3D-printed aligners are revolutionizing orthodontic treatment with significantly better accuracy than traditional methods. We've found that direct-printed aligners show greater trueness and precision compared to thermoformed options, with root mean square values of 0.140 mm versus 0.209 mm for conventional aligners.
Lower means better, but what makes this difference so important? When discrepancies exceed 0.25 mm, research shows it can lead to a lack of clinically appreciable tooth movement. In fact, inaccuracies in thermoformed aligners could reduce movement accuracy by up to 57% in some planned orthodontic movements. Direct printed aligners, meanwhile, maintain mean absolute discrepancies between 0.079 mm and 0.224 mm – well within the clinical effectiveness range.
3D-printed aligners offer additional advantages beyond just precision. They're produced directly from digital scans, significantly reducing production time and potentially enabling same-day treatment.
Additionally, the manufacturing process produces minimal waste compared to traditional thermoforming, making it a more sustainable option. The materials used in direct-printed aligners are also engineered for consistent performance, ensuring uniform thickness and strength throughout the aligner, and often offering polymer shape memory effects.
In this guide, we'll examine both manufacturing processes, measure dimensional accuracy, identify potential sources of error, and explore the clinical implications of each method. By the end, you'll understand why 3D printing technology might represent the future of orthodontic treatment.
The manufacturing processes behind clear aligners follow distinctly different workflows, each with unique advantages and limitations. Understanding these differences helps explain why the final products perform differently in clinical settings.
The conventional clear aligner manufacturing process follows a multi-step approach. First, practitioners acquire digital impressions through intraoral scanning or by digitizing physical impressions. Subsequently, tooth positions are manipulated virtually before the critical production phase begins. This traditional workflow requires printing physical 3D models for each treatment stage, followed by thermoforming plastic sheets over these models.
The thermoforming process itself involves several labor-intensive steps: printing the resin model, washing and UV curing the model, heating a thermoplastic sheet, pressure-forming it over the model, and finally hand-trimming past the gingival margins [1]. The entire process takes around 2 hours or even more [2].
A key limitation is the unpredictable changes in physical properties that occur during thermoforming. Research shows sheet thickness of 0.75mm before processing varies between 0.38-0.69 mm in the final aligner, with a 10% reduction in thickness potentially reducing forces by up to 30% [3]. This inconsistency creates challenges for treatment predictability.
In contrast, direct 3D printing eliminates intermediate steps by printing aligners directly from digital designs. This streamlined workflow utilizes digital light processing (DLP) printers with photopolymerizable resins specifically engineered for clear aligner treatments.
The process is markedly more efficient: printing the aligner (30-60 minutes), centrifugation to remove excess resin (6 minutes), UV light exposure in a nitrogen chamber (20 minutes), and a brief heating in boiling water to activate shape memory properties (60 seconds) [2]. The total manufacturing time ranges from 60-90 minutes—approximately 30-50% faster than thermoforming [2].
Furthermore, direct printing offers unprecedented design flexibility. Unlike thermoformed aligners that require blocking out undercuts, direct-printed aligners can maintain precise thickness control throughout the appliance [2]. Most notably, aligners are printed at a 45-degree angle to optimize dimensional accuracy, transparency and material properties [4].
Material selection fundamentally influences aligner performance. Thermoformed aligners typically use polyethylene terephthalate glycol (PETG) or polyurethane sheets due to their transparency and durability [5]. However, the thermoforming process itself alters material properties, affecting transparency, surface hardness, water absorption, and elastic modulus [3].
Conversely, 3D-printed aligners utilize specialized photopolymerizable resins that have received FDA (and MDR) approval specifically for direct printing of aligners [3]. These materials maintain uniform thickness (typically around 0.5mm) and exhibit valuable shape-memory properties that enhance tooth movement precision [2].
Nevertheless, some 3D printing resins still face challenges regarding surface roughness and color stability compared to thermoplastic materials [6]. Ongoing material science advancements continue to address these limitations.
Accurate measurement of aligner fit reveals critical differences between manufacturing methods. Comprehensive evaluation requires standardized techniques that quantify discrepancies between designed and produced appliances.
Researchers evaluate aligner accuracy through STL superimposition, where digital models of the aligner's intaglio surface are precisely aligned with reference dental arch models using best-fit algorithms [1]. This technique measures linear distances between corresponding mesh points at anatomically significant landmarks. Most studies employ three bilateral landmark categories: incisal/occlusal points (mid-incisal edges, central grooves), mid-crown landmarks (functional axis points, palatal surface midpoints), and gingival margin references (zenith points, highest palatal-gingival points) [1].
The superimposition process typically utilizes specialized metrology software like Geomagic Control X, which calculates point-to-point distances between meshes after alignment [7]. For clinical validity, landmark-based registration is often enhanced with surface-based methods utilizing iterative closest point (ICP) algorithms [8].
Trueness—how closely aligners match the intended design—is quantified through Root Mean Square (RMS) values, where measurements closer to zero indicate superior fit [1]. Direct-printed aligners consistently demonstrate superior trueness (0.140 ± 0.020 mm) compared to thermoformed aligners made with Zendura FLX™ (0.188 ± 0.074 mm) and Essix ACE™ (0.209 ±0.094 mm) [9].
Precision measures manufacturing consistency across multiple productions. Standard deviations for thermoformed aligners range from 0.057 mm to 0.422 mm, while direct-printed aligners show remarkably tighter ranges (0.033-0.055 mm) [1]. This substantial difference indicates direct printing delivers significantly more predictable results.
Intraclass correlation coefficients (ICC) confirm these findings, with values ranging from 0.802 to 1.000 across measurement points, indicating excellent reproducibility [1]. Operator measurement reliability is similarly high, with ICC values consistently above 0.90 in most studies [12].
Discrepancy patterns vary significantly across tooth regions. For direct-printed aligners, the lowest mean absolute discrepancy occurs at premolar groove landmarks (0.072 ± 0.035 mm), where as thermoformed aligners show minimum discrepancies at central incisor gingival zenith points (0.076 ± 0.057 mm) [1].
Conversely, maximum discrepancies for thermoformed aligners often occur at buccal pit landmarks (0.457 ± 0.350 mm for Essix ACE™), significantly exceeding those of direct-printed aligners at the same points [1]. Most notably, thermoformed aligners exhibit larger discrepancies at molar landmarks and mid-crown level points, particularly affecting orthodontic movement predictability in posterior regions [1].
Additionally, the American Board of Orthodontics considers discrepancies exceeding 0.5 mm in linear measurements or 2° in angular measurements clinically relevant—thresholds direct-printed aligners more consistently achieve [13].
Both manufacturing methods introduce unique sources of error that affect the final aligner accuracy, albeit in fundamentally different ways.
The thermoforming process inherently creates substantial thickness variations throughout the aligner. Essentially, the material undergoes extreme thinning—approximately 60-75% reduction at gingival and middle areas versus only 20% at incisal edges [14]. This inconsistent thickness directly affects force delivery and mechanical properties.
Moreover, material properties change drastically during heating. Studies indicate thermoforming alters transparency, increases water absorption, and modifies surface hardness [15]. The temperature and duration of heating creates unpredictable variations, as under heating specifically hinders dimensional accuracy [1].
The multi-step process compounds errors from model printing through to final trimming. Regardless of careful standardization, each additional production step introduces potential inaccuracies that propagate through the workflow [1].
Pirect-printed aligners face different challenges, primarily related to material behavior. Volumetric shrinkage remains a significant concern, with commercial resins exhibiting 9.19-11.2% shrinkage compared to 7.28% in newer experimental formulations [16]. This shrinkage occurs because monomer molecules transform into polymers with decreased free volume [2].
Another critical issue involves light overexposure during printing. The DLP printing process can cure transparent materials beyond intended dimensions, resulting in aligners approximately 12% thicker than designed [17]. This overbuilding prevents full seating on teeth [17].
Post-processing further affects accuracy. Primarily, residual resin remaining after mechanical removal gets polymerized during post-curing, contributing to dimensional inaccuracies [17]. Time and temperature during post-curing significantly impact the final mechanical properties [15].
Measurement techniques themselves introduce errors. The translucent nature of aligners necessitates contrast spray application, adding material thickness between 0.01899-0.0803 mm to the aligner's intaglio surface [1]. This unquantified layer affects all measurements.
Scanner technology introduces additional variables. Scatter commonly reduces accuracy when scanning reflective surfaces [18], while cumulative errors occur during alignment and stitching of images [18]. Different scanner technologies (laboratory scanners versus intraoral scanners) produce inconsistent results even when measuring identical objects [19].
Understanding these error sources helps clinicians interpret dimensional discrepancies and better predict actual clinical performance of both aligner types.
Despite impressive laboratory measurements, the real-world effectiveness of clear aligners in clinical practice presents amore nuanced picture. The accuracy of movements with aligners ranges on average from 55% to 72% [20], with certain movements proving particularly challenging. Canine rotation, for instance, achieves less than 36% accuracy [20], while the rotation of teeth with round-shaped crowns shows a ratio of approximately 0.4° per 1° prescribed [13].
Throughout their clinical use, aligners undergo significant degradation. Indeed, the intraoral environment subjects materials to temperature fluctuations, humidity, salivary enzymes, and elastic deformation [21]. Although the chemical composition remains largely unchanged, mechanical properties deteriorate through intraoral aging [20]. This deterioration leads to rapid force decay—aligners exhibit fast and important drops in force delivery due to stress-relaxation properties [20]. Consequently, more than half of aligner cases require refinements, corrections, or fixed appliances [20].
The degradation varies by material composition. Primarily, polyurethane-based aligners (like Zendura FLX) demonstrated better resilience when soaked in beverages compared to PETG and PET materials [22]. Furthermore, the engagement with attachments creates additional wear patterns, with studies showing abrasion-induced defects such as scratches, marginal cracks, and fractures appearing on attachment surfaces [3].
For 3D-printed aligners, clinical data remains limited. Given that the oral cavity differs significantly from other body cavities—combining chemical substances with mechanical forces—the materials face unique challenges [4]. Therefore, extensive testing before widespread clinical adoption remains essential [23]. Early comparative studies indicate that direct-printed aligners deliver more consistent vertical forces (0.73-1.69 N) than thermoformed alternatives (4.60-15.30 N) [23], potentially enabling more predictable tooth movement.
As a result, understanding these limitations helps clinicians predict treatment outcomes more accurately and establish realistic expectations for patients considering either manufacturing method.
The field of aligner therapy stands at a crossroads, with direct-printed aligners showing promising validation. Looking ahead, several key areas demand focused research attention.
Shape memory polymers (SMPs) represent a game-changing advancement for aligner therapy. These materials can alter their macroscopic shape upon exposure to stimuli like temperature changes [26], potentially requiring fewer aligners per treatment. Today, thermoresponsive aligners can reduce the number of needed steps by almost 50% [27]. Alongside material innovations, AI applications in clear aligner therapy are rapidly expanding [28]. AI technologies excel particularly in tooth segmentation (accuracy 0.89-0.98) and treatment outcome predictions [29]. Most importantly, AI-driven segmentation dramatically reduces processing time—from over 400 seconds with conventional software to under 7 seconds with AI solutions [29].
The environmental advantages of direct printing are substantial:
· Elimination of physical models, reducing plastic waste [27]
· Shorter supply chains with significantly reduced lead times [30]
· Lower transportation-related carbon footprint through in-house production [27]
From a workflow perspective, direct printing enables same-day aligner delivery, enabling immediate treatment initiation [31]. Additionally, the model-free manufacturing process proves more cost-effective [26] while enabling variable thickness designs that optimize force application for specific tooth movements [30].
The comparison between 3D printed and thermoformed aligners reveals a significant technological advancement in orthodontic treatment.
Direct‑3D‑printed aligners achieve an RMS of 0.140 mm vs. 0.209 mm for thermoformed, providing tighter, more predictable fits.
With a precision range of just 0.033–0.055 mm (vs. 0.057–0.422 mm), 3D‑printed aligners ensure more accurate tooth movement control.
The complete process—from design to finished aligner—takes just 60–90 minutes, cutting production time by about 50% compared to thermoforming.
3D printing eliminates the need for models, reducing material waste and supporting eco‑friendly production practices
Thanks to uniform thickness and stable mechanical (shape‑memory) properties, direct‑printed aligners deliver more consistent orthodontic forces.
Fewer production steps mean less risk of cumulative errors—versus multiple steps and manual trimming in thermoforming.
Shape‑memory resins and AI‑based design enhancements position 3D‑printed aligners as the next-generation solution in orthodontics.
Undoubtedly, 3D printed aligners represent a significant step forward in orthodontic technology.
At Sweeth, we’ve translated this technological leap into real-world efficiency. Our direct 3D printing approach is designed for dental clinics and labs seeking speed, precision, and full control—whether through our On-Demand Solution, which functions like a lab to deliver same-day aligners, or our All-In-One Solution, which brings clear aligner production fully in-house.
With Sweeth:
From scan to smile, Sweeth empowers professionals to deliver faster, smarter, and more sustainable orthodontic care.
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[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC9314211/
[2] https://www.mdpi.com/2073-4360/17/5/610
[3] https://academic.oup.com/ejo/article/46/4/cjae026/7694307
[4] https://www.sciencedirect.com/science/article/abs/pii/S1073874622000809
[5] https://pmc.ncbi.nlm.nih.gov/articles/PMC9588987/
[6] https://www.sciencedirect.com/science/article/pii/S0889540624002452
[7] https://www.sciencedirect.com/science/article/pii/S030057122400109X
[8] https://www.nature.com/articles/s41598-023-31339-8
[9] https://pubmed.ncbi.nlm.nih.gov/35466087/
[10] https://bmcoralhealth.biomedcentral.com/articles/10.1186/s12903-023-03025-8
[11] https://pmc.ncbi.nlm.nih.gov/articles/PMC10239183/
[12] https://e-kjo.org/journal/view.html?uid=2121&vmd=Full
[13] https://progressinorthodontics.springeropen.com/articles/10.1186/s40510-022-00453-0
[14] https://www.sciencedirect.com/science/article/pii/S0300571222003323
[15] https://pmc.ncbi.nlm.nih.gov/articles/PMC8038630/
[16] https://www.sciencedirect.com/science/article/abs/pii/S0300571222000148
[17] https://www.nature.com/articles/s41598-022-09831-4
[18] https://dimensionsofdentalhygiene.com/strategies-to-minimize-scatter-and-movement-artifacts/
[19] https://e-kjo.org/journal/view.html?volume=52&number=4&spage=249
[20] https://pmc.ncbi.nlm.nih.gov/articles/PMC9000684/
[21] https://pmc.ncbi.nlm.nih.gov/articles/PMC10282513/
[22] https://www.sciencedirect.com/science/article/pii/S1991790223001927
[23] https://journals.lww.com/joos/fulltext/2024/11250/the_new_additive_era_of_orthodontics__3d_printed.55.aspx
[24] https://pubmed.ncbi.nlm.nih.gov/37243819/
[25] https://www.quintessence-publishing.com/usa/en/article/4763243/journal-of-aligner-orthodontics/2023/04/impact-of-buccopalatal-translation-and-trimline-design-on-clear-aligners-an-in-vitro-study-of-the-maxillary-right-central-incisor
[26] https://www.mdpi.com/2076-3417/14/22/10084
[27] https://www.orthodontic-update.co.uk/content/orthodontics/the-ecological-impact-of-resin-printed-models-in-clear-aligner-treatment/
[28] https://www.sciencedirect.com/science/article/pii/S0300571225000107
[29] https://www.drbicuspid.com/dental-specialties/orthodontics/invisible-aligners/article/15712249/ai-applications-on-the-rise-in-clear-aligner-therapy
[30] https://www.frontiersin.org/journals/dental-medicine/articles/10.3389/fdmed.2022.1089627/full
[31] https://learn.voxeldental.com/blog/traditional-clear-aligners-vs.-direct-print-aligners-the-next-frontier-in-ortho
June 26, 2025
Jens Linard
Industry Insights
3D-printed aligners are revolutionizing orthodontic treatment with significantly better accuracy than traditional methods.
Our all-in-one dental system for cosmetic dentistry enables professionals to design and print customized dental appliances in-house.
