Here is the design of a clinical trial:

Official Title: Cognitive Changes and Neural Correlates After Rehabilitation of Masticatory Function in Older Adults - an Intervention Study

Included conditions:
- Chewing Problem
- Cognitive Decline
- Magnetic Resonance Imaging
- Degenerative; Dementia
- Mastication Disorder
- Neurocognitive Dysfunction

Study Armgroups:
- {'label': 'Experimental group (EG), the immediate rehabilitation group', 'type': 'EXPERIMENTAL', 'description': 'The experimental group will begin with the rehabilitation immediately after the first measurement of cognitive tests (pre-test). Three months after complete rehabilitation the first post-test (post-test 1) will be conducted on all participants. Participants will be recalled after about a year for a long-term follow up (post-test 2). The OHIP-14, chewing function test, saliva samples, neuropsychological assessments together with MRI assessments will also be recorded at different time points (i.e., pre-test, post-test 1 and post-test 2).', 'interventionNames': ['Procedure: Oral prosthetic rehabilitation']}
- {'label': 'Control group (CG), the test-retest group', 'type': 'ACTIVE_COMPARATOR', 'description': 'The control group will be tested with the cognitive tests two times (pre-test + post-test 1) at an interval of about three months or more inbetween tests and before the onset of the prosthodontic rehabilitation. Three months after complete rehabilitation the post-test (post-test 2) will be conducted on all participants. Further, participants will be recalled after about a year for a long-term follow up (post-test 3). The OHIP-14, chewing function test, saliva samples, neuropsychological assessments together with MRI assessments will also be recorded at these time points (i.e., pre-test, post-test 1, post-test 2 and post-test 3).', 'interventionNames': ['Procedure: Oral prosthetic rehabilitation']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Oral prosthetic rehabilitation', 'description': 'Individual treatment options will be discussed with the participants individually and rehabilitation will be provided as agreed by the dentist and the participant. The rehabilitation will include fixed prosthodontics. The procedures will involve a control phase involving scaling, root planing oral hygiene instructions etc., extractions and bone augmentation when needed and temporary removable dentures. Restoration of the lost vertical dimension (if needed) with occlusal splints, tooth preparations, placement of dental implants (if needed) and finally cementation of dental crowns. The rehabilitation phase is estimated to take approximately 3-18 months, or more.', 'armGroupLabels': ['Control group (CG), the test-retest group', 'Experimental group (EG), the immediate rehabilitation group']}

Primary Outcomes:
- {'measure': 'Change in Brief Visuospatial Memory Test Revised (BVMT-R)', 'description': 'Measuring non-verbal episodic memory. Measured in correct answers. Score: 0-36. A high score indicates a better performance.', 'timeFrame': '1: Baseline pre-test. 2: Change pre-test/post-test1, CG 3months after baseline, EG 3months after intervention (Int). 3: Change post-test1/post-test2, CG 3months after Int, EG 1year after Int. 4: Change post-test1/post-test2, CG 1year after Int.'}

Please estimate the sample size based on the assumption: 
Significance level (Î±) set to 0.05, power at 0.80, and a moderate dropout rate of 20-25%.
Sample size
        No studies are currently available that directly compare rehabilitation of chewing function with a control condition on neurocognitive measures. We, therefore, designed our RCT as a superiority trial with enough statistical power to detect a difference in outcome between treatments (if present) with a medium effect size (partial eta square, eta2). For the longitudinal analysis that assesses rehabilitation differences, we expect an effect size (partial eta square, eta2) on the NA of at least 0.06. With Î± set to 0.05 and power at 0.80, a sample of 30 participants in each group is required. The power calculation of the repeated measures analysis is estimated with within-participant factors, which also controls for the between-participant variance. However, due to the moderate rate of dropouts (20â25%) observed across different ongoing studies, optional non-participation of MRI screening, and technical difficulties (e.g., movement artifacts) during brain imaging, we estimate that inclusion of 40 participants in each group is required to meet the demands for statistical power. However, only the first 20 participants willing and eligible to participate in the MRI procedures in each group will undergo brain imaging due to practical and logistical reasons. The MRI acquisitions are optional since there are more contraindications medically and patients are more reluctant to participate. By making MRI optional participants can still be included in the study when MRI acquisitions are not feasible.