Periodontitis: orthodontic implications and management.

Orthodontics is increasingly ingrained in the overall management of patients with periodontitis. Advanced periodontitis is often characterised by pathological tooth migration, loss of posterior support and incisal proclination. Orthodontics may therefore offer both aesthetic and therapeutic benefit. A tailored approach to treatment, however, is necessary given the myriad of presentations and associated risk. The nuances underpinning effective treatment planning, space creation, treatment mechanics, and retention in the periodontal patient are described.

Early orthodontic treatment after periodontal surgery: a randomized controlled trial / Le traitement orthodontique précoce après la chirurgie parodontale : essai clinique randomisé et contrôlé.

Introduction: The pathological teeth migrations require correct multidisciplinary treatment which consists of periodontal surgery associated with early or late orthodontic treatment. The aim of this study was to know which of the two orthodontic treatments would have a better periodontal response. Material and Method: Two parameters, radiological (the height of the alveolar bone) and clinical (the depth of the periodontal pocket), were used to meet the objective of this work. Eighteen patients received early orthodontic treatment (straight wire appliance) after periodontal flap debridement surgery and eighteen others late orthodontic treatment (straight wire appliance). Results: The results showed the absence of significant difference between the two early and late orthodontic treatments after periodontal flap debridement surgery. Conclusion: Orthodontic treatment can be started early seven to ten days after periodontal surgery.

Introduction: Les migrations dentaires pathologiques exigent un traitement pluridisciplinaire correct qui consiste en une chirurgie parodontale associée à un traitement orthodontique précoce ou tardif. Le but de cette étude était de connaître lequel des deux traitements orthodontiques aurait une meilleure réponse parodontale. Matériel et méthode: Deux paramètres, radiologique (la hauteur du défaut osseux) et clinique (la profondeur de la poche parodontale), ont été utilisés afin de répondre à l'objectif de ce travail. Dix-huit patients ont reçu, après la chirurgie parodontale par un lambeau d'assainissement, un traitement orthodontique précoce (technique d'arc droit) et dix-huit autres un traitement orthodontique tardif (technique d'arc droit). Résultats: Les résultats ont montré l'absence de différence significative entre les deux traitements orthodontiques, précoce et tardif, après la chirurgie parodontale par un lambeau d'assainissement. Conclusion: Le traitement orthodontique peut débuter précocement dès sept à dix jours après la chirurgie parodontale.

Local factors relating to mandibular canine impaction: A retrospective study.

INTRODUCTION: This study aimed to investigate the characteristics of impacted and transmigrated mandibular canines and the association existing between them and some local factors, such as degrees of axial inclination of mandibular incisors, skeletal Class, and mandibular symphysis width. METHODS: A retrospective observational study was performed on the medical records and radiographic examination (panoramic radiographs and lateral cephalograms) of 102 orthodontic patients divided into a study group, with at least 1 impacted mandibular canine (51 subjects) and a control group, without mandibular impaction (51 subjects). A chi-square test, t test, and analysis of variance test analysis were used to analyze the data. RESULTS: Unilateral and buccal impaction and the presence of the deciduous canine were the more prevalent characteristics of impacted canines, whereas 39.2% presented transmigration. Furthermore, the persistence of the deciduous canine on the impaction side (P <0.0001) and the mesial axial inclination of the impacted canine (P <0.0001) were found to be statistically significant characteristics. A statistically significant association was found between the impaction of the mandibular canine and mandibular incisor to the mandibular plane angle (IMPA) (IMPA, 95.8°; P = 0.009). An additional statistically significant association was found with transmigrated canines (IMPA, 96.8°; P = 0.024). CONCLUSIONS: The mesialization of the canine cusp and the persistence of the mandibular deciduous canine are characteristics frequently found in the impaction of the mandibular canine. An accentuated vestibular inclination of the mandibular incisors is significantly associated with mandibular canine impaction.

A systematic and comprehensive protocol for rapid orthodontic extrusion.

OBJECTIVE: The aim of the present paper is to describe a systematic and detailed protocol for rapid orthodontic extrusion, and to summarize the main results of this protocol in terms of migration of dental, hard and soft tissues, for 10 cases. CLINICAL CONSIDERATIONS: The working design was to apply a protocol lasting 4 weeks of active phase with intense forces (greater than 300 g), perform weekly the circumferential supra-crestal fiberotomy procedure associated with root-planning, follow up with a passive stabilization phase of another 4 weeks and evaluate the results. CONCLUSIONS: We believe that despite the partial migration of periodontal tissue, the defined protocol we used is, for simplicity of application, brevity of treatment and results, a viable alternative to the surgical technique of clinical crown lengthening in those cases where it is necessary to have more dental tissue exposed for restorative and prosthetic purposes.

Desplazamiento de Tercer Molar Inferior a Espacio Submandibular: Reporte de Caso y Revisión de Literatura / Lower Third Molar Displacement to Submandibular Space: Case Report and Literature Review

El desplazamiento de un tercer molar a un espacio anatómico adyacente, ya sea en su totalidad o un fragmento de este, se encuentra descrito como una complicación rara pero posible de las exodoncias de terceros molares. En este reporte se aborda específicamente el desplazamiento accidental de un tercer molar inferior hacia el espacio submandibular izquierdo, el cual fue resuelto quirúrgicamente mediante un abordaje intraoral bajo anestesia general por el equipo de cirugía maxilofacial del Hospital de Urgencia Asistencia Pública, Santiago, Chile. Se realizó una revisión de literatura en la plataforma PubMed con las palabras claves "third molar - submandibular - displacement" obteniendo un total de 17 artículos en los cuales se reportan 15 casos. El propósito del presente escrito fue presentar recomendaciones sobre el manejo actual de esta complicación en base a la literatura disponible.

The displacement of a third molar into an adjacent anatomical space, either in its entirety or a fragment of it, has been described as a rare but posible complication of third molar extractions. This report will specifically address the accidental displacement of a lower third molar into the left submandibular space, which was surgically removed through an intraoral approach under general anesthesia, by the maxillofacial surgeon team of "Hospital de Urgencia Asistencia Pública", Santiago, Chile. An literature review was carried out on PubMed platform with the keywords ""third molar - submandibular - displacement"", obtaining a total of 17 articles where are reported 15 cases. The purpose of this paper is to present recommendations on the current management of this complication based on the available literature.

Adjacent tooth migration after maxillary first molar loss in patients with sinus augmentation: A retrospective research.

PURPOSE: The objectives of this study are to: (1) investigate the extent of antagonistic and distal neighboring tooth migration in the maxillary posterior single tooth-missing site during the healing period of bone augmentation and implant surgery; (2) identify factors associated with tooth migration. MATERIALS AND METHODS: One hundred and forty-three cases that lost the maxillary first molar were included, and their CBCT data during the edentulous period were obtained. Dentition models were reconstructed from CBCT, and superimpositions were performed, followed by measuring migration distances and calculating migration rates of antagonistic and distal neighboring teeth. Factors were analyzed using multivariate generalized estimating equations (GEE). RESULTS: The mean migration distances were 208 ± 137 µm and 403 ± 605 µm for antagonistic teeth and distal teeth, and the mean migration rates were 26.8 ± 21.2 µm/month and 48.5 ± 76.7 µm/month, respectively. One hundred and nineteen out of 143 distal neighboring teeth migrated toward the edentulous site, and all antagonistic teeth migrated occlusally. Occlusal contact loss and chronic apical periodontitis both significantly accelerated antagonistic tooth migration (p < 0.05), the latter also accelerated distal tooth migration (p < 0.05). Besides, the displacement of the distal teeth was somewhat accelerated by the impacted adjacent third molar and root protrusion into the sinus. CONCLUSIONS: The neighboring teeth tend to migrate toward the edentulous gap in the maxillary posterior region. Occlusal contact loss and chronic apical periodontitis are two significant risk factors for accelerating antagonistic tooth migration, and for distal teeth, chronic apical periodontitis is the risk factor. The impacted adjacent third molar and root protrusion into the sinus are also potential risk factors for accelerating the migration of the maxillary distal tooth. Thus, to prevent maxillary edentulous gap reduction, the factors mentioned above should be taken into consideration when planning treatment flow.

Multidisciplinary approach involving strategic implant placement before orthodontic (SIMBO) treatment for generalized stage IV grade C periodontitis: A case report with 10-year follow-up.

OBJECTIVE: The aim of this case report was to demonstrate the long-term effects of a multidisciplinary approach involving periodontal reconstructive surgery and strategic implant placement before orthodontic (SIMBO) treatment in a patient with severe periodontitis (e.g., stage IV/grade C). CLINICAL CONSIDERATIONS: The patient presented with severe periodontitis and pathologic tooth migration (PTM) without stable occlusion or occlusal support. After performing cause-related therapy, periodontal regenerative surgery, pre-orthodontic posterior implant placement, and orthodontic treatment involving anterior implant placement with papilla reconstruction, the patient achieved full-mouth rehabilitation and improvement of dental and smile esthetics. The clinical and radiographic results obtained were maintained over a 10-year period. CONCLUSION: Within the limits of this as a single case, multidisciplinary treatment involving the SIMBO approach appeared to allow long-term improvement of periodontal condition, stability of the dental arches and occlusion, and esthetics in a patient with severe periodontitis, PTM and posterior bite collapse. Future studies with more subjects are needed to evaluate and validate this approach. CLINICAL SIGNIFICANCE: When addressing periodontal disease, SIMBO approach-based multidisciplinary treatment appears safe and effective as a clinical protocol for establishing esthetic and functional rehabilitation in generalized stage IV/grade C periodontitis.

Saving teeth: Revisited. Esthetic improvement and long-term periodontal stability of a pathologic tooth migration case: An 84-month follow-up.

INTRODUCTION: Advances in implant dentistry, often influence our clinical treatment planning and steer us as periodontists from our fundamental values of preserving teeth. Pathologic tooth migration (PTM) of maxillary anterior teeth is a common sequela of periodontitis in patients and results in significant esthetic and functional problems. Patients' growing concern about the esthetics of their teeth and their fears of losing teeth are often reasons for them to seek treatment. We commonly assign a hopeless prognosis to these pathologically migrated teeth because of the significant loss of periodontal support and go with the "safer" choice of replacing them with implants. The purpose of this case report is to present the long-term (7-year) periodontal stability of compromised teeth and to emphasize the successful outcomes achieved when orthodontics, non-surgical periodontal, and restorative treatments are combined. METHODS AND RESULTS: A 38-year-old, otherwise healthy male with compromised function and esthetics, PTM, periodontal disease, and missing teeth presented to our clinic. Primary treatment objectives were to 1) eliminate the periodontal inflammation and 2) restore and stabilize the occlusion by employing non-surgical periodontal treatment, adult orthodontics, and prosthodontics. Following interdisciplinary treatment, clinical and radiographic re-evaluation revealed significant clinical attachment gain, reduction in tooth mobility, favorable esthetics, and better overall prognosis. At an 84-month follow-up, the patient was periodontally healthy and retained his natural dentition. CONCLUSIONS: Interdisciplinary collaboration along with patient compliance may increase the longevity of periodontally compromised teeth and improve esthetics for periodontitis patients who suffer from PTM. Such long-term favorable outcomes reaffirm the value of classic periodontal treatment and the success of multidisciplinary treatment to save teeth as a viable alternative to the extraction of teeth and the placement of implant retained restorations.

Malocclusions, pathologic tooth migration, and the need for orthodontic treatment in subjects with stage III-IV periodontitis. A cross-sectional study.

BACKGROUND: Literature is scarce on malocclusion prevalence and orthodontic treatment need (OTN) in subjects with stage III-IV periodontitis. Study aims were to assess prevalence of primary and secondary malocclusions in subjects with stage III-IV periodontitis and OTN based on pathologic tooth migration (PTM) and occlusal trauma of anterior teeth (AT). SUBJECTS AND METHODS: One hundred and twenty-one subjects with stage III-IV periodontitis were examined. A comprehensive periodontal-orthodontic examination was performed. Exclusion criteria: age <30 years, removable prosthetics, uncontrolled diabetes, pregnancy/lactation, and oncologic disease. RESULTS: Class II malocclusion was found in 49.6% (Class II div 1-20.7%, Class II div 2-9.9%, subdivision Class II-19.0%), Class I-31.4%, Class III-10.7%, no malocclusion-8.3% of subjects. PTM was observed in 74.4% of maxillary and 60.3% of mandibular AT. Spacing and extrusion were the main types of PTM of AT. Odds ratio for PTM of maxillary AT was 9.3 in cases with >30% of sites with clinical attachment loss ≥5 mm (P = 0.001). Spacing of maxillary AT was influenced by periodontitis, Class III malocclusion, and lost teeth. Tongue habit had impact on spacing of mandibular AT. Dental Health Component of Index of Orthodontic Treatment Need yielded that OTN was found in >50% and OTN due PTM, occlusal trauma and impaired function in 66.1% of subjects. CONCLUSIONS: The most prevalent malocclusion was Class II. Spacing and extrusion were prevalent types of PTM of AT. OTN was found in more than half of the subjects. The study highlights the need for preventive measures for PTM in subjects with stage III-IV periodontitis.

Pathological tooth migration-spontaneous correction of diastema after surgical periodontal therapy: a case report.

A common consequence of moderate to extreme periodontitis is pathologic migration. This denotes tooth movement when the periodontal disease interjects the equilibrium among the elements that preserve physiological tooth position. The balancing factors can migrate the teeth in any direction. The etiology of pathological migration tends to be multifactorial, thus achieving early diagnosis is imperative, which will ultimately lead to the prompt removal of the etiological factors while avoiding severe bone destruction. In this case maxillary central incisors had diastema due to pathological migration with mobility grade I in maxillary left central incisor. Many cases of moderate to severe pathological migration need a suitable, interdisciplinary approach. Nevertheless, since it is possible to detect mild cases of Pathological tooth migration (PTM) at an early stage, spontaneous correction of migrated teeth can be accomplished by periodontal therapy alone. Regardless of the treatment selected, maintenance of stable results should be considered as an aim of treatment.

Interrelación Entre Ortodoncia y Periodoncia en Periodonto Reducido. Estabilidad Periodontal Tras 6 Años de Seguimiento / Interrelation Between Orthodontics and Periodontics in Reduced Periodontium. Periodontal Stability After 6 Years of Follow-up

RESUMEN: En pacientes con periodontitis, la migración dentaria patológica es una consecuencia de la pérdida de soporte periodontal. El siguiente reporte de caso aborda el tratamiento periodontal y ortodóncico de una paciente con periodontitis y migración dentaria patológica. El protocolo utilizado fue el protocolo de la Unidad de Ortodoncia y Periodoncia de la Facultad de Odontología de la Universidad de Chile. La estabilidad periodontal se ha mantenido por al menos 6 años luego de finalizado el tratamiento de ortodoncia logran-do funcionalidad y estética de la dentición natural.

ABSTRACT: In patients with periodontitis, pathologic tooth migration is a consequence of loss of periodontal support. The following case report addresses the periodontal and orthodontic treatment of a patient with periodontitis and pathologic tooth migration. The protocol used was the protocol of the Orthodontics and Periodontics Unit of the Faculty of Dentistry of the University of Chile. The periodontal stability has been maintained for at least 6 years after the end of orthodontic treatment, achieving functionality and aesthetics of the natural dentition.

Factors affecting root migration after coronectomy of the mandibular third molar.

ABSTRACT: Nerve injury especially inferior alveolar nerve (IAN) is the one of the complications that occur when the mandibular third molar (M3) is extracted and in case of high risk patients, coronectomy might be an alternative to tooth extraction. The purpose of this retrospective study was to analyze root migration and its influencing factors at 6 months after coronectomy in both 2- and 3-dimensions using periapical view and cone-beam computed tomography (CBCT). We analyzed 33 cases of root remnant after coronectomy and measured the amount of migration in CBCT. The following factors that could possibly affect root migration were also analyzed: age, gender, number of M3 roots, shape of M3s, Pell, and Gregory classification, mesiodistal (MD) angulation, buccolingual (BL) angulation, contact point with the second molar, root curvature, and complete removal of the coronal portion. Migration of greater than 2 mm was found in 64% of the roots in the 2-dimensional (2D) analysis, and the average root migration was 4.11 mm in the 3-dimensional (3D) analysis. The factors affecting migration were the root morphology, complete removal of the coronal portion, impaction depth, and MD angulation in the 2D analysis, and MD and BL angulation in the 3D analysis. Ensuring sufficient space for root migration especially considering angulation, depth and complete removal of the coronal portion might be important factors after coronectomy of the M3. Root remnant after coronectomy of M3 may migrate in young patients who has sufficient empty coronal space and this may reduce the nerve damage by the separation of IAN and M3.

Comprehensive treatment for severe periodontitis with pathologic tooth migration-related bimaxillary protrusion: A case report with 3-year follow-up.

BACKGROUND AND OVERVIEW: Patients with severe periodontitis often experience pathologic tooth migration (PTM), which impairs esthetics and leads to occlusal disharmony (for example, premature contacts and traumatic occlusion) that can further exacerbate periodontitis. The authors describe a patient who exhibited severe periodontitis with PTM-related bimaxillary protrusion. This report includes 3-year clinical outcomes after periodontal regenerative therapy, implant-anchored orthodontic therapy, and implant prosthodontics intended to achieve both functional and esthetic improvements. CASE DESCRIPTION: A 63-year-old woman sought treatment with the chief complaint of maxillary anterior tooth mobility. Clinical examination revealed excessive tooth mobility, deep periodontal pockets, and infrabony defects in all teeth. All teeth exhibited PTM; the mandibular anterior teeth exhibited marked protrusion caused by the progression of periodontitis. After initial periodontal therapy, periodontal regenerative therapy was performed in all molar regions. At 6 and 9 months postoperatively, comprehensive orthodontic treatment was initiated for the mandible and maxilla, respectively, using orthodontic anchorage devices to achieve acceptable functional occlusion. After orthodontic treatment, staged guided bone regeneration was performed and dental implants were placed in the severely resorbed maxillary anterior ridge. This comprehensive treatment yielded favorable periodontal conditions, stable occlusion, and good esthetic outcomes. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Favorable esthetics, stable occlusion, and highly cleansable periodontal tissues were achieved with well-planned interdisciplinary and comprehensive treatment, although the patient had severe periodontitis and PTM-related bimaxillary protrusion.

The adult orthodontic patient over 40 years of age: association between periodontal bone loss, incisor irregularity, and increased orthodontic treatment need.

OBJECTIVES: Adult orthodontic treatment, especially in patients over 40 years, is steadily increasing. One causal factor for the treatment need in this age group is periodontal breakdown. The aim of this study was to detect correlations between periodontal problems and orthodontic parameters in interdisciplinary patients. METHODS: This observational, cross-sectional study included 118 patients over 40 years (51 men/67 women; mean age, 58.03 years) classified into three groups according to periodontal breakdown (group I, controls; group II, moderate periodontitis; group III, severe periodontitis). Clinical periodontal and orthodontic parameters as well as the index of orthodontic treatment need (IOTN) were assessed and compared between the groups. RESULTS: A gradual deterioration of all periodontal and orthodontic parameters according to periodontal bone loss (lowest values in group I; highest values in group III) was observed. Especially groups I and III differed significantly regarding the overjet (p < 0.001) and the little indices of the maxilla (p < 0.001) and mandible (p < 0.010). The IOTN was highest in group III: 90% of the patients with severe periodontitis were classified to have moderate to very great treatment need. CONCLUSIONS: The higher the degree of periodontal breakdown was, the more severe were overjet, overbite, irregularity of the anterior teeth, and the orthodontic treatment need. CLINICAL RELEVANCE: Adult patients over 40 years represent a challenge for an orthodontic/periodontal treatment approach with high incidence of pathologic tooth migration, orthodontic treatment need, and periodontal breakdown. Therefore, this special patient collective requires a focus in clinical orthodontics and research.

A retrospective study of orthodontic treatment on anterior tooth displacement caused by periodontal disease.

ABSTRACT: This retrospective study aimed to explore the effect of orthodontic treatment (ODT) on anterior tooth displacement (ATD) caused by periodontal disease (PD).A total of 72 patients were selected and were divided into a control group (n = 36) and an experimental group (n = 36). Patients in both groups received conventional periodontal treatment. In addition, patients in the experimental group also received ODT. Outcomes include probing depth, percentage of bleeding sites, clinical attachment loss, clinical crown length, tooth root length, and periodontal tissue of the affected tooth (alveolar bone height, periodontal pocket depth, bleeding index).After treatment, the patients in the experimental group achieved more improvements in probing depth (P < .01), percentage of bleeding sites (P < .01), clinical attachment loss (P < .01), clinical crown length (P = .04), and periodontal tissue of the affected tooth (periodontal pocket depth (P < .01), and bleeding index (P < .01)), than those of patients in the control group.This study suggests that ODT is beneficial for ATD caused by PD. Future studies are still needed to verify the findings of this study.

Effect of nicotine exposure on the rate of orthodontic tooth movement: A meta-analysis based on animal studies.

BACKGROUND: Nicotine exposure has been reported to modify bone cell function and the osseous metabolism with potential effects on the rate of orthodontic tooth movement. OBJECTIVES: To systematically investigate and quantitively synthesize the most recent available evidence from animal studies regarding the effect of nicotine exposure on the rate of orthodontic tooth movement. SEARCH METHODS: Unrestricted searches in 7 databases and hand searching were performed until July 2020 (PubMed, Central, Cochrane Database of Systematic Reviews, SCOPUS, Web of Science, Arab World Research Source, ProQuest Dissertations and Theses Global). SELECTION CRITERIA: We searched for controlled studies on healthy animals investigating the effect of nicotine on the rate of orthodontic tooth movement. DATA COLLECTION AND ANALYSIS: Following study retrieval and selection, relevant data was extracted and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. Exploratory synthesis and meta-regression were carried out using the random effects model. RESULTS: From the initially identified records, 5 articles meeting the inclusion criteria were selected and no specific concerns regarding bias were identified. Quantitative data synthesis showed that the rate of orthodontic tooth movement in the nicotine exposed rats was higher than in the control group animals (2 weeks of force application; 0.317 mm more movement in nicotine exposed rats; 95% Confidence Interval: 0.179-0.454; p = 0.000). No effect of the concentration or the duration force application was demonstrated following exploratory meta-regression. CONCLUSION: Rats administered with nicotine showed accelerated rates of orthodontic tooth movement. Although, information from animal studies cannot be fully translated to human clinical scenarios, safe practice would suggest that the orthodontist should be able to identify patients exposed to nicotine and consider the possible implications for everyday clinical practice.

Dietary Salt Accelerates Orthodontic Tooth Movement by Increased Osteoclast Activity.

Dietary salt uptake and inflammation promote sodium accumulation in tissues, thereby modulating cells like macrophages and fibroblasts. Previous studies showed salt effects on periodontal ligament fibroblasts and on bone metabolism by expression of nuclear factor of activated T-cells-5 (NFAT-5). Here, we investigated the impact of salt and NFAT-5 on osteoclast activity and orthodontic tooth movement (OTM). After treatment of osteoclasts without (NS) or with additional salt (HS), we analyzed gene expression and the release of tartrate-resistant acid phosphatase and calcium phosphate resorption. We kept wild-type mice and mice lacking NFAT-5 in myeloid cells either on a low, normal or high salt diet and inserted an elastic band between the first and second molar to induce OTM. We analyzed the expression of genes involved in bone metabolism, periodontal bone loss, OTM and bone density. Osteoclast activity was increased upon HS treatment. HS promoted periodontal bone loss and OTM and was associated with reduced bone density. Deletion of NFAT-5 led to increased osteoclast activity with NS, whereas we detected impaired OTM in mice. Dietary salt uptake seems to accelerate OTM and induce periodontal bone loss due to reduced bone density, which may be attributed to enhanced osteoclast activity. NFAT-5 influences this reaction to HS, as we detected impaired OTM and osteoclast activity upon deletion.

The migration of neighboring and antagonist teeth three months after implant placement in healed single tooth-missing sites.

OBJECTIVES: To quantify the neighboring and antagonist teeth migration of a single posterior tooth-missing site within 3 months using digital scanning and measuring techniques. MATERIALS AND METHODS: Intraoral scans (IOS) were made in 40 patients presenting a single posterior tooth-missing gap and receiving implant therapy. IOS were obtained at the day of and three months after implant surgery rendering a digital baseline model (BM) and a digital follow-up model (FM). Digital models were superimposed using the implant scan body as reference. Antagonist models were processed by the best fit alignment. Dimensional change between anatomical landmarks on neighboring teeth and that of featuring points on antagonistic teeth were measured using a three-dimensional analysis software. The Mann-Whitney U test was applied to compare the tooth-moving distance between the mesial and distal neighboring teeth. The Kruskal-Wallis one-way ANOVA was used to test the difference in dimensional change in tooth-missing site among age subgroups. RESULTS: The mean dimensional change in the tooth-missing site was -37.62 ± 106.36 µm (median: -28.33 µm, Q25 -72.65/Q75 38.97) mesial-distally and -67.91 ± 42.37 µm (median: -61.50 µm, Q25 -88.25/Q75 -36.75) occlusal-gingivally. Eighteen out of 40 mesial neighboring teeth and 24 out of 40 distal neighboring teeth showed migration towards the implants. When patients were grouped according to age, the mesial-distal reduction in the tooth-missing site was significantly larger in patients younger than 30 years compared with those older than 50 years (p < .05). CONCLUSIONS: The dimensions of posterior tooth-missing sites decreased over an observation period of 3 months.

Sympathetic nervous system contributes to orthodontic tooth movement by central neural regulation from hypothalamus.

Orthodontic tooth movement (OTM) is a specific treatment of malocclusion, whose regulation mechanism is still not clear. This study aimed to reveal the relationship between the sympathetic nervous system (SNS) and OTM through the construction of an OTM rat model through the utilization of orthodontic nickeltitanium coiled springs. The results indicated that the stimulation of SNS by dopamine significantly promote the OTM process represented by the much larger distance between the first and second molar compared with mere exertion of orthodontic force. Superior cervical ganglionectomy (SCGx) can alleviate this promotion effect, further proving the role of SNS in the process of OTM. Subsequently, the ability of orthodontic force to stimulate the center of the SNS was visualized by the tyrosin hydroxylase (TH) staining of neurons in ventromedial hypothalamic nucleus (VMH) and arcuate nucleus (ARC) of the hypothalamus, as well as the up-regulated expression of norepinephrine in local alveolar bone. Moreover, we also elucidated that the stimulation of SNS can promote osteoclast differentiation in periodontal ligament cells (PDLCs) and bone marrow-derived cells (BMCs) through regulation of receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) system, thus promoting the OTM process. In conclusion, this study provided the first evidence for the involvement of the hypothalamus in the promotion effect of SNS on OTM. This work could provide a novel theoretical and experimental basis for further understanding of the molecular mechanism of OTM.