兽研1. 引言
牙齿阻生是一种常见的牙齿异常，指牙齿未能在生理时间内萌出至口腔、滞留于牙槽骨中并可能已耗尽萌出力[1，2]。牙根已完成发育，萌出延迟通常超过一年[3]。除第三恒磨牙外，牙医和正畸医生在临床实践中最常遇到的阻生牙是上颌恒尖牙[4]。其在普通人群中的患病率范围为0.29%至4.7%，尽管不同人群间存在一定差异[5–9]。相反，下颌恒尖牙阻生非常罕见。其发生率经计算约为上颌尖牙的20倍低[10]。另一项统计研究指出，在全部858颗确诊阻生牙中，有91颗上颌尖牙阻生（10.6%），而仅有4颗下颌尖牙阻生，仅占全部阻生牙的0.46%，发生率比上颌尖牙低23倍[2]。根据人群、种族和测量方法的不同，其他研究中下颌尖牙阻生的发生率范围为0.3%–2.8%，尽管部分研究测得的发生率高达5.1%[11–15]。与下颌尖牙阻生相关的常见现象是迁移，即阻生尖牙至少一半的牙冠越过中线。这一现代定义源自Javid[16]，Joshi[17]将其修改为尖牙越过中线的倾向，因为当牙齿仅水平化其位置但尚未越过中线时即可诊断此牙齿异常。据认为该现象始于混合牙列早期（6–8岁）[18，19]；因此，这些研究的作者建议在此年龄段的常规检查中进行口腔全景片（OPG）检查。其发生率更低，范围为0.10%至0.31%[20，21]。早期曾认为迁移仅与下颌尖牙相关，但更新的研究证实上颌尖牙也可发生[22，23]。阻生的机制通常未知，尽管许多研究关注这一问题，尤其是对上颌尖牙。已确立两种主要理论：导引理论和遗传理论。根据导引理论（主要由Becker和Chaushu的研究[24–26]代表），上颌侧切牙的牙根发挥引导尖牙萌出的功能。如果牙根发育延迟、牙根过短或形态改变，对尖牙的引导不足，尖牙便会发生阻生。遗传理论则将阻生原因严格归因于遗传因素，即基因突变[27，28]。关于下颌尖牙阻生的文献不多。Dalessandri等[29]在其系统综述中仅找到13项研究。局部因素作为病因是明确的：牙瘤、多生牙、囊肿和拥挤[30]。然而仍有大量下颌尖牙阻生病因不明，其中大多数为迁移牙。一些作者声称下颌尖牙阻生具有强烈的遗传决定因素，因为此牙齿异常常伴有其他牙齿异常[12，31]。
既往文献中提及相关牙齿异常的研究不多，因为这少数涉及下颌尖牙迁移的研究大多主要是病例研究[19，32，33]。仅有少数回顾性研究旨在探讨下颌尖牙阻生与其他牙齿异常之间的关联，但样本量仅包含32颗下颌尖牙[34]。据我们所知，本研究是迄今为止样本量最大的研究，旨在调查下颌尖牙迁移与其他牙齿异常的存在之间是否存在任何关联，这有助于牙医或正畸医生进行早期诊断并使治疗更容易，因为下颌尖牙迁移始终是正畸治疗的挑战。
2. 方法
本回顾性研究的原始样本量包括2010年至2024年间布拉格查理大学第二医学院牙科系和一家私人诊所的4000名患者。所有这些患者均有规范的常规治疗前记录，包括OPG（Gendex GXDP‐700，KAVO）。根据三名工作人员（Dana Kloudová、Lucie Šimůnková Vítová和Bohumila Straková）对OPG的分析，选取了120名下颌尖牙迁移患者。所有这些下颌尖牙迁移均经锥形束计算机断层扫描（CBCT；i‐CAT 17–19，Imaging Science International，Hatfield，PA，USA）确认，并随后经手术确认。纳入本研究的纳入标准为：健康患者，至少有一颗下颌尖牙迁移，既往未接受过正畸治疗，治疗前记录质量良好，无外伤史。排除标准为：颅面综合征、牙瘤、其他肿瘤、纤维性发育不良、囊肿、外伤以及质量差的X线片。具有这些诊断的患者被排除，因此仅剩下病因不明的患者，这可能提示某些遗传因素。之后，由于这些选择标准，25名患者被从研究中剔除。最终，95名患者（48名男性，47名女性）平均年龄11.4 ± 1.3岁被纳入研究组（图1）。所有迁移的内外研究组均为阻生，无迁移尖牙。对照组由99名双侧下颌尖牙生理性萌出的患者组成。所有这些患者均接受过正畸治疗，年龄和性别与研究组患者相似（54名男性，45名女性，平均年龄11.5 ± 1.3岁）。本研究未进行CBCT检查。本研究获得布拉格查理大学第二医学院伦理委员会批准，并符合《赫尔辛基宣言》的准则。
[图：研究组参与者的流程图。]
研究组和对照组检查了16种牙齿异常的存在情况。
Tooth agenesis is a dental anomaly when there is a developmental absence of a tooth in the primary or permanent dentition [35]. Four types of tooth agenesis were evaluated as follows:
[内容请查看原文]
上颌侧切牙缺失。
[内容请查看原文]
上颌第二前磨牙缺失。
[内容请查看原文]
下颌第二前磨牙缺失。
[内容请查看原文]
下颌切牙缺失。
[内容请查看原文]
其他牙齿阻生定义为牙齿在生理萌出时间未能萌出至口腔内的一种牙齿异常[1]。所有阻生牙均纳入此组。
[内容请查看原文]
多发性阻生是指牙列中存在两颗或更多其他阻生牙[36]。
[内容请查看原文]
移位是一种牙齿异常，指两颗相邻牙齿之间位置互换[37]。
[内容请查看原文]
其他牙齿迁移是指阻生牙至少一半牙冠越过中线[16]。此组包括所有其他迁移牙。
[内容请查看原文]
多生牙定义为正常乳牙或恒牙系列之外的牙齿，可为单颗或多颗牙齿[38]。
[内容请查看原文]
乳磨牙低位咬合是指乳磨牙相对于相邻牙齿位于咬合平面以下[39]。
[内容请查看原文]
上颌侧切牙过小是一种牙齿异常，特征为牙冠或整个牙齿尺寸减小，通常在所有维度上均减小。与常见直径的差异超过2SD[40]。
[内容请查看原文]
第二前磨牙过小可类似地定义为侧切牙过小——牙齿小于正常。它们的体积也较小[41]。
[内容请查看原文]
钉状上颌侧切牙是一种牙齿异常，指牙齿牙冠形状改变。直径从牙颈部向切缘变窄[28]。
[内容请查看原文]
第二前磨牙远中成角是一种牙齿异常，指牙冠向远中倾斜；牙齿长轴与垂直于咬合平面的线之间的角度大于15°[42]。
[内容请查看原文]
牙齿旋转是指牙齿绕其长轴转动[43]。
[内容请查看原文]
牛牙症是一种牙齿异常，定义为发育障碍，牙齿髓腔扩大且髓室底向根尖移位。牙冠增大，牙根显著缩短[44]。
3. 统计分析
使用IBM SPSS Windows版软件（版本24.0，IBM Corp，纽约，美国）进行统计分析。为确定最小样本量，选择使用G*Power进行先验功效分析。结果显示，研究中所需的最小受试者数量为81（功效=0.81；α=0.05；效应量=0.29）。统计显著性水平预先设定为小于或等于0.05。采用Fisher精确检验比较下颌犬齿阻生患者与对照组的牙齿异常频率。该检验也用于计算研究组与对照组患者之间总牙齿异常患病率的统计学显著性。随后对p值进行错误发现率（FDR）校正。同时计算置信区间（CI=95%）和比值比（OR）。为分析诊断的可重复性，三位作者（Dana Kloudová、Bohumila Straková和Lucie Šimůnková Vítová）在1个月内对每种牙齿异常重复检查。为评估组内信度，计算了组内相关系数（ICC），采用双向混合模型。结果显示所有变量均具有极好的一致性（0.91–0.97）。对于组内测量，采用单向随机模型。结果证实所有变量均具有高信度（0.92–0.99）。
4. 结果
在本研究中，从4000例具有合格OPG的初始样本中，95例患者被诊断至少有一颗迁移下颌犬齿。所有 these 患者随后均接受了CBCT检查。男女比例几乎相等，研究组由50.5%男性和49.5%女性组成，全组男性平均年龄11.5 ± 1.4岁，女性平均年龄11.4 ± 1.3岁（表1）。
Table 1. Demographics of patients with mandibular canine impaction and control group.
| Sex | N | Age (year) mean + SD | |
|---|---|---|---|
| Study group | Male | 48 | 11.5 ± 1.4 |
| Female | 47 | 11.3 ± 1.2 | |
| Control group | Male | 54 | 11.8 ± 1.5 |
| Female | 45 | 11.2 ± 1.3 |
16种牙齿异常的患病率、分布、OR、置信区间和p值见表2和表3。统计检验证实，下颌犬齿迁移与其他牙齿异常之间无统计学重要关联，因为p值从未小于或等于0.05。
Table 2. Distribution of dental anomalies in patients with mandibular canine impaction and control group.
| Dental anomalies | Study group patients with anomaly | (%) | Control group patients with anomaly | (%) |
|---|---|---|---|---|
| Agenesis of maxillary lateral incisor | 1 | 1.05 | 0 | 0 |
| Agenesis of maxillary second premolar | 1 | 1.05 | 2 | 2.02 |
| Agenesis of mandibular incisor | 2 | 2.1 | 1 | 1.01 |
| Agenesis of mandibular second premolar | 3 | 3.15 | 3 | 3.03 |
| Peg shaped maxillary lateral incisor | 1 | 1.05 | 1 | 1.01 |
| Microdontia of maxillary lateral incisor | 1 | 1.05 | 0 | 0 |
| Microdontia of second premolar | 1 | 1.05 | 0 | 0 |
| Impaction of other tooth | 6 | 6.31 | 6 | 6.06 |
| Multiple impaction | 1 | 1.05 | 2 | 2.02 |
| Transposition | 0 | 0 | 1 | 1.01 |
| Transmigration of other teeth | 0 | 0 | 1 | 1.01 |
| Supernumerary teeth | 1 | 1.05 | 2 | 2.02 |
| Infraoclusion of deciduous molars | 4 | 4.21 | 4 | 4.04 |
| Distoangulation of mandibular second premolars | 1 | 1.05 | 0 | 0 |
| Taurodontism | 0 | 0 | 1 | 1.01 |
| Tooth rotation | 1 | 1.05 | 4 | 4.04 |
Table 3. Dental anomalies, p ‐value and other statistics.
| Dental anomalies | P ‐correct | OR | CI | p ‐Value |
|---|---|---|---|---|
| Agenesis of maxillary lateral incisor | 0.79 | 0 | (0; 37.42) | 0.49 |
| Agenesis of maxillary second premolar | 1 | 1.932 | (0.10; 115.46) | 1 |
| Agenesis of mandibular incisor | 1 | 0.476 | (0.01; 9.29) | 1 |
| Agenesis of mandibular second premolar | 0.9 | 0.959 | (0.13; 7.342) | 0.62 |
| Peg shaped maxillary lateral incisor | 1 | 0.959 | (0.01; 76.04) | 1 |
| Microdontia of maxillary lateral incisor | 0.79 | 0 | (0; 37.42) | 0.49 |
| Microdontia of second premolar | 0.79 | 0 | (0; 37.42) | 0.49 |
| Impaction of other tooth | 0.79 | 0.957 | (0.25; 3.73) | 0.12 |
| Multiple impaction | 1 | 1.932 | (0.1; 115.46) | 1 |
| Transposition | 0.79 | 0 | (0; Inf) | 0.49 |
| Transmigration of other teeth | 0.79 | 0 | (0; Inf) | 0.49 |
| Supernumerary teeth | 1 | 1.932 | (0.1; 115.46) | 1 |
| Infraoclusion of deciduous molars | 0.79 | 0.958 | (0.17; 5.31) | 0.37 |
| Distoangulation of mandibular second premolars | 0.79 | 0 | (0; Inf) | 0.49 |
| Taurodontism | 0.79 | 0 | (0; Inf) | 0.49 |
| Tooth rotation | 0.79 | 3.933 | (0.38; 196.76) | 0.37 |
研究组中最常见的牙齿异常为其他牙齿阻生：患病率为6.32%（6例患者）。对照组中出现了相同的患病率（6例患者）。下颌犬齿迁移患者中第二常见的牙齿异常为乳磨牙低位咬合（4例患者，4.21%），对照组中再次出现相同频率（4例患者，4.04%）。三例下颌犬齿迁移患者伴有下颌犬齿阻生缺失，一例患者被诊断为下颌切牙缺失，另一例患者被诊断为上颌侧切牙缺失。对照组中牙齿缺失的频率非常相似。研究组中仅有一例患者同时存在其他牙齿阻生和下颌第二前磨牙缺失。对照组中，没有患者同时存在两种或以上其他牙齿异常。
上颌侧切牙钉状在下颌犬齿阻生患者与对照组之间无差异（两组各1例患者）。小牙症（第二前磨牙和上颌侧切牙）仅发生于对照组。
其他牙齿的易位、迁移及牛牙症仅发生于对照组（1.01%），下颌第二前磨牙远中倾斜仅发生于研究组（1.05%）。
患者层面的比较（表4）显示，研究组与对照组之间牙齿异常的总患病率无显著差异（p = 0.64）。这表明，与对照组相比，研究组患者在发生至少一种其他牙齿异常方面并无更高的临床易感性。
Table 4. Patient‐level prevalence of dental anomalies: comparison between groups.
| Group | Patients with anomalies | Patients with no anomalies | Total | Prevalence (%) | Fisher´s exact test |
|---|---|---|---|---|---|
| Study group | 23 | 72 | 95 | 24 | 0.64 |
| Control group | 28 | 71 | 99 | 28 |
5. 讨论
本研究聚焦于发现下颌尖牙迁移与其他牙齿异常之间的任何关联。研究共纳入95例下颌尖牙迁移患者，据我们所知，这是迄今为止样本量最大的研究之一。
下颌尖牙迁移的诊断较为容易，且通常在全科牙医进行常规OPG检查时偶然发现，因为该病通常无症状[30, 45]。仅在极少数情况下，尖牙迁移是因患者因疼痛、敏感或恒尖牙缺失及其乳牙滞留而就诊时才被诊断[16]。这可被视为不利因素，因为诊断往往设定过晚，无法阻止病情进展。其他牙齿异常的存在可提醒全科牙医和正畸医生下颌尖牙迁移的发生概率较高，并应有助于更早解决问题。
在上颌尖牙阻生方面，上颌尖牙阻生与钉状侧切牙之间的关联已有充分文献记载。例如，Becker等[46]在其研究中发现16%的患者存在钉状侧切牙和上颌尖牙阻生（Stellzig等[47]甚至达35%）。Sacerdoti和Baccetti[48]发现17%的患者与小牙症相关（Marra等[49]为35%）。一些研究证实了与钉状上颌侧切牙及侧切牙先天缺失的关联[50]，一些作者证实了与钉状上颌侧切牙、侧切牙先天缺失、易位及其他牙齿阻生的关联[51]。
本研究分析了相对较多数量的下颌尖牙迁移患者，共95例。Sajnani等[52]分析了64例患者，Guarnieri等[21]分析了51例患者，但均未分析与其他牙齿异常的关联。在本研究中，下颌尖牙迁移患者与对照组之间在任何牙齿异常方面均未证实有统计学重要差异。本研究中下颌尖牙迁移患者最常见的牙齿异常是其他牙齿阻生（5颗上颌尖牙、1颗中切牙），但对照组中也有相同频率。易位、迁移和牛牙症仅存在于对照组（每种异常各1例患者）。第二前磨牙远中倾斜在对照组中不存在，仅见于研究组（1例患者）。
仅有少数研究分析了下颌尖牙阻生与其他牙齿异常之间的关联。Shapira等[53]分析了73例下颌尖牙阻生患者，发现9.5%的患者存在缺牙症。Azeem等[54]分析了20例患者，发现下颌尖牙阻生与形态、结构、数目或位置性牙齿异常之间无统计学显著性。迄今为止最大的样本量包含93例患者[55]，主要关注牙骨骼特征。在这项对93例波兰下颌尖牙迁移患者的回顾性研究中，临床检查期间仅发现三种其他牙齿异常：钉状上颌侧切牙、上颌侧切牙及下颌前磨牙先天缺失，但与我们的研究类似，研究组与对照组之间未发现统计学重要差异。最新的分析下颌尖牙阻生与其他牙齿异常关联的研究带来了非常令人惊讶的结果：在32例患者中证实了下颌尖牙阻生、牙齿阻生、易位和迁移的统计学重要性[34]。据我们所知，尚无研究分析研究组与对照组之间牙齿异常总体患病率的患者层面比较。在我们的结果中，无统计学重要差异。本研究的缺点是样本量相对较小，因此结果可能受偶然性影响。人工智能或其他方法可避免误判或遗漏牙齿异常。
牙齿阻生始终是延长治疗时间的并发症。因此，尽早诊断至关重要。由于下颌尖牙在早期混合牙列期萌出较早，且下颌尖牙迁移与其他牙齿异常的存在无关联，因此在7-8岁时拍摄OPG（口腔全景片）非常重要，这样可以分析牙齿的萌出路径，最终测量牙齿长轴与中线之间的角度。早期干预可以预防并发症和正畸治疗的延长。
6. 结论
这项回顾性研究证实，下颌尖牙迁移与任何牙齿异常之间没有统计学上重要的关联。由于下颌尖牙迁移的治疗始终困难且耗时较长，因此及时确立诊断非常重要。作为全科牙医，通过常规检查没有其他牙齿异常存在的提示，早期拍摄OPG对于早期发现下颌尖牙阻生仍然至关重要。
作者贡献
Dana Kloudová完成了材料准备。Dana Kloudová进行了数据收集。Dana Kloudová和Lucie Řehořová进行了分析。Dana Kloudová、Lucie Šimůnková Vítová、Lucie Řehořová和Bohumila Straková撰写了手稿的初稿。所有作者对手稿的各版本进行了评论，并对研究构思和设计做出了贡献。
资金
本研究未获得任何资金、资助或其他支持。
披露
所有作者均已阅读并批准了手稿的最终版本。通讯作者完全可以使用本研究中的所有数据，并对数据的完整性和数据分析的准确性承担全部责任。
伦理声明
本研究获得了布拉格查理大学第二医学院伦理委员会的批准，并符合《赫尔辛基宣言》的宗旨。
知情同意
无需知情同意，因为仅回顾性使用了匿名化的RTG或CBCT。
利益冲突
作者声明无利益冲突。
查看英文原文▾
1. Introduction
Tooth impaction is a common dental anomaly that occurs when a tooth fails to erupt into the oral cavity in its physiological time, is stuck in the alveolar bone and probably has exhausted its eruption force [1, 2]. Root has finished its development, and the delay of eruption is usually more than a year [3]. Except for third permanent molars, the most frequent impacted teeth dentists and orthodontists can meet with in their practice are permanent maxillary canines [4]. Their prevalence in the general population is in the range between 0.29% and 4.7%, although there are some differences for populations [5–9]. Vice versa, impaction of permanent mandibular canines is very rare. Their incidence was calculated approximately 20 times lower than by maxillary canines [10]. Another statistical research stated that from all diagnosed 858 impacted teeth, there were 91 impacted maxillary canines (10.6%) and only 4 impacted mandibular canines, which is only 0.46% of all impacted teeth and 23 times lower incidence than by maxillary canines [2]. According to population, race and methodologies of measurements, in other studies, there is an incidence of mandibular canine impaction in the range of 0.3%–2.8%, although some studies measured incidence up to 5.1% [11–15]. A common phenomenon associated with mandibular canine impaction is transmigration, when at least half of crown of impacted canines crosses the midline. This modern definition comes from Javid [16] and Joshi [17] modified it as a tendency of canine to cross the midline, as this dental anomaly can be diagnosed earlier when the tooth only horizontalized its position but has not crossed the midline yet. It is believed it commences at an early stage of mixed dentition (6–8 years) [18, 19]; therefore, authors of these studies recommend doing orthopantomogram (OPG) at this age during regular checkup. Their incidence is even lower, which ranges from 0.10% to 0.31% [20, 21]. Earlier, it was believed that transmigration is associated exclusively only with mandibular canines, but newer studies confirmed its occurrence also by maxillary canines [22, 23]. The mechanism of impaction is generally unknown, although many studies paid attention to this problematic, especially for maxillary canines. Two main theories have been established: the guidance theory and genetic theory. According to the guidance theory, represented mainly by Becker and Chaushu´s studies [24–26], root of maxillary lateral incisor fulfils functions of guidance for erupting canine. If development of root is delayed, root is too short or has an altered shape, guidance for canine is insufficient and canines becomes impacted. The genetic theory sees the cause of impaction strictly in the genetic factors, in genes mutation, respectively [27, 28]. Not much have been written about mandibular canine impaction. Dalessandri et al. [29] in their systematic review found only 13 studies. Local factors as aetiology are clear: odontomas, supernumerary teeth, cysts and crowding [30]. Yet there remains still large amount of impacted mandibular canines which aetiology is unknown, majority of them are transmigrated. Some authors claim mandibular canine impaction have strong genetic determinants, as this dental anomaly is often accompanied by other dental anomalies [12, 31].
In previous literature, there are not many studies mentioning associated dental anomalies, as most of this small number of studies dealing with mandibular canine transmigration are primarily case studies [19, 32, 33]. There are only a few retrospective studies aimed at the association between mandibular canine impaction and other dental anomalies, but sample size comprised from 32 mandibular canines only [34]. To our best knowledge, this study has the biggest sample size up to now with the aim to investigate whether there exist any association between mandibular canine transmigration and the presence of other dental anomalies, which could help dentists or orthodontists with early diagnosis and to contribute to make the treatment easier, because mandibular canine transmigration is always a challenge for orthodontic treatment.
2. Methods
The original sample size of this retrospective study comprised of 4000 patients from the Department of Dentistry, 2nd Faculty of Medicine, Charles University in Prague and one private practice between 2010 and 2024. All these patients had proper conventional pretreatment records, including OPGs (Gendex GXDP‐700, KAVO). On the basis of analysis of OPGs provided by three workers (Dana Kloudová, Lucie Šimůnková Vítová and Bohumila Straková), 120 patients with mandibular canine transmigration were selected. All these mandibular canine transmigrations were confirmed on cone beam computer tomography (CBCT; i‐CAT 17–19, Imaging Science International, Hatfield, PA, USA) and subsequently surgically. Inclusion criteria for embodiment into this study were healthy patients with at least one mandibular canine transmigration, no previous orthodontic treatment, good quality of pretreatment records and no trauma in history. Exclusion criteria were craniofacial syndromes, odontomas, other tumours, fibrous dysplasia, cysts, trauma and radiographs with poor quality. Patients with these diagnoses were excluded so there stayed only patients with unknown aetiology, which could indicate some genetic factor. Afterwards, 25 patients were removed from the research because of these selection criteria. Finally, 95 patients (48 males, 47 females) with a mean age of 11.4 ± 1.3 years were included into the study group (Figure 1). All transmigrated in–out study group were impacted, there was no transmigrated canine. The control group consisted of 99 patients with both physiologically erupted mandibular canines. All these patients underwent orthodontic treatment and were of a similar age and gender like patients from study group (54 males, 45 females, mean age 11.5 ± 1.3 years). No CBCT was made for the purpose of this study. This study obtained approval from Ethics Committee of 2nd Faculty of Medicine, Charles University in Prague and meets the tenets of the Declaration of Helsinki.
[图：Flowchart of participants in the study group.]
The study group and control group were examined for the presence of 16 dental anomalies.
Tooth agenesis is a dental anomaly when there is a developmental absence of a tooth in the primary or permanent dentition [35]. Four types of tooth agenesis were evaluated as follows:
[内容请查看原文]
Agenesis of maxillary lateral incisor.
[内容请查看原文]
Agenesis of maxillary second premolars.
[内容请查看原文]
Agenesis of mandibular second premolars.
[内容请查看原文]
Agnesis of mandibular incisor.
[内容请查看原文]
Impaction of other teeth is defined as a dental anomaly that occurs when a tooth fails to erupt into oral cavity during their physiological time of eruption [1]. All impacted teeth were included into this group.
[内容请查看原文]
Multiple impaction occurs when there are two or more other impacted teeth in the dentition [36].
[内容请查看原文]
Transposition is a dental anomaly that occurs when there is an exchange in the position between two adjacent teeth [37].
[内容请查看原文]
Transmigation of other teeth occurs when at least half of crown of impacted tooth crosses the midline [16]. This group involves all other transmigrated teeth.
[内容请查看原文]
Supernumerary teeth are defined as teeth that are in addition to the normal series of deciduous or permanent teeth, either as a single tooth or multiple teeth [38].
[内容请查看原文]
Infraocclusion of deciduous molars occurs when a deciduous molar is positioned below occlusal plane relative to the adjacent teeth [39].
[内容请查看原文]
Microdontia of maxillary lateral incisor is a dental anomaly characterised by a decreased size of a crown or the whole tooth, usually in all dimensions. The difference from common diameter is more than 2SD [40].
[内容请查看原文]
Microdontia of second premolars can be defined similarly as those in lateral incisor—teeth are smaller than normal. They have a smaller volume, too [41].
[内容请查看原文]
Peg‐shaped maxillary lateral incisor is a dental anomaly when a tooth has an altered shape of crown. The diameter narrows from the cervix to the incisal edge [28].
[内容请查看原文]
Distoangulation of second premolar is a dental anomaly that occurs when a crown is angulated distally; angle between long axis of the tooth and a line perpendicular to the occlusal plane is more than 15° [42].
[内容请查看原文]
Tooth rotation occurs when a tooth turns around its long axis [43].
[内容请查看原文]
Taurodontism is a dental anomaly defined as a developmental disturbance when the tooth has an enlarged pulp chamber and apical displacement of the pulpal floor. The crown is enlarged, the roots are significantly shorter [44].
3. Statistical Analysis
IBM SPSS Software for Windows (Version 24.0, IBM Corp, NY, USA) was used for statistical analysis. To determine the minimum sample size, an a priori power analysis using G∗Power was selected. It showed that the minimum needed number of subjects in the study is 81 (power = 0.81; α = 0.05; and effect size = 0.29). The level for statistical significance was predetermined to be lower or equal to 0.05. The frequencies of dental anomalies in patients with mandibular canine impaction were compared with the control group using Fisher´s exact test. This test was also used to calculate the statistical significance in the prevalence of total dental anomalies by patients between the study group and the control group. The p‐values were then false discovery rate (FDR) corrected. Confidence intervals (CI = 95%) and the odds ratio (OR) were also calculated. To analyse the reproducibility of diagnoses, re‐examining for every dental anomaly was repeated by the three authors (Dana Kloudová, Bohumila Straková and Lucie Šimůnková Vítová) within 1 month. To evaluate inter‐class reliability, an intraclass correlation coefficient (ICC), a two‐way mixed model was calculated. It showed excellent consistency for all variables (0.91–0.97). For intraclass measurements, one‐way random model was used. Results confirmed high reliability for all variables (0.92–0.99).
4. Results
In the present study, from an initial sample of 4000 patients with proper OPGs, 95 patients were diagnosed with at least one transmigrated mandibular canine. All these patients had CBCT consequently. Males:females ratio is almost equal as the study group consisted of 50.5% males (mean age 11.5 ± 1.4) and 49.5% females (mean age 11.4 ± 1.3) for the whole group (Table 1).
Table 1. Demographics of patients with mandibular canine impaction and control group.
| Sex | N | Age (year) mean + SD | |
|---|---|---|---|
| Study group | Male | 48 | 11.5 ± 1.4 |
| Female | 47 | 11.3 ± 1.2 | |
| Control group | Male | 54 | 11.8 ± 1.5 |
| Female | 45 | 11.2 ± 1.3 |
Prevalence and distribution of 16 dental anomalies, OR, confidence interval and p‐value are presented in Tables 2 and 3. Statistical tests confirmed that there is no statistically important association between mandibular canine transmigration and other dental anomaly as p‐value was never lower or equal to 0.05.
Table 2. Distribution of dental anomalies in patients with mandibular canine impaction and control group.
| Dental anomalies | Study group patients with anomaly | (%) | Control group patients with anomaly | (%) |
|---|---|---|---|---|
| Agenesis of maxillary lateral incisor | 1 | 1.05 | 0 | 0 |
| Agenesis of maxillary second premolar | 1 | 1.05 | 2 | 2.02 |
| Agenesis of mandibular incisor | 2 | 2.1 | 1 | 1.01 |
| Agenesis of mandibular second premolar | 3 | 3.15 | 3 | 3.03 |
| Peg shaped maxillary lateral incisor | 1 | 1.05 | 1 | 1.01 |
| Microdontia of maxillary lateral incisor | 1 | 1.05 | 0 | 0 |
| Microdontia of second premolar | 1 | 1.05 | 0 | 0 |
| Impaction of other tooth | 6 | 6.31 | 6 | 6.06 |
| Multiple impaction | 1 | 1.05 | 2 | 2.02 |
| Transposition | 0 | 0 | 1 | 1.01 |
| Transmigration of other teeth | 0 | 0 | 1 | 1.01 |
| Supernumerary teeth | 1 | 1.05 | 2 | 2.02 |
| Infraoclusion of deciduous molars | 4 | 4.21 | 4 | 4.04 |
| Distoangulation of mandibular second premolars | 1 | 1.05 | 0 | 0 |
| Taurodontism | 0 | 0 | 1 | 1.01 |
| Tooth rotation | 1 | 1.05 | 4 | 4.04 |
Table 3. Dental anomalies, p ‐value and other statistics.
| Dental anomalies | P ‐correct | OR | CI | p ‐Value |
|---|---|---|---|---|
| Agenesis of maxillary lateral incisor | 0.79 | 0 | (0; 37.42) | 0.49 |
| Agenesis of maxillary second premolar | 1 | 1.932 | (0.10; 115.46) | 1 |
| Agenesis of mandibular incisor | 1 | 0.476 | (0.01; 9.29) | 1 |
| Agenesis of mandibular second premolar | 0.9 | 0.959 | (0.13; 7.342) | 0.62 |
| Peg shaped maxillary lateral incisor | 1 | 0.959 | (0.01; 76.04) | 1 |
| Microdontia of maxillary lateral incisor | 0.79 | 0 | (0; 37.42) | 0.49 |
| Microdontia of second premolar | 0.79 | 0 | (0; 37.42) | 0.49 |
| Impaction of other tooth | 0.79 | 0.957 | (0.25; 3.73) | 0.12 |
| Multiple impaction | 1 | 1.932 | (0.1; 115.46) | 1 |
| Transposition | 0.79 | 0 | (0; Inf) | 0.49 |
| Transmigration of other teeth | 0.79 | 0 | (0; Inf) | 0.49 |
| Supernumerary teeth | 1 | 1.932 | (0.1; 115.46) | 1 |
| Infraoclusion of deciduous molars | 0.79 | 0.958 | (0.17; 5.31) | 0.37 |
| Distoangulation of mandibular second premolars | 0.79 | 0 | (0; Inf) | 0.49 |
| Taurodontism | 0.79 | 0 | (0; Inf) | 0.49 |
| Tooth rotation | 0.79 | 3.933 | (0.38; 196.76) | 0.37 |
The most frequent dental anomaly in study group was impaction of other teeth: prevalence rate is 6.32% (6 patients). The same prevalence occurred in control group (6 patients). The second most frequent dental anomaly in patients with mandibular canine transmigration was infraocclusion of deciduous molars (4 patients, 4.21%), the same frequency occurred again in control group (4 patients, 4.04%). Three patients with mandibular canine transmigration had agenesis of mandibular canine impaction, one patient was diagnosed with agenesis of mandibular incisor and another one patient with agenesis of maxillary lateral incisor. A very similar frequency of teeth agenesis occurred in control group. There was only one patient in study group who had both impaction of other tooth and agenesis of mandibular second premolar. In control group, no patient had two or more other dental anomalies simultaneously.
Peg‐shaped maxillary lateral incisors showed no difference between patients with mandibular canine impaction and control group (1 patient in both groups). Microdontia (of second premolar and maxillary lateral incisor) occurred only in control group.
Transposition, transmigration of other teeth and taurodontism occurred only in control group (1.01%), distoangulation of mandibular second premolar occurred only in study group (1.05%).
The patient‐level comparison (Table 4) revealed that the overall prevalence of dental anomalies did not significantly differ between the study and control groups (p = 0.64). This indicates that patients in the study group do not have a higher clinical predisposition to developing at least one other dental anomaly compared to the control group.
Table 4. Patient‐level prevalence of dental anomalies: comparison between groups.
| Group | Patients with anomalies | Patients with no anomalies | Total | Prevalence (%) | Fisher´s exact test |
|---|---|---|---|---|---|
| Study group | 23 | 72 | 95 | 24 | 0.64 |
| Control group | 28 | 71 | 99 | 28 |
5. Discussion
This study focused on the discovery of any association between mandibular canine transmigration and other dental anomalies. It consisted of 95 patients with mandibular canine transmigration, which is according to our knowledge one of the biggest sample size up to now.
Diagnosis of mandibular canine transmigration is easy and often coincidental during routine checkup by general dentists on an OPG, as it is usually asymptomatic [30, 45]. Only in a rare case is canine transmigration diagnosed because patients seek dentist due to pain, sensitivity or absence of permanent canine and persistence of its predecessor [16]. This could be considered as disadvantageous, because diagnosis is often set too late to prevent from progressing of the condition. The presence of other dental anomalies could alert general dentists and orthodontists of the presence of higher probability of mandibular canine transmigration and should enable to solve the problem sooner.
In maxillary canine impaction, association between maxillary canine impaction and peg‐shaped lateral incisors has been well documented. For example, Becker et al. [46] found in his study 16% patients with peg‐shaped lateral incisors and maxillary canine impaction (Stellzig et al. [47] even in 35%). Sacerdoti and Baccetti [48] found association with microdontia in 17% patients (Marra et al. [49] in 35%). Some studies confirmed association with peg‐shaped maxillary lateral incisor and agenesis of lateral incisor [50], some authors confirmed association with peg‐shaped maxillary lateral incisor, agenesis of lateral incisor, transposition and other tooth impaction [51].
In this study, a relatively high number of patients with mandibular canine transmigration were analysed, 95. Sajnani et al. [52] analysed 64 patients, Guarnieri et al. [21] 51 patients, but none of them analysed association with other dental anomalies. In our study, no statistically important difference has been confirmed for any dental anomaly between patients with mandibular canine transmigration and control group. The most frequent dental anomaly in patients with mandibular canine transmigration in our study was impaction of other teeth (5 maxillary canines, 1 central incisor), but the same frequency was also in the control group. Transposition, transmigration and taurodontism were present only in control group (one patients for every anomaly). Distoangulation of second premolars were not present in control group, only in study group (1 patient).
There are only a few studies analysing association between mandibular canine impaction and other dental anomalies. Shapira et al. [53] analysed 73 patients with mandibular canine impaction and found 9.5% patients with hypodontia. Azeem et al. [54] analysed 20 patients and found no statistical significance between mandibular canine impaction and shape, structural, number or positional dental anomalies. The biggest sample size up to now comprised 93 patients [55], focus was on dentoskeletal features primarily. In this retrospective study of 93 Polish patients with mandibular canine transmigration only three other dental anomalies were found during clinical examination: peg‐shaped maxillary lateral incisor, agenesis of maxillary lateral incisor and mandibular premolars, but similarly as in our study, there was found no statistically important difference between study and control group. Very surprising results brought the newest study analysing the association between mandibular canine impaction and other dental anomalies: in 32 patients were confirmed statistical importance in mandibular canine impaction, tooth impaction, transposition and transmigration [34]. To our best knowledge, there is no study analysing patient‐level comparison of overall prevalence of dental anomalies between the study and control groups. In our results, there was no statistically important difference. The disadvantage of this study is a relatively small sample size, so results could have been influenced by coincidence. AI or other methods could avoid misinterpreting or omitting dental anomalies.
Tooth impaction is always a complication that prolongs the treatment time. Therefore, it is important to diagnose it as soon as possible. As eruption of mandibular canine takes place sooner in early mixed dentition and there is no association between mandibular canine transmigration and presence of other dental anomalies, it is important to make OPGs at the age of 7–8 years that enables analysis of eruption path of the tooth eventually to measure the angle between long axis of the tooth and the midline. Early intervention can prevent from complication and prolongation of orthodontic treatment.
6. Conclusion
This retrospective study confirmed that there is no statistically important association between mandibular canine transmigration and any dental anomalies. As treatment of mandibular canine transmigration is always difficult and prolonged, it is important to set the diagnosis in time. As general dentists, by regular checkup have no hints in the presence of other dental anomalies, OPGs in early age remains crucial in early capture of mandibular canine impaction.
Author Contributions
Dana Kloudová created the material preparation. Dana Kloudová performed data collection. Dana Kloudová and Lucie Řehořová performed analysis. Dana Kloudová, Lucie Šimůnková Vítová, Lucie Řehořová and Bohumila Straková wrote the first draft of the manuscript. All the authors commented on versions of the manuscript and also contributed to the study conception and design.
Funding
This study received no funding, grants, or other support.
Disclosure
All authors have read and approved the final version of the manuscript. Corresponding author had full access to all of the data in this study and takes complete responsibility for the integrity of the data and the accuracy of the data analysis.
Ethics Statement
This study obtained approval from the Ethics Committee of 2nd Faculty of Medicine, Charles University in Prague and meets the tenets of the Declaration of Helsinki.
Consent
Consent was not required as there were only used anonymized RTG or CBCT retrospectively.
Conflicts of Interest
The authors declare no conflicts of interest.