Most "material comparison" content online repeats manufacturer marketing copy. This one doesn't — every claim below is drawn from published, peer-reviewed dental research, cited by source.
The Materials at a Glance
| Material | Manufacturer | Composition | Key Finding |
|---|---|---|---|
| Essix C+ | Raintree Essix (Dentsply) | Polypropylene | Most flexible of the four tested |
| Vivera | Align Technology | Polyurethane | Stiffest of the four tested |
| Zendura | Bay Materials | Polyurethane | Multi-layer variants (FLX, Viva) show lower force than single-layer |
| Duran | SCHEU-Dental (Germany) | PETG copolymer | Single-layer; higher force values in force-distribution testing |
Material Profiles
Essix C+
The most flexible material among the four compared in the Queen Mary University study. Flexibility can be an advantage for patient comfort in retainer applications, though it's a different property from the force-delivery characteristics that matter most for active aligner treatment.
Vivera
The stiffest material in the same comparison. Vivera is Align's proprietary retainer material, used specifically for their retainer product line rather than being available as a general aligner sheet material to third-party manufacturers.
Zendura
Available in single-layer and multi-layer (FLX, Viva) variants. A 2024 force-distribution study found the multi-layer variants produced meaningfully lower active and passive force values than single-layer materials — consistent with the "gentler, sustained force" positioning multi-layer materials are marketed on.
Duran
A single-layer PETG material widely used in Europe for both aligners and splint therapy. In force-distribution testing, single-layer Duran showed higher force values than multi-layer alternatives — not necessarily worse, since higher force can suit cases needing more assertive movement, but a different clinical tool than a multi-layer material.
What the Force Research Actually Shows
A 2024 in vitro study measured active and passive force values across single- and multi-layer materials at matched thickness. The clearest finding: multi-layer materials (Zendura FLX, CA Pro, Zendura Viva) consistently produced lower force values than single-layer materials (Duran, single-layer Zendura), and thicker material produced measurably higher force and retention regardless of layer structure.
Choosing Between Them
- Need gentler, sustained force over a longer wear cycle? Multi-layer materials (Zendura FLX and similar) have research support here.
- Need more assertive force for a specific movement? Single-layer materials at greater thickness show higher force in testing.
- Prioritizing retainer comfort and flexibility? Essix C+ tested as the most flexible in direct comparison.
- Working in Europe or with SCHEU-Dental equipment? Duran is the regionally standard PETG option.
See Which Material AlignerHub Uses, and Why
AlignerHub selects between FDA 510(k)-cleared Essix and Zendura material on a case-by-case basis.
Read the Essix vs. Zendura Deep Dive