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尖牙在口腔中具有重要的作用:牙根粗壮,可以支撑口角,维持面部的美观、丰满;具有强大的咀嚼功能,常常作为修复设计中的基牙。但是尖牙尤其是上颌尖牙是最常见的阻生牙之一,可以由于拥挤等多种原因造成阻生。尽可能的将阻生尖牙导萌至正常位置是正畸医师希望达到的目标,但是并不是所有的上颌阻生尖牙都能牵引至正常的位置。导致导萌失败的原因常有以下几种:1.年龄因素青少年的上颌尖牙导萌的成功率较高,甚至可以达到100%。而成年人的失败率较高,即使检查未发现异常,也可能导萌失败。30岁以上的病人尤其应注意。2.定位诊断有误牙科CT广泛应用前,对阻生尖牙的定位主要依靠对不同角度照射的根尖片的分析、临床检查,甚至是凭检验判断。这可能造成对尖牙定位的有误,不能将阻生牙按照预想牵引至正常位,或不当的施力方向引起邻牙的牙根吸收、松动。3.支抗控制不足牵引上颌尖牙常需要加强支抗,尤其对于双侧阻生的病人。若支抗不足会造成邻牙的压低、倾斜,前牙开合,导致失败。4.暴露位置不当或损伤阻生牙暴露过大或暴露位置的位置不当易引起釉牙骨质界的损伤,引起根骨黏连,一般暴露的范围以能粘接正畸附件为宜。5.骨黏连骨黏连一般的影像学检查很难诊断,临床上常见一些典型特征,例如对正畸的牵引力没有反应,邻牙发生明显的支抗丧失。6.侵袭性牙根颈部吸收(ICRR)ICRR一种进行性、侵袭性、破坏性的牙外吸收,临床上少见。发生于紧靠上皮附着下的牙根表面,多位于根颈部。ICRR早期并无症状,进展快,ICRR可造成牙颈部周围骨质沉积,与周围的骨质黏连,造成导萌失败。7.牵引链与周围组织的黏连此类原因较少见,主要由于粘接附件后,没有早期加力牵引尖牙,发生了牵引链与周围骨组织的黏连,造成导萌的失败。建议粘接附件后早期加力。除上述因素外,还可能有其它因素,如病人的依从性差等。临床上在对此类患者诊治时,需要仔细分析、检查,充分沟通,防止医患纠纷。
Fangs have an important role in the oral cavity: stout roots, can support the mouth angle, maintain facial appearance, fullness; has a strong chewing function, often as a repair abutments in the design. But the canine, especially the maxillary canine is one of the most common impacted teeth that can be impacted due to crowding and other causes. As much as possible the introduction of impacted canines to the normal position is the goal orthodontists hope to achieve, but not all maxillary impacted canines can be towed to their normal position. Lead to Meng failure often the following reasons: 1. Age factors adolescent maxillary canine adorable success rate is high, even up to 100%. The failure rate of adults is high, even if the examination found no abnormalities may also lead Meng failure. In particular, patients over the age of 30 should pay attention. 2. Positioning diagnosis is wrong Before dental CT is widely used, the positioning of impacted canines rely mainly on the analysis of different angles of the apical films, clinical examination, or even test to judge. This may result in incorrect positioning of the canine, can not be impacted teeth as expected to normal traction, or improper direction of force caused by the adjacent tooth root absorption, loosening. 3. Insufficient support control traction maxillary canine often need to strengthen the support, especially for patients with bilateral impaction. If the lack of support will cause the adjacent teeth down, tilt, opening and closing of the anterior teeth, leading to failure. 4. Improper exposure or injury Impacted teeth exposed or placed in an inappropriate position can easily lead to enamel cementum injury, causing the root bone adhesion, the scope of the general exposure to be able to adhere to the orthodontic attachment is appropriate. 5 bone adhesion bone adhesion imaging is difficult to diagnose the general diagnosis of some common features such as orthodontic traction, for example, there is no obvious loss of adjacent teeth. 6. Invasive root neck absorption (ICRR) ICRR A progressive, invasive, destructive absorption of the teeth, clinically rare. Occurred next to the epithelium attached to the root surface, mostly in the root of the neck. ICRR asymptomatic early, rapid progress, ICRR can cause bone deposition around the neck, with the surrounding bone adhesions, resulting in the introduction of Meng failure. 7. Traction chain and the surrounding tissue adhesions Such reasons are rare, mainly due to adhesive attachment, there is no early force traction canines, the traction chain and the surrounding bone tissue adhesion, resulting in the failure of the guide Meng. It is recommended to attach the attachment after the early force. In addition to the above factors, there may be other factors, such as poor patient compliance. Clinical diagnosis and treatment of such patients, the need for careful analysis, inspection, full communication, to prevent doctor-patient disputes.