Evaluation of the antimicrobial effect of silver ion tubing on dental unit waterlines.

PURPOSE: To assess the antimicrobial effects of silver ion tubing (ST) on dental unit waterlines (DUWLs) and their sustainability over time. METHODS: Six dental chair units (DCUs) equipped with ST and four with common tubing (CT) were included in the study. Repeated flushing with phosphate-buffered saline (PBS) was conducted to dislodge biofilms. Then, genetic analysis of the PBS was performed. The tubing was also detached and scanned under a scanning electron microscope (SEM) to observe the adherent biofilm on the lumen walls. RESULTS: Low bacterial levels were noted in both the CT and ST groups, but biofilm attachment was only observed in the CT group. CLINICAL SIGNIFICANCE: Silver ion tubing exhibited high antibacterial activity by reducing the colonization of pathogens in the dental unit water inhibiting biofilm formation, and showing promise as an efficient infection control method for dental unit waterlines.

Uprighting a mesially tilted mandibular left second molar with anchorage from a dental implant.

Mesial tilting of adjacent teeth may appear after the removal of a tooth, leading to a lack of restorative space. This dental technique presents a method of uprighting a mesially tilted adjacent tooth by using a dental implant as anchorage.

CoCl2 induces apoptosis via a ROS-dependent pathway and Drp1-mediated mitochondria fission in periodontal ligament stem cells.

Oxygen deficiency is associated with various oral diseases, including chronic periodontitis, age-related alveolar bone loss, and mechanical stress-linked cell injury from orthodontic appliances. Nevertheless, our understanding of the impact of hypoxia on periodontal tissues and its biochemical mechanism is still rudimentary. The purpose of this research was to elucidate the effects of hypoxia on the apoptosis of human periodontal ligament stem cells (PDLSCs) in vitro and the underlying mechanism. Herein, we showed that cobalt chloride (CoCl2) triggered cell dysfunction in human PDLSCs in a concentration-dependent manner and resulted in cell apoptosis and oxidative stress overproduction and accumulation in PDLSCs. In addition, CoCl2 promoted mitochondrial fission in PDLSCs. Importantly, CoCl2 increased the expression of dynamin-related protein 1 (Drp1), the major regulator in mitochondrial fission, in PDLSCs. Mitochondrial division inhibitor-1, pharmacological inhibition of Drp1, not only inhibited mitochondrial fission but also protected against CoCl2-induced PDLSC dysfunction, as shown by increased mitochondrial membrane potential, increased ATP level, reduced reactive oxygen species (ROS) level, and decreased apoptosis. Furthermore, N-acety-l-cysteine, a pharmacological inhibitor of ROS, also abolished CoCl2-induced expression of Drp1 and protected against CoCl2-induced PDLSC dysfunction, as shown by restored mitochondrial membrane potential, ATP level, inhibited mitochondrial fission, and decreased apoptosis. Collectively, our data provide new insights into the role of the ROS-Drp1-dependent mitochondrial pathway in CoCl2-induced apoptosis in PDLSCs, indicating that ROS and Drp1 are promising therapeutic targets for the treatment of CoCl2-induced PDLSC dysfunction.

Perturbation of mitochondrial dynamics links to the aggravation of periodontitis by diabetes.

Diabetes and periodontitis are prevalent diseases that considerably impact global economy and diabetes is a major risk factor of periodontitis. Mitochondrial dynamic alterations are involved in many diseases including diabetes and this study aims to evaluate their relevance with diabetes aggravated periodontitis. Sixty mice are randomly divided into 4 groups: control, periodontitis, diabetes and diabetic periodontitis. Periodontitis severity is evaluated by alveolar bone loss, inflammation and oxidative stress status. Mitochondrial structural and functional defects are evaluated by the mitochondrial fission/fusion events, mitochondrial reactive oxygen species (ROS) accumulation, complex activities and adenosine triphosphate (ATP) production. Advanced glycation end product (AGE) and Porphyromonas gingivalis are closely related to periodontitis occurrence and development. Human gingival fibroblast cells (HGF-1) are used to investigate the AGE role and lipopolysaccharide (LPS) from Porphyromonas gingivalis (P-LPS) in aggravating diabetic periodontitis by mitochondrial dynamic and function alterations. In vivo, diabetic mice with periodontitis show severe bone loss, increased inflammation and oxidative stress accumulation. Among mice with periodontitis, diabetic mice show worse mitochondrial dynamic perturbations than lean mice, along with fusion protein levels inducing more mitochondrial fission in gingival tissue. In vitro, AGEs and P-LPS co-treatment causes severe.

Glucose-primed PEEK orthopedic implants for antibacterial therapy and safeguarding diabetic osseointegration.

Diabetic infectious microenvironment (DIME) frequently leads to a critical failure of osseointegration by virtue of its main peculiarities including typical hyperglycemia and pathogenic infection around implants. To address the plaguing issue, we devise a glucose-primed orthopedic implant composed of polyetheretherketone (PEEK), Cu-chelated metal-polyphenol network (hauberk coating) and glucose oxidase (GOx) for boosting diabetic osseointegration. Upon DIME, GOx on implants sostenuto consumes glucose to generate H2O2, and Cu liberated from hauberk coating catalyzes the H2O2 to highly germicidal •OH, which massacres pathogenic bacteria through photo-augmented chemodynamic therapy. Intriguingly, the catalytic efficiency of the coating gets greatly improved with the turnover number (TON) of 0.284 s-1. Moreover, the engineered implants exhibit satisfactory cytocompatibility and facilitate osteogenicity due to the presence of Cu and osteopromotive polydopamine coating. RNA-seq analysis reveals that the implants enable to combat infections and suppress pro-inflammatory phenotype (M1). Besides, in vivo evaluations utilizing infected diabetic rat bone defect models at week 4 and 8 authenticate that the engineered implants considerably elevate osseointegration through pathogen elimination, inflammation dampening and osteogenesis promotion. Altogether, our present study puts forward a conceptually new tactic that arms orthopedic implants with glucose-primed antibacterial and osteogenic capacities for intractable diabetic osseointegration.

Osteogenic differentiation of bone marrow-derived mesenchymal stromal cells on bone-derived scaffolds: effect of microvibration and role of ERK1/2 activation.

Although in vivo studies have shown that low-magnitude, high-frequency (LMHF) vibration (LM: < 1 ×g; HF: 20-90 Hz) exhibits anabolic effects on skeletal homeostasis, the underlying cellular/molecular regulation involved in bone adaptation to LMHF vibration is little known. In this report, we tested the effects of microvibration (magnitude: 0.3 ×g, frequency: 40 Hz, amplitude: ± 50 µm, 30 min/12 h) on proliferation and osteodifferentiation of bone marrow-derived mesenchymal stromal cells (BMSCs) seeded on human bone-derived scaffolds. The scaffolds were prepared by partial demineralisation and deproteinisation. BMSCs were allowed to attach to the scaffolds for 3 days. Morphological study showed that spindle-shaped BMSCs almost completely covered the surface of bone-derived scaffold and these cells expressed higher ALP activity than those cultured on plates. After microvibration treatment, BMSC proliferation was decreased on day 7 and 10; however, numbers of genes and proteins expressed during osteogenesis, including Cbfa1, ALP, collagen I and osteocalcin were greatly increased. ERK1/2 activation was involved in microvibration-induced BMSC osteogenesis. Taken together, this study suggests that bone-derived scaffolds have good biocompatibility and show osteoinductive properties. By increasing the osteogenic lineage commitment of BMSCs and enhancing osteogenic gene expressions, microvibration promotes BMSC differentiation and increase bone formation of BMSCs seeded on bone-derived scaffolds. Moreover, ERK1/2 pathway plays an important role in microvibration-induced osteogenesis in BMSC cellular scaffolds.

Thrombin inhibitor argatroban modulates bone marrow stromal cells behaviors and promotes osteogenesis through canonical Wnt signaling.

AIMS: Coagulation is a common event that play a double-edged role in physiological and pathological process. Anti-coagulation methods were applied in joint surgery or scaffolds implantation to encourage new vascular formation and avoid coagulation block. However, whether anti-coagulation drug perform regulatory roles in bone structure is unknown. This study aims to explore a direct thrombin inhibitor, argatroban, effects on bone marrow stromal cells (BMSCs) and decipher the underlying mechanisms. MATERIALS AND METHODS: Argatroban effects on BMSCs were investigated in vivo and in vitro. The drug was applied in periodontal disease model mice and bone loss was evaluated by µCT and histology. BMSCs were treated with different doses argatroban or vehicle. Cellular reactions were analyzed using wound healing assay, qRT-PCR, Alizarin Red S staining and western blotting. KEY FINDINGS: We demonstrated that local injection of argatroban can rescue bone loss in periodontal disease in vivo. To explore the underlying mechanism, we examined that cell proliferation and differentiation capability. Proliferation and migration of BMSCs were both inhibited by applying lower dose of argatroban. Interestingly, without affecting osteoclastogenesis, osteogenic differentiation was significantly induced by argatroban, which were shown by extracellular mineralization and upregulation of early osteoblastic differentiation markers, alkaline phosphatase, Osteocalcin, transcription factors RUNX2 and Osterix. In addition, molecular analysis revealed that argatroban promoted ß-catenin nuclear translocation and led to an increase of osteogenesis through activating canonical Wnt signaling. SIGNIFICANCE: Taken together, our results show the novel application of the anti-coagulation compound argatroban in the commitment of BMSCs-based alveolar bone regeneration and remodeling.

[Uprighting a mesially tilted mandibular second molar by using a dental implant as anchorage: a case report].

After tooth has been removed for a long time, adjacent teeth may tilt to occupy the edentulous space, leading to a break in the occlusal 3D equilibrium and a lack of restorative space. This case report presents a mandibular second molar uprighting with anchorage from a dental implant.

[Suggestions for selection and use of masks for dental medical staff during outbreaks of novel coronavirus pneumonia].

During the outbreak of novel coronavirus pneumonia (NCP), dentists are at risk for more severe infection due to their professionalism. This article analyzed the route of infection during diagnosis and treatment of oral diseases. Following the related standards and guidelines of National Health Commission, the types, evaluation index and standards of medical and protective masks were summarized. It is expected to provide certain reference for the selection and use of masks of dental medical staff.

Haptic Rendering of Diverse Tool-Tissue Contact Constraints During Dental Implantation Procedures.

Motor skill learning of dental implantation surgery is difficult for novices because it involves fine manipulation of different dental tools to fulfill a strictly pre-defined procedure. Haptics-enabled virtual reality training systems provide a promising tool for surgical skill learning. In this paper, we introduce a haptic rendering algorithm for simulating diverse tool-tissue contact constraints during dental implantation. Motion forms of an implant tool can be summarized as the high degree of freedom (H-DoF) motion and the low degree of freedom (L-DoF) motion. During the H-DoF state, the tool can move freely on bone surface and in free space with 6 DoF. While during the L-DoF state, the motion degrees are restrained due to the constraints imposed by the implant bed. We propose a state switching framework to simplify the simulation workload by rendering the H-DoF motion state and the L-DoF motion state separately, and seamless switch between the two states by defining an implant criteria as the switching judgment. We also propose the virtual constraint method to render the L-DoF motion, which are different from ordinary drilling procedures as the tools should obey different axial constraint forms including sliding, drilling, screwing and perforating. The virtual constraint method shows efficiency and accuracy in adapting to different kinds of constraint forms, and consists of three core steps, including defining the movement axis, projecting the configuration difference, and deriving the movement control ratio. The H-DoF motion on bone surface and in free space is simulated through the previously proposed virtual coupling method. Experimental results illustrated that the proposed method could simulate the 16 different phases of the complete implant procedures of the Straumann® Bone Level(BL) Implants Φ4.8-L12 mm. According to the output force curve, different contact constraints could be rendered with steady and continuous output force during the operation procedures.

Effectiveness of surface texture simulation of fixed dental prostheses by curvature analysis.

OBJECTIVE: The current design methods for the surface texture of prostheses are unsatisfactory: the line-drawing method relies heavily on the subjective experience of technicians, and the powder-coating method requires high costs. A new innovative method is proposed: curvature-analysis with reverse engineering. The objective was to compare operation times and esthetic parameters in generating surface textures among the three methods. METHOD AND MATERIALS: Twenty-seven patients with maxillary central incisor fixed dental prostheses were randomly divided into three groups, and prostheses were built by three technicians using line-drawing, powder-coating, or curvature-analysis methods, respectively. Porcelain grinding times were recorded. The final prostheses were analyzed regarding the three-dimensional deviation from the control group that used the contralateral tooth. A senior technician and clinician made a single-blind evaluation of the prostheses' surface texture. RESULTS: In the curvature-analysis method, large, medium, and small curvatures effectively showed an intrinsic labial surface, the developmental groove, and other surface morphology structures, respectively. Operation times in the line-drawing, powder-coating, and curvature-analysis methods were 19.51 ± 0.95, 16.87 ± 1.30, and 12.41 ± 0.94 minutes, respectively, with statistically significant differences among the three methods; evaluation scores were statistically significantly different between the line-drawing and curvature-analysis methods. The three-dimensional deviation root mean square values were 0.451 ± 0.083, 0.396 ± 0.029, and 0.295 ± 0.080 mm, respectively, indicating curvature analysis had the smallest three-dimensional deviation. CONCLUSIONS: Curvature analysis helps manufacture the surface texture accurately with enhanced efficiency, improving esthetics and reducing operation time and material waste.

A three-dimensional finite element analysis of mechanical function for 4 removable partial denture designs with 3 framework materials: CoCr, Ti-6Al-4V alloy and PEEK.

Polyetheretherketone (PEEK) is a new material used for the frameworks of removable partial dentures (RPD). The questions whether the PEEK framework has similar stress distribution on oral tissue and displacement under masticatory forces as titanium alloy (Ti-6Al-4V) or cobalt-chromium alloy (CoCr) remain unclear and worth exploring. A patient's intraoral data were obtained via CBCT and master model scan. Four RPDs were designed by 3Shape dental system, and the models were processed by three-dimensional finite element analysis. Among three materials tested, PEEK has the lowest maximum von Mises stress (VMS) on periodontal ligament (PDL), the greatest maximum VMS on mucosa, the maximum displacement on free-end of framework, and the lowest maximum VMS on framework. Results suggested that PEEK framework has a good protective effect on PDL, suggesting applications for patients with poor periodontal conditions. However, the maximum displacement of the free-end under masticatory force is not conducive for denture stability, along with large stress on the mucosa indicate that PEEK is unsuitable for patients with more loss of posterior teeth with free-end edentulism.

Minimal invasive microscopic tooth preparation in esthetic restoration: a specialist consensus.

By removing a part of the structure, the tooth preparation provides restorative space, bonding surface, and finish line for various restorations on abutment. Preparation technique plays critical role in achieving the optimal result of tooth preparation. With successful application of microscope in endodontics for >30 years, there is a full expectation of microscopic dentistry. However, as relatively little progress has been made in the application of microscopic dentistry in prosthodontics, the following assumptions have been proposed: Is it suitable to choose the tooth preparation technique under the naked eye in the microscopic vision? Is there a more accurate preparation technology intended for the microscope? To obtain long-term stable therapeutic effects, is it much easier to achieve maximum tooth preservation and retinal protection and maintain periodontal tissue and oral function health under microscopic vision? Whether the microscopic prosthodontics is a gimmick or a breakthrough in obtaining an ideal tooth preparation should be resolved in microscopic tooth preparation. This article attempts to illustrate the concept, core elements, and indications of microscopic minimally invasive tooth preparation, physiological basis of dental pulp, periodontium and functions involved in tool preparation, position ergonomics and visual basis for dentists, comparison of tooth preparation by naked eyes and a microscope, and comparison of different designs of microscopic minimally invasive tooth preparation techniques. Furthermore, a clinical protocol for microscopic minimally invasive tooth preparation based on target restorative space guide plate has been put forward and new insights on the quantity and shape of microscopic minimally invasive tooth preparation has been provided.

[Minimal invasive microscopic tooth preparation based on endodontic, periodontal and functional health].

Tooth preparation is the primary and core operation technique for dental esthetic restoration treatment, due to its effect of providing restoration space, bonding interfaces and marginal lines for dental rehabilitation after tooth tissue reduction. The concept of microscopic minimal invasive dentistry put forward the issue of conducting high-quality tooth preparation, conserve tooth-structure, protect vital pulp and periodontal tissue simultaneously. This study reviewed the concepts, physiology background, design and minimal invasive microscopic tooth preparation, and in the meantime, individualized strategies and the two core elements of tooth preparation (quantity and shape) are listed.

Blockade of cyclophilin D rescues dexamethasone-induced oxidative stress in gingival tissue.

Glucocorticoids (GCs) are frequently used for the suppression of inflammation in chronic inflammatory diseases. Excessive GCs usage is greatly associated with several side effects, including gingival ulceration, the downward migration of the epithelium, attachment loss and disruption of transeptal fibers. The mechanisms underlying GCs-induced impairments in gingival tissue remains poorly understood. Mitochondrial dysfunction is associated with various oral diseases, such as chronic periodontitis, age-related alveolar bone loss and hydrogen peroxide-induced cell injury in gingival. Here, we reported an unexplored role of cyclophilin D (CypD), the major component of mitochondrial permeability transition pore (mPTP), in dexamethasone (Dex)-induced oxidative stress accumulation and cell dysfunctions in gingival tissue. We demonstrated that the expression level of CypD significantly increased under Dex treatment. Blockade of CypD by pharmaceutical inhibitor cyclosporine A (CsA) significantly protected against Dex-induced oxidative stress accumulation in gingival tissue. And the protective effects of blocking CypD in Dex-induced gingival fibroblasts dysfunction were evidenced by rescued mitochondrial function and suppressed production of reactive oxygen species (ROS). In addition, blockade of CypD by pharmaceutical inhibitor CsA or gene knockdown also restored Dex-induced cell toxicity in HGF-1 cells, as shown by suppressed mitochondrial ROS production, increased CcO activity and decreased apoptosis. We also suggested a role of oxidative stress-mediated p38 signal transduction in this event, and antioxidant N-acety-l-cysteine (NAC) could obviously blunted Dex-induced oxidative stress. These findings provide new insights into the role of CypD-dependent mitochondrial pathway in the Dex-induced gingival injury, indicating that CypD may be potential therapeutic strategy for preventing Dex-induced oxidative stress and cell injury in gingival tissue.

Preparation, in vitro degradability, cytotoxicity, and in vivo biocompatibility of porous hydroxyapatite whisker-reinforced poly(L-lactide) biocomposite scaffolds.

Biodegradable and bioactive scaffolds with interconnected macroporous structures, suitable biodegradability, adequate mechanical property, and excellent biocompatibility have drawn increasing attention in bone tissue engineering. Hence, in this work, porous hydroxyapatite whisker-reinforced poly(L-lactide) (HA-w/PLLA) composite scaffolds with different ratios of HA and PLLA were successfully developed through compression molding and particle leaching. The microstructure, in vitro mineralization, cytocompatibility, hemocompatibility, and in vivo biocompatibility of the porous HA-w/PLLA were investigated for the first time. The SEM results revealed that these HA-w/PLLA scaffolds possessed interconnected pore structures. Compared with porous HA powder-reinforced PLLA (HA-p/PLLA) scaffolds, HA-w/PLLA scaffolds exhibited better mechanical property and in vitro bioactivity, as more formation of bone-like apatite layers were induced on these scaffolds after mineralization in SBF. Importantly, in vitro cytotoxicity displayed that porous HA-w/PLLA scaffold with HA/PLLA ratio of 1:1 (HA-w1/PLLA1) produced no deleterious effect on human mesenchymal stem cells (hMSCs), and cells performed elevated cell proliferation, indicating a good cytocompatibility. Simultaneously, well-behaved hemocompatibility and favorable in vivo biocompatibility determined from acute toxicity test and histological evaluation were also found in the porous HA-w1/PLLA1 scaffold. These findings may provide new prospects for utilizing the porous HA whisker-based biodegradable scaffolds in bone repair, replacement, and augmentation applications.

A novel porous bioceramics scaffold by accumulating hydroxyapatite spherulites for large bone tissue engineering in vivo. II. Construct large volume of bone grafts.

In vivo engineering of bone autografts using bioceramic scaffolds with appropriate porous structures is a potential approach to prepare autologous bone grafts for the repair of critical-sized bone defects. This study investigated the evolutionary process of osteogenesis, angiogenesis, and compressive strength of bioceramic scaffolds implanted in two non-osseous sites of dogs: the abdominal cavity and the dorsal muscle. Hydroxyapatite (HA) sphere-accumulated scaffolds with controlled porous structures were prepared and placed in the two sites for up to 6 months. Analyses of retrieved scaffolds found that osteogenesis and angiogenesis were faster in scaffolds implanted in dorsal muscles compared with those placed in abdominal cavities. The abdominal cavity, however, can accommodate larger bone grafts with designed shape. Analyses of scaffolds implanted in abdominal cavities [an environment of a low mesenchymal stem cell (MSC) density] further demonstrated that angiogenesis play critical roles during osteogenesis in the scaffolds, presumably by supplying progenitor cells and/or MSCs as seed cells. This study also examined the relationship between the volume of bone grafts and the physiological environment of in vivo bioreactor. These results provide basic information for the selection of appropriate implanting sites and culture time required to engineer autologous bone grafts for the clinical bone defect repair. Based on these positive results, a pilot study has applied the grafts constructed in canine abdominal cavity to repair segmental bone defect in load-bearing sites (limbs).

Micromotions and combined damages at the dental implant/bone interface.

Micromotion and fretting damages at the dental implant/bone interface are neglected for the limitation of check methods, but it is particularly important for the initial success of osseointegration and the life time of dental implant. This review article describes the scientific documentation of micromotion and fretting damages on the dental implant/bone interface. The fretting amplitude is less than 30 µm in vitro and the damage in the interface is acceptable. While in vivo, the micromotion's effect is the combination of damage in tissue level and the real biological reaction.