Objective·To fabricate a 3D-printed dental crown and bridge resin slurry using digital light processing(DLP)technology,investigate the influence of different printing parameters on its mechanical properties,determine the optimal printing parameters,and optimize the composition ratio of DLP-printed crown and bridge resin.Methods·Based on the viscosity characteristics of the mixture,the optimal ratio of urethane dimethacrylate(UDMA)to poly(propylene glycol)dimethacrylate(PPGDMA)was explored.After silanizing silicon dioxide(SiO2),it was mixed with UDMA,PPGDMA,and 2,4,6-trimethylbenzoyl bis(p-tolyl)phosphine oxide(TMO)to prepare DLP-printed dental crown and bridge resin slurries with different solid contents,and their rheological properties were tested.The Beer-Lambert equation was used to calculate the light penetration depth and critical exposure energy of the printing slurry.Based on these values,different exposure intensities,exposure times,post-curing times,and layer thicknesses were set respectively to carry out a series of printing experiments.By comparing and analyzing the flexural strength of the products under different printing parameters,the optimal printing parameter combination was screened out.Results·Viscosity tests showed that the optimal UDMA-to-PPGDMA ratio was 6∶4.The rheological behavior of printing slurries with different solid contents was tested,and the results showed that the DLP-printed dental crown and bridge resin with a solid content of 22%exhibited the best printing performance.According to the Beer-Lambert analysis,the light penetration depth Dp of the printing slurry was 119.79 μm,and the critical exposure energy Ec was 25.54 mJ/cm2.When the exposure intensity was 20 mW/cm2,the flexural strength reached a maximum of(132.39±8.92)MPa,and the difference was statistically significant(P<0.05).The flexural results of different exposure times showed that the flexural strength could reach(131.73±9.43)MPa when the single-layer exposure time was 3.0 s,and there was no significant difference when the exposure time was further increased.The flexural results of different post-curing times showed that when the post-curing time reached 30 min,there was no significant relationship between the flexural strength value and the increase in post-curing time.Regarding the influence of different layer thicknesses on the flexural performance,the test results showed that when the layer thickness was 50 μm,the result was the best,and the difference was statistically significant(P<0.001).Conclusion·Based on viscosity and rheological tests,a DLP-printable crown and bridge resin slurry was successfully developed.The optimal printing parameters were determined through statistical analysis of flexural strength:exposure intensity of 20 mW/cm2,exposure time of 3.0 s,post-curing time of 30 min,and a layer thickness of 50 μm.

Objective·To fabricate a 3D-printed dental crown and bridge resin slurry using digital light processing(DLP)technology,investigate the influence of different printing parameters on its mechanical properties,determine the optimal printing parameters,and optimize the composition ratio of DLP-printed crown and bridge resin.Methods·Based on the viscosity characteristics of the mixture,the optimal ratio of urethane dimethacrylate(UDMA)to poly(propylene glycol)dimethacrylate(PPGDMA)was explored.After silanizing silicon dioxide(SiO2),it was mixed with UDMA,PPGDMA,and 2,4,6-trimethylbenzoyl bis(p-tolyl)phosphine oxide(TMO)to prepare DLP-printed dental crown and bridge resin slurries with different solid contents,and their rheological properties were tested.The Beer-Lambert equation was used to calculate the light penetration depth and critical exposure energy of the printing slurry.Based on these values,different exposure intensities,exposure times,post-curing times,and layer thicknesses were set respectively to carry out a series of printing experiments.By comparing and analyzing the flexural strength of the products under different printing parameters,the optimal printing parameter combination was screened out.Results·Viscosity tests showed that the optimal UDMA-to-PPGDMA ratio was 6∶4.The rheological behavior of printing slurries with different solid contents was tested,and the results showed that the DLP-printed dental crown and bridge resin with a solid content of 22%exhibited the best printing performance.According to the Beer-Lambert analysis,the light penetration depth Dp of the printing slurry was 119.79 μm,and the critical exposure energy Ec was 25.54 mJ/cm2.When the exposure intensity was 20 mW/cm2,the flexural strength reached a maximum of(132.39±8.92)MPa,and the difference was statistically significant(P<0.05).The flexural results of different exposure times showed that the flexural strength could reach(131.73±9.43)MPa when the single-layer exposure time was 3.0 s,and there was no significant difference when the exposure time was further increased.The flexural results of different post-curing times showed that when the post-curing time reached 30 min,there was no significant relationship between the flexural strength value and the increase in post-curing time.Regarding the influence of different layer thicknesses on the flexural performance,the test results showed that when the layer thickness was 50 μm,the result was the best,and the difference was statistically significant(P<0.001).Conclusion·Based on viscosity and rheological tests,a DLP-printable crown and bridge resin slurry was successfully developed.The optimal printing parameters were determined through statistical analysis of flexural strength:exposure intensity of 20 mW/cm2,exposure time of 3.0 s,post-curing time of 30 min,and a layer thickness of 50 μm.

Objective To explore the risk factors of frozen shoulder,and to provide the basis for the prevention of frozen shoulder.Methods A total of 114 patients with frozen shoulder who were hospitalized in the First Affiliated Hospital of Zhejiang Chinese Medical University from January 2020 to August 2022 were included in case group,and 114 physical examination patients with no history of frozen shoulder were included in control group.The clinical data of two groups were collected and the risk factors of frozen shoulder were analyzed by multivariate Logistic regression.Results There were statistically significant differences in cervical radiculopathy,type 2 diabetes mellitus,hepatitis,chronic non-atrophic gastritis,lumbar disc herniation,osteoporosis and thyroid sarcoidosis between two groups(P<0.05).Multivariate Logistic analysis showed that cervical radiculopathy(OR=6.114,95%CI:1.458-25.642)and type 2 diabetes mellitus(OR=24.069,95%CI:4.023-144.007)were independent risk factors for the onset of frozen shoulder.Conclusion Patients with type 2 diabetes mellitus and cervical radiculopathy have a higher risk of frozen shoulder,and should pay attention to early prevention.