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Journal ArticleDOI

Periodontal disease may associate with breast cancer

TL;DR: Chronic periodontal disease indicated by missing molars seemed to associate statistically with breast cancer.
Abstract: The main purpose was to evaluate the association between periodontal disease and the incidence of breast cancer in a prospective study of 3273 randomly selected subjects aged 30-40 years at baseline. Breast cancer incidence was registered from 1985 to 2001 according to the WHO International Classification of Diseases criteria. At baseline, 1676 individuals also underwent a clinical oral examination (Group A) whereas 1597 subjects were not clinically examined but were registered (Group B). The associations between breast cancer, periodontal disease, and missing molars were determined using multiple logistic regression models with several background variables and known risk factors for cancer. In total 26 subjects in group A and 15 subjects in group B had breast cancer. The incidence of breast cancer was 1.75% in subjects who had periodontal disease and/or any missing molars, and 0 in subjects who had periodontal disease but had no missing molars. For periodontally healthy subjects with no missing teeth the breast cancer incidence was 1%. For group B the respective incidence was 0.94%. Female gender (odds ratio (OR) 13.08) and missing any molar in the mandible (OR 2.36) were explanatory variables for breast cancer. Of the subjects with periodontal disease and any missing molars in the mandible 5.5% had breast cancer in comparison to 0.5% of the subjects who had periodontal disease but no missing molars in the mandible (P < 0.02). Chronic periodontal disease indicated by missing molars seemed to associate statistically with breast cancer.

Summary (2 min read)

Introduction

  • Inflammation is a key feature in many chronic diseases including cancer [1-2].
  • The associations between infectious agents of putative bacterial pathogens, herpes viruses, Epstein-Barr virus (EBV) type 1, cytomegalovirus (CMV) seems to play an important synergistic role in the pathogenesis of chronic periodontitis. [16-18] .
  • Breast cancer is the most common malignancy in women worldwide and it is the leading cause of cancer-related mortality [19].
  • In general, persistent and prevalent infections in populations appear to link with malignancies [22].
  • The results of an epidemiological study 2001, from their group, showed that fairly young individuals with periodontal disease and missing molars are at increased risk of premature death caused by life threatening diseases such as malignant neoplasm, cardiovascular diseases, and diseases of the digestive system [25].

Study population

  • In 1985 the authors undertook this longitudinal prospective study, which comprised a random sample cohort of 3273 individuals aged 30–40 years.
  • They were informed about the purpose of the study and offered a clinical oral examination.
  • The remaining 1597 subjects (849 men and 748 women) did not have the clinical examination and constituted Group B. Figure 1 shows the study profile.

Clinical examination

  • For all subjects of the clinically examined Group A the following parameters were recorded: the number of remaining teeth excluding third molars; gingival inflammation around every tooth as assessed using the gingival index [28]; and oral hygiene status as determined by using both the dental plaque [29] and the calculus indices to assess all six surfaces of six representative teeth.
  • Pocket depth was determined using a periodontal probe and recorded to the nearest higher millimetre for six sites of each tooth.
  • The smokers reported the number of cigarettes per day, and the number of years of smoking.
  • The Ethics Committee of the Karolinska Institute and Huddinge University Hospital, Sweden, approved the study protocol.
  • The data for cancer (malignant neoplasm) and causes of death were obtained from the Centre of Epidemiology, Swedish National Board of Health and Welfare, Sweden.

Statistical analyses

  • Analysis of variance, chi-square test, Fisher´s exact t-test and multiple logistic regression analyses were applied when appropriate.
  • Multiple logistic regression analysis was used to compare the incidence of cancer, according to the state of oral health at baseline, while simultaneously controlling for confounding variables.
  • Smoking habits were dichotomized into the number of smokers (ever smokers) and the number of never smokers.
  • The model with the confounders was correlated to the incidences of cancer.
  • The statistical model was tested according to Cox & Snell [30] and Nagelkerke [31].

Results

  • The difference between the groups was statistically not significant (NS).
  • The demographic and oral health data at baseline in 1985 for subjects with and without periodontal disease are shown in Table 1.
  • The incidence figures for breast cancer for the clinically examined Group A showed that 1.75% of those with any missing molar had breast cancer whereas only 0 % of the subjects with no missing molar had cancer (Table 4).

Discussion

  • This study addressed the issue of chronic dental infections, and periodontal disease in particular, as a risk factor for breast cancer.
  • The authors subjects were randomly chosen to avoid selection bias.
  • Further comments should be made about the missing molars which in this study were used as a proxy for chronic dental infections.
  • Hence, periodontal disease may indeed contribute to the increasing incidence of breast cancer in middle aged and older people.
  • The results also have public health consequences.

Conclusions

  • This is to their knowledge the first study presenting data about the eventual risk that longstanding dental infections may present risk for breast cancer.
  • Chronic periodontal disease indicated by missing molars seemed to associate statistically with breast cancer.
  • The Swedish Heart-Lung Foundation, the AFA Insurance, Sweden, Philips Oral Health Care, Sweden and the Karolinska Institutet, Stockholm, Sweden, and by grant TI020Y0003 from the Helsinki University Central Hospital, Finland.
  • Grant from The Medical Society of Finland.

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Periodontal disease may associate with breast cancer
Birgitta der, Maha Yakob, Jukka H. Meurman, Leif C. Andersson, Björn
Klinge, Per-Östen der
To cite this version:
Birgitta der, Maha Yakob, Jukka H. Meurman, Leif C. Andersson, Björn Klinge, et al.. Periodontal
disease may associate with breast cancer. Breast Cancer Research and Treatment, Springer Verlag,
2010, 127 (2), pp.497-502. �10.1007/s10549-010-1221-4�. �hal-00594472�

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1
Periodontal disease may associate with breast cancer
Birgitta Söder, Maha Yakob, Jukka H. Meurman, Leif C. Andersson, Björn Klinge,
Per-Östen Söder
B. Söder, M.Yakob, B. Klinge, P-Ö. Söder
Department of Dental Medicine, Division of Periodontology, Karolinska Institutet, Box 4064,
Huddinge, Sweden
J.H. Meurman
Institute of Dentistry and Department of Oral and Maxillofacial Diseases, Helsinki University
Central Hospital, Helsinki, Finland
L.C. Anderssson
Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland
Running title: Dental infections and breast cancer
Key words: Breast cancer; Periodontitis; Missing molar teeth,
Address for correspondence:
Dr Birgitta Söder
Department of Dental Medicine
Division of Periodontology
Karolinska Institutet
Box 4064
141 04 Huddinge, Sweden
Tel: +46 8 5248 8241
Fax +46 8 663 83 06
E-mail:birgitta.soder@ki.se

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Abstract
Purpose The main purpose was to evaluate the association between periodontal disease and
the incidence of breast cancer in a prospective study of 3273 randomly-selected subjects aged
3040 years at baseline.
Methods Breast cancer incidence was registered from 1985 to 2001 according to the WHO
International Classification of Diseases criteria. At baseline, 1676 individuals also underwent
a clinical oral examination (Group A) whereas 1597 subjects were not clinically examined but
were registered (Group B). The associations between breast cancer, periodontal disease and
missing molars were determined using multiple logistic regression models with several
background variables and known risk factors for cancer.
Results In total 26 subjects in group A and 15 subjects in group B had breast cancer. The
incidence of breast cancer was 1.75 % in subjects who had periodontal disease and/or any
missing molars, and 0 in subjects who had periodontal disease but had no missing molars. For
periodontally healthy subjects with no missing teeth the breast cancer incidence was 1%. For
Group B the respective incidence was 0.94%. Female gender (odds ratio [OR] 13.08) and
missing any molar in the mandible (OR 2.36) were explanatory variables for breast cancer. Of
the subjects with periodontal disease and any missing molars in the mandible 5.5% had breast
cancer in comparison to 0.5% of the subjects who had periodontal disease but no missing
molars in the mandible (p<0.02).
Conclusions Chronic periodontal disease indicated by missing molars seemed to associate
statistically with breast cancer.

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3
Introduction
Inflammation is a key feature in many chronic diseases including cancer [1-2]. Inflammation
caused by infections seems to be one of the most important preventable causes of cancer in
humans [3]. Periodontal disease is characterized by chronic infection and inflammation
leading to destruction of the bone surrounding the teeth. The disease may take decades to
develop and it ultimately leads to tooth loss [4-5]. An estimated 15-35% of the adult
population in industrialized countries suffers from this multifactor disease [6-8]. Periodontal
disease involves complex interactions of host defence, bacteria, and virus. Periodontal disease
is initiated by a biofilm of bacteria on the teeth which triggers an immune-inflammatory
response in the adjacent host tissues [4, 9] . Numerous oral bacterial species have been
associated with periodontal disease [10-11] .
Human cytomegalovirus (HCMV), Epstein-Barr virus (EBV) and HCMV-EBV co-infection
seems to be closely associated with disease-active periodontitis. [12-14] . Infection by HCMV
or EBV seems to inhibit the macrophages to respond to bacterial challenge, and thus have
pathogenic role in the development of periodontal disease. [15] The associations between
infectious agents of putative bacterial pathogens, herpes viruses, Epstein-Barr virus (EBV)
type 1, cytomegalovirus (CMV) seems to play an important synergistic role in the
pathogenesis of chronic periodontitis. [16-18] .
Breast cancer is the most common malignancy in women worldwide and it is the leading
cause of cancer-related mortality [19]. Incidence rates are high in developed countries and are
also increasing in the developing world [20]. National income and health expenditures are
known to affect breast cancer incidence but these factors only partly explain variations in
mortality rates [20]. Viral infections such as human papilloma virus infections seem to
associate with breast cancer as shown in a recent meta-analysis [21] In general, persistent and
prevalent infections in populations appear to link with malignancies [22]. In Sweden breast
cancer represents 29% of all cancers in the female [23]. Breast cancer also has a hereditary
component [24].
The results of an epidemiological study 2001, from our group, showed that fairly young
individuals with periodontal disease and missing molars are at increased risk of premature

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4
death caused by life threatening diseases such as malignant neoplasm, cardiovascular
diseases, and diseases of the digestive system [25]. Recently, periodontal disease was also
found to associate with head and neck cancer in patients who never smoked or consumed
alcohol [26]. Poor oral health has been statistically associated with the prevalence of many
types of cancer such as pancreatic and gastrointestinal cancer [27]. Consequently, the
hypothesis for the present study was that a low degree chronic inflammation such as seen in
periodontal disease is involved in carcinogenesis.
For that reason the specific aim of the present investigation was to study the incidence of
breast cancer from 2001 in subjects with periodontal disease and characteristic tooth loss in
our 16-year prospective investigation.
Materials and Methods
Study population
In 1985 we undertook this longitudinal prospective study, which comprised a random sample
cohort of 3273 individuals aged 3040 years. The subjects were selected from a registry
database of all inhabitants (n = 105,798) of Stockholm County born on the 20th of any month
from 1945 to 1954 inclusive. They were informed about the purpose of the study and offered
a clinical oral examination. In total, 1676 individuals (51.2%; 838 men and 838 women)
underwent a detailed clinical oral examination (Group A). The remaining 1597 subjects (849
men and 748 women) did not have the clinical examination and constituted Group B. Figure 1
shows the study profile.
Clinical examination
For all subjects of the clinically examined Group A the following parameters were recorded:
the number of remaining teeth excluding third molars; gingival inflammation around every
tooth as assessed using the gingival index [28]; and oral hygiene status as determined by using
both the dental plaque [29] and the calculus indices to assess all six surfaces of six
representative teeth. Pocket depth was determined using a periodontal probe and recorded to
the nearest higher millimetre for six sites of each tooth. Presence or absence of each tooth was
recorded. The prevalence of periodontal disease was determined in each age group year by
year from 31 years of the age to 40. All subjects in Group A also filled in a structured

Citations
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Reference EntryDOI
TL;DR: This review includes findings from 38 studies on community-based oral health promotion interventions delivered in a variety of settings and incorporating a range of health promotion strategies, to identify interventions that reduce inequality in oral health outcomes.
Abstract: Background Dental caries and gingival and periodontal disease are commonly occurring, preventable chronic conditions. Even though much is known about how to treat oral disease, currently we do not know which community-based population-level interventions are most effective and equitable in preventing poor oral health. Objectives Primary • To determine the effectiveness of community-based population-level oral health promotion interventions in preventing dental caries and gingival and periodontal disease among children from birth to 18 years of age. Secondary • To determine the most effective types of interventions (environmental, social, community and multi-component) and guiding theoretical frameworks.• To identify interventions that reduce inequality in oral health outcomes.• To examine the influence of context in the design, delivery and outcomes of interventions. Search methods We searched the following databases from January 1996 to April 2014: MEDLINE, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Education Resource Information Center (ERIC), BIOSIS Previews, Web of Science, the Database of Abstracts of Reviews of Effects (DARE), ScienceDirect, Sociological Abstracts, Social Science Citation Index, PsycINFO, SCOPUS, ProQuest Dissertations & Theses and Conference Proceedings Citation Index - Science. Selection criteria Included studies were individual- and cluster-randomised controlled trials (RCTs), controlled before-and-after studies and quasi-experimental and interrupted time series. To be included, interventions had to target the primary outcomes: dental caries (measured as decayed, missing and filled deciduous teeth/surfaces, dmft/s; Decayed, Missing and Filled permanent teeth/surfaces, DMFT/S) and gingival or periodontal disease among children from birth to 18 years of age. Studies had to report on one or more of the primary outcomes at baseline and post intervention, or had to provide change scores for both intervention and control groups. Interventions were excluded if they were solely of a chemical nature (e.g. chlorhexidine, fluoride varnish), were delivered primarily in a dental clinical setting or comprised solely fluoridation. Data collection and analysis Two review authors independently performed screening, data extraction and assessment of risk of bias of included studies (a team of six review authors - four review authors and two research assistants - assessed all studies). We calculated mean differences with 95% confidence intervals for continuous data. When data permitted, we undertook meta-analysis of primary outcome measures using a fixed-effect model to summarise results across studies. We used the I2 statistic as a measure of statistical heterogeneity. Main results This review includes findings from 38 studies (total n = 119,789 children, including one national study of 99,071 children, which contributed 80% of total participants) on community-based oral health promotion interventions delivered in a variety of settings and incorporating a range of health promotion strategies (e.g. policy, educational activities, professional oral health care, supervised toothbrushing programmes, motivational interviewing). We categorised interventions as dietary interventions (n = 3), oral health education (OHE) alone (n = 17), OHE in combination with supervised toothbrushing with fluoridated toothpaste (n = 8) and OHE in combination with a variety of other interventions (including professional preventive oral health care, n = 10). Interventions generally were implemented for less than one year (n = 26), and only 11 studies were RCTs. We graded the evidence as having moderate to very low quality.We conducted meta-analyses examining impact on dental caries of each intervention type, although not all studies provided sufficient data to allow pooling of effects across similar interventions. Meta-analyses of the effects of OHE alone on caries may show little or no effect on DMFT (two studies, mean difference (MD) 0.12, 95% confidence interval (CI) -0.11 to 0.36, low-quality evidence), dmft (three studies, MD -0.3, 95% CI -1.11 to 0.52, low-quality evidence) and DMFS (one study, MD -0.01, 95% CI -0.24 to 0.22, very low-quality evidence). Analysis of studies testing OHE in combination with supervised toothbrushing with fluoridated toothpaste may show a beneficial effect on dmfs (three studies, MD -1.59, 95% CI -2.67 to -0.52, low-quality evidence) and dmft (two studies, MD -0.97, 95% CI -1.06 to -0.89, low-quality evidence) but may show little effect on DMFS (two studies, MD -0.02, 95% CI -0.13 to 0.10, low-quality evidence) and DMFT (three studies, MD -0.02, 95% CI -0.11 to 0.07, moderate-quality evidence). Meta-analyses of two studies of OHE in an educational setting combined with professional preventive oral care in a dental clinic setting probably show a very small effect on DMFT (-0.09 weighted mean difference (WMD), 95% CI -0.1 to -0.08, moderate-quality evidence). Data were inadequate for meta-analyses on gingival health, although positive impact was reported. Authors' conclusions This review provides evidence of low certainty suggesting that community-based oral health promotion interventions that combine oral health education with supervised toothbrushing or professional preventive oral care can reduce dental caries in children. Other interventions, such as those that aim to promote access to fluoride, improve children's diets or provide oral health education alone, show only limited impact. We found no clear indication of when is the most effective time to intervene during childhood. Cost-effectiveness, long-term sustainability and equity of impacts and adverse outcomes were not widely reported by study authors, limiting our ability to make inferences on these aspects. More rigorous measurement and reporting of study results would improve the quality of the evidence.

111 citations

Journal ArticleDOI
TL;DR: The role of chronic inflammation as a biologically plausible mechanistic link between periodontal disease and risk of cancer is explored and studies that have examined the potential importance of certainperiodontal pathogens in this association are highlighted.
Abstract: Epidemiologic and cancer control studies on the association of periodontal disease and cancer risk mostly suggest a positive association with overall cancer risk and certain specific types of cancer. These findings are generally consistent among cross-sectional and longitudinal studies. In this paper, we review epidemiologic studies and current knowledge on periodontal disease and cancer, with a focus on those studies conducted in the years following the Joint European Federation of Periodontology/American Academy of Periodontology Workshop on "Periodontitis and Systemic Diseases" in November 2012. This review also explores the role of chronic inflammation as a biologically plausible mechanistic link between periodontal disease and risk of cancer. Furthermore, it highlights studies that have examined the potential importance of certain periodontal pathogens in this association.

84 citations

Journal ArticleDOI
TL;DR: The overall composition of the microbial communities, as well as the presence or absence of "key species" in relation to carcinogenesis is addressed and Alterations in the oral microbiota can potentially be used to predict the risk of cancer.
Abstract: Many studies show that the human microbiome plays a critical role in the chronic pathologies of obesity, inflammatory bowel diseases, and diabetes. More recently, the interaction between cancer and the microbiome has been highlighted. Most studies have focused on the gut microbiota because it represents the most extensive bacterial community, and the body of evidence correlating it with gut syndromes is increasing. However, in the strict sense, the gastrointestinal (GI) tract begins in the oral cavity, and special attention should be paid to the specific flora of this cavity. This study reviewed the current knowledge about the various microbial ecosystems of the upper part of the GI tract and discussed their potential link to carcinogenesis. The overall composition of the microbial communities, as well as the presence or absence of “key species”, in relation to carcinogenesis is addressed. Alterations in the oral microbiota can potentially be used to predict the risk of cancer. Molecular advances and the ...

64 citations

Journal ArticleDOI
TL;DR: periodontal disease, a common chronic inflammatory disorder, was associated with increased risk of postmenopausal breast cancer, particularly among former smokers who quit in the past 20 years.
Abstract: Background: Periodontal disease has been consistently associated with chronic disease; there are no large studies of breast cancer, although oral-associated microbes are present in breast tumors. Methods: In the Women's Health Initiative Observational Study, a prospective cohort of postmenopausal women, 73,737 women without previous breast cancer were followed. Incident, primary, invasive breast tumors were verified by physician adjudication. Periodontal disease was by self-report. HRs and 95% confidence intervals (CI) were estimated by Cox proportional hazards, adjusted for breast cancer risk factors. Because the oral microbiome of those with periodontal disease differs with smoking status, we examined associations stratified by smoking. Results: 2,124 incident, invasive breast cancer cases were identified after mean follow-up of 6.7 years. Periodontal disease, reported by 26.1% of women, was associated with increased breast cancer risk (HR 1.14; 95% CI, 1.03–1.26), particularly among former smokers who quit within 20 years (HR 1.36; 95% CI, 1.05–1.77). Among current smokers, the trend was similar (HR 1.32; 95% CI, 0.83–2.11); there were few cases ( n = 74) and the CI included the null. The population attributable fraction was 12.06% (95% CI, 1.12–21.79) and 10.90% (95% CI, 10.31–28.94) for periodontal disease among former smokers quitting within 20 years and current smokers, respectively. Conclusion: Periodontal disease, a common chronic inflammatory disorder, was associated with increased risk of postmenopausal breast cancer, particularly among former smokers who quit in the past 20 years. Impact: Understanding a possible role of the oral microbiome in breast carcinogenesis could impact prevention. Cancer Epidemiol Biomarkers Prev; 1–8. ©2015 AACR .

61 citations


Cites background from "Periodontal disease may associate w..."

  • ...In a cohort of 838 women in Sweden, there was a statistically significant increase in breast cancer among those with periodontal disease assessed by a clinical exam; again the number of breast cancer cases was small, only 24 (13)....

    [...]

Journal ArticleDOI
01 Jan 2012-BMJ Open
TL;DR: It is shown that poor oral hygiene, as reflected in the amount of dental plaque, was associated with increased cancer mortality, and this study hypothesis was confirmed.
Abstract: Objectives: To study whether the amount of dental plaque, which indicates poor oral hygiene and is potential source of oral infections, associates with premature death from cancer. Design: Prospective cohort study. Participants: 1390 randomly selected healthy young Swedes followed up from 1985 to 2009. All subjects underwent oral clinical examination and answered a questionnaire assessing background variables such as socioeconomic status and smoking. Outcome measures: Causes of death were recorded from national statistics and classified according to the WHO International Classification of Diseases. Unpaired t test, c 2 tests and multiple logistic regressions were used. Results: Of the 1390 participants, 4.2% had died during the follow-up. Women had died at a mean age of 61.0 (62.6 SD) years and men at the age of 60.2 (62.9 SD) years. The amount of dental plaque between those who had died versus survived was statistically significant (p<0.001). In multiple logistic regression analysis, dental plaque appeared to be a significant independent predictor associated with 1.79 times the OR of death (p<0.05). Age increased the risk with an OR of 1.98 (p<0.05) and gender (men) with an OR of 1.91 (p<0.05). The malignancies were more widely scattered in men, while breast cancer was the most frequent cause of death in women. Conclusions: This study hypothesis was confirmed by showing that poor oral hygiene, as reflected in the amount of dental plaque, was associated with increased cancer mortality.

38 citations


Cites background from "Periodontal disease may associate w..."

  • ...36.(10) The putative mechanisms involved in the association have been further reviewed by Meurman and Bascones-Martinez....

    [...]

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  • ...For all subjects of the clinically examined Group A the following parameters were recorded: the number of remaining teeth excluding third molars; gingival inflammation around every tooth as assessed using the gingival index [28]; and oral hygiene status as determined by using both the dental plaque [29] and the calculus indices to assess all six surfaces of six representative teeth....

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    [...]

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  • ...Table 1 Demographic clinical oral health data of subjects of Group A with or without diagnosed periodontal disease at the baseline examination in 1985 Data are expressed as mean ± SD * Fisher’s exact t test or Student’s t test for unpaired samples as appropriate No periodontal disease (n = 1390) number, mean ± SD Periodontal disease (n = 286) number, mean ± SD P* Gender (female/male) 159/825 127/851 \0.05 Age in 1985 (years) 35.6 ± 2.8 36.5 ± 2.8 \0.001 Education (compulsory/higher) 218/1172 73/286 \0.001 Smoking (pack-year) 3315.5 ± 5041.2 5060.5 ± 5455.7 \0.001 Income (Swedish Crowns 9 1000) 188.5 ± 102.9 186.4 ± 89.3 NS Plaque index [28] 0.67 ± 0.47 0.99 ± 0.53 \0.001 Gingival inflammation [29] 1.18 ± 0.47 1.76 ± 0.54 \0.001 Calculus index 0.39 ± 0.54 0.80 ± 0.73 \0.001 Missing teeth 1.19 ± 2.37 1.59 ± 2.40 = 0.01 Missing molars in the mandible 0.30 ± 0.74 0.44 ± 0.89 \0.01 Table 2 Demographic and clinical oral data for subjects with periodontitis 1985, with and without breast cancer 2001 Data are expressed as mean ± SD * Fisher’s exact t test or Student’s t test for unpaired samples as appropriate Periodontitis 1985 without breast cancer 2001 (n = 281) number, mean ± SD Periodontitis 1985 with breast cancer 2001 (n = 5) number, mean ± SD P* Gender (male/female) 0/161 5/125 0.01 Age in 1985 (years) 35.7 ± 2.9 36.6 ± 2.5 NS Education (compulsory/higher) 70/281 3/5 NS Smoking (pack-year) 5107.1 ± 5482.6 2445.5 ± 2814.3 NS Income (Swedish Crowns 9 1000) 178.7 ± 92.2 150.2 ± 53.0 NS Plaque index [28] 0.90 ± 0.537 0.87 ± 0.61 NS Gingival inflammation [29] 1.76 ± 0.54 2.12 ± 0.45 NS Calculus index 0.80 ± 0.72 0.97 ± 0.62 NS Number of deep pockets ([5 mm) 5.1 ± 5.1 8.6 ± 3.0 NS Number of remaining teeth 26.5 ± 2.3 23.6 ± 5.6 \0.01 Number of missing molars 0.7 ± 1.4 2.4 ± 2.6 0.01 Number of missing molars in the mandible 0.4 ± 0.9 1.6 ± 1.5 0.003 Number of missing front teeth 0.7 ± 1.4 2.4 ± 2.6 0.01 Table 3 Results of the multiple logistic regression analysis Dependent variable Explaining variable ß X2 P Odds ratio 95% confidence interval Breast cancer Gender (female) 2.57 12.21 \0.001 13.08 3.09–55.32 Missing any molar from the mandible 0.86 4.55 0.033 2.36 1.07–5.21 Breast cancer was the dependent variable and age, gender, education level, socio economic status, working history, yearly income, smoking in pack-years, dental appointments, dental plaque index, gingival bleeding index, and loss of any molar tooth in the mandible were used as explanatory variables Cox and Snell R2 = 0.017; Nagelkerke R2 = 0.11 Some comments should be made concerning the reliability of the results....

    [...]

Frequently Asked Questions (2)
Q1. What are the contributions mentioned in the paper "Periodontal disease may associate with breast cancer" ?

The main purpose was to evaluate the association between periodontal disease and the incidence of breast cancer in a prospective study of 3273 randomly-selected subjects aged 30–40 years at baseline. 

If their results will be confirmed in future studies the finding should have clinical consequences in advising the patients.