Basic And Clinical Study On Thermoplastic Magnetic Appliance In Treatment Of Early Skeletal Class ? Malocclusion

Part I The Study of Simulating Different Intensity Static Magnetic Field on Biological Effects to MyoblastBackgroundSurface jaw muscle plays an significant role in the occurrence,disease development,correction and treatment maintenance of dentofacial deformity.For dentofacial deformity,caused by abnormal function of masticatory muscles and perioral muscles,it is necessary to use teeth appliance to supply corrective force and mechanical signal that produce by contraction of surface jaw muscle,which can transfer the signal to the location that need to correct,such as teeth,dental arch and jaw.The dentofacial morphological consequently reconstruct.According to clinical research,it is found that the function of surface jaw muscle have not improved and the effect is also difficult to maintain.Therefore,it should be built a new coordinated relation in accordance with reconstruction on the shape of hard tissue.Only in this way can its function be improved,coordinated,and the effect will remain.Sodium channel has great importance for substance and energy transduction in and out of cells.Furthermore,it is essential to maintain normal physiological function for organism.Usually,Sodium channel may be in one of three functional states-standby state,active state and inactive state.The functional states with sodium channel decide whether it has activity of generating active potentials.Voltage-gated sodium channel is a kind of particular protein molecular that excitable cells generate electrical impulses,which widely exists in cell membrane of excitable cells-skeleton muscle,etc.SCN4A is an important subunit for voltage-gated sodium channel.Present studies suggest that SCN4A have an important role in the process of generation and transmission in skeleton muscle's action potentials.MethodsThis study is designed to culture myoblast in rat skeletal muscle cells through simulating different intensity static magnetic field.After culturing,the study also suggested that patch clamp technique is used by observing variation of the kinetics of sodium ion channel in skeleton muscle cells at different time point,and SCN4A subunit in the channel is measured by real-time PCR so as to evaluate the biological effects of static magnetic field on skeletal myoblast.ResultsThe static magnetic field did not alter the characteristics of rapid activation and deactivation of Na+ inward current.The ?-? curve kept consistent with the activation curve,the inactivation curve and the recovery curve in each group.Both the number of open channel and the qPCR of SCN4A Expression did not increase with time when it did not exposed to the static magnetic field.In the 180 mT static magnetic field,the Na+open channel did not change and had no effects on activation,inactivation,after-inactivation recovery.However,the qPCR of SCN4A Expression-180mT36h,180mT 60h was significant compared with the control group.There is a trend towards an increased number of Na+ open channels with time when it exposed to the static magnetic field(280mT),which results in a right-shift of the activation curve,suggesting the difficulty in channel activation with all unaltered velocity.The diminished absolute of inactivation voltage indicated a reduced likelihood of activation,which was accompanied by accelerated recovery from inactivated state.It gave the same result after using patch clamp technique.Research conclusionThe sodium ion(Na+)channel characteristics in skeletal myoblasts of L6 rats is steady,which provide experimental basis to detect the change with increased magnetize in differ--ent time.The magnetic field possess such functions as regulating migratory potential of the charged particles in histocyte,adjusting liquid-crystal structure of biological molecule-s,changing the penetrability of coating layer,promoting metabolism and accelerating the cell growth.The study is aim to evaluate bio-stimulating effects of the magnetic field based on voltage gated Na+Channel in cell membrane.The result is showed that bio-stimulating effect of ion channels of the cell membrane in the constant magnetic field(above 280mT36h)relate to the variation of the channel structure,but it still need to be validated further from the aspect of molecular biology and cell signal transduction.Part ? The study on mechanical properties of the thermoplastic BackgroundOrthodontic treatment have effects to patients' bone and dental-jaw growth by using functional appliance.Which mainly apply in a good treatment especially when children are in the vigorous growth stage.The good treatment period should be in children vigorous growth and mixed dentition stage.In this period,the effects of functional appliance is more complete than fixed appliance.At present,the functional appliances applying in clinic mainly are made by acrylic resin that the main component is polymethyl methacrylate.The appliances in clinic have not widely been spread and applied because of its large volume,fragility and discomfort.However,with the development of the thermoplastic technology,the thermoplastic materials modified appliance becomes being used in orthodontics.The thermoplastic materials modified appliance raise patients' comfort degree and improve its esthetics.In addition,it is easily to be shaped.there are many advantages of transparent chemical curing PMMA,called self-curing acrylic resin making functional appliance in mixed dentition period,such as fine color and cheap.After using long-period,the self-curing acrylic will be more fragile and also exacerbate oral cavity peculiar smell,while the structure of thermoplastics have a stable structure because of its main component-acrylic.That is so elastic that it may not become fragile after using it for a long time.The functional appliance combined with the advantages of these two materials could apply in clinic,but there have not reported both bond strength.There are many patches with various thickness in the market,of which mechanical properties is different.ZhangNing reported that the patches with three kind of thickness(below 1mm)have changed with law,but it is no clear that the variation rules in the mechanical properties of the patches(above 1 mm)be used as making functional appliance.The experiment was performed with thermoplastic material Simona with four kinds of thickness.The Simona were tested by universal testing machine in order to compare their bending mechanical properties with different treatment and to identify their mechanical difference with various thick thermoplastic material Simona.It is also expected to provide academic reference for choosing suitable patch to make functional appliance in clinic.Combined with self-curing acrylic resin and thermoplastic material,the measurement of its mechanical properties could provide the theory basis for combined using these two materials in clinic.Research methodsExperiment I was performed at room temperature of 25,and the thermoplastic material Simona with thickness of 1.0mm,1.2mm,1.5mm,and2.0mm were involved,10 pieces of each type.The Simona were tested by universal testing machine before treatment(area was 40 mm*25 mm)and after formation with different rectangle moulds(volume was 50 mm*10 mm*5 mm)in order to compare their bending mechanical properties.It should be made four samples connected by the bulk(volume is 40mm*50mm*1.2mm)in experiment ?.All of thermoplastic material in A forming group is pressed in vacuum.In D forming group,the samples consist of transparent PMMA with single-formation synthesis.In B and C forming group,the samples are made by thermoplastic material and PMMA.The experiment is to test bending mechanical properties by universal testing machine,and then calculate date in each group including the modulus,the yielding strength-load,maximum load,the yield strength,maximum-stress,maximum displacements.Finally,the result obtained are statistical-ly analyzed by using SPSS 13.0 soft package.Research conclusionIt was found that the modulus,yield strength and the maximum stress of the Simona 2.0 mm were the highest with different treatment(P<0.05),and there was no fracture in Experiment I.According to Experiment II,the modulus in D forming group were the highest and in A forming group were the lowest.Statistic difference was found in A forming group but not in B and C forming group.The data including yield strength-load,maximum load,yield strength-stress,maximum stress,which were used by the comparison between two data in each group.The result showed a statistic difference and an upward trend(P<0.05).The displacement was the highest in A forming group and the lowest in D forming group.The materials with different thicknesses and shapes have different mechanical properties.The Simona 2.0 mm is suitable for functional appliance base on its high mechanical properties.The test samples made by the thermoplastic materials and PMMA,was no fraction as increasing the plasticity of the materials.Meanwhile,the samples were elastic because of its materials.The functional appliance could be adopted a making process method combined the thermoplastic and PMMA as its main materials,which would increase materials'intensity under constant temperature and press.Part ? The clinical analysis of thermoplastic magnetic orthodontic technique in the treatment of early Angle class ? malocclusionBackgroundThe early and skeletal Angle class ? malocclusion has been a difficult but hot issues during orthodontic treatment.There has report from FuMinKui in 2005 that incidence of Angle class ? malocclusion in China was 3.69%.The most of patients have got class III malocclusion in the mixed dentition period.The growth increment and direction of craniofacial structure may be affected by changing external factors for patients in growth and development stage.Many scholars have gradually focused on improving soft tissue profiles among children.Good-shaped chin is a part of mandible,which plays an important role in appearance.There is a subtle relation between chin and orthodontics.The study is aim to modify thermoplastic magnetic appliance through utilizing the theory that magnetic is liable to form reciprocal anchorage in oral based on previous research,to investigate using thermoplastic magnetic appliance in the treatment of early and mild skeletal Angle class ? malocclusion and to analyze hard tissues,soft tissues profile and the mandible morphological changes at the baseline and after the treatment by cephalometric analysis.So it may promote the growth of maxillary and limit the development of mandible.Meanwhile,it is easily to make and comfortable to wear for 24 hours a day,but it has not been proved about its long-term effect in clinic.The study will comprehensively compare the appliance made of PMMA in clinic.It is observed whether the appliance is apt to form bacterial plaque,and to affect its hygienic condition with increasing using time compared with the special environment of thermoplastic materials in oral,which contribute to provide reference for clinics.Research methodsExperiment I:Twelve patients with early and mild skeletal Angle class ?malocclusion were treated with thermoplastic magnetic appliance.The result from cephalometric analysis of hard tissues,soft tissues profiles and the mandible morphological changes at the baseline and after the treatment was compared.Experiment ?:Eighteen patients with crossbite were selected and divided into polymethyl methacrylate plastics group(group A)and thermoplastic materials(group B),with 9 cases in each group.The indexes of observation included the compare between clinical and operation time;Patients'feeling after using appliances;The simple inspection for module of orthodontic effects after one year;The rates of subsequent visits for the problem of appliance in one year.Experiment ?:The two groups were observed with the indexes as follows:colony counting,peculiar smell,pigmentation,soft scale.Research resultAt an average period of 10.1 months after the treatment,the patient's facial profile was improved significantly.The crossbite of anterior teeth was corrected or even overcorrected to fulfilled Angel class ? molar relationship in some cases.SNB,SND and SL decreased,whereas ANB and SE increased.No significant changes were found in SNA,angles of upper and lower anterior teeth,and Po-NB.Ns-Sn-Pos,Ns-Pm-Pos,S-Ns-Si show a significant difference(P<0.05).Sn-Ns-Si,UL-E and LL-E increased and also show a significant difference,while no significant difference occurred in S-Ns-Sn and Cm-Sn-UL(P>0.05).Bs-LLPos increased(P<0.05)and that of LL-Pos,LL-Bs-Pos,Bs-Pos-Mes decreased(P<0.05)compared with pre-treatment.The indexes including LL-E,Bs-E,Mes-E all diminished.There were no obvious difference on the indexes including the clinical and operative time,the patient compliance,the rates of subsequent visits for the problem of appliance in one year.The difference in the indexes of the simple inspection for module of orthodontic effects after one year was no significant.Before treatment,there was no significant difference in colony counting between the two groups(P>0.05).After treatment for 6 months and 1 year.There were significant differences in colony counting,peculiar smell and pigmentation between the two groups(P<0.05),and increased with time.Research conclusionThermoplastic magnetic appliance may limit the development of mandible,and correct early skeletal Angle class III malocclusion,soft tissue profiles and improving chin soft tissue rapidly and effectively.But also it can make lower-chip line more smooth and fine,and it is comfortable to wear for 24 hours a day with easy operation.For the aspect of the patient compliance and clinical and technical operation,the thermoplastic magnetic appliance has many obvious advantages.For example,patients with the appliance do not worry about its retention,fraction and deformation,which have a good application prospect.Moreover,there also has many advantages of the appliance made of polymethyl methacrylate plastics,such as low cost and easy to maintain.The appliances are flexibly selected for patients according to their different situation.The thermoplastic materials are superior to polymethyl methacrylate plastics in oral hygiene.To achieve a good hygiene effect,it is essential to have oral health,healthy eating behaviors,maintenance and cleaning appliance.