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NCT Number: NCT07659041

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

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Key information

Age range

16 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

National University Of Malaysia, Kuala Lumpur, Malaysia

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About this study

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.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

3D printed retainer

Device

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

Hawley retainer

Device

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) .

Primary outcomes

  1. Retention of the maxillary expansion

    Time frame: 12 months

    • 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.

Secondary outcomes

  1. Patient acceptance

    Time frame: 12 months

    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.

  2. cost estimation

    Time frame: 6 months

    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.

Study contacts

Contact information is provided by the study sponsor or research team.

ALIZAE MARNY FADZLIN SYED MOHAMED

CONTACT

[email protected]

+6038921 5555

Asma Ashari, BDS Adel, MClinDent Lon, MOrth

CONTACT

[email protected]

+603 8921 5555

Sponsors and collaborators

Lead sponsor

National University of Malaysia

Other

Collaborators

  • Universiti Teknologi Mara
  • University of Malaya

Registry information

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Jun 22, 2026
Registry last updated
Jun 22, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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