Effectiveness, Patient Acceptance, and Cost Estimation of 3D-printed Retainer Compared to Hawley Retainer in Expansion Case: a Randomized Controlled Trial

Expansion of the arches is generally considered highly unstable and prone to relapse regardless of the type of expansion. Retention appliances play a vital role in preserving these changes. Hawley retainer users often avoid wearing them due to speech difficulties and less aesthetic appeal. They are also more prone to breakage, costlier, and require more labour. Despite the relatively recent introduction of 3D-printed retainers, they offer potential advantages in orthodontics, including the accuracy of digitally scanned images, reduced labour and material costs, and improved patient comfort. While 3D-printed retainers are quite new, most studies focus on laboratory testing of their mechanical properties, there is limited evidence directly comparing their effectiveness in retaining arch width increases, patient acceptance, and cost estimation. This knowledge gap creates uncertainty about the optimal choice of retainer for long-term stability, necessitating a comparative assessment of their performance. This study addresses this knowledge gap by evaluating the retention of arch width increases achieved using Hawley retainers versus 3D-printed retainers

Study Overview

• Status: Not yet recruiting
• Conditions: Orthodontic Relapse; Retention in Orthodontic
• Intervention / Treatment: Device: Hawley retainer; Device: 3D printed retainer

Detailed Description

Maxillary dentoalveolar expansion is a procedure to correct transverse discrepancies between the maxillary and mandibular arches by applying forces to widen the maxillary arch. This procedure is inherently unstable and is susceptible to relapse. While Hawley retainers (HR) have served as the established standard for retention after maxillary expansion, recent studies have shown that modified thermoforming retainers can be as effective as HR. The emergence of computer-aided design and computer-aided manufacturing (CAD-CAM) and three-dimensional (3D) printing technology has significantly streamlined fabricating appliances and prostheses. 3D printing material is more rigid, with superior compression and tensile strength. Thus, a normal shape 3D-printed retainer may be a viable choice for the retention of maxillary expansion. A recent systematic review highlighted a critical gap in knowledge regarding the long-term clinical efficacy and durability of 3D-printed retainers. Thus, the present study aimed to address this research gap by investigating the long-term clinical effectiveness, patient acceptance, and cost estimation of 3D-printed retainers in expansion cases. This study will be carried out as a multicentre prospective randomized controlled clinical trial (RCT) conducted at Universiti Kebangsaan Malaysia (UKM), Universiti Malaya (UM), and Universiti Teknologi MARA (UiTM). Orthodontic patients who fulfil the inclusion criteria will be randomly allocated into the HR or 3D-printed retainer groups. Dental casts of patients will be measured at intercanine width (ICW), inter-premolar width (IPMW), inter-first molar mesiobuccal cusp width 1 (IFMW1), and inter-first molar distobuccal cusp width 2 (IFMW2) for both groups at debond(T0), 3(T1), 6(T2), and 12(T3). The outcome assessor and data analyst will be blinded to the retention method. The researcher will evaluate the patient's acceptance at T2 & T3 and conduct a cost analysis at T1 post-debond. The findings of this study will contribute valuable data to the field of orthodontics, aiding clinicians in determining the most effective long-term retention strategy for patients who have undergone maxillary dentoalveolar expansion.

• Study Type: Interventional
• Enrollment (Estimated): 28
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Asma Ashari, BDS Adel, MClinDent Lon, MOrth; Phone Number: +603 8921 5555; Email: asmaashari@ukm.edu.my
• Study Contact Backup: Name: ALIZAE MARNY FADZLIN SYED MOHAMED; Phone Number: +6038921 5555; Email: alizaemarny@ukm.edu.my

Study Locations

• Malaysia
  • Kuala Lumpur
    • Kuala Lumpur, Kuala Lumpur, Malaysia, 50300
      • National University Of Malaysia
      • Contact: Fakulti pergigian UKM; Phone Number: +6039289 7741; Email: asmaashari@ukm.edu.my
      • Principal Investigator: Mei Ling Cheng
    • Kuala Lumpur, Kuala Lumpur, Malaysia, 50603
      • University Malaya
      • Contact: May Nak Lau; Phone Number: +60379674802; Email: minalau@um.edu.my
      • Sub-Investigator: Zhang Yi Tan
  • Selangor
    • Sungai Buloh, Selangor, Malaysia, 47000
      • University Teknologi Mara Selangor branch
      • Contact: Nik Mukhriz Nik Mustapha; Phone Number: +6036126 6103; Email: nikmukhriz@uitm.edu.my
      • Sub-Investigator: Siti Nor Hafizah Salehun

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Patients aged 16 years or older at the time of debonding
• Treatment plan of extraction or non-extraction followed by straight wire appliances in the upper arch only or both arches
• Undergone expansion treatment in the upper arch causing an arch width increase of 3-10mm, either using a Quadhelix, expansion with archwires, or URA with midline screw
• Had pretreatment dental cast
• Had no chronic medical condition.

Exclusion Criteria:

• Cleft lip and palate
• Chronic medical conditions
• Broken teeth or bubbles on study model at site of measurement.

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
Active Comparator: Hawley retainer; A screening will be done to select suitable patients for the study. Only patients who fulfil the criteria will be invited to participate in this study. Following informed consent, eligible subjects will be randomly allocated into one of two groups wither hawley retainer or 3D printed retainer. Fabrication of Hawley retainers will be done using a standardized design across all centres.	Device: Hawley retainer; Hawley retainers have served as the established standard for retention after maxillary expansion. Standard design of Hawley Retainer: - Labial bow (0.8mm hard stainless steel) from canine to canine - Adam clasp on the molar (0.7mm hard stainless steel) - acrylic baseplate (2-3mm thickness) .
Experimental: 3D printed retainer; A screening will be done to select suitable patients for the study. Only patients who fulfil the criteria will be invited to participate in this study. Following informed consent, eligible subjects will be randomly allocated into one of two groups wither hawley retainer or 3D printed retainer. Fabrication of 3d printed retainers will be done using a standardized design at one main centres by one technician using Nextdent Orhtoflex Resin.	Device: 3D printed retainer; 3D-printed retainer Using Nextdent Orthoflex resin Standard design of 3D printed retainer: Monolithic design (no wires); Thickness 0.8mm-1.0 mm; Fully cover the teeth and part of the gingiva (1-2mm); Undercut block - 0.25-0.5mm

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Retention of the maxillary expansion	Subjects will be scheduled for follow-up at T1-T3 after the initiation of retention wear. During these visits, impressions will be acquired with alginate impression material, and ICW, IPMW, IFMW1, and IFMW2 will be measured intraorally and on dental casts.; Calibrated researchers will collect the study models, and the ID and intervention will be covered by opaque tape once they are ready for measurement. Only one dental cast at a time will be picked out of its box without showing any previous measurements. Two dental casts from the same patient will not be measured in connection. Due to the prospective nature of the study, it was inconvenient to anonymize dental casts from the start of the study.; Intraclass correlation coefficient (ICC) will be done within and between researchers one week after the T0.	12 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Patient acceptance	Subjects will be given and asked to complete a questionnaire on patient acceptance (see attachment) at 6 and 12 months post-debond. The Questionnaire has been validated and published by (Saw et al. 2025). It uses a Visual Analogue Scale (VAS) to ask six questions related to subject acceptance of orthodontic retainers in fitting, speech, appearance, oral hygiene, durability, and comfort. Refer to Attachment 1 (Malay version) and Attachment 2 (English Version) for the questionnaires.	12 months
cost estimation	To estimate and compare the costs associated with the implementation and provision of 3D-printed retainers between clinics with existing in-house 3D-printing facilities and clinics planning to acquire 3D-printing services. The analysis will include direct costs such as equipment acquisition, materials, software, maintenance, laboratory procedures, and staff chairside time.	6 months

Collaborators and Investigators

• Sponsor: National University of Malaysia
• Collaborators: University of Malaya; Universiti Teknologi Mara
• Investigators: Study Director: Asma Ashari, MClinDent Lon, National University Of Malaysia

Publications and helpful links

General Publications

• Hichens L, Rowland H, Williams A, Hollinghurst S, Ewings P, Clark S, Ireland A, Sandy J. Cost-effectiveness and patient satisfaction: Hawley and vacuum-formed retainers. Eur J Orthod. 2007 Aug;29(4):372-8. doi: 10.1093/ejo/cjm039.
• Naeem OA, Bencharit S, Yang IH, Stilianoudakis SC, Carrico C, Tufekci E. Comparison of 3-dimensional printing technologies on the precision, trueness, and accuracy of printed retainers. Am J Orthod Dentofacial Orthop. 2022 Apr;161(4):582-591. doi: 10.1016/j.ajodo.2021.03.016.
• Firlej M, Zaborowicz K, Zaborowicz M, Firlej E, Domagala I, Pieniak D, Igielska-Kalwat J, Dmowski A, Biedziak B. Mechanical Properties of 3D Printed Orthodontic Retainers. Int J Environ Res Public Health. 2022 May 9;19(9):5775. doi: 10.3390/ijerph19095775.
• Tsoukala E, Lyros I, Tsolakis AI, Maroulakos MP, Tsolakis IA. Direct 3D-Printed Orthodontic Retainers. A Systematic Review. Children (Basel). 2023 Apr 3;10(4):676. doi: 10.3390/children10040676.
• Saw ZK, Yuen JJX, Ashari A, Ibrahim Bahemia F, Low YX, Nik Mustapha NM, Lau MN. Forward-backward translation, content validity, face validity, construct validity, criterion validity, test-retest reliability, and internal consistency of a questionnaire on patient acceptance of orthodontic retainer. PLoS One. 2025 Jan 3;20(1):e0314853. doi: 10.1371/journal.pone.0314853. eCollection 2025.
• Nakornnoi T, Bunjerdjin P, Santiwong P, Sipiyaruk K, Neoh SP, Chintavalakorn R. The Influence of Thickness on the Mechanical Behaviors of 3D Printing Resins for Orthodontic Retainers. Int J Biomater. 2024 Jun 25;2024:7398478. doi: 10.1155/2024/7398478. eCollection 2024.
• Ashari A, Xian L, Syed Mohamed AMF, Wahab RMA, Kit YC, Tata MD, Sinnasamy S, Kuppusamy E. One-year comparative assessment of retention of arch width increases between modified vacuum-formed and Hawley retainers. Angle Orthod. 2022 Mar 1;92(2):197-203. doi: 10.2319/050921-363.1.
• Ashari A, Nik Mustapha NM, Yuen JJX, Saw ZK, Lau MN, Xian L, Syed Mohamed AMF, Megat Abdul Wahab R, Yeoh CK, Deva Tata M, Sinnasamy S. A two-year comparative assessment of retention of arch width increases between modified vacuum-formed and Hawley retainers: a multi-center randomized clinical trial. Prog Orthod. 2022 Aug 26;23(1):40. doi: 10.1186/s40510-022-00424-5.
• Stoev YY, Uzunov TT, Stoyanova NS, Grozdanova-Uzunova RG, Kosturkov DN, Taneva IK. Mechanical properties of materials for 3D printed orthodontic retainers. Folia Med (Plovdiv). 2023 Dec 31;65(6):986-992. doi: 10.3897/folmed.65.e107299.
• Neoh SP, Khantachawana A, Chintavalakorn R, Santiwong P, Srikhirin T. Comparison of physical, mechanical, and optical properties between thermoplastic materials and 3-dimensional printing resins for orthodontic clear retainers. Am J Orthod Dentofacial Orthop. 2025 Jan;167(1):95-109.e1. doi: 10.1016/j.ajodo.2024.06.010.

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): December 1, 2027
• Study Completion (Estimated): December 1, 2027

Study Registration Dates

• First Submitted: June 8, 2026
• First Submitted That Met QC Criteria: June 15, 2026
• First Posted (Actual): June 22, 2026

Study Record Updates

• Last Update Posted (Actual): June 22, 2026
• Last Update Submitted That Met QC Criteria: June 15, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: orthodontic; 3D printed retainer
• Other Study ID Numbers: JEP 2025-630 (Other Identifier: National university of Malaysia)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Only data relevant to the study analyses will be provided. All personal identifiers and information that could reveal participant identity will be removed to protect confidentiality and comply with ethical requirements.

Drug and device information, study documents

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