Evaluation of Clinical Efficacy Between Forsus and Advansync Fixed Functional Appliance for the Treatment of Skeletal Class II Malocclusion Using 3D Cone Beam Computed Tomography (CBCT): A Prospective Randomized Clinical Trial

Objectives: The objective is to assess and compare whether AdvanSync gives better skeletal, dental, and soft tissue outcomes than Forsus fixed functional appliance in post-pubertal skeletal Class II malocclusion patients. Methodology: A prospective study was conducted using 3D-CBCT of patients taken before and after fixed functional appliance therapy. The sample consisted of 16 patients divided into two groups: Group 1 was treated with Forsus and group 2 with AdvanSync appliance. All subjects were in their post-pubertal growth phase. Treatment changes were evaluated between the study groups using 12 angular and 14 linear parameters. The data were subjected to statistical analysis. Results: Statistically significant changes in SNB (P:0.04) and ANB (P:0.01) in Forsus appliance and AdvanSync (SNB, P:008), (ANB, P: <0.001) were found between the pre and post-fixed functional appliance protocol. The effective mandibular length increased in both groups Forsus(P-value: 0.01) and AdvanSync (P-value: 0.01). Group 1 resulted in lower incisor proclination and intrusion, a reduction in an overbite, whereas group 2 resulted in lower incisor proclination, upper incisor extrusion, and retroclination. Both groups showed significant improvement in the molar relation and overjet. An increase in the total facial convexity was shown in group 1; group 2 showed an increase in the facial convexity and total facial convexity. There was no statistically significant difference between the effects of the Forsus and Advansync appliance groups in the post-fixed functional period. Both groups presented similar results. Conclusion: Forsus and Advansync appliances are effective with similar results in normalizing skeletal Class II malocclusion in post-pubertal patients. There was no statistically significant difference between the groups using Forsus or AdvanSync. The changes were minimal - mandibular skeletal effects, majorly dentoalveolar effects, and mild soft tissue effects.


Introduction
The subject of facial aesthetics is pre-eminently important to orthodontists [1]. The current trend of orthodontic diagnosis and treatment planning, treatment objectives, and assessment of treatment outcomes is towards an increasing emphasis on soft tissue relationships rather than underlying hard tissue relations. Evaluation of the patient's soft tissues is now a critical step that begins with the global approach of macro, mini, and microesthetic evaluations; started from the outside in, the evaluation of the soft tissue profile being the first [2].
Class II malocclusion is the most frequently encountered problem as it affects one-third of the population [3]. The most recommended therapeutic approach to Class II malocclusion in post-pubertal patients is using fixed functional appliances [3]. These appliances are classified into rigid, flexible, and hybrid fixed functional appliances. Rigid fixed functional appliances restrict mandibular movement and flexible fixed functional appliances have a frequency of breakage. These shortcomings led to the improvisation of "Hybrid fixed functional appliances" [4]. Of the many fixed functional appliances, Forsus fatigue-resistant devices and AdvanSync are used frequently because of their hybrid nature.
The Forsus Fatigue Resistant Device is one of the various fixed functional devices commonly used [5]. It has more of a dentoalveolar effect on the mandible. One of the major disadvantages is the lower incisor proclination that accompanies the treatment [5]. 1 1 1 1 1 1 1

Forsus Appliance Group
The treatment was started by bonding the upper and lower arches with 0.022*0.028 MBT prescription ( Figure  1). Leveling and alignment of the arches were achieved using initial round NiTi wires, rectangular NiTi archwire followed by rectangular stainless steel archwire. Once 19*25 SS was engaged, prefixed functional appliance CBCT was taken.
Forsus appliance was delivered with 0.019* 0.025" SS as the working archwire. The appropriate size of the appliance was selected for each patient using the measurement gauge supplied by 3M Unitek. The upper assembly was engaged in the headgear tube of the upper molar band and the push rod was engaged to the lower main archwire distal to the canine. Once the desired corrections were achieved, a post-fixed functional appliance CBCT was taken ( Figures 5, 6).

CBCT -Cone Beam Computed Tomography
After taking the scans, the scans were converted into digital imaging and communication in medicine (DICOM) format. The data were reconstructed into 3D images using Nemoceph 3D software. The anatomical landmarks were identified on 3D CBCT multiplanar and reconstructed images. The 3D images were oriented based on the midsagittal reference line formed by soft tissue nasion, subnasale and soft tissue pogonion. A lateral image was extracted, and various linear and angular measurements of skeletal, dental, and soft tissues were performed for both groups. The cephalometric linear and angular measurements assessed were as follows.

Skeletal Angular
SNA (angle drawn between sella-nasion to point A), SNB (angle drawn between sella-nasion to point B), ANB (angle drawn between point A to nasion and point B to nasion), GoGn-SN Plane (angle drawn between Gonion-Gnathion plane to Sella-Nasion plane), MPA (Mandibular plane angle), Gonial angle (the angle formed by the base of the mandible and posterior border of ramus), Beta angle (the angle formed between the A-B line and the perpendicular through point A from the apparent axis of the condyle).

Skeletal Linear
A perp N (line drawn from point A perpendicular to Nasion), ANS perp N (line drawn from anterior nasal spine perpendicular to nasion), ANS TO PNS (line drawn from anterior nasal spine to posterior nasal spine); Dental angular: U1-SN (upper incisor to sell-nasion), L1-SN (lower incisor to sell-nasion), L1-MP (lower incisor to the mandibular plane); Dental linear: U6-NF (line drawn between upper 1st molar to the nasal floor), L6-MP (line drawn between lower 1st molar to the mandibular plane); Molar Correction, U6-NF (angle drawn from upper molar to nasal floor), L1-MP (angle drawn from lower incisor to mandibular plane), Overjet, Overbite and; Soft tissue angular: Angle Of Total Facial Convexity, Facial Convexity, Nasolabial angle, and Mentolabial Angle.

Sample size calculation
Based on the mean and SD of group 1 and group 2 based on the studies of Arora et al. [10], the effect size was calculated and found to be 1.34, utilizing this effect size as input value in the G power software, the minimum sample size calculated was 16, with eight subjects in each group. The input data are as follows

Results
This study was done to assess the clinical efficacy of Forsus and Advansync fixed functional appliance for the treatment of skeletal Class II malocclusion patients in their post-pubertal growth phase using threedimensional CBCT. The objectives were: (1) To assess the skeletal, dental and soft tissue changes brought about by Forsus fixed functional device, (2) To assess the skeletal, dental and soft tissue changes brought about by AdvanSync fixed functional device. 3) To compare the skeletal, dental and soft tissue changes of AdvanSync and Forsus fixed functional appliance at the end of functional treatment Participant Flow: A total of 16 patients were recruited in the study.

Baseline Data
Two groups were matched for the pre-treatment skeletal and dental malocclusion, severity of the case and the soft tissue parameters. Table 1 represents the comparison of mean values of Angular Skeletal Parameters between the two groups at Pretreatment and suggests that there was no statistically significant difference in the SNA (P:0.17), SNB (P:0.38), ANB (P:0.89), MPA (P:0.70) and Gonial angle (P:0.41) at the baseline, when the level of significance was set at P<0.05).      Table 3 shows that there was no statistically significant difference between the two groups when comparing the pretreatment Angular dental parameters: U1-SN (P:0.37), L1-SN (P:0.52) and L1-MP (P:0.56) values. Table 3 also shows that there were no statistically significant difference between the two groups when comparing the pretreatment Linear dental parameters in vertical plane which included U1-NF ( Table 4 represents the mean values of Angular Facial Soft Tissue Parameters between two groups at Pretreatment and suggest that there was no significant difference in the facial convexity angle (P:0.65), total facial convexity angle (P:0.41), Nasolabial (P:0.16) and Mentolabial angle (P:0.32) at the baseline. The results suggest that there was no significant difference between the type of cases that were randomly allocated in the two groups. The pretreatment skeletal, dental and soft tissue baseline data was similar for both the treatment groups thereby reducing the selection bias in the study.

Post-treatment intergroup comparison between Forsus group and AdvanSync group
The comparison of mean values of Angular Skeletal Parameters at Post-treatment suggests that there was no statistically significant difference in the SNA (P:0.25), SNB (P:0.61), ANB (P:0.63), MPA (P:0.97) and Gonial angle (P:0.36) when the treatment results between Forsus group and AdvanSync appliance group were compared ( Table 5). This shows that both groups had similar results with the above angular parameters.      Table 7). The result showed that both Forsus and AdvanSync groups produced similar results related to angular dental parameters.    The results of our study showed that there was no significant difference between the two groups at post treatment. Both Forsus appliance and AdvanSync appliance produce similar skeletal, dental and soft tissue treatment outcomes.

Parameters
Intragroup pre and post-treatment comparison: Forsus group (group 1)    The results suggest that there was a significant change in ANS perp N value which is statistically significant but not clinically significant. There was significant increase in the effective condylar length in the post appliance phase (CO-GN, P:0.01).    Comparing pre and post treatment effects, Forsus appliance resulted in significant intrusion of lower incisors, improvement in the molar relationship, decrease in the overjet and decrease in the overbite.
The results suggest that Forsus appliance brought about significant change in the total facial convexity angle, whereas no change was found in the Facial convexity, Nasolabial and Mentolabial angle ( Table 12).     . Point A perp to N value changed from 0.17 ± 4.77 to -0.53 ± 5.00 mm, with no statistical significance (P:0.67). The ANS perp. N value increased from 4.74 ± 2.72 mm to 3.82 ± 2.71 mm, which was not statistically significant (P:0.07). On comparing the difference between pre and post Rx value of ANS-PNS, the value changed from 50.10 ± 3.44 to 50.39 ± 3.85 mm respectively, with no statistical significance (P:0.09). The N perp. Pog value increased from -4.06 ± 6.95 mm to -3.38 ± 5.22 mm, which was not statistically significant (P:0.40). The change in the Point B perp. N from -4.75 ± 5.91 mm to -5.12 ± 5.14 mm, was found to have not statistically significance (P:0.96). The effective condylar length Co-Gn increased from 101.11 ± 2.56 mm to 102.57 ± 2.57 mm, which was statistically significant (P value: 0.01). On comparing the difference between pre and post Rx value of Go-Gn, the value changed from 67.14 ± 3.64 to 67.06 ± 3.50 mm respectively, with no statistical significance (P:0.89). The results suggest that there was significant increase in the effective mandibular length post AdvanSync appliance therapy (P-value: 0.01).
In the Advansync group, the upper incisors retroclined and the lower incisors proclined significantly.

Dental Linear Parameters
U1-NF value increased from 23.80 ± 2.08 to 24.91 ± 2.45 mm, which was found to be statistically significant (P:0.01). U6-NF value increased from 20.41 ± 2.96 to 20.70 ± 2.28 mm, with no statistical significance (P:0.61). The L1-MP value increased from 36.67 ± 2.74 to 37.77 ± 2.21 mm and this difference was not statistically significant. L6-MP value changed from 28.37 ± 4.63 to 27.82 ± 2.50 mm, with no statistical significance (P:0.62). The value for Molar correction changed from 1.80 ± 0.67 to -2.47 ± 1.12 mm, which was highly significant (P: <0.001). The Overjet reduced from 7.32 ± 2.70 to 3.28 ± 1.43 mm, which was found to be highly significant (P:0.01). The Overbite changed from 4.16 ± 0.89 to 2.35 ± 0.44 mm which was not statistically significant. The dentoalveolar changes that were found in AdvanSync group were extrusion of upper incisors, improvement in molar relationship, and reduction in overjet.

Soft Tissue Angular Measurements
The facial convexity increased from 157.23 ± 5.39 to 159.63 ± 5.48 degrees, which was statistically significant (P:0.008). Similarly, Total facial convexity increased from 128.99 ± 5.36 to 131.54 ± 5.29 degrees, which was statistically significant (P:0.03). The Nasolabial angle changed from 100.64 ± 9.24 to 99.86 ± 11.55 degrees, with no statistical significance. The mentolabial sulcus changed from 103.49 ± 23.71 to 104.09 ± 20.31 degrees, with no statistical significance. Significant changes were found in the Facial convexity angle and Total facial convexity angle which resulted in improvement in the soft tissue facial profile.
The results suggest that AdvanSync appliance brought about significant change in the facial convexity angle and Total facial convexity, whereas no change was found in the Nasolabial and Mentolabial sulcus.

Discussion
Skeletal Class II malocclusion is one of the most common malocclusions in the general population. It occurs in about 25% to 30% of the general population. Moreover, mandibular retrognathism has been seen to be the most common causative factor for skeletal Class II malocclusion [7]. Functional appliances are well established as a means of correcting significant antero-posterior malocclusions [8]. To stimulate mandibular growth by the forward positioning of the mandible, various removable and fixed functional appliances are commonly used to alter the position of mandible [10]. The stimulation of mandibular growth, distal movement of the upper dentition, and mesial movement of the lower dentition contributes to the correction of Class II malocclusion with the use of fixed functional appliances [10]. The various treatment options for Class II correction apart from myofunctional/FFAs include orthopedic appliances like headgears, camouflage line of treatment by extractions of premolars, distalization of the maxillary arch or the surgical correction of the underlying skeletal discrepancy when growth has completed. For Class II growing patients in whom the mandible is retrognathic, the ideal means of correction is to target the source and try to alter the amount or direction of growth in that jaw. A wide range of functional appliances aimed to stimulate mandibular growth by forward posturing of the mandible are available to correct class II skeletal and occlusal disharmony [11]. FFAs are the most commonly used appliance to correct skeletal discrepancy in a growing stage, but still its enhancement effect on mandibular growth has been questionable [7].
The Forsus Fatigue Resistant Device (FRD) is a semirigid telescoping system incorporating a superelastic nickel titanium coil spring that can be assembled chair-side and that can be used in conjunction with complete fixed orthodontic appliances. Forsus appliance has proven to induce significant skeletal and dental changes, which remained relatively stable during the observation period in post-pubertal patients [12]. The AdvanSync appliance has the advantage of being used simultaneously with fixed mechanotherapy from the initial stage of treatment and claims to reduce the overall treatment duration. It also claims to eliminate the need for patient compliance and provides maximum comfort and range of movement. AdvanSync appliance is shown to have a significant maxillary sagittal restriction effect along with significant dentoalveolar effects [13].
Berco et al. found that CBCT allows for clinically accurate and reliable three-dimensional linear measurements of the craniofacial complex. Moreover, skull orientation during CBCT scanning does not affect the accuracy or the reliability of these measurements [14].
The purpose of our study was to assess and compare whether AdvanSync gives better skeletal, dental and soft tissue outcomes than Forsus fixed-resistant device for the correction of skeletal class II malocclusion in post-pubertal patients using 3-D CBCT.
The baseline parameters between the groups were statistically not significant, which shows that the type of cases and the severity of malocclusion of the subjects included in the study groups were similar at the pretreatment stage (Tables 1-4). We can conclude that, in the current study, the bias was minimized.
When comparison was made between the two study groups, the skeletal, dental and soft tissue parameters did not show any statistical significance. Forsus and AdvanSync appliance showed similar post treatment results, which were mainly dentoalveolar in nature with mild changes in the effective mandibular length and soft tissues ( Tables 5-8).
The appliance can be effectively used to correct skeletal class II malocclusion in post pubertal patients. These findings are consistent with previous studies on treatment effects of fixed functional appliances [15,16].
Zymperdikas et al. in a systematic review, concluded that FFAs seem to be effective in improving Class II malocclusion in the short term, although their effects seem to be mainly dentoalveolar and soft tissue changes rather than skeletal [15]. Similar results were obtained in current study wherein minimal skeletal sagittal effects were observed with improvement in SNB and ANB angles. However, there was no significant change in the SNA angle in the current study which contradicts the finding.
Shahi et al. found that the AdvanSync appliance resulted in inducing more changes in SNB and effective mandibular length as compared to Twin Block. This effective result with AdvanSync appliance may be attributed due to the effective full-time wear obtained whereas patient compliance may have been compromised with the Twin Block appliance. There was also reduction in SNA angle which was not significant [17]. Similar findings were found in the present study. The decrease in SNA could be explained by the distal reciprocal force exerted on the maxilla by the appliance. Both the appliances showed similar dentoalveolar changes. These findings are consistent with the current study, but results must be carefully interpreted since the study sample included patients in pubertal and post-pubertal growth phase.
Another literature review conducted by Linjawi and Abbassy revealed that the Forsus appliance showed positive effects on the maxillary incisors and first molars as well as overjet and overbite whereas multiple negative effects were reported on the occlusal plane and lower incisors which included protrusion, proclination, and intrusion of the lower incisors that need to be considered when using such appliance in treating Class II malocclusion [5]. In contrary, we found no significant effect on the maxillary incisors and maxillary molars in the vertical plane in the Forsus appliance group. Whereas the other dental parameters including overjet, overbite and sagittal molar relationship improved. And we also observed significant intrusion and worsening of the lower incisor inclination.
Jayachandran et al. concluded that AdvanSync and intermaxillary elastics were effective in class II corrections. AdvanSync produced its effects through maxillary skeletal growth restriction and mandibular dentoalveolar changes whereas class II elastics worked primarily through dentoalveolar changes [13]. The findings of the current study contradict the results of the above-mentioned study as there was no significant maxillary growth restriction effect in the AdvanSync group. Whereas the effects on the mandible and the dentoalveolar effects were found to be similar. These variations in observations could be contributed to the different methodologies used in the studies, variety of study designs, and that the patients' age.
The AdvanSync appliance resulted in significant extrusion and retroclination of upper incisor, proclination of lower incisors, improvement in molar relation and overjet. These findings are in agreement with earlier studies that evaluated the dentoalveolar effects of functional appliances [13,[15][16][17]. There was an improvement in the facial soft tissue convexity in both Forsus and AdvanSync appliance group in the current study.

Limitations
The treatment changes at the end of the comprehensive treatment were not assessed in the current study. The long-term stability of the fixed functional appliances was not evaluated. Some adverse effects with the AdvanSync appliance were observed immediately after removal of the appliance which included molar rotation and intrusion. These aspects can be further evaluated.