Close-up of dental professional examining a patient's occlusion

Insights for Clinicians: Finishing Invisalign Cases to a High Standard -- Why Cases Stall at 85%

Clinical
May 01, 2026

This article is written for dental professionals: dentists, orthodontists, and associates managing clear aligner cases. It is not intended as patient advice.

Every dentist doing Invisalign hits the same wall. The crowding is resolved. The spacing is closed. The patient looks at the mirror and says it looks great. You look at the occlusion and know it's not done.

The gap between "looks straight" and "finishes to a clinical standard" is where most aligner cases stall. After 18 years of Invisalign, I can tell you that this gap is predictable, researchable, and fixable. But it requires understanding why certain movements resist expression and how to plan for that resistance from the start.

I'm Dr. Abinaash Kaur, B.Sc., DDS, MFT. I trained at the University of Toronto Faculty of Dentistry and I've practised at The Village Dentist on Annette Street for 25 years. I train our associates on finishing Invisalign cases. This article covers what I teach them, backed by the current evidence.

How Do Invisalign Cases Actually Score Against Fixed Appliance Cases?

The data is honest, and we should be too.

Gu et al. (2017) compared 48 Invisalign patients to 48 fixed appliance patients using the PAR index. Post-treatment scores were not statistically different. Both groups achieved greater than 30% PAR reduction. But the odds of achieving "great improvement" with Invisalign were 0.329 times that of fixed appliances. Invisalign finished 5.7 months faster. So it's faster, but the finishing quality distribution skews lower.

Lin et al. (2022) evaluated 66 patients using the ABO Objective Grading System. For simple malocclusions, no meaningful differences in finished case quality between groups. However, the aligner group also showed worsening overjet during retention, which the fixed appliance group did not.

The takeaway: aligners can finish to a high standard. They just don't do it automatically. The clinician has to plan for the finishing details that fixed appliances handle mechanically.

Torque: The Movement That Defeats Most Aligner Cases

If there is one finding every GP doing aligners needs to internalise, it's this.

Kravitz et al. (2024) studied 35 patients requiring 10 degrees or more of lingual root torque on mandibular central incisors. The achieved accuracy was 58.2% of planned. Underexpression occurred in 94.3% of incisors. Clinically significant shortfall (5 degrees or more) in 68.6% of teeth. Published in the American Journal of Orthodontics.

The critical finding: power ridges did not significantly improve torque expression. This means the built-in ClinCheck feature that many GPs rely on for torque is not delivering what it promises.

A separate 2024 study by the same group confirmed similar underexpression for maxillary central incisor torque. Planned torque changes achieved less than half their target with the initial aligner series.

A 2023 finite element study showed that overtreatment combined with attachments on adjacent canines can improve incisor intrusion and palatal root torque expression. But standard aligner design alone is insufficient.

The 2025 international expert consensus stated it plainly: aligners move teeth primarily by tipping. When bodily control is needed, auxiliaries are required to make the plan predictable.

What I teach associates about torque:

  • If the ClinCheck shows 10 degrees of root torque on an anterior tooth, plan for 15 to 18 degrees. You'll express 58% of it. That gets you closer to your target.
  • Don't rely on power ridges alone. Use rectangular attachments on the teeth being torqued and on adjacent teeth for anchorage.
  • Stage torque before retraction. If you start both simultaneously, the retraction force overwhelms the torque moment and you get proclined roots.
  • Check torque clinically at every progress visit. If it's not tracking by the midpoint, order refinements early. Don't wait until the last tray.

Vertical Control: Why Posterior Open Bites Happen and How to Prevent Them

Extrusion remains the least predictable aligner movement. The original Kravitz (2009) study measured it at 29.6% accuracy. More recent systematic reviews put it between 54% and 62%, but it's still the weakest link.

The flip side is unplanned intrusion. 74.2% of adults experienced some degree of molar intrusion during aligner treatment. Average intrusion: 0.98 mm maxillary, 0.84 mm mandibular. This is iatrogenic, not therapeutic. The aligner material acts as a bite block on every posterior tooth.

For deep bite cases, a 2025 study found overall intrusion accuracy of 52.2%. Mandibular incisor intrusion was 63.5% accurate in adolescents versus 45.3% in adults. If you're treating an adult deep bite, plan significantly more overcorrection than the ClinCheck suggests.

Practical protocols for vertical control:

  • For deep bite cases: build 20 to 25% overcorrection for intrusion movements. More for adults than teens.
  • Program anterior bite ramps to shift intrusive force anteriorly and protect posterior occlusion.
  • Place occlusal attachments on first molars to resist iatrogenic intrusion.
  • If you see posterior open bite developing mid-treatment, don't wait. Scan for refinements and add posterior extrusion (even knowing it will underexpress).

Occlusal Settling: The First Three Months After the Last Tray

This is the finding that changed my retention protocol.

Quadri et al. (2023) measured posterior occlusal contacts in 82 patients. During treatment, total contacts dropped from 11.0 to 8.0. Occlusal contact area dropped from 48.42 mm2 to 21.8 mm2. That's a 55% reduction in functional occlusal area.

After 3 months of nighttime-only aligner wear, contacts recovered to 11.0 and area recovered to 34.93 mm2. The settling was primarily through physiologic eruption of posterior teeth after the bite block effect was removed.

What this means clinically: don't evaluate your final occlusion the day you finish the last tray. The posterior occlusion will improve on its own over 3 months if you transition to nighttime-only retention. Evaluate the case at the 3-month retention check.

I see associates panic about posterior contacts at debond. The evidence says: give it time. The teeth will erupt to find contact. Assess then.

Refinement Predictors: Which Cases Will Need Extra Rounds?

Kravitz et al. (2023) studied 500 patients. 94% needed at least one refinement. Average: 2.5 scans. 17.2% switched to braces entirely. Average treatment: 22.8 months (5.1 months over estimate).

A 2025 study by Konstantonis et al. of 116 patients identified tooth-specific predictors. Greater planned rotation and inclination increased refinement risk. Attachments reduced refinement need on some teeth (tooth 21: OR=0.05) but paradoxically increased it on others (tooth 12: OR=4.95).

The key finding: biomechanical response varies significantly among individual teeth. A uniform ClinCheck staging plan will underperform a tooth-specific one.

My approach to planning for refinements:

  • Tell the patient at the start: refinements are part of the process, not a complication. Set the expectation at consultation.
  • For cases with rotations exceeding 15 degrees or torque exceeding 10 degrees, I plan 2 refinement rounds into the timeline from day one.
  • Scan for refinements at tray 20 to 25, not at the end. This catches drift early and avoids the "we're so close, let's just finish" trap.
  • Use the overcorrection values from the Angle Orthodontist study: 28% for rotation, 22% for intrusion, 20% for inclination. These are evidence-based, not rules of thumb.

Root Resorption: What the CBCT Data Shows

Li et al. (2024) conducted a systematic review and meta-analysis of 9 studies (638 patients, 6,524 teeth). Mean root length reduction with clear aligners was 0.56 mm overall. Maxillary central incisors showed the greatest resorption at 0.74 mm. Severe resorption (greater than 20% root length) occurred in only 3.69 to 6.31% of teeth.

Yi et al. (2020) compared directly: fixed appliance root resorption prevalence was 82.11% versus 56.30% for clear aligners. Aligners are associated with lower root resorption prevalence and severity.

The 2025 Delphi consensus reached 78% agreement that clear aligners produce lower root resorption than fixed appliances, though evidence certainty was rated low.

Practical implication: root resorption risk is not a reason to avoid aligners. But it is a reason to take pre-treatment and mid-treatment periapical radiographs on teeth undergoing significant movements (intrusion, torque, bodily retraction). If you see early resorption, reduce force levels by adding rest stages into the ClinCheck.

Class II Correction: What Precision Wings Actually Deliver

If you're treating Class II cases with aligners, know the evidence before selecting mandibular advancement features.

A 2025 systematic review and meta-analysis of Precision Wings found ANB reduction of 0.81 degrees and SNB increase of 0.55 degrees versus untreated controls. However, GRADE certainty was "very low" for all outcomes. Precision Wings produce primarily dental effects, not skeletal correction.

A head-to-head comparison with Twin Block showed Twin Block was more efficient relative to treatment duration. Precision Wings provided superior lower incisor control and clinically relevant transverse expansion.

What I teach: Precision Wings are useful for mild dental Class II correction with lower incisor proclination control. Don't expect skeletal mandibular advancement. For growing patients with skeletal Class II, fixed functional appliances remain the stronger evidence base.

Straight vs Scalloped Trimlines: The Detail That Matters

This is an underappreciated variable.

A 2024 systematic review in the European Journal of Orthodontics found that straight-margin aligners exert 20 to 50% higher forces than scalloped margins for palatal root movement. Extended straight margins were up to 2.5 times more retentive than scalloped at the same height.

A 2023 finite element study confirmed that straight extended trimlines exhibit more uniform force transfer and stress distribution.

If you're requesting aligner modifications from your lab or through ClinCheck, consider straight trimlines for cases requiring significant root control or retention. The scalloped look is more aesthetic, but the straight design delivers more force where you need it.

Retention: What the Cochrane Review Says

The 2023 Cochrane Review of 47 studies and 4,377 participants found no moderate or high-certainty evidence to guide retention decisions. Fixed retainers showed less anterior and posterior relapse than Hawley or Essix retainers. Mandibular removable retainers showed mean irregularity increase of 0.72 mm. Mandibular fixed retainers showed no significant change.

A 5-year RCT found that by year five, only 28% of patients still wore removable retainers as recommended. Both vacuum-formed and bonded retainers showed irregularity increases below the 1.0 mm clinical significance threshold.

My retention protocol after Invisalign:

  • Bonded cuspid-to-cuspid retainer on the mandibular arch. Fixed stays in.
  • Vacuum-formed retainer for maxillary arch. Full-time for 3 months (allowing occlusal settling during the day), then nighttime-only indefinitely.
  • Re-evaluate at 3 months and 12 months. Take clinical photos for comparison.
  • If a patient declines the bonded retainer, I document the refusal and explain the 72% non-compliance rate at 5 years. Most change their mind.

The Takeaway: Plan for the Biology, Not Just the Software

ClinCheck is a planning tool, not a prediction engine. Kravitz's 2020 follow-up showed 50% mean accuracy. That's improved from 41% in 2009, but it means half of what the software shows you won't happen exactly as planned.

The clinicians who finish cases well are the ones who plan for the gap. Overcorrect torque. Stage movements sequentially. Measure IPR with a gauge. Check fit at every visit. Scan for refinements early.

The technology is excellent. SmartTrack achieves 73% of planned movement versus 43% for the earlier material. 22 million patients have been treated globally. The limiting factor is not the aligner. It's the treatment plan and the chairside execution.

If you're a GP finishing 10 to 20 aligner cases a year and your refinement rate feels high, you're not alone. Audit your torque planning, your vertical control, and your overcorrection values. That's where the evidence says the variance lives.

Dr. Abinaash Kaur, B.Sc., DDS, MFT The Village Dentist, 750 Annette Street, Toronto (416) 760-0404

Sources and Further Reading

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Dr. Abinaash Kaur

Dr. Abinaash Kaur is the founder and lead dentist at The Village Dentist in Toronto's Bloor West Village. She holds a Doctor of Dental Surgery (DDS) degree and is a registered member of the Royal College of Dental Surgeons of Ontario (RCDSO) and the Ontario Dental Association (ODA). With a gentle, patient-centred approach, Dr. Kaur provides comprehensive dental care for families across Bloor West Village and the greater Toronto area. She writes about oral health, preventive care, and the latest in dentistry to help patients feel confident and informed.

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