Development Of A Adjustable Magnetic Force Palatal Expansion Appliance With Diamond Like Carbon (DLC) Coating And The Preliminary Study Of Animal Experiments

ObjectiveThis research adopting the diamond-like coating N52NdFeB magnets,designedand developed a adjustable magnetic force palatal expansion appliance withindependent intellectual property rights, which could overcome the disadvantages ofprevious magnetic palatal expansion appliance: magnets corroding easily，magneticforce dramatic reduction with the distance increased. Through the determination ofmechanical properties and animal experimental research, the curative effect of theadjustable magnetic force palatal expansion appliance was preliminarily observed.Method1.Design and production of the adjustable magnetic force palatal expansionappliance.According to the principle that magnetic force is generated by magnet repulsionat the same level, the fault that the magnetic force is decreased dramatically with thedistance increased is overcome by combining release link with tooth spacinggroove.According to the oral required space、the magnetic force for the expansion、the precision of material processing and so on，the appropriate size of the N52typeNdFeB magnet was selected. After polishing, N52NdFeB coated withdiamond-like coating by Dual Magnetron Sputtering method, selection of high puritygraphite target, response for argon gas and methane. Then the magnet was magnetizedto saturation.According to the engineering drawing,304austenitic stainless steel platematerial was chose to process out of the stainless steel lid、the box body、the pushrod、push plate、the slider and so on by numerical control technique. And weldingaccording to the requirement. After assembled into new magnetic force palatalexpansion appliances, curve of magnetic expansion force-distance was tested byINSTRON universal dynamometer.2.Animal experiments4dogs of six months old and about8kg were matched into two groups randomly,with3dogs in experiment group and1dog in control group. In experiment group，3 dogs were weared adjustable magnetic force palatal expansion appliances withdiamond like carbon (DLC) coating. In control group, the dog was not wearedanything, Expansion lasted a month in experiment group.Before and after theexperiment, model test, CBCT observation and measurement were made. After theexperiment, Beagle dogs palatal suture cross section was made to bone sections. HEstaining was made. Then morphology of organizational change of palatal suture wasobserved under the microscope.Result1Structure and mechanical properties of the adjustable magnetic force palatalexpansion appliance.According to the principle that magnetic force is generated by Magnet repulsionat the same level, the palate was expaned. When the distance of expansion was up to3mm, the palate was continued to expand to6mm by combining release link withtooth spacing groove.Mechanical properties test of the adjustable magnetic forcepalatal expansion appliance showed the process in the first and second afterburnerwas two similar circular slow curve. The expansion force value was range of1.2-8.15N, which can meet the need of the palatal expansion.2Results of animal experiments2.1The meaument of the model in the experimental group before and after theexpansion.The average quantity of expansion between the maxillary cannines was5.64mm.The average quantity of expansion between the first molars was6.14mm. Theaverage quantity of base bone expansion between the maxillary cannines was2.81mm. The average quantity of base bone expansion between the first molars was2.29mm. But the quantity of the dental arch expansion was greater than the base bone, theproporsion of the qualntity of the base bone expansion in dental arch between themaxillary cannine expansion was49.75%. the proporsion of the qualntity of the basebone expansion in dental arch between the first molars expansion was37.30%.2.2The results of CBCT measurementsThe palatal suture was expaned after the experiment. the width of anterior teethsegment was greater than the posterior teeth segment, which was meet the result of the measurement of the model.2.3Palatal histologic changeThe palatal suture significantly broadening, growth in the number of fibroblastsand obvious, a number of the cell body larger osteoblast, which were arranged inrows and active, and having new bone formation.Conclusion:1. The Size of N52NdFeB magnet was9.00*2.73*2.30mm, which can meet thedemand of the palatal expansion.2. This study designed a adjustable magnetic palatal expansion device, Whichcould can meet the requirements of the palatal expansion. It could be repeated andadjustable by combining release link with tooth spacing groove.3. Animal experiments found that the maxillary was effectively expanded to6mm, that the palatal suture was stimulated and opened, that it could promote boneformation.