Risk Factors for Tooth Eruption Diseases

May 8, 2026 updated by: Fondazione Policlinico Universitario Agostino Gemelli IRCCS

Determination of Risk Factors for Eruption Disorders in the Primary and Permanent Dentition

Failure of eruption of primary and/or permanent teeth is a rare condition caused by four possible causes. The first is ankylosis of the tooth roots, which, in the absence, even partial, of the alveolar ligament, join the surrounding bone. The second possible cause is failure of eruption due to mechanical impediment, in the presence of a cyst or lack of resorption of the bone overlying the developing tooth, or due to severe lack of space or an abnormal inclination of the tooth's eruption path. The third cause, called Primary Failure of Eruption (PFE), is genetic in nature due to insufficient production of the factors that determine tooth eruption. In this case, molars are the most affected teeth, and pathogenic variants of the PTH1R gene are often observed. The fourth possibility is delayed tooth eruption. In cases of ankylosis and PFE, orthodontic treatments to help recover the teeth in the arch may fail.

This interventional study, comprising a retrospective cohort, aims to evaluate the clinical signs of dental eruption disorders to identify criteria to facilitate clinical diagnosis. Furthermore, in cases where PFE is suspected, diagnostic testing for the PTH1R gene will be performed.

The study will be conducted at the Fondazione Policlinico Universitario "A. Gemelli" IRCCS in Rome and will enroll 50 consecutive patients with dental eruption disorders of deciduous and/or permanent molars. The primary outcome will be to strengthen the differential diagnostic hypothesis. The study will also examine the phenotype/genotype correlation in patients tested for PTH1R gene variants. The characteristics of the sample will be compared with those of the sample enrolled in the previous study (C.E. UCSC ID 565-11/2015), which will be examined retrospectively. Extending the analysis to the patient cohort enrolled since 2015 is particularly valuable given the rarity of the diseases under study and the resulting small number of cases available for research.

The study results will provide new data on pathogenic variants of PTH1R and on the phenotype/genotype correlation of the various diseases characterized by tooth eruption disorder. They will also help identify more sustainable and effective clinical strategies.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Tooth eruption is characterized by the movement of the developing tooth from its origin in the bone to its functional position in the oral cavity [1]. In the mouse model, the eruption process is orchestrated by stem cells surrounding the tooth and the periodontal ligament (PDL). The development of the PDL is determined by the expression of Pth1r, a protein-coding gene encoding the parathyroid hormone receptor [2;3]. During this process, eruption failure may occur, which could be diagnosed as primary failure of eruption (PFE; OMIM # 125350) or ankylosis. In the case of PFE, loss of Pth1r function within Pthrp-expressing cells affects the PDL and root phenotype, resulting in eruption failure [4]. This condition is most evident in the first permanent molars, and the eruption phenotype is partially penetrant. The eruption path is unobstructed because parathyroid hormone-related protein (PTHLH; OMIM168470) is normally expressed in coronal dental epithelial cells, whereas it is deficient in mesenchymal cells surrounding the roots. In humans with pathogenic variants of parathyroid hormone receptor 1 (PTH1R, OMIM168468), the eruption path is unobstructed, but eruption ceases and the affected tooth partially erupts. Orthodontic forces may be futile to move the affected teeth. PTH1R is a receptor for both parathyroid hormone (PTH; OMIM 168450) and parathyroid hormone-related protein (PTHLH). Previous studies described the involvement of the PTH1R gene in 2010 [5;6]; Previously published studies generally refer to "unexplained cessation of eruption" or a "poorly understood condition" [7-9], observing clinical signs more representative of PFE. In cases with a high probability of PFE, it is useful to search for variants of the PTH1R gene. Since genetic testing is not accessible to some, determining whether there is a family history represents a valid alternative.

In the case of ankylosis, the distinctive differential diagnosis is fusion of the tooth root surface with the surrounding bone. The pathogenesis of ankylosis is less well understood but has been associated with a history of trauma [10;11]; the presence of residual Malassez epithelial cells has been found to be essential for preventing fusion between the alveolar bone and the tooth. Overexpression of WNT is responsible for cementum overgrowth and ankylosis [12]. Regardless of this distinctive histological feature, definitive diagnosis of ankylosis is difficult and often nearly impossible. In practice, the diagnosis of ankyloses relies more on the exclusion of other causes of eruption failure and the clinical context (i.e., usually isolated). Non-eruption of permanent molars is the rarest impaction of permanent teeth [13]. This finding is always challenging for the dentist, even more so when it affects a child. From a clinical point of view, it is very difficult to distinguish between PFE and ankyloses during an early diagnosis process. In both cases, the affected teeth either fail to erupt or occupy an infra-occluded position. Ankylosed teeth should elicit a high-pitched metallic sound upon percussion [14] and have little or no mobility [15]. However, relying on differences in percussive sounds elicited by percussion with an instrument can vary greatly from operator to operator and may not be reproducible. In contrast, the use of an Osstell Mentor (Osstell, Gothenburg, Sweden) that detects resonance frequency analysis, as used in implantology, offers some promise [16]. In PFE, the affected teeth are normally mobile but become ankylotic in response to orthodontic force. If ankylosis is suspected, panoramic radiography does not clearly and definitively demonstrate the absence of the periodontal ligament, especially in multirooted teeth. As demonstrated by Raghoebar et al. [17;18], the areas of ankylosis are small and often located between the roots.

Early diagnosis is based on the clinical observation of delayed first molar eruption and on signs detected on panoramic radiography of the dental arches. Unfortunately, differential diagnosis is very difficult. During childhood, the causes of Mechanical Failure of Eruption (MFE) are easier to identify, mainly due to lack of space in the arch or the presence of cysts or supernumerary teeth that prevent eruption. Another possible cause of the absence of the first permanent molars in the arch is delayed eruption, which alters the timing of occlusion development, but not the eruption mechanism [19].

Failure to erupt in permanent first molars is a rare event [Roulias et al., 2022], but it presents clinicians with two significant challenges. First, the correct diagnostic classification can be difficult to confirm, and second, the resulting treatment options are often limited and yield suboptimal outcomes. Among the professionals who may first discover an eruption disorder in a child (e.g., general practitioners and pediatric dentists), neither may choose to provide therapeutic management for this malocclusion, as it often falls within the scope of work most often performed by an orthodontist. However, when this problem is observed in a child, if the practitioner fails to make a timely and correct diagnosis and treatment, the prognosis is poor. This means that the affected tooth or teeth fail to erupt, their position within the jaws worsens, and more or less severe alterations in occlusal relationships are observed. Tongue function is also affected, and the patient's face may develop asymmetry.

With this study, we aim to refine the identification of the distinctive clinical features of ankylosis, MFE, PFE, and delayed tooth eruption. We also aim to broaden and deepen our understanding of the pathogenic variants of PTH1R related to PFE.

HYPOTHESIS The clinical signs associated with dental eruption failure may have a different prevalence and severity in relation to ankylosis, MFE, PFE, and delayed tooth eruption. Furthermore, the identification of new pathogenic variants of PTH1R related to PFE could help clarify the genetic mechanisms underlying primary eruption failure.

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Partial or complete failure of one or more deciduous and/or permanent molar teeth to erupt
  • Diagnostic records (medical history, orthopantomography, clinical photographs)
  • Age between 5 and 80 years
  • Ability to understand and sign consent forms from patients, if adults, or their parents/guardians

Exclusion Criteria:

  • Malformative syndromes and/or systemic diseases
  • Lack of diagnostic records
  • Failure of eruption due to traumatic causes

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Diagnostic
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Other: Patients with eruption disorders
Patients with eruption disorders of deciduous and/or permanent molars
Diagnostic test: PTH1R gene analysis

Diagnostic records will be reviewed and clinical signs related to the eruption defect will be identified and classified.

DNA samples will be collected using three cytobrushes (Cooper Surgical, Trumbull, CT, USA) and extracted with the QIAamp DNA mini kit (part number 51304, Qiagen). Amplification and nucleotide sequencing of the intronic/exonic regions of the PTH1R gene (NM_000316.3) will be performed as described in Grippaudo et al. (2021). All sequences will be aligned to the reference genome (GRCh38/hg38), and the frequency of variants in the general population will be verified against the Genome Aggregation Database (GnomAD) (https://gnomad.broadinstitute.org/) and the Single Nucleotide Polymorphism Database (dbSNP) (https://www.ncbi.nlm.nih.gov/snp/). The potential pathogenicity of the identified variants will be searched in the NCBI ClinVar database (https://www.ncbi.nlm.nih.gov/clinvar/).

The data will be collected using a password-protected Excel file.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Evaluation of delayed tooth eruption
Time Frame: 60 months
Differential diagnosis between ankylosis, MFE, PFE and delayed tooth eruption based on the presence and frequency of clinical signs and PTH1R gene variants.
60 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Fondazione Policlinico Universitario Agostino Gemelli IRCCS

Investigators

  • Principal Investigator: Cristina Grippaudo, Fondazione Policlinico Universitario Agostino Gemelli IRCCS

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

June 8, 2026

Primary Completion (Estimated)

June 8, 2029

Study Completion (Estimated)

December 31, 2030

Study Registration Dates

First Submitted

May 8, 2026

First Submitted That Met QC Criteria

May 8, 2026

First Posted (Actual)

May 14, 2026

Study Record Updates

Last Update Posted (Actual)

May 14, 2026

Last Update Submitted That Met QC Criteria

May 8, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 27111-1

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Tooth Eruption Disorder

Clinical Trials on PTH1R gene analysis

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Singapore

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe