J Periodont Res 2014 All rights reserved

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd JOURNAL OF PERIODONTAL RESEARCH doi:10.1111/jre.12191

Use of floss/interdental brushes is associated with lower risk for new cardiovascular events among patients with coronary heart disease

S. Reichert1, A. Schlitt2, V. Beschow1, A. Lutze1,3, S. Lischewski1, T. Seifert1,3, T. Dudakliewa3, R. Gawe3, K. Werdan3, B. Hofmann4, H.-G. Schaller1, S. Schulz1 1 Department of Operative Dentistry and Periodontology, Martin Luther University HalleWittenberg, Halle, Germany, 2Department of Cardiology, Paracelsus-Harz-Clinic Bad Suderode, Quedlinburg, Germany, 3Department of Internal Medicine III, Heart Centre of the University Clinics Halle (Saale), Martin Luther University Halle-Wittenberg, Halle, Germany and 4Department of Cardiothoracic Surgery, Heart Centre of the University Clinics Halle (Saale), Martin Luther University HalleWittenberg, Halle, Germany

Reichert S, Schlitt A, Beschow V, Lutze A, Lischewski S, Seifert T, Dudakliewa T, Gawe R, Werdan K, Hofmann B, Schaller H-G, Schulz S. Use of floss/interdental brushes is associated with lower risk for new cardiovascular events among patients with coronary heart disease. J Periodont Res 2014; doi: 10.1111/jre.12191 . © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Background and Objective: Periodontitis has been found to be associated with coronary heart disease (CHD) and stroke. However, only little is known about whether periodontitis and associated confounders are associated with new cardiovascular events among patients with CHD. Material and Methods: A total of 942 inpatients with CHD were examined regarding periodontitis, oral care habits, bacteria in the subgingival biofilm and the expression of interleukin-(IL)-6 c. (coding DNA)–174 genotypes (rs 1800793) to determine whether these confounders are associated with new cardiovascular events within a 1-year follow-up period. Adjusted hazard ratios (HR) with respect of age, gender, smoking, body mass index, use of aids for interdental hygiene, plaque index, occurrence of severe periodontitis and further internal diseases such as diabetes, hypertension, dyslipoproteinemia, number of missing teeth, serological parameters and IL-6 genotypes were generated with Cox regression. Results: In all, 941 cardiovascular patients completed the 1-year follow up and 7.3% of the patients achieved the primary endpoint (myocardial infarction: 2.1%, stroke/transient ischemic attack: 1.8%, cardiovascular deaths: 3.4%). Patients who reported practicing interdental cleaning were younger, less likely to be male or to have severe periodontitis, had a reduced tobacco exposure, had fewer missing teeth, less indices for plaque and bleeding on probing and a significant decreased adjusted risk for new cardiovascular events (HR = 0.2, CI 0.06–0.6, p = 0.01) than those patients with CHD who did not report practicing interdental cleaning. We did not obtain significant increased HR for patients with severe periodontitis (HR = 1.2, CI 0.7–2.1, p = 0.53), carriers of the IL-6 genotypes GC or CC (HR = 1.4, CI 0.8–2.5, p = 0.24) and did not find a significant association between the number of detected various oral species and the incidence of the combined endpoint (HR = 0.9, CI 0.8–1.01, p = 0.07).

Dr Stefan Reichert, PD, Department of Operative Dentistry and Periodontology, Martin Luther University Halle-Wittenberg, Große Steinstrasse 19, 06108 Halle (Saale), Germany Tel: +49 345 557 3772 Fax: +49 345 557 3773 e-mail: [email protected] Key words: coronary heart disease; gene

polymorphism; interleukin-6; periodontitis; prognostic marker Accepted for publication March 26, 2014

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Conclusions: These findings suggest that flossing and brushing of interdental spaces might reduce the risk for new cardiovascular events among patients with CHD. The hypothesis that interdental cleaning per se reduces the risk of new cardiovascular events should be examined in an interventional study.

In the last years numerous studies were carried out to investigate whether periodontitis is a putative risk factor for atherosclerosis (1,2) and subsequent diseases such as coronary heart disease (CHD) (3) and stroke(4). Indeed, meta-analyses have shown that periodontal disease is an independent risk factor for CHD (5–7) and cerebrovascular disease (8). Furthermore, the occurrence of periodontopathogens in the subgingival plaque was found to be associated with the occurrence of CHD (9). Interleukin (IL)-6 is a proinflammatory cytokine, which stimulates hepatic production of acute phase proteins such as C-reactive protein (CRP), modulates adhesion of monocytes on endothelial cells and promotes coagulation of platelets (10). Therefore, IL-6 might be involved in the pathogenesis of both periodontitis (11–13) and CHD (14–16). It has been reported that IL-6 c.–174G/C polymorphisms influenced IL-6 serum levels (17). The genotype GG was identified as a high-producer genotype whereas carriers of the GC and CC genotypes showed lower IL-6 serum levels. The IL-6 c.–174G/C polymorphism was found to be associated to both chronic (18) and aggressive periodontitis (19) as well as to the subgingival colonization with periodontopathogens (20). Furthermore, this polymorphism was found associated with CHD (21–23). Hence, IL-6 genotypes at promoter position –174 may be prognostic markers for CHD and periodontitis and should be considered in multivariate risk factor analyses. So far, only one study from Finland has investigated the role of dental infection for new coronary events among patients with proven coronary artery disease (24). Therefore, the aim

of the present, prospective, longitudinal study was to investigate whether oral hygiene habits, severe periodontitis, presence of periodontopathogens in the subgingival biofilm, or certain IL-6 c.–174 genotypes represent independent risk factors for the incidence of new cardiovascular events (combined endpoint: myocardial infarction, stroke/transient ischemic attack [TIA], myocardial death) among inpatients suffering from CHD.

Material and methods Study population

At baseline, 942 consecutive German patients of Caucasian origin from central Germany admitted to the Department of Internal Medicine III or Department of Cardiothoracic Surgery of the Martin Luther University Halle-Wittenberg with angiographically proven CHD were prospectively included from October 2009 to February 2011. The investigations were carried out in accordance with the ethical guidelines of the “Declaration of Helsinki” and its amendment in “Tokyo and Venice.” The study was approved by the ethics committee of the Martin Luther University HalleWittenberg. Informed written consent was obtained from each patient. Inclusion criteria were age ≥ 18 years and known CHD as defined by a stenosis of ≥ 50% of a main coronary artery by coronary angiography or percutaneous coronary intervention or coronary artery bypass surgery. At least four own teeth except for the third molars needed to be present. Exclusion criteria were pregnancy, antibiotic therapy during the last 3 mo, subgingival scaling and root planing during the last 6 mo or psychological reasons that rendered study participation impracti-

cal. Patients with current alcohol or drug abuse might be not completely able to understand the aim of the study and the necessity of an additional dental examination. If a drug or alcohol abuse was known from patient’s file or a patient reported during the interview about a current drug or alcohol abuse s/he was not included in the study. Ages, body mass index, current or past diseases (e.g. diabetes mellitus, hypertension and dyslipoproteinemia) were assessed as part of the patient’s medical history. Diabetes mellitus was diagnosed when it was known from the history and/or the patients were receiving dietary or antidiabetic drug therapy in the hospital, or had a fasting blood glucose of ≥ 7 mM. Dyslipoproteinemia was assumed if this had been prediagnosed, a therapy with lipid-lowering agents was being administered or a fasting cholesterol of > 5.2 mM or low-density lipoprotein cholesterol > 3.9 mM was present. Arterial hypertension was defined as hypertension that was diagnosed before the current hospitalization and/or the patient was taking antihypertensive medication or when a blood pressure of > 140/90 mmHg was measured. Furthermore, patients were asked about their smoking behaviors. A person who smoked a minimum of one cigarette per day at the time of questioning was considered a current smoker. For quantification of cigarette smoking, pack-year of each current smoker was calculated. When calculating the pack-year, former smokers were not considered. Furthermore, all patients underwent detailed clinical and biochemical investigation. For instance, serum parameters, including hemoglobin (mM), IL-6 (pg/mL), CRP (mg/dL) and creatinine (lM) were recorded.

Periodontitis and cardiovascular events During the periodontal examination, patients were asked about the frequency of tooth brushing per day and whether they use dental floss or interdental brushes to clean the interdental spaces. The clinical assessment involved determining the plaque index (PI) (25) and assessing bleeding on probing (BOP) (26). In both indexes, four sites around each tooth (mesiobuccal, mid-buccal, disto-buccal and mid-lingual) were examined. The measurements for both maximal clinical probing depth (distance between gingival margin and bottom of the pocket) and maximum clinical attachment loss (distance between cementoenamel junction and bottom of the pocket) were taken using a pressuresensitive probe (DB764R; Aesculap AG & Co. KG, Tuttlingen, Germany) at six sites around each tooth (mesiobuccal, mid-buccal, disto-buccal, mesio-lingual mid-lingual, disto-lingual). For the diagnosis of periodontitis, we used the published criteria for a twolevel periodontitis case definition for risk factor research. Periodontitis was defined as the presence of proximal attachment loss of ≥ 3 mm in ≥ 2 nonadjacent teeth. Severe periodontitis was defined as the presence of proximal attachment loss of ≥ 5 mm in at least 30% of the teeth (27). A 1-year follow-up was performed and the incidence of the combined endpoint defined as myocardial infarction, stroke/TIA and death from cardiovascular causes was calculated. For acquiring follow-up data, a standardized questionnaire was sent out. If patients did not return the questionnaires, a telephone interview was conducted with the patient or patient’s relatives and physician, when the patient was dead. At an unknown current address or telephone number, we contacted civil registration offices and requested information about current address or date of death. If the patient’s death was already known, for instance for individuals who died in our hospital, we did not send out a questionnaire. Instead, the information about the cause and date of death was obtained from electronic patient files.

Determination of interleukin-6 c.–174 G/C genotypes

The genomic DNA was obtained from leukocytes in venous EDTA blood using a commercial DNA extraction kit (QIAampâ; Qiagen, Hilden, Germany) in accordance with the manufacturer’s instructions. Genotype analyses were carried out using a commercial available polymerase chain reaction (PCR)-SSP kit (CTS-PCR-SSP Tray kit, Collaborative Transplant Study, Department of Transplantation Immunology of the University Clinic of Heidelberg, Germany) as described previously (28). After agarose gel electrophoresis, the results were evaluated visually. Bands of 430 bp correspond to the various IL-6 alleles. According to db single nucleotide polymorphism, the identification number of the single nucleotide polymorphism was rs 1800793. Molecular biological assessment of periodontal bacteria in subgingival pockets

Microbial samples were taken from the deepest pocket of each quadrant by inserting one sterile paper point for 20 s. The four bacterial plaque samples taken from each patient were pooled in one tube. Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Treponema denticola, Peptostreptococcus micros, Fusobacterium nucleatum, Campylobacter rectus, Eubacterium nodatum, Eikenella corrodens and a combination of Capnocytophaga sputigena, Capnocytophaga gingivalis and Capnocytophaga ochracea were specifically assessed by PCR in a commercial laboratory (micro-Ident plus test; HAINDiagnostica, Nehren, Germany). The procedure for detecting bacterial DNA can be divided into three steps: isolation of bacterial DNA, multiplex amplification with biotinylated species-specific primers by PCR, and reverse hybridization. These steps have been described in detail in a previously published paper of our group (29). The detection limit for all bacte-

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ria was 104 genome equivalents with the exception of Aggregatibacter actinomycetemcomitans with 103 genome equivalents. The numbers of detected bacterial species per individual that were over the detection limit were counted. Statistical evaluation

Statistical analyses were carried out using commercially available software (SPSS v.19.0 package; IBM, Chicago, IL, USA). Values of p ≤ 0.05 were considered significant. The distribution of the IL-6 c.–174GG, GC and CC among the inpatients with CHD was tested according to the Hardy– Weinberg equilibrium. Metric demographic, clinical and serological data were checked for normal distribution using the Kolmogorov–Smirnov test and the Shapiro–Wilk test. As all metric values were not normally distributed, they were plotted as median and 25th/75th percentiles. For statistical evaluation, the Mann–Whitney U test was used. Pack-year was calculated by multiplying the number of packs (one pack = 20 cigarettes) of cigarettes smoked per day by the number of years the person has smoked. To evaluate adjusted odds ratios for occurrence of severe periodontitis among patients with CHD, a logistic regression analysis was conducted with respect of the cofactors age, gender, body mass index, pack-year, number of detected different bacterial species per individual, frequency of tooth brushing per day, use of floss/ interdental brushes and expression of IL-6 c.–174 G/C genotypes. For survival evaluation, Kaplan– Meier analyses with the log-rank test were applied. Adjusted hazard ratios were generated with Cox regression and with respect of the variables age gender, body mass index, pack-year, hypertension, dyslipoproteinemia, diabetes, serum levels for IL-6, CRP, hemoglobin and creatinine, IL-6 c.– 174 genotypes (GC+CC vs. GG), number of missing teeth, number of detected different bacterial species per individual, frequency of tooth

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Table 1. Periodontal conditions, prevalence of internal diseases, biochemical parameters, distribution of c.–174 interleukin-6 genotypes among inpatients with coronary heart disease Stationary patients with coronary heart disease n = 942

Variables Demographic parameters Age (years), median (25th/75th percentiles) Males (%) Pack-years, mean (SD) Body mass index (kg/m2), median (25th/75th percentiles) Prevalence of internal diseases Diabetes (%) Hypertension (%) Dyslipoproteinemia (%) Oral care habits and periodontal conditions Frequency of tooth brushing per day (%) Once a day More than once a day Use of interdental floss/brush (%) No periodontitis (%) All periodontitis cases (%)a Severe periodontitis cases (%)b Plaque index (%), median (25th/75th percentiles) Bleeding index (%), median (25th/75th percentiles) Number of missing teeth, median (25th/75th percentiles) Number of detected oral species, median (25th/75th percentiles) Serological parameters C-reactive protein (mg/dL), median (25th/75th percentiles) Reference: < 0.5 Interleukin 6 (pg/mL) Median (25th/75th percentiles) Reference: < 6.4 Creatinine (lM), median (25th/75th percentiles) Reference: males: < 102; females: < 88 Hemoglobin (mM) Median (25th/75th percentiles) Reference: males 8.7–11.2; females: 7.3–9.9 IL-6 c.–174 G>C genotypes (rs 1800793) (%) GG GC CC

68.8 (59.5/74.9) 74.0 3.0 (9.7) 28.1 (25.3/30.8) 34.2 87.6 58.7

23.9 74.9 20.1 2.1 97.9 47.7 0.8 5.6 10.0 7.0

(0.5/1.4) (1.8/12.1) (5.0/18.0) (5.0/8.0)

8.9 (3.6/32.1) 7.4 (3.6/15.7)

87.0 (72.0/106.3) 8.3 (7.2/9.1)

29.8 49.3 20.95

Attachment loss of ≥ 3 mm in at least two non-adjacent teeth. Attachment loss of ≥ 5 mm in ≥ 30% of teeth present.

a

b

brushing per day and use of floss/ interdental brushes were included in one model.

Results Periodontal, microbial and serologic conditions in inpatients with coronary heart disease

All baseline data are presented in Table 1. The overall prevalence of severe periodontitis among our patients with CHD was almost 50%.

A median of 10 missing teeth (exception third molars) was recorded. The median for the number of detected bacterial species was 7. The majority of patients with CHD (74.9%) brushed their teeth more than once a day but only 20.1% used floss and/or interdental brushes. The overall median values for CRP and IL-6 were above the reference values for healthy persons. The distribution of the IL-6 c.-174 genotypes GG, GC and CC fulfilled the criteria of the Hardy–Weinberg

equilibrium. Of the patients, 70% were carriers of IL-6 c.–174 genotypes GC or CC. Factors associated to the occurrence of a severe periodontitis among patients with coronary heart disease

The age, male gender, the number of detected oral species, and occurrence of IL-6 c.–174 GC or CC genotypes were associated with an increased adjusted odds ratio for severe periodontitis whereas the use of floss/ interdental brushes was associated with a lower adjusted odds ratio (Table 2). Patients who used floss and/or interdental brushes were significantly younger, more often females, and had lower values for pack-years, occurrence of a severe periodontitis, missing teeth, PI and BOP in comparison to patients with CHD, who did not use any aids for interdental hygiene (Table 3). Association of severe periodontitis, periodontal and microbial conditions and IL-6 c.–174 genotypes with the incidence of the combined endpoint within the 1-year follow-up period

A total of 942 patients with CHD were prospectively included in the longitudinal cohort study. For one patient (0.1% dropout rate) we did not obtain 1-year follow-up data. During the mean follow-up of 54  11 wk, 20 (2.1%) myocardial infarctions, 17 (1.8%) strokes/TIAs and 32 (3.4%) cardiovascular deaths were recorded. The total incidence of the combined endpoint was 7.3%. Bivariate analyses— The Kaplan– Meier plot (Fig. 1) showed a significantly lower incidence for the combined endpoint among patients who used dental floss/interdental brushes than among individuals who did not use these aids for oral hygiene (1.6% vs. 8.8%, log-rank p = 0.001). Moreover, patients with CHD who had only 0–10 missing teeth showed a significantly lower incidence of the combined endpoint than individuals

Periodontitis and cardiovascular events Table 2. Logistic regression analysis for the occurrence of a severe periodontitisa among patients with cardiovascular heart disease

Confounding variables Age Male gender Body mass index Pack-years Frequency of tooth brushing per day Use of floss/interdental brushes Number of detected bacterial various species per individual Diabetes IL-6 c.–174 GC or CC vs. GG a

Odds ratio

95% lower

CI upper

p values

1.02 1.42 0.99 1.03 0.87 0.50 1.14

1.01 1.03 0.96 1.01 0.68 0.35 1.08

1.04 1.95 1.02 1.05 1.11 0.71 1.21

0.002 0.03 0.44 0.002 0.26 < 0.001 < 0.001

1.22 1.11

0.91 0.83

1.64 1.49

0.18 0.009

Attachment loss of ≥ 5 mm in ≥ 30% of teeth present.

Table 3. Demographic, general and periodontal conditions in patients with coronary heart diseases in depending on the use of aids for approximal hygiene

Variable Age (years), median (25th/75th percentiles) Males (%) Pack-years, mean (SD) Body mass index (kg/m2), median (25th/75th percentiles) Severe periodontitis (%)a Missing teeth (exception third molars), median (25th/75th percentiles) Plaque index (%), median (25th/75th percentiles) Bleeding upon probing (%), median (25th/75th percentiles) Number of bacterial species per individual, median (25th/75th percentiles)

No use of floss/ interdental brushes n = 753

Use of floss/ interdental brushes n = 189

69.2 (59.7/75.5)

67.3 (59.2/72.0)

0.006c

74.0 3.3 (10.4) 28.1 (25.2/30.8)

30.7 1.5 (5.9) 27.9 (25.4/30.5)

< 0.001b 0.045c 0.649c

51.9 12.0 (6.0/20.0)

30.7 7.0 (3.1/10.0)

< 0.001b < 0.0001c

0.9 (0.6/1.6)

0.6 (0.4/0.8)

< 0.0001c

6.3 (2.2/12.5)

3.5 (0.9//6.9)

< 0.0001c

7 (5.0/8.0)

7 (4.0/8.0)

0.963c

p

Severe periodontitis: Attachment loss of ≥ 5 mm in ≥ 30% of teeth present. Chi-squared test with Yates’ correction. c Mann–Whitney U-test. a

b

who had 11–24 missing teeth (4.9% vs. 9.8%, log-rank p = 0.004) (Fig. 2). The incidence for the combined endpoint tended to be higher in patients with severe periodontitis than in individuals who did not have severe periodontitis (8.9% vs. 5.9%, log-rank p = 0.095). There was no significant difference regarding the incidence of the combined endpoint in patients where none to five various bacterial species were detected in comparison to those with six to 11 bacteria (7.9% vs. 7.0%, log-rank p = 0.515). IL-6 c.–174 genotypes were not signifi-

cantly associated with different incidence rates of the combined endpoint (GG 6.1%, GC 7.1%, CC 9.6%, log-rank p = 0.340). Multivariate analysis— To generate adjusted hazard ratios the influence of severe periodontitis, oral hygiene habits, number of missing teeth and expression of IL-6 c.–174 genotypes on the cardiovascular endpoint, was investigated with Cox regression with respect to known confounders for both, periodontitis and CHD. Only the use of dental floss/interdental

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brushes was associated with a significantly decreased adjusted hazard ratio for the combined endpoint (Table 4).

Discussion Periodontitis, periodontopathogens, oral hygiene habits, number of missing teeth and polymorphisms in genes of cytokines such as IL-6 might be indicative for new cardiovascular events among patients who suffer from CHD. If such associations were identified, the diagnosis and therapy of periodontal diseases would need to be regularly integrated into cardiac rehabilitation programs to reduce the risk for such events. The purpose of the present study was to evaluate the impact of these periodontal and genetic conditions on further cardiovascular events (combined endpoint: myocardial infarction, stroke/TIA, myocardial death) within a 1-year follow-up period among inpatients with proven CHD. The hazard ratios should be controlled for known confounders for both periodontitis and CHD. Both the overall prevalence of periodontitis (97.9%) and prevalence of a severe periodontitis (47.7%) among our patients with CHD (Table 1) were slightly higher than the epidemiologic data obtained in the fourth German Dental Health Survey (DMS IV). In that study, the overall prevalence of periodontitis was 87.8% (Community Periodontal Index [CPI] Code 3 or 4) among individuals aged from 65 to 74 years and 39.9% had a severe periodontitis (CPI Code 4) (30). In contrast, the number of missing teeth (except for the third molars) was not higher among our patients with CHD (14.0 vs. 14.2) (31). The differences regarding the prevalence of periodontitis among patients with CHD in comparison to the DMS IV data should be interpreted with caution, however, and we cannot conclude from these data that the prevalence of periodontal disease is higher among patients with CHD in general. For instance, CPI codes were only recorded on index teeth and a pocket depth on 4–5 mm (Code 3) was defined as periodontitis. In the present

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Combined endpoint

0.8

0.6

0.4

0.2

Use of dental floss/interdental brushes No Yes

0.0 0

20

40 60 Wk of follow up

80

100

Fig. 1. Kaplan–Meier plot for combined endpoint (stroke/transient ischemic attack, cardiovascular death, myocardial infarction) according to the use of aids for interdental hygiene (use of floss/interdental brushes vs. no use of floss interdental brushes).

1.0

Combined endpoint

0.8

0.6

0.4

0.2 0–10 missing teeth 11–24 missing teeth

0.0 0

20

40 60 Wk of follow up

80

100

Fig. 2. Kaplan–Meier plot for combined endpoint (myocardial infarction, stroke/transient ischemic attack, myocardial death) according to the number of missing teeth (0–10 missing teeth vs. 11–24 missing teeth).

study, the threshold for diagnosis of a periodontitis case was a clinical attachment loss of at least 3 mm in at least two nonadjacent teeth. Moreover, all teeth were investigated. As only 20 (2.1%) of our study patients with CHD did not have peri-

odontitis, a separate statistical evaluation for this cohort would not be meaningful. Therefore, this group was added to patients who had no severe periodontitis. Our main results showed a significantly decreased adjusted HR for the

combined endpoint among patients who used dental floss/interdental brushes for oral hygiene (Table 4). According to our results this association might be due to the favorable effect of proper oral hygiene in the plaque and bleeding index, number of missing teeth and prevalence of severe periodontitis (Table 3). The inverse association between use of floss/interdental brushes and prevalence of a severe periodontitis was additionally confirmed in a binary logistic regression model (Table 2). The long-term effect of effective plaque control on periodontitis and tooth mortality has already been demonstrated (32). The use of aids for cleaning interdental spaces as an adjunct to brushing was found to remove more dental plaque than brushing alone (33). In contrast to our results, a Scottish health survey (34) obtained (Table 4) an inverse association between the frequency of dental brushing and the risk of CHD. The use of floss/interdental brushes, however, was not evaluated. Although our data suggest a direct link between oral hygiene and the incidence of the combined endpoint, further confounders should be discussed. For instance, patients who used aids for interdental hygiene were significantly younger, more often were females and had a lower smoke exposure than their counterparts who did not clean the interdental spaces (Table 3). These confounders might influence the risk for further cardiovascular events. It is also conceivable that patients with a proper interdental hygiene were in better general health and more motivated and/or able to use floss/interdental brushes regularly. Furthermore, good oral care habits such as use of aids for interdental hygiene might reflect a higher health consciousness in general. Despite this uncertainty regarding the underlying biologic effect of oral hygiene to the incidence of new cardiovascular events, the use of interdental brushes/ dental floss might be recommended, in particular, to patients with CHD. The hypothesis that interdental cleaning per se reduces the risk of new cardiovascular events should be examined in an interventional study.

Periodontitis and cardiovascular events

Hazard ratio

95% lower

CI upper

p values

0.99 0.65 0.95 0.99 0.96 0.86 0.97 1.51 1.00 1.00 1.00 1.20 1.41 0.99 1.25 0.91

0.97 0.37 0.89 0.96 0.45 0.53 0.78 0.90 0.99 0.99 1.00 0.68 0.79 0.96 0.89 0.82

1.02 1.16 1.00 1.02 2.02 1.41 1.20 2.56 1.01 1.00 1.00 2.09 2.49 1.03 1.77 1.01

0.52 0.15 0.07 0.43 0.91 0.55 0.77 0.12 0.29 0.71 0.13 0.53 0.24 0.74 0.20 0.07

(cross-sectional vs. longitudinal) or the different methods for detecting periodontopathogens and thus different detection limits. There was trend for a positive association between the individual expression of the genotypes IL-6 c.-174 GC or CC and the prevalence of a severe periodontitis among patients with CHD (Table 2). However, although our patients who were carriers of IL-6 c.–174 CC or GC genotypes usually met the combined endpoint, this was not significant after both log-rank test and Cox regression. Therefore, our results did not support previous crosssectional studies and meta-analyses, which identified the IL-6 c.–174 G/C polymorphism as indicative for cardiovascular diseases (21–23,36).

1.14 0.19

0.74 0.06

1.78 0.63

0.56 0.01

Limitations of the study

Table 4. Cox regression for the incidence of the combined endpoint (myocardial infarction, stroke/transient ischemic attack, myocardial death) within the 1-year follow-up period among patients with coronary heart disease. Significant data are highlighted in bold print.

Confounding variables Age Male gender Body mass index Pack-years Hypertension Dyslipoproteinemia Hemoglobin Diabetes IL-6 C-reactive protein Creatinine Severe periodontitisa IL-6 c.–174 GC or CC vs. GG Missing teeth Plaque index Number of detected various bacterial species per individual Frequency of tooth brushing per day Use of floss/interdental brushes

CI, confidence interval; IL, interleukin. a Severe periodontitis: Attachment loss of ≥ 5 mm in ≥ 30% of teeth present.

Although oral hygiene habits were associated to both, the prevalence of a severe periodontitis (Table 2) and incidence of the cardiovascular endpoint (Table 4) we found only a trend but not a significant association between severe periodontitis and the incidence of the combined endpoint at all. In contrast to our result, a previous study (24) showed a significant positive association between dental infection and the risk of new coronary events among patients with proven coronary artery disease. In particular, differences in the study design (e.g. number of studied individuals, followup intervals and definition of the endpoint, including cofactors) might be responsible for these inconsistent results. For instance, in a previous study (24) only 214 individuals were investigated but the follow-up period was 7 years. The endpoint was defined as incidence of fatal and nonfatal coronary events and overall mortality but incidence of TIA/stroke was not investigated. Moreover, in comparison to our multivariate Cox regression the socioeconomic status, the number of previous myocardial infarctions, and serum lipids were included as confounding variables.

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A Swedish longitudinal study (35) reported a dose-dependent relationship between number of teeth and all-cause and cardiovascular disease mortality. The authors assumed that severe tooth loss might be an indicator for life-long dental infections, which could represent an important risk factor for atherosclerotic vascular changes. The results of that study are partially confirmed by our findings because, according to the log-rank test (Fig. 2), the incidence of the combined endpoint was associated with the number of missing teeth. However, this was not significant in the multivariate model (Table 4). The positive association between the periodontal pathogen burden and the prevalence of CHD obtained in a previous cross-sectional controlled study (9) could not be confirmed by our results. According to our findings, the number of detected bacterial species per individual was indeed associated to the prevalence of a severe periodontitis (Table 2) but not to the incidence of the combined endpoint (Table 4). This different result in comparison to the preceding study (9) could be due to differences in study designs

The present study is a longitudinal cohort study to investigate predictors for new cardiovascular events among patients with CHD. Therefore, a gender- and age-matched non-CHD control group was not included and the prevalence of a severe periodontitis among patients with CHD was compared with data obtained in the fourth German Dental Health Survey (DMS IV). Not surprisingly, the comparison of patients with CHD to matched controls without CHD would extend conclusions. The present study does not provide information about whether use of aids for interdental hygiene among individuals without CHD reduced the risk for CHD events at all. In the study 118 patients were included who reported in the interview about a previous periodontitis therapy earlier than 6 mo before dental examination. Previous periodontal therapy might lower the risk for new cardiovascular events. Moreover, patients with CHD were heterogeneous regarding their status of internal diseases. For instance, patients with diabetes who had not yet started any diabetic control measures were included. It is feasible that patients with CHD where the concomitant internal diseases were well treated have a

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lower risk for further CHD events than patients with untreated internal diseases. We investigated Caucasian patients from central Germany. As the distribution of gene polymorphisms is also different with respect to ethnicity, our results regarding the IL-6 polymorphism cannot be transferred to groups with other ethnic affiliations. With multivariate analyses, we tried to identify independent risk indicators for the incidence of the cardiovascular endpoint. However, the results depend very strongly on the type and number of included confounding variables and duration of follow-up. This could explain different results in comparison to other investigations. In summary, the use of dental floss and/or interdental brushes was significantly associated with an adjusted decreased HR for new cardiovascular events among patients with CHD within a 1-year follow-up period whereas severe periodontitis, number of missing teeth, the amount of detected bacterial species and certain IL-6 c.–174 genotypes were not. Whether the use of aids for oral hygiene actually reduces the incidence of new cardiovascular events should be investigated in an interventional study.

Acknowledgements We would like to thank all patients for their cooperation in this study.

Source of funding The study was supported by a grant of the Deutsche Herzstiftung, Frankfurt am Main, Germany (F/34/08) and by an unrestricted grant from HAINDiagnosticaâ, Nehren, (Germany).

Conflict of interest The authors declare that they have no conflict of interest.

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