Descriptive analysis
Of the 44 documents retained for this review, 33 (75 %) were quantitative, 6 (13.6 %) qualitative, and 3 (6.8 %) mixed methods designs. One was a field report, and one a review article (Fig. 2). The majority of studies were from industrialized countries, including two-thirds (68 %) from United States, Australia, Sweden, and Canada (Fig. 3). On average, less than three articles addressing the oral health of refugees and asylum seekers were published annually (Fig. 4) and close to half (48 %) of the studies were published from 2008 to 2014. The articles appeared in both national and international journals that covered diverse health issues, with 18 (41 %) published in dental journals. Participants in these studies came from countries in Africa, Eastern Europe and Asia. Nine studies (20 %) focused on oral health in children [2, 26–33], six of which assessed oral disease levels [28–33]. Two studies explored oral health promotion strategies [26, 27]. Two studies had exclusively female participants [2, 13]; otherwise, gender was mostly balanced.
Quality appraisal
Forty-two of the 44 articles were included in the quality appraisal. The review article [15] and field report [34] were excluded, as both did not meet the criteria for quality appraisal. Of the 33 quantitative studies included in the quality assessment, 31 were cross- sectional [3–8, 13, 14, 16, 28–31, 33, 35–50], one a cohort design [51] and one a randomised trial [46]. The quantitative studies all met the following CASP criteria: study purpose or objective, study population and age of participants, and study location were all clearly stated. However, no quantitative study included a pre-sample size calculation with power consideration. Further, only 13 of the quantitative studies tested the statistical significance of obtained results and reported p- values [3, 4, 6–8, 28, 30, 36, 39, 43, 44, 48, 52] and only three of these calculated a confidence interval around the results [29, 44, 46].
The qualitative studies (n = 6) all used qualitative description [9, 26, 53–55] except for one which used ethnography [56]. Three qualitative studies fulfilled all CASP criteria [53, 55, 56] while three did not adequately describe the relationship between the researchers and participants [9, 26, 54].
Thematic analysis
Oral health perceptions, knowledge, attitudes, practices and beliefs
Three articles focused on caregivers perceptions of the oral health of their children. All of these articles were mainly concerned with Early Childhood Caries (ECC) [2, 26, 53], and all were published in the last five years. Caregivers had solid knowledge on the causes of oral disease and oral care for their children; however, some displayed important knowledge gaps [2, 26]. For example, in one Australian study, parents only initiated oral hygiene practices for their children when they started primary school [2]. In a similar study in Canada, parents did not consider it necessary to attend routine consultations if their child did not have any oral health symptoms [26].
Across the studies with adult participants, the majority of participants perceived their oral health as poor. In some studies where participants had a positive assessment of their oral health, this self-assessment was contrary to the results of clinical examinations [3, 9, 39]. For example, in a Canadian study, participants rated their oral health highly whereas clinical examination found 80 % with untreated caries and/or periodontal disease [3]. In one Australian study, refugees from Afghanistan mentioned that they were preoccupied with issues around safety and survival and thus did not pay close attention to the severe oral health conditions they were experiencing [9].
Eight studies addressed cultural practices related to oral health and mentioned culturally relevant information [6, 8, 30, 32, 33, 53, 54, 56]. Culturally-bound oral health beliefs and practices, such as brushing with a stick [54] and extraction of anterior teeth [6, 8] can affect the oral health status of adults and their children [53]. In one American study, resettled refugees from Sudan wanted to replace their lower anterior teeth; in their country of origin, it was a normal practice to extract all lower anterior teeth [56]. Where intergenerational conflicts in oral health beliefs and practices existed, the younger population were more likely to adopt oral health practices in line with their host culture [54].
Oral disease and treatment needs
The oral diseases covered in these studies included dental caries experience [3–5, 28–30, 32–34, 36, 41–43, 48], periodontal disease [3, 5, 8, 15, 36, 42, 43, 47, 48, 57], orthodontic treatment need [37], enamel fluorosis [28], oral lesions [51], and traumatic dental injuries [4, 6, 14, 56]. Dental caries experience and periodontal status were frequently assessed in accordance with the World Health Organisation recommendations [58]. Caries was the most assessed disease: caries experience was reported in all cases as the proportion of participants with untreated caries or using the Decayed, Missing and Filled Teeth index (DMFT/dmft).
Surveys to assess oral health status and treatment needs of participants used a variety of instruments and took place in different settings: refugee camps [16, 28, 34, 37]; hospitals [3, 52]; and community organisations [2, 26]. Self-administered or interviewer-administered structured questionnaire were combined with an oral health examination to collect data in most cases. The participants in these surveys included the following: refugees from one source country [8, 54]; refugees from more than one source country [9, 36, 49]; or a mix of refugees and other vulnerable population groups [3, 27, 29, 43].
Overall, across the studies it is clear that the refugee populations had a high burden of oral disease. Although disease prevalence varied from one study to another, levels were consistently higher among refugees compared to the least privileged populations in the host countries [3, 5, 16, 29, 33, 41]. Two exceptions included rare oral health conditions: orthodontic treatment needs [37] and enamel fluorosis [28] that were similar in refugee and host populations.
Self-perceived and professionally assessed oral treatment needs were largely unmet in this population. The treatment needs varied across the studies [4, 36, 42, 44]. Treatment needs were described as immediate or urgent [5, 9, 14, 40] and included prophylaxis, restorative, extractions and rehabilitative care [50]. Treatment of dental caries (fillings, root canal therapy and tooth extractions) and periodontal disease were most urgent [16, 50].
Access to oral health care and utilisation of dental services
Refugees and asylum seekers have limited access to oral health care [9, 15, 36, 39]. Access to and utilization of oral health care services is determined by the healthcare system, society, and personal oral health beliefs and behaviours. The healthcare policy of the host country is a key element in determining access to oral healthcare. For example, in Sweden and Finland, both asylum seeker and refugee who have been granted permanent resident status can receive oral health care funded by the government [44]. In Canada, only persons recognised by the federal government as refugees before arrival in Canada can benefit from care; however this is only for emergency and basic dental care and for the first twelve months in the country [36].
Overall, there was a low rate of utilisation of oral health care services even in settings where the migrants did not need to pay for such services [44]. Further, the interval between expressed treatment need and time to completion of treatment was longer for this population compared to nationals [15, 44, 57]. For example, Zimmerman and colleagues estimated that it took double the time to complete the same treatment procedure in this population compared to Swedish nationals [44, 49]. Legislation can limit the extent of treatment this population can benefit from [36]. In refugee camps, the limited access to oral health care services is mainly due to shortage or unavailability of dental professionals [16, 34]. Under such conditions, oral health care is often limited to tooth extractions [16, 34, 50].
At the individual level, previous oral care experiences and beliefs can influence oral hygiene and practices and care seeking behaviour for the individual and his/her dependents [53]. Further, the process of migration and adapting to a new culture can influence the use of dental services [7].
Strategies to improve oral health
The strategies to improve oral health for this population can be grouped into three overlapping categories: (i) educational; (ii) service provision; and (iii) emergency training.
Studies addressing educational interventions were aimed at improving the oral health knowledge and correcting misconceptions and unhealthy beliefs [7, 26, 27, 35, 45, 46]. The educational information was provided through oral health promotion sessions or printed as handbills that were distributed to the population [7, 27, 35]. Gunaratman and colleagues found that a multilingual oral health video significantly improved the oral health knowledge of newly arrived refugees and asylum seekers in Australia [35].
In two studies, oral health care professionals provided free oral treatment on a voluntary basis or through initiatives sponsored by non-governmental organizations [52, 54]. Interventions included the use of mobile dental units to provide oral care in the community. Although the scope of treatment was limited due to challenges of moving specialized equipment, some care providers delivered extensive treatment through this approach. In one American study, replacing missing anterior teeth of participants restored esthetics as well as led to significant reduction in psychological distress among participants [52]. In additional studies, service provision combined personalized oral care instructions, and dietary counselling using tailored health promotion strategies [7, 27, 35, 53].
Basic training in oral health care was provided to selected refugees in camps located in Ghana [34] and Tanzania [16] as a means to overcome an acute shortage of dental staff. These persons in turn provided basic dental care to camp dwellers and nearby communities.