Dental conditions associated with preventable hospital admissions in Australia: a systematic literature review

Background Over the past two decades, there has been a decrease in dental diseases in Australia; however, the number of preventable dental hospital admissions has not diminished. This review reports on the factors associated with preventable dental hospital admissions in Australia. Methods A search of five databases was conducted using Medical subject headings/Emtree terms and Index terms. All original studies, published between January1965 and March 2018 in English, based on the Australian population, and examining the prevalence of oral conditions as a cause for emergency department presentations and hospital admissions were included. The mixed method appraisal tool was used to evaluate the included studies. Results Eleven cross-sectional studies met inclusion and exclusion criteria. All the studies, except one from Tasmania, were from Western Australia. The most common reasons for preventable dental hospital admissions were dental caries, followed by embedded or impacted teeth. Malignant neoplasms were reported as main causes of preventable dental hospital admissions in the older population. Conclusions Most studies on preventable dental hospital admissions were from one Australian state (Western Australia). Further research is required to determine the national prevalence and incidence of preventable dental hospital admissions. A periodic audit of preventable dental hospital admission data is needed for delivery of a fair and effective dental services.


Background
Potentially Preventable Hospital Admissions (PHA) are defined as conditions that could be avoided for hospitalisation if timely management and primary care had been provided [1]. PHA is a health system performance indicator of the accessibility to and effectiveness of primary health care, providing information on socioeconomic and racial disparities in access to primary health care, health inequalities and literacy, and the prevalence of health conditions in the community [1,2]. Dental conditions, which are categorised as acute medical conditions, are one of the components of PHA according to the National Healthcare Agreement 2016 between the State and Commonwealth Governments of Australia [3].
There has been marked reductions in dental conditions in adults (tooth loss and dental decay) observed in two national surveys of adult oral health completed in 1987-88 and 2004-06 [4]. The reduction of dental caries in adults could be a result of reduction in tobacco consumption, adoption of better oral hygiene practices and public health interventions (water fluoridation and interventional procedures) [5], and provision of adult dental benefit schemes [6]. Time trend report suggests that dental caries experience among children 5-6 years and > 12 years declined significantly from 1970s until the late 1980s. However, the latest National Child Oral Health Survey (NCOHS) 2012-14 showed that the dental caries experience has been in fluctuation since 1987-88 survey, suggesting no serious decline in the dental caries experience in between the two time points [7].
In contrast to the above findings, the Preventable Dental Hospital Admissions (PDHA) have not diminished. Dental conditions contribute to 9 % of total PHA in Australia [8]. There were 57,955 cases of dental conditions leading to PHA in 2007-2008, which had increased to 63,456 in 2013-2014 [9].
Hence, to develop a sound understanding of dental causes that contributes towards PDHA, it is important to map the factors that may lead to preventable PDHA in the Australian population. This study aimed to synthesise the literature on the factors that lead to PDHA in Australia. This review will assist policy makers and oral health practitioners to understand the causes of PDHA and find methods to prevent PDHA, thereby reducing costs associated with PDHA.

Review question
The Population Intervention Comparator Outcome (PICO) criteria and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to devise and construct the review question. The review question was "What are the main causes of PDHA in Australia?"

Scope of review and search terms
Published results of studies examining the prevalence of oral / dental conditions as a cause for emergency department presentations and hospital admissions were reviewed. Articles were retrieved using searches performed in PubMed/MED-LINE, EMBASE, Web of Science, CINAHL and Google Scholar. The search terms used in the review were generated using the National Library of Medicine Medical Subject Headings (MeSH) terms, Emtree terms and free text terms. Table 1 shows the search terms used in the systematic review.

Inclusion and exclusion criteria
All original studies addressing the research question, published between January 1965 and March 2018 in English and based on the Australian population, including both adults and children, were included in the review. Studies were excluded if they were conducted outside Australia or were reviews, conference papers, short communications, letters or textbooks.

Quality appraisal
The Mixed Method Appraisal Tool (MMAT) was used for quality appraisal of the selected articles [10]. All of the articles included in the study were cross sectional studies, which fall under quantitative non-randomised study. Two independent reviewers (A.A. and H.H.) assessed the six criteria designed to evaluate the quality of methodology and overall quality score was calculated. All of the articles fulfilled methodological quality criteria as per MMAT. Table 2 shows the criteria and the summary of MMAT.

Selection of studies
The literature search and removal of duplicates identified 1856 papers as eligible for inclusion in the review. These studies underwent title and abstract screening independently by two reviewers (A.A and S.K), resulting in selection of 86 studies for full text review. After the full text review, 11 studies met the inclusion and exclusion criteria and were included in the table of synthesis (Table 3). The PRISMA diagram shows the flowchart of selection of studies in the systematic review (Fig. 1).

Study characteristics
All the studies were from Western Australia (WA) except one study, which was based in Tasmania [11]. Of all the studies, there was one study on age ranges 0-2 years [12], two among 0-5 years [13,14], one in 0-14 years [15], two in 0-17 years [16,17], two in 18 years and above [18,19], one in 65 years and above [20] and two from all age groups [11,21]. All studies were cross-sectional analysis.
Of the WA studies, six used data from Western Australian Hospital Morbidity Data System (WAHMDS) [15,16,[18][19][20][21]. Two used data collectively from multiple sources: WAHMDS, WA Maternal and Child Health Database for children born in WA, and the WA Intellectual Disability Database and Midwives Notification System Registrar General Database [13,14]. One study used data from WAHMDS, WA Maternal and Child Health Database for children, and WA Intellectual Disability Database [12]. One used data from the Health Department of WA database [17]. The study in Tasmania has reported on patients presenting with dental conditions to the Emergency Department of the Royal Hobart Hospital [11].
In all studies except one [11], the definition used to identify the PDHA was based on the International Classification of Diseases (ICD), however the ICD versions varied across the studies based on the year published and the update of the classification. Four used ICD 9 [12][13][14]17], and six used ICD 10 [15,16,[18][19][20][21]. The Tasmanian study did not report the classification system used to identify the dental causes stating that patients were allocated a code referring to their main complaint [11].

Dental reasons for PHA
Five out of the eleven studies included in the review identified diseases of the hard tissues of teeth particularly dental caries as the most common cause leading to PDHA in the Australian population [12][13][14][15]21]. The second most common cause of PDHA, reported in three studies, was embedded and impacted teeth [16,18,19]. One study listed both dental caries and embedded and impacted teeth as the main cause of PDHA [17]. Malignant neoplasms were reported as main causes of PDHA in one study which investigated PDHAs in the older population [20]. In the Tasmanian study, dental abscesses were the main causes of PDHA [11].

Discussion
A total of 11 studies were included in this systematic review designed to map the PDHA in the Australian population. Other than the study in Tasmania [11], all the studies were from one state in Australia, WA. This indicates that further research is needed to ascertain the PDHAs across all states and territories of Australia to understand the causes of PDHA, and to find methods to prevent PDHA thereby reducing costs associated with PDHA.
The most common reasons for PDHA across age ranges were dental caries followed by embedded or impacted teeth. Prevention of embedded or impacted teeth is difficult and treatment focuses on their identification and removal. Unfortunately, incidence of impacted teeth may increase as fewer teeth are lost from dental diseases. Preventively however, the high incidence of PDHA for dental caries is a concern. Proper oral hygiene, low sugar consumption, fluoride applications and routine dental visiting are strategies to prevent dental caries [22]. In addition, other preventative strategies recommended by the World Health Organisation [23] include water fluoridation, using fluoride toothpaste and salt fluoridation. There is a need to better prevent and reduce the incidence of dental caries as this will ultimately help to decrease PDHA.
In Australia the prevalence of dental caries is 25.5% in adults and 45-60% in children [24]. Low education, low income, rural location, having no insurance, risk behaviours such as smoking and alcohol, poor dental visiting behaviour and oral hygiene practices, and no fluoride in water are important risk factors associated with dental caries and, if not addressed, subsequent hospitalisation [25]. Similar findings have been reported in New Zealand. In a 20-year review of potentially preventable admissions to public hospitals for dental care, data suggest that dental caries is the most common cause for PDHA in New Zealand [26].
A preventable hospital admission is a measure of health care accessibility and effectiveness [3]. Hospital admissions due to dental conditions indicate the burden of dental conditions and their associated costs on the health care system [19]. Strategies that could reduce PDHA include (i) preventive dental practices such as water fluoridation and interventional procedures (fissure sealants and fluoride varnish) in public and private healthcare settings [27]; (ii) improved and better access to dental care (child and adult dental benefit schemes) across urban, rural and remote communities [6]; and (iii) oral health literacy and education programs across the population with the use of social media, education and primary health care network platforms. Figure 2 illustrates the schematic representation of risk factors and preventive strategies to prevent PDHAs. In the Tasmanian study, dental abscesses were the main causes of PDHA [11]. This makes sense because this study investigated dental emergencies presenting to a Royal Hobart hospital emergency department, where people could be expected to present with pain or infections. Important to note was that 68% of all the presentations to the emergency department were after hours, when dentists are unavailable. Hence it is important to consider an after hour dental service for any emergency dental presentation.
Malignant neoplasms were reported as a leading causes of PDHA in the older population in one of the studies [20]. This also does not come as a surprise because the research in this study was limited to people over the age of 65, the age group with the highest incidence of neoplasms [28,29].
PDHA were higher in indigenous population and aboriginal status [14,18,20]. Low education, lower annual income, rural and remote location, having no dental insurance, poor access to care, lack of transportation and unemployment are the associated factors with indigenous people [24]. As oral conditions are associated with systemic health conditions such as obesity and cardiovascular disease, unawareness of maintaining proper oral health by socially disadvantaged people might have negative impacts on their general health [30,31]. This study will help policy makers to prioritise the preventive approach to address the oral health of socially disadvantaged groups and consequently minimise the PDHA among this group.     The main limitation of this systematic review was the small number of published studies investigating PDHAs in Australia. Of the included studies, almost all were from one state of Australia indicating that further research is needed in PDHA across Australia. Databases with this potential information are available in each state. Investigators need to be encouraged to access, analyse and publish this information as an important preventative and public health issue. There was a high level of heterogeneity observed among the 11 included studies. This limited the authors from conducting a meta-analysis. The studies had a wide variation among two main factors: (i) age; and (ii) the ICD definitions used to define dental conditions that could have been employed in a meta-analysis to predict the effect size of the PDHA across the studies.
PDHA are expensive and they may be reduced by the impartial distribution of public dental clinics [32]. The extension of dental services into areas currently not receiving ICPC International Classification of Primary Care, AR-DRD Australian Refined Diagnosis Related Groups, ICD International Classification of Diseases IRSD Index of relative socio economic disadvantage, ARIA Accessibility/Remoteness Index of Australia, DRG Diagnostic Related Group, SEIFA Socio-Economic Indexes for Areas, WA Western Australia dental care will not only reduce cost associated with PDHA, but will improve access to oral health care. A periodic audit of PDHA is needed to mobilise government policy-makers and dental service providers for delivery of a fair and effective dental service for all Australians throughout their life course.

Conclusion
Dental caries is the most common cause of PDHA based on the included studies. As most of studies included are from WA, there is the need of Australia wide research to represent real scenario of PDHA.