Salivary Biomarkers in Denture Stomatitis: A Systematic Review.

OBJECTIVE: Denture stomatitis (DS) is an oral biofilm-associated inflammation of the denture-bearing mucosa. The objective of this review was to identify and evaluate the quality of evidence on the association between the levels of salivary biomarkers and DS among adults with and without palatal DS. MATERIALS AND METHODS: Following the PRISMA guidelines, Medline, PubMed, EMBASE, and the Cochrane Central Register for Controlled Trials were searched for eligible studies from the beginning of the archives until December 2018. Experimental and observational studies with adult participants were included that had a control group or subgroup analysis and provided data on salivary biomarkers and DS. Articles in languages other than English or French were excluded. The level of evidence and grades of recommendation were established with the 2011 scale of the Oxford Centre for Evidence-Based Medicine. Additionally, the assessment of methodological quality was conducted with the STROBE statement (Strengthening the Reporting of Observational Studies in Epidemiology) and graded according to the Olmos scale. RESULTS: From 1,008 citations, 9 studies were included in the systematic review (8 observational, 1 clinical trial). Seven studies suggested a statistically significant difference in the levels of salivary cytokines (IL-6, CCL3, TGF-ß, CXCL8, GM-CSF, and TNF-α) between participants with DS and controls (P < 0.05). In contrast, 2 studies concluded that the difference in the levels of several salivary cytokines (IL2, IL12, IFN-g, IL-4, IL-8, IL-10, IL-17, TNF-α, and ICAM-1) between the groups was not statistically significant. The level of evidence for the majority of studies was 3, while the grade of recommendation for all the studies was B, interpreted as "favorable." In terms of methodological quality, most studies met 50% to 80% of STROBE criteria and were graded B. CONCLUSION: Palatal inflammation in DS is significantly associated with the levels of salivary cytokines. KNOWLEDGE TRANSFER STATEMENT: The results of this study identified altered levels of specific salivary biomarkers associated with denture stomatitis, which may aid in the early diagnosis and treatment of this disease.

Favoring trauma as an etiological factor in denture stomatitis.

The etiology of denture stomatitis remains controversial. Trauma due to unstable dentures has been suggested as an etiological factor. Therefore, we tested the hypothesis that the prevalence of denture stomatitis is reduced when mandibular dentures are stabilized by implants. Data were collected at a one-year follow-up from 173 edentulous elders who had randomly received mandibular implant overdentures or conventional dentures. The diagnosis of denture stomatitis was determined according to the Newton classification. Elders wearing conventional dentures were almost 5 times more likely to have denture stomatitis than those wearing mandibular two-implant overdentures (P < 0.0001, Fisher's exact test). Adjusted odds ratios showed that only the type of the prosthesis (AOR = 4.54, 95% CI 2.20 to 9.40) and nocturnal wear (AOR = 3.03, 95% CI 1.24 to 7.40) predict the frequency of denture stomatitis. Thus, implant overdentures may reduce oral mucosal trauma and control denture stomatitis.

A microfluidic platform with pH imaging for chemical and hydrodynamic stimulation of intact oral biofilms.

A microfluidic platform with a fluorescent nanoparticle-based sensor is demonstrated for real-time, ratiometric pH imaging of biofilms. Sensing is accomplished by a thin patterned layer of covalently bonded Ag@SiO2+FiTC nanoparticles on an embedded planar glass substrate. The system is designed to be sensitive, responsive and give sufficient spatial resolution to enable new micro-scale studies of the dynamic response of oral biofilms to well-controlled chemical and hydrodynamic stimulation. Performance under challenging operational conditions is demonstrated, which include long-duration exposure to sheer stresses, photoexcitation and pH sensor biofouling. After comprehensive validation, the device was used to monitor pH changes at the attachment surface of a biofilm of the oral bacteria, Streptococcus salivarius. By controlling flow and chemical concentration conditions in the microchannel, biochemical and mass transport contributions to the Stephan curve could be probed individually. This opens the way for the analysis of separate contributions to dental caries due to localized acidification directly at the biofilm tooth interface.

Biofilms augment the number of free-living amoebae in dental unit waterlines.

Freshwater amoebae are ubiquitous. Some species can cause infections in humans while others can ingest and protect opportunistic bacteria. Although the presence of free-living amoebae in various water sources has been reported, few studies have looked at their concentration, which may be clinically relevant, especially if they are present in healthcare devices. A simple technique was used to detect, observe, and evaluate the concentration of free-living amoebae in dental unit and tap water samples. Fifty-three water samples were collected from 35 dental units (air/water syringes) and 18 water taps. The technique was based on the ability of waterborne bacteria to create a biofilm and serve as substratum for the development of amoebae naturally present in the water samples. Laboratory-grown freshwater biofilms support the proliferation of a wide variety of free-living amoebae. All the dental unit water samples tested contained amoebae at concentrations up to 330/mL, or more than 300 times the concentration in tap water from the same source. Hartmanella, Vanella, and Vahlkampfia spp. were the most frequently encountered. Naegleria and Acanthamoeba spp. were also present in 40% of the samples. Four of the samples collected from dental units, but none from water taps, contained amoebae able to proliferate at 44 degrees C. Biofilms that form inside some dental instruments can considerably increase the concentration of free-living amoebae, some of which are potential human pathogens.

Cross-contamination potential of saliva ejectors used in dentistry.

It has been postulated that evacuation systems used in dentistry could be a source of cross-contamination between patients through backflow of bacteria dislodged from the saliva ejector tubings. The bacterial microflora associated with these systems was characterized using transmission electron microscopy (TEM) and microbiological cultures. The potential for backflow was investigated by a study of pressure differentials in evacuation system tubing and by the presence of bacteria in backflow samples. Evacuation lines were coated with microbial biofilms in which microcolonies of Gram-positive cocci and Gram-negative bacilli predominated, embedded in an extensive polysaccharide matrix. Most bacteria were metabolically active. Occasionally, buccal material such as collagen, fibrin and eukaryotic cell debris was observed. In other experiments, flow reversal was detected several times during saliva ejector use though each of these events was brief (less than 0.1 s). Aspiration of saliva, or occlusion of the mouthpiece opening by the oral mucosa, were the major factors leading to backflow episodes. Bacteria associated with backflow were found in almost 25% assays, with counts ranging from 1-300 cfu/occurrence. The majority of the bacteria isolated from biofilm or backflow samples were staphylococci, micrococci and non-fermentive Gram-negative rods. Pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus were also isolated from backflow fluids. No oral streptococci could be recovered from biofilms in the tubing beyond 15 min from the last saliva ejector use however, suggesting that these species did not survive in the biofilms. These data suggest, although without direct proof of cross-contamination, the possible existence of an infectious risk associated with oral evacuation systems, as potential pathogens may be shed from tubing biofilms following backflow. Even if the risk of cross-contamination between patients is considered to be low, the necessity for regular disinfection of these systems must be stressed, since biofilms can serve as a reservoir for pathogens or harbor potentially infectious material.

Doctor, would you drink water from your dental unit?

Contamination of dental unit water lines is not new to dentistry, but this problem takes on a new dimension when considering immuno-deficient patients and existing infection-control measures. This study identifies the bacteria involved in the contamination process, estimates the contamination levels and reviews the methods that may be used to control the contamination.

Detection of Legionella spp. by fluorescent in situ hybridization in dental unit waterlines.

AIMS: To confirm the presence of viable Legionella spp. in dental unit waterlines (DUWL) using fluorescent in situ hybridization (FISH) and compare this method with culture approach and also to validate the utility of an enrichment to increase FISH sensitivity. METHODS AND RESULTS: Water samples from 40 dental units were analysed. Three different techniques for detecting Legionella spp. were compared: (i) culture approach, (ii) direct FISH and (iii) FISH with a previous R2A medium enrichment (R2A/FISH). The FISH detection was confirmed by PCR. The use of the direct FISH does not improve significantly the detection of legionellae when compared with the culture. On the contrary, when R2A/FISH was performed, sensitivity was, respectively, two- and threefold higher than that with the direct FISH and culture approach. Using R2A/FISH, 63% of water samples analysed showed a contamination by legionellae. CONCLUSIONS: Legionellae detection by direct FISH and R2A/FISH in dental unit water is possible but is more rapid and more sensitive (R2A/FISH) than the culture approach. SIGNIFICANCE AND IMPACT OF THE STUDY: R2A/FISH showed that several pathogens present in DUWL are viable but may not be culturable. Unlike PCR, R2A/FISH is designed to detect only metabolically active cells and therefore provides more pertinent information on infectious risk.

Waterborne biofilms and dentistry: the changing face of infection control.

Interest in and concern about the biofilms that occur in dental equipment and waterlines have been increasing in recent years. Dental unit waterlines are ideal environments for the growth of microorganisms entering dental units from the municipal water supply. This article describes the conditions in waterline tubing that favour development of biofilms and discusses the level of risk that such microbial growth poses for both dental professionals and their patients. It is stressed that very few cases of infection have been linked directly to contamination in dental unit waterlines. Finally, potential solutions for minimizing risks are presented and discussed.

Dental unit waterline microbiology: a cautionary tale.

The question of dental unit waterline contamination now concerns the dental profession on a number of levels and has become part of the landscape in dentistry. Researchers have identified the problem, studied it, and published their results. Official organizations have reacted to the problem by issuing press releases and recommendations. In the mean time, dental companies have jumped into the fray, ensuring a proliferation of products designed to mitigate a problem that certain people feel is imaginary are artificially inflated. Despite the number of publications describing waterline contamination, we still face the challenge of determining whether are picture of the problem is truly accurate. For example, it has become almost customary to use the term contamination when talking about waterlines, even though it is inadequate. In addition, we are moving ahead with water quality standards for dental units at a time when certain fundamental questions remain unanswered. What should we be measuring and what methods should we be using? Do certain disinfection procedures have an opposite effect to the one desired? Finally, the question of health risks linked to the colonization of waterlines has not been adequately addressed by researchers.

Biofilms, infectious agents, and dental unit waterlines: a review.

Aquatic biofilms, which are widespread not only in nature but also in medical and dental devices, can be the source of serious nosocomial infections. In these hardy microbial communities, pathogens like nontuberculous mycobacteria, Pseudomonas aeruginosa, Legionella pneumophila, and other bacteria not only survive but proliferate and lie in wait for susceptible hosts. Not only are these organisms intrinsically resistant to high temperatures and biocides, but the biofilms they inhabit enhance their resistance. This should be of concern to infection control practitioners. The bacterial colonization of dental unit waterlines can be used as a model to investigate the problem of waterborne biofilms in health care settings.

Multiparametric analysis of waterline contamination in dental units.

Microbial contamination of dental unit waterlines is thought to be the result of biofilm formation within the small-bore tubing used for these conduits. Systematic sampling of 121 dental units located at the dental school of Université de Montréal showed that none of the waterlines was spared from bacterial contamination. Multilevel statistical analyses showed significant differences between samples taken at the beginning of the day and samples taken after a 2-min purge. Differences were also found between water from the turbine and the air/water syringe. Random variation occurred mainly between measurements (80%) and to a lesser extent between dental units (20%). In other analyses, it was observed to take less than 5 days before initial bacterial counts reached a plateau of 2 x 10(5) CFU/ml in newly installed waterlines. Sphyngomonas paucimobilis, Acinetobacter calcoaceticus, Methylobacterium mesophilicum, and Pseudomonas aeruginosa were the predominant isolates. P. aeruginosa showed a nonrandom distribution in dental unit waterlines, since 89.5% of the all the isolates were located in only three of the nine clinics tested. Dental units contaminated by P. aeruginosa showed significantly higher total bacterial counts than the others. By comparison, P. aeruginosa was never isolated in tap water remote from or near the contaminated dental unit waterlines. In conclusion, dental unit waterlines should be considered an aquatic ecosystem in which opportunistic pathogens successfully colonize synthetic surfaces, increasing the concentration of the pathogens in water to potentially dangerous levels. The clinical significance of these findings in relation to routine dental procedures is discussed.