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The epithelial cell rests of Malassez (ERM) are essential in preventing ankylosis between the alveolar bone and the tooth (dentoalveolar ankylosis). Despite extensive research, the mechanism by which ERM cells suppress ankylosis remains uncertain; perhaps its varied population is to reason. Therefore, in this study, eighteen unique clones of ERM (CRUDE) were isolated using the single-cell limiting dilution and designated as ERM 1-18. qRT-PCR, ELISA, and western blot analyses revealed that ERM-2 and -3 had the highest and lowest amelogenin expression, respectively. Mineralization of human periodontal ligament fibroblasts (HPDLF) was reduced in vitro co-culture with CRUDE ERM, ERM-2, and -3 cells, but recovered when an anti-amelogenin antibody was introduced. Transplanted rat molars grown in ERM-2 cell supernatants produced substantially less bone than those cultured in other cell supernatants; inhibition was rescued when an anti-amelogenin antibody was added to the supernatants. Anti-Osterix antibody staining was used to confirm the development of new bones. In addition, next-generation sequencing (NGS) data were analysed to discover genes related to the distinct roles of CRUDE ERM, ERM-2, and ERM-3. According to this study, amelogenin produced by ERM cells helps to prevent dentoalveolar ankylosis and maintain periodontal ligament (PDL) space, depending on their clonal diversity., (© 2022. The Author(s).)

Primary molar ankylosis with infraocclusion can retard dental arch development and cause dental asymmetry. Despite its widespread prevalence, little is known about its molecular etiology and pathogenesis. To address this, RNA sequencing was used to generate transcriptomes of furcal bone from infraoccluded (n = 7) and non-infraoccluded (n = 9) primary second molars, all without succeeding biscuspids. Of the 18 529 expressed genes, 432 (2.3%) genes were differentially expressed between the two groups (false discovery rate < 0.05). Hierarchical clustering and principal component analysis showed clear separation in gene expression between infraoccluded and non-infraoccluded samples. Pathway analyses indicated that molar ankylosis is associated with the expression of genes consistent with the cellular inflammatory response and epithelial cell turnover. Independent validation using six expressed genes by immunohistochemical analysis demonstrated that the corresponding proteins are strongly expressed in the developing molar tooth germ, in particular the dental follicle and inner enamel epithelium. The descendants of these structures include the periodontal ligament, cementum, bone and epithelial rests of Malassez; tissues that are central to the ankylotic process. We therefore propose that ankylosis involves an increased inflammatory response associated with disruptions to the developmental remnants of the dental follicle and epithelial rests of Malassez.

Introduction: Nonsyndromic primary failure of eruption (PFE) is a rare autosomal dominant disorder of dental eruption with no obvious dental or soft tissue interference. The purposes of this study were to genetically and clinically characterize a family with many members affected by PFE and to describe the natural evolution of the disorder., Methods: Three generations of a family with 18 members, 10 of them clinically affected by PFE, were evaluated periodically during 20 years of clinical follow-up. PFE was observed in varying degrees of severity in both sexes. Clinical presentation became more severe in adulthood. One patient had spontaneous reeruption of 2 posterior teeth. Cervical root resorptions were observed in 3 members. Genetic analysis showed a deleterious heterozygous mutation in intron 9 of the PTH1R gene (c.639-2A>G) and diagnosed an additional affected member., Conclusions: The long-term follow-up of PFE cases in this family permitted the following observations: (1) the onset occurred from the preemergence to the postemergence phases, (2) PFE appeared to be closely related to ankylosis, (3) affected teeth maintained the eruptive potential even in adulthood, (4) the earlier the onset the more severe the open bite, and (5) cervical root resorptions occurred in 3 affected members., (Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Proper diagnosis and management of eruption disturbances remains challenging but is critical to a functional occlusion. The objective of this study was to establish definitive criteria to differentiate and diagnose eruption disorders, specifically primary failure of eruption (PFE) and ankylosis., Methods: Sixty-four affected persons were placed into 3 cohorts: PFE diagnosed through confirmed PTH1R mutation (n = 11), PFE diagnosed based on clinical criteria (n = 47), and ankylosis diagnosed based on clinical criteria (n = 6). These groups were assessed to identify clinical features that differentiate PFE and ankylosis., Results: Ninety-three percent of the subjects in the genetic and clinical PFE cohorts combined (n = 58) and 100% in the genetic PFE cohort had at least 1 infraoccluded first permanent molar. Additionally, a novel functional PTH1R mutation, 1092delG, was identified and linked to PFE in the deciduous dentition., Conclusions: An infraoccluded, supracrestal first molar is a hallmark of PFE, often involving both arches in the permanent or deciduous dentition, and with unilateral or bilateral affection, infraoccluded second premolar or second molar, and multiple affected adjacent teeth. Our results further suggest that PFE and ankylosis might be clinically indistinguishable without knowledge of prior trauma, treatment history, genetic information, or obliteration of the periodontal ligament space., (Copyright © 2013 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

The rare condition of secondary retention has been reported in the literature as being of genetic origin, with some authors suggesting an autosomal dominant pattern. We report the unusual case of two monozygotic biamniotic, bichorionic male twins, who were discordant for permanent first molar secondary retention, involving ankylosis. Twin A showed normal occlusion and eruption patterns, whereas Twin B displayed a left open bite, in relation with a totally submerged primary second molar leading to retention of the underlying premolar (35), and severe infraocclusion of the adjacent permanent molar (36). After orthodontic failure to close the open bite, ankylosis of 36 was confirmed, whereas 26 became severely infraoccluded.The mother had a history of bilateral molar ankylosis and presented reduced posterior alveolar height. Discordance in this twin pair demonstrates that environmental influences, in addition to epigenetic and local factors, may play a role in secondary retention, which is difficult to diagnose and challenging to treat., (Copyright © 2011 CEO. Published by Elsevier Masson SAS. All rights reserved.)

Introduction: Primary failure of eruption (PFE) is characterized by nonsyndromic eruption failure of permanent teeth in the absence of mechanical obstruction. Recent studies support that this dental phenotype is inherited and that mutations in PTH1R genes explain several familial cases of PFE. The objective of our study was to investigate how genetic analysis can be used with clinical diagnostic information for improved orthodontic management of PFE., Methods: We evaluated a family (n = 12) that segregated an autosomal dominant form of PFE with 5 affected and 7 unaffected persons. Nine available family members (5 male, 4 female) were enrolled and subsequently characterized clinically and genetically., Results: In this family, PFE segregated with a novel mutation in the PTH1R gene. A heterozygous c.1353-1 G>A sequence alteration caused a putative splice-site mutation and skipping of exon 15 that segregated with the PFE phenotype in all affected family members., Conclusions: A PTH1R mutation is strongly associated with failure of orthodontically assisted eruption or tooth movement and should therefore alert clinicians to treat PFE and ankylosed teeth with similar caution-ie, avoid orthodontic treatment with a continuous archwire.

Aim: This was to report a rare case of strong familiar tendency of ankylosis of maxillary second primary molars., Case Report: Three Caucasian children, male twins of 8.5 years and a sister of 10 years, were diagnosed as having severely infraccluded maxillary second primary molars with underlying second premolars. In all three cases, the early extraction of the infraoccluded molars and an active treatment with cervical extraoral traction allowed the physiologic eruption of second premolars. Follow-up showed that normal vertical relationship and bone height had been obtained., Conclusion: Early diagnosis, as well as appropriate treatment and careful follow-up are very important in the presence of severe infraocclusion, when the marginal ridge of affected primary teeth is at or below gingival level.