September 2nd, 2016

To: Mayor Naheed Nenshi Members of Council

From: Councillor Diane Colley-Urquhart Councillor Richard Pootmans Councillor Peter Demong

Re: Notice of Motion Water Fluoridation in The City of Calgary

Over the past many months since the research study on “Measuring the Short-Term Impact of Fluoridation Cessation on Dental Caries in Grade 2 Children” was released by lead author and Albertan Dr. Lindsay McLaren, we have been meeting frequently to consider not only the findings, but to determine what an objective go-forward plan could be for Calgary City Council to consider. We have attached our Notice of Motion and this study, along with a related article that appeared in the International Journal for Equity in Health (on children’s dental caries before and after cessation of community water fluoridation) for your review and consideration.

An important aspect of our meetings has included seeking professional expertise and advice from the University of Calgary’s O’Brien Institute for Public Health(OIPH) and from Dr. Richard Musto, MD, FRCPC – Medical Officer of Health – Calgary Zone – Alberta Health Services. While Dr. Musto is certainly an advocate for fluoridation, that is contrasted by Dr. William Ghali, the Scientific Director of the OIPH who approaches matters such as this from a purely scientific non-advocacy perspective.

It is because of these conversations and advice, that we have developed the approach outlined in our Notice of Motion. The Institute has established deep engagement and longitudinal partnerships with governments, health systems, and public health agencies that shape policies that influence our health. This engagement occurs locally through municipalities (especially The City of Calgary), provincially (through the Ministry of Health, Alberta Health Services, and the Health Quality Council of Alberta), nationally (through the Public Health Agency of Canada, Health Canada, and the Canadian Institute for Health Information, among others), and internationally (through the World Health Organization, the Organization for Economic Cooperation and Development, and the World Bank). The OIPH is a credible agency to undertake this work.

...1

Dr. Ghali has secured millions of dollars of peer-reviewed research funding from various agencies, has published over 350 papers in peer-reviewed journals, and has been the recipient of numerous local, national, and international awards. Dr. Ghali is involved in a number of research initiatives, with specific focus on interdisciplinary approaches to evaluating and improving health system performance to produce better patient outcomes and improved system efficiency.

The three of us believe that The Institute has the expertise and objectivity to undertake this work. Dr. Ghali and the OIPH have offered to conduct this scientific review at their own expense and to meet our timeline.

Go Forward (OIPH) Proposal

1) Individual meetings will be offered to City Councillors to address individual questions. Members of City Council will be interviewed by OIPH researchers to develop a set of questions to review in the literature. These include, but are not limited to, specific questions around risks, costs, ethical considerations and efficacy.

2) The Institute would undertake a thorough process of carefully responding to each of the questions in as comprehensive a manner as possible, drawing on evidence from all sources. They would encourage compilation of any and all questions, and the domains of inquiry could touch on questions of 1) effectiveness, 2) safety, 3) costs, and 4) ethical considerations relating to fluoridation of water supplies.

3) The content generated would be summarized in a readable, digestible, cross referenced, synthesized policy brief with appended detail where appropriate.

We look forward to any feedback you have for us as this proceeds to Council on September 12th, 2016.

Community Dent Oral Epidemiol Ó 2016 The Authors. Community Dentistry and Oral Epidemiology Published by John Wiley & Sons Ltd All rights reserved

Lindsay McLaren1, Steven Patterson2, Salima Thawer3, Peter Faris4, Measuring the short-term impact 5 6 Deborah McNeil , Melissa Potestio and Luke Shwart7 of fluoridation cessation on 1Department of Community Health Sciences and O’Brien Institute for Public Health, University of Calgary, Calgary, Alberta, dental caries in Grade 2 children Canada, 2School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada, 3Department of Community Health using tooth surface indices Sciences, University of Calgary, Calgary, Alberta, Canada, 4Research Facilitation, Research Priorities and Implementation, Alberta Health Services, Calgary, Alberta, Canada, 5Research and Innovation, Surveillance and Infrastructure, Population Public and Aboriginal Health, Alberta Health Services, Calgary, Alberta, Canada, McLaren L, Patterson S, Thawer S, Faris P, McNeil D, Potestio M, Shwart L. 6 Measuring the short-term impact of fluoridation cessation on dental caries in Alberta Cancer Prevention Legacy Fund, Population Public and Aboriginal Health, Grade 2 children using tooth surface indices. Community Dent Oral Epidemiol © Alberta Health Services and Department of 2016. 2016 The Authors. Community Dentistry and Oral Epidemiology Community Health Sciences, University of Published by John Wiley & Sons Ltd. Calgary, Calgary, Alberta, Canada, 7Formerly: Provincial Oral Health Office, This is an open access article under the terms of the Creative Commons Attribu- Alberta Health Services, Calgary, Alberta, tion-NonCommercial-NoDerivs License, which permits use and distribution in Canada any medium, provided the original work is properly cited, the use is non-com- mercial and no modifications or adaptations are made.

Abstract – Objectives: To examine the short-term impact of fluoridation cessation on children’s caries experience measured by tooth surfaces. If there is an adverse short-term effect of cessation, it should be apparent when we focus on smooth tooth surfaces, where fluoride is most likely to have an impact for the age group and time frame considered in this study. Methods: We examined data from population-based samples of school children (Grade 2) in two similar cities in the province of Alberta, Canada: Calgary, where cessation occurred in May 2011 and Edmonton where fluoridation remains in place. We analysed change over time (2004/2005 to 2013/2014) in summary data for primary (defs) and permanent (DMFS) teeth for Calgary and Edmonton, for all tooth surfaces and smooth surfaces only. We also considered, for 2013/2014 only, the exposed subsample defined as lifelong residents who reported usually drinking tap water. Results: We observed, across the full sample, an increase in primary tooth decay (mean defs – all surfaces and smooth surfaces) in both cities, but the magnitude of the increase was greater in Calgary (F-cessation) than in Edmonton (F-continued). For permanent tooth decay, when focusing on Key words: fluoridation; Public health smooth surfaces among those affected (those with DMFS>0), we observed a Lindsay McLaren, Department of non-significant trend towards an increase in Calgary (F-cessation) that was not Community Health Sciences and O’Brien apparent in Edmonton (F-continued). Conclusions: Trends observed for primary Institute for Public Health, University of Calgary, Calgary, Alberta, Canada teeth were consistent with an adverse effect of fluoridation cessation on Tel.: 403-210-9424 children’s tooth decay, 2.5–3 years post-cessation. Trends for permanent teeth Fax: 403-270-7307 hinted at early indication of an adverse effect. It is important that future data e-mail: [email protected] collection efforts in the two cities be undertaken, to permit continued Submitted 6 July 2015; monitoring of these trends. accepted 9 January 2016

Since its initial implementation in 1945, much Mechanistically, fluoride benefits teeth by inhibiting research has been conducted on community water tooth demineralization, enhancing re-mineralization, fluoridation (CWF) and its impact on dental caries. and inhibiting enzyme activity of plaque bacteria1. doi: 10.1111/cdoe.12215 1 McLaren et al.

While both a systemic (pre-eruptive) and a topical Tooth surface-level data would be preferable, if the (post-eruptive) mechanism of impact have been aim is to evaluate a prevention initiative20 such as studied intensively, experts now seem to agree that community water fluoridation or its cessation. fluoride’s major anti-cariogenic effect is post-erup- The purpose of this study was to examine the tive1,2; however, studies have continued to accrue impact of fluoridation cessation on children’s that are consistent with some pre-eruptive effect3. dental caries. Our analysis took advantage of the As a whole, the evidence base supports the bene- natural experiment opportunity provided by fluo- fits of fluoridation for preventing caries in popula- ridation cessation in the city of Calgary, Canada, tions4,5. However, systematic reviews have which occurred in May 2011 (after having been in highlighted methodological limitations of the evi- place since 1991). Published definitions of interven- dence base, such as weak study designs4,5. This tion in the research context highlight ‘intentional reflects that research on CWF and CWF cessation is change’21 and ‘to disturb the ‘natural’ order of observational (takes advantage of natural experi- things’22, and thus accommodate cessation (as well ment circumstances) and may rely on pre-existing as initiation) of CWF as a viable study focus. We data collected for another purpose. Contemporary compared caries rates in Calgary to those in the evidence was furthermore noted to be sparse: in a city of Edmonton, where fluoridation began in recent systematic review5, 71% of included studies 1967 and remains in place. Elsewhere (L. McLaren, were conducted prior to 1975. S. Patterson, S. Thawer, P. Faris, D. McNeil, M. To a large extent, the research literature is char- Potestio et al., unpublished results) we reported on acterized by studies of fluoridation initiation, early tooth-level data and showed that for primary (but in the intervention’s history6,7 and cross-sectional not permanent) teeth, a significant increase in car- comparisons of fluoridated and non-fluoridated ies between pre- and post-cessation was observed – communities8 10. There is less research on fluorida- in Calgary (F-cessation). The effect was smaller tion cessation circumstances11, even though cessa- and less consistent in Edmonton (F-continued). tion appears to be occurring with increasing These initial findings for primary teeth were con- frequency in some regions. For example, in Canada sistent with a short-term adverse effect of cessation alone since 2005, more than 30 communities have on caries experience. opted to discontinue fluoridation12. To inform fluo- The objective of this article was to report further ridation decision-making, high-quality research on on the impact of CWF cessation on children’s caries the impact of cessation is needed. In our context, experience, focusing on smooth tooth surfaces, there was demand from decision-makers for high- where fluoride is most likely to have an impact23 quality, locally relevant evidence on the impact of for the age group and time frame considered in this fluoridation cessation on dental caries experience. study. If there is an adverse effect of fluoridation A systematic review (L. McLaren and S. Singhal, cessation, as observed in our other paper, it should unpublished results) identified 15 instances of pub- be apparent using this more sensitive measure. lished research on fluoridation cessation in 13 countries. Those studies provided important insight into the impact of cessation on dental caries Materials and methods in different contexts. However, many of the studies had important methodological limitations, such as Design no comparison community13 or no questionnaire We used a pre–post cross-sectional design with data to assess important covariates14. Furthermore, comparison group. Data were collected from popu- many of the cessation studies were older: of the 15 lation-based samples of schoolchildren during the jurisdictions represented in the review, only six 2004/2005 and 2013/2014 school years (October– focused on cessation that occurred in 1990 or May/June). The target population was children in – later3,13,15 18 and only one3 since 2000. Older stud- grade 2 attending school in the Public or Catholic ies may not reflect contemporary circumstances school system in Calgary and Edmonton. Calgary such as historically low caries rates, skewed caries and Edmonton are well matched: they are the two distributions (smaller proportion of people largest cities in the province of Alberta and are accounting for the majority of problems) and mul- both large urban centres with diverse demographic tiple sources of exposure to fluoride19. Finally, with profiles. We ascertained fluoride content of important exceptions16, many studies examined municipal drinking water in the two cities by the impact of cessation using tooth-level data. securing annual water quality reports (L. McLaren,

2 Fluoridation cessation in Calgary, Canada

S. Patterson, S. Thawer, P. Faris, D. McNeil, M. November 2013) by a public health dentist with Potestio et al., unpublished results). considerable experience in survey calibration and an extensive knowledge and background in survey Pre-cessation data (2004/2005) methodology and tooth surface-level assessment. Pre-cessation data for Calgary and Edmonton were Signed parental consent and child verbal assent available from population-based surveys con- were secured for the open mouth examination. ducted by former health regions in Alberta in Post-cessation data collection also included a par- 2004/2005. Oral health data were collected via ent questionnaire and, for a small random subsam- open mouth examinations conducted in the schools ple in each city, fingernail clippings to assess total by trained and calibrated assessment teams, each fluoride intake (L. McLaren, S. Patterson, S. consisting of a registered dental hygienist and a Thawer, P. Faris, D. McNeil, M. Potestio et al., clerk. Decayed, missing/extracted, and filled teeth unpublished results). The 2013/2014 school-level and surfaces were recorded using standard crite- participation rates were 57.3% (Calgary) and 54.1% ria20. Decay referred to cavitated decay, defined as (Edmonton), and the student-level participation a lesion that ‘has a detectably softened floor, rate within participating schools were 49.1% (Cal- undermined enamel or softened wall. On inter- gary) and 47.0% (Edmonton). proximal surfaces, the point of the explorer must enter a lesion with certainty’24. Variables and data analysis For Calgary in 2004/2005, a stratified random In this article, we focused on summary data for sample was selected, with strata based on median tooth surfaces, both primary (defs) and permanent neighbourhood income quartile where the school (DMFS). Because both defs and DMFS tended to be was located. Within sampled schools, all children positively skewed, we examined both overall mean of eligible grades were invited to participate. An and the mean for those with one or more defs or opt-in consent process was used, and the participa- DMFS. We considered all tooth surfaces, as well as tion rate was 60%24. In Edmonton in 2004/2005, all smooth surfaces only. Our designation of smooth elementary schools in the two school boards were surfaces included all surfaces except the following: invited to participate, and within each school, a occlusal surfaces (whenever present), and surfaces sample was taken from each class with the sample where pit and fissure caries commonly occur, size predetermined based on class size (80–100% of namely buccal (vestibular) surfaces for teeth 46 the full class). The participation rate was approxi- and 36, and lingual surfaces for teeth 16 and 26 mately 89%. (Though we had codes to specifically indicate pit and fissure caries in the 2013/2014 data, we used Post-cessation data (2013/2014) the proxy approach of excluding certain surfaces to Data collection in 2013/2014 was designed to maxi- permit comparability with 2004/2005 (for which mize comparability with the 2004/2005 surveys. we did not have that specific information). When We drew a stratified random sample, with strata we computed smooth surface caries summary based on the median neighbourhood income quar- measures in 2013/2014 using the specific pit and tile where the school was located. Trained and cali- fissure designation, the estimates tended to be brated assessment teams, each consisting of a higher (for example, in Table 1b, mean DMFS registered dental hygienist and a clerk, conducted among those with DMFS>0 was 2.3 [versus 2.0] for open mouth examinations following the protocol Calgary and 2.1 [versus 1.7] for Edmonton).). from the Iowa Fluoride Study25, which is based on Permanent tooth summary data (DMFS) were 20 the WHO criteria and yields a d1d2-3mf index based on children with at least one permanent based on whole tooth codes and 2-digit surface- tooth. The percentage of children with at least one specific codes. Our analysis focused on d2-3 to permanent tooth, and the mean number of perma- permit comparability with the decay data in the nent teeth, did not differ appreciably across sur- 2004–05 surveys. Assessments were based on all veys: the percentages with zero permanent teeth primary teeth and a subset of 12 permanent teeth were 1.5% (Calgary 2004/2005), 1.1% (Edmonton (central incisors, lateral incisors and 1st molars). 2004/2005), 1.5% (Calgary 2013/2014) and 1.9% The same 12 permanent teeth were considered pre- (Edmonton 2013/2014), and the mean numbers of and post-cessation. Assessment teams were trained permanent teeth, of the 12 assessed, were 9.1 (Cal- together in the protocol, and each team was cali- gary 2004/2005), 9.0 (Edmonton 2004/2005), 8.8 brated on two occasions (early October and mid- (Calgary 2013/2014) and 8.7 (Edmonton 2013/

3 4 al. et McLaren

Table 1. Dental caries summary measures in Calgary and Edmonton, 2004/2005 and 2013/2014, Grade 2 students. Weighted estimates. Full sample Calgary 2004/2005 Calgary 2013/2014 Calgary Edmonton 2004/5 Edmonton 2013/4 Edmonton Year x city change change interaction term: (2013/ (2013/ Rate ratio and 95% 2014 – 2014 – confidence interval 2004/ 2004/ from Poisson Mean (95% CI), n Mean (95% CI), n 2005) Mean (95% CI), n Mean (95% CI), n 2005) regression a) All tooth surfaces Mean defs 2.6 (2.2–3.0) n = 599 6.4 (5.9–6.9) n = 3230 3.8a 4.5 (4.1–4.8) n = 6445 6.6 (6.0–7.2) n = 2307 2.1a 1.6 (1.4–1.8), P < 0.01c Mean defs among 5.4 (5.0–5.7) n = 273 11.3 (10.6–12.0) n = 1835 5.9a 8.3 (7.8–8.8) n = 3415 11.2 (10.5–11.9) n = 1334 2.9a 1.6 (1.4–1.8), P < 0.01 those with defs>0 Mean DMFS 0.45 (0.37–0.52) 0.15 (0.13–0.17) n = 3182 À0.3a 0.25 (0.22–0.28) n = 6373 0.21 (0.17–0.25) n = 2263 À0.04 0.8 (0.6–1.1), P = 0.3c n = 590 Mean DMFS among 2.2 (2.0–2.5) n = 99 2.0 (1.8–2.2) n = 253 À0.2 2.4 (2.2–2.6) n = 652 2.2 (2.0–2.4) n = 201 À0.2 0.96 (0.8–1.2), P = 0.6 those with DMFS>0 b) Smooth surfaces onlyb Mean defs 1.4 (1.2–1.6) n = 599 4.3 (3.9–4.7) n = 3230 2.9a 2.8 (2.5–3.0) n = 6445 4.4 (3.9–4.8) n = 2307 1.6a 1.8 (1.6–2.2), P < 0.01c Mean defs among 3.3 (3.0–3.6) n = 236 8.6 (8.0–9.2) n = 1583 5.3a 5.9 (5.4–6.4) n = 2999 8.9 (8.2–9.6) n = 1109 3.0a 1.7 (1.5–2.0), P < 0.01 those with defs>0 Mean DMFS 0.04 (0.00–0.07), 0.02 (0.01–0.03), n = 3182 À0.02 0.02 (0.01–0.02) n = 6373 0.02 (0.01–0.03) n = 2263 0.0 2.7 (1.0–7.4), P = 0.06c n = 590 Mean DMFS among 1.7 (1.4–2.0) n = 12 2.0 (1.5–2.6) n = 40 0.3 1.7 (1.4–2.1) n = 59 1.7 (1.3–2.1) n = 28 0.0 1.2 (0.8–1.8), P = 0.3 those with DMFS>0 defs = decayed, extracted (due to caries), filled primary tooth surfaces; DMFS = decayed, missing (due to caries), filled permanent tooth surfaces. aStatistically significant difference between 2004/2005 and 2013/2014, based on non-overlapping 95% confidence intervals (CI). bOmits occlusal surfaces whenever present; omits buccal (vestibular) surfaces for teeth 46 and 36; omits lingual surfaces for teeth 16 and 26. cInteraction terms based on zero-inflated Poisson regression. Fluoridation cessation in Calgary, Canada

2014). The median (6) and range (0–12) were the 2013/2014. The sample sizes for permanent teeth same for all four survey samples. were slightly smaller because the denominator For 2013/2014 only, we additionally considered included those with at least one permanent tooth. the subsample of lifelong residents who reported Sample sizes for the 2013/2014 subsample (lifelong usually drinking tap water (versus bottled water). residents who reported usually drinking tap water) This information was gleaned from the parent were: n = 930 and n = 916 for Calgary defs and questionnaires included as part of the 2013/2014 DMFS, respectively, and n = 575 and n = 565 for data collection. Edmonton defs and DMFS, respectively. We examined change over time in Calgary (F- The summary data for Calgary and Edmonton, cessation) compared to change over time in in 2004/2005 (pre-cessation) and 2013/2014 (post- Edmonton (F-continued). Change over time was cessation) are shown in Table 1. For primary teeth inferred from non-overlapping 95% confidence (defs), a statistically significant increase was intervals for means, which was then verified by apparent in both Calgary and Edmonton, although testing a year x city interaction term in a Poisson the absolute magnitude of the increase was greater regression. in Calgary (F-cessation). This was true for all pri- All analyses applied sampling weights developed mary tooth surfaces (Table 1a) and for primary for this project, which accounted for the clustered smooth surfaces only (Table 1b). In all cases (mean sampling design and response imbalances. We also defs, mean defs among those with defs>0; all sur- ran all analyses unweighted and results were faces and smooth surfaces only), the greater broadly similar (no change to statistical significance). increase in Calgary compared to Edmonton was Weighted estimates are presented below. confirmed in a Poisson regression that showed a The study received approval from the Conjoint statistically significant year x city interaction term Health Research Ethics Board at the University of (far right hand column in Table 1), indicating that Calgary (ID E-25219) and the Health Research the increase in primary tooth decay in Calgary (F- Ethics Board at the University of Alberta (ID cessation) over time was significantly greater than Pro00037808). Approval was also sought and that in Edmonton. granted by all four participating school boards. Table 1 also contains permanent tooth summary data (DMFS). For all tooth surfaces among perma- nent teeth (Table 1a), there was a statistically sig- Results nificant decrease in Calgary, for the overall mean DMFS, which was not observed in Edmonton. For Results for primary teeth were based on the follow- permanent tooth smooth surfaces only (Table 1b), ing sample sizes: n = 599 for Calgary 2004/2005; there was no statistically significant change over n = 6445 for Edmonton 2004/2005; n = 3230 for time in Calgary or Edmonton. However, we noted Calgary 2013/2014; and n = 2307 for Edmonton a trend (non-significant) towards an increase in

Table 2. Dental caries summary measures in Calgary and Edmonton, Grade 2 students, 2013/2014 only. Weighted esti- mates. Estimates are for the subsample of lifelong residents who reported usually drinking tap water Calgary 2013/2014 Edmonton 2013/4 Mean (95% CI), n Mean (95% CI), n a) All tooth surfaces Mean defs 5.2 (4.5–5.8), n = 930 5.5 (4.5–6.5), n = 575 Mean defs among those with defs>0 9.9 (8.9–11.0), n = 477 10.5 (9.0–12.0), n = 289 Mean DMFS 0.14 (0.09–0.18), n = 916 0.11 (0.07–0.16), n = 565 Mean DMFS among those with DMFS>0 2.0 (1.5–2.4), n = 63 1.8 (1.4–2.2), n = 37 b) Smooth surfaces onlya Mean defs 3.3 (2.8–3.8), n = 930 3.6 (2.9–4.4), n = 575 Mean defs among those with defs>0 7.3 (6.4–8.3), n = 409 9.0 (7.5–10.4), n = 225 Mean DMFS 0.04 (0.01–0.07), n = 916 0.01 (0.00–0.02), n = 565 Mean DMFS among those with DMFS>0 3.0 (1.9–4.0), n = 12 1.0 (variance could not be computed), n = 7 defs = decayed, extracted (due to caries), filled primary tooth surfaces; DMFS = decayed, missing (due to caries), filled permanent tooth surfaces; 95% CI = 95% confidence interval. aOmits occlusal surfaces whenever present; omits buccal (vestibular) surfaces for teeth 46 and 36; omits lingual surfaces for teeth 16 and 26.

5 McLaren et al. permanent tooth smooth surface decay severity in knowledge of enamel differences between primary Calgary, among those affected (mean DMFS and permanent teeth26,27, which make it likely that among those with DMFS > 0 increased by 0.3 effects of cessation would appear sooner in pri- between 2004/2005 and 2013/2014). There were no mary teeth, we suggested that the absence of an statistically significant (at P < 0.05) year x city increase in permanent teeth may have reflected the interaction terms for permanent teeth measures. short time frame since cessation in our study, and Table 2 shows summary data for 2013/2014, but that continued monitoring would be important to this time estimates were restricted to the subsample see if an adverse effect in permanent teeth emerges of lifelong residents who reported usually drinking as time passes. tap water. In general, the estimates for the subsam- In this study, though effects were not statistically ple (Table 2) tended to be similar to or lower than significant, the decrease in permanent tooth decay for the full sample (Table 1) for both Calgary and in Calgary (F-cessation) that we observed using Edmonton, with few exceptions (permanent tooth tooth-level data (L. McLaren, S. Patterson, S. measures for smooth surfaces in Calgary). The Thawer, P. Faris, D. McNeil, M. Potestio et al., 2013/2014 subsample estimates in Table 2 could unpublished results) and for all tooth surfaces (this not be compared directly to 2004/2005 data, due to manuscript, Table 1a) was muted when we lack of questionnaire data which with to define a focused on smooth surfaces only; and for mean comparable subsample in 2004/2005. DMFS among those with DMFS>0, the direction of change became positive (though non-significant). Further, though estimates from the 2013/2014 sub- Discussion sample (lifelong residents who reported usually drinking tap water) are based on small numbers, We set out to examine the short-term impact of flu- they were nonetheless consistent with an apparent oridation cessation on children’s caries experience, increase in Calgary (F-cessation), because the Cal- with a specific interest in whether findings we gary estimate of mean DMFS among those with observed based on tooth-level data (L. McLaren, S. DMFS>0 was even higher in the subsample (3.0) Patterson, S. Thawer, P. Faris, D. McNeil, M. Potes- (that is, even more discrepant from the 2004/2005 tio et al., unpublished results) – namely an adverse estimate) than in the full sample (2.0). Though we effect of cessation on caries experience for primary do not know what the subsample estimates would teeth – were also apparent when focusing on have been for 2004/2005 due to lack of question- smooth tooth surfaces, where fluoride is most naire data, we note that both residential mobility likely to have an impact23 for the age group and and bottled water consumption were lower in limited period of time considered in this study. If 2004/2005 than in 2013/2014. Specifically, net an adverse effect of cessation is indeed occurring, migration (inter- and intra-provincial) increased in it should be apparent when using this more sensi- Calgary from 14 099 in 2004/2005 to 16 781 in tive measure. 2013/2014, and in Edmonton from 9548 in 2004/ This line of thinking was borne out in our 2005 to 17 482 in 2013/201428 (that is, the popula- results. In primary teeth, an increase in caries expe- tion in both cities was more stable, in terms of rience was observed in Calgary (where cessation migration, in 2004/2005 than in 2013/2014), and occurred in 2011). A similar observation, which statistics on bottled water sales for Canada showed was smaller in magnitude, was noted in Edmonton an increase over time; for example, litres per (where fluoridation remained in place). Thus, for household (total volume) increased from 104.5 in primary teeth, our results presented here and else- 2004 to 173.8 in 201429 (Data on bottled water sales where (L. McLaren, S. Patterson, S. Thawer, P. or consumption for the specific parameters of Cal- Faris, D. McNeil, M. Potestio et al., unpublished gary, Edmonton, 2004/05 and 2013/14 could not results) provide consistent indication of an adverse be located.). Therefore, it seems reasonable to short-term effect of cessation. assert that the discrepancy between the estimates In permanent teeth, we elsewhere (L. McLaren, for the full sample and for the subsample would be S. Patterson, S. Thawer, P. Faris, D. McNeil, M. larger in 2013/2014 than in 2004/2005; or in other Potestio et al., unpublished results) reported a words, it would make less difference to exclude decrease in caries over time in both Calgary (F-ces- non-lifelong residents and bottled water drinkers sation) and Edmonton (F-continued), which was in 2004/2005 than in 2013/2014. However, we do larger and more consistent in Calgary. Based on not know this for certain.

6 Fluoridation cessation in Calgary, Canada

Taken together, our findings were consistent general decline in child caries prevalence during with an adverse effect of fluoridation cessation on recent decades19,36. The reasons for the increase are children’s caries experience, about 2.5–3 years not known but could have to do with various fac- post-cessation. The effect was most apparent for tors impacting the province or larger geographies. primary teeth, but it appeared from these analyses Some examples include the global economic reces- that an effect for permanent teeth, which, initially, sion of 2008 and its social and economic aftermath; we hypothesized would take longer to occur (if it shifts in the Alberta economy due to rising and fall- occurred at all), was emerging. If true, one might ing prices in the province’s primary industry of oil expect a statistically significant effect on perma- and gas, which have implications for employment nent teeth to become evident at further follow-up and migration (workers coming to Alberta); as the permanent teeth in the age group studied increasing ethnic diversity in Canadian cities have been present in the mouth for a longer period. including Alberta (for example, the percent of the As we reported elsewhere, findings were consis- Alberta population who only speak a non-official tent with lower fluoride in Calgary than in Edmon- language most often at home has shown an ton based on 1) annual estimates of fluoride in increasing trend, with 7.5%, 9.1% and 10.5% in the drinking water secured from each city and 2) esti- 2001, 2006 and 2011 census, respectively)37,38; and mates of total fluoride intake from biomarkers (fin- trends in bottled water consumption which, as gernail clippings) from a subsample in each city. noted above, has increased for Canada as a whole. Furthermore, estimates were robust to adjustment Although data on trends in sugar consumption are for socio-demographic and behavioural/dental not specifically available for our samples, national characteristics of the Calgary and Edmonton sam- data suggest that that may not present a likely ples in 2013/2014 (L. McLaren, S. Patterson, S. explanation: although the percentage of daily calo- Thawer, P. Faris, D. McNeil, M. Potestio et al., ries from sugar is higher among four- to eight-year unpublished results). olds (which contains the age group in our study) Our findings contribute to the published litera- than among the population as a whole (26%, ver- ture on fluoridation cessation and impact on dental sus 21%)39, overall, sugar consumption has caries. While several studies showed an increase in decreased for the Canadian population over time, caries following cessation of fluoridation17,30, sev- including between 2004 and 201340. The reasons eral others did not31,32. Among the studies that did for the increase in caries in our two cities is an observe an increase in caries, several were many important remaining question. years or decades old33,34, and it is important to Limitations of our study included the short dura- question whether an adverse effect of fluoridation tion of follow-up since cessation, the absence of cessation on caries experience is apparent contem- questionnaire data from 2004/2005, non-identical porarily. Our results were somewhat different examination criteria at the two time points from the one other Canadian study16,35 which, (although both were anchored in the WHO criteria based on repeated cross-sectional data, did not and yielded comparable summary measures), the observe an adverse trend in tooth decay in the ces- use of different (though highly-skilled) calibrators sation community, following cessation in 1992. in 2004/2005 and 2013/2014 and lack of blinding However, that finding may have reflected changes of examiners to residence of participants. Our pre- over time in treatment and preventive practices cessation data (2004/2005) were collected several such as an increase in application of protective sea- years prior to cessation (2011) and it would have lants, and the importance of investigating smooth been preferable to have data collected closer to the surfaces. Collectively, the literature (including our year of cessation. However, elsewhere (L. McLa- study) indicates that the impact of fluoridation ces- ren, S. Patterson, S. Thawer, P. Faris, D. McNeil, M. sation on dental caries is not uniformly positive or Potestio et al., unpublished results) we considered negative but varies by time and place, and sorting other possible explanations such as socio-demo- out the reasons for different patterns is important. graphic characteristics of the samples and dental The increase in caries (especially in primary treatment and preventive programming and con- teeth) observed in both cities in our study, though cluded that they did not appear to represent likely consistent with anecdotal reports from those alternative explanations for our findings. The regions (personal communication, Associate Den- greater increase over time in deciduous caries tal Public Health Officer, Alberta Health Services, experience observed in Calgary reflects, in part, the 19 January 2015), contrasts with other reports of a low estimates in 2004/2005 (compared to Edmon-

7 McLaren et al. ton). However, because of the rigorous sampling 2. Beltran ED, Burt BA. The pre- and posteruptive methods and development and application of sam- effects of fluoride in the caries decline. J Public Health Dent 1988;48:233–40. pling weights, we believe the 2004/2005 estimates 3. Cho HJ, Jin BH, Park DY, Jung SH, Lee HS, Paik DI to be an accurate reflection of the caries experience et al. Systemic effect of water fluoridation on dental at that time. The differences between Calgary and caries prevalence. Community Dent Oral Epidemiol Edmonton pre-cessation speak to the importance 2014;42:341–8. of using a study design that involves comparison 4. McDonagh M, Whiting P, Bradley M, Cooper J, Sutton A, Chestnutt I et al. A Systematic Review of of change over time when evaluating the impact of Public Water Fluoridation. York: NHS Centre for CWF cessation, versus a cross-sectional post-cessa- Reviews and Dissemination. University of York; tion study. 2000. (Report 18). Strengths of our study include: high-quality oral 5. Iheozor-Ejiofor Z, Worthington HV, Walsh T, O’Malley L, Clarkson JE, Macey R et al. Water health data gathered by trained and calibrated den- fluoridation for the prevention of dental caries tal professionals; population-based samples cou- (Review). Cochrane Database Syst Rev 2015;6:1–274. pled with development and application of 6. Brown HK, McLaren HR, Josie GH, Stewart BJ. The sampling weights to maximize representativeness Brantford-Sarnia-Stratford Fluoridation Caries Study 1955 Report. Can J Public Health 1956;47:149–59. of each sample of its underlying population; a 7. Ast DB, Finn SB, McCaffrey I. The Newburgh-King- comparative study design that permitted analysis ston caries Fluorine study; dental findings after three of change over time; and multiple sources of data years of water fluoridation. Am J Public Health – (open mouth examination; biomarker data; ques- 1950;40:716 24. 8. Armfield JM. 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Report prepared for the Public Health Agency toring of these trends. of Canada. April 2011. 12. Journal of the Canadian Dental Association (JCDA). Understanding public decision-making on commu- nity water fluoridation. J Can Dent Assoc 2013;79:d77. Acknowledgements 13. Kunzel W, Fisher T, Lorenz R, Bruhman S. Decline of caries prevalence after the cessation of water fluori- We gratefully acknowledge funding support for this pro- dation in the former East Germany. Community ject from the Canadian Institutes of Health Research Dent Oral Epidemiol 2000;28:382–9. (funding reference GIR 127083), Alberta Health, and 14. Attwood D, Blinkhorn AS. Trends in dental health of Alberta Health Services. Lindsay McLaren holds an ten-year-old school children in south-west Scotland Applied Public Health Chair award funded by the Cana- after cessation of water fluoridation. Lancet dian Institutes of Health Research (Institute of Popula- 1988;2:266–7. tion and Public Health, Institute of Musculoskeletal 15. SeppaL,K€ arkk€ ainen€ S, Hausen H. Caries trends Health and Arthritis), the Public Health Agency of 1992–1998 in two low-fluoride Finnish towns for- Canada, and Alberta Innovates – Health Solutions. We merly with and without fluoridation. Caries Res thank the following individuals and groups: Dr. Steven 2000;34:462–8. Levy, Dr. Eugenio Beltran, Dr. Kathy Phipps, Dr. Barry 16. Maupome G, Clark DC, Levy SM, Berkowitz J. Pat- Maze, Dr. Gary Whitford, Ms. Jodi Siever, Ms. Vicki terns of dental caries following the cessation of water Stagg, Ms. Leanne Rodine, Ms. Joanna Czarnobaj, Dr. fluoridation. Community Dent Oral Epidemiol Marianne Howell, Ms. Congshi Shi, the dental hygienists 2001;29:37–47. and clerks who worked on the project, and the partici- 17. Thomas FD, Kassab JY, Jones BM. Fluoridation in pating school boards, schools, and families. Anglesey 1993: a clinical study of dental caries in 5- year-old children who had experienced sub-optimal fluoridation. Br Dent J 1995;178:55–9. 18. Kunzel W, Fischer T. Caries prevalence after cessa- tion of water fluoridation in La Salud, Cuba. Caries References Res 2000;34:20–5. 1. Featherstone JDB. Prevention and reversal of dental 19. Burt BA. Prevention policies in light of the changed caries: role of low level fluoride. Community Dent distribution of dental caries. Acta Odontol Scand Oral Epidemiol 1999;27:31–40. 1998;56:179–86.

8 Fluoridation cessation in Calgary, Canada

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9 McLaren et al. International Journal for Equity in Health (2016) 15:24 DOI 10.1186/s12939-016-0312-1

RESEARCH Open Access Equity in children’s dental caries before and after cessation of community water fluoridation: differential impact by dental insurance status and geographic material deprivation Lindsay McLaren1*, Deborah A. McNeil2, Melissa Potestio3,1, Steve Patterson4, Salima Thawer1, Peter Faris5, Congshi Shi1 and Luke Shwart6

Abstract Background: One of the main arguments made in favor of community water fluoridation is that it is equitable in its impact on dental caries (i.e., helps to offset inequities in dental caries). Although an equitable effect of fluoridation has been demonstrated in cross-sectional studies, it has not been studied in the context of cessation of community water fluoridation (CWF). The objective of this study was to compare the socio-economic patterns of children’s dental caries (tooth decay) in Calgary, Canada, in 2009/10 when CWF was in place, and in 2013/14, after it had been discontinued. Methods: We analyzed data from population-based samples of schoolchildren (grade 2) in 2009/10 and 2013/14. Data on dental caries (decayed, missing, and filled primary and permanent teeth) were gathered via open mouth exams conducted in schools by registered dental hygienists. We examined the association between dental caries and 1) presence/absence of dental insurance and 2) small area index of material deprivation, using Poisson (zero-inflated) and logistic regression, for both time points separately. For small-area material deprivation at each time point, we also computed the concentration index of inequality for each outcome variable. Results: Statistically significant inequities by dental insurance status and by small area material deprivation were more apparent in 2013/14 than in 2009/10. Conclusions: Results are consistent with increasing inequities in dental caries following cessation of CWF. However, further research is needed to 1) confirm the effects in a study that includes a comparison community, and 2) explore possible alternative reasons for the findings, including changes in treatment and preventive programming. Keywords: Fluoridation, Dental health surveys, Health equity, Public health dentistry, Socioeconomic factors

* Correspondence: [email protected] 1Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada Full list of author information is available at the end of the article

© 2016 McLaren et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 2 of 9

Background inequitably patterned-is largely obviated [18]. Research on There are significant socio-economic inequities in dental population-level interventions and their implications for caries (tooth decay). Data from Canada [1], the U.S. [2], health equity is very important to the field of population/ Australia [3], the United Kingdom [4], Brazil [5] and public health, which is concerned with understanding and elsewhere [6] have demonstrated more, and more severe, reducing social inequities in health [19–21]. Social inequi- dental caries among children experiencing one or more ties in health refer to differences in health status between of: low family income, lower household educational at- social groups that are viewed as unfair and avoidable, as tainment, racial/ethnic minority status, lack of private distinct from inequalities in health which refer simply to dental insurance, and higher levels of deprivation based differences without accompanying moral and ethical di- on small area measures. In some cases, inequities were mensions [22]. Research on fluoridation and social inequi- shown to be increasing (worsening) over time [5, 7]. ties in dental health, thus, makes an important contribution Dental caries is largely preventable, and community to that broader field of inquiry. water fluoridation (CWF) (i.e., the controlled addition of Although an equitable effect of CWF has been shown a fluoride compound to a public water supply [8]) is one in cross-sectional studies, equity of impact has not been important option for prevention at the population level. investigated in the context of cessation (i.e., do inequities Extensive research supports the benefits of CWF for the in dental caries increase [worsen] after community water prevention of tooth decay in populations, although the fluoridation is stopped?). To illustrate, in a systematic overall methodological quality of the evidence is modest, review of research on cessation of CWF [McLaren L, due to problems such as weak study designs that inad- Singhal S. Does cessation of community water fluorid- equately account for potential confounders [9, 10]. A recent ation lead to an increase in tooth decay? A systematic Cochrane review concluded that high-quality recent evi- review of published studies. Unpublished], we identified dence was particularly sparse [10]. published research on cessation in 15 jurisdictions One of the main arguments made in favor of CWF is across 13 countries. None of these incorporated an ana- that it is equitable in its impact on dental caries [11]. In lysis of equity of impact. other words, it has been argued that CWF can help offset The objective of this paper was to explore the inequities in dental caries, by benefiting all but particularly equity implications of CWF cessation, by examining those experiencing lower socioeconomic circumstances, socio-economic patterns of children’s dental caries in who generally have the poorest oral health profiles. An Calgary, Canada, in 2009/10 when CWF was in place, equitable effect of CWF has been demonstrated in cross- and in 2013/14, after it had been discontinued. This paper sectional studies in several countries, including Canada is part of a larger project, the objective of which was to [12], Britain [13], Australia [14], New Zealand [15] and evaluate the short-term impact of CWF cessation on chil- South Korea [16]. For example, Jones and Worthington dren’s dental caries by comparing Calgary (where CWF [13] showed that a positive linear association between was discontinued in May 2011, after having been in place dental caries (decayed, missing, and filled deciduous teeth) since 1991) to Edmonton (where CWF began in 1967 and and small area deprivation score (based on the Townsend remains in place). Elsewhere [McLaren L, Patterson S, index) was much steeper in non-fluoridated Liverpool, Thawer S, Faris P, McNeil D, Potestio M, Shwart L. The UK, than in Newcastle where CWF had been in place short-term impact ofcommunity water fluoridation ces- since the 1960s. Recently, Cho et al. [16], in a study of 11- sation on children’s dental caries: a natural experiment year old children in 8 geographic areas in South Korea in Alberta, Canada. Unpublished; 23], we reported main (4fluoridatedareasand4non-fluoridatedareaswhich effects results from that comparative evaluation. In were similar in economic situation, population size, and those papers, we were not able to examine questions geography), showed a statistically significant negative about equity because socio-economic data were not association between socioeconomic status (family afflu- available in our pre-cessation (2004/05) surveys for both ence scale) and DMFT index (decayed, missing, or filled cities. permanent teeth) in the non-fluoridated areas, but no Here we use data from another Calgary survey, from association in the fluoridated areas. The multivariable 2009/10 [24], which contained some socio-economic in- analysis adjusted for intake of cariogenic snacks and formation, to explore trends over time by socio-economic beverages, oral hygiene behaviors (brushing and floss- indicators. The specific objective was to examine change ing), and use of piped water for drinking and cooking. over time in children’s dental caries in Calgary by 1) pres- An equitable effect is consistent with CWF as a ence or absence of dental insurance, and 2) a geographic population-level intervention that is structural in nature small area measure-namely, material deprivation of child’s [17, 18]. That is, rather than acting on individuals’ behav- community of residence (dissemination area). Based on iors, it acts on the circumstances in which behaviors consistent findings from cross-sectional studies, we occur, and thus the issue of active uptake-which is often hypothesized that we would see an increase in inequity of McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 3 of 9

dental caries, by dental insurance and small area material show different socio-economic patterns depending on deprivation, post-cessation relative to pre-cessation. access to treatment [27], we also examined untreated decay separately. Specifically, we considered those with Methods two or more teeth (primary or permanent) with untreated Data source decay (“decay2”) as a dichotomous variable (yes vs. no). Data for a population-based sample of grade 2 students Two socioeconomic indicators were considered, based in Calgary in 2009/10 were available from a survey con- on information available in both surveys. The informa- ducted by the former Calgary Health Region as part of tion was included on the parent questionnaire in 2013/ their surveillance activities [24]. Data for a population- 14, and on the parent consent form in 2009/10. The first based sample of grade 2 students in Calgary in 2013/14 indicator was reported presence vs. absence of dental in- were collected as part of a joint research - surveillance surance, where presence included any type of insurance initiative to evaluate the impact of CWF cessation in (i.e., private, employer-sponsored, or public). Second, we Calgary on children’s dental caries [25]. Methods used in used the Pampalon index, which describes the material 2013/14 were designed to maximize comparability with deprivation of a small geographic area [28]. The Pampalon the earlier survey. In both surveys, dental caries data index is based on age- and sex-adjusted census data from (decayed, missing/extracted, and filled teeth) were col- Statistics Canada (from the 2006 census1)forthe lected via open mouth exams conducted in schools, by population age 15 years and older within a dissemin- trained and calibrated assessment teams each consisting ation area. A dissemination area is a geographic unit of a registered dental hygienist and clerk. used in the Canadian census that contains a population of The target population for both surveys was children 400–700 persons. It is the smallest standard geographic (grade 2) attending school in the Public or Catholic area for which aggregate census data are released [29]. school systems in the city of Calgary. In both survey Material deprivation is a composite variable based on: years (2009/10 and 2013/14) a stratified random sample average individual income, employment to population ra- was drawn, with strata based on median neighbourhood tio, and proportion without a high school diploma or income where the school was located; within sampled equivalent. The Pampalon index was assigned to survey schools, all children of eligible grades were invited to respondents by linking each respondent’shomepostal participate. Signed parental informed consent was se- code to the corresponding dissemination area. In the cured, and verbal assent of each child was also secured. 2009/10 survey, school postal code was recorded if the The response rate in 2009/10 was 81 % [24]. In 2013/14 home postal code was not provided; we omitted cases in the response rate was lower: the overall school-level which that occurred (n = 43 cases, approx. 8 % of the response rate for Calgary was 57 %, and the overall sample). Material deprivation was expressed as a continu- student-level response rate within participating schools ous variable based on factor analysis. Using the continu- was 49 %. We developed sampling weights for both ous variable scores for the full Alberta population, we surveys. The weights account for both the probability of created both quintiles and tertiles which were then applied selection and the probability of non-response, and enhance to our sample, for use in regression analysis below. the extent to which each sample (2009/10 and 2013/14) is We first examined the association between socio- representative of its underlying target population. We also economic indicators and dental caries measures for ran all analyses unweighted. Results were broadly similar in 2009/10 and 2013/14 separately, using zero-inflated all cases (i.e., no change to statistical significance vs. not) Poisson regression (deft, DMFT) or logistic regression and weighted estimates are presented below. (decay2). We then confirmed apparent differences be- tween surveys using zero-inflated Poisson regression or Variables and analysis logistic regression including a year X socio-economic indi- Outcome variables examined were: the deft index and cator interaction term (where X = multiplied by), for each the DMFT index. These indices were created by sum- socio-economic indicator and each dental caries outcome ming, for each child, the number of decayed, extracted/ measure separately. missing (due to caries) or filled teeth for both primary Then, for material deprivation, we computed the con- teeth (deft) and permanent teeth (DMFT), based on the centration index of inequality [30] for each dental caries open mouth exam. We focus on tooth-level measures outcome variable. The concentration index, which can (versus tooth surface-level measures) because the 2009/ range from −1 to +1, quantifies the extent to which a 10 survey only contains tooth-level data. The deft and health problem is concentrated in lower (or higher) DMFT are well-established, commonly used summary socio-economic groups. Means and regression coeffi- measures for studies of tooth decay in child populations cients do not necessarily capture this information. For [26]. Because the deft and DMFT include both treated the concentration index we used the continuous version (fillings, extractions) and untreated decay, which could of the Pampalon material deprivation index, because the McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 4 of 9

concentration index requires socio-economic data that deprivation index is based on 2006 census data which are at least at the ordinal level of measurement. The omits some newer postal codes: n = 511 (deft) and n =505 continuous variable was transformed so that a negative (DMFT) for 2009/10, and n = 2980 (deft) and n = 2939 concentration index, as per convention, corresponds to (DMFT) for 2013/14. greater concentration of the health problem among Means or percentages and 95 % confidence intervals those with fewer resources (higher deprivation). To im- for all study variables are shown in Table 1, for 2009/10 prove the meaning of the concentration index, one can and 2013/14 separately. multiply the value by 75 which yields the percentage of Tables 2 and 3 shows associations between socio- the health variable that would need to be redistributed economic variables and dental caries summary measures from the less deprived half to the more deprived half of in 2009/10 and 2013/14 based on regression analyses. the population (if the inequality favors the less deprived) Table 2 focuses on dental insurance. Absence of dental in- to arrive at an equal distribution (i.e., a concentration surance was associated with higher mean DMFT in 2013/ index of 0) [30]. 14 but not in 2009/10. A statistically significant year X no The study received approval from the Conjoint Health dental insurance interaction term was observed for DMFT Research Ethics Board at the University of Calgary (ID E- (far right-hand column of Table 2), indicating that the as- 25219) and the Health Research Ethics Board at the sociation between no dental insurance and DMFT differed University of Alberta (ID Pro00037808). Approval was also significantly between 2009/10 and 2013/14. Absence of sought and granted by the participating school boards. dental insurance was associated with greater likelihood of having two or more instances of untreated decay, in both Results 2009/10 and 2013/14. Full sample sizes for primary teeth were: n = 557 (2009/10) Table 3 shows the associations between small area (dis- and n = 3230 (2013/14). Sample sizes for permanent teeth semination area-level) material deprivation (Pampalon were slightly lower because those measures are based on index) and dental caries summary measures. For primary individuals with at least one permanent tooth: n =551 tooth decay, there were statistically significant positive ef- (2009/10) and n = 3182 (2013/14). Sample sizes for ana- fects of material deprivation category (where categories lyses with dental insurance were approximately 98–99 % correspond to provincial tertiles) with highest and middle of the full sample, due to missing data on dental insurance: material deprivation categories having higher [worse] pri- n = 528 (deft) and n = 522 (DMFT) for 2009/10, and n = mary tooth caries, relative to lowest material deprivation 3164 (deft) and n = 3120 (DMFT) for 2013/14. For the category, in 2013/14 but not in 2009/10. Highest and small-area material deprivation index, sample size was ap- middle material deprivation, relative to lowest material proximately 92 % of the full sample, partly because the deprivation, had greater likelihood of two or more

Table 1 Descriptive statistics for study samples (weighted estimates) Variable Calgary 2009/10: Calgary 2013/14: Mean or % (95 % CI), n Mean or % (95 % CI), n Dental caries summary measures Mean number of decayed, extracted, or filled primary teeth (deft) 2.22 (1.87 to 2.57), n = 557 2.69 (2.52 to 2.86), n = 3230 Mean number of deft among those with deft > 0 4.22 (3.85 to 4.58), n = 284 4.73 (4.52 to 4.94), n = 1835 Mean number of decayed, missing, or filled permanent teeth (DMFT) 0.19 (0.11 to 0.27), n = 551 0.12 (0.10 to 0.14), n = 3182 Mean DMFT among those with DMFT > 0 1.85 (1.61 to 2.09), n = 56 1.52 (1.41 to 1.63), n = 254 Percent with 2 or more teeth with untreated decay (primary or permanent) 10 % (8 % to 13 %), n = 551 14 % (12 % to 15 %), n = 3182 Socio-economic variables Percent with no dental insurance 21 % (17 % to 25 %), n = 528 17 % (15 % to 19 %), n = 3164 Small area material deprivation (Pampalon index)a Percent within Category 1 (least deprived) 39 % (27 % to 52 %) 34 % (29 % to 40 %) Percent within Category 2 18 % (12 % to 27 %) 23 % (18 % to 28 %) Percent within Category 3 16 % (11 % to 23 %) 15 % (11 % to 19 %) Percent within Category 4 9 % (6 % to 12 %) 11 % (9 % to 13 %) Percent within Category 5 (most deprived) 19 % (10 % to 31 %) 18 % (14 % to 23 %) n = 511 n = 2980 aPampalon material deprivation categories are based on quintiles that apply to the whole province of Alberta. Category 1 = least deprived, 5 = most deprived. McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 5 of 9

Table 2 Weighted estimates from regression (zero-inflated Poisson, logistic) to assess associations between dental insurance (no vs. yes) and dental caries indices, Grade 2 students in Calgary, 2009–10 and 2013/14 Outcome variable Rate ratio (RR) or odds ratio (OR) for effect of absence (vs presence) of dental insurance on dental caries outcomes (reference = 1.0) 2009/10 2013/14 Interaction term (Year X No dental insurance): RR or OR RR or OR (95 % CI), p-value, (n) RR or OR (95 % CI), p-value, (n) (95 % CI), p-value, (n) defta RR = 1.05 (0.94 to 1.17), RR = 0.94 (0.86 to 1.03), p = 0.18 RR = 0.90 (0.78 to 1.04), p = .14 p = 0.40 (n = 528) (n = 3164) (n = 3692) DMFTa RR = 0.87 (0.65 to 1.16), p = 0.33 RR = 1.56 (1.05 to 2.33), p = 0.03* RR = 1.80 (1.10 to 2.93), p = .02* (n = 522) (n = 3120) (n = 3642) 2 or more teeth (primary or permanent) OR = 1.76 (1.34 to 2.32), OR = 2.0 (1.57 to 2.53), p < .001* OR = 1.13 (0.81 to 1.58), p = .46 with untreated decayb p < .001* (n = 522) (n = 3120) (n = 3642) deft number of decayed, missing, and filled primary teeth, DMFT number of decayed, missing, and filled permanent teeth, X multiplied by *Statistically significant effect of no dental insurance (vs. dental insurance) on dental caries outcome aZero-inflated Poisson regression bLogistic regression (yes vs. no) instances of untreated decay in 2013/14 (positive effects at decay showed statistically significant concentration p < .05). In 2009/10 a positive effect of highest material among those living in communities with higher ma- deprivation came close to statistical significance (p =.07). terial deprivation. In 2009/10, the deft (but not deft There were no statistically significant year X material if deft > 0) and the % with two or more instances of deprivation interactions for material deprivation. untreated decay showed statistically significant con- Concentration indices showing the extent to which den- centration with increasing material deprivation, with tal caries measures were concentrated across material an effect that came close to statistical significance deprivation (Pampalon index) are shown in Table 4, (p = .067) for DMFT if DMFT > 0. As noted above, and illustrated in Fig. 1. In 2013/14, the primary one can multiply the value of the concentration tooth measures (mean deft, mean deft if deft > 0) index by 75 to yield the percentage of the health and the % with two or more instances of untreated variable that would need to be redistributed from

Table 3 Weighted estimates from regression (zero-inflated poisson, logistic) to assess associations between Pampalon material deprivation index categories corresponding to provincial tertiles (highest deprivation and middle deprivation versus lowest deprivation) and oral health summary measures, grade 2 students in Calgary, 2009–10 and 2013/14 Outcome variable Rate ratio or odds ratio for effect of high or middle material deprivation (vs. low deprivation) on dental caries outcomes (reference = 1.0) 2009/10 2013/14 Interaction terms: RR or OR (95 % CI), p-value (n) RR or OR (95 % CI), RR or OR (95 % CI), p-value (n) p-value (n) defta Highest deprivation: RR = 1.07 Highest deprivation: Year X Highest deprivation: RR = 1.11 RR = 1.19 (0.93 to 1.23), p = .34 (1.08 to 1.30), p < .001* (0.95 to 1.30), p = .20 Middle deprivation: RR = 1.03 Middle deprivation: RR = 1.15 Year X Middle deprivation: RR = 1.12 (0.88 to 1.19), p = .73 (n = 511) (1.02 to 1.30), p = .023* (n = 2980) (0.91 to 1.37), p = .27 (n = 3491) DMFTa Highest deprivation: RR = 1.42 Highest deprivation: RR = 1.04 Year X Highest deprivation: RR = 0.74 (.74 to 2.69), p = .27 (0.68 to 1.59), p = 0.85 (0.36 to 1.50), p = 0.40 Middle deprivation: RR = 1.08 Middle deprivation: RR = 0.80 Year X Middle deprivation: RR = 0.74 (0.61 to 1.91), p = .77 (n = 505) (0.49 to 1.30), p = 0.37 (n = 2939) (0.36 to 1.51), p = 0.41 (n = 3444) 2 or more teeth (permanent or primary) Highest deprivation: OR = 2.95 Highest deprivation: OR = 2.23 Year X Highest deprivation: OR = 0.75 with untreated decayb (0.89 to 9.82), p = .07 (1.66 to 2.98), p < .001* (0.24 to 2.36), p = 0.63 Middle deprivation: OR = 0.90 Middle deprivation: OR = 1.43 Year X Middle deprivation: OR = 1.59 (0.31 to 2.62), p = .83 (n = 505) (1.05 to 1.94), p = .024* (n = 2939) (0.57 to 4.43), p = 0.37 (n = 3444) deft number of decayed, missing, and filled primary teeth, DMFT number of decayed, missing, and filled permanent teeth, X multiplied by *Statistically significant effect (at p < .05) of Pampalon material deprivation category (high or middle, versus low) on dental caries outcome aZero-inflated Poisson regression bLogistic regression (yes vs. no) McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 6 of 9

Table 4 Concentration indices for dental caries indices, by small-area material deprivation (Pampalon index) Outcome variable Concentration index which indicates the extent to which the dental caries index is concentrated by small-area deprivationa 2009/10 2013/14 Concentration index (95 % confidence interval), Concentration index (95 % confidence interval), p-value, (n) p-value, (n) deft Conc. index: −0.065 (−0.13 to −003), p = .039* Conc. index: −0.082 (−0.11 to −0.06), p < .001* (n = 511) (n = 2980) deft if deft > 0 Conc. index: −0.027 (−0.07 to 0.017), p = .23 Conc. index: −0.041 (−.06 to −02), p < .001* (n = 256) (n = 1678) DMFT Conc. index: −0.14 (−0.31 to 0.04), p = .13 Conc. index: −0.031 (−0.12 to 0.055), p = .48 (n = 505) (n = 2939) DMFT if DMFT > 0 Conc. index: −0.08 (−0.17 to .006), p = .067 Conc. index: −0.004 (−.042 to 0.034), p = .84 (n = 48) (n = 237) 2 or more teeth (permanent or primary) with Conc. index: −0.055 (−0.09 to −0.019), p = .003* Conc. index: −0.036 (−.048 to −024), p < .001* untreated decay (n = 505) (n = 2939) deft number of decayed, missing, and filled primary teeth, DMFT number of decayed, missing, and filled permanent teeth *Statistically significant at p < .05 aConcentration index is bounded by −1 (all problems concentrated in the lowest SES) and +1 (all problems concentrated in the highest SES). Concentration index of zero = perfect equality. Here, a statistically significant negative concentration index indicates that the dental caries outcome is significantly concentrated amongst those with higher material deprivation the less deprived half to the more deprived half of Discussion the population to arrive at an equal distribution (i.e., We set out to explore whether inequities in tooth-level a concentration index of 0) [30]. The percentages of measures of dental caries increased (worsened) following the outcome variable that would need to be distributed cessation of CWF, by examining the association of caries from the less deprived half to the more deprived half of measures with socio-economic indicators (dental insurance the population, computed for those measures with a con- and small area material deprivation [Pampalon index]) in centration index that was statistically significant at p <.10 Calgary in 2009/10 and in 2013/14. CWF cessation oc- (for this purpose only, we included the effects that came curred in 2011. This analysis was based on an argument close to statistical significance at the p < .05 level), ranged often made in favor of CWF; namely, that it can help offset from a low of 2.7 % (2013/14 decay2) to a high of 6.2 % inequities in dental health [11] and thus inequities could (2013/14 deft). hypothetically emerge or worsen following cessation.

Fig. 1 Extent to which dental caries is concentrated by small area deprivation. deft = number of decayed, missing, and filled primary teeth. DMFT = number of decayed, missing, and filled permanent teeth McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 7 of 9

Overall, we observed more evidence of inequities in (which represent a subset of the schools targeted in the 2013/14 (post-cessation) than in 2009/10 (pre-cessation). school-based program) to deliver services, including fluor- While inequities by dental insurance status and small ide varnish and application of protective dental sealants. area material deprivation were observed in both 2009/10 Collectively, therefore, preventive programming that is and 2013/14, they occurred more frequently, across delivered and funded by the provincial health authority more outcome measures, in 2013/14 than in 2009/10. for school-aged children in Calgary has-if anything- However in some cases, the statistically significant in- expanded over the time period, which is not consistent equities observed in 2013/14 did not significantly differ with it explaining our observed trend of an apparent in- from effects in 2009/10. Furthermore, the magnitude of creasing presence of dental caries inequities over the the inequities, especially as quantified using the concen- time period. The observation that inequities have in- tration index, was quite small in most cases. creased despite these programs, which are targeted to In the absence of a comparison community, it is im- socioeconomically disadvantaged populations, in fact portant to consider other factors that might explain an raises interesting questions about the role of targeted, apparent increase in dental caries inequities from pre- to versus more universal, preventive programming vis-à-vis post- fluoridation cessation. One possibility is changes to population dental health and health inequities [32]. Such the composition of the population over time. Although questions are particularly pertinent as more communi- Calgary’s population has increased (from approximately ties opt to discontinue CWF [33], which represents a 1.07 million in 2010 to approximately 1.20 million in universal or population-level approach to prevention 2014), the proportion of 5–14 year olds (the age range [17]. Discontinuation of CWF demands consideration of that includes our target population) has stayed the same viable, effective, and equitable alternatives. (11.5 % for both time points) (Calgary Civic Census). In A third possible reason for an observed increase in terms of socio-economic characteristics, our study data dental caries inequities is inequities in dental-related be- presented in Table 1 showed that there has been no clear haviors such as regular tooth brushing with fluoride shift in proportions across the provincial material toothpaste. A post hoc exploration of our 2013/14 data deprivation categories over the time period (the categor- (which included a questionnaire) indicated statistically ies correspond to quintiles developed for the province of significant inequities, by dental insurance status and by Alberta as a whole, so comparisons are meaningful). Un- small area material deprivation (Pampalon index), in 1) fortunately, we did not have data on other important reported brushing at least twice/day and 2) reported use population attributes at both time points, either from of fluoride toothpaste. Those without dental insurance, the Calgary civic census or from our data (the 2009/10 and those living in areas characterized by higher material survey did not include a questionnaire). And, it is pos- deprivation, were less likely to report brushing at least sible that the absolute material circumstances within the twice/day and less likely to report using fluoride tooth- deprivation categories has changed (to become more or paste, compared to those with insurance, and those liv- less inequitable), and we were not able to capture that. ing in less deprived areas, respectively (more detailed A second possibility relates to changes over time in analysis of socioeconomic inequities in dental-related publically-funded preventive dental programming. For behaviors in 2013/14 is planned for another paper). school-aged children (including Grade 2) in Calgary, there Thus, although our 2013/14 data indicate the presence is a targeted program of fluoride varnish application which of inequities in these behaviors, the lack of such infor- is administered by the provincial (and formerly regional) mation in 2009/10 precluded insight into whether or to health authority, and is delivered in schools by dental pub- what extent they may have contributed to apparently in- lic health professionals. The program is targeted to creasing inequities in dental outcomes observed here. schools located in communities characterized as having A fourth issue that must be considered, as possibly con- higher care needs based on household income data for tributing to an apparent increase in dental caries inequi- that community [31]. There have been some changes to ties from pre- to post- fluoridation cessation, is dental the programming during the last several years. Specifically, care in the private sector. A recent report [27] highlighted prior to 2008/09, children within targeted schools were in- the significant inequities in access to dental care across vited to receive the fluoride varnish only if they had not Canada, which reflects the overwhelmingly private nature received treatment at a dentist office within the previous of dental service delivery: of all oral health care expendi- 6 months or if their family did not have dental insurance. tures in Canada, approximately 95 % is privately financed Since 2008/09, all children within targeted schools have [27]. Theoretically, increasing inequities in dental caries been invited to receive the fluoride varnish. An additional following fluoridation cessation could reflect coincident change that occurred after CWF cessation in 2011 was trends toward less access to care, or greater inequities that some funds were re-allocated to a dental health bus, in access to care, during the time period in question. which travels to schools in lower-income communities However, that does not seem likely in this case, for McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 8 of 9

three reasons. Firstly, although the effect is not statistically we had information on type of insurance) in Table 2, omit- significant, Table 1 hinted at a decline, if anything, in the ting those with public insurance (who represented ap- proportions of our samples who did not have dental insur- proximately 10 % of the sample). The pattern of findings ance. On the other hand, if changes to dental insurance did not change (i.e., statistically significant positive effect have occurred such that those who responded “yes” had of no insurance on DMFT and on decay2). The material less coverage in 2013/14 than was the case in 2009/10, deprivation index (Pampalon index), while carefully con- then insurance might still play a role and we would not structed [28], is an ecological level variable and thus our have captured it here. understanding of the relationship between individual-level Furthermore, in another paper from the same project socio-economic characteristics and dental caries in the [McLaren L, Patterson S, Thawer S, Faris P, McNeil D, context of CWF cessation remains limited. Potestio M, Shwart L. The short-term impact of Strengths of our study included high-quality caries data community water fluoridation cessation on children’s collected by dental health professionals who underwent dental caries: a natural experiment in Alberta, Canada. intensive and ongoing training and calibration led by a Unpublished], we showed that the proportion of Calgary public health dentist with expertise and experience in sur- children in our study with “complete caries care”,defined vey calibration; population-based samples with sampling as one or more fillings or extractions but no untreated weights to permit better representation of the target popu- decay, had increased over time, while the proportion with lation; and our pre-post CWF cessation approach which “no caries care” (some untreated decay, but no fillings or builds importantly on the existing (cross-sectional) litera- extractions) had decreased over time. The opposite was ture of CWF and dental health inequities. observed in our comparison community of Edmonton. This suggested that care access has, if anything, increased Conclusions in Calgary. Our study objective was to compare the socio-economic Finally, the fact that we observed emerging inequities in patterns of children’s dental caries in Calgary, Canada, be- the composite caries measures (deft, DMFT, which fore and after cessation of community water fluoridation. include both treated and untreated problems), as well as Overall, results are consistent with increasing inequities in in the indicator of untreated decay (which would reflect dental caries following cessation of CWF. However, add- primary prevention rather than treatment), suggests that itional studies are needed to confirm the effects using a the factors driving the increasing inequity include factors study design that permits stronger control for potential that drive incidence. Overall, it seems unlikely that the confounding variables, such as a pre-post design with com- factors contributing to the observed increase in inequities parison community, or a prospective longitudinal design over time are predominantly dental care-related. Rather, where the same children are examined at multiple time the observed trends in inequities appear to have occurred points. Future research on the implications of CWF cessa- despite hints of improvements in treatment over time. tion for inequities in dental health outcomes should also A primary limitation of our study was the lack of com- ensure high-quality individual-level data on socio-economic parison community for this analysis; however, the fact that circumstances both pre- and post- cessation. we had a comparison community for the main analysis [McLaren L, Patterson S, Thawer S, Faris P, McNeil D, Endnotes Potestio M, Shwart L. The short-term impact of com- 1Following the 2006 national census, the mandatory munity water fluoridation cessation on children’sden- long-form census was discontinued, and its replacement tal caries: a natural experiment in Alberta, Canada. (the National Household Survey) was voluntary and may Unpublished; 23] permitted us to triangulate from have some bias (http://www12.statcan.gc.ca/census-recen- those findings to explore consistency of effects. In the sement/fc-rf/reports-rapports/r2_table-tableau_3-eng.cfm). absence of a comparison community, a longitudinal Abbreviations design where the same children are studied at multiple CWF: community water fluoridation; deft: decayed, extracted (due to caries), time points would have been a superior design, which and filled primary teeth; DMFT: decayed, missing (due to caries), and filled would have permitted better control for potential con- permanent teeth. founding factors. Another important limitation was that Competing interests we had only very limited socio-economic information The authors declare that they have no competing interests. available at both time points. The dental insurance vari- “ ” Authors’ contributions able was crude, and the yes category included those with LM contributed to the conceptualization of the study, led the implementation private or employer-sponsored insurance, as well as those of the study, and led the analysis and writing. DM contributed to the with public insurance. To explore whether the conflation conceptualization of the study, contributed significantly to the implementation of the study, and provided critical input to the analysis and writing. MP of different types of insurance influenced our findings, we contributed to the conceptualization of the study, contributed significantly to ran a post hoc re-analysis of the 2013/14 data (for which the implementation of the study and provided critical input to the analysis and McLaren et al. International Journal for Equity in Health (2016) 15:24 Page 9 of 9

writing. ST contributed significantly to the implementation of the study and 12. McLaren L, Emery JCH. Drinking water fluoridation and oral health provided critical input to the analysis and writing. SP contributed to the inequalities in Canadian children. Can J Public Health. 2012;103(1):S49–56. conceptualization of the study, contributed significantly to the implementation 13. Jones CM, Worthington H. Water fluoridation, poverty and tooth decay in of the study and provided critical input to the analysis and writing. PF 12-year-old children. J Dent. 2000;28(6):389–93. contributed to the conceptualization of the study, contributed significantly to 14. Slade GD, Spencer AJ, Davies MJ, Stewart JF. Influence of exposure to the implementation of the study and provided critical input to the analysis and fluoridated water on socioeconomic inequalities in children’s caries writing. CS contributed significantly to the analysis and provided critical input experience. Community Dent Oral Epidemiol. 1996;24(2):89–100. into the writing. LS contributed to the conceptualization of the study, 15. Treasure ET, Dever JG. Relationship of caries with socioeconomic status in contributed significantly to the implementation of the study and provided 14-year-old children from communities with different fluoride histories. critical input to the writing. All authors have read and approved the submitted Community Dent Oral Epidemiol. 1994;22(4):226–30. version of the manuscript. 16. Cho H-J, Lee H-S, Paik D-I, Bae K-H. Association of dental caries with socioeconomic status in relation to different water fluoridation levels. – Acknowledgements Community Dent Oral Epidemiol. 2014;42:536 42. We gratefully acknowledge funding support for this project from the 17. Rose G. The strategy of preventive medicine. Oxford: Oxford University Press; Canadian Institutes of Health Research (funding reference GIR 127083), 1992. ’ Alberta Health, and Alberta Health Services. 18. McLaren L, McIntyre L, Kirkpatrick S. Rose s population strategy of Lindsay McLaren holds an Applied Public Health Chair funded by the prevention need not increase social inequalities in health. Int J – Canadian Institutes of Health Research (Institute of Population and Public Epidemiol. 2010;39:372 7. Health, Institute of Musculoskeletal Health and Arthritis), the Public Health 19. Commission on Social Determinants of Health (CSDH). Closing the gap in Agency of Canada, and Alberta Innovates-Health Solutions. a generation: health equity through action on the social determinants of We thank the following individuals and groups: Dr. Steven Levy, Dr. Eugenio health, Final report of the commission on the social determinants of health. Beltran, Dr. Kathy Phipps, Dr. Barry Maze, Dr. Gary Whitford, Ms. Jodi Siever, Geneva: World Health Organisation; 2008. Ms. Vicki Stagg, Ms. Leanne Rodine, Ms. Joanna Czarnobaj, Dr. Marianne 20. Raphael D. A discourse analysis of the social determinants of health. Crit – Howell, the dental hygienists and clerks who worked on the project, and the Public Health. 2011;21(2):221 36. participating school boards, schools, and families. 21. Mackenbach JP, Kulhánová I, Menvielle G, Bopp M, Borrell C, Costa G, et al. Trends in inequalities in premature mortality: a study of 3.2 million deaths in – Author details 13 European countries. J Epidemiol Community Health. 2015;69(3):207 17. 1Department of Community Health Sciences, University of Calgary, Calgary, 22. Whitehead M. The concepts and principles of equity and health. Health – AB, Canada. 2Research and Innovation, Population, Public and Aboriginal Promotion Int. 1991;6:217 28. Health, Alberta Health Services, Calgary, AB, Canada. 3Alberta Cancer 23. McLaren L, Patterson S, Thawer S, Faris P, McNeil D, Potestio M, Shwart L. 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