Plans for assessment and collection of outcomes

Following the provision of informed consent, all participants will receive a questionnaire. This questionnaire will be administered through a structured interview. The questionnaire consists of five sections. The first section addresses general participant information, including date of birth, gender, education, income, place of residence, living arrangements (alone or with others), and whether the participant receives assistance from a home care nurse. Part 2 assesses the participant's frailty utilizing the Groningen Frailty Indicator, a validated and multidimensional screening tool [23, 24]. The tool consists of 15 questions addressing physical, cognitive, social, and psychological domains. The score, ranging from 0 to 15, reflects increasing limitations, with a score of ≥ 4 serving as the threshold for identifying frailty. The third section inquires about the participant’s family physician and whether the participant has a regular dentist. The fourth section focuses on the dental history, oral status, current issues related to their mouth, teeth or dentures, and oral hygiene practices including the frequency of care and the tools utilized (toothpaste, electric toothbrush, tongue scraper, etc.). They will be asked whether they currently perceive a need for dental treatment and what the reasons behind this perception is. A xerostomia questionnaire is administered in the final Sect. (25).

Next, participants will be allocated to either an intervention or control group. The intervention will be executed as described in Sect. 11a. Four months after T0, the participants will be contacted by phone. Information on any communication on oral health with a dental professional since the intervention and the reasons for this interaction will be gathered. Furthermore, it will be determined whether the participant has discussed this study with their family physician. In addition, they will be asked once more about self-care practices concerning teeth or dentures, the frequency of care, and used brushing materials, as well as whether the participant has reviewed the oral hygiene flyers at home.

Study data will be collected and managed using REDCap electronic data capture tools hosted at Ghent University. REDCap (Research Electronic Data Capture) is a secure, web-based software platform designed to support data capture for research studies, providing (1) an intuitive interface for validated data capture; (2) audit trails for tracking data manipulation and export procedures; (3) automated export procedures for seamless data downloads to common statistical packages; and (4) procedures for data integration and interoperability with external sources [26, 27].

Several validated questionnaires and screening tools will be used. The Groningen Frailty Indicator will be used to determine the level of frailty. The feasibility, reliability, and validity of this tool have been confirmed in previous research [23, 24]. The Dutch version of the Summated Xerostomia Inventory will be used, this is a valid tool for measuring xerostomia symptoms in clinical and epidemiological research [25]. Dental plaque will be evaluated by the Quigley-Hein plaque index, denture plaque will be evaluated according to the method of Augsburger and Elahi, and tongue plaque will be assessed through the Winkel tongue coating index. These tools are widely used methods for measuring dental plaque in clinical research and dental practices [28,29,30]. To evaluate the severity of untreated dental caries, the PUFA index will be used. The reliability of this index has been proven [19]. The periodontal condition will be screened by using the Miller index for tooth mobility and the validated Dutch Periodontal Screening Index [20, 31].

The study was piloted to examine the duration and feasibility of the intervention, software usability and to iron out mistakes. Following a brief training and calibration sessions provided by ADV, the intraclass correlation coefficient was calculated for all data screeners for the oral examination. These coefficients ranged from 0.833 to 0.967, indicating a strong to almost perfect level of agreement [32].

Researchers will be guided by an integrated script on REDCap, questions will be displayed and reminders will pop up in case of missing data. This will be further reinforced by mandatory selection per section that all questions are completed. REDCap will automatically generate a calendar for the telephonic questionnaire at timepoint 1.

Plans to promote participant retention and complete follow-up

At the end of the intervention, participants will be reminded that they will receive a phone call (or e-mail if requested by the participant) four months later. Contact information of a partner or caregiver will also be registered in case the participant does not answer the telephone call. Four attempts will be made on two different days to contact the participant or caregiver: two calls in the morning and two calls in the afternoon. If the participant prefers to be contacted back by e-mail, one reminder will be sent one week after the first e-mail.

During the piloting phase, it was observed that recruiting participants during social activities and game afternoons is not advisable. This approach leads to early drop-out, as individuals prefer to participate in the ongoing activities rather than to commit to the study. Hence, it was decided to minimize the recruitment of participants during this type of event.

All participants will receive a pen with the logo of Gerodent PLUS (i.e., the name of the study project) as a gift. This pen might serve as an additional reminder about the upcoming phone call by the researchers.

Data management

The data will exclusively be entered electronically within the REDCap system. Data quality is ensured within the REDCap platform through an integrated script and multiple measures to guarantee data completeness. The extent of actions that each user can undertake is restricted by the rights associated with their respective accounts.

Data collection will end two weeks after the last planned telephone questionnaire. Upon completion of data collection, data will be exported out of the REDCap platform for subsequent analysis. These files will be securely stored on servers maintained by Ghent University, only accessible by the members of the research team. For data transference, a Secure File Transfer platform, namely Belnet Filesender will be used.

Confidentiality

Each participant will receive a unique identification number to pseudonymize the data. The corresponding key will be kept on a secured server of Ghent University, exclusively accessible by the members of the research team. The hard copy informed consent forms will be scanned for electronic storage separately from the study participants’ records. Both collected data and informed consent forms will be kept for 10 years, as stipulated in the informed consent form. Following the publication of the research findings, raw pseudonymized data can be made available upon request.

Plans for collection, laboratory evaluation, and storage of biological specimens for genetic or molecular analysis in this trial/future use

N/A, no biological specimens will be collected.