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.

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.

Predisposing factors for external apical root resorption associated with orthodontic treatment

Objective

This study aimed to identify possible risk factors for external apical root resorption (EARR) in the maxillary incisors after orthodontic treatment.

Methods

The root length of 2,173 maxillary incisors was measured on periapical radiographs of 564 patients who received orthodontic treatment. The Kappa test was performed to evaluate intraexaminer and interexaminer reproducibility. Multiple binary logistic regression was used to determine the association between EARR and various factors. Odds ratios and 95% confidence intervals were reported.

Results

The risk of developing EARR was 70% higher in orthodontic treatment with maxillary premolar extraction (p = 0.004), 58% higher in patients with increased overjet (p = 0.012), 41% lower in two-phase orthodontic treatment (p = 0.037), and 33% lower in patients with deep bite (p = 0.039). The lateral incisors were 54% more likely to develop EARR (p < 0.001), dilacerated roots were 2.26 times more likely to develop EARR (p < 0.001), and for each additional millimeter of root length, the risk of EARR increased by 29% (p < 0.001).

Conclusions

The potential risk factors for EARR after orthodontic treatment included treatment with maxillary premolar extraction, increased overjet at the beginning of treatment, and dilacerated roots.

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.

RANK/RANKL/OPG Signalization Implication in Periodontitis: New Evidence from a RANK Transgenic Mouse Model

Periodontitis is based on a complex inflammatory over-response combined with possible genetic predisposition factors. The RANKL/RANK/OPG signaling pathway is implicated in bone resorption through its key function in osteoclast differentiation and activation, as well as in the inflammatory response. This central element of osteo-immunology has been suggested to be perturbed in several diseases, including periodontitis, as it is a predisposing factor for this disease. The aim of the present study was to validate this hypothesis using a transgenic mouse line, which over-expresses RANK (R^Tg) and develops a periodontitis-like phenotype at 5 months of age. R^Tg mice exhibited severe alveolar bone loss, an increased number of TRAP positive cells, and disorganization of periodontal ligaments. This phenotype was more pronounced in females. We also observed dental root resorption lacunas. Hyperplasia of the gingival epithelium, including Malassez epithelial rests, was visible as early as 25 days, preceding any other symptoms. These results demonstrate that perturbations of the RANKL/RANK/OPG system constitute a core element of periodontitis, and more globally, osteo-immune diseases.

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).

Cellular and Molecular Pathways Leading to External Root Resorption

External apical root resorption during orthodontic treatment implicates specific molecular pathways that orchestrate nonphysiologic cellular activation. To date, a substantial number of in vitro and in vivo molecular, genomic, and proteomic studies have supplied data that provide new insights into root resorption. Recent mechanisms and developments reviewed here include the role of the cellular component-specifically, the balance of CD68⁺, iNOS⁺ M1- and CD68⁺, CD163⁺ M2-like macrophages associated with root resorption and root surface repair processes linked to the expression of the M1-associated proinflammatory cytokine tumor necrosis factor, inducible nitric oxide synthase, the M1 activator interferon γ, the M2 activator interleukin 4, and M2-associated anti-inflammatory interleukin 10 and arginase I. Insights into the role of mesenchymal dental pulp cells in attenuating dentin resorption in homeostasis are also reviewed. Data on recently deciphered molecular pathways are reviewed at the level of (1) clastic cell adhesion in the external apical root resorption process and the specific role of α/β integrins, osteopontin, and related extracellular matrix proteins; (2) clastic cell fusion and activation by the RANKL/RANK/OPG and ATP-P2RX7-IL1 pathways; and (3) regulatory mechanisms of root resorption repair by cementum at the proteomic and transcriptomic levels.