A comparison of treatment effects produced by AdvanSync and forsus fatigue resistant device in growing class II patients - An study

Introduction

Angle first described Class II malocclusion in the 1890s. It is second most common malocclusion after class I.^[1] The prevalence of Class II malocclusion was reported 19.56% globally^[2] and 14.6% in India.^[3]

The class II malocclusion problem can be attributed to either retrognathic mandible or prognathic maxilla or a combination of both. Retrusion of mandible was found to be the most common etiological factor in this malocclusion.^[4]

Management of class II malocclusion becomes intricate because of its variable etiology^[5] and the age at which the patient presents to the orthodontists. During 1900s first fixed functional appliances (FFA) emerged and then plethora of appliances followed. If timed correctly, FFA can be an asset in patients with lesser growth potential^[6] and also helps in avoiding any future invasive surgical interventions during adulthood.^[7] he latest appliances are designed to decrease the treatment duration and reduce the need for patient co-operation^[8] while allowing complete utilisation of growth left.

Amongst various appliances AdvanSync™2 molar to molar appliance appears to be the latest addition to FFA in orthodontist’s arsenal for treating class II malocclusion with mandibular retrusion whereas Forsus™ Fatigue Resistance Device (FFRD) is the most widely accepted and used FFA.

FFRD has some disadvantages like it can only be installed after pre functional levelling and alignment is achieved till 19X25 SS wire, frequent dislodgement, causes lower incisor proclination, and requires extensive anchorage preparation.

AdvanSync™2 and MARA appliances allows concurrent full fixed treatment as there is no need to level and align both arches before installation which is beneficial in terms of growth considerations as well as duration of the treatment. AdvanSync™2 has shorter arms and is engaged from molar to molar which reduces direct force transfer on mandibular canine thereby reducing lower incisor proclination effect

Therefore, understanding the appliance design, treatment processes, and comparison of the treatment effects of various FFA will enable better treatment planning and help in obtaining optimal results.

The aim of this study was to compare the differences in the skeletal, dentoalveolar and soft tissue changes produced by the AdvanSync™2 and the Forsus™ Fatigue Resistance Device fixed functional appliances in growing patients, to correct class II division I malocclusion, due to retrognathic mandible.

Materials and Methods

Method of collection of data and ethical clearance

The sample comprised of patients who reported to the Department as outpatients. Patient selection was done based on inclusion and exclusion criterias of the study. The sample size was taken as 10 per group, Group 1 (AdvanSync™2) and Group 2 (Forsus™ Fatigue Resistance Device). The investigation was approved by the Institutional Ethics Committee after critically reviewing the research protocol and registration number 59/2020 was assigned to this study.

Radiographic method

Lateral cephalograms and photographs were taken as part of the routine diagnostic records. They were taken at two times, pre treatment (T1) and post functional orthodontic treatment (T2). The measurements were done by three operators and average was taken. A total of 9 angular,12 linear measurements and 10 soft tissue variables were considered in cephalometric analysis. (Suppl [Figure 6])

	Variables	AdvanSync™2 appliance Mean difference	Forsus™ Fatigue Resistance Device appliance - Mean difference	P value
Angular	SNA	1.150	0.900	0.028*
SNB	-0.900	-2.200	0.198
ANB	2.050	2.600	0.712
MPA	-1.300	1.100	0.168
L1MPA	-2.100	7.100	0.097
FHPP	-0.900	1.300	0.402
U1FH	10.300	6.700	0.002*
Gonial	-1.800	-1.400	0.047
SOFT TISSUE	Facial Angle	-0.600	-2.600	0.248
Facial Convexity157.6	-1.000	-3.600	0.404
H Angle	1.900	2.300	0.02*
Nasolabial Angle	-8.900	-13.700	0.401
Mentolabial Sulcus	1.900	2.000	0.821
Subnasale To H Plane	1.500	2.200	0.001*
Upperlip E Line	0.700	1.000	0.027
Lower Lip E Line	-1.100	0.000	0.015*
Upper Lip To Ptv	1.300	0.000	0.015*
Lower Lip To Ptv	-2.000	-2.000	0.411
LINEAR	Overjet	4.950	3.300	0.014*
Overbite	1.400	1.600	0.6
COGN	-3.800	-2.900	0.565
U1VRP	0.900	1.100	0.921
L1VRP	-0.300	-0.700	0.759
U6VRP	2.200	-0.200	0.534
L6VRP	-1.300	-1.000	0.341
U1HRP	-2.700	-1.300	0.799
L1HRP	-4.800	-1.300	0.574
U6HRP	-0.900	-5.100	0.206
L6HRP	-3.000	-1.300	0.006*
LAFH	-3.000	-2.000	0.774

Table 2 Comparison of Advan Sync™2 appliance andForsus™ Fatigue Resistance Device appliance mean difference for overall linear, angular and soft tissue measurements. (Unpaired T test)

	Variables	Mean ± SD	Mean ± SD	Mean difference	P VALUE
Angular	SNA	81.10 ±3.213	79.95 ±3.166	1.150	.000*
SNB	74.95 ±3.166	75.80 ±3.048	-0.900	.000*
ANB	6.20±1.398	4.15±0.669	2.050	.015
MPA	21.70±4.448	23.00±5.055	-1.300	.000*
L1MPA	108.20±7.005	110.30±4.809	-2.100	.000*
FHPP	2.50±1.900	3.40±2.951	-0.900	.006*
U1FH	119.00±14.937	108.70±8.744	10.300	.044*
GONIAL	68.20±4.849	70.00±4.876	-1.800	.000*
SOFT TISSUE	FACIAL ANGLE	88.40±1.776	89.00±4.714	-0.600	1.000
FACIAL CONVEXITY157.6	157.60±6.222	158.60±5.441	-1.000	.000*
H ANGLE	23.40±3.534	21.50±3.206	1.900	.001*
NASOLABIAL ANGLE	93.40±9.732	102.30±13.233	-8.900	.004*
MENTOLABIAL SULCUS	8.10±1.370	6.20±1.619	1.900	.001*
SUBNASALE TO H PLANE	9.50±2.550	8.00±2.667	1.500	.055*
UPPERLIP E LINE	0.50±2.506	-.20±1.814	0.700	.129
LOWER LIP E LINE	-0.35±3.448	0.75±2.252	-1.100	.011*
UPPER LIP TO PTV	69.50±4.478	68.20±4.417	1.300	.003*
LOWER LIP TO PTV	63.40±5.358	65.40±5.910	-2.000	.003*
LINEAR	OVERJET	8.25±3.066	3.30±0.483	4.950	.260
OVERBITE	4.20±1.033	2.80±0.632	1.400	.508
COGN	100.60±5.854	104.40±5.038	-3.800	.000*
U1VRP	68.60±6.867	67.70±6.961	0.900	.009*
L1VRP	63.20±6.179	63.50±7.153	-0.300	.000*
U6VRP	28.80±5.308	26.60±6.257	2.200	.000*
L6VRP	25.50±5.662	26.80±6.546	-1.300	.001*
U1HRP	67.50±2.759	70.20±4.392	-2.700	.001*
L1HRP	61.30±3.302	66.10±5.152	-4.800	.002*
U6HRP	56.90±2.378	57.80±4.185	-0.900	.000*
L6HRP	62.40±2.319	65.40±3.502	-3.000	.000*
LAFH	58.60±4.088	61.60±3.307	-3.000	.004*

Table 3 Measurements among AdvanSync™2 appliance (paired T test)

	Varuables	Mean ± SD	Mean ± SD	Mean difference	P Value
Angular	SNA	81.10±1.792	80.20±1.874	0.900	.000*
SNB	75.30±1.494	77.50±2.461	-2.200	.031*
ANB	5.30±1.252	2.70±1.160	2.600	.116
MPA	23.80±3.360	22.70±3.622	1.100	.000*
L1MPA	110.00±7.846	102.90±9.620	7.100	.101
FHPP	2.90±4.095	1.60±.503	1.300	.002*
U1FH	120.00±5.011	113.30±270	6.700	.173
GONIAL	69.30±3.164	70.70±2.359	-1.400	.000*
Soft Tissue	FACIAL ANGLE	85.90±1.197	88.50±.850	-2.600	.445
FACIAL CONVEXITY	155.70±3.713	159.30±4.322	-3.600	.005*
H ANGLE	24.30±1.252	22.00±.789	2.300	.010
NASOLABIAL ANGLE	95.20±6.250	108.90±6.008	-13.700	.611
MENTOLABIAL SULCUS	6.00±1.414	4.00±1.155	2.000	.013*
SUBNASALE TO H PLANE	10.30±.949	8.10±.994	2.200	.371
UPPERLIP E LINE	1.10±1.595	.10±1.197	1.000	.507
LOWER LIP E LINE	1.60±2.271	1.60±.699	0.000	.074
UPPER LIP TO PTV	69.50±6.399	69.50±5.911	0.000	.002*
LOWER LIP TO PTV	62.90±6.557	64.90±5.744	-2.000	.000*
Linear	OVERJET	6.30±1.767	3.00±1.054	3.300	.000*
OVERBITE	3.70±1.059	2.10±.316	1.600	.213
COGN	103.80±5.959	106.70±6.533	-2.900	.000*
U1VRP	72.00±5.774	70.90±.460	1.100	.000*
L1VRP	67.70±5.498	68.40±6.467	-700	.000*
U6VRP	30.30±6.667	30.50±6.671	-.200	.000*
L6VRP	29.70±6.567	30.70±433	-1.000	.009*
U1HRP	68.00±3.333	69.30±4.296	-1.300	.346
L1HRP	67.20±4.984	68.50±4.062	-1.300	.006*
U6HRP	56.80±9.151	61.90±3.784	-5.100	.901
L6HRP	63.50±6.258	64.80±5.554	-1.300	.012*
LAFH	60.30±3.164	62.30±.093	-2.000	.000*

Table 4 Comparison of pre-operative and post-operative changes in linear, angular and soft tissue measurements amongForsus™ Fatigue Resistance Device appliance. (Paired T test)

Results

Data was analysed using SPSS software version 26, and checked for normality using Kolmegorov smirnov test. Data was normality distributed. Comparison of pre-operative and post-operative changes in linear, angular and soft tissue measurements among AdvanSync™2 appliance and Forsus™ Fatigue Resistance Device appliance was carried out using paired T test. Comparison of AdvanSync™2 appliance and Forsus™ Fatigue Resistance Device appliance for overall linear, angular and soft tissue measurements was done using unpaired t test. The level of significance was kept as less than 0.05.

The overall Comparison of AdvanSync™2 appliance and Forsus™ Fatigue Resistance Device appliance, using unpaired T test in total study population for linear, angular and soft tissue measurements, showed significant difference among SNA angle, U1FH, H angle, subnasale to H plane, lower lip E line, upper lip to Ptm, overjet, L6HRP. ([Table 1] and [Figure 1]).

At individual level comparisons, skeletal parameters showed positive improvement in majority parameters of both the appliances. Initially the pre-operative(T1) and post-operative(T2) changes in cephalometric analysis using paired T test, among AdvanSync™2 appliance and Forsus™ Fatigue Resistance Device appliance group. ([Table 2], [Table 3])

Discussion

There are several treatment approaches being employed to address class II malocclusion. In this study, lateral cephalogram was chosen to study and compare the treatment effects of AdvanSync™2 and FFRD. It is a widely used diagnostic tool for examining skeletal, dental, and soft tissue craniofacial morphology. In this study, horizontal reference plane and vertical reference planes were derived to give standardization for correlation of pre-treatment and post functional orthodontic treatment results. ^[9]

The goal of adopting a functional appliance is to take advantage of remaining active growth phase and assist forward jaw posture, which cause the condylar head to develop and the glenoid fossa to remodel. ^[10] It has been observed that the efficiency of treatment of mandibular growth deficiencies is significantly dependent on the biological responsiveness of the condylar cartilage, which sequentially is dependent on the mandibular growth rate. ^[11] The resulting skeletal changes have been attributed to morphologic adaptations to altered muscular tone and a shift in masticatory muscle traction direction. A myostatic reflex is elicited, resulting in isometric contractions that stimulate the protractor muscles while inhibiting the mandibular retractor muscles. ^[12], ^[13]

Forsus™ Fatigue Resistance Device is a widely accepted FFA. It is attached from maxillary molar buccal tube to lower archwire distal to the mandibular canine which leads to direct force on incisor causing proclination. ^[14] The other disadvantages include cheek irritation and frequent dislodgement of rod. The cases treated with the appliance requires levelling and aligning of both the arches and should be kept in 19x25 SS prior to installation. It is amongst the drawbacks when the patient has minimal growth potential left.

AdvanSync™2 appliance is a molar to molar appliance which elimination direct force on canine and permits simultaneous orthodontic and orthopaedic corrections as it is not necessary to align and level the arches prior to its placement. Therefore, it becomes possible to capitalize on residual growth and reduce the duration of treatment. The appliance is approximately half the size of the former FFRD. It fits more conveniently in the back of the mouth due to its smaller size.

All the fixed functional appliances invariably cause lower incisor flaring. Gandedkar and Celikoglu et al. ^[13] study showed that it was one of the consistent drawback of all the FFA. This study also compared the effect on lower incisor inclination by both the devices. AdvanSync™2 caused comparatively less proclination than the FFRD

The appliance were inserted at a mean age of 12-14 years of age with CVMI⁽¹⁶⁾ 3-5 for 6-8 months. The findings demonstrated that, at the conclusion of the functional appliance period, only minor differences, predominantly dentoalveolar, existed between two appliances.

There are several scientific literatures on the therapeutic effects of Forsus™ Fatigue Resistance Device, but relatively few ^[15] on the AdvanSync™2 device. There is a scarce literature comparing the treatment effects of FFRD with the AdvanSync™2 appliance. Therefore, this study was done to compare and analyze the effects of two most used appliances.

The treatment effects of both the appliances can be divided into three broad categories –

Skeletal, Dentoalveolar and Soft tissue changes on maxilla and mandible

Skeletal effects

The mandibular effects can be attributed to anterior force ^[14] generated from the appliances while forward positioning of the mandible and maxillary effects can be attributed to reciprocal effect of the mandibular advancement caused by the appliance. ^[16]

Both the appliances showed increase in SNB angle (p<0.05), suggesting mandibular advancement. There was significant increase in mandibular length in both groups. (group 1= and group 2= ). AdvanSync™2 finding were consistent with the all previous studies except study which compared treatment effects of MARA and AdvanSync™2 ^[17]

Both the appliances showed reduction in SNA angle but was more with AdvanSync™2 appliance. Studies Raghav P et al. ^[18] and Jayachandran S et al concluded that AdvanSync™2 has headgear like effect. ^[19] Group 2 findings were consistent with the previous published studies. ^[20], ^[21], ^[22])

Decrease in ANB was seen with both the appliances which suggests improvement in relative anteroposterior position between the maxilla and mandible. ^[8]

The mandibular plane angle, gonial angle as observed by comparison cephalometric analysis showed increase in value in Group 1 therefore must be used cautiously in patients with vertical growth pattern. ^[15] Group 2 had less significant effects on mandibular plane angle and gonial angle than AdvanSync™2.

There was significant increase in lower anterior facial height with AdvanSync™2 group when compared to Forsus™ Fatigue Resistance Device group and was found to be consistent with all previous studies. ^[12], ^[15], ^[23]

Dentoalveolar Effects

The most important drawback of Fixed Functional Appliance is lower incisor proclination. Though some of the proclination changes can be attributed to relative intrusion. ^[24] FFRD group showed more proclination in L1MP angle and intrusion of lower anteriors than AdvanSync™2group which was consistent with the previous studies. ^[15] Low torque brackets (-11°) were used in combination with AdvanSync™2 appliance which might have prevented flaring of lower anteriors.

Both the appliances showed significant changes in the U1FH angle, U1HRP and U1VRP distance which suggests retroclination , extrusion and distalisation maxillary anteriors. ^[8], ^[24], ^[15] The extrusion of upper incisors was more in to AdvanSync™2group.

Mesialisation and intrusion of the L6(15) was more with AdvanSync™2. It can attributed to direct reciprocal force transfer to molar since it is a molar to molar appliance

Both the appliances showed distalisation and extrusion effect on upper molars but was significant with FFRD. The dentoalveolar effects were consistent with the previous studies. ^[25]

Al jewair et al ^[24] concluded that there was no significant effect on U6, which is not in accordance with present study. The evaluation of dentoalveolar effect of Forsus™ Fatigue Resistance Device showed similar effects to the previous study ^[26] except U6 extrusion.

Soft Tissue Changes

In modern orthodontics, facial esthetics is one of the primary factors motivating the patient to seek orthodontic treatment. Thus, the assessment of the patient's facial soft tissue is of great importance during orthodontic diagnosis and treatment planning. Pre and post treatment values showed significant soft tissue changes by both the appliances which resulted in improved facial esthetics

Soft tissue analysis of AdvanSync™2 group revealed significant increase in linear distance of lower lip from E line and PTV suggesting protrusion and forward displacement of lower lip. There was decrease seen in upper lip to Eline and PTV distance suggesting reduction protrusion of upper lip.

Comparison of pre-treatment to post-treatment Cephalometric values suggested improvement in H angle and nasolabial angle which indicates improvement in profile. FFRD showed more significant soft tissue changes in terms of facial convexity. This was in accordance with previous study ⁽⁸⁾ but the other studies did not report any significance change. ^[15] Both the appliances showed increase in the facial angle but was not statistically significant. ^[27]

Conclusion

This study concluded that –

Both the appliance were established as reliable as they were effective in correcting Class II malocclusions with mandibular retrusion.

The AdvanSync™2 Class II corrector enabled correction of the Class II malocclusion with shortened treatment time and was more comfortable for the patient as it is smaller in size and without the rod getting dislodged frequently as inFFRD. Maxillary restriction was more significant and mandibular advancement was higher in FFRD group.

Intrusion, mesialisation of lower molars and distalisation of upper molars was seen. FFRD caused significant extrusion and distalisation of upper molars.

Both the appliances led to lower incisor proclination but it was lesser with AdvanSync™2 appliance.

Both the appliance showed retroclination and extrusion of upper incisor. It was more with AdvanSync™2 appliance.

Pre and post treatment values showed significant soft tissue changes by both the appliances which resulted in improved facial esthetics.

Scope for Future Studies

AdvanSync™2 is molar to molar appliance, thus upper and lower molar bear the forces exerted during forward positioning. Second molar bonding will be useful to minimise distalisation effects on upper molars and mesiolingual rotation and intrusion of lower molars along with figure of 8 from molar to molar.

Because of the scarce literature, further researches are needed to provide a proof of these effects which will enable us to utilise the full potential of the appliances.

Number of patients can be increased and 3D Imaging can be used in further studie

Source of Funding

None.

Conflict of Interest

None.