REVIEW ARTICLE |
https://doi.org/10.5005/jp-journals-10015-2283 |
PowerScope™ for Class II Malocclusions: A Systematic Review and Meta-analysis
1-3Department of Orthodontics, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences (SIMATS) (Deemed to be University), Chennai, Tamil Nadu, India
Corresponding Author: Remmiya M Varghese, Department of Orthodontics, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences (SIMATS) (Deemed to be University), Chennai, Tamil Nadu, India, Phone: +91 9500085771, e-mail: remmiyav.sdc@saveetha.com
Received on: 06 June 2023; Accepted on: 08 July 2023; Published on: 31 August 2023
ABSTRACT
Aim: This systematic review and meta-analysis aimed to study the effects of PowerScope™ for the treatment of class II malocclusions.
Materials and methods: The review protocol was registered in the Prospective Register of Systematic Reviews (PROSPERO) database (www.crd.york.ac.uk/prospero, protocol number: CRD42022309678). A population, intervention, comparison, outcome, and study design (PICOS) criterion was developed to aid the search strategy and determine the eligibility of studies for inclusion in the review. A thorough systematic search of various scientific databases was performed to identify relevant studies. The risk of bias tool and methodological index for nonrandomized studies (MINORS) tool were used to evaluate the risk of bias.
Results: After screening of titles and abstracts, a total of 148 articles were identified. After the removal of duplicates, 82 articles remained. Finally, six studies were selected to be included in the qualitative analysis, and three studies were further included in the quantitative analysis. All of the included studies showed a high risk of bias, and the overall quality of the methodology was determined to be moderate. The quantitative analysis showed no significant difference in the treatment effects between the intervention and control groups.
Conclusion: The qualitative synthesis showed better skeletal changes with the Forsus Fatigue Resistant Device (FRD) appliance, whereas better dentoalveolar changes were seen with the PowerScope™ appliance. However, these results were not supported by results from the quantitative analysis.
Clinical significance: It is necessary to understand the clinical treatment outcomes of PowerScope™ in the management of class II malocclusions to recommend its utilization in contemporary clinical practice.
How to cite this article: Varghese RM, Subramanian AK, Maliael MT. PowerScope™ for Class II Malocclusions: A Systematic Review and Meta-analysis. World J Dent 2023;14(7):639–647.
Source of support: Nil
Conflict of interest: None
Keywords: Class II malocclusion, Functional appliances, Growth modulation, Malocclusion, Orthodontics, PowerScope
INTRODUCTION
Treating class II malocclusion has always been a challenging scenario for orthodontists, because of which the etiology and classification are of utmost significance in diagnosis and treatment procedures. In the 1890s, Edward H Angle, the father of orthodontics, presented a substantial classification that still holds in spite of the various drawbacks. Class II malocclusion denotes the state where the mandibular first molars occlude distal to the normal relationship with the maxillary first molar and consists of two components—one being dental class II and the second a skeletal class II. Class II malocclusion being one of the most common orthodontic problems is seen in about one-third of the population, with the most prominent diagnostic finding being mandibular skeletal retrusion.1-4 There is an eclectic array of functional appliances that facilitate mimicking mandibular growth by forward posturing of the mandible in order to correct this type of skeletal and occlusal conflict.5
The treatment options for class II malocclusion include extraction or nonextraction techniques. Several orthodontic appliances have been introduced with appropriate biological understanding and progressions in treatment mechanics to improve the competence of the orthodontic treatment.2-4 Certain myofunctional appliances, including the Activator, Bionator, Frankel’s functional regulator, and the Twin Block, are used to correct class II malocclusion during the active growth phase whereas, during the deceleration phases, other appliances like fixed twin block, Jasper Jumper, Herbst appliance, universal bite jumper, Forsus Fatigue Resistant Device (Forsus FRD) are frequently used.3,5,6
PowerScope™ is a modern invention developed by Dr Andy Hayes that exerts incessant force and harvests satisfactory dentoalveolar outcomes, including restraining maxillary growth, enhancing mandibular growth, distal maxillary movement, and mesial positioning of the mandibular arch. The protruded maxillary incisors are encroached to reveal the distally placed mandible, thus facilitating the path of mandibular closure. This functional appliance is devoid of patient amenability and can be used coupled with orthodontic brackets.7 PowerScope™ is available as an appliance that has a one-size-fits-all characteristic that is accumulated prior to rapid and easy chairside usage. It utilizes a wire-to-wire connection with add-ons placed mesial to the first molar in the upper arch and distal to the canine of the lower arch. They provide an anterior force to the mandible and a posterior force to the maxilla to initiate a dentoalveolar movement with mandibular skeletal advancement.8 Various authors have published their respective case reports of young individuals with the chief complaint of protruded anterior teeth inclining toward class II division I that was successfully corrected using PowerScope™ fixed functional appliances.7,15 The treatment effects of PowerScope™ fixed functional appliances have to be understood to be utilized in the contemporary clinical scenario. The treatment effects of PowerScope™ fixed functional appliances have to be compared with other treatment appliances and protocols that are already prevalent in the management of class II malocclusion to assess and evaluate the efficiency, efficacy, and intricacies of the PowerScope™ fixed functional appliance.
Hence, the aim of this systematic review and meta-analysis was to assess and evaluate the effects of PowerScope™ fixed functional appliance for the treatment of class II malocclusions.
MATERIALS AND METHODS
Protocol and Registration
The review protocol was registered into the Prospective Register of Systematic Reviews (PROSPERO) database (www.crd.york.ac.uk/prospero; protocol number: CRD42022309678). The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines16,17 were used to answer the following question: What skeletal, dental, and soft tissue changes occur when the PowerScope™ fixed functional appliance is used to treat class II malocclusion?
Eligibility Criteria
A population, intervention, comparison, outcome, and study design (PICOS) criterion (Table 1) was developed to aid the search strategy and determine the eligibility of studies for inclusion in the review. The formulated PICOS is as follows:
| Inclusion criteria | Exclusion criteria | |
|---|---|---|
| Population (sample) | Patients with skeletal class II with mandibular retrusion in the growth phase as assessed with the aid of skeletal maturity indicators. | Patients with skeletal class II with mandibular retrusion whose growth phase has been completed. |
| Intervention | PowerScope™ fixed functional appliance | Other fixed and removable class II and III functional appliances. |
| Control/comparison | Other fixed and removable class II functional appliances. | No control group or untreated control group. |
| Outcome | Skeletal, dental, soft tissue changes. | Airway changes. |
| Study design | Only randomized controlled trials and controlled clinical trials were included in the review. | Case reports, case series, animal studies, in vitro studies, material studies, microbial assays, and clinical trials without control groups. |
• Population (P): Patients in the growth phase having skeletal class II relation with mandibular retrusion.
• Intervention (I): Treatment of skeletal class II relation with mandibular retrusion with PowerScope™ fixed functional appliance.
• Comparison (C): Treatment of skeletal class II relation with mandibular retrusion with any other removable or fixed functional appliance.
• Outcome (O): The treatment effects on the skeletal, dental, and soft tissues.
• Study design (S): Only clinical trials with control groups were considered for inclusion in the review process.
This review considered only published articles. Articles published in English or with an English language translation attached were considered for inclusion in the review process.
Information Sources, Search Strategy, and Study Selection
A systematic search of the following listed databases, PubMed, Google Scholar, Cochrane CENTRAL, Scopus, Web of Science, China National Knowledge Infrastructure (CNKI), Ovid, Baidu Scholar, Scielo, and Latin American and Caribbean Health Sciences Literature (LILACS), was done to identify all peer-reviewed studies published from January 2009 to September 2021 pertinent to the review’s question. Detailed search strategies were developed for each database, taking into account the varying vocabulary and syntax limits of each database. The terms used for the search were “PowerScope,” “Functional,” “Fixed Functional,” and “Orthodontics.” Additionally, a manual search of various orthodontic journals, including the American Journal of Orthodontics and Dentofacial Orthopedics, Angle Orthodontist, Dental Press Journal of Orthodontics, European Journal of Orthodontics, Journal of Orthodontics, International Orthodontics, Journal of Oro-facial Orthopedics, Journal of World Federation of Orthodontists, Turkish Journal of Orthodontics, Journal of Indian Orthodontic Society, Korean Journal of Orthodontics, Taiwan Journal of Orthodontics, Clinical and Investigative Orthodontics, and Orthodontic Waves, was performed to identify studies to be included in the review. A search for gray literature was done on the databases Open Gray, and GreyNet International to identify any further studies that could be included in the review. References of the included studies were also reviewed to identify any studies that could be included in the review process.
The search was carried out independently by two authors (Remmiya M Varghese and Aravind S Kumar). The reviewers were not blinded to the results of the other’s search. The titles of the articles that were identified through the search were first screened to determine eligibility. Full-text studies that were found to be relevant were sought and evaluated for inclusion in the qualitative analysis. To resolve any disagreements that arose between the primary reviewers during the search and review process, a third reviewer (Mathew T Maliael) was consulted.
Data Collection Process
For each article included in the qualitative analysis, the following information was gathered: author names, year of publication, study design, sample size, number and mean age of participants, type of intervention, comparison groups, and results obtained (Table 2).
| S. no. | Author and year of publication | Type of study | Groups | Sample size | Mean age | Treatment time | Parameters evaluated | Conclusion |
|---|---|---|---|---|---|---|---|---|
| 1 | Kamoltham and Charoemratrte, 2018 (Songkhla, Thailand)38 | RCT | Group I—PowerScope™ Group II—class II elastics. |
Overall - 31 Group I—16 (9 females and 7 males) Group II—15 (9 females and 6 males) |
Group I—11.72 ± 1.09 years Group II—11.41 ± 0.9 years |
12 months | Skeletal, dental, and soft tissue changes. | Group I had a greater maxillary dento-alveolar restrictive effect. |
| 2 | Arora et al, 2018 (Rohtak, India)33 | RCT | Group I—PowerScope™ Group II—Forsus Fatigue Resistant Device. |
Overall—26 Group I—13 (6 females and 8 males) Group II—13 (9 females and 5 males) |
Group I—14.11 ± 1.3 years Group II—15.5 ± 1.1 years |
6 months | Skeletal changes, dental changes, patient comfort and operator convenience. | Group I group had a greater percentage of dentoalveolar effects than group II. |
| 3 | Kaur et al., 2021 (Ambala, India)36 | CCT | Group I—PowerScope™ Group II—Forsus fatigue resistant device. |
Overall—20 Group I—10 Group II—10 (12 females and 8 males) |
12 to 15 years | 6–9 months | Skeletal, dental, and soft tissue changes. | Skeletal, dental, and soft tissue changes were similar between the groups. |
| 4 | Shetty et al., 2021 (Deralakatte, India)37 | RCT | Group I—PowerScope™ Group II—Forsus fatigue resistant device. |
Overall - 20 Group 1–10 Group 2–10 |
11.6 ± 1.2 years. | Until class I molar relation was obtained. | Skeletal, dental, and soft tissue changes. | Group I had greater dentoalveolar and airway changes than group II. Group II had greater skeletal changes. |
| 5 | Varghese et al., 2021 (Chennai, India)34 | RCT | Group I—PowerScope™ Group II—Forsus fatigue resistant device. |
Overall—12 Group I—6 Group II—6 |
14–16 years | 6 months | Skeletal and dental changes. | Group II had a greater restraint on the maxilla and forward movement of mandibular molars. |
| 6 | Shalu et al., 2021 (Calicut, India)42 | CCT | Group I—PowerScope™ Group II—Forsus fatigue resistant device. Group III—class II elastics. |
Overall—36 Group I—12 Group II—12 Group III—12 |
– | Not specified. | Dental changes. | Dental changes were similar between the groups. |
CCT, controlled clinical trial; RCT, randomized controlled trials
Quality Assessment of the Included Studies
The Cochrane Collaboration’s tool for assessing the risk of bias in randomized trials was used for the randomized controlled trials,18 and the methodological index for nonrandomized studies (MINORS) tool19 was used to assess the risk of bias of the nonrandomized controlled trials included in the review. The methodological score for clinical trials, developed by Lagravere et al. and modified by Sharshar and El-Bialy was used to assess the quality of the included studies (Fig. 1).20,21 Publication bias was assessed using Egger’s test.22,23
Fig. 1: Methodological scoring criteria for the clinical trials
RESULTS
Relevance Determination, Validation, and Data Extraction from Included Studies
After searching the various databases, 148 studies were identified. After the duplicates were removed, 82 articles remained. After screening the titles, 17 articles were deemed relevant. After reviewing the abstract, nine studies were removed from consideration because they did not have control groups.1,24-31 The full text was retrieved for the remaining eight studies. After a review of the full text, two studies were eliminated as one study did not satisfy the outcome evaluation parameter of the eligibility criteria,32 and another did not report its findings clearly.33 The PRISMA flowchart describes the reasons for elimination (Flowchart 1). Finally, six studies were included in the qualitative analysis,33-38 and three studies were included in the quantitative analysis.33,34,37
Flowchart 1: Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) diagram outlining the article selection process for the review
Risk of Bias and Quality Assessment in the Studies
All of the studies in the qualitative analysis33,38 had a high risk of bias (Table 3 and Fig. 1). Three of the included studies showed a good quality of methodology,33,34,38 in contrast, the remaining three studies showed a poor quality of methodology (Table 4).35-37 Since the number of studies included in the qualitative analysis was <10, the test for publication bias was not performed.
| Quality item | Kaur et al., 2021 | Shalu et al., 2021 |
|---|---|---|
| A clearly stated aim | 2 | 2 |
| Inclusion of consecutive patients | 2 | 2 |
| Prospective collection of data | 2 | 2 |
| Endpoints appropriate to the aim of study | 2 | 2 |
| Unbiased assessment of the study endpoint | 0 | 0 |
| Follow-up period appropriate to the aim of the study | 2 | 2 |
| Loss to follow up <5% | 2 | 2 |
| Prospective calculation of the study size | 0 | 0 |
| An adequate control group | 2 | 2 |
| Contemporary groups | 2 | 2 |
| Baseline equivalence of groups | 2 | 2 |
| Adequate statistical analyses | 2 | 2 |
| Total | 20 | 20 |
| S. no. | Articles | A | B | C | D | E | F | G | H | I | J | K | L | M | N | Total no. of checks | Percentage of total |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Kamoltham and Charoemratrte, 2018 | + | + | ++ | ++ | + | + | + | + | ++ | ++ | / | +/ | / | +/ | 16 | 80 |
| 2 | Arora et al., 2018 | + | + | ++ | ++ | + | + | + | + | ++ | ++ | / | +/ | / | ++ | 17 | 85 |
| 3 | Kaur et al., 2021 | + | + | ++ | // | + | / | / | + | // | // | / | +/ | / | +/ | 8 | 40 |
| 4 | Shetty et al., 2021 | + | + | ++ | // | + | + | + | + | // | // | / | +/ | / | +/ | 10 | 50 |
| 5 | Varghese et al., 2021 | + | + | ++ | ++ | + | + | + | + | ++ | ++ | / | +/ | / | +/ | 16 | 80 |
| 6 | Shalu et al., 2021 | + | + | ++ | // | + | + | / | + | // | // | / | +/ | / | +/ | 9 | 45 |
Results of Individual Studies
Difference of Skeletal Changes between the Intervention and Control Groups
Kamoltham and Charoemratrte reported a significant increase in Co-A [midfacial length (distance from condylion to point A)] by 1.32 mm/year, and Co-Gn [mandibular length (distance from condylion to gnathion)] by 1 mm/year in the class II elastics group than the PowerScope™ group. They also reported a significant decrease in A-Np (distance from point A to N-perpendicular) by 0.3 mm/year and a significant decrease in Sn-GoMe [angle between the sella-nasion plane and mandibular plane (plane tangent to gonial angle and gnathion) by 0.6°/year in the PowerScope™ group when compared to the class II elastics group. Additionally, they also reported that the Frankfort horizontal-mandibular plane angle (FH-MP) (plane tangent to lower border of the mandible and the lowest point at symphysis) decreased by 0.9°/year in the PowerScope™ group and increased by 0.4°/year in the class II elastics group.38 Arora et al. reported that sella-nasion-point B angle (SNB) and accumulation of maxillary and mandibular growth relative to cranial base (ABCH) (ABCH = Max + Mand) were greater in the Forsus FRD group (SNB—3.76 ± 0.55°/ABCH—3.08 ± 0.32°) than the PowerScope™ group (SNB—2.92 ± 0.52°/ABCH—2.25 ± 0.37°).33 Kaur et al. reported a significant increase in angle between sella-nasion-point A (SNA) in the PowerScope™ group when compared to the Forsus FRD group. They also reported a significant decrease in the gonial angle and lower gonial angle in the Forsus FRD group when compared to the PowerScope™ group.36 Shetty et al. reported a significant difference in angle between the sella-nasion plane and occlusal plane (Sn-OP) (the line connecting the region of the overlapping cusps of first premolars and first molars), and hyoid triangle (the hyoid triangle relates the hyoid bone to the vertebrae and to the mandible) between the PowerScope™ group and Fosrus FRD groups with the Forsus FRD group showing a greater increase.37 Varghese et al. did not identify any significant difference in skeletal parameters between the PowerScope™ group and Fosrus FRD groups (Fig. 2).34
Fig. 2: Risk of bias chart of the randomized trials included in the review
Difference of Dental Changes between the Intervention and Control Groups
Kamoltham and Charoemratrte reported a significant increase of the perpendicular distance from the mesiobuccal cusp tip of the first molar with the functional occlusal plane to the inferior border of palate (PDH) by almost 1 mm in the class II elastics group. In contrast, it remained unchanged in the PowerScope™ group. The sagittal dental and overbite changes were insignificant between the groups.38 Arora et al. reported a significantly better Overjet correction (Forsus FRD—6.63 ± 0.59 mm; PowerScope™—5.91 ± 0.47 mm), change in molar relation (Forsus FRD—5.8 ± 0.51 mm; PowerScope™—5.37 ± 0.45 mm), and increase the palatal movement of upper incisors (Forsus FRD—1.26 ± 0.31 mm; PowerScope™—0.86 ± 0.12 mm) in Forsus FRD group than the PowerScope™ group.33 Whereas the mesial movement of the lower molar was significantly greater in the PowerScope™ group when compared to the Forsus FRD group (Forsus FRD—1.94 ± 0.21 mm; PowerScope™—2.37 ± 0.34 mm).33 Shalu et al. reported a significant difference in the change in molar relation when the PowerScope™ and Forsus FRD were compared to the control (class II elastics) group. Still, the difference was not significant when the PowerScope™ group and Forsus FRD group were compared against each other.35 They also reported a significant difference in the mesial position of the mandibular molar, with the PowerScope™ group showing the greater value (Forsus FRD—6.1 mm; PowerScope™—9.2 mm).35 Kaur et al. reported a significantly higher distance between the incisal tip of the mandibular incisors and the line from nasion to point B (L1-NB) and significantly higher interincisal angle of the mandibular plane to the lower incisor axis (IMPA) (it is the angle formed between the line passing tangent to the lower border of the mandible and the long axis of the lower incisor) in the PowerScope™ group when compared to the Forsus FRD.36 Shetty et al. reported distal movement of the maxillary molars was greater in the Forsus FRD group (Forsus FRD—1.3 mm; PowerScope™—0.8 mm) and mesial movement of the mandibular incisors (Forsus FRD—2.3 mm; PowerScope™—2.8 mm) and molars (Forsus FRD—1.9 mm; PowerScope™—2.3 mm) was greater in the PowerScope™ group.37 Varghese et al. did not identify any significant difference in dental parameters between the PowerScope and Forsus groups.34
Difference of Dental Changes between the Intervention and Control Groups
Kamoltham and Charoemratrte did not identify significant soft tissue changes between the PowerScope™ and Class II groups.38 Shetty et al. reported a significant change in angle between the line tangents to the base of the nose and upper lip (NLA) in the PowerScope™ group (became more obtuse; by nearly 4°/year), but it did not change in the class II group.37 Kaur et al. reported a significantly better change in NLA in the Forsus FRD group and a significantly better change to the upper lip to E line value in the PowerScope™ group.36
Results of Quantitative Analysis of Included Studies
For the parameters evaluated in the quantitative analysis [SNA, SNB, A point-nasion-B point angle (ANB), and IMPA], no significant difference was identified between the PowerScope™ and the Forsus FRD groups (Figs 3A to D).
Figs 3A to D: (A) Forest plot for SNA difference between the PowerScope™ and Forsus FRD groups; (B) Forest plot for SNB difference between the PowerScope™ and Forsus FRD groups; (C) Forest plot for ANB difference between the PowerScope™ and Forsus FRD groups; (D) Forest plot for IMPA difference between the PowerScope™ and Forsus FRD groups
DISCUSSION
Summary of Evidence
This systematic review protocol was designed with a clear objective to evaluate the treatment effects, mainly the skeletal, dental, and soft tissue changes occurring due to the management of class II malocclusion due to mandibular retrusion in patients at their peak mandibular growth phase. As such, an exhaustive effort was made to scour through the various scientific databases, various journals, and other sources to select studies that can be included in this scientific review process. In the end, six studies were selected for qualitative analysis, and three of these studies were further evaluated quantitatively. The data extracted in the qualitative synthesis showed that when skeletal parameters were considered, especially in the mandible, the control groups (Forsus FRD and class II elastics groups) had better changes; thus, these appliances were better than PowerScope™ in bringing out a positive skeletal change in the mandible. However, Kamoltham and Charoemratrte state that class II elastics requires more treatment time than PowerScope™ to achieve the desired treatment result.38 The assessment of dental parameters showed mixed results. The mesial movement of the lower molars and proclination was significantly greater in the PowerScope™ group when compared to the Forsus FRD group.33,36,37 The IMPA was significantly greater in the PowerScope™ group. Whereas the palatal movement of the upper incisors, change in molar relation, and the overjet correction were better in the Forsus FRD group.33,36,37 The observation by Shalu et al. was that the change in molar relation was significant in the post hoc test when PowerScope™ and Forsus FRD groups were compared to the control group (class II elastics group).35 Shalu et al. also reported that mesial molar movement was significantly higher in the PowerScope™ group than in the Forsus FRD group.35 The soft tissue changes showed that the NLA changes were better with Forsus FRD, but the upper lip to E line change was better with PowerScope™.36,37 Kamoltham and Charoemratrte did not identify any significant changes in the soft tissue with treatment with PowerScope™ and class II elastics,38 but they observed that the posterior dental height significantly increased in the PowerScope™, but it did not increase in the class II elastics group. Varghese et al. was the only study included in the review that did not identify any significant changes in the skeletal and dental parameters between the PowerScope™ and Forsus FRD groups.34
The results from the quantitative synthesis showed that the parameters evaluated showed no significant changes between the PowerScope™ and Forsus FRD groups. The overall risk of bias in the studies included in the review was high, and the overall methodological quality was determined to be moderate. Three of the studies included displayed a good quality of methodology, but the remaining three studies displayed a poor quality of methodology. This poor quality of methodology was attributed to the lack of randomization35,36 and to a lack of evaluation of interoperator reliability.35-37
Arora et al. in their study also investigated the patient and operator comfort when using PowerScope™ and Forsus FRD groups. Their results showed that the initial discomfort was comparable between the appliances but PowerScope™ patients had significantly more discomfort while eating initially. The installation time was significantly lesser in the PowerScope™ group compared to the Forsus FRD group.33
The greater skeletal change seen Forsus FRD group was seen and concurred in the meta-analysis by Linjawi and Abbassy.39 Various other studies also came to a similar conclusion.40-48 The improvement in the mandibular dental changes seen in the PowerScope™ group when compared to the Forsus FRD group was postulated by Hong et al. and Khumanthem et al.10,43 due to the point of attachment of PowerScope™ appliance directly on the mandibular archwire. The impact of maxillary dental changes in the Forsus FRD group when compared to the PowerScope™ group was attributed by Mahamad et al. to be due to the attachment of the Forsus FRD appliance on the maxillary molars.44 Studies that evaluated the treatment effects of class II elastics mostly focused on dentoalveolar changes.45,46 Although these studies recommend that class II elastics were a satisfactory treatment option in the management of class II malocclusion, the outcome and treatment were dependent on patient compliance.45,47 The dentoalveolar changes reported on treatment with class II elastics in the included studies did not replicate the results of other studies that have reported effects of class II elastics in the correction of class II malocclusion.35,38,45,47 The soft tissue changes seen in the included studies have been attributed by Jones et al. and Heinig and Göz to be due to the reciprocal distal force on the upper dentition.47,48
Limitations and Recommendations for Future Research
A major limitation of this review is the small number of studies, the limited sample sizes in these studies that were included for both the qualitative and quantitative analyses, and the high risk of bias of the included studies. The poor quality of methodology of three of the included studies also poses a major limitation in achieving the objective of this review. The inconclusive result of the quantitative analysis also poses a limitation for clearly assessing and comparing the treatment effects of PowerScope™ when utilized for correction class II malocclusion. The treatment effect on the airway due to PowerScope™ was not clearly studied in the included studies. All these limitations hinder the translation of the results of the included studies into contemporary clinical practice. A few more trials with larger sample sizes, standard reporting of the results and longitudinal follow-up will help better assess and evaluate the treatment effects of PowerScope™ in correcting class II malocclusion.
CONCLUSION
After a careful evaluation of the extracted data from the included studies, the qualitative synthesis showed better skeletal changes with the Forsus FRD appliance, whereas better dentoalveolar changes were seen with the PowerScope™ appliance. However, these results were not supported by results from the quantitative analysis, which indicated that the difference in treatment effects between Forsus FRD and PowerScope™ appliances was not significant. Thus, studies with better quality methodologies, greater sample size, and longitudinal follow-up are required to better assess the treatment effects of the PowerScope™ appliance.
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