Hypoxic dental pulp stem cells-released succinate promotes osteoclastogenesis and root resorption.

Introduction: Clinical studies have shown that endodontically-treated nonvital teeth exhibit less root resorption during orthodontic tooth movement. The purpose of this study was to explore whether hypoxic dental pulp stem cells (DPSCs) can promote osteoclastogenesis in orthodontically induced inflammatory root resorption (OIIRR). Methods: Succinate in the supernatant of DPSCs under normal and hypoxic conditions was measured by a succinic acid assay kit. The culture supernatant of hypoxia-treated DPSCs was used as conditioned medium (Hypo-CM). Bone marrow-derived macrophages (BMDMs) from succinate receptor 1 (SUCNR1)-knockout or wild-type mice were cultured with conditioned medium (CM), exogenous succinate or a specific inhibitor of SUCNR1 (4c). Tartrate-resistant acid phosphatase (TRAP) staining, Transwell assays, qPCR, Western blotting, and resorption assays were used to evaluate osteoclastogenesis-related changes. Results: The concentration of succinate reached a maximal concentration at 6 h in the supernatant of hypoxia-treated DPSCs. Hypo-CM-treated macrophages were polarized to M1 proinflammatory macrophages. Hypo-CM treatment significantly increased the formation and differentiation of osteoclasts and increased the expression of osteoclastogenesis-related genes, and this effect was inhibited by the specific succinate inhibitor 4c. Succinate promoted chemotaxis and polarization of M1-type macrophages with increased expression of osteoclast generation-related genes. SUCNR1 knockout decreased macrophage migration, M1 macrophage polarization, differentiation and maturation of osteoclasts, as shown by TRAP and NFATc1 expression and cementum resorption. Conclusions: Hypoxic DPSC-derived succinate may promote osteoclast differentiation and root resorption. The regulation of the succinate-SUCNR1 axis may contribute to the reduction in the OIIRR.

A case of radicular cyst on deciduous tooth in a 7-year-old child.

Radicular cysts are the most common cystic lesions in the oral cavity, and have a rare occurrence in the primary dentition. We report a case of radicular cyst of mandible in child by multimodal imaging including panoramic radiography, CT, and MR imaging. A 7-year-old girl presented with swelling and without pain, and hypoesthesia on the right side of the mandible. On clinical examination, an expansive lesion with undulation was found to the buccal cortex of the right side of the mandible. Panoramic radiograph showed a unilocular radiolucency with well-defined margin, displaced tooth, and root resorption in the right mandible. Regarding CT imaging, axial soft tissue algorithm CT and bone tissue algorithm CT showed a low-attenuation internal structure and expansion of the buccal cortex of the right side of the mandible. Three-dimensional-CT showed expansion of the buccal cortex of the right side of the mandible. Multiplanar reformation imaging showed displaced tooth, root resorption, and expansion of the buccal cortex of the right side of the mandible. On T1-weighted image, the expansive lesion showed low signal intensity, and T2-weighted and STIR images revealed high signal intensity. A partial biopsy of the mandibular region was performed. Histopathological diagnosis was radicular cyst caused by apical periodontitis with abscess. This case suggests that multimodal imaging, especially CT and MR imaging, could be effective for evaluating mandibular lesions in child.

Effect of intra-alveolar delivery of Frondoside A on inflammatory response of delayed tooth replantation.

BACKGROUND/AIM: Frondoside A is a sea cucumber extract which is well known for its anti-inflammatory and immunomodulatory properties. The purpose of this study was to evaluate the effect of Frondoside A application in the alveolar socket on inflammatory responses after delayed replantation in rat teeth. MATERIALS AND METHODS: Human periodontal ligament cells were cultured and exposed to Frondoside A. Cell-counting kit-8 assay was performed to evaluate the cell viability and nitric oxide assay was performed to assess the anti-inflammatory effect of Frondoside A. Molars were extracted from 32 Sprague-Dawley rats and randomly divided into control and Frondoside A groups. After 30 min of extra-oral dry time, molars were replanted. In the Frondoside A group, Frondoside A solution was applied in the alveolar socket before replantation. The animals were sacrificed after 28 days and histologically and immunohistochemically evaluated. RESULTS: 0.5 µM Frondoside A showed higher cellular viability at 6 h and lower production of nitric oxide compared with other Frondoside A solutions (p < .05). The Frondoside A group demonstrated lower inflammatory resorption scores in both middle 1/3 and apical 1/3 of root compared to the control group (p < .05). The Frondoside A group showed lower levels of expression in both cathepsin K and CD45 compared with the control group (p < .05). CONCLUSIONS: Within the limits of this study, intra-alveolar delivery of Frondoside A alleviates inflammatory root resorption in delayed replantation of rat teeth.

Clinical and radiographic features of external cervical resorption - An observational study.

AIM: To determine the prevalence of symptoms, clinical signs and radiographic presentation of external cervical resorption (ECR). METHODOLOGY: This study involved 215 ECR lesions in 194 patients referred to the Endodontic postgraduate Unit at King's College London or Specialist Endodontic practice (London, UK). The clinical and radiographic findings (periapical [PA] and cone beam computed tomography [CBCT]) were readily accessible for evaluation. A checklist was used for data collection. Inferential analysis was carried out to determine if there was any potential association between type and location of tooth in the jaw as well as sex, age of the patient and ECR presentation and radiographic feature. RESULTS: Eighty-eight patients (94 teeth) were female and 106 patients were male (121 teeth), the mean age (±SD) was 41.5 (±17.7) years. Fifteen patients (7.7%) had more than one ECR lesion. The most affected teeth were maxillary central incisors (21.4% [46 teeth]) and mandibular first molars (10.2% [22 teeth]). ECR was most commonly detected as an incidental radiographic finding in 58.1% [125 teeth] of the cases. ECR presented with symptoms of pulpal/periapical disease in 23.3% [n = 50] and clinical signs (e.g. pink spot, cavitation) in 16.7% [36 teeth] of the cases. Clinical signs such as cavitation (14%), pink spot (5.1%) and discolouration (2.8%) were uncommon, but their incidence increased up to 24.7% when combined with other clinical findings. ECR was detected in the resorptive and reparative phases in 70.2% and 29.8% of the cases respectively. CONCLUSION: ECR appears to be quiescent in nature, the majority being asymptomatic and diagnosed incidentally from PA or CBCT. When assessed with the Patel classification, most lesions were minimal to moderate in relation to their height (1 or 2) and circumferential spread (A or B). However, the majority of ECRs were in (close) proximity to the pulp. Symptoms and clinical signs were associated with (probable) pulp involvement rather than the height and circumferential spread of the lesion. Clinical signs were more frequently associated when ECR affected multiple surfaces.

A Cone-beam Computed Tomography Evaluation of External Invasive Resorption of Unerupted Teeth. Report of Three Cases.

Tooth resorption can occur either physiologically or pathologically and can be classified as internal or external. The term "external invasive resorption" (EIR) has been used to describe lesions originating from any surface defect exposing dentin. The absence of bacterial contamination, an intact pulp space, and a lesion consisting mainly of fibrovascular tissue characterize EIR. This study presents three cases of invasive resorption in unerupted teeth, emphasizing the importance of cone-beam computed tomography (CBCT). In two cases, the primary defect localized on the enamel surface, while in the third case, the focal point of the defect was not clear. CBCT provided detailed visualization of the resorption lesion's size and its relationship with surrounding structures, enhancing the diagnosis of EIR. Histological analysis of the third case confirmed the initial diagnosis. Invasive resorption can occur due to any surface defect in the case of unerupted teeth. Further research and correlation between radiographic and histological analysis are essential for the detection and classification systems in unerupted teeth.

Histologic Features of External Cervical Resorption Affecting Impacted Maxillary Canines: A Report of 2 Cases.

Reports on the histopathologic features of external cervical resorption (ECR) in unerupted teeth are scarce. This article reports on 2 maxillary impacted canines from different patients that showed ECR lesions and were surgically removed and histologically evaluated. Case 1 showed symptoms associated with oral communication of the dental follicle and pulpal exposure. Radiographs and cone-beam computed tomographic imaging showed that resorption affected a large part of the root and the crown. Case 2 was asymptomatic, and the resorption cavity was restricted to the tooth crown. Both teeth were extracted and subjected to histologic processing and analysis. In case number 1, the coronal pulp was necrotic and infected, showing areas of exposure to the resorption channels. The apical pulp was vital and uninflamed. The pulp space was surrounded by a continuous pericanalar resorption-resistant sheet. Part of the resorbed area of dentin was occupied by inflamed granulation tissue. More apically, a network of trabecular bone was present in the resorbed area. In case number 2, the pulp around the resorbed area was uninflamed and vital. A large fraction of the lost dentin was replaced by trabecular bone, closely adapted to the irregularly resorbed dentin surface, and no inflammatory cells. Our findings indicate that impacted teeth with ECR may remain asymptomatic until associated with infection. Histologic features of resorption in impacted teeth were similar to those in erupted teeth. In the case associated with infection, the resorbed area was occupied by inflamed tissue and newly formed bone. In the case with no infection, the resorption area was filled with bone undergoing a remodeling process.

ESE position statement on root resorption.

This Position Statement on root resorption represents the consensus of an expert committee convened by the European Society of Endodontology (ESE). The statement is based on current clinical and scientific evidence as well as the expertise of the committee. The aim is to provide clinicians with authoritative information on the aetiology, histopathology, clinical presentation and recommendations for the management of root resorption. It is the intention of the committee to update this position statement at appropriate intervals as further evidence emerges.

Central odontogenic fibroma with amyloid: a diagnostically challenging case.

Odontogenic fibroma is a rare benign mesenchymal odontogenic tumor, with its histological diversity possibly posing diagnostic challenges. A case of the amyloid variant of central odontogenic fibroma, with epithelial cells in perineural and intraneural locations, is reported herein. The 46-year-old female patient had experienced discomfort related to her anterior right hard palate for approximately 25 years. Clinical examination revealed a depression in the anterior hard palate, and radiographic examination showed a well-defined radiolucent lesion with root resorption of the adjacent teeth. Histologically, the well-circumscribed tumor was composed of hypocellular collagenous connective tissue with small islands of odontogenic epithelium. In addition, the juxta-epithelial deposition of amyloid globules without calcification and epithelial cells in perineural and intraneural locations were observed, which posed a diagnostic challenge in differentiating the lesion from the non-calcifying variant of calcifying epithelial odontogenic tumor and sclerosing odontogenic carcinoma. However, on the basis of the clinical and radiographic findings, which were suggestive of a benign and slowly progressive process given the corticated, unilocular radiolucency, the considerable root resorption, and the long history of this finding in an otherwise healthy patient, the final diagnosis was amyloid variant of central odontogenic fibroma. Increased recognition of this variant of odontogenic fibroma and its differentiation from other more aggressive lesions could help the clinician to avoid overdiagnosis and overtreatment.

Immunohistochemistry of resorption and inflammation factors in the periodontal ligament of human deciduous teeth.

The understanding of the biological mechanisms involved in root resorption in deciduous teeth is important to the future development of preventive measures and treatments of this condition. The aim of the present study was to compare the expression and immunostaining of iNOS, MMP-9, OPG and RANKL in the periodontal ligament (PDL) of deciduous teeth with physiologic root resorption (GI), inflammatory pathological root resorption (GII) and permanent teeth (GIII), the negative control. Teeth in GI (n = 10), GII (n = 10) and (GIII) (n = 10) were submitted to immunohistochemical analysis to determine the expression of iNOS, MMP-9, OPG, and RANKL. The immunostaining was analysed by optical density. Statistical analysis included one-way ANOVA, followed by Student-Newman-Keuls post hoc test (p < 0.05). The results showed that iNOS, MMP-9 and RANKL expression in the PDL was higher in GII compared to GI and GIII (p < 0.05). Moreover, RANKL expression was higher in GI compared to GIII (p < 0.001), while OPG immunolabelling was lower in GII compared to GI and GIII (p < 0.001). The PDL of deciduous teeth bearing inflammatory processed exhibited upregulation of resorption-associated factors as well as enzymes related to tissue degradation which, in turn explains the exacerbation and greater susceptibility of those teeth to root resorption process.

Tooth transplantation and replantation: Biological insights towards therapeutic improvements.

Transplantation and replantation of teeth are effective therapeutic approaches for tooth repositioning and avulsion, respectively. Transplantation involves transplanting an extracted tooth from the original site into another site, regenerating tissue including the periodontal ligament (PDL) and alveolar bone, around the transplanted tooth. Replantation places the avulsed tooth back to its original site, regenerating functional periodontal tissue. In clinical settings, transplantation and replantation result in favorable outcomes with regenerated PDL tissue in many cases. However, they often result in poor outcomes with two major complications: tooth ankylosis and root resorption. In tooth ankylosis, the root surface and alveolar bone are fused, reducing the PDL tissue between them. The root is subjected to remodeling processes and is partially replaced by bone. In severe cases, the resorbed root is completely replaced by bone tissue, which is called as "replacement resorption." Resorption is sometimes accompanied by infection-mediated inflammation. The molecular mechanisms of ankylosis and root resorption remain unclear, although some signaling mechanisms have been proposed. In this mini-review, we summarized the biological basis of repair mechanisms of tissues in transplantation and replantation and the pathogenesis of their healing failure. We also discussed possible therapeutic interventions to improve treatment success rates.

Dietary salt and myeloid NFAT5 (nuclear factor of activated T cells 5) impact on the number of bone-remodelling cells and frequency of root resorption during orthodontic tooth movement.

PURPOSE: The aim of the study was to investigate the impact of dietary salt and the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5) in myeloid cells on bone remodelling cells as osteocytes, osteoblasts and osteoclasts and on force-induced dental root resorptions in a mouse model. METHODS: Control mice and mice lacking myeloid NFAT5 (nuclear factor of activated T cells 5) were either kept on low, normal or high salt diets. After one week on the specified diet an elastic band was inserted between the first and second molar to induce orthodontic tooth movement. One week later the mice were euthanised and jaws were fixed for histological analysis. Osteocyte, osteoblast and osteoclast numbers as well as extent of root resorptions were assessed histologically. RESULTS: Osteocyte number was diminished with high salt diet in wildtype mice. Osteoblast numbers increased with low salt diet in control mice and reduced with high salt diet in mice without NFAT5 in myeloid cells. High salt diet tended to increase osteoclast number in control mice. In mice without myeloid NFAT5, numbers of osteoclasts were reduced under high salt diet. Frequency of force-induced root resorptions tended to be dependent on dietary salt content in control mice. CONCLUSION: During orthodontic tooth movement dietary salt impacts on the frequency of root resorptions and the number of osteoclasts and osteoblasts in alveolar bone of mice. This can affect bone remodelling during orthodontic treatment. Myeloid NFAT5 impacts on this salt-dependent reaction.

Comparison of surface roughness of root cementum and orthodontically induced root resorption craters from high- and low-fluoridation areas: a 3D confocal microscopy study.

BACKGROUND: Fluoride has a major role in strengthening the structure of enamel against acids. Despite differences between caries and root resorption processes, both events inherently involve acidic dissolution of dental tissues. The aim of the present study was to investigate the effects of water fluoridation levels on the surface roughness of root cementum and resorption craters. The findings provided more insight into the influence of fluoride on the surfaces of intact cementum surface and resorption craters. METHODS: Twenty-eight orthodontic patients were recruited from two cities in Turkey, with high (≥ 2 ppm) and low (≤ 0.05 ppm) water fluoridation. These patients needed bilateral maxillary first premolar extraction as part of their orthodontic treatment and were allocated into two study groups (n = 14 in each group) based on water fluoridation exposure level: the high-fluoride group (HF) and low-fluoride group (LF). 150 g of buccal tipping forces was applied to all maxillary first premolar teeth for 12 weeks with a beta-titanium spring which was reactivated every 4 weeks. All maxillary premolars were removed at the end of the experiment for surface roughness assessment using three-dimensional confocal microscopy and the associated software. The buccal root surface and the largest buccal resorption crater were investigated. RESULTS: Resorption craters were significantly rougher in LF group compared to HF group (p = 0.002). Craters were rougher than the intact root surfaces (p = 0.000). Cervical and apical regions were significantly rougher than the middle region (p = 0.000 and p = 0.024, respectively). CONCLUSIONS: Higher water fluoridation level of ≥ 2 ppm resulted in significantly smoother root resorption craters than low water fluoridation level of ≤ 0.05 ppm when the teeth were subjected to 150 g of buccal tipping force. Fluoride seems to have a protective role at the interface of root resorption, and further mineral or histological studies may shed light on the exact protective process against root resorption.

Tooth resorption-Part 2: A clinical classification.

Tooth resorption is either a physiological or a pathological process resulting in loss of dentin and/or cementum. It may also be associated with bone loss. Currently there is no universal classification for the different types of tooth resorption. This lack of a universal classification leads to both confusion amongst practitioners and poor understanding of the resorptive processes occurring in teeth which can result in incorrect/inappropriate diagnoses and mis-management. When developing a classification of diseases and/or conditions that occur within the body, several criteria should be followed to ensure a useful classification. The classification should not only include pathological conditions but also physiological conditions. Since tooth resorption can be either pathological or physiological, a classification of tooth resorption should include both of these categories. Any classification of diseases should be possible to use clinically, meaningful, useful, clear and universal. It should enable easy storage, retrieval and analysis of health information for evidenced-based decision-making. It should also be possible to share and compare data and information between different institutions, settings and countries. A classification of tooth resorption should be developed by combining anatomical, physiological and pathological approaches. For some types of resorption, the aetiological approach should also be incorporated. A classification of tooth resorption that uses simple, relevant and appropriate terminology based on the nature and location of the resorptive process occurring in teeth is proposed. There are two broad categories of internal and external tooth resorption which are sub-divided into three types of internal tooth resorption (surface, inflammatory, replacement) and eight types of external tooth resorption (surface, inflammatory, replacement, invasive, pressure, orthodontic, physiological, idiopathic). The clinician's understanding, diagnosis and management of tooth resorption can be facilitated by using this simple classification which should ideally be used universally by the entire dental profession to ensure clarity and to avoid confusion.

Canines and inflammatory external apical resorption in healthy maxillary lateral incisors due to occlusal trauma: when to detect the position of maxillary canines, to prevent it?

JUSTIFICATION: Canines represent corners in the dental arch, and are important features in facial esthetics, as they support the upper lip, wing of the nose, and influence the nasolabial fold and the appearance of facial aging. In the laterality movements, the canines guidance coordinate the opening and closing of the teeth, saving the TMJ from sudden movements. DISCUSSION: As a result of the lack of eruption or the inadequate positioning of the maxillary canine, the loss of the laterality guide may occur, which will then occur in the maxillary lateral incisor, inducing lesions of "occlusal trauma", such as inflammatory root resorption. Likewise, without well positioned canines, there may be premature aging and change in facial esthetics. CONCLUSION: In order to avoid problems with eruption and positioning of the maxillary canines, early diagnosis is made by analyzing their position and their relationship with the other teeth, and in the three-dimensional context of the maxilla, between 8-10 years of age. Preventive measures can create bone space and direction so that the maxillary canines can occupy their position in the dental arch.

Sequential Loss of Mandibular Permanent Incisors in Noonan Syndrome.

BACKGROUND: Noonan syndrome (NS) is a multigenic disorder with a highly variable phenotype. Cardiac disorders and a predisposition to neoplasm often require early medical attention. Central giant central lesions (CGCLs) of the jaws are part of the phenotype. CASE REPORT: In a patient with genetically confirmed NS and multiple teeth loss presumably caused by CGCL, careful review of the medical history and radiographic findings made it probable that the cause of tooth loss was cervical root resorption (CRR) of the teeth following long-term orthodontic therapy. CONCLUSION: CRR is a rare dental disease of unknown origin. However, association with prior orthodontic therapy is well documented. In NS, mandibular lesions can occur which, at first glance, might lead the examiner to assume that it is a CGCL, but on closer analysis, obviously are of non-tumorous origin and should be assessed as coincidental. The report adds relevant information to orthodontic treatment of NS patients.

The diagnostic value of orthopantomograms in detecting resorption of lateral incisors associated with ectopic canines: a CBCT study.

OBJECTIVE: To examine the diagnostic value of orthopantomograms (OPG) in the identification of root resorption of lateral incisors, secondary to an impacted canine, as confirmed by a cone-beam computed tomography (CBCT) scan. DESIGN: Retrospective observational cohort study. SETTING: South Wales secondary care setting: Royal Gwent Hospital, Newport and Nevill Hall Hospital, Abergavenny. METHODS: A total of 40 consecutive patients with impacted canines between January 2018 and December 2019 were selected. For each patient, one consultant orthodontist examined the OPG in isolation to detect the presence and extent of resorption of lateral incisors. The CBCT report was then studied to confirm the presence and extent of pathology. Sensitivity, specificity, accuracy, positive predictive values and negative predictive values were calculated. RESULTS: In total, 19 maxillary right canines, 18 maxillary left canines, one mandibular right canine and two mandibular left canines were examined. Impactions were more prevalent in the maxilla (92.5%) with higher predilection towards female patients (65%). There was higher prevalence of root resorption in the maxillary right quadrant (57.1%), in concordance with other studies. OPGs were found to have a sensitivity of 81.0% and a specificity of 10.5%, with an accuracy value of 47.5%. Positive and negative predictive values were found to be 50.0% and 33.3%, respectively. The extent of root resorption was incorrectly estimated from the OPG in 84% of cases. Correct estimation occurred in 16% of cases, with overestimation and underestimation occurring in equal proportion (42%). CONCLUSION: This study demonstrates the limitations of plain film radiographs and the merits of using CBCT in the accurate diagnosis of resorption of lateral incisors with an associated impacted canine. It also gives an indication into the location prevalence of resorption in a small cohort of patients. This preliminary study establishes the basis for future, larger-scale studies where outcomes can be generalisable at a population level.

Surgical placement of third molars to replace other teeth: "spare wheels" / Mise en place chirurgicale des dents de sagesse en remplacement d'autres dents : « les roues de secours ¼

Introduction: The prognostic improvement for dental auto-transplants is the result of a better understanding in the physiopathology of the periodontium and also of the refining of the technical operative procedure. This fact allows the use of third molars as donor site for the replacement of absent, or first or second badly decayed molars. Discussion: This possible therapy is a supplement argument for the conservation of third molars and their extraction must be indicated only when the anatomic situation presents a pathological risk. Results: If, in adults, it is possible to compare the advantages and disadvantages with the classical implant or prosthetic techniques, it should however be considered as first choice therapy for adolescents and young adults. Indeed, in these cases, the lower risk of root ankylosis avoids passive intrusion and the osteogenic effect of the desmodontium allows normal alveolar bone formation.

Introduction: L'amélioration du pronostic des autogreffes dentaires, envisageable par une meilleure compréhension de la physiopathologie du parodonte et par un affinement de la technique opératoire qui en résulte, permet d'utiliser à bon compte les dents de sagesse comme site donneur dans le remplacement de molaires absentes ou trop fortement délabrées. Discussion: Cette possibilité thérapeutique est un argument supplémentaire à la conservation des dents de sagesse dont l'extraction ne devrait être indiquée que lorsque la situation anatomique de ces dents présente un risque pathologique. Résultats: Si, chez l'adulte, il est possible d'en discuter les avantages et les inconvénients avec les techniques prothétiques et implantaires classiques, les autogreffes dentaires doivent en revanche être considérées comme la solution de choix chez l'adolescent ou le jeune adulte. En effet, dans ces cas, le risque moindre d'ankylose radiculaire évite l'ingression passive de la dent remplacée et l'action ostéogénique de son desmodonte permet une formation normale de l'os alvéolaire qui l'environne.

Runx1/miR-26a/Jagged1 signaling axis controls osteoclastogenesis and alleviates orthodontically induced inflammatory root resorption.

BACKGROUND: MicroRNAs (miRNAs) are involved in the regulation of osteoclast biology and several pathogenic progression. This study aimed to identify the role of miR-26a in osteoclastogenesis and orthodontically induced inflammatory root resorption(OIIRR). METHODS: Rat orthodontic tooth movement (OTM) model was established by ligating a closed coil spring between maxillary first molar and incisor, and 50 g orthodontic force was applied to move upper first molar to middle for 7 days. Human periodontal ligament (hPDL) cells were isolated from periodontium of healthy donors, and then subjected to compression force (CF) for 24 h to mimic an in vitro OTM model. The levels of associated factors in vivo and in vitro were measured subsequently. RESULT: The distance of tooth movement was increased and root resorption pits were occurred in rat OTM model. The expression of miR-26a was decreased in vivo and vitro experiments. CF treatment enhanced the secretion of inflammatory factors receptor activator of nuclear factor-kappa B ligand (RANKL) and IL-6, osteoclast marker levels, and the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, while miR-26a overexpression reversed these results. Furthermore, miR-26a overexpression inhibited the osteoclastogenesis and rescued the root resorption in OTM rats through inhibition of Jagged1. Additionally, Runx1 could bind to miR-26a promoter and promote its expression, thereby suppressing the osteoclastogenesis. CONCLUSION: We concluded that Runx1/miR-26a/Jagged1 signaling axis restrained osteoclastogenesis and alleviated OIIRR.

Low-intensity pulsed ultrasound attenuates replacement root resorption of avulsed teeth stored in dry condition in dogs.

This study aimed to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on replacement root resorption after replantation of avulsed teeth stored in a dry condition in dogs. A total of 73 premolar roots from four male mongrel dogs were intentionally avulsed with forceps and divided into four groups-HN, HL, DN, and DL-according to storage conditions and whether or not they received LIPUS treatment. Thirty-eight roots were kept in Hanks' Balanced Salt Solution for 30 min (HN and HL groups), whereas the remaining 35 roots were left to dry in the air for an hour (DN and DL groups) prior to replantation. Following replantation, the roots in the HL and DL groups (21 and 18 roots, respectively) received a 20-min daily LIPUS treatment for 2 weeks. The animals were euthanized 4 weeks after the operation. Micro-computed tomography images were acquired for each root and the amount of replacement root resorption was measured three-dimensionally. Histological assessments were also carried out. There was significantly less replacement root resorption for the roots in the DL group compared to the DN group (p < 0.01). Histological findings in the DN group demonstrated evident replacement root resorption, whereas the DL group revealed less severe resorption compared to the DN group. Within the limitations, these results suggest that LIPUS could attenuate the replacement resorption of avulsed teeth stored in a dry condition, thereby improving their prognosis.

Is Inflammation a Friend or Foe for Orthodontic Treatment?: Inflammation in Orthodontically Induced Inflammatory Root Resorption and Accelerating Tooth Movement.

The aim of this paper is to provide a review on the role of inflammation in orthodontically induced inflammatory root resorption (OIIRR) and accelerating orthodontic tooth movement (AOTM) in orthodontic treatment. Orthodontic tooth movement (OTM) is stimulated by remodeling of the periodontal ligament (PDL) and alveolar bone. These remodeling activities and tooth displacement are involved in the occurrence of an inflammatory process in the periodontium, in response to orthodontic forces. Inflammatory mediators such as prostaglandins (PGs), interleukins (Ils; IL-1, -6, -17), the tumor necrosis factor (TNF)-α superfamily, and receptor activator of nuclear factor (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) are increased in the PDL during OTM. OIIRR is one of the accidental symptoms, and inflammatory mediators have been detected in resorbed roots, PDL, and alveolar bone exposed to heavy orthodontic force. Therefore, these inflammatory mediators are involved with the occurrence of OIIRR during orthodontic tooth movement. On the contrary, regional accelerating phenomenon (RAP) occurs after fractures and surgery such as osteotomies or bone grafting, and bone healing is accelerated by increasing osteoclasts and osteoblasts. Recently, tooth movement after surgical procedures such as corticotomy, corticision, piezocision, and micro-osteoperforation might be accelerated by RAP, which increases the bone metabolism. Therefore, inflammation may be involved in accelerated OTM (AOTM). The knowledge of inflammation during orthodontic treatment could be used in preventing OIIRR and AOTM.