Bonding


Bonding Indirect Anchorage Wires from TOMAS Miniscrews to Enamel and Porcelain

John M. Pobanz, DDS, MS South Ogden, Utah

Pobanz-headshotThe TOMAS miniscrew design allows for efficient and simple creation of indirect anchorage. The cross slot is easy to orient to the tooth or teeth in the anchorage unit as it emerges from the TAD head at each 45º angle. A piece of .019 x .025 stainless steel can be bent chairside to run through the cross-slot and bonded to the TOMAS miniscrew head with a nonfilled resin such as Heliosit (Vivaclar), which will flow into the undercut of the miniscrew head to create a mechanical lock of the auxiliary anchorage wire. When it comes time for miniscrew removal or when the indirect anchorage unit needs to be changed, the wire auxiliary can be removed by fracturing the material with the squeeze of a pin and ligature cutter.

The cervical third of the anatomical crown of a tooth experiences more flexion under occlusal loads. When heavy and repetitive, these loads can even result in abfraction lesions. With this knowledge, a savvy clinician should consider bonding the leg of the indirect anchorage wire on a vertical pattern relative to the clinical crown of the tooth, rather than hugging the gingival margin on a horizontal pattern. This generally results in less failure of the bond (Figure 1).

The Transbond LR lingual retainer from 3M Unitek is a great product formulated to allow micromovement of individual teeth bonded to a lingual wire retainer. Transbond LR is a great choice when bonding a miniscrew-supported anchor wire to the enamel of a tooth intended to be included in the anchorage unit because the tooth will experience micromovement within its periodontal ligament space of the alveolus, whereas the miniscrew will not.

Untitled-1Figure 1: Bonding the leg of the indirect anchorage wire on a vertical pattern relative to the clinical crown results in less failure of the bond.

 When faced with bonding to a porcelain surface with a bracket, bonded wire retainer, or miniscrew-supported anchor wire, consider Fast Fix porcelain primer from Sullivan Schein. (Jep Pascal, DMD, of Madison, Georgia, introduced the use of Fast Fix for orthodontic bonding at several recent study club meetings.) This material uses an organic acid/silane primer combination that prepares a roughened porcelain surface for bonding with your favorite adhesive primer and paste with as little as 15 seconds of conditioning time (according to the product instructions). This is a huge time-saver relative to other two-step products available.

 We err on the side of excess time, allowing the material to sit for up to 60 seconds, resulting in bond strengths comparable to other two-step products that require hydrofluoric acid. This strong acid is one we are happy to eliminate from the operatory, since it can inadvertently be applied to gingival tissue or splashed into a patient’s eyes.

Figures 2 and 3 demonstrate the use of an indirect anchor to facilitate intrusion of anterior teeth in the absence of posterior teeth in one quadrant and in preparation for post-orthodontic restorations. All of the products mentioned were used in this successful clinical example: Heliosit for the microscrew head, Fast Fix and Transbond LR for the lingual surface of the tooth adjacent to the edentulous space, with an indirect wire bonded vertically.

Untitled-2Figure 2: The patient presented with missing posterior teeth in one quadrant and was treated in preparation for post-orthodontic restoration.

Untitled-3Figure 3: An indirect anchor facilitated intrusion of anterior teeth in the absence of posterior teeth.