Effect of different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium crowns produced by computer-aided designing and selective laser melting processes.

PURPOSE: To evaluate the impact of five different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium (CoCr) crowns produced by computer-aided designing (CAD) and selective laser melting (SLM) processes. MATERIALS AND METHODS: Five preparation data were constructed, after which design crowns were obtained. Actual crowns were fabricated using an SLM process. After the data of actual crowns were obtained with structural light scanning, intaglio surfaces of the design crown and actual crown were virtually superimposed on the preparation. The fit-discrepancies were displayed with colors, while the root means square was calculated and analyzed with one-way analysis of variance (ANOVA), Tukey's test or Kruskal-Wallis test (α =.05). RESULTS: The marginal or internal color-coded images in the five design groups were not identical. The shoulder-lip and sharp line angle groups in the CAD or SLM process had larger marginal or internal fit discrepancies compared to other groups (P < .05). In the CAD process, the mean marginal and internal fit discrepancies were 10.0 to 24.2 µm and 29.6 to 31.4 µm, respectively. After the CAD and SLM processes, the mean marginal and internal fit discrepancies were 18.4 to 40.9 µm and 39.1 to 47.1 µm, respectively. The SLM process itself resulted in a positive increase of the marginal (6.0 - 16.7 µm) and internal (9.0 - 15.7 µm) fit discrepancies. CONCLUSION: The CAD and SLM processes affected the fit of CoCr crowns and varied based on the preparation designs. Typically, the shoulder-lip and sharp line angle designs had a more significant effect on crown fit. However, the differences between the design groups were relatively small, especially when compared to fit discrepancies observed clinically.

Evaluation of bone formation in neonatal mouse calvariae using micro-CT and histomorphometry: an in vitro study.

Neonatal calvarial bone has been widely used for investigating the biological behaviour of intramembranous bones. This work evaluated the bone formation of neonatal calvarial bone by microcomputed tomography (micro-CT) and histomorphometry. Moreover, the viability of neonatal calvarial bone and the effect of micro-CT radiation exposure on neonatal calvarial bone viability were investigated. The calvarial bones of 4-day-old CD-1 mice were cultured in Dulbecco's modified Eagle's medium (DMEM) or osteogenic medium (OM) for 23 days. Micro-CT scanning and histological analysis were performed on days 2, 9, 16 and 23. An "OM-control" group was scanned only on days 2 and 23 to evaluate the effect of a single micro-CT radiation dose on calvarial bones. Histomorphometric measurements revealed that the number of osteoblasts per unit bone surface area (N. Ob/BS, /mm2) (days 9, 16 and 23) and the number of osteoclasts per unit bone surface area (N. Oc/BS, /mm2) (days 9 and 16) were higher and lower, respectively, in the OM group than in the DMEM group. Moreover, the calvarial bone survived for at least 16 days in vitro, as indicated by tartrate-resistant acid phosphatase (TRAP)-positive staining. Micro-CT assessment revealed that the bone surface (BS), bone volume (BV), bone surface density (BS/TV(Tissue volume)) and percent bone volume (BV/TV) were greater in the OM group than in the DMEM group except at baseline on day 2. All bone parameters of calvariae cultured in OM and OM-control conditions were not significantly different on days 2 and 23. Thus, the radiation dose from micro-CT in our study design had no perceptible effect on the formation of mouse calvarial bone in vitro.

Titanium clasp fabricated by selective laser melting, CNC milling, and conventional casting: a comparative in vitro study.

PURPOSE: This study aimed to investigate the effects of selective laser melting (SLM), milling methods, and casting on the behavior of titanium clasp. METHODS: The clasp and its die simulating the molar were designed using 3D software. Clasp specimens were fabricated using SLM approaches (SLM Ti) and computerized numerical control (CNC) milling technology (Milling CPTi). Cast clasps of the same forms were also prepared as controls using titanium alloy powder (Cast Ti) and commercial pure titanium (Cast CPTi), following the conventional casting methods. The surface roughness and accuracy of clasps were analyzed. The changes in retentive force and permanent deformation were measured up to 10,000 insertion/removal cycles. One-way analysis of variance and Tukey's test or Kruskal-Wallis H test were performed for data analysis and comparisons. RESULTS: The Milling CPTi clasps had a smoother inner surface than the other groups (p<0.05). The accuracy of the inner surface showed no significant difference among the groups, whereas that of the outer surface showed significant differences (p<0.05). The SLM Ti clasp had significantly higher retentive forces than the other groups (p<0.05), but it rapidly reduced after 2000 insertion/removal cycles until the fracture of all specimens was at 4000 cycles. The Milling CPTi clasps had more permanent deformation, but the rate of reduction of retentive force was only 9.5% (at 10,000 cycles). CONCLUSIONS: Milling has the potential to replace casting for fabricating removable partial denture (RPD) titanium clasps. However, SLM should be further improved for fabricating RPD titanium clasps before clinical application.

Accuracy and reproducibility of 3D digital tooth preparations made by gypsum materials of various colors.

PURPOSE: The study aimed to identify the accuracy and reproducibility of preparations made by gypsum materials of various colors using quantitative and semi-quantitative three-dimensional (3D) approach. MATERIALS AND METHODS: A titanium maxillary first molar preparation was created as reference dataset (REF). Silicone impressions were duplicated from REF and randomized into 6 groups (n=8). Gypsum preparations were formed and grouped according to the color of gypsum materials, and light-scanned to obtain prepared datasets (PRE). Then, in terms of accuracy, PRE were superimposed on REF using the best-fit-algorithm and PRE underwent intragroup pairwise best-fit alignment for assessing reproducibility. Root mean square deviation (RMSD) and degrees of similarity (DS) were computed and analyzed with SPSS 20.0 statistical software (α=.05). RESULTS: In terms of accuracy, PREs in 3D directions were increased in the 6 color groups (from 19.38 to 20.88 µm), of which the marginal and internal variations ranged 51.36 - 58.26 µm and 18.33 - 20.04 µm, respectively. On the other hand, RMSD value and DS-scores did not show significant differences among groups. Regarding reproducibility, both RMSD and DS-scores showed statistically significant differences among groups, while RMSD values of the 6 color groups were less than 5 µm, of which blue color group was the smallest (3.27 ± 0.24 µm) and white color group was the largest (4.24 ± 0.36 µm). These results were consistent with the DS data. CONCLUSION: The 3D volume of the PREs was predisposed towards an increase during digitalization, which was unaffected by gypsum color. Furthermore, the reproducibility of digitalizing scanning differed negligibly among different gypsum colors, especially in comparison to clinically observed discrepancies.

Morphologic Analysis of the Temporomandibular Joint Between Patients With Facial Asymmetry and Asymptomatic Subjects by 2D and 3D Evaluation: A Preliminary Study.

Signs and symptoms of temporomandibular joint (TMJ) dysfunction are commonly found in patients with facial asymmetry. Previous studies on the TMJ position have been limited to 2-dimensional (2D) radiographs, computed tomography (CT), or cone-beam computed tomography (CBCT). The purpose of this study was to compare the differences of TMJ position by using 2D CBCT and 3D model measurement methods. In addition, the differences of TMJ positions between patients with facial asymmetry and asymptomatic subjects were investigated. We prospectively recruited 5 patients (cases, mean age, 24.8 ±â€Š2.9 years) diagnosed with facial asymmetry and 5 asymptomatic subjects (controls, mean age, 26 ±â€Š1.2 years). The TMJ spaces, condylar and ramus angles were assessed by using 2D and 3D methods. The 3D models of mandible, maxilla, and teeth were reconstructed with the 3D image software. The variables in each group were assessed by t-test and the level of significance was 0.05. There was a significant difference in the horizontal condylar angle (HCA), coronal condylar angle (CCA), sagittal ramus angle (SRA), medial joint space (MJS), lateral joint space (LJS), superior joint space (SJS), and anterior joint space (AJS) measured in the 2D CBCT and in the 3D models (P < 0.05). The case group had significantly smaller SJS compared to the controls on both nondeviation side (P = 0.009) and deviation side (P = 0.004). In the case group, the nondeviation SRA was significantly larger than the deviation side (P = 0.009). There was no significant difference in the coronal condylar width (CCW) in either group. In addition, the anterior disc displacement (ADD) was more likely to occur on the deviated side in the case group. In conclusion, the 3D measurement method is more accurate and effective for clinicians to investigate the morphology of TMJ than the 2D method.

[Effect of low-intensity pulsed ultrasound on periodontitis in Beagle dogs].

OBJECTIVE: To investigate the effect of low intensity pulsed ultrasound (LIPUS) on periodontitis in Beagle dogs. METHODS: The animal model of chronic periodontitis was established with elastic ligature-induced alveolar bone defect in Beagle dogs. LIPUS with different intensity (50 mW/cm2, 100 mW/cm2) pulse wave and 50 mW/cm2 continuous wave, 1.5 MHz of frequency, 200 micros of pulse width modulated signal, and 1 kHz of repetition rate were applied to the dogs for 8 weeks (once a day and 20 minutes every time). The periodontal clinical examinations and histological biopsy were performed. RESULTS: With increased exposure to LIPUS, gum tissue swelling of the dogs was reduced. The plaque index (PLI), gingival index (GI), pocket depth (PD) of the treatment groups were lower than the control groups (P < 0.05). No significant gingival recession, attachment loss or furcation was found. The histological examination revealed that there was no obvious gingival hyperplasia in epithelial tissues, but there were significant activities in relation to collagen formation, decrease of bone resorption, and generation of active osteoblasts. CONCLUSION: LIPUS may help repair periodontal tissues and should be considered in guided tissue regeneration (GTR).

[Immortalization of the SD rats' dental follicle cell with simian virus 40 large tumor antigen gene].

OBJECTIVE: To construct SD rat immortalized dental follicle cells (rDFC) induced by simian virus 40 large tumor antigen (SV40Tag) gene to provide a reliable cell source for periodontal tissue engineering research. METHODS: The rDFC was isolated by tissue mass method combined with enzyme digestion method and evaluated by immunohistochemistry. Cell293 were transfected with plasmid pSSR69/pAmpho containing SV40Tag gene by mediating liposome. Normal rDFC were infected with virus-contained supernate and the successfully transfected cell lines were screened with hygromycin, and positive clones were cultured. While non-transfected cells served as negative controls, the cell morphology was observed, the proliferation characteristics was evaluated by calculating cell population. The expression of SV40Tag gene and telomerase in cells was detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting respectively. The biological property of immortalized rDFC was assessed with calculating formation rate of flat cloning, soft agar colony formation test and tumor-forming test. RESULTS: Morphology of immortalized rDFC was not different from that of normal rDFC. The RT-PCR results of SV40Tag revealed amplification band at 357 bp, while no band was seen in the normal cells. The expression of telomerase in immortalized rDFC was higher than that in normal rDFC. The two groups had no significant difference in growth curves, but the immortalized rDFC exhibited stronger proliferative activity. No significant differences of formation rate in flat cloning were observed between the immortalized rDFC [34% (33/96)] and normal rDFC at passage four [22% (21/96)] (χ(2) = 3.71, P > 0.05). No cell cloning was seen in soft agar and the tumor formation was not observed in nude mice. CONCLUSIONS: The rDFC induced by SV40Tag gene could be cultured and passaged in vitro, which retained the stable proliferation and differentiation characteristics and could be used for periodontal tissue engineering research.

[Low intensity pulsed ultrasound combined with guided tissue regeneration for promoting the repair of defect at canines periodontal fenestration in Beagle dogs].

OBJECTIVE: To evaluate the effects of low intensity pulsed ultrasound (LIPUS) combined with guided tissue regeneration (GTR) for the repair of the periodontal fenestration defect at the canines in Beagle dogs. METHODS: Four Beagle dogs were used for establishing the periodontal fenestration defect. Sixteen canines of four Beagle dogs were simple randomly assigned into experimental group 1 [LIPUS (60 mW/cm(2), 20 min/d) irradiation + GTR + the periodontal fenestration defect], experimental group 2 [LIPUS (60 mW/cm(2), 20 min/d) irradiation + the periodontal fenestration defect], experimental group 3 (GTR + the periodontal fenestration defect) and control group (the periodontal fenestration defect). Experiments conducted 28 d. The temperature of the gingive's surface of each group was tested every 14 days (analyzed by Wilcoxon rank sum test with SPSS 13.0). The demineralized bone tissue slices of the periodontal fenestration were obtained for histologic staining after 4 weeks treatment. RESULTS: Clinically all the treatment groups healed well. The change of gingive's surface temperature [M(Q)] before and after LIPUS irradiating were: 0.225 (0.463)°C (experimental group 1), 0.265 (0.133)°C (experimental group 2), 0.090 (0.115)°C (experimental group 3); -0.175 (0.370)°C (control group). The P value of experimental group 1 and 2 with pre-and post-treatment each time were both 0.027. Histology of the demineralized bone tissue revealed that in experimental group 1, the bone defect was filled with fresh bone-like tissues, proliferatively active osteoblasts and newly formed cementum-like tissues along the defect surface. In experimental group 3, there were more new cementum- and bone-like tissues than in experimental group 2 and control group. In experimental group 2, the new bone collagen was more mature than in experimental group 3 and control group. In control group, there was less growth of new cementum along the notch, and the new bone collagen was immature. CONCLUSIONS: LIPUS combined with GTR may have the potential of promoting the repair of periodontal fenestration defect.

[Influence of the peri-implantitis to the microscrew-bone interface].

OBJECTIVE: To study the histological change of microscrew-bone interface, detect the relative cytokine of gingival crevicular fluid, and explore the impossible mechanism of peri-implantitis. METHODS: Four male Beagles were collected. Randomly select one side of animals jaw as the experimental group to induce the peri-implantitis, and another side as the control group. Four microscrews were implanted on each side. In the 1st, 2nd, 3rd, 4th weeks after implantation, collect peri-implant sulcular fluid (PISF) and detect tumor necrosis factor-alpha (TNF-alpha) levels before sacrificed, and the harvest tissue were observed in histological ways. RESULTS: According to the extension of time after implantation, the experimental group showed visible progress of interface destruction: 1st week after implantation showed large numbers inflammatory cells collected at the neck but did not undermine the cortical bone; 2nd week after implantation, cortical bone were observed angular absorption; Bone resorption continued to develop and at the 4th week, bone resorption were enlarged to the second thread of microscrew and the interface was filled with a large number of collagen fibers. CONCLUSION: The destruction of interface began at the neck of microscrew, and the further development was along the interface in depth. Both microscrews with peri-implantitis and the healthy controls showed the presence of TNF-alpha. Inflammation accumulation might trigger the up-regulation of TNF-alpha level, and the onset of inflammation would enhance the up-trend.

[Biomechanical study of "mandible-temporomandibular joint" under different loading angles with forsus].

OBJECTIVE: To identify the best loading angle with Forsus for mandible-temporomandibular joint. METHODS: The changes in stress, displacement and rotation of "mandible-temporomandibular joint" were tested under -30 degrees, -15 degrees, 0 degrees, 15 degrees and 25 degrees of loading angles using a primary three dimensional finite element model. RESULTS: From 0 degrees to 25 degrees, with the increases of loading angles the displacement gradually increased. The maximum displacement occurred at chin, with 1.692 mm, 3.456 mm and 4.630 mm displacement under 0 degrees, 15 degrees and 25 degrees respectively. The maximum displacement occurred at the alveolar ridge under -15 degrees loading, which was 0.069 mm. No special stress concentration region was identified. The displacements from infradentale to pogonion gradually increased under all conditions except for the -15 degrees loading. With the loading angles deviated from the baseline farther, the porrect displacements of chin and the counterclockwise rotation became more obvious. CONCLUSION: The loading angles of Forsus appliance should be controlled between 0 degrees and 25 degrees.

[Repairing effects of low-intensity pulsed ultrasound on alveolar bone defects in Beagle dogs].

OBJECTIVE: To evaluate the potential repairing effects of low-intensity pulsed ultrasound (LIPUS) irradiation on acute horizontal alveolar bone defects at the mandibular pre-molar areas in Beagle dogs. METHODS: Horizontal alveolar bone defect models were established under enamelo-cemental junction 6 mm at the mandibular third and forth pre-molar buccal regions on both sides in 4 beagle dogs, and bilateral sides of each dog were randomly divided into two groups: Experimental groups with LIPUS irradiation (I(SATA) 30 mW X cm(-2), 20 min x d(-1)) and control groups without opening power source of LIPUS radiation. Dual energy X-ray bone densitometer was used to detect the bony density after an 8 weeks' irradiation. Meanwhile, decalcified bone tissue sections were used to assess the histological effects of new alveolar bone. RESULTS: The results of new bony density detection in experimental group and control group were (0.6053 +/- 0.0566) g x cm(-2), (0.6047 +/- 0.0552) g x cm(-2), respectively, and there was no statistical significance between the differences of the two groups (P = 0.9839). Hematoxylin-eosin staining of decalcified bone tissue sections demonstrated that there were more osteoblasts lining at the edge of new alveolar bone in the experimental groups than that scattered in the control groups, and Masson staining revealed that collagens in new alveolar bone stained bright red indicating higher maturity in the experimental groups, while in the control groups mainly stained blue with some virescent areas indicating lower maturity. CONCLUSION: LIPUS irradiation on acute horizontal alveolar bone defects has potential repairing effects.

[Three dimensional finite element analysis of maxillary anterior teeth retraction with micro-implant anchorage and sliding mechanics].

OBJECTIVE: To investigate the biomechanical effects of micro-implant anchorage technique with sliding mechanics on maxillary anterior teeth retraction under different implant insertion heights and different retraction hook heights. METHODS: The three dimensional finite element model of maxillary anterior teeth retraction force system was constructed with CT scanning and MIMICS software and the relationships between brackets, teeth, wire and micro-implant were simulating the clinical factions. Then the initial tooth displacement was calculated when the insertion heights were 4 mm and 8 mm and the retraction hook heights were 1, 4, 7, 10 mm respectively. RESULTS: With retraction hook height added, the anterior teeth movement changed from lingual crown tipping to labial crown tipping and the intrusion movement was more apparent when the micro-implant was inserted in a higher location. CONCLUSION: The ideal teeth movement control could be achieved by different insertion heights of micro-implant and different retraction hook heights in straight wire retraction force system.

[Three-dimensional finite element analysis of stress distribution in mandible advanced with Forsus].

OBJECTIVE: To construct a three-dimensional finite element model of mandible and to analyze the stress distribution in mandible advanced with Forsus. METHODS: One growing patient with mandibular retrusion was selected. After leveling and aligning with MBT (Mclaughlin Bennett Treriri) straight-wire appliance to achieve the request of forsus with the spiral CT, a three-dimensional finite element model was constructed and the stress distribution in mandible after advancing at 1 second, 15 seconds and 300 seconds was analyzed. RESULTS: The three-dimensional finite element model included MBT straight-wire appliance. The stress concentration areas were located in the front side of the condylar process, the sigmoid notch and mandibular molar areas at 15 seconds and 300 seconds after mandibular advancement. The maximum stress values were 34.47 MPa and 34.45 MPa, respectively. With the extension of loading time, the largest displacement increased from 3.30 x 10(-2) mm to 1.15 mm and the region of the largest displacement extended backwards along the body of mandible. However, the displacement of condyle reduced from 1.65 x 10(-2) mm at 1 second to 3.27 x 10(-5) mm at 300 seconds after mandibular advancement. CONCLUSIONS: The three-dimensional finite element model considered the viscoelasticity and viscoelasticity of mandibular. The result suggested that the stress distribution in the mandible gradually became stable after the application of Forsus and the appliance caused downward and forward mandibular modification.

[Distraction osteogenesis in correcting facial asymmetry malformation caused by temporomandibular joint ankylosis: a case report].

A facial asymmetry patient caused by temporomandibular joint ankylosis was operated by putting a distraction osteogenesis (DO)-appliance. One week after surgery, the right mandible was distracted. Twenty days after distraction, the height of right mandibular ramus and body increased obviously. Four months after retain of DO-appliance, the right maxilla down-grew automatically and the occluding relation recovered to normal. The DO-appliance was taken out. MEDPOR prosthesis was imbedded in new bone and genioplasty was operated. The facial asymmetry and abnormal occluding relation of the patient were improved obviously.

[Preliminary study of cranio-maxillofacial hard tissue structure feature of young mandibular retrusion orthognathic patients with delaire cephalometric analysis].

OBJECTIVE: To guide the orthodontic diagnosis, treatment planning and prognosis by analyzing the craniofacial morphology and reimbursement mechanism of young patients with mandibular retrusion in Chongqing territory by Delaire cephalometric analysis. METHODS: Both conventional cephalometric analysis and Delaire cephalometric analysis were conducted on the basis of the lateral cephalograms from 56 young mandibular retrusion patients and 40 teenagers with normal occlusion. RESULTS: Decreases in angle SNB, Co-Go, Co-Pog, U1-L1 and increases in angle ANB, angle SN-MP, L1-MP were seen in mandibular retrusion group by conventional cephalometric analysis. Decreases in angle 1, angle 5, (Cp-Oi)/C2 and increases in angle 2, (M-Cp)/C2, angle 3, angle 4 were seen in mandibular retrusion group by Delaire cephalometric analysis. Me-F1 and Me-Met were -8.70 mm +/- 2.48 mm and 5.74 mm +/- 2.58 mm respectively. CONCLUSION: Delaire cephalometric analysis could evaluate cranio-maxillofacial architectural features of mandibular retrusion patients more visually and quantitatively, which suggests that mandibular retrusion is usually caused by the retrusion of mandibular position and the hypodevelopment of mandibule.

[Study of computer-assisted Delaire cephalometric analysis system].

OBJECTIVE: The purpose of this study was to establish the computer -assisted Delaire cephalometric analysis system with WinCeph8.0 in order to simplify the procedure of manual Delaire cephalometric analysis. METHODS: On the basis of the theory of Delaire cephalometric analysis and the program module of WinCeph8.0, the landmark points and the auxiliary line were defined, the measurement and analysis program were written, then the computer-assisted Delaire cephalometric analysis system was established. Paired t-test and dispersion analysis of the computer-assisted and manual measurements were taken. RESULTS: Computer-assisted Delaire cephalometric analysis system was convenient and accurate to trace the landmark points and the auxiliary line. It was able to proceed the measurement and calculation automatically and display the analysis results. Statistical analysis showed that computer-assisted analysis was more accurate than manual analysis. CONCLUSION: This study provided a convenient, simplified, accurate computer-assisted analysis platform for Delaire cephalometric analysis which facilitated its clinical application.

[Construction of the three-dimensional finite element model of micro -implant -maxilla].

OBJECTIVE: To explore a new method to construct the three-dimensional finite element model of micro-implant-maxilla using Materialise's interactive medical image control system (Mimics). METHODS: The maxilla with all teeth was scanned with Spiral CT and the images were transferred into the Mimics 9.0 software to obtain the three-dimensional images. The Abaqus 6.5 software was used to mesh the three-dimensional model and to establish the finite element model. RESULTS: A detachable three-dimensional finite element model of micro-implant-maxilla based on Mimics was constructed rapidly, which can be flexibly re-assembled. CONCLUSION: The method of constructing the three-dimensional finite element model of micro-implant-maxilla is available and effective. The geometrical analogy of the model was greatly improved by using the Mimics system.

[Researches on biomechanics of micro-implant-bone interface and optimum design of micro implant's neck].

OBJECTIVE: To compare and analyze the stress distribution at the micro-implant-bone interface based on the different micro-implant-bone conditioned under orthodontic load, and to optimize the design of micro implant's neck. METHODS: An adult skull with all tooth was scanned by spiral CT, and the data were imported into computer for three-dimensional reconstruction with software Mimics 9.0. The three dimensional finite element models of three micro-implant-bone interfaces(initial stability, full osseointegration and fibrous integration) were analyzed by finite element analysis software ABAQUS6.5. The primary stress distributions of different micro-implant-bone conditions were evaluated when 2N force was loaded. Then the diameter less than 1.5 mm of the micro implant's neck was added with 0.2 mm, to compare the stress distribution of the modified micro-implant-bone interface with traditional type. RESULTS: The stress mostly concentrated on the neck of micro implant and the full osseointegration interface in all models showed the lowest strain level. Compared with the traditional type, the increasing diameter neck of the micro implant obviously decreased the stress level in all the three conditions. CONCLUSION: The micro-implant-bone interface and the diameter of micro implant's neck both are the important influence factors to the stress distribution of micro implant.

[Time varied stress effects on the shape-alteration of myoblast in rats].

OBJECTIVE: To investigate the effects of time varied stress on the shape-alteration of myoblast in rats and to provide a theoretic base to determine the mechanics of myoblast in orthodontic therapy. METHODS: Based on the pulsatile mechanical system our group founded, this study loaded different strain (2.5 kPa, 5.0 kPa and 10.0 kPa) to the myoblast of lateral pterygoid muscle. The alterations in shape under time varied stress of 6 h and 12 h were assessed by phase-contrast microscopy, scanning electron microscope. RESULTS: The orientation of myoblast seemed no obvious orderliness before loading. But after loading the lower time varied strain (2.5 kPa, 5.0 kPa), they were changed their orientation to paralel with the direction of strain along with the membrane. Meanwhile, there had one trend to set the shape of myoblast more upright along with the membrane after loading the higher time varied stress (10.0 kPa). CONCLUSION: It was proved that the different time varied stress in vitro expressed the different influence on the remolding of myoblast.