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
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
Cleft lip and palate
Chronic medical conditions
Broken teeth or bubbles on study model at site of measurement.
Parallel
3D printed retainer
Device3D-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
DeviceHawley 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) .
Retention of the maxillary expansion
1. 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. 2. 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. 3. Intraclass correlation coefficient (ICC) will be done within and between researchers one week after the T0.
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.
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.
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National University of Malaysia
Lead sponsor
University of Malaya
Collaborator
Universiti Teknologi Mara
Collaborator
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