Novel Dietary Guidelines for Elderly Denture-wearers to Ensure Adequate Nutritional Intake, Good Quality of Life and Enhanced Performance on Cognitive Tasks

This clinical trial evaluates the effectiveness of a multidimensional nutritional intervention on the functional, physiological, and cognitive health of older adults wearing complete removable dentures. The study employs a convergent parallel mixed-methods design to integrate quantitative with qualitative outcomes.

1. Methodological Evaluation Protocols

Participants will undergo comprehensive clinical and laboratory assessments:

• Masticatory Function and Muscle Health: Chewing kinematics will be evaluated using 3D electromagnetic articulography (3D-EMA). Maximum bite force will be measured with a digital gnatodynamometer. Masticatory performance will be determined through a standardized peanut-sieving method. Additionally, masseter and temporalis muscle thickness will be assessed via ultrasonography.
• Salivary Biomarkers: Saliva samples will be collected to quantify markers of physiological stress and muscle health: Cortisol, Insulin-like Growth Factor 1 (IGF-1), and Creatine Kinase (CK). Oxidative stress and antioxidant capacity will be analyzed using ROS, DPPH, and ORAC parameters.
• Baseline Sociodemographic Characteristics: Sociodemographic characteristics will be collected at baseline using a structured questionnaire. The questionnaire will include information on age, sex, educational level, marital status, occupation or employment status, income level, and other relevant background variables.
• Nutritional Status Assessment: Nutritional status will be monitored monthly through anthropometric measurements and body composition assessment. These include weight, height, body mass index (BMI), waist circumference, and body fat percentage determined by bioelectrical impedance analysis (BIA).
• Cognitive Performance and Cerebral Blood Flow: Cognitive tasks will be evaluated using the Addenbrooke's Cognitive Examination-Revised (ACE-R) and a digital Stroop test to measure attention and executive function. Additionally, transcranial Doppler ultrasonography will be used to monitor cerebral blood flow.
• Qualitative Dimension: Individual semi-structured interviews based on Grounded Theory will explore participants' life experiences regarding tooth loss, denture adaptation, and psychosocial barriers before and after the intervention.

2. Intervention Logistics and Groups

The 40 participants will be randomly allocated into two balanced groups (20 participants per arm):

• Intervention Group: Participants will receive a 6-month educational nutritional intervention. This will include in-person nutritional counseling before starting the intervention, and again during the 3rd and 6th months. In addition, telephone nutritional counseling will be provided during the 4th and 5th months. All counseling sessions will be delivered by a trained nutritionist. During the first nutritional counseling session, participants will receive a dietary guideline booklet for users of removable dentures. This guide was developed based on the results of the first stage of the project and promotes foods that support chewing function, as well as adherence to a Chilean-adapted Mediterranean diet. The guideline will also include healthy recipes. During the 2nd month of the study, participants will be invited to attend a practical workshop led by a nutritionist and a chef, where they will prepare recipes included in the dietary guide. All participants in the intervention group will receive a monthly food box containing non-perishable components of the diet. This intervention is complemented by a custom-developed mobile application tailored to meet the study's requirements. Through this app, participants can access the full nutritional guide in PDF format, view new educational and instructional videos uploaded biweekly, and receive automated push notifications as reminders to enhance usability and compliance.
• Control Group: Participants will maintain their usual diet for 6 months and undergo the same follow-up assessments as the intervention group. To ensure ethical equity, at the end of the intervention, all participants in the control group will receive one food box, the dietary guideline for users of removable dentures, access to the mobile application, and will be invited to attend a practical workshop led by a nutritionist and a chef.