Permanent maxillary canines – review of eruption pattern and local etiological factors leading to impaction

The position of the permanent maxillary canine at the angle of the mouth is strategically significant in maintaining the harmony and symmetry of the occlusal relationship. However, the maxillary canine is the second most frequently impacted tooth, with prevalence reported to be between 1% and 2%. Moreover, treatment of this condition is often complex and involves substantial time and financial cost. Hence, it is only prudent to monitor the eruption and identify the etiological factors that lead to impaction of the maxillary canine. Numerous researchers have tried to identify specific and nonspecific etiological factors responsible for displacement of canines. The purpose of this review was to track the development processes of maxillary canines and determine the hindrances that affect the eruption at different ages. Awareness of the eruption process and etiology of noneruption will help to reduce the incidence of impacted canines by allowing for early recognition and interceptive treatment.     

泸州地区青少年尖牙阻生的X线分析

目的：通过X线全景片分析泸州地区青少年的尖牙阻生情况。方法：选取2011年1月。2012年12月在泸州医学院附属口腔医院接受x线检查的1800例12—14岁青少年的X线全景片,统计分析阻生尖牙所占比例以及患者的性别、尖牙阻生部位和阻生类型的差异。结果：尖牙阻生在所有患者中所占比例为3．72％（67／1800）,男性：女性为1：1．79;上颌尖牙阻生占3．33％（60／1800）,下颌尖牙阻生占0．33％（6／1800）,上下颌尖牙同时阻生1例;近中向阻生在阻生尖牙中占92％（69／75）,迁徙尖牙占0．22％（4／1800）。结论：本组患者尖牙阻生以女性、单侧上颌尖牙阻生多见,且以近中向阻生为主。     

预置支点介导下的上颌近远中阻生尖牙的矫治

目的 探讨预置支点在矫治上颌水平阻生尖牙的作用.方法 水平埋伏阻生上颌尖牙5例,均位于邻牙根方.用直丝弓矫治器进行间隙预备,外科开窗暴露埋伏尖牙的牙冠,将预置支点置于牙颈部,进行正畸牵引,曲面断层片观察邻牙牙根吸收情况.结果 水平阻生尖牙以预置支点为转动中心而移动至正常位置,牙髓和牙周情况良好,邻牙牙根无吸收现象.结论 预置支点水平阻生上颌尖牙的转动中心,对正畸临床治疗有指导意义.     

Maxillary impacted canine with congenitally absent premolars

Multiple treatment options are available to patients who have impacted canines in addition to congenitally absent premolars. Management options for impacted maxillary canines can include (1) continued observation, (2) extraction of the primary canine to aid spontaneous eruption, (3) uncovering and bonding of the impacted tooth and its eruption using orthodontic traction, (4) autotransplantation, and (5) extraction followed by prosthetic replacement. The options for the treatment of missing premolars can include the following: (1) maintaining the primary molars, (2) spontaneous space closure after early extraction of the primary molar, (3) autotransplantation, (4) prosthetic replacement, and (5) orthodontic space closure. In this case report, treatment of a patient with an impacted maxillary canine and agenesis of three second premolars will be presented.     

Long-term follow-up of severely resorbed maxillary incisors after resolution of an etiologically associated impacted canine

BACKGROUND: Resorption of maxillary incisor roots because of an impacted canine is a well-recognized phenomenon that occurs in a surprisingly high proportion of patients with impacted canines. In this retrospective study, we studied a sample of patients in whom the resorption was particularly severe. METHODS: The sample consisted of 11 patients (age, 11.8 +/- 1.2 years) with 20 severely resorbed maxillary incisors. The amount of resorption was measured at the outset (T1), when the impacted canine was distanced from the incisor root area (T2), at the completion of the orthodontic treatment (T3), and at a follow-up appointment at least 1 year posttreatment (T4). RESULTS: A 17.2% increase in the crown/root ratio occurred due to aggressive continued resorption between T1 and T2. The resorption rate reduced to an almost insignificant level, despite continued and often appreciable orthodontic movement of the resorbed teeth from T2 to T3. CONCLUSIONS: Patients with impacted canines should be screened for resorption and the impacted tooth treated as soon as possible. The resorption process can be halted and the affected tooth moved orthodontically without further risk of resorption. In the long term, with early treatment, even severely resorbed teeth do not suffer from increased mobility or discoloration and might not require splinting.     

Comparisons of different treatment methods and their outcomes for impacted maxillary and mandibular canines: A retrospective study

BackgroundImpacted canines may pose a functional and an esthetic problem for patients and can affect neighboring incisors. The aim of the study was to compare different treatment methods and their outcomes for impacted maxillary and mandibular canines.MethodsThe authors included 102 patients with 118 impacted canines (82 maxillary and 36 mandibular canines). Impacted canine were confirmed during clinical and radiologic examinations. Eighty-five patients (83%) with 97 impacted canines started the treatment. The authors analyzed treatment types and outcomes. Two maxillary and 4 mandibular canines were scheduled for extraction.ResultsOrthodontic extrusion was used most frequently to treat impacted maxillary canines (89%), whereas orthodontic extrusion and transalveolar transplantation were performed most frequently in impacted mandibular canines (33% and 37.5%, respectively). The treatment was successful in 96% of the maxillary and 95% of the impacted mandibular canines.ConclusionsDifferent methods were used for impacted maxillary and mandibular canines, but their overall success rate was high.Practical ImplicationsSuccessful outcome is determined via a well-planned and carefully executed orthodontic and surgical treatment. Early diagnosis is pivotal in facilitating spontaneous canine eruption and implementing transalveolar transplantation in a timely way.     

The radiographic localization of impacted maxillary canines: a comparison of methods

This study compared two different radiographic techniques for localization of impacted maxillary canines: vertical parallax (from a panoramic and a maxillary anterior occlusal radiograph) and magnification (from a single panoramic radiograph). The radiographs and the information regarding the impacted canines were obtained retrospectively from records of patients treated in the Day Stay Unit of the Eastman Dental Hospital. The two different radiographic techniques were tested blind and compared for localization of the impacted canine by six examiners. The 'gold standard' used for the radiographic comparisons was the true position of the canine as recorded at operation. The results showed a wide variation between the six examiners in the prediction of the canine position with the two different techniques. Localization with vertical parallax was more successful overall than with magnification, although the difference failed to reach significance. Seventy-six per cent of the impacted canines could be successfully located with vertical parallax and 66 per cent with magnification. Further analysis showed that, while almost 90 per cent of the palatally impacted canines could be correctly detected with both techniques, less than half of the buccal canines could be detected with parallax and only one in 10 buccal canines could be detected with magnification. If a canine is suspected to be buccally placed from its appearance on a panoramic film and cannot be palpated, further views are justified.     

基于锥形束CT的多生牙新分类方法临床意义研究

目的　应用锥形束CT（cone-beam CT,CBCT）对多生牙进行新的临床分类,并分析新分类方法的临床意义。方法　收集2016—2019年首都医科大学附属北京友谊医院口腔科的CBCT影像资料5100例,其中多生牙患者209例,共计多生牙278颗。应用CBCT对多生牙进行新的临床分类,包括萌出型、骨埋伏高位型、骨埋伏低位型、骨埋伏复杂型和牙弓外型,并分析其临床意义。结果　（1）临床资料分析：多生牙发生率为4.1%,其中有1颗多生牙的患者占76.6%,有2颗多生牙的患者占19.1%,有3颗及以上多生牙的患者占4.3%。多生牙好发部位依次为：上颌切牙区、上颌磨牙区、下颌尖牙及前磨牙区、上颌尖牙及前磨牙区、下颌磨牙区。34.9%的多生牙对邻近恒牙产生了继发影响,以萌出错位及阻生为主,主要发生在上颌切牙区。（2）新分类方法的临床意义分析：上颌切牙区多生牙以骨埋伏低位型及萌出型为主,尖牙、前磨牙及磨牙区多生牙以萌出型为主。不同类型多生牙对邻近恒牙产生继发影响的发生率不同或不全相同（χ2 = 26.057,P < 0.001）,提示对邻近恒牙易产生继发影响的多生牙类型依次为：萌出型、骨埋伏复杂型、骨埋伏高位型、牙弓外型、骨埋伏低位型。结论　基于CBCT的多生牙新分类方法简单实用,其中萌出型、骨埋伏复杂型及骨埋伏高位型多生牙更易产生错牙合畸形,建议尽早拔除多生牙、定期随访,必要时正畸治疗。     

基于锥形束CT的多生牙新分类方法临床意义研究

 目的　应用锥形束CT（cone-beam CT，CBCT）对多生牙进行新的临床分类，并分析新分类方法的临床意义。方法　收集2016-2019年首都医科大学附属北京友谊医院口腔科的CBCT影像资料5100例，其中多生牙患者209例，共计多生牙278颗。应用CBCT对多生牙进行新的临床分类，包括萌出型、骨埋伏高位型、骨埋伏低位型、骨埋伏复杂型和牙弓外型，并分析其临床意义。结果　（1）临床资料分析：多生牙发生率为4.1%，其中有1颗多生牙的患者占76.6%，有2颗多生牙的患者占19.1%，有3颗及以上多生牙的患者占4.3%。多生牙好发部位依次为：上颌切牙区、上颌磨牙区、下颌尖牙及前磨牙区、上颌尖牙及前磨牙区、下颌磨牙区。34.9%的多生牙对邻近恒牙产生了继发影响，以萌出错位及阻生为主，主要发生在上颌切牙区。（2）新分类方法的临床意义分析：上颌切牙区多生牙以骨埋伏低位型及萌出型为主，尖牙、前磨牙及磨牙区多生牙以萌出型为主。不同类型多生牙对邻近恒牙产生继发影响的发生率不同或不全相同（χ2 = 26.057，P < 0.001），提示对邻近恒牙易产生继发影响的多生牙类型依次为：萌出型、骨埋伏复杂型、骨埋伏高位型、牙弓外型、骨埋伏低位型。结论　基于CBCT的多生牙新分类方法简单实用，其中萌出型、骨埋伏复杂型及骨埋伏高位型多生牙更易产生错牙合畸形，建议尽早拔除多生牙、定期随访，必要时正畸治疗。     

上颌埋伏阻生尖牙在锥形束CT和曲面体层片中的位置分布及特征研究

目的　通过分析上颌埋伏阻生尖牙在曲面体层片上牙冠和牙根所在区域、牙轴倾斜度及牙齿长度,对照其在锥形束CT（cone-beam computed tomography,CBCT）上的位置,找出上颌埋伏阻生尖牙的曲面体层片预测因素。方法　选取2006—2018年于中国医科大学附属口腔医院正畸科就诊的单侧上颌埋伏阻生尖牙患者135例,共计上颌埋伏阻生尖牙135颗为研究组,同一患者对侧非埋伏阻生尖牙135颗为对照组。（1）采用NNT Viewer软件、Planmeca Dimaxis Pro软件分别对患者的CBCT图像和曲面体层片进行测量,将曲面体层片中上颌埋伏阻生尖牙近远中向位置分为5区（Ⅰ ~ Ⅴ区）,其唇腭侧位置由CBCT判定,分析两者相关性。（2）在曲面体层片中测量分析研究组与对照组牙冠及牙根的近远中向位置分布、牙轴倾斜度以及牙齿长度的差异。结果　（1）不同性别患者上颌埋伏阻生尖牙唇腭侧位置分布的差异有统计学意义（χ2 = 13.542,P = 0.001）。曲面体层片中上颌埋伏阻生尖牙牙根近远中向的区域定位与CBCT中相应阻生尖牙的唇腭侧位之间有显著相关性（r = 0. 225,P = 0.009）;但其牙冠间无相关性（r = 0.001,P = 0.991）。（2）两组尖牙牙冠及牙根近远中向位置分布差异有统计学意义（χ2值分别为219.263、68.447,均P < 0.001）。研究组较对照组尖牙牙齿长度短,牙轴倾斜度大（均P < 0.05）。结论　利用曲面体层片中上颌阻生尖牙牙根近远中向的区域定位可预测其唇腭侧位。在曲面体层片中牙根近远中向位置和牙齿长度的测量结果可用于预测上颌埋伏阻生尖牙的发生。     

Maxillary canine impactions: orthodontic and surgical management

With the exception of the maxillary and mandibular third molars, the maxillary canine is the most commonly encountered impaction. In North America, palatally located impactions appear to predominate over labially impacted canines and occur more frequently in women. Because of the common nature of this phenomenon, the general dentist should know how to properly diagnose and manage potential disturbances in the eruption of the maxillary canine. If diagnosed early, and when clinically and radiographically indicated, extraction of the deciduous canine may help correct the eruption path of the permanent tooth and prevent impaction. This article reviews the etiology, prevention, and surgical and orthodontic management of impacted cuspids. Because the general dentist is often the first dental care provider to come in contact with patients with impacted canines, knowledge about this common dental anomaly is essential to provide proper comprehensive therapy.     

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.     

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??Objective??To propose a new panoramic tomographic predictor of maxillary impact canines by the analysis of the sector of crown and root??the inclination of the dental axis and the teeth length of the maxillary impacted canines on panoramic tomographs and by comparing the position of maxillary impact canines with that on cone-beam computed tomographys??CBCT??. Methods??Collect the general datas of 135 patients who had unilateral impacted maxillary canines. A total of 135 maxillary impacted canines were included as the experimental group??the 135 non-impacted canines on the opposite side in the same patients were as the control group. ??1??The NNT Viewer software and Planmeca Dimaxis Pro software were used to measure the cone-beam computed tomographys and panoramic tomographs respectively. The mesial and distal position of the maxillary impacted canine in the panoramic tomographs was divided into 5 sectors???? ~ ?? sector????the position of labiopalatal side was determined by CBCT??and the relationship between them was analyzed. ??2??The difference between the mesial and distal position distribution of crown and root??the inclination of the dental axis and the teeth length of the teeth of the experimental group and the control group was measured and analyzed in the panoramic tomographs. Results????1??The labiopalatal distribution of the maxillary impacted canines was significantly different between sexes??χ2 = 13.542??P = 0.001??. A statistically significant association was observed between the labiopalatal positions in the cone-beam computed tomographys and the root sectors in panoramic tomographs of the impacted canines ??r = 0. 225??P = 0.009????but not the crown sectors??r = 0.001??P = 0.991??.??2??There are differences in the distribution of the mesial and distal positions of the crown and root between the two groups??χ2 = 219.263??68.447??both P < 0.001??. The maxillary impacted canine of the experimental group was shorter than that of the control group??and the dental axis was more inclined??P < 0.05??. Conclusion??The labiopalatal position can be predicted by the location of the mesial and distal position of the maxillary impacted canine root in the panoramic tomographs. The sector of root and the tooth length can be used to predict the probability of maxillary impacted canines.     

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.     

A retrospective study on the influence of maxillary canine impaction on premolar root morphology

Objectives

The root morphology of the maxillary first premolar differs from the other premolars by presenting a high incidence of separated roots. This study addressed the spatial conditions during root development as a possible influencing factor. Therefore, maxillary computed tomographic (CT) scans of patients with regularly erupted or impacted permanent canines were evaluated on the root morphology of the premolars.

Methods

The following parameters were retrospectively analysed in 250 maxillary CT scans (100 patients with regular erupted permanent canines, 150 patients with at least one impacted permanent canine): sex, status of the canines (erupted/impacted), position of the impacted canines (buccal/palatal; vertically inclined inside/outside the dental arch/horizontally inclined) and root morphology of the premolars.

Results

Of the patients, 68 % with at least one impacted canine were female; the canine was impacted palatally in 75.6 % and in a horizontally inclined position in 58.4 %. In patients with an impacted canine, the number of first and second premolars with separated roots was significantly reduced on the ipsilateral as well as on the contralateral side (all p values?<?0.01).

Conclusions

The present study detected an influence of maxillary canine impaction on the root morphology of all premolars, in that impaction and the associated surplus of space resulted in decreased root separation. This supports the hypothesis that root development is at least partly influenced by increased spatial conditions of the dental arch. However, root development can be regarded as a multifactorial event, influenced by space, direct mechanical interferences, as well as genetic predetermination. The retrospective nature of this observational study did not allow for conclusive differentiation between these factors. Alternatively, root separation and the mesial concavity of the first premolar may represent a path for canine eruption similar to the lateral incisor.

Clinical relevance

A single-rooted maxillary first premolar might represent an additional risk factor for canine impaction.     

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.     

Orthodontic screws to extrude impacted maxillary canines

Objective

The impaction of maxillary canines is a frequently encountered clinical problem in orthodontic practice. Patients?? refusal to participate in long-term treatment or ankylosis of the impacted tooth result in various treatment difficulties. The aim of this study was to evaluate the possible role of mini-screws in the management of unerupted upper canines.

Patients and methods

In a series of 63 consecutive patients (27 males and 36 females, age range 14?C49?years, mean 22.7?years) with a total of 69 impacted maxillary canines, each impacted tooth was surgically exposed and an attachment bonded. An intraosseous screw with an endosseous body and intraoral neck section was inserted into the premolar?Cmolar interradicular space. Following soft tissue healing, orthodontic traction was initiated. After correction of the canine angulation, the mini-screw was removed and conventional orthodontic therapy completed.

Results

Of the 69?canines, 61 (88.41%) were extruded successfully. In the 7?cases that failed, skeletal anchorage spared both patients and clinicians the disappointment of customary long-term, unsuccessful orthodontic therapy. In one patient, the mini-screw was removed because of inflammation and pain before initiating orthodontic traction.

Conclusion

Our results demonstrate that mini-screw anchorage should be taken into consideration when extrusion of an impacted canine is planned.     

Three-dimensional localization of maxillary canines with cone-beam computed tomography.

INTRODUCTION: Precise 3-dimensional (3D) localization of impacted canines is central to their clinical management. Recently introduced dental 3D volumetric imaging systems make precise localization possible. The purpose of this study was to describe the spatial relationship of impacted canines by using images obtained with the NewTom QR-DVT 9000 (QR Srl, Verona, Italy). METHODS: Unilaterally and bilaterally impacted canines (n = 27) from 19 consecutive patients (15 female, 4 male) were evaluated on images taken with the NewTom QR-DVT 9000. The spatial relationships of the impacted canines relative to adjacent structures and incisor resorption were assessed with 3D visualization software. RESULTS: Most (92.6%) of the 27 impactions were palatal. Incisor resorption adjacent to the impacted canine was present in 66.7% of the lateral incisors and 11.1% of the central incisors. Follicle size did not play a major role in influencing impacted canine position. The alveolus was narrower at the impacted canine side compared with the erupted canine side; however, the width of the alveolus on the impacted canine side is independent of the deciduous canines. A correlation was found between the proximity of the impacted canine to the incisors and their resorption. There was no common location where eruption was arrested, and great variation in the inclination of the impacted canine was found. CONCLUSIONS: 3D volumetric imaging of impacted canines can show the following: presence or absence of the canine, size of the follicle, inclination of the long axis of the tooth, relative buccal and palatal positions, amount of the bone covering the tooth, 3D proximity and resorption of roots of adjacent teeth, condition of adjacent teeth, local anatomic considerations, and overall stage of dental development. In short, 3D imaging is clearly advantageous in the management of impacted canines.     

Initial vertical and horizontal position of palatally impacted maxillary canine and effect on periodontal status following surgical-orthodontic treatment

OBJECTIVE: To evaluate the impact of surgical-orthodontic treatment and the initial vertical and mesiodistal position of palatally impacted maxillary canines on the periodontal health of impacted canines and adjacent teeth. MATERIALS AND METHODS: The study group consisted of 32 patients with unilateral palatally impacted maxillary canines. The initial position of the impacted canines was assessed on panoramic images. The treatment protocol of the impacted canines included surgical exposure with the closed-eruption technique and fixed orthodontic appliances. RESULTS: A significant increase in pocket depth was found at the canine mesiopalatal point after surgical-orthodontic treatment. Also, a correlation was found between the initial mesiodistal and vertical position of the impacted canine and the posttreatment periodontal status of the impacted canine, the adjacent lateral incisor, and the first premolar. CONCLUSIONS: A combined surgical-orthodontic approach in the treatment of impacted maxillary canines produces clinically acceptable periodontal conditions. The average increase in pocket depth was less than 4 mm and clinically unimportant for most patients.