Abstract

The aim of this study was to investigate the factors associated with public dental care use by adults in the State of São Paulo, Brazil. A cross-sectional study was conducted with a representative sample of adults aged 35 to 44 years using data from the 2015 Epidemiological Survey of the Oral Health Status of the Population of the State of São Paulo (SBSP-2015). Multivariate logistic regression was performed using variables based on a model proposed by Andersen for predicting access to public dental services. Results: 3,421 (59.9%) adults visited private services and 2,288 (40.1%) visited public services. Prevalence of the use of public dental services was greatest among women (41.8%) and adults with a lower education level (50.2%). Being non-white (OR = 1.32, 95% CI: 1.16, 1.50), lower household income (OR = 2.37, 95% CI: 2.11, 2.65), having had toothache (OR = 1.60, 95% CI: 1.39, 1.83), and need for endodontic treatment (OR = 1.44, 95% CI: 1.12, 1.85) were associated with public dental service use. Predisposing, enabling, and need factors were associated with public dental care use.

Key words
Adult; Access to health services; Oral health; Cross-sectional studies

Introduction

Health service use is the functioning core of health systems and recent studies have shown inequalities in dental service use among adults¹1 Gilbert HG, Duncan RP, Bruce V. Determinants of dental care use in dentate adults: six monthly use during a 24-month period in the Florida Dental Care Study. Soc Sci Med 1998; 47(6):727-737.

2 Tennstedt SL, Brambilla DL, Jette AM, McGuire SM. Understanding dental service use by older adults socio behavioral factors vs. need. J Public Health Dent 1994; 54(4):211-219.

3 Nguyen L, Häkkinen U. Choices and utilization in dental care Public vs. private dental sectors, and the impact of a two-channel financed health care system. Eur J Health Econ 2006; 7(2):99-106.

4 Luzzi L, Spencer AJ. Public dental service utilization among adults in South Australia. Aust Dent J 2009; 54(2):154-160.

5 Brennan DS, Luzzi L, Roberts-Thomson KF. Dental service patterns among private and public adult patients in Australia. BMC Health Serv Res 2008; 3:1-8.

6 Hancock M, Calnan M, Manley G. Private or NHS General Dental Service care in the United Kingdom? A study of public perception and experience. J Public Health Med 1999 Dec; 21(4):415-20.

7 Ajayi DM, Arigbede AO. Barriers to oral health care utilization in Ibadan, South West Nigeria. Afr Health Sci 2012; 12(4):507-513.

8 Locker D, Maggirias J, Quiñonez C. Income, dental insurance coverage, and financial barriers to dental care among Canadian adults. J Public Health Dent 2011; 71(4):327-334.^-99 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.. Access to dental services is a complex issue, particularly in countries like Brazil, which follows a universal healthcare model and where access to health services is a right for all citizens²2 Tennstedt SL, Brambilla DL, Jette AM, McGuire SM. Understanding dental service use by older adults socio behavioral factors vs. need. J Public Health Dent 1994; 54(4):211-219.^,33 Nguyen L, Häkkinen U. Choices and utilization in dental care Public vs. private dental sectors, and the impact of a two-channel financed health care system. Eur J Health Econ 2006; 7(2):99-106.^,55 Brennan DS, Luzzi L, Roberts-Thomson KF. Dental service patterns among private and public adult patients in Australia. BMC Health Serv Res 2008; 3:1-8.

6 Hancock M, Calnan M, Manley G. Private or NHS General Dental Service care in the United Kingdom? A study of public perception and experience. J Public Health Med 1999 Dec; 21(4):415-20.

7 Ajayi DM, Arigbede AO. Barriers to oral health care utilization in Ibadan, South West Nigeria. Afr Health Sci 2012; 12(4):507-513.

8 Locker D, Maggirias J, Quiñonez C. Income, dental insurance coverage, and financial barriers to dental care among Canadian adults. J Public Health Dent 2011; 71(4):327-334.^-99 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100..

In Brazil, a nationwide survey conducted in 2010 showed that the prevalence of the need for dental treatment among adults was 75.2% and that 38.3% of respondents used public dental services¹⁰10 Brasil. Ministério da Saúde (MS). SB Brasil 2010: pesquisa Nacional de Saúde Bucal: Resultados Principais. Brasília: MS; 2012., while a study with adults living in Minas Gerais undertaken in 2012 reported that 31.8% of respondents used public dental services¹¹11 Minas Gerais. Secretaria de Estado de Saúde (SES). Pesquisa das condições de saúde bucal da população mineira - Resultados principais. Belo Horizonte: Editora Autêntica; 2013..

To tackle inequities in access to oral healthcare, the Brazilian government introduced oral health teams (OHT) into the Family Health Strategy (FHS) and reshaped the National Oral Health Policy (NOHP) to expand and decentralize the healthcare system, increasing the provision of public specialist and non-specialist dental services⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,1212 Pucca Jr GA, Gabriel M, Araújo ME, Almeida FCS. Ten Years of a National Oral Health Policy in Brazil: Innovation, Boldness, and Numerous Challenges. J Dent Res 2015; 94(10):1333-1337.. However, inequities persist and studies indicate that dental service use is influenced by interacting individual and contextual factors, including the need for treatment and organization of dental services¹1 Gilbert HG, Duncan RP, Bruce V. Determinants of dental care use in dentate adults: six monthly use during a 24-month period in the Florida Dental Care Study. Soc Sci Med 1998; 47(6):727-737.

2 Tennstedt SL, Brambilla DL, Jette AM, McGuire SM. Understanding dental service use by older adults socio behavioral factors vs. need. J Public Health Dent 1994; 54(4):211-219.

3 Nguyen L, Häkkinen U. Choices and utilization in dental care Public vs. private dental sectors, and the impact of a two-channel financed health care system. Eur J Health Econ 2006; 7(2):99-106.^-44 Luzzi L, Spencer AJ. Public dental service utilization among adults in South Australia. Aust Dent J 2009; 54(2):154-160.^,88 Locker D, Maggirias J, Quiñonez C. Income, dental insurance coverage, and financial barriers to dental care among Canadian adults. J Public Health Dent 2011; 71(4):327-334.^,1313 Manhães ALD, Costa AJL. Acesso a e utilização de serviços odontológicos no Estado do Rio de Janeiro, Brasil, em 1998: um estudo exploratório a partir da Pesquisa Nacional por Amostra de Domicílios. Cad Saude Publica 2008; 24(1):207-218.

14 Matos DL, Lima-Costa MFF, Guerra HL, Marcenes W. Projeto Bambuí: estudo de base populacional dos fatores associados com o uso regular de serviços odontológicos em adultos. Cad Saude Publica 2001; 17(3):661-668.

15 Peres KG, Peres MA, Boing AF, Bertoldi AD, Bastos JL, Barros AJD. Redução das desigualdades sociais na utilização de serviços odontológicos no Brasil entre 1998 e 2008. Rev Saude Publica 2012; 46(2):250-258.

16 Pinheiro RS, Torres TZG. Uso de serviços odontológicos entre os Estados do Brasil. Cien Saude Colet 2006; 11(4):999-1010.

17 Gomes AMM, Thomaz EBAF, Alves MTSSB, Silva AAM, Silva RA. Fatores associados ao uso dos serviços de saúde bucal: estudo de base populacional em municípios do Maranhão. Brasil. Cien Saude Colet 2014; 19(2):629-640.

18 Baldani MH, Antunes JLF. Inequalities in access and utilization of dental services: a cross-sectional study in an area covered by the Family Health Strategy. Cad Saude Publica 2011; 27(Supl. 2):272-283.

19 Pereira CRS, Patrício AAR, Araújo FAC, Lucena EES, Lima KC, Roncalli AG. Impacto da Estratégia Saúde da Família com equipe de saúde bucal sobre a utilização de serviços odontológicos. Cad Saude Publica 2009; 25(5):985-996.

20 Araújo CS, Lima RC, Peres MA, Barros AJD. Utilização de serviços odontológicos e fatores associados: um estudo de base populacional no Sul do Brasil. Cad Saude Publica 2009; 25(5):1063-1072.^-2121 Camargo MBJ, Dumith SC, Barros AJD. Uso regular de serviços odontológicos entre adultos: padrões de utilização e tipos de serviço. Cad Saude Publica 2009; 25(9):1894-1906..

It is therefore essential to investigate the type of dental service used by the adult population, given that health services should be structured to meet demand for dental care⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,1313 Manhães ALD, Costa AJL. Acesso a e utilização de serviços odontológicos no Estado do Rio de Janeiro, Brasil, em 1998: um estudo exploratório a partir da Pesquisa Nacional por Amostra de Domicílios. Cad Saude Publica 2008; 24(1):207-218.^,1515 Peres KG, Peres MA, Boing AF, Bertoldi AD, Bastos JL, Barros AJD. Redução das desigualdades sociais na utilização de serviços odontológicos no Brasil entre 1998 e 2008. Rev Saude Publica 2012; 46(2):250-258.^,1717 Gomes AMM, Thomaz EBAF, Alves MTSSB, Silva AAM, Silva RA. Fatores associados ao uso dos serviços de saúde bucal: estudo de base populacional em municípios do Maranhão. Brasil. Cien Saude Colet 2014; 19(2):629-640.^,2020 Araújo CS, Lima RC, Peres MA, Barros AJD. Utilização de serviços odontológicos e fatores associados: um estudo de base populacional no Sul do Brasil. Cad Saude Publica 2009; 25(5):1063-1072.. Research on dental service use can provide important insights to help determine the profile of health service users, understand the reasons why people seek care, and assess oral health status, central aspects of health policy and planning. However, a better understanding of public dental service use among adults is required³3 Nguyen L, Häkkinen U. Choices and utilization in dental care Public vs. private dental sectors, and the impact of a two-channel financed health care system. Eur J Health Econ 2006; 7(2):99-106.^,99 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,2121 Camargo MBJ, Dumith SC, Barros AJD. Uso regular de serviços odontológicos entre adultos: padrões de utilização e tipos de serviço. Cad Saude Publica 2009; 25(9):1894-1906.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544..

This study therefore investigated the factors associated with public dental service use among adults living in the State of São Paulo.

Methods

A cross-sectional population-based study was conducted with a representative sample of adults living in the State of São Paulo.

Located in the Southeast Region of Brazil and made up of 645 municipalities, the State of São Paulo is Brazil's most populous state. In 2016, the state had an estimated population of more than 44 million inhabitants (22% of the Brazilian population), per capita income of R$1,723, Human Development Index of 0.783 (high), life expectancy at birth in 2015 of 77.8 years, and literacy rate of 95.9%²³23 Instituto Brasileiro de Geografia e Estatística (IBGE). Censo Demográfico 2010. Estimativa população para o ano de 2016 e dados sócio-demográficos do Estado de São Paulo [Internet]. Rio de Janeiro: IBGE; 2016 [citado 2017 Maio 18]. Disponível em: http://ibge.gov.br/estadosat/perfil.php?sigla=sp
http://ibge.gov.br/estadosat/perfil.php?... .

This study used data from the 2015 Epidemiological Survey of the Oral Health Status of the Population of the State of São Paulo (SBSP, acronym in Portuguese). The survey used two-stage cluster sampling with probability proportional to size, taking into account sampling weights and design effect in the respective sampling stages. The correction factor for the weighted analysis was calculated using the inverse probability of selection. The state was stratified into six Macro Regions called domains²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016.. Thirty-three municipalities (primary sampling units) were randomly selected in each domain, with the exception of Macro Region I (Metropolitan Region of the Capital), where 12 municipalities were selected in addition to the capital²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016.. Two census tracts (secondary sampling units - SSU) were then randomly selected in each selected municipality using probability proportional to the size of the tract population. In Macro Region I, 36 SSUs were selected, corresponding to 18 collection points. All households within the selected tracts were visited to locate adults in the relevant age group²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016..

The age group considered by the present study was 35 to 44 years. The World Health Organization recommends this age for epidemiological surveys because it allows for the assessment of oral health and the general effects of treatment provided, thus providing a good measure of the overall oral health status of the adult population²²22 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.^,2424 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016..

The reference standard used to calculate sample size was prevalence of dental caries, as used by recent national surveys and because tooth decay is the leading oral health problem¹⁰10 Brasil. Ministério da Saúde (MS). SB Brasil 2010: pesquisa Nacional de Saúde Bucal: Resultados Principais. Brasília: MS; 2012.^,2424 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016.. In addition, we used the calculation basis from data on periodontal status and use of and need for a dental prosthesis for the Southeast Region gathered by the National Oral Health Survey (SB Brasil 2010)¹⁰10 Brasil. Ministério da Saúde (MS). SB Brasil 2010: pesquisa Nacional de Saúde Bucal: Resultados Principais. Brasília: MS; 2012.. The sample size formula was adjusted for the size of the reference adult population of each municipality based on data from the Population Projection System run by Fundação SEADE, resulting in a final sample of 6,051 adults²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016..

Data was collected in each SSU (census tract) using the exhaustive method to obtain the minimum sample size, where all households along a planned route are visited and all persons from the relevant age group present are examined²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016.. Data collection is finalized when the minimum number of adults is obtained²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016..

Individuals who had never visited the dentist or were unable to recall the last time they visited the dentist and those who reported that they had used other dental services were excluded⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544..

The data was collected by teams of dental surgeons and dental assistants who received training in consensus methods. Cohen's kappa coefficient was calculated in the final round and weighted for each examiner, age group, and problem, adopting a minimum acceptable value of 0.65²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016..

The dependent variable was type of dental service used in the last visit: public or private/health plan. Independent variables were selected based on the behavioral model of health services use revisited by Andersen (1995) and used by previous studies of the use of dental services⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,1717 Gomes AMM, Thomaz EBAF, Alves MTSSB, Silva AAM, Silva RA. Fatores associados ao uso dos serviços de saúde bucal: estudo de base populacional em municípios do Maranhão. Brasil. Cien Saude Colet 2014; 19(2):629-640.^,2121 Camargo MBJ, Dumith SC, Barros AJD. Uso regular de serviços odontológicos entre adultos: padrões de utilização e tipos de serviço. Cad Saude Publica 2009; 25(9):1894-1906.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.^,2525 Andersen RM. Revisiting the behavioral model and access to medical care: does it matter? J Health Soc Behav 1995,36(1):1-10.. According to this model, health service use is a function of interacting individual and contextual characteristics, the health system, and past use of services²⁵25 Andersen RM. Revisiting the behavioral model and access to medical care: does it matter? J Health Soc Behav 1995,36(1):1-10.. The author divides the determinants into three groups: predisposing factors (individual and sociodemographic characteristics), enabling factors (income and health service characteristics), and need factors (perceived health status and health needs)⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,2121 Camargo MBJ, Dumith SC, Barros AJD. Uso regular de serviços odontológicos entre adultos: padrões de utilização e tipos de serviço. Cad Saude Publica 2009; 25(9):1894-1906.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.. The predisposing variables were: age (35 to 45 years); sex (male and female); education level (≤ 9 years and ≥ 10 years of study); self-declared skin color (white and non-white, black, brown, yellow, and indigenous); and whether the respondent had had toothache (yes, no). The enabling variables were: household income (≤ R$1,500, R$1,501 to R$2,500, and ≥ R$ 2,501); last dental visit (less than a year, more than a year); reason for the last dental visit (check-up, treatment/pain/extraction); and satisfaction with treatment (satisfied, indifferent/unsatisfied). The need variables were: need for endodontic treatment (yes, no); need for upper or lower dental prosthesis (yes, no); and satisfaction with oral health status/teeth (satisfied, indifferent/unsatisfied). The variables were dichotomized using the median as a parameter.

The prevalence of public and private dental service use was calculated for each independent variable and a crude analysis was performed using Pearson's chi-squared test to test the strength of association. Since a complex sample design was employed, the 95% confidence interval was calculated for the prevalence rates weighted using the census tract densification rate, number of respondents/examined individuals, and non-response rate. This information is essential for data correction, since it allows for weighting within census tracts and macro regions. Variables with a p-value of < 0.20 were then included in the adjusted logistic regression model. The odds ratios (OR) and its 95% confidence interval were calculated. It is important to note, however, that the OR calculated using this technique may overestimate associations and therefore the possibility of overestimation cannot be ruled out¹⁴14 Matos DL, Lima-Costa MFF, Guerra HL, Marcenes W. Projeto Bambuí: estudo de base populacional dos fatores associados com o uso regular de serviços odontológicos em adultos. Cad Saude Publica 2001; 17(3):661-668.. The variables with significance level of < 0.05 were maintained in the final model. Since sex, household income, and education level are considered confounding variables¹⁴14 Matos DL, Lima-Costa MFF, Guerra HL, Marcenes W. Projeto Bambuí: estudo de base populacional dos fatores associados com o uso regular de serviços odontológicos em adultos. Cad Saude Publica 2001; 17(3):661-668., three alternative logistic models were constructed: the first including the variables education level and sex, the second with household income and sex, and the third with education level and household income¹⁴14 Matos DL, Lima-Costa MFF, Guerra HL, Marcenes W. Projeto Bambuí: estudo de base populacional dos fatores associados com o uso regular de serviços odontológicos em adultos. Cad Saude Publica 2001; 17(3):661-668.. The first model is presented because it showed the greatest strength of association with public dental service use¹⁴14 Matos DL, Lima-Costa MFF, Guerra HL, Marcenes W. Projeto Bambuí: estudo de base populacional dos fatores associados com o uso regular de serviços odontológicos em adultos. Cad Saude Publica 2001; 17(3):661-668.. However, statistically significant associations between household income and sex and public dental service use were also shown in the other two models. Statistical analysis was performed using the program PSPP for Windows Version 0.8.

The research project was approved by the Research Ethics Committee at the Piracicaba School of Dentistry (number 111/2015) and conducted in accordance with Resolution 466 (12 December 2012) regarding research involving human subjects issued by the National Health Council. Each individual examined under the study signed an informed consent form²⁴24 Pereira AC, Frias AC, Vieira V. Pesquisa Estadual de Saúde Bucal. - SB São Paulo 2015. Águas de São Pedro: Livronovo; 2016..

Results

Three hundred and forty-two (5.65%) of the 6,051 respondents were excluded, resulting in a final total of 5,709 (94.3%) study participants, of which 2,288 (40.1%) used public services on their last dental visit and 3,421 (59.9%) used private services/health plan.

The prevalence rates of public and private dental service use for the predisposing variables are presented in Table 1. Adults in the younger age group (51.2%), women (68.0%), adults with a higher education level (50.5%), whites (62.4%), and those who had not had toothache (68.5%) visited the dentist more often. The prevalence of public service use was highest in adults who had had toothache (51.1%), followed by those with a lower education level (50.2%), and non-whites (46.4%), while the prevalence of use of private services/health plan was highest among adults with a higher education level (69.9%), followed by those who reported not having had toothache (65.1%), whites (63.7%), men (63.5%), and adults in the older age group (60.8%).

Dental service use was greatest in adults with lower household income (41.3%), those who had visited the dentist within the last year (56.1%), those where the reason for visiting the dentist was treatment/pain/extraction (75.0%), and those who were satisfied with last treatment received (86.0%). Prevalence of public dental service use was 52.1% in adults who had a household income of less than R$1,500, 41.4% in those who had not visited the dentist in the last year, 43.1% in those who reported that the reason for visiting the dentist was treatment/pain/extraction, and 40.2% in those who were satisfied with the last treatment received. On the other hand, prevalence of the use of private dental services/health plan was greatest among adults with a higher household income (77.8%), followed by those who reported that the reason for their last dental visit was a check-up (67.8%), those who had visited the dentist within the last year (61.3%), and those who were indifferent/unsatisfied with the last treatment received (61.2%) (Table 2).

With respect to the need variables, 351 (6.1%) of the adults needed endodontic treatment, 1,835 (32.2%) needed an upper dental prosthesis, 2,654 (46.6%) needed a lower dental prosthesis, and 3,132 (55.3%) were indifferent/unsatisfied with their oral health status/teeth. Among the adults who sought public dental services, 187 (53.3%) needed endodontic treatment, 887 (48.3%) needed some type of upper dental prosthesis, 1,220 (46.0%) needed some type of lower dental prosthesis, and 1,355 (43.3%) reported being indifferent/unsatisfied with their oral health status/teeth (Table 3).

Table 4 shows the results of the final logistic regression model predicting the factors associated with public dental service use. The model included predisposing, enabling, and needs factors associated with public dental service use. In the multivariate model, a strong association was maintained between most of the predisposing and enabling variables and the outcome. An association was maintained between the following predisposing factors and public dental service use: being a woman, lower education level, being non-white, and having had toothache. Public dental service use was a protective factor for men (OR = 0.85; 95% CI: 0.74; 0.96) and adults with a higher education level ( ≥ 10 years of study) (OR = 0.52; 95% CI: 0.46; 0.60). Individuals who reported having had toothache were 1.6 times (95% CI_:1.39;1.83) more likely to seek public services than those who did not, while adults with lower household income were 2.37 times (95% CI: 2.11; 2.65) more likely to seek public services than those with a higher income. The need for endodontic treatment was associated with public dental service use (OR = 1.44; 95% CI:1.12; 1.85). The removal of the variable “household income” from the model changed the variance of the estimates of the crude model. This change was more pronounced for the variable “sex”. In the adjusted model, men were 1.21 times more likely to seek public dental services than women. Statistically significant associations were maintained between public dental service use and the other variables in the model without household income, with gains in the strength of association for the variables sex and need for endodontic treatment.

Discussion

The prevalence of public dental service use among adults was a little over 40%, which is higher than the rate reported by a study conducted in Minas Gerais in 2012¹1 Gilbert HG, Duncan RP, Bruce V. Determinants of dental care use in dentate adults: six monthly use during a 24-month period in the Florida Dental Care Study. Soc Sci Med 1998; 47(6):727-737.. A study involving municipalities with more than 100,000 inhabitants in the State of Maranhão using data from 2007 showed that the prevalence of the use of private services/health plan among adults was 55.6%¹⁷17 Gomes AMM, Thomaz EBAF, Alves MTSSB, Silva AAM, Silva RA. Fatores associados ao uso dos serviços de saúde bucal: estudo de base populacional em municípios do Maranhão. Brasil. Cien Saude Colet 2014; 19(2):629-640.. A nationwide study conducted in 2003 showed that 51.8% of adults used public services on their last dental visit²²22 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.. The discrepancies in the prevalence of dental service use may be explained by differences in the age groups used to characterize the adult population¹¹11 Minas Gerais. Secretaria de Estado de Saúde (SES). Pesquisa das condições de saúde bucal da população mineira - Resultados principais. Belo Horizonte: Editora Autêntica; 2013.^,1717 Gomes AMM, Thomaz EBAF, Alves MTSSB, Silva AAM, Silva RA. Fatores associados ao uso dos serviços de saúde bucal: estudo de base populacional em municípios do Maranhão. Brasil. Cien Saude Colet 2014; 19(2):629-640.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544..

According to Andersen, predisposing and enabling factors related to the individual and family should consider how people view their own general health and whether or not they judge their problems to be of sufficient importance and magnitude to seek professional help²⁵25 Andersen RM. Revisiting the behavioral model and access to medical care: does it matter? J Health Soc Behav 1995,36(1):1-10.. With regard to predisposing and enabling factors, women, people with a lower education level, non-whites, and people with a lower household income were more likely to use public dental services⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.. The greater use of public dental services by women may be related to the fact that women have more time available to visit public health centers during opening hours²²22 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544..

Education level (predisposing factor) and household income (enabling factor) were associated with the outcome in the multivariate model. Household income influences purchasing power for dental services, while education level is related to the level of understanding or awareness regarding illnesses and dental care¹1 Gilbert HG, Duncan RP, Bruce V. Determinants of dental care use in dentate adults: six monthly use during a 24-month period in the Florida Dental Care Study. Soc Sci Med 1998; 47(6):727-737.^,33 Nguyen L, Häkkinen U. Choices and utilization in dental care Public vs. private dental sectors, and the impact of a two-channel financed health care system. Eur J Health Econ 2006; 7(2):99-106.

4 Luzzi L, Spencer AJ. Public dental service utilization among adults in South Australia. Aust Dent J 2009; 54(2):154-160.^-55 Brennan DS, Luzzi L, Roberts-Thomson KF. Dental service patterns among private and public adult patients in Australia. BMC Health Serv Res 2008; 3:1-8.^,99 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,2121 Camargo MBJ, Dumith SC, Barros AJD. Uso regular de serviços odontológicos entre adultos: padrões de utilização e tipos de serviço. Cad Saude Publica 2009; 25(9):1894-1906.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.. For Andersen¹⁵15 Peres KG, Peres MA, Boing AF, Bertoldi AD, Bastos JL, Barros AJD. Redução das desigualdades sociais na utilização de serviços odontológicos no Brasil entre 1998 e 2008. Rev Saude Publica 2012; 46(2):250-258. and other authors²⁵25 Andersen RM. Revisiting the behavioral model and access to medical care: does it matter? J Health Soc Behav 1995,36(1):1-10., differences in socioeconomic status (household income) indicate the presence of inequity (unfair inequality) in dental service use.

The variable toothache (predisposing factor) and need variables associated with public dental service use provide important insights into the impacts of oral health policy on collective oral health and quality of life¹²12 Pucca Jr GA, Gabriel M, Araújo ME, Almeida FCS. Ten Years of a National Oral Health Policy in Brazil: Innovation, Boldness, and Numerous Challenges. J Dent Res 2015; 94(10):1333-1337.^,2626 Antunes JLF, Narvai PC. Políticas de saúde bucal no Brasil e seus impactos sobre as desigualdades em saúde. Rev Saude Publica 2010; 44(2):360-365.. In this respect, studies show that there is a high prevalence of oral health problems and tooth loss among adults in Brazil¹⁰10 Brasil. Ministério da Saúde (MS). SB Brasil 2010: pesquisa Nacional de Saúde Bucal: Resultados Principais. Brasília: MS; 2012.^,2727 Baldani MH, Brito WH, Lawder JAC, Mendes YBE, Silva FFM, Antunes JLF. Determinantes individuais da utilização de serviços odontológicos por adultos e idosos de baixa renda. Rev Bras Epidemiol 2010; 13(1):150-162.. The inclusion of OHTs in the FHS in 2000 and restructuring of the NOHP in 2004 led to major advances at all levels of attention, including the creation of oral health teams and implementation of dental specialty centers and regional dental prosthesis laboratories¹²12 Pucca Jr GA, Gabriel M, Araújo ME, Almeida FCS. Ten Years of a National Oral Health Policy in Brazil: Innovation, Boldness, and Numerous Challenges. J Dent Res 2015; 94(10):1333-1337.^,2626 Antunes JLF, Narvai PC. Políticas de saúde bucal no Brasil e seus impactos sobre as desigualdades em saúde. Rev Saude Publica 2010; 44(2):360-365.^,2828 Soares CLM, Paim JS. Aspectos críticos para a implementação da política de saúde bucal no Município de Salvador, Bahia, Brasil. Cad Saude Publica 2011; 27(5):966-974., resulting in the decentralization of oral health actions and expansion of access to non-specialist and specialist public dental services¹²12 Pucca Jr GA, Gabriel M, Araújo ME, Almeida FCS. Ten Years of a National Oral Health Policy in Brazil: Innovation, Boldness, and Numerous Challenges. J Dent Res 2015; 94(10):1333-1337.^,2626 Antunes JLF, Narvai PC. Políticas de saúde bucal no Brasil e seus impactos sobre as desigualdades em saúde. Rev Saude Publica 2010; 44(2):360-365.^,2828 Soares CLM, Paim JS. Aspectos críticos para a implementação da política de saúde bucal no Município de Salvador, Bahia, Brasil. Cad Saude Publica 2011; 27(5):966-974.. The increased demand for private dental services in Brazil may have been influenced by improvements in average income and a reduction in the unemployment rate (employability). On the other hand, currently, high unemployment rates may be leading adults to seek public services, with strong evidence showing the need to strengthen the NOHP as a policy to drive social inclusion and equity.

However, it is not clear whether the increase in the provision of non-specialist and specialist dental services and decentralization of the NOHP have led to a reduction in inequalities in access to dental healthcare²⁷27 Baldani MH, Brito WH, Lawder JAC, Mendes YBE, Silva FFM, Antunes JLF. Determinantes individuais da utilização de serviços odontológicos por adultos e idosos de baixa renda. Rev Bras Epidemiol 2010; 13(1):150-162.^,2828 Soares CLM, Paim JS. Aspectos críticos para a implementação da política de saúde bucal no Município de Salvador, Bahia, Brasil. Cad Saude Publica 2011; 27(5):966-974.. The National Health Survey, which assessed access to and utilization of dental services among Brazilians aged over 18, showed that primary care centers account for 19.6% of all dental care and that 11.0% of adults had lost all their teeth, corresponding to 16 million lost teeth²⁹29 Instituto Brasileiro de Geografia e Estatística (IBGE). Pesquisa Nacional de Saúde: 2013: acesso e utilização dos serviços de saúde, acidentes e violências: Brasil, grandes regiões e unidades da federação [Internet]. Rio de Janeiro: IBGE; 2015. [citado 2017 Jan 10]. Disponível em: http://biblioteca.ibge.gov.br/visualizacao/livros/liv94074.pdf
http://biblioteca.ibge.gov.br/visualizac... . Previous studies have shown that the prevalence of dental service use for check-ups or prevention is lower in public dental services⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,1010 Brasil. Ministério da Saúde (MS). SB Brasil 2010: pesquisa Nacional de Saúde Bucal: Resultados Principais. Brasília: MS; 2012.. A study conducted in Minas Gerais using data from 2012 reported that only 22.6% of adults visited the dentist for prevention or check-ups⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.. In this respect, research suggests that the inclusion of OHTs in family healthcare centers has not led to a major change in traditional patterns of service delivery, indicating that this may be due to the historic lack of access to dental care for the adult population and that preventive actions tend to prioritize children and fail to reach adults²²22 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.^,2626 Antunes JLF, Narvai PC. Políticas de saúde bucal no Brasil e seus impactos sobre as desigualdades em saúde. Rev Saude Publica 2010; 44(2):360-365.

27 Baldani MH, Brito WH, Lawder JAC, Mendes YBE, Silva FFM, Antunes JLF. Determinantes individuais da utilização de serviços odontológicos por adultos e idosos de baixa renda. Rev Bras Epidemiol 2010; 13(1):150-162.^-2828 Soares CLM, Paim JS. Aspectos críticos para a implementação da política de saúde bucal no Município de Salvador, Bahia, Brasil. Cad Saude Publica 2011; 27(5):966-974..

Level of need indicates the immediate reason for use of dental services²⁷27 Baldani MH, Brito WH, Lawder JAC, Mendes YBE, Silva FFM, Antunes JLF. Determinantes individuais da utilização de serviços odontológicos por adultos e idosos de baixa renda. Rev Bras Epidemiol 2010; 13(1):150-162.. In this respect, the need for endodontic treatment was associated with type of dental service in the adjusted analysis. This finding suggests that public service users demand more complex curative and rehabilitative treatment and have poorer oral health status²²22 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.. It also indicates that there is a suppressed demand for this type of service among the study population and that socioeconomically disadvantaged populations have limited access to specialist dental services, which has also been shown by international³3 Nguyen L, Häkkinen U. Choices and utilization in dental care Public vs. private dental sectors, and the impact of a two-channel financed health care system. Eur J Health Econ 2006; 7(2):99-106.

4 Luzzi L, Spencer AJ. Public dental service utilization among adults in South Australia. Aust Dent J 2009; 54(2):154-160.^-55 Brennan DS, Luzzi L, Roberts-Thomson KF. Dental service patterns among private and public adult patients in Australia. BMC Health Serv Res 2008; 3:1-8. and national⁹9 Pinto RS, Abreu MHNG, Vargas AMD. Comparing adult users of public and private dental services in the state of Minas Gerais, Brazil. BMC Oral Health 2014; 14:100.^,1515 Peres KG, Peres MA, Boing AF, Bertoldi AD, Bastos JL, Barros AJD. Redução das desigualdades sociais na utilização de serviços odontológicos no Brasil entre 1998 e 2008. Rev Saude Publica 2012; 46(2):250-258.^,1818 Baldani MH, Antunes JLF. Inequalities in access and utilization of dental services: a cross-sectional study in an area covered by the Family Health Strategy. Cad Saude Publica 2011; 27(Supl. 2):272-283.^,2727 Baldani MH, Brito WH, Lawder JAC, Mendes YBE, Silva FFM, Antunes JLF. Determinantes individuais da utilização de serviços odontológicos por adultos e idosos de baixa renda. Rev Bras Epidemiol 2010; 13(1):150-162. studies. This may be related to the organization of service delivery in Brazil, which prioritizes maternal and child health, schoolchildren, and individuals with a higher level of need for care²⁶26 Antunes JLF, Narvai PC. Políticas de saúde bucal no Brasil e seus impactos sobre as desigualdades em saúde. Rev Saude Publica 2010; 44(2):360-365.^,2828 Soares CLM, Paim JS. Aspectos críticos para a implementação da política de saúde bucal no Município de Salvador, Bahia, Brasil. Cad Saude Publica 2011; 27(5):966-974.. The problem-solving approach to dental care contradicts the modern approach to oral health care, which is centered on oral health surveillance and monitoring and prevention, thereby minimizing the need for dental restoration and extractions⁵5 Brennan DS, Luzzi L, Roberts-Thomson KF. Dental service patterns among private and public adult patients in Australia. BMC Health Serv Res 2008; 3:1-8.^,2222 Pinto RS, Matos DL, Loyola Filho AI. Characteristics associated with the use of dental services by the adult Brazilian population. Cien Saude Colet 2012 Fev; 17(2):531-544.. However, some predisposing (toothache) and need variables are potentially modified by health professionals through prevention, empowering subjects to change their behavior and the beliefs, attitudes, and values they have regarding oral health²¹21 Camargo MBJ, Dumith SC, Barros AJD. Uso regular de serviços odontológicos entre adultos: padrões de utilização e tipos de serviço. Cad Saude Publica 2009; 25(9):1894-1906..

Due to the cross-sectional study design, it was not possible to determine the cause-and-effect relationship between variables and we sought to identify individual markers of the type of dental service used. Although the rate of refusal to participate in the study was low, the timing of data collection may have precluded individuals who were not at home/at work at the time of the interview from participating. This resulted in a larger proportion of women in the sample, meaning that the greater use of dental services by women may have been overestimated, adversely affecting external validity. Furthermore, the OR can influence the variance of estimates, suggesting that caution should be taken when interpreting the results³⁰30 Francisco PMSB, Donalisio MR, Barros MBA, Cesar CLG, Carandina L, Goldbaum M. Medidas de associação em estudo transversal com delineamento complexo: razão de chances e razão de prevalência. Rev Bras Epidemiol 2008; 11(3):347-355.. On the other hand, the study has a wide reach, richness of data obtained from clinical examinations, and adopted robust methodological criteria, despite the low non-response rate and exclusion of adults who reported never having visited the dentist/ having used other types of dental services, who may show different patterns of use of dental services. Finally, some of the variables rely on the memory of the respondents and therefore may have been affected by response bias. In this respect, some individuals may have exaggerated care-seeking and reported recent visits to the dentist to not appear that they neglected their oral health.

In short, the findings show inequalities in access to dental services among adults in the State of São Paulo. The prevalence rates suggest that private services/health plans were used more than public dental services. The use of the model proposed by Andersen allowed us to identify some of the predisposing, enabling, and need factors that explain public dental service use among adults. The variables associated with public dental service use (education level, having had toothache, and need for endodontic treatment) suggest that mechanisms designed to enhance access should be improved, particularly those linked to information. It is hoped that the findings of this study may prompt positive changes in oral health care for Brazilian adults, regardless of the type of service used.

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