The following factors should be taken into account when deciding orthodontic tooth extraction.1 the crowding degree of teeth was measured di
The following factors should be taken into account when deciding orthodontic tooth extraction.
1 the crowding degree of teeth was measured directly. The congestion of each 1mm requires 1mm clearance of the dental arch. The greater the crowding degree, the greater the possibility of tooth extraction.
2 the degree of dental arch protrusion to the front of the tongue to move, to restore the normal position requires arch gap. The incisal edge of the lower incisor moved 1mm to the lingual side, which required 2mm of the dental arch. Incisor protrusion, the greater the possibility of tooth extraction.
3.Spee curve height in the mandibular arch model to measure the second premolar buccal cusp to the vertical distance between the plane and lower anterior teeth and second molar buccal groove formation, Spee curve height. Each level the 1mm Spee curve to arch space 1mm.
4 anchorage molar extraction space considering forward should be accounted for in the determination of premolar tooth. If the extraction treatment, when closing gap Anchorage Molar forward is inevitable. The number of orthodontists use different measures to control the premolar by anchorage, clearance of premolar accounted for less than the tooth gap 1/4; use medium anchorage for 1/4 - 1/2; weak anchorage of at least 1/2.
There are three types of 5 vertical facial facial vertical development, usually below the steepness of the mandibular plane to distinguish three. The normal SN MP vertical facial angle was 34.3 degrees (+ 5 degrees), FH MP angle was 27.2 degrees (4.7 degrees). When SN - MP angle greater than 40 degrees, or FH - MP angle greater than 32 degrees, for the vertical overgrowth, known as high angle cases. SN - MP angle of less than 29 degrees or FH - MP angle less than 22 degrees, reflecting the lack of vertical development, is a "low angle" case.
On the issue of orthodontic tooth extraction, high angle cases and low angle cases have different considerations: high angle cases extraction standards can be relaxed, low angle cases to strictly grasp the extraction. This is because:
The high angle cases of chin after shrinking, at the end of treatment should be to maintain the upright incisor, nose lips Chin - - coordination relationship; more upright incisor can compensatory skeletal vertical adjustment, establish the morphology and function of lower incisor relationship between the proper. Low angle cases the situation is just the opposite, the majority of patients with chin, appropriate compensatory labial inclination of incisors, which is conducive not only to the surface, but also conducive to the function of incisor.
The high angle cases of masticatory muscles are weak, the jaw bone density is low, easy to move, Anchorage Molar increased, closing extraction space more easily; at the same time for opening and closing molars moved forward correct high angle cases is often accompanied by the tendency of anterior teeth. Low angle cases on the contrary, chewing force, bone density, molar anchorage is not easy to reach, increase extraction space mainly by anterior teeth closed distal movement, the correction of excessive tooth adduction to low angle cases is often accompanied by the anterior deep overbite.
Adopts the method of molar distalization or expand dental arch aligned dentition, mandibular plane angle can cause the opening, the high angle cases surface and anterior teeth overbite were adversely affected, but for the low angle cases are more favorable.
In determining the tooth tooth position at high angle and low angle cases is different and can control the anterior teeth of anterior teeth and high angle cases if the removal of posterior teeth; low angle cases should be removed by extraction if necessary, arch front teeth, it is not only easy to close the extraction gap, and is conducive to the bite open.
6 sagittal facial type ANB mandibular teeth when coordination, bow shaped angle is normal, if the need for extraction, usually on the dental arch and symmetry extraction (unless the Bolten index discrepancy). But if there is the upper and lower teeth bow shaped relationship is not adjustable, decide whether extraction should be considered when the difference between the upper and lower dental arch. Class II malocclusion on the relative rate of maxillary and mandibular arch is on ANB, to compensate for the large angle, bones, the end of treatment can be slightly proclined incisor, mandibular tooth should be cautious. III malocclusion on the contrary, because the relative deficiency, relative maxillary mandibular angle ANB is too large, small, at the end of treatment allows the upper incisor labial inclination of lower incisors slightly, slightly lingual inclination to compensate, class III skeletal deformities of the maxillary teeth with special care.
7 facial soft tissue profile in the determination of extraction and nonextraction orthodontic treatment, can not be ignored on the soft tissue profile, especially the analysis and evaluation of the nasal cavity and the relationship between the lips - chin. There are two commonly used measurement indicators.
The upper and lower lip to esthetic plane from the aesthetic plane is composed of nose and soft tissue pogonion connection.
The formation and labrale superius nasolabial angle nasal columella, nose angle.
8 the growth and development of dental crowding, especially crowded, in determining whether or not to take into account the other factor is the growth and development. Evaluation of growth and development to determine the patient's current stage of development, the choice of appropriate treatment. The treatment of simple crowding can be carried out in the period of rapid growth of youth, complicated with the complicated relationship between the jaw and jaw. If we consider the control of the growth of the jaw, we should treat it in the first 1 to 2 years of rapid growth. Growth assessment also includes the process of orthodontic treatment in patients with craniofacial growth forecast. Because of the difference between the normal and the wrong and the differences among the individuals, the average growth data of the normal combination can be used to predict the growth errors of the patients with malocclusion.