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The Effect of Intermaxillary Elastics in Orthodontic Therapy
1 Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, Victor Babes University of Medicine and Pharmacy Timisoara

Correspondence to:
Dr.Dana Cristina Bratu, Department of Pediatric Dentistry and Orthodontics, Revolutiei Blvd. 9, Tel. +40-256-491943
Orthodontic elastics are used in all kinds of malocclusions: Class I, Class II, Class III and open bite. Their aim is to increase the movement of the mandible, without the need of multipe activations by the orthodontist. Their effects are: horizontal, vertical, transersal movements, mandible distalizing and mesializing, dental extrusion, space closing, midline shift and intercanine relation correction, opening the bite. Our study will pesent some of the clinical applications of orthodontic elastics in Class II and fronto-bilateral openbite malocclusions.

Orthodontic treatment represents a major investment in the future dental health and appearance.1 Teeth move as a reaction to forces applied to them.2 In many cases, we use other teeth in the same jaw to give them resistance or anchorage, needed to provide the required forces.3 Most often, usually when several teeth need to move in the same direction, it is not possible to produce the change required using appliances anchored in just one jaw. During some phases of orthodontic treatment, elastics or rubber bands are used to move teeth or jaws, or sometimes both.4,5 By carefull treatment planning and controlling the strength, direction and duration of forces, we aim to keep our use of elastics and headgear to a minimum. In some cases a good treatment outcome will be impossible without a lot of work using elastics, headgear or both.
The first known elastic was used by the Inca and Maya civilizations and was extracted from Hevea trees.2 Later, in 1728, Pierre Fouchard proposed to close anterior diastema with silk ligature.1 From this moment on the history of using elastics in orthodontics abounds in writers, culminating with Ricketts in 1970, which applyed the Bioprogressive segmented light square wire technique advising the closing elastics conduct in open bite cases.2 Roth recommends short Class II intermaxillary elastics to help leveling the curve of Spee in association with extraoral forces. Langlade has the merit of developing clinical applications of elastic forces in different situations, proposing rules of biomechanics .6

Material and method

Intermaxillary Class II elastics are placed on the anterior maxilla and posterior mandible.6 We used intraoral elastics produced by GAC International Inc. NY USA, made from latex and available in different sizes and shapes. They are available in “light”, “medium”, “heavy” and “super heavy” types, each of them performig a different force on the teeth. Each bag of GAC elastics contains a bright white placer for the patient.
Fig. 1. Orthodontic elastics in different clinical situations.
This study was conducted on a number of 20 patients with Class II/1 and fronto-bilateral open bite anomalies. Application of the elastics was different, depending on the clinical situation. We used classic, triangular and rectangular elastics. Figure 1 shows orthodontic elastics in different clinical situations.
Elastics were inserted at the maxillary arch, anterior from a canine bracket hook, a Class II utility arch, a Kobayashi wire ligature or a continuous archwire with anterior loop.
At the mandibular arch, elastics were inserted posterior, labial or lingual: distal to a molar tube, different teeth (M2, M1, Pm 2, Pm 1), a Kobayashi wire ligature, a hook or a loop.
Effect of Class II elastics is the maxillary distalizing, mandibular advancement and closing the bite.
With a mouth open of 10 mm during speech, the force varies with different angulation of the Class II elastic and has different effects upon the maxillary and mandibular arches.6
Biomechanic influence of elastics in Class II anomalies is showed in Figure 2.
In the maxillary arch, the vertical component of extrusion is smaller than the horizontal component of distalizing.
In the mandibular arch, the horizontal component of advancement is smaller than the vertical force of extrusion. In different clinical situations, the patients were instructed to wear the elastics during night and day. During daytime,6 intermaxillary elastics have a vertical component of extrusion that is much more significant than the horizontal component, their effect being increased by the functional movements (mastication, phonation). According to the orthodontist’s prescription, they must be changed 1-2-3 times/day. During the night,6 intermaxillary elastics have an equivalent vertical and horizontal component. Class II elastic indications:
Fig. 2. Biomechanic influence of elastics in Class II anomalies.
Class II elastics may be used for main and secondary objectives in the following clinical situations: skeletal and/or dental Class II malocclusions, anchorage reinforcement, backward movement of the upper incisors, mandibular arch advancement, buccal tipping of retruded lower incisors, bite opening (class II/2), midline deviation correction.6
They are recommended only after the correction of overbite and segmentation of the maxillary archwire.
The class II elastics have different effects:6
a. effects upon the maxillary arch:upper incisors are more vertical, extrusion and downward movement of anterior occlusal plane, backward movement of the upper arch, dental distalization.
b. effects upon the mandibular arch: buccal tipping of lower incisors, forward movement of the entire mandibular arch, extrusion of the lower first molars.
c. effects on the facial patterns: forward movement of the chin, forward movement of the mandible with a posterior rotation; The lower facial height will depend on the wearing time and the amount of elastic force used.
d. effects on the occlusal plane:lowering of the anterior occlusal plane, sagital correction of the Class II relationship.


Representative clinical cases
Case 1
Patient S.A. presented a Class II/1 malocclusion. After retraction of the frontal group and obtaining a functional overjet, the patient wears Class II elastics.
Effects of Class II elastics: mandible distalizing, mesial movement of the mandible, lateral extrusion.
Clinical case and representation of Class II elastics is showed in figure 3.

Case 2
Patient A.M. presented narrow upper arch and and bilateral canine ectopy. After alignment of the canines, triangular elastics were applied. Figure 4.
Triangular elastics produce canine extrusion, occlusal and vertical stability of the canine, and the presence of two oblic forces, with the movement of the tooth along the bisector line direction.

Case 3
Patient F.M. presented with a Class II/1 malocclusion. In the final stage, we applied rectangular intermaxillary elastics for occlusal setlling. Figure 5.
Effects of lateral rectangular elastics: distalizing of the upper arch, advancement of the lower arch, horizontal and vertical equal forces which rearrange the oclussion in the finishing stage.

Case 4
Patient A.B. presented a fronto-bilateral open bite. After solving the lateral occlusal problems, we applied frontal rectangular elastics in order to close the bite. Figure 6.
Frontal elastics in rectangular shape produce:7 transversal changes, upper and lower anterior group extrusion, mandibular rotation.
Fig. 3. Clinical case and representation of Class II elastics.
Fig. 4. Clinical case with triangular elastics.

Fig. 5. Rectangular elastics.
Fig. 6. Rectangular elastics to close the open bite.


Some clinical problems may appear even with careful clinical observation: 6 excessive or insufficient wearing, periodontal problems of the lower teeth, unwanted space opening or closing, loss of anchorage, unwanted rotation or extrusion, abnormal tipping, temporomandibular disorders, incorrect placement of the elastics by the patient, the elastic properties may decrease or be lost.
After 2 hours from the insertion of elastics6 in the oral cavity, the elastic properties decrease with 30%, and after 3 hours, with 40%. After 1 month after insertion, elasticity was 50% off.10
After comparing the effects of Class II elastics and the fixed functional appliances such as Herbst, other authors8,9,10 have found more pronounced vertical changes after elastic treatment.
The disadvantages of intermaxillary elastics are minimal and the results are optimal, with the condition of a carefull diagnosis and treatment planning.


Our conclusion is that it would be advisable to use intermaxillary elastics in the finishing stage of orthodontic treatment, in order to obtain an optimal occlusion and a long time stability of the orthodontic results.

1. Glăvan F.: Ortodonţie curs, Editura Mirton 2001.
2. Bratu E. şi colaboratorii: Ortodonţie. Curs pentru studenţii anului VI. LITO UMF Victor Babeş Timişoara, 2003.
3. Glăvan F: Forţe ortodontice. Editura Waldpress, 1995.
4. Kersey ML, Glover KE, Heo G, Raboud D, Major PW. A comparison of dynamic and static testing of latex and nonlatex orthodontic elastics. Angle Orthod. 2003 Apr;73(2):181-6.
5. Aras A, Cinsar A, Bulut H.: The effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- and hyperdivergent growth patterns. A pilot study. Eur J Orthod Aug; 23(4): 393-402.
6. Langlade M.: Optimization of Orthodontic elastics. Edited by GAC International, New York 2000.
7. McSherry PF, Bradley H: Class II correction-reducing patient compliance: a review of the available techniques.J Orthod. 2000 Sep;27(3):219-25.
8. Rock WP, Wilosn HJ, Fisher SE: Force reduction of orthodontic elastomeric chains after one month in the mouth. Br J Orthod 1986; 13(3): 147-50.
9. Reddy P, Kharbanda OP, Duggal R, Parkash H. Skeletal and dental changes with nonextraction Begg mechanotherapy in patients with Class II Division 1 malocclusion. Am J Orthod Dentofacial Orthop. 2000 Dec;118(6):641-8
10. Nelson B, Hansen K, Hagg U. Class II correction in patients treated with class II elastics and with fixed functional appliances: a comparative study. Am J Orthod Dentofacial Orthop. 2000 Aug;118(2):142-9

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