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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 periimplant 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.
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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 periimplant 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.
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Objective@#To compare the biomechanical characteristics of four-implants mandibular overdentures supported by Locator attachment or bar-clip attachment under different mechanical loads using three-dimensional finite element analysis method.@*Methods@#Two different models of four-implants supported mandibular overdentures using Locator attachment and bar-clip attachment (hereinafter called Locator model and bar-clip model) were established. Each model was subjected to five different mechanical loading conditions: 100 N vertical loading in central incisor (vertical load of incisor), 100 N vertical loading or oblique loading in canine (vertical or oblique loads of canines), 100 N vertical or oblique loading in mandibular first molar (vertical or oblique loads of mandibular first molar). The stress distributions in implants, peri-implant bone and mucosa were recorded under the above five conditions to evaluate the effects of different attachments on the biomechanical properties of implant-supported mandibular overdentures.@*Results@#Regardless of loading conditions and types of attachments, the stress concentration in implants were located at the neck of implants, and the stress concentration in peri-implant bone was located in the cortical bone. The stress values in mucosa were always much smaller than those in implants and cortical bone. Regardless of loading positions (on canine or on mandibular first molar), the maximum stress at the bone interface around the implant under lateral loading was much higher than that under vertical loading. Under various loading conditions, the stress in implants and cortical bone of the Locator model (the highest von Mise stress value was respectively 79.5 and 22.3 MPa) were lower than that of bar-clip model (the highest von Mise stress value was 110.3 and 28.7 MPa respectively) while the maximum compressive stress in mucosa (0.198 MPa) in Locator model was slightly higher than that in the bar-clip model (0.137 MPa).@*Conclusions@#In clinical practice, the lateral force applied to the implant-retained overdenture should be minimized to avoid complications caused by pathological loads. Under the same loading condition, the stress distributions in overdenture using Locator attachment are more dispersed, which is more conducive to long-term stability of implants.
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Objective@#To analyze the stress distribution of different types of bone tissue around porous titanium implant in different mechanical loads and to further evaluate the biomechanical properties of porous titanium implant.@*Methods@#Finite element (FE) models of implant restorations for the maxillary first premolar was established, and the diameter of implants in the models was 4.1 mm. Five models was constructed according to diameter of implant central pillar and the thickness of outer porosity: solid group (group A), central pillar 1.5 and 3.1 mm and outer porosity 30% (group B and C), central pillar 1.5 and 3.1 mm and outer porosity 40% (group D and E). Different loads (150 N vertical force, 50 N lateral force) were applied to the occlusal surface of implant restorations in type Ⅲ bone and maximal von Mises stress was evaluated. Meanwhile, a couple of simplified maxillary part models varied in four types of bone were constructed with the implants bearing load of simulation ultimate force to evaluate the stress distribution of different types of bone.@*Results@#With different mechanical loading, the stress value of bone tissue around porous implant (group B-E) was greater than that in the solid structure (group A). Under the load of simulation ultimate force, the maximum stress of the bone rised with the increase of porosity and thickness of the porous implant. And the maximum stress value of the surrounding bone tissue changed with the change of bone. Under vertical loading, the maximal von Mises stress of the bone around solid implants of group A was 17.56 MPa, which was a little lower than that of group B and C. And the maximal equivalent von Mises stress of group D and E was 69.24 MPa. The results of lateral force and simulation ultimate force loading were similar. The stress of the bone tissue around implant increased with the decrease of bone quality. The maximum stress value of group D implant was 134.95 MPa.@*Conclusions@#Porous structure of the implant is conducive to transmit stress to surrounding bone tissue and increases the mechanical stimulation of bone. However, if the value and direction of load are inappropriate or quality of bone is poor, pathological stress may be produced.
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<p><b>OBJECTIVE</b>To compare the effect of different surface processes on bond strength and microscopic structure using a scanning electron microscope (SEM) and an energy distribution spectrum (EDS) at the bonding interface between zirconia framework and veneering ceramic.</p><p><b>METHODS</b>WIELAND zirconia core material was cut into 33 rectangular specimens and fired on into rectangular specimens (10 mm×5 mm×5 mm). The specimens were randomly divided into three groups (n= 11). The sandblasting group was sandblasted before firing. The sandblasting and liner coverage group was sandblasted before firing and then sintered with liner coverage after firing. The control group was not processed. All the veneering ceramics (5 mm× 5 mm×5 mm) were fired on into the zirconia substructure by slip-casting technique. One bilayered specimen in each group was prepared for SEM and EDS to examine the bonding conditions. The other specimens were measured for shear force using an electronic universal dynamometer. The data obtained were analyzed by using the statistical software SPSS 17.0.</p><p><b>RESULTS</b>The values of the shear bond strength test were (13.80±1.54) MPa for the control group, (18.06±0.59) MPa for the sandblasting group, and (21.04±1.23) MPa for the sandblasting and liner coverage group. Significant differences existed among the three groups (P<0.01).</p><p><b>CONCLUSIONS</b>Abrasion before firing significantly increases the shear bond strength of zirconia to veneering porcelain. The use of porcelain combined with liner increases the shear bond strength.</p>
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<p><b>OBJECTIVE</b>To explore the differentially expressed genes and related signaling pathways in MC3T3-E1 osteo- blasts in response to suitable fluid shear stress values and action time with cDNA microarrays.</p><p><b>METHODS</b>MC3T3-E1 cells cultured on a cover slip were subjected to fluid shear stress using a parallel plate flow chamber. The harvested RNA was used for microarray hybridization comprising approximately 44 170 genes, as well as for the subsequent real-time quantitative polymerase chain reaction validation of expression levels for selected genes. Microarray results were analyzed by using both GO and Pathway analysis.</p><p><b>RESULTS</b>Microarray analysis indicated that 884 differentially expressed genes were found. Among these genes, 444 were upregulated, whereas 440 were downregulated. The Notch signal and RIG- I -like receptor signaling pathways were involved in the Pathway analysis. GO analysis mainly involved different functional classifications, such as prostaglandin biosynthesis, nitric oxide-mediated signal transduction, calcium mediated signal, and cellular immune response, among others.</p><p><b>CONCLUSION</b>The mechanism underlying the protective effect of fluid shear stress on MC3T3-E1 cells might be related to promoting cell survival- and inhibiting cell apoptosis-related signaling pathways and biological processes.</p>
Subject(s)
Humans , Apoptosis , Calcium , Oligonucleotide Array Sequence Analysis , Osteoblasts , Signal Transduction , Stress, MechanicalABSTRACT
<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>
Subject(s)
Animals , Rats , Alkaline Phosphatase , Cell Differentiation , Estradiol , Osteoblasts , Stress, MechanicalABSTRACT
<p><b>OBJECTIVE</b>To study the intercellular communication of alveolar bone during traumatic occlusion at early stage in rats.</p><p><b>METHODS</b>The occlusal surface of the upper left first molar of rat was raised by placing a stainless steel wire to induce occlusal trauma in the lower left first molar. After 24 hours, the alveolar bone tissues of the lower jaws first molars at the both sides were taken out under anesthesia The various 27 000 genes were identified with genome-wide microarray, and further were investigated with reverse transcription-polymerase chain reaction (RT-PCR) and Pathway analysis.</p><p><b>RESULTS</b>Total 586 gene were found to be changed, 106 different signal pathways got involved with Pathway analysis, including cell adhesion molecules(CAMS), adhesions junction, gap junction, focal adhesion and tight junction, and the cytokines associated with bone metabolism in above 5 signal pathways were all down-regulated.</p><p><b>CONCLUSION</b>At the early phase of the occlusal trauma, intercellular communication in rat's alveolar bone were inhibited.</p>
Subject(s)
Animals , Rats , Alveolar Process , Bone and Bones , Dental Occlusion , Dental Occlusion, Traumatic , MolarABSTRACT
<p><b>OBJECTIVE</b>To study the gene expression profiles of traumatic occlusion in early stage with the animal model of rats.</p><p><b>METHODS</b>The occlusal surface of the upper left first molar of rat was raised by placing a stainless steel wire to induce occlusal trauma in the lower left first molar. After 24 hours, the alveolar bone tissue of the first molars at the both sides of rats' lower jaws were taken out under anesthesia. The different expressive genes were shown by genome-wide microarray, which comprises about 27 000 genes and analyzed the different expressive genes with Pathway and GO analysis, finally the results of the microarray were examined by real time-polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>In the results of the study, 586 different expressions were found, of which the expressions of 166 genes increased and 420 genes decreased. 106 different pathways were involved with Pathway analysis and 270 different functional classification related to GO analysis.</p><p><b>CONCLUSION</b>The balance of the lower alveolar bone is destroyed after 24 hours of traumatic occlusion. At early phase of the occlusal trauma, osteogenesis and bone formation in alveolar bone are inhibited, yet osteoblast genesis and bone resorption are not significant.</p>
Subject(s)
Animals , Rats , Alveolar Bone Loss , Bone Resorption , Dental Occlusion , Dental Occlusion, Traumatic , Mandible , Molar , Osteoblasts , Osteogenesis , TranscriptomeABSTRACT
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.