Tooth color change and tolerability evaluation of a hydrogen peroxide whitening strip compared to a strip, paste, and rinse regimen containing plant-based oils and Dead Sea salt.

PURPOSE: To assess tooth color changes and tolerability with use of a hydrogen peroxide whitening strip compared to a regimen of a strip, rinse and paste for tooth whitening. METHODS: This was a single-center, parallel-group, double-blind, randomized controlled clinical trial. Qualified generally healthy adult participants were assigned to one of two treatment groups. The test group included peroxide-free strips, a fluoride-free whitening toothpaste, and a whitening mouthwash (all Lumineux Oral Essentials); all test products contain plant-based oils (coconut, sage, and lemon peel) and Dead Sea salt. The control group included hydrogen peroxide whitening strips (Crest 3DWhitestrips Classic White) and a sodium fluoride non-whitening toothpaste (Crest). Both groups used a soft manual toothbrush (Oral-B). Strips (for both groups) and rinse (for test group) were used once daily. Changes in tooth color were assessed objectively and quantitatively by digital image analysis after 7, 10 and 14 treatments. RESULTS: 50 participants were enrolled and randomized to treatment and 48 completed the trial. Participants had an average age of 40.8 years (range 18 to 62 years) and 64% were female. At the end of treatment, the test group did not provide statistically significant changes in yellowness (b*) or lightness (L*) from baseline (P≥ 0.411), whereas the control group demonstrated a statistically significant mean yellowness reduction (SD) of 1.55 (0.703) and a mean lightness improvement (SD) of 1.57 (1.141) compared to baseline (P< 0.001 for both). The control group also provided statistically significantly greater mean yellowness reductions and mean lightness improvements compared to the test group at all time points (P< 0.002). Products in both groups were well tolerated, with minor oral irritation and tooth sensitivity representing the most common findings during treatment. CLINICAL SIGNIFICANCE: The Crest Whitestrips control whitening strip provided significant tooth whitening efficacy, whereas the Lumineux Oral Essentials test regimen containing plant-based oils and Dead Sea salt did not. This evidence is important for dental professionals to consider when making recommendations for patients seeking at-home whitening treatments.

Post-prophylaxis gingivitis prevention with two-step stannous fluoride dentifrice plus whitening gel sequence or chlorhexidine gluconate mouthrinse.

PURPOSE: To assess use of a two-step dentifrice/gel sequence versus chlorhexidine gluconate mouthrinse on gingivitis prevention after dental prophylaxis. METHODS: A 12-week, randomized controlled trial was conducted to compare the effectiveness and safety of a two-step dentifrice/gel sequence to a positive control in healthy adults with established gingivitis. After informed consent, gingivitis and stain levels were assessed by clinical examination. Eligible subjects received a dental prophylaxis and were randomly assigned to twice daily unsupervised use of either (1) two-step oral hygiene sequence:0.454% stannous fluoride dentifrice followed by 3.0% hydrogen peroxide whitening gel for the test group; or (2) 0.12% chlorhexidine gluconate oral rinse and 0.76% sodium monofluorophosphate dentifrice for the control group. Clinical measurements of gingivitis bleeding sites and tooth stain area/intensity were collected after 4, 8 and 12 weeks use, while safety was assessed via clinical examination and oral status interview of the subjects. RESULTS: A total of 44 subjects were enrolled and 35 completed the 12-week study. At baseline, bleeding sites ranged from 10-33. After prophylaxis and assigned treatment, both groups exhibited significant (P≤ 0.0001) reductions in bleeding sites. Responses were directionally better in the two-step sequence at all post-baseline timepoints, with groups differing significantly (P < 0.05) at Week 8. Tooth stain measurements demonstrated that the two-step dentifrice/gel sequence did not contribute to any significant (P> 0.13) stain accumulation. In contrast, stain accumulation was evident (P< 0.003) in the chlorhexidine group beginning at the Week 4 visit. Adverse events were more common in the positive control, and contributed to early termination. CLINICAL SIGNIFICANCE: Twice daily use of a two-step stannous fluoride dentifrice and peroxide whitening gel sequence after prophylaxis provided comparable or superior gingivitis benefits to chlorhexidine gluconate rinse without the concomitant side effect of staining.

Response of chronic gingivitis to hygiene therapy and experimental gingivitis. Clinical, microbiological and metabonomic changes.

PURPOSE: To compare the clinical, microbiological and metabonomic profiles of subjects with high and low levels of chronic gingival bleeding during a controlled oral hygiene regimen intervention including sequential phases of rigorous therapeutic oral hygiene followed by experimental gingivitis (EG). METHODS: Two cohorts of qualified study subjects with differences in gingival bleeding on probing levels at their baseline clinical examination were entered into the study. These two cohorts were followed through three separate study phases including a 1-week baseline phase, a 2-week phase of rigorous oral hygiene including dental prophylaxis, and a 3-week EG phase of no oral hygiene to encourage relapse of gingivitis. The 58 subjects were assessed during each phase of the study for clinical presentation of gingivitis and concurrently had plaque sampled for real-time polymerase chain reaction (RTPCR) microbiological characterization and salivary lavage samples for 'systems biology' metabonomics assessment by 1H-NMR. RESULTS: Subjects presenting with different levels of gingival bleeding on probing when they entered the study responded differently to rigorous oral hygiene and EG. Specifically, the high bleeding cohort responded sluggishly to rigorous oral hygiene and exhibited markedly greater relapse to gingivitis during EG. RTPCR analysis showed changes in bacterial populations that were associated with study phases, particularly the increases in putative periodontal pathogens during EG. However, the microbiological profiles of high- and low-susceptibility gingival bleeding patients were largely similar. Metabonomic analysis likewise revealed significant changes in metabolite composition during study phases associated with differences in plaque toxicity, especially the short chain carboxylic acids propionate and n-butyrate, which tracked clinical changes in gingivitis severity. Systems analysis of metabonomic changes suggested differences between cohorts, although analysis to date has not elucidated whether these differences are causative (population predictive) or simply diagnostic of clinical status within populations.

Role of quorum sensing in Sinorhizobium meliloti-Alfalfa symbiosis.

The ExpR/Sin quorum-sensing system of the gram-negative soil bacterium Sinorhizobium meliloti plays an important role in the establishment of symbiosis with its host plant Medicago sativa. A mutant unable to produce autoinducer signal molecules (sinI) is deficient in its ability to invade the host, but paradoxically, a strain lacking the quorum-sensing transcriptional regulator ExpR is as efficient as the wild type. We compared the whole-genome expression profile of the wild-type strain with strains missing one of the quorum-sensing regulatory components to identify genes controlled by the ExpR/Sin system throughout the different phases of the bacterial growth cycle, as well as in planta. Our analyses revealed that ExpR is a highly versatile regulator with a unique ability to show different regulatory capabilities in the presence or absence of an autoinducer. In addition, this study provided us with insight into the plant invasion defect displayed by the autoinducer mutant. We also discovered that the ExpR/Sin quorum-sensing system is repressed after plant invasion. Therefore, quorum sensing plays a crucial role in the regulation of many cell functions that ensures the successful invasion of the host and is inactivated once symbiosis is established.

Regulation of motility by the ExpR/Sin quorum-sensing system in Sinorhizobium meliloti.

A successful symbiotic relationship between Sinorhizobium meliloti and its host Medicago sativa (alfalfa) depends on several signaling mechanisms, such as the biosynthesis of exopolysaccharides (EPS) by S. meliloti. Previous work in our laboratory has shown that a quorum-sensing mechanism controls the production of the symbiotically active EPS II. Recent microarray analysis of the whole-genome expression profile of S. meliloti reveals that the ExpR/Sin quorum-sensing system regulates additional physiological processes that include low-molecular-weight succinoglycan production, nitrogen utilization, metal transport, motility, and chemotaxis. Nearly half of the flagellar genes and their dependence on quorum sensing are prominently displayed in our microarray analyses. We extend those observations in this work and confirm the findings by real-time PCR expression analysis of selected genes, including the flaF, flbT, flaC, cheY1, and flgB genes, involved in motility and chemotaxis. These genes code for regulators of flagellum synthesis, the chemotactic response, or parts of the flagellar apparatus. Gene expression analyses and visualization of flagella by electron microscopy performed at different points in the growth phase support our proposed model in which quorum sensing downregulates motility in S. meliloti. We demonstrate that the ExpR/Sin quorum-sensing system controls motility gene expression through the VisN/VisR/Rem relay. We also show that the ExoS-dependent two-component system suppresses motility gene expression through VisN and Rem in parallel to quorum sensing. This study contributes to our understanding of the mechanisms that govern motility in S. meliloti.

The ExpR/Sin quorum-sensing system controls succinoglycan production in Sinorhizobium meliloti.

Sinorhizobium meliloti is a gram-negative soil bacterium capable of forming a symbiotic nitrogen-fixing relationship with its plant host, Medicago sativa. Various bacterially produced factors are essential for successful nodulation. For example, at least one of two exopolysaccharides produced by S. meliloti (succinoglycan or EPS II) is required for nodule invasion. Both of these polymers are produced in high- and low-molecular-weight (HMW and LMW, respectively) fractions; however, only the LMW forms of either succinoglycan or EPS II are active in nodule invasion. The production of LMW succinoglycan can be generated by direct synthesis or through the depolymerization of HMW products by the action of two specific endoglycanases, ExsH and ExoK. Here, we show that the ExpR/Sin quorum-sensing system in S. meliloti is involved in the regulation of genes responsible for succinoglycan biosynthesis as well as in the production of LMW succinoglycan. Therefore, quorum sensing, which has been shown to regulate the production of EPS II, also plays an important role in succinoglycan biosynthesis.