The purpose of this clinical trial is to test a nutritional intervention. This study helps older adults who wear complete removable dentures improve their health.

The main questions the study aims to answer are:

• What are the participants life experiences living with complete dentures before the intervention?
• Does the intervention improve the diet quality of the participants?
• Does the intervention improve nutritional status of the participants?
• Does the intervention improve chewing performance and muscle strength?
• Does the intervention increase the thickness of the masticatory muscles?
• Does the intervention improve stress and muscle health markers in saliva?
• Does the intervention improve cognitive performance and oral health-related quality of life?
• Does the intervention improve cerebral blood flow? The study will include a total of 40 participants, who will be assigned to two groups. One group of 20 participants will receive the nutritional intervention, while the other group of 20 participants will maintain their usual diet during the study period. This comparison will allow the investigators to assess the effectiveness of the intervention.

Participants will:

• Take part in a personal interview about their life experience with dentures.
• Follow a dietary guide with recommendations on specific food textures for six months.
• Receive personalized nutritional counseling and participate in healthy cooking workshops.
• Use a custom-built mobile application to access the educational content of the nutritional guide, view instructional videos uploaded biweekly, and receive automated reminder notifications.
• Attend clinical follow-up assessments, including chewing performance, muscle assessment, saliva markers, assessment of diet quality and nutritional status, cognitive tests, and oral health-related quality of life.
• Complete these assessments at three main time points: baseline, 3 months, and 6 months.

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.

Inclusion Criteria:

• Men and women aged 60 to 80 years.
• Systemically healthy individuals or those with controlled chronic systemic conditions under regular medical supervision.
• Functionally independent individuals, or those with a dedicated family member or caregiver available to provide support throughout the study period.
• Wearers of both maxillary and mandibular complete removable dentures.
• Adequate stability, retention, and functionality of both complete dentures allowing the participant to chew effectively during daily meals (accepting minor retention or stability limitations in the mandibular prosthesis, provided routine functional mastication is maintained).
• Acceptable centric occlusion and jaw relationship allowing functional mastication.
• Intact oral mucosa without active lesions or severe soreness in the denture-bearing areas.

Exclusion Criteria:

• Altered salivary flow (hyposalivation or xerostomia) identified via anamnesis and sialometry, with an unstimulated salivary flow rate < 0.1 mL/min or a stimulated salivary flow rate < 0.5 mL/min.
• Active oral mucosa diseases or lesions (e.g., cheilitis, denture stomatitis, ulcers, or aphthae) verified through intraoral examination.
• Diagnosis of a major neurocognitive disorder by a qualified professional, verified via medical records and/or caregiver interview.
• Color blindness (daltonism or color vision deficiency).
• Presence of signs or symptoms of temporomandibular disorders (TMD).
• Known history of allergy to peanuts or latex.
• Underweight or severe undernutrition, defined as a Body Mass Index (BMI) < 18.5 kg/m².

To protect participant privacy and maintain data confidentiality, individual participant data will not be shared publicly. Final study results will be disseminated through peer-reviewed publications and doctoral thesis presentations.