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.