|Year : 2018 | Volume
| Issue : 4 | Page : 513-523
Evaluation of treatment outcomes of en masse retraction with temporary skeletal anchorage devices in comparison with two-step retraction with conventional anchorage in patients with dentoalveolar protrusion: A systematic review and meta-analysis
Hanin Nizar Khlef1, Mohammad Younis Hajeer1, Mowaffak A Ajaj1, Omar Heshmeh2
1 Department of Orthodontics, University of Damascus Dental School, Damascus, Syria
2 Department of Oral and Maxillofacial Surgery, University of Damascus Dental School, Damascus, Syria
|Date of Web Publication||6-Nov-2019|
Dr. Mohammad Younis Hajeer
Department of Orthodontics, University of Damascus Dental School, PO Box 9309, Mazzeh, Damascus
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: The main objective is to evaluate the effectiveness of en masse retraction with temporary skeletal anchorage devices (TSADs) versus two-step retraction with conventional anchorage (CA) in terms of the skeletal, dental, and soft-tissue variables, as well as the duration of retraction or overall orthodontic treatment. Materials and Methods: An electronic search of PubMed and nine other major databases for prospective, randomized controlled trials (RCTs) and clinical controlled trials (CCTs) was carried out between January 1990 and April 2018. The bibliography in each identified article was checked out. In addition, manual searching was performed in the same time frame in five major orthodontic journals. Adult patients undergoing fixed orthodontic treatment with extraction of maxillary premolars followed by an en masse retraction in the experimental group and two-step retraction of upper anterior teeth in the control group. Methodological index for nonrandomized studies for CCTs and Cochrane's risk of bias tool for RCTs were applied. Results: Four articles (two RCTs and two CCTs) were included in this review and all articles were appropriate for the quantitative synthesis. There was no significant difference between the en masse retraction and two-step retraction groups in terms of SNA, SNB, ANB, and MP-SN angles. Using TSADs gave significantly better results in terms of posterior anchorage and incisors inclination, and greater anterior teeth retraction in comparison with CA (standardized mean difference [SMD] = –3.03 mm, P < 0.001; SMD = 0.74°, P = 0.003; SMD = –0.46 mm, P = 0.03, respectively). En masse/TSAD combination caused a significantly greater increase in nasolabial angle, higher decrease in facial convexity angle, and greater lower lip retraction in comparison with two-step/CA combination (weighted mean difference = 4.73°, P = 0.007; P = 0.0435; SMD = –0.95 mm, P = 0.01, respectively). Conclusion: There is weak-to-moderate evidence that using either en masse/TSAD combination or two-step/CA combination would lead to similar skeletal improvement. There is a very weak-to-moderate evidence that using TSADs with en masse retraction would cause better posterior anchorage and incisors inclination, and greater anterior teeth retraction than using CA with two-step retraction. There is weak-to-moderate evidence that using en masse/TSAD combination would lead to a better improvement in the facial profile. According to the quality of evidence, we confirm the need for more well-conducted RCTs in the en masse retraction field.
Keywords: Anchorage, anterior teeth, en masse, extraction, meta-analysis, orthodontic, protrusion, retraction, systematic review, two-step
|How to cite this article:|
Khlef HN, Hajeer MY, Ajaj MA, Heshmeh O. Evaluation of treatment outcomes of en masse retraction with temporary skeletal anchorage devices in comparison with two-step retraction with conventional anchorage in patients with dentoalveolar protrusion: A systematic review and meta-analysis. Contemp Clin Dent 2018;9:513-23
|How to cite this URL:|
Khlef HN, Hajeer MY, Ajaj MA, Heshmeh O. Evaluation of treatment outcomes of en masse retraction with temporary skeletal anchorage devices in comparison with two-step retraction with conventional anchorage in patients with dentoalveolar protrusion: A systematic review and meta-analysis. Contemp Clin Dent [serial online] 2018 [cited 2020 Sep 25];9:513-23. Available from: http://www.contempclindent.org/text.asp?2018/9/4/513/270376
| Introduction|| |
The problem of bimaxillary protrusion of the dental arches is widespread across the world. In addition, the maxillary dentoalveolar protrusion is one of the most prevalent cases seen in the orthodontic clinics. Treatment of these types of malocclusion often requires extraction of maxillary or bimaxillary first or second premolars and the use of maximum anchorage., When treating patients with an excessive dentoalveolar protrusion, anchorage control is necessary to obtain the good results., To reinforce anchorage, various auxiliary methods can be used such as the transpalatal arch, Nance button, headgear, intermaxillary elastics, and bonding of second molars., Lately, temporary skeletal anchorage devices (TSADs) have been offered as an alternative method for anchorage control.
Closing extraction spaces can be performed by a one-step technique (en masse retraction) with anchorage reinforcement or by a two-step technique involving canines' retraction followed by the incisors' retraction. The one-step technique is preferred on the two-step technique because when canines are retracted individually, they tend to tip and rotate more than when the six anterior teeth are retracted as one unit, thus requiring more time and effort to relevel and realign the dental arch.
The en masse retraction of the anterior teeth after the premolar extraction has been practiced in the Begg and Tip-Edge edgewise techniques for several years. In the straight-wire appliances, the en masse retraction of upper anterior teeth was first presented by Andrews, and then it has been used routinely by Bennett and McLaughlin in their preadjusted appliance system.
There are three systematic reviews that have evaluated the en masse retraction technique, but several points could be raised regarding these reviews. The systematic review carried out by Xu and Xie and Antoszewska-Smith et al. merged between en masse retraction and two-step retraction in the control group, so there was no concentration on one retraction technique. The systematic reviews carried out by Antoszewska-Smith et al. and Rizk et al. did not evaluate the skeletal and soft-tissue variables and focused only on some dental variables. It should be noted that Xu and Xie and Antoszewska-Smith et al. systematic reviews had included retrospective studies, which is known to suffer from a high risk of bias, rather than confining the results to prospective randomized controlled trials (RCTs) and clinical controlled trials (CCTs).
Given the shortfalls listed above, a new systematic review seemed desirable to answer the following explicit focused review question: “What is the overall effectiveness of en masse retraction versus two-step retraction of the upper anterior teeth in adult patients with maxillary or bimaxillary dentoalveolar protrusion?”
| Materials and Methods|| |
A PubMed scoping search was done to verify the existence of similar systematic reviews and to explore potentially eligible articles before writing up the final systematic review protocol. The protocol was registered during the first stages of this review in PROSPERO (CRD42018085596). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist and the Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 were used for writing and submitting this systematic review and meta-analysis.
The PICOS framework was as follows:
Participants: Healthy adult patients, both males and females, the minimum age is 14 years old to minimize the effects of growth, with Class I or II dentoalveolar protrusion, undergoing fixed orthodontic treatment with maxillary or bimaxillary first or second premolar extraction and retraction of upper anterior teeth. Intervention: En masse retraction of the upper anterior teeth associated with TSADs for anchorage reinforcement. Comparison: Two-step retraction of the upper anterior associated with conventional anchorage (CA). Outcome measures: Skeletal, dental, and soft-tissue variables, and retraction or overall treatment duration.
Prospective RCTs and CCTs that were published from January 1990 to April 2018 in the English language only.
Retrospective studies, studies performing en masse retraction or two-step retraction in both evaluated groups, non-English language trials, animal studies, finite element analysis studies,in vitro studies, split-mouth-design studies, editorials, personal opinions, case reports or case series reports, articles without a reported sample, reviews and technique description articles, absence of a control group or the presence of a control group of nontreated participants, fewer than 10 patients in the experimental group, a control group of patients being treated on a nonextraction basis, and/or age range >15 years.
An electronic literature search was done using PubMed, Medline, Embase, OVID SP, EBSCO, Scopus, Google Scholar, the Cochrane Central Register of Controlled Trials, OpenGrey, and Web of Science. The databases were searched between January 1990 and April 2018. Electronic searching was supplemented with reviewing the bibliography in each included article. In addition, manual searching was carried out in the same time frame in the American Journal of Orthodontics and Dentofacial Orthopedics, the European Journal of Orthodontics, Orthodontics and Craniofacial Research, the Angle Orthodontist, and the Journal of Orthodontics. ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform Search Portal were also checked electronically to identify any clinical trials in progress and those that have been completed but not published yet.
Search strategy and study selection
The search strategy for PubMed is presented in [Table 1]. Keywords used in the search strategy are shown in [Supplementary Table 1]. Two reviewers (HNK and MYH) assessed the articles for eligibility independently, and in the event of any discrepancy, the reviewers resolved it by discussion until consensus was reached. First, the two reviewers checked titles and abstracts of articles during the search by using the eligibility criteria. Second, the same two reviewers evaluated the full text of all articles that might be included in the review. Articles were discarded from the review when they did not fulfill one or more of the eligibility criteria.
Data collection process
Initially, data extraction tables were developed, then the first reviewer (HNK) retrieved the data from the included articles according to the data extraction tables, and the second reviewer (MYH) checked the extracted data. Any conflict was resolved by discussion between the two reviewers and reexamination of the original article. If no consensus could be reached, a third reviewer (OH) was asked to decide and resolve the controversy. In the event of lack of information, the authors of the included studies were E-mailed and asked for more data.
In this systematic review, the following data were extracted from the included studies: Author's name, year and country of publication, study design, malocclusion type, types of devices used for anchorage reinforcement, gender of the patients, sample size, age of the patients at the start of the treatment, magnitude and source of force applied during the retraction, length and diameter of miniscrews, retraction or overall treatment duration, brackets' prescription, slots' size, and working archwire.
Lateral cephalometric measurements were also extracted from the included articles to evaluate the skeletal, dental, and soft-tissue variables. These measurements are presented in [Supplementary Table 2].
| Assessment of Risk of Bias in Individual Studies and Strength of Evidence|| |
The Methodological index for nonrandomized studies (MINORS) Index was applied to assess the risk of bias for CCTs. The Cochrane Collaboration tool was used to assess the risk of bias for RCTs, and it was evaluated as a judgment (high, low, or unclear) for individual elements from seven domains. An additional summary of the reliability of the conclusions and strength of the evidence was developed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. The strength of evidence was evaluated as high, moderate, low, or very low for seven outcomes.
| Summary Measures, Synthesis of Results, Additional Analysis, and Risk of Bias Across Studies|| |
Meta-analysis was carried out using Review Manager, Version 5.3. Copenhagen: The Nordic Cochrane Centre, the Cochrane Collaboration. The random-effects model was used for the continuous outcomes, in which studies were weighted with the inverse of their variance and the heterogeneity parameter. The mean, standard deviation, and sample size of the included studies were used to combine the results into a weighted mean difference (WMD) with 95% confidence intervals when the outcome measurements in all included articles were made on the same scale; but when the same outcome was measured in a variety of ways, the standardized mean difference (SMD) was used as a summary statistic in meta-analysis.
The P value was used to discover any significant heterogeneity when P < 0.05. I2 index was used to describe the percentage of heterogeneity across the studies. The forest plots were applied to present a graphical assessment of the analysis results. Sensitivity analysis was conducted by tracing sensitivity plots to investigate the influence of the CCTs on the results and discarding them when appropriate. The publication bias was not evaluated because we did not collect 10 studies. Therefore, the funnel plots were not used in this meta-analysis.
| Results|| |
Initially, 2925 articles were found from all the searches combined. After taking off the duplicates, 572 articles remained. After reviewing the titles and abstracts, 540 articles were discarded because they failed to meet the eligibility criteria. The full text of the 32 remaining articles was examined in depth. Twenty-eight articles did not meet the inclusion criteria as described. A summary of the excluded articles along with reasons for exclusion is shown in [Supplementary Table 3]. Finally, four articles (two RCTs, and two CCTs,) met the inclusion criteria and were included in the systematic review. The PRISMA flow diagram of the study selection process is shown in [Figure 1].
|Figure 1: Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2009 flow diagram of the study selection process|
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Baseline characteristics of the patients in the retrieved articles are shown in [Table 2]. Characteristics of the included studies are shown in [Table 3] and [Table 4]. The skeletal, dental, and soft-tissue measurements are shown in [Supplementary Table 4], [Supplementary Table 5], [Supplementary Table 6], [Supplementary Table 7], respectively. All included studies were of a two-arm parallel-group design. Extraction-based treatments were supplied in the two groups in all the retrieved studies. The experimental group (G1) consisted of an en masse retraction of the upper anterior teeth associated with TSADs for anchorage reinforcement, whereas the control group (G2) consisted of a two-step retraction of the upper anterior teeth associated with CA devices.
|Table 2: Baseline characteristics of the patients in the included studies|
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In total, 150 adult patients were included: 74 patients in G1 (57 female and 17 male patients), and 76 in G2 (59 female and 17 male patients). Three papers,, evaluated the skeletal, dental and soft-tissue variables and one paper studied the dental variables only. Two papers, mentioned the retraction duration, one paper presented the overall treatment duration, and one paper did not give these details.
Risk of bias of the included studies
The risk of bias in the RCTs is shown in [Figure 2], and the overall risk of bias for each domain is shown in [Figure 3]. The two included RCTs, were of low risk of bias (quality assessment is shown in [Supplementary Table 8]). Methodological quality assessment of the CCTs, is presented in [Table 5]. The global ideal score was 24 when using the MINORS scale. Studies'scores were both 17 points, which showed that the included CCTs were of fair quality.
|Table 5: Methodological quality of the selected nonrandomized studies according to the methodological index for nonrandomized studies assessment tool|
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Results of individual studies, synthesis of results, and additional analysis
En-masse retraction with temporary skeletal anchorage devices (G1) versus two-step retraction with conventional anchorage (G2)
Two studies, measured skeletal variables and the related forest plots are shown in [Supplementary Figure 1]. There was no significant difference between the two groups in the SNA, SNB, ANB, and MP-SN angles (WMD = 0.03°, P = 0.88 WMD = 0.47°, P = 0.58; WMD=−0.29°, P = 0.46; WMD=–0.16°, P = 0.89, respectively).
Dentally, a sensitivity analysis was carried out in all the dental changes and it was decided not to include CCTs, with RCTs, for more reliable results. A distal movement of maxillary first molar (U6) was reported in G1, while a mesial movement of U6 was reported in G2 with a significant difference between the two groups (SMD = –3.03 mm, P < 0.0001), [Figure 4]. A greater retraction of incisors (U1) with better inclination were detected in G1 with a significant difference between the two groups [SMD = –0.46 mm, P = 0.03; SMD = 0.74°, P = 0.003, [Figure 5] and [Figure 6], respectively]. An intrusion force was applied on U1 and U6 in G1, while an extrusion force was applied on U1 and U6 in G2 with a significant difference between the two groups in the vertical movement of U1 and U6 [SMD = –2.48 mm, P < 0.00001; SMD = –0.61 mm, P = 0.010, [Figure 7] and [Figure 8], respectively].
|Figure 4: Forest plot showing the amount of horizontal movement of U6 in en masse/ temporary skeletal anchorage devices group versus two-step/conventional anchorage group|
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|Figure 5: Forest plot showing the amount of horizontal movement of upper incisal edges in en massel temporary skeletal anchorage devices group versus two-step/conventional anchorage group|
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|Figure 6: Forest plot showing the incisors' inclination variable in en massel temporary skeletal anchorage devices group versus two-step/conventional anchorage group|
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|Figure 7: Forest plot showing the amount of vertical movement of incisors in en massel temporary skeletal anchorage devices group versus two-step/conventional anchorage group|
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|Figure 8: Forest plot showing the amount of vertical movement of U6 in en massel temporary skeletal anchorage devices group versus two-step/conventional anchorage group|
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Regarding soft-tissue variables, two articles, reported a significantly greater increase in the nasolabial angle (NLA) in G1 (WMD = 4.73°, P = 0.007) [Supplementary Figure 2]. One study measured the facial convexity angle, with significantly higher decrease in G1 (P = 0.0435). Sensitivity analysis was carried out in the UL-E and LL-E, and it was decided to exclude one CCT in the analysis. No significant difference between the two groups was observed regarding the UL-E (SMD = –0.28 mm, P = 0.18), [Supplementary Figure 3], while there was a significantly greater lower lip retraction in G1 (SMD = –0.95 mm, P = 0.01), [Supplementary Figure 4].
There was no significant difference between the two groups in the duration of retraction in two studies,. In constant, one study reported a significantly shorter treatment duration in G1 with an average of 4 months.
The strength of the evidence in the collected data
Based on the GRADE recommendations, the strength of evidence for the skeletal and soft-tissue measurements ranged from low to medium, while it ranged from very low to medium for dental changes, as shown in [Table 6]. The decline in the strength of the evidence occurred because of the imprecision, high heterogeneity, or existence of CCTs.
|Table 6: Summary of findings table according to the Grading of Recommendations Assessment, Development, and Evaluation guidelines for the included studies|
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| Discussion|| |
The SNA and ANB angles decreased with no significant difference between the two groups. This decrease would indicate that point A had moved back during the upper anterior teeth retraction. Al-Sibaie and Hajeer reported a decrease in the SNB and MP-SN angles in both groups with no significant difference between them, while Upadhyay et al. reported an increase in the SNB and decrease in the MP-SN in the en masse/TSAD group, which could be related to the molars intrusion in both arches causing counterclockwise rotation of the mandible.
Since there were no significant differences in the skeletal variables between both retraction methods, there is no preference for one method over the other in terms of the skeletal improvement. The strength of evidence in this context ranged from low to medium.
The horizontal movement of first molars
Using TSADs seem to supply not only less mesial movement of first molars but also a distal movement of them when interdental contact occurs between the canine and second premolar, so a retraction force would translate to the first molars, as reported in all the included studies,,,. Hence, using TSADs for anchorage appears to be better than CA. The strength of evidence ranged between very low to medium.
The vertical movement of first molars
Intrusion of first molars occurred when anchoring the anterior teeth retraction with TSADs; while in contrast, extrusion of first molars occurred when using the CA devices. Hence, using TSADs are expected to prevent the worsening of the profile with clockwise rotation of the mandible in cases with increased vertical dimensions. The strength of the evidence ranged between very low to medium in this aspect.
The horizontal movement of upper incisal edges
It was higher when using TSADs in comparison with CA because CA allowed posterior teeth to move mesially so that the anterior teeth were retracted a less amount. Therefore, it is preferable to use TSADs when a larger amount of retraction is needed. The strength of evidence ranged between very low to medium.
The vertical movement of incisors
The incisor edges and apices were exposed to an intrusion force when using the TSADs, due to the placement of TSADs 8–10 mm apically to the occlusion line, so the point of force application is apical to the center of resistance (CR). Furthermore, the height of the power arm influenced the amount of intrusion force. By reducing it, a higher intrusion could be achieved. In contrast, extrusion of incisal edges and apices would occur in the CA group, due to the coronal orientation of the force vector in relation to the CR. Therefore, using TSADs prevents the incidence of a postretraction increase in the overbite. The strength of the evidence in this context ranged between very low to medium.
The incisors inclination
It is one of the hardest and most important goals in the camouflage treatment. In the en masse/TSAD group, the upper incisors were retracted by controlled tipping and bodily movement, whereas in the two-step/CA group the retraction was primarily accomplished through controlled and uncontrolled tipping. Therefore, the upper incisor axis would show an optimal inclination when using TSADs with en masse retraction of the upper anterior teeth.
The NLA increased in both groups after retraction because of the backward movement of the upper incisors. This increase was significantly greater in the TSADs/en masse group in comparison with the CA/two-step group because of the larger amount of upper anterior teeth retraction in the TSADs/en masse group.
The facial convexity angle decreased in both groups because of the retraction of the upper incisors and that improved the appearance of the facial profile. Upadhyay et al. reported that this decrease was significantly higher in the en masse retraction compared to the two-step retraction. The reason for this seems to be the significant difference between the two techniques in the amount of upper anterior teeth retraction.
The upper lip retraction was higher in the en masse retraction with TSADs in comparison with two-step retraction with CA, but it was not significantly difference between the two groups. This could be explained by the differences in thickness and lip strain between the patients. In addition, the mobile and flexible lip texture could cause large variations of lip position on the lateral cephalogram. The strength of evidence ranged from low to medium.
The lower lip retracted in the en masse/TSADs group and two-step/CA groups because it contacts the upper and lower incisors, so it is influenced by both incisors retraction. This could explain the reason for lower lip retraction in class II division 1 cases where the extraction was performed only in the upper dental arch, as reported in Al-Sibaie and Hajeer. However, the lower lip retracted due to the retraction of the upper anterior teeth.
Retraction or overall treatment duration
Regarding the overall treatment duration, Al-Sibaie and Hajeer reported a significantly shorter treatment duration in the en masse/TSAD group and that because performing a two-step retraction technique prolonged the duration of space closure as it took 6–8 months just to retract the canine into the extraction site. Surprisingly, Upadhyay et al., reported no significant difference between the two groups in the retraction duration with indicating that the incorporation of skeletal anchorage devices may enhance the treatment outcomes without affecting the retraction duration, but the explanation given in their paper was not convincing.
Limitations of the current review
Being confined to the papers written in English is one limitation. Despite the separation between RCTs and CCTs, heterogeneity remained high in some comparisons. Only two prospective RCTs and two CCTs were found in the medical literature comparing between en masse retraction and two-step retraction in adult patients with a strength of evidence ranged between weak/very weak to moderate. Therefore, the results of this systematic review should be taken cautiously. The methodologic quality of the included studies was assessed rigorously, and none of the selected CCTs were of high quality. The cephalometric analyses were conducted by different reference points and planes, but the ability to arrive at conclusions was possible since the accomplished comparisons were based on the treatment-induced changes and not the actual values per se.
| Conclusion|| |
Implications for practice
There is weak-to-moderate evidence that performing either en masse retraction with TSADs or two-step retraction with CA can lead to similar skeletal improvements. There is very weak-to-moderate evidence that using TSADs would lead to better posterior anchorage and incisors inclination and a greater amount of upper anterior teeth retraction in comparison with the CA. An intrusion force was found to be applied on incisors and molars when using TSADs, whereas an extrusion force was found to act on them when using CA, however, the strength of evidence in this regard is very weak to moderate. There is a weak-to-moderate evidence that using en masse/TSAD combination would lead to better improvement in the facial profile by causing a decrease in the facial convexity angle and increase the NLA and retracting the upper and lower lips.
Implications for research
As the quality of evidence ranged between low to moderate in terms of the skeletal and soft-tissue variables and very low to moderate in term of the dental variables, therefore, we confirm the need for more well-conducted RCTsin the en masse retraction field.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]