Research progress on surface modification of titanium implants by strontium ions / 口腔疾病防治

@#Traditional titanium implants do not completely meet the clinical requirements because they are bioinert. The surface of titanium implants, modified by strontium ions, can enhance osseointegration and reduce peri-implantitis. In this paper, the biological properties of titanium implant surfaces modified by strontium ions were reviewed. Strontium ions can be coated on the implant surface by hydrothermal treatment, electrochemical deposition, phosphate chemical conversion, flame-spraying, supramolecular self-assembly, magnetron sputtering, laser deposition and alkali etching. Implant surfaces modified by strontium ions can not only promote osteogenesis and early osseointegration but also inhibit bacterial growth and reduce postoperative infections. Even better osseointegration and antibacterial effects can be achieved when strontium ions are incorporated with other elements, such as silver, zinc, gallium, and calcium. However, most of the studies on the use of strontium ion-modified titanium implants are animal experiments and in vitro experiments, and the observation time is short compared with the actual service life of the implants. Thus, the conclusions obtained may be different from the actual clinical application, and the long-term effects need to be studied. In addition, the osteogenic effects of various modification methods also need to be compared. Future research can focus on the following points: ① to find efficient modification methods that can be widely used in the clinic; ②to study how to control the concentration of strontium ions near the implant to exert their biological function and reduce their toxic side effects; and ③ to conduct long-term follow-up clinical trials to observe their osteogenic and antibacterial effects.

Multiple idiopathic root resorption: a case report and literature review / 口腔疾病防治

Objective @#To explore the etiology, clinical manifestations, diagnosis and treatment of multiple idiopathic root resorption to provide a reference for clinical diagnosis and treatment. @*Methods@# The clinical data of a case of multiple idiopathic root resorption were analyzed retrospectively, and the related literature was reviewed.@*Results@#The patient had no history of orthodontic correction, occlusal trauma, trauma history or other causes of root resorption. Clinical examination revealed full-mouth gingival congestion, redness, a loose texture, and variable degrees of destruction of the alveolar bone. Imaging examination showed that teeth 13, 16, 26, 36, 46 had idiopathic root resorption. The diagnoses were multiple idiopathic root resorption and periodontitis. The pathology tests showed that a large number of osteoclasts were present in the soft tissue surrounding the teeth. Whole-exome sequencing showed that there was a strong correlation between gene mutations (WNT7a and HSPG2) and the present phenotype. Root resorption of teeth without periodontitis was stopped after periodontal treatment during the 19-month follow-up. Tooth 13 was removed, and extraction socket preservation was performed. The etiology of idiopathic root resorption may be related to gene mutations, but it is not clear. At present, there is no effective treatment. @* Conclusion @#Multiple idiopathic root resorption has an unknown etiology, but it may be related to WNT7A and HSPG2 gene mutations. The rate of root resorption can be slowed by controlling periodontal inflammation.

Titanium Mesh Exposure in Guided Bone Regeneration Procedures: A Systematic Review and Meta-analysis.

PURPOSE: To investigate whether titanium mesh exposure is influenced by the type of titanium mesh, the type of bone graft material, or the associated employment of absorbable membranes. MATERIALS AND METHODS: Electronic literature searches were conducted using four databases: PubMed, EMBASE, Web of Science, and Cochrane. Articles reporting titanium mesh exposure rates were included, and exposure rates in different subgroups were compared to determine whether a factor significantly influenced titanium mesh exposure. The review protocol was registered in the PROSPERO registry (CRD42020210187). RESULTS: Twenty and 12 articles were included in the qualitative and quantitative synthesis, respectively. The weighted exposure rates of employing conventional titanium mesh or 3D-customized titanium mesh were 19.9% and 15.2% (P = .34). When employing autogenous bone combined with anorganic bovine bone material as bone graft material, the weighted exposure rate was 21.7%, whereas when using other bone graft material, the exposure rate was 23.5% (P = .74). The weighted exposure rate of using titanium mesh associated with absorbable membranes is 23.9%, while the weighted exposure rate of using titanium mesh without absorbable membranes is 20.2% (P = .36). Meta-regression showed that when analyzing one factor, the other two confounding factors did not influence the result (P = .28). CONCLUSION: It seemed that the type of titanium mesh, the type of bone graft material, or the combined employment of absorbable membranes did not statistically significantly influence the titanium mesh exposure rate in guided bone regeneration.

Analysis of factors related to early failure of 1 001 implants with 3.3 mm narrow-diameter / 口腔疾病防治

Objective@# To explore the early failure of narrow-diameter implants (NDIs) and to provide a reference for clinical implant restoration.@*Methods@# From April 2017 to April 2020, data from a total of 725 patients (with 1 001 NDIs) who accepted implant restoration due to dentition defects were collected from the department of dental implantology in a stomatological hospital; 353 males and 372 females were included. The early failure rate of 1 001 NDIs was retrospectively analyzed. Univariate generalized estimated equation (GEE) and multivariate GEE were used to explore risk factors, including age, sex, implant location, materials, surface modification, length, bone augmentation and healing procedure, associated with early failure of NDIs.@*Results@#There were 34 cases of early failure among 725 patients, including 38 NDIs. The early failure rate of NDIs was 4.69% at the patient level and 3.80% at the implant level. There was no significant difference in the early failure rate of NDIs among different age groups, sexes, implant materials, surface modifications, lengths, and healing procedures (P>0.05). Univariate analysis showed that there was a significant difference between the early failure rate of NDIs in the anterior maxilla group (2.16%) and the anterior mandible group (8.64%) at the implant level (P<0.001). However, there was no significant difference in the early failure rate between the anterior maxilla group and the posterior group (3.35%) (P>0.05). In addition, in the anterior region, the early failure rate of NDIs in the group with simultaneous bone augmentation was significantly lower than that of the group without bone augmentation (P<0.05). However, multivariate GEE analysis showed that the early failure rate of NDIs was only significantly positively correlated with implants in the mandibular anterior region (P<0.01). @*Conclusion @#The overall early survival rate of Straumann 3.3 mm NDIs is greater than 95%. The early failure of NDIs in the anterior mandible region is much higher than that in the anterior maxilla region and posterior region.

Zinc Promotes Patient-Derived Induced Pluripotent Stem Cell Neural Differentiation via ERK-STAT Signaling.

Nerve regeneration remains a challenge. Patient-derived induced pluripotent stem cell (iPSC)-differentiated neural stem cells (NSCs) provide a promising hope. Zinc is closely involved in central nervous system development and metabolism, but its role on iPSC neural differentiation is elusive and zinc detection methods in live cells are limited. In this study, intracellular zinc was detected in real time by a zinc fluorescent chemosensor and was shown to be increased during the iPSC neural induction process. iPSC neural differentiation was promoted with the addition of zinc chloride (ZnCl2) and inhibited with the addition of zinc chelator N,N,N0,N0-tetrakis(2-pyridylmethyl)-ethylenediamine, indicated by western blot and enzyme-linked immunosorbent assay analysis of NSC marker Nestin expression and measurement of neurite-like structures. Mechanistically, the phosphorylation level of ERK1/2 and STAT3 was changed with the zinc level, suggesting that zinc may affect the neural differentiation of iPSCs through ERK-STAT signaling. In conclusion, our study shows the important role of zinc in iPSC neural differentiation and suggests a new idea for iPSC-derived NSC application in nerve regeneration.

Small molecule inhibitor of TGF-ß signaling enables robust osteogenesis of autologous GMSCs to successfully repair minipig severe maxillofacial bone defects.

BACKGROUND: Clinically, for stem cell-based therapy (SCBT), autologous stem cells are considered better than allogenic stem cells because of little immune rejection and no risk of communicable disease infection. However, severe maxillofacial bone defects restoration needs sufficient autologous stem cells, and this remains a challenge worldwide. Human gingival mesenchymal stem cells (hGMSCs) derived from clinically discarded, easily obtainable, and self-healing autologous gingival tissues, have higher proliferation rate compared with autologous bone marrow mesenchymal stem cells (hBMSCs). But for clinical bone regeneration purpose, GMSCs have inferior osteogenic differentiation capability. In this study, a TGF-ß signaling inhibitor SB431542 was used to enhance GMSCs osteogenesis in vitro and to repair minipig severe maxillofacial bone defects. METHODS: hGMSCs were isolated and cultured from clinically discarded gingival tissues. The effects of SB431542 on proliferation, apoptosis, and osteogenic differentiation of hGMSCs were analyzed in vitro, and then, SB431542-treated hGMSCs composited with Bio-Oss® were transplanted into immunocompromised mice subcutaneously to explore osteogenic differentiation in vivo. After that, SB431542-treated autologous pig GMSCs (pGMSCs) composited with Bio-Oss® were transplanted into circular confined defects (5 mm × 12 mm) in minipigs maxillary to investigate severe bone defect regeneration. Minipigs were sacrificed at 2 months and nude mice at 8 weeks to retrieve specimens for histological or micro-CT or CBCT analysis. Effects of SB431542 on TGF-ß and BMP signaling in hGMSCs were investigated by Western Blot or qRT-PCR. RESULTS: One micromolar of SB431542 treatment induced a robust osteogenesis of hGMSCs in vitro, without adverse effect on apoptosis and growth. In vivo, 1 µM SB431542 treatment also enabled striking osteogenesis of hGMSCs subcutaneously in nude mice and advanced new bone formation of pGMSCs in minipig maxillary bone defect model. In addition, SB431542-treated hGMSCs markedly increased bone-related proteins expression, and BMP2 and BMP4 gene expression. Conversely, SMAD3 protein-dependent TGF-ß signal pathway phosphorylation was decreased. CONCLUSIONS: Our study show that osteogenic differentiation of GMSCs treated with TGF-ß signaling inhibitor SB431542 was increased, and SB431542-treated autologous pig GMSCs could successfully repair minipig severe maxillofacial bone defects. This preclinical study brings about a promising large bone regeneration therapeutic potential of autologous GMSCs induced by SB431542 in clinic settings.