Mechanical Properties and Clinical Significance of Orthodontic Wires

Orthodontic treatment is usually conducted by applying forces to certain teeth to move them into a targeted position. Orthodontic wires have been reported to be the primary modalities used in fixed-appliances-based orthodontic treatment to induce favorable tooth movement events. Accordingly, acquiring adequate knowledge about these approaches' clinical applications and biochemical behavior is essential when planning for a successful orthodontic treatment. Orthodontic wires are widely used and are mainly composed of composites, polymers, alloys and metals. Accordingly, the physical properties and clinical application of orthodontic wires vary based on their composition. In this context, it was recommended that achieving favorable outcomes of orthodontic treatment obliges clinicians to decide the best orthodontic wire and treatment plan based on the chemical properties and related clinical applications of each wire. Therefore, wires that tend to produce increasing stiffness gradually are generally used. However, it should be noted that no ideal wire exists. Therefore, favoring the application of a wire over the other should be based on the intended outcomes and stage of the treatment process.

Age-related osteogenesis on lateral force application to rat incisor – Part III: Periodontal and periosteal bone remodeling

Objectives: This study was aimed to compare the histological pattern of bone modeling on either periodontal or periosteal side induced by lateral orthodontic tooth movement in different age groups. Material and Methods: A total of 50 male Sprague-Dawley rats (25 rats in the adult group – 52 weeks and 25 rats in the young group – 10 weeks) were utilized in this study. Each age group was classified into the control, 3 days, 7 days, 14 days, and 21 days groups (five rats in each) by the duration of experimental device application. A double-helical spring was produced using 0.014” stainless steel wire to provide 40 g lateral force to the left and right incisors. Hematoxylin-eosin staining, proliferating cell nuclear antigen (PCNA) immunohistochemical staining, fibroblast growth factor receptor 2 (FGFR2) immunohistochemical staining, and Masson trichrome staining were performed; and the slides were subject to histological examination. Results: In 7 days, active bone modeling represented by the scalloped surface was observed on the periosteal side of the crestal and middle alveolus at the pressure side in the young group, while similar changes were observed only on the crestal area in the adult group. In the young group, the number of PCNA-positive cells increased significantly on the crestal area and middle alveolus on the 3, 7, and 14 day groups, with subsequent decrease at 21 days. In the adult group, PCNA-positive cells were localized on the crestal area throughout the period. In the young group, FGFR2-positive cells were observed mainly on the crestal and middle alveolus at 3, 7, and 14 days than the control group. In the adult group, these cells appeared on the crestal and middle alveolus in the 3 days group, but mainly on the crestal area at 14 days. In the young group, FGFR2-positive cells were observed on the crestal and middle alveolus on the 3, 7, and 14 days groups more than on the control group. In the adult group, these cells appeared on the crestal and middle alveolus in the 3 days group, but mainly on the crestal area in the 14 days group. In Masson trichrome stain, an increased number of type I collagen fibers were observed after helical spring activation in both age groups. Large resorption lacunae indicating undermining bone resorption were progressively present in both young and adult groups. Conclusion: According to these results, orthodontic tooth movement may stimulate cell proliferation and differentiation primarily on the periosteal side according to progressive undermining bone resorption on the periodontal side. This response may lead to prominent bone modeling during tooth movement in the young group, compared to the relatively delayed response in the adult group.

Oleic acid-related anti-inflammatory effects in force-stressed PdL fibroblasts are mediated by H3 lysine acetylation associated with altered IL10 expression

The initiation of a spatially and temporally limited inflammation is essential for tissue and bone remodeling by the periodontal ligament (PdL) located between teeth and alveolar bone. Obesity-associated hyperlipidemic changes may impair PdL fibroblast (PdLF) functions, disturbing their inflammatory response to mechanical stress such as those occurring during orthodontic tooth movement (OTM). Recently, we reported an attenuated pro inflammatory response of human PdLF (HPdLF) to compressive forces when stimulated with monounsaturated oleic acid (OA). Fatty acids, including OA, could serve as alternative source of acetyl-CoA, thereby affecting epigenetic histone marks such as histone 3 lysine acetylation (H3Kac) in a lipid metabolism-dependent manner. In this study, we therefore aimed to investigate the extent to which OA exerts its anti-inflammatory effect via changes in H3Kac. Six-hour compressed HPdLF showed increased H3Kac when cultured with OA. Inhibition of histone deacetylases resulted in a comparable IL10 increase as observed in compressed OA cultures. In contrast, inhibition of histone acetyltransferases, particularly p300/CBP, in compressed HPdLF exposed to OA led to an inflammatory response comparable to compressed control cells. OA-dependent increased association of H3Kac to IL10 promoter regions in force-stressed HPdLF further strengthened the assumption that OA exhibits its anti-inflammatory properties via modulation of this epigenetic mark. In conclusion, our study strongly suggests that obesity-related hyperlipidemia affect the functions of PdL cells via alterations in their epigenetic code. Since epigenetic inhibitors are already widely used clinically, they may hold promise for novel approaches to limit obesity-related risks during OTM.

Axin2+ PDL Cells Directly Contribute to New Alveolar Bone Formation in Response to Orthodontic Tension Force

Wnt–β-catenin signaling plays a key role in orthodontic tooth movement (OTM), a common clinical practice for malocclusion correction. However, its targeted periodontal ligament (PDL) progenitor cells remain largely unclear. In this study, we first showed a synchronized increase in Wnt–β-catenin levels and Axin2+ PDL progenitor cell numbers during OTM using immunostaining of β-catenin in wild-type mice and X-gal staining in the Axin2-LacZ knock-in line. Next, we demonstrated time-dependent increases in Axin2+ PDL progenitors and their progeny cell numbers within PDL and alveolar bones during OTM using a one-time tamoxifen-induced Axin2 tracing line ( Axin2CreERT2/+; R26RtdTomato/+). Coimmunostaining images displayed both early and late bone markers (such as RUNX2 and DMP1) in the Axin2Lin PDL cells. Conversely, ablation of Axin2+ PDL cells via one-time tamoxifen-induced diphtheria toxin subunit A (DTA) led to a drastic decrease in osteogenic activity (as reflected by alkaline phosphatase) in PDL and alveolar bone. There was also a decrease in new bone mass and a significant reduction in the mineral apposition rate on both the control side (to a moderate degree) and the OTM side (to a severe degree). Thus, we conclude that the Axin2+ PDL cells (the Wnt-targeted key cells) are highly sensitive to orthodontic tension force and play a critical role in OTM-induced PDL expansion and alveolar bone formation. Future drug development targeting the Axin2+ PDL progenitor cells may accelerate alveolar bone formation during orthodontic treatment.

Analysis of the Changes in Occlusal Plane Inclination in a Class II Deep Bite “Teen” Patient Treated with Clear Aligners: A Case Report

Background: Optimal management of hypodivergent growing patients demands a strict control of vertical dimension and to exploit the growth potential. If a deep bite malocclusion causes a traumatic contact between the upper and lower incisors and affects the facial appearance, an early interceptive treatment is recommended. The aim of this case report is to outline the clinical management of the occlusal plane of a growing Class II division 1 deep bite patient treated with aligners and Class II elastics. Methods: The treatment lasted 11 months and was divided into two phases. Treatment goals included improvement of the soft tissue profile and basal bone relationships through an increase in the mandibular third of the face and a sagittal advancement of the mandible. The correction of the curve of Spee involved intrusion of the mandibular incisors and extrusion of the mandibular premolars. Results: The cephalometric analysis at the end of the treatment displayed significant differences in the skeletal and occlusal pattern along with aesthetic improvements. Conclusion: The final cephalogram showed a consistency between the planned tooth movement and the clinical results. Although definitive recommendations must be withheld until longer follow-up is available, the patient presented here shows that the treatment protocol yielded positive mandibular growth.

Accelerated orthodontic tooth movement: surgical techniques and the regional acceleratory phenomenon

Background Techniques to accelerate tooth movement have been a topic of interest in orthodontics over the past decade. As orthodontic treatment time is linked to potential detrimental effects, such as increased decalcification, dental caries, root resorption, and gingival inflammation, the possibility of reducing treatment time in orthodontics may provide multiple benefits to the patient. Another reason for the surge in interest in accelerated tooth movement has been the increased interest in adult orthodontics. Review This review summarizes the different methods for surgical acceleration of orthodontic tooth movement. It also describes the advantages and limitations of these techniques, including guidance for future investigations. Conclusions Optimization of the described techniques is still required, but some of the techniques appear to offer the potential for accelerating orthodontic tooth movement and improving outcomes in well-selected cases.

Fluctuation of bone turnover markers’ levels in samples of gingival crevicular fluid after orthodontic stimulus: a systematic review

Background The aim of the present study was to provide an overview of gingival crevicular fluid (GCF) bone turnover markers (BTMs) concerning the physiology of orthodontic tooth movement (OTM) and assess their potential contributions to regulating bone remodeling, that could prove useful in designing future approaches to modulating orthodontic tooth movement. Methods Multiple electronic databases (MEDLINE/PubMed, Ovid MEDLINE, Ovid Embase, LILACS, and Cochrane Library) were searched up to October 1st, 2020. Randomized controlled trials (RCTs), controlled clinical trials, observational studies of prospective and retrospective designs, and cross-sectional studies reporting on levels of BTMs in GCF were eligible for inclusion. The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0), whereas the risk of bias of the included cohort studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool. Results Five RCTs, 9 prospective cohort studies, and 1 cross-sectional study fulfilled the inclusion criteria. The risk of bias was deemed as high for the RCTs and 4 of the prospective studies and moderate for the rest of the studies. The following biomarkers for bone formation were assessed: bone alcaline phosphatase (BALP), alcaline phosphatase (ALP), and osteocalcin (OC). For bone resorption, the following BTMs were assessed: deoxypyridinoline (DPD) and pyridinoline (PYD), N-terminal telopeptide (NTX), osteopontin (OPN), and tartrate-resistant acid phosphatase (TRAP). The follow-up period ranged mainly from baseline to 45 days, although one study had an expanded follow-up period of up to 16 months. The results of the included studies comparing different BTMs were heterogeneous and qualitatively reported. Conclusions Current evidence continues to support the potential for BTMs to provide clinically useful information particularly for adjusting or standardizing the orthodontic stimulus. The present systematic review has retrieved studies of high, overall, risk of bias, and has unveiled a substantial clinical and methodological heterogeneity among included studies. Further data of the relationships between the clinical assays and the physiological or pre-analytical factors contributing to variability in BTMs’ concentrations are required. Systematic review registration CRD42020212056.

Positive Osteocalcin Expressions in Periodontium Regenerated by Nano Bioceramics after Orthodontic Tooth Movement

The research is to analyse the immunohistochemical reaction of orthodontic force on the periodontium reformed by nanobiphasic calcium phosphate ceramics (nBCP). Two third incisors were selected randomly and operated as experimental groups in 2 Beagle dogs. In the labial aspects of the third incisors, alveolar bone defects were surgically made and implanted with NBCP. The contralateral teeth in the same jaw did not receive any treatment as control. After 24 weeks, all the third incisors were moved labially. The dogs were euthanized 4 weeks later. The expression levels of osteocalcin were detected by immunohistochemical staining. Positive osteocalcin expressions in regenerated periodontium were observed and compared with the normal periodontium in the control groups. There were no significant differences within and between them. It means the periodontium regenerated by nBCP can bear orthodontic forces with a normal function. Based on these findings, we concluded that nBCP may offer a new bone graft choice for periodontic disease patients who have demands for orthodontic treatment.