Aligner sheets (also known as thermoplastic sheets or foils) are the raw materials used to manufacture clear aligners and retainers. These sheets are vacuum-formed or pressure-formed over a 3D-printed model of a patient’s teeth to create the final orthodontic appliance.
Description
Aligner sheets are high-performance thermoplastic polymers, typically supplied as thin, circular or square transparent discs. The most common materials used are PETG (Polyethylene Terephthalate Glycol), TPU (Thermoplastic Polyurethane), or advanced multi-layer co-polyester blends.
Modern “multi-layer” sheets often feature a hard outer shell for durability and a soft inner core for consistent, gentle force delivery.
Key Features
- High Transparency: Engineered for maximum clarity to remain “invisible” when worn.
- Stress Relaxation Resistance: High-quality sheets maintain their shape and continue to exert force on the teeth over the 7–14 day wear cycle without becoming “loose.”
- Crack Resistance: Designed to withstand the constant stress of being clipped on and off the teeth without fracturing.
- Biocompatibility: Must be BPA-free, phthalate-free, and medically graded for long-term intraoral use.
- Moisture Stability: Low water absorption ensures the material doesn’t become cloudy or brittle over time.
Usage and Manufacturing Process
The transformation from a flat sheet to a functional aligner involves several technical steps:
| Step | Action |
| Model Prep | A 3D-printed resin model (representing a specific stage of tooth movement) is placed in a thermoforming machine. |
| Heating | The aligner sheet is heated to its specific glass transition temperature until it becomes pliable. |
| Forming | Using positive pressure (3-6 bar) or a vacuum, the sheet is forced over the 3D model to capture every detail of the tooth anatomy. |
| Cooling | The material is allowed to cool and harden in its new shape. |
| Finishing | The excess plastic is trimmed (manually or via CNC/Laser), and the edges are polished to ensure patient comfort. |
Comparison of Common Aligner Materials
| Material Type | Primary Characteristic | Common Use Case |
| PETG | Rigid and easy to form. | Retainers or simple tooth movements. |
| TPU / Blends | Highly flexible with high elasticity. | Complex orthodontic movements (active aligners). |
| Multi-layer | Combines stiffness and comfort. | Premium aligner brands (e.g., Zendura FLX). |
Thickness Specifications
Sheets come in various thicknesses depending on the clinical goal:
- 0.75mm / 0.030″: The industry standard for active orthodontic aligners.
- 1.0mm / 0.040″: Commonly used for final retainers (Essix style) or bruxism splints.
- 1.5mm – 2.0mm: Used for heavy-duty night guards or athletic mouthguards.