Socioeconomic inequalities in dental health services in Sao Paulo, Brazil, 2003–2008

Data have been taken from the population-based health surveys ‘Inquéritos de Saúde no Município de São Paulo’ (ISA-Capital), carried out in 2003 and in 2008, which are based on a representative sample of non-institutionalized residents from São Paulo-Brazil. They comprised two cross-sectional population-based household surveys which investigated living conditions, lifestyle, health status and use of health care services.

Both surveys were based on similar probability samples. The only differences were the number of randomly selected census tracts and the sampling errors. The two-stage sampling was performed within census tracts (primary sampling unit) and households (second stage) [16, 17]. In 2003, 60 sectors were randomly sampled from the 264 census tracts previously selected by the Brazilian Institute of Geography and Statistics (IBGE) [18] for the Brazilian Household Survey. In 2008, 70 sectors were randomly sampled from the 267 census tracts selected by the IBGE [19] for the Brazilian Household Survey. First, the census tracts were stratified according to educational level (lower, middle, higher), defined by the educational level of the head of each household, then the desired number of tracts were selected. In the second stage, households were sampled from the selected tracts in order to obtain an adequate sample size for each domain. The domains were based on gender (male, female) and age group (<1 year, 1–11 years, 12–19 years, 20–59 year, >60 years). A stratified sample of 420 respondents in each domain was approached for interview. The response rate was 78.62% in 2003 and 76.41% in 2008. A total of 3357 respondents were interviewed in 2003 and 3271 in 2008.

Data were collected through a structured questionnaire with mostly closed questions Additional file 1. All interviews were conducted by trained staff who were supervised throughout the study. For quality control, another interview by phone or face to face was carried out in a random sample of 5% of the interviews. The Research Ethics Committee of the University of São Paulo approved the design and conduct of the study. The design and characteristics of ISA-Capital 2003 and ISA-Capital 2008 have been described in detail in: http://​www.​fsp.​usp.​br/​isa-sp.

The following demographic factors were examined: age (20–59 years and 60 or over) and gender. The present study examines adults and the elderly. There is a reduced supply of services and considerable inequalities in the use of dental services by these groups [2]. We are not studying children or teenagers since they have different oral needs and require specific oral policies with more focus on the prevention of oral diseases [4].

The socioeconomic factors studied were: ethnicity (Caucasian, when respondent reported white, and non-Caucasian, when the respondent reported black/mixed/other), education (0–3 years of study, 4–7, 8–11 and 12 or more), household income (≤1 minimum legal wage (mlw), >1 to 2.5 mlw, ≥ 2.5 to 6 mlw, ≥6 mlw), housing condition and having a private health plan. Assuming that ethnicity might be a basis for social differentiation in Brazil [20] we included ethnicity as a socioeconomic indicator. The minimum legal wage (monthly) in 2003 was R$240.00 ($68.00^a) and in 2008 R$415.00 ($233.00^b). Monthly family income per head was not adjusted for inflation but was used to rank each individual at each year along the income distribution and is treated as a relative measure of social position in each time period. Housing condition was divided into adequate or inadequate; it was considered adequate when the house had piped water from the public network, had electric lighting, was connected to the sewer system and had an internal lavatory, and when the street had street lighting. If any of these factors were missing, the housing was considered inadequate.

The samples ISA-Capital 2003 and ISA-Capital 2008 were weighted to compensate for the different selection probabilities. The weighting was performed at an individual level, the sectors were weighted for the use of different sampling fractions in the strata. The trends from 2003 to 2008 regarding socioeconomic characteristics and use were analyzed by Chi-square tests. Crude and adjusted (by age and gender) logistic regressions were used to explore the associations between socioeconomic factors and the different measures related to use. The dental health service use difference between 2003 and 2008 was analyzed by interactions of time and each socioeconomic factor. The interactions in the logistic regression model were tested for their departure from multiplicativity. The reasons for not seeking a dentist in relation to educational level and income were analyzed by Chi-square tests. Significance was judged with α = 0.05. Analyses were carried out in Stata 12.0 using the survey package, which considers the effects of complex study design and allows the different weights of the observations to be embedded.

The deeper knowledge about inequalities in use provided by this study is important to facilitate the formulation of appropriate public policies and to provide better understanding of the potential barriers to reducing inequalities in health care services use. However, some limitations should be borne in mind when interpreting the results of this study. Due to small number of people who reported dental service use from public sector (5.80% in 2003 and 6.82% in 2008), some results were relatively imprecise. Since the questionnaire does not have questions about dental care needs, we were not able to adjust for different needs across socioeconomic groups. However, by adjusting for age and gender, we did try to minimize bias due to need across all socioeconomic groups. Although there are different private health plans, we were not able to analyze the quality of these plans; thus we were not able to discuss the quality of dental health care provided by the private sector and compare it with that provided by the public sector in this study. This would be very interesting since there may be large quality differences between services delivered to different socioeconomic groups. Finally, ISA-Capital 2008 does not specifically inquire whether the use of dental health services was due to the newly implemented national oral health policy and we can therefore not know for sure whether the observed increase of dental health service use is specifically due to this policy. There could be other changes in society that have biased the results. However, since the Smiling Brazil program was very important in Brazil to increase access to dental health services and there were large changes related to dental care services within the timeframe of the study, we are confident that this program at least partly contributed to the observed changes.

Previous studies have shown that the use of dental health services is more common in more affluent socioeconomic groups [14, 21, 22]. This was confirmed in our study since we found that the use of dental health services was greater in those who had higher income, higher education, adequate housing conditions and who were Caucasian.

Additionally, our study found that, in 2008, the use of dental health services was greater among those with a private health care plan than those in the population who do not have a private health care plan and thus rely on public sector coverage. Almost half the population in São Paulo had a private health plan in 2008 [9]. In general, people with a private health plan have higher education, higher income, more often have adequate housing condition and are more often Caucasian [9]. These socioeconomic disparities in the distribution of private health plans can also been seen in the different regions of São Paulo; in the more affluent regions, a large majority of the population is covered by private health plans while in the more deprived areas, almost everyone relies on public health care coverage [9, 23]. Nowadays, in more deprived areas in São Paulo, there are private dental health plans specifically for the low-income population, which is increasing access to dental health care by this population [2, 9, 23].

The lower socioeconomic groups were much more often covered by the public sector than the higher socioeconomic groups and the use of by public sector scarcely increased from 5.8% in 2003 to 6.8% in 2008. This confirms the need for expansion of the existing national oral health policy, as reported in the study by Manfredini et al. [2]. According to Wallace and MacEntee [15], there is a poor fit between private practice dentistry, public dental benefits and the oral health needs of low-income communities. In countries with public coverage on dental health services, there are less socioeconomic inequalities in use of dental health services, comparing to countries without public coverage [24]. However, despite the increase in access and public coverage in Brazil, inequalities in the use of dental care still persist in Sao Paulo, which could indicate that further improvements in the care and coverage system are necessary.

The inequalities in use of dental care services may also reflect socioeconomic inequalities in dental health in Brazil and particularly in São Paulo. Our study shows that the reasons ‘not having teeth’ and ‘financial difficulties’ were reported more often by lower educated and lower income respondents. The reason ‘did not think the dental care was necessary’ was more often reported in higher income respondents in 2003 and in 2008. The high percentage of toothless people in this population of adults and the elderly, especially in the lower socioeconomic groups, may indicate historical inequalities in dental care use; these people may have needed to use dental health service in the past but did not have access at that time and this may have contributed to the loss of teeth. In the past, tooth loss was often believed to be a natural phenomenon [25]. However, today it is seen as a something that can and should be prevented by health policies [25]. Some studies have explored the trends in social inequality in tooth loss [26, 27] and found high percentages of toothless people in lower socioeconomic groups, which confirms the results of the present study.

There was an increase of use of dental health services between 2003 and 2008 in São Paulo: from 46.8% in 2003 to 55.4% in 2008. The increase followed a trend: in 1990, use of dental health services in the previous 12 months in the São Paulo metropolitan area was 31.8% [28]. The increase of dental service use between 2003 and 2008 was significant across all socioeconomic groups, including the lowest socioeconomic groups. The increasing of income of the population and the increase in private dental health plans may have contributed to the increase in dental service use. The implementation of the Smiling Brazil program may have contributed to the slight increase in dental service use from public sector in the lowest income group, the non-Caucasians and the population with inadequate housing condition between 2003 and 2008. However, these increases were not significant and we did not see an increase in use from public sector in the lowest educational groups. Compared to other policies, such as the immunization program, the Smiling Brazil program is new and in a period of expansion. Its implementation indicates numerical expansion and extended health care coverage [5] and improved the organization and planning of oral health services [4]. The dental care use has increased in all socioeconomic groups, including the lower socioeconomic groups but there were persistent socioeconomic inequalities in the use of dental health services in 2003 and 2008, despite the aim of the oral health policy to decrease inequalities [5] and the favorable indications regarding the effectiveness of this policy in reducing disparities in oral health [29]. The lack of significant improvements in decreasing inequalities may be partly due to the small window between the implementation (2003–2006) and our time of measurement (2008). However, since 2008, according the Brazilian National Health Survey [30], the frame did not change: only 53.9% used dental services in the previous 12 months in São Paulo state in 2013 and was higher in higher education groups (73.4%) compared to lower education groups (46.3%). Also, Scherer and Scherer [31] analyzed oral health work changes in primary health care after a decade of the “Smiling Brazil” Program and found very few changes in oral health work. The population-based health survey ISA-Capital 2015¹ is almost completed and will provide monitoring on access and use of dental health services in São Paulo city.

Potential problems of the policy may include a lack of regular supply of materials to health facilities and maintenance of dental equipment, in addition to the inability to pay the full contract personnel in health facilities [32]. Structural problems in the Brazilian health system such as the limited funding [3, 32], the disjunction between the public and private sectors [32] and the fragmentation of policies represent challenges to the implementation of universal access to dental health services from the public sector and the decrease of inequalities in dental health service use.