Molar incisor malformation in six cases: description and diagnostic protocol

Prevalence and morphological features of molar-root incisor malformation in children attending a specialist paediatric dental unit

BACKGROUND

Molar-root incisor malformation (MRIM) is a rare dental anomaly featuring constricted cervical margins and tapered, narrow root and pulp morphology, often associated with severe toothache and infection.

AIM

The aim of this study was to determine the prevalence of MRIM in children seen in a specialist paediatric dental unit of a tertiary referral hospital and to describe the characteristics of affected individuals.

DESIGN

This study was an audit of children attending from November 2020 to November 2021. Radiographs were used to identify individuals with MRIM, and clinical data were collated. In addition, histology and microcomputed tomography (microCT) imaging were performed on teeth extracted from an affected individual.

RESULTS

The prevalence of MRIM was five cases of 1054 children examined (0.47% or 1:210). The permanent first molars were affected in all five children and the primary second molars in two children; all children had medical comorbidities and multiple exposures to general anesthesia before 4 years of age. In addition, histological and microCT analyses displayed numerous microchannels connecting the pulp chamber to the external surface of the tooth at the furcation.

CONCLUSIONS

Molar-root incisor malformation is an uncommon dental anomaly affecting paediatric patients with multiple comorbidities and is characterized by porosities extending from the pulp chamber to the external tooth surface, predisposing the risk of bacterial ingress from the oral cavity into the pulp chamber. Early detection may prevent atypical odontogenic facial pain and infection.

Molar-root incisor malformation - a systematic review of case reports and case series

OBJECTIVES

Molar-root incisor malformation (MRIM) is a seldom reported condition characterised by disturbances in root development of first permanent molars. This systematic review aimed to collate the clinical characteristics of individuals diagnosed with MRIM.

MATERIALS AND METHODS

A systematic search strategy using PubMed, Embase, Web of Science, and SCOPUS databases was performed through to March 2023. Inclusion criteria were case reports or case series including a diagnosis consistent with MRIM. Critical appraisal for all included studies utilised the Joanna Briggs Institute (JBI) critical appraisal checklist for case reports and case series and collation of clinical characteristics was performed in JBI System for the Unified Management, Assessment and Review of Information program.

RESULTS

The search identified 157 studies from which 35 satisfied the inclusion criteria. After full-text review, a total of 23 papers described the MRIM dental anomaly and were included in this paper. A total of 130 reported cases were retrieved, with age ranging 3-32 years, and males affected 1.16:1 females. Presence of neurological conditions, premature birth history, medication, and surgery within first years of life were synthesised and described.

CONCLUSIONS

The aetiology of MRIM is yet to be determined but epigenetic changes from significant medical history in the first years of life are likely to influence the development of this root malformation. First permanent molars were most commonly affected, but clinicians should be aware that permanent central incisors, primary teeth and other permanent teeth may also be affected.

Morphological, histological, and chemical analysis of first permanent molars with molar incisor malformation

PURPOSE

Molar incisor malformation (MIM) is a dental anomaly rendering first permanent molar pulps inflamed/necrotic at a young age. It often affects permanent incisors, primary second molars and less frequently other teeth. The purpose of this study was to investigate the anatomy and histology of MIM in seeking insight into its pathogenesis.

METHODS

Five MIM first permanent molars were examined with micro-computed tomography (micro-CT) for 3D morphology, with scanning electron microscopy for microanatomy, with energy-dispersive X-ray spectrometer (EDS) for chemical composition and for histology with optical microscopy. Composition differences were statistically determined using one-way ANOVA.

RESULTS

Micro-CT confirmed dentin abnormalities in the middle and cervical third of the crown in the form of the radiodense 'cervical mineralized diaphragm' (CMD). This was peripherally intertwined with enamel fjords and projections severely disrupting the integrity of pulp chamber and its continuity with root canals. EDS showed increased Ca in CMD compared to dentin. The histological examination revealed anomalous osteodentin-like hard tissue with denticles in the CMD.

CONCLUSION

An interconnection of anomalous cervical enamel with crown CMD dentin preceded to the severe pulp chamber and root dysplasias in MIM molar teeth.

Management of Severely Aberrant Permanent First Molars in Molar Root-Incisor Malformation Patients: Case Series and a Guideline

Recently, a new type of dental anomaly, a molar–incisor malformation or molar root–incisor malformation (MRIM), was recognized. The disease phenotype is now relatively well characterized; however, its etiology and disease-mechanism need to be elucidated. The affected teeth do not respond well to conventional treatment because of severe malformation and an unusual root structure. In this study, we present the treatment of MRIM cases with the extraction of severely aberrant permanent first molars (PFMs) and suggest that the PFM extractions are performed when it is clear that third molars will develop. The purpose of this report was primarily to present amendments to the guidelines for the treatment of patients with MRIM.

Molar-incisor malformation: Eight new cases and a review of the literature

BACKGROUND

Molar-incisor malformation (MIM) is a recently described dental abnormality. While MIM mimics dentin dysplasia, it presents in a localized pattern. Furthermore, it is speculated that MIM is caused by significant early-life medical history.

AIM

The purpose of this study is to present a series of MIM cases and compare the findings with the literature.

DESIGN

An extensive search of all published cases of MIM in the English-language literature was conducted. Additionally, an institutional review board-approved retrospective search was performed within the University of Florida oral pathology biopsy service archives. Radiographic consultation cases were also included. Cases lacking radiographs were excluded.

RESULTS

Seventy-nine cases were identified in the literature, and eight cases were identified in our retrospective search. All but one case involved the permanent first molars. The average age at diagnosis was 9 years. Many patients reported significant early-life medical histories.

CONCLUSIONS

MIM usually affects the permanent first molars and may be linked to early-life medical conditions or interventions. Oral healthcare providers, especially paediatric dentists, should be aware of MIM to avoid misdiagnosing it as dentin dysplasia. Long-term follow-up studies with thorough medical history documentation are essential to understand the pathogenesis and aetiology and to create treatment guidelines.

Clinical Considerations for Dental Management of Children with Molar-Root Incisor Malformations

Molar root-incisor malformation (MRIM) or molar-incisor malformation (MIM) is a new type of dental anomaly characterized by dysplastic roots of permanent first molars, occasionally second primary molars, and the crowns of maxillary central incisors. MRIM involving permanent first molars and second primary molars is characterized by normal crowns with short, thin, and narrow roots, whereas MRIM involving permanent maxillary central incisors exhibits constrictions of the crown in the cervical area. In the first case, we extracted the affected first permanent molars at the optimal timing to minimize space deficiencies and induce space closure. In addition, composite resin restorations were performed on the anterior central incisors. In the second case, a mandibular lingual arch was used to stabilize the affected teeth in order to mitigate discomfort by reducing rotational biting forces.

Mandibular Carnassial Tooth Malformations in 6 Dogs-Micro-Computed Tomography and Histology Findings

Objective: To document the clinical, radiographic, and histological characteristics of mandibular first molar teeth with developmental abnormalities previously attributed to dens invaginatus and enamel pearls in dogs. Materials and Methods: Affected mandibular first molar teeth from dogs were evaluated grossly and via intraoral radiography. Endodontically and/or periodontally compromised teeth were extracted and subjected to some combination of micro-computed tomography, histopathology, and immunohistochemistry with anti-amelogenin antibody. Results: Six dogs with developmental abnormalities of mandibular first molar teeth were identified, representing 11 affected teeth. The condition was bilateral in 5 dogs, while in 1 dog, only one mandibular first molar tooth was present. Patient weight ranged from 1.7 to 6 kg (median = 4.09 kg). On intraoral radiographs, root convergence or parallelism was noted in 6 of 11 teeth, and root dilaceration was noted in 3 of 11 teeth. Eight teeth required extraction due to periapical lucencies or periodontitis. On micro-CT, the abnormal teeth were characterized by the presence of abnormal, heterogenous hard tissue with beam attenuation characteristics midway between that of enamel and dentin. Enamel fissures were identified in 4 of 8 teeth, while ectopic radicular enamel was identified in 2 of 8 teeth. The abnormal tissue was traversed by channels measuring 20-40 μm in diameter. Channels communicated with the enamel fissures in 2/8 teeth, the furcation in 2/8 teeth and the pulp in 4/8 teeth. The abnormal tissue was frequently surrounded by disorganized dentin. Histologic features of enamel and dentin were absent from the abnormal tissue and immunohistochemistry to detect amelogenin in the abnormal tissue was negative in all samples. Conclusion: The dental abnormalities described here correspond to a previously unrecognized developmental abnormality involving the mandibular first molar teeth in dogs. The developmental origin of the abnormal tissue could not be ascertained, and further investigations are required to determine the mode of formation, origin of the abnormal tissue, and factors associated with development. These developmental abnormalities more closely resemble molar-incisor malformation, rather than dens invaginatus or enamel pearls as described in humans. The authors propose that affected mandibular first molar teeth simply be referred to as having carnassial tooth malformations.

Clinico-radiologic features of molar-incisor malformation in a case series of 38 patients: A retrospective observational study

Molar-incisor malformation (MIM) is a recently defined dental abnormality of molar root and incisors, and introduced as one of the causes of periapical and periodontal abscess. The purpose of this study was to investigate the clinical and radiological features of MIM, with special emphasis on various medical history. A total of 38 patients with MIM were included in this study. Radiographic features and clinical data, including medical history, chief complaint, associated complications, treatment, and prognosis, were retrospectively investigated. On radiographs, the affected molars showed short, slender, underdeveloped roots and constricted pulp chambers. All affected incisors and canines exhibited dilacerated short roots, wedge-shaped defect on the cervical part of the crown. Complications included periodontal bone loss (52.6%), endodontic lesion (50.0%), and endodontic-periodontal lesion (28.9%). The medical histories of the patients with MIM indicate that almost all (94.7%) were hospitalized due to problems during the neonatal period. MIM may cause various dental problems, such as periapical and periodontal abscess and early loss of the affected teeth. The early diagnosis of MIM on radiographs and appropriate treatment will contribute to a favorable prognosis, especially for young and adolescent patients.

Molar-incisor malformation: A case report and clinical considerations

Molar-incisor malformation (MIM) is a dental anomaly that has recently been presented in the literature. It features morphological root abnormalities affecting the permanent first molars, resulting in narrow, shortened or almost completely absent roots in patients who interestingly still present with clinically normal crowns. In some cases, this condition also involves the roots of the deciduous second molars in a similar manner and the maxillary central incisors may exhibit notching around the cervical region of the clinical crown. Root dysplasia of the permanent first molars compromises the long-term survival of these teeth and, in itself, presents a challenge when attempting to undertake any orthodontic treatment. This case report describes an incidental finding of a patient presenting with similar features to that of MIM, discusses the features and clinical implications of this newly discovered condition, and highlights the importance of undertaking a comprehensive radiological investigation before treatment.

Elements of morphology: Standard terminology for the teeth and classifying genetic dental disorders

Dental anomalies occur frequently in a number of genetic disorders and act as major signs in diagnosing these disorders. We present definitions of the most common dental signs and propose a classification usable as a diagnostic tool by dentists, clinical geneticists, and other health care providers. The definitions are part of the series Elements of Morphology and have been established after careful discussions within an international group of experienced dentists and geneticists. The classification system was elaborated in the French collaborative network "TÊTECOU" and the affiliated O-Rares reference/competence centers. The classification includes isolated and syndromic disorders with oral and dental anomalies, to which causative genes and main extraoral signs and symptoms are added. A systematic literature analysis yielded 408 entities of which a causal gene has been identified in 79%. We classified dental disorders in eight groups: dental agenesis, supernumerary teeth, dental size and/or shape, enamel, dentin, dental eruption, periodontal and gingival, and tumor-like anomalies. We aim the classification to act as a shared reference for clinical and epidemiological studies. We welcome critical evaluations of the definitions and classification and will regularly update the classification for newly recognized conditions.

Case report of a molar-root incisor malformation in a patient with an autoimmune lymphoproliferative syndrome

Background

Molar-root incisor malformation (MRIM) is a novel dental phenotype likely related to a patient’s past medical history. This case aimed to confirm MRIM by histological and scanning electron microscopy (SEM) examination for the first time in a patient diagnosed with autoimmune lymphoproliferative syndrome (ALPS) and to propose a possible link between ALPS and MRIM that could be attributable to abnormally proliferated bone marrow.

Case presentation

A 12.5-year-old boy with an extensive medical history, including diagnosis of ALPS, was examined clinically and radiologically to elucidate the reason for pain primarily originating from the area of the lower left permanent first molar tooth (PFM; tooth 36). Dental examination and radiographic survey revealed abnormal pulp cavity morphology of all four PFMs, and these were extracted, resolving the dental pain in the patient. The extracted PFMs were subjected to light microscopy, SEM evaluation and mineral density and elemental composition analyses. Histology of two PFMs revealed the presence of dentin-, bone- and cartilage-like tissues with abundant blood vessels occupying the majority of the pulp chamber. The root canals were obliterated with mineralized structures resembling pulp stones. Two different, highly mineralized abnormal tissues filling the majority of the pulp chamber revealed by SEM and confirming the diagnosis of MRIM displayed a mineral density and elemental composition similar to those of enamel and dentin, respectively.

Conclusions

It appears likely that in addition to the complex medical history during early childhood in the present case, extensive lymphoid infiltrates that are possible in ALPS patients can be regarded as a cofactor in the development of MRIM by exerting considerable pressure on the developing tooth bud and providing cells capable of differentiating into diverse cell types.