Red and Green Fluorescence from Oral Biofilms

Red/Orange Autofluorescence in Selected Candida Strains Exposed to 405 nm Laser Light

BACKGROUND

Candida albicans and similar species are significant pathogens in immunocompromised and hospitalized individuals, known for mucosal colonization and bloodstream/organ invasion. Many pathogenic fungi, including these species, exhibit autofluorescence (R/OF) under specific light conditions, a feature crucial for their detection.

AIM

We investigated the use of a 405 nm diode laser for the direct observation of red/orange autofluorescence of Candida spp., common in the oral cavity, exploring its potential in health screenings.

METHODS

This study utilized cultures of Candida spp. on Sabouraud dextrose agar with Qdot 655 and 685 for fluorescence benchmarking, illuminated using a 405 nm diode laser (continuous wave, power 250 mW, 0.0425 J/cm² fluence, 0.0014 W/cm² power density). Images were captured using a yellow-filter camera at set intervals (48 to 144 h). Visual and computational analyses evaluated the R/OF in terms of presence, intensity, coloration, and intra-colony variation.

RESULTS

Most Candida strains displayed red/orange autofluorescence at all observation times, characterized by varied coloration and intra-colony distribution. Initially, there was an increase in R/OF intensity, which then stabilized in the later stages of observation.

CONCLUSIONS

The majority of the Candida strains tested are capable of emitting R/OF under 405 nm laser light. This finding opens up new possibilities for integrating R/OF detection into routine dental screenings for Candida spp.

The consistent application of hydrogen peroxide controls biofilm growth and removes Vermamoeba vermiformis from multi-kingdom in-vitro dental unit water biofilms

The water systems inside a dental unit are known to be contaminated with a multi-kingdom biofilm encompassing bacteria, fungi, viruses and protozoa. Aerosolization of these micro-organisms can potentially create a health hazard for both dental staff and the patient. Very little is known on the efficacy of dental unit disinfection products against amoeba. In this study we have examined the effect of four different treatment regimens, with the hydrogen peroxide (H₂O₂) containing product Oxygenal, on an in-vitro multi-kingdom dental unit water system (DUWS) biofilm. The treatment efficacy was assessed in time using heterotrophic plate counts, the bacterial 16S rDNA, fungal 18S rDNA gene load and the number of genomic units for Legionella spp. the amoeba Vermamoeba vermiformis. The results indicated that a daily treatment of the DUWS with a low dose H₂O₂ (0.02% for 5 h), combined with a weekly shock dose (0.25% H₂O₂, 30 min) is necessary to reduce the heterotrophic plate count of a severely contaminated DUWS (>10⁶ CFU.mL^-1) to below 100 CFU.mL^-1. A daily treatment with a low dose hydrogen peroxide alone, is sufficient for the statistically significant reduction of the total amount of bacterial 16S rDNA gene, Legionella spp. and Vermamoeba vermiformis load (p < 0.005). Also shown is that even though hydrogen peroxide does not kill the trophozoite nor the cysts of V. vermiformis, it does however result in the detachment of the trophozoite form of this amoeba from the DUWS biofilm and hereby ultimately removing the amoeba from the system.

Porphyrin-associated fluorescence spectroscopy (Photogen®) for the optical diagnosis of dental biofilm in orthodontic treatment: an observational clinical trial

OBJECTIVE

This study assessed the presence of dental biofilm with fluorescence spectroscopy associated with porphyrin (Photogen®) in users of orthodontic appliances.

METHODS

This cross-sectional observational clinical trial included 21 patients with metallic orthodontic fixed appliances. The presence of biofilm was evaluated by fluorescence spectroscopy (Evince-MMÓptics. São Carlos-SP, Brazil) with a porphyrin photo-evidence device (Photogen®). Digital images of the buccal surface of the upper anterior teeth (central and lateral incisors and canines) without and with porphyrin were analyzed using the histogram R (red) function in ImageJ software. The results were analyzed using the maximum and mode values of the red pixels from the histograms. The statistical analysis considered the significance level of 5%.

RESULTS

The maximum values and modes of the red pixels were significantly higher in biofilms analyzed by porphyrin-associated optical spectroscopy compared to optical spectroscopy alone.

CONCLUSIONS

Porphyrin-associated fluorescence spectroscopy was able to detect dental biofilm in the oral environment of patients with orthodontic treatment. This method better evidenced the presence of biofilm on the buccal surfaces of the upper teeth compared to that observed with fluorescence spectroscopy without porphyrin.

Non-invasive biomedical sensors for early detection and monitoring of bacterial biofilm growth at the point of care

Bacterial infections have long been a serious global health issue. Biofilm formation complicates matters even more. The biofilm's extracellular polymeric substances (EPSs) matrix protects bacteria from the host's immune responses, yielding strong adhesion and drug resistance as the biofilm matures. Early bacterial biofilm detection and bacterial biofilm growth monitoring are crucial to treating biofilm-associated infections. Current detection methods are highly sensitive but not portable, are time-consuming, and require expensive equipment and complex operating procedures, limiting their use at the point of care. Therefore, there is an urgent need to develop affordable, on-body, and non-invasive biomedical sensors to continuously monitor and detect early biofilm growth at the point of care through personalized telemedicine. Herein, recent advances in developing non-invasive biomedical sensors for early detection and monitoring bacterial biofilm growth are comprehensively reviewed. First, biofilm's life cycle and its impact on the human body, such as biofilm-associated disease and infected medical devices, are introduced together with the challenges of biofilm treatment. Then, the current methods used in clinical and laboratory settings for biofilm detection and their challenges are discussed. Next, the current state of non-invasive sensors for direct and indirect detection of bacterial biofilms are summarized and highlighted with the detection parameters and their design details. Finally, commercially available products, challenges of current devices, and the further trend in biofilm detection sensors are discussed.

Detection of invisible dental biofilm using light-induced autofluorescence in adult patients-A systematic review

BACKGROUND

Autofluorescence (AF) spectroscopy is a potent yet non-invasive technique with diagnostic and therapeutic applications. It identifies and characterizes changes occurring in the human body based on the changes in the fluorescence signatures.

AIM

The primary purpose of this systematic review is to address the question "Is it feasible to detect dental plaque using light-induced auto-fluorescence in adult patients with invisible grade 1 plaque?"

MATERIALS AND METHODS

The literature search was conducted independently MEDLINE, Embase, Cochrane Library, Web of Science, Google Scholar, and Scopus databases for relevant studies from January 2000 and June 2021, using the following terms in various combinations: detection, dental biofilm, plaque, light, auto-fluorescence, caries, gingivitis, sensitivity and specificity. Studies describing various fluorescence techniques for the detection of plaque, including sensitivity and specificity, were included.

RESULTS

The majority of the studies indicated that AF spectroscopy allows fluorescence-based detection of various diseases, including early-stage dental plaque. While results of conventional plaque detection techniques are inconsistent, the data from the AF technique is reliable and reproducible, which can be used for patient documentation. However, a wide range of non-uniformity existed in these studies. AF spectroscopy, as a non-invasive technique, represents a viable and patient-friendly clinical tool for the early detection of dental biofilm plaque, and its meticulous removal has been directly responsible for the prevention of this disease.

CONCLUSION

Despite the heterogeneity and limitations of studies included in this review, the future for light-induced autofluorescence spectroscopy technologies in diagnostic dentistry certainly presents an accurate and potentially applicable option.

In vitro model systems for exploring oral biofilms: From single-species populations to complex multi-species communities

Numerous in vitro biofilm model systems are available to study oral biofilms. Over the past several decades, increased understanding of oral biology and advances in technology have facilitated more accurate simulation of intraoral conditions and have allowed for the increased generalizability of in vitro oral biofilm studies. The integration of contemporary systems with confocal microscopy and 16S rRNA community profiling has enhanced the capabilities of in vitro biofilm model systems to quantify biofilm architecture and analyse microbial community composition. In this review, we describe several model systems relevant to modern in vitro oral biofilm studies: the constant depth film fermenter, Sorbarod perfusion system, drip-flow reactor, modified Robbins device, flowcells and microfluidic systems. We highlight how combining these systems with confocal microscopy and community composition analysis tools aids exploration of oral biofilm development under different conditions and in response to antimicrobial/anti-biofilm agents. The review closes with a discussion of future directions for the field of in vitro oral biofilm imaging and analysis.

Use of wide-field optical fluorescence for visualization of oral biofilm in a patient with peri-implant mucositis: a new approach

Peri-implant diseases, caused by bacteria from biofilm related to dental implants, are one of the main causes of late loss of implants. In this sense, peri-implant diseases are divided into peri-implant mucositis, when it affects only the soft tissues, and peri-implantitis, when there is a bone involvement, which can lead to the failure of dental implant therapy. Thus, biofilm removal is essential for peri-implant health, allowing long-term success in implant therapy. To improve the visualization of oral biofilm, which is usually transparent or colorless, disclosing agents have been routinely used. However, disclosing agents have allergenic potential and can cause staining extrinsically in restorative and prosthetic materials, leading to aesthetic impairment. Thus, the use of fluorescence has been studied as an alternative for visualization of oral biofilm. Therefore, this report describes the use of wide-field optical fluorescence for visualization of oral biofilm associated with implants and teeth, in a routine appointment and follow-up of a partially edentulous patient with peri-implant mucositis. In addition, this report showed wide-field optical fluorescence can be used in a clinical routine of care of patients with dental implants. In this sense, wide-field optical fluorescence allowed easy and immediate visualization of the mature oral biofilm for its adequate removal, evaluation of the quality of restoration to sealing of screw access-hole of implant and identification of cariogenic lesions, without risk of allergic reactions or staining of prostheses and restorations.

Diagnosis of Biofilm-Associated Peri-Implant Disease Using a Fluorescence-Based Approach

Dental implants have become a routine component of daily dental practice and the demand for dental implants is expected to increase significantly in the future. Despite the high success rates of dental implants, failures do occur, resulting in discomfort, rampant destruction of the oral health, or painful and costly surgical replacement of a failed implant. Peri-implant diseases are inflammatory conditions affecting the soft/hard tissues surrounding a functional dental implant. Plenty of experimental evidence indicates that the accumulation of dental plaque at the soft tissue-implant interface and the subsequent local inflammatory response seems to be key in the pathogenesis of the peri-implant mucositis. Such peri-implant-soft tissue interface is less effective than natural teeth in resisting bacterial invasion, enhancing vulnerability to subsequent peri-implant disease. Furthermore, in certain individuals, it will progress to peri-implantitis, resulting in alveolar bone loss and implant failure. Although early diagnosis and accurate identification of risk factors are extremely important to effectively prevent peri-implant diseases, current systematic reviews revealed that a uniform classification and diagnostic methodology for peri-implantitis are lacking. Recent progress on fluorescence-based technology enabled rapid diagnosis of the disease and effective removal of plaques. Here, we briefly review biofilm-associated peri-implant diseases and propose a fluorescence-based approach for more accurate and objective diagnoses. A fluorescence-based diagnosis tool through headlights combined with special-filtered dental loupes may serve as a hands-free solution for both precise diagnosis and effective removal of plaque-biofilms.

Noninvasive multimodal imaging by integrating optical coherence tomography with autofluorescence imaging for dental applications

We report the development of an integrated multifunctional imaging system capable of providing anatomical (optical coherence tomography, OCT), functional (OCT angiography, OCTA) and molecular imaging (light-induced autofluorescence, LIAF) for in vivo dental applications. Blue excitation light (405 nm) was used for LIAF imaging, while the OCT was powered by a 1310 nm swept laser source. A red-green-blue digital camera, with a 450 nm cut-on broadband optical filter, was used for LIAF detection. The exciting light source and camera were integrated directly with the OCT scanning probe. The integrated system used two noninvasive imaging modalities to improve the speed of in vivo OCT data collection and to better target the regions of interest. The newly designed system maintained the ability to detect differences between healthy and hypomineralized teeth, identify dental biofilm and visualize the microvasculature of gingival tissue. The development of the integrated OCT-LIAF system provides an opportunity to conduct clinical studies more efficiently, examining changes in oral conditions over time.

Temporomandibular joint function, periodontal health, and oral microbiome in early rheumatoid arthritis and at-risk individuals: a prospective cohort study protocol

Objectives/aims

Rheumatoid arthritis (RA) is an autoimmune disease affecting the joints, including the temporomandibular joint (TMJ). Early diagnosis and treatment can alleviate symptoms and prevent progression. Predictors for disease outcome in individuals at risk for RA are therefore valuable. While limited information is available on the prevalence of TMJ involvement in early RA, previous studies suggest that RA, periodontitis and the oral microbiome are interrelated. Predictive factors for RA development may thus be present in the oral cavity. Our two aims are: (1) to assess the prevalence of TMJ involvement in early RA, and (2) to investigate the predictive value of oral factors in RA development.

Materials and methods

We will include 150 individuals in this multi-center, prospective cohort study: 50 patients with early RA, 50 at-risk individuals, and 50 healthy controls. At baseline, the TMJ, periodontal health, and the oral microbiome will be examined. The general health will be followed over time, on four occasions up to 3 years.

Discussion

Our results will provide insight into the prevalence and clinical characterization of TMJ involvement in early RA. For at-risk individuals, oral factors can be studied as possible predictors for the development of RA.

Comparison of Quantitative light-induced fluorescence-digital (QLF-D) images and images of disclosed plaque for planimetric quantification of dental plaque in multibracket appliance patients

The purpose of the present cross-sectional clinical study was to check the ability of plaque detection and quantification by QLF-D against conventional digital photographs of disclosed plaque in multibracket appliance (MB) patients. 20 patients were included according to the following criteria: (1) upper and lower jaw treated by MB appliance, (2) patients being 16 years of age or older, (3) all central and lateral incisors as well as canines in situ, (4) absence of developmental defects, carious lesions, surface fillings, prosthetic restorations or recessions greater than 1/3 of root length in central/lateral incisors and canines as well as (5) declaration of consent. QLF-D and conventional photographs were analyzed planimetrically regarding plaque coverage on buccal and oral surfaces of central/lateral incisors and canines. The conventional photographs of stained plaque served as gold standard. On average, in QLF-D pictures 20.7% ± 17.4 of the tooth surfaces were covered with plaque, while the conventional photographs of disclosed plaque presented a mean plaque-covered area of 36.2% ± 23.5. The Bland-Altman plot for both imaging modalities showed a very large inconsistent scattering with both negative and positive deviations. The method discrepancy increased with increasing plaque coverage, thus indicating a systematic method error. On average, the deviation of the methods from the optimal line of accordance was -15.5%. In patients wearing MB appliances, there was no clinical significant agreement regarding the plaque-covered tooth surface depicted by QLF-D respectively conventional images of disclosed plaque. Due to the large method discrepancy, QLF-D is currently not reliable for precise plaque quantification in MB patients.

Phytosphingosine Prevents the Formation of Young Salivary Biofilms in vitro

Dental biofilms are formed in a multistep process that is initiated by the adhesion of oral bacteria to the dental hard surface. As dental biofilms are associated with oral diseases their control is necessary in order to maintain oral health. Recently, it was revealed that phytosphingosine (PHS)-treated hydroxyapatite discs showed anti-adhesive activity in a static in vitro biofilm model against Streptococcus mutans. The goal of the present study was to further unravel the anti-adhesive and anti-biofilm properties of PHS in both static and dynamic in vitro biofilm models against a full salivary inoculum. After 3 h under static conditions, bacterial adherence on PHS-treated cover glass slides was reduced by 60% compared to the untreated surface. After 6 and 24 h under static conditions, no significant differences in bacterial adherence were observed between PHS-treated and untreated cover glass slides. However, under dynamic conditions, i.e., the presence of shear forces, virtually no bacterial adherence was observed for up to 16 h on PHS-coated surfaces. Besides, PHS showed a strong bactericidal activity on salivary biofilms. Treatment of a 3- and 6-h statically grown biofilm resulted in a 99 and 94% reduction of viable cells, respectively, which was effectuated within minutes. In principle, these anti-adherence and anti-biofilm properties make PHS a promising candidate ingredient for use in oral care products aimed at oral microbial control.

Oral health of older residents in care and community dwellers: nursing implications

BACKGROUND

Poor oral health is associated with a reduced quality of life and serious illnesses. Consequently, nurses need to be more aware of oral health to improve the general health of residents in care.

AIM

To evaluate and compare oral health behaviours and levels of salivary haemoglobin and dental biofilm acidogenicity, which can be used to evaluate oral disease activity, between residents and community dwellers in South Korea.

METHODS

This cross-sectional study included 133 participants: 64 residents and 69 community dwellers. All participants completed a questionnaire and tests to measure their salivary haemoglobin and dental biofilm acidogenicity.

RESULTS

A higher percentage of community dwellers than of residents brushed their teeth three times a day, cleaned their tongue, used interdental cleaning devices and had visited a dental clinic within 1 year. The levels of salivary haemoglobin and dental biofilm acidogenicity tended to be higher in residents than in community dwellers.

CONCLUSION

Residents showed poorer oral health behaviours and higher levels of gingival bleeding and acid production by oral bacteria than did community dwellers.

IMPLICATIONS FOR NURSING PRACTICE

Nursing staff should enhance their monitoring of oral hygiene status and provide quality oral care to residents through cooperation with dental professionals.

IMPLICATIONS FOR NURSING AND HEALTH POLICY

Policymakers should be aware that oral health is an essential component of improving general health and well-being and therefore strive to develop policies to promote oral care services provided to residents. Nursing policies, such as mandating oral care and hands-on training in oral care for nursing staff, are important. We also suggest that factors related to oral care be added to the establishment or accreditation standards of care facilities.

Spectroscopic characterization and fluorescence imaging of Helicobacter pylori endogenous porphyrins

Conventional antimicrobial strategies have become increasingly ineffective due to the rapid emergence of antibiotic resistance among pathogenic bacteria. In order to overcome this problem, antimicrobial PhotoDynamic Therapy (PDT) is considered a promising alternative therapy. PDT has a broad spectrum of action and low mutagenic potential. It is particularly effective when microorganisms present endogenous photosensitizing pigments. Helicobacter pylori (Hp), a pathogen notoriously responsible of severe gastric infections (chronic gastritis, peptic ulcer, MALT lymphoma and gastric adenocarcinoma), produces and accumulates the photosensitizers protoporphyrin IX and coproporphyrin, thus it might be a suitable target of antimicrobial PDT. With the aim to design and develop an ingestible LED-based robotic pill for intragastric phototherapy, so that irradiation can be performed in situ without the use of invasive endoscopic light, photophysical studies on the Hp endogenous photosensitizers were carried out. These studies represent an important prerequisite in order to select the most effective irradiation conditions for Hp eradication. The photophysical characterization of Hp porphyrins, including their spectroscopic features in terms of absorption, steady-state and time-resolved fluorescence, was performed on bacterial extracts as well as within planktonic and biofilm growing Hp cells.