Abstract
Background
This RCT aimed to test the impact of an educational intervention, supported by a Personalized Oral Health Instruction Form (POIF), on oral health indices in institutionalized older adults.
Methods
Older adults aged 65 years and above living in a long-term care facility were recruited. Baseline oral health indices were recorded for all participants. Caregivers received training on oral health care in small groups. Custom-made software was used to create a POIF for each participant, which was then implemented alongside verbal instructions and the provision of an oral hygiene kit in the intervention group, whereas in the control group, the participants received verbal instructions and an oral hygiene kit only. After three weeks, a second examination was conducted by the same examiner, who was blinded to participants' group allocation. Plaque index (PI), denture cleanliness (DCI), and tongue coating (TCI) were recorded at baseline and after intervention. Oral health-related quality of life (OHRQoL), assessed at baseline and after intervention using the Geriatric Oral Health Assessment Index (GOHAI). Wilcoxon signed rank tests were conducted with the level of significance set at P<0.05.
Results
A total of 46 patients (mean age: 85.5 ± 7.7 years) were included. Plaque index (PI) significantly decreased in both groups from baseline to postintervention (p < 0.001), with a significantly lower median score in the intervention group (31.6%, IQR=51.1) than in the control group (53.9%, IQR=51.1; P = 0.023). DCI improved significantly within the intervention group (Wilcoxon P = 0.046), with a greater proportion of patients showing no visible plaque after the intervention than at baseline (66.7% vs. 33.3%). TCI did not change significantly over time in either group (n.s.). A combined hygiene outcome based on the PI and DCI showed significantly better plaque control in the intervention group (P =0.006). GOHAI total score increased from 50 (IQR=9) to 54 (IQR= 4). This improvement was statistically significant within the intervention group (P = 0.006), whereas it was not significant between groups at the final assessment.
Conclusions
The findings confirm that POIFs using tailored, visually supported, printed oral health guidance improve oral health outcomes in institutionalized older adults.
Trial registration
This study was approved by the ethics committee of the canton of Geneva (CCER 2022--00086) and registered on the Swiss national registry for clinical trials (SNCTP000004829) and was retrospectively registered on clinical trials with the registration number NCT07063927 on 2025-07-02.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12903-025-07102-y.
Keywords: Geriatric care, Oral care, Old adults, Personalized oral care, Plaque index, Denture hygiene, Oral hygiene intervention.
Background
Long-term care facilities are residences where older adults whose physical and mental health require regular assistance in performing activities of daily living but do not require hospitalization. Physical and/or psychological limitations due to chronic diseases such as hypertension, dementia, depression, arthritis, diabetes, reflux, arteriosclerosis, heart failure, cerebrovascular diseases and anemia are most commonly found in people living in institutions, leading to a decrease in autonomy [1, 2]. Research consistently shows that institutionalized elderly individuals tend to have poorer oral health compared to their non-institutionalized counterparts. This includes higher rates of dental caries, periodontal disease, and edentulism [3–5]. There is growing evidence that general health and well-being are related to good oral health and adequate oral hygiene. Good oral hygiene reduces the risk of developing aspiration pneumonia [6, 7]. Furthermore, maintaining periodontal health improves diabetes control [8, 9] and self-esteem, comfort and quality of life, i.e., the perception of overall health [10, 11].
Caregivers aim to maximize the independence of residents and maintain their autonomy. Hence, residents are encouraged to carry out their own oral hygiene. However, caregivers often do not verify whether oral hygiene was conducted or that the residents are capable of performing their oral care correctly [12]. Caregivers may not verify oral hygiene performance due to time constraints and the assumption that residents who appear independent are performing adequate self-care. When caregivers undertake oral care for residents, they are often faced with barriers that prevent them from performing effective management [12].
Most caregivers’ curricula provide them with basic theories and often little to no practical education in oral hygiene for their patients, leaving them to draw on their personal knowledge and experience [13]. Improving the education of health care providers in their oral care can improve the oral hygiene of the patients they care for. Other obstacles to oral care are raised, such as the lack of patient compliance and interest in oral care; moreover, the barrier can be logistic, with a lack of time and adequate instrumentation or materials [13, 14].
Annamari Nihtilä studied the effectiveness of a preventive oral health intervention in people receiving home care who are 75 years of age or older. Oral or written instructions were given to nurses on how to proceed with dental care. The results showed that the intervention had a positive effect on oral hygiene, but the results were not significant, as the number of teeth with plaque remained high, even after the intervention [15]. Denture plaque reduction and denture cleanliness seem to be easier to control for caregivers; however, intraoral plaque control remains a challenge [16].
Gibney et al. [17] conducted a prospective study in two hospitals in three phases: (1) preintervention; (2) intervention by an oral health therapist; and (3) nurse-led intervention where theoretical and practical instruction on real patients was implemented. This time, the results were more favorable. With this coaching, nurses improved the oral health of elderly patients in the same way as an oral health therapist did.
Previous interventions lacked personalization and visual support, which we can hypothesize can enhance adherence and improve outcomes. The large variability in the dental state, prosthodontic reconstructions and oral health conditions between residents must be taken into consideration for care guidelines, which require adequate knowledge. Caregivers are often not trained for this level of expertise, and the responsibility of the dentist or medical professional is to provide the appropriate instructions.
We hypothesize that educational training of caregivers, along with the implementation of a personalized oral instruction form (POIF), will lead to significant improvements in oral health indicators and oral health-related quality of life (OHRQoL) in institutionalized older adults compared with standard verbal instructions.
The null hypothesis is that there will not be a difference in the oral health indices namely (PI TCI, DCI) and OHRQoL between the intervention group and the control group. Our secondary objective is to obtain an assessment from participants and caregivers about POIF.
Materials and methods
This study is a single-center, two-arm study, which is reported according to the CONSORT extension and feasibility trials and the STROBE statement, as far as applicable, and according to available guidelines for randomized studies, it was approved by the ethics committee of the canton of Geneva (CCER 2022–00086) and registered on the Swiss national registry for clinical trials (SNCTP000004829) and clinical trial (NCT0706927).
Setting
The study was conducted in the Maison de Vessy (Geneva, Switzerland), a long-term care facility (LTC) accommodating approximately 250 residents with varying degrees of dependency and employing approximately 160 caregivers.
Cohort
The eligibility criteria included being a resident in the abovementioned LTC, being aged 65 years or older, living in the institution for more than 6 weeks, and understanding the French language. Participants were excluded if they were noncooperative, presented with an infectious disease or were receiving dental treatment. Informed consent was obtained from all participants or their legal guardians.
Training of the caregivers
Caregivers were invited to 6 training sessions in small groups of no more than 15 participants from January 2023 to March 2023. The training session covered the dental and prosthetic care of dependent and independent older adults and lasted for one hour. These training further emphasized the link between oral hygiene/health and systemic diseases. The trainers explained the oral health care for dependent and independent elders by covering the completely dentate, as well as partially and completely edentulous, residents. The tools, instruments and disinfecting products that are available for various clinical scenarios were also reviewed, along with relief strategies for dry mouth. The trainers described different implant attachment systems and reviewed the related care procedures. Finally, the situations where a referral to a dentist would be deemed necessary were explained. The caregivers were given a 7-question quiz to answer at the beginning of the training. The 7 questions were conceived by S.R. and edited for clarity and relevance by the senior authors (F.M., N.C.). The caregivers were asked to answer the same questions at the end of the training session to assess the effectiveness of the training. The questionnaire is in the supplementary material (Supplementary Material 1).
Clinical examination
The oral examination recorded the dental state (number of teeth, presence and type of prosthesis) and the plaque index (PI) according to O’Leary [18]. The surfaces with plaque were divided by the total number of available tooth surfaces and multiplied by 100. The PI percentages range from a minimum of 0 (i.e., no plaque on any tooth surface) to a maximum of 100%.
The denture cleanliness index by Ambjornsen was modified (DCI) [19] and was used to rate in a binary manner whether plaque or debris were located on the dental prosthesis. A score of 0 was given when no plaque was visible or when it was visible only by scraping on the denture base with a blunt instrument, and a score of 1 was given when a moderate or abundant accumulation of plaque and debris was visible on the prosthesis.
PI was expressed as a percentage for analysis, and a categorical cut-off (PI < 25%) was used when defining ‘good overall hygiene’ for the combined PI/DCI measure. Overall hygiene was assessed by combining PI and DCI data to account for individuals with or without dentures, ensuring inclusion of both dentate and edentulous participants.
Good overall hygiene was defined as one of the following: [1] a plaque index (PI < 25%) with no available denture cleanliness index (DCI) data (indicating that the patient had natural teeth but no prosthesis); [2] a DCI score of 0 (no debris on the prosthesis) with no PI available (indicating that the patient had a prosthesis but no natural teeth); or [3] both a PI score of 1 and a DCI score of 0. All other combinations were classified as poor hygiene (score = 0).
The tongue coating index (TCI) by Shimizu [20] was used to assess the tongue-coating status on the basis of observations of the coated thickness according to 3 scores: 0, tongue coating not visible; 1, tongue coating thin, papillae of tongue visible; and 2, tongue coating very thick, papillae of the tongue not visible. The tongue was divided into 9 areas that were scored after visual inspection of the tongue dorsum. If the TCI is 50% or higher, the patient is considered to have poor tongue hygiene.
Oral health-related quality of life (GOHAI)
To evaluate OHRQoL, the French version of the general oral health assessment index (GOHAI) was used. This validated questionnaire comprises 12 questions and is divided into the domains “pain and discomfort”, “psychosocial aspects”, and “function”. Patients were asked to fill out the questionnaire independently, and when unable, the researchers read out the questions and helped in recording the answers. The scores for the GOHAI items 3, 5 and 7 were maintained, whereas the remaining items were reversed to obtain a positive oral health GOHAI score [21, 22]. The oral examination and questionnaire were conducted in the resident’s room at baseline and were repeated approximately 3 weeks after the intervention. Intervention was implemented only after the inclusion and examination of all the participants at baseline.
Personalized oral health instruction form (POIF)
The POIF was performed via custom-made software designed for the purpose of the study (www.tomamedical.ch) for all participants. The software was built to include 3 unique characteristics: a toolbox, a visual care component that allows the insertion of patients’ photos and a text box where the personalized recommendation can be written. The visual component of the POIF consisted of intraoral photographs taken during the clinical examination. These images were uploaded into the software, which allows for the addition of visual markers such as arrows pointing to specific problem areas, indications of the tools or cleaning aids to be used in those zones. Written annotations indicated the presence of prostheses, implants or attachments.
The toolbox menu comprised brushes, interproximal brushes of different sizes, chlorhexidine-based products, fluoridated toothpastes, other fluoridated products and dry mouth droplets.
The photo of the necessary product and cleaning aid were dragged from the toolbox menu and added to the visual instruction. The written recommendations were also customized to each participants’ needs. The investigators elaborated the POIF (S.R., N.C.), and the care recommendations were reviewed according to experience and evidence-based knowledge (N.C., F.M.) [23].
Evaluation of POIF
The participants and caregivers were asked to complete an assessment questionnaire on the use of the POIF. The questionnaire comprises 10 questions and uses a numerical scale from 1 to 10. The study asked about the ease of understanding and interpretation, whether having POIF is helpful in providing daily oral care, whether it is better than verbal instructions, whether it has a positive impact on the health of the participants and whether it has changed the way in which they conduct oral care. The questionnaire then asked if the display of the POIF in the bathroom was embarrassing, whether they would continue to follow the written recommendation after the end of the study and whether they would recommend it to a relative or a friend. Then, they were asked if the price of the tools recommended was an obstacle and whether they had any suggestions to improve POIF. The original questionnaire is listed in Supplementary Material 2.
Oral hygiene kit
All participants received an oral hygiene kit that included a manual toothbrush and toothpaste and was customized according to each participant’s needs and the recommendations outlined in the POIF. The kit could also include appropriately sized interproximal brushes, tongue scrapers when indicated, fluoridated mouthwash, and 2% chlorhexidine paste.
Group allocation
The participants were randomized using www.randomizer.org via simple randomization. Group allocation was kept in sealed opaque envelopes. The outcome assessor (SR) was blinded to the group assignments. Caregivers were not informed which residents were included in the study but were not blinded to group assignments, as the POIF was displayed in the bathrooms of residents in the intervention group.
Protocol
Information about the study was published in the weekly newsletter of the LTC in June 2022, and further information was provided to residents and their families during an information session in May 2022. Residents were approached by the investigators before their lunch break or during leisure activities, and an information sheet was provided from May 2022 to October 2022. After screening for the inclusion and exclusion criteria, written consent was obtained from all participants or their legal guardians. Two investigators (S.R., N.M.) conducted the experiments. First, the participants’ demographic data (age, sex, former employment status, number of chronic diseases, number of medications taken daily and oral hygiene habits) were recorded. The autonomy status was set according to the residential aged care facility staff categorization (as dependent or independent for oral care). The oral examination and questionnaire were conducted in the resident’s room at baseline and were repeated approximately 3 weeks after the intervention. The elaborated POIF (S.R., N.C.) and the care recommendation were reviewed according to experience and evidence-based knowledge (N.C., F.M) [23].
In the intervention group, both dependent and independent participants received verbal instructions, in addition to the personalized written and visual POIF materials (N.M., N.C.) that was placed in the private bathroom of the participant, as shown in Fig. 1.
Fig. 1.
An example of the personal oral health instruction form (POIF) placed in the bathroom of the resident
For dependent residents, the personalized oral instruction form was handed to the caregivers along with the personalized oral hygiene kit and installed in the bathroom.
In the control group, independent and dependent residents received a hygiene kit along with verbal instructions. Independent residents in the control group conducted their own oral care, and for dependent residents, caregivers provided oral care. The observation period was a minimum of 3 weeks, after which all participants underwent a second examination, where oral hygiene indices were reassessed in the room and the GOHAI was completed. The bathroom door was closed for all participants by the second investigator to ensure concealment of group allocation from the examiner (S.R.). Participants in the control group received their POIF after of the final examination. Finally, the participants and caregivers were asked to complete the assessment form of the POIF.
Statistical analysis
The primary outcome is the plaque index according to O’Leary: data recently reported in the literature were used to conduct a power analysis. Nobre et al. [24] compared the plaque index before and after the intervention, and the difference in the plaque index reported as percentage of dental surfaces with plaque was 30 ±14 in the control group and 22±12 in the intervention group [24]. According to this analysis, a sample size of 70 was used to detect a significant difference between the intervention and control groups (Type I error = 0.05, β = 0.2, two-sided test).
Statistical analyses were performed via the Statistical Package for the Social Sciences (SPSS, version 29; Chicago, IL, USA). Kolmogrov‒Smirnov tests were used to assess the normality distribution of the continuous variables Plaque index, DCI, and TCI in each group. Caregivers’ assessment questionnaire results were compared via the Wilcoxon signed rank test, with significance set to P<0.01. The Kendall Tau B test was used to test the correlation between scores.
Changes in the PI, TC, and DCI from baseline to postintervention within each group were analyzed via the Wilcoxon signed-rank test. The differences between the control and intervention groups at each time point (baseline and postintervention) were assessed via the Mann‒Whitney U test. The distribution of DCI was compared between the control and intervention groups at baseline and postintervention via Pearson’s chi-square test. When the expected cell counts were less than five, Fisher’s exact test was used to ensure robust results.
To assess changes in hygiene status (combined PI/DCI) within each group over time, McNemar's test for paired nominal data was applied separately for the control and intervention groups. An additional McNemar test was performed on the full sample to evaluate the overall effect of the intervention across all participants. Statistical significance was set at P< 0.05.
Results
Participant demographics
The study included a total of 46 participants from September 2022 to December 2023, with 23 in the intervention group and 23 in the control group. Both groups presented no statistical difference between the demographic characteristics presented in Table 1. The mean age was 88.5 years (±3.6) in the control group and 90.0 years (±1.7) in the intervention group. The average number of medications taken daily was 9.0 (±1.6) in the control group and 11.3 (±2.9) in the intervention group. The number of chronic conditions was 5.17 (± 2.08) in the control group and 4.33 (± 1.2) in the intervention group. The mean number of teeth in the maxilla was 6 (±2.03) in the control group and 4 (±4) in the intervention group; in the mandible, the control group had 8.33 (±2.1) teeth, and the intervention group had 4.67 (±6.7) natural teeth. There were no statistically significant differences between the control and intervention groups in reported cleaning habits, including the use of electric toothbrushes, interdental tools, or prosthesis care techniques. Chi-square tests and Fisher’s exact tests revealed no group differences in the frequency of brushing, use of cleaning agents, or use of oral hygiene aids. Similarly, self-reported behavior related to mouthwash, denture disinfection, and sleep hygiene practices did not differ significantly between the groups. Four participants were lost to follow-up after the baseline examination. Detailed information about the participants’ characteristics and cleaning habits is reported in Table 1.
Table 1.
Demographic characteristics of participants and oral hygiene habits
| Demographics | Control | Intervention | Total | |
|---|---|---|---|---|
| Age (Mean±SD) | 88,5 ±3,64 | 90±1,7 | 46 | |
| Number of medication taken daily (Mean±SD) | 9±1,6 | 11,3±2,9 | ||
| Number of Chronic diseases (Mean±SD) | 5,17±2,08 | 4,33±1,2 | ||
| Number of teeth in the maxilla (Mean±SD) | 6±2,033 | 4±4 | ||
| Number of teeth in the mandible (Mean±SD) | 8,33±2,15 | 4,67±2,67 | ||
| Independent Samples t- Test n.s | ||||
| Gender | Male | 17 | 14 | 31 |
| Female | 6 | 9 | 15 | |
| Autonomy | Independant | 19 | 15 | 34 |
| Dependant | 4 | 8 | 12 | |
| Pearson Chi square ns. | ||||
| Past professional activity | Control | Intervention | Total | |
| Military professions | 1 | 0 | 1 | |
| Directors, executives managers | 1 | 2 | 3 | |
| Intellectual and scientific professions | 3 | 4 | 7 | |
| Intermediate professions | 3 | 1 | 4 | |
| Administrative type employees | 5 | 4 | 9 | |
| Staff providing direct services to individuals, merchants, and sellers | 3 | 3 | 6 | |
| Skilled trades in industry and crafts | 3 | 5 | 8 | |
| Plant and machine operators, and assembly workers | 1 | 0 | 1 | |
| Elementary professions | 3 | 3 | 6 | |
| Total | 23 | 22 | 45 | |
| Pearson Chi square ns. | ||||
| Changes during the course of the study | no changes during the study | 18 | 20 | 38 |
| Cognitive decline | 1 | 1 | ||
| Death | 1 | 1 | ||
| Change in dental status | 3 | 3 | 6 | |
| Total | 23 | 23 | 46 | |
| Pearson Chi square n.s. | ||||
| Dental status | Control | Intervention | Total | |
| Maxilla | No prosthesis | 7 | 4 | 11 |
| Upper prosthesis | 10 | 8 | 18 | |
| Pearson Chi square n.s. | 17 | 12 | 29 | |
| Mandible | No prosthesis | 9 | 6 | 15 |
| Lower prosthesis | 8 | 6 | 14 | |
| Pearson Chi square n.s. | 17 | 12 | 29 | |
| Need for a prosthesis | does not need a prosthesis | 9 | 6 | 15 |
| needs a prosthesis | 8 | 6 | 14 | |
| Pearson Chi square n.s. | 17 | 12 | 29 | |
| Type of prosthesis in the maxilla | No prosthesis on upper | 7 | 4 | 11 |
| Complete denture | 6 | 4 | 10 | |
| Resine partial denture | 1 | 0 | 1 | |
| Cast partial denture | 3 | 4 | 7 | |
| Not applicable | 6 | 11 | 17 | |
| Pearson Chi square, Fisher's Exact test when applicable n.s. | 23 | 23 | 46 | |
| Type of prosthesis in the mandible | No prosthesis | 9 | 6 | 15 |
| Conventional prosthesis | 3 | 2 | 5 | |
| Resine partial | 1 | 2 | 3 | |
| Cast partial | 4 | 2 | 6 | |
| Not applicable | 6 | 11 | 17 | |
| Pearson Chi square, Fisher's Exact test when applicable n.s. | 23 | 23 | 46 | |
| Number of occluding pairs | FU=0 | 10 | 7 | 17 |
| FU=1 | 3 | 1 | 4 | |
| FU=2 | 0 | 1 | 1 | |
| FU=3 | 1 | 2 | 3 | |
| FU=4 | 9 | 12 | 21 | |
| Pearson Chi square, Fisher's Exact test when applicable n.s. | 23 | 23 | 46 | |
| Hygiene habits | Total | |||
| Manual tooth brush | No manual Tooth brush | 3 | 3 | 6 |
| Manual tooth brush | 17 | 19 | 36 | |
| Total | 20 | 22 | 42 | |
| Electric toothbrush | No Electric Tooth brush | 17 | 19 | 36 |
| Electric tooth brush | 3 | 3 | 6 | |
| Total | 20 | 22 | 42 | |
| Fluoridated tooth paste | No fluoridated tooth paste | 0 | 1 | 1 |
| Fluoridated tooth paste | 20 | 22 | 42 | |
| Total | 20 | 23 | 43 | |
| Prosthesis Brush | No prosthesis brush | 1 | 0 | 1 |
| Prosthesis brsuh | 9 | 10 | 19 | |
| Not applicable | 1 | 0 | 1 | |
| Total | 11 | 10 | 21 | |
| Desinfecting tabs/products | No desinfecting tabs | 10 | 7 | 17 |
| Desinfecting tabs or products | 1 | 2 | 3 | |
| Total | 11 | 9 | 20 | |
| Sleeps with prosthesis | Does not sleep with the prosthesis | 7 | 7 | 14 |
| Sleeps with the prosthesis | 4 | 3 | 7 | |
| Total | 11 | 10 | 21 | |
| Interproximal brushes | No interpoximal brushes | 11 | 19 | 30 |
| Uses interproximal brushes | 7 | 3 | 10 | |
| Total | 18 | 22 | 40 | |
| Mouthwash | Does not use mouth wash | 13 | 19 | 32 |
| Uses mouthwash | 10 | 4 | 14 | |
| Total | 23 | 23 | 46 | |
| Cleans tongue | Does not clean tongue | 17 | 18 | 35 |
| Cleans tongue | 6 | 5 | 11 | |
| Total | 23 | 23 | 46 | |
| Number of times teeth are brushed per day | 0 | 2 | 3 | 5 |
| 1 | 5 | 8 | 13 | |
| 2 | 3 | 1 | 4 | |
| 3 | 1 | 1 | 2 | |
| Total | 11 | 13 | 24 | |
| Number of times desinfecting products are used per week | 0 | 10 | 8 | 18 |
| 1 | 1 | 1 | 2 | |
| 7 | 0 | 1 | 1 | |
| Total | 11 | 10 | 21 | |
| Number of times interproximal cleaning tools are used per week | 0 | 11 | 19 | 30 |
| 1 | 2 | 0 | 2 | |
| 3 | 1 | 0 | 1 | |
| 5 | 1 | 0 | 1 | |
| 7 | 2 | 2 | 4 | |
| 14 | 0 | 1 | 1 | |
| 21 | 1 | 0 | 1 | |
| Total | 18 | 22 | 40 | |
| Number of times mouthwashing products are used per week | 0 | 13 | 19 | 32 |
| 1 | 2 | 0 | 2 | |
| 2 | 1 | 0 | 1 | |
| 3 | 0 | 2 | 2 | |
| 5 | 2 | 0 | 2 | |
| 7 | 3 | 1 | 4 | |
| 14 | 2 | 1 | 3 | |
| Total | 23 | 23 | 46 | |
| Number of times the tongue is cleaned per week | 0 | 17 | 18 | 35 |
| 1 | 2 | 1 | 3 | |
| 7 | 4 | 4 | 8 | |
| Total | 23 | 23 | 46 | |
Pearson Chi square, Fisher's Exact test when applicable n.s
Caregivers’ training and assessment
Sixty-five caregivers participated in the training sessions and completed the assessment of the 7 questions. Caregivers were 23 nurses, 39 nursing aids and 5 apprentices. Thirteen were aged 20–25, 17 were between 35 and 50 and 27 between 50 and 65 years. They had an average experience of 17.7 ± 10.2 years. The mean total score improved significantly from baseline with an M score of 10 (IQR = 8) before to 14 (IQR = 6), with a Wilcoxon signed rank test of p < 0.01. The caregivers who had a good score prior to the training also had a good score on the assessment after the training (Kendall Tau B, P < 0.01).
Oral hygiene indices
At baseline, there were no significant differences between the control and intervention groups in terms of PI1 or TCI1. At the second examination, the intervention group presented a significant reduction in plaque accumulation, with a median PI2 of 31.6% (IQR: 29.05) compared with 54% (IQR: 51.14) in the control group (P = 0.04, Mann‒Whitney U). The within-group comparison also revealed a significant decrease in plaque levels in the intervention group (P < 0.001, Wilcoxon signed-rank test). There was no statistically significant difference in the TCI between the groups postintervention.
At the end of the observation period, a significant reduction in debris on prostheses was observed in the intervention group (P = 0.046, Wilcoxon signed rank test), although the difference between groups remained nonsignificant. The detailed results of the oral hygiene indices are presented in Tables 2 and 3.
Table 2.
Plaque index and tongue coating index at baseline and post intervention for the control and intervention group
| Outcome | Control (N, Median, IQR) | Intervention (N, Median, IQR) | P-value* | P-value§ |
|---|---|---|---|---|
| PI baseline | 20, 86.76 [34.36] | 22, 78.94 [38.4] | .707 | .757 |
| Pl post-intervention | 18, 53.89 (51.14) | 20, 31.58 [29.05] | .067 | .023 |
| p-value† | <.001 | <.001 | ||
| TCI Baseline | 23, 11.11 [36.11] | 23, 11.11 (27.78) | .421 | .766 |
| TCI Post intervention | 21, 16.67 (43.06) | 20, 11.11 (16.67) | .198 | .256 |
| p-value† | .851 | .851 |
*by Mann-Whitney test, § by Independent Median Test, † by Wilcoxon Signed-Rank Test
Table 3.
Denture cleanliness index at baseline and post intervention for the control and for the intervention group
| Outcome | Category | Control (N=11, % in Category) | Intervention (N=10, % in Category) | P-value* |
|---|---|---|---|---|
| DCI baseline | No Visible Plaque | 2 (66.7%) | 1 (33.3%) | .593 |
| Moderate Accumulation of Plaque | 9 (50%) | 9 (50%) | ||
| DCI post intervention | No Visible Plaque | 2 (33.3%) | 4 (66.7%) | .115 |
| Moderate Accumulation of Plaque | 8 (72.7%) | 3 (27.3%) | ||
| P-value† | .046 | .046 |
*by Pearson Chi-Square, †Wilcoxon Signed-Rank Test
At baseline, 4.3% of the participants in the control group and 4.4% of those in the intervention group had good oral hygiene. After the intervention, the proportion increased to 33.3% in the intervention group (McNemar P = 0.006), whereas no significant change was observed in the control group (Table 4).
Table 4.
Oral hygiene status (PI/DCI) baseline and post intervention for the control and for the intervention group
| Outcome | Category | Control % | Intervention % | p-value* |
|---|---|---|---|---|
|
Oral Hygiene baseline N=46 |
Poor plaque control | 22 (95.7%) | 22 (95.7%) | |
| Good plaque control | 1 (4.3%) | 1 (4.4%) | ||
| Oral Hygiene post intervention N=42 | Poor plaque control | 16 (76.2%) | 14 (66.7%) | |
| Good plaque control | 5 (23.8%) | 7 (33.3%) | .006 | |
| P-value* | .125 | .07 |
*by Mc Nemar Test
Oral health-related quality of life
Oral health-related quality of life, as assessed by the GOHAI score, improved in the intervention group postintervention, with the GOHAI total score increasing from 50 (IQR = 9) to 54 (IQR = 4). This improvement was statistically significant within the intervention group (P = 0.006), whereas it was not significant between groups at the final assessment. Details on the evaluation of the different domains are presented in Table 5.
Table 5.
The subjective perception of oral health related quality of life as evaluated by the GOHAI questionnaire at baseline and post intervention for the control and for the intervention group
| Outcome | Domains | Control (M [IQR]) | Intervention (M [IQR]) | P-value *(Control vs. Intervention) | P-value † (Within Intervention Group) |
|---|---|---|---|---|---|
| GOHAI Total – Baseline (N=46) | 50 [11] | 51 [7.5] | .609 | ||
| Physical Function | 17[5] | 18.5[4] | .488 | ||
| Pain & Discomfort | 11 [2] | 13 [3.3] | .262 | ||
| Psychosocial | 22 [4] | 23[3] | .544 | ||
|
GOHAI Total- after intervention (N=40) |
53 [6.5] | 54 [4] | .320 | .006 | |
| Physical Function – | 18 [3.5] | 19 [3.75] | >.5 | .07 | |
| Pain & Discomfort | 14 [2] | 14 [8] | >.5 | .001 | |
| Psychosocial | 22 [4] | 23 [3] | >.5 | .7 |
*by Mann-Whitney, † by Wilcoxon
POIF assessment
Caregivers’ ratings of POIF indicated relatively high ease of reading (6. 9 ± 2.20), a positive perception of POIF as support in providing care (6.5 ± 2.23), a slight preference for pictures/images over written instructions (6.5 ± 2.23) and a positive perception of the impact of POIF on the oral health of residents (Fig. 2).
Fig. 2.
Caregivers and participants responses to the evaluation questionnaire on the personal oral instruction form (N=56)
On their part, residents found POIF easy to read and interpret, and it was perceived to have a positive impact on their oral care performance (Fig. 2). Caregivers were more reticent in the display of the POIF in the bathroom, whereas residents mostly disagreed that the display was embarrassing. Most caregivers would recommend the use of POIF to colleagues and would continue following the instructions after the study (Fig. 3).
Fig. 3.
Caregivers and participants responses to the evaluation questionnaire on the personal oral instruction form (N=56)
The pooled responses from the open-ended questions suggested increasing the font on the form, removing the portrait photos of the residents, improving the infographics and adding nutritional advice.
Discussion
This randomized clinical trial demonstrated that the use of a Personalized Oral Health Instruction Form (POIF), coupled with caregiver training and the provision of an oral health tool kit, significantly improved oral hygiene among institutionalized older adults. Compared with the control group, the intervention group presented a significant reduction in the plaque index and better denture cleanliness, thus rejecting the first part of our null hypothesis. The oral health-related quality of life score improved from baseline in both groups, but no difference was reported between the groups. Therefore, the second part of the null hypothesis cannot be rejected.
Our findings align with those of studies by Gibney in 2019 [17], which demonstrated that education and coaching significantly improved oral hygiene in hospitalized older adults, as improvements were noted in both groups. Improving knowledge does not lead to an improvement in the oral care skills of the caregivers [25]. The assessment given before and after the training confirmed the variability in oral care knowledge between caregivers and confirmed that training has a benefit on knowledge. However, our study expands on these results by incorporating a personalized, photobased instruction form, a strategy not extensively explored in previous trials.
Samson, Berven and Strand [24] incorporated a program aimed at improving and maintaining the oral hygiene of residents in a LTC. Their method encompasses 3 elements: the motivation and oral care training of LTC staff, the production of picture-based oral care procedure cards, and the distribution of dental hygiene equipment. Thirty-six percent of the residents had initially an acceptable oral hygiene, whilst 70% of the residents had acceptable oral hygiene at the end of the 6-year follow-up period of the study. These results concur with the results of our study showing the potential of these oral health bundles comprising education, oral hygiene tools and visual oral care procedures. Our study also shows that even when initiatives are implemented and that most residents are successful, some do not achieve acceptable levels of oral hygiene, with various reasons accounting for this finding [26].
Janssens compared the oral hygiene levels of LTC residents who were included in an oral healthcare program with those of those who were not and reported that the plaque and denture plaque indices of residents in the oral care program were better than those of their counterparts outside the program. Importantly, both groups received basic oral care; however, the residents in the oral care plan had access to additional oral hygiene tools such as denture brushes [27]. Ensuring the continuation of good practices in the long term is a challenge, with high turnover of staff being identified as a problem and the difficulty in maintaining improvements in plaque indices in the long term [28]. The supervised implementation of oral health guidelines has also been suggested to improve denture hygiene but has lower benefits for dental plaque, and barriers to carrying out oral hygiene measures for demented elderly individuals are always present [29]. Hence, our suggestions are to provide instructions in writing and make them visible to various staff shifts.
The nursing staff and caregivers in our study seemed to appreciate the information in the POIF on how the oral health care of the individual residents should be carried out. Nursing staff are given a standard of operating procedures to enable them to carry out medical procedures in the same way to achieve a specific goal, and in the context of oral health, adequate daily oral care of the residents should be ensured. The success of POIF might be attributed to its visual components, which provide clear and personalized instructions, improving caregiver compliance and residents' oral care routines. The step-by-step instructions are particularly useful for residents with mild cognitive decline or loss of memory. Moreover, POIF allows the transfer of information to new and temporary staff, and infographics are of particular interest to non-native language speakers. Several studies have demonstrated that oral health improvement following targeted interventions is possible, but few have had an effect that lasts beyond the observation period. A printed POIF can remain a source of motivation and instruction beyond the duration of a study. It may also be particularly helpful in LTCs where staff turnover is high. The visual and graphical display simplifies the message to a level such that it may even be followed by non-trained caring staff or family.
Tongue coating is associated with halitosis or malodor, a frequent source of personal discomfort or social discomfort, and the oral microbiome is responsible for the production of odiferous gases such as volatile sulfur compounds [30]. The level of oral hygiene is a strong determinant of the presence of tongue coating: smoking, the presence of complete dental prostheses and periodontal status can also lead to tongue coating [31]. The lack of a significant change in the tongue coating index may indicate that either more time or longer follow-up is necessary to improve this measure or that the tongue coating can be reformed in a patient within a very short time (e.g., between cleaning and the oral examination), especially in patients with oral hypofunction, where the self-cleaning effect of the tongue is limited. Furthermore, the intervention may not have addressed sufficiently the tongue cleanliness and coating, as to most people, these gestures are less familiar than tooth brushing.
The improvement in oral health-related quality of life can be attributed to the oral hygiene counseling intervention and improvements in pain- and discomfort-related perceptions of oral health. This improvement emphasizes the need for oral health professionals to be more present and involved in residential aged care facility settings because of their perceptions of the well-being of residents.
A major strength of this study is the combination of personalized oral care instructions with caregiver education and the provision of an oral hygiene tool kit, which allowed for tailored interventions addressing the unique oral health needs of each participant. Moreover, blinding the examinator and the design of the study allows us to analyze the effect of using visual and personalized instructions. Additionally, the incorporation of subjective assessments from both caregivers and residents adds depth to the findings, confirming the practical benefits of POIF. Despite these encouraging findings, this study has several limitations. First, the number of participants required on the basis of our initial power calculation for detecting differences in plaque levels between groups was not achieved. As the study design required that all participants undergo baseline assessment prior to the implementation of the POIF, delays in data collection affected recruitment. Although the intervention period was relatively short the time needed to complete baseline assessments for all participants was considerable, and the duration extended to 18 months. Logistic problems precluded reaching full target sample size.
Nevertheless, the findings demonstrated the short-term usefulness and feasibility of POIF in improving oral hygiene. Although PI2 showed a statistically significant difference between groups, post-hoc analysis indicated the study was underpowered for this endpoint (0.43), highlighting the need for larger samples to confirm the finding. In contrast, the combined oral hygiene outcome demonstrated a large effect in the intervention group, suggesting a clearer benefit that warrants validation in larger cohorts.
Additionally, the study was conducted in a single LTC, which limits the generalizability of the findings to broader populations. Moreover, caregivers and residents may have provided socially desirable responses to the questionnaire.
Further research should focus on long-term outcomes to determine the sustainability of the observed improvements in oral hygiene indices. The custom-made software used to produce the POIF streamlined the prescription process, and further development of this software will enable clinicians to provide clear care recommendations in a timely manner. Additionally, exploring the cost-effectiveness of widespread POIF implementation could provide valuable insights for policymakers and healthcare administrators.
Conclusions
In conclusion, the use of a personalized oral care instruction form (POIF), supported by caregiver education and the provision of an oral hygiene tool, offers a promising strategy to improve oral hygiene among institutionalized older adults. Their use is well perceived by health workers and residents. These findings support the POIF as a feasible strategy in LTC. Future research should focus on long-term outcomes, scalability across diverse healthcare settings, and cost-effectiveness to inform broader policy implementation.
Supplementary Information
Acknowledgements
The authors would like to express our gratitude to the director of the LTC facility, Mrs Megan Bowyer, for granting us access to the institution and for the invaluable logistic support provided throughout the study. We are also grateful to the caregiving staff of the ‘Maison de Vessy’ for their cooperation and assistance during examinations and data collection.
Abbreviations
- POIF
Personalized oral health instruction form
- OHRQoL
Oral health-related quality of life
- LTC
Long-term care facility
- PI
Plaque index
- DCI
Denture cleanliness index
- TCI
Tongue coating index
- GOHAI
General oral health assessment index
Authors’ contributions
Najla Chebib and Sara Rotzinger contributed equally to this work and share first authorship. Conception and design of study: N.C, S.R.,F. M., acquisition of data N.C, S.R. N.M.R, data analysis P.M., N.C, creation of the software R.S., N.C., drafted the manuscript F.M., N.C., S.R. All authors have approved the submitted version and have agreed to be personally be accountable for their contribution.
Funding
Open access funding provided by University of Geneva. The study was funded by the institutional funds for research of the division of Gerodontology and removable prosthodontics of the University of Geneva. The authors received no financial support for the research authorship, and/or publication of this article.
Data availability
The data that supports the findings of this study are available from the corresponding author upon reasonable request.
Declarations
Ethics approval and consent to participate
The study was conducted in accordance with the Declaration of Helsinki. Ethics approval and consent to participate: the study was approved by the ethics committee of the canton of Geneva (CCER 2022–00086) and registered on the Swiss national registry for clinical trials (SNCTP000004829) and registered retrospectively on Clinical trials under the registration number NCT07063927 on 2025-07-02.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Najla Chebib and Sara Rotzinger contributed equally to this work.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The data that supports the findings of this study are available from the corresponding author upon reasonable request.