1. 牙列拥挤的治疗 Treatment of Crowed Teeth
西安交通大学口腔医学院
口腔正畸教研室

2. Definition
Teeth in the dental arch (or arch jaw) on the location or lack of space, the rules can not be arranged in a normal arch, and showed the phenomenon of overlapping dislocation.

3. Crowding is a deformity in one of the most common manifestations。It can be separate, but the majority of malformations are in conjunction with other deformities.

4. 1 pathogen of crowding Mechanism ：
1 Teeth is greater than the volume of bone mass (relative and absolute)
Teeth greater normal greater
Bone normal smaller smaller

5. Heredity factors Evolution factors
Mandibular hypoplasia Tooth number, size, shape

6. Environmental factors
Obstacles of teeth eruption
Early loss of deciduous teeth,
Molars forward Retention of deciduous teeth
Eruption of permanent teeth dislocation Oral bad habits

7. 2 Performance
Simply crowding is little effect opposite type Impact on the dental arch

8. According to the level : By model measurement
3 Degree of crowding
According to the level :
By model measurement
Mild < 5.0mm
Moderately > 5.0mm
< 8.0mm
Severe > 8.0mm

9. By location :
Anterior
Middle
Posterior

10. General treatment of dentofacial deformities
Treatment principles
1. Correction standard :individual normal occlusion
2. Treatment according to the mechanism of malformation Remove the causing

11. Treatment principles 4. In line with the growth and development of the law 5. In line with the patients own body's physiological characteristics 6. Appliance design should be simple and practical

12. The key to the treatment of crowding is gaining space.
How to effectively meet the individual physiological characteristics and keep stable of gained space is the basis for successful treatment.

13. 4 The method of gaining space
1 expansion of the dental arch width
1. orthopaedic expansion
Branch-type base frame and two forms. To open the palate raphe extended mainly to expand 0.5mm/ day, the cheek teeth to tilt less mobile. Adults need assisted rapid palatal expansion for zygomatic alveolar ridge cortical incision, reducing the resistance to expansion.

14. Haas-type
Hyrax expander

15. slow palatal expansion
rapid palatal expansion

16. pre
after

17. Dental arch expansion ：
1.0mm of Palatal expansion can get 0.7mm space
relapse rate:      10% - 30%

18. 2. Orthodontic expansion
Dental arch expansion Appliance-use activities in the spring or split spring fixed to the expansion of the expansion. Mainly to the buccal tooth inclination mobile. The general availability of gap mm. The application of the tongue by the teeth of the arch to the tilt caused by stenosis.

19. Removable appliance
Quad helix

20. 2. functional expansion FH

21. 2 Molar distalization： Removable appliance
1.Acrylic cervical occipital appliance (ACCO)
Removable appliance
Face bow
lip bumper

22. Acrylic cervical occipital appliance (ACCO)

24. Each side can get 4.0mm.
As to rely on the activities of the mobile appliance on the crown
And face-bow to the root of the combined mobile.

25. Face-bow to the root is the key to mobile-line traction to the teeth against the center is located at the top, traction generally about 150g, traction time was hours one day. Force of Oral appliance on the crown is about 30 g, required to wear all day.

27. lip bumper ：
The main role is to use the force of lip vertical mandibular molar (Upright) and molar re-gap (due to early loss of deciduous teeth); to stop the forces of muscular buccal premolar arch area to expand.

28. 3 Reducing circumference treatment ：
（1）. Indications
Adult patients;    For the bell-shaped central incisors;    Mild anterior crowding;    People with little or no dental caries

29. （2) treatment Reduce the diameter of the teeth 0
（2) treatment Reduce the diameter of the teeth mm on each side can be reduced Attention to the restoration of the original contact point
Restoration of surface finish Not suitable for patients with a higher rate of caries

30. (3) procedures Aligned teeth to normal relations
(3) procedures Aligned teeth to normal relations. Determine the number, and the order is from back to front. Separate the contact points. Fine curved nose drilling, fluoride.

31. 4 Extraction : The factors of extraction to consider: The space requirements of Correction
The adjustment of the dental arch midline Crowding of the site

32. The principle of extraction The first premolar is the first choice Generally, incisors and canines do not consider to extract
Teeth extracted should be closed to the crowding site

33. Permanent teeth germ should be chceked in Mixed dentition extraction Symmetry extraction

34. 5 The principle of correction of crowding
Mild crowding: Mild crowding can be treated by expanding the arch or molar distalization. In the mixed dentition, the leeway space can be used to disarm the crowded dentition.

35. Moderately crowded: Non-extraction treatment should be possibly considered in the growing season, like molar distalization. The direction of the face-bow is according to mandibular plane angle and height of 1 / 3 surface

36. Moderate crowding: Extraction orthodontic treatment may be considered in the non-growth season. The space obtained by extraction is mainly used to ease the crowded dentition, and the remaining space will enable the posterior teeth to move to mesial. Anchorage control should also be paid attention in the treatment of moderately crowding, especially in maxillary.

37. Severe crowding: Extraction treatment should be considered in growing and non-growing season in general. The space obtained by extraction is used to lifting the crowding. Anchorage control is the critical point in severe crowding treatment. Loss of anchorage will lead the failure of treatment.

38. Anchorage controlled manner: 1
Anchorage controlled manner:      1. Against the tooth movement by the bending such as tip-back bending .      2. Reducing the friction： such as the single point ligation      3. To increase the number of anchorage teeth： 7 band .      4. Using the opposite jaw to provide anchorage; using II, III type traction.      5. Extraoral anchorage; Top, Pillow, neck.      6. Implant Anchorage

39. 小结 crowding teeth greater bone smaller Reducing tooth Increasing bone
volume mass
Extraction Expand Reducing diameter Distraction
osteogenesis

40. Comprehensive space analysis
1 severity of crowding
2 protrusion of anteriors
3 curve of spee
4 mesial drift of anchorage molar
5 maxillofacial skeletal patterns
6 facial profile
7 growth status