Oral Lactobacillus zeae exacerbates the pathological manifestation of periodontitis in a mouse model

INTRODUCTION

The worldwide prevalence of periodontitis is considerably high, and its pathogenic mechanisms must be investigated and understood in order to improve clinical treatment outcomes and reduce the disease prevalence and burden. The exacerbation of the host immune system induced by oral microbial dysbiosis and the subsequent tissue destruction are the hallmarks of the periodontitis. However, the oral bacteria involved in periodontitis are not fully understood. We used the Oxford Nanopore Technologies (ONT) sequencing system to analyze metagenomic information in subgingival dental plaque from periodontitis and non-periodontitis patients. The number of Lactobacillus zeae (L. zeae) in the periodontitis patients was 17.55-fold higher than in the non-periodontitis patients, suggesting that L. zeae is a novel periodontitis-associated pathogen. Although several Lactobacillus species are used in vivo as probiotics to treat periodontitis and compete with Porphyromonas gingivalis (P. gingivalis), the roles of L. zeae in periodontitis progression, and the relationship between L. zeae and P. gingivalis needs to be investigated.

METHODS

Both L. zeae and P. gingivalis were inoculated in the ligature-implant site of periodontitis mice. We collected mouse gingival crevicular fluid to analyze inflammatory cytokine secretion using a multiplex assay. Intact or sliced mouse maxilla tissue was used for micro-computed tomography analysis or hematoxylin and eosin staining, immunohistochemistry, and tartrate-resistant acid phosphatase staining to evaluate alveolar bone loss, neutrophil infiltration, and osteoclast activation, respectively.

RESULTS

We observed that L. zeae competed with P. gingivalis, and it increased inflammatory cytokine secretion at the ligature-implant site. Similar to P. gingivalis, L. zeae promoted ligature-induced neutrophile infiltration, osteoclast activation, and alveolar bone loss.

DISCUSSION

We, therefore, concluded that L. zeae accelerated the progression of periodontitis in the ligature-induced periodontitis mouse model.

Comparison of the physical, thermal, and biological effects on implant bone site when using either zirconia or stainless-steel drill for implant bone site preparation

BACKGROUND/PURPOSE

Zirconia has been a popular material in dental implantology with good biocompatibility. But few research focused on its application in implant drills. This study aimed to investigate the physical, thermal, and biological effects on using the zirconia and stainless-steel drills for implant bone site preparation.

METHODS

We performed a series of experiments to evaluate the physical wearing properties of zirconia and stainless-steel drills of identical diameter and similar shape. During the implant site preparation thermal test, we subjected both drills onto a resin-embedded bone, utilizing a thermal couple device without irrigation. Moreover, we conducted a cell study by collecting bone cells in vivo while preparing the implant site with both tested drills. The cell activity was evaluated through cell proliferation colorimetric analysis (XTT) and alkaline phosphatase (ALP) activity measurements.

RESULTS

The zirconia drill outperforms the stainless-steel drill in terms of requiring less force, maintaining stability over repeated cutting tests, and generating lower temperatures during drilling (stainless-steel drill: 45.48 ± 1.31 °C; zirconia-coated drill: 32.98 ± 1.21 °C, P = 0.000247). Meanwhile, both types of drills show similar results in XTT colorimetric analysis and ALP activity test.

CONCLUSION

The thermal effect study is more favorable for using the zirconia drill than the stainless-steel drill for bone preparation. Cytological analysis indicate that the zirconia drill produces a similar impact on bone cells activity as the stainless-steel drill. Therefore, we conclude that the zirconia drills offer a good cutting effect similar to currently available stainless-steel drills in various aspects.

Biofabricated poly (γ-glutamic acid) bio-ink reinforced with calcium silicate exhibiting superior mechanical properties and biocompatibility for bone regeneration

Background/purpose

The modification in 3D hydrogels, tissue engineering, and biomaterials science has enabled us to fabricate novel substitutes for bone regeneration. This study aimed to combine different biomaterials by 3D technique to fabricate a promising all-rounded hydrogel for bone regeneration.

Materials and methods

In this study, glycidyl methacrylate (GMA)-modified poly γ-glutamic acid (γ-PGA-GMA) hydrogels with calcium silicate (CS) hydrogel of different concentrations were fabricated by a 3D printing technique, and their biocompatibility and capability in bone regeneration were also evaluated.

Results

The results showed that CS γ-PGA-GMA could be successfully fabricated, and the presence of CS enhanced the rheological and mechanical properties of γ-PGA-GMA hydrogels, thus making them more adept at 3D printing and implantations. SEM images of the surface structure showed that higher CS concentrations (5% and 10%) contributed to denser surface architectures, thus achieving improved cellular adhesion and stem cell proliferation. Furthermore, higher concentrations of CS resulted in elevated expressions of osteogenic-related markers such as alkaline phosphatase (ALP) and osteocalcin (OC), as well as enhanced calcium deposition represented by the increased Alizarin Red S staining. In vivo studies referring to critical defects of rabbit femur further showed that the existence of hydrogels alone was able to induce partial bone regeneration, demonstrated by the results from quantitative and qualitative analysis of micro-CT scans. However, CS alterations caused significant increases in bone regeneration, as indicated by micro-CT and histological staining.

Conclusion

These results robustly suggest combining different biomaterials is crucial to producing a well-rounded hydrogel for tissue regeneration. We hope this study could be applied as a platform for others to brainstorm potential out-of-the-box solutions, contributing to developing high-potential biomaterials for bone regeneration.

Reliability of clinical examination methods for postoperative pain after primary root canal treatment

Background/purpose

Clinical test results may have lower reliability due to the varying range of test stimulation or patient subjectiveness. This study aimed to verify a reliable clinical test method by comparing pain intensity levels of a tooth at rest, during function, and after the clinical tests of percussion and chewing.

Materials and methods

A total of 36 asymptomatic necrotic teeth that required root canal treatment, one in each patient, were included. All treatment procedures were performed in a single visit by an experienced endodontist. Patients were asked to mark their pain levels on a vertical visual analog scale (VAS) while the relevant tooth was at rest and during function 24 h after the treatment. In addition, patients marked their pain levels after the clinical tests of percussion and chewing. Finally, the pain levels were compared using Pearson's correlation for the reliability of the test methods at a significance level of 95%.

Results

The postoperative pain levels measured during the clinical tests and functions were significantly higher than the pain levels at rest (P < 0.05). The pain levels after percussion tests were significantly higher than that during the function and chewing tests (P < 0.05). Pain intensity during the function was simulated with a higher correlation when using the chewing strip method rather than the percussion method.

Conclusion

The bite test using the chewing strips as a pain intensity assessment can mimic the actual postoperative pain experience, whereas the percussion test fails to provide the accuracy of this pain experience.

Third-generation sequencing-selected Scardovia wiggsiae promotes periodontitis progression in mice

BACKGROUNDS

Periodontitis is an oral-bacteria-directed disease that occurs worldwide. Currently, periodontal pathogens are mostly determined using traditional culture techniques, next-generation sequencing, and microbiological screening system. In addition to the well-known and cultivatable periodontal bacteria, we aimed to discover a novel periodontal pathogen by using DNA sequencing and investigate its role in the progression of periodontitis.

OBJECTIVE

This study identified pathogens from subgingival dental plaque in patients with periodontitis by using the Oxford Nanopore Technology (ONT) third-generation sequencing system and validated the impact of selected pathogen in periodontitis progression by ligature-implanted mice.

METHODS

Twenty-five patients with periodontitis and 25 healthy controls were recruited in this study. Subgingival plaque samples were collected for metagenomic analysis. The ONT third-generation sequencing system was used to confirm the dominant bacteria. A mouse model with ligature implantation and bacterial injection verified the pathogenesis of periodontitis. Neutrophil infiltration and osteoclast activity were evaluated using immunohistochemistry and tartrate-resistant acid phosphatase assays in periodontal tissue. Gingival inflammation was evaluated using pro-inflammatory cytokines in gingival crevicular fluids. Alveolar bone destruction in the mice was evaluated using micro-computed tomography and hematoxylin and eosin staining.

RESULTS

Scardovia wiggsiae (S. wiggsiae) was dominant in the subgingival plaque of the patients with periodontitis. S. wiggsiae significantly deteriorated ligature-induced neutrophil infiltration, osteoclast activation, alveolar bone destruction, and the secretion of interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α in the mouse model.

CONCLUSION

Our metagenome results suggested that S. wiggsiae is a dominant flora in patients with periodontitis. In mice, the induction of neutrophil infiltration, proinflammatory cytokine secretion, osteoclast activation, and alveolar bone destruction further verified the pathogenic role of S. wiggsiae in the progress of periodontitis. Future studies investigating the metabolic interactions between S. wiggsiae and other periodontopathic bacteria are warranted.

The neutrophil elastase-upregulated placenta growth factor promotes the pathogenesis and progression of periodontal disease

BACKGROUND

Periodontal disease is a chronic inflammatory disease. Given its high prevalence, especially in aging population, the detailed mechanisms about pathogenesis of periodontal disease are important issues for study. Neutrophil firstly infiltrates to periodontal disease-associated pathogen loci and amplifies the inflammatory response for host defense. However, excessive neutrophil-secreted neutrophil elastase (NE) damages the affected gingival. In lung and esophageal epithelium, NE had been proved to upregulate several growth factors including placenta growth factor (PGF). PGF is an angiogenic factor with proinflammatory properties, which mediates the progression of inflammatory disease. Therefore, we hypothesize excessive NE upregulates PGF and participates in the pathogenesis and progression of periodontal disease.

METHODS

In gingival epithelial cells (GEC), growth factors array demonstrated NE-increased growth factors and further be corroborated by Western blot assay and ELISA. The GEC inflammation was evaluated by ELISA. In mice, the immunohistochemistry results demonstrated ligature implantation-induced neutrophil infiltration and growth factor upregulation. By multiplex assay, the ligature-induced proinflammatory cytokines level in gingival crevicular fluid (GCF) were evaluated. Finally, alveolar bone absorption was analyzed by micro-CT images and H &amp; E staining.

RESULTS

NE upregulated PGF expression and secretion in GEC. PGF promoted GEC to secret IL-1β, IL-6, and TNF-α in GCF In periodontal disease animal model, ligature implantation triggered NE infiltration and PGF expression. Blockade of PGF attenuated the ligature implantation-induced IL-1β, IL-6, TNF-α and MIP-2 secretion and ameliorated the alveolar bone loss in mice.

CONCLUSION

In conclusion, the NE-induced PGF triggers gingival epithelium inflammation and promotes the pathogenesis and progression of periodontal disease.

In vitro evaluation of injectable Tideglusib-loaded hyaluronic acid hydrogels incorporated with Rg1-loaded chitosan microspheres for vital pulp regeneration

Injectable systems receive attention in endodontics due to the complicated and irregular anatomical structure of root canals. Here, injectable Tideglusib (Td)-loaded hyaluronic acid hydrogels (HAH) incorporated with Rg1-loaded chitosan microspheres (CSM) were developed for vital pulp regeneration, providing release of Td and Rg1 to trigger odontoblastic differentiation of human dental pulp stem cells (DPSC) by Td and vascularization of pulp by Rg1. The optimal concentrations were determined as 90 nM and 50 μg/mL for Td and Rg1, and loaded in HA and CSM in HAH, respectively. Odontogenic (COL1A1, ALP, OCN, Axin-2, DSPP, and DMP1) and angiogenic (VEGFA, VEGFR2, and eNOS) differentiation of DPSC cultured in the presence of hydrogels was shown at gene expression level. Our results suggest that our injectable hydrogel formulation has potential to improve strategies for vital pulp regeneration. In vivo evaluations are needed to test the feasibility and potential of these hydrogels for vital pulp regeneration.

Quantification of bone marrow interstitial pH and calcium concentration by intravital ratiometric imaging

The fate of hematopoietic stem cells (HSCs) can be directed by microenvironmental factors including extracellular calcium ion concentration ([Ca2+]e), but the local [Ca2+]e around individual HSCs in vivo remains unknown. Here we develop intravital ratiometric analyses to quantify the absolute pH and [Ca2+]e in the mouse calvarial bone marrow, taking into account the pH sensitivity of the calcium probe and the wavelength-dependent optical loss through bone. Unexpectedly, the mean [Ca2+]e in the bone marrow (1.0 ± 0.54 mM) is not significantly different from the blood serum, but the HSCs are found in locations with elevated local [Ca2+]e (1.5 ± 0.57 mM). With aging, a significant increase in [Ca2+]e is found in M-type cavities that exclusively support clonal expansion of activated HSCs. This work thus establishes a tool to investigate [Ca2+]e and pH in the HSC niche with high spatial resolution and can be broadly applied to other tissue types.

Development of antibacterial composite resin containing chitosan/fluoride microparticles as pit and fissure sealant to prevent caries

OBJECTIVE

Develop a fissure sealant containing chitosan/fluoride microparticles (C/F) with antibacterial, fluoride release and recharge ability.

MATERIALS AND METHODS

Chitosan/fluoride microparticles were synthesized and added to Bis-GMA as C/F. The experimental group comprised 0%, 2%, 4% C/F, with ClinproTM fissure sealant as control. Antibacterial activity was detected by Alamar Blue assay and colony-forming units (CFU). Biocompatibility was determined by WST-1 and LDH test. Curing depth, flowability, tensile strength and flexural strength were measured according to the ISO standard; microhardness by Vickers hardness test. Fluoride release and recharge were recorded through ionic chromatography. Statistical analysis was performed with an independent t-test, one-way and two-way ANOVA. P values less than 0.05 were considered significant.

RESULTS

2% and 4% C/F showed antibacterial ability with CFU ratios decreasing to 10% and 25% respectively (P < 0.01). Nonetheless, 4% C/F was concerned because biocompatibility revealed cytotoxicity compared to medium (P < 0.001). 2% C/F had superior mechanical properties to ClinproTM fissure sealant in terms of curing depth (P < 0.001), microhardness and tensile strength (P < 0.01). It had good fluoride release and recharge ability (P = 0.67).

CONCLUSIONS

2% C/F could be an antibacterial sealant with good mechanical strength, fluoride release and recharge ability.

[Debulking strategy of endovascular treatment for lower extremity artery lesions]

Objective: To explore the debulking strategy of lower extremity artery lesions. Methods: Retrospectively analyzed the clinical data of 101 patients underwent debulking therapy at Department of Vascular Surgery,Zhongshan Hospital,Fudan University from June 2019 to June 2020.There were 74 males and 27 females,aged (73.2±11.7)years (range:35 to 93 years).There were 31 cases in Rutherford class 3,39 cases in class 4 and 31 cases in class 5. Hypertension occurred in 72 patients. One hundred and forty lesions were treated in 101 patients. Among them, there were 13 lesions(9.3%) in iliac artery,72 lesions(51.4%) in superficial femoral artery,41 (29.3%) lesions in popliteal artery,10 lesions(7.1%) in tibiofibular trunk,and 4 lesions(2.9%) in below the knee artery.Percutaneous mechanical thrombectomy (PMT) was mainly used in acute thrombosis,excimer laser ablation (ELA) was mainly used for chronic in-stent restenosis and chronic stenosis or totally occlusive lesions,while directional atherectomy (DA) was mainly used for short calcified lesions. Results: All of the patients underwent debulking therapy. Eighty-two lesions(58.6%,82/140) were treated by PMT, 56 (40.0%,56/140) were treated by ELA,and 2 (1.4%,2/140) were treated by DA.The ankle-brachial index of the patient was 0.44±0.19 before surgery, 0.87±0.17 immediately after surgery (t=-16.26, P<0.01), and 0.81±0.20 at 6 months after surgery(t=-14.67,P<0.01),and 0.79±0.15 (t=-14.12,P<0.01) at 12 months after surgery. At 12 months,the primary patency was 86.1% (87/101),mortality was 5.0% (5/101), freedom from major-amputation survival rate was 93.1% (94/101),and target lesion reintervention rate was 9.9% (10/101). Conclusions: Debulking is feasible and effective to eliminate the arterial contents and maximize the acquisition of lumen.Selection of suitable debulking methods for different segments and lesions would be helpful to improve the technical success and obtain satisfactory results.

3D-Printed Ginsenoside Rb1-Loaded Mesoporous Calcium Silicate/Calcium Sulfate Scaffolds for Inflammation Inhibition and Bone Regeneration

Bone defects are commonly found in the elderly and athletic population due to systemic diseases such as osteoporosis and trauma. Bone scaffolds have since been developed to enhance bone regeneration by acting as a biological extracellular scaffold for cells. The main advantage of a bone scaffold lies in its ability to provide various degrees of structural support and growth factors for cellular activities. Therefore, we designed a 3D porous scaffold that can not only provide sufficient mechanical properties but also carry drugs and promote cell viability. Ginsenoside Rb1 (GR) is an extract from panax ginseng, which has been used for bone regeneration and repair since ancient Chinese history. In this study, we fabricated scaffolds using various concentrations of GR with mesoporous calcium silicate/calcium sulfate (MSCS) and investigated the scaffold’s physical and chemical characteristic properties. PrestoBlue, F-actin staining, and ELISA were used to demonstrate the effect of the GR-contained MSCS scaffold on cell proliferation, morphology, and expression of the specific osteogenic-related protein of human dental pulp stem cells (hDPSCs). According to our data, hDPSCs cultivated in GR-contained MSCS scaffold had preferable abilities of proliferation and higher expression of the osteogenic-related protein and could effectively inhibit inflammation. Finally, in vivo performance was assessed using histological results that revealed the GR-contained MSCS scaffolds were able to further achieve more effective hard tissue regeneration than has been the case in the past. Taken together, this study demonstrated that a GR-containing MSCS 3D scaffold could be used as a potential alternative for future bone tissue engineering studies and has good potential for clinical use.

Mechanical assessment and odontogenic behavior of a 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone composite scaffold

BACKGROUND/PURPOSE

Tissue engineering in dentistry has fundamentally changed the way endodontists assess treatment options. Our previous study found that quercetin-contained mesoporous calcium silicate/calcium sulfate (MSCSQ) could induce hard tissue defect region regeneration. This study focused on whether the MSCSQ scaffold could also be effective in regulating odontogenesis and dentin regeneration.

METHODS

In this study, we fabricated MSCSQ composite scaffolds using the 3D printing technique. The characteristics of the MSCSQ scaffold were examined by scanning electron microscope (SEM), and mechanical properties were also assessed. In addition, we evaluated the cell viability, cell proliferation, odontogenic-related protein expression, and mineralization behavior of human dental pulp stem cells (hDPSCs) cultured on different scaffolds.

RESULTS

We found the precipitation of spherical-apatite on the scaffold surface rapidly in short periods. The in-vitro results for cell behavior revealed that hDPSCs with an MSCSQ scaffold were significantly higher in cell viability as followed time points. In addition, the specific makers of odontogenesis, such as DSPP and DMP-1 proteins, were induced obviously after culturing the hDPSCs on the MSCSQ scaffold.

CONCLUSION

Our results demonstrated that MSCSQ scaffolds could enhance physicochemical and biological behaviors compared to mesoporous calcium silicate/calcium sulfate (MSCS) scaffolds. In addition, MSCSQ scaffolds also enhanced odontogenic and immuno-suppressive properties compared to MSCS scaffolds. These results indicated that MSCSQ scaffolds could be considered a potential bioscaffold for clinical applications and dentin regeneration.

Vitamin B12 deficiency and anemia in 140 Taiwanese female lacto-vegetarians

BACKGROUND/PURPOSE

Lacto-vegetarians (LVs) tend to have vitamin B12 deficiency (B12D). This study assessed whether 140 female LVs, including 16 B12D/LVs and 124 non-B12D/LVs, had significantly higher frequencies of microcytosis, macrocytosis, and of blood hemoglobin (Hb), red blood cell (RBC), and serum vitamin B12 deficiencies than 140 healthy control subjects (HCSs).

METHODS

The complete blood count and serum vitamin B12 level in 140 female LVs and 140 female HCSs were measured and compared.

RESULTS

We found that 8.6%, 4.3%, 22.9%, 20.0%, and 11.4% of 140 LVs had microcytosis, macrocytosis, and blood Hb, RBC, and serum vitamin B12 deficiencies, respectively. The 140 LVs, 16 B12D/LVs, and 124 non-B12D/LVs had significantly higher frequencies of microcytosis as well as blood Hb and RBC deficiencies than 140 HCSs (all P-values < 0.005). Moreover, both 140 LVs and 124 non-B12D/LVs had significantly higher frequencies of macrocytosis than 140 HCSs. In this study, 32 (22.9%) of 140 LVs including 5 B12D/LVs and 27 non-B12D/LVs had anemia. Of the 5 anemic B12D/LVs, three had normocytic anemia, one had iron deficiency anemia (IDA), and one had thalassemia trait-induced anemia. Moreover, of the 27 anemic non-B12D/LVs, 18 had normocytic anemia, one had IDA, one had thalassemia trait-induced anemia, and 7 had microcytic anemia other than IDA and thalassemia trait-induced anemia.

CONCLUSION

LVs have significantly higher frequencies of microcytosis, macrocytosis, blood Hb, RBC, and serum vitamin B12 deficiencies than HCSs. Normocytic and microcytic anemias are the two most common types of anemia in our LVs.

[Application and value of excimer laser ablation in the treatment of lower limb atherosclerotic obliterans]

Objective: To evaluate the results of excimer laser ablation (ELA) in the treatment of lower limb atherosclerotic obliterans (ASO). Methods: From June 2019 to March 2020, patients who underwent ELA combined with drug-coated balloon (DCB) for lower limb atherosclerotic obliterans (ASO) were enrolled. Demographics, lesion characteristics, procedure-related outcomes and complications were collected and analyzed. Results: Thirty patients were enrolled, including 21 males and 9 females. The mean age was (76.5±10.5) years. The mean lesion length was (11.7±6.4) cm. A total of 41 lesions, including in-stent restenosis (ISR) in 12 (29.3%), chronic totally occlusion (CTO) at initial treatment in 24 (58.5%), and severe stenosis in 5 (12.2%) patients. Sixteen (51.6%) patients were classified as Peripheral Arterial Calcium Scoring System (PACSS) category 4. The technical success rate was 93.5%. Incidence of distal embolization and bailout stenting was 12.9% and 6.5%, respectively. The mean follow-up time was (6.6±3.0) months. Ankle-brachial index (ABI) was significantly increased from 0.43(0.32,0.55) preoperatively to 0.91(0.87,1.01) postoperatively (Z=-5.43, P<0.01) and 0.82(0.73,1.02) (Z=-3.99, P<0.01) three months after surgery. The 3-month major-amputation free survival rate was 96.7%, primary patency rate was 100%, the target lesion reintervention (TLR) rate was 0 and ulcer healing rate was 76.9%. Conclusion: Debulking of ELA is feasible and effective for both ISR and CTO at initial treatment, providing a new option for DCB preparation and reducing stent implantation.

Nitrogen-Doped Titanium Dioxide Mixed with Calcium Peroxide and Methylcellulose for Dental Bleaching under Visible Light Activation

The available tooth whitening products in the market contain high concentrations of hydrogen peroxide (H₂O₂) as an active ingredient. Therefore, in order to curb the high H₂O₂ concentration and instability of liquid H₂O₂, this study evaluated the efficacy and cytotoxicity of the bleaching gel composed of 10% calcium peroxide (CaO₂) and visible-light-activating nitrogen-doped titanium dioxide (N-TiO₂) with methyl cellulose as a thickener. Extracted bovine teeth were discolored using coffee and black tea stain solution and were divided into two groups (n = 6). Bleaching was performed thrice on each tooth specimen in both the groups, with one minute of visible light irradiation during each bleaching time. The CIELAB L*a*b* values were measured pre- and post-bleaching. The N-TiO₂ calcinated at 350 °C demonstrated a shift towards the visible light region by narrowing the band gap energy from 3.23 eV to 2.85 eV. The brightness (ΔL) and color difference (ΔE) increased as bleaching progressed each time in both the groups. ANOVA results showed that the number of bleaching significantly affected ΔE (p < 0.05). The formulated bleaching gel exhibits good biocompatibility and non-toxicity upon exposure to 3T3 cells. Our findings showed that CaO₂-based bleaching gel at neutral pH could be a stable, safe, and effective substitute for tooth whitening products currently available in the market.

The synergistic effects of quercetin-containing 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis in mesenchymal stem cells

BACKGROUND/PURPOSE

Several growth factors were proven to be effective in the treatment of bone defects and fractures and thus have great potential for bone regeneration applications. However, it needs low-temperature storage and transportation. This study aimed to investigate the herbal extract quercetin, a candidate for natural flavonoid compounds that have been reported to be involved in regulating inflammation and improving immunity and health.

METHODS

In this study, we prepared quercetin (Q)/mesoporous calcium silicate calcium sulfate (MSCS)/polycaprolactone (PCL) composite scaffolds using the 3D printing technique, where we immersed it in simulated body fluid (SBF) solution and soaked it for up to 60 days. The characteristics of quercetin scaffold were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), immunofluorescence, and Alizarin Red S staining.

RESULTS

We found precipitation of apatite on the surface of the scaffold. The in vitro results for cell proliferation, cytotoxicity, and immunofluorescence staining revealed that Wharton's jelly mesenchymal stem cells (WJMSCs) with a 2% quercetin (Q2) scaffold were significantly higher in number than with 1% quercetin (Q1) and MSCS scaffolds. The phalloidin staining of cell skeletons on the surface of Q2 revealed powerful cell-to-cell adhesion and high expression of green fluorescence. The Q2 scaffold also had the highest calcium deposit levels based on Alizarin Red S staining in all scaffolds. This indicated that quercetin was able to induce cell growth and mitosis, echoing the previous preliminary results.

CONCLUSION

Our initial results indicate that this natural herbal extract can be a good bone-based gene substitution for bone regeneration.

Differences in the biomechanical behaviors of natural teeth and dental implants

OBJECTIVE

The lack of a PDL, which acts as an energy absorber, is a contributor to implants' early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo.

METHODS

We designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load-control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants.

RESULTS

Biphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load-time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300g in a loading rate 3g/s could dissipate the energy of 7.35±1.18×10^-2 mJ, approximately 50 times that of the dental implants (1.47±1.22×10^-3) with statistically significant (p<0.05).

SIGNIFICANCE

We confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.

Incorporation of Calcium Sulfate Dihydrate into a Mesoporous Calcium Silicate/Poly-ε-Caprolactone Scaffold to Regulate the Release of Bone Morphogenetic Protein-2 and Accelerate Bone Regeneration

Tissue engineering and scaffolds play an important role in tissue regeneration by supporting cell adhesion, proliferation, and differentiation. The design of a scaffold is critical in determining its feasibility, and it is critical to note that each tissue is unique in terms of its morphology and composition. However, calcium-silicate-based scaffolds are undegradable, which severely limits their application in bone regeneration. In this study, we developed a biodegradable mesoporous calcium silicate (MS)/calcium sulfate (CS)/poly-ε-caprolactone (PCL) composite and fabricated a composite scaffold with 3D printing technologies. In addition, we were able to load bone morphogenetic protein-2 (BMP-2) into MS powder via a one-step immersion procedure. The results demonstrated that the MS/CS scaffold gradually degraded within 3 months. More importantly, the scaffold exhibited a gradual release of BMP-2 throughout the test period. The adhesion and proliferation of human dental pulp stem cells on the MS/CS/BMP-2 (MS/CS/B) scaffold were significantly greater than that on the MS/CS scaffold. It was also found that cells cultured on the MS/CS/B scaffold had significantly higher levels of alkaline phosphatase activity and angiogenic-related protein expression. The MS/CS/B scaffold promoted the growth of new blood vessels and bone regeneration within 4 weeks of implantation in rabbits with induced critical-sized femoral defects. Therefore, it is hypothesized that the 3D-printed MS/CS/B scaffold can act both as a conventional BMP-2 delivery system and as an ideal osteoinductive biomaterial for bone regeneration.

Comparing image qualities of dental cone-beam computed tomography with different scanning parameters for detecting root canals

BACKGROUND/PURPOSE

Cone-beam computed tomography (CBCT) is a useful device in creating 3-dimensional images in the examining area of dentistry and is one of the most common clinical methods in detecting second mesiobuccal (MB2) canals in maxillary molars. The aim of this in vitro study was to compare the image quality of the small field of view (FOV) CBCT with different rotation arcs and scanning speeds in the use of detecting root canals.

METHODS

A dentate human skull was scanned in Morita 3D Accuitomo 170 with 4 × 4 cm FOV under 5 mA and 90 kVp. Two different rotation arcs (360° and 180°) and three different scanning modes (slow-speed mode, standard mode and high-speed mode) combined into six different groups. Five different levels of axial sections were selected from each group. Five endodontic specialists rated the image quality by focusing on the sharpness of the MB2 canal of the upper right first molar and the surrounding structures.

RESULTS

Despite the rotation arcs, all the observers gave excellent ratings to images taken with slow-speed mode. The high-speed mode taken with 360° and 180° got the second lowest and the lowest ratings, respectively. Under the same scanning speed, the rotation arc did not have a significant difference in image quality.

CONCLUSION

Slow-speed mode is inevitable in maintaining adequate image quality during taking CBCT. However, endodontists can use the half rotation mode to significantly reduce radiation dose, exposure time, and still maintain sufficient image quality for root canal anatomy assessment.

Development of calcium phosphate/calcium sulfate biphasic biomedical material with hyaluronic acid containing collagenase and simvastatin for vital pulp therapy

OBJECTIVE

In vital pulp therapy (VPT), a barrier is created with appropriate capping to protect the remaining pulp and thus maintain pulp vitality. Here, we evaluated the feasibility of a biphasic calcium phosphate cement (CPC)-calcium sulfate hemihydrate (CSH) biomaterial containing simvastatin (Sim) and collagenase (Col) for VPT.

METHODS

Combinations of varying CPC and CSH concentrations were analyzed for their handling properties and setting times, with their structures observed through scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS). Drug release patterns of simvastatin and collagenase combined with CPC-CSH (CPC-CSH-Sim-Col) were also analyzed, followed by biocompatibility and bioactivity tests on human dental pulp stem cells (hDPSCs) and in vivo animal study in canine models; the in vivo results were obtained through microcomputed tomography and histological analysis.

RESULTS

The results revealed that 70 wt% CPC (CPC7) with 30 wt% CSH (CSH3) exhibited optimal setting time and porous structure for clinical use. The cell viability and cytotoxicity analysis demonstrated that CPC7-CSH3 with or without simvastatin or collagenase did not injure hDPSCs. In vivo, the CPC7-CSH3-Sim-Col induced dentin bridge formation.

SIGNIFICANCE

CPC7-CSH3-Sim-Col in this study has great potential as a VPT biomaterial to enhance the dentin bridge formation.

Evaluation of Carbon Dioxide-Based Urethane Acrylate Composites for Sealers of Root Canal Obturation

A new root canal sealer was developed based on urethane acrylates using polycarbonate polyol (PCPO), a macrodiol prepared in the consumption of carbon dioxide as feedstock. The superior mechanical properties and biostability nature of PCPO-based urethane acrylates were then co-crosslinked with a difunctional monomer of tripropylene glycol diarylate (TPGDA) as sealers for resin matrix. Moreover, nanoscale silicate platelets (NSPs) immobilized with silver nanoparticles (AgNPs) and/or zinc oxide nanoparticles (ZnONPs) were introduced to enhance the antibacterial effect for the sealers. The biocompatibility and the antibacterial effect were investigated by Alamar blue assay and LDH assay. In addition, the antibacterial efficiency was performed by using Enterococcus faecalis (E. faecalis) as microbial response evaluation. These results demonstrate that the PCPO-based urethane acrylates with 50 ppm of both AgNP and ZnONP immobilized on silicate platelets, i.e., Ag/ZnO@NSP, exhibited great potential as an antibacterial composite for the sealer of root canal obturation.

Fluorinated Montmorillonite and 3YSZ as the Inorganic Fillers in Fluoride-Releasing and Rechargeable Dental Composition Resin

Dental caries (tooth decay) is the most frequent oral disease in humans. Filling cavities with a dental restorative material is the most common treatment, and glass ionomer cements are the main fluoride ion release restorative materials. The goal of this study was to develop a restorative compound with superior fluoride ion release and recharge abilities. Previously developed fluorinated bentolite and hydrophobized 3YSZ were used as two different inorganic fillers mixed in a bisphenol A-glycidyl methacrylate (Bis-GMA) matrix. XRD, FTIR, and TGA were used to determine the hydrophobic modification of these two inorganic fillers. In mechanical tests, including diameter tensile strength, flexural strength, and wear resistance, the developed composite resin was significantly superior to the commercial control. A WST-1 assay was used to confirm that the material displayed good biocompatibility. Furthermore, the simulation of the oral environment confirmed that the composite resin had good fluoride ion release and reloading abilities. Thus, the composite resin developed in this study may reduce secondary caries and provide a new choice for future clinical treatments.

Characterization of Phosphorus Species in Human Dentin by Solid-State NMR

The rat has been considered as an appropriate animal model for the study of the mineralization process in humans. In this work, we found that the phosphorus species in human dentin characterized by solid-state NMR spectroscopy consist mainly of orthophosphate and hydrogen phosphate. Some orthophosphates are found in a disordered phase, where the phosphate ions are hydrogen-bonded to structural water, some present a stoichiometric apatite structure, and some a hydroxyl-depleted apatite structure. The results of this study are largely the same as those previously obtained for rat dentin. However, the relative amounts of the various phosphorus species in human and rat dentin are dramatically different. In particular, stoichiometric apatite is more abundant in human dentin than in rat dentin, whereas the converse is true for disordered-phase orthophosphates. Furthermore, spatial proximity among all phosphorus species in human dentin is identical within experimental error, in contrast to what observed for rat dentin. Although it is not clear how these spectroscopic data could relate to the hierarchical structure or the mechanical properties of teeth, our data reveal that the molecular structures of human and rat dentin at different growth stages are not exactly the same.

Effect of different zinc concentrations on partially-stabilized cement for vital pulp therapy

BACKGROUND/PURPOSE

We have developed and investigated the partially-stabilized cements (PSC) with Zn for vital pulp therapy due to their short setting time and high cell biocompatibility. However, the effect of PSC with different concentrations of Zn on setting time and biocompatibility remained unknown. Therefore, the purpose of this study was to determine the optimal concentration of Zn to be synthesized with PSC for vital pulp therapy.

METHODS

PSC with different weight percentages of Zn (5%, 7%, 10%) were synthesized to attain 5%Zn-PSC, 7%Zn-PSC, and 10%Zn-PSC. The initial and final setting times were measured using the Gillmore needles method, and the compressive strength tests were conducted using a universal testing machine. The phases of Zn-PSC powders were observed using an X-ray diffractometer (XRD). Human dental pulp stem cells (hDPSCs) were used to evaluate the biocompatibility and cytotoxicity of the materials via Alamar blue and LDH assays. Mineral trioxide aggregate (MTA) was used to be compared with Zn-PSC samples.

RESULTS

The initial and final setting times of PSC with different concentrations of Zn were reduced considerably compared to those of MTA. The results also indicated that the initial and final setting times decreased as the weight % of Zn increased. 5%Zn-PSC had the highest compressive strength among all tested materials. 5%Zn-PSC samples also displayed comparatively higher cell biocompatibility than 7% and 10% Zn-PSC samples. However, there was no significant difference between the 5%Zn-PSC and MTA in cell biocompatibility. In addition, the results of the LDH release assay indicated a low level of cytotoxicity among all the test samples.

CONCLUSION

5%Zn-PSC has a shorter setting time, better mechanical properties, and good biocompatibility and thus it has great potential for vital pulp therapy.

Enhanced Capability of Bone Morphogenetic Protein 2-loaded Mesoporous Calcium Silicate Scaffolds to Induce Odontogenic Differentiation of Human Dental Pulp Cells

INTRODUCTION

Calcium silicate bioceramics have been broadly used as reparative or grafting materials with good bioactivity and biocompatibility in dental application. It has been shown that applying a mesoporous process to calcium silicate gives it great potential as a controlled drug delivery system.

METHODS

The aim of this study was to investigate a novel osteoinductive scaffold by loading bone morphogenetic protein 2 (BMP-2) to mesoporous calcium silicate (MesoCS) and fabricating it as 3-dimensional scaffolds using fused deposition modeling combined with polycaprolactone.

RESULTS

The MesoCS/BMP-2 scaffold showed similar patterns to that of a calcium silicate scaffold in releasing calcium and silicon ions in a simulated body fluid (SBF) immersion test for 7 days, but BMP-2 continued releasing from the MesoCS/BMP-2 scaffold significantly more than the CS scaffold from 48 hours to 7 days. Adhesion and proliferation of human dental pulp cells cultured on a MesoCS/BMP-2 scaffold were also more significant than scaffolds without BMP-2 or mesoporous as well as the results of the test on alkaline phosphatase activity.

CONCLUSIONS

The results support that the novel 3-dimensional-printed MesoCS scaffold performed well as BMP-2 delivery system and would be an ideal odontoinductive biomaterial in regenerative endodontics.

Characteristics of an alternative antibacterial biomaterial for mouthwash in the absence of alcohol

Background/purpose

The purpose of this study was to investigate whether poly-gamma-glutamic acid (γ-PGA), a naturally derived biomaterial, was suitable as an alternative antibacterial mouthwash in the absence of alcohol.

Materials and methods

Three bacterial strains, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, were used for testing the antibacterial activity of mouthwashes. In addition, cell viability, cytotoxicity, and genotoxicity experiments were conducted for testing the toxicity of mouthwashes.

Results

We demonstrated that 10000 ppm of γ-PGA without alcohol could efficiently inhibit 99% of bacterial growth. In addition, γ-PGA did not cause any cytotoxicity or genotoxicity.

Conclusion

10000 ppm of γ-PGA in an alcohol-free mouthwash is an alternative biomaterial for mouthwashes.

The dentin permeability of anti-inflammatory and antibacterial drugs: In vitro study

BACKGROUND/PURPOSE

Stimuli from the oral cavity may penetrate through exposed dentinal tubules and evoke inflammatory pulp response. Anti-bacterial and anti-inflammatory drugs applied to exposed dentin may infiltrate through the dentinal tubules and cause pulp recovery. This study investigated the dentin permeability of anti-bacterial and anti-inflammation drugs via an in-vitro transwell dentin disc tube model.

METHODS

Twenty-seven dentin discs prepared from extracted human molars were collected. Nine kinds of drugs were investigated with three dentin discs in each group. These nine drugs included two anti-bacterial drugs (ampicillin sodium and clindamycin phosphate), two corticosteroids (betamethasone sodium phosphate and hydrocortisone sodium succinate), three non-steroidal anti-inflammatory drugs (NSAIDs, piroxicam, lysine acetylsalicylate, and diclofenac sodium), and two natural extracts with anti-inflammatory effect (Ginsenoside Rg1 and Hinokitol). The drugs were introduced to the transwell dentin disc tube model and the 4-hour cumulative release of the drug was detected and recorded by UV-visible spectroscopy.

RESULTS

We found that ampicilin sodium had better dentin permeability than clindamycin phosphate. Betamethasone sodium phosphate revealed better dentin permeability than hydrocortisone sodium succinate. Lysine acetylsalicylate showed the best dentin permeability among the three NSAIDs. Ginsenoside Rg1 had the best dentin permeability among the nine drugs tested. However, Hinokitiol could not penetrate the dentin disc after 4 h.

CONCLUSION

Regarding the dentin permeability, Ginsenoside Rg1 is the best among the seven anti-inflammatory drugs tested and ampicilin sodium is the better one between the two anti-bacterial drugs tested. Therefore, these two drugs may have high potential for treating exposed dentinal tubule diseases.

Pure type-1 collagen application to third molar extraction socket reduces postoperative pain score and duration and promotes socket bone healing

BACKGROUND/PURPOSE

Extraction of the third molar may cause post-operative complications. This study assessed whether application of pure type-1 collagen to the third molar extraction socket can reduce post-operative pain score and duration and promote socket bone healing.

METHODS

Fourteen patients who underwent 20 bilateral and symmetric third molar extractions were included in this study. After two tooth extractions at two different occasions in the same patient, one socket was filled with pure type-1 collagen (experimental group, n = 20) and the other socket received nothing but the blood clot (control group, n = 20). The post-operative pain score and duration, mouth-opening limitation, and the bone density at the socket site were assessed at weeks 1, 2, 4, and 8 after tooth extraction.

RESULTS

Patients in the experimental group had a significantly lower mean post-operative pain score (2.6 ± 1.2) than patients in the control group (4.7 ± 2.0), and had a significantly shorter post-operative pain duration (2.7 ± 1.4 days) than patients in the control group (3.7 ± 1.8 days). We also observed a significantly lower frequency of mouth-opening limitation in 20 experimental-group patients (45%) than in 20 control-group patients (90%, P = 0.007). Moreover, a significantly higher mineralization ratio (10.2%) was found in the experimental socket site than in the control socket site.

CONCLUSION

Application of pure type-1 collagen to the third molar extraction socket can reduce post-operative pain score and duration, decrease the frequency of mouth-opening limitation, and increase mineralization ratio at the extraction socket site.

Effects of bone morphogenic protein-2 loaded on the 3D-printed MesoCS scaffolds

BACKGROUND/PURPOSE

The mesoporous calcium silicate (MesoCS) 3D-printed scaffold show excellent bioactivity and can enhance the bone-like apatite formation. The purpose of this study aims to consider the effects of the different loading methods on the novel grafting materials which composed of bone morphogenetic protein-2 (BMP-2) loaded MesoCS scaffold by employing 3D-printing technique.

METHODS

The MesoCS scaffold were fabricated by fused deposition modeling. In this study, there are two methods of loading BMP-2: (1) the pre-loading (PL) method by mixing MesoCS and BMP-2 as a raw material for a 3D-printer, and (2) the direct-loading (DL) method by soaking the 3D-printed MesoCS scaffold in a BMP-2 solution. The characteristics of MesoCS scaffold were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their physical properties, biocompatibility, and osteogenic-related ability were also evaluated.

RESULTS

The 3D MesoCS/PCL scaffolds showed excellent biocompatibility and physical properties. After soaking in simulated body fluid, the bone-like apatite layer of the PL and DL groups could be formed. In addition, the DL group released fifty percent more than the PL group at the end of the first day and PL showed a sustained release profile after 2 weeks.

CONCLUSION

The 3D MesoCS/PCL porous scaffolds were successfully fabricated via a 3D printing system and were tested in vitro and were found to show good cellular activity for cell behavior although the PL method was not favorable for clinical application in relation with the preservation of BMP-2. With regards to different growth factor loading methods, this study demonstrated that PL of BMP-2 into MesoCS prior to printing will result in a more sustained drug release pattern as compared to traditional methods of scaffolds directly immersed with BMP-2.

Efficient induction of functional ameloblasts from human keratinocyte stem cells

Background

Although adult human tissue-derived epidermal stem cells are capable of differentiating into enamel-secreting ameloblasts and forming teeth with regenerated enamel when recombined with mouse dental mesenchyme that possesses odontogenic potential, the induction rate is relatively low. In addition, whether the regenerated enamel retains a running pattern of prism identical to and acquires mechanical properties comparable with human enamel indeed warrants further study.

Methods

Cultured human keratinocyte stem cells (hKSCs) were treated with fibroblast growth factor 8 (FGF8) and Sonic hedgehog (SHH) for 18 h or 36 h prior to being recombined with E13.5 mouse dental mesenchyme with implantation of FGF8 and SHH-soaked agarose beads into reconstructed chimeric tooth germs. Recombinant tooth germs were subjected to kidney capsule culture in nude mice. Harvested samples at various time points were processed for histological, immunohistochemical, TUNEL, and western blot analysis. Scanning electronic microscopy and a nanoindentation test were further employed to analyze the prism running pattern and mechanical properties of the regenerated enamel.

Results

Treatment of hKSCs with both FGF8 and SHH prior to tissue recombination greatly enhanced the rate of tooth-like structure formation to about 70%. FGF8 and SHH dramatically enhanced stemness of cultured hKSCs. Scanning electron microscopic analysis revealed the running pattern of intact prisms of regenerated enamel is similar to that of human enamel. The nanoindentation test indicated that, although much softer than human child and adult mouse enamel, mechanical properties of the regenerated enamel improved as the culture time was extended.

Conclusions

Application of FGF8 and SHH proteins in cultured hKSCs improves stemness but does not facilitate odontogenic fate of hKSCs, resulting in an enhanced efficiency of ameloblastic differentiation of hKSCs and tooth formation in human–mouse chimeric tooth germs.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0822-4) contains supplementary material, which is available to authorized users.

Effects of fluoride and epigallocatechin gallate on soft-drink-induced dental erosion of enamel and root dentin

BACKGROUND/PURPOSE

Fluoride and epigallocatechin gallate (EGCG) have been proven to prevent dental caries. The purpose of this study was to evaluate the effects of fluoride and EGCG on soft-drink-induced dental erosion in vitro.

METHODS

Forty enamel and dentin specimens were prepared from extracted human teeth. The specimens were divided into 4 groups and treated separately with distilled water (as control), 0.5 M sodium fluoride (NF), 400 μM EGCG (EG), and a solution containing 0.5 M NaF and 400 μM EGCG (FG). Cyclic erosive treatment was performed according to the experimental procedures. The specimens were analyzed using laser scanning confocal microscopy, scanning electron microscopy, and a microhardness tester. The data were analyzed using ANOVA and Bonferroni's post hoc test. The significance level was set at 5%.

RESULTS

The amount of substance loss was lower in the NF and EG groups than in the control group (p < 0.05). The erosion-caused substance loss was more pronounced in the dentin than in the enamel specimens. Surface microhardness loss was lower in the NF and EG groups than in the control group (p < 0.05). The diameter of the dentinal tubule was wider in the control group than in the NF and EG groups (p < 0.05). No combined effects were observed in the FG group.

CONCLUSION

Both fluoride and EGCG are effective in preventing soft-drink-induced erosion compared with the control group. Fluoride and EGCG may interfere with each other. The mechanisms of the anti-erosive effect need to be explored in the future.

Influence of heat treatment on cyclic fatigue and cutting efficiency of ProTaper Universal F2 instruments

BACKGROUND/PURPOSE

Heat pretreatment can improve the cyclic fatigue life of nickel-titanium (NiTi) instruments. This study evaluated the effects of two different heat treatments on the cyclic fatigue resistance and cutting efficiency of ProTaper Universal F2 files.

MATERIALS AND METHODS

The files were divided into three groups: no treatment (control), heat treatment at 400°C (HT400) and heat treatment at 600°C (HT600). The phase transformation of the files was evaluated by differential scanning calorimetry. In cyclic fatigue tests, the differences in file performance in four simulated canals among the three groups were assessed. The cutting efficiency was tested at four cutting portions (3 mm, 6 mm, 9 mm, and 12 mm) from the tip of the file.

RESULTS

Differential scanning calorimetry showed a prolonged phase transformation of the files only after 600°C treatment. At 3 mm cutting portion, 400°C heat-treated files had significantly better cutting ability than those in the control group. However, the files in the HT600 group had significantly lower cutting efficiency than those in the other two groups at the four tested positions. In the cyclic fatigue test, fatigue lives of the files after 400°C and 600°C treatment were prolonged from 2.1 to 2.8 times and from 1.7 to 5.5 times, respectively.

CONCLUSION

Although 600°C treatment increased resistance to cyclic fatigue, it reduced the cutting efficiency of the files. The 400°C treatment maintained the cutting ability and prolonged the cyclic fatigue life of the files. Therefore, for clinical use of ProTaper Universal F2 files, 400°C pretreatment is a better choice than 600°C pretreatment.

Fracture resistance of dental nickel-titanium rotary instruments with novel surface treatment: Thin film metallic glass coating

BACKGROUND/PURPOSE

Dental nickel-titanium (NiTi) rotary instruments are widely used in endodontic therapy because they are efficient with a higher success rate. However, an unpredictable fracture of instruments may happen due to the surface characteristics of imperfection (or irregularity). This study assessed whether a novel surface treatment could increase fatigue fracture resistance of dental NiTi rotary instruments.

METHODS

A 200- or 500-nm thick Ti-zirconium-boron (Ti-Zr-B) thin film metallic glass was deposited on ProTaper Universal F2 files using a physical vapor deposition process. The characteristics of coating were analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. In cyclic fatigue tests, the files were performed in a simulated root canal (radius=5 mm, angulation=60°) under a rotating speed of 300rpm. The fatigue fractured cross sections of the files were analyzed with their fractographic performances through scanning electron microscopy images.

RESULTS

The amorphous structure of the Ti-Zr-B coating was confirmed by transmission electron microscopy and X-ray diffractometry. The surface of treated files presented smooth morphologies without grinding irregularity. For the 200- and 500-nm surface treatment groups, the coated files exhibited higher resistance of cyclic fatigue than untreated files. In fractographic analysis, treated files showed significantly larger crack-initiation zone; however, no significant differences in the areas of fatigue propagation and catastrophic fracture were found compared to untreated files.

CONCLUSION

The novel surface treatment of Ti-Zr-B thin film metallic glass on dental NiTi rotary files can effectively improve the fatigue fracture resistance by offering a smooth coated surface with amorphous microstructure.

Nanocrystalline calcium sulfate/hydroxyapatite biphasic compound as a TGF-β1/VEGF reservoir for vital pulp therapy

OBJECTIVES

Vital pulp therapy aims to treat reversible pulpal injuries via protective dentinogenesis and to preserve more tooth structure. Mineral trioxide aggregate (MTA)-based capping materials demonstrate prolonged setting time increases the risk of pulpal infection during multi-visit treatment. Their non-degradable property occupies pulp space and limits dentin-pulp regeneration. This study reports an inorganic degradable biomaterial that presents a short initial setting time and acts as a growth factor reservoir to promote reparative dentinogenesis.

METHODS

We synthesize nanocrystalline calcium sulfate hemihydrate (nCS), hydroxyapatite (HAp) and calcium sulfate hemihydrate (CS) as a reservoir to which transforming growth factor-beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) are added (denoted as nCS/HAp/CS/TGF-β1/VEGF). In vitro biocompatibility and mineralization (the activity and expression of alkaline phosphatase, ALP) were evaluated. Rat animal model was created to test in vivo efficacy.

RESULTS

Cultured human dental pulp cells (HDPCs) showed that nCS/HAp/CS/TGF-β1/VEGF cement has excellent biocompatibility and the potential to elevate the activity and expression of ALP. The in vivo efficacy (rat animal model) indicates protective dentin by micro-computed tomography (μ-CT) measurements and histological analyses. The 3D μ-CT non-destructive analysis also determines volume changes during pulpotomy, suggesting that the degraded space of the nCS/HAp/CS/TGF-β1/VEGF cement is repaired by the formation of dentin-pulp tissue.

SIGNIFICANCE

These findings demonstrate that nCS/HAp/CS cement acts as a potent reservoir for the sustained release of growth factors, and that nCS/HAp/CS/TGF-β1/VEGF cement has a high potential to form the reparative dentinogenesis in vivo.

Cyclic fatigue behavior of nickel-titanium dental rotary files in clinical simulated root canals

BACKGROUND/PURPOSE

Dental rotary instruments can be applied in multiple conditions of canals, but unpredictable fatigue fracture may happen. This study evaluated the fatigue lives of two batches of nickel-titanium (NiTi) dental rotary files operating in clinically simulated root canals.

METHODS

Single-step cyclic fatigue tests were carried out to assess the performance of two batches of NiTi files (ProTaper and ProFile) in nine combinations of simulated canals (cylinder radii 5 mm, 7.5 mm, and 10 mm, and insertion angles 20°, 40°, and 60°). Two-step cyclic fatigue tests were carried out in simulated root canals with the same radius by using the following two sets of insertion angles: (20°, 40°), (20°, 60°), (40°, 20°), and (60°, 20°). Fracture surfaces were observed by scanning electron microscopy.

RESULTS

The single-step cyclic fatigue results showed that cyclic fatigue lives of the files decreased with increasing insertion angles or decreasing cylinder radius. The ProFile #25 .04 file was more fatigue resistant than the ProTaper F2 file. In two-step cyclic fatigue tests, the total fatigue lives were usually more than 100% when the files operated at a lower strain and then at a higher strain. By scanning electron microscopy, a larger area of fatigue striation corresponded to a longer fatigue life.

CONCLUSION

Cyclic fatigue life can be influenced by the strains and geometries of files. The fatigue life was prolonged when the files operated at a lower strain and then at a higher strain. However, the fatigue life was shortened if the loading sequence was reversed.

Hafnium-doped hydroxyapatite nanoparticles with ionizing radiation for lung cancer treatment

Recently, photodynamic therapy (PDT) is one of the new clinical options by generating cytotoxic reactive oxygen species (ROS) to kill cancer cells. However, the optical approach of PDT is limited by tissue penetration depth of visible light. In this study, we propose that a ROS-enhanced nanoparticle, hafnium-doped hydroxyapatite (Hf:HAp), which is a material to yield large quantities of ROS inside the cells when the nanoparticles are bombarded with high penetrating power of ionizing radiation. Hf:HAp nanoparticles are generated by wet chemical precipitation with total doping concentration of 15mol% Hf(4+) relative to Ca(2+) in HAp host material. The results show that the HAp particles could be successfully doped with Hf ions, resulted in the formation of nano-sized rod-like shape and with pH-dependent solubility. The impact of ionizing radiation on Hf:HAp nanoparticles is assessed by using in-vitro and in-vivo model using A549 cell line. The 2',7'-dichlorofluorescein diacetate (DCFH-DA) results reveal that after being exposed to gamma rays, Hf:HAp could significantly lead to the formation of ROS in cells. Both cell viability (WST-1) and cytotoxicity (LDH) assay show the consistent results that A549 lung cancer cell lines are damaged with changes in the cells' ROS level. The in-vivo studies further demonstrate that the tumor growth is inhibited owing to the cells apoptosis when Hf:HAp nanoparticles are bombarded with ionizing radiation. This finding offer a new therapeutic method of interacting with ionizing radiation and demonstrate the potential of Hf:HAp nanoparticles in tumor treatment, such as being used in a palliative treatment after lung surgical procedure.

STATEMENT OF SIGNIFICANCE

Photodynamic therapy (PDT) is one of the new clinical options by generating cytotoxic reactive oxygen species (ROS) to kill cancer cells. Unfortunately, the approach of PDT is usually limited to the treatment of systemic disease and deeper tumor, due to the limited tissue penetration depth of visible light (620-690nm). Here we report a ROS-enhanced nanoparticle, hafnium-doped hydroxyapatite (Hf:HAp), which can trigger ROS when particles are irradiated with high penetrating power of ionizing radiation. The present study provides quantitative data relating ROS generation and the therapeutic effect of Hf:HAp nanoparticles in lung cancer cells. As such, this material has opened an innovative window for deeper tumor and systemic disease treatment.

Characteristics of sepsis-induced cardiac dysfunction using speckle-tracking echocardiography: a feasibility study

Septic cardiomyopathy is commonly encountered in patients with severe sepsis and septic shock. This study explores whether novel global and segmental echocardiographic markers of myocardial deformation, using two-dimensional speckle tracking, are associated with adverse sepsis outcomes. We conducted a retrospective observational feasibility study, at a tertiary care centre, of patients admitted to the ICU with a diagnosis of sepsis who underwent an echocardiogram within the first week of sepsis diagnosis. Data were collected on chamber dimensions, systolic and diastolic function, demographics, haemodynamics, and laboratory parameters. Global and segmental left ventricular longitudinal strain (LVLS) and tissue mitral annular displacement (TMAD) were assessed on 12 left ventricular segments and six mitral annulus segments in apical views, respectively. We explored associations of abnormal LVLS and TMAD with duration of mechanical ventilation, hospital length of stay, and mortality. Fifty-four patients were included. Global LVLS was not associated with any of the primary study endpoints. However, reduced systolic LVLS of the basal anterior segment was associated with in-hospital mortality. There was a suggestion that patients with a reduced global TMAD were associated with an increased risk of mortality and a short length of hospital stay but these associations were not statistically significant. Reduced global LVLS was associated with lower ejection fraction. Reduced global TMAD was associated with reduced global and segmental LVLS, reduced left ventricular ejection fraction, and increased left ventricular end-systolic and end-diastolic volumes. Speckle-tracking echocardiography can be performed feasibly in patients in sepsis. Global and segmental left ventricular deformation indices are associated with ejection fraction. Further studies need to evaluate the ability of these new indices to predict sepsis outcomes.

3D Printing Bioceramic Porous Scaffolds with Good Mechanical Property and Cell Affinity

Artificial bone grafting is widely used in current orthopedic surgery for bone defect problems. Unfortunately, surgeons remain unsatisfied with the current commercially available products. One of the major complaints is that these products cannot provide sufficient mechanical strength to support the human skeletal structure. In this study, we aimed to develop a bone scaffold with better mechanical property and good cell affinity by 3D printing (3DP) techniques. A self-developed 3D printer with laser-aided gelling (LAG) process was used to fabricate bioceramic scaffolds with inter-porous structures. To improve the mechanical property of the bioceramic parts after heating, CaCO3 was added to the silica ceramic slurry. CaCO3 was blended into a homogenous SiO2-sol dispersion at weight ratios varying from 0/100 to 5/95 to 9/91 (w/w). Bi-component CaCO3/SiO2-sol was prepared as a biocomposite for the 3DP scaffold. The well-mixed biocomposite was used to fabricate the bioceramic green part using the LAG method. The varied scaffolds were sintered at different temperatures ranging from 900 to 1500°C, and the mechanical property was subsequently analyzed. The scaffolds showed good property with the composite ratio of 5:95 CaCO3:SiO2 at a sintering temperature of 1300°C. The compressive strength was 47 MPa, and the porosity was 34%. The topography of the sintered 3DP bioceramic scaffold was examined by SEM, EDS and XRD. The silica bioceramic presented no cytotoxicity and good MG-63 osteoblast-like cell affinity, demonstrating good biocompatibility. Therefore, the new silica biocomposite is viable for fabricating 3DP bone bioceramics with improved mechanical property and good cell affinity.

Effect of the precrack preparation with an ultrasonic instrument on the ceramic bracket removal

BACKGROUND/PURPOSE

In terms of fracture mechanics, a precrack preparation may facilitate the propagation of a break through the expected fracture plane during the bracket debonding process. The purpose of this study was to evaluate the effect of an ultrasonic precrack preparation on the debonding force and failure modes of ceramic bracket removal.

METHODS

Eighty extracted premolars were assigned to four groups: Inspire, precrack Inspire, Clarity, and precrack Clarity groups, with each group containing 20 teeth. The precrack preparations were made at the mesial gingival line angle of Inspire brackets and on the mesial side of Clarity brackets with an ultrasonic tip. Debonding force, failure modes, and bracket breakage score were measured and recorded. Fracture surfaces after bracket debonding were observed with scanning electron microscopy (SEM).

RESULTS

We found that the ultrasonic precrack preparation could significantly decrease the average debonding force and the mean bracket breakage scores of both kinds of ceramic brackets. After bracket debonding, 80% of brackets in the precrack Inspire group and 100% of brackets in the precrack Clarity group showed no bracket failure. However, only 25% of brackets in the Inspire group and 75% of brackets in the Clarity group showed no bracket failure. SEM micrographs showed a precrack notch at the adhesive resin after precrack preparation, and no enamel damage was noted after the bracket debonding.

CONCLUSION

The ultrasonic precrack preparation can significantly decrease the debonding force and may guide the bracket debonding through a favorable fracture plane without damage to either the bracket or the enamel.