Palatally impacted canines: aetiology of impaction and the scope for interception. Report of cases outside the guidelines for interception

Patients with palatally impacted canines have an increased incidence of missing or anomalous lateral incisors adjacent to the impacted canines. Their arches are often uncrowded and this, in part, is linked to the increased incidence of missing or anomalous lateral incisors. Other teeth are also more frequently missing. The present guidelines for the relief of palatally impacted canines by extraction of the deciduous canine require that the patient is aged between 10–13 years and that normal space conditions are present. Two successful case reports are presented which were outside the recommended guidelines. The technique of relieving a palatal impaction by extraction of the deciduous canine has wide application.     

Maxillary incisor impaction and its relationship to canine displacement.

This study aimed to examine the eruption status of unerupted maxillary permanent canines in patients who also had an impacted central incisor. Seventy-five unilateral cases of the incisor anomaly were retrospectively examined. Using the initial panoramic films, we assessed the positions of the ipsilateral and contralateral canines and the lateral incisors and the timing (eruption progress) of the canines. The final position of the canines was evaluated from patient records and progress photographs. The data showed a significant increase in prevalence and severity of displaced canines in the ipsilateral side (41.3%) compared with the contralateral side (4.7%). Palatally displaced canines occurred in 9.5%, buccally displaced canines in 30.2%, and canine-lateral incisor transposition in 1.6% of the patients. Half of the buccally displaced canines in the ipsilateral side were pseudotransposed with the adjacent lateral incisor. The eruption timing of ipsilateral undisplaced canines was either similar or delayed, relative to the contralateral tooth, but never accelerated. The ipsilateral lateral incisor was strongly angulated because of a more distally located apex (5 mm) rather than a mesially tipped crown. The ipsilateral canine was relatively more superiorly positioned (undererupted). Patients who had trauma had a significantly higher prevalence and severity of canine displacement and more distally displaced lateral incisor apices. Initial height of incisor impaction did not influence the results. These data provide evidence of a significant environmental influence of an impacted maxillary central incisor in delaying and altering the eruption path of the ipsilateral maxillary canine.     

上颌中切牙与尖牙同时阻生的临床特征分析

目的分析上颌中切牙与同侧尖牙同时阻生病例的临床特征。方法选择上颌中切牙与同侧尖牙同时阻生病例21例,分析上颌中切牙阻生类型与尖牙阻生情况,测量阻生侧及对侧侧切牙发育或萌出异常情况。结果与中切牙阻生同时发生的尖牙76.2%为唇侧阻生,其中完全易位与不完全易位占唇侧阻生尖牙的68.8%,尖牙唇侧阻生病例中侧切牙根远中倾斜和伴牙冠近中倾斜者占87.5%,尖牙唇侧或腭侧阻生病例中,出现锥形或过小等畸形侧切牙的比例分别为31.25%和40.00%。上颌中切牙与尖牙不同阻生类型患者,前牙反牙合比例都超过40%,且多为牙型反牙合。结论与中切牙阻生同时发生的尖牙阻生多为唇侧阻生,与中切牙阻生类型无关,与侧切牙根远中倾斜高度相关,尖牙完全易位与过小或锥形等畸形侧切牙有关。     

The etiology of maxillary canine impactions

The etiology of tooth impactions has long been related to an arch-length deficiency. This is valid for most impactions, but not for palatal impaction of the maxillary canine. This study shows that 85 percent of the palatally impacted canines have sufficient space for eruption. The bud of the maxillary canine is wedged between the nasal cavity, the orbit, and the anterior wall of the maxillary sinus. The buds of the lateral incisor and the first premolar are located behind the canine's palatal surface. An arch-length deficiency will not allow the maxillary canine to "jump" the buds, the nasal cavity, or the sinus in order to reappear in the palate. A canine can be palatally impacted if an extra space is available in the maxillary bone. This space can be provided by (1) excessive growth in the base of the maxillary bone, (2) space created by agenesis or peg-shaped lateral incisors, or (3) stimulated eruption of the lateral incisor or the first premolar. In those conditions the canine is free to "dive" in the bone and to become palatally impacted. A dysplasia in the maxillary-premaxillary suture can also modify the direction of the maxillary canine's eruption.     

The etiology of palatal displacement of maxillary canines.

OBJECTIVES: To test the hypothesis that palatal displacement of the maxillary canine is completely under genetic influence. DESIGN: A randomized controlled design studied cases affected by a severe expression of lateral incisor anomaly on one side and by milder expression of the same anomaly on the other. Comparison of frequency of occurrence of unilateral palatally displaced canine measured in each. Each side acted as control for the other within the same individual. SETTING AND SAMPLE POPULATION: The Departments of Orthodontics of the Universities of Jerusalem and Tel Aviv and in private practice. From approximately 12,000 consecutively treated patients, all those exhibiting an anterior maxilla with a missing lateral incisor on one side, a peg-shaped or reduced lateral incisor on the other, and a palatally displaced canine (n = 19). OUTCOME MEASURE: Missing lateral incisors, peg-shaped, and reduced lateral incisors (all genetically determined characters) have been shown to be associated with palatal displacement of the canine. The canine displacement is presumed by some authorities to be similarly genetically determined. If this is so, then the impacted canine should occur with equal frequency on either side in the patient with a missing lateral incisor on one side and a peg-shaped or reduced lateral incisor on the other. RESULTS: The canine aberration occurred far more frequently on the side of the diminutive lateral incisor. CONCLUSION: There is an environmental factor involved in the palatal displacement of maxillary canines.     

The sequential hypothesis of impaction of maxillary canine – A hypothesis based on clinical and radiographic findings

The aetiology of impacted maxillary canines remains obscure. Numerous researchers have focused on identifying specific and non-specific aetiological factors responsible for canine displacement. Currently, the two most popular hypotheses that have gained consensus worldwide are the guidance theory and the genetic theory. However, no single hypotheses, can completely explain the aetiology of impaction of maxillary canines. This retrospective study was used to develop and postulate the aetiology of both buccally and palatally impacted maxillary canines. The study was conducted on a sample of 533 patients for whom the pattern and distribution of the impacted maxillary canines, sex differences, the dental age of the patients, dental anomalies and various geometric measurements which were made on the panoramic radiographs were recorded. Based on these findings, the sequential hypothesis of impaction of the maxillary canine was postulated. The hypothesis states that both buccally and palatally impacted canines have similar aetiological factors leading to their impaction. It is suggested that genetic mechanisms strongly influence the potential of the maxillary canine to be impacted and the guidance from the lateral incisor and the stage of development plays a vital role in determining the ultimate position of the impacted canine.     

Dental Anomalies as a Microsymptom of Palatal Canine Displacement

AIM: A retrospective study was performed to investigate whether palatal canine displacement is associated with other dental features permitting early clinical diagnosis of the eruption disturbance. PATIENTS AND METHODS: The study was based on the complete records of 235/8556 patients at the Department of Orthodontics, School of Dental Medicine, University of Freiburg i.Br. (mean age = 14.11 years) with at least one palatally displaced permanent canine. These patients were examined for ten different morphologic parameters, e.g. impaction and congenital absence of further teeth, hypoplastic, peg-shaped, rotated and congenitally missing upper lateral incisors, supernumerary teeth, Angle classification, and cover-bite (= "Deckbiss"). The data were compared with those of a control sample of the same size with physiologic upper canine eruption (mean-age = 10.0 years). Furthermore, in a right/left comparison the local influence of anomalies of the upper lateral incisors on palatal canine displacement was evaluated by multiple linear regression analysis. RESULTS: The statistical analyses revealed that the risk of palatal canine displacement was significantly higher in patients with hypoplasia, peg shape or congenital aplasia of upper lateral incisors, further impacted and congenitally missing teeth and cover-bite. The intergroup differences in terms of gender, rotation of upper lateral incisors and Angle classification were not statistically significant. The right/left comparison revealed a significantly higher risk of palatal canine displacement in association with an adjacent hypoplastic or peg-shaped lateral incisor and with aplasia of the contralateral upper incisor. CONCLUSION: The clinical significance of the study is that the occurrence of palatally displaced canines is often closely linked with other dental anomalies. In this context, anomalies of upper lateral incisors, aplasia or impaction of further teeth, and the anomaly of cover-bite may serve as indicators of palatal canine displacement. A retarded development of the upper lateral incisor seems to be more disturbing for physiologic canine eruption than aplasia. In patients exhibiting the stated microsymptoms, close clinical follow-up of the maxillary permanent canine eruption during the late exfoliation period is strongly recommended.     

Prediction of maxillary canine impaction using eruption pathway and angular measurement on panoramic radiographs

ObjectivesTo compare the normal eruption pattern and angulation in impacted maxillary canines using panoramic radiographs to predict maxillary canine impaction.Materials and MethodsPatients aged 6 to 15 years were classified into the normal eruption group (n = 229) and the impaction group (n = 191). At least two panoramic radiographs were taken in the normal eruption group during the eruption process of the maxillary canine. The growth pattern of the maxillary canine was analyzed using an XY coordinate system, with the tip of the maxillary lateral incisor as the origin and the tooth''s long axis as the Y-axis and measurement of the relative position of the crown tip and angulation of the maxillary canine.ResultsThe crown tips of normally erupted maxillary canines were intensively distributed along the distal surface of the maxillary lateral incisor, while those of impacted canines were widely distributed. The angulations of the normally erupted canines increased as eruption increased along the lateral incisor and then decreased at the cervical point of the lateral incisor. The angulations of the impacted canines were scattered, with no uniform pattern.ConclusionsWhile using the normal eruption path of the maxillary canine and the pattern of change in angulation based on the distal surface of the maxillary lateral incisor, early intervention or regular follow-up is needed to prevent maxillary canine impaction.     

Early and unusual incisor resorption due to impacted maxillary canines.

A very early and severe case of maxillary incisor resorption caused by impacted canines is reported. An estimated 50,000 cases of ectopic eruption and impaction of maxillary canines occur each year in the United States. Although incisor resorption due to ectopically positioned permanent maxillary canines can be swift, silent, and devastating, an effective protocol has been developed for early detection and management of this condition. Palpation and, if indicated, radiographic evaluation are combined with primary canine removal in selected cases. These strategies--particularly when used early--can prevent the vast majority of palatally impacted maxillary canines and the potentially devastating resorption of adjacent incisors.     

Radiographic examination of ectopically erupting maxillary canines

This study analyzes the need for and possibility of obtaining further information from different radiographic procedures in 125 children with potential ectopic eruption of the maxillary canines. After clinical examination of 3,000 10 to 15-year-old children, it was found that 7% needed radiographic examinations for determination of the canine position. Eighty-four children (2.8%), with a total of 125 potential ectopically erupting maxillary canines diagnosed clinically and by means of periapical radiographs, were selected and a stepwise extended radiographic diagnostic procedure was used. Most canines in ectopic eruption were positioned palatally; the positions could be assessed with sufficient accuracy from conventional periapical films in 92% of the cases. Only in 37% of the cases, however, could the lateral incisor be projected free from the ectopic canine by the intraoral technique. The lamina dura of the lateral incisor facing the canine was often found to be interrupted. For 29% of the ectopic canines, the lateral incisors could neither be projected free nor judged free from resorptions and a supplementary polytomographic investigation was believed to be necessary. The number of resorbed teeth was doubled by polytomography and altogether 12.5% of the ectopic canines caused resorptions. A stepwise radiographic procedure including polytomography is described and recommended in cases of ectopic eruption of maxillary canines for determining the correct position and ruling out or confirming resorptions on incisors, thereby optimizing the orthodontic treatment planning.     

Morphology of anterior teeth associated with displaced canines.

Abstract

This clinical study compared tooth dimensions of maxillary central and lateral incisors on the same side as a palatally impacted maxillary canine with those of the contralateral side with a normally erupted canine, in a group of 33 consecutively referred patients. The dimensions recorded were the mesio-distal width, labio-palatal depth, obtained from models of the four upper anterior teeth and total tooth length obtained from an orthopantomographic radiograph. The results showed that there was no statistically significant evidence to support the view that palatally impacted maxillary canines are associated with diminutive maxillary lateral incisors.     

Treatment of a transmigrated and an impacted mandibular canine along with missing maxillary central incisor: A case report

IntroductionTreatment of a case with impacted canines is complex and numerous options are available ranging from disimpaction to forced eruption.ObjectiveThe objective of this case report was to describe the treatment of a 19-year-old male, with a skeletal Class II, dental Class II Division 1 malocclusion, prognathic maxilla, proclined maxillary incisors, with missing left maxillary central incisor and bilateral mandibular canine impaction.MethodologyThe orthodontic treatment plan included forced eruption of the impacted canines and conversion of maxillary left lateral incisor to central incisor.ConclusionProper diagnosis and implementation of orthodontic biomechanics can minimize the amount of prosthetic and surgical intervention needed in the management of transmigrated canine and smile designing.     

改良Nance弓在矫治上颌腭侧埋伏尖牙的作用

目的 探讨改良Nance弓在矫治上颌腭侧埋伏尖牙时矫治力方向设计及支抗设计的作用.方法 7例单侧上颌腭侧埋伏尖牙均采用外科-正畸联合治疗.手术暴露埋伏尖牙牙冠,粘接舌侧扣;戴入改良Nance弓,利用改良Nance弓位于腭侧不锈钢丝上的附钩,先将尖牙冠向后牵引绕过侧切牙的牙根,直到位于正常尖牙间隙的腭侧,如尖牙间隙不足,则粘结上颌托槽,预备尖牙间隙;再采用直丝弓技术将埋伏尖牙向唇侧移动,排齐牙列,调整咬合关系.对治疗后牙齿的松动度、牙髓活力等进行观察.结果 7位埋伏尖牙均被牵引至牙弓的正常位置;牙髓活力测试正常,牙周附着良好.结论 改良Nance弓在矫治上颌腭侧埋伏尖牙时,在矫治力方向设计和支抗控制方面有独特优点和作用.     

Diagnosis and surgical removal of a rare type of permanent maxillary canine impaction: a case report.

The maxillary canine has a long path of eruption, and the frequency of its impaction is second only to that of third molars. It usually impacts palatally or buccally, and the etiologies of these two types of impaction are quite different. This article highlights the importance of a meticulous radiographic examination and describes the surgical procedure used to treat a permanent maxillary canine impacted buccally to the lateral incisor but palatally to the central incisor.     

上颌尖牙腭侧埋伏阻生的锥形束CT定位诊断

目的应用锥形束CT（CBCT）探讨上颌腭侧埋伏阻生尖牙的埋伏特征及邻牙牙根吸收情况。方法选取南京医科大学附属口腔医院正畸科就诊的上颌尖牙腭侧埋伏阻生的青少年患者22例,获取CBCT三维数据,应用Dolphin imaging 11.0软件,分析腭侧埋伏尖牙的埋伏状况、与邻牙位置关系并分类,观察邻牙牙根的吸收情况。结果上颌腭侧埋伏尖牙大多近中、腭向倾斜阻生,近中异位以Ⅰ类和Ⅳ类较为多见,分别占30.8%和38.5%;近中倾斜角度多在53.8°~68.5°,腭侧异位距正中矢状面多在5.4~8.4 mm。年龄越大,上颌腭侧埋伏尖牙近中腭向异位越远,近中倾斜角度越大。84.6%的相邻侧切牙及19.2%的中切牙牙根与埋伏尖牙接触;50%的相邻侧切牙及15.4%的邻中切牙牙根吸收,相邻侧切牙吸收多位于根尖1/3,而相邻中切牙吸收多位于根中1/3;相邻切牙牙根吸收概率与腭侧埋伏尖牙与切牙间的最小距离呈反比关系。结论CBCT能在三维方向诊断上颌尖牙埋伏状况及与邻近组织的关系,准确判断邻牙根吸收情况,准确测量埋伏尖牙倾斜度及埋伏深度,为上颌腭侧埋伏尖牙的治疗提供指导。     

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。     

Radiographic assessment of dental anomalies in patients with ectopic maxillary canines

Background.  The aetiology of palatally and labially located ectopic maxillary canines is multifactorial. Accordingly, early prediction of this eruptional disturbance is in most cases not possible.
Aim.  The purpose of this study was to analyse dental deviations in cases with either palatal or labial ectopic canines.
Design.  Panoramic and intra-oral radiographs from 50 patients with palatally located (38 females and 12 males) and 19 patients with labially located ectopic canines (11 females and 8 males), aged 10 years, 2 months–18 years, 1 month, were analysed. Dental deviations registered were crown and root malformations, agenesis, and eruption deviations. Registrations were performed in the maxillary incisor field and in the dentition in general.
Results.  The study documented that palatally as well as labially located ectopic canines can occur in dentitions without other dental deviations. Dental deviations occurred in approximately two-thirds of all cases, more often in females and in cases with palatally located canines. More than half of the females with palatally located canines had deviations in the maxillary incisors and in the dentition in general.
Conclusion.  Dental deviations may be considered a risk factor for maxillary canine ectopia. Early identification of patients at risk and appropriate interceptive treatment may reduce ectopic eruption of maxillary canines.     

Root resorptions related to ectopic and normal eruption of maxillary canine teeth – A 3D study

Abstract

Objective. To assess the incidence and severity of root resorption of maxillary incisors caused by ectopically and normally erupting maxillary canines and to analyse factors influencing root resorption of incisors using cone beam computed tomography. Subjects and methods. The study sample comprised 59 patients with a total of 80 canines. Forty-six of the canines, in 37 patients, were defined as ectopic and 34 canines, in 22 patients, were defined as normal. The severity of root resorptions were analysed according to studies by Ericson and Kurol. Multiple logistics regression was used to evaluate the association between various factors and root resorptions. Results. The prevalence of root resorptions was significantly higher in the ectopic canine group, 11.0% of the central incisors and 67.6% of the lateral incisors in comparison to 0% and 36.2% in the normal erupting group. Most resorptions were defined as ‘slight’ and were located in the middle third of the root. There was a statistically significant relationship between canines located mesial to the midline of the lateral incisor and root resorption on the maxillary incisors. Conclusion. The present results show that root resorption of maxillary lateral incisors was common in patients referred to CBCT imaging due to maxillary canine eruption disturbances. Although significantly more frequent in patients with ectopically erupting canines, lateral incisor resorption was also found in association with approximately every third of the normally erupting canines. The best predictor for root resorption seemed to be location of the canine mesial in relation to the midline of the lateral incisor root.     

曲面断层片诊断阻生上颌尖牙造成的切牙牙根吸收的有效性研究

目的：评价全口曲面断层片对上颌阻生尖牙造成的切牙牙根吸收诊断的有效性。方法：选取上颌尖牙阻生病例19例,拍摄全口曲面断层片及螺旋CT扫描,邀请10名口腔正畸学研究生通过曲面断层片判断阻生尖牙造成的切牙牙根吸收的数目和位置,以螺旋CT扫描结果为实际牙根吸收量,计算曲面断层片诊断的灵敏度和特异度。结果：曲面断层片对上颌尖牙阻生造成的切牙牙根吸收诊断的灵敏度为46.3%、特异度为86.5%。阴性诊断有一定的参考价值,阳性诊断因为缺少可靠的牙根吸收定性指标而准确性较低。结论：不能单独依靠曲面断层片做出是否存在切牙牙根吸收的诊断。     

Resorption of maxillary lateral incisors caused by ectopic eruption of the canines : A clinical and radiographic analysis of predisposing factors

Factors predisposing to resorption of adjacent permanent lateral incisors caused by ectopic eruption of maxillary canines were evaluated. The subjects consisted of two groups: one with 40 lateral incisors with resorption caused by ectopic eruption and a control group of 118 ectopic eruption cases with no lateral incisor resorption. The mean age of the children in the two groups differed by only 0.7 of a year and ranged from 10.0 to 15.0 years, covering the normal eruption period of the maxillary canine. Resorption of lateral incisors was three times as common in girls as in boys. The resorption cases showed a more advanced dental development, a more medial canine position in the dental arch, and a slightly more mesial horizontal path of eruption (an average of 10 degrees) than that of the control cases. Factors such as the width of the dental follicle and proclination or distal tilting of the lateral incisor showed no correlation to the resorption. Potential resorption cases are always those in which the canine cusp in periapical and panoramic films is positioned medially to the midline of the lateral incisor. Such situations should be carefully investigated with polytomography if necessary. The risk of resorption also will increase with a more mesial horizontal path of eruption. From 10 years of age or younger, annual clinical examination by palpation of the canine eruption path is recommended. This clinical examination should be supplemented with a stepwise extended radiographic procedure in cases in which ectopic eruption of the maxillary canines is suspected.