2019, Number 3
Comparison of external root reabsorption in MBT prescription using conventional versus self-ligating brackets
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Language: English/Spanish [Versión en español]
References: 14
Page: 139-145
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ABSTRACT
Introduction: External root resorption (ERR) is an inflammatory process associated with orthodontic treatment. Among the different risk factors for ERR is the type of fixed device used in bracket prescription. Objective: To compare ERR in patients with MBT prescription using conventional and self-ligating brackets. Material and methods: An observational, comparative, longitudinal study was carried out examining 116 panoramic radiographs of patients with MBT prescription at the Faculty of Stomatology of the Autonomous University of Puebla. Two groups of patients were formed, one using conventional brackets and the other using self-ligating brackets. Root length was measured before the start of the orthodontic treatment and after 18 months. To compare between groups, the Student's t test and Mann-Whitney's U test were used. To determine the difference between the means of the groups, paired Wilcoxon test was used. Tests were interpreted as statistically significant with a p-value less than 0.05. Results: In both the conventional and the self-ligating bracket groups, women represented more than 50% of the population studied (55.8 vs 60.9%, respectively). Patients' ages ranged from 19 to 23 years. No statistically significant difference was found after comparison of ERR between the two groups and the two dental arches; however, the group with conventional brackets showed higher ERR. After comparison between pretreatment measures and those taken after 18 months, both types of brackets showed a statistically significant ERR. Sex and crowding are not related to ERR. Conclusion: ERR was similar in patients with MBT prescription using either conventional or self-ligating brackets.INTRODUCTION
Orthodontic treatment is based on the principle that a prolonged pressure applied to a tooth will cause movement. The bone selectively disappears from some areas and is added to others. When the tooth is overloaded, the force is transmitted to the alveolar bone exceeding the ligament limits and producing deformation. The ligament is adapted to short-lived forces; when the forces are prolonged, the thrust of the tooth against the alveoli generates the start of bone remodeling, even if the force is not very intense. Orthodontic tooth movement is achieved with prolonged and gentle forces. The maximum force for a tooth to move without interrupting capillary irrigation of the periodontal ligament is 26 g/cm2; excessive force produces hyalinization.1 That is, when an excess of force is applied to a tooth, a vascular occlusion is caused and the blood supply to the periodontal ligament is cut off. Afterward, there is no more stimulus to cells in the compressed area of the ligament to achieve differentiation in osteoclasts, and aseptic necrosis occurs.2 A force increase from 20 to 26 g/cm2 leads to periodontal ischemia, which can generate root reabsorption.3
The application of forces on a tooth to produce movement has some risks, such as external root reabsorption (ERR). This condition involves the decrease or shortening of the root apex, which is a pathological process initiated by an external stimulus that advances from cement to dentin and affects the external or lateral surface of a tooth.4
In 16.5% of patients who use or used an orthodontic treatment a root reabsorption of about 1 mm in the upper incisors is observed. Those teeth are the most susceptible to this condition.5
In teeth subjected to orthodontics, ERR originates from biological and mechanical factors. Most studies deny a correlation between root reabsorption and sex, but there are indications that point to women as more likely to experience root reabsorption, possibly from constant hormonal changes.6
Computed axial tomography detects orthodontically induced root resorptions located in vestibular and lingual regions that would not be detected by conventional techniques. Its cost, however, limits its systematic use in clinics and public institutions. On the other hand, periapical radiographs are accurate to determine lesions before treatment and are recommended when the roots are not well observed or other risk factors for root reabsorption coexist. Lastly, panoramic radiographs have been shown to accurately detect lesions at the end of treatment and the cost of the procedure is accessible.7 The observation of periapical lesions on a digital panoramic radiograph yielded a sensitivity of 88.7%, a specificity of 88.6%, a positive predictive value of 92.2%, and a negative predictive value of 83.8%, which are acceptable values.8
Currently, self-ligating stainless-steel brackets are proven to generate lower static and kinetic frictional force compared with conventional stainless-steel brackets, although both have shown increased frictional forces as the arch wire thickness increases.9 The use of self-ligating brackets, coupled with next-generation wires, exerts less force than that generated by a conventional force system. This prevents the appearance of hyalinization areas and indirect reabsorption.10
Pandis et al. compared the reabsorption between self-ligating and conventional treatment but found no difference in the amount of ERR between systems. Age, sex, and extractions were not reliable predictive factors. Nevertheless, he did find a positive association between ERR and treatment duration.11
Herrera et al. compared ERR in Roth and MBT prescriptions. He observed that in both techniques there was ERR in all the teeth, with and without extraction. In both techniques the most affected teeth were the upper incisors. With the MBT prescription, the most affected were central and right lateral teeth in the lower dental arch. However, no correlation existed between ERR and Roth and MBT techniques (p > 0.05) or between ERR and sex (p > 0.05).4
Another study compared the ERR between the standard technique and the MBT technique. In patients treated with the MBT technique, RRE occurred in 18.26% (n = 321) of the treated teeth, while with the other technique it occurred in 14.82% (n = 416) of the analyzed teeth (p < 0.05). Men had a higher rate of ERR compared with women with statistically significant difference (p < 0.05). The study concluded that ERR was higher using the MBT technique than the standard technique.12
Jianru et al. conducted a systematic review and a meta-analysis on ERR comparing self-ligating vs. conventional orthodontic treatment. The ERR of the upper central incisors in the self-ligating bracket group was significantly lower than that in the conventional bracket group (-0.31; 95% CI: -0.60 to -0.01). However, there were no significant differences regarding other teeth. Jianru et al. concluded that evidence was insufficient to assert that treatment with self-linking brackets is better than that with conventional brackets in terms of ERR reduction.13
In all previous studies, measurements were performed using panoramic radiographs; yet, there is only one article comparing the MBT technique on its two aspects, i.e. self-ligating and conventional brackets. Jacobs et al. also compared ERR in self-ligating and conventional systems. They found ERR in 4.5% of patients treated with the conventional system vs. 3.0% of patients treated with the self-ligating system. In total, these authors analyzed 1,704 teeth, of which 1,112 were treated with the self-ligating system, and 0.3% presented ERR, while of 592 teeth treated with the conventional system, 0.5% presented ERR. Jacobs et al. concluded that there was no difference between the two systems regarding the incidence of ERR.14
Orthodontic treatments have as a consequence the occurrence of ERR. It is necessary to know this response in order to act in a timely manner, minimize it, and prevent it from causing irreversible damage. The detection of ERR in early stages is also essential to provide an appropriate and correct follow-up to each case.
ERR is asymptomatic, so neither the patient nor the orthodontist is aware until the affected tooth has mobility, pain, irreversible chronic pulpitis, and even pulp necrosis.
Thus, it is clinically relevant to compare the different bracket options (conventional vs. self-ligating) in the same prescription (MBT).
MATERIAL AND METHODS
The goal of this study was to compare ERR radiographically in patients with MBT prescription using conventional vs. self-ligating brackets.
This was an observational, comparative, longitudinal, retrospective, and homodemic study examining 116 panoramic radiographs of patients who underwent orthodontic treatment at the Faculty of Dentistry of the Benemérita Universidad Autónoma de Puebla. All patients had MBT prescription, using either conventional (n = 52) or self-ligating brackets (n = 64). The researcher's standardization was previously completed. The intraclass correlation was calculated through Cronbach's alpha coefficient (intraobserver 0.89, p < 0.00; and interobserver 0.91, p < 0.00).
Root length was measured before starting orthodontic treatment and 18 months after the brackets were placed on both dental arches. A database was developed in the SPSS program.
Kolmogorov-Smirnov test was used to assess the distribution of variables. Student's t-test and Mann-Whitney's U test were used to compare, between the groups, numeric variables with Gaussian and variables with non-Gaussian distribution, respectively. Wilcoxon test was used to determine the difference between the means of the study groups. P-values less than 0.05 were considered statistically significant.
RESULTS
The description of the population in the two groups was similar in terms of age (19 to 23 years). Dental crowding was also similar between the two groups without statistically significant differences. As for sex, in both groups more than 50% of individuals were women (Table 1).
The comparison of ERR in patients with MBT prescription using conventional vs. self-ligating brackets showed that reabsorption was higher in patients with conventional brackets on both dental arches, and the upper incisors were the most affected. However, there were no statistically significant differences (Table 2).
The comparison of the difference between baseline measurements and measurements after 18 months of starting orthodontic treatment with either conventional or self-ligating brackets showed that ERR was found in both types of fixed appliances, in the upper and lower arches with statistically significant differences (Table 3).
The comparison of ERR by sex in each study group revealed that sex has no impact on ERR, there being no statistically significant differences (Table 4).
DISCUSSION
Pandis et al. compared conventional vs. self-ligating bracket systems and found no statistically significant difference between them. Also, no differences were found by sex to assume that it is a risk factor.11 The same results are reported in this research; we found neither statistically significant differences between the groups nor a significant value when comparing by sex.
Herrera et al. observed in the comparison of two prescriptions, Roth and MBT, that there was ERR in all the teeth. In our investigation, comparing conventional vs self-ligating brackets in MBT prescription, we also found ERR in both groups in all teeth. Herrera et al. reported that the most affected teeth were the upper incisors;4 likewise, in our study, a greater ERR was observed in the upper dental arch with the two types of brackets.
Jianru et al. reported in their meta-analysis that self-ligating brackets cause less ERR compared with conventional brackets.13 Similarly, the present investigation found that the self-ligating system produces less ERR.
Herrera did not find a correlation between ERR and sex, and neither did we. However, Zahed et al. found a higher rate of ERR in men compared with women with statistically significant difference.4,12
Jacobs et al. also compared ERR in MBT prescription with conventional and self-linking brackets and concluded that there is no difference between the two systems.14 We reached the same conclusion in this study; we did not find statistically significant differences between the two systems in MBT prescription.
CONCLUSIONS
- 1. ERR in patients with MBT prescription is similar for both conventional and self-ligating brackets.
- 2. ERR in the use of the two types of brackets showed statistically significant differences in both dental arches, so ERR does not decrease or increase according to the type of brackets used.
- 3. Neither sex nor dental crowding is a risk factor for increased ERR.
REFERENCES
Herrera M, Montesinos A, Meléndez A. Incidencia de reabsorción radicular en pacientes terminados del Departamento de Ortodoncia de la División de Estudios de Postgrado e Investigación de la Facultad de Odontología UNAM, en el periodo 2010-2012. Rev Mex Ortodon. 2015; 3 (3): 176-185. Disponible en: https://www.medigraphic.com/pdfs/ortodoncia/mo-2015/mo153f.pdf.
Cacciafesta V, Sfondrini MF, Ricciardi A, Scribante A, Klersy C, Auricchio F. Evaluation of friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire combinations. Am J Orthod Dentofacial Orthop. 2003; 124 (4): 395-402. Available in: https://www.ncbi.nlm.nih.gov/pubmed/14560269.
Zahed Zahedani S, Oshagh M, Momeni Danaei SH, Roeinpeikar S. A comparison of apical root resorption in incisors after fixed orthodontic treatment with standard edgewise and straight wire (MBT) method. J Dent (Shiraz). 2013; 14 (3): 103-110. Available in: https://www.ncbi.nlm.nih.gov/pubmed/24724131.
AFFILIATIONS
1 Alumno de la Maestría en Ortodoncia Universidad Autónoma De Nuevo León y Docente de la Facultad de Estomatología de la Benemérita Universidad Autónoma de Puebla.
2 Docente de la Facultad de Estomatología de la Benemérita Universidad Autónoma de Puebla.
3 Docente de la Facultad de Odontología de la Universidad Autónoma de Nuevo León.
CORRESPONDENCE
Luis Raúl Cruz Peternell. E-mail: cp-en@hotmail.comReceived: Noviembre 2019. Accepted: Enero 2020.