Fibroblast growth factor signalling regulates the development of tooth root.

Fibroblast growth factor (FGF) signalling plays a crucial role in the morphogenesis of multiple tissues including teeth. While the role of the signal has been studied in tooth crown development, little is known about root development. Of several FGF ligands involved in hard tissue formation, we suggest that FGF18 regulates the development of murine tooth roots. We implanted FGF18-soaked heparin beads into the lower first molar tooth buds at postnatal day 6 (P6), followed by transplantation under the kidney capsule. After 3 weeks, FGF18 significantly facilitated root elongation and periodontal tissue formation compared to the control. In situ hybridisation showed that Fgf18 transcripts were initially localised in the dental pulp along Hertwig's epithelial root sheath at P6 and P10 and subsequently in the dental follicle cells at P14. Fgf receptors were expressed in various dental tissues during these stages. In vitro analysis using the dental pulp stem cells revealed that FGF18 inhibited cell proliferation and decreased expression levels of osteogenic markers, Runx2, Alpl and Sp7. Consistently, after 1 week of kidney capsule transplantation, FGF18 application did not induce the expression of Sp7 and Bsp, but upregulated Periostin in the apical region of dental mesenchyme in the grafted molar. These findings suggest that FGF18 facilitates molar root development by regulating the calcification of periodontal tissues.

Effect of root immaturity and depth of intrusion on spontaneous re-eruption and healing complications: A retrospective analysis.

BACKGROUND/AIMS: Dental trauma resulting in tooth intrusion is a severe injury of permanent dentition, with a prevalence of 0.5%-1.9% among traumatic dental injuries. Currently, treatment guidelines for intruded permanent teeth depend on root development and the degree of intrusion. However, the categorization of tooth maturity as mature or immature simplifies a complex continuum of root development stages. This study aims to investigate the impact of various stages of root development on the success of spontaneous re-eruption (SRE) of intruded teeth. MATERIALS AND METHODS: This retrospective study analysed data from 80 children (125 teeth) aged 6-12 years who experienced dental intrusion between 2018 and 2022. Root maturation was classified based on Cvek's classification, eight were categorized as stage 1, 29 as stage 2, 44 as stage 3, 25 as stage 4, and 19 as stage 5. Intruded teeth with immature roots (Cvek's class 1-4) underwent SRE, while mature teeth (Cvek's class 5) were treated with SRE, orthodontic repositioning, or surgical repositioning based on the degree of intrusion. Primary outcome measures were successful re-eruption and secondary outcomes included observed complications during follow-up. RESULTS: Regression analysis revealed that the patient's age, degree of root maturation, and degree of intrusion significantly affected spontaneous re-eruption (p < .05). SRE was more successful in teeth with Cvek's stages 1 and 2 compared to stages 3 and 4. Complications were associated with the treatment method, degree of root immaturity, and degree of intrusion. CONCLUSION: The study demonstrates that as root maturation progresses, the likelihood of re-eruption decreases, and the risk of pulp necrosis and infection increases. Therefore, teeth in later stages of immaturity (Cvek stage 4) should be repositioned orthodontically or surgically without waiting for spontaneous re-eruption.

[Research progress in methylation modification in tooth root development].

Methylation modification is one of the most common epigenetic modification regulation in eukaryotes, including histone methylation, DNA methylation, RNA methylation, etc., which plays an important regulatory role in physiological processes and pathologic occurrence and development. Tooth root development is carried out by both epithelial and mesenchymal cells and involves a variety of cell-molecular interactions. In recent years, a large number of studies have found that methylation plays a key role in the regulation of tooth root development and expands the mechanism network of tooth root development. In this paper, we review the role and mechanism of methylation modification during root development.

Notum regulates the cusp and root patterns in mouse molar.

Notum is a direct target of Wnt/ß-catenin signaling and plays a crucial role as a Wnt inhibitor within a negative feedback loop. In the tooth, Notum is known to be expressed in odontoblasts, and severe dentin defects and irregular tooth roots have been reported in Notum-deficient mice. However, the precise expression pattern of Notum in early tooth development, and the role of Notum in crown and root patterns remain elusive. In the present study, we identified a novel Notum expression in primary enamel knot (EK), secondary EKs, and dental papilla during tooth development. Notum-deficient mice exhibited enlarged secondary EKs, resulting in broader cusp tips, altered cusp patterns, and reduced concavity in crown outline. These alterations in crown outline led to a reduction in cervical tongue length, thereby inducing root fusion in Notum-deficient mice. Overall, these results suggest that the secondary EK size, regulated by the Wnt/Notum negative feedback loop, has a significant impact on the patterns of crown and root during tooth morphogenesis.

FGF signaling modulates mechanotransduction/WNT signaling in progenitors during tooth root development.

Stem/progenitor cells differentiate into different cell lineages during organ development and morphogenesis. Signaling pathway networks and mechanotransduction are important factors to guide the lineage commitment of stem/progenitor cells during craniofacial tissue morphogenesis. Here, we used tooth root development as a model to explore the roles of FGF signaling and mechanotransduction as well as their interaction in regulating the progenitor cell fate decision. We show that Fgfr1 is expressed in the mesenchymal progenitor cells and their progeny during tooth root development. Loss of Fgfr1 in Gli1+ progenitors leads to hyperproliferation and differentiation, which causes narrowed periodontal ligament (PDL) space with abnormal cementum/bone formation leading to ankylosis. We further show that aberrant activation of WNT signaling and mechanosensitive channel Piezo2 occurs after loss of FGF signaling in Gli1-CreER;Fgfr1fl/fl mice. Overexpression of Piezo2 leads to increased osteoblastic differentiation and decreased Piezo2 leads to downregulation of WNT signaling. Mechanistically, an FGF/PIEZO2/WNT signaling cascade plays a crucial role in modulating the fate of progenitors during root morphogenesis. Downregulation of WNT signaling rescues tooth ankylosis in Fgfr1 mutant mice. Collectively, our findings uncover the mechanism by which FGF signaling regulates the fate decisions of stem/progenitor cells, and the interactions among signaling pathways and mechanotransduction during tooth root development, providing insights for future tooth root regeneration.

Evergrowing incisors of diprotodont marsupials record age and life history.

OBJECTIVE: Tooth growth and wear are commonly used tools for determining the age of mammals. The most speciose order of marsupials, Diprotodontia, is characterised by a pair of procumbent incisors within the lower jaw. This study examines the growth and wear of these incisors to understand their relationship with age and sex. DESIGN: Measurements of mandibular incisor crown and root length were made for two sister species of macropodid (kangaroos and wallabies); Macropus giganteus and Macropus fuliginosus. Histological analysis examined patterns of dentine and cementum deposition within these teeth. Broader generalisability within Diprotodontia was tested using dentally reduced Tarsipes rostratus - a species disparate in body size and incisor function to the studied macropodids. RESULTS: In the macropodid sample it is demonstrated that the hypsodont nature of these incisors makes measurements of their growth (root length) and wear (crown length) accurate indicators of age and sex. Model fitting finds that root growth proceeds according to a logarithmic function across the lifespan, while crown wear follows a pattern of exponential reduction for both macropodid species. Histological results find that secondary dentine deposition and cementum layering are further indicators of age. Incisor measurements are shown to correlate with age in the sample of T. rostratus. CONCLUSIONS: The diprotodontian incisor is a useful tool for examining chronological age and sex, both morphologically and microstructurally. This finding has implications for population ecology, palaeontology and marsupial evolution.

Uncommon disturbance of root development after tooth replantation: five-year follow-up period case report / Trastorno del desarrollo radicular poco frecuente posterior a reimplante dentario: reporte de caso con 5 años de seguimiento

To present an uncommon disturbance of root development with ingrowth of bone and periodontal tissue into the pulp space in a delayed replanted immature permanent incisor at five years of follow-up. Severe arrest of root formation with uncommon healing of an immature permanent maxillary incisor after delayed replantation is reported. Continued development of a tooth root separate from the body of the tooth was not observed. A 6-year-old girl sustained an avulsion injury to her upper left central permanent incisor. The tooth was replanted and splinted 2 hours after the accident. Patient has been monitored clinically and with radiography for 5 years. The periodontal tissues presented good healing without replacement resorption. However, severe arrest of root formation with development of hard-like tissue and internal periodontal ligament inside the pulp canal have been observed. Despite being a delayed tooth replantation, the patient has been asymptomatic, and has maintained alveolar bone volume. Clinicians must be vigilant and monitor traumatized immature teeth closely.

El objetivo de este trabajo fue presentar una alteración poco frecuente del desarrollo de la raíz con el crecimiento del tejido óseo y periodontal en el espacio pulpar en un incisivo permanente inmaduro reimplantado de manera tardía, a los cinco años de seguimiento.Se observó una suspensión severa de la formación de raíces con cicatrización poco común, de un incisivo maxilar permanente inmaduro después de una reimplantación tardía. No se observó el desarrollo continuo de la raíz dentaria separada del diente. Una niña de 6 años de edad sufrió una lesión por avulsión en su incisivo central superior izquierdo. El diente fue replantado dos horas después del accidente. La paciente ha sido monitoreada clínicamente y con exámenes radiológicos durante 5 años. Los tejidos periodontales presentaron buena cicatrización sin reabsorción de reemplazo. Sin embargo, se ha observado una detención severa de la formación de las raíces, con desarrollo de tejido duro y ligamento periodontal interno dentro del canal pulpar. A pesar de ser una reimplantación tardía del diente, la paciente presenta asintomática, y ha mantenido el volumen del hueso alveolar. Los médicos deben estar atentos y mantener en observación los dientes inmaduros traumatizados.

Evaluación in vitro de la resistencia a la fractura en dientes con desarrollo radicular incompleto reforzados intraconducto con diferentes materiales / In vitro evaluation of fracture resistance of teeth with incomplete root development and intracanal reinforcement with different materials

El objetivo de este trabajo fue evaluar la resistencia a la fractura de dientes con desarrollo radicular incompleto y refuerzo intrarradicular con materiales adhesivos. 50 dientes incisivos centrales y laterales maxilares humanos fueron instrumentados y preparados intraconducto para simular un diente inmaduro y obturado apicalmente con MTA. Las muestras fueron divididas en cuatro grupos experimentales y un grupo control. Grupo 1: Resina compuesta Filtek™ P90; Grupo 2: Ionómero de vidrio Vitremer™; Grupo 3: Resina compuesta Filtek™ Z350 XT; Grupo 4: Ionómero de vidrio Ketac™ N 100; Grupo 5: Control negativo (Instrumentado pero no se reforzó intraconducto). Luego se realizó la prueba de fractura utilizando una maquina de ensayo universal (Instron™). Los valores máximos de resistencia antes de la fractura catastrófica fueron recolectados y analizados mediante la prueba Anova (p = 0,05). Como resultado se encontró diferencia significativa entre los grupos comparados (p = 0,02). Fue encontrada diferencia significativa entre los grupos 1 (847,73N) y el grupo 5 (474,77N) (p = 0,02) aplicando el test de Bonferroni. Pese a las limitaciones del estudio se puede concluir que las resinas compuestas microhíbridas se muestran como un material óptimo para reforzar intrarradicularmente dientes con desarrollo radicular incompleto tratados endodónticamente.

The aim of this study was to evaluate the fracture resistance of teeth with incomplete root development and intracanal reinforcement with adhesives materials. 50 human central and lateral incisors were instrumented and prepared to simulate an immature tooth and filled apically with MTA. The samples were divided into four experimental groups and one control group. Group 1: resin composite Filtek™ P90; Group 2: glass Ionomer Vitremer™; Group 3: resin composite Filtek™ Z350 XT; Group 4: glass Ionomer Ketac™ N 100; Group 5: negative control (instrumented but not reinforced). After, the fracture test was performed using a fracture universal testing machine (Instron™). The maximum values of resistance before catastrophic fracture were collected and analyzed by Anova (p = 0.05). The results show a significant difference between the groups compared (p = 0.02). A significant difference was found between group 1 (847.73 N) and group 5 (474.77 N) (p = 0.02) applying the Bonferroni test. Despite the limitations of the study, the conclusion is that micro-hybrid composite resins are ideal materials to strengthen teeth with incomplete root development endodontically treated.

Dilaceración de diente primario asociado a un mesiodens en niño de 4 años / Dilaceration temporary tooth associated with a mesidens in 4 year old

Dilaceración es un término utilizado para describir la distorsión que ocurre en la raíz durante el desarrollo dentario, el cual se manifiesta alterando la normal relación axial entre la corona y la raíz dentaria. La dilaceración radicular es una angulación o curvatura de la raíz dentaria. Esta alteración es frecuentemente observada en dientes permanentes como consecuencia de un traumatismo de su correspondiente temporario, con una incidencia de 3 %. En la literatura hay solamente cinco casos de dilaceración que involucran a incisivos temporarios. El propósito de este artículo fue hacer una revisión y presentar un caso clínico que fue un hallazgo radiográfico

Dilaceration is a term used to describe the distortion that occurs in the root during tooth development, which manifests itself by altering the normal axial relationship between the crown and the dental root. The root is dilaceration, angulation or curvature of the tooth root. This alteration is frequently observed in permanent teeth as a result of trauma to the corresponding temporary, with an incidence of 3%. In the literature there are only five cases involving dilaceration temporary incisors. The purpose of this article was to review and present a clinical case was a radiographic finding

Lactate dehydrogenase isoenzymes in dental pulp of rats according to stage of root development

The objective of this study was to present a classification of the root development stage of female rat molar teeth and to evaluate the variation in the lactate dehydrogenase (LDH) activity and electrophoretic isoenzyme profile according to the stage of root development of the molar teeth. We also studied the LDH activity and isoenzymes of the pulp of incisor teeth. The stage of development of the rat first molar at the age of 15 days and that of the second molar at the age of 18 days was classified as the beginning of root formation. At the age of 15 days, the electrophoretic profile of the isoenzymes for the first molar showed a prevalence of LDH-1 followed by LDH-2. However, for the maxillary second molar there was a prevalence of LDH-4 followed by LDH-1, while for the mandibular second molar LDH-1 predominated followed by LDH-2 and LDH-4. From 18 days of age, the prevalence was always of LDH-1. The electrophoretic profile of LDH isoenzymes from the pulp of the incisor teeth at the ages studied (25 and 60 days) showed the following order of prevalence: LDH-1 > LDH-2 > LDH-3 > LDH-4 > LDH-5. These results suggest that there are variations in the prevalence of the various forms of LDH isoenzymes in the dental pulp of rats according to the developmental stage of the root

Apecificação em adulto: relato de um caso / Apexification in adult: case report

Neste trabalho o autor relata o fechamento apical de um incisivo lateral superior de uma paciente adulta através dos procedimentos de apecificação com pasta de hidróxido de cálcio

Diferenciación de las fibras nerviosas pulpares en relación al grado de desarrollo radicular / Pulpal nerve differentiation in relation to the degree of radicular developement

Se realizó un estudio histológico y morfométrico de la inervación pulpar en piezas dentarias con distinto grado de desarrollo radicular. Se utilizaron premolares jóvenes, sanos, extraídos por indicación ortodóncica y con examen radiográfico previo para determinar su grado de desarrollo radicular, clasificándose en 5 niveles. Las piezas dentarias se fijaron en formol al 10 por ciento, se descalcificaron en Ana Morse y se incluyeron en parafina. Cortes seriados de 6 um se tiñeron con hematoxilina-eosina y con las técnicas de Bielschowsky y de Cajal para axones y fibras nerviosas. El recuento de las fibras nerviosas del plexo subodontoblástico de Raschkow, mostró que en los niveles iniciales está escasamente desarrollado, aumentando progresivamente junto con el desarrollo radicular, existiendo un aumento peak entre los niveles 3 y 4. En un mismo nivel se observó mayor desarrollo nervioso en la zona coronaria disminuyendo gradualmente hacia la zona radicular. Los resultados obtenidos se correlacionaron con tests de vitalidad pulpar

Morfologia radicular de dentes decíduos na fase de rizólise, implicaçöes clínicas e terapia endodôntica / Dental root morfhology of primary teeth during root resorption, clinical implications and endodontic treatment

Neste trabalho de revisäo de literatura buscou-se demonstrar a importância do acompanhamento e monitoramento da fase de rizólise de dentes decíduos e dos aspectos clínicos envolvidos durante este período de desenvolvimento

Dentes permanentes jovens com rizogênese incompleta e necrose pulpar / Nonvital young permanent teeth with incomplete root formation

Os autores fazem uma revisäo da literatura e relatam tratamentos endodônticos em incisivos centrais superiores com necrose pulpar e rizogênese incompleta, através da introduçäo de pasta de hidróxido de cálcio nos canais radiculares, como curativo expectante. Obtendo-se fechamento apical, os dentes obturados convencionalmente

Evaluación clínica y radiográfica de autotrasplantes y reposiciones dentales / Clinical and radiographic evaluation of autotransplantations and dental repositions

Se realizó un estudio prospectivo de 8 autotrasplantes y 2 reposiciones dentales en 8 pacientes que consultaron entre agosto de 1994 y abril de 1996, los que se controlaron en el período de un año. Se evaluaron parámetros clínicos como dolor, cambio de color, sangrado, movilidad e índice de Russell, también se evaluaron parámetros radiográficos como espacio del ligamento periodontal, reabsorción radicular interna y externa, obliteración de la cámara pulpar y estadio de desarrollo radicular. Todos los casos se realizaron de diferentes dientes donantes a diferentes sitios receptores, notándose que los autotrasplantes más frecuentemente realizados son del tercer molar al primer molar y las reposiciones en zona de premolares. La tasa de supervivencia fue del 100 por ciento a los seis meses y del 75 por ciento a los 12 meses, teniendo en cuenta que no todos los casos han completado los períodos de control. Uno de los autotrasplantes no sobrevivió aunque se le intentó realizar tratamiento pulpar con hidróxido de calcio. Los resultados iniciales de este estudio piloto demuestran que los autotrasplantes y las reposiciones dentales son alternativas de tratamiento con altos porcentajes de éxito en caso de pérdida dentaria o alteración en la erupción por malposición

Avaliação da vitalidade pulpar em dentes permanentes jovens com rizogênese incompleta / Pulp vitality evaluation of young permanent teeth with incomplete root formation

No intuito de avaliar a confiabilidade dos testes de vitalidade pulpar em dentes permanentes jovens com rizogênese incompleta, os autores compararam a aplicação do gelo, teste elétrico e DDM (gás refrigerante) - diclorofluorometano em 86 incisivos centrais superiores de crianças com idade variável entre 7 e 8 anos. Pôde-se verificar que o DDM proporcionou maior porcentagem de respostas positivas que o teste elétrico e o gelo nesta ordem, observadno ademais, uma maior rapidez na obtenção da resposta com gás refrigerante, devendo porém ser utilizado como recurso adicional somente quando os métodos usuais não se mostrarem eficazes na avaliação da vitalidade pulpar