Study on the role of pyroptosis in bone resorption induced by occlusal trauma with or without periodontitis.

BACKGROUND AND OBJECTIVE: Occlusal trauma is considered to be a contributing factor to bone loss associated with inflammatory periodontal disease. We hypothesized that pyroptosis, a recently discovered inflammation-induced programmed cell death pathway, plays a role in occlusal trauma. MATERIALS AND METHODS: The occlusal trauma model was established using a cemented 1-mm elevated computer-aided design and manufacturing (CAD/CAM) metal crown. The periodontitis model was established by periodontal wire ligation with lipopolysaccharide (LPS) injection. The rats were sacrificed at 1, 2, 3, and 4 weeks. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the expression of pyroptosis-, inflammation-, and osteoclast-related markers. Micro-computed tomography (micro-CT) was used to determine bone morphology parameters. Tissue morphology was evaluated using hematoxylin and eosin staining (H&E). Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP) staining. The expression and distribution of factors related to pyroptosis and inflammation were evaluated by immunohistochemistry (IHC). The colocalization of dead cells and cysteinyl aspartate-specific proteinase-1 (caspase-1)-positive cells was analyzed by immunofluorescence. RESULTS: Quantitative real-time polymerase chain reaction and IHC results showed that occlusal trauma induced the expression of pyroptotic factors during the early stages, while occlusal trauma with periodontitis upregulated the expression of pyroptotic factors at the later stages. The results of qRT-PCR, TRAP staining, and micro-CT showed that occlusal trauma with periodontitis increased the production of proinflammatory cytokines, leading to severe bone loss. Glyburide, an NOD-like receptor pyrin domain containing protein 3 (NLRP3)inhibitor, reduced the expression of pyroptosis markers induced by occlusal trauma with periodontitis and reversed bone resorption. CONCLUSIONS: Pyroptosis was involved in bone loss induced by occlusal trauma with or without periodontitis, while glyburide reversed inflammation and bone resorption.

Correlation between clinical parameters of crown and gingival morphology of anterior teeth and periodontal biotypes.

BACKGROUND: In this study, we conducted a quantitative analysis of the clinical parameters of crown and gingival morphology (CGM) of the maxillary anterior teeth (MAT). We also analyzed the correlation of these parameters with periodontal biotype (PB), with a view to providing objective standards for PB diagnosis. METHODS: The three-dimensional (3D) maxillary digital models of 56 individuals were obtained using an intra-oral scanner. The following parameters were measured with the SpaceClaim software: gingival angle (GA), papilla width (PW), papilla height (PH), crown length (CL), crown width (CW), crown width/crown length ratio (CW/CL), bucco-lingual width of the crown (BLW), contact surface width (CSW), and contact surface height/crown length ratio (CS/CL). The PB were determined based on the transparency of the periodontal probe through the gingival sulcus. Independent factors influencing PB were analyzed by logistic regression, and the optimal cutoff values for the independent influencing factors were analyzed using receiver operating characteristic curves (ROC curves). RESULTS: There was no significant difference in the parameters of CGM of the MAT at the left and right sides. The thick biotype accounted for 69.6%, and the parameters of GA, PW, PH, CW, CW/CL and CS/CL were significantly correlated with PB (P ≤ 0.2). GA (odds ratio (OR) = 1.206) and PW (OR = 5.048) were identified as independent predictive factors of PB, with areas under the ROC curve (AUC) of 0.807 and 0.881, respectively, and optimal cutoff values of 95.95° and 10.01 mm, respectively. CONCLUSION: The CGMs of the MAT at the left and right side are symmetrical. The thin biotype accounts for a small proportion, and GA and PW are independent influencing factors of PB. GA of 95.95° and PW of 10.01 mm are the optimal cutoff values for categorization of individuals as thick biotype. This indicates that when the GA and PW of the right maxillary central incisor are G ≥ 95.95° and ≥ 10.01 mm, respectively, there is a higher probability that these individuals will be categorized as thick biotype.

A quantitative research on clinical parameters of gingival contour for anterior teeth esthetic analysis and design.

OBJECTIVES: To provide reference for computer-aided esthetic analysis and design of the maxillary anterior teeth. MATERIALS AND METHODS: Intraoral scanner was used to obtain the maxillary three-dimensional digital models of subjects with healthy periodontal tissue. In SpaceClaim, the occlusal plane was established as the horizontal reference plane to measure the positional relation between the gingival zenith (GZ) of the maxillary anterior teeth, the angle formed between the gingival line and the maxillary midline (GLA), the distance between the GZ of the lateral incisor and gingival line (LID), and the distance between the GZ and the vertical bisected middle surface along the long axis of the clinical crown (VBMS). RESULTS: The GLA was 92.7 ± 3.2°. The GZ of the canine, lateral incisor, and left central incisor were located to the GZ of the right central incisor coronally at 0.68 ± 0.91, 0.65 ± 0.66 mm, and apically at 0.12 ± 0.42 mm, respectively. The LID was 0.65 ± 0.92 mm. The GZ of the canine, lateral incisor, and central incisor were located distally to the VBMS at 0.00 ± 0.06, 0.27 ± 0.19, and 0.73 ± 0.21 mm, respectively. CONCLUSION: The GZ at different tooth position are in different heights. The direction and degree of the GZ deviation from the VBMS are also related to tooth position. CLINICAL SIGNIFICANCE: The clinical parameters of the gingival contour obtained in this research can be used for patients with unsound contour of periodontal soft tissue to do the anterior teeth esthetic analysis. Besides, it can also be used to determine the proper position between the GZs of the maxillary anterior teeth in anterior teeth esthetic design.

New clinical application of digital intraoral scanning technology in occlusal reconstruction: A case report.

BACKGROUND: Digital intraoral scanning, although developing rapidly, is rarely used in occlusal reconstruction. To compensate for the technical drawbacks of current occlusal reconstruction techniques, such as time consumption and high technical requirements, digital intraoral scanning can be used in clinics. This report aims to provide a way of selecting the most suitable maxillo-mandibular relationship (MMR) during recovery. CASE SUMMARY: A 68-year-old man with severely worn posterior teeth underwent occlusal reconstruction with fixed prosthesis using digital intraoral scanning. A series of digital models in different stages of treatment were obtained, subsequently compared, and selected using digital intraoral scanning together with traditional measurements, such as cone beam computed tomography, joint imaging, and clinical examination. Using digital intraoral scanning, the MMR in different stages of treatment was accurately recorded, which provided feasibility for deciding the best occlusal reconstruction treatment, made the treatment process easier, and improved patient satisfaction. CONCLUSION: This case report highlights the clarity, recordability, repeatability, and selectivity of digital intraoral scanning to replicate and transfer the MMR during occlusal reconstruction, expanding new perspectives for its design, fabrication, and postoperative evaluation.

[A review on progress of in vitro research of fluid shear stress influence on signaling networks of osteoblasts].

Mechanical stress plays an important role in bone growth and bone remodeling. It causes stretch stress and fluid shear stress (FSS), which can be sensed by mechanosensory cells, e.g. osteocytes and osteoblasts, and further induce changes of gene expression in those cells. The FSS is thought to be the main cause in this process. However, up to now, it is still not clear what signals are triggered in the mechanosensory cells cultured in vitro and how the FSS exactly affects the expression of specific proteins. Evidences have shown that Ca2+ signaling pathway, Cyclooxygenase-prostaglandin E2 pathway, protein kinase A/protein kinase C (PKA/PKC) pathway, and drosophila mothers against decapentaplegic (Smad) protein pathway may be the key players in osteoblast differentiation by FSS. The precise mechanism involved in mechanotransduction and signal transduction remains to be elucidated. The present review gives a brief summary on the effects of these signaling pathways on the differentiation of osteoblasts cultured in vitro under FSS, to get the message of the present situation of the research on the stress transmission and signal transduction influencing osteoblast molecular activity, and to provide reference for further study on its specific mechanism.

Evaluating the accuracy of three intraoral scanners using models containing different numbers of crown-prepared abutments.

BACKGROUND/PURPOSE: The scanning accuracy of intraoral scanners' data collection plays a key role in the success of the final treatment. However, few studies start from scanning technology itself to directly evaluate it. The aim of this study was to evaluate the scanning accuracy of three intraoral scanners, to provide a reference for relevant research and clinical applications. MATERIALS AND METHODS: Six types of resin models containing different numbers of crown-prepared abutments were three-dimensionally printed, and a model scanner, as well as three intraoral scanners, were used to digitally scan the six models. The obtained data were uploaded to three-dimensional reverse software for registration and comparison, and the accuracy of the models were analyzed. RESULTS: When scanning the six groups of models, the Omnicam outperformed both the TRIOS and iTero in terms of accuracy in all groups except the second molar group. The TRIOS and iTero scanners also exhibited decreased degrees of accuracy when scanning the long dental arch. The accuracy decreased as the scanning scope increased; however, the Omnicam scanner exhibited a relatively high degree of accuracy when scanning the three-unit fixed bridge and anterior areas. All scanners exhibited the lowest degree of accuracy when scanning the full-arch model. Certain deviations were observed, and the scanning areas at the incisal edges of the anterior teeth and end of the dental arch exhibited relatively large deviations. CONCLUSION: With the model scanner data as reference, the scanning accuracy of the three scanners exhibited differences and certain deviations, which were within clinical tolerance.

Mechanism of Exosomes Involved in Osteoimmunity Promoting Osseointegration Around Titanium Implants With Small-Scale Topography.

Exosomes are nanoscale extracellular vesicles. Several studies have shown that exosomes participate in intercellular communication and play a key role in osseointegration. However, it is unclear whether exosomes and their contents participate in the communication between the immune and skeletal systems in the process of osseointegration. In this study, we obtained smooth titanium disks by polishing and small-scale topography titanium disks by sandblasted large-grit acid-etched (SLA) technology combined with alkali thermal reaction. After stimulating mouse RAW264.7 cells with these two kinds of titanium disks, we co-cultured the MC3T3-E1 cells and the RAW264.7 cells, obtained and identified the exosomes derived from RAW264.7 cells, and studied the effect of the osteoimmune microenvironment and the exosomes on the osseointegration of mouse MC3T3-E1 cells. Cell counting kit-8 (CCK-8), real time quantitative PCR, western blotting, alizarin red staining, and quantitative and confocal fluorescence microscopy were used to study the effects of exosomes on MC3T3-E1 cells; RNA sequencing and correlation analysis were performed. We found that the osteoimmune microenvironment could promote the osseointegration of MC3T3-E1 cells. We successfully isolated exosomes and found that RAW264.7 cell-derived exosomes can promote osteogenic differentiation and mineralization of MC3T3-E1 cells. Through RNA sequencing and gene analysis, we found differentially expressed microRNAs that targeted the signal pathways that may be related, such as mTOR, AMPK, Wnt, etc., and thus provide a reference for the mechanism of osteoimmunue regulation of implant osseointegration. The study further elucidated the mechanism of implant osseointegration and provided new insights into the effect of exosomes on implant osseointegration, and provided reference for clinical improvement of implant osseointegration and implant success rate.

The role of autophagy in the process of osseointegration around titanium implants with micro-nano topography promoted by osteoimmunity.

Osteoimmunity plays an important role in the process of implant osseointegration. Autophagy is a conservative metabolic pathway of eukaryotic cells, but whether the interaction between autophagy and osteoimmunity plays a key role in osseointegration remains unclear. In this study, we prepared smooth titanium disks and micro-nano topography titanium disks, to study the immune microenvironment of RAW264.7 cells, and prepared the conditioned medium to study the effect of immune microenvironment on the osteogenesis and autophagy of MC3T3-E1 cells. Autophagy inhibitor 3-MA was used to inhibit autophagy to observe the change of expression of osteogenic markers. The results showed that the micro-nano topography titanium disks could stimulate RAW264.7 cells to differentiate into M2 type, forming an anti-inflammatory immune microenvironment; compared with the control group, the anti-inflammatory immune microenvironment promoted the proliferation and differentiation of osteoblasts better. The anti-inflammatory immune environment activated the autophagy level of osteoblasts, while the expression of osteogenic markers was down-regulated after inhibition of autophagy. These results indicate that anti-inflammatory immune microenvironment can promote cell proliferation and osteogenic differentiation, autophagy plays an important role in this process. This study further explains the mechanism of implant osseointegration in osteoimmune microenvironment, and provides reference for improving implant osseointegration.

Effect of the immune responses induced by implants in a integrated three-dimensional micro-nano topography on osseointegration.

In order to explore the abilities of an integrated three-dimensional micro-nano topography in immunomodulation and promoting bone formation, present study focuses on the titanium sheets used in the micro-nano topography by treating them with the sandblasted, large-grit and acid-etched (SLA)and alkaline thermal reaction. Further, we characterized and obtained the surface morphology, roughness, and hydrophilicity of the titanium sheets. Moreover, we detected their in vitro cytocompatibility and cell proliferation as well. In addition, investigation was carried out for the immunomodulatory ability of the titanium sheets in a micro-nano topography by observing the expression of M1 (classical activated macrophage) and M2 (alternatively activated macrophage) type marker factors, inflammatory factors, and morphological changes of RAW264.7 cells cultured on the titanium sheets in different topographies. Through cell migration experiments and coculture, we observed the effects of different titanium sheet immune environments on osteoblast migration, extracellular matrix mineralization, and osteoblast gene expression. These results showed that the micro-nano topography constructed through SLA and alkaline thermal treatment improved the hydrophilicity and promoted the cell proliferation. Moreover, it promoted RAW264.7 cells to polarize as M2 phenotype, thereby leading to the anti-inflammatory effect of local microenvironments. This facilitated osteoblasts to secrete bone morphogenetic protein-2 (BMP2) and vascular endothelial growth factor. Nonetheless, these findings provided a theoretical basis for the molecular biological mechanism related to implants in a micro-nano topography which promoted the osteointegration while offering a meaningful theoretical basis for the clinical treatment of such implants.

Chitosan/hydroxyapatite composite coatings on porous Ti6Al4V titanium implants: in vitro and in vivo studies.

PURPOSE: Titanium implants are widely used in the treatment of dentition defects; however, due to problems such as osseointegration failure, peri-implant bone resorption, and peri-implant inflammation, their application is subject to certain restrictions. The surface modification of titanium implants can improve the implant success rate and meet the needs of clinical applications. The goal of this study was to evaluate the effect of the use of porous titanium with a chitosan/hydroxyapatite coating on osseointegration. METHODS: Titanium implants with a dense core and a porous outer structure were prepared using a computer-aided design model and selective laser sintering technology, with a fabricated chitosan/hydroxyapatite composite coating on their surfaces. In vivo and in vitro experiments were used to assess osteogenesis. RESULTS: The quasi-elastic gradient and compressive strength of porous titanium implants were observed to decrease as the porosity increased. The in vitro experiments demonstrated that, the porous titanium implants had no biological toxicity; additionally, the porous structure was shown to be superior to dense titanium with regard to facilitating the adhesion and proliferation of osteoblast-like MC3T3-E1 cells. The in vivo experimental results also showed that the porous structure was beneficial, as bone tissue could grow into the pores, thereby exhibiting good osseointegration. CONCLUSIONS: Porous titanium with a chitosan/hydroxyapatite coating promoted MC3T3-E1 cell proliferation and differentiation, and also improved osseointegration in vitro. This study has meaningful implications for research into ways of improving the surface structures of implants and promoting implant osseointegration.

Verification of osteoblast differentiation on airborne-particle abrasion, large-grit, acid-etched surface of titanium implants regulated by yes-associated protein and transcriptional coactivator with PDZ-binding motif.

Although airborne-particle abrasion, large-grit, acid-etched (SLA) surface technology can promote implant osseointegration; its mechanism remains unclear. By preparing the SLA titanium (Ti) plate (SLA Ti) and Polished Ti plate (Polished Ti), this experiment investigates the expression and distribution of the Yes-associated protein (YAP) and transcriptional coactivator with the PDZ-binding motif (TAZ) in MC3T3-E1 cells. In addition, gene YAP and TAZ silencing on the SLA Ti was conducted to observe changes in the osteoblast differentiation markers, runt-related transcription factor-2 (Runx2) and bone sialoprotein (BSP). The results demonstrated that SLA Ti surface microtopography could induce YAP/TAZ's transfer from the cytoplasm to the nuclei of MC3T3-E1 cells. The expression of YAP/TAZ increased in terms of mRNA and protein. After silencing the YAP/TAZ genes, Runx2 and BSP decreased, suggesting that YAP/TAZ plays an important regulatory role in this process. Meanwhile, the results also showed that SLA microtopography enhanced the expression of integrins α1, α2, and ß1. After silencing the integrin α1, α2, and ß1 genes, YAP and TAZ decreased in terms of mRNA and protein. Therefore, this experiment was the first to confirm that SLA surface microtopography facilitates osteoblast differentiation by regulating YAP/TAZ and confirms that the process can be related to integrins α1, α2, and ß1.

How to deal with esthetically overcritical patients who need complete dentures: a case report.

AIM: The purpose of this report is to present a strategy for making a diagnosis and providing appropriate treatment for denture patients with high esthetic demands. BACKGROUND: Some edentulous patients have critical requirements for the esthetic aspect of dentures. REPORT: A 55-year-old edentulous female presented with a complaint of dissatisfaction with the appearance of two sets of old dentures. A complex method was used during the fabrication of a new set of dentures in order to meet her demand for esthetics. SUMMARY: This method essentially improves the mutual communication and cooperation between dentists and patients; therefore, it improves satisfaction of the patients.

A modification of a direct technique for the fabrication of posts and using wax pattern.

This new direct technique for the fabrication of posts and cores using a wax pattern is easy to manipulate. It requires no special armamentarium and is appropriate for various situations. It provides the advantage of a direct technique and ensures the post pattern's precise fit. It also avoids the disadvantage of other direct techniques, the limitation of the direction of the cores by the placement of the broaches, the pins, or the prefabricated dowels.

[Selective laser sintering and performances of porous titanium implants].

OBJECTIVE: This work aims to analyze the mechanical properties and biocompatibility of porous titanium (Ti) implants fabricated by selective laser sintering (SLS) and investigate the promotion of osseointegration by porous titanium implant combined with chitosan (CS)/hydroxyapatite(HA) composite coating. METHODS: Ti6Al4V specimens were prepared, and CS/HA composite coating was fabricated on the surface of a portion of the specimens. The mechanical properties of the samples were observed by scanning electron microscope. MC3T3-E1 cells were cultured in vitro, and their biological properties in vitro were analyzed using live and dead viability cell staining method, methyl thiazolyl tetrazolium (MTT) staining, and alkaline phosphatase (ALP) level detection. The thread implant specimens were implanted in the femoral condyle of rabbits, and biological performance was evaluated in vivo. RESULTS: Quasi-elastic gradient of porous specimens decreased with increasing porosity, and the quasi-elastic gradient were close to cortical and cancellous bone when the porosities were 30% and 70%. The specimens showed good biocompatibility. Combined with CS/HA coating, the implants promoted the proliferation and differentiation of MC3T3-E1 cells and facilitated the entry of bone tissue into pores and good osteogenesis. CONCLUSIONS: The porous titanium implant exhibited favorable mechanical properties and biocompatibility. Combined with CS/HA coating, the implant exhibited bone inducibility, which leads to stable osteogenesis.

The Protocol of Fixed Reconstruction for Severely Worn Teeth Combined with Anterior Deep Bite.

Full mouth reconstruction is one of the most effective methods to restore severe worn teeth that have suffered reduced vertical dimension. Although the use of the overlay splint restoration for a trial period allowing the patient to adapt to an increased vertical dimension is the recognized method, the specific protocol from the transitional splint to the fixed reconstruction is yet to be established. This case report describes a 50-year-old female patient who has severely worn teeth combined with an anterior deep bite and chewing pain. The protocol of the treatment process is described.

[Experimental study on the reconstruction of bone defects in vivo and the osteoinduction with degradation products of alpha-tricalcium phosphate cements in vitro].

OBJECTIVE: This study was aimed to clarify the characteristics of alpha-tricalcium phosphate cements in reconstructing bone defects and the action of degradation products of cements in vitro. METHODS: The defect (diameter 1.5 cm) was created in the calvaria of rabbit. Alpha-tricalcium phosphate cements were planted in the treatment groups. All groups were observed by histological examination and roentgenography. Bone marrow stromal cells (BMSc) were cultured in the degradation products of cements in vitro, and were observed by means of cytology and ALP. RESULTS: Degradation of artificial bone, new bone formation, and osteogenesis between artificial bone particles were observed at 12 weeks after implantation. Osteoinduction was observed in vitro. CONCLUSION: Alpha-tricalcium phosphate cements have good biocompatibility, osteoinductivity and degradability, and are ideal bone substitute material for reconstruction.

Influence of inner circular sealing area impression method on the retention of complete dentures.

The aims of the present study were to describe an impression method of "inner circular sealing area" and to evaluate the effect of the method on retention, aesthetics and comfort of complete dentures, which lack labial base for patients with maxillary protrusions. Three patients were subjected to the experiment, and two sets of complete maxillary dentures were made for each patient; the first set was made without labial base via an inner circular sealing area method (experimental group) and the second had an intact base that was made with conventional methods (control group). Retention force tests were implemented with a tensile strength assessment device to assess the retention and a visual analogue scale (VAS) was used to evaluate the comfort between the two groups. Results showed larger retention force, better aesthetics and more comfort in the experimental group. The improved two-step impression method formed an inner circular sealing area that prevented damage to the peripheral border seal effect of the denture caused by incomplete bases and obtained better denture retention.

[Evaluation of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 levels in peri-implant sulcular fluid].

OBJECTIVE: To investigate the levels of MMP-9 and TIMP-1 in healthy and diseased peri-implant tissue. METHODS: Fifty-one implants in 39 patients were selected and divided into the healthy group and the inflammatory group according to the absence or presence of gingival redness, bleeding on probing, and progressive horizontal absorption of alveolar bone. The clinical parameters included: depth of gingival pocket(PD), plaque & calculus index (PLI), gingival bleeding index (GBI), and MMP-9, TIMP-1 levels in peri-implant sulcular fluid (PISF). RESULTS: PD, PLI, GBI and MMP-9 levels were significantly higher in inflammatory group than in healthy group (P < 0.001). CONCLUSION: MMP-9 level in PISF was closely associated with the clinical parameters.

Differentially expressed genes and signalling pathways are involved in mouse osteoblast-like MC3T3-E1 cells exposed to 17-ß estradiol.

Oestrogen is essential for maintaining bone mass, and it has been demonstrated to induce osteoblast proliferation and bone formation. In this study, complementary DNA (cDNA) microarrays were used to identify and study the expression of novel genes that may be involved in MC3T3-E1 cells' response to 17-ß estradiol. MC3T3-E1 cells were inoculated in minimum essential media alpha (α-MEM) cell culture supplemented with 17-ß estradiol at different concentrations and for different time periods. MC3T3-E1 cells treated with 10⁻8 mol⋅L⁻¹ 17-ß estradiol for 5 days exhibited the highest proliferation and alkaline phosphatase (ALP) activity; thus, this group was chosen for microarray analysis. The harvested RNA was used for microarray hybridisation and subsequent real-time reverse transcription polymerase chain reaction (RT-PCR) to validate the expression levels for selected genes. The microarray results were analysed using both functional and pathway analysis. In this study, microarray analysis detected 5403 differentially expressed genes, of which 1996 genes were upregulated and 3407 genes were downregulated, 1553 different functional classifications were identified by gene ontology (GO) analysis and 53 different pathways were involved based on pathway analysis. Among the differentially expressed genes, a portion not previously reported to be associated with the osteoblast response to oestrogen was identified. These findings clearly demonstrate that the expression of genes related to osteoblast proliferation, cell differentiation, collagens and transforming growth factor beta (TGF-ß)-related cytokines increases, while the expression of genes related to apoptosis and osteoclast differentiation decreases, following the exposure of MC3T3-E1 cells to α-MEM supplemented with 17-ß estradiol. Microarray analysis with functional gene classification is critical for a complete understanding of complementary intracellular processes. This microarray analysis provides large-scale gene expression data that require further confirmatory studies.

[Research of the synergetic action of fluid shear stress and 17-beta estradiol on the proliferation of MC3T3-E1 cells].

OBJECTIVE: To explore the suitable level and action time of 17-beta estradiol and fluid shear stress (FSS) and their combined effect on the proliferation of rat osteoblasts in vitro. METHODS: MC3T3-E1 osteoblasts were adopted after subcultured and different concentrations of 17-beta estradiol and FSS values were applied respectively on MC3T3-E1, the suitable level of 17-beta estradiol and FSS were selected through MTT and alkaline phosphatase (ALP). Then the two factors at the suitable level were applied simultaneously to MC3T3-E1 to detect the proliferation activity. RESULTS: Seventeen-beta estradiol(10(-8) mol x L(-1) for 5 d and 12 x 10(-5) N FSS for 60 min exhibited better effects on the proliferation activity than the other groups respectively, and the combined effect of both factors was better than any single-factor treated group. CONCLUSION: Both 17-beta estradiol and FSS have a suitable threshold in promoting proliferation of osteoblasts, and two-factor treated group exhibits better effect than any other single-factor treated groups. Therefore 17-beta estradiol and FSS have a synergetic action on differentiation and proliferation of osteoblasts.