molars, and their dentinal tubules were exposed to EDTA. Subsequently, they were randomly selected and treated with or without IgY@ACP for 7 days. The tubule occlusion morphologies and newly formed layers were observed by scanning electron microscopy (SEM) and x-ray diffraction, respectively. To evaluate the acid resistance and abrasion resistance of IgY@ACP, dentin disks that were treated for 1 day were immersed in acid solution or subjected to a toothbrush. The antibacterial effects against Streptococcus mutans (S. mutans) were evaluated by colony-forming unit (CFU) counting, adhesion property assessment, and crystal violet and live/dead bacterial staining. Finally, the occlusion effect was evaluated in rat incisors in vivo. One-way analysis of variance (ANOVA) was performed for statistical analysis. The level of significance was set at 0.05. Results: IgY@ACP presented an amorphous phase with a nanosize (60–80 nm) and sustained release of protein within 48 h. The CCK-8 results showed that IgY@ACP had good biocompatibility. After treatment with IgY@ACP for 1 day, the majority of dentinal tubules were occluded by a 0.3-μm-thick mineralized layer. Seven days later, all dentinal tubules were occluded by mineralization with a thickness of 1.4 μm and a depth of 16 μm. The newly mineralized layer showed hydroxyapatite-like diffraction peaks. In addition, IgY@ACP had good acid and abrasion resistance. After treatment with IgY@ACP, the CFU counting and adhesion rate of S. mutans were significantly reduced, the crystal violet staining was lighter, and the S. mutans staining revealed more dead cells. Most importantly, IgY@ACP had a certain occluding property in rat incisors in vivo. Conclusion: IgY@ACP can effectively occlude dentinal tubules with acid-resistant stability and has prominent anti-S. mutans effects, rendering it a potentially suitable desensitization material in the clinic.

Investigating the Effects of Dehydrated Human Amnion-Chorion Membrane on Periodontal Healing.

Each growth factor (GF) has different effects and targets, and plays a critical role in periodontal healing. Dehydrated human amnion-chorion membrane (dHACM) contains various GFs and has been used to enhance wound healing. The purpose of this study was to evaluate the effects of dHACM on periodontal healing, using in vitro and in vivo experimental approaches. Standardized periodontal defects were created in rats. The defects were randomly divided into three groups: Unfilled, filled with hydroxypropyl cellulose (HPC), and dHACM+HPC. At 2 and 4 weeks postoperatively, periodontal healing was analyzed by microcomputed tomography (micro-CT), and histological and immunohistochemical analyses. In vitro, periodontal ligament-derived cells (PDLCs) isolated from rat incisors were incubated with dHACM extract. Cell proliferation and migration were evaluated by WST-1 and wound healing assay. In vivo, micro-CT examination at 2 weeks revealed enhanced formation of new bone in the dHACM+HPC group. At 4 weeks, the proportions of vascular endothelial growth factor (VEGF)-positive cells and α-smooth muscle actin (α-SMA)-positive blood vessels in the dHACM+HPC group were significantly greater than those in the Unfilled group. In vitro, dHACM extracts at 100 µg/mL significantly increased cell proliferation and migration compared with control. These findings suggest that GFs contained in dHACM promote proliferation and migration of PDLCs and angiogenesis, which lead to enhanced periodontal healing.

Role of Garlic (Allium Sativum) on Lead Induced Delayed Eruption of Incisors in Albino Wistar Rats

Role of Garlic (Allium Sativum) on Lead Induced Delayed Eruption of Incisors in Albino Wistar Rats

Impact of dams' diet on the levels of magnesium and zinc in the incisors of offspring rats

Impact of dams' diet on the levels of magnesium and zinc in the incisors of offspring rats

Craniofacial Bones and Teeth in Spacefarers: Systematic Review and Meta-analysis.

Estimating the risk of dental problems in long-duration space missions to the Moon and Mars is critical for avoiding dental emergencies in an environment that does not support proper treatment. Previous risk estimates were constructed based on the experience in short-duration space missions and isolated environments on Earth. However, previous estimates did not account for potential changes in dental structures due to space travel, even though bone loss is a known problem for long-duration spaceflights. The objective of this study was to systematically analyze the changes in hard tissues of the craniofacial complex during spaceflights. Comprehensive search of Medline, Embase, Scopus, the NASA Technical Report Server, and other sources identified 1,585 potentially relevant studies. After screening, 32 articles that presented quantitative data for skull in humans (6/32) and for calvariae, mandible, and lower incisors in rats (20/32) and mice (6/32) were selected. Skull bone mineral density showed a significant increase in spacefaring humans. In spacefaring rodents, calvariae bone volume to tissue volume (BV/TV) demonstrated a trend toward increasing that did not reach statistical significance, while in mandibles, there was a significant decrease in BV/TV. Dentin thickness and incisor volume of rodent incisors were not significantly different between spaceflight and ground controls. Our study demonstrates significant knowledge gaps regarding many structures of the craniofacial complex such as the maxilla, molar, premolar, and canine teeth, as well as small sample sizes for the studies of mandible and incisors. Understanding the effects of microgravity on craniofacial structures is important for estimating risks during long-duration spaceflight and for formulating proper protocols to prevent dental emergencies. Avoiding dental emergencies in long-duration spaceflights is critical since this environment does not support proper treatment. Prior risk estimates did not account for changes in dental structures due to space travel. We reviewed and synthesized the literature for changes in craniofacial complex associated with spaceflight. The results of our study will help clinicians and scientists to better prepare to mitigate potential oral health issues in space travelers on long-duration missions.

Age-related osteogenesis on lateral force application to rat incisor – Part III: Periodontal and periosteal bone remodeling

Objectives: This study was aimed to compare the histological pattern of bone modeling on either periodontal or periosteal side induced by lateral orthodontic tooth movement in different age groups. Material and Methods: A total of 50 male Sprague-Dawley rats (25 rats in the adult group – 52 weeks and 25 rats in the young group – 10 weeks) were utilized in this study. Each age group was classified into the control, 3 days, 7 days, 14 days, and 21 days groups (five rats in each) by the duration of experimental device application. A double-helical spring was produced using 0.014” stainless steel wire to provide 40 g lateral force to the left and right incisors. Hematoxylin-eosin staining, proliferating cell nuclear antigen (PCNA) immunohistochemical staining, fibroblast growth factor receptor 2 (FGFR2) immunohistochemical staining, and Masson trichrome staining were performed; and the slides were subject to histological examination. Results: In 7 days, active bone modeling represented by the scalloped surface was observed on the periosteal side of the crestal and middle alveolus at the pressure side in the young group, while similar changes were observed only on the crestal area in the adult group. In the young group, the number of PCNA-positive cells increased significantly on the crestal area and middle alveolus on the 3, 7, and 14 day groups, with subsequent decrease at 21 days. In the adult group, PCNA-positive cells were localized on the crestal area throughout the period. In the young group, FGFR2-positive cells were observed mainly on the crestal and middle alveolus at 3, 7, and 14 days than the control group. In the adult group, these cells appeared on the crestal and middle alveolus in the 3 days group, but mainly on the crestal area at 14 days. In the young group, FGFR2-positive cells were observed on the crestal and middle alveolus on the 3, 7, and 14 days groups more than on the control group. In the adult group, these cells appeared on the crestal and middle alveolus in the 3 days group, but mainly on the crestal area in the 14 days group. In Masson trichrome stain, an increased number of type I collagen fibers were observed after helical spring activation in both age groups. Large resorption lacunae indicating undermining bone resorption were progressively present in both young and adult groups. Conclusion: According to these results, orthodontic tooth movement may stimulate cell proliferation and differentiation primarily on the periosteal side according to progressive undermining bone resorption on the periodontal side. This response may lead to prominent bone modeling during tooth movement in the young group, compared to the relatively delayed response in the adult group.

Mechanical properties, microstructure and chemical composition of naked mole rat incisors

The naked mole rat incisors (NMRI) exhibit excellent mechanical properties, which make it a good prototype for design and fabrication of bionic mechanical systems and materials. In this work, we characterised the chemical composition, microstructure and mechanical properties of NMRI, and further compared these properties with the laboratory rat incisors (LRI). We found out that (i) Enamel and dentin are composed of organic matter, inorganic matter and water. The ratio of Ca/P in NMRI enamel is higher than that of LRI enamel. (ii) The dentin has a porous structure. The enamel has a three-dimensional reticular structure, which is more complex, regular and denser than the lamellar structure of LRI enamel. (iii) Enamel has anisotropy. Its longitudinal nano-hardness is greater than that of transverse nano-hardness, and both of them are higher than that of LRI enamel. Their nano-hardness and elastic modulus increase with the increase in distance from enamel-dentin boundary. The nano-hardness of dentin is smaller than that of enamel. The chemical composition and microstructure are considered to be the reasons for the excellent properties of NMRI. The chemical composition and unique microstructure can provide inspiration and guide for the design of bionic machinery and materials.

Biomimetic Fe‐hydroxyapatite nanoparticle‐reinforced bisphenol A‐glycol methacrylate/triethyleneglycol‐dimethacrylate resins for dental restorative application

AbstractCommercial bisphenol A‐glycol methacrylate (BisGMA)/triethyleneglycol‐dimethacrylate (TEGDMA) have been widely used as dental restorative material; however, the poor mechanical and anti‐wear properties greatly limited their applied range. In this study, iron‐containing hydroxyapatite (FeHA) nanoparticles that mimic the chemical composition and microstructure of natural bamboo rat incisor enamel were synthesized and used as reinforcement in BisGMA/TEGDMA resins. The as‐prepared polycrystalline FeHA have a rod like morphology with uniformly dispersed iron. The effects of nanoparticle–resin weight ratios on the mechanical properties, tribological properties, and bioactivity of FeHA‐BisGMA/TEGDMA resins were investigated. In vitro bioactivity of the studied resin composites in artificial saliva showed that a dense and continuous apatite layer was formed on the surface of the resin composite. Findings revealed that doping a suitable content of FeHA nanoparticle, especially at 0.75 wt% FeHA, would significantly improve the tribological and mechanical properties as well as bioactivity of the dental resin composites.