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- Hasslöf, Pamela, 1978-
(författare)
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Probiotic Lactobacilli in the context of dental caries as a biofilm-mediated disease
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The World Health Organization defines probiotics as ‘live microorganisms which, when administered in adequate amounts, confer a health benefit to the host’. Traditionally, probiotic microorganisms have been used to prevent or treat gastrointestinal tract diseases. In the last 15 years, there has been increasing interest of a possible probiotic impact on the oral microbiota and dental caries. Dental caries is a multifactorial disease, and the causative factor in the oral microbiota includes a shift from a balanced microflora to a microflora that includes more aciduric species such as mutans streptococci (MS), non-mutans streptococci, and Actinomyces. MS is considered an opportunistic pathogen although several other bacteria also contribute to the disease. Early acquisition of MS is associated with early development of caries; therefore a desirable complement to other prophylactic measures would be a MS colonization inhibitor.Objective: To better understand how selected strains of probiotic lactobacilli interact with MS in vitro and in vivo and to study the impact of probiotic lactobacilli on caries development during childhood. Material and methods: The in vitro properties of probiotic lactobacilli were studied with regard to (i) acid production from sugars and sugar alcohols, (ii) growth inhibition capacity on clinical isolates and reference strains of MS as well as Candida albicans and (iii) the capacity to co-aggregate with MS. A randomized controlled trial (RCT) tested the short-term effect of intervention with two Lactobacillus reuteri strains on MS, which was evaluated after treatment with chlorhexidine. The re-growth patterns of MS and 19 other selected strains were also evaluated. In the second clinical study we investigated the long-term effect on MS prevalence and dental caries after an intervention with Lactobacillus paracasei ssp. paracasei F19 (LF19) between 4 and 13 months of age.Results: The results from the in vitro testing showed that strains of probiotic lactobacilli differed in their fermentation patterns, inhibition capacity and their capacity to co-aggregate, which should be kept in mind in the translation to clinical research. The clinical study on short-term effects of two L. reuteri strains on MS and other oral strains showed no effect on re-growth patterns after intervention. The clinical study on long-term effects of LF19 showed no effect on the prevalence of MS. Furthermore, the clinical follow-up at 9 years of age showed no differences in either decayed, missing, and filled surface (dmfs) or DMFS between the probiotic and placebo groups. Evaluation of saliva samples showed no signs of oral colonization with LF19 in the study group.Conclusion: The in vitro testing showed potentials of the selected probiotic Lactobacillus strains for interference with MS and C. albicans. The results from the clinical studies showed no such effect on MS or dental caries. Evidence regarding the effectiveness of specific probiotic applications in the prevention of dental caries is limited and does not allow for conclusions concerning the use of probiotic bacteria as a preventive measure.
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| 2. |
- Eriksson, Linda, 1979-
(författare)
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Oral microbiota in relation to host traits, environment, and dental caries
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Dental caries still appears at high prevalence worldwide. Disease distribution is skewed with more disease in socio-economically weak groups. However, also in populations considered as “low caries” there is a significant fraction with continuous disease development. Caries develops when the hard tissues of the tooth is demineralized, which occurs when pH drops below approximately 5.5 for enamel and 6.2 for dentine. The pH drop follows fermentation and acid production by tooth colonising bacteria upon dietary carbohydrate exposure. Thus, understanding the interactions between oral bacteria, diet and host factors is essential for managing the disease. The overall aim of this thesis was to study the oral microbiota in relation to caries and its association with sugar intake and driving forces behind sugar intake.Material and method: Saliva and tooth biofilm samples, information on caries status, dietary habits and other lifestyle data were collected from 17-23 year old participants. The participants also carried out a tasting session for the tastes sour, sweet and bitter. Genomic DNA was extracted from saliva and tooth biofilm and analysed using 16S rDNA amplicon sequencing with two platforms. Taxa were classified against the eHOMD database. Taste gene genotyping was done by mass spectrometry. Data were compared by univariate and multivariate statistical methods.Results: Oral microbiota was analysed in 64 adolescents. Streptococcus mutans, Scardovia wiggsiae, Bifidobacterium longum and Lepotrichia sp. HOT 498 displayed strong association with having caries, whereas Corynebacterium matruchotii and tooth brushing were associated with being caries-free. It was also confirmed that S.mutans was not compulsory for having caries. The oral microbiota in caries affected adolescents without S. mutans in was evaluated, and found to be characterised by a wide panel of saccharolytic non-S.mutans species. In contrast, tooth biofilms in individuals with caries and S. mutans were enriched for relatively few saccharolytic species in addition to S.mutans. Further, the overall microbiota pattern fell into four distinct clusters with deviating caries prevalence. The association with a set of lifestyle factors was searched, and sugar intake was found to differ between the groups. In the cluster with the highest sugar intake, the microbiota was less diverse and low sugar intake was characterized by enumeration of C. durum, C. matruchotiiand S. sanguinis. To deepen the knowledge on mechanisms behind sweet food intake, single nucleotide polymorphisms (SNP) genotyping in genes reported to be associated with taste regulation or sugar intake was done. SNPs in four genes were associated with sensitivity and preference for sweet taste and in the SLC2A2 gene also with caries.Conclusions: This project confirmed that dental caries is not a single species disease, and in the present population S. mutans, S. wiggsiae, and B. longum were significant for having caries. It was also confirmed that S. mutans is not essential for having caries. Tooth biofilm microbiota in S. mutans free adolescents was characterised by a larger diversity of species than seen in those with caries and S. mutans. It may be hypothesised that sugar intake and associated pH drops alone or in interaction with host biology play a role in the differentiation of the microbiota into the distinct profiles. This was supported by the finding that sugar intake was related to microbiota clustering and less community diversity. In this perspective the genetically based influence on sugar preference should be taken into account in dietary counselling which is an important aspect in caries prevention and treatment.
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| 3. |
- Persson, Anitha, 1944-
(författare)
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In vivo evaluations of the neutralizing effect of a hydroxyl ion-releasing resin composite and a prophylactic gel on plaque acidogenicity : measured by the microtouch method
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The prevalence of dental caries has decreased dramatically in most developed countries since the sixties and the number of remaining teeth in adults has increased during the last decades. Elderly as a group will during aging become an increasing risk group for caries. Especially older individuals with hyposalivation are at increased risk for coronal and root caries and need increased oral care. A large part of the time spent by the dental team is occupied by prevention and treatment of secondary caries, which is the main reason of replacement or repair of restorations. Traditionally, prevention of caries is directed against the different risk factors of the individual such as oral hygiene, intake of fermentable carbohydrates, cariogenic microflora and oral dryness. In some restorative materials the release of fluoride can be used to decrease the risk of secondary caries alone or in combination with other preventive methods. New alternative preventive methods are necessary to complete traditional methods in order to decrease the caries risk in elderly and/or to prevent secondary caries. Addition of methods with buffering properties have been suggested and developed to supplement the biological buffering capacity of saliva. The neutralizing effects of a hydroxyl ion-releasing resin composite and a prophylactic gel containing buffering properties on dental plaque acidogenicity was evaluated by the microtouch method. In this method, a skin reference electrode was validated in comparison with a glass capillary reference electrode and used in the subsequent studies. Change of plaque acidogenicity on proximal surfaces of aged restorations of the hydroxyl ion-releasing resin composite was compared intra-individually a conventional hybrid resin composite and a non-filled enamel proximal surface. Relative frequencies of cariogenic microorganisms in plaque on these surfaces were studied. The effect of a single application of the prophylactic gel with buffering substances was evaluated on plaque acidogenicity in healthy individuals with low and normal salivary secretion rate. It was compared intra-individually with the same gel without buffering substances. The effect of multiple applications of the prophylactic gel on plaque acidogenicity was studied in institutionalized elderly individuals with subjectively reported oral dryness and compared intra-individually with the same gel without buffering substances. Major results and conclusions from the studies are: • The use of the skin reference electrode, in combination with the microtouch electrode, showed high validity in comparison with the conventional glass capillary reference electrode • The hydroxyl ion-releasing composite resin countered plaque acidogenicity fall at two time points of the aged restorations and maintained it at levels where lesser demineralization occurs. No influence of the ion-release on the amount of cariogenic plaque microorganisms on the resin composite surface was observed • A single application of the prophylactic gel with buffering substances showed a neutralizing effect of plaque pH in healthy individuals with normal salivary secretion rate. No effect was observed in low secretion rate individuals. • Multiple applications of the prophylactic gel did not neutralize dental plaque acidogenicity in elderly individuals with subjective oral dryness
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