Primary Retention of Molars and RANKL Signaling Alteration during Craniofacial Growth

Abstract

The primary retention of molars observed in clinic corresponds to a still-unexplained absence of molar eruption despite the presence of an eruption pathway, resembling the experimental transient inhibition of RANKL signaling in mice. The aim of the present study was to confront the hypothesis according to which the primary retention of molars is associated with transitory perturbations to RANKL signaling during growth as part of a wider craniofacial skeleton pattern. The experimental strategy was based on combining a clinical study and an animal study corresponding to the characterization of the craniofacial phenotypes of patients with primary retention of molars and analyses in mice of the consequences of transient inhibition of RANKL signaling on molar eruption and craniofacial growth. The clinical study validated the existence of a particular craniofacial phenotype in patients with primary retention of molars: a retromandibular skeletal class II typology with reduced mandibular dimensions which manifests itself at the dental level by a class II/2 with palatoversion of the upper incisors and anterior overbite. The animal study demonstrated that transient invalidation of RANKL signaling had an impact on the molar eruption process, the severity of which was dependent on the period of inhibition and was associated with a reduction in two craniofacial morphometric parameters: total skull length and craniofacial vault length. In conclusion, primary retention of molars may be proposed as part of the craniofacial skeleton phenotype associated with a transitory alteration in RANKL signaling during growth.

Review and case report of the treatment in a young girl with primary failure of eruption

“…Transitory alteration to RANKL functions during the initial stage of dental root elongation and tooth eruption have also been reported in mouse models of PFE 21 …”

“…19,20 Transitory alteration to RANKL functions during the initial stage of dental root elongation and tooth eruption have also been reported in mouse models of PFE. 21 Indepth analysis of chronological regulation and spatial localization of genes is key for improved understanding. Also, validation of the protein expression is essential for derivation of therapeutic interventions.…”

The Shape of Nasopalatine Canal as a Determining Factor in Therapeutic Approach for Orthodontic Teeth Movement—A CBCT Study

“…Although using of traditional exams such as a lateral X-ray (cephalometric analyzes) may allow the identification of NPC [ 13 ], 2D imaging could not provide complete visualization of the size and position of the canal, as previously reported [ 14 ]. Thus, we classified NPC shapes by using CBCT sagittal cross section, according to Mardinger and coworkers [ 40 ], and confirmed that the most represented NPC shape was funnel (34.59%), followed by cylindrical (28.57%), and hourglass (24.81%), while the banana type was observed only in 12.03% participants.…”

“…In addition, Uesugi and coworkers [ 12 ] reported that CBCT may be useful for simulating the post-treatment position of the maxillary incisors and NPC in order to provide safe teeth movement. On the other hand, using lateral cephalogram, the position of NPC could also be evaluated [ 13 ], although CBCT provides more detailed information about NPC such as morphology and morphometric characteristics [ 14 ].…”

Severe Posterior Infra-occlusion on a Young Girl Posing a Diagnostic Challenge- Review and Report of a Case of Primary Failure of Eruption

“…8,13,14,15,16 Transitory alteration to RANKL functions during the initial stage of dental root elongation and tooth eruption have also been reported in mouse models of PFE. 17 In-depth analysis of chronological regulation and spatial localization of genes is key for improved understanding. Also, validation of the protein expression is essential for derivation of therapeutic interventions.…”