Influence of low-level laser therapy on orthodontically-induced inflammatory root resorption. A systematic review

Effect of low-level laser therapy on en masse retraction in females with bimaxillary dentoalveolar protrusion : A single-center randomized clinical trial

BACKGROUND

Acceleration of tooth movement has gained remarkable attention during the last decade. The aim of this study was to evaluate the effect of low-level laser therapy (LLLT) on en masse retraction of upper anterior teeth in adult women with bimaxillary dentoalveolar protrusion.

MATERIALS AND METHODS

In this two-arm parallel trial, 36 women with bimaxillary dentoalveolar protrusion were randomly divided into two equal groups. Eligibility criteria included class I Angle molar relationship, good general and oral health as well as no systemic disease or syndrome. Four temporary anchorage devices (TADs) were used in the upper and lower arches for anchorage purposes. A 0.019×0.025-inch stainless steel wire with crimped hooks just distal to the maxillary canines was inserted. Nickle titanium (NiTi) closed coil springs (200 g/side) were employed for en masse retraction following extraction of the first premolars. In the laser group (LG), retraction of the upper anterior teeth was done along with the application of LLLT on days 0, 3, 7, and 14 after extraction and then repeated biweekly until the end of retraction. Retraction was completed without LLLT application in the nonlaser group (NLG). Data concerning the rate of retraction as well as first molars and anterior positional changes were gained from digitized models and cone beam computed tomography (CBCT) scans taken just before extraction and at the end of retraction. Treatment-associated pain and root resorption were evaluated using visual analogue scale (VAS) and CBCT scans, respectively.

RESULTS

Four patients dropped out prior to follow-up. The duration of retraction was 10.125 ± 2.876 and 13.643 ± 3.455 months in the LG and NLG, respectively. The LG showed a statistically significant faster rate of en masse retraction (0.833 ± 0.371 mm/month) compared to the NLG (0.526 ± 0.268 mm/month; P ≤ 0.035). The observed root resorption was significantly less in the LG (P ≤ 0.05) with comparable pain scores in both groups.

CONCLUSIONS

Within the constraints of the parameters of the LLLT used in the current study and despite the statistically significant results on the rate of en masse retraction and the associated root resorption, LLLT did not demonstrate a clinically relevant effect that justifies its use to enhance en masse retraction.

NAME OF THE REGISTRY

Clinicaltrials.gov TRIAL REGISTRATION NUMBER: NCT05183451 DATE OF REGISTRATION: January 10, 2022, "Retrospectively registered" URL OF TRIAL REGISTRY RECORD: https://www.

CLINICALTRIALS

gov/study/NCT05183451.

Effective Parameters for Orthodontic Tooth Movement Acceleration with Photobiomodulation: An Umbrella Review

Objective: To answer this research question: What are the effective wavelength, power, and energy density parameters for achieving dental movement acceleration? Background Data: Photobiomodulation (PBM) has been clinically studied for its ability to accelerate dental movements in orthodontics. However, its effectiveness is dose dependent. Methods: The search was carried out in PubMed, SCOPUS, and ISI Web of Science. The quality of the included systematic reviews was performed using the AMSTAR 2 tool. The risk of bias was assessed using the ROBIS tool. Results: In total, 29 articles in PubMed, 75 in Scopus, and 61 in ISI Web of Science. Finally, only five systematic reviews were included. Conclusions: The results showed the range from 730 to 830 nm as the most effective range of wavelength to accelerate the orthodontic dental movement. A power range of 0.25-200 mW, with emphasis on the direct correlation between power, wavelength, and energy density. Energy density has not been adequately reported in the most randomized controlled clinical trials.

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.

Effects of Low-Level Laser Therapy and Bracket Systems on Root Resorption during Orthodontic Treatment: A Randomized Clinical Trial

This study aimed to assess the outcomes of low-level laser therapy (LLLT) with the conventional bracket (CB) and self-ligating (SL) bracket systems on root resorption (RR) during orthodontic treatment. A total of 32 patients were included in this randomized clinical trial. All the patients were randomly divided into four individual groups (SLL: self-ligating laser, CBL: conventional bracket laser, SLNL: self-ligating non-laser, CBNL: conventional bracket non-laser). RR was measured from the cone-beam computed tomography (CBCT) radiographs which were taken at two stages of the orthodontic treatment: pre-treatment (T1) and after leveling and alignment stage (T2). Wilcoxon rank test for the comparison was conducted to compare the RR at T1 and T2 stages within each group and showed a significant difference (p < 0.05) for various variables. Mann Whitney test compared the RR in laser and non-laser groups irrespective of the bracket systems and exhibited no significant differences except the left lateral incisor. Moreover, CB and SL groups showed no significant difference in RR among any tooth. Kruskal Wallis test was performed to compare the RR among all groups which presented no significant differences. LLLT and bracket systems have no consequences on RR until the leveling and alignment stage of orthodontic treatment.

Antimicrobial efficacy, optical properties and flexural strength following antimicrobial photodynamic therapy over vacuum-formed orthodontic retainers

BACKGROUND AND AIMS

Vacuum-formed retainers (VFRs) are widely used in dental practices because of their superior esthetics. However, simultaneous maintenance of their hygiene, mechanical and optical properties is challenging. This study aimed to evaluate and compare the disinfection efficacy of antimicrobial photodynamic therapy (aPDT), chlorhexidine (CHX), sodium hypochlorite (NaOCl) and water over VFRs specimens, along with their effect on flexural strength and color stability.

MATERIALS AND METHODS

Fabricated VFRs of thicknesses 1 mm and 2 mm were contaminated with S. mutans and C. albicans. Brain Heart Infusion agar was used to seed Streptococcus Mutans whereas Candida Albicans was seeded in Sabourand Dextrose Agar. The contaminated retainers were divided into four groups and decontaminated using four different treatment protocols: aPDT, CHX, NaOCl and water, with 10 specimens per group. Microbial viability following decontamination, was assayed using MTT. To assess the color stability, pre and post decontamination color difference of 10 specimens was recorded using a spectrophotometer by blinding technique. The flexural strength of 10 specimens was measured using a universal testing machine by a standardized 3-point flexural strength (FS) test.

RESULT

aPDT showed the highest reduction in the viability of S. mutans (28%) and C. albicans (20%) species in 1 mm thickness group while the second highest reduction following disinfection with CHX (40%) in followed by NaOCl disinfection (50%). On comparison between 1 mm and 2 mm, a statistically significant difference was noted for S. mutans in aPDT (p = 0.033) and NaOCl (p = 0.028) groups, and for C. albicans, a significant difference was noted within NaOCl (p = 0.001) and CHX (p = 0.043) groups. For FS, a statistically significant difference (p < 0.05) was observed between aPDT and the rest of the groups, whereas there was no statistically significant difference in the flexural strength between the CHX, NaOCl and water groups (p > 0.05) in both 1 mm and 2 mm specimens. Between 1 mm and 2 mm specimens, no statistically significant difference in the mean color difference was noted after any disinfection protocol (p > 0.05).

CONCLUSION

Antimicrobial photodynamic therapy showed a remarkable reduction in candidal and bacterial viability over VFRs. aPDT treated VFR specimens showed increased flexural strength and a higher color difference post treatment compared to other reagents.

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.

Effect of the photobiomodulation for acceleration of the orthodontic tooth movement: a systematic review and meta-analysis

To determine whether the application of photobiomodulation (PBM), as an adjunctive treatment for patients with orthodontic fixed appliances, decreased the total treatment time compared to conventional orthodontics. Studies were collected from four electronic databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for systematic reviews. Eligibility criteria were full-text articles in English or Spanish with the design of randomized (RCT), non-randomized clinical trials (non-RCT), and retrospective cohort, without any restriction regarding the publication time, in which the effect of PBM using low-level laser irradiation (LLLI) and light-emitting diode (LED) for the acceleration of the orthodontic movement had been evaluated. Data collection and analysis: Two authors independently extracted data for the characteristics and outcomes of the studies selected for inclusion. The risk of bias (RoB 2 and Robins-I) and the quality assessments (GRADE) were performed. For the quantitative synthesis, the standardized mean difference was calculated for each individual study selected and then the data were combined using a random-effects meta-analysis. The total number of included studies was n = 22 (only RCT and non-RCT were found) with a total of 515 participants. The included studies exhibited high risk of bias and some concerns, though none of them presented a low risk of bias. The quality of the studies was very low. The meta-analysis showed that the means (mm) and 95% confidence intervals (95% CI) of acceleration of tooth movement at 1, 2, and 3 months were 0.50 (- 0.28, 1.28), 1.40 (0.27, 2.53), and 0.46 (- 0.33, 1.24), respectively. The analysis showed that there is no evidence to support the use of LLLI to accelerate the orthodontic movement. LED for the acceleration of orthodontic movement does not have sufficient evidence to generate conclusions about it.

Orthodontically Induced External Apical Root Resorption in Class II Malocclusion

Orthodontic-induced external apical root resorption is one of the idiopathic phenomena as an effect, with force generated through mechanotherapy as the cause and the biological tissues with their diversified variations as witness. It is also classified as iatrogenic as a result of indeterminate application of orthodontic forces with subconscious appreciation of the existing underlying conditions. Numerous factors were identified to relate to this irreversible pathologic condition, but none were proven scientifically. Genetics and salivary markers have proved the reliability with time, but the application became insignificant limiting mostly to the research field. Different assessment methods were also identified to clinically diagnose it both subjectively and objectively. Mostly, it is identified through routine radiographic stage records like orthopantomogram or certain prediction radiographs for root resorption probability assessment like in this case. This case report discusses one such encounter which was experienced after stage 1 and 2 mechanics involving quite a few teeth. Considering the biotype of the individual and tooth morphology, the ongoing treatment was terminated and recovery measures were briefed to uplift the self-esteem of the individual. Furthermore, the prognosis is compromised to be very poor with unpredictability to any other treatment modalities.

Microcracks on the Rat Root Surface Induced by Orthodontic Force, Crack Extension Simulation, and Proteomics Study

Root resorption is a common complication during orthodontic treatment. Microcracks occur on the root surface after an orthodontic force is applied and may be related to the root resorption caused by the orthodontic process. However, the mechanisms underlying root resorption induced by microcracks remain unclear. In this study, a rat orthodontic model was used to investigate the biological mechanisms of root resorption caused by microcracks. First, the first molar was loaded with 0.5-N orthodontic force for 7 days, and microcracks were observed on the root apex surface using a scanning electron microscope. Second, to describe the mechanical principle resulting in microcracks, a finite element model of rat orthodontics was established, which showed that a maximum stress on the root apex can cause microcrack extension. Third, after 7 days of loading in vivo, histological observation revealed that root resorption occurred in the stress concentration area and cementoclasts appeared in the resorption cavity. Finally, proteomics analysis of the root apex area, excluding the periodontal ligament, revealed that the NOX2, Aifm1, and MAPK signaling pathways were involved in the root resorption process. Microcrack extension on the root surface increases calcium ion concentrations, alters the proteins related to root resorption, and promotes cementoclast formation.

Effect of photobiomodulation on external root resorption during orthodontic tooth movement - a randomized controlled trial

OBJECTIVE

The objective of the study was to compare external root resorption during orthodontic tooth movement between patients who were subjected to photobiomodulation and those who were not.

MATERIALS AND METHODS

The study was designed as a split-mouth, single-blind randomized controlled trial conducted on twenty-two orthodontic patients requiring extraction of maxillary first premolars (age group 13-30years). A buccal force was applied to all the premolars using a 0.019″×0.025″ beta-titanium cantilever spring for 28days. The test group premolars were irradiated by indium-gallium-arsenide (InGaAs) diode laser (980nm, 100mW) 0, 3, 7, 11, 15 and 28days after force application. Each premolar was irradiated at ten locations on the buccal and palatal gingiva resulting in a total energy of 10J delivered per tooth. After 28days, the root surface of all the premolars were studied for the number and volume of resorption craters using three-dimensional optical profilometry by a blinded assessor. One-sample Kolmogorov-Smirnov test was used to ascertain normality and Mann-Whitney U test was applied for data analysis.

RESULTS

All twenty-two patients enrolled completed the study. The root surface analysis showed formation of 32.78% less number of resorption craters (P<0.05) and 39.49% less volume of resorption craters (P<0.05) in the test group premolars relative to the control group premolars.

CONCLUSIONS

The results of the present study, therefore, suggest that photobiomodulation reduces external root resorption during orthodontic tooth movement.

TRIAL REGISTRATION/REGISTRATION NUMBER

CTRI/2018/04/013520.

Impact of riboflavin mediated photodynamic disinfection around fixed orthodontic system infected with oral bacteria

PURPOSE

The aim of this laboratory study was to investigate the amount of bacterial destruction through riboflavin mediated photodynamic therapy (PDT) around fixed orthodontic devices by using the two strains of bacteria Streptococcus mutans and Streptococcus sanguinis.

MATERIALS AND METHODS

A total of 80 metallic brackets were divided into four groups consisting of 20 brackets each. Group-I: riboflavin + LED irradiation; Group-II: riboflavin alone; Group-III: immersion in 0.2 % chlorhexidine gluconate solution and Group-IV: not submitted to any treatment. All metallic brackets were immersed in the standard bacterial solutions and incubated at 48 h. All samples were subjected to MTT assay for microbial cell viability testing after treatment. After 24 h of incubation, biofilms adhered on the mesh of metallic brackets after treatment were assessed by confocal laser microscopy. The total CFU/mL was estimated, and the results were log-transformed (log₁₀) and analyzed using one-way analysis of variance and Tukey-Kramer test. P-value was set to <0.05 that indicated statistical significance.

RESULTS

The samples from group-IV showed the highest amount of relative biofilm viability compared to any other group while group-I (PDT) showed the least viability of the two bacterial strains studied (p < 0.05). Group-I showed no significant difference when compared with group-III (chlorhexidine) (p > 0.05). The biofilms on the samples from group-II and group-IV were largely viable indicating thick green staining across the mesh of the brackets. Among the group-III samples, there were predominantly dead cells as compared to the live cell staining. A considerable amount of red staining was observed with noticeable less green staining in group-I samples.

CONCLUSION

This laboratory investigation revealed that riboflavin mediated PDT significantly reduced the amounts of S. mutans and S. sanguinis around the orthodontic brackets.

Effects of different wavelengths of low-level laser therapy on orthodontically induced inflammatory root resorption in rats investigated with micro-computerized tomography

INTRODUCTION

The objective of this research was to investigate the effects of different wavelengths low-level laser therapies on orthodontically induced inflammatory root resorption (OIIRR) during orthodontic tooth movement in rats by micro-computerized tomography.

METHODS

Forty Wistar albino rats were divided into 5 groups: control group (A), 405-nm laser group (B), 532-nm laser group (C), 650-nm laser group (D), and 940-nm laser group (E). The left side of group A was used as a positive control (A-PC), and the right side of group A was used as a negative control (A-NC) group. In all groups, the maxillary left first molars were moved mesially by 50 g of force for 14 days. The lasers were performed for 9 minutes on the maxillary left first molar tooth. At the end of the experimental period, OIIRR measurements were performed at the mesial and the distal sides along the mesial root of the maxillary first molars.

RESULTS

The root resorption volume was significantly lower in group A-NC than in groups A-PC, B, and D. The percentage of root resorption was significantly lower in group A-NC than in all other groups. The root resorption volume and the percentage of root resorption in groups C, D, and E were significantly lower than group A-PC. The depth and the width of the lacuna and even the number of mesial lacunae were similar between groups. The distal and the total lacunae were significantly lower in group A-NC than in all other groups except group C.

CONCLUSIONS

The 532-nm, 650-nm, and 940-nm lasers significantly reduced the volume of OIIRR. In addition, the 532-nm laser reduced the number of lacunae both distally and totally than all the other groups.

Influence of mini-screw implant-assisted intrusion on orthodontically induced inflammatory root resorption: a systematic review

AIM

To systematically review indexed literature related to the influence of mini-screw implant (MSI)-assisted intrusion on orthodontically induced inflammatory root resorption (OIIRR).

METHODS

Indexed databases were searched without time and language restrictions using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The inclusion criteria were: (a) original studies; (b) patients/subjects undergoing MSI-assisted intrusion; and (c) tomographic and/or histological assessment of OIIRR. Letters to the Editor, commentaries, case reports/series, reviews, and studies based on two-dimensional radiographic assessment of OIIRR were excluded. For experimental and clinical studies, the risk of bias assessment was performed using the Systematic Review Centre for Laboratory animal Experimentation risk of bias tool and the Risk of Bias in Non-randomized Studies of Interventions guidelines, respectively.

RESULTS

The initial search yielded 453 studies, out of which 6 (3 clinical and 3 on animal-models) were included. The clinical studies were performed on males and females with a mean age ranging between 16.07 and 25.5 years. Duration of the clinical studies ranged from 3.8 to 9 months. The animal studies were performed on mini-pigs, rats, and dogs. The mean age in the studies on rats and mini-pigs was 2.76 and 18 months, respectively. In the study on canine models, mean age was not reported. In all studies, MSI-assisted intrusion was shown to cause OIIRR. Power analysis was performed in one study. All studies had a moderate risk of bias.

CONCLUSIONS

MSI-assisted intrusion is a risk factor for OIIRR; however, from a clinical perspective, further well-designed and power-adjusted studies are needed.

Chemerin/ChemR23 regulates cementoblast function and tooth resorption in mice via inflammatory factors

BACKGROUND

Periodontitis and orthodontic treatment can lead to inflammatory root resorption (IRR) through an unclear mechanism. Chemerin, a novel chemoattractant protein, is closely associated with inflammation, affects osteoblast and osteoclast differentiation, and may play a role in IRR. We aimed to explore possible roles of the chemerin/ChemR23 interaction in cementoblast function and IRR and reveal a new IRR therapeutic target.

METHODS

Cementoblast function-related gene and protein expression in the immortalized murine cementoblast cell line OCCM-30 after treatment with chemerin and siChemR23 was examined by qRT-PCR and Western blotting.The roles of the MAPK and PI3K-Akt signaling pathways were studied using specific inhibitors. Cementoblast cytokine production under different treatment conditions was measured by ELISA and qRT-PCR. Additionally, we modeled IRR in wild-type and chemerin-overexpressing mice and injected transgenic mice with anti-ChemR23 antibody to block ChemR23. We then calculated the root resorption volume and examined periodontal tissue cathepsin K, Runx2, TNF-α, and IL-6 expression.

RESULT

Chemerin suppressed cementoblast differentiation and mineralization and exerted a proinflammatory effect on cementoblasts. These effects were partially reversed by siChemR23 and reversed to different extents by p38, Erk1/2 and PI3K-Akt pathway inhibition, suggesting p38, Erk1/2 and PI3K-Akt pathways as signaling pathways downstream of chemerin/ChemR23. In vivo, chemerin overexpression worsened IRR. Moreover, chemerin expression was positively correlated with TNF-α, IL-6, and cathepsin K expression and negatively correlated with Runx2 expression. ChemR23 downregulation reversed these effects.

CONCLUSION

Chemerin/ChemR23 induced TNF-α and IL-6 expression dependent on Erk1/2, p38 MAPK and PI3K-Akt signaling pathway activation, thereby regulating cementoblast function and affecting IRR. This article is protected by copyright. All rights reserved.

Orthodontic treatment and root resorption: an overview of systematic reviews

BACKGROUND

Root resorption can be considered the most unfortunate complication of orthodontic treatment.

OBJECTIVE

To evaluate the available evidence regarding orthodontically induced inflammatory root resorption (OIIRR).

SEARCH METHODS

A comprehensive literature search was conducted for the systematic reviews investigating OIIRR published up to 24 May 2020. This was accomplished using electronic databases: MEDLINE via OVID, EMBASE, AMED (Allied and Complementary Medicine Database), PubMed, and Web of Science. Any ongoing systematic reviews were searched using Prospero and a grey literature search was undertaken using Google Scholar and OpenGrey (www.opengrey.eu/). No language restriction was applied.

SELECTION CRITERIA

Only studies investigating OIIRR were included.

DATA COLLECTION AND ANALYSIS

Screening, quality assessment [using the AMSTAR 2 tool (A Measurement Tool to Assess Systematic Reviews)], and data extraction were performed by two authors independently. Information was categorized and narratively synthesized for the key findings from moderate and high-quality reviews.

RESULTS

A total of 2033 potentially eligible studies were identified. After excluding the non-relevant studies, 28 systematic reviews were included. Of which, 20 systematic reviews (71.5%) were of moderate and high-quality level of evidence. The incidence and severity of OIIRR increase with the fixed appliance, especially with heavy force, intrusion, torqueing movements, increased treatment duration, and treatment with extractions or with long apical displacement (particularly for maxillary incisors). There was insufficient evidence regarding most other treatment- and patient-related factors on OIIRR. Following all precautionary measures, pausing treatment and regular monitoring benefits patients with OIIRR.

CONCLUSIONS AND IMPLICATIONS

There is a limited number of high-quality studies in terms of OIIRR. The influence of fixed appliance on root resorption was noted; however, the cause and effect relationship between OIIRR and orthodontic biomechanics has not been confirmed. Avoiding heavy, continuous forces and a greater amount of apical displacement over a long duration of treatment is recommended. Precautionary measures should be carefully considered when treating patients with a high risk of OIIRR.

REGISTRATION

CRD42020166629.

Influence of thyroxine supplementation on orthodontically induced tooth movement and/or inflammatory root resorption: A systematic review

The role of thyroxine administration on orthodontically induced tooth movement and/or inflammatory root resorption remains unclear. The aim was to assess the influence of thyroxine administration on orthodontically induced tooth movement and/or inflammatory root resorption. The study protocol was registered in PROSPERO (CRD42020164151). An electronic search of indexed databases was conducted without time or language restrictions up to and including May 2020. The following eligibility criteria were imposed: (a) original prospective controlled clinical studies and/or experimental studies on animal models; (b) subjects undergoing orthodontic therapy with fixed appliances; (c) presence of a control group [orthodontic tooth movement without thyroxine administration]; and (d) intervention: orthodontic tooth movement with thyroxine administration. Review articles, commentaries, letters to the editor, case reports/series, studies with no control group, cross-sectional studies, retrospective studies and studies where thyroxine was administered along with other interventions such as calcitonin and prostaglandins were excluded. Quality of available evidence and risk of bias within studies were assessed. Any disagreements were resolved via consensus discussions. Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, 8 animal studies were included. Four studies reported that thyroxine administration increases the rate of orthodontic tooth movement; 3 studies did not show a significant difference. Three studies showed that thyroxine administration decreases orthodontically induced inflammatory root resorption; 2 studies found no significant difference. The risk of bias among studies was high. In conclusion, the influence of thyroxine administration on orthodontic tooth movement and/or orthodontically induced inflammatory root resorption in animal models remains unclear.

The effect of a root-dentin pretreatment technique combining PIPS with MTAD aiming to improve the bond strength of glass fiber post

The aim of this study was to evaluate the combined effect of MTAD and photon-induced photoacoustic streaming (PIPS) technique on the smear layer removal and the bond strength of glass fiber post. Fifty-five human mandibular premolars were chosen. After root canal therapy and post space preparation, the teeth were equally divided to five groups according to the methods of root-dentin pretreatment: G1: distilled water (control); G2: 2.5% NaOCl+17% EDTA; G3: MTAD; G4: PIPS; G5: MTAD+PIPS. One sample was randomly selected from each group, and scanning electron microscope (SEM) was used to observe the microscopic morphology of the coronal, middle and apical level of the root-dentin. The remaining ten samples from each group were glued to glass fiber posts, and the bond strength was assessed by push-out test. SEM evaluation showed that the most complete smear layer removal was found in MTAD + PIPS group, especially in coronal third. Push-out test results exhibited that there was a statistically significant interaction between the experimental groups and root canal third (p < .0005). Significant differences could be found among five groups (p < .05): G5 > G4 > G3 > G2 > G1. G5 had the highest bond strength. In conclusion, post space pretreatments with MTAD or PIPS technique can significantly remove smear layer and improve the bond strength of glass fiber post, and combination of them works best.