Dental Materials and Restorations

State of the evidence

The evidence establishes that resin-based dental materials consistently leach monomers (e.g., TEGDMA, HEMA) into the oral environment, particularly within the first 24 hours 1,6,7. There is a strong correlation between the degree of monomer conversion and the subsequent mechanical stability and biocompatibility of the material 3,5. Orthodontic aligners, whether thermoformed or 3D-printed, exhibit significant stress relaxation over time, which impacts their corrective force 2,9. While 3D printing offers a manufacturing alternative to vacuum thermoforming, it introduces specific challenges regarding the removal of uncured resin to ensure cell viability 4,10.

Key findings

• Resin-based materials leach cytotoxic monomers like TEGDMA and HEMA, which can cause mucosal irritation and tissue sensitization 1,6,7. 1 6 7
• The degree of monomer conversion (DC) directly influences the mechanical properties, water sorption, and solubility of dental composites 3,5. 3 5
• All analyzed thermoplastic aligner materials show significant stress relaxation within 24 hours of constant deflection 2,9. 2 9
• 3D-printed aligners using photocurable resins (e.g., TC-85) exhibit distinct thermo-mechanical and shape-memory properties compared to PET-G 4. 4
• Centrifugation and temperature control are critical for removing uncured resin from 3D-printed aligners to maintain biocompatibility and geometry 10. 10
• Hydrolysis of monomer and composite components is a primary mode of degradation in the oral cavity 3. 3

Where the evidence disagrees

• The effectiveness of different cleaning methods (IPA vs. centrifugation) for 3D-printed resins varies in terms of balancing resin removal with material transparency and geometry 10.
• There is a tension between the need for high-stiffness materials for tooth movement and the desire for low-load, bio-adaptive force profiles to increase patient comfort 2,9,Bio-Adaptive Force-Profile Aligners.

Open opportunities

What the research supports that no idea in the catalog takes yet.

• Post-Print Leaching Validation Kit

  P9 and P0 highlight that uncured resin and monomer leaching are critical biocompatibility risks; a rapid test kit for clinicians to verify the 'cleanliness' of a 3D-printed aligner before patient fitting is missing.

• Hydrolysis-Resistant Monomer Library

  P2 emphasizes that hydrolysis is a principal mode of degradation. While ideas focus on 'stability', there is no specific effort to replace hydrolytically unstable bonds in the monomer chemistry itself.

• Dynamic-Stress Aligner Material for Specific Tooth Rotations

  P1 and P8 show that stress relaxation is universal. A material engineered with a non-linear stress-relaxation curve specifically for rotational movements (which are harder to correct) could improve efficacy.

References

1. 1.Biocompatibility of Resin-Modified Filling MaterialsWerner Geurtsen · 2000 · 411 citations
2. 2.Stress relaxation properties of four orthodontic aligner materials: A 24-hour in vitro studyLuca Lombardo, Elisa Martines, Valentina Mazzanti et al. · 2016 · 211 citations
3. 3.Relation of Dental Composite Formulations To Their Degradation and the Release of Hydrolyzed Polymeric-Resin-Derived ProductsJ. Paul Santerre, Leylanaz Shajii, Beatrice W Leung · 2001 · 474 citations
4. 4.Thermo-mechanical properties of 3D printed photocurable shape memory resin for clear alignersSe Yeon Lee, Hoon Kim, Hyun‐Joong Kim et al. · 2022 · 155 citations
5. 5.Monomers used in resin composites: degree of conversion, mechanical properties and water sorption/solubilityV.E.S. Gajewski, Carmem S. Pfeifer, Nívea Regina Fróes-Salgado et al. · 2012 · 390 citations
6. 6.Biocompatibility of polymethylmethacrylate resins used in dentistryRupali Gautam, Raghuwar Dayal Singh, Vinod Sharma et al. · 2012 · 220 citations
7. 7.Identification of organic eluates from four polymer‐based dental filling materialsVibeke B. Michelsen, Henning Lygre, Rita Skålevik et al. · 2003 · 134 citations
8. 8.Principles of Polymer EngineeringN. G. McCrum, C. P. Buckley, Clive B. Bucknall · 2026 · 578 citations
9. 9.Stress Relaxation Properties of Five Orthodontic Aligner Materials: A 14-Day In-Vitro StudyPaolo Albertini, Valentina Mazzanti, Francesco Mollica et al. · 2022 · 38 citations
10. 10.Evaluation of the effects of temperature and centrifugation time on elimination of uncured resin from 3D-printed dental alignersJi-Eun Kim, Utkarsh Mangal, Jae-Hun Yu et al. · 2024 · 33 citations