European Journal of Orthodontics, 2016, 324–333 doi:10.1093/ejo/cjv057 Advance Access publication 25 August 2015
Systematic Review
The effectiveness of the Herbst appliance for patients with Class II malocclusion: a meta-analysis Xin Yang, Yafen Zhu, Hu Long, Yang Zhou, Fan Jian, Niansong Ye, Meiya Gao and Wenli Lai Department of Orthodontics, State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China Correspondence to: Wenli Lai, Department of Orthodontics, State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, No. 14, Section 3, Ren Min South Road, Chengdu, China. E-mail: [email protected]
Summary Objective: To systematically investigate review in literature the effects of the Herbst appliance for patients with Class II malocclusion patients. Method: We performed a comprehensive literature survey on PubMed, Web of Science, Embase, CENTRAL, SIGLE, and ClinicalTrial.gov up to December 2014. The selection criteria: randomized controlled trials or clinical controlled trials; using any kind of Herbst appliances to correct Class II division 1 malocclusions; skeletal and/or dental changes evaluated through lateral cephalograms. And the exclusion criteria: syndromic patients; individual case reports and series of cases; surgical interventions. Article screening, data extraction, assessment of risk of bias, and evaluation of evidence quality through GRADE were conducted independently by two well-trained orthodontic doctors. Consensus was made via group discussion of all authors when there is inconsistent information from the two. After that, sensitivity analysis and subgroup analysis were performed to evaluate the robustness of the meta-analysis. Results: Twelve clinical controlled trials meet the above-mentioned criteria, and were included in this analysis. All included studies have eleven measures taken during both active treatment effect and long term effect periods, including four angular ones (i.e., SNA, SNB, ANB, mandibular plane angle) and seven linear ones (i.e. Co-Go, Co-Gn, overjet, overbite, molar relationship, A pointOLp, Pg-OLp) during active treatment effect period were statistically pooled. Meta-analysis and sensitivity analysis demonstrated that all these measures showed consistent results except for SNA, ANB, and overbite. Subgroup analysis showed significant changes in SNA, overbite, and PgOLp. Publication bias was detected in SNB, mandibular plane angle, and A point-OLp. Conclusion: The Herbst appliance is effective for patients with Class II malocclusion in active treatment period. Especially, there are obvious changes on dental discrepancy and skeletal changes on Co-Gn. As to its long-term effects, more evidence is needed to draw conclusions.
Introduction In patients with Class II malocclusion, large overjet and unfavorable profile may lead to negative feelings of self-image and self-esteem (1). Therefore, aesthetic improvement is a main treatment objective
(2). Among all functional appliances for Class II malocclusion, the Herbst appliance is one of the most commonly used one. It was developed by Emil Herbst in the early 1900s and reintroduced by Pancherz in the late 1970 (3). As a bilateral telescope anchored to
© The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: [email protected]
324
325
X. Yang et al. the upper and lower arches, it keeps the mandible in a continuous anteriorly postured position during all the mandibular functional movements (3), thereby resulting in sagittal and vertical dentoskeletal changes. In clinical settings, there are several variants of the Herbst appliance, including cast Herbst appliance and acrylic splint Herbst appliance (4–6). Herbst appliance does not require patients’ cooperation due to its fixation on dental arches (7). Although pertinent systematic reviews have been published previously (8,9), definitive conclusions are not drawn due to limited number of included studies. With new evidences in the past several years, we revisit this topic and present here an up-to-date systematic review and meta-analysis to investigate the effectiveness of Herbst appliance for patients with Class II malocclusion.
Materials and methods Data acquisition Literature query Literature search was conducted online on several major medical databases, including PubMed, Web of Science, Embase, CENTRAL, SIGLE, and ClinicalTrial.gov up to December 2014. In particular, we included grey literature on SIGLE and ongoing studies for ClinicalTrial.gov. The specific search strategies are detailed in Table 1. Article inclusion and exclusion criteria The following inclusion criteria were adopted to select abstracts from potential articles retrieved from the databased: randomized controlled trials or clinical controlled trials; using any kind of Herbst appliances to correct Class II division 1 malocclusions; skeletal and/or dental changes evaluated through lateral cephalograms. The exclusion criteria included syndromic patients, individual case reports and series of cases and surgical interventions. Data extraction The following data were extracted: study design, participant information, the skeletal maturation of subjects, appliance types and
active treatment durations. The skeletal maturity indicators were HWM (hand wrist maturation) and CVM (cervical vertebrae maturation). The stage of CVM 2 (HWM 3–4) and CVM 3 (HWM 5–6) are around the peak growth period (10). Quality assurance To avoid subjectiveness during data acquisition, two orthodontic doctors independently conducted the acquisition following the above-mentioned strategies. Risk of bias was assessed according to Downs and Black quality assessment tool. Any disagreement was solved by discussion or judged by a third reviewer.
Meta-analysis The present study adopted Pancherz cephalometric analysis or PCA, which is considered as the standard method, to evaluate effects of the Herbst appliance. Besides the common items covered in PCA, other important clinical indices were also included for the evaluation. In specific, proposed outcomes included angular measurements (SNA, SNB, ANB, mandibular plane angle) and linear measurements [mandibular ramus height (Co-Go), total mandibular length (CoGn), overjet, overbite, molar relationship, sagittal position of the maxillary base (A point-OLp), sagittal position of the mandibular base (Pg-OLp)]. Egger’s test (11) and Begg’s test (12) were used to assess the publication bias through Stata 12.1. Furthermore, sensitivity analysis and subgroup analysis were performed to evaluate the robustness of the pooled results from the meta-analysis. Moreover, the quality of evidence was assessed by using GRADE system of rating quality of evidence (13–18).
Results The procedures of the electronic searching and selection are presented in Figure 1. Moreover, the details of the search strategy, as well as the number of abstracts selected from each database, are displayed in Table 1. According to the procedure in Figure 1 and strategy in Table 1, we retrieved 654 articles from those databases
Table 1. Database search and results. Database
Search terms
Pubmed
#1:Malocclusion, Angle Class II OR Angle Class II OR Class II, Angle OR Class II OR Distocclusion* OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: randomized controlled trial [pt] OR controlled clinical trial [pt] OR randomized [tiab] OR placebo [tiab] OR clinical trials as topic [mesh: noexp] OR randomly [tiab] OR trial [ti] #4: #1 AND #2 AND #3 #1: Angle Class II OR Class II, Angle OR Class II OR Distocclusion*OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: #1 AND #2 #1:Angle Class II OR Class II, Angle OR Class II OR Distocclusion* OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: #1 AND #2 #1: Angle Class II OR Class II, Angle OR Class II OR Distocclusion* OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: #1 AND #2 (Angle Class II or distocclusion) and (Herbst or Herbst appliance) (Angle Class II or distocclusion) and (Herbst or Herbst appliance)
Web of science
Embase
Central
SIGLE ClinicalTrial.gov
Results
Included
29
2
375
2
211
11
39
0
0 0
0 0
326
European Journal of Orthodontics, 2016, Vol. 38, No. 3 ANB Eight studies (20,22–25,28–30) investigated this outcome. The meta-analysis revealed that the pooled MD of ANB for active treatment effect was −1.08 degrees [95% CI: −2.16, −0.00] (Figure 2). Mandibular plane angle Eight studies (5,20,22–26,30) investigated this outcome. The metaanalysis revealed that the pooled MD for active treatment effect was 0.17 degrees [95% CI: −0.09, 0.42] (Figure 2).
Linear measurements Overjet Seven studies (5,21,23,27–30) investigated overjet. The meta-analysis revealed that the pooled MD of overjet for active treatment effect was −4.82 mm [95% CI: −5.83, −3.80] (Figure 3). Overbite Six studies (21,23,26,28–30) investigated overbite. The active treatment effect outcome was a significant decrease in overbite and the meta-analysis revealed that the pooled MD of overbite was −1.69 mm [95% CI: −3.18, −0.21] (Figure 3). Figure 1. PRISMA flow diagram for studies retrieved through the searching and selection processes.
and 597 of them were identified as irrelevant initially. The remaining 57 articles were further assessed for eligibility resulting 12 final controlled clinical trial studies (CCTs). All inclusions were prospective studies and recruited only adolescents. The sample size ranges from 8 to 55; the active Herbst treatment duration ranges from 5 months to 30 months. The general information of each study is summarized in Table 2. The study quality scores using Downs and Black scale (19) were shown in Table 3. Because of the differences between studies and the high heterogeneity, we used the random model in all the outcomes’ analysis.
Description of outcomes For each outcome examined in this meta-analysis, measurements at active treatment effect period (the changes between before-Herbst treatment and immediately-after-Herbst treatment) were conducted. All included studies investigated the net changes before and after Herbst treatment except that the study reported annualized outcome changes instead. The GRADE assessments for quality of evidence for each outcome were shown in Table 4.
Description of interventions The intervention in this meta-analysis was Herbst appliance—one of the most commonly used treatment modality for Class II patients.
Effects of interventions In this section, we reports the meta-analysis results for each examined measure as follows.
Skeletal angular measurements SNA and SNB Eight studies (20,22–25,28–30) investigated SNA and SNB. However, all of them examined the active treatment effects only. As depicted in Figure 2, our meta-analysis revealed that the pooled differences in mean or MDs of SNA and SNB for active treatment effect were −0.56 degrees [95% CI: −0.99, −0.14] and 1.06 degrees [95% CI: 0.53, 1.60], respectively.
Co-Go Four studies (5,21,25,30) investigated the outcome of Co-Go. The active treatment effect was a significant increase in Co-Go with the pooled MD being 1.76 mm [95% CI: 1.27, 2.26] (Figure 3). Co-Gn Five studies (21,22,25,29,30) investigated the outcome of Co-Gn. The meta-analysis revealed that the pooled MD for active treatment effect was 1.74 mm [95% CI: 0.95, 2.53] (Figure 3). Molar relationship. Four studies (5,21,27,29) showed a significant decrease in molar relationship in active treatment period with the pooled MD being −5.70 mm [95% CI: −6.71, −4.69] (Figure 3). A point-OLp Six studies (5,21,22,24,27,29) showed a significant decrease in A point-OLp with the pooled MD being −0.52mm [95% CI: −0.73, −0.30] (Figure 3). Pg-OLp Seven studies (5,21,22,24,27–29) showed a significant increase in Pg-OLp with the pooled MD being 1.45 mm [95% CI: 0.43, 2.47] (Figure 3).
Sensitivity analysis and subgroup analysis The results of sensitivity analysis and subgroup analysis are summarized in Table 5 and Table 6, respectively. We conducted sensitivity analysis to examine the stability of present meta-analysis. In Wigal et al. (29), the brackets were bonded on upper anterior teeth. When this article was excluded in the sensitivity analysis, results regarding to ANB and overbite are unstable. We also performed a subgroup analysis since different types of Herbst appliances in the included studies may influence the results of present meta-analysis. These studies were divided into three subgroups, that is banded type (22,23,26,27), splint type (5,20,21,25,28) and edgewise crowned type (24,29,30), as shown
327
X. Yang et al. Table 2. General information provided in the included studies. Study Baysal and Uysal (20)
Design
Participates
CCT (prospective) T: n = 20, M/F = 9/11, age = 12.74 ± 1.43 y C: n = 20, M/F = 11/9, age = 12.17 ± 1.47 y Baysal and Uysal CCT (prospective) T: n = 20, M/F = 9/11, (21) age = 12.74 ± 1.43 y C: n = 20, M/F = 11/9, age = 12.17 ± 1.47 y de Almeida et al. (22) CCT (prospective) T: n = 30, M/F = 15/15, age = 8.2 y–11 y C: n = 30, M/F = 15/15, age = 8.0 y–10.9 y Franchi et al. (5) CCT (prospective) T: n = 55, M/F = 28/27, age = 12 y 10 m ± 1 y 2m C: n = 30, M/F = 15/15, age = 14 y 2 m ± 1 y 2 m Küçükkeleş and CCT (prospective) T: n = 10, C: n = 10 Sandalli (23) 8 F (10.2 y), 12 M (10.6 y) LaHaye et al. (24) CCT (prospective) T: n = 19, M/F = 9/10, age = 11.7 ± 3 y C: n = 29, M/F = 14/15, age = 12.4 ± 1.5 y McNamara et al. CCT (prospective) T: n = 45, M/F = 27/18, (25) age = 12 y C: n = 21, M/F = 8/13, age = 11 y 1 m Pancherz et al. (26) CCT (prospective) T: n = 22, M/F = 19/3, age = 12 y C: n = 20, M/F = 17/3, age = 12 y Pancherz et al. (27) CCT (prospective) T: n = 22, M/F = 19/3, age = 12 y 1 m ± 11 m C: n = 20, M/F = 17/3, age = 11 y 2 m ± 9 m Sidhu et al. (28) CCT (prospective) T: n = 8, M/F = 0/8, age = 11 y 9 m C: n = 8, M/F = 0/8, age = 11 y Wigal et al. (29) CCT (prospective) T: n = 22, M/F = 7/15, age = 8.4 ± 1.0 y C: n = 22, age = 8.4 ± 1.1, M/F(N/A) Jakobsone et al. (30) CCT (prospective) T: n = 40, M/F = 20/20, age = 13.6 ± 1.3 y C: n = 18, M/F = 11/7, age = 13.9 ± 1.6
Criteria
Active treatment Skeletal maturation duration (m)
Appliance
Skeletal class II Stage 4 – Stage 5 (HWM)
T: 15.81 ± 5.96 C: 15.53 ± 3.13
Cast splint Herbst appliance
Skeletal class II Stage 4–Stage 5 (HWM)
T: 15.81 ± 5.96 C: 15.53 ± 3.13
Cast splint Herbst appliance
Skeletal class II Stage 1–Stage 3 (CVM)
T: 12 C: 12
Banded type Herbst appliance
Skeletal class II Stage 3–Stage 4 (CVM)
T: 1 y (±6 m) C: 1 y (±2 m)
Acrylic splint Herbst appliance
Skeletal class II Peak growth period (HWM)
T: 12 C: 12
Banded type Herbst appliance
Skeletal class II N/A
T: 12.7 ± 7 C: 2.2 ± 0.6 y
Edgewise crowned Herbst appliances
Skeletal class II N/A
T: 12 C: 22
Acrylic splint Herbst appliance
Skeletal class II Peak growth period (HWM)
T: 6 m 7d ± 14 d Banded type Herbst C: 6 m 6 d ± 11 d appliance
Skeletal class II Peak growth period (HWM)
T:6 m 7 d ± 14 d C:6 m 6 d ± 11 d
Banded type Herbst appliance
Skeletal class II N/A
T: 8 C: 8
Acrylic splint Herbst appliance
Skeletal class II NA
NA
Edgewise crowned Herbst appliance
Skeletal class II Stage 3–Stage 5 (CVM)
T: 12 m C: 12 m
Stainless steel crown Herbst appliance
M, male; F, female; N/A, not available; T, Herbst appliance treatment; C, control group; HWM, hand wrist maturation; CVM, cervical vertebrae maturation.
in Table 6. Our results demonstrated that different types of Herbst appliances have significant effect toward some examined measures. In specific, the subgroup analysis for the banded Herbst appliance resulted in a significant change in SNA, SNB, and Pg-OLp; the subgroup analysis for splint Herbst appliance revealed a significant change in SNA, ANB, overbite, and A point-OLp; and, Pg-OLp was detected to change significantly for the subgroup analysis of edgewise crowned Herbst appliance. Moreover, we divided the splint type into cast and acrylic splint types for a further subgroup analysis. The results showed significant differences exist in SNA (pooled
MD = 0.02, 95% CI: −1.10, 1.15) and ANB (pooled MD = 0.10, 95% CI: −4.08, 4.27). Furthermore, changes in effect models (fixed-effect or randomeffect model) failed to reveal any significant change.
Meta-regression Taking into account of the main factors of the Herbst treatment, the meta-regression was performed for this analysis. We extracted the age of the subjects and the treatment duration for the main factors. The results showed that age has no effect on the meta-analysis,
1
1 1 1 1 1 1 1
1
1
1 1 1 1 1 1 1
Franchi et al. (5)
Küçükkeleş and Sandalli (23) LaHaye et al. (24) McNamara et al. (25) Pancherz (26) Pancherz (27) Sidhu et al. (28) Wigal et al. (29) Jakobsone et al. (30) 1 1 1 1 1 1 1
1
1
1 1 1
3
1 1 1 1 1 1 1
1
1
1 1 1
4
0 0 0 0 0 0 0
0
0
0 0 0
5
2 2 2 2 2 2 2
2
2
2 2 2
6
1 2 2 2 2 2 2
2
2
2 2 2
7
0 0 0 0 0 0 0
0
0
0 0 0
8
0 1 0 0 0 0 2
0
0
0 0 2
9
0 2 2 2 2 2 0
2
0
2 2 2
10
1 1 1 1 1 1 1
1
1
1 1 0
11
0 0 0 0 0 1 0
0
0
0 0 0
12
1 1 0 0 0 1 1
1
0
1 1 1
13
0 0 0 0 0 0 0
0
0
0 0 0
14
0 0 0 0 0 0 0
0
0
0 0 0
15
0 0 0 0 1 0 1
1
0
0 0 1
16
0 0 0 0 1 0 1
1
0
0 0 1
17
1 1 1 1 1 1 1
1
1
1 1 1
18
1 1 1 1 1 1 1
1
1
1 1 1
19
1 1 1 1 1 0 1
1
1
1 1 1
20
0 0 0 0 1 0 0
1
0
1 1 0
21
0 0 0 0 0 0 0
0
0
0 0 0
22
0 0 0 0 0 0 0
0
0
0 0 0
23
0 0 0 0 0 0 0
0
0
0 0 0
24
0 0 0 0 0 0 0
0
0
0 0 0
25
1 0 1 1 1 1 1
1
1
1 1 1
26
0 0 0 0 0 0 0
0
0
0 0 0
27
13 16 15 15 18 16 18
19
13
17 17 19
Quality score
Internal validity—bias: ‘Yes = 1,’ ‘No = 0,’ ‘Unable to determine = 0’ 14. Was an attempt made to blind study subjects to the intervention they have received? 15. Was an attempt made to blind those measuring the main outcomes of the intervention? 16. If any of the results of the study were based on ‘data dredging’ was this made clear? 17. In trials and cohort studies, do the analyses adjust for different lengths of follow-up of patients, or in case-control studies, is the time period between the intervention and outcome the same for cases and controls? 18. Were the statistical tests used to assess the main outcomes appropriate? 19. Was compliance with the intervention/s reliable? 20. Were the main outcome measures used accurate (valid and reliable)?
External validity: ‘Yes = 1,’ ‘No = 0,’ ‘Unable to determine = 0’ 11. Were the subjects asked to participate in the study representative of the entire population from which they were recruited? 12. Were those subjects who were prepared to participate representative of the entire population from which they were recruited? 13. Were the staff, places, and facilities where the patients were treated, representative of the treatment the majority of patients receive?
‘Yes = 2,’ ‘Partially = 1,’ ‘No = 0’ 6. Are the main findings of the study clearly described? 7. Does the study provide estimates of the random variability in the data for the main outcomes? 8. Have all important adverse events that may be a consequence of the intervention been reported? 9. Have the characteristics of patients lost to follow-up been described? 10. Have actual probability values been reported (e.g., 0.035 rather than
Systematic Review
The effectiveness of the Herbst appliance for patients with Class II malocclusion: a meta-analysis Xin Yang, Yafen Zhu, Hu Long, Yang Zhou, Fan Jian, Niansong Ye, Meiya Gao and Wenli Lai Department of Orthodontics, State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China Correspondence to: Wenli Lai, Department of Orthodontics, State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, No. 14, Section 3, Ren Min South Road, Chengdu, China. E-mail: [email protected]
Summary Objective: To systematically investigate review in literature the effects of the Herbst appliance for patients with Class II malocclusion patients. Method: We performed a comprehensive literature survey on PubMed, Web of Science, Embase, CENTRAL, SIGLE, and ClinicalTrial.gov up to December 2014. The selection criteria: randomized controlled trials or clinical controlled trials; using any kind of Herbst appliances to correct Class II division 1 malocclusions; skeletal and/or dental changes evaluated through lateral cephalograms. And the exclusion criteria: syndromic patients; individual case reports and series of cases; surgical interventions. Article screening, data extraction, assessment of risk of bias, and evaluation of evidence quality through GRADE were conducted independently by two well-trained orthodontic doctors. Consensus was made via group discussion of all authors when there is inconsistent information from the two. After that, sensitivity analysis and subgroup analysis were performed to evaluate the robustness of the meta-analysis. Results: Twelve clinical controlled trials meet the above-mentioned criteria, and were included in this analysis. All included studies have eleven measures taken during both active treatment effect and long term effect periods, including four angular ones (i.e., SNA, SNB, ANB, mandibular plane angle) and seven linear ones (i.e. Co-Go, Co-Gn, overjet, overbite, molar relationship, A pointOLp, Pg-OLp) during active treatment effect period were statistically pooled. Meta-analysis and sensitivity analysis demonstrated that all these measures showed consistent results except for SNA, ANB, and overbite. Subgroup analysis showed significant changes in SNA, overbite, and PgOLp. Publication bias was detected in SNB, mandibular plane angle, and A point-OLp. Conclusion: The Herbst appliance is effective for patients with Class II malocclusion in active treatment period. Especially, there are obvious changes on dental discrepancy and skeletal changes on Co-Gn. As to its long-term effects, more evidence is needed to draw conclusions.
Introduction In patients with Class II malocclusion, large overjet and unfavorable profile may lead to negative feelings of self-image and self-esteem (1). Therefore, aesthetic improvement is a main treatment objective
(2). Among all functional appliances for Class II malocclusion, the Herbst appliance is one of the most commonly used one. It was developed by Emil Herbst in the early 1900s and reintroduced by Pancherz in the late 1970 (3). As a bilateral telescope anchored to
© The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: [email protected]
324
325
X. Yang et al. the upper and lower arches, it keeps the mandible in a continuous anteriorly postured position during all the mandibular functional movements (3), thereby resulting in sagittal and vertical dentoskeletal changes. In clinical settings, there are several variants of the Herbst appliance, including cast Herbst appliance and acrylic splint Herbst appliance (4–6). Herbst appliance does not require patients’ cooperation due to its fixation on dental arches (7). Although pertinent systematic reviews have been published previously (8,9), definitive conclusions are not drawn due to limited number of included studies. With new evidences in the past several years, we revisit this topic and present here an up-to-date systematic review and meta-analysis to investigate the effectiveness of Herbst appliance for patients with Class II malocclusion.
Materials and methods Data acquisition Literature query Literature search was conducted online on several major medical databases, including PubMed, Web of Science, Embase, CENTRAL, SIGLE, and ClinicalTrial.gov up to December 2014. In particular, we included grey literature on SIGLE and ongoing studies for ClinicalTrial.gov. The specific search strategies are detailed in Table 1. Article inclusion and exclusion criteria The following inclusion criteria were adopted to select abstracts from potential articles retrieved from the databased: randomized controlled trials or clinical controlled trials; using any kind of Herbst appliances to correct Class II division 1 malocclusions; skeletal and/or dental changes evaluated through lateral cephalograms. The exclusion criteria included syndromic patients, individual case reports and series of cases and surgical interventions. Data extraction The following data were extracted: study design, participant information, the skeletal maturation of subjects, appliance types and
active treatment durations. The skeletal maturity indicators were HWM (hand wrist maturation) and CVM (cervical vertebrae maturation). The stage of CVM 2 (HWM 3–4) and CVM 3 (HWM 5–6) are around the peak growth period (10). Quality assurance To avoid subjectiveness during data acquisition, two orthodontic doctors independently conducted the acquisition following the above-mentioned strategies. Risk of bias was assessed according to Downs and Black quality assessment tool. Any disagreement was solved by discussion or judged by a third reviewer.
Meta-analysis The present study adopted Pancherz cephalometric analysis or PCA, which is considered as the standard method, to evaluate effects of the Herbst appliance. Besides the common items covered in PCA, other important clinical indices were also included for the evaluation. In specific, proposed outcomes included angular measurements (SNA, SNB, ANB, mandibular plane angle) and linear measurements [mandibular ramus height (Co-Go), total mandibular length (CoGn), overjet, overbite, molar relationship, sagittal position of the maxillary base (A point-OLp), sagittal position of the mandibular base (Pg-OLp)]. Egger’s test (11) and Begg’s test (12) were used to assess the publication bias through Stata 12.1. Furthermore, sensitivity analysis and subgroup analysis were performed to evaluate the robustness of the pooled results from the meta-analysis. Moreover, the quality of evidence was assessed by using GRADE system of rating quality of evidence (13–18).
Results The procedures of the electronic searching and selection are presented in Figure 1. Moreover, the details of the search strategy, as well as the number of abstracts selected from each database, are displayed in Table 1. According to the procedure in Figure 1 and strategy in Table 1, we retrieved 654 articles from those databases
Table 1. Database search and results. Database
Search terms
Pubmed
#1:Malocclusion, Angle Class II OR Angle Class II OR Class II, Angle OR Class II OR Distocclusion* OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: randomized controlled trial [pt] OR controlled clinical trial [pt] OR randomized [tiab] OR placebo [tiab] OR clinical trials as topic [mesh: noexp] OR randomly [tiab] OR trial [ti] #4: #1 AND #2 AND #3 #1: Angle Class II OR Class II, Angle OR Class II OR Distocclusion*OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: #1 AND #2 #1:Angle Class II OR Class II, Angle OR Class II OR Distocclusion* OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: #1 AND #2 #1: Angle Class II OR Class II, Angle OR Class II OR Distocclusion* OR Distal occlusion* #2: Herbst appliance* OR Herbst #3: #1 AND #2 (Angle Class II or distocclusion) and (Herbst or Herbst appliance) (Angle Class II or distocclusion) and (Herbst or Herbst appliance)
Web of science
Embase
Central
SIGLE ClinicalTrial.gov
Results
Included
29
2
375
2
211
11
39
0
0 0
0 0
326
European Journal of Orthodontics, 2016, Vol. 38, No. 3 ANB Eight studies (20,22–25,28–30) investigated this outcome. The meta-analysis revealed that the pooled MD of ANB for active treatment effect was −1.08 degrees [95% CI: −2.16, −0.00] (Figure 2). Mandibular plane angle Eight studies (5,20,22–26,30) investigated this outcome. The metaanalysis revealed that the pooled MD for active treatment effect was 0.17 degrees [95% CI: −0.09, 0.42] (Figure 2).
Linear measurements Overjet Seven studies (5,21,23,27–30) investigated overjet. The meta-analysis revealed that the pooled MD of overjet for active treatment effect was −4.82 mm [95% CI: −5.83, −3.80] (Figure 3). Overbite Six studies (21,23,26,28–30) investigated overbite. The active treatment effect outcome was a significant decrease in overbite and the meta-analysis revealed that the pooled MD of overbite was −1.69 mm [95% CI: −3.18, −0.21] (Figure 3). Figure 1. PRISMA flow diagram for studies retrieved through the searching and selection processes.
and 597 of them were identified as irrelevant initially. The remaining 57 articles were further assessed for eligibility resulting 12 final controlled clinical trial studies (CCTs). All inclusions were prospective studies and recruited only adolescents. The sample size ranges from 8 to 55; the active Herbst treatment duration ranges from 5 months to 30 months. The general information of each study is summarized in Table 2. The study quality scores using Downs and Black scale (19) were shown in Table 3. Because of the differences between studies and the high heterogeneity, we used the random model in all the outcomes’ analysis.
Description of outcomes For each outcome examined in this meta-analysis, measurements at active treatment effect period (the changes between before-Herbst treatment and immediately-after-Herbst treatment) were conducted. All included studies investigated the net changes before and after Herbst treatment except that the study reported annualized outcome changes instead. The GRADE assessments for quality of evidence for each outcome were shown in Table 4.
Description of interventions The intervention in this meta-analysis was Herbst appliance—one of the most commonly used treatment modality for Class II patients.
Effects of interventions In this section, we reports the meta-analysis results for each examined measure as follows.
Skeletal angular measurements SNA and SNB Eight studies (20,22–25,28–30) investigated SNA and SNB. However, all of them examined the active treatment effects only. As depicted in Figure 2, our meta-analysis revealed that the pooled differences in mean or MDs of SNA and SNB for active treatment effect were −0.56 degrees [95% CI: −0.99, −0.14] and 1.06 degrees [95% CI: 0.53, 1.60], respectively.
Co-Go Four studies (5,21,25,30) investigated the outcome of Co-Go. The active treatment effect was a significant increase in Co-Go with the pooled MD being 1.76 mm [95% CI: 1.27, 2.26] (Figure 3). Co-Gn Five studies (21,22,25,29,30) investigated the outcome of Co-Gn. The meta-analysis revealed that the pooled MD for active treatment effect was 1.74 mm [95% CI: 0.95, 2.53] (Figure 3). Molar relationship. Four studies (5,21,27,29) showed a significant decrease in molar relationship in active treatment period with the pooled MD being −5.70 mm [95% CI: −6.71, −4.69] (Figure 3). A point-OLp Six studies (5,21,22,24,27,29) showed a significant decrease in A point-OLp with the pooled MD being −0.52mm [95% CI: −0.73, −0.30] (Figure 3). Pg-OLp Seven studies (5,21,22,24,27–29) showed a significant increase in Pg-OLp with the pooled MD being 1.45 mm [95% CI: 0.43, 2.47] (Figure 3).
Sensitivity analysis and subgroup analysis The results of sensitivity analysis and subgroup analysis are summarized in Table 5 and Table 6, respectively. We conducted sensitivity analysis to examine the stability of present meta-analysis. In Wigal et al. (29), the brackets were bonded on upper anterior teeth. When this article was excluded in the sensitivity analysis, results regarding to ANB and overbite are unstable. We also performed a subgroup analysis since different types of Herbst appliances in the included studies may influence the results of present meta-analysis. These studies were divided into three subgroups, that is banded type (22,23,26,27), splint type (5,20,21,25,28) and edgewise crowned type (24,29,30), as shown
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X. Yang et al. Table 2. General information provided in the included studies. Study Baysal and Uysal (20)
Design
Participates
CCT (prospective) T: n = 20, M/F = 9/11, age = 12.74 ± 1.43 y C: n = 20, M/F = 11/9, age = 12.17 ± 1.47 y Baysal and Uysal CCT (prospective) T: n = 20, M/F = 9/11, (21) age = 12.74 ± 1.43 y C: n = 20, M/F = 11/9, age = 12.17 ± 1.47 y de Almeida et al. (22) CCT (prospective) T: n = 30, M/F = 15/15, age = 8.2 y–11 y C: n = 30, M/F = 15/15, age = 8.0 y–10.9 y Franchi et al. (5) CCT (prospective) T: n = 55, M/F = 28/27, age = 12 y 10 m ± 1 y 2m C: n = 30, M/F = 15/15, age = 14 y 2 m ± 1 y 2 m Küçükkeleş and CCT (prospective) T: n = 10, C: n = 10 Sandalli (23) 8 F (10.2 y), 12 M (10.6 y) LaHaye et al. (24) CCT (prospective) T: n = 19, M/F = 9/10, age = 11.7 ± 3 y C: n = 29, M/F = 14/15, age = 12.4 ± 1.5 y McNamara et al. CCT (prospective) T: n = 45, M/F = 27/18, (25) age = 12 y C: n = 21, M/F = 8/13, age = 11 y 1 m Pancherz et al. (26) CCT (prospective) T: n = 22, M/F = 19/3, age = 12 y C: n = 20, M/F = 17/3, age = 12 y Pancherz et al. (27) CCT (prospective) T: n = 22, M/F = 19/3, age = 12 y 1 m ± 11 m C: n = 20, M/F = 17/3, age = 11 y 2 m ± 9 m Sidhu et al. (28) CCT (prospective) T: n = 8, M/F = 0/8, age = 11 y 9 m C: n = 8, M/F = 0/8, age = 11 y Wigal et al. (29) CCT (prospective) T: n = 22, M/F = 7/15, age = 8.4 ± 1.0 y C: n = 22, age = 8.4 ± 1.1, M/F(N/A) Jakobsone et al. (30) CCT (prospective) T: n = 40, M/F = 20/20, age = 13.6 ± 1.3 y C: n = 18, M/F = 11/7, age = 13.9 ± 1.6
Criteria
Active treatment Skeletal maturation duration (m)
Appliance
Skeletal class II Stage 4 – Stage 5 (HWM)
T: 15.81 ± 5.96 C: 15.53 ± 3.13
Cast splint Herbst appliance
Skeletal class II Stage 4–Stage 5 (HWM)
T: 15.81 ± 5.96 C: 15.53 ± 3.13
Cast splint Herbst appliance
Skeletal class II Stage 1–Stage 3 (CVM)
T: 12 C: 12
Banded type Herbst appliance
Skeletal class II Stage 3–Stage 4 (CVM)
T: 1 y (±6 m) C: 1 y (±2 m)
Acrylic splint Herbst appliance
Skeletal class II Peak growth period (HWM)
T: 12 C: 12
Banded type Herbst appliance
Skeletal class II N/A
T: 12.7 ± 7 C: 2.2 ± 0.6 y
Edgewise crowned Herbst appliances
Skeletal class II N/A
T: 12 C: 22
Acrylic splint Herbst appliance
Skeletal class II Peak growth period (HWM)
T: 6 m 7d ± 14 d Banded type Herbst C: 6 m 6 d ± 11 d appliance
Skeletal class II Peak growth period (HWM)
T:6 m 7 d ± 14 d C:6 m 6 d ± 11 d
Banded type Herbst appliance
Skeletal class II N/A
T: 8 C: 8
Acrylic splint Herbst appliance
Skeletal class II NA
NA
Edgewise crowned Herbst appliance
Skeletal class II Stage 3–Stage 5 (CVM)
T: 12 m C: 12 m
Stainless steel crown Herbst appliance
M, male; F, female; N/A, not available; T, Herbst appliance treatment; C, control group; HWM, hand wrist maturation; CVM, cervical vertebrae maturation.
in Table 6. Our results demonstrated that different types of Herbst appliances have significant effect toward some examined measures. In specific, the subgroup analysis for the banded Herbst appliance resulted in a significant change in SNA, SNB, and Pg-OLp; the subgroup analysis for splint Herbst appliance revealed a significant change in SNA, ANB, overbite, and A point-OLp; and, Pg-OLp was detected to change significantly for the subgroup analysis of edgewise crowned Herbst appliance. Moreover, we divided the splint type into cast and acrylic splint types for a further subgroup analysis. The results showed significant differences exist in SNA (pooled
MD = 0.02, 95% CI: −1.10, 1.15) and ANB (pooled MD = 0.10, 95% CI: −4.08, 4.27). Furthermore, changes in effect models (fixed-effect or randomeffect model) failed to reveal any significant change.
Meta-regression Taking into account of the main factors of the Herbst treatment, the meta-regression was performed for this analysis. We extracted the age of the subjects and the treatment duration for the main factors. The results showed that age has no effect on the meta-analysis,
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Franchi et al. (5)
Küçükkeleş and Sandalli (23) LaHaye et al. (24) McNamara et al. (25) Pancherz (26) Pancherz (27) Sidhu et al. (28) Wigal et al. (29) Jakobsone et al. (30) 1 1 1 1 1 1 1
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13 16 15 15 18 16 18
19
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17 17 19
Quality score
Internal validity—bias: ‘Yes = 1,’ ‘No = 0,’ ‘Unable to determine = 0’ 14. Was an attempt made to blind study subjects to the intervention they have received? 15. Was an attempt made to blind those measuring the main outcomes of the intervention? 16. If any of the results of the study were based on ‘data dredging’ was this made clear? 17. In trials and cohort studies, do the analyses adjust for different lengths of follow-up of patients, or in case-control studies, is the time period between the intervention and outcome the same for cases and controls? 18. Were the statistical tests used to assess the main outcomes appropriate? 19. Was compliance with the intervention/s reliable? 20. Were the main outcome measures used accurate (valid and reliable)?
External validity: ‘Yes = 1,’ ‘No = 0,’ ‘Unable to determine = 0’ 11. Were the subjects asked to participate in the study representative of the entire population from which they were recruited? 12. Were those subjects who were prepared to participate representative of the entire population from which they were recruited? 13. Were the staff, places, and facilities where the patients were treated, representative of the treatment the majority of patients receive?
‘Yes = 2,’ ‘Partially = 1,’ ‘No = 0’ 6. Are the main findings of the study clearly described? 7. Does the study provide estimates of the random variability in the data for the main outcomes? 8. Have all important adverse events that may be a consequence of the intervention been reported? 9. Have the characteristics of patients lost to follow-up been described? 10. Have actual probability values been reported (e.g., 0.035 rather than
