顺序拔牙矫治安氏Ⅰ类前牙拥挤

牙列拥挤是常见的错(牙合)畸形;造成牙列拥挤的机制是牙量大于骨量,而前牙拥挤比后牙拥挤更常见,作者对85例安氏I类错(牙合)畸形患者,用顺序拔牙法进行预防性矫治取得了满意的效果。方法为:①拍全颌曲面断层片,推断全部恒牙及牙胚均存在。②在恒侧切牙已萌出,恒尖牙和第一双尖牙根已形成1/3时,拔除乳尖牙为恒侧切牙的萌出提供间隙。③第一双尖牙在牙槽骨内即将萌出拔除第一乳磨牙,在第一双尖牙刚萌出并出现于口腔时将其拔除。结果85例患者中有59例未用任何矫治器,4例用活动矫治器稍微局整后即很满意,22例顺序拔牙后用Begg固定矫治器,全部病例均矫治良好,达到了矫治目的,全部下颌牙齿漂移后自行调整,未用任何矫治器,即达到了矫治的目的。     

第二磨牙拔除的问题

每当提到正畸拔牙这个名词时,立刻会想到的是第一双尖牙,这是因为以下原因:1.除了第一磨牙外,它常常在其它牙齿之前萌出;2.拔除第一双尖牙有利于恒尖牙萌出;3.它位于牙弓的中间,拔牙间隙可供前后牙解除拥挤。第二磨牙的大小及萌出时间上下颌第二磨牙在2(1/2)～3岁时钙化,牙冠完全形成是在7～8岁。下颌第二恒磨牙在11～13岁萌出,牙根在14～15岁仍未完全形成。上颔第二磨牙在     

安氏Ⅱ^1类错He上颌尖牙远中移位后切牙及磨牙位置变化的研究

目的探讨安氏Ⅱ1类错拔牙矫治中,上下颌磨牙及切牙的位置变化。方法选择15名11－16岁拔除四个第一双尖牙的安氏Ⅱ1类错病例,用方丝弓矫治技术,口外力加强上颌磨牙支抗,治疗前及以间断力后移上颌尖牙到与第二双尖牙接触时,进行X线头影测量及统计分析。结果上颌磨牙前移了0.9mm,比下颌磨牙整体前移少约2mm;上切牙舌侧斜移动了4.1mm;下切牙舌向移动了1.8mm,比上颌磨牙前移少1mm。结论控制上颌磨牙支抗并增大弓丝的滑动,可使上颌切牙在未主动内收前舌向移动;减少下颌尖牙的后移则有利于下颌磨牙的前移。     

拔牙与不拔牙矫正治疗对牙弓宽度的影响

目的比较拔牙与不拔牙矫正治疗对牙弓宽度的影响。方法选择25例拔除第一或第二前磨牙的正畸患者,25例未拔牙的正畸患者,测量治疗前后的牙颌模型,记录上、下颌牙弓宽度,其中包括尖牙间、前磨牙间及磨牙间宽度,比较拔牙与不拔牙矫正治疗对牙弓宽度的影响。结果上、下颌尖牙牙弓宽度的比较中,拔牙组比不拔牙组大,上颌大1.79mm,下颌大1.95mm,(P<0.01)。磨牙区牙弓宽度差异无显著性。结论拔牙治疗不会导致尖牙区宽度的减小。     

安氏Ⅱ~1类错上颌尖牙远中移位后切牙及磨牙位置变化的研究

目的　探讨安氏Ⅱ1类错拔牙矫治中 ,上下颌磨牙及切牙的位置变化。方法　选择 15名11— 16岁拔除四个第一双尖牙的安氏Ⅱ1类错病例 ,用方丝弓矫治技术 ,口外力加强上颌磨牙支抗 ,治疗前及以间断力后移上颌尖牙到与第二双尖牙接触时 ,进行X线头影测量及统计分析。结果　上颌磨牙前移了 0 9mm ,比下颌磨牙整体前移少约 2mm ;上切牙舌侧斜移动了 4 1mm ;下切牙舌向移动了 1 8mm ,比上颌磨牙前移少 1mm。结论　控制上颌磨牙支抗并增大弓丝的滑动 ,可使上颌切牙在未主动内收前舌向移动 ;减少下颌尖牙的后移则有利于下颌磨牙的前移     

正畸拔除下颌第一磨牙对第三磨牙位置变化的影响

目的：通过比较正畸采用不同拔牙模式后第三磨牙位置的改变,探讨拔除下颌第一磨牙后对第三磨牙萌出的影响。方法：选择拔除下颌第一磨牙（15例）、第一前磨牙（20例）及非拔牙（20例）的3组青少年病例,3组患者正畸治疗前后及保持2年后拍全颌曲面断层片,对第三磨牙萌出的各项评价指标变化量进行比较研究。结果：在正畸治疗前后,第三磨牙萌出间隙改变量,拔第一磨牙组大于拔第一前磨牙组和非拔牙组,且差异均具有统计学意义。第三磨牙萌出角度改变量,拔第一磨牙组大于拔第一前磨牙组和非拔牙组,且差异均具有统计学意义。正畸保持2年后萌出间隙变化量虽均有增加但不具有统计学意义,第三磨牙萌出角度变化量拔第一磨牙组大于拔第一前磨牙组和非拔牙组,且差异均具有统计学意义。结论：正畸治疗中拔除下颌第一磨牙可增大下颌第三磨牙萌出间隙,第三磨牙更加直立,对第三磨牙的萌出有利。     

安氏I类错[牙合]非常规拔牙模式的矫治体会

目的：观察安氏I类错[牙合]拔除上颌第一前磨牙，下颌第二前磨牙后对支抗的不同需求，以及对咬合关系的影响。方法：选择安氏I类错[牙合]需减数治疗病例25例，拔除上颌第一前磨牙，下颌第二前磨牙后，常规直丝弓矫治器矫治。结果：25例均获得正常覆耠覆盖，尖牙和磨牙中性关系，患者侧貌发生明显改变。结论：安氏I类错[牙合]非常规拔牙模式可消耗下颌支抗，保护上颌支抗，更好地维护了磨牙的中性关系，使疗程缩短。     

拔除第一磨牙矫治后第三磨牙萌出情况初探

目的:通过比较不同拔牙方法矫治后第三磨牙萌出的情况,评价拔除第一磨牙矫治对第三磨牙萌出的影响.方法:选取拔除第一磨牙矫治、拔除第一前磨牙矫治和非拔牙矫治3组病例(上颌各20例、下颌各30例),对全颌曲面断层片中测得矫治前后第三磨牙萌出的各项评价指标变化量进行比较研究.结果:(1)第三磨牙萌出间隙及其与牙冠近远中径的比值变化量在3组之间均有统计学差异(P<0.05),拔第一磨牙组大于拔第一前磨牙组和非拔牙组.(2)上颌第三磨牙萌出角度变化量在3组之间均有统计学差异(P<0.05),拔第一磨牙组大于拔第一前磨牙组和非拔牙组;下颌第三磨牙萌出角度的改变量在各组之间没有统计学差异(P>0.05).结论:上颌拔除第一磨牙矫治较常规矫治能明显增加第三磨牙的萌出间隙并改善其萌出角度;下颌拔除第一磨牙矫治较常规矫治能明显增加第三磨牙萌出间隙,而对于第三磨牙萌出角度3组间并无明显差异.     

正畸减数第二恒磨牙相关问题的研究进展

拔牙矫治是正畸治疗中的常规手段。在正畸减数中最常选择的牙位是前磨牙。但临床上有些患者（特别是青少年）在正畸治疗初期拔除了第一或第二双尖牙，但在矫治结束后，由于第三磨牙萌出间隙不足或萌出角度不佳，常常也需要拔除。这种情况下，患者共需拔除8颗牙齿，对患者来讲难以接受。因此在上世纪，就有学者提出拔除第二磨牙结合功能矫治器、头帽或口外弓等手段矫治各类错骀畸形，待日后第三磨牙萌出后代替第二磨牙行使功能，以此达到减少拔牙数目，保存牙列完整性的目的。     

拔除病变第一磨牙后上、下颌第三磨牙正畸近移疗效比较

目的探讨拔除病变第一磨牙后上、下颌第三磨牙近移进行正畸治疗的效果。方法收集20例第一磨牙病变同时需要进行正畸治疗的患者,平均年龄18.6岁。根据患者口内情况将患者分为2组,每组10例。第一组上颌无明显拥挤,仅拔除病变的上颌第一磨牙,下颌拔牙或非拔牙矫治;第二组下颌无明显拥挤,仅拔除病变的下颌第一磨牙,上颌牙列拔牙或非拔牙治疗。全部病例均采用方丝弓矫治器,排齐整平牙列,关闭拔牙间隙,精细调整咬合关系。结果 20例患者都达到良好的矫治效果,双侧的磨牙、尖牙均达到良好的咬合关系。上颌第三磨牙前移平均8.8个月,平均近移7.94mm;下颌第三磨牙前移平均9.7个月,平均近移7.12mm。结论上、下颌由于存在骨质结构的差异,拔除无法保存的第一磨牙后,上颌第三磨牙近移比下颌磨牙较快。扶正簧的使用使倾斜的下颌磨牙得以直立。     

Total impaction of deciduous maxillary molars: two case reports

AIM: The purpose of this report is to present two cases of totally impacted maxillary deciduous molars, considered a rarity in dental practice. BACKGROUND: Primary tooth impaction is quite rare during the development of primary dentition. Various factors contribute to the impaction of a deciduous tooth, including anklyosis, congenitally missing permanent teeth, defects in the periodontal membrane, trauma, injury of the periodontal ligament, precocious eruption of the first permanent molar, defective eruptive force, or a combination of these factors. REPORTS: Case #1: An 18-year-old male presented with a complaint of spontaneous repetitious pain in the maxillary right premolar region. The maxillary right second premolar was clinically absent. Panoramic and periapical radiographs revealed an impacted second premolar close to the inferior wall of the maxillary sinus and an impacted deciduous molar deeply embedded in bone within the maxillary sinus. Case #2: A 14-year-old girl presented with a complaint of crowding of the maxillary teeth. The maxillary right second premolar and the maxillary permanent canines were clinically absent. A panoramic radiograph revealed an impacted maxillary right second premolar and an impacted deciduous molar embedded within bone close to the inferior wall of the maxillary sinus. SUMMARY: The total impactation of deciduous teeth is a rare condition, and few cases have been reported in the literature. The condition generally affects the mandibular second deciduous molar and the maxillary first deciduous least often. In this paper, two cases of totally impacted maxillary deciduous molars are reported.     

单侧上颌尖牙阻生对牙颌三维结构的影响

目的: 采用锥形束CT（CBCT）研究单侧尖牙阻生病例牙颌的三维结构特征,评估发生上颌尖牙阻生的相关风险因素,为正畸临床早期干预提供依据。方法: 选取30例单侧上颌尖牙阻生患者的CBCT,利用Romexis软件进行三维重建,测量、比较两侧牙颌三维结构特征指标,采用SPSS17.0软件包进行配对t检验和相关数据的回归分析。结果: 阻生侧尖牙和侧切牙倾斜度明显增大,尖牙牙冠更向近中、侧切牙向远中倾斜（P<0.001）;阻生侧尖牙体积更大、侧切牙体积更小（P<0.05）,当尖牙体积增大或侧切牙体积减小时,上颌尖牙的阻生概率增加;阻生侧牙弓弧形长度更短,牙弓宽度在尖牙区和前磨牙区更短（P<0.001）,而宽度在磨牙区无显著差异（P>0.05）,两侧牙弓长度在尖牙区、前磨牙区和磨牙区无显著差异（P>0.05）。结论: 上颌尖牙阻生伴随或导致同侧牙及牙槽骨三维方向发育异常,上颌尖牙阻生的严重程度与周围牙颌结构异常密切相关,提示上颌尖牙阻生可以早期预判、诊断,且可以实施有效的早期干预。     

Degeneration of tooth germ in the developing dentition of the gray short-tailed opossum (Monodelphis domestica)

The aim of this study was to examine the developmental aspects of the dental lamina and the tooth germ of the marsupial opossum (Monodelphis domestica), and to clarify the dental formula of this animal. Specimens were 12-, 16-, and 18-d-old opossums. 3-D reconstructions were constructed from frontal serial sections. In these animals, the tooth germs of the deciduous maxillary and mandibular canine, deciduous third premolar and first molar, and the deciduous maxillary first incisor and second molar had a successional dental lamina and a replacement tooth germ. The tooth germ of the deciduous maxillary fourth incisor and the mandibular first incisor were reduced. The dental lamina was continuous in each jaw except for the deciduous maxillary first incisor. The first dentition (deciduous dentition) remained as the permanent dentition on the deciduous maxillary first incisor, and the deciduous maxillary and mandibular canine and first molar. The maxillary fourth incisor and the mandibular first incisor were the second dentition (successional dentition). Only the deciduous third premolars were replaced. These results showed monophyodonty caused by both deciduous and replacement tooth germ degeneration.     

低位乳磨牙伴下颌第一前磨牙水平阻生1例

低位乳牙是一种牙齿异位萌出,又称乳牙下沉或乳牙粘连,指乳牙高度不能达到咬合平面,多见于乳磨牙。本文报道1例左下颌第一乳磨牙粘连同时伴左下颌第一前磨牙水平阻生病例的诊治过程,并结合相关文献进行讨论。     

Conservative management of lower second premolar impaction

Lower second premolars account for approximately 24 per cent of impactions, excluding third molars, even though most reports in the literature relating to impacted teeth address the maxillary canine, with relatively few reports on the lower second premolar. Conservative management involves surgical exposure of the crown, however, subsequent premolar eruption is unpredictable. A case is described in which removal of a deciduous second molar was followed by eruption of an unfavourably inclined premolar located deep within the alveolus. Sufficient time must be allowed for eruption and in the present case 16 months elapsed before the tooth had erupted to the level of the occlusal plane.     

Therapeutic strategies for impacted maxillary canines

A disturbance in the normal eruption pattern of one or both of the maxillary canines is found in 1% to 2% of the teenagers aged ten to thirteen years. Frequently, dentists refer these patients to orthodontists who, in turn, seek the assistance of an oral and maxillofacial surgeon to retrieve the impacted canine, either by exposure alone or by exposure and attachment of a bracket and ligature for orthodontic extrusion. A common request in this procedure is the extraction of the persistent upper deciduous canine and/or, in case of an Angle Class II molar relationship, extraction of the upper first premolar. It has been shown, however, that on average 15% of these exposed or ligated maxillary canines fail to erupt. Therefore, one should be reluctant to extract the deciduous canine or the permanent first premolar before it is clear that the impacted maxillary canine will indeed erupt after surgical exposure and/or placing of a bracket and ligature for orthodontic extrusion.     

Double transmigration and hyperdontia

Transmigrated teeth are rare, though reports have increased with the advent of panoramic radiography. Ectopic eruption of canines and other dental anomalies as retained deciduous teeth and supernumerary teeth have a genetic etiology and may be linked. A case report is presented which exhibits transmigration of both a mandibular canine and lateral incisor as well as the presence of a supplemental premolar and retained deciduous molar roots. The possible etiology of these abnormalities is discussed.     

Unusual teeth transpositions: two case reports

Tooth transposition is a rare dental anomaly that is characterized by the interchanged position of two adjacent permanent teeth in the same quadrant or ectopic eruption of one tooth in the place of another. This article presents two case reports of transpositions. In the first case, a 21-year-old man presented with a left maxillary canine to molar site transposition. Radiographs showed that the canine was transposed completely. In the second case, a 35-year-old man presented with a right mandibular second premolar that had erupted between the first and second molars. Radiographs showed that the second premolar was positioned between the first and second molars. Maxillary canine to first molar site transpositions are extremely rare. To date, just eight cases have been reported in the English literature. Early loss of the first permanent molar may trigger distal migration of a developing canine bud. A mandibular second premolar erupting between the first and second molars is also a rare position anomaly that has not been reported in the English literature.     

Eruption of teeth associated with a dentigerous cyst by only marsupialization treatment: a case report

The purpose of this case report was to describe the management of a mandibular dentigerous cyst in a 10-year-old male patient. Without any clinical symptom, the lesion was detected in a routine panoramic radiograph showing a well-defined osteolytic lesion that measured 3 cm in diameter, partially surrounding the crown of the canine, first molar, and second premolar displacing the teeth to the mandible's lower border. The apex of the teeth were still open. Under local anesthesia, the patient was treated by: extraction of the left deciduous canine and first and second deciduous molars; and marsupialization of the cystic cavity. After 30 months, the premolar had erupted and an orthodontic therapy was started to maintain space for the canine.     

Delayed eruption of premolars with periodontitis of primary predecessors and a cystic lesion: a case report

Apical periodontitis after pulp therapy in a primary tooth can cause delayed eruption of the permanent successor. A case of bilateral delayed eruption of mandibular premolars is presented. The patient. a 13-year-old girl, was referred by her dentist. Oral findings showed that the right first and left second primary molars were retained. Other premolars had erupted. An orthopantomogram revealed apical periodontitis, affecting both retained primary molars. The right first mandibular premolar was impacted against the alveolar bone and root of the second premolar, and there was a large cystic lesion in close association with the left second mandibular premolar. Both primary molars were extracted, and the cystic lesion was treated by marsupialization. Fenestration and traction were performed on the right first premolar. Correct tooth alignment was achieved with orthodontic appliances. If the problem had been detected earlier, treatment of the premolars might have been easier. Clinical and radiological follow-up, therefore, of primary teeth that have undergone pulp therapy procedures should be performed until eruption of succedaneous teeth.