Effect of a 2-week Sugar Stress on Bacterial Profiles in Whole Saliva
Condition: Dental Caries; Gingivitis
MeSH terms: Gingivitis; Dental Caries
Study type: Interventional

Summary: 
      Dental caries is a non-communicable biofilm-mediated disease affecting both crown and exposed
      root surfaces in the primary and permanent dentitions. The carious process involves
      interactions between the biofilm formed on the tooth surface, sugars, salivary and genetic
      factors. Based on more than 100 years of research, there is unequivocal evidence that dietary
      fermentable carbohydrates (sugars and starch) play a key role in caries initiation and
      progression. In this context, sucrose deserves special attention; apart from being rapidly
      converted into acids it is also synthesized into extracellular glucans, fructans and
      intracellular storage compounds. According to the ecological plaque hypothesis, it is
      generally accepted that sucrose exposure is fueling and driving the stable and diverse
      symbiotic oral biofilm to a dysbiotic form with a reduced diversity and overgrowth of
      acidogenic and acid-tolerating species. Such typical bacterial profiles have demonstrated in
      subjects with different stages of caries in cross-sectional settings but the timing
      associated with a sugar provocations is less known. Moreover, the use of probiotic bacteria
      in adjunct to regular oral care to support biofilm diversity and prevent dental caries has
      gained momentum in recent years. It has been demonstrated that probiotic supplements can
      increase salivary pH, and reduce the counts of salivary S. mutans, thereby exert a
      stabilizing effect on the oral microbiota. In this context, it is of interest to explore
      whether or not the use of beneficial bacteria can counteract a sugar-driven shift in the
      salivary microbiota. Another question of interest is to study if the oral biofilm has a
      colonization memory similar to that of the gastro-intestinal tract and the suggested study
      design could possibly enlighten this area of research.
    

Detailed description: 
      Objective

      The aim of this study is to investigate the bacterial profiles in whole saliva before and
      after a 2-week sugar provocation with and without probiotic supplements in healthy young
      adults. A second aim is to study the bacterial profiles 3 weeks after the termination of the
      sugar stress. The null hypothesis are:

        1. Sucrose-induced stress does not affect the bacterial profiles in whole saliva compared
           with stress induced by a non-fermentable pentitol (xylitol)

        2. The intake of lactobacilli-derived probiotic bacteria does not affect the sugar-induced
           changes in the bacterial profiles in whole saliva when compared with placebo

        3. The bacterial profiles in saliva do not differ from baseline 3 weeks after the
           termination of the intervention.

      Material The study group will consist of 80 young adults with uncompromised oral health that
      volunteer after informed consent. The inclusion criteria are i) over 18 years with more than
      20 own natural teeth, ii) no chronic systemic diseases affecting salivary functions, iii) no
      medication except for contraceptives, and iv) being a non-smoker. The project will be
      submitted for ethical approval.

      Study design The study will employ a randomized triple-blind, placebo controlled design with
      four parallel arms as shown in Figure 1. The group allocation will be arranged through
      computer-generated envelopes and concealed for all parts (subjects, investigators, laboratory
      staff). After the baseline registration (Day 0), the participants are asked to rinse their
      mouth with 10 mL of a sucrose- or xylitol-containing solution every second hour (7-8 times
      per day) during 14 days (day 14). The solution should be "swished" around and between the
      teeth for at least 30 seconds and then spitted out. No after-rinsing with water is allowed.
      In addition, the subjects are provided with tablets containing either probiotic lactobacilli
      or placebo for daily use during the 14-day rinsing period. The participants will be
      thoroughly instructed to maintain their normal eating and drinking habits as well as their
      daily oral hygiene procedures.

      Intervention - probiotics and placebo The active and placebo lozenges for the 14-day
      intervention period will be distributed to the participants after baseline examination and
      sampling. The active lozenges contain two strains of probiotic bacteria; Lactobacillus
      rhamnosus PB01 (DSM 14869) and Lactobacillus curvatus EB10 (DSM 32307) at a concentration of
      109 colony forming units each. The tablets have previously been used in a randomized
      controlled trial with gingival inflammation and microbial endpoints (Keller et al., 2018).
      The full composition is shown in Appendix X. The placebo lozenges have an identical
      composition, except for the bacteria, with the same size and taste. The participants are
      instructed to let one tablet slowly dissolve in the mouth two times per day (morning,
      evening) after regular tooth brushing. They are also required to keep a daily logbook
      covering the sugar rinses and tablet intakes and to return non-consumed tablet at the first
      follow-up. The sugar rinses will be prepared and distributed in non-marked bottles and the
      participants will be supplied with a dose spoon indicating 10 mL. The participants will also
      be given a standardized fluoride toothpaste for use during the entire study. An independent
      monitor at Copenhagen University will guarantee the allocation concealment.

      Clinical examination and saliva samplings At baseline, a clinical examination is performed by
      one experienced and calibrated dentist. No radiographs are exposed. The following variables
      are registered: a) caries experience, expressed as decayed, missed and filled teeth (DMFT),
      b) the amount of supragingival plaque (s-PI), c) the level of gingival inflammation (s-GI),
      and d) bleeding-on-probing (s-BOP). The PI, GI and BOP will be scored in a simplified manner
      on six pre-selected teeth and re-evaluated at the follow-ups after 14 and 35 days. Stimulated
      whole saliva samples (approximately 1.0 mL) will be collected at baseline and after 14 and 35
      days in a standardized way by one trained investigator. All samples are stored at -80°C until
      further processing.

      Laboratory procedures The DNA will be extracted using a Pathogen_Universal_200 protocol
      (Roche) in accordance with the manufacturer's guidelines at the Institute for Inflammatory
      Research, Rigshospitalet, København, Danmark. The profiles of the salivary microbiome will be
      analysed with Next Generation Sequencing (NGS) and qPCR as preciously described (Keller et
      al., 2018).

      Endpoints Salivary bacterial profiles will be analyzed by means of the Human Oral Microbe
      Identification using Next Generation Sequencing (HOMINGS) in co-operation with the Costerton
      Center at University of Copenhagen. Secondary endpoints are simplified plaque index (PI),
      gingival index (GI) and bleeding-on-probing (BOP) as scored after 15 and 35 days.

      Statistical methods All data will be checked for normality and processed with the IBM-SPSS
      software. Clinical data are compared using the Freidman test with Dunn's comparison. Relative
      abundance of bacterial DNA reads are compared between groups of samples at genus and species
      level using the Kruskal-Wallis and Mann-Whitney tests with Benjamini-Hochberg correction for
      multiple dependent analyses. P-values less than 0.05 will be considered statistically
      significant.
    

Intervention name(s): Succrose rinsing; Probiotic lozenges; xylitol rinsing; Placebo tablets
Intervention type(s): Dietary Supplement; Dietary Supplement; Other; Other
Intervention description(s): Sucrose rinsing 7-8 times a day for 14 days; Probiotic lozenges 2 times a day for 35 days; Xylitol rinsing 7-8 times a day for 14 days; Placebo lozenges 2 times a day for 35 days
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: The study will employ a randomized triple-blind, placebo controlled design.
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: Dental Caries; Salivary microbiota; Probiotics