Publications by authors named "Marja L Laine"

40 Publications

Role of the oral microbiome, metabolic pathways, and novel diagnostic tools in intra-oral halitosis: a comprehensive update.

Crit Rev Microbiol 2021 Mar 3:1-17. Epub 2021 Mar 3.

Oral Health ACP, Duke NUS Medical School, Singapore, Singapore.

Halitosis or oral malodor is one of the most common reasons for the patients' visit to the dental clinic, ranking behind only dental caries and periodontitis. In the present times, where social and professional communications are becoming unavoidable, halitosis has become a concern of growing importance. Oral malodor mostly develops due to the putrefaction of substrates by the indigenous bacterial populations. Although culture-based studies have provided adequate information on halitosis, the high throughput omics technologies have amplified the resolution at which oral microbial community can be examined and has led to the detection of a broader range of taxa associated with intra-oral halitosis (IOH). These microorganisms are regulated by the interactions of their ecological processes. Thus to develop effective treatment strategies, it is important to understand the microbial basis of halitosis. In the current review, we provide an update on IOH in context to the role of the oral microbiome, metabolic pathways involved, and novel diagnostic tools, including breathomics. Understanding oral microbiota associated with halitosis from a broader ecological perspective can provide novel insights into one's oral and systemic health. Such information can pave the way for the emergence of diagnostic tools that can revolutionize the early detection of halitosis and various associated medical conditions.
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http://dx.doi.org/10.1080/1040841X.2021.1888867DOI Listing
March 2021

Surgical treatment of peri-implantitis defects with two different xenograft granules: A randomized clinical pilot study.

Clin Oral Implants Res 2020 Nov 9;31(11):1047-1060. Epub 2020 Sep 9.

Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands.

Objectives: To investigate whether xenograft EB (EndoBon) is non-inferior to xenograft BO (Bio-Oss) when used in reconstructive surgery of peri-implant osseous defects.

Materials And Methods: Dental patients with one implant each demonstrating peri-implantitis were randomized to receive surgical debridement and defect fill with either BO or EB. Changes in bone level (BL) and intrabony defect depth (IDD) evaluated radiographically were the primary outcomes. The secondary outcomes included changes in probing pocket depth (PPD), bleeding on probing (BoP), and suppuration on probing (SoP). All outcomes were recorded before treatment and at 6 and 12 months post-treatment.

Results: Twenty-four patients (n = 11 BO, n = 13 EB) completed the study. Both groups demonstrated significant within-group improvements in all clinical and radiographic parameters at 6 and 12 months (p ≤ .001). At 12 months, both groups presented with IDD reductions of 2.5-3.0 mm on average. The inter-group differences were not statistically significant at all time points and for all the examined parameters (p > .05). While the radiographic defect fill in both groups exceeded > 1 mm and can be considered treatment success, successful treatment outcomes as defined by Consensus Reporting (no further bone loss, PPD ≤ 5 mm, no BOP, and no SoP) were identified in 2/11 (18%) BO and 0/13 (0%) EB individuals (Fisher's exact test, p = .199).

Conclusions: Within the limitations of this pilot study, the application of xenograft EB showed to be non-inferior to xenograft BO when used in reconstructive surgery of peri-implant osseous defects.
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http://dx.doi.org/10.1111/clr.13651DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693249PMC
November 2020

Three periodontitis phenotypes: Bone loss patterns, antibiotic-surgical treatment and the new classification.

J Clin Periodontol 2020 11 14;47(11):1371-1378. Epub 2020 Sep 14.

Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Aim: To compare three periodontitis clusters (A, B and C) for alveolar bone loss (ABL) patterns, antibiotic prescriptions and surgeries and to relate them to the new classification of periodontitis.

Materials And Methods: ABL patterns, prescription of systemic antibiotics and the number of surgeries were retrieved for all patients (n = 353) in the clusters. Comparisons and possible predictors for antibiotics were assessed, and results also evaluated in relation to the new classification.

Results: Cluster A is characterized by angular defects often affecting the first molars and localized stage III/IV grade C periodontitis. Cluster B contains mainly localized or generalized stage III/IV, grade C patients. Cluster C contains mainly patients with generalized stage III/IV grade C periodontitis. Patients in cluster A received significantly more antibiotics compared to B and C (78% vs. 23% and 17%); the predictors for antibiotic prescription were young age and localized ABL. No differences in numbers of periodontal surgeries were observed between clusters (A = 1.0 ± 1.4, B = 1.3 ± 1.4 and C = 1.3 ± 1.5).

Conclusions: Within stage III/IV grade C periodontitis, we could detect three clusters of patients. The distinct localized ABL pattern and younger age in cluster A presumably prompted clinicians to prescribe antibiotics.
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http://dx.doi.org/10.1111/jcpe.13356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693056PMC
November 2020

The Underestimated Problem of Intra-Oral Halitosis in Dental Practice: An Expert Consensus Review.

Clin Cosmet Investig Dent 2020 3;12:251-262. Epub 2020 Jul 3.

Department of Periodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.

Approximately 90% of halitosis cases originate within the oral cavity (intra-oral halitosis). With a focus on intra-oral halitosis, this narrative review article provides a current summary of the epidemiology, diagnosis and management of halitosis and discusses practical considerations for healthcare professionals (HCPs), including dentists, dental hygienists, general practitioners, community pharmacists, nurses and medical specialists. MEDLINE and PubMed were searched up to 31 December 2019. Additional information was sourced from reference lists of relevant published literature. Full-text articles which reported on the epidemiology, diagnosis and management of halitosis were considered for inclusion. Halitosis affects substantial numbers of individuals globally and is an underestimated problem in dental practice. Current estimates of the prevalence of halitosis, in addition to diagnostic methods and management considerations for halitosis, are discussed. Although not a life-threatening condition, halitosis has a significant impact on patients' quality of life and can result in psychological consequences including social, professional and affective limitations. Using a simple step-wise approach for diagnosis and treatment, dentists and dental hygienists are ideally placed to respond to an initial consultation for halitosis.
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http://dx.doi.org/10.2147/CCIDE.S253765DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7342603PMC
July 2020

A stepwise approach investigating salivary responses upon multisensory food cues.

Physiol Behav 2020 11 1;226:113116. Epub 2020 Aug 1.

Division of Human Nutrition and Health, Wageningen University, 6708 WE Wageningen, the Netherlands.

Exposure to sensory food cues such as smell, vision, taste and/or texture may trigger anticipatory physiological responses such as salivation, participating on adequate metabolism of the signaled food. However, the individual contribution of each sensory modality as well as the impact of particular food products on salivation and salivary composition remains unclear. Therefore, by systematically varying sensory modalities and nutrient content of food stimuli, we investigated their effect on saliva secretion, α-amylase activity and other salivary characteristics (pH level, buffering capacity, MUC5B concentration, and total protein content). Over 3 sessions, 46 normal-weight healthy participants were exposed to 12 conditions, consisting of 4 levels of sensory stimulation (odor, odor + vision, odor + vision + taste, and odor + vision + taste + mastication) and 3 types of stimuli (bread, high-in-starch; cucumber, low-in-starch; and parafilm as non-food control) during which saliva was collected. Linear mixed models showed a significant increase in salivation with increasing levels of sensory stimulation. α-amylase secretion rate increased upon the highest level of stimulation, which involved mastication, compared to odor and odor + visual level of stimulation. Other salivary characteristics varied with the level of sensory stimulation, which might be related to the total volume of salivation. The type of stimuli did not influence the saliva composition (α-amylase concentration nor other salivary components). Our findings indicate that cumulative sensory information, rather than specific (food) product, play a vital role in anticipatory salivary responses.
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http://dx.doi.org/10.1016/j.physbeh.2020.113116DOI Listing
November 2020

Adjunctive effect of mouthrinse on treatment of peri-implant mucositis using mechanical debridement: A randomized clinical trial.

J Clin Periodontol 2020 07 27;47(7):883-891. Epub 2020 May 27.

Department of Oral Implantology and Prosthetic Dentistry, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Aim: To study effect of delmopinol hydrochloride (DEL) in comparison with chlorhexidine digluconate (CHX) and a placebo (PLA) in addition to non-surgical mechanical debridement in patients with peri-implant mucositis.

Materials And Methods: Eighty-nine patients with at least one implant diagnosed with peri-implant mucositis were randomly assigned to one of three study groups (DEL, CHX and PLA). Professional non-surgical mechanical debridement was performed at baseline. Mouth rinsing was carried out by the patients twice a day in addition to their regular oral hygiene practices. Assessments of efficacy were performed for the primary outcome - Implant bleeding on probing (IBOP%) and secondary outcomes - modified Bleeding Index (mBI) and modified Plaque Index (mPI) at 1 and 3 months.

Results: At 3 months, there was statistically significant reduction in IBOP% and mBI within the study groups compared to baseline. However, there was no statistically significant difference between the study groups at 3 months follow-up. Moreover, there was a statistically significant difference according to mPI at 1 month between the chlorhexidine and placebo group (p = .004).

Conclusions: This study confirms that mechanical debridement combined with oral hygiene instruction is effective in treatment of peri-implant mucositis. The clinical effects between groups were comparable.
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http://dx.doi.org/10.1111/jcpe.13295DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317778PMC
July 2020

Occlusal Migration of Teeth Adjacent to Implant Prostheses in Adults: A Long-Term Study.

Int J Oral Maxillofac Implants 2020 Mar/Apr;35(2):342-349

Purpose: To evaluate the effect of continuous tooth eruption on the outcomes of single-implant-supported restorations in the anterior maxilla of adults.

Materials And Methods: Seventy-six patients (age: 21 to 78 years) treated with single-implant-supported restorations in the esthetic zone were included. Radiographs obtained at crown placement and follow-up examinations from 1 to 15 years postloading were analyzed with regard to vertical incisal plane changes of the implant-supported crown relative to adjacent teeth.

Results: Infraocclusion increased over time by 0.08 ± 0.02 mm/year. Infraocclusion was more pronounced (P = .04) for delayed (0.09 mm/year) versus immediate implant placement (0.06 mm/year) and for younger versus older adults (0.0013 mm/year per additional year of age; P = .014). No statistically significant association between infraocclusion and sex, ethnicity, implant site, timing of implant temporization, surgical protocol, and type of restoration was found.

Conclusion: Infraocclusion of single-implant-supported maxillary anterior restorations may result in esthetic concerns over time. Greater infraocclusion occurs in delayed implant placement and in younger individuals.
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http://dx.doi.org/10.11607/jomi.7784DOI Listing
August 2020

Hidden noise in immunologic parameters might explain rapid progression in early-onset periodontitis.

PLoS One 2019 1;14(11):e0224615. Epub 2019 Nov 1.

Department of Periodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

To investigate in datasets of immunologic parameters from early-onset and late-onset periodontitis patients (EOP and LOP), the existence of hidden random fluctuations (anomalies or noise), which may be the source for increased frequencies and longer periods of exacerbation, resulting in rapid progression in EOP. Principal component analysis (PCA) was applied on a dataset of 28 immunologic parameters and serum IgG titers against periodontal pathogens derived from 68 EOP and 43 LOP patients. After excluding the PCA parameters that explain the majority of variance in the datasets, i.e. the overall aberrant immune function, the remaining parameters of the residual subspace were analyzed by computing their sample entropy to detect possible anomalies. The performance of entropy anomaly detection was tested by using unsupervised clustering based on a log-likelihood distance yielding parameters with anomalies. An aggregate local outlier factor score (LOF) was used for a supervised classification of EOP and LOP. Entropy values on data for neutrophil chemotaxis, CD4, CD8, CD20 counts and serum IgG titer against Aggregatibacter actinomycetemcomitans indicated the existence of possible anomalies. Unsupervised clustering confirmed that the above parameters are possible sources of anomalies. LOF presented 94% sensitivity and 83% specificity in identifying EOP (87% sensitivity and 83% specificity in 10-fold cross-validation). Any generalization of the result should be performed with caution due to a relatively high false positive rate (17%). Random fluctuations in immunologic parameters from a sample of EOP and LOP patients were detected, suggesting that their existence may cause more frequently periods of disease activity, where the aberrant immune response in EOP patients result in the phenotype "rapid progression".
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0224615PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824576PMC
March 2020

Impact of food odors signaling specific taste qualities and macronutrient content on saliva secretion and composition.

Appetite 2019 12 8;143:104399. Epub 2019 Aug 8.

Division of Human Nutrition and Health, Wageningen University, 6708, WE Wageningen, the Netherlands.

Olfactory food cues can induce appetite for similar food products in humans. Odors may thus signal essential information about a foods' composition such as taste or even macronutrient content and may stimulate specific physiological responses in anticipation of food intake. Several studies have shown that sensory food cues could stimulate saliva secretion. However, potential differences between food odors in their effect on saliva secretion, or the effects of olfactory stimulation on changes in saliva composition remain to be elucidated. To gain more insight, we conducted two studies to determine the influence of various odors, representing different taste qualities (study 1) and macronutrients (study 2), on salivary biomarkers. In study 1, 36 participants were randomly exposed to no-odor, non-food, and odors signaling sweet, savory, and sour taste. In study 2, 60 participants were randomly exposed to no-odor, non-food, and odors signaling carbohydrates, protein, fat, and low-calorie food. For each condition, whole-mouth saliva was collected and saliva secretion rate determined. Furthermore, we determined mouth-watering perception (subjective salivation), visco-elasticity (study 1 only), mucin concentration, α-amylase and lingual lipase activity (study 2 only). For both studies, linear mixed model analyses showed that saliva secretion rate significantly increased by food odor exposure compared to no-odor and non-food conditions. However, no changes in salivary composition were observed. These findings indicate that food odors play a crucial role in anticipatory saliva responses and can thereby affect subsequent eating behavior.
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http://dx.doi.org/10.1016/j.appet.2019.104399DOI Listing
December 2019

Qualitative and quantitative differences in the subgingival microbiome of the restored and unrestored teeth.

J Periodontal Res 2019 Aug 8;54(4):405-412. Epub 2019 Feb 8.

Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.

Background And Objective: Metal-based dental restorations with a subgingival outline may enhance plaque accumulation and bacterial colonization. This study aimed to investigate whether metal-based restorations influence the composition of subgingival microbiome.

Material And Methods: Per subject one site with a metal-based restoration and one contra-lateral site without a restoration were selected on basis of radiographic bone loss ≤2 mm, restoration outline at sulcus level/subgingivally, pocket depth ≤4 mm, and no root canal treatments. Subgingival samples were collected with sterile paper-points, and microbial profiles were obtained by 16S rRNA gene amplicon sequencing. Restorations were sampled with an Arkansas-stone and the metal composition was determined using energy-dispersive X-ray spectroscopy.

Results: A total of 22 sites from 11 subjects were included. No significant differences for the clinical parameters were found between the restored and unrestored sites. The average age of the restorations was 14.9 ± 7.1 years. Firmicutes was the most prevalent phylum at the restored sites (32% vs 20% of the reads of the unrestored sites, P = 0.016), and Actinobacteria at the unrestored sites (33% vs 18% of the reads of the restored sites, P = 0.01). Overall, sequences clustered into 573 operational taxonomic units (OTUs). Species richness of the restored sites was significantly higher than species richness of the unrestored sites (117 ± 32 and 96 ± 20 OTUs, respectively, P = 0.013). No associations between the metal composition and bacterial profiles were found.

Conclusion: This study shows that metal-based restorations may enhance colonization of Firmicutes and the neighboring pocket may harbor more diverse microbial communities.
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http://dx.doi.org/10.1111/jre.12642DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6766957PMC
August 2019

Microcosm biofilms cultured from different oral niches in periodontitis patients.

J Oral Microbiol 2019 27;11(1):1551596. Epub 2018 Nov 27.

Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

: Periodontal diseases are triggered by dysbiotic microbial biofilms. Therefore, it is essential to develop appropriate biofilm models. Aim of the present study was to culture microcosm biofilms inoculated from different niches in periodontitis patients and compare their microbial composition to those inoculated from subgingival plaque. : Saliva, subgingival plaque, tongue and tonsils were sampled in five periodontitis patients to serve as inocula for culturing biofilms in an active attachment model. Biofilms were grown for 14 or 28 d and analyzed for their microbial composition by 16S rDNA sequencing. : As classified by HOMD, all biofilms were dominated by periodontitis-associated taxa, irrespective which niche had been used for inoculation. There was a low similarity between 14 d biofilms and their respective inocula (Bray-Curtis similarity 0.26), while biofilms cultured for 14 and 28 d shared high similarity (0.69). Principal components analysis showed much stronger clustering per patient than per niche indicating that the choice of patients may be more crucial than choice of the respective niches in these patients. : Saliva, tongue scrapings or tonsil swabs may represent sufficient alternative inocula for growing microcosm biofilms resembling periodontitis-associated microbial communities in cases when sampling subgingival plaque is not possible.
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http://dx.doi.org/10.1080/20022727.2018.1551596DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6263112PMC
November 2018

Efficacy of probiotics: clinical and microbial parameters of halitosis.

J Breath Res 2018 08 21;12(4):046010. Epub 2018 Aug 21.

Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Background & Aim: Halitosis is defined as an offensive breath odour of whatever source and therefore may affect a person's social interactions. Intra-oral halitosis is a result of bacterial activity. Therefore, probiotics may offer an appropriate and biological solution as a part of the therapy of intra-oral halitosis. The aim of this systematic review was to study the effect of the administration of probiotics alone or as an adjunct to other treatments on the level of halitosis as measured by volatile sulphur compound (VSC) levels, organoleptic scores (ORG) or hydrogen sulphide, methyl mercaptan and dimethyl sulphide levels. In addition, the effect of probiotic usage on oral microbial composition was summarised.

Methods: The MEDLINE-PubMed and Embase databases were searched up to September 2017 with language restricted to English. Eligible papers were selected according to pre-set criteria; the data was extracted and analysed descriptively.

Results: The search resulted in 1104 original research articles and a final six were selected as being eligible including 129 subjects. These studies used different detection methods and combinations thereof to measure halitosis. Five studies were randomised placebo-controlled clinical trials of which two studies reported a significant reduction in ORG between probiotic and placebo groups, and two studies on the basis of total VSC levels. The two studies reporting a significant improvement in ORG did not find an improvement in total VSC levels. Three studies included a microbiological assessment. In these three studies, the probiotic strain was detected at the end of the treatment period, but no detailed data was reported on the abundance of the strain before and after the treatment period.

Conclusions: Probiotics may be beneficial in treating intra-oral halitosis. However, due to limited data and the heterogeneity of the studies, the efficacy of probiotics remains unclear. Studies with more subjects and standardised protocols need to be designed.
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http://dx.doi.org/10.1088/1752-7163/aacf49DOI Listing
August 2018

At least three phenotypes exist among periodontitis patients.

J Clin Periodontol 2017 Nov;44(11):1068-1076

Department of Periodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Aim: To identify phenotypes of periodontitis patients by the use of an unsupervised modelling technique (clustering), based on pre-treatment radiographic and microbiological characteristics.

Materials And Methods: This retrospective study included data from 392 untreated periodontitis patients. Co-regularized spectral clustering algorithm was used to cluster the patients. The resulting clusters were subsequently characterized based on their demographics, radiographic bone loss patterns and microbial data.

Results: The vast majority of patients fitted into one of the three main clusters (accuracy 90%). Cluster A (n = 18) was characterized by high prevalence and high proportions of Aggregatibacter actinomycetemcomitans, a trend for a more localized pattern of alveolar bone loss and young individuals. Clusters B (n = 200) and C (n = 135) differed clearly in disease severity patterns and smoking habits, but not in microbiological characteristics.

Conclusion: On the basis of alveolar bone loss patterns and microbiological data, untreated periodontitis patients can be clustered into at least three phenotypes. These results should be validated in other cohorts, and the clinical utility needs to be explored on the basis of periodontal treatment outcomes and/or disease progression.
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http://dx.doi.org/10.1111/jcpe.12797DOI Listing
November 2017

Interaction of lifestyle, behaviour or systemic diseases with dental caries and periodontal diseases: consensus report of group 2 of the joint EFP/ORCA workshop on the boundaries between caries and periodontal diseases.

J Clin Periodontol 2017 Mar;44 Suppl 18:S39-S51

Department of Special Care Dentistry, Dental School, Witten/Herdecke University, Witten, Germany.

Periodontal diseases and dental caries are the most common diseases of humans and the main cause of tooth loss. Both diseases can lead to nutritional compromise and negative impacts upon self-esteem and quality of life. As complex chronic diseases, they share common risk factors, such as a requirement for a pathogenic plaque biofilm, yet they exhibit distinct pathophysiologies. Multiple exposures contribute to their causal pathways, and susceptibility involves risk factors that are inherited (e.g. genetic variants), and those that are acquired (e.g. socio-economic factors, biofilm load or composition, smoking, carbohydrate intake). Identification of these factors is crucial in the prevention of both diseases as well as in their management.

Aim: To systematically appraise the scientific literature to identify potential risk factors for caries and periodontal diseases.

Methods: One systematic review (genetic risk factors), one narrative review (role of diet and nutrition) and reference documentation for modifiable acquired risk factors common to both disease groups, formed the basis of the report.

Results & Conclusions: There is moderately strong evidence for a genetic contribution to periodontal diseases and caries susceptibility, with an attributable risk estimated to be up to 50%. The genetics literature for periodontal disease is more substantial than for caries and genes associated with chronic periodontitis are the vitamin D receptor (VDR), Fc gamma receptor IIA (Fc-γRIIA) and Interleukin 10 (IL10) genes. For caries, genes involved in enamel formation (AMELX, AMBN, ENAM, TUFT, MMP20, and KLK4), salivary characteristics (AQP5), immune regulation and dietary preferences had the largest impact. No common genetic variants were found. Fermentable carbohydrates (sugars and starches) were the most relevant common dietary risk factor for both diseases, but associated mechanisms differed. In caries, the fermentation process leads to acid production and the generation of biofilm components such as Glucans. In periodontitis, glycaemia drives oxidative stress and advanced glycation end-products may also trigger a hyper inflammatory state. Micronutrient deficiencies, such as for vitamin C, vitamin D or vitamin B12, may be related to the onset and progression of both diseases. Functional foods or probiotics could be helpful in caries prevention and periodontal disease management, although evidence is limited and biological mechanisms not fully elucidated. Hyposalivation, rheumatoid arthritis, smoking/tobacco use, undiagnosed or sub-optimally controlled diabetes and obesity are common acquired risk factors for both caries and periodontal diseases.
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http://dx.doi.org/10.1111/jcpe.12685DOI Listing
March 2017

Java project on periodontal diseases: effect of vitamin C/calcium threonate/citrus flavonoids supplementation on periodontal pathogens, CRP and HbA1c.

J Clin Periodontol 2015 12 21;42(12):1097-104. Epub 2015 Dec 21.

Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.

Objective: To assess in a periodontally diseased rural population deprived from regular dental care and having poor dietary conditions, the effect of vitamin C/calcium threonate/citrus flavonoids (VitC/Ca/Fl) supplementation on subgingival microbiota and plasma levels of vitamin C, HbA1c and hsCRP.

Material & Methods: The study population consisted of 98 subjects who previously participated in a prospective study on the natural history of periodontitis. Participants were instructed to consume one tablet/day containing 200 mg Ester C(®) calcium ascorbate, 25 mg calcium threonate and 100 mg citrus flavonoids for 90 days. Following parameters were evaluated: prevalence/amount of seven traditional periodontal pathogens, cytomegalovirus, Epstein-Barr virus (EBV); and plasma levels of vitamin C, HbA1c and hsCRP.

Results: After VitC/Ca/Fl supplementation, 100% of subjects showed normal plasma vitamin C values compared to 55% before. At baseline, 48% of subjects harboured Aggregatibacter actinomycetemcomitans, >97% the other periodontal pathogens and 73% EBV. Supplementation with VitC/Ca/F reduced the subgingival load of all studied bacteria (p-values: 0.014-0.0001) and EBV (p < 0.0001) substantially in all initially positive subjects. Plasma levels of HbA1c and hsCRP dropped in all subjects (p < 0.0001).

Conclusion: This uncontrolled study suggested that supplemental VitC/Ca/Fl may be helpful in reducing subgingival numbers of periodontal pathogens and EBV, and promoting systemic health.
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http://dx.doi.org/10.1111/jcpe.12478DOI Listing
December 2015

What is the Contribution of Genetics to Periodontal Risk?

Dent Clin North Am 2015 Oct 1;59(4):761-80. Epub 2015 Aug 1.

Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam, VU University Amsterdam, Gustav Mahlerlaan 3004, Amsterdam 1081 LA, The Netherlands.

This review addresses the multicausal etiology of periodontitis, in which genetic factors play a role. The various proposed causes for periodontitis always work simultaneously, but the relative contribution of each of these varies from case to case. We are still at an early stage to identify the genes involved, in comparison with other chronic diseases. To date, the genetic variations firmly and repeatedly associated with periodontitis in some populations are found within the following genes: ANRIL, COX2, IL1, IL10, DEFB1, whereas many other proposed periodontitis candidate genes have not been firmly proven or replicated.
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http://dx.doi.org/10.1016/j.cden.2015.06.005DOI Listing
October 2015

A Lead ANRIL Polymorphism Is Associated with Elevated CRP Levels in Periodontitis: A Pilot Case-Control Study.

PLoS One 2015 8;10(9):e0137335. Epub 2015 Sep 8.

Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, Amsterdam, the Netherlands.

Elevated high sensitive C-reactive protein (hsCRP) is a marker for systemic inflammation and a risk marker for atherosclerotic cardiovascular disease (ACVD), and has also been associated with periodontitis. Inter-individual variation for hsCRP in periodontitis has been shown. ANRIL is the strongest genetic susceptibility locus for both periodontitis and ACVD, and it is speculated that genetic variation in ANRIL may modulate inflammatory processes. Therefore, we explored the possible association between hsCRP plasma levels and a leading ANRIL single nucleotide polymorphism (SNP) in periodontitis patients and controls. 171 healthy subjects with North European descent (115 periodontitis and 56 controls) were included in this case-control study. hsCRP levels were determined and subjects were genotyped for the leading ANRIL SNP rs1333048. In a multivariate analysis, periodontitis, female gender, increasing BMI and homozygosity for the major allele (AA-genotype) of rs1333048 were significantly associated with elevated hsCRP plasma levels (p = 0.012, p = 0.004, p = 0.007 and p = 0.003, respectively). Periodontitis patients with rs1333048 AA-genotype showed higher levels of hsCRP than those carrying the minor C allele (median: 4.5 mg/L vs. 1.6 mg/L, padjusted = 0.007). This study is the first to show that, in addition to gender and BMI, also a leading SNP in ANRIL is explanatory for inter-individual variation in hsCRP levels in periodontitis patients of North European descent.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137335PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4562619PMC
May 2016

Java project on periodontal diseases: periodontal bone loss in relation to environmental and systemic conditions.

J Clin Periodontol 2015 Apr 24;42(4):325-32. Epub 2015 Mar 24.

Department of Periodontology, Padjadjaran State University, Bandung, Indonesia.

Objective: To assess in a population deprived from regular dental care the relationship between alveolar bone loss (ABL) and environmental/systemic conditions.

Material & Methods: The study population consisted of subjects from the Purbasari tea estate on West Java, Indonesia. A full set of dental radiographs was obtained of each subject and amount of ABL was assessed. In addition, the following parameters were evaluated: plasma vitamin C, vitamin D3 , HbA1c and CRP, the haptoglobin phenotype, presence of putative periodontopathic bacteria and viruses, dietary habits, smoking and anthropometrics.

Results: In this population 45% showed vitamin C depletion/deficiency, 82% had vitamin D3 insufficiency/deficiency, 70% were in a pre-diabetic state, 6% had untreated diabetes, 21% had elevated CRP values ranging from 3.1 to 16.1 mg/l. Results of the regression analysis, including all above mentioned parameters, showed four significant predictors, explaining 19.8% of the variance of ABL. Number of Porphyromonas gingivalis cells and CRP values showed a positive relationship with ABL, whereas BMI and number of guava fruit servings were negatively related.

Conclusion: Results confirm previous findings that elevated levels of P. gingivalis may be indicative for periodontitis progression. A new finding is that guava fruit consumption may play a protective role in periodontitis in a malnourished population.
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http://dx.doi.org/10.1111/jcpe.12381DOI Listing
April 2015

Sterile paper points as a bacterial DNA-contamination source in microbiome profiles of clinical samples.

J Dent 2013 Dec 14;41(12):1297-301. Epub 2013 Oct 14.

Department of Oral Function and Restorative Dentistry, Section of Oral Implantology and Prosthodontics, Research Institute MOVE, Academic Centre for Dentistry Amsterdam (ACTA), Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands. Electronic address:

Objectives: High throughput sequencing of bacterial DNA from clinical samples provides untargeted, open-ended information on the entire microbial community. The downside of this approach is the vulnerability to DNA contamination from other sources than the clinical sample. Here we describe contamination from sterile paper points (PPs) used in microbial sample collection.

Methods: Peri-implant samples from 48 individuals were collected using sterile PPs. Control samples contained only PPs or DNA extraction blank controls. 16S rRNA gene libraries were sequenced using 454 pyrosequencing. 16S rRNA gene copy numbers were measured by quantitative PCR.

Results: Nearly half of the sequencing reads belonged to two OTUs classified as Enterococcus (25% of reads) or Exiguobacterium (21%), which are not typical oral microorganisms. Of 87 peri-implant samples, only 10 samples (11%) contained neither of the two OTUs. The relative abundance of both unusual OTUs correlated with each other (p<0.001; r=0.828, Spearman correlation). The control samples showed that 2 of 4 (50%) of the sterile unused PPs contained bacterial DNA equivalent to 1.2 × 10(3) and 1.1 × 10(4) cells respectively, which was within the range of DNA in the clinical samples (average 1.8 × 10(7), SD 4.8 × 10(7), min 4.4 × 10(2), max 2.8 × 10(8)). The microbial profile from these PPs was dominated (>83% of reads) by the two unusual OTUs.

Conclusions: Sterile PPs can contain contaminating bacterial DNA. The use of PPs as a sampling tool for microbial profiling of clinical samples by open-ended techniques such as sequencing or DGGE should be avoided.

Clinical Significance: Clinicians working with PPs as sampling tools for bacterial DNA should consider using an alternative sampling tool, because sterile unused PPs can be a considerable source of foreign bacterial DNA. We recommend sterile curettes for collecting clinical samples for open-ended techniques, such as sequencing or DGGE.
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http://dx.doi.org/10.1016/j.jdent.2013.10.008DOI Listing
December 2013

Influence of titanium on in vitro fibroblast-Porphyromonas gingivalis interaction in peri-implantitis.

J Clin Periodontol 2013 Sep 22;40(9):841-9. Epub 2013 Jul 22.

Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam ACTA, University of Amsterdam, Amsterdam, The Netherlands.

Aim: Titanium wear particles have been found in peri-implant tissues, but their role in the pathogenesis of peri-implantitis remains unclear. We aimed to determine the in vitro inflammatory responses of peri-implant granulation tissue fibroblasts (PIGFs) to titanium particles alone and in the presence of viable Porphyromonas gingivalis.

Materials & Methods: Peri-implant granulation tissue fibroblasts were challenged either with TiO2 particles, P. gingivalis or a combination of TiO2 particles and P. gingivalis. Gene expression and protein production of pro-inflammatory mediators by PIGFs were measured with PCR and ELISA, respectively.

Results: Higher doses of TiO2 were toxic to PIGFs and in sub-toxic doses, TiO2 caused an increase in gene expression of tumour necrosis factor (TNF)-A and increased protein production of TNF-α, interleukin (IL)-6 and IL-8. A challenge with P. gingivalis alone induced gene expression of TNF-A, IL-1β, IL-6 and IL-8. A combined challenge with TiO2 and P. gingivalis caused a stronger increase in gene expression of TNF-A and protein production of TNF-α and MCP-1 than P. gingivalis alone.

Conclusions: TiO2 particles and P. gingivalis, individually, can induce pro-inflammatory responses in PIGFs. Furthermore, TiO2 particles and viable P. gingivalis further enhance gene expression and production of TNF-α by PIGFs. Therefore, Ti wear particles in the peri-implant tissues in combination with P. gingivalis infection may contribute to the pathogenesis of peri-implantitis by enhancing the inflammation in peri-implant tissues.
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http://dx.doi.org/10.1111/jcpe.12136DOI Listing
September 2013

Subgingival microbiome in smokers and non-smokers in periodontitis: an exploratory study using traditional targeted techniques and a next-generation sequencing.

J Clin Periodontol 2013 May 13;40(5):483-92. Epub 2013 Mar 13.

Department of Periodontology, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.

Aim: To compare the results of two targeted techniques to an open-ended technique in periodontitis patients, differentiated on the basis of smoking habit.

Materials & Methods: Thirty periodontitis patients (15 smokers and 15 non-smokers) provided subgingival plaque samples for 16S rRNA gene amplicon sequencing, culturing and quantitative polymerase chain reaction (qPCR).

Results: No differences were found in the composition of the subgingival microbiome between smokers and non-smokers with culture and qPCR. With pyrosequencing, operational taxonomic units (OTUs) classified to genera Fusobacterium, Prevotella and Selenomonas were more abundant in smokers, while OTUs belonging to the genera Peptococcus and Capnocytophaga were more abundant in non-smokers. Principal coordinate analysis identified two clusters; one was composed mainly of smokers (80%) and revealed significantly lower taxonomic diversity, higher attachment loss and higher proportion of the genera Fusobacterium, Paludibacter and Desulfobubus.

Conclusion: In periodontitis, there is a difference in the composition of the subgingival microbiome between smokers and non-smokers, as revealed by pyrosequencing. This difference was not identified by the targeted techniques. Low taxonomic diversity was associated with higher disease severity, especially in smokers. This supports the hypothesis of the ecological microbial-host interaction in the severity of periodontal disease.
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http://dx.doi.org/10.1111/jcpe.12087DOI Listing
May 2013

In vitro invasion and survival of Porphyromonas gingivalis in gingival fibroblasts; role of the capsule.

Arch Immunol Ther Exp (Warsz) 2012 Dec 5;60(6):469-76. Epub 2012 Sep 5.

Section of Preventive Dentistry, Department of Conservative and Preventive Dentistry, Academic Centre for Dentistry Amsterdam, ACTA, University of Amsterdam and Vrije University Amsterdam, Amsterdam, The Netherlands.

Porphyromonas gingivalis is a Gram-negative, anaerobic bacterium involved in periodontitis and peri-implantitis that can invade and survive inside host cells in vitro. P. gingivalis can invade human gingival fibroblasts (GF), but no data are available about the role of P. gingivalis' capsule in GF invasion. In the current study, we aimed to determine the ability of three strains of P. gingivalis (encapsulated wild type W83, non-encapsulated HG91 and the non-encapsulated insertional isogenic knockout mutant of W83, ΔEpsC) to invade GF and the ability of internalized P. gingivalis to survive in vitro antibiotic treatment. The ability of P. gingivalis strains to invade GF was tested using an antibiotic protection assay at multiplicity of infection (MOI) 100 and 1000. The survival of internalized P. gingivalis cells was further analyzed by subsequent in vitro treatment with either metronidazole or amoxicillin alone or a combination of metronidazole and amoxicillin and anaerobic culture viability counts. All strains of P. gingivalis used in this study were able to invade GFs. The non-encapsulated mutant of W83 (ΔEpsC mutant) was significantly more invasive than the wild type W83 at MOI 100 (p value 0.025) and MOI 1000 (p value 0.038). Furthermore, internalized P. gingivalis was able to resist in vitro antibiotic treatment. As demonstrated by the differences in invasion efficiencies of P. gingivalis strain W83 and its isogenic mutant ΔEpsC, the capsule of P. gingivalis makes it less efficient in invading gingival fibroblasts. Moreover, internalized P. gingivalis can survive antibiotic treatment in vitro.
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http://dx.doi.org/10.1007/s00005-012-0196-8DOI Listing
December 2012

Functional foods/ingredients and periodontal diseases.

Eur J Nutr 2012 Jul;51 Suppl 2:S27-30

Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands.

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http://dx.doi.org/10.1007/s00394-012-0325-5DOI Listing
July 2012

Common genetic risk variants of TLR2 are not associated with periodontitis in large European case-control populations.

J Clin Periodontol 2012 Apr 18;39(4):315-22. Epub 2012 Jan 18.

Christian-Albrechts-University, Institute for Clinical Molecular Biology, Kiel, Germany.

Aim: Involvement of TLR2 in the pathophysiology of periodontitis has widely been discussed, but hitherto, no validated genetic associations were reported. Previous association studies lacked sufficient statistical power and adequate haplotype information to draw unambiguous conclusions. The aim of this study was to comprehensively investigate TLR2 linkage disequilibrium (LD) regions for their potential associations with periodontitis in two large analysis populations of aggressive (AgP) and chronic periodontitis (CP) of North West European descent.

Materials And Methods: The study population comprised 598 AgP patients, 914 CP patients and 1804 healthy controls. Analysis of TLR2 LD regions was performed with haplotype tagging SNPs (tagSNPs) using SNPlex and TaqMan genotyping assays. Genotypic, dominant, multiplicative, and recessive genetic models were tested. The genotypes were adjusted for the covariates smoking, diabetes, and gender. Resequencing was performed by Sanger technology.

Results: Upon covariate adjustment and correction for multiple testing, no tagSNPs showed significant associations with AgP or CP. Targeted resequencing of exon 3 in 47 AgP cases identified carriership of two common and three rare variants.

Conclusion: Common LD regions of TLR2 do not show genetic associations with periodontitis in the North West European population. Resequencing of exon 3 could not identify disease-associated rare variants in TLR2.
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http://dx.doi.org/10.1111/j.1600-051X.2011.01846.xDOI Listing
April 2012

The capsule of Porphyromonas gingivalis leads to a reduction in the host inflammatory response, evasion of phagocytosis, and increase in virulence.

Infect Immun 2011 Nov 12;79(11):4533-42. Epub 2011 Sep 12.

Philips Institute of Oral and Craniofacial Molecular Biology, School of Dentistry, Virginia Commonwealth University, 521 North 11th St., Richmond, VA 23298-0566, USA.

Periodontal disease is a chronic oral inflammatory disease that is triggered by bacteria such as Porphyromonas gingivalis. P. gingivalis strains exhibit great heterogeneity, with some strains being encapsulated while others are nonencapsulated. Although the encapsulated strains have been shown to be more virulent in a mouse abscess model, so far the role of the capsule in P. gingivalis interactions with host cells is not well understood and its role in virulence has not been defined. Here, we investigated the contribution of the capsule to triggering a host response following microbial infection, as well as its protective role following bacterial internalization by host phagocytic cells with subsequent killing, using the encapsulated P. gingivalis strain W50 and its isogenic nonencapsulated mutant, PgC. Our study shows significant time-dependent upregulation of the expression of various groups of genes in macrophages challenged with both the encapsulated and nonencapsulated P. gingivalis strains. However, cells infected with the nonencapsulated strain showed significantly higher upregulation of 9 and 29 genes at 1 h and 8 h postinfection, respectively, than cells infected with the encapsulated strain. Among the genes highly upregulated by the nonencapsulated PgC strain were ones coding for cytokines and chemokines. Maturation markers were induced at a 2-fold higher rate in dendritic cells challenged with the nonencapsulated strain for 4 h than in dendritic cells challenged with the encapsulated strain. The rates of phagocytosis of the nonencapsulated P. gingivalis strain by both macrophages and dendritic cells were 4.5-fold and 7-fold higher, respectively, than the rates of phagocytosis of the encapsulated strain. On the contrary, the survival of the nonencapsulated P. gingivalis strain was drastically reduced compared to the survival of the encapsulated strain. Finally, the encapsulated strain exhibited greater virulence in a mouse abscess model. Our results indicate that the P. gingivalis capsule plays an important role in aiding evasion of host immune system activation, promoting survival of the bacterium within host cells, and increasing virulence. As such, it is a major virulence determinant of P. gingivalis.
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http://dx.doi.org/10.1128/IAI.05016-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257911PMC
November 2011

Diverse effects of Porphyromonas gingivalis on human osteoclast formation.

Microb Pathog 2011 Sep 27;51(3):149-55. Epub 2011 Apr 27.

Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, The Netherlands.

Porphyromonas gingivalis is associated with periodontitis, a chronic inflammatory disease of the tooth-supporting tissues. A major clinical symptom is alveolar bone loss due to excessive resorption by osteoclasts. P. gingivalis may influence osteoclast formation in diverse ways; by interacting directly with osteoclast precursors that likely originate from peripheral blood, or indirectly by activating gingival fibroblasts, cells that can support osteoclast formation. In the present study we investigated these possibilities. Conditioned medium from viable or dead P. gingivalis, or from gingival fibroblasts challenged with viable or dead P. gingivalis were added to human mononuclear osteoclast precursors. After 21 days of culture the number of multinucleated (≥3 nuclei) tartrate resistant acid phosphatase (TRACP)-positive cells was determined as a measure for osteoclast formation. Conditioned medium from viable P. gingivalis, and from fibroblasts with viable P. gingivalis stimulated osteoclast formation (1.6-fold increase p < 0.05). Conditioned medium from dead bacteria had no effect on osteoclast formation, whereas conditioned medium from fibroblasts with dead bacteria stimulated formation (1.4-fold increase, p < 0.05). Inhibition of P. gingivalis LPS activity by Polymyxin B reduced the stimulatory effect of conditioned medium. Interestingly, when RANKL and M-CSF were added to cultures, conditioned media inhibited osteoclast formation (0.6-0.7-fold decrease, p < 0.05). Our results indicate that P. gingivalis influences osteoclast formation in vitro in different ways. Directly, by bacterial factors, likely LPS, or indirectly, by cytokines produced by gingival fibroblasts in response to P. gingivalis. Depending on the presence of RANKL and M-CSF, the effect of P. gingivalis is either stimulatory or inhibitory.
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http://dx.doi.org/10.1016/j.micpath.2011.04.006DOI Listing
September 2011

Association of serum immunoglobulin G (IgG) levels against two periodontal pathogens and prothrombotic state: a clinical pilot study.

Thromb J 2010 Nov 4;8:16. Epub 2010 Nov 4.

Department of Periodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije University, Amsterdam, The Netherlands.

Objective: Periodontitis is associated with cardiovascular diseases (CVD). In our previous studies a prothrombotic state has been observed in periodontitis, which contributes to the risk of CVD. The aim of this study was to investigate whether serum IgG levels against Aggregatibacter actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) in periodontitis were associated with a prothrombotic state.

Materials And Methods: Patients with moderate (n = 38) and severe periodontitis (n = 30) and controls (n = 24) were recruited. We explored correlations between serum anti-Aa and anti-Pg IgG and plasma levels of markers of prothrombotic state (von Willebrand Factor [vWF], prothrombin fragment 1+2 [F1+2], plasminogen activator inhibitor-1 [PAI-1] and D-dimer). Multivariate analyses were performed considering several major potential contributing factors.

Results: Periodontitis patients showed higher anti-Aa IgG (p = 0.015) than controls but not for Pg (p = 0.320). In periodontitis patients, body mass index and anti-Aa IgG showed a positive correlation with vWF (β = 0.297, p = 0.010 and β = 0.248, p = 0.033 respectively).

Conclusions: In periodontitis, infection with Aa together with other well accepted risk factors for CVD, may play a role in increasing the risk for prothrombotic state.
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http://dx.doi.org/10.1186/1477-9560-8-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2989307PMC
November 2010

CDKN2BAS is associated with periodontitis in different European populations and is activated by bacterial infection.

J Med Genet 2011 Jan 26;48(1):38-47. Epub 2010 Oct 26.

Christian-Albrechts-University Kiel, Institute for Clinical Molecular Biology, Kiel, Germany.

Epidemiological studies have indicated a relationship between coronary heart disease (CHD) and periodontitis. Recently, CDKN2BAS was reported as a shared genetic risk factor of CHD and aggressive periodontitis (AgP), but the causative variant has remained unknown. To identify and validate risk variants in different European populations, we first explored 150 kb of the genetic region of CDKN2BAS including the adjacent genes CDKN2A and CDKN2B, covering 51 tagging single nucleotide polymorphisms (tagSNPs) in AgP and chronic periodontitis (CP) in individuals of Dutch origin (n=313). In a second step, we tested the significant SNP associations in an independent AgP and CP population of German origin (n=1264). For the tagSNPs rs1360590, rs3217992, and rs518394, we could validate the associations with AgP before and after adjustment for the covariates smoking, gender and diabetes, with SNP rs3217992 being the most significant (OR 1.48, 95% CI 1.19 to 1.85; p=0.0004). We further showed in vivo gene expression of CDKN2BAS, CDKN2A, CDKN2B, and CDK4 in healthy and inflamed gingival epithelium (GE) and connective tissue (CT), and detected a significantly higher expression of CDKN2BAS in healthy CT compared to GE (p=0.004). After 24 h of stimulation with Porphyromonas gingivalis in Streptococcus gordonii pre-treated gingival fibroblast (HGF) and cultured gingival epithelial cells (GECs), we observed a 25-fold and fourfold increase of CDKN2BAS gene expression in HGFs (p=0.003) and GECs (p=0.004), respectively. Considering the global importance of CDKN2BAS in the disease risk of CHD, this observation supports the theory of inflammatory components in the disease physiology of CHD.
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http://dx.doi.org/10.1136/jmg.2010.078998DOI Listing
January 2011

The core genome of the anaerobic oral pathogenic bacterium Porphyromonas gingivalis.

BMC Microbiol 2010 Sep 29;10:252. Epub 2010 Sep 29.

Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam, University of Amsterdam and Free University Amsterdam, Amsterdam, The Netherlands.

Background: The Gram negative anaerobic bacterium Porphyromonas gingivalis has long been recognized as a causative agent of periodontitis. Periodontitis is a chronic infectious disease of the tooth supporting tissues eventually leading to tooth-loss. Capsular polysaccharide (CPS) of P. gingivalis has been shown to be an important virulence determinant. Seven capsular serotypes have been described. Here, we used micro-array based comparative genomic hybridization analysis (CGH) to analyze a representative of each of the capsular serotypes and a non-encapsulated strain against the highly virulent and sequenced W83 strain. We defined absent calls using Arabidopsis thaliana negative control probes, with the aim to distinguish between aberrations due to mutations and gene gain/loss.

Results: Our analyses allowed us to call aberrant genes, absent genes and divergent regions in each of the test strains. A conserved core P. gingivalis genome was described, which consists of 80% of the analyzed genes from the sequenced W83 strain. The percentage of aberrant genes between the test strains and control strain W83 was 8.2% to 13.7%. Among the aberrant genes many CPS biosynthesis genes were found. Most other virulence related genes could be found in the conserved core genome. Comparing highly virulent strains with less virulent strains indicates that hmuS, a putative CobN/Mg chelatase involved in heme uptake, may be a more relevant virulence determinant than previously expected. Furthermore, the description of the 39 W83-specific genes could give more insight in why this strain is more virulent than others.

Conclusion: Analyses of the genetic content of the P. gingivalis capsular serotypes allowed the description of a P. gingivalis core genome. The high resolution data from three types of analysis of triplicate hybridization experiments may explain the higher divergence between P. gingivalis strains than previously recognized.
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http://dx.doi.org/10.1186/1471-2180-10-252DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2955634PMC
September 2010