Mechanical plaque removal in step-1 of care.

Maintaining a regular oral hygiene routine is essential for taking care of our mouths, ensuring healthy teeth, and achieving fresh breath. Patient education on oral hygiene is an important component of their overall treatment. Firstly, patients should be informed about the direct connection between bacteria in dental plaque and oral diseases. It is important for patients to understand that these conditions can be treated, but the success of treatment greatly depends on their level of oral hygiene. This journey begins by selecting the appropriate toothbrush and mastering the correct brushing technique to effectively remove dental plaque while avoiding any potential damage to the gums. In addition to toothbrushes, there are other devices available for comprehensive dental cleaning, such as floss, interdental sticks, interdental brushes, and oral irrigators. These aids are particularly beneficial for eliminating dental plaque from hard-to-reach areas. Moreover, tongue brushing or tongue scraping can effectively reduce breath odor and tongue coating. Currently, self-care recommendations for dental implants are primarily based on existing knowledge regarding natural teeth cleaning. Evidence-based recommendations are derived from comprehensive systematic evaluation of various oral hygiene aids.

Health action process approach in oral health behaviour: Target interventions, constructs and groups-A systematic review.

OBJECTIVE: The aim of this study was to systematically map the Health Action Process Approach (HAPA)-based interventions in dentistry in relation to the type of intervention, the target groups and the constructs of the HAPA model that are used in the study and to assess the clinical relevance of the studies. METHODS: A search in the databases of the National Library of Medicine (MEDLINE-PubMed), PsychINFO and Cochrane-CENTRAL was conducted. A quality assessment to estimate the risk of bias and a qualitative descriptive analysis were performed. The overall gathered evidence was graded. RESULTS: Ten randomized controlled trials and three observational studies thus in total 13 studies were included. Flossing was the targeted behaviour in ten studies. The target groups consisted of students, adolescents and dental patients. Overall, all nine HAPA constructs were used, but only one study used all HAPA constructs. Six studies presented the used behavioural change techniques according to the BCT taxonomy. Based on the number of the used constructs, only two studies were classified as HAPA intervention studies. The most frequently used constructs were action control as an intervention and behaviour as an outcome measure. The overall evidence was graded with moderate certainty. CONCLUSION: In the majority of the studies, the targeted intervention was flossing and the population consisted of students, adolescents and dental patients. All studies used only a selection of the HAPA constructs. Therefore, only a minority of the studies can be considered real HAPA intervention studies.

The Effect of Various Fluoride Products on Dentine Lesions during pH-Cycling.

This study compared the effect of topically applied fluoride products on dentine lesions in an in vitro experiment. Demineralized bovine dentine specimens were treated once with either SDF solution (35,400 ppm F), NaF varnish (22,600 ppm F), TiF4 solution (9,200 ppm F), SnF2 gel (1,000 ppm F), no treatment (control), or preserved as baseline lesions. After the application and subsequent removal of the fluoride products, the specimens were subjected to pH-cycling. Calcium loss and uptake in the de- and remineralization buffers were assessed daily. Fluoride release into the buffers was analyzed on days 1, 2, 3, 5, 8, and 13. After the pH-cycling period, mineral distribution throughout the lesion depth was analyzed using transversal microradiography (TMR). X-ray energy-dispersive spectroscopy (EDS) examined the deposition of silver, titanium, and tin after application of SDF, TiF4, and SnF2, respectively. Overall, calcium loss and uptake analysis in the de- and remineralization buffers revealed that the SDF product was the most effective in inhibiting lesion progression, followed by the TiF4, NaF, and SnF2 products. Fluoride analysis disclosed a steep reduction of the amount of fluoride released into de- and remineralization buffers with time. The fluoride effects on de- and remineralization continued beyond the days that fluoride was released into the buffers. TMR analysis showed significant remineralization in the outer zone of the dentine lesions for all fluoride products, with SDF giving hypermineralization in this zone. In the inner zone, lesions developed in all fluoride groups, with the smallest in the SDF group. EDS showed silver and titanium deposition in depth up to 85 µm and 8 µm, respectively, while no tin deposition was observed. The silver in the dentine lesions did not contribute significantly to the density of the TMR profiles in the SDF group. In conclusion, all topical fluoride products protected the dentine lesions against lesion progression, but at different degrees. SDF showed a superior effect in protection against further demineralization and enhancement of remineralization. This was probably attributed to its fluoride concentration that was the highest among the fluoride products.

The effect of equal fluoride concentrations in silver diamine fluoride and potassium fluoride on demineralized dentin during pH-cycling: chemical data.

The actual contribution of silver in silver diamine fluoride (SDF) towards the anti-demineralizing effect is unclear. This study compared the effects of single applications of three concentrations of fluoride (4.1%, 1.025%, 0.26% F- ) in the form of SDF and potassium fluoride (KF) on demineralized dentin in a 15-day non-microbial pH-cycling model. Calcium loss and uptake in de- and remineralization buffers were analyzed daily. Fluoride release in both buffers was analyzed on days 1, 2, 3, and 8. The net calcium results of de- and remineralization cycles revealed dose-response protection without significant differences between equal fluoride concentrations of SDF and KF. In the demineralization cycles, all fluoride treatments, except KF 0.26% F- , significantly inhibited demineralization, with KF 4.1% F- being the most effective. In the remineralization cycles, remineralization was enhanced in all fluoride concentration groups in a dose-response manner with no difference between similar fluoride concentrations of SDF and KF. Daily fluoride effects were constant throughout the experiment. Fluoride analysis revealed statistically significant differences in fluoride release between the treatments on day 1 that diminished on days 2 and 3. The non-microbial model showed no differences between SDF and KF in inhibiting demineralization and enhancing remineralization of dentin lesions.

The effect of using a mobile application ("WhiteTeeth") on improving oral hygiene: A randomized controlled trial.

OBJECTIVE: To evaluate the effectiveness of the WhiteTeeth mobile app, a theory-based mobile health (mHealth) program for promoting oral hygiene in adolescent orthodontic patients. METHODS: In this parallel randomized controlled trial, the data of 132 adolescents were collected during three orthodontic check-ups: at baseline (T0), at 6-week follow-up (T1) and at 12-week follow-up (T2). The intervention group was given access to the WhiteTeeth app in addition to usual care (n = 67). The control group received usual care only (n = 65). The oral hygiene outcomes were the presence and the amount of dental plaque (Al-Anezi and Harradine plaque index), and the total number of sites with gingival bleeding (Bleeding on Marginal Probing Index). Oral health behaviour and its psychosocial factors were measured through a digital questionnaire. We performed linear mixed-model analyses to determine the intervention effects. RESULTS: At 6-week follow-up, the intervention led to a significant decrease in gingival bleeding (B = -3.74; 95% CI -6.84 to -0.65) and an increase in the use of fluoride mouth rinse (B = 1.93; 95% CI 0.36 to 3.50). At 12-week follow-up, dental plaque accumulation (B = -11.32; 95% CI -20.57 to -2.07) and the number of sites covered with plaque (B = -6.77; 95% CI -11.67 to -1.87) had been reduced significantly more in the intervention group than in the control group. CONCLUSIONS: The results show that adolescents with fixed orthodontic appliances can be helped to improve their oral hygiene when usual care is combined with a mobile app that provides oral health education and automatic coaching. Netherlands Trial Registry Identifier: NTR6206: 20 February 2017.

Biomineralization of dentin.

A single biomineralization of demineralized dentin is significant to restore the demineralized dentin due to dental caries or erosion. In recent years, meaningful progress has been made regarding the mechanisms involved in the biomineralization of dentin collagen. Concepts changing from the classical ion-based crystallization to non-classical particle-based crystallization, inspired a different strategy to infiltrate the demineralized dentin collagen. The remarkable discovery was the report of liquid-like amorphous calcium phosphate as nanoprecursor particles to carbonated hydroxyapatite. The non-collagenous proteins and their analogues are widely investigated, for their key role in controlling mineralization during the process of crystal nucleation and growth. The in-depth studies of the gap zone provided significant improvements in our understanding of the structure of collagen and of the intrafibrillar remineralization of collagen fibrils. The collagen is not a passive substrate as previously supposed, and the active role of guiding nanoprecursor infiltration and mediating its nucleation has been demonstrated. Furthermore, recovery of mechanical properties has been evaluated to determine the effectiveness of dentin remineralization. Finally, the problems regarding the origin formation of the calcium phosphate that is deposited in the collagen, and the exact interactions between the non-collagenous proteins, amorphous calcium phosphate and collagen are still unclear. We reviewed the importance of these findings in enriching our understanding of dentin biomineralization, while addressing certain limitations that are inherent to in vitro studies.

Sugar Restriction for Caries Prevention: Amount and Frequency. Which Is More Important?

The World Health Organization guideline to use less sugar may be an opportunity and support for dentistry in its goal to get the message of using less sugar across to the public. Two ways (with all the combinations of these) to achieve a reduction of sugar consumption are the reduction of the amount of sugar in products or the reduction of the frequency of consumption of sugar-containing products. Which sugar-reducing strategy is best for caries prevention? To answer this question, this manuscript discusses the shape of the dose-response association between sugar intake and caries, the influence of fluoridated toothpaste on the association of sugar intake and caries and the relative contribution of frequency and amount of sugar intake to caries levels. The results suggest that when fluoride is appropriately used, the relation between sugar consumption and caries is very low or absent. The high correlation between amount and frequency hampers the decision related to which of both is of more importance, but frequency (and stickiness) fits better in our understanding of the caries process. Reducing the amount without reducing the frequency does not seem to be an effective caries preventive approach in contrast to the reciprocity. Goals set in terms of frequency may also be more tangible for patients to follow than goals set in amount. Yet, in sessions of dietary counselling to prevent dental caries, the counsellor should not forget the importance of quality tooth brushing with fluoride toothpaste.

European Organization for Caries Research Workshop: Methodology for Determination of Potentially Available Fluoride in Toothpastes.

Toothpastes are the most universally accepted form of fluoride delivery for caries prevention. To provide anti-caries benefits, they must be able to release fluoride during the time of tooth brushing or post brushing into the oral cavity. However, there is no standard accepted procedure to measure how much fluoride in a toothpaste may be (bio) available for release. The European Organization for Caries Research proposed and supported a workshop with experts in fluoride analysis in toothpastes and representatives from industry. The objective of the workshop was to discuss issues surrounding fluoride analysis in toothpaste and reach consensus on terminology and best practices, wherever the available evidence allowed it. Participants received a background paper and heard presentations followed by structured discussion to define the problem. The group also reviewed evidence on the validity, reliability and feasibility of each technique (namely chromatography and fluoride electroanalysis) and discussed their strengths and limitations. Participants were able to reach a consensus on terminology and were also able to identify and summarize the advantages and disadvantages of each technique. However, they agreed that most currently available methods were developed for regulatory agencies several decades ago, utilizing the best available data from clinical trials then, but require to be updated. They also agreed that although significant advances to our understanding of the mechanism of action of fluoride in toothpaste have been achieved over the past 4 decades, this clearly is an extraordinarily complex subject and more work remains to be done.

Dental caries and externalizing behaviour problems in a high-risk child population.

The aim of this study was to assess the association between externalizing behaviour problems and dental caries in children. A further objective was to explore direct and indirect pathways between sociodemographic factors, family functioning and parenting factors, oral health behaviours, externalizing behaviour problems, and dental caries using structural equation modelling. Cross-sectional data were collected on 251, 5- to 8-yr-old children from a paediatric dental practice in the Netherlands. Children's decayed, missing, and filled primary teeth (dmft) scores were obtained from their dental records. Validated self-report questionnaires were used to collect sociodemographic, behavioural, and family-related data. Externalizing problem behaviour was significantly associated with a higher dmft score [incidence risk ratio (IRR) = 1.19; 95% CI: 1.06-1.34], but this association did not remain significant after adjustment for sociodemographic factors (IRR = 1.11; 95% CI: 0.99-1.26). A valid path model was presented after applying some modifications. Findings from the model suggest that it is plausible that child behaviour problems are directly associated with dental caries via toothbrushing behaviour. The model also provided support that maternal education level, the restrictiveness and warmth of parenting, and the communication of the family, play an indirect role in the association between children's externalizing behavioural problems and dental caries experience.

Study protocol of a randomized controlled trial to test the effect of a smartphone application on oral-health behavior and oral hygiene in adolescents with fixed orthodontic appliances.

BACKGROUND: Adolescents with fixed orthodontic appliances are at high risk of developing dental caries. To date, new smartphone technologies have seldom been used to support them in the preventive behavior that can help prevent dental caries. After an intervention-mapping process, we developed a smartphone application (the WhiteTeeth app) for preventing dental caries through improved oral-health behavior and oral hygiene. The app, which is intended to be used at home, will help adolescents with fixed orthodontic appliances perform their oral self-care behavior. The app is based on the Health Action Process Approach (HAPA) theory, and incorporates several behavior-change techniques that target the psychosocial factors of oral-health behavior. This article describes the protocol of a randomized controlled trial (RCT) to evaluate the effects of the WhiteTeeth app on oral-health behavior and oral-hygiene outcomes (presence of dental plaque and gingival bleeding) compared with those of care as usual, in patients aged 12-16 with fixed orthodontic appliances. METHODS/DESIGN: The RCT has two conditions: an experimental group that will receive the WhiteTeeth app in addition to care as usual, and a control group that will only receive care as usual. Care as usual will include routine oral-health education and instruction at orthodontic check-ups. In the western part of the Netherlands 146 participants will be recruited from four orthodontic clinics. Data will be collected during three orthodontic check-ups: baseline (T0), 6 weeks of follow-up (T1) and 12 weeks of follow-up (T2). The primary study outcomes are the presence of dental plaque (measured with a modified Silness and Loë Plaque Index); and gingival bleeding (measured with the Bleeding on Marginal Probing Index). Secondary outcomes include changes in self-reported oral-health behaviors and its psychosocial factors identified by the HAPA theory, such as outcome expectancies, intention, action self-efficacy, coping planning and action control. DISCUSSION: Since the intervention was designed to target psychosocial factors in the motivational and volitional components of the behavior-change process, we hypothesize that the app will cause greater improvements in oral-health behavior and oral hygiene more than traditional oral-health-promotion programs (i.e., care as usual). TRIAL REGISTRATION: The trial has been registered with the Dutch Trial Register ( NTR6206 : 20 February 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.

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.

An application of the Health Action Process Approach model to oral hygiene behaviour and dental plaque in adolescents with fixed orthodontic appliances.

BACKGROUND: The Health Action Process Approach (HAPA) model addresses health behaviours, but it has never been applied to model adolescents' oral hygiene behaviour during fixed orthodontic treatment. AIM: This study aimed to apply the HAPA model to explain adolescents' oral hygiene behaviour and dental plaque during orthodontic treatment with fixed appliances. METHODS: In this cross-sectional study, 116 adolescents with fixed appliances from an orthodontic clinic situated in Almere (the Netherlands) completed a questionnaire assessing oral health behaviours and the psychosocial factors of the HAPA model. Linear regression analyses were performed to examine the factors associated with dental plaque, toothbrushing, and the use of a proxy brush. RESULTS: Stepwise regression analysis showed that lower amounts of plaque were significantly associated with higher frequency of the use of a proxy brush (R2 = 45%), higher intention of the use of a proxy brush (R2 = 5%), female gender (R2 = 2%), and older age (R2 = 2%). The multiple regression analyses revealed that higher action self-efficacy, intention, maintenance self-efficacy, and a higher education were significantly associated with the use of a proxy brush (R2 = 45%). CONCLUSION: Decreased levels of dental plaque are mainly associated with increased use of a proxy brush that is subsequently associated with a higher intention and self-efficacy to use the proxy brush.

Anti-erosive effects of fluoride and phytosphingosine: an in vitro study.

A selection of commercially available products containing stannous fluoride (SnF2 )/sodium fluoride (NaF), SnF2 /amorphous calcium phosphate (ACP), SnF2 /NaF/ACP, tin (Sn)/fluorine (F)/chitosan were compared with phytosphingosine (PHS) with respect to their anti-erosive properties in vitro. One-hundred and twenty bovine enamel specimens were immersed in the respective product slurries for 2 min, twice daily. The formulations were diluted with either remineralization solution or artificial saliva. After each treatment, an erosive challenge was performed for 10 min, twice daily, using citric acid, pH 3.4. The specimens were stored in remineralization solution or artificial saliva until the next treatment-erosion challenge. After 10 d, tissue loss was determined using profilometry. Enamel softening was determined through surface microhardness measurements. Tissue-loss values (measured in µm and expressed as mean ± SD) for PHS, SnF2 /NaF, SnF2 /ACP, SnF2 /ACP/NaF, and Sn/F/chitosan treatment groups and for the negative-control group, were, respectively, 35.6 ± 2.8, 15.8 ± 1.8, 22.1 ± 2.0, 22.9 ± 1.8, 16.2 ± 1.2, and 51.2 ± 4.4 in the presence of remineralization solution and 31.7 ± 3.3, 15.6 ± 2.9, 16.5 ± 2.7, 16.8 ± 2.1, 13.1 ± 3.0, and 50.7 ± 2.8 in the presence of artificial saliva. There were no significant differences in surface microhardness measurements between the treatment groups. In conclusion, PHS resulted in a significant reduction of tissue loss compared with the negative control, but in comparison, the toothpastes containing Sn(2+) and F(-) ions were significantly more effective compared with PHS.

Epithelial cell detachment by Porphyromonas gingivalis biofilm and planktonic cultures.

Porphyromonas gingivalis is present as a biofilm at the sites of periodontal infections. The detachment of gingival epithelial cells induced by P. gingivalis biofilms was examined using planktonic cultures as a comparison. Exponentially grown planktonic cultures or 40-h biofilms were co-incubated with epithelial cells in a 24-well plate for 4 h. Epithelial cell detachment was assessed using imaging. The activity of arginine-gingipain (Rgp) and gene expression profiles of P. gingivalis cultures were examined using a gingipain assay and quantitative PCR, respectively. P. gingivalis biofilms induced significantly higher cell detachment and displayed higher Rgp activity compared to the planktonic cultures. The genes involved in gingipain post-translational modification, but not rgp genes, were significantly up-regulated in P. gingivalis biofilms. The results underline the importance of including biofilms in the study of bacterial and host cell interactions.

Relationship between Child and Parental Dental Anxiety with Child's Psychological Functioning and Behavior during the Administration of Local Anesthesia.

OBJECTIVES: The aims of this study were to determine: 1) the relationship between children's psychological functioning, dental anxiety and cooperative behavior before and during local anesthesia, 2) the relationship of parental dental anxiety with all the above child characteristics. STUDY DESIGN: There was a convenient sample of 100 children (4-12 years). Child dental anxiety and psychological functioning were measured using the "Children's Fear Survey Schedule" (CFSS-DS) and the "Strengths and Difficulties Questionnaire" (SDQ) respectively. Parental dental anxiety was measured using the "Modified Dental Anxiety Scale" (MDAS). All questionnaires were completed by parents. Before and during local anesthesia, the child behavior was scored by one experienced examiner, using the Venham scale. Non-parametric tests and correlations (Mann-Whitney, Spearman's rho) were used for the analysis. RESULTS: The mean SDQ score was 10±5.6 for boys (n=60) and 8.3±4.8 for girls (n=40) (p=0.038), but there was no correlation with children's age. The mean CFSS-DS score was 33.1±11.86 and there was no correlation with age or gender. Children with higher levels in the pro-social subscale of the SDQ had significantly less anxiety and better behavior before local anesthesia. Higher mean CFSS-DS scores were significantly associated with uncooperative behavior during local anesthesia (p=0.04). There was no correlation between parents' and their children's dental anxiety, psychological functioning and behavior. 46% of the children had previous dental experience in the last 6 months. As time since the last dental treatment increased, an improvement was found in children's behavior during local anesthesia. CONCLUSIONS: Child psychological functioning was related to dental anxiety and behavior during dental appointment involving local anesthesia.

Establishing oral health promoting behaviours in children - parents' views on barriers, facilitators and professional support: a qualitative study.

BACKGROUND: The prevention of childhood dental caries relies on adherence to key behaviours, including twice daily tooth brushing with fluoride toothpaste and reducing the consumption of sugary foods and drinks. The aim of this qualitative study was to explore parents' perceptions of barriers and facilitators that influence these oral health behaviours in children. A further objective was to explore parents' views on limitations and opportunities for professional support to promote children's oral health. METHODS: Six focus group interviews were conducted, including a total of 39 parents of 7-year old children, who were recruited from paediatric dental centres in The Netherlands. Interviews were held with Dutch parents of low and high socioeconomic status and parents from Turkish and Moroccan origin. Focus group interviews were conducted on the basis of a pre-tested semi-structured interview guide and topic list. Content analysis was employed to analyse the data. RESULTS: Analysis of interview transcripts identified many influences on children's oral health behaviours, operating at child, family and community levels. Perceived influences on children's tooth brushing behaviour were primarily located within the direct family environment, including parental knowledge, perceived importance and parental confidence in tooth brushing, locus of control, role modelling, parental monitoring and supervision, parenting strategies and tooth brushing routines and habituation. The consumption of sugary foods and drinks was influenced by both the direct family environment and factors external to the family, including the school, the social environment, commercials and television, supermarkets and affordability of foods. Parents raised several suggestions for professional oral health support, which included the provision of clear and consistent oral health information using a positive approach, dietary regulations at school and a multidisciplinary approach among dental professionals, child health centres and other institutions in providing parental support. CONCLUSION: In conclusion, this qualitative study provided detail regarding parental views on the influences on children oral health behaviours and their opinions on what further support is needed to promote children's dental health. Parents' suggestions for professional oral health support can guide the development or improvement of caries preventive interventions.

Modelling community, family, and individual determinants of childhood dental caries.

This cross-sectional study empirically tested a theoretical model of pathways and inter-relationships among community, family, and individual determinants of childhood dental caries in a sample of 630, 6-year-old children from the Netherlands. Children's decayed, missing, and filled teeth (dmft) scores were extracted from dental records. A validated parental questionnaire was used to collect data on sociodemographic characteristics, psychosocial factors, and oral hygiene behaviours. Data on neighbourhood quality were obtained from the Dutch Central Bureau of Statistics. Structural equation modelling indicated that the model was valid after applying a few modifications. In the revised model, lower maternal education level was related to poorer family organization, lower levels of social support, lower dental self-efficacy, and an external dental health locus of control. These, in turn, were associated with poorer oral hygiene behaviours, which were linked to higher levels of childhood dental caries. In addition, lower maternal education level and poorer neighbourhood quality were directly associated with higher caries levels in children. This model advances our understanding of determinants of childhood dental caries and the pathways in which they operate. Conception of these pathways is essential for guiding the development of caries-preventive programmes for children. Clues for further development of the model are suggested.

The influence of oral bacteria on epithelial cell migration in vitro.

Oral ulcerations often arise as a side effect from chemo- and radiation therapy. In a previous clinical study, Porphyromonas gingivalis was identified as a positive predictor for oral ulcerations after hematopoetic stem cell transplantation, possibly incriminating P. gingivalis in delayed healing of the ulcerations. Therefore, it was tested whether P. gingivalis and its secreted products could inhibit the migration of oral epithelial cells in an in vitro scratch assay. To compare, the oral bacteria Prevotella nigrescens, Prevotella intermedia, Tannerella forsythia, and Streptococcus mitis were included. A standardized scratch was made in a confluent layer of human oral epithelial cells. The epithelial cells were challenged with bacterial cells and with medium containing secretions of these bacteria. Closure of the scratch was measured after 17 h using a phase contrast microscope. P. gingivalis, P. nigrescens, and secretions of P. gingivalis strongly inhibited cell migration. A challenge with 1000 heat-killed bacteria versus 1 epithelial cell resulted in a relative closure of the scratch of 25% for P. gingivalis and 20% for P. nigrescens. Weaker inhibitory effects were found for the other bacteria. The results confirmed our hypothesis that the oral bacteria may be involved in delayed wound healing.