Adjusting your orthodontics to TADs

Orthodontics is an evolving discipline and temporary anchorage devices (TADs) are just one of the new faces of orthodontics. TADs came on the market some 10 years ago and the pioneers came mainly from Korea. TADs have come a long way, from complex systems requiring cumbersome procedures to newer self tapping systems that have been downsized in smaller kits presented in a more organized way.The inventory is thus less impressive and costly. It is difficult today to open an orthodontic magazine and not being exposed to multiple and various articles on the subject. TADs were first called mini-implants, but clinicians soon realized that they do not integrate. Most of the authors are now using the terminology “miniscrews”. As the name says “temporary”, they are normally not used for a long period of time. The use of TADs has opened doors to the possibility of treatment of some major orthodontic problems that could not be treated easily before. Some movements like molar intrusion (correction of excessive lower face height), distalization of the entire mandibular dentition 4 (correction of Class III), and better control of anchorage (less use of headgear) are facilitated and done with no need for cooperation 1,2. These are just some of the possibilities of TADs and your imagination is your only limit 3.

TADs can be used as direct or indirect anchorage devices. When using TADs, the clinician must adapt his mechanics to the way he uses the TADs. I encourage all clinicians to incorporate TADs into their daily orthodontic practice because they really fill a gap that no other technique of treatment can easily replace (Figure 1).

TADs are very easy to use and the learning curve is very easily climbed. Before TAD insertion, the clinician must decide whether he is going to use the TAD for direct or indirect anchorage. Direct anchorage means that the force system will be directly attached to the TAD. In this use, the elastic or coil spring will unite both the TAD and the segment to be moved. The TAD will be submitted to an active force. Indirect anchorage is different; no active force is attached to the anchorage unit, in the sense that no elastic or coil spring force will be attached to the TAD. The TAD will only anchor a tooth or segment of teeth to prevent their movement (Figure 2-3).

Using TADs for indirect anchorage will not change your day to day mechanics. The clinician only reinforces the anchorage unit with TADs and can use his normal mechanics without wondering of the possibility of unusual effects. Using them in this very simple approach will get you in the world of TADs easily and rapidly.  On the other end, when TADs are used as direct anchorage, the clinician must evaluate his mechanics with more caution. If your force system is directly attached to the TADs, you have to rethink your entire force system to prevent and avoid secondary tooth movement effects that you never planned when using traditional mechanics. Segments of teeth may move out of your control because you are incorporating new vectors of force that do not exist in traditional mechanics.

As an example, think of upper molar intrusion where a TAD has been inserted on the buccal of your upper molars and an elastic traction is applied from the TAD to the molars. Since the TAD lies buccal to the center of resistance of the molar, the resultant vector of force will intrude and move the molar crowns buccaly. To avoid this effect, a second TAD has also to be placed on the palatal side (Figure 4).

Another example is the retraction of the anterior segment in direct anchorage from a TAD placed in the molar area. You always have to take into consideration your resultant force vector (Figure 5). With a better understanding of the vectors of force, you will be able to move from indirect anchorage to direct anchorage. This way, even more challenging cases can be solved with ease.

Bibliography
1. Treatment of Severe Maxillary Protrusion With Miniscrew Anchorage: Treatment and Complications. Mimura H: Aust Orthod J; November 2008 (24):156-163.
2. Simultaneous Incisor Retraction and Distal Molar Movement With Microimplant Anchorage. Park H-S, Bae S-M, et al:World J Orthod; 2004; 5 (2): 164-171.
3. Clinical Applications of the Miniscrew Anchorage System. Carano A, Velo S, et al:J Clin Orthod; 2005; 39 (January): 9-24.
4. Class III Nonextraction Treatment With Miniscrew Anchorage. Paik CH, Nagasaka S, Hirashita A:J Clin Orthod; 2006; 40 (August): 480-484.

 
Figures
Figure 1. Insertion of a TAD from the Vector system of Ormco.
Figure 2. TADs as direct anchorage.
Figure 3. TADs as indirect anchorage.
Figure 4. Molar intrusion.
Figure 5. Anterior retraction causing unplanned and unwanted effects.

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Publié dans : DENTISTES - CLINIQUE