The etiology of palatal displacement of maxillary canines

Palatal displacement of maxillary canines occurs with greater frequency in patients with certain genetically determined abnormalities, including peg-shaped, reduced and congenitally missing lateral incisors. One view is that the canine aberration is similarly genetically determined, while a second view is that the genetically determined anomalies of the lateral incisors provide an environment that deprives the erupting canine of its normal guidance. Earlier work has shown that canine displacement occurs more frequently in patients with peg-shaped or reduced lateral incisors than in those with missing lateral incisors, which has been explained away by variability due to gene penetrance and individual thresholds. A group of individuals was examined, in whom a missing lateral incisor on one side, a peg-shaped or reduced lateral incisor on the other, and a palatal canine were present in the same individual, in order to eliminate gene penetrance and individual thresholds as factors. A distinct preference for the canine anomaly to occur on the side of the peg-shaped or reduced lateral incisor was found. This was considered to provide evidence in support of the existence of non-genetic, environmental factors in the causation of palatal canine displacement.     

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.     

Tooth-size reduction associated with occurrence of palatal displacement of canines

This study investigates mesiodistal crown size of the maxillary and mandibular incisors of patients with palatally displaced canines (PDC). Pretreatment dental casts of orthodontic patients with PDC of 1 or both maxillary canines (N = 31; M10:F21) were collected. This PDC sample was matched according to age and sex with pretreatment dental casts from unaffected orthodontic patients. For the PDC and matched control samples, maximum mesiodistal crown diameters were recorded for the 4 incisors on the left side only. The results showed that, on average, the mesiodistal crown diameters for the maxillary and mandibular incisors measured smaller in the PDC sample than in the control sample. These findings of statistically significant tooth-size reductions associated with PDC occurrence indicate a generalized pattern of reduced tooth size as a characteristic associated with the PDC anomaly. Further, the presence of generalized tooth-size reduction in cases with palatally displaced canines helps explain why most orthodontic treatment plans for PDC patients are of the nonextraction type.     

Dentoskeletal characteristics in patients with palatally and buccally displaced maxillary permanent canines

The aim of this retrospective study was to analyse dentoskeletal characteristics in patients with eruption disturbances of the maxillary permanent canines. Pre-treatment panoramic radiographs and lateral cephalograms of 636 consecutive orthodontic patients were assessed. The control group included 456 patients with physiologically erupted maxillary permanent canines (261 females and 195 males, mean age 12.6 and 12.4 years, respectively). The other groups comprised 144 subjects with palatally displaced canines (PDCs) (92 females and 52 males, mean age 14.2 and 14.7 years, respectively) and 36 patients with buccally displaced canines (BDCs) (16 females and 20 males, mean age 12.4 and 12.8 years, respectively). The selected dentoskeletal parameters were compared with classic cephalometric norms using the method of analysis of variance, chi-square, and Fisher's exact tests. The PDC patients showed a significantly more prognathic maxilla, a significantly more frequent occurrence of skeletal class I, retroinclination of maxillary central incisors, hypodivergent relationship, and mandibular anteriorotation and less frequent posteriorotation. A significantly more frequent retrognathic maxilla and skeletal class III and less frequent retroinclination of the maxillary central incisors were found in the BDC patients. The results of this study indicate the existence of different facial morphology and more likely also etiopathogenesis of eruption disturbances of the canines in the PDC and BDC patients.     

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。     

Tooth resorption associated with the eruption of maxillary canines

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

上颌腭侧埋伏阻生尖牙 CBCT 导引下的牵引治疗

目的:探讨锥形束CT(CBCT)三维(3D)重建在上颌腭侧埋伏阻生尖牙牵引治疗中的指导作用。方法:对22例上颌尖牙(共26颗)腭侧埋伏阻生的青少年患者行CBCT检查。CBCT三维重建观察尖牙形态、腭侧埋伏状况,测量分析与邻近组织的位置关系及相邻切牙牙根吸收情况。结果:CBCT能够真实再现颌骨内埋伏的上颌尖牙。埋伏尖牙均近中倾斜,与平面平均成角61.1°±18.1°,近中异位分别为Ⅰ类埋伏尖牙8颗、Ⅱ类5颗、Ⅲ类3颗、Ⅳ类10颗。3颗相邻侧切牙及2颗中切牙因严重牙根吸收而拔除;26颗上颌腭侧埋伏尖牙均成功牵引至平面排入牙弓并建立正常咬合。结论:CBCT能立体再现上颌尖牙腭侧埋伏阻生特征及与邻近牙的关系等,对治疗方案的制定、开窗牵引具有指导作用,可提高疗效。     

Favourable spontaneous eruption of severely displaced maxillary canines with associated follicular disturbance

Cases of severely displaced unerupted maxillary canines are presented, related to disturbance of the follicle. Removal of the deciduous predecessor produced favourable eruption of the permanent canine and should be considered as a treatment option in similar cases.     

Supplemental permanent maxillary canines: report of two rare bilateral cases.

Supernumerary teeth in the permanent maxillary canine areas are uncommon, and are usually in the form of small conical-shaped teeth. Only a few reports of supplemental maxillary canines have been published in the literature, and most relate to unilateral cases. Bilateral occurrence of such supplemental teeth in non-syndromic patients has been reported to be extremely rare. This article reports two cases of bilateral supplemental permanent maxillary canines in children with no associated syndrome.     

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阻生牙是临床上常见的牙齿发育障碍之一,尖牙阻生是最常见的类型,其中腭侧阻生尖牙发生率较唇侧阻生更常见。如何准确地诊断、治疗腭侧阻生的尖牙,一直是正畸中非常有挑战的内容。借助锥形束CT的帮助,阻生尖牙的诊断变得越来越容易。激光的应用使开窗手术更易止血,粘接操作更准确可靠。灵活、有序的正畸牵引,使牵引过程更可控,从而提高了治疗效率。对牙周的关注,更加提高了阻生尖牙治疗后的质量。阻生牙牵引后更需注意保持,3～6个月的固定保持更有利于牙周的改建。     

Eruption of maxillary canines

Abstract – In 79 of 124 children with bilaterally located widened follicles around non-erupted canines one of the maxillary canines was chosen by lot for surgical exposure of the tooth crown. In seven cases both maxillary canines were exposed. The remaining 38 children were radiographically controlled at certain time intervals as were the 86 cases where surgery was perfomed. The follicles removed from 52 cases were tooth. The histologic examination showed that the histologic appearance of the extirpated follicle did not correspond to the radiolographically verified width of the pericoronal space. The specimens were composed of a losely arranged fibrous connective tissue with an epithelial lining occurring in 77% of the cases. The epithelial lining consisted of reduced enamel epithelium and showed in none of the cases squamous metaplasia or keratinization. Nor was there any clinical or histologic sign of a neoplastic or cystic change of the follicle.     

Dental arch parameters of the displacement and nondisplacement sides in subjects with unilateral palatal canine ectopia

Objective:To compare arch perimeter and teeth size, number, and shape between the two sides of the dental arch—the canine displacement side (DS) and the nondisplacement side (NDS)—in subjects with unilateral palatally displaced canine (PDC).Materials and Methods:Orthopantomograms (OPTs) of 240 subjects with unilateral PDC and 240 OPT matching controls were used. Additionally, study casts of 100 study subjects and 100 controls were used. The age of subjects ranged between 14 and 25 years. Dental casts were digitized and several parameters were recorded.Results:The transverse width from midpalatal line to the buccal segment and the palatal area on the DS was larger than that in the NDS (P < .05 to .001), with no difference in tooth size between both sides. Maxillary second premolars, canines, and lateral incisors in the PDC group were smaller than those in control group. Peg-shaped lateral incisors were significantly more frequent in the study group (P < .001).Conclusions:The transverse width of the DS was larger than that of the NDS. Both sides were generally smaller than those of the control group. Tooth size in the DS was comparable to that in the NDS but smaller than those of the control group. A missing or peg-shaped lateral incisor was the most common reported anomaly.