1.Stress distribution on the maxilla when wearing the Twin-block appliance for Class Ⅱ malocclusion
Shuai LI ; Hua LIU ; Yonghui SHANG ; Yicong LIU ; Qihang ZHAO ; Wen LIU
Chinese Journal of Tissue Engineering Research 2025;29(5):881-887
BACKGROUND:The Twin-block orthodontic appliance is commonly used for the correction of Class Ⅱ malocclusion.Its mechanism of action in stimulating mandibular growth has been confirmed in many studies,but its impact on maxillary growth is not very clear. OBJECTIVE:By establishing a finite element model to analyze the stress distribution of the maxillary complex,surrounding bone sutures,and maxillary dentition in patients with Class Ⅱ malocclusion wearing Twin-block orthodontic appliances. METHODS:One patient with Class Ⅱ malocclusion who underwent orthodontic treatment at Qingdao Hospital/Qingdao Municipal Hospital of Shandong Rehabilitation University was selected.The bite force data of the patient when wearing the Twin-block orthodontic appliance was measured,and CBCT data were collected.A finite element model was established,including the maxillary complex,peripheral sutures,Twin-block orthodontic appliance,and maxillary dentition.ABAQUS software was used to simulate the stress distribution in the maxilla and maxillary dentition when the patient was wearing the Twin-block appliance. RESULTS AND CONCLUSION:The equivalent stress on the maxillary anterior teeth was significantly smaller than that on the posterior teeth,and the maximum equivalent stress on both sides of the teeth were 4.797 5 Mpa and 8.716 1 Mpa,respectively,which were located at the first premolar.The maximum displacements were presented at the maxillary incisors on both sides of the teeth,which were 0.080 5 mm and 0.081 0 mm,respectively.The maximum equivalent stress on the bone suture was 1.284 Mpa,which was mainly concentrated in the pterygopalatine suture and the frontal-maxillary suture on both sides,and there was almost no difference in the force of the rest of bone sutures;the maximum displacement of the bone suture was 0.07 mm,with the pterygopalatine suture having the largest displacement,followed by the frontal-maxillary suture.The maximal equivalent stress on the maxillary complex was 27.18 Mpa,which was mainly concentrated on both sides of the anterior pyriform foramen of the maxilla,around the nasofrontal suture and around the pterygopalatine suture at the posterior part of the jaws.The maximal displacement of the maxilla was 0.07 mm,which was mainly concentrated on the maxillary alveolar bone.All these findings show that the occlusal force acts on the maxillary complex through the Twin-block appliance,resulting in clockwise rotation of the maxilla and steepening of the dentition plane.Measures should be taken to compensate for this tendency,for example,by considering maxillary molar elongation and intrusion in the process of occlusion,which are not only able to flatten the occlusal plane,but facilitate the mandibular protraction,thereby further improving Class Ⅱ malocclusion orthodontic treatment.
2.Zuoguiwan Regulates Pdx1 Pathway to Improve Pancreas Development in Offspring of Gestational Diabetes Mellitus Model Rats
Wanqiu LIANG ; Rang CHEN ; Le ZHAO ; Xiaoyi REN ; Qianhui SU ; Yonghui WANG
Chinese Journal of Experimental Traditional Medical Formulae 2025;31(18):10-19
ObjectiveTo explore the mechanism by which Zuoguiwan improves the pancreas development in the gestational diabetes mellitus (GDM) model by observing the effects of Zuoguiwan on the expression of key regulatory factors in different stages of pancreas development. MethodsPregnant Wistar rats were randomly assigned into blank, model, insulin detemir (20 U·kg-1) and Zuoguiwan (1.89 g·kg-1) groups (n=18). GDM was induced by peritoneal injection of streptozotocin on day 6.5 (E6.5d) in the embryonic stage, and the blank group was given an equal volume of sodium citrate buffer. The modeling performance was assessed by measuring the blood glucose of pregnant rats. Except the blank group and model group, pregnant rats in other groups were administrated with corresponding drugs from E9.5d to delivery. The random blood glucose of pregnant rats was monitored, and the embryos and offspring rats were measured for the length and weighed on E12.5d, E18.5d and day 21 after birth (B21d). The Lee's index of rats on B21d was calculated. Enzyme-linked immunosorbent assay (ELISA) was employed to measure the fasting insulin (FINS) levels of B22d rats and the Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) was calculated. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TBIL), total cholesterol (CHO), triglyceride (TG), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL) in E18.5d pregnant rats and B22d offspring were determined. The pathological changes in the pancreas of E12.5d, E18.5d and B22d rats were observed by hematoxylin-eosin (HE) staining. Western blot was used to determine the protein levels of pancreatic duodenal homeobox 1 (Pdx1), pancreas-specific transcription factor 1a (Ptf1a), and sex-determining region Y-box protein 9 (Sox9) in the pancreas of E12.5d embryos, Pdx1, Nkx2 homeobox 2 (Nkx2.2), and hairy and enhancer of split-1 (Hes1) in the pancreas of E18.5d embryos, and Pdx1, v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (Mafa), and NK transcription factor-related homeobox gene family 6 locus 1 (Nkx6.1) in the pancreas of B22d rats. ResultsCompared with the blank group, the model group showed elevated blood glucose levels in pregnant rats on B0d, E9.5d, E12.5d, E15.5d, and E18.5d (P<0.05, P<0.01), decreased body weight and body length (P<0.01) and increased Lee's index in the offspring. In addition, the B22d offspring showed rising levels of FBG, FINS, HOMA-IR, AST, and TG (P<0.01), a declined level of HDL (P<0.01), and pancreatic acinous cells with edema and loose arrangement. The pregnant rats on E18.5d exhibited raised levels of ALT, AST, and TG (P<0.05, P<0.01) in the pancreas and a declined level of HDL (P<0.05). The E12.5d embryos showed up-regulated protein levels of Pdx1, Sox9, and Ptf1a in the pancreas (P<0.01) and the E18.5d embryos exhibited down-regulated protein levels of Pdx1, Nkx2.2, and Hes1 in the pancreas (P<0.01). The protein levels of Pdx1, Nkx6.1, and Mafa in the pancreas of B22d offspring were down-regulated (P<0.01). Compared with the model group, the insulin group exhibited lowered blood glucose in pregnant rats on B0d, E15.5d, and E18.5d (P<0.05, P<0.01). The offspring in all treatment groups showcased increased body weight and body length (P<0.01) and decreased Lee's index. The B22d offspring exhibited declined levels of FBG, FINS, and HOMA-IR in the insulin group (P<0.01) and lowered levels of FBG and HOMA-IR in the Zuoguiwan group (P<0.01). The B22d offspring in all the treatment groups showed reduced levels of ALT, AST, TBIL, CHO, TG, and LDL, a raised level of HDL, and alleviated edema of pancreatic acinous cells. The pregnant rats on E18.5d demonstrated declined levels of TG and ALT (P<0.05, P<0.01) and an elevated level of HDL (P<0.05). The pancreas of E12.5d embryos presented down-regulated protein levels of Pdx1 and Sox9 and an up-regulated protein level of Ptf1a in the insulin group (P<0.05). The pancreas of E12.5d embryos in the Zuoguiwan group presented down-regulated protein levels of Pdx1, Sox9, and Ptf1a (P<0.01). All the treatment groups showed up-regulated protein levels of Pdx1, Nkx2.2, and Hes1 in the pancreas of E18.5d embryos (P<0.01) and Pdx1, Nkx6.1, and Mafa in the pancreas of B22d embryos (P<0.05, P<0.01). ConclusionZuoguiwan can promote the growth and development and ameliorate the pathological changes in the pancreas of the offspring of GDM model by regulating the expression of Pdx1 pathway-related regulatory factors in different stages of pancreas development.
3.Effects of peripheral blood-derived exosomes intervened by Naozhenning on injury of neuron induced by microglia
Li GAO ; Le ZHAO ; Liya WU ; Weiyi ZHANG ; Nan LI ; Nannan WEI ; Yonghui WANG
China Pharmacy 2025;36(19):2393-2398
OBJECTIVE To study the effects of peripheral blood-derived exosomes (Exo) intervened by Naozhenning (NZN) on injury of neuron cells HT22 induced by microglia BV-2 cells. METHODS Wistar rats were selected to prepare peripheral blood- derived Exo intervened by NZN (66.83 g/kg), referred to as NZN-Exo; peripheral blood-derived Exo intervened by normal saline and piracetam (PLXT, 1.62 g/kg) were prepared using the same method, denoted as KB-Exo and PLXT-Exo respectively, and all Exo were subsequently identified. Meanwhile, BV-2 cells were stimulated with 1 μg/mL lipopolysaccharide (LPS) to prepare LPS- stimulated supernatant, and non-LPS-stimulated supernatant was prepared following the same protocol. HT22 cells were divided into four groups: KB-Exo group (treated with non-LPS-stimulated supernatant+KB-Exo), model group (treated with LPS-stimulated supernatant+KB-Exo), PLXT-Exo group (treated with LPS-stimulated supernatant+PLXT-Exo), and NZN-Exo group (treated with LPS-stimulated supernatant+NZN-Exo), with the concentration of the corresponding Exo in all groups being 50 μg/mL. After 24 hours of culture, the proliferation of HT22 cells was detected by the CCK-8 assay and EdU assay; the apoptosis of HT22 cells was detected; the microstructure of HT22 cells was observed; the contents of interleukin-1β (IL-1β), IL-10, nuclear factor-κB (NF- κB), and tumor necrosis factor-α (TNF-α) in HT22 cells were measured, as well as the expression levels of TNF-α, NOD-like receptor thermal protein domain associated protein 3 (NLRP3), Caspase-1, B-cell lymphoma-2( Bcl-2), and Bcl-2-associated X protein (Bax). RESULTS KB-Exo, PLXT-Exo and NZN-Exo were successfully prepared, and all Exo exhibited typical cup-shaped contours and membrane-enclosed characteristics. Compared with KB-Exo group, model group showed significantly decreased cell proliferation rates (detected by CCK-8 and EdU), intracellular IL-10 levels, and Bcl-2 protein expression levels (P<0.05); while the cell apoptosis rate, intracellular levels of IL-1β, TNF-α, and NF-κB, as well as the expression levels of NLRP3, TNF-α, Caspase-1, and Bax proteins were significantly increased (P<0.05). Additionally, in the model group, the cells showed volume swelling, incomplete cell membrane, nucleolar rupture, significant swelling and deformation of mitochondria, and severe vacuolization. Compared with model group, the above quantitative indicators in the PLXT-Exo group and NZN-Exo group were significantly reversed (P<0.05), with large and round cell nuclei, intact nuclear membranes, and reduced mitochondrial vacuolization. CONCLUSIONS Peripheral blood-derived Exo intervened by naozhenning can alleviate the injury of neuronal cells HT22 by inhibiting inflammatory responses and cell apoptosis.
4.Three-dimensional finite element analysis of digital wire loop space maintainers for missing deciduous teeth.
Lijuan MA ; Yonghui TENG ; Yong WANG ; Yijiao ZHAO ; Xinyue ZHANG ; Qingzhao QIN ; Dong YIN
Journal of Peking University(Health Sciences) 2025;57(2):376-383
OBJECTIVE:
To establish a three-dimensional finite element model of a digital wire loop space maintainer for the mandible and primary tooth loss, in order to investigate the stress, deformation, and shear force experienced by patients with the loss of the second primary molar when wearing the wire loop space maintainer.
METHODS:
Cone beam computed tomography (CBCT) scans were performed on the patients to create a digital model of the mandible with the absence of the second primary molar using Mimics 21.0 software. A digital model integrating the crown's retention and the wire loop structure of the full crown and ring wire loop space maintainer was constructed using pediatric space maintainer design software, utilizing three different materials: cobalt-chromium alloy, polyether ether ketone (PEEK), and titanium alloy. In ANSYS Work Beach 2023 R2 software, vertical loads of 70 N, tilted 45° along the long axis of the tooth loads of 70 N, and a 10 N load on the surface of the wire loop were applied to the occlusal surfaces of models 46 and 84, simulating centric and lateral occlusions during chewing with the wire loop space maintainer in place. The stress states of the wire loop space maintainer and supporting teeth were analyzed.
RESULTS:
Under various loading conditions, the maximum principal stress of the ring wire loop space maintainer was significantly lower than that of the full crown. Stress contour maps indicated that the peak of the maximum principal stress occurred at the junction of the wire loop and crown structure, indicating that this area was more susceptible to fracture. The ring wire loop space maintainer made from PEEK material exhibited the lowest maximum shear stress on the internal organizational surfaces, with equivalent stresses of 23.18 MPa and 36.35 MPa for models 46 and 84, respectively. Stress contour maps demonstrated that the maximum stress on tooth 46 was located at its mesial, while the maximum stress on tooth 84 was situated near the root area on its distal, in contact with the wire loop space maintainer.
CONCLUSION
In cases of second primary molar loss, wearing the digital ring wire loop space maintainer can effectively distribute stress, and the ring wire loop space maintainer made from PEEK material reduces the stress experienced by supporting teeth to some extent, demonstrating its superiority in clinical application.
Finite Element Analysis
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Humans
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Tooth, Deciduous
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Cone-Beam Computed Tomography
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Space Maintenance, Orthodontic/methods*
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Imaging, Three-Dimensional
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Orthodontic Wires
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Dental Stress Analysis
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Mandible
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Stress, Mechanical
5.Amoenucles A-F, novel nucleoside derivatives with TNF-α inhibitory activities from Aspergillus amoenus TJ507.
Yeting ZHANG ; Zhengyi SHI ; Chunhua ZHAO ; Lanqin LI ; Ming CHEN ; Yunfang CAO ; Fengqing WANG ; Bo TAO ; Xinye HUANG ; Jieru GUO ; Changxing QI ; Weiguang SUN ; Yonghui ZHANG
Chinese Journal of Natural Medicines (English Ed.) 2025;23(1):111-118
Amoenucles A-F (1-6), six previously undescribed nucleoside derivatives, and two known analogs (7 and 8) were isolated from the culture of Aspergillus amoenus TJ507. Their structures were elucidated through spectroscopic analysis, single-crystal X-ray crystallography, and chemical reactions. Notably, 3 and 4 represent the first reported instances of nucleosides with an attached pyrrole moiety. Of particular significance, the absolute configuration of the sugar moiety of 1-4 was determined using nuclear magnetic resonance (NMR), electric circular dichroism (ECD) calculations, and a hydrolysis reaction, presenting a potentially valuable method for confirming nucleoside structures. Furthermore, 1, 2, and 5-8 exhibited potential tumor necrosis factor α (TNF-α) inhibitory activities, which may provide a novel chemical template for the development of agents targeting autoimmune and inflammatory diseases.
Aspergillus/chemistry*
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Tumor Necrosis Factor-alpha/antagonists & inhibitors*
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Molecular Structure
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Nucleosides/isolation & purification*
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Crystallography, X-Ray
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Animals
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Humans
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Mice
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Magnetic Resonance Spectroscopy
6.(±)-Talapyrones A-F: six pairs of dimeric polyketide enantiomers with unusual 6/6/6 and 6/6/6/5 ring systems from Talaromycesadpressus.
Meijia ZHENG ; Xinyi ZHAO ; Chenxi ZHOU ; Hong LIAO ; Qin LI ; Yuling LU ; Bingbing DAI ; Weiguang SUN ; Ying YE ; Chunmei CHEN ; Yonghui ZHANG ; Hucheng ZHU
Chinese Journal of Natural Medicines (English Ed.) 2025;23(8):932-937
(±)-Talapyrones A-F (1-6), six pairs of dimeric polyketide enantiomers featuring unusual 6/6/6 and 6/6/6/5 ring systems, were isolated from the fungus Talaromyces adpressus. Their structures were determined by spectroscopic analysis and HR-ESI-MS data, and their absolute configurations were elucidated using a modified Mosher's method and electronic circular dichroism (ECD) calculations. (±)-Talapyrones A-F (1-6) possess a 6/6/6 tricyclic skeleton, presumably formed through a Michael addition reaction between one molecule of α-pyrone derivative and one molecule of C8 poly-β-keto chain. In addition, compounds 2/3 and 4/5 are two pairs of C-18 epimers, respectively. Putative biosynthetic pathways of 1-6 were discussed.
Polyketides/isolation & purification*
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Talaromyces/chemistry*
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Stereoisomerism
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Molecular Structure
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Circular Dichroism
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Pyrones/chemistry*
7.Discovery of bioactive polycyclic polyprenylated acylphloroglucinol from Hypericum patulum that protects against hepatic ischemia/reperfusion injury.
Bo TAO ; Xiangli ZHAO ; Zhengyi SHI ; Jie LI ; Yulin DUAN ; Xiaosheng TAN ; Gang CHEN ; Changxing QI ; Yonghui ZHANG
Chinese Journal of Natural Medicines (English Ed.) 2025;23(9):1104-1110
Hepatic ischemia/reperfusion injury (IRI) remains a critical complication contributing to graft dysfunction following liver surgery. As part of an ongoing search for hepatoprotective natural products, five previously unreported homoadamantane-type polycyclic polyprenylated acylphloroglucinols (PPAPs), named hyperhomanoons A-E (1-5), and one known analog, hypersampsone O (6), were isolated from Hypericum patulum. Among these, compound 6 demonstrated potent protective effects against CoCl₂-induced hypoxic injury in hepatocytes. Furthermore, in a murine model of hepatic IRI induced by vascular occlusion, pretreatment with 6 markedly alleviated liver damage and reduced hepatocyte apoptosis. This study is the first to identify PPAPs as promising scaffolds for the development of therapeutic agents targeting hepatic IRI, underscoring their potential as lead compounds in drug discovery efforts for ischemic liver diseases.
Reperfusion Injury/prevention & control*
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Animals
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Hypericum/chemistry*
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Phloroglucinol/administration & dosage*
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Mice
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Humans
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Male
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Liver/blood supply*
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Apoptosis/drug effects*
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Molecular Structure
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Protective Agents/pharmacology*
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Hepatocytes/drug effects*
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Mice, Inbred C57BL
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Liver Diseases/drug therapy*
8.Mechanism of Naozhenning granules in regulating mitochondrial energy metabolism in multiple cerebral concussion rats
Li GAO ; Le ZHAO ; Nannan WEI ; Liya WU ; Tiantian WANG ; Weiyi ZHANG ; Yonghui WANG
China Pharmacy 2024;35(9):1050-1056
OBJECTIVE To explore the mechanism of Naozhenning granules in regulating mitochondrial energy metabolism in hippocampal tissue of multiple cerebral concussion (MCC) model rats. METHODS SPF grade Wistar rats were used to prepare MCC models using the “free fall impact method”. The successfully modeled rats were divided into model group, piracetam group, and Naozhenning granule low-dose, medium-dose and high-dose groups, and a normal group was also set up, with 8 rats in each group. Rats in each treatment group orally administered corresponding drugs at doses of 0.324 g/kg for the piracetam group and 2.25, 4.5 and 9 g/kg for the Naozhenning granule low-dose, medium-dose and high-dose groups; the normal group and model group were given equal volumes of normal saline; once a day, for 14 consecutive days. The motor exploration ability, learning and memory ability of rats were tested; the adenosine triphosphate (ATP) content in the hippocampal tissue of rat was detected; the changes in the mitochondrial structure of hippocampal tissue was observed; the fluorescence intensity of mitochondrial dynamin- related protein 1 (Drp1), mitochondrial fission protein 1 (Fis1), mitochondrial fusion 1 (Mfn1), and optic atrophy protein 1 (Opa1) were detected in the hippocampal tissue of rat; the protein expression levels of peroxisome proliferator activated receptor gamma coactivator-1α(PGC-1α), nuclear respiratory factor-1(NRF-1),mitochondrial transcription factor A(TFAM), Wnt-3a,β-catenin in hippocampal tissue of rat were detected. RESULTS Compared with the normal group, the total exercise distance, number of central grid entries, number of upright positions, new object recognition index, mitochondrial ATP content, fluorescence intensity of Mfn1 and Opa1, the protein expression levels of PGC-1α、NRF-1、TFAM、Wnt-3a、 β-catenin in the model group were significantly reduced (P<0.01), while the rest time and fluorescence intensity of Drp1 and Fis1 in hippocampal tissue were significantly increased (P<0.01). The results of transmission electron microscopy showed that the mitochondria in the hippocampal tissue were significantly swollen, with a large number of broken and reduced cristae, and some mitochondria had myeloid changes in the membrane. Compared with the model group, the levels/contents of the above indicators in rats of each administration group showed varying degrees of reversal, and most of the differences were statistically significant (P<0.05 or P<0.01); the degree of mitochondrial swelling in the hippocampal tissue was reduced, with a small amount of broken and reduced cristae, fuzzy fractures appeared in local areas of the rough endoplasmic reticulum. CONCLUSIONS Naozhenning granules can improve the motor exploration, learning and memory abilities of MCC model rats, repair neuronal damage, and exert neuroprotective effects. Its mechanism may be related to activating Wnt/β-catenin signaling pathway,maintaining the balance of mitochondrial division and fusion,and promoting mitochondrial biosynthesis.
9.Conical beam CT measurement of alveolar bone structure remodeling in patients with skeletal class Ⅲ malocclusion after orthodontic-orthognathic treatment
Qihang ZHAO ; Xin LU ; Lei TONG ; Yonghui SHANG ; Shuai LI ; Wen LIU ; Jianhua ZHOU ; Rongtao YUAN ; Qingyuan GUO
Chinese Journal of Tissue Engineering Research 2024;28(23):3729-3735
BACKGROUND:Most of the studies on combined orthodontic-orthognathic treatment of skeletal class Ⅲ malocclusions have focused on the improvement of the patient's lateral appearance and recovery in the later stages of the treatment,while there are fewer studies observing the microcosmic nature of the alveolar bone remodeling of the lower anterior teeth. OBJECTIVE:To evaluate the therapeutic effect of lower anterior tooth decompensation and alveolar bone remodeling in patients with skeletal class Ⅲ malocclusion before and after orthodontic-orthognathic treatment based on oral X-ray lateral films and oral cone-beam CT. METHODS:From January 2015 to May 2023,15 patients with skeletal class Ⅲ malocclusion who underwent orthodontic-orthognathic surgery at Qingdao Hospital of Rehabilitation University were enrolled.All patients underwent lateral cephalography and cone beam computed tomography before and after treatment.Cephalometric measurement items related to the angle and line distance,lip/lingual bone cracking length(d-La/d-Li)and bone cracking/bone fenestration of the lower anterior teeth before and after treatment were measured. RESULTS AND CONCLUSION:Lateral X-ray films showed that the amount of alveolar bone remodeling after decompensation of the lower anterior teeth showed significant changes compared to before treatment.The root of the tooth moved significantly towards the center of the alveolar bone,and the specific data was closer to normal data,but there were still some differences compared with normal individuals.Based on the cone-beam CT measurement,the bone cracking/bone fenestration length and width of the alveolar bone were improved in almost all the teeth after orthodontic-orthognathic combined treatment,alveolar bone remodeling in some teeth even reached the level of healthy individuals.Before treatment,most patients often experienced bone fenestration/cracking on the lip/lingual side of the lower incisor due to compensatory tooth growth.However,during the preoperative orthodontic stage,decompensation triggered alveolar bone remodeling and significant changes in tooth angle.Preoperative orthodontic treatment caused the upper anterior teeth to retract and the lower anterior teeth to tilt and control the root,but the amount of decompensation before surgery was often insufficient.In the orthognathic surgery stage,the jaw was removed through the positioning guide plate,the maxilla moved forward,and the mandible retreated.During the postoperative orthodontic process,the effect of fine adjustment was better.Although there is a certain degree of recurrence trend in the position of teeth and jawbones,the postoperative orthodontic treatment is closer to the normal value.
10.Three-dimensional finite element study on the effect of posterior tooth forward movement on temporomandibular joint stress in orthodontic reduction patients
Yonghui SHANG ; Shuai LI ; Yicong LIU ; Qihang ZHAO ; Wen LIU
Chinese Journal of Tissue Engineering Research 2024;28(34):5516-5520
BACKGROUND:Temporomandibular joint disorders are closely related to high stress in temporomandibular joint.With the change of molar position after tooth reduction extraction,the establishment of new occlusal relationship often leads to the change of internal stress environment of the temporomandibular joint. OBJECTIVE:To analyze the stress distribution of temporomandibular joint in patients undergoing orthodontic reduction tooth extraction with different degrees of molar forward movement using the three-dimensional finite element model of the maxillary complex and temporomandibular joint. METHODS:A case of individual normal occlusal patient was selected from the Orthodontics Department of Qingdao Municipal Hospital,Shandong Province,and the finite element models of 1/3 anterior molar space(extraction of four second premolar teeth)before and after reduction and 2/3 anterior molar space(extraction of 4 second premolar teeth)after reduction were established based on the cone-beam CT and MRI data.ABAQUS software was used to analyze the stress distribution of various parts of the temporomandibular joint during the interposition of tooth tips. RESULTS AND CONCLUSION:The stress distribution of the condyle,articular disc,and osteoarticular fossa in the model before and after the reduction was basically the same.The stress of the condyle was mainly distributed in the anterior and apical part of the condyle,the stress of the articular disc was mainly distributed in the middle band and lateral part of the articular disc,and the stress of the articular fossa was mainly concentrated in the anterior and apical part of the articular fossa.However,the equivalent stress value of the condyle,articular disc and articular fossa decreased after reduction.After orthodontic reduction extraction,the equivalent stress values of condyle and articular disc in the 1/3 anterior molar space model were smaller than those in the 2/3 anterior molar space model.From the perspective of biomechanics,orthodontic reduction extraction can reduce the stress of the temporomandibular joint and provide a good biomechanical environment.

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