Establishment Of The Perioral Muscle Pressure Measuring System And Study Of Cheek And Tongue Pressures Following Rapid Maxillary Expansion

It is more than one hundred years since Tomes initially put forward the concept of perioral muscle pressure and the Equilibrium Theory. Afterwards, plentiful results were achieved. Research on this field is of great importance in orthodontics.Maxillary constriction with posterior teeth crossbite is one of the common types of malocclusion in clinic. Treatment using Rapid Maxillary Expansion (RME) was first reported by Angell in 1860.Then,animal experiments and clinical observation were done in the following one hundred years with focus on treatment and retention after RME. However, there were few reports on the changes in perioral muscle pressures following RME treatment and retention and none domestically.In this study, a new perioral muscle measuring system was invented to measure the values and changes in cheek and tongue pressures before, after treatment and retention in order to supply experiment foundation and theoretical guiding for clinical research and treatment.The study consisted of two parts as follows:In the first part, we invented a new perioral muscle measuring system. The system comprised the hardware and software. The hardware included the resistance strain gauge transducer, the perioral muscle pressure measuring instrument and computer. The perioral muscle pressure measuring instrument consisted of connection bridge box, magnifying apparatus, direct current power supply, digital monitor and meeting gob to computer. It had stable capability and convenience. Many methods were adopted including the temperature compensating piece, connection bridge box, reliable sticking technique, slight compensation on zero digit output and magnifying circuit of high precision. For the computer, 586CPU, 8M internal storage, 1G hard plate, 1.44 soft drive, 14" indicator and one "ISA" extending slot were enough. Software designing was based on UCDOS7.0. The computer had high speed of collecting and managing data resulting in capture of the change of pressure immediately and showing it on the screen. The system was of small error and high efficiency to provide a direct and true foundation for the scientific research. The software was written with Visual C and the program had modularization structures. So the system could display, plot, count , store and inquire about the data. It is easy to the practical use in research and clinic.In the second part, the characteristics and changes of cheek and tongue pressures were studied following RME. 18 patients were selected. They were 9 boys and 9 girls aged 11.3 to 15.8 . The situation of their oral cavity were as follows: early permanent dentition, normal width in mandibular arch, constricted maxillary arch, the difference of width in upper and lower arch^4mm,no oral babbits.Pressures acting on upper and lower first molars, first premolars and cuspids were measured buccally and lingually. There were such conclusions as follows:1.Cheek pressures and tongue pressures after treatment in maxillary regions were higher than those before treatment and in mandibular regions were lower than those before treatment.2.After treatment,cheek pressures were similar with those with normal posterior overjet. Tongue was located in the normal position so tongue pressures were stable.3.The change in arch form could cause significant changes in perioral soft tissues. After retention, perioral soft tissues were adaptive to the changed arch form.4.Good retention measures after RME must be taken so that perioral soft tissues could have adaptive changes.