The International Journal of Prosthodontics 730 CLINICAL RESEARCH *Equal contributions as senior author. Correspondence to: Dr Frauke Müller Division of Gerodontology and Removable Prosthodontics 1, Rue Michel-Servet, 1211 Geneva-4, Switzerland Fax: +41 22 3794052 Email: frauke.mueller@unige.ch Submitted June 2, 2020; accepted September 22, 2020. ©2022 by Quintessence Publishing Co Inc. Purpose: To evaluate the effects of overnight storage conditions on the dimensional stability and retention of prostheses, as well as participants’ subjective perceptions of these interventions. Materials and Methods: Subjects with maxillary complete prostheses (CRPs) were randomly assigned to receive two interventions in a crossover design: storage of their CRPs overnight in a dry environment or in a wet environment with a cleansing tablet. The denture intaglio surface was scanned, and outcome measures were collected before each intervention (BLN), postintervention (PIS), and after immersion in water for 15 minutes (WOC) following each intervention. Dimensional changes were analyzed for the total surface, anterior fange, palate, and tuberosities. Retention force was measured using a dynamometer, and the participants’ subjective assessments of comfort, ft, and retention of their CRPs were collected. After verifying normal distribution, paired t and Wilcoxon signed rank tests were used to check for statistical signifcance (α = .05). Results: Ten participants (mean age: 76.5 ± 5.9 years) were recruited. Between BLN and PIS, the dimensional changes after dry intervention were signifcantly less than the wet intervention for the total surface (P = .009), anterior fange (P = .028), and palate (P = .005). No difference was found between the effects of storage or washout interventions on objectively measured CRP retention. However, after WOC following dry storage, participants perceived a lower retention (P = .021), and after WOC following wet storage, participants perceived a more comfortable palate (P = .018). Conclusion: For dimensional stability, dry overnight storage of removable prostheses can be safely recommended when indicated. Immersion in water for 15 minutes does not seem to add advantages. Int J Prosthodont 2022;35:730–737. doi: 10.11607/ijp.7158 Effects of Overnight Storage Conditions on Conventional Complete Removable Prostheses Yasmine Bouattour, Med Dent, MAS Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland. Nicole Kalberer, Med Dent, MAS Najla Chebib, Dr Med Dent, MS Philippe Mojon, Dr Med Dent Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland. Albert Mehl, Prof Dr Med Dent Habil Division of Computerized Restorative Dentistry, Clinic of Conservative and Preventive Dentistry, Center of Dental Medicine, University of Zürich, Zürich, Switzerland. Murali Srinivasan, Prof Dr Med Dent, BDS, MDS, MAS* Clinic of General Special Care and Geriatric Dentistry, Center of Dental Medicine, University of Zürich, Zürich, Switzerland. Frauke Müller, Prof Dr Med Dent Habil* Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland. P oor oral and denture hygiene have been advocated as precursors of aspiration pneumonia and mortality. 1–4 Hence, it has been frequently advised not to wear complete removable prostheses (CRPs) during sleep. The issue then arises as to whether to store CRPs in a dry or wet environment during the night. Storing CRPs dry helps avoid microbial growth and Candida colonization. 5 However, in order to avoid warpage, it is recommended that CRPs be stored under wet conditions while not in use, and preferably with an added denture cleanser. 6 Still, a consensus has not yet been achieved for the storage conditions of dentures while not in use. 7 The acrylic resin polymethyl methacrylate (PMMA) is a material that has been com- monly used as a denture base since the 1930s due to its low cost, easy and simple manipulation, and favorable esthetics, as well as its appropriate mechanical and © 2023 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART M AY BE REPRODUCED OR TRANSM ITTED IN ANY FORM WITHOUT WRITTEN PERM ISSION FROM THE PUBLISHER.