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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 8  |  Issue : 3  |  Page : 157-162

Comparison of apical resorption of endodontically treated teeth before and after orthodontic movement with clear aligner: A preliminary radiometric study


1 College of Dentistry, Riyadh Elm University, Riyadh, Saudi Arabia
2 Department of Preventive Dental Science, Security Forces Hospital, Riyadh, Saudi Arabia

Date of Submission19-Sep-2021
Date of Decision06-Oct-2021
Date of Acceptance19-Oct-2021
Date of Web Publication30-Dec-2021

Correspondence Address:
Deema Ali Alshammery
Department of Preventive Dental Science, College of Dentistry, Riyadh Elm University, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjoralsci.sjoralsci_48_21

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  Abstract 


Introduction : Patients treated with orthodontics show short root due to apical root resorption.
Aim: The aim of the study was to compare the external apical root resorption (EARR) of endodontically treated teeth before and after orthodontic movements using clear aligner therapy.
Materials and Methods: The study group comprised 22 class I adult healthy patients with a mean age of (28 ± 8.2) years treated with clear aligner therapy. Thirty-four endodontically treated teeth (maxillary incisors and molars) were measured for the extent of the EARR in panoramic radiographs at the beginning and at the end of clear aligner therapy. Root resorption was measured using an electrical digital caliper (Mitutoyo Manufacturing Co. Ltd., Tokyo, Japan) on the dental panoramic radiographs from the mesial cusps of the first molar tooth to the apex of the root, and from the incisal edge to the apex of the root for the central incisors.
Results and Discussion: All the endodontically treated teeth demonstrated reduction in pretreatment root length. Less than one percent of EARR was found in 4 teeth, and 1%–4.9% of the EARR was observed in 23 teeth. Six teeth showed EARR of 5–7.9 while only one tooth EARR in the range of 8–10. A pretreatment versus posttreatment comparison of median root lengths of #16, #26, #36, and #46 showed a statistically significant difference (P < 0.05). The mean differences of root lengths after clear aligner therapy among different teeth showed no significant difference (P = 0.981).
Conclusion: All the endodontically treated teeth showed minimal external root resorption after orthodontic treatment with a clear aligner.

Keywords: Clear aligner, endodontic, external apical root resorption, orthodontic


How to cite this article:
Alshammery DA, Alabdulkarim A, Alkanhal N, AlTammami M. Comparison of apical resorption of endodontically treated teeth before and after orthodontic movement with clear aligner: A preliminary radiometric study. Saudi J Oral Sci 2021;8:157-62

How to cite this URL:
Alshammery DA, Alabdulkarim A, Alkanhal N, AlTammami M. Comparison of apical resorption of endodontically treated teeth before and after orthodontic movement with clear aligner: A preliminary radiometric study. Saudi J Oral Sci [serial online] 2021 [cited 2022 May 20];8:157-62. Available from: https://www.saudijos.org/text.asp?2021/8/3/157/334300




  Introduction Top


External apical root resorption (EARR) is the irreversible loss of cementum from the apex of the tooth root, resulting in reduced tooth length and tooth mobility. It is an iatrogenic consequence of orthodontic therapy.[1],[2],[3],[4] Orthodontic root resorption is a kind of pathological root resorption that is caused by an inflammatory reaction surrounding the tooth root.[5] Past studies have reported that the EARR is more than 90% with orthodontic movements.[2],[6] The etiology of EARR is not completely understood, and multiple factors affect the external resorption such as anatomical features, orthodontic mechanotherapy, genetic predisposition, and individual susceptibility.[2],[5]

The EARR frequently occurs after orthodontic movement, and the mean score of shortening ranges from 0.5 to 3 mm, and it could be affected by some clinical factors such as root shape, treatment type, force application, gender, age, and type of malocclusion type.[7],[8],[9]

Brezniak and Wasserstein classified EARR induced by orthodontic movement into three severity levels: Cemental with repair (surface resorption) the resorption occurs on the outer cemental layers, and they are later completely repaired, Dentinal resorption with repair (deep resorption) the process of resorption progress through the cementum and external layers of the dentin and is repaired with cementum material and circumferential resorption in which the root shortening is evident, causing the resorption to involve the hard tissue of the apex. No regeneration is possible when the root loses apical material beneath the cementum.[10] Root resorption shows on the radiograph after 3–4 months of treatment, but it starts within 2–5 weeks.[6] Previous studies have reported that the maxillary central incisors are more prone to resorption.[11]

In recent years, clear aligners are widely used in orthodontic clinics. Some advantages of a clear aligner are better esthetics, comfort, shorter treatment time with an average duration of 1–2 years.[12] Furthermore, one of the advantages of a clear aligner over fixed appliances is that it can be removed before eating and tooth brushing. As a result, intermittent forces exerted on the teeth allow healing of the cementum during the absence of force.[13],[14] compared to fixed appliances where continuous force is applied to the teeth.[14]

Previous studies have reported that the clear aligners produced a similar or higher incidence of EARR than the conventional fixed appliance in vital teeth.[11],[12] However, a few reports suggested that the endodontically treated teeth exhibited less resorption than the vital teeth following orthodontic movement.[15],[16] Further elucidation of root resorption of endodontically treated teeth following orthodontic treatment using a clear aligner is needed. Hence, the objective of the present study was to compare the EARR of endodontically treated teeth before and after orthodontic movements using clear alignertherapy.


  Materials and Methods Top


Study design and setting

A retrospective radiometric study was conducted in the orthodontic clinics of Riyadh Elm University Hospital, Riyadh, Saudi Arabia. This study was conducted from September 2019 to March 2020.

Ethical approval

The institutional review board of Riyadh Elm Research Center formally approved the study (RC/IRB/2019/268).

Study sample

A convenience sampling methodology was employed to select the study participants who have received Invisalign treatment in the orthodontic division of Riyadh Elm University Hospital, Riyadh, Saudi Arabia.

Sample size

A sample of 34 endodontically treated teeth of male and female patients who have received clear aligner therapy was calculated based on an assumed effect size of 0.5, the alpha error probability of 0.05, and a power of the study 0.80 for the Wilcoxon signed-rank test (matched pairs).

Inclusion criteria

  • Patients treated with Invisalign within the Orthodontic clinics of Riyadh Elm University Hospital
  • Adult patients above the age of 18 years
  • Orthodontic cases treated for Class I malocclusion
  • Absence of any medical complications
  • Patients who had the previous endodontically treated central incisors or 1st molar. Orthodontic treatment and duration of the treatment not exceeding 18 months.


Exclusion criteria

  • Cases with the previous history of dental trauma
  • History of root resorption or severe tooth dilacerations
  • Nonendodontically treated teeth
  • Crown or root fractures. Genetic or developmental anomalies of teeth and
  • Congenitally missing laterals.


Measurement of root resorption

The dental panoramic radiographs obtained at the beginning of treatment and after orthodontic treatment using Orthopantomogram (Planmeca OP 2, OP 3, or Cranex DC, Charlotte, USA) were utilized to record the root resorption. Teeth with straight roots were selected to avoid measurement errors. Root resorption was measured using an electrical digital caliper (Mitutoyo Manufacturing Co. Ltd., Tokyo, Japan) on the dental panoramic radiographs from the mesial cusps of 1st molars tooth to the apex of the root and from the incisal edge to the apex of the root for the central incisors. Pretreatment and posttreatment difference in root length measurements was quantified as EARR [Figure 1] and [Figure 2].
Figure 1: Pretreatment measurement of root length

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Figure 2: Posttreatment measurement of root length after Invisalign treatment

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Intra-examiner reliability was established by comparing the difference between the first and the second measurements recorded by a single examiner (DA) between 10 days intervals on a similar sample of panoramic radiographs. The inter-examiner reliability between the two examiners was obtained through intra-class correlation. The measurement was taken in a random sequence of panoramic radiographs by two clinicians (AA, NK) to avoid errors from distortion.

Statical analysis

Data analysis was performed by using the IBM-SPSS software program (version 25 Armonk: New York: USA). Inter-examiner reliability was examined by intra-class correlation tests at pre and posttreatment data between examiners. Normality tests indicated the nonnormal distribution of the data (P < 0.05). A descriptive statistic of mean, standard deviation, median, maximum, and minimum root resorption values were recorded for pretreatment and posttreatment panoramic radiographs. An overall and individual root resorption data of before and after treatment were compared using the Wilcoxon-Signed rank test. A value of P < 0.05 was considered significant for all statistical tests.


  Results Top


A high degree of reliability was found between two examiners at pre-and post-measurements of the apical root. The average measure (Intra Class Correlation) ICC was found to be 0.998 with a 95% confidence interval from 0.997 to 0.999 (F = 603.157, P < 0.001) with the pretreatment examination. Similarly, a high degree of reliability was observed between the two examiners posttreatment examination of the panoramic radiographs between the examiners two examiners. The average measure ICC was 0.999 with a 95% confidence interval from 0.998 to 1.00 (F = 1109.972, P < 0.001) [Table 1].
Table 1: Intraclass correlation coefficient between the first and second examiner

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The study group comprised 22 Class I adult healthy patients with a mean age of (28 ± 8.2) years treated with clear aligner therapy. Panoramic radiographs of 34 endodontically treated teeth were measured for the extent of the EARR. The right mandibular first molar teeth #46 (n = 15), followed by left maxillary first molar #26 (n = 7), mandibular left first molar #36 (n = 5), maxillary right first molar #16 (n = 5), and left maxillary central incisors #21 (n = 2) were included in this study. Descriptive statistics of median, mean and standard deviation values of EARR at pre/post clear aligner therapy are displayed in [Table 2] and [Figure 3].
Table 2: Comparison of Individual tooth root resorption in pre- and post-treatment

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Figure 3: Pretreatment and Posttreatment root lengths of teeth with clear aligner therapy

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A pretreatment versus post treatment comparison of median root lengths of #46 (27.75 vs. 27.58, Z = −3.408, P = 0.001), #36 (26.68 vs. 25.63, Z = −2.032, P = 0.042), #26 (25.68 Vs. 24.24, Z = −2.366, P = 0.018), #16 (24.25 vs. 24.02) showed a statistically significant difference [Table 2].

Nonparametric Kruskal-Wallis test was applied to compare the mean differences of root lengths after Clear aligner therapy among different teeth showed no significant difference (P = 0.981) [Table 3].
Table 3: Comparison of mean differences root resorption among different tooth types

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An overall comparison of pretreatment versus posttreatment median lengths of roots of studied teeth after clear aligner therapy demonstrated a statistically significant difference (26.87 vs. 25.71, Z = −5.087, P < 0.001), suggesting EARR [Table 4]. The percentage distribution of EARR varied across different teeth. Less than one percent of EARR was found in 4 teeth, and 1%–4.9% of the EARR was observed in 23 teeth. Six teeth showed EARR of 5–7.9 while only one tooth EARR in the range of 8–10 [Table 5].
Table 4: Overall comparison of pretreatment vs posttreatment root resorption

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Table 5: Percentage distribution of external apical root resorption

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  Discussion Top


EARR is common during orthodontic treatment and has a detrimental impact on patients' quality of life as well as the treatment outcome. Clear aligners have grown in popularity,[17] and a high level of awareness is reported among Saudis as an orthodontic treatment option.[18] However, EARR during clear aligner therapy is not well understood with endodontically treated teeth. Unlike previous studies that were focused on EARR with conventional orthodontic treatment, this study focused on EARR on endodontically treated teeth that received clear aligner therapy. However, this study did not separate the data on gender and age since previous studies on root resorption showed that gender and age were not potentially confounding factors.[11],[19]

A total of 76 teeth were assessed for eligibility in this study, but 42 of them were excluded because they did not meet the criteria. However, it was difficult to find a patient who had an endodontically treated central incisor before being treated with a clear aligner, unlike first molars in panoramic radiographs. Therefore, the present study was investigated molars more than incisors. Although anterior teeth were more susceptible to EARR than the posterior teeth.[20]

Upon radiographic measurement of apical root lengths before and after treatment with Clear aligner demonstrated a significant decrease due to EARR. Almost all the teeth examined in this study demonstrated a certain extent EARR. Of the 34 teeth, 80% demonstrated EARR <5%, indicating higher incidence and minimal severity of apical root resorption. This finding is somewhat similar to the other study in which 81% of 1083, teeth presented a reduction of the pretreatment root length. A reduction of 1%–10% root length was found in 25.94% (n = 281) of teeth.

At the individual tooth level, #21 showed a prevalence of EARR ranging between 0% and 7.9% a finding similar to that reported by Gay et al.[6] wherein the prevalence of root resorption in maxillary incisors ranged from 1.54% to 7.81%. A higher mean EARR was observed in maxillary central incisors (#21) than molars (#46). This finding could be due to the wider range of movement of incisor teeth than the remainder of the dentition, and the root structure of the incisors, its relation to bone, and the periodontal membrane, which transmits the majority of stresses to the apex.[11]

Similarly, pretreatment versus posttreatment comparison of root lengths of molars exhibited minimal root resorption (<10%) with significant differences in mean EARR. Amongst the molar teeth, #16 showed higher EARR followed by #46, #36, and #16. This variation in EARR in molar teeth could be attributed to many factors including the anatomy of the root, pressure applied to the root, and duration of the wearing of Clear aligner, etc. However, a comparison of mean differences in root lengths postoperatively across different teeth did not show any significant differences in EARR.

Previous studies have reported that the maxillary incisors had the highest average apical root resorption followed by mandibular incisors and mandibular first molars.[21],[22],[23] AlSagr et al. pointed out that after orthodontic treatment with Clear aligner Invisalign®, the incidence of root resorption on vital teeth was high, and the severity was very low and limited to the root surface resorption.[12]

Yi et al. reported that the treatment with a clear aligner had resulted in significantly less EARR than fixed orthodontic treatment.[24] On the contrary, a study conducted by Iglesias-Linares showed similar EARR using either removable aligners or fixed appliances.[8] While Esteves et al. found no significant difference in apical root resorption in the endodontically treated teeth compared to the vital teeth.[15] Similarly, Kolcuoğlu and Oz reported no significant difference in apical root resorption in the endodontically treated teeth compared to the group of vital teeth in a micro-computed tomographic study.[25] Moreover, it was noted that most of the resorption areas in vital teeth were observed in the cervical third, while the apical third is mainly affected in endodontically treated teeth.

In our study, the overall clear aligner orthodontic treatment showed significant EARR as evidenced by Pre/post difference in root lengths. This could be because the light continuous forces are perceived as intermittent by the periodontium because of the viscoelastic nature of PDL and the application of vertical forces during function and parafunction,[26] leading to the root resorption.

In general, clear aligner, orthodontic therapy demonstrated substantial EARR in our study, as indicated by the pre/post difference in root lengths. This might be because the periodontium perceives light continuous forces as intermittent due to the viscoelastic nature of the ligament and the application of vertical forces during function and parafunction[25] that results in root resorption.

Limitations

This study did not take into account several factors influencing orthodontic root resorption, including genetics, ethnicity, systemic diseases, gender and age, and quantity of orthodontic forces. The inclusion of a small sample of only incisors and molar teeth is another limitation. The linear measurement of EARR using Panoramic radiographs could have resulted in the random error. Biological variability is another factor that could have influenced the measurement of EARR. Hence further study with a higher sample size with inclusion of all types of endodontically treated teeth and use Cone-beam computed tomography as with three-dimensional images measurement of root resorption could provide higher accuracy of the findings.[4]


  Conclusion Top


The current preliminary investigation revealed that all the endodontically treated teeth showed minimal external root resorption after orthodontic treatment with a clear aligner. Maxillary incisor teeth were the most affected with EARR compared to the molars.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Yi J, Sun Y, Li Y, Li C, Li X, Zhao Z. Cone-beam computed tomography versus periapical radiograph for diagnosing external root resorption: A systematic review and meta-analysis. Angle Orthod 2017;87:328-37.  Back to cited text no. 4
    
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Gay G, Ravera S, Castroflorio T, Garino F, Rossini G, Parrini S, et al. Root resorption during orthodontic treatment with invisalign®: A radiometric study. Prog Orthod 2017;18:12.  Back to cited text no. 6
    
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Al-Sagr H, Al-Mujel S, Al-Shiha S, Al-Shathri N, Al-Shammary D. External root resorption after orthodontic treatment with invisalign®: A retrospective study. Glob J Health Sci 2020;12:p125.  Back to cited text no. 12
    
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24.
Yi J, Xiao J, Li Y, Li X, Zhao Z. External apical root resorption in non-extraction cases after clear aligner therapy or fixed orthodontic treatment. J Dent Sci 2018;13:48-53.  Back to cited text no. 24
    
25.
Kolcuoğlu K, Oz AZ. Comparison of orthodontic root resorption of root-filled and vital teeth using micro-computed tomography. Angle Orthod 2020;90:56-62.  Back to cited text no. 25
    
26.
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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