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Stem cells support homeostasis and injury repair of adult organs. It remains unclear when and how adult stem cells form during development. Here, we discover that incisor mesenchymal stem cells, marked by an extracellular matrix molecule Smoc2 , establish their identity and quiescence between E14.5 and E16.5, and persist into adulthood. They support both embryonic tooth development and postnatal organ turnover. Concurrently, the incisor mesenchyme evolves from a homogenous dental papilla into a heterogeneous dental pulp consisting of a complete lineage hierarchy, which persists into adulthood. Smoc2 and its homologous molecule Smoc1 are indispensable for maintaining the quiescence and hierarchy of mesenchymal stem cells. They function by disrupting the binding between canonical WNT ligands and glypican, a process critical for transporting hydrophobic WNT ligands within the aqueous niche. In conclusion, mesenchymal stem cells establish their quiescence during development through autocrine extracellular matrix molecules to keep canonical WNT ligands from accessing them. This study identifies Smoc2 as a marker of mesenchymal stem cells in mouse incisors and shows that Smoc1/2 establishes stem cell quiescence by inhibiting Wnt signaling during development.

The extent to which heterogeneity within mesenchymal stem cell (MSC) populations is related to function is not understood. Using the archetypal MSC in vitro surface marker, CD90/Thy1, here we show that 30% of the MSCs in the continuously growing mouse incisor express CD90/Thy1 and these cells give rise to 30% of the differentiated cell progeny during postnatal development. In adulthood, when growth rate homeostasis is established, the CD90/Thy1 + MSCs decrease dramatically in number. When adult incisors are cut, the growth rate increases to rapidly re-establish tooth length and homeostasis. This accelerated growth rate correlates with the re-appearance of CD90/Thy + MSCs and re-establishment of their contribution to cell differentiation. A population of Celsr1 + quiescent cells becomes mitotic following clipping and replenishes the CD90/Thy1 population. A sub-population of MSCs thus exists in the mouse incisor, distinguished by expression of CD90/Thy1 that plays a specific role only during periods of increased growth rate. Mouse incisors constantly renew from a slow cycling population of mesenchymal stem cells. Here, the authors show that upon cutting of adult incisors, a sub-population of dental mesenchymal stem cells reactivates, allowing an increased growth rate and rapid regeneration.

Mammalian dentition exhibits distinct heterodonty, with more simple teeth located in the anterior area of the jaw and more complex teeth situated posteriorly. While some region-specific differences in signalling have been described previously, here we performed a comprehensive analysis of gene expression at the early stages of odontogenesis to obtain complete knowledge of the signalling pathways involved in early jaw patterning. Gene expression was analysed separately on anterior and posterior areas of the lower jaw at two early stages (E11.5 and E12.5) of odontogenesis. Gene expression profiling revealed distinct region-specific expression patterns in mouse mandibles, including several known BMP and FGF signalling members and we also identified several new molecules exhibiting significant differences in expression along the anterior–posterior axis, which potentially can play the role during incisor and molar specification. Next, we followed one of the anterior molecules, SATB2, which was expressed not only in the anterior mesenchyme where incisor germs are initiated, however, we uncovered a distinct SATB2-positive region in the mesenchyme closely surrounding molars. Satb2 -deficient animals demonstrated defective incisor development confirming a crucial role of SATB2 in formation of anterior teeth. On the other hand, ectopic tooth germs were observed in the molar area indicating differential effect of Satb2 -deficiency in individual jaw regions. In conclusion, our data provide a rich source of fundamental information, which can be used to determine molecular regulation driving early embryonic jaw patterning and serve for a deeper understanding of molecular signalling directed towards incisor and molar development.

Achieving an apical seal is critical for apexification treatment of nonvital immature teeth. While this is commonly accomplished using biocompatible mineral trioxide aggregate (MTA), its limitations, such as prolonged setting time, discoloration, and challenging handling, have driven the search for alternative materials. This study aimed to compare the clinical and radiographic success of bioceramic putty Well-Root PT apical plug compared to MTA in the treatment of nonvital immature permanent incisors. Fifty immature nonvital maxillary permanent central incisors in thirty-eight children aged 8–11 years were randomly divided into two groups (25 teeth/group). Group I received MTA apical plugs, and Group II was treated with Well-Root PT apical plugs. Both groups were recalled at 6 and 12 months for clinical and radiographic evaluations. Statistical analysis was done for the gathered data. Both groups showed improved clinical signs and symptoms during all follow-up periods with no statistically significant difference. Regarding the periapical radiolucency (PAR) area, at twelve months, the mean PAR area in the Well-Root PT group was (0.14 ± 0.08) compared to (2.3 ± 0.9) in the MTA group, with highly statistically significant differences (p < 0.001). The mean periapical bone radiodensity in the Well-Root PT group was (178.2 ± 5.4) compared to (164.8 ± 9.4) in the MTA group at twelve-month follow-up, with highly statistically significant differences(p < 0.001). Well-Root PT, with its reduced technical sensitivity, demonstrates satisfactory clinical and radiographic success as an apical plug for nonvital immature permanent incisors compared to MTA.

Background For orthodontists, the position of the incisors is a key factor in setting treatment goals. Achieving maximum stability requires that they be positioned in the medullary portion of the alveolar bone, balanced with the lingual and labial musculature. Incorrect orthodontic movements can result in root resorption, dehiscences, or even fenestrations. Methods A systematic review of the bibliography was conducted in accordance with PRISMA recommendations. Searches were made in PubMed, Scopus, and Cochrane Library databases, using the same search terms in each, with no limitation on publication data, up to July 1st, 2024. The review accepted articles in any language. Randomized controlled trials, case-control studies, and cohort studies were included, both retrospective and prospective. Systematic reviews, meta-analyses, case reports, case series, literature reviews, and editorials were excluded. The quality of the articles was determined according to the CONSORT criteria. Results The initial database search identified 167 articles: 89 in PubMed, 74 in Scopus, and 4 in the Cochrane Library. Of these, 75 were duplicates, leaving 92. After applying the inclusion criteria, a total of 8 articles were included in this systematic review. Conclusions This systematic review highlights the significant relationship between alveolar bone thickness and incisor inclination as assessed by CBCT. The bone thickness varies regionally, with the maxilla generally having thicker palatal bone and the mandible having thinner labial bone. CBCT is indispensable for evaluating cases involving severe skeletal discrepancies, preexisting bone defects, or planned movements beyond the alveolar limits, while traditional methods may suffice for less complex cases. Standardizing methodologies and conducting longitudinal studies with diverse populations are crucial for improving clinical guidelines and ensuring safe, effective treatment planning.

The use of regenrative endodontics is restoring the health status of the root canals of retreated mature teeth is a novel approach. Therefore, the current trial aimed to compare the effectiveness of regenerative endodontic procedures (REPs) to non-surgical root canal retreatment (NS-RCR) in reducing periapical radiolucency over one year for the retreatment of mature incisors with periapical periodontitis. The secondary purpose was to assess clinical success and regain pulp sensibility. A parallel randomized controlled trial, 66 mature incisors with periapical radiolucencies were randomly divided into two equal groups and retreated with either REPs or NS-RCR. At baseline and after 6 and 12 months, teeth were assessed clinically and radiographically using a periapical index (PAI). The Mann–Whitney test was used to analyze nonparametric PAI scores. The Electric pulp test readings were analyzed using the repeated measure analysis of variance (ANOVA). Over the follow-up intervals, there was no significant intergroup difference in the PAI medians, the majority of the teeth displayed a reduction in periapical radiolucency. At the end of the follow-up period, the clinical successes for the REP and NS-RCR groups were 93.9% and 97%, respectively ( p  = 0.555). Positive pulp sensibility was recorded in 54.54% of cases in the REPs after 12 months. Both approaches showed a comparable diminishing of periapical radiolucencies and equivalent clinical results. A conventional, non-surgical endodontic retreatment may not always be necessary.

Understanding cell types and mechanisms of dental growth is essential for reconstruction and engineering of teeth. Therefore, we investigated cellular composition of growing and non-growing mouse and human teeth. As a result, we report an unappreciated cellular complexity of the continuously-growing mouse incisor, which suggests a coherent model of cell dynamics enabling unarrested growth. This model relies on spatially-restricted stem, progenitor and differentiated populations in the epithelial and mesenchymal compartments underlying the coordinated expansion of two major branches of pulpal cells and diverse epithelial subtypes. Further comparisons of human and mouse teeth yield both parallelisms and differences in tissue heterogeneity and highlight the specifics behind growing and non-growing modes. Despite being similar at a coarse level, mouse and human teeth reveal molecular differences and species-specific cell subtypes suggesting possible evolutionary divergence. Overall, here we provide an atlas of human and mouse teeth with a focus on growth and differentiation. Unlike human teeth, mouse incisors grow throughout life, based on stem and progenitor cell activity. Here the authors generate single cell RNA-seq comparative maps of continuously-growing mouse incisor, non-growing mouse molar and human teeth, combined with lineage tracing to reveal dental cell complexity.

Aim To update the existing European Academy of Paediatric Dentistry (EAPD) 2010 policy document on the ‘Best Clinical Practice guidance for clinicians dealing with children presenting with Molar-Incisor-Hypomineralisation (MIH).’ Methods Experts, assigned the EAPD, worked on two different topics: (A) Aetiological factors involved in MIH, and (B) Treatment options for the clinical management of MIH. The group prepared two detailed systematic reviews of the existing literature relevant to the topics and following a consensus process produced the updated EAPD policy document on the ‘Best Clinical Practice guidance for clinicians dealing with children presenting with molar-incisor-hypomineralisation (MIH).’ The GRADE system was used to assess the quality of evidence regarding aetiology and treatment which was judged as HIGH, MODERATE, LOW or VERY LOW, while the GRADE criteria were used to indicate the strength of recommendation regarding treatment options as STRONG or WEAK/CONDITIONAL. Results (A) Regarding aetiology, it is confirmed that MIH has a multifactorial aetiology with the duration, strength and timing of occurrence of the aetiological factors being responsible for the variable clinical characteristics of the defect. Perinatal hypoxia, prematurity and other hypoxia related perinatal problems, including caesarean section, appear to increase the risk of having MIH, while certain infant and childhood illnesses are also linked with MIH. In addition, genetic predisposition and the role of epigenetic influences are becoming clearer following twin studies and genome and single-nucleotide polymorphisms analyses in patients and families. Missing genetic information might be the final key to truly understand MIH aetiology. (B) Regarding treatment options, composite restorations, preformed metal crowns and laboratory indirect restorations provide high success rates for the posterior teeth in appropriate cases, while scheduled extractions provide an established alternative option in severe cases. There is great need for further clinical and laboratory studies evaluating new materials and non-invasive/micro-invasive techniques for anterior teeth, especially when aesthetic and oral health related quality of life (OHRQoL) issues are concerned. Conclusions MIH has been studied more extensively in the last decade. Its aetiology follows the multifactorial model, involving systemic medical and genetic factors. Further focused laboratory research and prospective clinical studies are needed to elucidate any additional factors and refine the model. Successful preventive and treatment options have been studied and established. The appropriate choice depends on the severity of the defects and the age of the patient. EAPD encourages the use of all available treatment options, whilst in severe cases, scheduled extractions should be considered.

This study aimed to compare the effects of clear aligners and fixed appliances on root resorption, incisive canal (IC) morphology, and the spatial relationship between the maxillary central incisors (U1) and the IC following incisor retraction in dental/skeletal Class I and II extraction cases. Sixty-six adult patients (132 maxillary central incisors) with comparable baseline characteristics (based on the ABO Discrepancy Index) were retrospectively analyzed. Patients received either clear aligners ( n  = 33) or fixed appliances ( n  = 33) following first premolar extraction. Pre- and post-treatment CBCT measurements were recorded at three vertical reference planes (H1, H2, H3: 2 mm, 4 mm, and 6 mm above the labial cementoenamel junction), including IC width, cortical bone width (CBW), U1–IC distance, IC height, and U1 root length/width. Both groups showed reductions in IC width, CBW, and U1–IC distance, with greater changes in the fixed appliance group. U1–IC distance was significantly reduced in the fixed group at H1 (1.79 ± 0.76 mm vs. 1.24 ± 1.04 mm), H2 (1.78 ± 1.08 mm vs. 1.33 ± 0.86 mm), and H3 (1.61 ± 1.35 mm vs. 1.16 ± 0.90 mm) ( P  < 0.05). Root resorption was also significantly higher in the fixed group (1.81 ± 1.55 mm vs. 0.87 ± 0.77 mm, P  < 0.001). Root–IC proximity patterns included 7.6% separation, 63.1% approximation, 15.9% contact, and 13.4% invasion, with contact and invasion more prevalent in the fixed group. Root resorption increased with IC proximity, peaking at 3.65 ± 1.97 mm in invasion cases. Regression analysis identified tooth movement, root length, and inter-root distance as predictors of U1–IC proximity, while root resorption was associated with treatment duration, U1 movement, IC height, and incisor inclination (U1–SN angle). These findings underscore the importance of individualized planning and appliance selection in cases requiring maximum anterior retraction to reduce the risk of root resorption and IC-related complications.