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第一恒磨牙在萌出过程中过于偏近中可导致第二乳磨牙牙根吸收。第一恒磨牙异位萌出常常造成间隙丧失和牙弓长度减少,严重者可导致第二乳磨牙早失。第一恒磨牙异位萌出分为可逆性和不可逆性,对于不可逆性异位萌出应进行积极的治疗。治疗方法包括主动治疗和被动治疗。前者常用的方法有分牙法以及采用推第一恒磨牙向后的装置;后者通常采用截冠或拔牙的方法。本文对第一恒磨牙异位萌出的临床表现和常用的治疗方法进行了阐述。     

Resorption of incisors after ectopic eruption of maxillary canines: a CT study

The purpose of the study was to analyze the extent and prevalence of resorption of maxillary incisors after ectopic eruption of the maxillary canines in a sample of subjects referred to an orthodontic specialist clinic for consultation. The subjects consisted of 107 children, 39 boys and 68 girls, between 9 and 15 years of age (mean 12.5 years), with 156 ectopically and 58 normally erupting maxillary canines. All children were subjected to a basic clinical and intraoral radiographic investigation. These radiographs were supplemented with computerized tomography (CT) of the upper alveolar bones in order to get more precise information on the positions and relationships between the maxillary canines and adjacent incisors and to evaluate resorptions on the roots of the incisors. The results showed that, relative to the roots of the adjacent incisors, the crowns of 21% the ectopically positioned canines were located to the buccal, 18% to the distobuccal, 27% to the lingual, 23% to the distolingual, 5% apically and 6% between the central and lateral incisors. Ninety-three percent of the ectopically positioned canines were in contact with the roots of the adjacent lateral incisor and 19% were in contact with the central incisor. The corresponding figures for the normally erupting canines were 49%. Resorptions on the roots of the incisors adjacent to the ectopically positioned canine occurred in 38% of the laterals and in 9% of the centrals. The resorptions were graded and tended to be extensive. Among the 58 resorbed lateral incisors, resorptions were slight in 31%, moderate in 9%, and severe with pulpal involvement in 60%. The corresponding figures for the 14 resorbed centrals were 36%, 21%, and 43%, respectively. About 60% of the resorptions involved the middle and apical thirds, the tip of the apex not included. On the sides with normally erupting canines, 3 lateral maxillary incisors were slightly or moderately resorbed distally. In all, 51 of the 107 subjects with ectopically erupting maxillary canines (48%) had resorbed maxillary incisors during the eruption of the maxillary canines. There were statistically significant correlations between ectopic eruption of the maxillary canine, contacts between the teeth and resorptions on the adjacent incisors. It was concluded that resorption on maxillary incisors after ectopic eruption of the maxillary canines is a more common phenomenon than previously reported and has to be considered in all cases with seriously diverging eruption of maxillary canines. It was also concluded that the resorptions of the roots of the incisors were caused by pressure during the eruption of the adjacent, aberrant canine. Finally, it was shown that CT scanning substantially increased the detection of root resorptions on incisors adjacent to ectopically erupting maxillary canines (about 50%). The sensitivity of intraoral films was low when diagnosing the resorptions, being calculated to 0.68.     

第一恒磨牙异位萌出治疗方案选择的考量

第一恒磨牙异位萌出分为可逆性异位萌出和不可逆性异位萌出.第一恒磨牙异位萌出的临床危害主要是造成间隙丧失、牙弓长度减少等.本文通过3例推第一恒磨牙向远中开展间隙的病例,阐述第一恒磨牙异位萌出治疗方案选择的考量.     

Palatally ectopic canines: Closed eruption versus open eruption

This paper reviews the available evidence supporting 2 commonly used methods of surgically exposing palatally ectopic canines. The closed eruption method (a bonded attachment is placed at operation and the palatal flap is sutured back intact) is compared with the open eruption method (a window of palatal mucosa is excised and the canine allowed to erupt naturally). The choice of surgical technique is reviewed in terms of the long-term periodontal implications, the rate of repeat surgery, and treatment time.     

上颌腭侧阻生尖牙非手术与手术助萌的比较研究

目的探讨上颌腭侧阻生尖牙通过正畸开辟间隙等非手术助萌的适应证、矫治时间及其临床效果。方法选取9例患者的12颗上颌腭侧阻生尖牙为研究对象,通过曲面全景及头颅侧位片判断阻生尖牙在颌骨内的位置、牙齿的发育阶段及患者骨成熟阶段,通过正畸治疗配合头帽口外弓为阻生尖牙开辟间隙,定期拍摄曲面全景片观察阻生尖牙的萌出潜力。结果 7颗阻生尖牙自动萌出,3颗阻生尖牙采取外科开窗联合正畸牵引治疗,2颗阻生尖牙选择外科拔除。结论正畸开辟间隙后阻生尖牙成功萌出的主要因素可以概括为:萌出路径无干扰、骨成熟早期,根尖孔未闭合,而骨发育阶段比牙发育阶段更有指导意义。     

上颌埋伏尖牙非手术助萌的正畸治疗

[摘要] 目的 探讨上颌埋伏尖牙非手术助萌正畸治疗的适应证及其临床效果。方法 选取10～15岁上颌埋伏尖牙患者20例,应用螺旋CT三维重建技术对其进行诊断,明确埋伏尖牙颌骨内位置、方向及牙根发育情况,选取适合病例12例通过正畸手段为埋伏尖牙开辟间隙,等待其自行萌出;8例采用外科翻瓣导萌术牵引导萌。结果 12例非手术助萌患者,正畸拓展足够间隙后经3～10个月上颌埋伏尖牙均自行萌出至正常位置,牙周附着健康;8例外科手术导萌患者,上颌埋伏尖牙正畸牵引到位后均有不同程度的牙周附着丧失,影响龈缘美观。结论采用螺旋CT三维重建技术可以立体直观的提供埋伏尖牙的信息,为临床医师明确诊断及制定治疗方案提供依据,减少手术适应证,使用非手术助萌的方法可使上颌埋伏尖牙自行萌出,避免手术创伤痛苦,萌出后牙周附着好。     

弹弓式磨牙远移器治疗上颌第一恒磨牙异位萌出

目的评价使用弹弓式磨牙远移器治疗第一恒磨牙异位萌出的临床效果。方法选择替牙期不可逆性第一恒磨牙异位萌出患者8例,男3例,女5例,年龄6.8~9.5岁,平均8.6岁。所有病例均存在不同程度的第二乳磨牙远中根吸收。采用弹弓式磨牙远移器标准型或简化型矫治器治疗,推第一恒磨牙向远中移动,使第一恒磨牙与第二乳磨牙远中面脱离接触并最终萌出到正常位置。结果所有病例第一恒磨牙牙冠均向远中移动并竖直,与第二乳磨牙脱离接触。治疗时间1.5~4.0个月,平均2.2个月。结论弹弓式磨牙远移器是治疗第一恒磨牙异位萌出的有效方法。     

Tooth resorption associated with the eruption of maxillary canines

Six cases of root resorption of lateral incisors, associated with buccally displaced maxillary canines are presented. In each case, the clinical appearance is described followed by a discussion drawing attention to the possible common features and the importance of a detailed radiographic investigation.     

Concurrent relationship between additional canals of mandibular first molars and maxillary first molars using cone-beam computed tomography

Objective

To investigate the bilateral concurrence and relationships between distolingual (DL) roots and DL canals of the mandibular first molars and second mesiobuccal (MB2) canals of the maxillary first molars using cone-beam computed tomography (CBCT).

Methods

A total of 150 CBCT images showing all mandibular and maxillary first molars were retrospectively investigated in a South Korean subpopulation. The patient age, sex, positions of first molars, and presence of roots and canals were assessed. The frequency, bilateral concurrence of DL roots, DL canals, and MB2 canals, and concurrent relationship of DL roots or DL canals with MB2 canals were investigated. Data were analyzed using Fisher’s exact test and odds ratios from binary logistic regression.

Results

The prevalences of DL roots, DL canals, and MB2 canals were 24.7, 42.7, and 56.0 %, respectively, and showed significant bilateral concurrence. A concurrent relationship between DL roots and MB2 canals was not demonstrated, whereas the presence of a DL canal was significantly correlated with the presence of an MB2 canal on the same side.

Conclusions

The presence of a DL root of the mandibular first molar, a strong ethnic characteristic, could not predict the presence of an MB2 canal of the maxillary first molar. The correlation between DL canals and MB2 canals on the same side and the significant bilateral concurrence, whether present or absent, of DL roots, DL canals, and MB2 canals can aid clinicians in the prediction of additional canals in the first molars.