IRAK1 variant is protective for orthodontic-induced external apical root resorption

Investigation of the association between COX-2 polymorphisms and external apical root resorption in orthodontically treated patients

OBJECTIVE

To evaluate the association between single nucleotide polymorphisms (SNPs) in cyclooxygenase-2 (COX-2) and external apical root resorption (EARR) after orthodontic treatment.

MATERIALS AND METHODS

This study analyzed the orthodontic records of patients from Regensburg University Hospital and two collaborating private practices. EARR was analyzed in the maxillary central incisors and first mandibular molars using pre- and post-treatment cephalometric and panoramic radiographs, respectively. Genomic DNA was obtained from salivary oral cells. Two SNPs in COX-2, rs5275 (3 prime untranslated region variant) and rs689466 (upstream transcript variant, downstream transcript variant), were genotyped using real-time Polymerase chain reaction (PCR). The linear regression models were fitted to assess the effects of the evaluated SNPs at a significance level of 5%.

RESULTS

A total of 143 biologically unrelated patients (mean age: 13.5 ± 4.5 years) were included in the study. The F-test showed that only the regression for EARR in the mandibular molars in the dominant model for rs5275 G allele had a good fit (F = 3.50, P = 0.034). The model showed that individuals carrying at least one G allele for rs5275 had a 17% increase in EARR in the molars compared to common AA homozygotes (exp(B) = 1.17; 95% CI: 1.04, 1.32; P = 0.010). Although an effect of the G allele (rs5275) was detected, this effect did not explain much of the variability in EARR (adjusted R2 = 0.04).

CONCLUSION

The results suggested that patients carrying the polymorphic form of the rs5275 were more likely to have EARR in the mandibular molars; therefore, COX-2 could have an effect on EARR.

CLINICAL RELEVANCE

The knowledge of the genetic background concerning EARR after orthodontic treatment would aid in clinical practice to screen for associated genetic factors and potentially aid its prevention and management, considering that patients' genetic profiles would soon be available.

Genetic polymorphisms in external apical root resorption and orthodontic tooth movements: A systematic review

Objective

External apical root resorption (EARR) is characterized by permanent loss of dental structure at the root apex. This study aimed to systematically review gene polymorphisms associated with EARR in orthodontic patients.

Methods

Electronic database searches were performed across several databases.

Results

This systematic review included 21 studies. Outcome measures were based on tooth dimensions observed on radiographs obtained before and after treatment. Polymorphisms in the following genes were genotyped using polymerase chain reaction-restriction fragment length polymorphism analysis: purinergic-receptor-P2X, ligand-gated ion channel 7 (P2RX7), caspase-1/interleukin-converting enzyme (CASP1/ICE), caspase-5 (CASP5), IL-1beta (IL1B), IL-1alpha (IL1A), interleukin-1 receptor antagonist gene (IL1RN), tissue non-specific alkaline phosphatase (TNSALP), tumor necrosis factor-alpha (TNFα), tumor necrosis factor receptor superfamily gene member 11a (TNFRSF11A), secreted phosphoprotein 1 (SPP1), tumor necrosis factor receptor superfamily gene member 11b (TNFRSF11B), interleukin 17A (IL17), interleukin 6 (IL6), receptor activator of nuclear factor-kappa B (RANK), osteoprotegerin (OPG), stromal antigen 2 (STAG2), vitamin D receptor (VDR), cytochrome P450 family 24 subfamily A member 1 (CYP24A1), cytochrome P450 family 27 subfamily B (CYP27B1), group-specific component (GC), and interleukin-1 receptor-associated kinases 1 (IRAK1).

Conclusions

Almost all studies suggested that IL1 gene is associated with EARR. Additionally, P2RX7 may be an important factor contributing to the etiopathogenesis of EARR. TNFRSF11A, SPP1, IL1RN, IL6, TNFRSF11B, STAG2, VDR, IRAK1, IL-17, CASP1/ICE and CASP5 have been identified in isolated studies. Further observational studies are needed to better explain the association between these genes and EARR.

Bibliometric analysis of publications on genetic polymorphism and external apical root resorption research

OBJECTIVE

This study aimed to analyze the scientific production of genetic polymorphisms and external apical root resorption (EARR) to establish main findings, geographic trends, and research gaps for possible future investigations.

METHODS

Unrestricted publications were searched using the Scopus database (March 2023) to include studies that addressed the association between genetic polymorphisms and EARR. Case-control, cohort, cross-sectional, and review studies were considered eligible. The softwares VOS viewer™ and Bibliometrix were used for data analysis.

RESULTS

Of the 44 studies analyzed, "Iglesias-Linares A" was the most cited author. The University of Seville (Spain) conducted the most research on this topic. Brazil, Spain, and the USA were the leading countries in terms of citations. The most frequent term in the co-occurrence of keywords was "EARR." The journal American Journal of Orthodontics and Dentofacial Orthopedics presented a great relevance in the area, demonstrating a high number of publications. Several genetic polymorphisms have been investigated, with interleukins being the most studied.

CONCLUSION

Endodontics is an area of research that should focus more on root resorption and genetic polymorphisms, as it still underexplored, compared to orthodontics. Polymorphisms have been studied as possible predictors of EARR caused by orthodontic tooth movement. However, the gap in the research indicates a need to search for new genes associated with EARR.

Association of genetic polymorphism of interleukin 1-alpha and interleukin 1-beta with external apical root resorption in orthodontic patients

OBJECTIVE

To assess the allele rs 1143634 in IL-1β and rs1800587 in IL-1α in patients for orthodontically induced external apical root resorption (EARR).

MATERIAL AND METHODS

Intra-oral periapical radiograph (IOPA) of maxillary incisors of 142 Patients were evaluated for resorption at two time points; before the start of fixed mechanotherapy (T1) and after one year of treatment (T2). The individuals with root resorption<2mm were categorized as a control group (group 1; n=90), and resorption>2mm were categorized as case group (group 2; n=52). Buccal swabs of all patients were taken and DNA could be isolated in 95 out of 142 samples (group 1 {n=58}, group 2 {n=37}), which were then screened for the selected two polymorphic targets to determine the nucleotide status of these targets. Tetra-primer ARMS PCR reactions were carried out using all 4 primers for each polymorphism.

RESULTS

rs11800587 was not associated with risk of EARR in any inheritance model. Chi-square test for association of alleles with EARR revealed that rs1143634 was associated with the risk of EARR in an allelic model in such a way that A allele of this SNP increased the risk of EARR 4 folds [OR=4.375; P=0.016]. However, the adjusted level of significance using the Holm-Bonferroni method for rs1143634 was P<0.010 for A and G comparison rendering the results non-significant.

CONCLUSION

SNP rs1143634 and SNP rs11800587 were not associated with risk of EARR in any inheritance model.

Genetic and other factors contributing to external apical root resorption in orthodontic patients

OBJECTIVE

External apical root resorption (EARR) is a multifactorial disorder with adverse clinical outcomes in orthodontic practices often resulting in significant root shortening. This study examined the effect that specific single nucleotide polymorphisms (SNPs) have on the risk of developing EARR in orthodontic patients in X. We also evaluated how other selected patient- and treatment-related factors may contribute to root resorption in these patients.

SETTING/SAMPLE

Patients included in this case-control study were treated at the University of Alabama at Birmingham School of Dentistry, Department of Orthodontics.

METHODS

Panoramic radiographs were used to measure root resorption of the maxillary incisors. EARR was recorded when at least 20% of the root length had been lost with orthodontic treatment. Factors evaluated for association with EARR included ethnicity, sex, age, dental and skeletal classifications, ANB, U1-SN, overjet, treatment type and time, and SNPs in IL-1A (rs1800587), IL-1B (rs1143634), IL-1RN (rs419598), P2RX7 (rs1718119 and rs2230912), IRAK1 (rs1059703) and CASP1 (rs530537, rs580253 and rs554344). Chi-square test, Student's t test, Wilcoxon test, Benjamin-Hochberg false discovery rate (FDR) adjustment and logistic regression were used to analyse the data. The significance level was defined as P < .05.

RESULTS

We found that extraction treatment protocol and dental classification displayed significant association with root resorption. Furthermore, the GG genotype of IL-1A rs1800587 variant (in individuals with an increased overjet) predisposed Caucasians to EARR. While CASP1 (rs530537) variant may contribute to the risk of root resorption, it was not statistically significant after FDR adjustment (P = .09).

CONCLUSIONS

Both patient- and treatment-related factors contributed to EARR.

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).

Targeted next-generation sequencing for comprehensive genetic analysis of external apical root resorption during orthodontic treatment with premolar extraction in the Korean population

INTRODUCTION

External apical root resorption (EARR) is one of the most common unfavorable consequences of orthodontic treatment and causes loss of tooth structure. The present study aimed to investigate the genetics of EARR using next-generation sequencing comprehensively.

METHODS

Targeted next-generation sequencing was performed for comprehensive genetic analysis of 118 Korean orthodontic patients. The patients were divided into 2 groups on the basis of their EARR value. The association of clinical and genetic parameters with EARR was assessed using the χ2 test or t test for matched pairs, followed by Bonferroni correction and linear regression analysis. In addition, haplotype analysis and in silico prediction were conducted to evaluate functional effects.

RESULTS

No statistically significant difference was observed between clinical and treatment-related parameters and EARR. The single nucleotide polymorphisms SPP1 rs9138 (P = 0.001) and SFRP2 rs3810765 (P = 0.04) showed only nominal significance between EARR groups. However, these 2 SNPs were not significant after Bonferroni correction for multiple testing (cutoff P = 0.05/142 = 3.52 × 10-4). Variations in SPP1 rs9138 and SFRP2 rs3810765 may be related to EARR during orthodontic treatment. In summary, not only genes related to inflammatory reactions but also those related to Wnt signaling to affect the degree of EARR during orthodontic teeth movement.

Immune System Acts on Orthodontic Tooth Movement: Cellular and Molecular Mechanisms

Orthodontic tooth movement (OTM) is a tissue remodeling process based on orthodontic force loading. Compressed periodontal tissues have a complicated aseptic inflammatory cascade, which are considered the initial factor of alveolar bone remodeling. Since skeletal and immune systems shared a wide variety of molecules, osteoimmunology has been generally accepted as an interdisciplinary field to investigate their interactions. Unsurprisingly, OTM is considered a good mirror of osteoimmunology since it involves immune reaction and bone remolding. In fact, besides bone remodeling, OTM involves cementum resorption, soft tissue remodeling, orthodontic pain, and relapse, all correlated with immune cells and/or immunologically active substance. The aim of this paper is to review the interaction of immune system with orthodontic tooth movement, which helps gain insights into mechanisms of OTM and search novel method to short treatment period and control complications.

Influence of clinical factors on the protective or deleterious impact of genetic variants in orthodontically induced external root resorption: an observational study

BACKGROUND

Prediction of susceptibility to Orthodontically Induced External Apical Root Resorption (OIEARR) has been hampered by the complex architecture of this multifactorial phenotype. The aim of this study was to analyze the impact of the interaction of multiple variables in the susceptibility to OIEARR.

METHODS

The study evaluated 195 patients requiring orthodontic treatment. Nine clinical and treatment variables, single nucleotide polymorphisms (SNPs) from five genes and variables interactions were analyzed as risk factors for OIEARR using a multiple linear regression model.

RESULTS

The model explained 29% of OIEARR variability (ANOVA: p < 0.01). Duration of treatment was the most important predictor and gender was the second, closely followed by premolar extraction. For genes encoding osteoprotegerin (OPG), the receptor activator of nuclear factor κ B (RANK) and the IL1 receptor antagonist (IL1RN), the effect of analyzed variants changed from protective to deleterious depending on the duration of treatment and the age of the patient.

CONCLUSIONS

This work shows that in OIEARR the impact of genetic susceptibility factors is dynamic changing according to clinical variables.

Orthodontic root resorption

External apical root resorption (EARR) is one of the most frequently reported iatrogenic side effects of orthodontic movement. Nevertheless, no robust and unequivocal scientific evidence is yet available in the literature regarding the clinical and biological factors that trigger EARR. The purpose of the present position paper is to provide clinicians, residents, and investigators a summary of our current understanding about root resorption caused by orthodontic tooth movement, based on up-to-date available scientific evidence. Morphological, structural, biomechanical, and biological differences account for predisposing the apical third to EARR compared to other root surfaces during orthodontic treatment. In addition, a relevant number of patient and treatment-related factors increase risk of EARR. The main patient-related factors are reviewed and discussed: genetic factors, tooth anatomy, demographic factors, malocclusion factors, previous endodontic treatment, medical history, short root anomaly. Similarly, the influence of treatment-related factors are analyzed with regard to the effect of: biomechanical factors, type of orthodontic appliance, adjunctive therapies to accelerate tooth movement, early treatment, maxillary expansion, teeth extractions, the duration of treatment and the amount of apical displacement. Clinical management of EARR from pre-treatment records to the monitoring strategy as well as recommendations for the post orthodontic-treatment period are presented as a guide for the clinician. Despite years of studies, we still do not fully understand EARR, but the future is promising. True three-dimensional imaging with higher resolution and low radiation, and predictive tools towards an earlier detection without radiographs, will mark future developments in the field of EARR in orthodontics.

Genetic variation involved in the risk to external apical root resorption in orthodontic patients: a systematic review

OBJECTIVE

To perform a systematic review/meta-analysis to elucidate the scientific basis for the association between genetic variations and risk of external apical root resorption (EARR) in orthodontic patients.

MATERIALS AND METHODS

Four databases (PubMed, Web of Science, Scopus, LILACS) were electronically searched until November 22, 2020, followed by manual and gray literature search. Case-control or cross-sectional studies that evaluated genes involved in the susceptibility of orthodontic patients to EARR were eligible. Two reviewers applied the inclusion and exclusion criteria, extracted qualitative data, as well as assessed methodological quality using instrument proposed for genetic studies. For synthesis results, narrative and quantitative data (meta-analysis) were performed. The certainty of the evidence was tested using the GRADE Working Group approach.

RESULTS

Of 201 articles in total, 16 studies were included in the review. Of these, 11 presented moderate and 5 of high methodological quality. In the narrative analysis, from 16 studies, 15 studies (10 genes) showed a significant association with EARR and 9 studies were included in the meta-analysis. Only the polymorphism rs208294 in P2RX7 (dominant model) was associated with EARR (OR = 0.52, 95%CI = 0.29-0.95, p = 0.03) and presented a very low certainty of the evidence.

CONCLUSION

Narrative analyses of individual studies demonstrated an association of many genes. The number of studies for each genetic variation was very low, and methodological heterogeneity between the studies was observed. Quantitative analyses (meta-analysis) could only show an involvement for P2RX7 (rs208294) in the risk of orthodontic patients to EARR at a very low certainty of evidence. (CRD42018085411).

CLINICAL RELEVANCE

The knowledge regarding the molecular aspects involved in the etiology of EARR will allow orthodontists to use a personalized treatment and early diagnosis of risk patients. This systematic review demonstrates that more studies are necessary to unravel the role of genetic variation for patients' risk to EARR during orthodontic tooth movement.

External apical root resorption in orthodontic patients: molecular and genetic basis

External apical root resorption is one of the most deleterious complications after orthodontic treatment. Studies to explain the causal relationship between orthodontic tooth movement and external apical root resorption have been inconclusive till date. Individual variations in external apical root resorption sometimes overshadow the treatment related factors which indicate genetic predisposition and/or multifactorial etiology. Mechanism of root resorption is not completely understood. Inflammatory root resorption induced by orthodontic treatment is a part of process of elimination of hyaline zone. An imbalance between bone resorption and deposition may contribute to root resorption by the cementoclasts/osteoclasts. This narrative review article explains the molecular pathway involved in external apical root resorption and also role of various genes involved at different level. It also reviews the literature published during the past 20 years concerning the association studies linking EARR to genetic polymorphisms. This literature review provides an insight into genetic predisposition of external apical root resorption that can be used in orthodontic practice to enable 'high-risk' subjects to be identified on the basis of their genetic information before orthodontic treatment is initiated.

GWAS of Post-Orthodontic Aggressive External Apical Root Resorption Identified Multiple Putative Loci at X-Y Chromosomes

Personalized dental medicine requires from precise and customized genomic diagnostic. To conduct an association analysis over multiple putative loci and genes located at chromosomes 2, 4, 8, 12, 18, X, and Y, potentially implicated in an extreme type of external apical root resorption secondary to orthodontic forces (aEARR). A genome-wide association study of aEARR was conducted with 480 patients [ratio~1:3 case/control]. Genomic DNA was extracted and analyzed using the high-throughput Axiom platform with the GeneTitan^® MC Instrument. Up to 14,377 single nucleotide polymorphisms (SNPs) were selected at candidate regions and clinical/diagnostic data were recorded. A descriptive analysis of the data along with a backward conditional binary logistic regression was used to calculate odds ratios, with 95% confidence intervals [p < 0.05]. To select the best SNP candidates, a logistic regression model was fitted assuming a log-additive genetic model using R software [p < 0.0001]. In this sample the top lead genetic variants associated with aEARR were two novel putative genes located in the X chromosome, specifically, STAG 2 gene, rs151184635 and RP1-30E17.2 gene, rs55839915. These variants were found to be associated with an increased risk of aEARR, particularly restricted to men [OR: 6.09; 95%CI: 2.6–14.23 and OR: 6.86; 95%CI: 2.65–17.81, respectively]. Marginal associations were found at previously studied variants such as SSP1: rs11730582 [OR: 0.54; 95%CI: 0.34–0.86; p = 0.008], P2RX7: rs1718119 [OR: 0.6; 95%CI: 0.36–1.01; p = 0.047], and TNFRSF11A: rs8086340 [OR: 0.6; 95%CI: 0.38–0.95; p = 0.024]), found solely in females. Multiple putative genetic variants located at chromosomes X and Y are potentially implicated in an extreme phenotype of aEARR. A gender-linked association was noted.

Effectiveness of Low-Level Laser Therapy during Tooth Movement: A Randomized Clinical Trial

The present study evaluated the effects of low-level laser therapy (LLLT) by means of a diode laser in accelerating orthodontic tooth movement (OTM). After extraction of the first upper premolars for orthodontic purpose, 82 maxillary canines which needed distalization were analyzed in 41 enrolled patients (21 males, 20 females, mean age 13.4 ± 2.1 years). On all experimental sites, an orthodontic force of 50/N was applied by a nickel-titanium (NiTi) closed coil spring (G&H, Franklin, IN, USA) in order to obtain the space closure. Using a split mouth randomized design, the test side was treated using a diode laser (Wiser Laser Doctor Smile, Brendola, Italy) operating at 810 nm wavelength in continuous wave mode at both the buccal and palatal side on three points/side (distal, medial and mesial) (1 W output power, continuous wave of 66.7 J/cm2, energy density of 8 J) at baseline and at 3, 7, and 14 days and every 15 days until the space closed. On the control side, the opposite selected canine was treated only using orthodontic traction. The primary outcome chosen was the overall time needed to complete the levelling and closing space, measured on a study cast. The secondary outcome chosen was the evaluation of pain levels related to tooth traction, using a Visual Analogue Scale (VAS), recorded at 3, 7, and 14 days after treatments. The mean space closures of the maxillary canines were comparable between groups [Test, 4.56 mm (95% CI 3.9-4.8); Control, 4.49 mm (95% CI 3.8-4.7), p = 0.456]. The laser group yielded less mean time [84.35 ± 12.34 days (95% CI 79.3-86)] to accomplish space closure compared to the control group [97.49 ± 11.44 days (91.7-102.3)] (p < 0.001). The test side showed a significant reduction in the average range of dental pain at 3 [Test, 5.41 (95% CI 5.1-5.6); Control, 7.23 (95% CI 6.9-7.6), p < 0.001], 7 [Test, 4.12 (95% CI 3.8-4.7); Control, 5.79 (95% CI 5.4-5.8), p < 0.001], and at 14 days [Test, 2.31 (95% CI 1.8-2.3); Control, 3.84 (95% CI 3.3-4.2), p < 0.001] after treatment (p < 0.001). This study demonstrates that the use of LLLT therapy was effective in accelerating tooth movement and reducing pain levels related to OTM.

Association between genetic polymorphisms and external apical root resorption: A systematic review and meta-analysis

Objective

To date, only a few studies have investigated the relationships between genetic polymorphisms and external apical root resorption (EARR). Hence, the aim of this systematic review was to explore the relationship between different gene polymorphisms and their association with EARR.

Methods

A complete literature search was conducted by two independent reviewers. The PubMed, Science Direct, and Scopus databases were searched. In addition, the bibliographies of all textbooks and relevant articles were searched manually. A meta-analysis was performed using data entered into the electronic databases until February 28, 2017.

Results

On the basis of the search, we identified 17 and 7 publications for the systematic review and meta-analysis, respectively. Odds ratio (OR) was used to evaluate the association of the interleukin 1B (+3954) polymorphism and the risk of EARR. The overall OR from the studies was used to estimate the risk of EARR. However, no association was found and no publication bias was apparent for the risk of EARR in patients receiving orthodontic treatment.

Conclusions

More research on the relationship between gene polymorphism and EARR is necessary to determine better specificity of possible interactions.

Heredity, Genetics and Orthodontics - How Much Has This Research Really Helped?

Uncovering the genetic factors that correlate with a clinical deviation of previously unknown etiology helps to diminish the unknown variation influencing the phenotype. Clinical studies, particularly those that consider the effects of an appliance or treatment regimen on growth, need to be a part of these types of genetic investigations in the future. While the day-to-day utilization of "testing" for genetic factors is not ready for practice yet, genetic testing for monogenic traits such as Primary Failure of Eruption (PFE) and Class III malocclusion is showing more promise as knowledge and technology advances. Although the heterogeneous complexity of such things as facial and dental development, the physiology of tooth movement, and the occurrence of External Apical Root Resorption (EARR) make their precise prediction untenable, investigations into the genetic factors that influence different phenotypes, and how these factors may relate to or impact environmental factors (including orthodontic treatment) are becoming better understood. The most important "genetic test" the practitioner can do today is to gather the patient's individual and family history. This would greatly benefit the patient, and augment the usefulness of these families in future clinical research in which clinical findings, environmental, and genetic factors can be studied.

External apical root resorption concurrent with orthodontic forces: the genetic influence

Root resorption is a pathological process of multifactorial origin related to the permanent loss of dental root structure in response to a mechanical, inflammatory, autoimmune or infectious stimulus. External apical root resorption (EARR) is a frequent clinical complication secondary to orthodontic tooth movement; apart from variables related to treatment, environmental factors and/or interindividual genetic variations can confer susceptibility or resistance to its occurrence. In this context, genetic predisposition has been described as an etiological factor, together with mechanical factors derived from orthodontic treatment. In recent years, international research groups have determined the degree of influence of some genetic biomarkers in defining increased/reduced susceptibility to postorthodontic EARR. The influences of the IL1 gene cluster (IL1B, IL1A, IL1RN, IL6), P2RX7, CASP1, OPG (TNFRSF11B), RANK (TNFRSF11A), Osteopontin (OPN), TNFα, the vitamin D receptor (TaqI), TNSALP and IRAK1 have been analyzed. The objective of the present review study was to compile and analyze the latest information about the genetic background predisposing to EARR during orthodontic treatment. Genetics-based studies along with other basic science research in the field might help to clarify the exact nature of EARR, the influence of genetic inheritance and possibly lead to the prevention or even eradication of this phenomenon during orthodontic treatment.

Bone Density and Dental External Apical Root Resorption

When orthodontic patients desire shorter treatment times with aesthetic results and long-term stability, it is important for the orthodontist to understand the potential limitations and problems that may arise during standard and/or technology-assisted accelerated treatment. Bone density plays an important role in facilitating orthodontic tooth movement (OTM), such that reductions in bone density can significantly increase movement velocity. Lifestyle, genetic background, environmental factors, and disease status all can influence a patients' overall health and bone density. In some individuals, these factors may create specific conditions that influence systemic-wide bone metabolism. Both genetic variation and the onset of a bone-related disease can influence systemic bone density and local bone density, such as observed in the mandible and maxilla. These types of localized density changes can affect the rate of OTM and may also influence the risk of unwanted outcomes, i.e., the occurrence of dental external apical root resorption (EARR).