INTRODUCTION:

The functional appliances are classified in to fixed or removable appliance¹. They bring about alteration in the position of the mandible and result in the change of the neuromuscular environment which brings about a modification of growth. A wide range of functional appliances are available for the correction of Class II skeletal pattern². The Forsus Fatigue Resistant Device and Twin block are the most commonly used appliances for the correction of Class II skeletal malocclusion in patients who have not completed their growth. In 1905, Emil Herbst introduced fixed functional appliance for a patient with tempero-mandibular joint problems . After this, the Herbst appliance was not talked about until Hanz Pancherz reintroduced the appliance in 1979³. After this period numerous fixed functional appliances were developed. The fixed functional appliances eliminate the need for patient compliance and places the treatment outcome under the control of orthodontist.

The Forsus appliance was introduced by William Vogt ⁴. The Forsus Fatigue Resistant Device is a fixed and a hybrid functional appliance⁵. Forsus appliance is the most widely used rigid fixed functional appliance. It is used along with conventional fixed appliance and cannot be removed by the patient. Forsus Fatigue Resistant Device is very effective in correction of class II malocclusion by bringing about a combination of skeletal and dentoalveolar modifications⁶.

COMPONENTS OF FORSUS APPLIANCE:

The Forsus appliance consists of a rod and a spring module. The spring module is attached to the buccal tube of the upper first molar while the push rods area attached to the lower arch wire distal to the canine bracket. The appliance is available in 6 sizes based on length required. The push rods go inside the spring module for a short distance. The size of appliance must be selected such that when the appliance is in place, the mandible must close in a Skeletal Class I. The various components of the Forsus are as below.

Push Rods: The push rods have six differ sizes for each side ie left and right side. The sizes are 22 mm, 25 mm, 29 mm, 32 mm, 35 mm and 38 mm.

The spring module:

The spring module is available as two types, in the traditional appliance, the spring module (EZ2 module) is attached to the occlusal head gear tube of the upper buccal tube by using the a ball end type pin. The newer appliance (L-Pin Spring module) has a clip on system which can be used even with the gingival head gear tube.

EZ2 module: The EZ2 module allows for a more consistent installation and automatically prevents the spring from pivoting toward the cheek. The right and left side spring modules cannot be interchanged.

L-pin Spring Module: The L-pin module allows for more flexible installation options and movement in the mouth. It can be used with a gingival or occlusal headgear tube. The left and right sides are universal.

Headgear Tube on Band:

A band with an occlusal or gingival headgear tube is needed to be used with the Forsus Fatigue Resistant Device. An occlusal headgear tube measuring about 3.6 - 4.3 mm is required for the Forsus EZ2 Module. The L-pin module can be used with either occlusal or gingival tubes of varying lengths.

Measurement Gauge: The measurement gauge which is used to select the correct size of the appliance.

Split Crimps: As treatment progresses, Split crimps are used to reactivate the spring module.

After placement of the appliance in the patient, if the push rod is visible at the upper end of the coil spring, it is advisable to use a shorter one. Sometimes two small bends at the push rod may increase patient comfort considerably as this allows the spring to rest in the buccal fold more comfortably. Breakage is extremely rare and if it occurs, it is the spring component that will commonly break and replacement of the spring is indicated⁷. If the push rod protrudes distal of the spring module in centric occlusion, the spring is over-activated because the push rod is too long. So, shorter push rod is indicated. Over-activation can result in debonding of brackets, unwanted dental movements, flaring of the mandibular incisors, unplanned rotations and breakage

When the appliance is properly placed in the mouth, it brings about forward positioning of the mandible and prevents the patient from biting in a Class II position. The Forsus appliance brings about mandibular advancement by changing the neuromuscular pattern thus stimulating the mandible to grow. It also brings about a mild distalisation of maxillary molars. The appliance is used along with fixed Orthodontics, after dental arches are properly aligned and the required dental corrections have been carried out. This addition to the braces treatment is designed to correct not only the overjet but also the overbite while maintaining or improving facial aesthetics. The Forsus appliance being a rigid fixed appliance, limits lateral movement of the mandible to an extent.

ADVANTAGE OF FORSUS APPLIANCE:

· It is placed posteriorly in the mouth and is virtually undetectable.

· It allows for normal jaw movement and Mastication, thus it is well tolerated by patients

· It is durable, which results in few emergencies

· The patient can’t remove the spring and hence the result is not compliance driven

· The Forsus springs allow for correction of Class II correction in a 3 to 6 month time period thus allowing treatment of difficult cases in the shortest duration possible^8,9.

DISADVANTAGE OF FORSUS APPLAINCE:

· Most of the patients experience discomfort and mastication problems initially, however it reduces with time.

· Some of the patients experience sensitivity, soreness of the lip and cheek irritation.

· It may leads to development of ulcers in the buccal mucosa^8,9

TREATMENT EFFECTIVENESS:

The Forsus is an effective and comfortable fixed functional appliance which is very effective in repositioning the mandible in a forward position for the treatment of skeletal mandibular retrognathism. The significant skeletal changes commonly seen are the restriction of the maxillary growth and the increase in mandibular length. However, the restriction of the maxillary growth is more predominant than that of the increase in mandibular length. The most significant changes in the mandible are more dentoalveolar than the skeletal.

The dentoalveolar changes that are commonly associated with Forsus treatment in the maxillary arch are mild retrusion and extrusion of the maxillary incisors. The significant changes seen were increase in the lower incisor proclination and advancement of the lower incisor position. There is also a mesial movement and extrusion of the mandibular molars. The lower incisors were also found to be intruded with the appliance treatment. All these changes brought about an decrease in overjet and overbite^10-14.

CONCLUSION:

The Forsus is a very valuable appliance in the treatment of Class II cases with mandibular retrognathism. It is Advantageous especially in patients who are at the end of their growth by bringing about a great magnitude of dentoalveolar change thereby significantly reducing the overbite and overjet.

REFERENCE:

1. Dandajena T. Hybrid functional appliances for management of Class II malocclusions. Current Therapy in Orthodontics. St Louis, Mo: Mosby Elsevier; 2010:103–113.

2. Proffit WR, Fields HW, Moray LJ. Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES-III survey. Int J Adult Orthod Orthogn Surg. 1998;13:97–106.

3. Woodside DG, Metaxa A, Altuna G. the influence of functional appliance therapy on glenoidossa remodelling. Am J Orthod Dentofacial Orthop 1987;92:181-198.

4. Divya Ahuja, Anup K Holla, Sandeep Parashar. A brief review of forsus: frd; hybrid fixed functional appliance. Asian Journal of Dental Research 2015; Volume I, Issue II:1-14.

5. Wahl N. Orthodontics in 3 millennia. Chapter 9: functional appliances to midcentury. Am J Orthod Dentofacial Orthop. 2006;129:829–833.

6. Cacciatore G, Huanca Ghislanzoni L, Alvetro L, Giuntini V, Franchi L. Treatment and post treatment effects induced by the Forsus appliance: a controlled clinical study. Angle Orthodontist; 2014:84(6):1010-1017.

7. Min-Ho Jung. The Forsus™ Appliance: Characteristics and Clinical Cases. Orthodontic Clinical Information for the Orthodontic Professional;2009:Volume XVI No. 1

8. Stewart F, Kerr J, Taylor, P. Appliance wear: the patient’s point of view. Eur J Orthod. 1997;19:377–382.

9. Amy C. Bowmana; Humam Saltajib; Carlos Flores-Mirc; Brian Prestond; Sawsan Tabbaa ; Patient experiences with the Forsus Fatigue Resistant Device. Angle Orthodontis; 2013: 83(3):437-446

10. Ankur Chaukse, Sandhya Jain, M.S. Rami Reddy, Rachna Dubey, Shan Mammen John, Suma S. Treatment of Skeletal Class II Malocclusion Using The “Forsus” Appliance: A Case Report. People’s Journal of Scientific Research.Jan. 2011; 4(1):39-42.

11. Veronica Giuntinia; Andrea Vangelistia; Caterina Masuccia; Efisio Defraiab; James A. McNamara Jrc; Lorenzo Franchi. Treatment effects produced by the Twin-block appliance vs the Forsus Fatigue Resistant Device in growing Class II patients; Angle Orthod. 2015 Sep;85(5):784-9

12. Lorenzo Franchi, Lisa Alvetro, Veronica Giuntini, Caterina Masucci, Efisio Defraia, and Tiziano Baccetti (2011) Effectiveness of comprehensive fixed appliance treatment used with the Forsus Fatigue Resistant Device in Class II patients. The Angle Orthodontist: July 2011, Vol. 81, No. 4, pp. 678-683.

13. Esen Ali Gunaya, Tulin Arunb, Didem Nalbantgil. Evaluation of the Immediate Dentofacial Changes in Late Adolescent Patients Treated with the Forsus^TM FRD. European Journal of Dentistry. October 2011 ;Vol.5 :423-432.

14. Meenu goel et al,.Pitchfork analysis of class II correction using Forsus FRD. Journal of Indian Orthodontic Society. Oct-Dec 2013;47(4):240-244.

Received on 16.02.2017 Modified on 26.02.2017

Research J. Pharm. and Tech. 2017; 10(5): 1528-1530.

DOI: 10.5958/0974-360X.2017.00269.4