Comparison of Single-Layer and Triple-Layer TPU MaxFlex Aligners After Intraoral Use (TPU-ALIGN)

Effects of Intraoral Aging on Mechanical Properties and Surface Morphology of Single-Layer Versus Triple-Layer Thermoplastic Polyurethane (TPU) MaxFlex Aligner Sheets: A Randomized Controlled Trial

This study aims to compare two types of clear orthodontic aligner materials used in dental treatment: single-layer and triple-layer thermoplastic polyurethane (TPU) aligners (MaxFlex). Clear aligners are commonly used to straighten teeth and are preferred for their comfort and aesthetic appearance.

Participants will be provided with aligners and instructed to wear them for approximately 22 hours per day for 10 days. The aligners will be collected before use and after the 10-day period. The study will evaluate how the oral environment affects the properties of these materials over time.

Laboratory tests will be conducted to measure mechanical properties such as strength, flexibility, and deformation, as well as to examine surface changes under a microscope. The results of this study may help improve the performance and durability of aligners and contribute to better orthodontic treatment outcomes.

Study Overview

• Status: Completed
• Conditions: Malocclusion; Orthodontic Treatment; Clear Aligner Therapy
• Intervention / Treatment: Device: Single-Layer Thermoplastic Polyurethane Aligner; Device: Triple-Layer Thermoplastic Polyurethane Aligner

Detailed Description

Clear aligner therapy (CAT) has become an increasingly popular alternative to fixed orthodontic appliances due to its aesthetic advantages, improved patient comfort, and ease of oral hygiene maintenance. Thermoplastic materials, particularly thermoplastic polyurethane (TPU), are widely used in the fabrication of aligners due to their favorable mechanical and elastic properties.

Recent advancements in aligner materials have led to the development of multilayer TPU systems designed to enhance flexibility, force delivery, and clinical performance. Triple-layer TPU aligners typically consist of a soft inner layer for patient comfort, a rigid intermediate layer for structural strength, and a flexible outer layer to improve adaptability and fit. In contrast, single-layer TPU aligners are composed of a homogeneous material and are generally more cost-effective.

Despite these developments, limited evidence exists regarding the comparative behavior of single-layer and multilayer TPU materials following intraoral exposure. The oral environment, characterized by temperature fluctuations, moisture, masticatory forces, and enzymatic activity, may contribute to material degradation, potentially affecting aligner performance.

This randomized controlled trial is designed to evaluate the effects of intraoral aging on the mechanical properties and surface morphology of single-layer and triple-layer TPU aligners (MaxFlex). Participants will be randomly assigned to receive one type of aligner material and will be instructed to wear the aligners for a standardized duration of 10 days (minimum 22 hours per day).

Aligners will be collected at baseline (prior to intraoral use) and after the 10-day wear period. Following retrieval, samples will undergo standardized cleaning procedures before laboratory analysis.

Mechanical testing will be performed using dynamic mechanical analysis to assess tensile properties, stress relaxation behavior, and creep characteristics. Surface morphology will be evaluated using scanning electron microscopy to identify features such as roughness, cracks, and voids. Additionally, Fourier transform infrared spectroscopy will be used to detect potential chemical changes in the material composition.

The primary objective of this study is to compare the mechanical performance of single-layer and triple-layer TPU aligners before and after intraoral use. Secondary outcomes include evaluation of surface morphology and chemical structure changes associated with intraoral aging.

The findings of this study are expected to provide insight into the durability and clinical performance of different aligner materials, which may help guide material selection and improve orthodontic treatment outcomes.

• Study Type: Interventional
• Enrollment (Actual): 66
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Pakistan
  • Punjab Province
    • Lahore, Punjab Province, Pakistan
      • Akhtar Saeed Medical & Dental College

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Patients aged 18-30 years Fully erupted permanent dentition Good periodontal health Patients undergoing orthodontic treatment with clear aligners Mild crowding or spacing requiring labiolingual tooth movement Willingness to wear aligners for at least 22 hours per day Provision of informed consent

Exclusion Criteria:

Use of aligners from manufacturers other than study-specific TPU aligners Damaged or fractured aligners Poor compliance (wear time less than 22 hours/day) Presence of parafunctional habits (e.g., bruxism) Hypodontia or partially erupted dentition Cases involving bonded attachments on maxillary incisors Cases requiring rotational movement of maxillary incisors Patients with systemic or oral conditions affecting saliva composition or the oral environment

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Single-Layer TPU Aligner Group; Participants in this group will receive single-layer thermoplastic polyurethane (TPU) MaxFlex aligners. The aligners will be worn intraorally for 10 days for a minimum of 22 hours per day under standardized conditions. Aligners will be collected at baseline and after the wear period for evaluation of mechanical properties and surface morphology.	Device: Single-Layer Thermoplastic Polyurethane Aligner; Single-layer thermoplastic polyurethane (TPU) clear aligners fabricated from a homogeneous TPU sheet using thermoforming techniques. These aligners are designed to deliver orthodontic forces for tooth movement. Participants will be instructed to wear the aligners intraorally for 10 days for a minimum of 22 hours per day. The aligners will be evaluated before use and after intraoral exposure to assess changes in mechanical properties and surface morphology.
Experimental: Triple-Layer TPU Aligner Group; Participants in this group will receive triple-layer thermoplastic polyurethane (TPU) MaxFlex aligners consisting of a soft inner layer, a rigid intermediate layer, and a flexible outer layer. The aligners will be worn intraorally for 10 days for a minimum of 22 hours per day. Aligners will be collected at baseline and after use for mechanical and surface analysis.	Device: Triple-Layer Thermoplastic Polyurethane Aligner; Triple-layer thermoplastic polyurethane (TPU) clear aligners composed of a multilayer structure including a soft inner layer, a rigid intermediate layer, and a flexible outer layer. These aligners are fabricated using thermoforming techniques and are designed to provide improved force delivery and adaptability. Participants will wear the aligners intraorally for 10 days for at least 22 hours per day. Pre- and post-use evaluations will be conducted to assess mechanical properties and surface morphology changes.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effect of Oral Environment on Elastic Modulus of TPU Aligners	This outcome measures the change in elastic modulus (MPa) of thermoplastic polyurethane (TPU) orthodontic aligners following intraoral exposure. Measurements are obtained using a dynamic mechanical analyzer and compared between single-layer and multilayer TPU aligners at baseline and after two weeks of clinical use to assess changes in stiffness and material integrity.	Baseline (0 week) and after 2 weeks of intraoral use (minimum 22 hours/day)
Effect of Oral Environment on Stress Relaxation of TPU Aligners	This outcome measures the percentage stress relaxation (%) of TPU aligners following intraoral exposure. Stress decay over time is recorded using a dynamic mechanical analyzer and compared between single-layer and multilayer TPU aligners at baseline and after two weeks to evaluate force retention capacity.	Time Frame: Baseline (0 week) and after 2 weeks of intraoral use (minimum 22 hours/day)
Effect of Oral Environment on Creep Behavior of TPU Aligners	This outcome measures creep (% strain) in TPU aligners under constant stress conditions using a dynamic mechanical analyzer. Comparisons are made between single-layer and multilayer TPU aligners at baseline and after two weeks to assess susceptibility to permanent deformation.	Time Frame: Baseline (0 week) and after 2 weeks of intraoral use (minimum 22 hours/day)

Collaborators and Investigators

• Sponsor: Ayub Medical College, Abbottabad

Study record dates

Study Major Dates

• Study Start (Actual): September 13, 2025
• Primary Completion (Actual): March 5, 2026
• Study Completion (Actual): March 16, 2026

Study Registration Dates

• First Submitted: April 19, 2026
• First Submitted That Met QC Criteria: April 27, 2026
• First Posted (Actual): May 5, 2026

Study Record Updates

• Last Update Posted (Actual): May 5, 2026
• Last Update Submitted That Met QC Criteria: April 27, 2026
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: Clear Aligners; Scanning Electron Microscopy (SEM); Thermoplastic Polyurethane (TPU); MaxFlex Aligners; Intraoral Aging
• Additional Relevant MeSH Terms: Stomatognathic Diseases; Tooth Diseases; Malocclusion
• Other Study ID Numbers: TPU-ALIGNER-01; no identifier (Other Identifier: Akhtar Saeed Medical & Dental College)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No