Three-dimensional volumetric evaluation of root resorption in maxillary anteriors following en-masse retraction with varying force vectors - a randomized control trial.

BACKGROUND: Root resorption in orthodontics is associated with direction and magnitude of force application as primary etiological factors. Well-controlled trials that utilize three-dimensional segmentation to detect volumetric changes in tooth structure are required to assess the quantitative nature of root resorption. OBJECTIVE: To assess the severity of root resorption (RR) during retraction of maxillary anteriors with three different force vectors (with and without skeletal anchorage) via cone-beam computed tomography (CBCT) superimpositions. TRIAL DESIGN: Three-arm parallel randomized clinical trial (RCT). MATERIALS AND METHODS: Forty-two (16 males, 26 females) patients, (17-28 years), in permanent dentition with bimaxillary protrusion were randomly allocated to three groups of 14 patients each using block randomization (1:1:1 ratio) and allocation concealment. En-masse anterior retraction post first premolar extractions was carried out with modified force vectors in the three groups based on anchorage type [Molar, Mini-implant and Infrazygomatic crest (IZC) bone screws]. Volumetric root loss and linear dimensional changes were blindly assessed on initial (T0) and final (T1, end of space closure) CBCT scans. Normality distribution of values was done using Shapiro-Wilk's test. ANOVA and Post-hoc Tukey HSD test were done to compare measurements between groups at significance levels (P < .05). RESULTS: Forty patients were analysed (14, 14, and 12 in three groups). Significant volumetric loss was noted in all groups. Central incisors demonstrated a significant reduction in IZC group (81.5 ± 21.1 mm3 ) compared to conventional (50.1 ± 26.5 mm3 ) and mini-implant groups (76.1 ± 27.6 mm3 ). Canines demonstrated a significant reduction in mini-implant group (108.9 ± 33.9 mm3 ) compared to conventional (68.8 ± 42.5 mm3 ) and IZC groups (103.1 ± 29.1 mm3 ). Regarding linear parameters, central incisors and canines revealed significant root length reduction in both skeletal anchorage groups. Lateral incisors showed no significant changes between groups. CONCLUSIONS: Intrusive force vectors generated during skeletally anchored retraction can predispose anteriors to an increased risk of resorption. Greater loss of root volume was noted in the centrals and canines when retracted with skeletal anchorage. LIMITATIONS: Small sample size and variations during CBCT acquisition. HARMS: Low-dose CBCT scans were taken at T0 and T1 treatment intervals.

Non-surgical adjunctive interventions for accelerating tooth movement in patients undergoing orthodontic treatment.

BACKGROUND: Deviation from a normal bite can be defined as malocclusion. Orthodontic treatment takes 20 months on average to correct malocclusion. Accelerating the rate of tooth movement may help to reduce the duration of orthodontic treatment and associated unwanted effects including orthodontically induced inflammatory root resorption (OIIRR), demineralisation and reduced patient motivation and compliance. Several non-surgical adjuncts have been advocated with the aim of accelerating the rate of orthodontic tooth movement (OTM).         OBJECTIVES: To assess the effect of non-surgical adjunctive interventions on the rate of orthodontic tooth movement and the overall duration of treatment. SEARCH METHODS: An information specialist searched five bibliographic databases up to 6 September 2022 and used additional search methods to identify published, unpublished and ongoing studies. SELECTION CRITERIA: We included randomised controlled trials (RCTs) of people receiving orthodontic treatment using fixed or removable appliances along with non-surgical adjunctive interventions to accelerate tooth movement. We excluded split-mouth studies and studies that involved people who were treated with orthognathic surgery, or who had cleft lip or palate, or other craniofacial syndromes or deformities. DATA COLLECTION AND ANALYSIS: Two review authors were responsible for study selection, risk of bias assessment and data extraction; they carried out these tasks independently. Disagreements were resolved by discussion amongst the review team to reach consensus.  MAIN RESULTS: We included 23 studies, none of which were rated as low risk of bias overall. We categorised the included studies as testing light vibrational forces or photobiomodulation, the latter including low level laser therapy and light emitting diode. The studies assessed non-surgical interventions added to fixed or removable orthodontic appliances compared to treatment without the adjunct. A total of 1027 participants (children and adults) were recruited with loss to follow-up ranging from 0% to 27% of the original samples.  Certainty of the evidence For all comparisons and outcomes presented below, the certainty of the evidence is low to very low. Light vibrational forces  Eleven studies assessed how applying light vibrational forces (LVF) affected orthodontic tooth movement (OTM). There was no evidence of a difference between the intervention and control groups for duration of orthodontic treatment (MD -0.61 months, 95% confidence interval (CI) -2.44 to 1.22; 2 studies, 77 participants); total number of orthodontic appliance adjustment visits (MD -0.32 visits, 95% CI -1.69 to 1.05; 2 studies, 77 participants); orthodontic tooth movement during the early alignment stage (reduction of lower incisor irregularity (LII)) at 4-6 weeks (MD 0.12 mm, 95% CI -1.77 to 2.01; 3 studies, 144 participants), or 10-16 weeks (MD -0.18 mm, 95% CI -1.20 to 0.83; 4 studies, 175 participants); rate of canine distalisation (MD -0.01 mm/month, 95% CI -0.20 to 0.18; 2 studies, 40 participants); or rate of OTM during en masse space closure (MD 0.10 mm per month, 95% CI -0.08 to 0.29; 2 studies, 81 participants). No evidence of a difference was found between LVF and control groups in rate of OTM when using removable orthodontic aligners. Nor did the studies show evidence of a difference between groups for our secondary outcomes, including patient perception of pain, patient-reported need for analgesics at different stages of treatment and harms or side effects.  Photobiomodulation Ten studies assessed the effect of applying low level laser therapy (LLLT) on rate of OTM. We found that participants in the LLLT group had a statistically significantly shorter length of time for the teeth to align in the early stages of treatment (MD -50 days, 95% CI -58 to -42; 2 studies, 62 participants) and required fewer appointments (-2.3, 95% CI -2.5 to -2.0; 2 studies, 125 participants). There was no evidence of a difference between the LLLT and control groups in OTM when assessed as percentage reduction in LII in the first month of alignment (1.63%, 95% CI -2.60 to 5.86; 2 studies, 56 participants) or in the second month (percentage reduction MD 3.75%, 95% CI -1.74 to 9.24; 2 studies, 56 participants). However, LLLT resulted in an increase in OTM during the space closure stage in the maxillary arch (MD 0.18 mm/month, 95% CI 0.05 to 0.33; 1 study; 65 participants; very low level of certainty) and the mandibular arch (right side MD 0.16 mm/month, 95% CI 0.12 to 0.19; 1 study; 65 participants). In addition, LLLT resulted in an increased  rate of OTM during maxillary canine retraction (MD 0.01 mm/month, 95% CI 0 to 0.02; 1 study, 37 participants). These  findings were not clinically significant. The studies showed no evidence of a difference between groups for our secondary outcomes, including OIIRR, periodontal health and patient perception of pain at early stages of treatment. Two studies assessed the influence of applying light-emitting diode (LED) on OTM. Participants in the LED group required a significantly shorter time to align the mandibular arch compared to the control group (MD -24.50 days, 95% CI -42.45 to -6.55, 1 study, 34 participants). There is no evidence that LED application increased the rate of OTM during maxillary canine retraction (MD 0.01 mm/month, 95% CI 0 to 0.02; P = 0.28; 1 study, 39 participants ). In terms of secondary outcomes, one study assessed patient perception of pain and found no evidence of a difference between groups.   AUTHORS' CONCLUSIONS: The evidence from randomised controlled trials concerning the effectiveness of non-surgical interventions to accelerate orthodontic treatment is of low to very low certainty. It suggests that there is no additional benefit of light vibrational forces or photobiomodulation for reducing the duration of orthodontic treatment. Although there may be a limited benefit from photobiomodulation application for accelerating discrete treatment phases, these results have to be interpreted with caution due to their questionable clinical significance. Further well-designed, rigorous RCTs with longer follow-up periods spanning from start to completion of orthodontic treatment are required to determine whether non-surgical interventions may reduce the duration of orthodontic treatment by a clinically significant amount, with minimal adverse effects.

Combined orthodontic and prosthodontic treatment in an adolescent patient with traumatically ankylosed incisors: A case report.

Symmetric extraction of premolars is a frequently used orthodontic treatment for dental crowding and protrusion. However, when a patient has incisors with ankylosis, the establishment of a treatment protocol often plagues orthodontists. An adolescent patient with a history of incisor trauma sought treatment for dental protrusion and crowding. Upon percussion of his infrapositioned maxillary central incisors, characteristic dull metallic sounds were noted, and a lack of normal mobility of these teeth under the application of external forces was detected. Follow-up radiographs after the trauma showed replacement root resorption of the maxillary central incisors. Based on clinical and radiological findings, ankylosis of the maxillary central incisors was tentatively diagnosed. A combination of orthodontic and prosthodontic treatment options involving extraction of the maxillary central incisors and mandibular first premolars was chosen to resolve the functional and esthetic problems. After treatment, well-aligned dentition, improved smile esthetics, and a more harmonious facial profile were achieved, and these outcomes remained stable during the follow-up period. This case report illustrates a viable treatment strategy for tackling predicaments caused by ankylosed incisors, which is unusual in the literature.

Effectiveness of platelet-rich concentrates on the rate of orthodontic tooth movement: a systematic review and meta-analysis.

BACKGROUND: Autologous platelet-rich concentrates (PRCs) are recently used as a local biological substance in orthodontics to accelerate the rate of tooth movement. OBJECTIVES: This systematic review aimed to evaluate the effects of PRCs on the rate of orthodontic tooth movement (OTM). SEARCH METHODS: Unrestricted search of five electronic databases supplemented by the manual and gray literature search were undertaken in March 2022. SELECTION CRITERIA: Randomized controlled trials (RCTs) evaluating the effect of PRCs on the rate of OTM with their side effect were included in this systematic review. DATA COLLECTION AND ANALYSIS: Data items were extracted by two authors using a pre-piloted extraction form. Similar outcomes within a comparable time frame were synthesized in a meta-analysis. RESULTS: Fourteen studies were deemed eligible for inclusion and seven RCTs were pooled in a meta-analysis. Canine retraction rate was higher in the side of PRCs injection than the control side by 0.28 mm/month (95% CI: 0.16-0.40, I2 = 95.6 per cent, P < 0.001, 345 patients) in the first 4 months after PRCs injection. There was no statistically significant difference between the PRCs side and the control side regarding molar anchorage loss (MAL) (MD = 0.03 mm, 95% CI: -0.18 to 0.24, I2 = 46.3 per cent, P = 0.78, 44 patients), canine rotation (MD = -0.19o, 95% CI: -1.95 to 1.57, I2 = 45.4 per cent, P = 0.96, 48 patients), or en-masse retraction. Likewise, there was no difference between both groups in terms of the duration of de-crowding. The mandibular canine retraction was statistically higher on the PRCs side than on the control side by 0.17 mm/month (P < 0.001, one trial). Regarding root resorption, there was no statistically significant difference between the experimental and control sides within the follow-up time. Mild pain scores were reported by the patients in the first 24 hours after injections. CONCLUSIONS: Low-level evidence indicates that the effect of PRCs on OTM is minor and clinically insignificant. The findings should be interpreted with caution due to the inherent limitations in the included RCTs. REGISTRATION: PROSPERO (CRD42022300026).

May alcoholic and non-alcoholic drinks affect the rate of orthodontic tooth movement? A systematic review of animal studies.

BACKGROUND: Humans may consume various beverages in everyday life. Previous research has shown that the administration of different substances (medicinal or not) may affect bone turnover and, thus, orthodontic tooth movement. It would be anticipated that the substances contained in beverages could have an impact on tooth movement, as well. OBJECTIVE: To investigate in a systematic way and appraise the quality of the available evidence from animal studies regarding the impact of various drinks or the main ingredients included in beverages on the rate of orthodontic tooth movement. SEARCH METHODS: Search without restriction in six databases (including grey literature) and hand searching were performed until March 2022. SELECTION CRITERIA: We looked for controlled animal studies investigating the effect of drinks, or the main ingredients included in beverages, on the rate of orthodontic tooth movement. DATA COLLECTION AND ANALYSIS: After study retrieval and selection, relevant data was extracted, and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. The quality of available evidence was assessed with the Grades of Recommendation, Assessment, Development, and Evaluation. RESULTS: The initially identified records were finally reduced to nine studies conducted on animals. Carbonated soft drinks were shown to decrease the rate of tooth movement, but alcohol consumption did not have an impact. Exploratory meta-analysis showed that caffeine exhibited an acceleratory effect after 3 weeks of force application. Exploratory meta-regression results indicated that high dosages of caffeine reduced the rate of tooth movement. CONCLUSIONS: The located animal experiments reported that caffeine accelerates, carbonated drinks decelerate, while alcohol does not affect the rate of orthodontic tooth movement. However, due to various limitations it remains unclear whether caffeine, alcohol, or carbonated drinks finally influence tooth movement in animal studies. REGISTRATION: Open Science Framework (https://osf.io/jyhbd/).

Under pressure-mechanisms and risk factors for orthodontically induced inflammatory root resorption: a systematic review.

BACKGROUND: The application of orthodontic forces causes root resorption of variable severity with potentially severe clinical ramifications. OBJECTIVE: To systematically review reports on the pathophysiological mechanisms of orthodontically induced inflammatory root resorption (OIIRR) and the associated risk factors based on in vitro, experimental, and in vivo studies. SEARCH METHODS: We undertook an electronic search of four databases and a separate hand-search. SELECTION CRITERIA: Studies reporting on the effect of orthodontic forces with/without the addition of potential risk factors on OIIRR, including (1) gene expression in in-vitro studies, the incidence root resorption in (2) animal studies, and (3) human studies. DATA COLLECTION AND ANALYSIS: Potential hits underwent a two-step selection, data extraction, quality assessment, and systematic appraisal performed by duplicate examiners. RESULTS: One hundred and eighteen articles met the eligibility criteria. Studies varied considerably in methodology, reporting of results, and variable risk of bias judgements.In summary, the variable evidence identified supports the notion that the application of orthodontic forces leads to (1) characteristic alterations of molecular expression profiles in vitro, (2) an increased rate of OIIRR in animal models, as well as (3) in human studies. Importantly, the additional presence of risk factors such as malocclusion, previous trauma, and medications like corticosteroids increased the severity of OIIRR, whilst other factors decreased its severity, including oral contraceptives, baicalin, and high caffeine. CONCLUSIONS: Based on the systematically reviewed evidence, OIIRR seems to be an inevitable consequence of the application of orthodontic forces-with different risk factors modifying its severity. Our review has identified several molecular mechanisms that can help explain this link between orthodontic forces and OIIRR. Nevertheless, it must be noted that the available eligible literature was in part significantly confounded by bias and was characterized by substantial methodological heterogeneity, suggesting that the results of this systematic review should be interpreted with caution. REGISTRATION: PROSPERO (CRD42021243431).

The effect of micro-osteoperforation on the rate of tooth movement during the alignment stage in patients with mandibular crowding: a randomised controlled trial.

BACKGROUND: Orthodontic treatment is a long process that requires patient cooperation. Risks of side effects such as caries formation, periodontal problems, and root resorption increases as well as problems in patient cooperation arises with longer treatments. Several different techniques were developed that may shorten the treatment time. OBJECTIVE: The aim of this study was to evaluate the effectiveness of micro-osteoperforations (MOPs) performed during the alignment stage. TRIAL DESIGN: Randomized controlled trial. METHODS: Twenty-eight subjects who had crowding in the mandibular arch were included in the study. The first group (4 boys and 10 girls, mean age = 17.21 ± 3.76 years) was treated with MOP (MOP) and the second group (8 boys and 6 girls, mean age = 15.29 ± 1.77 years) was treated without MOP (control). Cephalometric variables, periodontal parameters, Little irregularity index, alignment duration, patient satisfaction, and ease of operation were evaluated. The level of statistical significance was P ≤ 0.05. RESULTS: Alignment duration was shorter (P = 0.000) in the MOP group (105.57 ± 18.34 days) compared to control group (135.86 ± 15.12 days). Alleviating of the crowding was more in the MOP group, compared to the control group in all time points. The pain level in the MOP group in the first appointment was higher compared to control group (P = 0.002). There was no significant difference between the groups in cephalometric parameters. Higher increases were found for gingival index (P = 0.008) and bleeding index (P = 0.039) in the control group compared to MOP group at the end of treatment. LIMITATIONS: The study was a single-centre study. CONCLUSION: Alignment stage was shortened with MOP application. There was no difference between groups for patient satisfaction and pain level except for the first appointment. No difference was observed between the groups regarding cephalometric values. Clinically insignificant inflammation was observed in periodontal tissues for both groups. REGISTRATION: This study was registered at the Clinical Trials Registry (ClinicalTrials.gov NCT03652454).

Effects of Increasing the Orthodontic Forces over Cortical and Trabecular Bone during Periodontal Breakdown-A Finite Elements Analysis.

Background and Objectives: Herein we used numerical analysis to study different biomechanical behaviors of mandibular bone subjected to 0.6 N, 1.2 N, and 2.4 N orthodontic loads during 0-8 mm periodontal breakdown using the Tresca failure criterion. Additionally, correlations with earlier FEA reports found potential ischemic and resorptive risks. Materials and Methods: Eighty-one models (nine patients) and 243 simulations (intrusion, extrusion, rotation, tipping, and translation) were analyzed. Results: Intrusion and extrusion displayed after 4 mm bone loss showed extended stress display in the apical and middle third alveolar sockets, showing higher ischemic and resorptive risks for 0.6 N. Rotation, translation, and tipping displayed the highest stress amounts, and cervical-third stress with higher ischemic and resorptive risks after 4 mm loss for 0.6 N. Conclusions: Quantitatively, rotation, translation, and tipping are the most stressful movements. All three applied forces produced similar stress-display areas for all movements and bone levels. The stress doubled for 1.2 N and quadrupled for 2.4 N when compared with 0.6 N. The differences between the three loads consisted of the stress amounts displayed in color-coded areas, while their location and extension remained constant. Since the MHP was exceeded, a reduction in the applied force to under 0.6 N (after 4 mm of bone loss) is recommended for reducing ischemic and resorptive risks. The stress-display pattern correlated with horizontal periodontal-breakdown simulations.

Semaphorin 3A protects against alveolar bone loss during orthodontic tooth movement in mice with periodontitis.

OBJECTIVE: This study investigated the effect of local semaphorin 3A (Sema3A) administration on alveolar bone loss during OTM in a mouse model of periodontitis. BACKGROUND: Orthodontic tooth movement (OTM) for patients with periodontal disease is known to increase the risk of exacerbating alveolar bone loss due to inflammation of the periodontal tissue. However, its mechanism of action and prevention remains unclear. METHODS: Mice (male 7-8 weeks old, C57BL/6J, n = 12) were divided into six groups: untreated group (control), without OTM and recovered from induced periodontitis (RP), with OTM and administered PBS or Sema3A to the gingiva after induced periodontitis (VehPO, SemaPO), with OTM and administered PBS or Sema3A to the gingiva without periodontitis induction (VehNO, SemaNO). Samples were collected on 14 days, and bone loss, histological analysis, cytokine production level, and tooth movement were assessed. Cultured human periodontal ligament (hPDL) cells were stimulated with lipopolysaccharide (LPS) and compressive force (CF), and mRNA expression levels of Sema3A and its receptors were analyzed. RESULTS: The bone loss was significantly lower in the SemaPO group than in the VehPO group. The number of TRAP-positive cells in the SemaPO group was significantly lower than that in the VehPO group and was at the same level as that in the control group. The receptor activator of nuclear factor (NF)-kB-ligand/osteoprotegerin (RANKL/OPG) ratio and the levels of proinflammatory cytokines, including interleukin (IL)-1ß, IL-6, IL-17, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ, in the gingival tissues were significantly lower in the SemaPO group than in the VehPO group. Additionally, Sema3A mRNA expression in hPDL cells was significantly decreased by co-stimulation with LPS and CF compared with that in the control group. Finally, the distance moved (dist.) and the mesial tipping angle (θ) was significantly smaller in the SemaPO group than in the VehPO group and was not significantly different from that of VehNO. CONCLUSION: Pathological alveolar bone loss exacerbated by OTM in periodontitis might be prevented by local administration of Sema3A without inhibiting OTM.

Effects of high-frequency near infrared laser irradiation on experimental tooth movement-induced pain in rats.

Discomfort and dull pain are known side effects of orthodontic treatment. Pain is expected to be reduced by near-infrared (NIR) lasers; however, the mechanism underlying effects of short-pulse NIR lasers in the oral and maxillofacial area remains unclear. This study aimed to examine the effects of high-frequency NIR diode laser irradiation on pain during experimental tooth movement (ETM) on 120 J. NIR laser with 910 nm wavelength, 45 W maximum output power, 300 mW average output power, and 200 ns pulse width (Lumix 2; (Lumix 2; Fisioline, Verduno CN, Italy) was used for the experiment. A nickel-titanium-closed coil was used to apply a 50-gf force between the maxillary left-side first molar and incisor in 7-week-old Sprague-Dawley rats (280-300 g) to induce ETM. We measured facial-grooming frequency and vacuous chewing movement (VCM) period between laser-irradiation and ETM groups. We performed immunofluorescent histochemistry analysis to quantify levels of Iba-1, astrocytes, and c-fos protein-like immunoreactivity (Fos-IR) in the trigeminal spinal nucleus caudalis (Vc). Compared with the ETM group, the laser irradiation group had significantly decreased facial-grooming frequency (P = 0.0036), VCM period (P = 0.043), Fos-IR (P = 0.0028), Iba-1 levels (P = 0.0069), and glial fibrillary acidic protein (GFAP) levels (P = 0.0071). High-frequency NIR diode laser irradiation appears to have significant analgesic effects on ETM-induced pain, which involve inhibiting neuronal activity, microglia, and astrocytes, and it inhibits c-fos, Iba-1, and GFAP expression, reducing ETM-induced pain in rats. High-frequency NIR diode laser application could be applied to reduce pain during orthodontic tooth movement.

Molecular mechanism in trigeminal nerve and treatment methods related to orthodontic pain.

BACKGROUND: Orthodontic treatment is the main treatment approach for malocclusion. Orthodontic pain is an inevitable undesirable adverse reaction during orthodontic treatment. It is reported orthodontic pain has become one of the most common reason that patients withdraw from orthodontic treatment. Therefore, understanding the underlying mechanism and finding treatment of orthodontic pain are in urgent need. AIMS: This article aims to sort out the mechanisms and treatments of orthodontic pain, hoping to provide some ideas for future orthodontic pain relief. MATERIALS: Tooth movement will cause local inflammation. Certain inflammatory factors and cytokines stimulating the trigeminal nerve and further generating pain perception, as well as drugs and molecular targeted therapy blocking nerve conduction pathways, will be reviewed in this article. METHOD: We review and summaries current studies related to molecular mechanisms and treatment approaches in orthodontic pain control. RESULTS: Orthodontics pain related influencing factors and molecular mechanisms has been introduced. Commonly used clinical methods in orthodontic pain control has been evaluated. DISCUSSION: With the clarification of more molecular mechanisms, the direction of orthodontic pain treatment will shift to targeted drugs.

PD-L1, a Potential Immunomodulator Linking Immunology and Orthodontically Induced Inflammatory Root Resorption (OIIRR): Friend or Foe?

Orthodontically induced inflammatory root resorption (OIIRR) is considered an undesired and inevitable complication induced by orthodontic forces. This inflammatory mechanism is regulated by immune cells that precede orthodontic tooth movement (OTM) and can influence the severity of OIIRR. The process of OIIRR is based on an immune response. On some occasions, the immune system attacks the dentition by inflammatory processes during orthodontic treatment. Studies on the involvement of the PD-1/PD-L1 immune checkpoint have demonstrated its role in evading immune responses, aiming to identify possible novel therapeutic approaches for periodontitis. In the field of orthodontics, the important question arises of whether PD-L1 has a role in the development of OIIRR to amplify the amount of resorption. We hypothesize that blocking of the PD-L1 immune checkpoint could be a suitable procedure to reduce the process of OIIRR during orthodontic tooth movement. This review attempts to shed light on the regulation of immune mechanisms and inflammatory responses that could influence the pathogenesis of OIIRR and to acquire knowledge about the role of PD-L1 in the immunomodulation involved in OIIRR. Possible clinical outcomes will be discussed in relation to PD-L1 expression and immunologic changes throughout the resorption process.

Displacement and stress distribution of mandibular incisors after orthodontic treatment in the presence of alveolar bone loss under occlusal loads: A finite element analysis.

INTRODUCTION: This study evaluated the initial stress produced in the periodontal ligament (PDL) and the displacements of mandibular incisors under masticatory force in patients with alveolar bone loss (ABL) after orthodontic treatment. METHODS: Four horizontal absorption models (zero, one third, one half, and two thirds of root length) and 2 labiolingual absorption models (labial two thirds, lingual one third of root length, and vice versa) of the mandibular anterior segment were constructed. A total force of 285.3 N was applied vertically to the edges of incisors. The tooth displacement and principal stresses in the PDL were evaluated in a finite element analysis. RESULTS: In all models, the labial movements of the central incisors ascended more significantly, whereas there was obvious compressive stress and tensile stress concentrated in the labial and lingual cervical margins of the PDL, respectively. For the lateral incisors, augmentation of the distal motions was more evident. Compressive stress was apparent in the labial-distal margin, and tensile stress was concentrated in the lingual-mesial cervical margin. With the same proportion of ABL, more significant displacement and stress concentration in the PDL occurred in the central incisors. In labiolingual absorption models, labial ABL caused greater incisors displacement and periodontal stress concentration. When horizontal ABL extended from one half to two thirds of the root length, mobility of the central incisors and stresses in the PDL increased significantly. CONCLUSIONS: Mandibular incisors follow the different movement and stress distribution patterns under occlusal loads. Special consideration should be given to the retention of mandibular incisors when horizontal ABL exceeds half of the root length.

Unplanned molar intrusion after Invisalign treatment.

INTRODUCTION: The objectives of this study were to analyze and quantify molar intrusion after the use of clear aligners and to analyze the relationship with other variables such as age, duration of treatment, and a series of cephalometric osseous and dental measurements at the start of treatment. METHODS: A retrospective descriptive-analytical study was designed with a sample of 58 patients aged 18-60 years who had undergone treatment with Invisalign. The cephalometric measurements were carried out after lateral x-rays were taken of the cranium; these were compared at the start (T0) and conclusion of treatment. Parametric and nonparametric tests were used to compare means, whereas Pearson correlations and multivariate lineal regression analyses were used to establish the variables associated with molar intrusion. RESULTS: Approximately 74.2% of the patients presented some degree of molar intrusion after treatment. Furthermore, 32.8% of patients presented intrusion only at the mandibular molar, whereas 25.9% experienced intrusion at both molars, maxillary and mandibular, simultaneously. However, 15.5% presented intrusion only at the maxillary molar. The average magnitude of intrusion here was 0.98 ± 0.54 mm, whereas the mandibular molar was 0.84 ± 0.29 mm. Statistically significant reductions exist for the distance L6_MP and U6_SN between T0 and at conclusion of treatment. Maxillary molar intrusion correlates negatively with mandibular molar intrusion (r = -0.270). The number of days of treatment did not correlate with either maxillary or mandibular molar intrusion. CONCLUSIONS: Clear aligners give rise to molar intrusion in 74.2% of patients. The cephalometric variables L6_MP T0, mandibular plane angle T0, and facial axis T0 were negatively and significantly associated with maxillary molar intrusion, whereas age and facial axis T0 were negatively associated with mandibular molar intrusion allowing smaller magnitudes of intrusion to be predicted when these variables present high values at T0.

Overall stress in periodontal ligament under orthodontic movement during a periodontal breakdown.

INTRODUCTION: This research aimed to assess qualitatively and quantitatively the overall stress in the periodontal ligament during gradual periodontal breakdown (0-8 mm) under orthodontic movements. Correlations between the applied forces, the level of bone loss, the decrease of force magnitude, and the increase of stress were also assessed. METHODS: On the basis of cone-beam computed tomography examinations (voxel size, 0.075 mm), nine 3-dimensional models of a mandibular second premolar with intact periodontium were created and then individually subjected to various levels of horizontal bone loss. Orthodontic forces (intrusion at 0.2 N; extrusion, rotation, and tipping at 0.6 N; translation at 1.2 N) were applied on the brackets. Finite elements analysis was performed, and von Mises (VM) stresses were quantitatively and qualitatively determined. RESULTS: Rotation and translation induced the highest stress apically and cervically, whereas intrusion determined the lowest. Apical stress was lower than cervical stress. In intact periodontium, VM stress was under maximum hydrostatic pressure (MHP) and maximum tolerable stress (MTS). In reduced periodontium, VM stress was lower apically than MHP, whereas cervically, the rotation, translation, and tipping exceeded MHP. CONCLUSIONS: A force of 1.2 N seemed safe to be used in the intact periodontium. Forces higher than 0.6 N could produce stresses exceeding MHP and MTS endangering the reduced periodontium. VM stress failure criterion (despite its limited use) seemed to be more adequate for accurate quantitative results. An overall correlation between the applied force, VM stress increase, and periodontal breakdown applicable to all 5 movements could not be established. This was possible only for individual movements.

Physical properties of root cementum: Part 28. Effects of high and low water fluoridation on orthodontic root resorption: A microcomputed tomography study.

INTRODUCTION: Transient inflammatory surface resorption, referred to as orthodontic induced inflammatory root resorption (OIIRR), is an iatrogenic consequence of orthodontic tooth movement. Systemic fluoride has been associated with a reduction of OIIRR. This study aimed to investigate the effects of water fluoridation levels on OIIRR in a clinically applicable human orthodontic model. METHODS: Twenty-eight patients who required bilateral maxillary first premolar extraction as part of orthodontic treatment were selected from 2 cities with high and low water fluoridation of ≥2 ppm and ≤0.05 ppm, respectively. Patients were separated into high fluoride (HF) and low fluoride (LF) groups on the basis of water fluoridation levels. Bilateral maxillary first premolar teeth were subjected to 150 g of buccal tipping forces for 12 weeks with reactivation every 4 weeks. Teeth were extracted at the end of 12 weeks. Root resorption crater volume was determined using microcomputed tomography and 3-dimensional reconstruction. RESULTS: HF group showed significantly less mean root resorption volume on the palatal root surface when compared with the LF group (P = 0.025). This difference was specifically displayed at palatal apical regions (P = 0.041). When root resorption volumes from the zones of orthodontic pressure (buccal cervical, palatal apical) were combined, the mean difference between HF and LF groups was statistically significant (P = 0.045). CONCLUSIONS: Findings of the present study indicated a positive correlation between water fluoridation and the reduction of OIIRR, especially at the zones of orthodontic pressure, using a clinically relevant human orthodontic model.

The influence of bracket torque on external apical root resorption in bimaxillary protrusion patients: a retrospective study.

BACKGROUND: To evaluate the difference in root resorption between standard torque self-ligating brackets and high torque self-ligating brackets in bimaxillary protrusion patients after orthodontic treatment. METHODS: Pre-treatment and post-treatment Cone beam computed tomography (CBCT) of 32 patients (16 treated with the high torque DamonQ 0.022″ bracket and 16 with the 0.022″ standard torque self-ligating bracket) were selected. The first premolars were extracted from all patients before treatment. After mini-screw implants were inserted into the buccal region between the second premolar and first molar, 150 g of force was applied to retract the upper and lower anterior teeth to close the extraction space on each side. CBCT images of all patients were taken before and after treatment. Three-dimensional reconstruction of the maxillary central incisor, lateral incisor and canine was conducted with Mimics 20.0 software. The volumes of the roots were calculated using Gomagics Studio 12.0 software. The differences between the pre-treatment and post-treatment root volumes were statistically evaluated with a paired-samples t-test. RESULTS: There was no statistically significant difference in root resorption degree between the two kinds of torque brackets. The patient's degree of root resorption in the high torque self-ligating group was greater than that in the standard torque group. CONCLUSIONS: There was no significant difference in root external apical resorption between the high torque self-ligating brackets and the standard torque self-ligating brackets in bimaxillary protrusion patients.

The influence of two photobiomodulation protocols on orthodontically induced inflammatory root resorption (a randomized controlled clinical trial).

BACKGROUND: Controversial results have been reported regarding the impact of photobiomodulation (PBM) on orthodontically induced inflammatory root resorption (OIIRR). The aim of this study was to evaluate the influence of two PBM protocols, one of them requiring a high application frequency (on days 0, 3, 7, 14, then every 2 weeks), while the second requires less frequent applications (every 3 weeks), on OIIRR accompanying orthodontic treatment. METHODS: Twenty female patients were recruited for this randomized controlled trial, requiring the therapeutic extraction of maxillary first premolars, and they were randomly divided into 2 equal groups. In Group A, one side of the maxillary arch randomly received PBM on days 0, 3, 7, 14, and every 2 weeks thereafter, while in Group B, one side was randomly chosen to receive PBM every 3 weeks. The laser applied was a Diode laser with a wavelength of 980 nm, in a continuous mode. Canine retraction in both groups was carried out using closed-coil springs, delivering 150 g of force, and the force level was checked every 3 weeks, over a 12-week study period. Pre-retraction and post-retraction cone-beam computed tomography (CBCT) was done for the evaluation of OIIRR. RESULTS: No significant differences in the amount of OIIRR have been reported between the laser and control sides in both groups A and B. Also, no significant differences have been reported between the laser sides in both groups. CONCLUSIONS: Photobiomodulation does not affect OIIRR, whether by increasing or decreasing its occurrence, with both laser application protocols. Therefore, it can be stated that PBM does not result in root resorption less than the commonly observed range elicited with conventional orthodontic treatment, and that it has no effect on OIIRR. Trial registration Two Low-level Laser Irradiation Protocols on the Rate of Canine Retraction (NCT04926389), 15/06/2021-retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT04926389 .

Mechanical force regulates root resorption in rats through RANKL and OPG.

BACKGROUND: External root resorption is one of common complications of orthodontic treatment, while internal root resorption is rarely observed, and the difference between pulp and periodontal tissues during orthodontic treatment is still unknown. The purpose of this study was to evaluate the effects of orthodontic forces on histological and cellular changes of the dental pulp and periodontal tissues. METHODS: Orthodontic tooth movement model was established in Forty-eight adult male Wistar rats. The distance of orthodontic tooth movement was quantitatively analyzed. The histological changes of pulp and periodontal tissues were performed by hematoxylin-eosin staining, tartrate-resistant acid phosphate staining was used to analyze the changes of osteoclast number, immunohistochemistry analysis and reverse transcription polymerase chain reaction were used to examine the receptor of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) expression. The width of tertiary dentine was quantitatively analyzed. Tartrate-resistant acid phosphate staining and the erosion area of osteo assay surface plate was used to evaluate osteoclast activity. RESULTS: The orthodontic tooth movement distance increased in a force dependent manner, and reached the peak value when orthodontic force is 60 g. Heavy orthodontic force increased the RANKL expression of periodontal ligament srem cells (PDLSCs) which further activated osteoclasts and resulted in external root resorption, while the RANKL expression of dental pulp stem cells (DPSCs) was relatively low to activate osteoclasts and result in internal root resorption, and the dental pulp tend to form tertiary dentine under orthodontic force stimulation. CONCLUSIONS: Heavy orthodontic forces activated osteoclasts and triggered external root resorption by upregulating RANKL expression in rat periodontal tissues, while there was no significant change of RANKL expression in dental pulp tissue under heavy orthodontic forces, which prevented osteoclast activation and internal root resorption.

Effects of vibrations induced by electric tooth brush on amount of canine retraction: A cross sectional study done at University of Lahore.

OBJECTIVE: To evaluate the effect of localized vibration on amount of canine retraction after 1st premolar extractions and to assess the anchorage loss. Methods: This quasi-experimental clinical study was conducted at University College of dentistry, Department of Orthodontics, University of Lahore. Data was collected from 30 patients who were already undergoing orthodontic treatment after taking their consent. The study was completed in one year, from Jan 2019 to Feb 2020. Results were compared with independent samples t-test using IBM-SPSS version 23.0. RESULTS: There was no statistically significant difference in the amount of tooth movement between the experimental and control side (p= 0.22). There was also no significant difference in the loss of anchorage (in terms of mesial movement of molar and rotation of canine) between both the groups (p > 0.05). Patients reported the use of electric tooth brush very practical and comfortable. No harm was observed. Conclusion: Supplemental vibrations induced by electric tooth brush did not increase the amount of tooth movement in terms of canine retraction nor did it decrease the loss of anchorage.