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K Clear vs Six Month Smiles

Starting price, treatment length, supervision, FDA safety record and full spec sheet for K Clear and Six Month Smiles, side by side. Every figure links to the source that states it.

Prices verified Sep 30, 2026FDA records verified Sep 30, 2026
20comparisons with K Clear
22comparisons with Six Month Smiles

K Clear (K Clear aligners, ClearX)·Six Month Smiles (6MS Invisible Aligners, 6MS Relapse Aligners, 6MS Mixed Appliance)

K Clear
In-office
Six Month Smiles
In-office
At a glance
Starting price
Provider-setnot published
Provider-setnot published

Blue marks the lower price only where every compared price is quoted the same way (a monthly price in US dollars); prices quoted in another currency, as a one-time fee or as a provider-set range are shown exactly as stated and never converted. Adverse-event figures are raw counts of reports filed with the FDA, not rates (what the reports mean). Each spec value opens that brand's spec sheet, and its numbered sources verify the specs as a set. None of this is a recommendation: the right choice depends on your case, your budget and, above all, an in-person exam by a dentist or orthodontist.

The bottom line

What actually differs

  • Neither is marked lower, since only monthly prices quoted in US dollars are ranked against each other: K Clear Provider-set and Six Month Smiles Provider-set.
Go deeper

Open the full record

K Clear
  • Prices
  • Treatment length
  • Supervision
  • FDA safety
  • Specs
  • Sources
  • Where to get it
Six Month Smiles
  • Prices
  • Treatment length
  • Supervision
Keep comparing

Every comparison with these brands

Each brand against every other brand on the market. All comparisons

All 20 comparisons with K Clear

  • vs Alineadent
  • vs Angel Aligner
  • vs Clarity Aligners
  • vs ClearCorrect
  • vs ClearPath
  • vs Dandy Clear Aligners
  • vs Glidewell Clear Aligners
InvisibleBraces is an informational data platform, not a dentist, an orthodontist, or a seller of aligners. Nothing here is dental or medical advice, a diagnosis, or a recommendation to start, stop, or change any treatment. At-home clear aligners are not right for every case, and moving teeth without an in-person exam carries real risk. Data is aggregated from public sources and each brand's own terms and can be incomplete or out of date. Always consult a licensed dentist or orthodontist and confirm current prices and terms with the provider.
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The independent, fully-cited comparison of at-home clear aligner brands. Every figure traces to its source. Informational only, not dental or medical advice.

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Typical treatment
Not published
6-10 months
Supervision
In-office
In-office
FDA safety
No recalls
No recalls
FDA adverse-event reports
0
0
Treatment
Treats
CrowdingSpacing and gapsBite correction (per the treating provider)
CrowdingSpacing and gapsCrossbiteOpen biteDeep biteRelapse after bracesMild to moderate misalignment
Product lines
K Clear aligners, ClearX
6MS Invisible Aligners, 6MS Relapse Aligners, 6MS Mixed Appliance
Wear schedule
20 to 22 hrs/day; each tray worn about 1 to 2 weeks (7 to 14 days), with the change interval set by the treating doctor
Trays changed every 2 weeks; wear hours not published
Spec sheet
Start method
In-office 3D digital scan (or impressions) taken by a dentist or orthodontist, who submits the case to K Line
Taken by the dentist in the practice: an intraoral scan (3Shape, iTero, Cerec or STL files accepted) or PVS impressions, with x-rays and photos; there is no at-home kit.
Material
K Flex, K Line's proprietary multi-layered thermoplastic (a soft inner layer between firmer outer layers); K Line's US material has also been described as a Zendura Flex multi-layer material
Zendura FLX, a dual-shell material (hard outer shell, elastomeric middle layer), 0.76 mm (0.030 in), per 6MS; the FDA summary describes a thermoformed polyurethane-polyester composite.
Retainers
Not published for patients (provider-dependent; K Line manufactures retainers on an OEM basis and inclusion is set by the practice)
Not included in the patient tray kit; the dentist orders removable retainers from 6MS after treatment and sets their price
Whitening
Not published (not a standard brand inclusion; any whitening is arranged by the treating provider)
Not published
Refinements / touch-ups
Manufacturer claims a best-in-class 15.8% refinement rate; refinement trays are handled through the treating provider
Up to 2 refinements within 2 years are included in the 6MS Invisible Aligners product (aligner page); a no-charge upgrade to a braces solution is offered to the dentist if braces would produce a better outcome.
Guarantee
Not published (no manufacturer patient money-back guarantee; any guarantee is set by the treating provider)
No patient guarantee in the current terms: a limited warranty to the dentist covers defects in material and workmanship, not the outcome
Clinical oversight
Direct in-office supervision by a licensed dentist or orthodontist throughout treatment; K Line states its treatment plans are designed by its in-house orthodontists and dentists rather than by AI software
In-office: a trained dentist examines, prescribes, fits and monitors; 6MS specialists prepare the plan, overseen by its orthodontists, and the dentist approves it
Financing
Not published (arranged by the treating provider)
Set by each practice
HSA / FSA
Generally HSA / FSA eligible in the US as qualifying orthodontic treatment, billed through the treating provider
The brand's cost page says HSA or FSA accounts can help offset the cost; acceptance is the practice's decision
Insurance
Not published (provider-billed; orthodontic coverage varies by plan)
Some dental plans may cover part of treatment (brand's cost page)
Availability
Made in Germany; sold through dentists, orthodontists, DSOs and aligner brands in 40+ countries, with US distribution from a Florida center since 2023
United States and United Kingdom through trained dentists (the company says its providers are in over 50 countries, without separating braces from aligners)
Headquarters
Duesseldorf, Germany
Carrollton, Texas, United States
Spec sources
  1. 1.dentalproductsreport.com
  2. 2.dentistrytoday.com
  3. 3.klinealigner.com
  1. 1.6monthsmiles.com
  2. 2.6monthsmiles.com
  3. 3.6monthsmiles.com
  4. 4.6monthsmiles.com
  5. 5.6monthsmiles.com
  6. 6.6monthsmiles.com
  7. 7.6monthsmiles.com
  8. 8.6monthsmiles.com
  9. 9.6monthsmiles.com
  10. 10.6monthsmiles.com
  11. 11.api.fda.gov
Company
On the market since
2022
2019
Parent company
K Line Europe GmbH (filed with the FDA as Kline Europe GmbH), Duesseldorf, Germany
Xplora USA LLC, doing business as Six Month Smiles, Carrollton, Texas, United States
  • FDA safety
  • Specs
  • Sources
  • Where to get it
  • vs Graphy
  • vs Invisalign
  • vs Modern Clear
  • vs Motto
  • vs Nuvola
  • vs Orthocaps
  • vs OrthoFX
  • vs OrthoSnap
  • vs Six Month Smiles (this page)
  • vs Smilers
  • vs Spark
  • vs SureSmile
  • vs uLab

    • All 22 comparisons with Six Month Smiles

    • vs 32Co
    • vs Alineadent
    • vs Angel Aligner
    • vs Clarity Aligners
    • vs ClearCorrect
    • vs ClearPath
    • vs Dandy Clear Aligners
    • vs Glidewell Clear Aligners
    • vs Graphy
    • vs Invisalign
    • vs K Clear (this page)
    • vs Motto
    • vs Nuvola
    • vs Orthocaps
    • vs OrthoFX
    • vs OrthoSnap
    • vs Smartee
    • vs Smilelign
    • vs Smilers
    • vs Spark
    • vs SureSmile
    • vs uLab