Interleukin-1 Polymorphisms in Relation to External Apical Root Resorption (EARR)

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.

Genetic polymorphisms linked to extreme postorthodontic external apical root resorption in Koreans

BACKGROUND

External apical root resorption (EARR) is a common undesirable outcome of orthodontic treatment, this study aimed to identify genetic polymorphisms associated with the susceptibility to extreme orthodontic-induced EARR in a Korean population using extreme phenotype analysis sampling.

METHODS

Genomic DNA was isolated from the saliva of 77 patients who underwent orthodontic treatment involving two maxillary premolar extractions. The patients were divided into two groups based on EARR values measured on periapical radiographs: The significant resorption group (SG, EARR ≥ 4 mm) and the normal group (NG, EARR < 2 mm). In the NG group, patients with EARR < 1 mm were named the non-resorption group (NonG). Targeted next-generation sequencing was performed using the screened single nucleotide polymorphisms (SNPs), and firth logistic regression analysis was used to determine genetic associations with EARR. Haplotype-based association analysis was performed for specific SNPs.

RESULTS

SNPs related to genes TNFSF11, TNFRSF11B, WNT3A, SFRP2, LRP6, P2RX7, and LRP1 were found to be significantly associated with severe EARR (p < 0.05, pre-Bonferroni correction p-values). Additionally, the haplotype CCA of rs17525809, rs208294, and rs1718119 P2RX7 had a higher frequency in the SG group.

CONCLUSION

Extreme phenotype analysis has identified eleven SNPs related to genes TNFSF11, TNFRSF11B, WNT3A, SFRP2, LRP6, P2RX7, and LRP1 that are associated with severe root resorption in the Korean population. These findings will contribute to the development of predictive diagnostic tools for identifying severe root resorption that may occur during orthodontic treatment.

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).

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.

External apical root resorption after orthodontic treatment: analysis in different chronological periods

Introduction:

External apical root resorption (EARR) is characterized by the definitive loss of tooth root structure, with a higher incidence in lateral and central maxillary incisors.

Objective:

To identify, in different chronological periods, the incidence of EARR in the maxillary incisors (MI) of patients orthodontically treated with or without premolars extraction.

Methods:

Periapical radiographs before and after orthodontic treatment of 1,304 MIs from 326 patients (205 women and 121 men) were evaluated for EARR, divided into five groups, according to the chronological period in which treatments were started: G90) from 1990 to 1994, G95) from 1995 to 1999, G00) from 2000 to 2004, G05) from 2005 to 2009, G10) from 2010 to 2015. The evaluation was performed in each group, in patients who underwent maxillary first premolars extraction and those who did not. For statistical analysis, Fisher’s exact test was used, with a significance level of p < 0.05. The EARR was measured using the adapted Levander and Malmgren classification.

Results:

Incidence of EARR was higher in MIs of patients treated with maxillary premolar extraction (p < 0.05) in two chronological periods (G00 and G10), also being influenced by orthodontic treatments with longer duration, and due to possible individual genetic factors.

Conclusion:

Even with the limitations of a retrospective study, the lack of a defined EARR pattern in the MIs at different chronological periods was larger in the experimental group, due to the sum of factors such as premolars extraction, prolonged orthodontic treatment, possible genetic characteristics, and root shape, without the influence of the sex and age.

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.

Association between Polymorphisms in the IL-1β, TNFRSF11B, CASP1, and IL-6 Genes and Orthodontic-Induced External Apical Root Resorption

Orthodontic-induced external apical root resorption (EARR) is a severe condition affecting the roots of the teeth, whose genetic causes have been inconclusive to date. The aim of the present study was to assess the influence of selected single nucleotide polymorphisms (SNPs) IL-1β, TNFRSF11B, CASP1, and IL-6 genes on post-orthodontic EARR. A sample of 101 patients with clearly assessable orthopantomograms and lateral cephalometric radiographs taken before and at the end of the orthodontic treatment was used to evaluate the presence of EARR. The association between genetic polymorphisms and EARR was assessed with the Chi² test. A binary logistic multi-level model was built to evaluate the ability of patient- and tooth-level variables to predict EARR occurrence. The overall prevalence of EARR resulted to be around 40%. Within the limitations of this study, a significant association was found between EARR presence and the SNP for the IL-1β gene but not for the TNFRSF11B, CASP1, and the IL-6 genes. The final multi-level model demonstrated that the SNP for the IL-1β gene increases the odds of developing EARR by around four times. Since there is currently no accurate method to determine which patients will develop EARR prior to orthodontic treatment, further studies are needed to investigate the predictive ability of further genetic variants on EARR development.

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.

Effect of interleukin-33 on cementoblast-mediated cementum repair during orthodontic tooth movement

OBJECTIVE

This study aims to uncover the role of interleukin-33 on cementoblast-mediated cementum repair.

METHODS

6-8-week-old C57BL/6 mice were used to establish the model of orthodontic tooth movement. Interleukin-33 and suppression of tumorigenicity2 (ST2) expressions were immunohistochemically detected in the periodontal tissue. In vitro, cementoblast-like (OCCM-30) cells were cultured in the presence of recombinant mouse interleukin-33 protein (rmIL-33) at a 1-14 d time frame. ST2 expressions were immunofluorescently labeled and quantitatively examined. The effects of interleukin-33 on cementoblast differentiation, mineralization and proliferation were examined by alkaline phosphatase, alizarin red staining and cell counting kit-8, respectively. To further clarify the effect of interleukin-33 on cementogenesis-related protein expressions, runt-related transcription factor 2 (RUNX2), osterix, osteopontin, bone sialoprotein(BSP), osteocalcin, osteoprotegerin (OPG) and receptor activator of NF-КB ligand (RANKL) expressions were examined by western blot.

RESULTS

Orthodontic load of high magnitude induces external apical root resorption, and increases interleukin-33 expression in the periodontal tissue of mice. Cells in the cementum express ST2. Interleukin-33 initially down-regulates but later recovers ST2 mRNA and protein levels in OCCM-30 cells. Interleukin-33 abates cementoblast differentiation and mineralization, and suppresses RUNX2, osterix, BSP and osteopontin expressions in OCCM-30 cells at the later stage of the culture period. Interleukin-33 enhances RANKL expression, and reduces the ratio of OPG/RANKL in OCCM-30 cells.

CONCLUSION

Orthodontic load of high magnitude induces interleukin-33 expression in the periodontal tissue. Interleukin-33 has a negative effect on cementogenesis via suppressing cementoblast differentiation, mineralization and cementogenesis-related protein expressions.

Association of clinical variables and polymorphisms in RANKL, RANK, and OPG genes with external apical root resorption

OBJECTIVES

The aim of this study was to investigate the association of clinical variables and polymorphisms in the RANKL, RANK, and OPG genes with external apical root resorption (EARR).

METHODS

The sample was composed of 338 unrelated patients of both sexes, average age 14.9 years (range 8-21) with Class II Division 1 malocclusion, orthodontically treated. Periapical radiographs of the maxillary central incisor with the longer root (reference tooth) were taken before treatment and 6 months after starting treatment. DNA was extracted from buccal epithelial cells with the use of 10 mol/L ammonium acetate and 1 mmol/L EDTA. The analysis of 42 polymorphisms in the RANKL, RANK, and OPG genes was performed by means of real-time polymerase chain reaction. Univariate and multivariate analyzes were performed to verify the association of clinical and genetic variables with EARR (P <0.05).

RESULTS

The initial root length and patient age were associated with EARR. Considering the study of polymorphisms of RANKL, no significant association was found of genetic polymorphisms with EARR. For RANK polymorphisms, only rs12455775 was associated with EARR. Regarding OPG polymorphisms, an association of rs3102724, rs2875845, rs1032128, and rs3102728 with EARR was found. After multivariate analysis, the initial root length, rapid maxillary expansion, and rs3102724 of the OPG gene were associated with EARR.

CONCLUSIONS

Longer roots of upper central incisors and rapid maxillary expansion, as well as allele A of the rs3102724 polymorphism of the OPG gene, were associated with EARR in the study population.

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.

Genetic and clinical risk factors of root resorption associated with orthodontic treatment

INTRODUCTION

External apical root resorption (EARR) is a common complication in orthodontic treatment. Despite many studies on EARR, great controversies remain with regard to its risk factors. The objective of this study was to explore the relationship among sex, root movement, IL-1RN single nucleotide polymorphism (SNP) rs419598, IL-6 SNP rs1800796, and EARR associated with orthodontic treatment.

METHODS

Altogether 174 patients (with 174 maxillary left central incisors) were selected for this study. Cone-beam computed tomography was performed before the start of the treatment and at the end of the treatment. Cone-beam computed tomography data were used to reconstruct a 3-dimensional image of each tooth; the volume and the root resorption volume of each tooth were calculated. Three-dimensional matching was used to measure the amount of movement of each root. Genomic DNA was extracted from buccal swabs, and genotypes of SNP rs419598 and SNP rs1800796 of each subject were determined using TaqMan polymerase chain reaction genotyping (Applied Biosystems, Foster City, Calif). The data were analyzed with multiple linear regression analysis.

RESULTS

The statistical analysis indicated no relationship between sex, tooth movement amount, and IL-1RN SNP rs419598 with EARR. The IL-6 SNP rs1800796 GC was associated with EARR, and root resorption differed significantly between SNP rs1800796 GC and CC.

CONCLUSIONS

IL-6 SNP rs1800796 GC is a risk factor for EARR. The amount of root movement, IL-1RN SNP rs419598, and sex as risk factors for EARR need further study.

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).

Pain and Tissue Damage in Response to Orthodontic Tooth Movement: Are They Correlated?

AIM

To evaluate the correlation between pain and tissue damage in response to orthodontic tooth movement (OTM), such as hyalinization and external apical root resorption (EARR).

MATERIALS AND METHODS

The literature review was used as a methodological strategy, following the knowledge development process - constructivist (ProKnow-C). Study axes were defined and keywords that best represented each axis were selected. The terms were submitted to an adherence test and validation, resulting in 12 keyword combinations. Searches were carried out in the most representative databases for the selected terms, without restriction as for language or publication dates. Retrieved studies were filtered using the EndNote X6 program and classified according to analysis of title, abstract, and keywords. The final portfolio of articles was submitted to bibliometric and systematic analysis.

RESULTS

A total of 1,091 studies were retrieved, out of which 719 were repeated and 335 were removed in the classification stage. A total of 37 articles remained in the final portfolio. Only one article was in line with the purpose of this study, indicating absence of correlation between pain and EARR in response to OTM.

CONCLUSION

Further studies are necessary to confirm whether orthodontic pain might serve as a criterion for the use of appropriate mechanical forces, contributing to minimize tissue damage following OTM.

CLINICAL SIGNIFICANCE

This article presents a systematic literature review, in which scientific evidence of the correlation between pain and tissue damage during orthodontic movement was studied, providing a scientific answer for the following question: Is pain reported by patients associated with application of inappropriate orthodontic force? Thus, it aims at aiding the orthodontist in the definition of clinical parameters for the use of optimal orthodontic force.

Genetic determinants and postorthodontic external apical root resorption in Czech children

OBJECTIVE

Genes, involved in the modulation of inflammatory response and bone remodeling, play a role in the development of postorthodontic external apical root resorption (EARR). The aim of our study was to analyze possible associations between seven single nucleotide polymorphisms (SNPs) in interleukin-17A (IL-17), osteopontin (SPP1), purinoreceptor P2X7 (P2RX7), and tumor necrosis factor receptor superfamily member 11B (TNFRSF11B) genes and EARR in children after orthodontic treatment.

SUBJECTS AND METHODS

This case-control study comprised 99 orthodontically treated patients (69 controls and 30 subjects with EARR). Genotype determinations of rs2275913, rs11730582, rs9138, rs208294, rs1718119, rs3102735, and rs2073618 were based on polymerase chain reaction using 5' nuclease TaqMan^® assays.

RESULTS

While no significant differences were observed in allele or genotype frequencies of all seven studied SNPs, specific haplotype of P2RX7 (rs208294 and rs1718119) modified the risk of EARR development (P < 0.05). In addition, the length of treatment with a fixed orthodontic appliance positively correlated with the presence of EARR (P < 0.05).

CONCLUSIONS

Although the effect of individual SNPs studied on the EARR development was not confirmed in the Czech population, complex analysis suggested that variability in the P2RX7 gene and the length of orthodontic treatment may be important factors contributing to the etiopathogenesis of postorthodontic EARR.

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

OBJECTIVE

Interleukin-1 beta (IL1B) pathway is a key player in orthodontic-induced external apical root resorption (EARR). The aim of this work was to identify the genes related to the IL1 pathway as possible candidate genes for EARR, which might be included in an integrative predictive model of this complex phenotype.

MATERIALS AND METHODS

Using a stepwise multiple linear regression model, 195 patients who had undergone orthodontic treatment were assessed for clinical and genetic factors associated with %EARRmax (maximum %EARR value obtained for each patient). The four maxillary incisors and the two maxillary canines were assessed. Three functional single nucleotide polymorphisms (SNPs) were genotyped: rs1143634 in IL1B gene, rs315952 in IL1RN gene, and rs1059703 in X-linked IRAK1 gene.

RESULTS

The model showed that four of the nine clinical variables and one SNP explained 30% of the %EARRmax variability. The most significant unique contributions to the model were gender (P = 0.001), treatment duration (P < 0.001), premolar extractions (P = 0.003), Hyrax appliance (P < 0.001), and homozygosity/hemizygosity for variant C from IRAK1 gene (P = 0.018), which proved to be a protective factor.

CONCLUSION

IRAK1 polymorphism is proposed as a protective variant for EARR.

Genetic and treatment-related risk factors associated with external apical root resorption (EARR) concurrent with orthodontia

OBJECTIVE

As genetic variation accounts for two-thirds of the variation in external apical root resorption (EARR) concurrent with orthodontic treatment, we analyzed the association of selected genetic and treatment-related factors with EARR concurrent with orthodontic treatment.

SETTING AND SAMPLE POPULATION

This case-control study of 134 unrelated, orthodontically treated Caucasian individuals was conducted in part at an Indiana Private Practice, Indiana University and the University of Kentucky.

METHODS

Utilizing a research data bank containing information from ~1450 orthodontically treated patients, pre- and post-treatment radiographs from 460 individuals were evaluated for EARR of the four permanent maxillary incisors. Sixty-seven unrelated Caucasians with moderate to severe EARR were identified and were age-/sex-matched with orthodontically treated Caucasian controls yielding 38 females and 29 males per group. Factors tested for an association with EARR included the following: 1) treatment duration, 2) extraction of maxillary premolars, 3) numerous cephalometric measurements, and 4) DNA polymorphisms within/near candidate genes in a pathway previously implicated in EARR such as the purinergic-receptor-P2X, ligand-gated ion channel 7 (P2RX7; rs208294, rs1718119, and rs2230912), caspase-1 (CASP1; rs530537, rs580253, and rs554344), interleukin-1 beta (IL1B; rs1143634), interleukin-1 alpha (IL1A; rs1800587), and interleukin-1 receptor antagonist (IL1RA; rs419598) genes. Stepwise logistic regression was utilized to identify the factors significantly associated (significance taken at or less than the layered Bonferroni correction alpha) with the occurrence of EARR.

RESULTS

A long length of treatment and the presence of specific genotypes for P2RX7 SNP rs208294 were significantly associated with EARR.

CONCLUSION

EARR occurrence was associated with both genetic and treatment-related variables, which together explained 25% of the total variation associated with EARR in the sample tested.

Association of genetic polymorphism and external apical root resorption

Objective:

To evaluate the relationship between genetic polymorphism and external apical root resorption.

Methodology:

The protocol was prepared and registered on PROSPERO. Two reviewers independently conducted a comprehensive literature search. The MEDLINE, Embase, Cochrane, and PubMed databases were searched. In addition, the bibliographies of all relevant articles and textbooks were manually searched.

Results:

Thirteen studies met the inclusion criteria. Four studies were classified as low-quality studies (score &lt;10), and nine studies were classified as high-quality studies.

Discussion:

The results of the present review suggest that, although some authors have reported that genetic polymorphism may play a role in external apical root resorption, others have not supported this association. Future studies should be more consistent in their research methodologies to determine with clarity whether an association exists.

Conclusion:

Future investigations should include larger sample sizes with matching cases/controls, adjust for confounders, provide power calculation and odds ratios, and report genetic analyses with the Hardy-Weinberg equilibrium. The current investigation suggests guidelines and recommendations for future investigators studying genetic polymorphism in patients undergoing orthodontic treatment.

A study of the interleukin-1 gene cluster polymorphisms and inflammatory external root resorption in replanted permanent teeth

AIM

To investigate whether single nucleotide polymorphisms (SNPs) within the interleukin-1 gene cluster (IL1) are associated with the occurrence and severity of inflammatory external root resorption (IERR) after replantation of avulsed permanent teeth.

METHODOLOGY

Indexes of IERR were radiographically assessed in 182 mature replanted permanent teeth from 146 patients at the onset of endodontic therapy. DNA was extracted from buccal mucosa cells and genotyped using TaqMan probes-based assays for the SNPs IL1A -889C/T (rs 180058), IL1B +3954C/T (rs1143634) and IL1RN +2018C/T (rs419598). Teeth were grouped into two categories: IERR absent to mild (indexes ≤ 4) and moderate to severe IERR (indexes > 4). Genetic variations in the IL1 gene cluster were tested for their effect on the occurrence and extension of IERR using the GEE model (generalized estimation equation). Patient's age at the moment of injury, timing of pulpectomy, extra-alveolar period and storage condition of the avulsed teeth was included as possible confounders.

RESULTS

No association was found between SNPs IL1A -889C/T, IL1B +3954C/T (rs1143634) and IL1RN +2018C/T (rs419598) and IERR indexes. Timing of pulpectomy (OR 3.5 IC 95% 2.0-6.2 P < 0.001) and patient's age at the moment of trauma (OR 0.29 IC 95% 0.12-0.67 P = 0.004) significantly affected the risk of developing severe IERR.

CONCLUSIONS

While timing of pulpectomy and patient's age at the moment of trauma were confirmed as important risk factors, SNPs within the IL1 gene cluster did not affect the susceptibility for IERR after replantation of permanent teeth.

Apical root resorption during orthodontic treatment with aligners? A retrospective radiometric study

Introduction

Objective of this study was to investigate the incidence and severity of apical root resorptions (ARR) during orthodontic treatment with aligners.

Materials and methods

The sample comprised 100 patients (17–75 years of age) with a class I occlusion and anterior crowding before treatment, treated exclusively with aligners (Invisalign®, Align Technologies, Santa Clara, CA, USA). The following teeth were assessed: upper and lower anterior teeth and first molars. Root and crown lengths of a total of 1600 teeth were measured twice in pre- and post-treatment panoramic radiographs. Afterwards, relative changes of the root length during treatment were calculated by a root-crown-ratio taking pre- and post-treatment root and crown lengths into consideration. A reduction of this ratio was considered as a shortening of the initial root length. Additionally, tooth movements of the front teeth were assessed by lateral cephalograms and the 3-dimensonal set up of each patient.

Results

All patients had a reduction of the pre-treatment root length with a minimum of two teeth. On average 7.36 teeth per patient were affected. 54% of 1600 measured teeth showed no measurable root reduction. A reduction of >0%-10% of the pre-treatment root length was found in 27.75%, a distinct reduction of >10%-20% in 11.94%. 6.31% of all teeth were affected with a considerable reduction of >20%. We found no statistically significant correlation between relative root length changes and the individual tooth, gender, age or sagittal and vertical orthodontic tooth movement; except for extrusion of upper front teeth, which was considered as not clinical relevant due to the small amount of mean 4% ARR.

Conclusions

The present study is the first analyzing ARR in patients with a fully implemented orthodontic treatment with aligners (i.e. resolving anterior crowding). The variety was high and no clinical relevant influence factor could be detected. A minimum of two teeth with a root length reduction was found in every patient. On average, 7.36 teeth per patient were affected.

Osteopontin gene SNPs (rs9138, rs11730582) mediate susceptibility to external root resorption in orthodontic patients

OBJECTIVE

External apical root resorption (EARR) is a frequent iatrogenic effect of orthodontic treatment. Substantial variability in responses to postorthodontic EARR has been observed among patients even when similar treatment protocols were used. This observation suggests that environmental and/or genetic variations between individuals may confer susceptibility or resistance to developing EARR. The objective of this study is to determine whether variants in the osteopontin gene, an essential mediator in the odontoclast fusion and attachment process, are positively/negatively associated with postorthodontic EARR.

MATERIALS AND METHODS

Genetic screening of eighty-seven orthodontic patients was performed for two polymorphisms in the osteopontin gene cluster (rs9138 and rs11730582). Subjects were divided into groups, according to the presence or absence of EARR (>2 mm). Genotype distributions and allelic frequencies were calculated using the chi-square test. Logistic regression analysis was used to assess the extent to which clinical-related parameters interfered with the EARR. Odds ratios (OR) and 95% confidence intervals were also calculated.

RESULTS

Data from this study show that subjects heterozygous and homozygous for the most frequent allele of the osteopontin gene at position 89261521 [OR: 0.035 (P = 0.035*) (allele A)] and 89253600 [OR: 0.20 (P = 0.025*) (allele T)], respectively, are protected against postorthodontic EARR. Nevertheless, a highly significant association was found in the comparative analysis of homozygous subjects [2/2 (CC)] for the osteopontin gene (rs9138), resulting in an increased risk of suffering postorthodontic EARR[OR: 4.10; P = 0.045*; CI: 95%]. Subjects who were homozygous [2/2 (CC)] for the osteopontin gene (rs11730582) were more likely, and to a greater extent, to be affected with EARR [OR: 11.68; P < 0.039*; CI: 95%] compared with other genotypes.

CONCLUSION

Variations in the osteopontin gene (rs9138 and rs11730582) are determinants of a genetic predisposition to suffer EARR secondary to orthodontic treatment.

Association analysis of clinical aspects and vitamin D receptor gene polymorphism with external apical root resorption in orthodontic patients

INTRODUCTION

Vitamin D is responsible for the regulation of certain genes at the transcription level, via interaction with the vitamin D receptor, and influences host immune responses and aspects of bone development, growth, and homeostasis. Our aim was to investigate the association of TaqI vitamin D receptor gene polymorphism with external apical root resorption during orthodontic treatment.

METHODS

Our subjects were 377 patients with Class II Division 1 malocclusion, divided into 3 groups: (1) 160 with external apical root resorption ≤1.43 mm, (2) 179 with external apical root resorption >1.43 mm), and (3) 38 untreated subjects. External apical root resorption of the maxillary incisors was evaluated on periapical radiographs taken before and after 6 months of treatment. After DNA collection and purification, vitamin D receptor TaqI polymorphism analysis was performed by polymerase chain reaction-restriction fragment length polymorphism. Univariate and multivariate analyses were performed to verify the association of clinical and genetic variables with external apical root resorption (P <0.05).

RESULTS

There was a higher proportion of external apical root resorption in orthodontically treated patients compared with the untreated subjects. In patients orthodontically treated, age higher than 14 years old, initial size of the maxillary incisor root superior to 30 mm, and premolar extraction were associated with increased external apical root resorption. Genotypes containing the C allele were weakly associated with protection against external apical root resorption (CC + CT × TT [odds ratio, 0.29; 95% confidence interval, 0.07-1.23; P = 0.091]) when treated orthodontic patients were compared to untreated individuals.

CONCLUSIONS

Clinical factors and vitamin D receptor TaqI polymorphism were associated with external apical root resorption in orthodontic patients.

IL1 gene polymorphisms in relation to external apical root resorption concurrent with orthodontia

OBJECTIVE

External apical root resorption (EARR) is permanent shortening of the end of the tooth root. It is a common clinical complication of orthodontic treatment. Polymorphisms in the interleukin 1 (IL1) gene cluster have been related to an increased EARR risk. The aim of this study was to analyze possible associations of IL1 gene variants with EARR in Czech population.

SUBJECTS AND METHODS

In this case-control study, 32 patients with EARR (age 15.0 ± 4.1 years) and 74 controls (age 15.2 ± 5.3 years) were genotyped using PCR-based methods for IL1A (-889C/T), IL1B (+3953C/T), and IL1RN [IL1 receptor antagonist, variable number tandem repeat (VNTR)] gene polymorphisms.

RESULTS

While no statistical significant differences in the IL1A and IL1B genotype, allele and reconstructed IL1 haplotype frequencies between patients with EARR and controls were found, marginally significant differences were observed in the frequencies of IL1RN variant (P = 0.05 for *22 genotype and P = 0.06 for a short (2) allele). In addition, significant associations between IL1RN*12, *22 genotypes and the short (2) allele and EARR were identified in the subgroup of girls (P = 0.04 and P = 0.02, P = 0.02).

CONCLUSIONS

Although no significant role of IL1A (-889C/T) and IL1B (+3953C/T) variants in EARR was confirmed, IL1RN VNTR may be associated with EARR, especially in girls.

Severe external apical root resorption--local cause or genetic predisposition?

BACKGROUND

Current data suggest that a large extent of the variation in orthodontic root resorption may be explained by differences in individual genetic predisposition. This would imply, however, a similar root resorption reaction in all teeth.

OBJECTIVE

To determine the incidence and extent of severe external apical root resorptions (SEARR) in maxillary incisors during multibracket (MB) appliance treatment.

PATIENTS AND METHODS

Of the whole sample of patients having completed MB treatment at the University of Giessen between 1991 and 2010 (P(Total)=3198), all subjects exhibiting severe root resorptions on at least one maxillary incisor were selected. SEARR were defined according to Malmgren et al. [39] (grade-IV RR=resorption >1/3 root length). Evaluation was performed using orthopantomograms from before and after MB treatment. The crown and root length of the affected teeth were measured. The extent of SEARR was assessed taking pretreatment crown length into consideration.

RESULTS

SEARR was detected in 16 patients. Thus, the incidence of SEARR on maxillary incisors during MB treatment totalled 0.5%. The median of SEARR of the affected incisors was 38.6% of the initial root length (minimum=33.4%, maximum=61.0%). Most subjects exhibited only single affected teeth. Only two subjects (0.06% absolute/12.5% relative) presented four maxillary incisors with SEARR.

CONCLUSIONS

The incidence of SEARR on maxillary incisors during MB treatment (0.5%) was very low compared to the literature. With only 12.5% of SEARR patients presenting four affected teeth, local rather than systemic/genetic factors seem to have predisposed the present subjects to SEARR.