Appropriate timing of treatment contributes to better root development of impacted anterior teeth in children.

INTRODUCTION: This study investigated the effects of different timings of orthodontic treatment on the root development of impacted anterior teeth in children. METHODS: The cone-beam computed tomography (CBCT) data of 45 children with impacted anterior teeth were divided into unformed root (UR) group or basically formed root (BFR) group to evaluate root length (RL) and root growth length (RGL) of impacted teeth and contralateral nonimpacted teeth pretreatment and posttreatment. In addition, 22 patients with impacted dilaceration were selected to assess the effects of the crown-root angle and root development stage on RL and RGL. The Student t test, Wilcoxon test, analysis of variance, and multiple linear regression analysis were used for statistical evaluations. RESULTS: The RL of treated impacted teeth pretreatment and posttreatment was significantly shorter than contralateral nonimpacted teeth values (P <0.05). Posttreatment, the RL and RGL of impacted teeth of the UR group were significantly greater than those of the BFR group (P <0.05). The RGL of the dilacerated root in the UR group was considerably higher than in the BFR group (P <0.05). The larger crown-root angle group had a longer posttreatment RL (P <0.05). Multiple linear regression analysis revealed that the Nolla stage of impacted teeth and RL of contralateral teeth pretreatment significantly influenced the RL of impacted teeth posttreatment. CONCLUSIONS: Prompt orthodontic treatment is necessary for children with impacted anterior teeth to release the impacted state and achieve better root development. The root length of a dilacerated tooth continued to develop under treatment, but the crown-root angle partly constrained it.

Full life cycle changes of low impacted mandibular third molar associated cystic lesions and adjacent tooth root resorption: a retrospective study.

OBJECTIVE: Low impacted third molars are usually asymptomatic and are often found by X-ray examination. The removal of asymptomatic low impacted third molars is one of the most controversial clinical issues in oral and maxillofacial surgery. METHODS: In this study, 806 patients with low impacted mandibular third molars (LIMTMs) (full bony impaction) were analyzed to determine the prevalence and risk factors for cystic lesions and adjacent tooth root resorption throughout the patients' entire life cycle. RESULTS: The results showed that the prevalence of adjacent tooth root resorption and cystic lesions was age-related, exhibiting a trend of first increasing and then decreasing; prevalence peaked at the age of 41 to 45 years old, the prevalence rates were 12.50% and 11.11% respectively. And the lowest prevalence rate was 2.86% and 2.44% in ≥ 61 group and 56- to 60-year age group respectively. Age was an independent risk factor for adjacent tooth root resorption of LIMTMs, whereas age and impaction type (especially inverted impaction) were independent risk factors for cystic lesions. CONCLUSIONS: The full life cycle management strategy for LIMTMs may need to be individualized. Surgical removal is recommended for LIMTMs in patients younger than 41 to 45 years, especially for inverted, mesioangular, and horizontally impacted LIMTMs. LIMTMs in patients older than 41 to 45 years may be treated conservatively with regular follow-up, but surgical removal of inverted impacted LIMTMs is still recommended to avoid cyst formation.

Comparative efficacy of the bone-anchored maxillary protraction protocols for orthopaedic treatment in skeletal Class III malocclusion: A Bayesian network meta-analysis.

OBJECTIVE: To compare the treatment effects of five bone-anchored maxillary protraction protocols (BAC3E, BAMP, BARME-FM, BARME-ME, SAFM) for skeletal Class III malocclusion. METHODS: We conducted a systematic literature search through CENTRAL, EBSCO, PubMed and Web of Science and included the randomized controlled trials and clinical controlled trials, which met the criteria. A Bayesian network meta-analysis (NMA) for SNA, SNB, ANB, SN-MP and Wits appraisal was performed in R software using a random consistency model. The additional analyses included node-splitting analysis, statistical heterogeneity analysis, sensitivity analysis and ranking probability by SUCRA. RESULTS: A total of 598 articles were initially obtained; 13 articles involving 482 individuals were eventually included. Among the five bone-anchored maxillary protraction protocols, the largest increment in SNA and Wits appraisal was observed in the BAMP group and BAC3E group, respectively; the SAFM, BAC3E and BAMP groups showed similar capability in terms of changes of ANB; least clockwise rotation of the mandible was found in the BARME-ME group, followed by the BAMP group; dental compensation appears to be most pronounced in the BAC3E group; and intermaxillary traction seems to reduce the lingual inclination of lower incisors and even cause labial inclination. CONCLUSIONS: The SAFM, BAMP and BAC3E groups seem to be advantageous in the improvement of the maxillo-mandibular relationship, followed by the BARME-FM and BARME-ME groups. The findings of this study should be interpreted with caution as only short-term effects were compared and the quality of evidence ranged from very low to moderate. More RCTs with high-quality and long-term investigation are needed.

The Role of TNF-α in the Pathogenesis of Temporomandibular Disorders.

Temporomandibular disorder (TMD) is an oral dentofacial disease that is related to multiple factors such as disordered dental occlusion, emotional stress, and immune responses. In the past decades, tumor necrosis factor-alpha (TNF-α), a pleiotropic cytokine, has provided valuable insight into the pathogenesis of TMD, particularly in settings associated with inflammation. It is thought that TNF-α participates in the pathogenesis of TMD by triggering immune responses, deteriorating bone and cartilage, and mediating pain in the temporomandibular joint (TMJ). Initially, TNF-α plays the role of "master regulator" in the complex immune network by increasing or decreasing the production of other inflammatory cytokines. Then, the effects of TNF-α on cells, particularly on chondrocytes and synovial fibroblasts, result in pathologic cartilage degradation in TMD. Additionally, multiple downstream cytokines induced by TNF-α and neuropeptides can regulate central sensitization and inflammatory pain in TMD. Previous studies have also found some therapies target TMD by reducing the production of TNF-α or blocking TNF-α-induced pathways. All this evidence highlights the numerous associations between TNF-α and TMD; however, they are currently not fully understood and further investigations are still required for specific mechanisms and treatments targeting specific pathways. Therefore, in this review, we explored general mechanisms of TNF-α, with a focus on molecules in TNF-α-mediated pathways and their potential roles in TMD treatment. In view of the high clinical prevalence rate of TMD and damage to patients' QOL, this review provides adequate evidence for studying links between inflammation and TMD in further research and investigation.

Ectopic eruption of the first permanent molar: Predictive factors for irreversible outcome.

INTRODUCTION: The present study aimed to analyze possible factors involved in irreversible (IRR) ectopic eruption (EE) of the first permanent molar and explore potential predictors for the IRR outcome. METHODS: Children aged 4-11 years, with at least 1 EE and who took their first panoramic radiograph before the age of 8 years, were selected in this study. The subjects were assigned to the self-correcting (SC) and IRR groups. Patients' age, sex, distribution of EE, and accompanying dental anomalies were recorded. Eruptive angulation (EA) of the first permanent molar, the grade of root resorption in the second deciduous molar, the magnitude of impaction index (MOII), and horizontal distance were measured on the panoramic radiographs. Chi-square tests and independent-sample t test were used for nominal and continuous variables, respectively. The receiver operative characteristic curve was used to determine the critical value. RESULTS: A total of 406 children with 634 first permanent molars, presenting EE, were enrolled, with 61.3% of the teeth in the SC group. Sex of children with EE and distribution of EE were not relevant to the IRR outcome. The presence of supernumerary teeth might be a protective factor for the IRR outcome. The increasing severity of root resorption in the second primary molar indicated an IRR outcome. A higher MOII and a larger EA suggested an IRR outcome with moderate-to-high quality. The horizontal distance exhibited debatable results, with a low predictive quality. CONCLUSION: Close monitoring and early intervention would benefit children with increasing severity of distal atypical resorption in the second primary molar, higher MOII, and larger EA.

Effect of visual method vs plaque disclosure in enhancing oral hygiene in adolescents and young adults: a single-blind randomized controlled trial.

INTRODUCTION: Enamel demineralization and gingival inflammation are the most prevalent consequences of biofilm formation in orthodontics. Our hypothesis was that educating patients about the severe consequences of biofilm accumulation could enhance their oral hygiene while wearing fixed appliances. METHODS: This study was designed as a randomized controlled 4-arm parallel trial. A total of 148 participants in Chengdu, China, matching the eligibility criteria of 11 to 25 years of age, at least 20 natural teeth, and a treatment plan that included conventional stainless steel brackets, were randomly assigned to 4 intervention groups based on computer-generated random sequencing using simple randomization without blocking. In group A (n = 37), the subjects were shown images illustrating the severe consequences of biofilm formation, including enamel demineralization and gingival inflammation; subjects in group B (n = 40) were given biofilm disclosing tablets; those in group C (n = 38) received a combination of A and B; the subjects in group D (n = 33) served as the controls. The investigators were blinded to the allocations, and the researcher managing the random sequence did not participate in allocation or measurement. All groups received routine oral hygiene instructions. Plaque index and gingival index scores were recorded at each appointment during a 6-month follow-up. RESULTS: Eighteen participants were lost during follow-up, resulting in a total of 130 participants after the trial (group A, 35; group B, 32; group C, 34; group D, 29). No adverse events were recorded. Groups A and C exhibited a significantly lower plaque index scores (parameter-estimate [95% confidence interval] = -1.20 [-1.76 to -0.63] for group A, and -1.12 [-1.69 to -0.56] for group C) and gingival index scores (-0.13 [-0.21 to -0.04], and -0.19 [-0.28 to -0.10]), respectively, compared with group D (P <0.001 for all), whereas no significant difference was found between groups B and D, or between groups A and C (P >0.05). The adults had significantly lower plaque index (0.48 [0.13-0.84], P <0.001) and gingival index (0.06 [0.01-0.11], P = 0.018) scores than did the teenagers, and the female subjects had significantly higher gingival index (-0.06 [-0.11 to -0.01], P = 0.040) scores than did the male subjects. CONCLUSIONS: The use of images showing the severe consequences of biofilm accumulation enhanced the oral hygiene of patients treated with fixed appliances.

Ectopic eruption of maxillary first permanent molars: Risk factors and association with alveolar and maxillary characteristics on children.

Background/purpose: The etiology of the ectopic eruption (EE) of the maxillary first permanent molars (FPM) remains unclear and controversial. This study was designed to explore the dental and skeletal factors for EE of the FPM in children. Materials and methods: Children aged 6-10 years were recruited to this study. Subjects were assigned to the ectopic eruption group (EEG) and the normal eruption group (NEG). Lateral cephalometric radiographs and panoramic radiographs were measured by angular and linear indices. Results: The prevalence of EE of maxillary FPM was higher in males and at younger ages. Subjects with skeletal class III malocclusion were more likely to be diagnosed with EE of maxillary FPM. The SNA, ANB, FMIA, Wits, Ptm-A, ANS-PNS, overbite, and overjet were significantly different between the EEG and the NEG. The length of the posterior region of the maxillary alveolar bone, U6-OP, and eruptive angulation of the maxillary FPM were statistically different between the two groups. Conclusion: Male sex, skeletal class III malocclusion, mesial inclination of the maxillary FPM, hypoplasia of the maxilla, and insufficient length of the posterior region of the maxillary alveolar bone were related to EE of the maxillary FPM.

Young people's esthetic perception of dental midline deviation.

OBJECTIVE: To test the hypothesis that young people's esthetic perception of dentition midline deviation or the threshold below which they find the deviation "acceptable" depends on the gender and face type of the person with the deviation and the gender of the evaluator. MATERIALS AND METHODS: Facial images of six young subjects with three different face types were captured, and their dentition midlines were altered digitally. The images were evaluated by young people with no dental training. Statistical analysis was carried out to determine the threshold for acceptable dentition midline deviation and factors influencing perception. RESULTS: The mean value for the threshold below which a deviation was judged "acceptable" was 2.403 mm (95% confidence interval, 2.315-2.491). The preferences of evaluators did not significantly depend on the direction of the deviation. Both male and female evaluators were significantly less tolerant of deviation in female subjects than in male subjects. However, female evaluators were significantly more tolerant of midline deviations in male subjects than were male evaluators. In addition, the same degree of deviation was most noticeable in male subjects with a tapered face type and least noticeable in female subjects with a square face type. CONCLUSIONS: The gender and face type of an individual with dentition midline deviation and the gender of the evaluator do affect young people's esthetic perception of a dentition midline deviation and the threshold below which they find the deviation "acceptable."

Epigenetic Regulation of Dental Pulp Stem Cell Fate.

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs, affects gene expression without modifying the primary DNA sequence and modulates cell fate. Mesenchymal stem cells derived from dental pulp, also called dental pulp stem cells (DPSCs), exhibit multipotent differentiation capacity and can promote various biological processes, including odontogenesis, osteogenesis, angiogenesis, myogenesis, and chondrogenesis. Over the past decades, increased attention has been attracted by the use of DPSCs in the field of regenerative medicine. According to a series of studies, epigenetic regulation is essential for DPSCs to differentiate into specialized cells. In this review, we summarize the mechanisms involved in the epigenetic regulation of the fate of DPSCs.

Non-syndromic occurrence of true generalized microdontia with hypodontia: A case report.

RATIONAL: Dental abnormalities can occur at any stage of tooth development. Of these abnormalities, true generalized microdontia is a rare condition in which all teeth are smaller than normal, while hypodontia is defined as the absence of 1 to 5 teeth. As far as we are aware, no article has reported a case of the non-syndromic occurrence of true generalized microdontia with hypodontia. PATIENT CONCERNS: A 9-year-old girl who had no systemic diseases presented with congenital absence of maxillary lateral incisors bilaterally and small teeth involving the whole dentition. DIAGNOSES: Based on intraoral examinations and panoramic radiograph, the patient was diagnosed with the simultaneous occurrence of true generalized microdontia, hypodontia, and a variation of maxillary 1st molar with a single root and single canal. Also, the patient had premature loss of mandibular molars and canines, periapical periodontitis in the mandible left 1st primary molar and deep caries in mandible left secondary primary molar. INTERVENTIONS: A removable appliance to hold space for early loss of mandibular molars and canines was made at the present stage. The mandible left 1st primary molar had periapical periodontitis and the affected tooth was extracted. Furthermore, the distal surface of the mandible left 2nd primary molar was filled with complex resin materials. A multi-disciplinary therapy plan was carefully designed including orthodontics, dental implants and esthetic restoration in the future. OUTCOMES: The patient complied well with instructions for wearing the removable space maintainer, which helps prevent mesial migration of the permanent 1st molars, at the current stage. The therapeutic efficiency on periapical periodontitis and caries lesions was also good. LESSONS: The non-syndromic presence of true generalized microdontia is extremely rare. A personalized treatment plan with multi-disciplinary considerations should be given for these patients. The pathogenesis remains unclear but may be related to genetic as well as environmental factors. More studies are urgently needed to explore the pathogenesis and treatment options for the future.

Epiregulin enhances odontoblastic differentiation of dental pulp stem cells via activating MAPK signalling pathway.

OBJECTIVES: The odontoblastic differentiation of dental pulp stem cells (DPSCs) contributes to tertiary dentin formation. Our previous study indicated that epiregulin (EREG) enhanced odontogenesis potential of dental pulp. Here, we explored the effects of EREG during DPSC odontoblastic differentiation. METHODS: The changes in EREG were detected during tertiary dentin formation. DPSCs were treated with recombinant human EREG (rhEREG), EREG receptor inhibitor gefitinib and short hairpin RNAs. The odontoblastic differentiation was assessed with ALP staining, ALP activity assay, alizarin red S staining and real-time RT-PCR of DSPP, OCN, RUNX2 and OSX. Western blot was conducted to examine the levels of p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (Erk1/2). The expression of EREG and odontoblastic differentiation-related markers was investigated in human dental pulp from teeth with deep caries and healthy teeth. RESULTS: Epiregulin was upregulated during tertiary dentin formation. rhEREG enhanced the odontoblastic differentiation of DPSCs following upregulated p38 MAPK and Erk1/2 phosphorylation, but not JNK, whereas depletion of EREG suppressed DPSC differentiation. Gefitinib decreased odontoblastic differentiation with decreased phosphorylation of p38 MAPK and Erk1/2. And suppression of p38 MAPK and Erk1/2 pathways attenuated DPSC differentiation. In human dental pulp tissue, EREG upregulation in deep caries correlates with odontoblastic differentiation enhancement. CONCLUSION: Epiregulin is released during tertiary dentin formation. And EREG enhanced DPSC odontoblastic differentiation via MAPK pathways.

The Origin and Identification of Mesenchymal Stem Cells in Teeth: from Odontogenic to Non-odontogenic.

BACKGROUND: Mesenchymal stem cells (MSCs) in teeth have been exploited as vital seed cells for stem cell-based dental medicine. To date, several mesenchymal stem cell populations originated from odontogenic tissue have been isolated and characterized by their expression of MSC surface markers and capacity of multi-lineage differentiation, including dental pulp stem cells (DPSCs), stem cells from human exfoliated deciduous teeth (SHED), stem cells from apical papilla (SCAP) and so on. However, their identity in vivo remains elusive, which hinders further understanding of their application in stem cell-based tooth regeneration. Label retaining and lineage tracing analyses, which serve as gold standards for identification of stem cells in vivo, provide feasibility for identifying MSCs in teeth. OBJECTIVES: In this review, we will discuss the issues of MSCs, including the origin and identification of both odontogenic and non-odontogenic MSCs, and address the role of nerve-derived Sonic hedgehog (Shh) in the regulation of MSCs in the neurovascular bundle (NVB). CONCLUSION: Based on label retaining and lineage tracing analyses, latest studies have found new populations of non-odontogenic MSCs in teeth, periarterial-derived and glial-derived, regulated by the Shh derived from nerves in the NVB, which provides a new hope for tooth regeneration.

Spatial signalling mediated by the transforming growth factor-ß signalling pathway during tooth formation.

Tooth development relies on sequential and reciprocal interactions between the epithelial and mesenchymal tissues, and it is continuously regulated by a variety of conserved and specific temporal-spatial signalling pathways. It is well known that suspensions of tooth germ cells can form tooth-like structures after losing the positional information provided by the epithelial and mesenchymal tissues. However, the particular stage in which the tooth germ cells start to form tooth-like structures after losing their positional information remains unclear. In this study, we investigated the reassociation of tooth germ cells suspension from different morphological stages during tooth development and the phosphorylation of Smad2/3 in this process. Four tooth morphological stages were designed in this study. The results showed that tooth germ cells formed odontogenic tissue at embryonic day (E) 14.5, which is referred to as the cap stage, and they formed tooth-like structures at E16.5, which is referred to as the early bell stage, and E18.5, which is referred to as the late bell stage. Moreover, the transforming growth factor-ß signalling pathway might play a role in this process.