Influence of orthodontic treatment on root resorption: a systematic review

 

Influência do tratamento ortodôntico na reabsorção radicular: uma revisão sistemática

 

Luiz Fernando Nogueira de Brito ^I; Tadeu Evandro Mendes ^II; Anderson Paulo Barbosa Lima ^III; Renata Rodrigues de Almeida Pedrin ^IV; Catielma Nascimento Santos ^V; Luiz Renato Paranhos ^VI

 

^I DDS, Private Practice, Três Pontas, MG, Brazil
^II DDS, MSc, Professor, National Higher Education and Post-Graduation Institute Padre Gervásio, Inapós, Varginha, MG, Brazil
^III DDS, Master's student in Orthodontics, Health Sciences Center, Sagrado Coração University, Bauru, SP, Brazil
^IV DDS, MSc, PhD, Professor, Health Sciences Center, Sagrado Coração University, Bauru, SP, Brazil
^V DDS, MSc, Dentist, Department of Dentistry, Federal University of Sergipe, Lagarto, SE, Brazil
^VI DDS, MSc, PhD, Professor, Department of Dentistry, Federal University of Sergipe, Lagarto, SE, Brazil

Endereço para correspondência

 

 

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Abstract

Objective: To perform a systematic review relating the existence of root resorption during orthodontic treatment. Methods: The research was performed in two electronic databases (PubMed and OpenGrey). The OpenGrey database was used exclusively for searching the "grey literature", avoiding selection and publication bias. Eligibility criteria included full texts available online, but with no language restriction. Aiming to work with more current articles on the subject, a filter for the last ten years was applied. Articles that had no direct relation with the main outcome of this study were excluded, as well as clinical case reports and opinions, literature review articles, editorials, and letters to the editor. All eligible studies were assessed for risk of bias and individual quality, and all research steps were performed independently by two eligibility reviewers. Results: Initially, 77 articles were selected, but after the application of exclusion criteria, only 71 were included. Six articles were eligible for qualitative assessment. Overall, incisors are the teeth most affected by root resorption and there is a higher rate of root resorption in retraction mechanics. Conclusion: There is a relationship between root resorption and orthodontic treatment.

Keywords: Orthodontic appliances. Root resorption. Tooth movement.

 

Resumo

Objetivo: realizar uma revisão sistemática relacionando a existência da reabsorção radicular durante o tratamento ortodôntico. Metodologia: a pesquisa foi realizada em duas bases de dados eletrônicas (Pub- Med e OpenGrey). A base OpenGrey foi utilizada, exclusivamente, para captação da "literatura cinza", evitando viés de seleção e publicação. Como critérios de elegibilidade, foram utilizados os textos completos disponíveis on-line, sem restrição de idioma; propondo trabalhar com artigos mais atuais sobre o tema, foi aplicado o filtro para os últimos dez anos. Os artigos que não tinham relação direta com o principal resultado deste estudo foram excluídos, bem como os relatos de casos clínicos e opiniões, artigos de revisão da literatura, os editoriais e as cartas ao editor. Todos os estudos elegíveis foram avaliados quanto ao risco de viés e qualidade individual. Todas as fases da revisão foram realizadas por dois revisores de elegibilidade de forma independente. Resultados: inicialmente, 77 artigos foram indicados, mas, após a aplicação dos critérios de exclusão, apenas 71 foram selecionados. Assim, elegeram-se para avaliação qualitativa seis artigos. De maneira geral, os incisivos são os dentes mais acometidos pela reabsorção radicular, sendo que, em mecânicas de retração, o índice de reabsorção radicular é maior. Conclusão: existe relação entre a reabsorção radicular e o tratamento ortodôntico.

Palavras-chave: Aparelhos ortodônticos. Reabsorção da raiz. Movimentação dentária.

 

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Introduction

Orthodontic treatment is important for aesthetic and functional rehabilitation of the stomatognathic system¹. The mechanical forces promoted by orthodontic therapy may cause undesirable effects, such as apical root resorption. Genetic disposition and individual biological variability are its main causes², and the most affected teeth are upper incisors and bicuspids³. Most resorptions are clinically insignificant; however if achieving a severe level, they threaten the longevity of the affected teeth⁴.

Several studies^3-6 report a correlation between root resorption and orthodontic treatment time. The amount and type of mechanics used are also critical for the presence or absence of root resorption³. Root length is usually measured in order to assess resorption, using periapical radiographs taken with the parallelism technique, since they have a higher level of reliability^4,5,7.

The assessment of incidence and severity of root resorption is essentially important for the stability and longevity of orthodontic treatment. By applying a more simplified orthodontic therapy, orthodontists reveal the concern to reduce the time of treatment and the effect of mechanical forces on teeth, thus preventing root resorption. In this aspect, this study aimed to analyze through a systematic review whether orthodontic treatment is a factor that influences root resorption.

 

Methods

Research strategy for identification of studies and eligibility criteria

Studies reporting the incidence of apical root resorption during orthodontic treatment and assessed by periapical and/or panoramic radiographs were selected. The point of the research was based on the PICO strategy. Eligibility and exclusion criteria are explained in Table 1.

 

 

 

It is a systematic literature review performed in the electronic databases PubMed and OpenGrey. The OpenGrey database was used to search the "grey literature" in order to avoid potential selection bias. The following descriptors were selected with MeSH: "Orthodontic Appliances", "Root Resorption", and "Tooth Movement." The Boolean operators AND and OR were applied to make the combinations.

Titles and abstracts of the identified studies were selected by two eligibility reviewers (L.F.N.B. and A.P.B.L.) working independently. Reviewers were not blinded to the names of authors and journals. The research was performed on December 13, 2014. Table 2 shows the search strategy used.

 

 

 

Titles and abstracts were systematically assessed. Studies rejected in this stage or subsequent stages were recorded in the exclusion table. When studies that were preliminarily included presented insufficient data in the title and abstract for making a clear decision, their full texts were obtained and assessed to determine whether they included all eligibility criteria. If there were questions about study data, the authors were contacted by e-mail for clarification.

Individual quality of the studies

The full texts of all eligible studies were assessed by methodological quality, through the checklist based on 8 criteria, adapted by Cericato et al.⁸ (2015): 1) Adequate study design scores 3 points; 2) Adequate presentation of the objectives scores 1 point; 3) Adequate sample size scores 1 point; 4) Adequate description of the sample selection process and sample loss scores 1 point; 5) Method used to analyze error scores 1 point; 6) Valid statistical method with declared value of p scores 1 point; 7) Clear and objective presentation of the results scores 1 point; 8) Demographic characteristics of the cited studied population score 1 point. The assessment score could range from 0 to 10. The studies were classified as low (score 0-4), moderate (score 5-7), or high (score 8-10) by methodological quality. The studies assessed as low quality (score 0 to 4) were considered methodologically poor and discarded. This entire research stage was analyzed by two eligibility reviewers (L.F.N.B. and A.P.B.L.) In case of disagreement, a third examiner (L.R.P.) was consulted. At this moment, reviewers were blinded to the authors and journals, avoiding any selection bias and conflicts of interest.

Data extraction and analysis

After screening, the full texts of selected articles were re-analyzed using a standardized data extraction sheet, in which authorship, publication year, sample qualification, age, objectives, results, and outcome of the studies were verified.

The process of data synthesis was performed through a descriptive analysis of the studies selected after the previous stage, and the final product of the analysis was presented in narration/ dissertation form.

 

Results

Research strategy and individual quality of the studies

The initial search resulted in a sample of 77 records in PubMed and OpenGrey databases. The main reasons for exclusion were studies not directly related to the primary outcome of the present study (n = 56), clinical case reports (n = 1), literature reviews (n = 12), and editorials and/or letter to the editor (n = 2). Thus, the sample included a number of six articles, as shown in Figure 1.

 

 

 

In assessing the quality of studies, performed according to the aforementioned criteria, no article failed to be considered methodologically as "low quality" (0-4 score). It is worth mentioning the following important characteristic that was evident in the eligible studies: from the six selected articles, only one7 commented on ethical criteria involved in the research.

Included studies and intervention effects

Table 3 explains the studies selected. The studies by Apajalahti & Peltola³ (2007) and Nigul & Jagomagi5 (2006) analyzed root resorption through panoramic radiograph, Mohandesan et al.⁶ (2007), Loenen et al.⁷ (2007), and Ramanathan & Hofman⁹ (2009) assessed root resorption through periapical radiographs, and Jiang et al.⁴ (2010) used both radiographic techniques to assess root resorption.

 

 

 

Some studies^3,5 claim that treatment time directly influences level of resorption and therapy used. Upper incisors showed greater resorption (60%), followed by lower incisors (20%)³.

No level of influence of external factors, such as age, gender, dental position, and time of treatment was statistically significant on root resorption⁵.

Periapical and/or panoramic radiographs were used to predict and anticipate possible root resorption of higher intensity^4,6,7,9. Ramanathan & Hofman⁹ (2009) radiographically assessed root resorption after fixed appliance bonding (T1) and after intrusion and retraction (T2), and found more root resorption in the intrusion and retraction stage when compared to other stages of the treatment.

External root resorption, measured in millimeters over a period of 12 months, confirmed to be greater in upper incisors (11.1 mm for central incisor and 12.7 mm for lateral incisors) when the treatment plan required tooth extractions⁶.

The Tip-Edge™ appliance (Appliance TP Orthodontics, La Porte, Indiana, USA) at T1 (baseline) presented the length of 13 mm for central and lateral incisors, at T2 (after the alignment and leveling stage) of 12.1 mm for central and lateral incisors, and at T3 (after torque stage) of 11.6 mm for central incisors and 11.1 mm for lateral incisors⁷.

 

Discussion

Root resorption in permanent teeth is potentially a scar from orthodontic treatment. Opinions among researchers about the incidence and severity of root resorption assessed during orthodontic treatment are divergent. Root resorption appears to be multifactorial, combined with mechanical effects and a genetic disposition of the individual. Faced with different statements, this study became necessary to clarify whether orthodontic treatment influences dental resorption.

Nigul & Jagomagi⁵ (2006) state that root shape is major for root resorption. It is characterized morphologically and radiographically by a root apex rounding; however, it may present itself in varying levels⁵. Most root resorptions are clinically irrelevant, but if severe, they may influence tooth longevity⁴.

Panoramic and periapical radiographs were used by authors^3-7,9 to assess root resorption and its relation to orthodontic treatment, although some authors⁴ state that teleradiography is the technique with the best location method to compare root length before and after treatment.

The use of panoramic radiographs to assess root resorption and shape presents a few negative points. The use of this technique may maximize the length of root loss by 20 percent⁴. The study described by Apajalahti & Peltola³ (2007) used the measure of root length, and pre- and posttreatment, instead of measuring absolute values of apical root loss. Incisor angulations may change during orthodontic treatment, which may interfere with the measurement of root length in the radiographic image; however, in the panoramic radiograph, buccolingual inclinations intervene in root length only by a limited range of 10 mm, which when interpreted, causes a difference of only five percent³.

In the study by Jiang et al.⁴ (2010), the authors state that there was no statistically significant difference in root resorption between men and women. Nigul & Jagomagi⁵ (2006) found that men present more root resorption, but with no statistically significant differences. Adults had more root resorption than children, but the results were not statistically different⁵.

Intrusion and retraction, whether performed simultaneously or consecutively, do not affect root length9. The authors state that the most causal variable of root resorption in this movement would be the force applied, suggesting that 10 cN per incisor would be ideal. They suggest these claims should be substantiated by further studies⁹.

Although torque is not the only causal aggravating factor to root resorption, it needs to be considered⁷. The authors measured the root length of central and lateral incisors early in the treatment after the alignment and leveling stage, and finally, after the additional stage of torque applications. They concluded that central and lateral incisors had an average root length of 12.1 mm in the alignment and leveling stage. By the end of treatment, central incisors presented an average root length of 11.6 mm and the lateral ones presented an average length of 11.1 mm⁷.

Orthodontic treatment with dental extraction is favorable to root resorption and the pattern of extraction was a significant factor. Orthodontic therapy with four extractions of the first bicuspids presented more root resorptions than patients treated with no extractions⁵. In the study by Jiang et al.⁴ (2010), only anterior and mandibular teeth had a statistically significant correlation with root resorption and extraction.

Patients with longer treatment time presented a higher level of root resorption. The mechanics employed in tooth movement is also a determining factor³. Potential for root resorption tends to vary among patients treated orthodontically, whereas it occurs in a varying level in teeth of the same patient. Individual biological factors, alveolar shape, bone density, vascularity, and tooth structure may explain these characteristics³.

Root shape directly influences the level of resorption. The resorption of small, torn, and pipette-shaped roots is almost twice than for other root shapes⁵. The authors found no association between root resorption and previous history of trauma⁵. Further studies with a larger sample and better definition of the study groups are required to increase the strength of this evidence.

Limitations

A clear limitation of the study is the genetic disposition and individual biological variability of each patient treated orthodontically, considering it may or may not cause root resorption, regardless of the number of predisposing factors^2,3. There may be bias in sample selection when determining an orthodontic therapy with less time (with no extraction)^4,5, since the level of root resorption will be reduced. Another limitation would be the uniformity of the analyzed teeth, in which some authors of this study^5,6 state that incisors are more prone to root resorption. The therapy³ and force used in tooth movement is a variable to be considered⁹. The adequate force used for orthodontic movement without generating iatrogenic root resorption is still uncertain, and new studies should be performed⁹. Developing more uniform studies with similar therapy is required, as well as analyzing numerous brands and models of orthodontic appliances, along with various techniques described in the literature.

 

Conclusion

All studies showed that individuals who were subjected to orthodontic treatment are likely to present root resorption, thus, there is a relationship between root resorption and orthodontic treatment. However, the heterogeneity of the eligible studies was evident, and therefore this conclusion should be interpreted with caution.

 

References

1. Limpanichkul W, Godfrey K, Srisuk N, Rattanayatikul C. Effects of low-level laser therapy on the rate of orthodontic tooth movement. Orthod Craniofac Res 2006; 9(4):38-43.         [ Links ]

2. Weltman B, Vig KWL, Fiels HW, Shanker S, Kaizar EE. Root resorption associated with orthodontic tooth movement: A systematic review. Am J Orthod Dentofacial Orthop 2010; 137(9):462-76.

3. Apajalahti S, Peltola JS. Apical root resorption after orthodontic treatment – a retrospective study. Eur J Orthod 2007; 29(1):408-12.

4. Jiang R, McDonald JP, Fu M. Root resorption before and after orthodontic treatment: a clinical study of contributory factors. Eur J Orthod 2010; 32(1):693-7.

5. Nigul K, Jagomagi T. Factors related to apical root resorption of maxillary incisors in orthodontic patients. Stomatologija 2006; 8(3):76-9.

6. Mohandesan H, Ravanmehr H, Valaei N. A radiographic analysis of external apical root resorption of maxillary incisors during active orthodontic treatment. Eur J Orthod 2007; 29(2):134-9.

7. Loenen MV, Dermaut LR, Degrieck J, De Pauw GA. Apical root resorption of upper incisors during the torquing stage of the tip-edge technique. Eur J Orthod 2007; 29(1):583-8.

8. Cericato GO, Bittencourt MAV, Paranhos LR. Validity of the assessment method of skeletal maturation by cervical vertebrae: a systematic review and meta-analysis. Dentomaxillofac Radio 2015; 44(4):20.140.270.

9. Ramanathan C, Hofman Z. Root resorption during orthodontic tooth movements. Eur J Orthod 2009; 31(1):578-83.

 

 

Endereço para correspondência:
Luiz Renato Paranhos
Al. Jordão de Oliveira, 996
Residencial Vista do Atlântico, ap. 1.402
Bairro Atalaia
49037-330 Aracaju, Sergipe
e-mail: paranhos.lrp@gmail.com

 

Recebido: 14/07/2016
Aceito: 22/09/2016