3D-Printed vs. Thermoformed Aligners: How Do They Hold Up Over Time?

Understanding Clear Aligner Technology

Clear aligners have become a common choice for individuals looking to straighten their teeth without the visible metal wires of traditional braces. Traditionally, these aligners are manufactured using a process called “thermoforming.” In thermoforming, a thin plastic sheet is heated and pressed over a physical mold of a patient’s teeth. However, newer manufacturing methods now allow dental laboratories to “3D-print” aligners directly from liquid resin materials, skipping the physical mold step entirely.

As these two technologies exist side-by-side, researchers are studying how they compare in durability and how they perform over the typical lifetime of a single aligner tray. A recent laboratory study investigated the effects of a 30-day simulated wear period on both types of aligners to see how their physical thickness and the force they apply to teeth change over time.

How the Study Was Conducted

The researchers compared two specific types of aligners:

• 3D-printed aligners made from a material called Tera Harz TC-85 resin.
• Thermoformed aligners made from a material called Zendura FLX.

The study utilized 10 aligners of each type (a total of 20 aligners). To simulate the physical environment of a human mouth over a standard wear cycle, the researchers subjected the aligners to “thermomechanical ageing” for up to 30 days. This laboratory procedure exposes the dental plastics to repeating temperature changes and physical stresses to mimic real-world wear.

The researchers measured the physical forces transmitted by the aligners to a specific tooth—the maxillary right central incisor (a front tooth in the upper jaw, designated as Tooth 11)—using a resin model. Measurements were taken at multiple points: before the ageing process began (Day 0), and then after 2, 7, and 30 days of simulated wear.

To capture these forces accurately, the study used two distinct tools: Fuji pressure-sensitive films to measure “normal contact forces” (direct perpendicular pressure) and an orthodontic measurement and simulation system (OMSS) to record complex three-dimensional forces. They also measured how the thickness of the aligners changed using digital calipers and micro-computed tomography (micro-CT), which is a detailed, high-resolution 3D scanning technology.

Key Findings on Force and Thickness

The laboratory testing revealed several distinct differences between the two materials:

• Initial Force Levels: Before any wear occurred (Day 0), the 3D-printed aligners generated significantly higher initial contact forces compared to the thermoformed aligners. The 3D-printed aligners recorded a force of 149.7 ± 25.6 Newtons, while the thermoformed aligners recorded 69.8 ± 9.0 Newtons.
• Force Loss Over Time: Both materials showed a significant drop in force (referred to as force decay) as the 30-day ageing process progressed.
• Directional Forces: Before ageing, the overall combined forces (resultant forces) measured by the simulation system were highly comparable between both materials, ranging from 0.1 ± 0.07 Newtons to 0.5 ± 0.09 Newtons. The “facial forces” (the pressure pushing the tooth forward toward the lips) remained relatively stable over the 30-day period. However, the “lingual forces” (the pressure pushing the tooth backward toward the tongue) dropped significantly for both types.
• Thickness Changes: The manufacturing process and subsequent wear had opposite effects on the thickness of the two aligner types. The thermoformed aligners showed notable thinning, ending up at approximately 0.5 ± 0.05 millimeters. In contrast, the 3D-printed aligners showed thickening, measuring approximately 1.0 ± 0.09 millimeters. The researchers associated the higher initial forces of the 3D-printed aligners with this greater post-manufacturing thickness and their reported ability to adapt closely to the teeth.

Limitations of the Research

While these findings provide helpful details about how aligner materials behave, there are important limitations to consider. First, this was a laboratory study conducted on a physical resin model, not a clinical trial in living human patients. The study cannot replicate the complex biological environment of the human mouth, which includes saliva, temperature fluctuations from eating hot and cold foods, and the continuous microscopic movement of live teeth. Additionally, the study evaluated a small sample size of only 10 aligners per group and looked at the forces exerted on only one specific upper front tooth. Different teeth and different dental movements might yield different results.

What This Means for Patients

If you are considering clear aligners to correct your smile, this research highlights how different manufacturing methods—like traditional thermoforming and newer 3D printing—can affect the thickness and physical behavior of your aligner trays. 3D-printed trays may start out thicker and apply higher initial forces than thermoformed alternatives, but both types will naturally lose some of their pushing power over a standard 30-day wear cycle.

Because orthodontic needs are highly individual, there is no single option that is right for everyone. Your dentist or orthodontist will evaluate your specific teeth, discuss your lifestyle, and help you select the most appropriate material and treatment design to safely and effectively guide your teeth into their proper positions.