Non-Cochrane · intervention · PM42656921
From Polyethylene Terephthalate Glycol (PETG) to 3D-Printed Resins: A Systematic Review and Meta-Analysis of Clear Aligner Material Performance and Safety.
Altawil Fadi M, Abuzanoona Roba I · Cureus · 2026 · PubMed · doi:10.7759/cureus.113427
Findings
10 findings
| Population | ||||
|---|---|---|---|---|
| Orthodontic clear aligner materials | Mixed material and thickness comparisons | Other materials or thicknesses | Comparative flexural performance Laboratory testing | Hedges g 0.31 [-0.78, 1.40] GRADE not reported 3 studies |
| Orthodontic clear aligner materials | Clear aligner materials | None | Cytotoxicity classification Laboratory testing | Proportion (%) 21.4 [8.8, 43.5] GRADE not reported 2 studies |
| Orthodontic clear aligner materials | Clear aligner materials | None | Baseline modulus (MPa) Laboratory testing | MEAN 1895.10 [1658.69, 2131.50] GRADE not reported 3 studies |
| Orthodontic clear aligner materials | Clear aligner materials | None | Stress relaxation (%) Laboratory testing | MEAN 33.09 [21.39, 44.79] GRADE not reported 2 studies |
| Clear aligner materials (laboratory cytotoxicity testing) | Thermoplastic aligner materials (PETG, PET, PU) tested on human gingival cells | No comparator (single-group event rate) | Cytotoxicity event rate (logit) Not applicable · Laboratory (in vitro) | Logit event rate -1.30 [-2.34, -0.26] GRADE not reported 2 studies |
| Orthodontic clear aligner materials | Aged clear aligner materials | Before aging | Modulus change (MPa) Laboratory testing | MD -238.82 [-520.14, 42.49] GRADE not reported 2 studies |
| Orthodontic clear aligner materials | Aged clear aligner materials | Before aging or intraoral wear | Surface roughness change (μm) Laboratory testing | MD 0.15 [-0.08, 0.38] GRADE not reported 2 studies |
| Clear aligner materials (laboratory specimens) | PET, PETG and TPU aligner materials after 7 days in saliva or beverages | No comparator (single-group mean) | Force decay percentage after seven days 7 days · Laboratory (in vitro) | Mean (pooled) 33.14 [30.50, 35.78] GRADE not reported 1 study |
| Thermoformed Essix ACE aligners (laboratory) | Aging in deionized water or artificial saliva | Baseline before aging | Change in force (N) after aging After aging (14 days) · Laboratory (in vitro) | MD -0.03 [-0.28, 0.22] GRADE not reported 1 study |
| Clear aligner materials | Aligner materials (thermoformed and 3D-printed) | Other aligner materials | Tooth movement accuracy, retention force and patient comfort Not applicable · Laboratory (in vitro) | Direct clinical outcomes, such as tooth movement accuracy, retention force, and patient-reported comfort, were not reported in the included studies. No studies found 0 studies |
Included primary studies 45
Open in Studies| Study | Year | Also included by | Outcomes it informs here | Trial data |
|---|---|---|---|---|
| Daniele et al. (2020) Tricyclic antidepressants: therapeutic properties and affinity for alpha-noradrenergic receptor binding sites in the brain. PMID:202024 | 1978 | 3 other reviews | not stated | not extracted yet |
| Chen et al. (2025) Cell-mediated cytotoxicity: comparison of primary and secondary immune reactions after parainfluenza type 1 virus inoculation. PMID:202521 | 1978 | 2 other reviews | not stated | not extracted yet |
| Bhate 2024 Assessment of the Effect of Thermoforming Process and Simulated Aging on the Mechanical Properties of Clear Aligner Material. PMID:39156374 | 2024 | 1 other review | not stated | not extracted yet |
| Chen et al. (2023) Properties of three different forms of angiotensin I-converting enzyme from human lung. PMID:202323 | 1978 | 1 other review | not stated | not extracted yet |
| Cintora-Lopez 2023 In vitro analysis of the influence of the thermocycling and the applied force on orthodontic clear aligners DOI:10.3389/fbioe.2023.1321495 | 2023 | 1 other review | not stated | not extracted yet |
| Daniele 2020 Thermoplastic Disks Used for Commercial Orthodontic Aligners: Complete Physicochemical and Mechanical Characterization DOI:10.3390/ma13102386 | 2020 | 1 other review | Surface roughness change (μm) | not extracted yet |
| Elshazly et al. (2023) Redox potentials in hydro-organic media at normal and subzero temperatures. Ferro-ferricyanide and cytochrome c as models. PMID:202313 | 1978 | 1 other review | not stated | not extracted yet |
| Fang et al. (2013) [Microcirculatory changes following the combined action of the toxin of C1. perfringens type A and biological products of C1. butyricum]. PMID:201314 | 1977 | 1 other review | not stated | not extracted yet |
| Khalil and Zaher (2025) A biochemical study of the effects of cAMP pulses on aggregateless mutants of Dictyostelium discoideum. PMID:202529 | 1978 | 1 other review | not stated | not extracted yet |
| Lo et al. (2024) Pyrophosphate levels and magnesium oxide therapy in osteogenesis imperfecta. PMID:202425 | 1977 | 1 other review | not stated | not extracted yet |
| Puchert 2026 Influence of Water Storage on the Mechanical Properties of 3D-Printed Aligners: An In Vitro Study DOI:10.3390/bioengineering13010021 | 2025 | 1 other review | PM42656921-P7-O1 | not extracted yet |
| Xiang et al. (2021) matched by author and year (probable) | NR | 1 other review | not stated | not extracted yet |
| Bandic 2025 In Vitro Cytotoxicity Assessment of Different Thermoplastic Aligner Materials DOI:10.15644/asc59/2/2 | 2025 | this review only | not stated | not extracted yet |
| Bandić et al. (2025) matched by author and year (probable) | NR | this review only | not stated | not extracted yet |
| Bhate and Nagesh (2024) [Association of multicystic dysplasia of the kidney and nephroblastoma in a 3-year-old child]. PMID:202415 | 1977 | this review only | not stated | not extracted yet |
| Chen 2023 Force degradation study on aligner plates immersed in various solutions DOI:10.1016/j.jds.2023.06.017 | 2023 | this review only | Force decay percentage after seven days | not extracted yet |
| Chen 2025 Advances in clear aligner therapy: comparative evaluation of the optical properties and bacterial adhesion of 3D direct-printed and… DOI:10.1186/s40510-025-00600-3 | 2025 | this review only | not stated | not extracted yet |
| Choi 2025 Mechanical and viscoelastic properties of a temperature-responsive photocurable resin for 3D printed orthodontic clear aligners DOI:10.1038/s41598-025-93026-0 | 2025 | this review only | not stated | not extracted yet |
| Choi et al. (2025) Secretion of plasminogen activator by Sertoli cell enriched cultures. PMID:202528 | 1977 | this review only | not stated | not extracted yet |
| Cintora-López et al. (2023) Subunit structure of Achromobacter collagenase. PMID:202322 | 1978 | this review only | not stated | not extracted yet |
| Cui 2025 Effects of simulated intraoral temperatures and wet environments on the stress relaxation properties of thermoplastic aligner materials DOI:10.1186/s13005-025-00497-7 | 2025 | this review only | not stated | not extracted yet |
| Cui et al. (2025) [Local temperature characteristics of the isolated cortex in wakefulness and alteration of the sleep stages]. PMID:202512 | 1977 | this review only | not stated | not extracted yet |
| Dalaie 2021 Dynamic mechanical and thermal properties of clear aligners after thermoforming and aging DOI:10.1186/s40510-021-00362-8 | 2021 | this review only | PM42656921-P7-O1 | not extracted yet |
| Dalaie et al. (2021) A mixed outbreak of epidemic keratoconjunctivitis due to adenoviruses types 29 and 8. PMID:202111 | 1977 | this review only | not stated | not extracted yet |
| Das 2026 Cytotoxicity evaluation of different clear aligner systems on human primary gingival fibroblasts: an in vitro study DOI:10.2340/biid.v13.46006 | 2026 | this review only | Cytotoxicity event rate (logit) | not extracted yet |
| Das et al. (2026) Effects of d-amphetamine and strychnine on cycloheximide- and diethyldithiocarbamate-induced amnesia in mice. PMID:202616 | 1977 | this review only | not stated | not extracted yet |
| Divakar 2026 matched by author and year (probable) | NR | this review only | not stated | not extracted yet |
| Divakar et al. (2026) Interaction of polymorphonuclear neutrophils with Escherichia coli. Effect of enterotoxin on phagocytosis, killing, chemotaxis, and cyclic… PMID:202610 | 1978 | this review only | not stated | not extracted yet |
| Elshazly 2023 Effect of thermomechanical aging of orthodontic aligners on force and torque generation: An in vitro study DOI:10.1016/j.jmbbm.2023.105911 | 2023 | this review only | Change in force (N) after aging | not extracted yet |
| Fang 2013 Dynamic stress relaxation of orthodontic thermoplastic materials in a simulated oral environment DOI:10.4012/dmj.2013-131 | 2013 | this review only | PM42656921-P8-O1 | not extracted yet |
| Khalil 2025 Effect of printing orientation and resin thickness on flexural strength of direct 3D-printed aligners DOI:10.1186/s12903-025-05556-8 | 2025 | this review only | Comparative flexural performance | not extracted yet |
| Kwok 2022 matched by author and year (probable) | NR | this review only | Surface roughness change (μm) | not extracted yet |
| Lo 2024 The cytotoxicity assessment of different clear aligner materials DOI:10.1016/j.jds.2024.05.025 | 2024 | this review only | not stated | not extracted yet |
| Orilisi 2026 Can wear time, material composition, and manufacturing processes affect microplastic release from clear orthodontic aligners? A… PMID:41877679 | 2026 | this review only | not stated | not extracted yet |
| Orilisi et al. (2026) Coronary bypass surgery in chronic stable coronary artery disease. PMID:202627 | 1978 | this review only | not stated | not extracted yet |
| Pendse 2025 matched by author and year (probable) | NR | this review only | Cytotoxicity event rate (logit) | not extracted yet |
| Pendse et al. (2025) [Regulation of hormone receptor (author's transl)]. PMID:202517 | 1977 | this review only | not stated | not extracted yet |
| Puchert et al. (2026) Method for extraction, isolation, and detection of free polybrominated biphenyls (PBBs) from plasma, feces, milk, and bile using… PMID:202619 | 1978 | this review only | not stated | not extracted yet |
| Simunovic 2023 Differential Stability of One-layer and Three-layer Orthodontic Aligner Blends under Thermocycling: Implications for Clinical Durability DOI:10.15644/asc57/4/1 | 2023 | this review only | not stated | not extracted yet |
| Šimunović et al. (2023) Evidence for the non-identity of proteins having synthase phosphatase, phosphorylase phosphatase and histone phosphatase activity in rat… PMID:202320 | 1978 | this review only | not stated | not extracted yet |
| Wendl 2026 Analysis of orthodontic aligner biocompatibility: leachable compounds of different aligner materials DOI:10.1515/bmt-2025-0131 | 2025 | this review only | not stated | not extracted yet |
| Wendl et al. (2026) Chest film showing hilar enlargement and miliary infiltrates. PMID:202626 | 1978 | this review only | not stated | not extracted yet |
| Xiang 2021 The force effects of two types of polyethylene terephthalate glyc-olmodified clear aligners immersed in artificial saliva DOI:10.1038/s41598-021-89425-8 | 2021 | this review only | not stated | not extracted yet |
| Zecca 2025 Comparative microscopic analysis of plastic dispersion from 3D-printed and thermoformed orthodontic aligners DOI:10.1093/ejo/cjaf014 | 2025 | this review only | not stated | not extracted yet |
| Zecca et al. (2025) [Receptor diseases (author's transl)]. PMID:202518 | 1977 | this review only | not stated | not extracted yet |
Overlap with other reviews
Reviews that include the same primary studies are not independent evidence. Shared counts match studies by PMID, DOI or NCT, and otherwise by author and year (a probable match). Only the non-Cochrane dental reviews have study lists, so overlap with Cochrane reviews is not counted yet.
Review question
| Element | Planned (methods) | Found (results) |
|---|---|---|
| Population | Orthodontic clear aligner materials (laboratory, ex vivo and clinical studies) | Clear aligner materials; 22 in vitro studies and 1 prospective clinical/laboratory study (n=23) |
| Intervention | PETG, TPU, PU, EVA, PP, PC, PP/PE, PVC derivatives, copolyesters, multilayer polymers, 3D-printed aligner resins | PETG, TPU, PU, copolyester, multilayer, PP/PE-based materials and direct 3D-printed resins (n=23) |
| Comparison | Other aligner materials; pre vs post thermoforming; pre vs post aging; different immersion or loading environments; controls | Other aligner materials, pre vs post thermoforming and aging, different media (n=23) |
| Outcomes | Elastic modulus, flexural and tensile strength, stress relaxation, force decay, hardness, surface roughness, thickness change, optical change, cell viability, BPA and chemical release, microplastic release, retention force, tooth movement accuracy, comfort | Mechanical properties, aging behavior, cytotoxicity, chemical release, microplastic release and surface roughness; no direct clinical outcomes |
| Study designs | In vitro, ex vivo, in vivo, clinical, observational, comparative and experimental studies; English, full text, 2000 onward | 22 in vitro studies; 1 prospective clinical/laboratory study (n=23) |
| Timing | Not specified | Not specified |
AMSTAR 2 items
Two independent extractors rated each item. Their ratings are shown side by side because they have not been reconciled yet. The overall rating follows Shea et al. 2017: one critical flaw gives Low, more than one gives Critically Low.
| Item | Extractor A | Extractor B | Agree |
|---|---|---|---|
| 1Research question includes PICO components | Yes | Yes | yes |
| 2Protocol established before the reviewcritical | No | No | yes |
| 3Choice of study designs explained | No | No | yes |
| 4Comprehensive literature searchcritical | Partial Yes | Partial Yes | yes |
| 5Study selection in duplicate | Yes | Yes | yes |
| 6Data extraction in duplicate | Yes | Yes | yes |
| 7List of excluded studies with reasonscritical | No | No | yes |
| 8Included studies described in detail | Partial Yes | Yes | no |
| 9Risk of bias assessed satisfactorilycritical | RCT: N/A · NRSI: Partial Yes | RCT: N/A · NRSI: Yes | no |
| 10Funding of included studies reported | No | No | yes |
| 11Appropriate meta-analysis methodscritical | RCT: N/A · NRSI: No | NRSI: No · RCT: N/A | no |
| 12Impact of risk of bias on the pooled results | No | No | yes |
| 13Risk of bias accounted for in interpretationcritical | Yes | Yes | yes |
| 14Heterogeneity explained | Yes | Yes | yes |
| 15Publication bias investigatedcritical | No | No | yes |
| 16Conflicts of interest reported | Yes | Yes | yes |
| Overall | Critically Low | Critically Low | yes |