Applying Brackets
Brackets are metal rectangles affixed to each individual tooth. To install a bracket, the surface of the tooth is scraped clean of plaque and polished to remove any sugar, protein or saliva residues. The dental assistant then hits the surface with a burst of pressurized air to dry it before applying a special "conditioner" which dissolves any remaining contaminants from the surface and prepared the tooth to receive the cement primer later on. After 20 seconds, the conditioner is rinsed off with water and the tooth is dried with another burst of air.
Next, the assistant applies a liquid primer to the surface of the tooth. Meanwhile, at the workstation next to the examination chair, another assistant mixes zinc oxide powder with phosphoric acid in a small dish to create a zinc phosphate paste.
The assistant dabs the paste on to primed surface and then presses a bracket on top of it. Using a tiny scooping instrument, the assistant removes excess paste from around the bracket. To activate the drying process (a.k.a. "curing"), a powerful LED light gun is trained on the zinc phosphate cement for about six seconds.
After 20 minutes, the cement is strong enough to hold the bracket on its own. However, the arch wire often won't be applied until the next day to ensure maximum bracket stability.
Applying Bands
Bands are wide, circular strips of malleable metal designed for rear teeth (molars) and provide an anchor for the arch wire and buccal tubes.
First, special devices called "spacers" are placed between the molars one week in advance to give proper room for fitting and cementing. At the end of the week, the spacers are removed and the orthodontist slides a pre-made band designed for the molar around the top of the tooth. The orthodontist then places a "bite stick" over the top of the band and instructs the patient to bite down, pushing the band into place.
The band is then removed and dried. A dental assistant lines the inside of the band with cement and fits it onto the patient's molar where it cures and hardens.
Applying Archwires & Liganding Modules
Archwires link the brackets and bands together, creating the tension that supplies the underlying physical mechanism for braces. To install arch wires, the orthodontist fits the pre-formed archwire into the brackets, ensuring proper fit and making any last-minute adjustments.
Then, the orthodontist and/or dental assistant will set about the task of locking the archwire permanently into place by installing plastic or wire ligatures. Depending on the forces acting on each bracket, either a thick, circular plastic band (less stress) or nickel-titanium wire (greater stress) will be looped around the bracket. This tension will squeeze the parts of the bracket together, creating a friction on the archwire that will keep it from slipping. By preventing slippage, the force will be directed into the tooth (via the cement), restricting blood flow in specific areas in the gums to encourage corrective movement and growth.
While the plastic bands are stretched around the various edges of the bracket with pliers, the wire requires a bit more doing. Usually, it requires looping followed by a powerful "twisting" process to shorten the circumference of the loop (thus tightening it). Once complete, the twisted ends are cut and tucked back into the bracket to keep them from poking the inside of the mouth. In certain cases, the archwire is bent into small, ornate shapes to allow for more reliable attachment to the bracket. If this is the case, the ligature wires must weave around both the bracket and the archwire.
Tags: dental assistant, arch wire, around bracket, into place, surface tooth, together creating