Correct orthodontic design is not only the basis of successful treatment, but also the key point to reflect the clinical level of orthodontists. There are many contents of orthodontic design, mainly including analyzing clinical materials, setting orthodontic objectives, establishing gap distribution or scheme, selecting appropriate orthodontic devices and anchorage forms, formulating maintenance strategies and so on.

        Orthodontic design steps

        Interrogation is the first step of the design step. The purpose of interrogation is to understand the motivation of patients, enhance mutual trust, and explore the pathogenesis and factors that may affect treatment. The next step is the clinical examination, which has been described in detail in the previous children's chapter. The examination should be combined with the patient's visual and palpation, model, X-ray film, photos and other data, including the general health status, face shape, jaw shape and relationship, tooth arrangement and occlusal relationship, oral and jaw function, surrounding soft tissue, etc

        Through the above process, we can check out a series of problems of patients, collect these problems, communicate with patients, and then arrange the problems according to the priority of these problems and establish a list, which can make both patients and doctors have a clear purpose. Combined with the list of problems, design various possible treatment schemes, further communicate with patients, achieve informed consent and formulate the design scheme. We should change the paternalistic scheme formulation strategy that was dominated by our students in the past. Our students should consider possible child treatment schemes in combination with the problems of patients, describe the expected objectives, precautions, advantages and disadvantages of various treatment schemes, and determine the scheme through consultation between patients and doctors in combination with their own conditions. At the initial stage of treatment, we should reach a consensus with patients: due to the complexity of orthodontic treatment, the treatment plan initially formulated may be changed according to the specific situation in the process of orthodontic treatment. For example, non subtractive correction will be changed to subtractive correction occasionally in the process of orthodontic treatment. Patients can give informed consent to the correction plan, which makes it easier to get the cooperation and trust of patients in the later treatment and reduce the contradiction between doctors and patients. Non subtractive design

        In clinical treatment, most patients need to provide space to solve common problems such as crowding, protrusion, deep powder coating and so on. Methods for providing gaps can be divided into two categories: non subtractive methods and subtractive methods. Non subtractive methods include adjacent enamel removal, expansion of arch width, lip development of anterior teeth, and far and medium grinding teeth.

        l. Adjacent surface Deglazing

        Indications: 1 degree dentition crowding; Adult patients; A tooth with a bell shaped crown; Upper and lower arch size

        The proportion is not adjusted; Patients with good oral hygiene and less prone to dental caries.

        This method can avoid tooth extraction and adjust the size and proportion of dental arch. Adjacent enamel removal is limited by the thickness of enamel on the adjacent surface of the tooth and the width of the proximal and distal edge of the crown and neck. Generally speaking, the thickness of the adjacent surface of a tooth that can be removed is 0.25mm. In addition, indications should be strictly selected for adjacent surface Deglazing. In the process of operation, pay attention to keep the correct adjacency relationship between teeth, and apply krypton to the deglazed surface. After enamel removal, patients should be informed to pay attention to the maintenance of oral hygiene to prevent caries.

        2. Arch width expansion

        Some studies have shown that the bone changes caused by maxillary arch expansion before the peak of individual growth and development are more significant. According to the research of Michigan University student growth and development center, if the arch width of patients in mixed dentition stage is less than 31mm, only

        Depending on the growth and development, the width of dental arch is difficult to reach the normal value. At this time, arch expansion treatment is particularly important. Dental arch expansion includes orthopedic expansion, functional expansion and orthodontic expansion. It is mainly applicable to the cases of crowded dentition caused by dental arch stenosis or backward teeth. Orthopedic expansion and functional expansion are generally suitable for thousands of cases with growth and development potential, while orthodontic expansion can also be used for thousands of adults. Some studies have found that before the age of 12, the central fissure can be opened and the dental arch can be widened by bone deposition. After the age of 16, it is more the change of teeth, while the change of midriff gradually decreases. In the process of dental arch expansion, whether it is the opening of the ridge raphe or the change of teeth, the posterior teeth will inevitably tilt to the cheek and the ridge tip will sag, resulting in pick-up interference, causing the lower jaw to rotate downward and backward. Therefore, the expansion arch should be used carefully in the cases of large buccal inclination, open tendency and high angle of thousands of teeth. In order to prevent recurrence after arch expansion, we should first emphasize over correction, and it is best to use the original arch expansion device for 3 months.

        3. Labial development of anterior teeth. Labial development of anterior teeth is suitable for mild cases with crowded anterior teeth and upright anterior teeth or tongue inclination. On the fixed appliance, the vertical extended curved lip can be used to develop the anterior teeth; Or use 0 (omega) curve in the buccal canal of molars. When the arch wire in the front of the curve is not in the groove, leave a 1mm gap with the lip surface of the anterior teeth. After the arch wire is ligated into the groove, apply a lip inclined force skid to the anterior teeth.

        4. Push the grinding teeth to the far center

        Push the molar to the distal center, that is, through various orthodontic devices and punishments, the molar will be upright to the distal center or move as a whole, so as to increase the length of the arch, obtain the gap and relieve the crowding of the dentition. It is suitable for thousands of mild dentition crowding cases to push the grinding teeth to the far middle; Or deep coverage of the anterior teeth, distal relationship of the molars, pushing the molars to the distal center can correct the molars to neutral relationship, and retract the anterior teeth to normal coverage. When pushing the molar to the far center, the second molar whisker has not yet erupted, and the third molar is best missing.

        The commonly used device for pushing and grinding teeth to the far side is extraoral arch, but it needs the cooperation of patients. Use the traction force of extraoral bow for at least 12 hours on each side every day. If the wearing time is insufficient, it will not play the role of pushing and grinding teeth to the far center. In addition to the extraoral arch, the intraoral ridge side fixed appliance can also be used, such as

        Pendulum appliance. This kind of appliance does not need the cooperation of patients, but there will be more or less anterior tooth loss of resistance. In addition to the traditional orthodontic devices, implant anchorage can now be used to push the molars distally