BACKGROUND:The threaded conical implant has a good ability to control micro movements and is conducive to immediate loading.However,the effects of double-threaded conical cylindrical implants and conical cylindrical implants on stress distribution and initial stability of implant-bone interface after immediate loading have not been reported. OBJECTIVE:To investigate the impact of double-threaded conical cylindrical implants and conical cylindrical implants on the biological distribution of the implant and the surrounding bone interface during immediate loading in the mandibular molar region. METHODS:(1)Three-dimensional finite element analysis:Conical beam CT scans of the mandible and first molar of a volunteer were used to develop a basal model of the mandible.The double-threaded conical cylindrical implants and conical cylindrical implants were assembled with the mandibular models,and an immediate-load(or delayed implantation)implant model(a total of four models)for the first mandibular molar was established.Loads in four directions(100 N):axial,lingual and buccal 45°,mesial and distal,and buccal and lingual,were applied to the central fossa of each model's crown.Three-dimensional finite element method was used to analyze the implant displacement and the stress distribution at the implant-bone interface.(2)In vitro experiment:With the assistance of the oral implant robot,the double-threaded conical cylindrical implants and conical cylindrical implants were implanted on the same artificial bone pieces,separately,and the immediate load model of immediate implant implantation(or delayed implantation)was established in vitro(a total of four groups of models).Osstell resonance frequency analyzer and SmartPeg sensor were used to measure the implant stability coefficient in four vertical directions:front,rear,left,and right measurements,evaluate the initial stability,and verify the finite element analysis results. RESULTS AND CONCLUSION:(1)The displacement difference between double-threaded conical cylindrical implants and conical cylindrical implants was small when the immediate loading of delayed implantation was applied,but the maximum stress value of conical cylindrical implant-bone interface was greater than that of double-threaded conical cylindrical implant-bone interface.When the immediate loading of immediate implantation was applied,the maximum stress value and the maximum displacement of bone around the implant appeared when the load was applied in mesiodistal direction.The stress value of the conical cylindrical implant reached 298.84 MPa and the maximum displacement was 0.31 mm,both of which were larger than that of the double-threaded conical cylindrical implant.(2)The results of in vitro experiments showed that the stability coefficient of the double-threaded conical cylindrical implant was greater than that of the conical cylindrical implant.(3)Compared with the conical cylindrical implant,the double-threaded conical cylindrical implant has higher initial stability under immediate loading,suggesting that the use of double-threaded conical cylindrical implant should be given priority in clinical immediate loading.

BACKGROUND:Temporomandibular joint osteoarthritis is a common oral disease with a high incidence.However,temporomandibular joint osteoarthritis is not easy to be detected in the early stage,and it is difficult to obtain clinical pathological specimens,so it is difficult to carry out related research.The application of digital 3D printing technology to animal models of Temporomandibular joint osteoarthritis increases the consistency of the animal models,thus promoting the study of temporomandibular joint osteoarthritis. OBJECTIVE:To establish a standardized animal model of temporomandibular joint osteoarthritis using novel digital technology. METHODS:According to the different modeling methods of unilateral anterior crossbite,30 female Sprague-Dawley rats were randomly divided into traditional model group,digital model group,and control group(n=10 per group).Cartilage specimens of the condyles were collected at 4 and 8 weeks after modeling.The apparent morphology was observed by stereoscopic microscope.The pathological morphology was observed by hematoxylin-eosin staining and Safranin O/fast green staining.Changes in the expression of interleukin-1β and tumor necrosis factor-α were observed by ELISA,and changes in the expression of aggrecan,type Ⅱ collagen and matrix metalloproteinase-13 were observed by immunohistochemical staining. RESULTS AND CONCLUSION:Different degrees of degeneration were observed in the digital and traditional model groups.The body mass of rats in both the model groups decreased during the 1st week after intervention and subsequently demonstrated growth trend and were significantly lower than that in the control group.The results of stereoscopic microscope showed that at 4 and 8 weeks after modeling,the deformation and defect degree of the digital model group was significantly higher than that of the traditional model group.At these two time points,the Osteoarthritis Research Society International scores of the digital model group and the traditional model group were higher than those of the control group,and the Osteoarthritis Research Society International score of the digital model group was higher than that of the traditional model group(P＜0.05).Histopathological observation showed that the modified Mankin score and Osteoarthritis Research Society International score of the two model groups were significantly higher than those of the control group of the same age at 4 and 8 weeks after modeling(P＜0.05).Immunohistochemical staining results showed that at two time points,compared with the control group of the same age,the expression of aggrecan and type Ⅱ collagen decreased in the traditional model group and the digital model group,while the expression of matrix metalloproteinase 13 increased(P＜0.05).ELISA results showed that the expression levels of inflammatory factors interleukin-1β and tumor necrosis factor-α in the traditional and digital model groups were higher than those in the control group at 8 weeks,and the expression levels of interleukin-1β and tumor necrosis factor-α in the digital model group were higher than those in the traditional model group(P＜0.05).To conclude,the personalized metal tube designed and produced by 3D printing technology can quickly guide the osteoarthritis-like lesions of the temporomandibular joint without repeated trial and adjustment,which is reproducible and suitable for promotion and application.

Objective Summarizes the current research status of defensive medicine in China and provides references for future research.Methods The search period spans from the inception of the database to March 2024.CNKI,Wan-fang Data,Web of Science,PubMed databases were queried,followed by literature screening based on predeter-mined inclusion and exclusion criteria.The current landscape of defensive medicine research in China was synthe-sized and categorized based on fundamental research characteristics,measurement methodologies,influencing fac-tors,and other relevant aspects.Results A total of 24 Chinese literature sources and 4 foreign literature sources were incorporated,indicating a prevalent occurrence of defensive medicine in China.Measurement tools for defen-sive medicine exhibit variability across different studies.Key influencing factors encompass doctor's demographic vari-ables such as gender,age,and professional status,institutional factors like legal frameworks and medical in-surance,and sociol-cultural factors such as doctor-patient relationships and adverse public perceptions.Conclusion Defensive medicine is relatively widespread and influenced by various factors in China.It's urgent to explore the for-mation mechanism of defensive medicine from multiple perspectives and provide evidence for passive defen-sive medicine governance.

Objective To clarify the influencing factors of defensive medicine and provide ideas for preventing and re-solving defensive medicine.Methods Literature related to defensive medicine was searched,personnel related to de-fensive medicine were interviewed,and literature and interview data were coded with the method of grounded theo-ry,and related concepts and categories were summarized.Results After three levels of coding,52 initial concepts,23 initial categories,7 sub-categories and 3 main categories were sorted out,and the correlation among influencing factors was analyzed to build a three-dimensional model of"doctor-patient relationship-institutional system-social environment"influencing factors and their mechanism of action.Conclusion The influencing factors of defensive medi-cine mainly include doctor-patient relationship,institutional system and social environment.The three factors have an impact on defensive medicine through different mechanisms of action,which provides qualitative evidence for comprehensive analysis of factors in related studies of defensive medicine.

Objective To understand the status of behavioral intentions of defensive medical treatment in medical students,and explore the relationship between practice environment and behavioral intentions of defensive medical treatment.To provide reference for reducing the tendency of defensive medicine(DM)behavior of medical students and improving the negative effects of DM.Methods A web-based questionnaire survey was conducted among medi-cal students in four medical colleges in Heilongjiang Province.The structural equation modeling of the relationship be-tween practice environment and behavioral intentions of defensive medical treatment in medical students was con-structed by Amos 26.0 software.Results The mean score of medical students'behavioral intentions of positive and negarive defensive medical treatment was 44.49-6.90 and 20.06-6.83,respectively.The behavioral intention of posi-tively defensive medical treatment was positively associated(β=0.892,P＜0.05)with cognition of doctor-patient relationship.While the behavioral intention of negative defensive medical treatment was positively correlated(β=0.403,0.343,P＜0.05)with environment cognition,perception of risk and negatively correlated(β=-0.726,P＜0.05)with cognition of doctor-patient relationship.As an intermediary variable,the direct and indirect effects of cog-nition of doctor-patient relationship on negative defensive medical behavior tendency were-0.470 and 0.043,the difference was statistically significant(P＜0.05).Conclusion Improving cognition of medical students'doctor-pa-tient relationship is beneficial to understand defensive medical treatment for medical students.The negative defen-sive medical behavior tendency of medical students should be reduced by reducing their negative cognition of environ-ment or improving their cognition of doctor-patient relationship.

Objective:To explore the operational accuracy and operative time of oral surgery robot-assisted endodontic microsurgery on a head-simulator for clinical reference.Methods:Three pairs of surgical simulation models were set up on head-simulator. Each model included 10 positions anteriorly and posteriorly, 20 teeth for each technique, for a total of 60 teeth. An attending physician with more than 3 years clinical experience in endodontic microsurgery completed fixed-point osteotomy and apicoectomy in three groups of endodontic microsurgery under freehand (FH), static navigation (SN), and surgery robot (SR). The duration of each operation was recorded. Cone-beam CT was taken before the operation and the surgical path was planned in the software; after surgery, a plug gauge (precision gauge for measuring hole dimensions) was inserted into the surgical path for intraoral scanning. Surgical accuracy (starting point, end point, and angular deviation) was assessed in all 3 groups, and surgery time was compared.Results:The deviation at the starting point and the end point, and angular deviation was (0.37±0.11), (0.37±0.10) mm, and 0.71°±0.17°in the SR group. The deviations in the SR group were significantly lower than those in the SN group [(0.59±0.14), (0.65±0.18) mm, and 2.64°±0.75°] ( P<0.05), and both groups were significantly lower than the FH group [(1.37±0.31), (1.10±0.21) mm, and 9.84°±3.15°] ( P<0.05). The operative time in the SN group [(1.20±0.03) min] was significantly less than that in the SR group [(2.18±0.03) min] ( P<0.05), and both groups were significantly less than that in the FH group [(8.70±3.15) min] ( P<0.05). Starting point deviation, end point deviation, and angular deviation [(1.09±0.10), (0.90±0.07) mm, 7.22°±1.13°] in anterior teeth using the FH was significantly lower than the starting deviation, endpoint deviation, and angular deviation [(1.65±0.14), (1.30±0.06) mm, 12.46°±2.10°] in the posterior teeth using FH ( P<0.05), and the operative time in the anterior teeth using the FH [(5.75±0.57) min] was significantly less than that in the posterior teeth using [(11.65±1.14) min] ( P<0.05). The difference in accuracy and operative time between using SN and SR on anterior and posterior teeth was not statistically significant ( P>0.05). Conclusions:Oral surgery robot-assisted endodontic microsurgery helps improving the accuracy of clinicians′ operations and shorten the operation time.

Objective:To evaluate direct and indirect costs for schizophrenia,major depressive disorder(MDD)and bipolar disorder,and to compare their differences of cost composition,and to explore the drivers of the total costs.Methods:A total of 3 175 inpatients with schizophrenia,MDD,and bipolar disorder were recruited.In-patient's self-report total direct of medical costs outpatient and inpatient,out-of-pocket costs,and direct non-medical costs were regarded as direct costs.Productivity loss and other loss caused by damaging properties were defined as indirect costs.The perspectives of this study included individual and societal levels.Multivariate regression analysis was applied for detecting the factors influencing disease costs.Results:The total cost of schizophrenia was higher than those of MDD and bipolar disorder at individual and societal levels.The indirect costs of three mental disorders were higher than the direct costs,and the indirect cost ratio of bipolar disorder was higher than those of schizophre-nia and MDD.Age,gender,working condition and marital status(P＜0.05)were the important drivers of total costs.Conclusion:The economic burden of the three mental disorders is relatively heavy.Schizophrenia has heaviest disease burden,and the productivity loss due to mental disorders is the driving force of the soaring disease cost

Objective Summarizes the current research status of defensive medicine in China and provides references for future research.Methods The search period spans from the inception of the database to March 2024.CNKI,Wan-fang Data,Web of Science,PubMed databases were queried,followed by literature screening based on predeter-mined inclusion and exclusion criteria.The current landscape of defensive medicine research in China was synthe-sized and categorized based on fundamental research characteristics,measurement methodologies,influencing fac-tors,and other relevant aspects.Results A total of 24 Chinese literature sources and 4 foreign literature sources were incorporated,indicating a prevalent occurrence of defensive medicine in China.Measurement tools for defen-sive medicine exhibit variability across different studies.Key influencing factors encompass doctor's demographic vari-ables such as gender,age,and professional status,institutional factors like legal frameworks and medical in-surance,and sociol-cultural factors such as doctor-patient relationships and adverse public perceptions.Conclusion Defensive medicine is relatively widespread and influenced by various factors in China.It's urgent to explore the for-mation mechanism of defensive medicine from multiple perspectives and provide evidence for passive defen-sive medicine governance.

Objective To clarify the influencing factors of defensive medicine and provide ideas for preventing and re-solving defensive medicine.Methods Literature related to defensive medicine was searched,personnel related to de-fensive medicine were interviewed,and literature and interview data were coded with the method of grounded theo-ry,and related concepts and categories were summarized.Results After three levels of coding,52 initial concepts,23 initial categories,7 sub-categories and 3 main categories were sorted out,and the correlation among influencing factors was analyzed to build a three-dimensional model of"doctor-patient relationship-institutional system-social environment"influencing factors and their mechanism of action.Conclusion The influencing factors of defensive medi-cine mainly include doctor-patient relationship,institutional system and social environment.The three factors have an impact on defensive medicine through different mechanisms of action,which provides qualitative evidence for comprehensive analysis of factors in related studies of defensive medicine.

Objective To understand the status of behavioral intentions of defensive medical treatment in medical students,and explore the relationship between practice environment and behavioral intentions of defensive medical treatment.To provide reference for reducing the tendency of defensive medicine(DM)behavior of medical students and improving the negative effects of DM.Methods A web-based questionnaire survey was conducted among medi-cal students in four medical colleges in Heilongjiang Province.The structural equation modeling of the relationship be-tween practice environment and behavioral intentions of defensive medical treatment in medical students was con-structed by Amos 26.0 software.Results The mean score of medical students'behavioral intentions of positive and negarive defensive medical treatment was 44.49-6.90 and 20.06-6.83,respectively.The behavioral intention of posi-tively defensive medical treatment was positively associated(β=0.892,P＜0.05)with cognition of doctor-patient relationship.While the behavioral intention of negative defensive medical treatment was positively correlated(β=0.403,0.343,P＜0.05)with environment cognition,perception of risk and negatively correlated(β=-0.726,P＜0.05)with cognition of doctor-patient relationship.As an intermediary variable,the direct and indirect effects of cog-nition of doctor-patient relationship on negative defensive medical behavior tendency were-0.470 and 0.043,the difference was statistically significant(P＜0.05).Conclusion Improving cognition of medical students'doctor-pa-tient relationship is beneficial to understand defensive medical treatment for medical students.The negative defen-sive medical behavior tendency of medical students should be reduced by reducing their negative cognition of environ-ment or improving their cognition of doctor-patient relationship.