Relationship between formation/eruption of maxillary teeth and skeletal pattern of maxilla.

Previous reports have indicated that formation and eruption of the maxillary teeth, especially the molars, are delayed in skeletal Class III patients compared with Class I and Class II patients. However, the relationship between the formation/eruption of maxillary teeth and the skeletal pattern of the maxilla is not yet clear. To examine this relationship, we studied 81 skeletal Class III Japanese patients (mean age, 8.8 years). The sample was divided into 2 groups: a maxillary retrusion (MR) group, characterized by a small SNA angle and a short palatal length, and a control group in which those values were in the normal range for patients of Japanese descent. There was no significant difference in the rate of formation for the maxillary and mandibular teeth between the 2 groups. The eruption of the maxillary second molars was delayed in the MR group compared with the control group. There were no significant differences between the 2 groups for any other teeth. A multiple-regression analysis was carried out to examine whether the skeletal pattern of the maxilla is a useful indicator for predicting the eruption of the maxillary teeth. The results showed that palatal length and chronologic age were significant independent (explanatory) variables for predicting eruption of the maxillary second molars. These findings indicated that the skeletal pattern of the maxilla is a useful indicator for predicting the timing of maxillary molar eruption when considering treatment of skeletal Class III malocclusions.     

Tooth anomalies associated with failure of eruption of first and second permanent molars

The occurrence of tooth anomalies in association with failure of the first and second molars to erupt was assessed in a sample of 1520 nonsyndromic subjects with uncrowded dental arches (mean age, 14 years 4 months) and compared with the prevalence rate calculated in a matched control group of 1000 subjects. The tooth anomalies examined included infraocclusion of deciduous molars, palatal displacement of maxillary canines, rotation of maxillary lateral incisors, aplasia of second premolars, and small size of maxillary lateral incisors. Associations among arrested eruption of first and second permanent molars and anomalies in tooth eruption and position (infraoccluded deciduous molars, palatally displaced canines, rotated maxillary lateral incisors) were highly significant (P <. 001). No significant association was found among the occurrence of molar eruption disturbances, aplasia of premolars, and small-sized laterals. These findings point to a common biologic cause for the appearance of failure of eruption of molar teeth and other disturbances in tooth eruption and position, most likely under genetic influence.     

328颗上颌恒切牙异常萌出原因的临床分析

目的分析导致上颌恒切牙异常萌出的原因,为提高诊疗水平提供理论依据。方法收集上颌恒切牙异常萌出的患者239例,共计328颗上领恒切牙,记录并分析导致上颌恒切牙异常萌出的原因,对数据进行统计学分析。结果328颗异常萌出的上颌恒切牙中,阻生或弯曲牙者64颗;上颌恒切牙已萌出,但位置异常者264颗,其中唇侧异常萌出45颗,腭侧异常萌出187颗,远中异常萌出32颗。对异常萌出的原因进行分析,上颌乳前牙根尖感染患者92例（38．5％）,上颌乳前牙外伤患者30例（12．6％）,上颌乳前牙滞留患者（非感染和外伤所致）26例（10．9％）,多生牙患者18例（7．5％）,上唇系带肥厚患者11例（4．6％）,口腔不良习惯、骨量不足等其它原因患者19例（7．9％）,另有43例（18．0％）患者合并局部或全身多种相关疾病。结论乳前牙根尖周炎是导致上颌恒切牙异常萌出的主要病因,儿童口腔医生应积极治疗乳牙疾病,去除或减轻导致上颌恒切牙异常萌出的因素,诱导儿童牙列和咬合功能的正常发育。     

Apical fenestration and ectopic eruption – effects from trauma to primary tooth: a clinical case report

Abstract – The study describes a multidisciplinary treatment of fenestration in the apical of a primary maxillary right central incisor due a trauma and also its sequel, an ectopic eruption of the permanent maxillary right central incisor, on 7‐year‐old boy. Clinically, the primary tooth had an enamel and dentin fracture with no pulp exposure. There was an apical fenestration in the vestibular region, and the permanent tooth had an ectopic palatal eruption. The primary tooth was extracted, and for the physiological reposition of the permanent tooth, which was crossed with its antagonist, a Haas appliance was used for the rapid expansion of the maxilla for a period of 9 days.     

Rapid forced eruption: a case report and review of forced eruption techniques

This article reviews the infrequently utilized treatment method of forced eruption and how it can serve as an alternative to the sacrifice of the natural root system. Forced eruption can preserve the natural root system and related periodontal architecture, resulting in years of additional service for the patient. It also can maintain adjacent tooth structure while retaining the option for future implant reconstruction. Given the reported success of forced eruption, the technique requires greater attention and increased application among dentists. A case of forced eruption in the anterior maxilla utilizing a removable device is described. An overview of forced eruption technique also is provided.     

上颌阻生尖牙闭合式助萌与开窗式助萌后牙周指数差异分析

目的：探讨上颌阻生尖牙闭合式助萌与开窗式助萌后牙周指数差异。方法：选择30例上颌阻生尖牙成功助萌患者（闭合式助萌与开窗式助萌各15例）,分别测量尖牙矫治入列后6、12个月时的牙菌斑指数（PLI）、牙龈出血指数（BI）、牙龈指数（GI）及边缘骨吸收量。结果：所选取的病例的阻生尖牙均被成功矫治排入牙列,开窗组的PLI、BI、GI均值及边缘骨吸收的量在矫治结束后6个月时均高于闭合组,差异有显著性;开窗组的PLI、BI、GI均值及边缘骨吸收的量在矫治结束12个月时略高于闭合组,但差异无显著性。结论：上颌阻生尖牙闭合式助萌后尖牙牙周状况明显好于开窗式助萌。     

原发性牙齿萌出障碍(PFE)的研究现状

原发性牙齿萌出障碍(PFE)是一种比较罕见的牙齿萌出异常性疾病,它是由于萌出机制本身异常而导致的牙齿萌出障碍,而非其他局部或全身因素所致。发病机制尚不十分明确,可能与基因突变有关,甲状旁腺激素受体1(PTH1R)突变是已经被证实的病因之一。临床表现以牙齿萌出不全和后牙开牙合为主要特征,正畸牵引无效。因其具有明显的家族聚集性,基因遗传分析是必要的辅助检查手段,对PFE的筛查、诊断和治疗具有重要意义。目前PFE尚无较好的治疗方法,可摘局部义齿、种植义齿和外科手术治疗等是可以参考的治疗手段。该文将从PFE的发病机制、临床特征、诊断和治疗等方面的研究现状作一综述。     

Geometric morphometric analysis of the palatal morphology in children with impacted incisors: A three-dimensional evaluation

Objective:To analyze variations in palatal morphology in subjects presenting unilaterally impacted maxillary permanent central incisors compared with a control group of subjects without eruption anomalies using a three-dimensional (3D) analysis.Materials and Methods:Twenty-six white subjects (10 girls and 16 boys; mean age 9.5 ± 1.5 years) with unilaterally impacted maxillary permanent central incisors (impacted incisor group [IIG]) were compared with a control group (CG) of 26 subjects (14 girls and 12 boys, mean age 8.7 ± 1.6 years) presenting no eruption disorders. For each subject, dental casts were taken and the upper arch was scanned using a 3D laser scanner. To study the entirety of the shape of the palate in any point of the surface, 3D geometric morphometrics was applied.Results:Subjects with impacted maxillary incisors showed skeletal adaptations of the maxilla. In the IIG, both the superior palatal region and lateral palatal surface showed significantly different morphology when compared with CG, with a narrower and higher palatal vault.Conclusion:The absence of maxillary central incisors over the physiological age of eruption influenced the development of the palatal morphology compared with subjects without eruption anomalies.     

磨牙倾斜角度和萌出间隙对第三磨牙萌出的影响

目的研究影响第三磨牙阻生或萌出的一些客观因素。方法选择86例(男37例,女49例)平均年龄25.4岁,上下颌第三磨牙均存在的患者,将其分为萌出组和阻生组,利用曲面断层片对患者上下颌第三磨牙的近中倾斜角、牙冠近远中径、磨牙后间隙、磨牙后间隙和牙冠近远中径的比值进行测量分析。结果上颌萌出组萌出间隙较阻生组大1.95mm,第二磨牙和第三磨牙长轴交角相差12.53°,萌出组第三磨牙近远中径比阻生组小0.69mm,有统计学差异。下颌萌出组萌出间隙L-ES(R)较阻生组平均值大3.33mm;第三磨牙与牙合平面交角阻生组较萌出组大32.48°;萌出组与阻生组的磨牙后间隙/牙冠近远中径平均值分别为1.05、0.85,3项指标差异均有显著性(P<0.01)。下颌第三磨牙近远中径相差0.3mm,无统计学意义。结论第三磨牙萌出受萌出间隙和磨牙间交角的影响,对于上颌第三磨牙,磨牙交角影响更大,对于下颌第三磨牙无足够的间隙萌出,是导致下颌第三磨牙阻生的重要原因。     

Tooth eruption symmetry in functional lateralities

Dental casts and oral photographs from a cross-sectional sample of 2092 young North Americans with detailed information on functional lateralities (eyedness, handedness and footedness) were examined to compare the proportions of symmetrical and asymmetrical eruption of the antimeric (left-right, contralateral pair) permanent teeth using a four-grade eruption scale. The proportion of symmetrically erupting antimeric teeth was higher for some teeth in those with non-right-sidedness of the feet and eyes, but not significantly so in the case of handedness. Left-footedness was significantly (95% confidence interval) associated with an increased proportion of symmetrical pairs of the maxillary first molar and mandibular lateral incisor, and non-right-eyedness with an increased proportion of symmetrical eruption and left/right non-balanced proportions of asymmetrical eruption in maxillary central incisors. True right-sidedness (hand, foot and eye) was significantly (P< or =0.05) associated with advanced eruption of the left mandibular first molar. It is suggested that while the timing of antimeric tooth emergence and clinical eruption is primarily programmed before crown mineralization, starting approximately at the 30th gestational week in the case of first permanent molars, symmetrical/asymmetrical tooth emergence and eruption may provide information a posteriori on prenatal and early postnatal growth and development.     

How to...mechanically erupt a palatal canine

Management of ectopic permanent maxillary canines represents one of the greatest challenges to orthodontists. This paper outlines a variety of techniques and mechanics which may facilitate expedient, predictable and safe eruption of palatal canines. While each method may be useful in isolation, the varying presentations of palatal canines ensure that the ability to apply an array of techniques is essential if successful outcomes are to be consistently achieved.     

Third molar eruption among rural Nigerians

Times of eruption of third molars were studied in rural Nigerian adolescents--125 males and 133 females. Results of this study showed that the average age for the initial eruption of third molars was 15 years in male subjects and 13 years for female subjects. The incidence of eruption showed a steep rise after the age of 16 years for male subjects and 14 years for female subjects. By the age of 19 years, all third molars had erupted into the oral cavity. The eruption of lower third molars was generally ahead of the upper third molars for all age groups. The results of this study suggest that (1) the timing of third molar eruption is strongly influenced by the availability of mandibular trigone space, (2) the attrition and shrinkage of the dental arch, probably as the result of nonrefined highly fibrous diets, produce larger mandibular trigone spaces, and (3) the early eruption of third molars observed in the present study may be due to the nature of the diet used and the vigorous employment of the masticatory apparatus (from infancy) by the subjects examined.     

Acceleration and circadian rhythm of eruption rates in the rat incisor.

The eruption of the rat mandibular incisor was measured at 4 or 6 hr intervals by a photographic method. Acceleration of eruption occurred immediately after the experimental shortening of the incisors with some further acceleration from 12 hr afterwards. A circadian rhythm of eruption rate was found in incisors with functional occlusion and also in those without biting contacts; that is, the eruption was slower during the night when the animals were physically most active.     

Delayed eruption of permanent teeth in hyperimmunoglobulinemia E recurrent infection syndrome

OBJECTIVE: To determine the incidence of abnormal tooth eruption in patients with hyperimmunoglobulinemia E (hyper-IgE) syndrome. STUDY DESIGN: This study evaluated 34 individuals with hyper-IgE syndrome (age range, 2-40 years). A comprehensive dental history and a head and neck evaluation were performed on all patients. Dental age was assessed in patients younger than 17 years by 2 methods: (1) clinical assessment of tooth eruption and (2) a radiographic method. Relationships between the chronologic age, dental developmental age, and age at tooth eruption were determined. Other oral or dental anomalies were recorded. RESULTS: Of patients older than 7 years, 75% reported problems with permanent tooth eruption, as evidenced by retained primary teeth or the need for elective extractions of primary teeth to allow eruption of permanent teeth. None of the patients experienced problems with eruption of primary teeth. Eruption of the first and second permanent molars also occurred on time. Dental maturity scores were established for 14 patients 17 years of age or younger. In each case, the difference between chronologic age and the estimated dental developmental age was less than 12 months; however, we found a significant discrepancy between the chronologic age and the mean age of tooth eruption in 80% of these patients when using a particular set of standardized values. Persistence of Hertwig's epithelial root sheath was observed on histologic examination. Chronic multifocal oral candidiasis was a consistent feature in patients with hyper-IgE recurrent infection syndrome. Other oral anomalies were also noted. CONCLUSION: We confirmed that a disorder of tooth eruption is part of the hyper-IgE syndrome. This problem occurs because of delayed primary tooth exfoliation rather than a developmental delay in the formation of the permanent dentition. The persistence of Hertwig's epithelial root sheath is unusual and may be associated with the lack of resorption of the primary teeth. Dentists should be aware of this feature of hyper-IgE syndrome because timely intervention will allow normal eruption to occur.     

A case of eruption guidance for eruption disturbances of the bilateral second molars caused by supernumerary teeth

We report a rare case of eruption disturbance of the bilateral second molars caused by supernumerary teeth in a 7-year-old Japanese boy. The supernumerary teeth were detected by radiographic examination. Computed tomography (CT) was used to examine the positional relationship of the supernumerary teeth and neighboring second molars. CT images showed conical-shaped supernumerary teeth on the upper buccal side of the unerupted mandibular second molars. The cusps of the supernumerary teeth pointed toward the lingual side. Because the two supernumerary teeth threatened to disturb the eruption of the second molars, they were surgically removed at 2 years and 4 months after diagnosis. After removal of the supernumerary teeth, the mandibular second molars erupted at a normal age and aligned normally within the dentition. To the best of our knowledge, this is only one case report of eruption guidance for eruption disturbances of the bilateral second molars caused by supernumerary teeth.     

A systematic review of the consequences of premature birth on palatal morphology, dental occlusion, tooth-crown dimensions, and tooth maturity and eruption

This systematic review addresses the question whether prematurity results in alteration of palatal morphology, dental occlusion, tooth-crown dimensions, and tooth maturation. A literature survey from the PubMed database covering the period from January 1966 to November 2002 used the Medical Subject Headings terms "infant, premature," and "infant, low birth weight" in combination with "jaws," "dental physiology," "dentition," and "tooth abnormalities." Controlled studies written in English and with definitions of premature birth according to the World Health Organization were selected. Two reviewers selected and extracted the data independently and also assessed the quality of the studies. The search strategy resulted in 113 articles, of which 13 met the inclusion criteria. Scientific evidence was found for altered palatal morphology in the short term among the premature children, and oral intubation was a contributing factor to the alterations. If corrected age was considered for the premature children, no delay in dental development and eruption was found compared with normally born children. Thus, the early birth of premature children must be taken in account when planning for orthodontic treatment. Because of the contradictory results and lack of longitudinal studies, the scientific evidence was too weak to answer the questions whether premature birth causes permanent alteration of palatal morphology, alteration of dental occlusion, and altered tooth-crown dimensions. To answer these questions and obtain reliable scientific evidence whether premature children are at risk for malocclusions from possible alterations of palatal morphology such as asymmetry and high arched palates, further well-designed controlled studies as well as longitudinal studies are needed.     

Retrospective analysis of the factors influencing mesiodentes eruption

Aim.  This study aimed to evaluate the factors that predict the spontaneous eruption of mesiodens.
Design.  From the records of 431 patients (346 boys and 85 girls, average age 8.8 years) who visited Samsung Medical Center from January 2002 to December 2006, 471 mesiodentes were reviewed. The eruption rate was investigated according to the width/length ratio, angulation, location, and shape determined from periapical or panoramic radiographs.
Results.  The regression model showed that the width/length ratio and angulation were important determinants influencing the eruption of mesiodentes ( P  < 0.001, Pearson's r  = 0.619). The location of the mesiodentes also affected their eruption ( P  < 0.01). However, no significant relationship was detected between the shape and eruption rate of mesiodentes ( P  > 0.05).
Conclusions.  A lower probability of spontaneous eruption existed when the tooth had a greater angulation, shorter length, and wider width. Spontaneous eruption occurs more often when the mesiodens is located between the permanent incisors.     

Requirement of alveolar bone formation for eruption of rat molars

Tooth eruption is a localized event that requires a dental follicle (DF) to regulate the resorption of alveolar bone to form an eruption pathway. During the intra-osseous phase of eruption, the tooth moves through this pathway. The mechanism or motive force that propels the tooth through this pathway is controversial but many studies have shown that alveolar bone growth at the base of the crypt occurs during eruption. To determine if this bone growth (osteogenesis) was causal, experiments were designed in which the expression of an osteogenic gene in the DF, bone morphogenetic protein-6 (Bmp6), was inhibited by injection of the first mandibular molar of the rat with a small interfering RNA (siRNA) targeted against Bmp6. The injection was followed by electroporation to promote uptake of the siRNA. In 45 first molars injected, eruption was either delayed or completely inhibited (seven molars). In the impacted molars, an eruption pathway formed but bone growth at the base of the crypt was greatly reduced compared with the erupted first-molar controls. These studies show that alveolar bone growth at the base of the crypt is required for tooth eruption and that Bmp6 may be essential for promoting this growth.     

Primary tooth resorption and its role in the normal tooth eruption process

The objective of this article is to review the process of permanent tooth eruption and primary tooth resorption in the context of the major theories of tooth eruption. This review will also focus on diagnostic criteria including radiographic, clinical, and genetic analysis to help distinguish between eruption anomalies such as isolated ankylosis of primary or permanent teeth versus eruption failure. Our studies of eruption failure have revealed that a much greater number of cases than previously suspected account for a hereditary form of eruption failure versus an isolated ankylosis. The importance of distinguishing eruption failure from isolated ankylosis (in primary and especially permanent teeth) is that the resultant management and prognosis differs greatly between the two. Management of isolated ankylosis is definitively treated by extraction of the offending tooth while eruption failure from a genetic defect may result in no treatment at all or multiple single tooth osteotomies. A complete understanding of the clinical presentation and biological mechanisms underlying eruption and eruption disorders will facilitate the best diagnosis and patient management of difficult clinical cases.     

The influence of calibrated loads upon the rate of eruption of mandibular rat incisors

A method for the application of constant intrusive loads on the rat mandibular incisor is described. In 20 rats, occlusion of the left incisor was eliminated and the tooth was subjected to direct light, medium and heavy intrusive loads. Light loads (1.8–3.2 g) reduced eruption by 34 per cent and medium loads (4.9–7.4 g) by 61 per cent on the first day of application. On the following days, the eruption decreased steadily and ceased almost entirely after 2 weeks. Heavier axial loads stopped eruption immediately. The eruption rate of the contralateral incisor was slightly retarded in all experimental animals.