Years of material science for one outcome: a retainer your body can break down.
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Ensuring our retainer has no contaminants.
Verifying our retainer's strength and stability.
Why we trust PHA when we distrust everything else.
PHA is a polymer that bacteria produce as an energy reserve. It occurs throughout nature, and the body already has the enzymes to break it down into 3-hydroxybutyric acid, a compound your body makes and uses for energy. We do not want a material that persists in your body for years.
This is also why we do not call PHA inert. Inertness is the conventional-plastic problem: a material the body cannot process, so its particles persist. PHA is the opposite, it degrades along a biological pathway because biology recognizes it.
How it is made
Our material is produced through biological fermentation. The result is a high-performance polymer engineered for durability while remaining compatible with biological systems.
- 1Feedstock. Renewable biological substrate.
- 2Fermentation. Microbial polymerization under controlled conditions.
- 3Extraction. Isolation and purification of the polymer chains.
- 4Characterization. Molecular weight, purity, and property verification.
- 5Medical grade. Ultra-high-purity standards, validated by third-party labs.
No additives
Our retainer is PHA, and nothing else. No plasticizers, colorants, UV stabilizers, or processing aids. Every ingredient in the final product is listed in the published composition.
The literature
PHA has a decades-long record across chemistry, medicine, and environmental science.
Müller & Seebach, 1993. Poly(hydroxyalkanoates): A Fifth Class of Physiologically Important Organic Biopolymers? Angewandte Chemie International Edition, 32(4), 477. Recognized PHA as a distinct class of biopolymers more than 30 years ago, the intellectual starting point for the field. Read the study.
Sudesh, Abe & Doi, 2000. Synthesis, Structure and Properties of Polyhydroxyalkanoates: Biological Polyesters. Progress in Polymer Science, 25(10), 1503. The canonical characterization of PHA as biological polyesters, the long-standing materials baseline. Read the study.
Lenz & Marchessault, 2005. Bacterial Polyesters: Biosynthesis, Biodegradable Plastics and Biotechnology. Biomacromolecules, 6(1), 1. Frames PHA alongside nucleic acids and proteins as a natural polymer family. Read the study.
Chen, 2009. A Microbial Polyhydroxyalkanoates (PHA) Based Bio- and Materials Industry. Chemical Society Reviews, 38(8), 2434. Documents an organized PHA value chain by 2009, a mature field with industry behind it. Read the study.
Suriyamongkol et al., 2007. Biotechnological Approaches for the Production of Polyhydroxyalkanoates in Microorganisms and Plants. Biotechnology Advances, 25(2), 148. Reviews roughly two decades of production research across microbes and plants. Read the study.
Taguchi, Iwata, Abe & Doi, 2012. Poly(hydroxyalkanoate)s. In Polymer Science: A Comprehensive Reference, Vol. 9, 157. PHA has its own chapter in a major polymer-science reference work. Read the study.
Laycock et al., 2013. The Chemomechanical Properties of Microbial Polyhydroxyalkanoates. Progress in Polymer Science, 38(3-4), 536. A definitive chemo-mechanical property dataset, thoroughly characterized rather than speculative. Read the study.
Wu, Wang & Chen, 2009. Medical Application of Microbial Biopolyesters Polyhydroxyalkanoates. Artificial Cells, Blood Substitutes, and Biotechnology, 37(1), 1. Surveys PHA across medical devices, tissue repair, and drug delivery. Read the study.
Brigham & Sinskey, 2012. Applications of Polyhydroxyalkanoates in the Medical Industry. International Journal of Biotechnology for Wellness Industries, 1(1), 53. Covers PHA sutures, implants, scaffolds, and drug release, including the FDA-cleared PHA polymer P4HB. Read the study.
Koller, 2018. Biodegradable and Biocompatible Polyhydroxyalkanoates (PHA): Auspicious Microbial Macromolecules for Pharmaceutical and Therapeutic Applications. Molecules, 23(2), 362. A broad review of in-vivo use and biocompatibility, reporting no carcinogenicity across decades of testing. Read the study.
Elmowafy et al., 2019. Polyhydroxyalkanoate (PHA): Applications in Drug Delivery and Tissue Engineering. Expert Review of Medical Devices, 16(6), 467. A recent review showing PHA research in drug delivery and tissue engineering is active and ongoing. Read the study.
Qu et al., 2006. In Vivo Studies of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Based Polymers: Biodegradation and Tissue Reactions. Biomaterials, 27(19), 3540. In-vivo data showing PHA implants biodegrade in living tissue, with the degradation rate tunable by composition. Read the study.
Yang et al., 2004. Studies on Bone Marrow Stromal Cells Affinity of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). Biomaterials, 25(7-8), 1365. Shows PHA supports cell attachment and growth and is broken down biologically rather than staying bioinert. Read the study.
Derippe et al., 2024. Marine Biodegradation of Tailor-Made Polyhydroxyalkanoates (PHA) Influenced by the Chemical Structure and Associated Bacterial Communities. Journal of Hazardous Materials, 462, 132782. A primary marine study showing PHA biodegrades in seawater, with the rate driven by its chemical structure. Read the study.
Tepha, Inc., 2007. FDA Clearance for the First Medical Device Derived from a New Class of Biopolymers. Medical Device Online. The first FDA-cleared device made from a PHA, commercialized as TephaFLEX. PHA is an approved, marketed medical material. Read the announcement.
Does it work as a retainer, and does it last?
Material properties
The fundamental question behind any retainer is whether it can apply and maintain enough force to prevent relapse. We benchmarked our PHA against PETG, the most common clear-retainer material, on the properties that actually govern that.
Flexural modulus (stiffness)
13% stiffer
Unplastic (PHA)
3.07 GPa
PETG
2.72 GPa
Flexural strength
~80% of PETG; both far exceed any load a retainer sees in wear
Unplastic (PHA)
77.3 MPa
PETG
96.2 MPa
Creep at 37°C
maintains its shape over time
Unplastic (PHA)
0.007% strain
PETG
0.025% strain
Stress relaxation, 24 h
47% higher force retention
Unplastic (PHA)
4.7 MPa
PETG
3.2 MPa
| Property | Unplastic (PHA) | PETG |
|---|---|---|
| Flexural modulus (stiffness)13% stiffer | 3.07 GPa | 2.72 GPa |
| Flexural strength~80% of PETG; both far exceed any load a retainer sees in wear | 77.3 MPa | 96.2 MPa |
| Creep at 37°Cmaintains its shape over time | 0.007% strain | 0.025% strain |
| Stress relaxation, 24 h47% higher force retention | 4.7 MPa | 3.2 MPa |
Independent mechanical testing against a conventional PETG retainer material: flexural per ASTM D790 (3-point bend, n = 3, by Covalent), creep under a 1.0 N load over 60 minutes at 37°C, and stress relaxation reported as retained stress after 24 hours.
Stress relaxation over 24 hours
Retained extensional stress under a fixed strain. Higher means the material keeps applying force for longer. Unplastic held about 4.7 MPa vs. about 3.2 MPa for PETG at 24 hours.
What this means for your retainer.
PHA and PETG are close across the board. Our material matches or beats the established standard on everything that drives how a retainer performs.
- A higher flexural modulus means more of the force goes into holding your teeth in place instead of flexing away. Our PHA tested 13% stiffer than PETG (3.07 GPa vs. 2.72 GPa).
- In creep testing at body temperature, our PHA deformed about 70% less than PETG under the same load, an early indicator of better shape retention.
- In stress-relaxation testing, our PHA maintained about 47% more retentive force after 24 hours than PETG (4.7 MPa vs. 3.2 MPa). Sustained force is what keeps teeth from drifting.
- We tested the material against common staining agents including coffee, tea, red wine, orange juice, energy drinks, and soft drinks. While good oral hygiene is always recommended, the material was built to hold up to everyday use.
Lifespan
Each retainer is built for a six-month wear cycle. PHA is a new material system, so we set that replacement window conservatively on data we can stand behind today rather than a number we hope holds.
So far it holds up. After 28 cleaning cycles, a full month of peroxide tablets, ultrasonic, and UV, the material showed no meaningful change in strength, stiffness, or elongation, and a month of aggressive biofilm exposure left its mechanical properties intact.
Longer claims need longer data, and we are still gathering it. We are tracking dimensional stability out to a full six-month cleaning schedule to learn whether our retainer safely lasts beyond six months, and we will publish the results.
What this retainer sheds during wear, and what happens to it.
Microplastic generation and fate
Every retainer sheds particles under normal wear. The question is what happens to them after they leave the device.
Generation
Using a chewing simulator, we characterize the particles produced under realistic wear: size distribution, count, and morphology, compared against conventional materials.
Fate
We follow those particles two ways: a model of human digestion, and an anaerobic biodegradation test that measures whether live microbes can metabolize the material. These studies are underway, and we will publish the results once they are complete.
Peer-reviewed work on microplastic shedding from orthodontic devices and its biological effects.
Warunek et al., 2026. Orthodontic-derived microplastics impact macrophage differentiation and homeostasis. Progress in Orthodontics, 27:3. Read the study.
Quinzi et al., 2023. A spectroscopic study on orthodontic aligners: first evidence of secondary microplastic detachment after seven days of artificial saliva exposure. Science of the Total Environment, 866:161356. Read the study.
Shariff et al., 2025. Microplastics and nanoplastics in clinical dentistry and orthodontics: leaching, health implications, and future directions. Progress in Orthodontics, 26(1):49. Read the study.
Contamination testing
Independent labs validate our contamination and safety testing, and we publish the reports.
Contamination panel
Paranoid, so you don’t have to be
We test every batch, and we publish the results.
Every research arm runs through independent, accredited labs. We test every batch we make for contaminants and publish the results, so you can look up the exact data for the product in your hand. The law sets a low bar, so we set our own. You should not have to think about any of this. That is our job.
Concerned about a specific contaminant? Let us know at hello@unplastic.com.
Third Party Verified by
Ensuring our retainer has no contaminants.
Verifying our retainer's strength and stability.
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