Phase 1 used all 3 stages of BCW (Figure 1) to understand parents’ barriers and enablers, mapping these to intervention functions, behavior change techniques (BCTs), and text message content. Co-design workshops and semistructured interviews were conducted between February 2, 2023, and July 15, 2023. Data were collected by a trained qualitative researcher who had experience working within NSW Health public dental services, and sessions were conducted in person or via video calls if requested by participants. All workshop participants’ anonymity was maintained through pseudonyms, and transcription was managed with the NVivo (Lumivero) qualitative data analysis software [35]. Parent and health professional sessions were held separately to reduce power dynamics and encourage open discussions [36,37].

In the first stage, qualitative workshops and interviews were conducted with parents and oral health professionals to explore barriers and enablers related to 3 key oral health behaviors: oral hygiene, dietary sugar intake, and bedtime routines. These were mapped to the COM-B model to define a target behavior that could be supported by mHealth messaging.

Stage 2 used the BCW mapping process to select intervention functions and policy areas to address the barriers and enablers identified in stage 1. These identified intervention functions also had to have the capacity to be incorporated into the format of the mHealth program.

In stage 3, BCTs were chosen based on the Acceptability, Practicability, Effectiveness, Affordability, Safety, and Equity (APEASE) [38] criteria, and content for the intervention was drafted and mapped to the original barriers and enablers. Within the BCW, the APEASE criteria ensures that the content is pragmatic and relevant for both the parents and the health system’s existing digital infrastructure [28]. This process informed the content of the initial draft text message bank.

Phase 2 developed the information gathered from the phase 1 co-design workshops by conducting a broader consultation with parents and health professionals to further evaluate the content (stage 4) before finalising the content and functionality of the SmilesUp program (stage 5).

A questionnaire based on previously published methodologies [15] was developed to measure the understandability, usefulness, and appropriateness of the draft content. This questionnaire was given to a wider group of parents and health professionals to assess the acceptability of SMS text message content [15]. We recruited until all messages were reviewed by at least 2 parents and 2 health professionals. The SMS text message content reviews were collected through questionnaires on REDCap and through paper forms when requested by parents [39]. To prevent survey fatigue, each participant was only required to provide feedback on the understandability, usefulness, and appropriateness of approximately 20 messages [15]. Additionally, to ensure the readability of the messages, a grade 5 reading level or below was set to ensure the readability of the program for our target population. All final messages were assessed using the Sydney Health Literacy Lab (SHeLL) reader to verify this reading level was met before they were included in the final set [40].

In the finalization phase, messages were mapped back to the originally identified barriers and enablers (phase 1) to ensure that all identified needs and BCTs were addressed. Qualitative data were also analyzed to inform decisions about the program’s functionality, including the duration, frequency, timing, and sequencing of the SMS text message schedule.

Workshops with parents and health professionals identified 15 enablers and 10 barriers to address 3 key oral health risk behavioral categories: oral hygiene, diet, and healthy bedtime routines. These barriers and enablers were mapped to BCW’s COM-B model of behavior categories: physical capability, psychological capability, physical opportunity, social opportunity, reflective motivation, and automatic motivation. We found that while parents had the physical capability to perform oral health–promoting behaviors, they lacked specific knowledge (psychological capability) about selecting the best toothpaste, brushing techniques, and choosing low sugar snacks for their children. Most of the enablers were linked to motivation (automatic) and capability (knowledge) where parents sought reminders and information to help them develop consistent oral health habits.

Therefore, the problem was defined as the need to increase parents’ oral health literacy encompassing both knowledge (psychological capability) and motivation (automatic and reflective) for adopting healthy oral behaviors to prevent ECC. A comprehensive tabulated description of the target behavior for the SmilesUp SMS text message program using BCW framework is found in Table 1.

Intervention options and policy areas from the BCW were identified based on the initial data around barriers and enablers collected from parents and clinicians. These were then mapped to the previously identified barriers and enablers (Multimedia Appendices 1 and 2). Parents and clinicians recommended incorporating 5 intervention functions and 10 theoretical domains into the SmilesUp mHealth intervention. The 5 intervention functions were education, persuasion, modeling, enablement, and environmental restructuring [38]. The 10 theoretical domains framework included knowledge, skills, beliefs about capabilities, optimism, beliefs about consequences, reinforcement, intentions, goals, memory, and social influences [38].

The SmilesUp program aligns with two specific policy areas identified in the BCW: (1) communication and marketing and (2) service provision [38]. The program sits at the intersection of these policies because it is delivered as a communication tool to support and encourage behavior change as part of the comprehensive, value-based clinicalservice provided to families with the NSW public dental service.

Specific BCTs were determined using a feasibility lens based on the APEASE criteria with perspectives from parents and high-level stakeholders [28]. A total of 16 BCTs were identified and mapped to the 15 enablers and 10 barriers previously determined by the consumer co-designers in stages 1 and 2 (Multimedia Appendices 1 and 2). These BCTs were chosen for their feasibility and relevance to an mHealth intervention with the goal of enhancing parents’ capability and motivation of oral health–promoting behaviors in the home context (Multimedia Appendices 1 and 2). The specific BCTs included were as follows: “1.4 Action planning”; “2.4 Self-monitoring of behavior”; “4.1 Instructions on how to perform behavior”; “5.1 Information about health consequences”; “5.3 Information about social and environmental consequences”; “5.6 Information about emotional consequences”; “6.1 Demonstration of the behavior”; “7.3 Reducing the prompts/cues”; “7.6 Satiation”; “8.2 Behavioral substitution”; “8.3 Habit formation”; “9.1 Credible source”; “12.1 Restructuring the physical environment”; “12.4 Distraction”; “13.1 Identification of self as a role model”; “15.1 Verbal persuasion about capability.” An example of how the BCTs were comprehensively mapped to the barriers or enablers, theoretical domains framework, and policy functions is provided in Multimedia Appendices 1 and 2. This information informed the program’s functionality, including the need for semipersonalization of the messages to include the child’s name, and for parents to select the timing of the messages to suit their lifestyles, thereby supporting ongoing engagement and sustained long-term behavior change.

The draft content, co-designed with 20 participants including 6 (30%) parents and 14 (70%) health professionals, addressed the barriers and enablers and corresponded to the intervention functions and BCTs identified earlier. The draft message bank included 111 messages, some of which were adapted from the bank of messages from the WHO’s BeHealthy BeMobile program, with locally relevant web-based links specific to the target population [7]. These web-based resources were in alignment with Australia’s National Consensus Statement on Oral Health Messages [41] and were developed by government agencies and professional associations including NSW Health and the Australian Dental Association [41]. New messages were created to address specific knowledge barriers identified by the parents, such as the consumption of dried fruit and vitamin gummies that had been noted in stage 1. Additionally, BCTs were incorporated into the content and features of the mHealth program to support parents using the final SmilesUp program.

In phase 2, of the 31 participants, 14 (45.2%) parents and 17 (54.8%) health professionals reviewed the 111 draft SMS text messages, providing a total of 2045 ratings, which included 805 (39.4%) parent reviews and 1240 (60.6%) health professional reviews. The sample size was determined by data saturation, which was reached when all messages were reviewed twice—once by a health professional and once by a parent consumer accessing NSW public dental clinics. For a message to be considered acceptable, it needed to receive a “yes” favorably on all 3 categories of understandability, usefulness, and appropriateness. Of the 111 draft messages, 86 (77.5%) messages were rated favorably by parents, while 68 (61.3%) messages were rated favorably by health professionals. A total of 56 (50.5%) messages were considered acceptable and useful by both parents and health professionals.

These 56 messages were further tested for readability using the SHeLL reader [40]. Two (1.8%) messages that exceeded the grade 5 reading level were removed.

The final set of messages was mapped to oral health behaviors, barriers, enablers, intervention functions, and BCTs. Based on the final functionality determination, only 36 messages were required. Therefore, 18/56 (32%) messages that addressed similar barriers and enablers were removed to avoid redundancy. The final set included 12/36 (33.3%) messages addressing oral hygiene, 16/36 (44.4%) addressing dietary sugar intake, and 6/36 (16.7%) on bedtime routines. An example of how a barrier is mapped to an intervention function, a BCT and the SMS text message content for the program, is found in Table 2.

Finalizing the program’s functionality included decisions about the duration, frequency, timing, and sequencing of the SMS text message algorithm. After consulting parents and considering the behavior change literature [42], the program was set for 12 weeks with an average of 3 messages per week, totaling 36 messages. Parents could semipersonalize the program by including their child’s name in the messages and choosing the time they received the messages to best fit their lifestyles. The sequencing initially focused on bridging knowledge gaps identified by parents during the first month, with more reminders and messages targeting motivation scheduled for later in the program.

The message schedule and practice sequence were delivered using the Westmead Applied Research Centre’s TextCare platform, a cloud-based system designed to semipersonalize the content and frequency of SMS text messages. TextCare includes built-in safety, privacy, and security systems with in-built data analytics, including an automated opt-out feature to measure engagement from parents. The messages are primarily 1-way, providing practical tips and strategies to prompt behavior change. The TextCare platform was monitored by a clinician researcher. RC tested the program for 1 month before delivering the program to parents.