Abnormal bone remodelling activity of dental follicle cells from a cleidocranial dysplasia patient.

OBJECTIVES: To explore the role of dental follicle cells (DFCs) with a novel cleidocranial dysplasia (CCD) causative gene RUNX2 mutation (DFCsRUNX2+/m ) in delayed permanent tooth eruption. MATERIALS AND METHODS: A CCD patient with typical clinical features was involved in this study. DFCsRUNX2+/m were cultured and DNA was extracted for RUNX2 mutation screening. Measurements of cell proliferation, alkaline phosphatase (ALP) activity, alizarin red staining and osteoblast-specific genes expression were performed to assess osteogenesis of DFCsRUNX2+/m . Co-culture of DFCs and peripheral blood mononuclear cells (PBMCs), followed tartrate-resistant acid phosphatase (TRAP) staining, real-time PCR and western blot were performed to evaluate osteoclast-inductive capacity of DFCsRUNX2+/m . RESULTS: A missense RUNX2 mutation (c. 557G>C) was found in DFCsRUNX2+/m from the CCD patient. Compared with normal controls, this mutation did not affect the proliferation of DFCsRUNX2+/m , but down-regulated the expression of osteogenesis-related genes, leading to a decrease in ALP activity and mineralisation. Co-culture results showed that DFCsRUNX2+/m reduced the formation of TRAP+ multinucleated cells and the expression of osteoclastogenesis-associated genes. Furthermore, the mutation reduced the ratio of RANKL/OPG in DFCsRUNX2+/m . CONCLUSIONS: DFCsRUNX2+/m disturbs bone remodelling activity during tooth eruption through RANK/RANKL/OPG signalling pathway and may thus be responsible for impaired permanent tooth eruption in CCD patients.

The Relationship between Dental Follicle Width and Maxillary Impacted Canines' Descriptive and Resorptive Features Using Cone-Beam Computed Tomography.

OBJECTIVES: To assess the relationship between dental follicle width and maxillary impacted canines' descriptive and resorptive features with three-dimensional (3D) cone-beam computed tomography (CBCT). METHODS: The study comprised 102 patients with cone-beam computed tomography 3D images and a total of 140 impacted canines. The association between maxillary impacted canine dental follicle width and the variables of gender, impaction side (right and left), localization of impacted canine (buccal, central, and palatal), and resorption of the adjacent laterals was compared. Measurements were analyzed with Student's t-test, Kruskal-Wallis test, and Mann-Whitney U statistical test. RESULTS: According to gender, no statistically significant differences were found in the follicle size of the maxillary impacted canine between males and females (p > 0.05). Widths of the follicles were determined for the right and left impaction sides, and no statistically significant relation was found (p > 0.05). There were statistically significant differences between root resorption degrees of lateral incisors and maxillary impacted canine follicle width (p < 0.05). Statistically significant higher follicle width values were present in degree 2 (mild) resorption than in degree 1 (no) and degree 3 (moderate) resorption samples (p < 0.05). CONCLUSIONS: No significant correlation was found between follicle width and the variables of gender, impaction side, and localization of maxillary impacted canines. Our study could not confirm that increased dental follicle width of the maxillary impacted canines exhibited more resorption risk for the adjacent lateral incisors.

RUNX2 mutation impairs bone remodelling of dental follicle cells and periodontal ligament cells in patients with cleidocranial dysplasia.

RUNX2 is an important osteo-specific factor with crucial functions in bone formation and remodelling as well as resorption of teeth. Heterozygous mutation of RUNX2 can cause cleidocranial dysplasia (CCD), a systemic disease with extensive skeletal dysplasia and abnormality of tooth growth. In our study, dental follicle cells (DFCs) and periodontal ligament cells (PDLCs) were isolated, cultured and identified from one patient with CCD and compared with normal controls. This CCD patient was confirmed to have a heterozygous frameshift mutation of RUNX2 (c.514delT, p.Ser172fs) in the previous study. The results showed that the proliferation abilities of DFCs and PDLCs were both disturbed by the RUNX2 mutation in the CCD patient compared with the normal control. A co-culture system of these cells with human peripheral blood mononuclear cells was then used to investigate the effect of RUNX2 mutation on osteoclastogenesis. We found that the RUNX2 mutation in CCD reduced the expression of osteoclast-related genes, such as RUNX2, CTR, CTSK, RANKL and OPG The ability of osteoclastogenesis in DFCs and PDLCs detected by tartrate-resistant acid phosphatase staining in the co-culture system was also reduced by the RUNX2 mutation compared with the normal control. These outcomes indicate that the RUNX2 mutation disturbs the modulatory effects of DFCs and PDLCs on the differentiation of osteoclasts and osteoblasts, thereby interfering with bone remodelling. These effects may contribute in part to the pathological manifestations of retention of primary teeth and delayed eruption of permanent teeth in patients with CCD.

Root resorption of the maxillary lateral incisor caused by impacted canine: a literature review.

Root resorption of maxillary lateral incisors caused by erupting canines is well known and a relatively common phenomenon. However, much debate and conflicting evidence exists with regard to the actual resorption trigger and potential etiological factors involved. Consequently, there are no obvious clinical clues concerning prevention and diagnosis as well as subsequent treatment decisions. The introduction of cone beam computer tomography has recently allowed drawing a new and much more documented light on the diagnostic and therapeutic strategies. However, no investigations have determined that this new information may result in another and better diagnostic approach and an improved treatment outcome. Therefore, the present review will attempt to summarize the existing evidence on two- and three-dimensional images and try to link the radiological observations to any further preventive, diagnostic, and/or therapeutic measures. Detection thresholds, accuracy, and reliability of impacted canine localization and neighboring root resorption risks will also be considered. This review demonstrates how adding a third-dimension to the radiographic information may notably alter the prevalence of root resorptions and descriptions of this prevalence. In any case, further investigation is needed to determine resorption detection thresholds in various two-dimensional and three-dimensional imaging techniques, as well as to determine therapeutic thresholds and criteria for strategic tooth extraction based on radiographic manifest and not manageable resorption lesions.

Colocación quirúrgica de sistemas de anclaje para la tracción ortodóncica de los caninos incluidos / Surgical placement of attachment systems for orthodontic traction of impacted canines

El tratamiento de los casos que presentan caninos incluidos requiere un enfoque multidisciplinar en el que participan el ortodoncista y el periodoncista, y la coordinación de ambos profesionales y el establecimiento de criterios de actuación comunes son clave para conseguir los objetivos propuestos. En este artículo se revisan los aspectos fundamentales del diagnóstico y del manejo de estos casos, así como las técnicas quirúrgicas que la periodoncia pone a disposición de la ortodoncia para el abordaje de dichos dientes y la colocación de elementos de anclaje que permitan una posterior tracción ortodóncica (AU)

Cisto dentígero x folículo pericoronário espessado: possibilidades do diagnóstico histopatológico / Dentigerous cyst x hiperplasic pericoronal follicle: possibilities of histophatological diagnostic

A distinção clinicopatológica entre um cisto dentígero incipiente e um folículo pericoronário espessado representa, usualmente, uma tarefa difícil. Neste estudo, os autores procederam a uma reavaliação microscópica dos 113 casos diagnosticados como cisto dentígero na Disciplina de Patologia Oral da Universidade Federal do Rio Grande do Norte (UFRN), no intuito de estabelecer critérios histopatológicos para a distinção entre as duas entidades. Constatou-se que o limitante epitelial do tipo reduzido de órgão do esmalte, descontínuo e delgado, bem como um tecido conjuntivo capsular frouxo, com escassas células mononucleadas poderiam ser sugestivos de um folículo pericoronário espessado. Ressalta-se, entretanto, a importância das informações clínicas e cirúrgicas para emissão de um correto diagnóstico

The fate of developing teeth in mandibular lengthening by distraction: an experimental study.

PURPOSE: The purpose of this study was to observe developing teeth in a lengthened mandible after distraction. MATERIAL: Ten mongrel dogs with deciduous dentitions were used. METHODS: A corticotomy was carefully made around a tooth bud and the external distractor (Orthofix M-100) was connected. After a 5-day latent period, distraction was started at a rate of 0.75 mm per day for 10 consecutive days. Then, the lower jaw was stabilized by an external fixation to allow ossification. While the operation was performed on the left side (Distraction group), the contralateral side was studied for comparison (Control). In addition, a corticotomy, artificial fracture and external fixation were carried out to confirm the influence of the operation (Fracture group). Then macroscopic, radiographic and histological evaluations were carried out. RESULTS: In the Distraction group, the space between the wall of the dental follicle and the crown expanded as distraction began. The end of the calcified root became wider and irregular during the distraction period, and finally, the apex closed. In the Fracture group, the teeth erupted although slight alterations of the root shape were observed in association with the operation period. CONCLUSION: The root became irregular, but the teeth erupted within the distraction area.

External resorption associated with tooth eruption.

A case is presented with severe resorption on the mesial root of the mandibular first permanent molar in a patient with Juvenile Periodontitis. The follicle of the bicuspid is seen in contact with mesial root of the molar.

The effects of local trauma to the enamel-related periodontal tissues in the eruption of the rat incisor.

The periodontal tissues related to enamel (PTE) of the rat incisor comprise a connective tissue derived from the dental follicle and the enamel organ with its successive stages of development. Localized damage to these tissues in rat lower incisors was done surgically in three ways: with an endodontic file introduced into the labial periodontal space through either (i) its basal or (ii) its incisal extremities, or (iii) by the partial removal of the mandibular lower border, at the level of the molar teeth, together with the introduction of an endodontic file into the incisal part of that space. The lesions in the molar region of the PTE produced first a variable period of retarded eruption, and, depending upon their extent or degree were followed by a cessation of the eruptive movement and, in the majority of the operated teeth, a recovery of the normal eruption rate before the end of the experiment (17 weeks after surgery). Access to the PTE through the basal portion of the socket was erratic, but when the tissues were damaged produced similar effects. Effects on eruption of lesions produced through the alveolar crest were minimal or even absent. Localized injury to the periodontal ligament of either lower or upper incisors did not produce similar effects on tooth eruption. The dental follicle and the enamel organ of teeth of limited growth when their crown is completed are similar to the PTE in the molar region of continuously growing rodent incisors. In teeth of limited growth these tissues play an essential part in the intraosseous stage of eruption. The results here suggest that the PTE may also have a role in the supraosseous stage of eruption, which is continuous in teeth such as rat incisors due to the presence of a continuously functioning odontogenic organ.

Eruption of maxillary canines.

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 performed. The follicles removed from 52 cases were histologically examined. The result showed that surgical exposure did not enhance the eruption of the tooth. The histological examination showed that the histologic appearance of the extirpated follicle did not correspond to the radiographically verified width of the pericoronal space. The specimens were composed of a loosely 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.