Tooth eruption is a localised event whereby the signals for eruption for a given tooth are synthesised in the dental follicle of that tooth with a possible cross talk of signals coming from the adjacent stellate reticulum. The eruption process requires alveolar bone resorption that is primarily regulated by the dental follicle. This is reflected by the fact that failures of eruption often can be traced to either osteoclast deficiencies or to dental follicle abnormalities. Recent advances in application of molecular techniques to animal models allowed for better understanding of gene regulatory events involved in the physiology of tooth eruption. This article attempts to consolidate and organise the facts that offshoot from animal studies.
Tooth Eruption ; Dental Sac ; Molecular Biology

The regulatory processes in developmental biology research are significantly influenced by long non-coding RNAs (lncRNAs). However, the dynamics of lncRNA expression during human tooth development remain poorly understood. In this research, we examined the lncRNAs present in the dental epithelium (DE) and dental mesenchyme (DM) at the late bud, cap, and early bell stages of human fetal tooth development through bulk RNA sequencing. Developmental regulators co-expressed with neighboring lncRNAs were significantly enriched in odontogenesis. Specific lncRNAs expressed in the DE and DM, such as PANCR, MIR205HG, DLX6-AS1, and DNM3OS, were identified through a combination of bulk RNA sequencing and single-cell analysis. Further subcluster analysis revealed lncRNAs specifically expressed in important regions of the tooth germ, such as the inner enamel epithelium and coronal dental papilla (CDP). Functionally, we demonstrated that CDP-specific DLX6-AS1 enhanced odontoblastic differentiation in human tooth germ mesenchymal cells and dental pulp stem cells. These findings suggest that lncRNAs could serve as valuable cell markers for tooth development and potential therapeutic targets for tooth regeneration.
Humans ; RNA, Long Noncoding/metabolism* ; Odontogenesis/genetics* ; Tooth Germ/embryology* ; Cell Differentiation ; Gene Expression Regulation, Developmental ; Mesoderm/metabolism* ; Tooth/embryology* ; Gene Expression Profiling ; Sequence Analysis, RNA ; Dental Pulp/cytology*

Periodontal bone defects, primarily caused by periodontitis, are highly prevalent in clinical settings and manifest as bone fenestration, dehiscence, or attachment loss, presenting a significant challenge to oral health. In regenerative medicine, harnessing developmental principles for tissue repair offers promising therapeutic potential. Of particular interest is the condensation of progenitor cells, an essential event in organogenesis that has inspired clinically effective cell aggregation approaches in dental regeneration. However, the precise cellular coordination mechanisms during condensation and regeneration remain elusive. Here, taking the tooth as a model organ, we employed single-cell RNA sequencing to dissect the cellular composition and heterogeneity of human dental follicle and dental papilla, revealing a distinct Platelet-derived growth factor receptor alpha (PDGFRA) mesenchymal stem/stromal cell (MSC) population with remarkable odontogenic potential. Interestingly, a reciprocal paracrine interaction between PDGFRA⁺ dental follicle stem cells (DFSCs) and CD31⁺ Endomucin⁺ endothelial cells (ECs) was mediated by Vascular endothelial growth factor A (VEGFA) and Platelet-derived growth factor subunit BB (PDGFBB). This crosstalk not only maintains the functionality of PDGFRA⁺ DFSCs but also drives specialized angiogenesis. In vivo periodontal bone regeneration experiments further reveal that communication between PDGFRA⁺ DFSC aggregates and recipient ECs is essential for effective angiogenic-osteogenic coupling and rapid tissue repair. Collectively, our results unravel the importance of MSC-EC crosstalk mediated by the VEGFA and PDGFBB-PDGFRA reciprocal signaling in orchestrating angiogenesis and osteogenesis. These findings not only establish a framework for deciphering and promoting periodontal bone regeneration in potential clinical applications but also offer insights for future therapeutic strategies in dental or broader regenerative medicine.
Receptor, Platelet-Derived Growth Factor alpha/metabolism* ; Humans ; Neovascularization, Physiologic/physiology* ; Dental Sac/cytology* ; Single-Cell Analysis ; Transcriptome ; Mesenchymal Stem Cells/metabolism* ; Bone Regeneration ; Animals ; Dental Papilla/cytology* ; Periodontium/physiology* ; Stem Cells/metabolism* ; Regeneration ; Angiogenesis

Positional information plays a crucial role in embryonic pattern formation, yet its role in tooth development remains unexplored. In this study, we investigated the regional specification of lingual and buccal dental mesenchyme during tooth development. Tooth germs at the cap stage were dissected from mouse mandibles, and their lingual and buccal mesenchymal regions were separated for bulk RNA sequencing. Gene ontology analysis revealed that odontogenesis, pattern specification, and proliferation-related genes were enriched in the lingual mesenchyme, whereas stem cell development, mesenchymal differentiation, neural crest differentiation, and regeneration-related genes were predominant in the buccal mesenchyme. Reaggregation experiments using Wnt1^creERT/+; R26R^tdT/+ and WT mouse models demonstrated that lingual mesenchyme contributes to tooth formation, while buccal mesenchyme primarily supports surrounding tissues. Furthermore, only the lingual part of tooth germs exhibited odontogenic potential when cultured in vitro and transplanted under the kidney capsule. Bulk RNA transcriptomic analysis further validated the regional specification of the lingual and buccal mesenchyme. These findings provide novel insights into the molecular basis of positional information in tooth development and pattern formation.
Animals ; Mice ; Odontogenesis/genetics* ; Tooth Germ/cytology* ; Mesoderm/cytology* ; Cell Differentiation ; Mesenchymal Stem Cells ; Tooth/embryology*

OBJECTIVES: The mechanism of the odontogenic differentiation of apical papillary cells (APCs) stimulated by bioactive glass 45S5 is still unclear. This study aims to investigate the effect of autophagy on the odontogenic differentiation of APCs stimulated by bioactive glass 45S5. METHODS: APCs were isolated and cultured in vitro, and the cell origin was identified by flow cytometry. The culture medium was prepared with 1 mg/mL 45S5, and its pH and ion concentration were determined. The experiments were divided into control, 45S5, and 3-methyladenine (3-MA) 45S5 groups. In the 45S5 group, APCs were induced to culture with 1 mg/mL 45S5. In the 3-MA 45S5 group, the autophagy inhibitor 3-MA was added to 1 mg/mL 45S5. Protein immunoblotting assay (Western blot) was used to detect the expression of autophagy-associated proteins of microtubule-associated protein 1 light-chain 3β (LC3B) and P62 after 24 h of induction culture in each group. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of bone sialoprotein (BSP), Runt-related transcription factor 2 (Runx2), dentin sialophosphoprotein (DSPP), and dentin matrix protein-1 (DMP-1) after 7 d of induction culture. Cellular alkaline phosphatase (ALP) staining analyzed cellular ALP activity at 7 d of induction, and alizarin red staining evaluated the formation of mineralized nodules at 21 d of induction. RESULTS: The pH of the 45S5 extract culture medium was 8.65±0.01, which was not significantly different from that of the control group (P>0.05). The silicon ion concentration of the 45S5 induction culture medium was (1.56±0.07) mmol/L, which was higher than that of the control group (0.08±0.01) mmol/L (P<0.05). The calcium ion concentration of the 45S5 induction culture was (1.57±0.15) mmol/L, which was not significantly different from that of the control group (P>0.05). Western blot results showed that LC3B-Ⅱ/Ⅰ ratio increased and P62 expression decreased in the 45S5 group compared with those in the control group (P<0.05). By contrast, the ratio decreased and the expression increased in the 3-MA 45S5 group compared with those in the 45S5 group (P<0.05). RT-qPCR results showed that the expression of BSP, Runx2, DMP-1, and DSPP enhanced in the 45S5 group compared with that in the control group (P<0.05), but the expression decreased in the 3-MA 45S5 group compared with that in the 45S5 group (P<0.05). Semi-quantitative analysis of ALP staining and alizarin red staining showed that the ALP activity was enhanced, and the formation mineralized nodule increased in the 45S5 group compared with those in the control group. The ALP activity weakened, and the formation mineralized nodules were reduced in the 3-MA 45S5 group compared with that those in the 45S5 group. CONCLUSIONS Cell autophagy participates in the odontogenic differentiation of APCs induced by 1 mg/mL 45S5 in vitro.
Autophagy/drug effects* ; Cell Differentiation/drug effects* ; Odontogenesis/drug effects* ; Dental Papilla/cytology* ; Humans ; Microtubule-Associated Proteins/metabolism* ; Glass/chemistry* ; Cells, Cultured ; Core Binding Factor Alpha 1 Subunit/metabolism* ; Extracellular Matrix Proteins/metabolism* ; Ceramics/pharmacology* ; Adenine/pharmacology* ; Sialoglycoproteins/metabolism* ; Phosphoproteins/metabolism* ; Integrin-Binding Sialoprotein/metabolism* ; Alkaline Phosphatase/metabolism* ; RNA-Binding Proteins

In light of the lack of reliable molecular markers for odontogenic myxoma (OM), the detection of copy number variation (CNV) may present a more objective method for assessing ambiguous cases. In this study, we employed multiregional microdissection sequencing to integrate morphological features with genomic profiling. This allowed us to reveal the CNV profiles of OM and compare them with dental papilla (DP), dental follicle (DF), and odontogenic fibroma (OF) tissues. We identified a distinct and robustly consistent CNV pattern in 93.75% (30/32) of OM cases, characterized by CNV gain events in chromosomes 4, 5, 8, 10, 12, 16, 17, 20, and 21. This pattern significantly differed from the CNV patterns observed in DP, DF, and OF. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated potential links between this CNV patterns and the calcium signaling pathway and salivary secretion, while Gene Ontology (GO) term analysis implicated CNV patterns in tumor adhesion, tooth development, and cell proliferation. Comprehensive CNV analysis accurately identified a case that was initially disputable between OF and OM as OM. Our findings provide a reliable diagnostic clue and fresh insights into the molecular biological mechanism underlying OM.
Humans ; DNA Copy Number Variations ; Odontogenic Tumors/diagnosis* ; Myxoma/genetics* ; Female ; Male ; Adult ; Adolescent ; Middle Aged ; Dental Papilla ; Young Adult ; Fibroma/genetics* ; Dental Sac ; Child

Tooth germ injury can lead to abnormal tooth development and even tooth loss, affecting various aspects of the stomatognathic system including form, function, and appearance. However, the research about tooth germ injury model on cellular and molecule mechanism of tooth germ repair is still very limited. Therefore, it is of great importance for the prevention and treatment of tooth germ injury to study the important mechanism of tooth germ repair by a tooth germ injury model. Here, we constructed a Tg(dlx2b:Dendra2-NTR) transgenic line that labeled tooth germ specifically. Taking advantage of the NTR/Mtz system, the dlx2b⁺ tooth germ cells were depleted by Mtz effectively. The process of tooth germ repair was evaluated by antibody staining, in situ hybridization, EdU staining and alizarin red staining. The severely injured tooth germ was repaired in several days after Mtz treatment was stopped. In the early stage of tooth germ repair, the expression of phosphorylated 4E-BP1 was increased, indicating that mTORC1 is activated. Inhibition of mTORC1 signaling in vitro or knockdown of mTORC1 signaling in vivo could inhibit the repair of injured tooth germ. Normally, mouse incisors were repaired after damage, but inhibition/promotion of mTORC1 signaling inhibited/promoted this repair progress. Overall, we are the first to construct a stable and repeatable repair model of severe tooth germ injury, and our results reveal that mTORC1 signaling plays a crucial role during tooth germ repair, providing a potential target for clinical treatment of tooth germ injury.
Animals ; Mice ; Mechanistic Target of Rapamycin Complex 1/pharmacology* ; Signal Transduction ; Tooth/metabolism* ; Tooth Germ/metabolism* ; Odontogenesis

OBJECTIVES: To summarize the open-eruption technique of impacted anterior maxillary teeth, this study reports a technically improved operation on surgical exposure based on dental follicles and evaluates post-treatment periodontal health considering the effect of dental follicles. METHODS: Patients who underwent open-eruption technique with unilateral labially impacted maxillary central incisors were selected. The impacted teeth were assigned to the experimental group, and the contralateral unimpacted maxillary central incisors were assigned to the control group. In the surgical exposure, the new technique makes use of dental follicles to manage the soft tissue, so as to preserve soft tissue for better aesthetic results and healthier periodontal tissue. Tooth length, root length, alveolar bone loss, and alveolar bone thickness were recorded after the therapy. RESULTS: A total of 17 patients with unilateral maxillary central incisor impaction were successfully treated. The tooth length and root length of the two groups showed a statistically significant difference between the impacted and homonym teeth, with a shorter length in the impacted tooth (P<0.05). More labial alveolar bone loss was found in the experimental group compared with that in the control group (P<0.05). The outcomes of the cementoenamel junction width, pa- latal alveolar bone loss, and alveolar bone thickness did not indicate statistical significance between the experimental and control groups (P>0.05). CONCLUSIONS In the surgical exposure, the new technique uses dental follicles to manage the soft tissue and preserve it for better aesthetic results and healthier periodontal tissues.
Humans ; Tooth, Impacted/surgery* ; Incisor ; Alveolar Bone Loss/diagnostic imaging* ; Tooth Root ; Dental Sac ; Maxilla/surgery* ; Esthetics, Dental

Multiple signaling pathways are involved in the regulation of cell proliferation and differentiation in odontogenesis and dental tissue renewal, but the details of these mechanisms remain unknown. Here, we investigated the expression patterns of a transcription factor, Krüppel-like factor 6 (KLF6), during the development of murine tooth germ and its function in odontoblastic differentiation. KLF6 was almost ubiquitously expressed in odontoblasts at various stages, and it was co-expressed with P21 (to varying degrees) in mouse dental germ. To determine the function of Klf6, overexpression and knockdown experiments were performed in a mouse dental papilla cell line (iMDP-3). Klf6 functioned as a promoter of odontoblastic differentiation and inhibited the proliferation and cell cycle progression of iMDP-3 through p21 upregulation. Dual-luciferase reporter assay and chromatin immunoprecipitation showed that Klf6 directly activates p21 transcription. Additionally, the in vivo study showed that KLF6 and P21 were also co-expressed in odontoblasts around the reparative dentin. In conclusion, Klf6 regulates the transcriptional activity of p21, thus promoting the cell proliferation to odontoblastic differentiation transition in vitro. This study provides a theoretical basis for odontoblast differentiation and the formation of reparative dentine regeneration.
Animals ; Cell Differentiation/physiology* ; Cell Proliferation ; Mice ; Odontoblasts/metabolism* ; Odontogenesis ; Tooth Germ

Devitalization has been widely used in the root canal therapy of primary and permanent teeth in China more than ten years ago. With the development of local anesthetic drugs and injection technologies, this treatment method with high potential risks has been gradually abandoned. However, a questionnaire survey targeted all the participants at the 2018 China Pediatric Dentistry Conference showed that the devitalizer utilization proportion was still as high as 38.1% (383/1 005), even though the ratio was much lower than 75.5% (105/139) in 2003. These doctors had pay more attention to tissue burn caused by devitalizer marginal leakage or direct leakage, and know how to identify and handle with devitalizer burn. Devitalizers were usually made of arsenic trioxide, metal arsenic or paraformaldehyde, which have cytotoxicity, allergenicity, mutagenicity, carcinogenicity, and teratogenic effects on animals. Marginal leakage of devitalizers have high risks of causing soft and hard tissue necrosis. Most of the dentists have an understanding of the potential damages of arsenic containing devitalizers, so they will choose parafor maldehyde with relatively less toxicity. Paraformaldehyde has a certain self limitation, and there are few cases reported, so some dentists lack of vigilance. Paraformaldehyde can also causes tissue necrosis if leakage happens, and the treatment methods are similar to that of arsenic containing devitalizers. When handling with devitalizers burn, the necrosed soft and hard tissue, for example gingiva, alveolar bone or teeth that cannot keep, must be completely removed until fresh blood appears, then rinse with large amount of saline and seal with iodoform gauze. This paper described two cases of devitalizer burn during the root canal treatment of primary molars, both of the doctors failed to identify the devitalizer burn symptoms in the early stage, thus didn't do proper treatments immediately after burning. Resulting in the necrosis of large area of gingiva and alveolar bone, loss of primary molars and permanent tooth germs 1-2 months after devitalizer burn. This paper reported these two cases in detail in order to warn dentists the high risks of using any kind of devitalizers, help them learn how to identify and treat devitalizer burn, and remind them to stop using devitalizers as soon as possible.
Arsenic/toxicity* ; China ; Dental Pulp Devitalization ; Humans ; Necrosis ; Root Canal Therapy ; Tooth Germ ; Tooth Loss/chemically induced* ; Tooth, Deciduous