Introduction: Misconceptions are associated with the teething process in Nigeria and is often blamed for symptoms in infants. A horrendous incident occurred in Nigeria in 2008 which recorded 84 infant deaths due to co...Introduction: Misconceptions are associated with the teething process in Nigeria and is often blamed for symptoms in infants. A horrendous incident occurred in Nigeria in 2008 which recorded 84 infant deaths due to consumption of adulterated teething syrup to prevent teething problems. In the quest to engage the populace, particularly mothers, in health education to change this erroneous mindset about teething, it will be necessary and more cost effective to involve Traditional Birth Attendants (TBA’s) who can be invaluable in assisting to dispel myths associated teething as they live and work among the local populace and many times give counsel to mothers. Aim: To assess the attitude and beliefs of TBA’s in Ibadan, to teething in infants. Methods: A cross sectional survey was conducted among TBA’s in Ibadan, Nigeria. A thirteen item interviewer administered questionnaire was distributed to all 163 TBA’s in the five urban local government areas who agreed to be part of the study. Results: Over half of the respondents (59.5%) and (55.8%) associated the teething process with fever and diarrhea respectively. Other beliefs included boils (49.1%), loss of appetite (48.5%), weight loss (44.2%), and sleeplessness (42.3%). A greater proportion of the older and less educated TBA’s associated teething with fever, diarrhea, boils, loss of appetite and weight loss. The respondents would advise analgesics (55.8%), teething powder (67.5%), antibiotics (12.3%), concoctions (4.3%) and sedatives (4.3%) as teething remedies. There was a greater tendency for less educated TBA’s to advise the use of concoctions?and antibiotics. Conclusion: The study reveals grave misconceptions among TBA’s who in developing countries like Nigeria give counsel to mothers in the various communities. There is an urgent need for health education to the TBA’s particularly the older and less educated ones.展开更多
“Last scene of all that ends this strange,eventful history,is second childishness and mere oblivion.I am sans teeth,sans eyes,sans taste,sans everything.”William Shakespeare‘As You Like It'Act 2,Sc.7,l.139Aging...“Last scene of all that ends this strange,eventful history,is second childishness and mere oblivion.I am sans teeth,sans eyes,sans taste,sans everything.”William Shakespeare‘As You Like It'Act 2,Sc.7,l.139Aging of the human brain is characterized by a progressive decline of its functional capacity;this decline however varies widely,and cognitive longevity differs substantially between individuals.展开更多
Intentional tooth replantation(ITR)is an advanced treatment modality and the procedure of last resort for preserving teeth with inaccessible endodontic or resorptive lesions.ITR is defined as the deliberate extraction...Intentional tooth replantation(ITR)is an advanced treatment modality and the procedure of last resort for preserving teeth with inaccessible endodontic or resorptive lesions.ITR is defined as the deliberate extraction of a tooth;evaluation of the root surface,endodontic manipulation,and repair;and placement of the tooth back into its original socket.Case reports,case series,cohort studies,and randomized controlled trials have demonstrated the efficacy of ITR in the retention of natural teeth that are untreatable or difficult to manage with root canal treatment or endodontic microsurgery.However,variations in clinical protocols for ITR exist due to the empirical nature of the original protocols and rapid advancements in the field of oral biology and dental materials.This heterogeneity in protocols may cause confusion among dental practitioners;therefore,guidelines and considerations for ITR should be explicated.This expert consensus discusses the biological foundation of ITR,the available clinical protocols and current status of ITR in treating teeth with refractory apical periodontitis or anatomical aberration,and the main complications of this treatment,aiming to refine the clinical management of ITR in accordance with the progress of basic research and clinical studies;the findings suggest that ITR may become a more consistent evidence-based option in dental treatment.展开更多
Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs,but the interaction mechanism among impact loads,drilling teeth and rock has not been sufficiently investigated.F...Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs,but the interaction mechanism among impact loads,drilling teeth and rock has not been sufficiently investigated.For this reason,shales with different bedding angles are used to carry out impact compression and tensile experiments as well as the rock-breaking experiments by single axe-shaped tooth,the variation of dynamic strengths,rock failure characteristics,fractal dimensions,and tensile/compression ratios under different load-bedding angles(α)are investigated.Then,the three-dimensional scanning device is used to measure the penetration depth and rock-breaking volume under different load-bedding angles.The results show that with the increase of load-bedding angle(0°-90°),the compressive strength decreases and then increases,with the lowest strength atα=45°and the highest strength atα=0°;the tensile strength decreases and then increases,with the lowest strength nearα=30°and the highest strength atα=90°.With the growing impact rate,the effect of load-bedding angle on dynamic compressive strength decreases,and the effect on dynamic tensile strength becomes more significant.When the impact velocity is high(≥8.0 m/s),the tensile-compressive ratio first decreases and then increases,and both reach a minimum at a load-bedding angle of 30°and a maximum at 60°.With the increasing of the load-bedding angle,the depth of tooth penetration increases and then decreases,and the highest depth of tooth penetration and the highest energy absorption efficiency are achieved atα=45°;the width of the impact pit increases and then decreases,and the maximum width value is achieved atα=30°,with the smallest value of the specific work value of the rock-breaking.The results have significant reference value for improving the rock-breaking efficiency of percussion drilling in deep anisotropic formations.展开更多
The instance segmentation of impacted teeth in the oral panoramic X-ray images is hotly researched.However,due to the complex structure,low contrast,and complex background of teeth in panoramic X-ray images,the task o...The instance segmentation of impacted teeth in the oral panoramic X-ray images is hotly researched.However,due to the complex structure,low contrast,and complex background of teeth in panoramic X-ray images,the task of instance segmentation is technically tricky.In this study,the contrast between impacted Teeth and periodontal tissues such as gingiva,periodontalmembrane,and alveolar bone is low,resulting in fuzzy boundaries of impacted teeth.Amodel based on Teeth YOLACT is proposed to provide amore efficient and accurate solution for the segmentation of impacted teeth in oral panoramic X-ray films.Firstly,a Multi-scale Res-Transformer Module(MRTM)is designed.In the module,depthwise separable convolutions with different receptive fields are used to enhance the sensitivity of the model to lesion size.Additionally,the Vision Transformer is integrated to improve the model’s ability to perceive global features.Secondly,the Context Interaction-awareness Module(CIaM)is designed to fuse deep and shallow features.The deep semantic features guide the shallow spatial features.Then,the shallow spatial features are embedded into the deep semantic features,and the cross-weighted attention mechanism is used to aggregate the deep and shallow features efficiently,and richer context information is obtained.Thirdly,the Edge-preserving perceptionModule(E2PM)is designed to enhance the teeth edge features.The first-order differential operator is used to get the tooth edge weight,and the perception ability of tooth edge features is improved.The shallow spatial feature is fused by linear mapping,weight concatenation,and matrix multiplication operations to preserve the tooth edge information.Finally,comparison experiments and ablation experiments are conducted on the oral panoramic X-ray image datasets.The results show that the APdet,APseg,ARdet,ARseg,mAPdet,and mAPseg indicators of the proposed model are 89.9%,91.9%,77.4%,77.6%,72.8%,and 73.5%,respectively.This study further verifies the application potential of the method combining multi-scale feature extraction,multi-scale feature fusion,and edge perception enhancement in medical image segmentation,which provides a valuable reference for future related research.展开更多
Objective:To explore the clinical effect of improved incision in the extraction of impacted mandibular wisdom teeth.Methods:160 patients who were treated in our hospital from October,2024 to April,2025 and had their m...Objective:To explore the clinical effect of improved incision in the extraction of impacted mandibular wisdom teeth.Methods:160 patients who were treated in our hospital from October,2024 to April,2025 and had their mandibular impacted wisdom teeth removed according to the doctor’s advice were randomly divided into observation group and control group.The observation group used modified incision,while the control group used traditional triangular incision.The operation time,intraoperative visual analogue scale(VAS)pain score,pain VAS score on the 1st,2nd and 3rd day after operation,facial swelling on the 2nd day after operation,mouth opening limitation on the 2nd day after operation and the incidence of dry socket after operation were recorded and compared between the two groups.Results:There was no significant difference in operation time between the two groups(p>0.05).The VAS score of pain in the observation group was significantly lower than that in the control group at each time point during and after operation(p<0.05).On the second day after operation,the facial swelling and mouth opening limitation in the observation group were significantly lighter than those in the control group(p<0.05).The incidence of dry socket in the observation group was 1.25%(1/80),which was significantly lower than that in the control group(8.75%,7/80),and the difference was statistically significant(p<0.05).Conclusion:The application of modified triangular incision in the extraction of impacted mandibular wisdom teeth can effectively relieve the pain during and after operation,reduce postoperative facial swelling and mouth opening limitation,and reduce the incidence of dry socket.展开更多
Tooth cracks may occur in spiral bevel gear transmission system of the aerospace equipment.In this study,an accurate and efficient loaded tooth contact analysis(LTCA)model is developed to predict the contact behavior ...Tooth cracks may occur in spiral bevel gear transmission system of the aerospace equipment.In this study,an accurate and efficient loaded tooth contact analysis(LTCA)model is developed to predict the contact behavior and time-varying meshing stiffness(TVMS)of spiral bevel gear pair with cracked tooth.The tooth is sliced,and the contact points on slices are computed using roll angle surfaces.Considering the geometric complexity of crack surface,a set of procedures is formulated to generate spatial crack and determine crack parameters for contact points.According to the positional relationship between contact point and crack path,each sliced tooth is modeled as a non-uniform cantilever beam with varying reduced effective load-bearing tooth thickness.Then the compliance model of the cracked tooth is established to perform contact analysis,along with TVMS calculations utilizing three different models.By employing spiral bevel gear pairs with distinct types of cracks as examples,the accuracy and efficiency of the developed approach are validated via comparative analyses with finite element analysis(FEA)outcomes.Furthermore,the investigation on effects of cracks shows that tooth cracks can induce alterations in meshing performance of both entire gear pair and individual tooth pairs,including not only cracked tooth pair but also adjacent non-cracked tooth pairs.Hence,the proposed model can serve as a useful tool for analyzing the variations in contact behavior and meshing stiffness of spiral bevel gears due to different cracks.展开更多
The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,co...The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,combining soft material with fractal,a composite pre-tightened multi-hierarchy tooth joint is proposed,and the bearing performance and failure process of the joint through experiments and finite element method under tensile load.First,the ultimate bearing capacity,load distribution ratio,and failure process of different hierarchies of teeth joints are studied through experiments.Then,the progressive damage models of different hierarchies of tooth joints are established,and experiments verify the validity of the finite element model.Finally,the effects of soft material and increasing tooth hierarchy on the failure process and bearing capacity of composite pre-tightened tooth joints are analyzed by the finite element method.The following conclusions can be drawn:(1)The embedding of soft materials changed the failure process of the joint.Increasing the tooth hierarchy can give the joint more load transfer paths,but the failure process of the joint is complicated.(2)Embedding soft materials and increasing the tooth hierarchy simultaneously can effectively improve the bearing capacity of composite pre-tightened tooth joints,which is 87.8%higher than that of traditional three-tooth joints.展开更多
This paper deeply discusses the causes of gear howling noise,the identification and analysis of multi-source excitation,the transmission path of dynamic noise,simulation and experimental research,case analysis,optimiz...This paper deeply discusses the causes of gear howling noise,the identification and analysis of multi-source excitation,the transmission path of dynamic noise,simulation and experimental research,case analysis,optimization effect,etc.,aiming to better provide a certain guideline and reference for relevant researchers.展开更多
In aerospace industry,gears are the most common parts of a mechanical transmission system.Gear pitting faults could cause the transmission system to crash and give rise to safety disaster.It is always a challenging pr...In aerospace industry,gears are the most common parts of a mechanical transmission system.Gear pitting faults could cause the transmission system to crash and give rise to safety disaster.It is always a challenging problem to diagnose the gear pitting condition directly through the raw signal of vibration.In this paper,a novel method named augmented deep sparse autoencoder(ADSAE)is proposed.The method can be used to diagnose the gear pitting fault with relatively few raw vibration signal data.This method is mainly based on the theory of pitting fault diagnosis and creatively combines with both data augmentation ideology and the deep sparse autoencoder algorithm for the fault diagnosis of gear wear.The effectiveness of the proposed method is validated by experiments of six types of gear pitting conditions.The results show that the ADSAE method can effectively increase the network generalization ability and robustness with very high accuracy.This method can effectively diagnose different gear pitting conditions and show the obvious trend according to the severity of gear wear faults.The results obtained by the ADSAE method proposed in this paper are compared with those obtained by other common deep learning methods.This paper provides an important insight into the field of gear fault diagnosis based on deep learning and has a potential practical application value.展开更多
The aim of this study is to define optimal tooth modifications, introduced by appropriately chosen head-cutter geometry and machine tool setting, to simultaneously minimize tooth contact pressure and angular displacem...The aim of this study is to define optimal tooth modifications, introduced by appropriately chosen head-cutter geometry and machine tool setting, to simultaneously minimize tooth contact pressure and angular displacement error of the driven gear （transmission error） of face-hobbed spiral bevel gears. As a result of these modifications, the gear pair becomes mismatched, and a point contact replaces the theoretical line contact. In the applied loaded tooth contact analysis it is assumed that the point contact under load is spreading over a surface along the whole or part of the ‘‘potential’’ contact line. A computer program was developed to implement the formulation provided above. By using this program the influence of tooth modifications introduced by the variation in machine tool settings and in head cutter data on load and pressure distributions, transmission errors, and fillet stresses is investigated and discussed. The correlation between the ease-off obtained by pinion tooth modifications and the corresponding tooth contact pressure distribution is investigated and the obtained results are presented.展开更多
AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been i...AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-andthrough defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue(P = 0.248), woven bone(P = 0.248) and compact bone(P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.展开更多
To investigate whether masticatory fatigue affects the fracture resistance and pattern of lower premolars restored with quartz-fiber post-core and full crown, 44 single rooted lower premolars recently extracted from o...To investigate whether masticatory fatigue affects the fracture resistance and pattern of lower premolars restored with quartz-fiber post-core and full crown, 44 single rooted lower premolars recently extracted from orthodontic patients were divided into two groups of 22 each. The crowns of all teeth were removed and endodontically treated and then restored with quartz-fiber post-core and full crown. Twenty-two teeth in one group were selected randomly and circularly loaded at 45° to the long axis of the teeth of 127.4 N at a 6 Hz frequency, and the other group was not delivered to cyclic loading and considered as control. Subsequently, all teeth in two groups were continually loaded to fail at 45° to the long axis of the teeth at a crosshead speed of 1 mm.min-1. The mean destructive force values were （733.88±254.99） and （869.14±280.26） N for the experimental and the control group, respectively, and no statistically significant differences were found between two groups （P〉O.05）. Bevel fracture and horizontal fracture in the neck of root were the major fracture mode of the specimens. Under the circumstances of this study, it seems that cyclic loading does not affect the fracture strength and pattern of the quartz-fiber post-core-crown complex.展开更多
To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Thr...To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Three different materials （composite resin, ceramage and ceramic） were studied and two loading conditions （vertical and oblique load） were simulated. Mohr-Coulomb failure criterion of enamel, dentine, endocrown and cement were evaluated separately. It is indicated that under both loading conditions, the highest values of Mohr-Coulomb failure criterion were observed in Ceramage-restored group for remaining tooth structure while in ceramic-restored group for the restoration. Compared to composite resin and Ceramage, ceramic endocrown transferred less stress, namely was more protective to the tooth structure.展开更多
We report on a new species of enantiornithine bird from the Lower Cretaceous Qiaotou Formation of northern Hebei, China. The new taxon, Shenqiornis mengi gen. et sp. nov., possesses several enantiornithine synapomorph...We report on a new species of enantiornithine bird from the Lower Cretaceous Qiaotou Formation of northern Hebei, China. The new taxon, Shenqiornis mengi gen. et sp. nov., possesses several enantiornithine synapomorphies but is unique from other known species. The specimen has a well-preserved skull that reveals new information about enantiornithine cranial morphology. The new taxon possesses a large postorbital with a long tapering jugal process indicating that some enantiornithines may have had a fully diapsid skull, as in Confuciusornis. The tooth morphology of the specimen is unique and likely represents a previously unknown trophic specialization within Enantiornithes.展开更多
This study was designed to compare the impact of post and core systems on resistance to fracture of endodontically treated anterior teeth with flared root canals and to assess their fracture pattern. Sixty central inc...This study was designed to compare the impact of post and core systems on resistance to fracture of endodontically treated anterior teeth with flared root canals and to assess their fracture pattern. Sixty central incisors were cut horizontally 2 mm coronal to the cementoenamel junction(CEJ). After root canal therapy, teeth were assigned into 6 groups(n = 10 each) based on a post system and used as follows: Group C, non-flared root received size #1 glass fiber posts(Control); Group AP, flared root restored with anatomical post; Group RC, flared root restored with size #1 fiber post and cemented with thick layer of resin cement; Group CR, flared root restored with size #1 and reinforced with composite resin; Group CM, cast post-core; Group CP, CAD/CAM polymer-infiltrated ceramic post and core.Following post cementation, core build-up and crown insertion, the specimens were thermo-cycled up to 10,000 cycles(5 C/55 C; 30 seconds dwell time, 6 seconds transition time) and then statically loaded at 1 mm/minute crosshead speed using a universal testing machine. One-way ANOVA and Tukey HSD post hoc test(α= 0.05) were used for data analysis. Group C recorded significantly higher resistance to fracture values [(826.9±39.1) N] followed by group CP [(793.8±55.6) N] while group RC yielded the lowest fracture resistance values [(586.7±51.4) N]. The resistance to fracture of wide root canals can be enhanced by using one-piece CAM/CAM post and core as an alternative to the use of either glass fiber post, relined with composite resin increasing the thickness of luting cement or the use of cast post and core system. However, this was an in vitro investigation and further in vivo studies are necessary.展开更多
BACKGROUND An extra tooth in the normal tooth sequence in any region of the dental arch is regarded as a supernumerary tooth(SNT).Due to the large variation in location and morphology,the extraction of impacted SNTs i...BACKGROUND An extra tooth in the normal tooth sequence in any region of the dental arch is regarded as a supernumerary tooth(SNT).Due to the large variation in location and morphology,the extraction of impacted SNTs is an extensive and complex procedure with high risks of several complications.This report presents a rare case of seven impacted SNTs in the bilateral upper and lower arch that were successfully extracted with the use of digital positioning guide plates.CASE SUMMARY In January 2022,a 21-year-old male was referred to our department with a chief complaint of pain in relation to tooth#36.Clinical examination showed a deep carious lesion with pulpal involvement in tooth#36 and lingual swelling of the bilateral mandibular posterior area.Radiographic examination revealed seven deeply impacted SNTs in the bilateral posterior area and bilateral impacted mandibular third molars.Based on these findings,the patient was diagnosed with bilateral,multiple impacted SNTs and tooth#36 chronic pulpitis.A root canal treatment and an all-ceramic crown restoration for tooth#36 were performed.An individualized digital positioning guide plate was designed by computer-aided design/computer-aided manufacturing technology and cone-beam computed tomography for extraction of the impacted SNTs.During the operation,the digital positioning guide plate allowed rapid positioning and exposure of the SNTs while avoiding adjacent important anatomical structures.At 3-month follow-up,regeneration of bone and soft tissues was visible.CONCLUSION The application of digital positioning guide plates is useful for the individualized and minimalized extraction of impacted supernumerary teeth.展开更多
文摘Introduction: Misconceptions are associated with the teething process in Nigeria and is often blamed for symptoms in infants. A horrendous incident occurred in Nigeria in 2008 which recorded 84 infant deaths due to consumption of adulterated teething syrup to prevent teething problems. In the quest to engage the populace, particularly mothers, in health education to change this erroneous mindset about teething, it will be necessary and more cost effective to involve Traditional Birth Attendants (TBA’s) who can be invaluable in assisting to dispel myths associated teething as they live and work among the local populace and many times give counsel to mothers. Aim: To assess the attitude and beliefs of TBA’s in Ibadan, to teething in infants. Methods: A cross sectional survey was conducted among TBA’s in Ibadan, Nigeria. A thirteen item interviewer administered questionnaire was distributed to all 163 TBA’s in the five urban local government areas who agreed to be part of the study. Results: Over half of the respondents (59.5%) and (55.8%) associated the teething process with fever and diarrhea respectively. Other beliefs included boils (49.1%), loss of appetite (48.5%), weight loss (44.2%), and sleeplessness (42.3%). A greater proportion of the older and less educated TBA’s associated teething with fever, diarrhea, boils, loss of appetite and weight loss. The respondents would advise analgesics (55.8%), teething powder (67.5%), antibiotics (12.3%), concoctions (4.3%) and sedatives (4.3%) as teething remedies. There was a greater tendency for less educated TBA’s to advise the use of concoctions?and antibiotics. Conclusion: The study reveals grave misconceptions among TBA’s who in developing countries like Nigeria give counsel to mothers in the various communities. There is an urgent need for health education to the TBA’s particularly the older and less educated ones.
文摘“Last scene of all that ends this strange,eventful history,is second childishness and mere oblivion.I am sans teeth,sans eyes,sans taste,sans everything.”William Shakespeare‘As You Like It'Act 2,Sc.7,l.139Aging of the human brain is characterized by a progressive decline of its functional capacity;this decline however varies widely,and cognitive longevity differs substantially between individuals.
文摘Intentional tooth replantation(ITR)is an advanced treatment modality and the procedure of last resort for preserving teeth with inaccessible endodontic or resorptive lesions.ITR is defined as the deliberate extraction of a tooth;evaluation of the root surface,endodontic manipulation,and repair;and placement of the tooth back into its original socket.Case reports,case series,cohort studies,and randomized controlled trials have demonstrated the efficacy of ITR in the retention of natural teeth that are untreatable or difficult to manage with root canal treatment or endodontic microsurgery.However,variations in clinical protocols for ITR exist due to the empirical nature of the original protocols and rapid advancements in the field of oral biology and dental materials.This heterogeneity in protocols may cause confusion among dental practitioners;therefore,guidelines and considerations for ITR should be explicated.This expert consensus discusses the biological foundation of ITR,the available clinical protocols and current status of ITR in treating teeth with refractory apical periodontitis or anatomical aberration,and the main complications of this treatment,aiming to refine the clinical management of ITR in accordance with the progress of basic research and clinical studies;the findings suggest that ITR may become a more consistent evidence-based option in dental treatment.
基金supported by the National Natural Science Foundation of China(52374001,52104001).
文摘Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs,but the interaction mechanism among impact loads,drilling teeth and rock has not been sufficiently investigated.For this reason,shales with different bedding angles are used to carry out impact compression and tensile experiments as well as the rock-breaking experiments by single axe-shaped tooth,the variation of dynamic strengths,rock failure characteristics,fractal dimensions,and tensile/compression ratios under different load-bedding angles(α)are investigated.Then,the three-dimensional scanning device is used to measure the penetration depth and rock-breaking volume under different load-bedding angles.The results show that with the increase of load-bedding angle(0°-90°),the compressive strength decreases and then increases,with the lowest strength atα=45°and the highest strength atα=0°;the tensile strength decreases and then increases,with the lowest strength nearα=30°and the highest strength atα=90°.With the growing impact rate,the effect of load-bedding angle on dynamic compressive strength decreases,and the effect on dynamic tensile strength becomes more significant.When the impact velocity is high(≥8.0 m/s),the tensile-compressive ratio first decreases and then increases,and both reach a minimum at a load-bedding angle of 30°and a maximum at 60°.With the increasing of the load-bedding angle,the depth of tooth penetration increases and then decreases,and the highest depth of tooth penetration and the highest energy absorption efficiency are achieved atα=45°;the width of the impact pit increases and then decreases,and the maximum width value is achieved atα=30°,with the smallest value of the specific work value of the rock-breaking.The results have significant reference value for improving the rock-breaking efficiency of percussion drilling in deep anisotropic formations.
基金supported in part by the National Natural Science Foundation of China(Grant No.62062003)Natural Science Foundation of Ningxia(Grant No.2023AAC03293).
文摘The instance segmentation of impacted teeth in the oral panoramic X-ray images is hotly researched.However,due to the complex structure,low contrast,and complex background of teeth in panoramic X-ray images,the task of instance segmentation is technically tricky.In this study,the contrast between impacted Teeth and periodontal tissues such as gingiva,periodontalmembrane,and alveolar bone is low,resulting in fuzzy boundaries of impacted teeth.Amodel based on Teeth YOLACT is proposed to provide amore efficient and accurate solution for the segmentation of impacted teeth in oral panoramic X-ray films.Firstly,a Multi-scale Res-Transformer Module(MRTM)is designed.In the module,depthwise separable convolutions with different receptive fields are used to enhance the sensitivity of the model to lesion size.Additionally,the Vision Transformer is integrated to improve the model’s ability to perceive global features.Secondly,the Context Interaction-awareness Module(CIaM)is designed to fuse deep and shallow features.The deep semantic features guide the shallow spatial features.Then,the shallow spatial features are embedded into the deep semantic features,and the cross-weighted attention mechanism is used to aggregate the deep and shallow features efficiently,and richer context information is obtained.Thirdly,the Edge-preserving perceptionModule(E2PM)is designed to enhance the teeth edge features.The first-order differential operator is used to get the tooth edge weight,and the perception ability of tooth edge features is improved.The shallow spatial feature is fused by linear mapping,weight concatenation,and matrix multiplication operations to preserve the tooth edge information.Finally,comparison experiments and ablation experiments are conducted on the oral panoramic X-ray image datasets.The results show that the APdet,APseg,ARdet,ARseg,mAPdet,and mAPseg indicators of the proposed model are 89.9%,91.9%,77.4%,77.6%,72.8%,and 73.5%,respectively.This study further verifies the application potential of the method combining multi-scale feature extraction,multi-scale feature fusion,and edge perception enhancement in medical image segmentation,which provides a valuable reference for future related research.
文摘Objective:To explore the clinical effect of improved incision in the extraction of impacted mandibular wisdom teeth.Methods:160 patients who were treated in our hospital from October,2024 to April,2025 and had their mandibular impacted wisdom teeth removed according to the doctor’s advice were randomly divided into observation group and control group.The observation group used modified incision,while the control group used traditional triangular incision.The operation time,intraoperative visual analogue scale(VAS)pain score,pain VAS score on the 1st,2nd and 3rd day after operation,facial swelling on the 2nd day after operation,mouth opening limitation on the 2nd day after operation and the incidence of dry socket after operation were recorded and compared between the two groups.Results:There was no significant difference in operation time between the two groups(p>0.05).The VAS score of pain in the observation group was significantly lower than that in the control group at each time point during and after operation(p<0.05).On the second day after operation,the facial swelling and mouth opening limitation in the observation group were significantly lighter than those in the control group(p<0.05).The incidence of dry socket in the observation group was 1.25%(1/80),which was significantly lower than that in the control group(8.75%,7/80),and the difference was statistically significant(p<0.05).Conclusion:The application of modified triangular incision in the extraction of impacted mandibular wisdom teeth can effectively relieve the pain during and after operation,reduce postoperative facial swelling and mouth opening limitation,and reduce the incidence of dry socket.
基金co-supported by the National Natural Science Foundation of China (No. 52175104)the Postdoctoral Fellowship Program of CPSF (No. GZC20233008)
文摘Tooth cracks may occur in spiral bevel gear transmission system of the aerospace equipment.In this study,an accurate and efficient loaded tooth contact analysis(LTCA)model is developed to predict the contact behavior and time-varying meshing stiffness(TVMS)of spiral bevel gear pair with cracked tooth.The tooth is sliced,and the contact points on slices are computed using roll angle surfaces.Considering the geometric complexity of crack surface,a set of procedures is formulated to generate spatial crack and determine crack parameters for contact points.According to the positional relationship between contact point and crack path,each sliced tooth is modeled as a non-uniform cantilever beam with varying reduced effective load-bearing tooth thickness.Then the compliance model of the cracked tooth is established to perform contact analysis,along with TVMS calculations utilizing three different models.By employing spiral bevel gear pairs with distinct types of cracks as examples,the accuracy and efficiency of the developed approach are validated via comparative analyses with finite element analysis(FEA)outcomes.Furthermore,the investigation on effects of cracks shows that tooth cracks can induce alterations in meshing performance of both entire gear pair and individual tooth pairs,including not only cracked tooth pair but also adjacent non-cracked tooth pairs.Hence,the proposed model can serve as a useful tool for analyzing the variations in contact behavior and meshing stiffness of spiral bevel gears due to different cracks.
基金funded by the National Natural Science Foundation of China(52478138).
文摘The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,combining soft material with fractal,a composite pre-tightened multi-hierarchy tooth joint is proposed,and the bearing performance and failure process of the joint through experiments and finite element method under tensile load.First,the ultimate bearing capacity,load distribution ratio,and failure process of different hierarchies of teeth joints are studied through experiments.Then,the progressive damage models of different hierarchies of tooth joints are established,and experiments verify the validity of the finite element model.Finally,the effects of soft material and increasing tooth hierarchy on the failure process and bearing capacity of composite pre-tightened tooth joints are analyzed by the finite element method.The following conclusions can be drawn:(1)The embedding of soft materials changed the failure process of the joint.Increasing the tooth hierarchy can give the joint more load transfer paths,but the failure process of the joint is complicated.(2)Embedding soft materials and increasing the tooth hierarchy simultaneously can effectively improve the bearing capacity of composite pre-tightened tooth joints,which is 87.8%higher than that of traditional three-tooth joints.
文摘This paper deeply discusses the causes of gear howling noise,the identification and analysis of multi-source excitation,the transmission path of dynamic noise,simulation and experimental research,case analysis,optimization effect,etc.,aiming to better provide a certain guideline and reference for relevant researchers.
基金supported by the Natural Science Foundation of China(No.51675089).
文摘In aerospace industry,gears are the most common parts of a mechanical transmission system.Gear pitting faults could cause the transmission system to crash and give rise to safety disaster.It is always a challenging problem to diagnose the gear pitting condition directly through the raw signal of vibration.In this paper,a novel method named augmented deep sparse autoencoder(ADSAE)is proposed.The method can be used to diagnose the gear pitting fault with relatively few raw vibration signal data.This method is mainly based on the theory of pitting fault diagnosis and creatively combines with both data augmentation ideology and the deep sparse autoencoder algorithm for the fault diagnosis of gear wear.The effectiveness of the proposed method is validated by experiments of six types of gear pitting conditions.The results show that the ADSAE method can effectively increase the network generalization ability and robustness with very high accuracy.This method can effectively diagnose different gear pitting conditions and show the obvious trend according to the severity of gear wear faults.The results obtained by the ADSAE method proposed in this paper are compared with those obtained by other common deep learning methods.This paper provides an important insight into the field of gear fault diagnosis based on deep learning and has a potential practical application value.
基金the Hungarian Scientific Research Fund (OTKA) for their financial support of the research under Contract No.K77921
文摘The aim of this study is to define optimal tooth modifications, introduced by appropriately chosen head-cutter geometry and machine tool setting, to simultaneously minimize tooth contact pressure and angular displacement error of the driven gear （transmission error） of face-hobbed spiral bevel gears. As a result of these modifications, the gear pair becomes mismatched, and a point contact replaces the theoretical line contact. In the applied loaded tooth contact analysis it is assumed that the point contact under load is spreading over a surface along the whole or part of the ‘‘potential’’ contact line. A computer program was developed to implement the formulation provided above. By using this program the influence of tooth modifications introduced by the variation in machine tool settings and in head cutter data on load and pressure distributions, transmission errors, and fillet stresses is investigated and discussed. The correlation between the ease-off obtained by pinion tooth modifications and the corresponding tooth contact pressure distribution is investigated and the obtained results are presented.
文摘AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-andthrough defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue(P = 0.248), woven bone(P = 0.248) and compact bone(P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.
基金supported by the Guangdong Province Science and Technology Commission (2008B080703019, 2011B080701010 and 2011B080701086)
文摘To investigate whether masticatory fatigue affects the fracture resistance and pattern of lower premolars restored with quartz-fiber post-core and full crown, 44 single rooted lower premolars recently extracted from orthodontic patients were divided into two groups of 22 each. The crowns of all teeth were removed and endodontically treated and then restored with quartz-fiber post-core and full crown. Twenty-two teeth in one group were selected randomly and circularly loaded at 45° to the long axis of the teeth of 127.4 N at a 6 Hz frequency, and the other group was not delivered to cyclic loading and considered as control. Subsequently, all teeth in two groups were continually loaded to fail at 45° to the long axis of the teeth at a crosshead speed of 1 mm.min-1. The mean destructive force values were （733.88±254.99） and （869.14±280.26） N for the experimental and the control group, respectively, and no statistically significant differences were found between two groups （P〉O.05）. Bevel fracture and horizontal fracture in the neck of root were the major fracture mode of the specimens. Under the circumstances of this study, it seems that cyclic loading does not affect the fracture strength and pattern of the quartz-fiber post-core-crown complex.
基金Founded by National Natural Science Foundation of China(No.51305306)Hubei Province Science and Technology Support Program(No.2013BCB025)Fundamental Research Funds for the Central University(No.2042014kf0274)
文摘To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mand^ular first molar, restoration, and cement layer were created. Three different materials （composite resin, ceramage and ceramic） were studied and two loading conditions （vertical and oblique load） were simulated. Mohr-Coulomb failure criterion of enamel, dentine, endocrown and cement were evaluated separately. It is indicated that under both loading conditions, the highest values of Mohr-Coulomb failure criterion were observed in Ceramage-restored group for remaining tooth structure while in ceramic-restored group for the restoration. Compared to composite resin and Ceramage, ceramic endocrown transferred less stress, namely was more protective to the tooth structure.
基金funded by the National Science Foundation(DEB-0317140)National Natural Science Foundation of China(40902012)support from Carl and Lynn Cooper,Ron and Judy Perlstein,and Richard and Eileen Garson
文摘We report on a new species of enantiornithine bird from the Lower Cretaceous Qiaotou Formation of northern Hebei, China. The new taxon, Shenqiornis mengi gen. et sp. nov., possesses several enantiornithine synapomorphies but is unique from other known species. The specimen has a well-preserved skull that reveals new information about enantiornithine cranial morphology. The new taxon possesses a large postorbital with a long tapering jugal process indicating that some enantiornithines may have had a fully diapsid skull, as in Confuciusornis. The tooth morphology of the specimen is unique and likely represents a previously unknown trophic specialization within Enantiornithes.
文摘This study was designed to compare the impact of post and core systems on resistance to fracture of endodontically treated anterior teeth with flared root canals and to assess their fracture pattern. Sixty central incisors were cut horizontally 2 mm coronal to the cementoenamel junction(CEJ). After root canal therapy, teeth were assigned into 6 groups(n = 10 each) based on a post system and used as follows: Group C, non-flared root received size #1 glass fiber posts(Control); Group AP, flared root restored with anatomical post; Group RC, flared root restored with size #1 fiber post and cemented with thick layer of resin cement; Group CR, flared root restored with size #1 and reinforced with composite resin; Group CM, cast post-core; Group CP, CAD/CAM polymer-infiltrated ceramic post and core.Following post cementation, core build-up and crown insertion, the specimens were thermo-cycled up to 10,000 cycles(5 C/55 C; 30 seconds dwell time, 6 seconds transition time) and then statically loaded at 1 mm/minute crosshead speed using a universal testing machine. One-way ANOVA and Tukey HSD post hoc test(α= 0.05) were used for data analysis. Group C recorded significantly higher resistance to fracture values [(826.9±39.1) N] followed by group CP [(793.8±55.6) N] while group RC yielded the lowest fracture resistance values [(586.7±51.4) N]. The resistance to fracture of wide root canals can be enhanced by using one-piece CAM/CAM post and core as an alternative to the use of either glass fiber post, relined with composite resin increasing the thickness of luting cement or the use of cast post and core system. However, this was an in vitro investigation and further in vivo studies are necessary.
基金Supported by National Natural Science Foundation of China,No.81970972Applied Basic Research Projects of the 920th Hospital of Joint Logistics Support Force,No.2020YGB06。
文摘BACKGROUND An extra tooth in the normal tooth sequence in any region of the dental arch is regarded as a supernumerary tooth(SNT).Due to the large variation in location and morphology,the extraction of impacted SNTs is an extensive and complex procedure with high risks of several complications.This report presents a rare case of seven impacted SNTs in the bilateral upper and lower arch that were successfully extracted with the use of digital positioning guide plates.CASE SUMMARY In January 2022,a 21-year-old male was referred to our department with a chief complaint of pain in relation to tooth#36.Clinical examination showed a deep carious lesion with pulpal involvement in tooth#36 and lingual swelling of the bilateral mandibular posterior area.Radiographic examination revealed seven deeply impacted SNTs in the bilateral posterior area and bilateral impacted mandibular third molars.Based on these findings,the patient was diagnosed with bilateral,multiple impacted SNTs and tooth#36 chronic pulpitis.A root canal treatment and an all-ceramic crown restoration for tooth#36 were performed.An individualized digital positioning guide plate was designed by computer-aided design/computer-aided manufacturing technology and cone-beam computed tomography for extraction of the impacted SNTs.During the operation,the digital positioning guide plate allowed rapid positioning and exposure of the SNTs while avoiding adjacent important anatomical structures.At 3-month follow-up,regeneration of bone and soft tissues was visible.CONCLUSION The application of digital positioning guide plates is useful for the individualized and minimalized extraction of impacted supernumerary teeth.
