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.     

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.     

Canine impactions: incidence and management

Impacted teeth present many problems for the orthodontist. They can compromise tooth movement, esthetics, and functional outcomes. The second most commonly impacted tooth, after the maxillary third molar, is the maxillary canine, with an incidence from 1% to 2.5%. Maxillary canines can be impacted facially or palatally and are more common in female patients than in male patients. Therefore, the purpose of this paper is to address the incidence and etiology associated with impacted maxillary canines, the clinical and radiographic evaluation of the situation, and the techniques for managing this problem. Papers related to this topic were identified and reviewed thoroughly. A decision tree involving the various techniques employed to expose impacted canines is presented, together with methods used to identify the location of impacted canines. The impacted canine can be properly managed with proper diagnosis and technique.     

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。     

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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.     

Pre-treatment radiographic features for the periodontal prognosis of treated impacted canines

AIM: The aim of this study is to evaluate the prognostic role of the pre-treatment radiographic features on the post-treatment periodontal status of intra-osseous impacted maxillary canines. MATERIAL AND METHODS: A study population of 168 patients (211 canines) was evaluated at the end of the overall surgical-orthodontic treatment consisting of a combined surgical (flap) and orthodontic (direct traction to the centre of the ridge) approach. The pre-treatment variables on the panoramic radiograph were alpha-angle, d-distance and s-sector while the post-treatment periodontal variables were pocket depth (PD) and keratinized tissue width (KT). Multilevel statistical analysis was used to evaluate the role of the pre-treatment radiographic factors on the post-treatment periodontal variables at patient, tooth and site levels. RESULTS: No significant differences in PD or KT were found at the end of surgical-orthodontic treatment with respect to age, gender, site of impaction or pre-treatment radiographic position of the impacted canine. The only statistically, but not clinically, significant difference (about 0.5 mm) was found for the KT that was greater for the palatally impacted canines than for the buccally impacted ones. CONCLUSIONS: alpha-angle, d-distance and s-sector measured on the pre-treatment panoramic radiographs did not represent prognostic indicators of final periodontal status of orthodontically re-positioned canines.     

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.     

The position of maxillary canine impactions and the influenced factors to adjacent root resorption in the Korean population

The purpose of this study was to evaluate the position and aspects of maxillary canine impactions in the Korean population and investigate its comparison with the previous reports, while aiding in the establishment of diagnosis and treatment planning by revealing the influential factors of root resorption associated with such impactions. The subjects of this study consisted of 186 teeth from 148 patients, who had visited Seoul National University Dental Hospital due to impacted canines and had taken computerized tomographic images and panorama radiographic images. As a result, maxillary canine impaction in the Korean population occurred 1.5 times more often in females (F:M = 89:59) than males. Regarding the position of impaction, there were three times more buccal impactions (B:P = 140:46) than palatal impactions. The occurrence of root resorption was as high as 49.5 per cent. In evaluating the influential factors affecting adjacent root resorption, the significance of the impacted angulation was insufficient (P = 0.652). However, the buccopalatal position (P < 0.0001) and mesiodistal placement (P = 0.006, 0.037) of the impacted tooth were determined to be significant factors. Therefore, the adjacent root resorption caused by impacted maxillary canines can be stated to exhibit a greater amount of resorption as the positional proximity of the canine crown and lateral incisor root increases.     

Localization of the unerupted maxillary canine: how to and when to.

Reasons for localizing impacted maxillary canines are outlined and methods of localization described. The favored method of radiographic localization is the parallax method (image/tube shift method). Tube shifts can be carried out in both the horizontal and the vertical planes. For a horizontal tube shift, two occlusal radiographs are recommended; for a vertical tube shift, a rotational panoramic radiograph and an occlusal radiograph are recommended. This latter combination is usually the combination of choice because the panoramic radiograph, which provides information about all the teeth in both arches, the two jaws, and the surrounding structures, is often taken as an initial radiograph and this combination only requires one additional exposure, the occlusal radiograph. To facilitate the interpretation of a vertical tube shift, the angle of the tube in the occlusal radiograph should be increased from the customary 60 degrees to 65 degrees to 70 degrees to 75 degrees. Less accurate methods of radiographic localization are to use (1) image magnification of the impacted maxillary canines and (2) image superimposition of the impacted maxillary canines on the central or lateral incisor. Reasons why periapical radiographs are not recommended to be used for a horizontal tube shift or for a vertical tube shift in combination with a panoramic radiograph are explained. Indications to suspect palatal impaction may occur in the future if the patient is less than 10 years of age, and indications to suspect impaction may have occurred if the patient is more than 10 years of age are discussed. Patient questionnaires are advocated to aid the clinician in anticipating palatal impaction, the most frequent impaction.     

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.     

曲面断层片和锥形束CT对上颌阻生尖牙的定位分析

目的:通过对曲面断层片中上颌阻生尖牙近远中向和垂直向的影像学分区,判定其与锥形束CT (cone-beam computed tomography, CBCT)中相应尖牙唇腭侧位及相邻恒切牙根吸收之间的关系。方法:对68例患者的94颗上颌阻生尖牙进行曲面断层片的拍摄和CBCT扫描。将曲面断层片中上颌阻生尖牙近远中向牙尖所处的位置分为5区(Ⅰ区-Ⅴ区),将牙冠所处的垂直向高度分为3部分(牙冠段,根中段,根尖段),其唇腭侧位置和相邻恒切牙的根吸收情况则由CBCT判定。结果:曲面断层片中上颌阻生尖牙近远中向的区域定位与CBCT中相应阻生牙的唇腭侧位之间有显著相关(P＜0.001),唇侧阻生的尖牙常出现在曲面断层片中的Ⅰ、Ⅱ、Ⅲ区域,正中牙槽阻生的多在Ⅳ区域,腭侧阻生的常在Ⅴ区域,而垂直向的分段与之无显著相关。CBCT中相邻恒切牙的根吸收常发生在Ⅳ、Ⅴ区域和根中段、根尖段。曲面断层片中阻生尖牙近远中向和垂直向的区域划分均与CBCT中相邻恒切牙的根吸收之间有统计学意义(P＜0.05)结论:利用曲面断层片中上颌阻生尖牙近远中向的区域定位可以预测其唇腭侧位和相邻恒切牙的根吸收,垂直向的分段可用来判断相邻恒切牙的根吸收,而不可推测其唇腭侧阻生情况。     

The effect of changes in tooth position of unerupted canines on cephalograms

Although many radiographic procedures have been described to localize an impacted canine, they all submit the patient to extra radiation. The purpose of the entire study was to evaluate if the combined interpretation of cephalograms and dental panoramic tomograms (DPTs), which are used in orthodontic practice, can provide adequate information as to the position of impacted canines. In a previous study the radiographic image of impacted canines on DPTs was evaluated. In this investigation, the effect of changes in position and inclination of an impacted canine on cephalograms was studied in an experimental set-up. An upper canine was removed from a human skull and placed in a positioning device to imitate various positions of impaction. Starting from a buccally impacted position, three different displacements were simulated: 10 mm frontally, 10 mm sagittally, and 5 mm vertically. In each of these positions nine different changes in inclination (in the sagittal and the frontal plane) were registered, resulting in 36 different cephalographic exposures. Analysis revealed the following: the degree of vertical and sagittal displacement of the incisal point of the impacted canine, the angulation of the tooth as well as the tooth length, measured on a cephalogram, appeared to give an accurate representation of the experimental set-up. Combining these findings and those from the previous study, it became possible to define a series of points to enable an adequate three-dimensional (3D) estimation of the canine's position. A clinical case of an impacted canine is used as an illustration of this experimental set-up.     

Correction of a superiorly displaced impacted canine due to a large dentigerous cyst.

One of the more difficult situations dealt with by orthodontists is the treatment of impacted maxillary canines. This case report describes an impacted canine positioned near the floor of the orbit that was brought into a normal position. Diagnostic records revealed impacted and displaced teeth resulting from a large radiolucent lesion. The patient was referred to an oral surgeon. The lesion was diagnosed as a dentigerous cyst and marsupialized over 12 months. After decompression of the cyst, the impacted teeth were exposed and orthodontically brought into their proper position.     

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.     

上颌埋伏尖牙定位及邻牙牙根吸收的多层螺旋CT分析

目的:应用多层螺旋CT(MSCT)对上颌埋伏尖牙进行三维立体定位,同时对邻牙牙根的吸收程度进行评估。方法:应用MSCT扫描38例上颌埋伏尖牙,在多平面重建和容积再现软件中对其三维定位,上颌切牙牙根吸收程度进行分析,并与传统X线平片进行比较。结果:38例上颌埋伏尖牙都能使用MSCT进行准确定位,侧切牙牙根吸收率为36.6%,中切牙的牙根吸收率为16.3%,在牙列中受埋伏尖牙影响最大的是侧切牙的牙根。MSCT评价上颌中切牙及侧切牙牙根吸收的阳性率高于传统X线平片,其差异具有统计学意义。结论:使用MSCT多平面重建和容积再现技术能直观准确地对埋伏尖牙进行定位、诊断邻牙牙根吸收程度,对临床正畸治疗埋伏牙有很高的应用价值。     

正畸治疗诱导阻生上颌尖牙的自发萌出

目的 探讨阻生上颌尖牙正畸治疗诱导自发萌出的方法,总结合适的临床处理策略,为阻生尖牙的合理治疗提供依据.方法 选择13例恒牙列患者(男6例,女7例)的17颗阻生上颌尖牙,通过正畸治疗在相应牙弓位置为尖牙预留充足的间隙,待其自发萌出后直接粘结矫正装置排入牙列正常位置.结果 预留间隙2～24个月后阻生尖牙自发萌出,治疗后尖牙及邻牙牙周状况良好.结论 当阻生尖牙错位不严重,扩弓或减数拔牙即能为阻生尖牙提供足够萌出间隙,判断其能自行萌出时,可采取正畸诱导自萌的方法进行治疗.     

Three-dimensional evaluation of angular,linear, and resorption features of maxillary impacted canines on cone-beam computed tomography

Objectives

The aim of this study was to evaluate the localization, angulation, and resorption features of maxillary impacted canines on cone-beam computed tomography (CBCT).

Methods

This retrospective study examined the CBCT scans of 140 maxillary impacted canines in 102 patients (43 males, 59 females; mean age: 16.25 ± 6.31 years). The following impacted canine-related parameters were analyzed on the CBCT images: impaction side; location; root resorption levels of adjacent teeth; occlusal plane and midline distances of impacted canines; and angulations of impacted canines to midline, lateral incisor, and occlusal plane.

Results

Bilateral canine impaction was found in 38 subjects, and unilateral canine impaction was present in 64 subjects. Severe resorption was found in 14 canines. There were no significant differences between the occlusal plane and midline distances to the impacted canine cusp tip and root apex (p > 0.05). The midline angulation of right maxillary impacted canines was significantly higher than that of left maxillary impacted canines (p < 0.05), while the occlusal plane angulation of left maxillary impacted canines was significantly higher than that of right maxillary impacted canines (p < 0.05).

Conclusions

Maxillary canine impaction was more frequently seen in female subjects than in male subjects. Lateral incisors were more frequently affected than first premolars, and slight resorption was more frequently seen in adjacent teeth. CBCT assessment of maxillary impacted canines can provide accurate measurements of angular, linear, and resorption parameters.

     

Transmigration of mandibular canines: a report of six cases and a review of the literature

BACKGROUND: The transmigration of a mandibular canine is a rare phenomenon, the etiology of which is not clear. The literature on this rare condition is reviewed, and six cases of transmigrated mandibular canines are presented. REPORT: Panoramic radiographic examination of six patients revealed each patient had one impacted transmigrated mandibular canine. Of the six impacted teeth, the left mandibular canine was involved in four instances and the right in two. In one case the transmigrated canine was associated with a dentigerous cyst. SUMMARY: Transmigration of the mandibular canine is a rare event, and early radiographic examination of the patient is important for treatment. In addition, future studies may lead to a better understanding of this rare anomaly and improvement of the classification criteria.     

5-year longitudinal study of survival rate and periodontal parameter changes at sites of maxillary canine autotransplantation

BACKGROUND: Although dental transplantation is an accepted treatment modality, few studies have evaluated the prognosis for autotransplantation of maxillary canines, and changes in clinical periodontal parameters still need to be demonstrated. The objectives of this long-term study were to evaluate the prognosis and changes in clinical attachment level (CAL), probing depth (PD), soft tissue recession (REC), and radiographic bone level changes between years 1 and 5 for autotransplanted maxillary canines. METHODS: Thirty subjects with 32 impacted canines were scheduled for transplantation. Transplanted teeth were splinted for 4 weeks, and endodontic treatments were performed within 1 year after the operation. Radiographs were taken, and PD and CAL were measured for up to 5 years. Progressive root resorption was observed in two teeth, and one tooth was extracted during year 4. RESULTS: The survival rate was 93.5%. CAL and PD tended to increase slightly at all sites, especially at palatal sites after transplantation, whereas the greatest CAL and PD were found at approximal sites, and REC was the same as natural teeth. CONCLUSIONS: Maxillary canine transplantation can be a reliable treatment alternative. Clinical measurements demonstrated long-term stability. Based on the literature and the present findings, maxillary canine transplantation can be suggested as a promising treatment modality.