The Hidden Workhorse by Dr. Courtney Barry

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The Hidden Workhorse 

Solving aligners’ rotation problem with lingual power chain

by Dr. Courtney Barry

If you’re anything like me, you have found yourself lying awake some nights thinking about your patients’ cases and occasionally waking up in a pool of sweat after having a nightmare about rotated lateral incisors. Lucky for me, I no longer have these nightmares because I have finally found a consistent tool in my toolbox to address them more predictably.

A 2025 systematic review pooling 12 studies on rotational accuracy with clear aligners found that accuracy in adults ranged from 36% to 85%, averaging around 65%, with a mean absolute error of roughly 2.3 degrees per tooth.1 I found these numbers validating rather than surprising.

As an orthodontist who uses roughly 98% clear aligners at my private practice in New York City, rotation has always been the movement I trust least when I look at the digital treatment plan. The biomechanical reasoning is intuitive once you think about it: Cylindrically shaped teeth like lateral incisors or canines simply don’t offer the surface area or undercuts that aligner plastic needs to generate a true rotational couple (Figs. 1–2). You can ask the software for 8 degrees of rotation on a lateral incisor, and it will dutifully draw you a tooth that’s 8 degrees straighter. Whether that tooth actually gets there is a different question entirely.
Diagram showing a rotated lateral incisor and limited aligner engagement surface
Fig. 1: Diagram showing a rotated lateral incisor and the limited surface area available for aligner engagement.
Maxillary occlusal view from intraoral scan
Fig. 2: Maxillary occlusal view from intraoral scan.

For my adult patients specifically, being unable to predictably derotate a lateral incisor isn’t an abstract accuracy statistic. It’s a smile-zone problem. Take my 30-year-old patient, Barbara, who is currently in treatment. Her chief complaint was overall crowding, with her rotated upper lateral incisors being her biggest insecurity. They are distolingually rotated, prominent on smiling, and the single feature she fixated on in every photo. The plan: comprehensive treatment with clear aligners, no extractions, address her bite, and align her teeth over an estimated 12–15 month period (Figs. 3–4).
Barbara's pretreatment smiling photo showing rotated lateral incisor
Fig. 3: Barbara’s pretreatment smiling photo showing rotated lateral incisor.

The approach: A lingual power chain, designed as a force couple
Most orthodontists who use auxiliary power chain with aligners place the buttons buccally, because that’s what the software supports by default. For my adult patients, this is often a non-starter. Many of my patients choose clear aligners specifically because they’re discreet, and a visible buccal button or chain undercuts the entire value proposition of the treatment they selected (Fig. 5).
Barbara's intraoral photo at start showing occlusal view of rotation
Fig. 4: Barbara’s intraoral photo at start showing occlusal view of rotation.
A less-aesthetic facial button on an upper lateral incisor made from a minimold
Fig. 5: A less-aesthetic facial button on an upper lateral incisor (made from a minimold).

So I place the buttons lingually, whenever possible (Fig. 6).
A more-aesthetic lingual button on an upper lateral incisor with a power chain attached
Fig. 6: A more-aesthetic lingual button on an upper lateral incisor with a power chain attached to aid in its derotation.

As of this writing, most aligner software does not natively support lingual cutouts for buttons. I work around this in one of two ways. At the design stage, I’ll ask the technician to “extend the lingual gingival margin on the lateral incisor 3–4 mm to allow me to place a lingual button” to create a block-out zone, an area where no aligner material is fabricated, thus leaving an opening for the button (Fig. 7). While I ask for this cutout, the aligners don’t always arrive with enough clearance for the lingual button.

Alternatively, once the trays arrive, and if the lingual of the upper lateral incisors do not indeed have the cutouts because it’s not foolproof, I will use a hole-punch instrument to create the lingual cutout myself, chairside. Note: one of my favorite features of some aligner systems (like Angel Aligners) is that their software allows me to design lingual button cutouts on all upper incisors (Fig. 8). Other systems don’t support it yet.
Gingival margin extension used to create a faux button cutout on the lingual of the upper incisors
Fig. 7: Gingival margin extension used to override the planning software and create a faux button cutout on the lingual of the upper incisors.
Digital treatment plan showing a lingual button cutout
Fig. 8: Digital treatment plan showing a lingual button cutout, a feature supported by some aligner systems.

The mistake I see most often with auxiliary power chain is treating it as a single point of force. Every action has an equal and opposite reaction. Hook a chain from point A to point B, and you’re not derotating a tooth predictably; you’re creating an unbalanced force that has to go somewhere. If I’m derotating an upper lateral incisor by pulling its mesiolingual surface lingually, that same force is transmitted through the chain to whatever tooth anchors the other end. Left unaddressed, the anchor tooth will simply rotate toward the lateral incisor, undoing progress on one tooth while creating a new problem on another. Luckily, this is typically a premolar tooth that is less in the aesthetic zone, so I don’t hear about any temporary aesthetic complaints from the patient.

For Barbara, the design looked like this: a lingual button on the rotated lateral incisor, positioned to engage its mesial aspect, paired with a second lingual button on the second premolar. Critically, I built a small counter-rotational moment into the aligner itself on the premolar, essentially pre-loading it to resist the reciprocal force the power chain would generate. The chain could then do its job on the lateral incisor without the premolar drifting into its own rotation (Fig. 9).
Barbara: lingual buttons with power chain and aligners
Fig. 9: Barbara: lingual buttons with power chain and aligners.
Overjet view of crowded upper incisors with minimal lingual access, pretreatment
Fig. 10: Overjet view of crowded upper incisors with minimal lingual access, pretreatment.

Timing: Aligner No. 1 isn’t always possible
My stated preference is to build this auxiliary in from aligner No. 1. But “I like to start early” and “I can always start early” are two different statements, and adult patients with significant incisor crowding are often where those two statements diverge.

The issue is access. To bond a lingual button, I need an accessible surface on the lingual aspect of the tooth with enough clearance for the composite to seat properly and for the button itself to sit without immediately catching on the adjacent tooth or interfering with the occlusion. In a crowded arch with significant lingual tipping or rotation overlap on the incisors, that clearance often doesn’t exist at the outset. The teeth are stacked too tightly for there to be any real surface to bond to (Fig. 10).

When I run into this, I have two options. The first is to simply wait and let the first several aligners do their work of resolving gross crowding and creating some initial separation between the teeth, then introduce the lingual button and power chain once there’s enough room to bond it properly. This is the more common path, and it means the auxiliary doesn’t start at aligner No. 1 but rather possibly at the first refinement or halfway through the set of aligners once the arch has opened up enough.

The second option, for cases where I want to start the rotational force earlier, is to plan for some deliberate flaring or “round-tripping” of the crowded incisors in the early stages, intentionally moving them labially first, even slightly beyond their final planned position, purely to create lingual access. Once there’s enough clearance to bond the button, the tooth can then be brought back through its final trajectory, now with the power chain assisting the rotation on the way. Sometimes I’ll even bond bite turbos to make sure there is enough vertical clearance in deep bite cases, typically found in your Class II Division 2 cases.

Neither approach is wrong, and the choice often comes down to how much total rotation needs correcting and how much time the case can absorb. I’m more inclined to plan the round-tripping early, even though it adds a step, because it gets the auxiliary engaged sooner and gives more total aligners to work with the power chain in place.

Sequencing and chairside protocol
In Barbara’s case, and in every adult case where I anticipate needing this auxiliary, I now build it in from aligner No. 1 rather than waiting to see whether attachments alone will be enough. Patients are going to experience some soreness with a new aligner regardless, so this is the lowest-friction point to introduce it.

I’ve also changed how I instruct patients on tray-change timing when a power chain is involved. Normally, at a treatment start appointment where the patient gets all of their attachments and aligners, I tell patients to start a new aligner at night, so the first several uncomfortable hours pass while they sleep.

However, with an active power chain at a treatment start appointment, I flip the script; I have patients start the new aligner right away while they are in the dental chair rather than waiting until nighttime. In my experience, the combination of fresh plastic and an active power chain can initiate meaningful rotational movement quickly, and I’d rather the patient be wearing the aligner to keep things in place and ensure the aligner fits on that lateral incisor tooth by the end of the day.

Patients return every 4–6 weeks for power chain adjustment. At each visit, I assess remaining rotation and either replace the chain or remove a link, depending on how much correction is left. One trade-off worth setting expectations for: An aligner with an active power chain may lose full tracking on the target tooth sooner than a standard aligner would. In my experience, this is acceptable as the rotational gain outweighs the minor tracking loss, and the next aligner in the series picks up the slack. And if it doesn’t, that’s what a refinement is for.

A second use for the same button
One reason I’ve come to particularly value the lingual button on upper laterals: It has a second life. Lateral incisors are notoriously prone to needing extra extrusive force, and a button already in place for derotation can later be repurposed, paired with a button on the opposing canine, to help guide the lateral into extrusion using the same chain mechanics (Fig. 11). Some systems now offer buttons built directly onto the aligner, which make it easy for a patient to run vertical elastics without having to bond another button on the buccal surface in the precious “aesthetic zone.”
Diagram showing the lateral incisor button repurposed with a canine button for extrusion
Fig. 11: Diagram showing the lateral incisor button repurposed with a canine button for extrusion.

Rather than waiting to discover that a lateral incisor is under-tracking or under-extruding and then scrambling to add an auxiliary mid-treatment, I find it far more efficient, and far less disruptive for the patient, to plan for this possibility from the get-go. The aesthetic zone is where my adult patients are most sensitive to anything going wrong, and addressing both rotation and extrusion proactively, in the same design, has become standard in my practice.

Closing thoughts
Rotation remains, by a wide margin, the least predictable movement in clear aligner therapy, and canines and lateral incisors are consistently among the worst performers in the published literature, regardless of attachment type.2 For adult patients, where discretion is often the reason they chose aligners in the first place, and where residual rotation in the smile zone is the most common source of post-treatment dissatisfaction, relying on attachments alone often isn’t enough.

A lingually placed power chain, designed as a true force couple with a counter-rotation built into the anchor tooth, introduced at aligner No. 1, and adjusted every 4–6 weeks, has become one of the most reliable tools in my toolbox. It’s brand-agnostic, low-cost, and addresses precisely the failure point the research consistently identifies. More importantly, it addresses the thing patients actually came in for: a smile that finally looks right.

References
1. Evaluating the Clinical Success of Clear Aligners for Rotational Tooth Movements in Adult Patients: A Systematic Review, 2025.
2. Predictability of tooth rotations in patients treated with clear aligners, Scientific Reports, 2024.

Author Bio
Dr. Courtney Barry Dr. Courtney Barry is a board-certified orthodontist and founder of Smile Pop, her private orthodontic and aesthetic practice in New York City. Barry earned her DMD from Southern Illinois University, and upon graduating, continued her education with a one-year fellowship in orthodontics at the University of Florida and a three-year orthodontic specialty training at Montefiore Medical Center in New York. She shares her insights with the orthodontic community through contributions on Instagram and YouTube.
Email: drcourtney@smilepop.com
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