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Of the many distalizing appliances, the ACCO (ACrylic Cervical Occipital) has been shown
to be successful among orthodontists. This is partly due to its effectiveness when used in conjunction with extra-oral traction. (Fig. 1 ) Fig. 1- The Original Ac.C.O |
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This removable appliance, introduced in Italy by Dr. Cetlin, is equipped with two finger springs located mesial to the first molars. These springs deliver a very small distal force (30-40 gr. according to Cetlin).(Fig. 2) |
| Extra-oral traction (150-200 gr.) should be worn for
10-12 hours per day. The purpose of extra-oral traction is to control tipping of the molars. The most appreciable advantage of this appliance is that using low forces, it allows for bodily movement of molars (single force+ couple force) with complete occlusal clearance (due to the anterior bite plane). The distalization achieved is therefore more stable and less prone to relapse. |
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However, in clinical use, some drawbacks may occur causing treatment delay. The most common difficulty is related to the insertion of the finger spring into the space between the molar and the tooth mesial to it, since this contact is often tight, preventing full seating of the appliance (Fig. 3). To solve this problem, it is usually necessary to separate the teeth prior to insertion. |
| Another difficulty concerns the necessity for periodic activation of the springs so that the force levels are continuous. The continuous force delivered is one of the advantages of this appliance. | |
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The modified Ac.C.O.
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These nickel-titanium springs can deliver a constant force of 50 gr. in a progressive manner and are therefore very elastic. (Fig. 5) A .022" x 0.028" sheath is soldered on the lingual of each molar band. The sheaths can then accept the coil spring assembly.Tipping control is achieved using the wire guides inserted in the sheath and from their natural reactivation when distorted, from the temperature of the oral cavity. (Fig. 6) |
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As with the original Ac.C.O., this appliance is stabilized by two Adams clasps on the first bicuspids and also undercuts at the upper central and lateral incisors. For this reason Dr. Cetlin recommends re-adapting the acrylic periodically (Fig.7) |
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| Clinical cases: To evaluate the clinical effectiveness of this appliance we will demonstrate a case. An 11 year old female patient presented with dental and skeletal Class II division I malocclusion and skeletal dolico-facial characteristics. (Fig. 8) To evaluate whether the distalization achieved was bodily or not, we used only the Ac.C.O. plate without the use of extra-oral traction. |
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