By Jeffery Gerhardt, DDS
My clear aligner journey started in 2002, when an orthodontist friend called me and recommended that I become Invisalign-certified.
“You can’t do that much with their aligners, but they have great marketing,” he said. “Patients come in for an Invisalign consult, and most of the time the case is too complicated, so we do braces on them.”
I took my friend’s advice and signed up for a two-day continuing education class in Dallas, TX. Being from Austin, a casual sort of place, I wore workout clothes to class. I thought I was the only general dentist in the class. Most of the students wore ties and jackets. I sat down next to the only other person wearing workout clothes and found out he was also from Austin. We became friends.
REVISITING HISTORY
When I first used aligners, I finished many of my cases with braces because it was hard to achieve the results I wanted. At that time, all diagnostic and aligner work was done with impressions. Because I was never happy with the results aligners delivered, I did not want to buy a $42,000 iTero scanner to commit to Invisalign. I tried a few other aligner companies but, again, never loved the results. I stopped using clear aligners for years and stuck to fixed appliances.
In 2021, another orthodontic specialist called me. “I know you do not want to do aligners anymore and are sending all your aligner cases to me, but I’ve started using Spark Aligners and really like them,” he said. “You may want to consider doing aligners again.” According to the specialist, Spark’s three-layer plastic design was allowing him to finish patients faster than ever before, and any scanner can be used with the product.
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UNDERSTANDING CLEAR ALIGNERS
Aligners are about 50 percent accurate. When you do a simulation with an aligner company, the simulation will look perfect after the first round. In reality, the results rarely match the simulation. To try to overcome the concern, practitioners treat their patients with refinements. According to a presenter at the American Association of Orthodontists Winter Conference 2024 in San Antonio, the average number of refinements worldwide is 2.75.
The most difficult cases to treat with aligners are deep bites and extractions. Guidelines we have come up with to produce predictable results with aligners suggest using the devices only in cases where we are:
- Treating deep bites that are less the 50 percent over-closed.
- Treating patients with 4 mm or less of crowding in the lower arch.
- Treating Class I molar and canine abnormalities.
- Treating patients with rotation of canines or bicuspids of less than 25 degrees.
BIOMECHANICS & EXPANSION
Fig. 2 shows a textbook on the biomechanics of clear aligners. In this article, I have based some of the information on what is found in this textbook.
When using braces to perform treatment, you are pulling teeth buccally. With aligners, you are pushing teeth out buccally. So, what specifically happens with aligners? The teeth are tipped buccally during treatment, which is not stable. What practitioners must do, then, is place attachments on the teeth so that when the aligners push them buccally, they also push them occlusally so the teeth move bodily, rather than simply tipping out (see Figs. 3 and 4). You can also use cross bite elastics to achieve this goal.
ROTATING TEETH & SETTLING A BITE
Tooth rotation can be challenging with aligners. To help with unrotating teeth, you can pre-rotate the involved teeth with braces (see Figs. 5 and 6). In addition, you can place an attachment on the buccal and lingual portions of the involved teeth (Fig. 7).
If the posterior bite begins to open during treatment, you can add buttons and use boxing elastics to help close the bite (see Figs. 8 and 9).
I am currently working on a deep bite case (Fig. 10), and a posterior open bite has started to develop. To correct this, we added buttons for nighttime boxing elastics and told the lab to torque the anteriors facially to help close the bite.
To further aid in deep bite cases, practitioners can have their lab place built in bite turbos on the lingual of the maxillary aligner in a 3-3 configuration (see Fig. 11). The patient can then wear Class II elastics (0.25-inch medium) to help extrude the lower first molars to help open the bite (see Fig. 12).
Overall, clear aligners can be an effective service to offer patients. Remember, however, that patient selection is a critical part of achieving successful treatment outcomes. In the future, I plan to attempt to use aligners on increasingly complicated cases as the technology improves.
| SPARK | INVISALIGN |
|---|---|
| Introduced to U.S. market in 2017 | Introduced to U.S. market in 1997 |
| Owned by Ormco (known for Damon brackets) | Provides aligners only |
| Minimal marketing | Well known to consumers |
| TruGen (three-layered plastic) intended to move teeth quickly | Smart Track (one-layered plastic) |
| Compatible with any scanner | Compatible with Iterro scanner |
| Does not accept impressions | Accepts impressions |
| Spark on-demand aligners for $30 each | Offered in five- to 10-aligner cases |
| Program to provide braces free of charge if needed | No brace program |
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