The protective role of Ephrin-B2/EphB4 signaling in osteogenic differentiation under inflammatory environment.

Inflammation and alveolar bone destruction constitute the main pathological process of periodontitis. However, the molecular mechanisms of bone destruction under the inflammation environment remain unclear. This study aims to explore the role of Ephrin-B2/EphB4 signaling in osteogenic differentiation under the inflammation environment. Mouse pre-osteoblasts MC3T3-E1 were pretreated with lipopolysaccharide of Porphyromonas gingivalis (Pg-LPS). The Ephrin-B2/EphB4 signaling was activated, and the osteogenic differentiation of cells was examined. The results showed that activation of Ephrin-B2/EphB4 signaling promoted the expression levels of osteogenic differentiation-related genes, and also relieved the inhibitory effect of Pg-LPS on osteogenesis. Noticeably, the effect of Ephrin-B2/EphB4 signaling might be related to the mitogen-activated protein kinase (MAPK) pathway. While applying Ephrin-B2-Fc and EphB4-Fc to periodontitis mice, we observed the reduction of alveolar crest destruction. The current study revealed the possible role of Ephrin-B2/EphB4 signaling in reducing bone destruction in periodontitis and suggested its potential values for further research.

Finite element analysis of maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule restored with fiber-reinforced composite resin posts and resin core: The number and placement of the posts.

STATEMENT OF PROBLEM: Whether fiber-reinforced composite (FRC) posts should be inserted in root canals to restore teeth with multiple roots remains unclear. PURPOSE: The purpose of this finite element analysis (FEA) study was to determine the optimal use of FRC posts in an endodontically treated maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule. MATERIAL AND METHODS: Eight different models of a maxillary first molar were established: no post (NP), post in palatal root (P), post in distobuccal root (DB), post in mesiobuccal root (MB), posts in palatal root and distobuccal root (P+DB), posts in palatal root and mesiobuccal root (P+MB), posts in 2 buccal roots (DB+MB), and posts in all roots (P+DB+MB). Two types of loading were applied: a force of 800 N parallel to the long axis of the tooth to simulate the vertical masticatory force and another force of 225 N at 45 degrees to the long axis of the tooth to simulate the lateral masticatory force. The equivalent stresses on the external surfaces of the tooth tissue, the internal surfaces of the root canals and in the posts, as well as the maximal shear stresses on the post-core interface and the core-dentin interface, were calculated with FEA. RESULTS: All the models showed similar maximal equivalent stress values on the external surfaces of the tooth tissue, and stress concentrations were found at the cervical and furcation area. On the internal surfaces of root canals, an increase of equivalent stress at the middle third of the canals with posts and a decrease at the cervical third were observed. Under vertical loading, the P+DB+MB group showed the largest equivalent stress in the post (76.45 MPa in the palatal post), the DB+MB group showed the largest shear stress on the post-core interface (19.02 MPa), and the MB group showed the largest shear stress on the core-dentin interface (12.07 MPa). Under lateral loading, the P+DB+MB group showed the largest equivalent stress in the post (60.11 MPa in the mesiobuccal post) and the largest shear stress on the post-core interface (13.48 MPa) and the DB group showed the largest shear stress on the core-dentin interface (21.03 MPa). CONCLUSIONS: One post in the palatal canal was found to be appropriate for the FRC post and resin core restoration of a maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule. An additional post in the mesiobuccal canal could help disperse lateral occlusal force and improve retention of the restoration.

Evaluation of Outcomes of Dental Implants Inserted by Flapless or Flapped Procedure: A Meta-Analysis.

PURPOSE: The purpose of this meta-analysis was to evaluate the failure risk and marginal bone loss of dental implants inserted by flapless or flapped procedure. MATERIALS AND METHODS: Studies were identified by searching PubMed, Web of Knowledge, and the Cochrane Library within 10 years, along with a hand search of the reference lists of the retrieved articles. RESULTS: A total of 2717 articles were filtered after the searching strategy, and 31 studies were finally selected. Failure rate of dental implants was statistically affected by different insertion procedures (flapless or flapped) with a risk ratio (RR) of 1.70 (95% confidence interval [CI]: 1.13-2.55; P = 0.01; heterogeneity: I = 0.0%; P heterogeneity = 0.97). Subgroup analysis indicated that in the situation of immediate/early loading, the flapless procedure showed a higher risk of implant failure comparing with flapped procedure (RR = 2.24; 95% CI: 1.05-4.78; P = 0.04; heterogeneity: I = 0.0%; P heterogeneity = 0.91). Mean difference of marginal bone loss between the flapless group and the flapped group was -0.10 mm (95% CI: -0.18 to -0.02; P = 0.02; heterogeneity: I = 82%; P heterogeneity = 0.00). CONCLUSIONS: This meta-analysis revealed that flapless procedure may increase the failure risk of the dental implants, especially in the situation of immediate/early loading. Nevertheless, flapless procedure showed a superiority in preserving bone tissues.

Immediate dental implant placement into infected vs. non-infected sockets: a meta-analysis.

OBJECTIVE: This meta-analysis was aimed at assessing whether immediate dental implant placement into infected vs. non-infected sites produced different effects on implant failure risk and marginal bone loss. MATERIAL AND METHODS: Relevant studies were identified by searching articles in PubMed, Web of Knowledge, and the Cochrane Library through February 2015 and by reviewing the reference lists of the retrieved articles. When an intervention led to dichotomous outcomes, the outcomes were expressed as risk ratios, whereas continuous outcomes were expressed as mean differences in millimeters; each had a 95% confidence interval. Study-specific estimates were combined using fixed-effects models. RESULTS: A total of 1743 articles were identified following the search process. Seven studies were finally included in the meta-analysis, which comprised a total of 1586 implants and 25 failures. Compared to the immediate insertion of a dental implant into a non-infected site, the insertion of an implant into an infected site showed 116% increase in the risk of implant failure, which had borderline statistical significance (risk ratio = 2.16, 95% confidence interval: 0.97, 4.80, P = 0.058; heterogeneity: I2  = 0.0%, Pheterogeneity  = 0.997). With regard to marginal bone loss, we observed no statistically significant difference between insertions into infected vs. non-infected sites (mean difference = -0.04, 95% confidence interval: -0.09, 0.02, P = 0.173, heterogeneity: I2  = 0.0%, Pheterogeneity  = 0.765). CONCLUSION: This meta-analysis suggests that immediately placing a dental implant into an infected site may increase the risk of implant failure. Given the presence of uncontrolled confounders in the studies that were assessed, the results should be interpreted with caution.

Evaluate the effects of low-intensity pulsed ultrasound on dental implant osseointegration under type II diabetes.

Objective: The objective of this study is to assess the impact of low-intensity pulsed ultrasound (LIPUS) therapy on the peri-implant osteogenesis in a Type II diabetes mellitus (T2DM) rat model. Methods: A total of twenty male Sprague-Dawley (SD) rats were randomly allocated into four groups: Control group, T2DM group, Control-LIPUS group, and T2DM-LIPUS group. Implants were placed at the rats' bilateral maxillary first molar sites. The LIPUS treatment was carried out on the rats in Control-LIPUS group and T2DM-LIPUS group, immediately after the placement of the implants, over three consecutive weeks. Three weeks after implantation, the rats' maxillae were extracted for micro-CT, removal torque value (RTV), and histologic analysis. Results: Micro-CT analysis showed that T2DM rats experienced more bone loss around implant cervical margins compared with the non-T2DM rats, while the LIPUS treated T2DM rats showed similar bone heights to the non-T2DM rats. Bone-implant contact ratio (BIC) were lower in T2DM rats but significantly improved in the LIPUS treated T2DM rats. Bone formation parameters including bone volume fraction (BV/TV), trabecular thickness (Tb.Th), bone mineral density (BMD) and RTV were all positively influenced by LIPUS treatment. Histological staining further confirmed LIPUS's positive effects on peri-implant new bone formation in T2DM rats. Conclusion: As an effective and safe treatment in promoting osteogenesis, LIPUS has a great potential for T2DM patients to attain improved peri-implant osteogenesis. To confirm its clinical efficacy and to explore the underlying mechanism, further prospective cohort studies or randomized controlled trials are needed in the future.

Cone-beam CT evaluation of post-extraction alveolar bone changes at the maxillary incisor sites in an East Asian population: A cross-sectional study.

Objective: Understanding the characteristics of alveolar bone resorption in an East Asian population after maxillary incisor extraction and providing a reference for implant treatment plans. Study design: Cone-beam computerized tomography (CBCT) data of 125 East Asian patients with unilateral extraction of maxillary incisors for 3 months were collected. The alveolar bone width and height in the extraction sites were measured and compared with the corresponding contralateral sites. Results: The differences in alveolar bone width between the extraction site and contralateral site were as follows: 4.11 mm, 2.68 mm, and 2.09 mm (3 mm, 5 mm, 7 mm apical from CEJ of the contralateral tooth). Data are expressed as the median. The horizontal resorption ratio of alveolar bone was 49.94 %, 31.5 %, and 24.46 %. The difference in alveolar bone height was 0.78 mm. The vertical resorption ratio was 7.78 %. The resorption did not differ significantly between sexes and was not significantly affected by tooth positions. Conclusions: In the studied East Asian population, significant horizontal and vertical alveolar bone resorption occurs after natural healing of maxillary incisor extraction for 3 months. The closer to the alveolar ridge crest, the more significant the horizontal resorption, resulting in an "inverted triangle" shape residual alveolar bone.

Finite element analysis of maxillary first molar with mesial-occlusal-distal-palatal defect restored with different post-and-core strategies.

Purpose: To explore which restoration strategy generates the most favorable stress distribution in an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect. Methods: Models with one post in palatal canal (PP), each post in palatal and distobuccal canals (PDP), each post in palatal and mesiobuccal canals (PMP), and each post in all canals (PDMP) were established for an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect either with fiber-reinforced composite (FRC) post or gold alloy cast (GAC) post. A 400-N vertical force and a 225-N lateral force were respectively applied. The Mohr-Coulomb stress ratio (σMC ratio) in the residual tooth structure (RTS), the resin cement, and the crowns, the tensile stress (σt) and compressive stress (σc) in the FRC posts, the von-Mises stress ratio (σvM ratio) in the GAC post-and-cores, and the σt and shear stress (σs) at the adhesive interfaces were calculated using finite element analysis. Results: FRC posts generated lower σMC ratio than GAC posts in the RTS (0.3274-0.3643 vs. 0.3399-0.4118). Among the FRC post groups, the PDMP group got the lowest σs at the dentin-post interface (14.92 MPa) and the abutment-crown interface (8.242 MPa) under vertical loading, as well as the lowest σMC ratio in the RTS (0.3381) and the lowest σs at the dentin-post interface (38.00 MPa) under lateral loading. Conclusions: From the point of stress distribution, placing FRC posts in the palatal, distobuccal, and mesiobuccal canals is the optimal strategy in restoring a severely damaged maxillary first molar, provided that lateral occlusal force is reduced.

Suppressing ROS generation by apocynin inhibited cyclic stretch-induced inflammatory reaction in HPDLCs via a caspase-1 dependent pathway.

It has been reported that cyclic stretch could induce inflammatory reaction in human periodontal ligament cells (HPDLCs). Though reactive oxygen species (ROS) has been reported to be involved in pathogen-induced periodontal inflammatory reaction, its role in the force-related periodontal diseases has not been well clarified. This study inspected the role of ROS in the cyclic stretch-induced inflammatory reaction in HPDLCs and studied the inhibitory effect of antioxidant apocynin on this inflammatory reaction. Results confirmed that cyclic stretch induced inflammatory reaction and production of ROS in HPDLCs. This inflammatory reaction was inhibited by apocynin through blocking the production of ROS. The cyclic stretch also induced the expression of caspase-1 and NLRP3 inflammasome, which could also be inhibited by apocynin. Moreover, the cyclic stretch-induced inflammatory reaction was inhibited by caspase-1 inhibitor. Collectively, it is the first time that increased intracellular ROS was proved to play as an intermediate signal in the cyclic stretch-induced inflammatory reaction in HPDLCs, via a caspase-1-dependent pathway. The inhibitory effect of apocynin on the cyclic stretch-induced inflammatory reaction in HPDLCs shows the potential of antioxidants in the treatment of force-related periodontal inflammatory diseases.

Effect of polyimide addition on mechanical properties of PMMA-based denture material.

The aim of the study was to evaluate the effect of modifying polymethyl methacrylate (PMMA) denture base material with polyimide (PI) on its flexural property and biocompatibility. Low molecular weight (1,500 g/mol) PI was synthesized and small amount of PI (0.4, 0.6, 0.8 and 1 wt%) was dispersed into the PMMA matrix. Three-point bending tests, scanning electron microscopy and thermal cycling were used to measure the mechanical properties, while MTT assay was used to evaluate the biocompatibility of the denture base material. The results showed that 0.6% addition of PI significantly increased flexural strength of PMMA denture base material by 13.5%, compared with the control group (p<0.05). Even after 5,000 hydrothermal cycling the reinforce effect still existed. However, when the PI content further increased, flexural strength of the denture base material decreased due to particle agglomeration. The MTT assay confirmed that the addition of PI did not change the biocompatibility of the PMMA denture base material. The present study suggested that blending polyimide in the proper proportion can be a potential method to strengthen the PMMA-based denture base material.

Cyclic stretch induced gene expression of extracellular matrix and adhesion molecules in human periodontal ligament cells.

OBJECTIVE: Periodontal ligament (PDL) cells play an important role in maintaining periodontal homeostasis upon force loading caused by mastication or orthodontic force. Previous studies revealed stretch-induced realignment of human PDL cells, but the mechanism for this phenomenon still remains unclear. As extracellular matrix (ECM) and adhesion molecules play critical roles in cell migration and alignment, this study aimed to identify mechanoresponsive genes related to ECM and adhesion in human PDL cells. DESIGN: Human PDL cells were exposed to 10% stretch strain for 6 or 24 h, and the expression of 84 genes related to ECM and adhesion were analyzed with real-time PCR array. The protein expression of integrin α5 was examined by Western blot and flow cytometric analysis. RESULTS: Among the genes screened, 6 were up-regulated and 3 were down-regulated after 6 h stretch. There were 12 up-regulated and 2 down-regulated genes after 24 h stretch. These differentially expressed genes included genes encoding cell-cell adhesion molecules (CD44, ICAM1), cell-matrix adhesion molecules (ITGA5, ITGA6, ITGAL, ITGB2, SPP1), basement membrane constituents (SPARC, TNC), collagens and ECM constituents (COL5A1, COL11A1, FN1), ECM proteases (ADAMTS1, ADAMTS8, MMP8) and inhibitors (TIMP1), as well as other adhesion-related molecules (CTGF, CTNND2, TGFBI, CLEC3B). Both the cytosolic and membrane integrin α5 protein levels were up-regulated in response to stretch. CONCLUSION: This study identified several force-sensitive genes related to ECM and adhesion in stretched human PDL cells and should facilitate future studies on the stretch-induced cell realignment and mechanic force related periodontal remodelling by providing potential target genes.

[Early complications of surgery for chronic suppurative otitis media].

OBJECTIVE: To explore early post-operative complications following surgery for chronic suppurative otitis media. METHOD: From Jan 1992 to July 2000, 291 cases of chronic suppurative otitis media have been treated in our department. 79 cases underwent myringoplasty, 82 cases tympanoplasty, 88 cases modified radical mastoidectomy and 42 cases radical mastoidectomy. RESULT: Facial nerve palsies occurred in 3 cases (1.03%), bone conduction threshold elevation occurred in 13 cases (4.47%), wound infection occurred in 11 cases (3.78%), 7 patients (2.41%) reported symptoms related with chorda tympani trauma, symptoms of jaw discomfort were reported by 7 patients (2.41%) and imbalance or vertigo by 13 patients(4.47%). CONCLUSION: The incidence of early complications of surgery for chronic suppurative otitis media in this report was similar to previous reports.