The search culminated in five studies that fulfilled both the inclusion and exclusion criteria and which were conducted from 1 January 2014 to 1 January 2019 (figure 1).
According to these criteria, the articles selected for our systematic review about the following levels of evidence and degrees of recommendation are shows in table 2.
Of the five studies selected for this systematic review, two were carried out in Europe 9,20, two in Asia21, 22, and one in Australia23.
All the works were based on with a sample size that could offer extrapolated data (more than 50 elderly patients): Poisson et al.9 159 patients, Gerritsen et al.20 355, Chen et al.21 120, and that smallest, Murray et al.23 and Nakayama et al. 22 with 89 and 50 patients, respectively, making a total of 773 patients.
Although only two studies 20, 21 specified the age range of the patients; the average age of all participants in the studies was over 70 years.
In three studies 9, 20, 21 the proportion of women in the sample was higher than that of men. As regards the total number of participants in the papers included in the review, the proportion of women who participated in the studies was higher (1:1.6 male to female ratio), which can be explained by the greater life expectancy of women.
Gerritsen and co-workers 20 took as their sample a group of elderly subjects from three retirement homes, while Chen et al. 21 studied subjects from a geriatric medical centre and Murray et al. 23 patients from three rehabilitation centres for patients who had suffered a cerebrovascular accident (CVA). Poisson et al. and Nakayama et al. 9, 22 developed their studies in hospitals, and Poisson et al. (Poisson et al., 2014) worked in the geriatrics area of a hospital. Nakayama et al. 22 focused on patients suffering ALS (Amyotrophic Lateral Sclerosis) with nasogastric and artificial respiration. None of the selected studies specified whether they were in public or private centres.
Causes of admission of patients
Except for Murray et al.23 and Nakayama et al. (Nakayama et al., 2017), who worked with very specific types of patient (patients in rehabilitation after CVA and patients with ALS, respectively), none of the studies specified the reason for admission to the centres, although Gerritsen et al.20 and Chen et al.21 gave a general outline. In particular, Gerritsen et al.20 specified that 47% were in the residence for somatic reasons and 53% for psychogeriatric reasons, while Chen et al.21 pointed out that the main diagnoses of their sample at admission were pneumonia, sepsis, idiopathic fever and infection of the urinary tract.
Two of the studies22, 23 did not specify the length of the stay in the institution, but, from the information provided in the articles, we understand that all the studied patients had been in institution for at least 7 days21, 23, while the longest times were those mentioned by Gerritsen et al.20 (more than two years). Therefore, the subjects who had been the longest time in care were those mentioned in the only study carried out in retirement homes.
Three of the five studies 9, 21, 23 specify at least part of the systemic pathology that participants were suffering. The remaining two 20, 22 did not mention whether the patients described in their studies suffered any other pathologies beyond those specified as the time of admission: somatic or psychogeriatric reasons in the case of Gerritsen et al. 20, and ALS in the case of Nakayama et al. 22. In the study of Poisson et al. 9, 74.2% of the patients had some sort of cognitive problem. Murray et al. 23 mentioned only comorbidities derived from the CVA suffered by their patients (aphasia, apraxia, dependency, among others) and Chen et al. 21 describes the degree of dependence of their patients (total 45%; severe 35% and slight 20%), along with the more common pathologies such as Diabetes Mellitus (58.3% of patients) and high blood pressure (77.5%). However, the most striking thing in all the studies was the number of patients who had some sort of cognitive problem or degree of dependence that made them vulnerable if they did not receive good oral care (Table 3).
None of the studies evaluated the medication that the participants were taking despite the fact that medication could be associated with the state of their oral health. Nakayama et al. 22, who measured the salivation index of their participants, only mentioned that none of the patients in the study were following any treatment that would have affected their salivary flow (radiotherapy or botulinum toxin treatment).
Oral health and hygiene
Regarding the oral health of the participants in the studies, we conclude that the authors used different methods of assessment, and only Poisson et al. 9 and Nakayama et al. 22 used the DMFT index (Decayed, Missing, Filled Teeth). However, the vast majority of patients in all the studies had poor oral health and, we understand that they were also in great need of treatment, although only Gerritsen et al. 20 specified so.
As regards oral care measures, only one study 9 did not mention that subjects follow any kind of oral hygiene protocol. Gerritsen et al. 20 mentioned that patients in the caring homes had access to 16 hours of dental care a week and 8 hours of oral hygiene. This is probably why new patients had greater need of treatment than long-standing residents, although this relationship was only clear in the group of edentulous patients admitted for psychogeriatric reasons, possibly because the very fact that they had no teeth made it easier to offer care and because their mental condition meant that they received special attention because of their. Nakayama et al. 22 described the protocol followed by nurses twice a day, in which they paid attention to both the hard and soft tissues. However, it must be borne in mind that the patients who participated in the study by these authors suffered from ALS, suggesting that they followed a special protocol (even though, in our opinion, such care should be considered normal). Chen et al.21 suggested that the oral hygiene of patients is the responsibility of the nursing staff, but did not specify any guidelines or the frequency concerning the same. However, the authors do mention the improvements shown following the intervention (brushing and rinsing twice a day) with regard to halitosis, plaque and the state of mucous membranes. No significant differences were observed between the three types of rinses used for the different groups (chlorhexidine, saline solution and boiled water) during the examinations carried out on the 7th day of the intervention, except for cases of halitosis, for which the best result was seen in the group that used boiled water as a rinse.
In the case of Murray et al. 23 it seems that patients only had their teeth brushed in the morning but that, due to the hygiene guidelines provided during the study (brushing with toothpaste after breakfast and dinner, and rinsing with water after the main meal, with the assistance of the staff when necessary), the oral situation of most of the patients with dysphagia improved; patients without dysphagia also improved, but not significantly so. In addition, the authors established a relationship between patient autonomy and their oral status. Improvement in the oral health of patients were recorded in the only two studies that provided oral hygiene guidelines during the studies and reassessed the oral situation of patients later 23. It should be noted that only the studies of Poisson et al. and Gerritsen et al.9, 20 were supervised by dentists (Table 4).
In general, the studies included in our systematic review 9, 20-3 found that the attention that should be given to the hygiene and oral care of patients is simply not given, and that staff, by implementing measures that are considered basic for maintaining good oral health, could improve the oral health of many people in this population.