Comparison of dentoskeletal changes in skeletal class II cases using two different fixed functional appliances: Forsus fatigue resistant device and powerscope class II corrector—A clinical study

Remmiya Mary Varghese; Aravind Kumar Subramanian; Swapna Sreenivasagan

doi:10.4103/jioh.jioh_246_20

ORIGINAL RESEARCH

Year : 2021 | Volume : 13 | Issue : 3 | Page : 234-244

Comparison of dentoskeletal changes in skeletal class II cases using two different fixed functional appliances: Forsus fatigue resistant device and powerscope class II corrector—A clinical study

Remmiya Mary Varghese, Aravind Kumar Subramanian, Swapna Sreenivasagan
Department of Orthodontics, Saveetha Dental College, Saveetha Institute of Medical And Technical Sciences, (SIMATS), Saveetha University, Chennai, Tamil Nadu, India

Date of Submission	23-Jul-2020
Date of Decision	15-Feb-2021
Date of Acceptance	21-Feb-2021
Date of Web Publication	18-Jun-2021

Correspondence Address:
Dr. Aravind Kumar Subramanian
Department of Orthodontics, Saveetha Dental College, Saveetha Institute of Medical And Technical Sciences, (SIMATS), Saveetha University, Chennai, Tamil Nadu.
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jioh.jioh_246_20

Abstract

Aim: To compare the dentoskeletal changes of patients diagnosed with skeletal class II (14–16 years of age) treated with Forsus fatigue resistant device (FFRD) and Powerscope class II corrector (PS). Materials and Methods: The study is a prospective clinical study, with a sample of 12 patients who were diagnosed with skeletal class II with a CVMI stage IV and at the end of the leveling and aligning phase of a fixed multibracket orthodontic therapy. A total of 17 patients were included in this study by using a simple randomization method, which used sealed opaque envelopes; five patients dropped out during the course of the study. Data were analyzed for 12 patients, and each group comprised six patients. The FFRD was compared with the PS. Lateral cephalograms, photographs, and study models of the patients were obtained for the analysis. Statistical analysis was done by using SPSS software. The statistical analysis performed comprised Dahlberg’s error test, paired T test, and independent T test. Results: Treatment effects demonstrated that the Forsus and Powerscope had significant restraint of the maxilla. Vertical changes as seen by assessing FH-MP and OP-SN angles were found to be increased in both groups. Lower incisors moved labially by 2.5 mm in the Powerscope group and 1.98 mm in the Forsus group, which also contributed to the correction of the overjet. Linear measurements showed that the Powerscope led to a greater mandibular lengthening (4.06 mm) as compared with that of Forsus (3 mm). Anterior mandibular displacement accounted for 3.23 mm of 5.10 mm by using Powerscope appliance and 3.16 mm of 4.90 by using Forsus appliance. Conclusions: Pre- and posttreatment changes were statistically significant for both FFRDs and PS. Both the PS and FFRD are acceptable compliance-free appliances for class II correction. The PS has a greater restraint on the maxilla, more forward displacement of mandibular molars, and lower incisor proclination as compared with the Forsus appliance.

Keywords: Fixed Functional Appliances, Forsus Fatigue Resistant Device, Powerscope Class II Corrector, Skeletal Class II Malocclusion

How to cite this article:
Varghese RM, Subramanian AK, Sreenivasagan S. Comparison of dentoskeletal changes in skeletal class II cases using two different fixed functional appliances: Forsus fatigue resistant device and powerscope class II corrector—A clinical study. J Int Oral Health 2021;13:234-44

How to cite this URL:
Varghese RM, Subramanian AK, Sreenivasagan S. Comparison of dentoskeletal changes in skeletal class II cases using two different fixed functional appliances: Forsus fatigue resistant device and powerscope class II corrector—A clinical study. J Int Oral Health [serial online] 2021 [cited 2023 Jun 7];13:234-44. Available from: https://www.jioh.org/text.asp?2021/13/3/234/318446

Introduction

Fixed functional appliances are reported to correct class II skeletal problems by encouraging mandibular growth and by eliciting dentoalveolar effects.^[1],[2] Different compliance-free appliances include: the Herbst, Mandibular Anterior Repositioning Appliance (MARA), Mandibular Protraction Appliance, Jasper Jumper, Bio bite corrector, Twin force bite corrector, FFRD, and PS. These appliances have the ability to be used in conjunction with comprehensive fixed therapy. However, some side effects from these fixed interarch appliances may be lower incisor proclination^{[3],[4],[5],[6],[7],[8],[9]}; and upper molar tipping.^[9]

The FFRD is a fixed Class II appliance that was developed by Vogt.^[10] The FFRD (3M Unitek corps, Monrovia, CA) is a three-piece, semirigid telescoping system incorporating a super elastic nickel–titanium coil spring that can be assembled chair-side in a relatively short amount of time. The distal end of the maxillary molar tube to the distal side of the mandibular canine with the patient in centric occlusion is measured by using the measuring guide. An L-pin serves to attach it to the maxillary headgear tube. A circular loop is placed in the mandibular arch distal to the canine bracket for attachment of the push rod. It is compatible with complete fixed orthodontic appliances and can be incorporated into pre-existing appliances. The push rod, which is the mesial end of the appliance, is attached to the mandibular arch wire distal to the canine or first premolar bracket. The telescoping cylinder is inserted into the maxillary molar headgear tube.^[11] There are numerous studies that have evaluated the effects of the Forsus^[3],[7],[10] and compared it with intermaxillary elastics^[2] and untreated controls.

Powerscope has a ready-to-use concept, and unlike other Class II correctors,^[12],[13] there is no need for assembly, measuring, or appliance manipulation. The appliance is placed mesial to the first molar in the maxillary arch and distal to the canine of the mandibular arch. There are case reports showcasing the treatment effects of the PS. Thus, the aim of the present study was to compare the dentoskeletal changes in cases diagnosed with skeletal Class II by using the FFRD and PS.

Materials and Methods

This is a prospective clinical study conducted in the Department of Orthodontics and Dentofacial Orthopaedics, Postgraduate Institute of Dental Sciences, Chennai, India. The randomization was done by a computer-generated sequence.

The sample size was calculated based on the statistical evaluation of the previous study.^[14] A total of 12 patients were required to obtain a power of 95% and an alpha error of 0.05, with six participants per group. After detailed explanation of the procedure, informed consent was taken from all patients who matched the inclusion criteria and agreed to participate. All doubts of the patients regarding the study were clarified. Initially, 17 patients were selected for the study according to the inclusion and exclusion criteria mentioned. However, five patients dropped out during the course of the study due to various reasons. Those five patients were not analyzed in the study.

The inclusion criteria of the participants are: patients with skeletal class II malocclusion, aged 14–16 years, CVMI stage IV, overjet >/−4 mm, at the end of the leveling and aligning stage of a fixed multibracket orthodontic therapy. The exclusion criteria for this study include: other types of skeletal malocclusion, congenitally missing teeth, impacted teeth, malformed and retained deciduous teeth, periodontally compromised patients, medically compromised patients, previous history of active orthodontic treatment, and patients with temporomandibular disorders or any other systemic diseases affecting bone and growth. The patients were scheduled for a six-month follow-up period. The appliances used in this study include the MBT bracket prescription, FFRD (3M), and PS (AO).

All the treatment interventions in both groups were done by the same principal investigator. Fixed orthodontic treatment using 0.022 MBT prescription (3M Unitek) was initiated for all patients. Initial leveling and aligning was done. Leveling and aligning was sequentially carried out up to 19 × 25 SS wire in all the patients. Before the placement of the fixed functional appliance, diagnostic records were taken. At the end of the six-month follow-up period, post-functional appliance records, namely the extraoral photographs, intraoral photographs; study models, and lateral cephalograms (T1), were used.

GROUP 1 (G1): FFRD

GROUP 2 (G2): PS

The cephalograms taken at T1 and T2 were traced by a single operator to avoid errors due to interexaminer variability. The cephalograms were traced on matte acetate paper with a 3H pencil under double illumination. The coinvestigator who analyzed pre- and post-functional radiographs of both groups and the statistician were blinded with regard to the group to which each of the lateral cephalograms belonged.

Statistical analysis

The various parameters that were measured [Table 1] were tabulated by using an excel sheet. The values obtained were subjected to statistical evaluation by using SPSS software (SPSS Inc., Chicago, IL, USA), and the statistical analysis performed included Dahlberg’s error test, paired T test, and independent T test. The pitchfork analysis portrays the changes in molar and incisor relationships as an algebraic sum of skeletal growth relative to the cranial base and dental movements relative to the basal bone. The apical base change (ABCH) is the total amount of the maxillary and mandibular skeletal growth changes, and it signifies the overall effect of skeletal growth. These measurements are all made relative to the mean functional occlusal plane.

Table 1: Parameters used for cephalometric analysis in this study. Skeletal parameters used are helpful in assessing the efficacy of other functional appliances. Dental parameters indicate the tipping and angulation changes in the molar and incisor regions

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Results

The results obtained from statistical evaluation are given in the following tables [Figure 1]. Dahlberg’s method of error determination did not show any intraoperator error (correlation coefficient <0.001).^[15] The arithmetic mean and standard deviation were calculated. Paired T test with a 95% confidence interval (PCI) was conducted for both Groups 1 and 2. Statistical significance level was established at P < 0.05. An independent T test to test the equality of dentoskeletal changes between the two fixed functional appliances, that is, FFRD and PS, was conducted.

Figure 1: Consort flow diagram representing the flow of the patients throughout the study

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There was significant improvement in the maxillomandibular relationship with significant lengthening of the mandible. There was retroclination of maxillary incisors, proclination of mandibular incisors, extrusion and sagittal displacement of mandibular molars, and clockwise rotation of occlusal plane. The amount of dentoskeletal changes was significant in both groups, as shown by the paired t test, but between both groups the independent T test showed no significant difference. Treatment effects demonstrated that the Forsus and Powerscope had significant restraint of the maxilla (SNA); however, when compared between the groups, the results were not significant. A significant decrease in the inclination of upper incisors (U1 to SN) was seen in both Forsus and Powerscope groups [Figure 2] and [Figure 3]; however, any result was found to be statistically not significant when compared between both groups. A vertical change as seen by assessing FH-MP and OP-SN angles was found to be increased in both groups, respectively. When compared between the groups, the results were found to be statistically not significant.

Figure 2: Treatment using FFRD

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Figure 3: Treatment using PS

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Vertical measurement showed significant extrusion of upper incisors and molars in both groups [Table 1] and [Table 2]. When compared between the two groups, both upper incisors and molars were shown to have nonsignificant differences. Extrusion of lower incisors and molars was found in the Forsus and Powerscope group [Table 3]. When compared between two groups, differences were found to be not significant [Table 4]. Anteroposterior disharmony between the jaws was corrected, as assessed by ANB angle. When compared, this was found to be statistically significant in both groups (P = 0.002, P = 0.020). When compared between two groups, differences were found to be insignificant. Linear measurements showed that Powerscope led to greater mandibular lengthening (4.06 mm) as compared with that of Forsus (3 mm). When compared, the difference was found to be insignificant. The pitchfork analysis summarizes the sagittal maxillary and mandibular molar movements relative to the cranial base. ABCH, the anteroposterior change in the relationship between the maxilla and mandible, made a mean positive contribution in both the groups.

Table 2: Comparison between pre- and post-treatment mean and standard deviation of the skeletal and dentoalveolar changes in patients treated with FFRD

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Table 3: Comparison between pre- and post-treatment mean and standard deviation of the skeletal and dentoalveolar changes in patients treated with PS

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Table 4: Independent T test to compare the mean and standard deviation of the skeletal and dentoalveolar changes in patients treated with FFRD and PS

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Mandibular base measurement showed significantly greater increments in both groups. Anterior mandibular displacement accounted for 3.23 mm of 5.10 mm by using Powerscope appliance and 3.16 mm of 4.90 by using Forsus appliance. Lower incisors moved labially by 2.5 mm in the Powerscope group and 1.98 mm in the Forsus group, which contributed to the correction of overjet. Upper incisors moved palatally by 1.16 mm in the Powerscope appliance and 1.00 mm in the Forsus appliance, which contributed to the reduction of overjet.

Discussion

A wide range of orthopedic appliances is available for the correction of class II skeletal and occlusal disharmonies. The main objective is to induce supplementary lengthening of the mandible by stimulating an increase in growth at the condylar cartilage. The functional appliance affects remodeling of the mandibular condyle and glenoid fossa, repositioning of the mandibular condyle, and autorotation of the mandibular bone.^[16] Both fixed functional appliances were able to induce significant skeletal and dentoalveolar changes in subjects with class II malocclusion during the period of active treatment. The discussion is categorized into five sections: maxillary skeletal, mandibular skeletal, maxillary dental, mandibular dental, and overall effects.

In most of the functional appliances, maxilla comes forward, which is an expected pattern of normal growth^[17]; however, the overall treatment effects demonstrated that the Forsus and Powerscope had some amount of restraint of the maxilla. This finding is supported by Franchi et al,^[18] who observed that the Forsus had significant restriction on the maxilla. In this study, the greater restraint of the maxilla observed by the Powerscope appliance as compared with the Forsus appliance gives a greater orthopedic effect. Vertical changes as seen by assessing OP-SN angles were found to be increased in both groups. When compared within the groups, the results were found to be significant; however, the results were not significant between the groups.

In previous investigations of the Forsus, different methods were used to measure mandibular length; in a study by Jones et al, who used the pitchfork analysis for the Forsus, the mandibular skeletal findings were similar.^[19] In the overall treatment effects, the Powerscope appliance portrayed a statistically significant increase in mandibular protraction in comparison to the Forsus. Vertical changes, as seen by assessing FH-MP, were found to be increased in both groups, respectively. Longitudinal effects (T0-T1) were found to be statistically significant; however, intergroup comparison did not show any statistically significant difference. The overall movement of the maxillary dentition was significant in the Forsus and Powerscope groups. This distal displacement of the upper molar could be due to the greater force placed on the upper molar by the spring of the Powerscope appliance. In both groups, the upper molar crowns moved distally.^[13] The upper incisors in both groups were slightly distalized and more upright.

Between the Forsus and the Powerscope, the overall mandibular dental treatment effects were statistically significant. During the appliance treatment phase, the Powerscope group had a greater amount of lower incisor proclination in comparison to the Forsus group. Extrusion of lower incisors and molars was found in the Forsus group, whereas significant extrusion was found in both incisors and molars in the Powerscope group. When compared within the groups, the results were found to be significant; however, between the groups, the results were not significant. The overall treatment effects show that most of the molar correction in both the Forsus and Powerscope came from skeletal and dental effects. The largest contribution to the skeletal changes came from the mandible in both groups. Vertical changes were seen in both groups, as assessed by OP-SN and FH-MP. The results were found to be more in the Powerscope group as compared with the Forsus group. This may be due to increased extrusion of upper and lower molars seen with Powerscope than the Forsus. Another significant difference was seen in Incisor Mandibular Plane Angle (IMPA) between the two groups. Significant mandible sagittal advancement (SNB) with dental protraction was observed with a significant increase in the mandibular length. The maxilla-mandibular skeletal relation (ANB) reduced considerably, which improved the profile and facial aesthetics. Pronounced correction of the overjet was seen.

Weiland and Bantleon^[20] reported a minimal posterosuperior displacement of the maxilla. Our study showed a similar effect on the maxillary dentition. The retrusion and extrusion of maxillary incisors and the distalization of the maxillary molars seen in the present study have also been reported by several investigators. We observed a mesial displacement of the mandibular dentition. This displacement has also been documented by Cope et al^[9] (Cope et al. 1994), Covell et al.^[4] (Covell DA Jr et al. 1999), and Weiland and Bantleon^[20] (Weiland and Bantleon 1995). Proclination of the mandibular incisors was the most pronounced dental side effect reported in the present study. Several cephalometric studies have supported this finding, although there were variations in the extent of this effect. Oliveira et al^[5] (Alves and Oliveira 2008) reported a very similar finding, stating the significant mesial migration of the mandibular molars during Herbst treatment. Stucki and Ingervall and others demonstrated an increase in mandibular length.^[21]

On completion of treatment, the patient’s facial profile was orthognathic because of the soft-tissue modifications and the mandibular advancement. The lower incisors were slightly proclined, whereas the upper incisors were upright. Significant improvement was observed in the patient’s dental aesthetics, including achievement of ideal overjet. When looking at the skeletal effects of the FFRD, the articles by Franchi, Heinig, Karacay, and Bilgic all found that the Forsus TM had a restraining effect on the maxilla. Karacay found an increase in mandibular length and posterior face height due to adaptive growth of the condyle. Aras agreed with Karacy about the increase in mandibular length. Jones also found mandibular displacement that was somewhat negated by the mesial dental movement of the lower dentition. On the other hand, he also found a distal movement of the maxilla in the Forsus. Forsus TM may have a restraining effect on the maxilla; the majority of its class II molar correction is derived from mandibular dentoalveolar movements.

Significant dental effects were noted by every article. Franchi, Heinig, Karacay, Gunay, and Bilgic all noted that the maxillary incisors were retroclined during the course of treatment. In addition to these articles, the article by Aras also agreed that these incisors were also extruded during the course of treatment. The article by Jones disagreed with these other six and found that the upper incisors moved mesially, not distally during the course of treatment. In terms of the maxillary first molars, Karacy, Bilgic, and Gunay all noted intrusion, whereas Karacy, Bilgic, Aras and Heinig also noted distalization. This supports the claims that the Forsus TM has a headgear-like effect on the upper arch. The FFRD (Forsus; 3M Unitek, Monrovia, Calif) is a fixed functional appliance that has received increasing interest as an effective and noncompliant option for class II division 1 treatment.^[22]

Flaring of lower incisors has been a long-standing consequence of functional appliance treatment. The mandibular first molars were noted to be mesialized in all articles except Gunay, which made a more generalized note of mesialization of the mandibular dentition with significant flaring of the lower incisors [Table 5]. Often, the mesialization of the mandibular molars negated some of the skeletal effect created by the functional appliance through mandibular advancement. Jones specifically noted this by saying that mandibular displacement accounted for 3.8 mm or 138% change, and mesial molar movement was 56% of the total correction. These dentoalveolar effects accounted for the reduction in overjet in patients treated with fixed functional appliances.

Table 5: Independent T test using Pitchfork analysis to compare the dentoskeletal changes between FFRD and PS. Statistically significant values were seen in ANB post-treatment and mandibular length post-treatment values

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As previous studies have shown, fixed functional appliances will also have effects on dentoalveolar structures. In the present study, overjet was significantly reduced in both treatment groups, with mandibular incisor proclination and maxillary incisor retrusion contributing to these results. ABCH, the anteroposterior change in the relationship between the maxilla and mandible, made a mean positive contribution in both Forsus and Powerscope groups. The difference between the two groups was statistically insignificant. Results in a case report in “Early prevention and intervention of Class II division1 in growing patients” 2016, Keerthi V N et al. using PS was similar to the results found in our study.^[23] The lower incisors were proclined, whereas the upper incisors were upright. These dentoalveolar effects accounted for the reduction in overjet. In a case report in “Correction of Class II using Powerscope Appliance,” the results of Khumanthem et al. were also in agreement with the results of our study.^[24] They found more skeletal and dentoalveolar changes with the Powerscope appliance. There was a marked reduction of overjet with a restraint in the maxilla and increased mandibular length. The present study has evaluated the dental and skeletal effects by using pitchfork analysis in young adults treated with FFRD and PS. The results of our study were in agreement with the results of the study by Servello et al. in “Analysis of Class II patients, successfully treated with the straight-wire and Forsus appliances.”^[25] The results showed that the molar relationships of the patients treated were corrected primarily due to mandibular growth changes. Anterior mandibular displacement accounted for 3.23 mm of 5.10 mm by using Powerscope appliance and 3.16 mm of 4.90 by using Forsus appliance.

The results of our study were similar to the results of the study by Goel et al. in 2013 “Pitchfork analysis of class II correction using Forsus Appliance” [Graph 1][Graph 2][Graph 3].^[26] A net reduction of 4.66 mm for Powerscope appliance and 4.33 for Forsus appliance was recorded for the overjet, whereas a net improvement of 3.23 mm of 5.10 mm using Powerscope appliance and 3.16 mm of 4.90 using Forsus appliance was obtained for the molar relationship, which accounts for the class II correction. Lower incisors moved labially by 2.5 mm in the Powerscope group and 1.98 mm in the Forsus group, which also contributed to the correction of overjet.

Graph 1: Bar graph representing the comparison between the treatment changes before and after the treatment when using FFRD. X-axis depicts the parameters being analyzed, and Y-axis depicts the treatment changes. Blue color represents the pretreatment, and green color represents the post-treatment changes. Paired t test was done. There were significant changes in parameters post-treatment (p<0.05).

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Graph 2: Bar graph representing the comparison between the treatment changes before and after the treatment when using PS appliance. X-axis depicts the parameters being analyzed, and Y-axis depicts the treatment changes. Blue color represents the pretreatment, and green color represents the post-treatment changes. Paired t test was done. There were significant changes in parameters post-treatment (p<0.05).

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Graph 3: Treatment changes comparison between fixed functional resistant device and PS using Pitchfork analysis. X-axis depicts the parameters being analyzed, and Y-axis depicts the treatment changes. Blue color represents the FFRD, and red color represents the PS appliance. An independent t test was done .There were no statistically significant changes when compared between the appliances (p>0.05).

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The limitation of this study is that the amount of increase in mandibular growth produced by the normal growth and that can be attributable to the fixed functional appliance therapy cannot be differentiated. The two-dimensional measurements on the lateral cephalometric radiographs cannot reveal the changes in the transverse dimension. PS has a disadvantage, where the appliance slips out from the arch wire that requires more appointments for the patient. The FFRD has a risk of fracture, which can be resolved only by soldering or replacement of the appliance. The study reveals that all the 12 patients exhibited a statistically significant increase in the dentoskeletal changes. The increase was more significant with the Powerscope appliance.

The FFRD is an effective mechanism for class II correction, especially in patients with retrognathic mandible. Forsus has been shown to have both skeletal and dental effects for class II correction. In literature, there has not been a direct comparison between these two appliances: FFRD and PS. The purpose of this study is to evaluate the skeletal and dental differences between these devices by using lateral cephalograms.^[27]

The class II molar correction is mainly achieved through mandibular dentoalveolar movements. The mandibular molars are also mesialized during fixed functional appliance therapy and this accounts for most of the molar correction into class I. The overbite and overjet are also mainly corrected through dentoalveolar movements. The lower incisors are proclined, protruded, as well as intruded.

The advantage of both the FFRD and PS, being noncompliance appliances, has been increasing in appeal over the years. Their ease of insertion, adjustment, activation, and progress checks make them ideal appliances for a busy practice. They also allow a larger range of motion than most functional appliances and after a short period patients adapt quickly to eating, speaking, and maintaining oral hygiene.

Conclusion

Significant amounts of dentoskeletal changes were achieved during the fixed functional appliance treatment. The biggest advantage of this appliance is that being a noncompliance appliance it facilitates fulltime wear by the patient. To conclude, both appliances proved to be good cost-effective appliances in treating class II skeletal malocclusion. The PS has a greater restraint on the maxilla, produces greater forward displacement of the mandible, and may produce greater lower incisor proclination when compared with the Forsus appliance. Most of the molar correction is obtained from mandibular skeletal effects in both groups.

The understanding of the different fixed functional appliances helps in determining the chances that a clinician could come across in a clinical setup. The success of the orthodontic treatment depends majorly on the identification, diagnosis, and formulation of the treatment plan based on each case.

Acknowledgment

This research was supported by Saveetha Dental College and Hospital. The authors acknowledge the support rendered by the department of Orthodontics, Saveetha Dental College for providing insight and expertise that greatly assisted this research.

Financial support and sponsorship

These authors did not receive funding from any external organization, person, or agency.

Conflict of interest

The authors have declared that there is no potential conflict of interest.

Author contributions

RMV: data collection, analyzing data and interpreting statistics, and manuscript writing. AS: conception of study title, study design, analyzed the collected data, statistics and interpretation, and revision of the manuscript. SS: Revision of manuscript. Finally, the manuscript has been read and approved by all the authors.

Ethical policy and Institutional Review board statement

This study was approved by the institutional scientific review board before starting the study, under the reference number SRB/SDMDS12ORT19.

Patient declaration of consent: (If In vivo Study / Case reports)

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/ have given his/ her/ their consent for his/ her/ their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Data availability statement

The authors on request are willing to share the data collected during the course of the study.

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