Extra-oral halitosis: an overview

Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts

The precise and reversible detection of hydrogen sulfide (H2S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H2S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic details of these excellent H2S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

Laser Therapy: An Alternative Approach for the Management of Halitosis

Halitosis is the result of combining the Greek word "osis" (pathological alteration) with the Latin phrase "halitus" (breath). No matter what the cause, halitosis can be described as the presence of a foul odour. Effective treatment of halitosis may be facilitated by knowledge of the illnesses and factors that contribute to the condition as well as its symptoms. To properly diagnose and treat patients, healthcare professionals, general practitioners, and dentists must comprehend the cause of the ailment and the best course of treatment. A prevalent issue affecting a large proportion of the global population is halitosis. In 90% of cases, the onset of this illness is oral; however, in 10% of cases, it is systemic. The primary source of the unpleasant smell is the volatile sulphur compounds that Gram-negative bacteria create. The majority of halitosis sufferers find their disease humiliating which makes it difficult for them to go about their daily lives and social lives. A thorough examination was carried out. An evaluation of the tongue was done. The halitosis was treated in afflicted areas using the "Epic Biolase Laser". It is the most robust dental laser and has a low power output which uses a solid-state diode to produce invisible infrared radiation. This device operates aseptically and offers more convenience due to its wireless design, which is powered by a Bluetooth foot pedal. This is used to lower the number of bacteria, and then periodic maintenance is performed to keep them under control. Benefits and outcomes were accomplished. Laser therapy destroys the bacteria that produce volatile compounds and efficiently treats foul breath for a longer period of time. But with a combination of conventional techniques, the results we obtain are even better.

P-N Heterojunction formation: Metal Sulfide@Metal Oxide Chemiresistor for ppb H2S Detection from Exhaled Breath and Food Spoilage at Flexible Room Temperature

The development of a portable, low-cost sensor capable of accurately detecting H2S gas in exhaled human breath at room temperature is highly anticipated in the fields of human health assessment and food spoilage evaluation. However, achieving outstanding gas sensing performance and applicability for flexible room-temperature operation with parts per billion H2S gas sensors still poses technical challenges. To address this issue, this study involves the in situ growth of MoS2 nanosheets on the surface of In2O3 fibers to construct a p-n heterojunction. The In2O3@MoS2-2 sensor exhibits a high response of 460.61 to 50 ppm of H2S gas at room temperature, which is 19.5 times higher than that of the pure In2O3 sensor and 322.1 times higher than that of pure MoS2. The In2O3@MoS2-2 also demonstrates a minimum detection limit of 3 ppb and maintains a stable response to H2S gas even after being bent 50 times at a 60° angle. These exceptional gas sensing properties are attributed to the increase in oxygen vacancies and chemisorbed oxygen on In2O3@MoS2-2 nanofibers as well as the formation of the p-n heterojunction, which modulates the heterojunction barrier. Furthermore, in this study, we successfully applied the In2O3@MoS2-2 sensor for oral disease and detection of food spoilage conditions, thereby providing new design insights for the development of portable exhaled gas sensors and gas sensors for evaluating food spoilage conditions at room temperature.

The association between halitosis and periodontitis: a systematic review and meta-analysis

OBJECTIVES

The purpose of this systemic review and meta-analysis was to explore the association between halitosis and periodontitis in observational studies.

MATERIALS AND METHODS

A systematic search covered PubMed, Web of Science, Embase, Scopus, and Cochrane Library until August 18, 2023. Nine observational studies (585 cases, 1591 controls) were analyzed using Stata 17, with odds ratios (ORs) and 95% confidence intervals (CIs). Subgroup analyses considered halitosis assessment methods.

RESULTS

The review found a positive association between halitosis and periodontitis. Significant differences were observed with organoleptic test (OR = 4.05, 95% CI: 1.76, 9.30, p < 0.01) and volatile sulfur compound readings (OR = 4.52, 95% CI: 1.89, 10.83, p < 0.01).

CONCLUSIONS

A positive association was observed between halitosis and periodontitis, supported by significant differences in both organoleptic and volatile sulfur compound readings. However, conclusive findings are limited by statistical heterogeneity, emphasizing the need for additional research.

CLINICAL RELEVANCE

Understanding the halitosis and periodontitis association is clinically significant, informing potential interventions for improved oral health. Further research is vital to refine understanding and guide effective clinical strategies, acknowledging the limitations in current findings.

Oral microbiota transplantation for intra-oral halitosis: a feasibility analysis based on an oral microbiota colonization trial in Wistar rats

BACKGROUND

Intra-oral halitosis (IOH) is bad breath produced locally by the mouth in addition to systemic diseases and is one of the main causes of interpersonal communication and psychological disorders in modern society. However, current treatment modalities still only alleviate IOH and do not eradicate it. Therefore, based on the differential performance of oral microecology in IOH patients, we propose a microbiota transplantation treatment aimed at restoring oral microecological balance and analyze its feasibility by oral flora colonization test in Wistar rats.

OBJECTIVE

Saliva flora samples were collected from IOH patients and healthy subjects to analyze the feasibility of oral microbiota transplantation (OMT) for the treatment of IOH by the Wistar rat oral flora colonization test.

METHODS

Seven patients with IOH who visited the First Affiliated Hospital of Xinjiang Medical University from June 2017 to June 2022 with the main complaint of halitosis and three healthy subjects were randomly selected. A Halimeter portable breath detector was used to record breath values and collect saliva flora samples. Sixteen SPF-grade male Wistar rats were housed in the Animal Experiment Center of Xinjiang Medical University and randomly divided into an experimental group (Group E) and a control group (Group C) for the oral flora colonization test. Species composition and associated metabolic analysis of oral flora during the Wistar rat test using 16SrRNA sequencing technology and PICRUSt metabolic analysis. Also, the changes in the breath values of the rats were recorded during the test.

RESULTS

The proportion of Porphyromonas, Fusobacterium, Leptotrichia, and Peptostreptococcus was significantly higher in group E compared to group C after colonization of salivary flora of IOH patients (all P < 0.05), and the abundance with Gemella was zero before colonization, while no colonization was seen in group C after colonization compared to baseline. PICRUSt metabolic analysis also showed significantly enhanced IOH-related metabolic pathways after colonization in group E (all P < 0.05), as well as significantly higher breath values compared to baseline and group C (all P < 0.0001). After colonization by salivary flora from healthy subjects, group E rats showed a decrease in the abundance of associated odor-causing bacteria colonization, a reduction in associated metabolism, and a significant decrease in breath values. In contrast, group C also showed differential changes in flora structure and breath values compared to baseline after salivary flora colonization of IOH patients.

CONCLUSIONS

OMT for IOH is a promising green treatment option, but the influence of environmental factors and individual differences still cannot be ignored.

Halitosis in young patients with chronic kidney disease: findings from a randomized controlled trial

BACKGROUND

Chronic kidney disease (CKD) directly affects oral health. Yet data about halitosis in young CKD patients and the impact of dental prophylaxis is limited. Therefore, as part of this randomized clinical trial, halitosis in young CKD patients undergoing intensive or standard oral preventive procedures was to be explored.

METHODS

Three volatile sulfur compounds (hydrogen sulfide, methyl mercaptan and dimethyl sulfide) were measured in 30 young patients with CKD (mean age 14.2 years; 16 males, 14 females). Breath samples were taken after 3 and 6 months and analyzed with selective gas chromatography (OralChroma). Tongue coating (Winkel Index) and clinical indices to determine local inflammation or oral hygiene (Papillary Bleeding Index and Quigley-Hein Index) were assessed. Within an extended anamnesis, patients and their mothers and nurses were questioned about the perceived halitosis. Corresponding quotes were noted verbatim. Patients were randomized to either intensive need-related oral health care measures (oral preventative program, OPP) or a one-stage standard prevention (treatment as usual, TAU).

RESULTS

While there were no differences in volatile sulfur compound levels between TAU and OPP at the three time points of measurements (p > 0.05), there was a tendency towards a reduction in dimethyl sulfide and hydrogen sulfide of affected patients within the OPP group over time. Looking at potential differences between both groups with regard to tongue coating, significant differences were observed between baseline and 3 months after study start in the OPP group, and between baseline and 6 months after study start in the TAU group (p < 0.05). The burden of halitosis was frequently reported by patients' mothers and nurses.

CONCLUSIONS

Young CKD patients regularly suffered from halitosis and dimethyl sulfide was its main source. Preventive measures mainly resulted in a reduction of tongue coating.

TRIAL REGISTRATION

The German Clinical Trial Register (# DRKS00010580).

Narrative review on artificially intelligent olfaction in halitosis

Halitosis, commonly known as oral malodor, is a multifactorial health concern that significantly impacts the psychological and social well-being of individuals. It is the third most frequent reason for individuals to seek dental treatment, after dental caries and periodontal diseases. For an in-depth exploration of the topic of halitosis, an extensive literature review was conducted. The review focused on articles published in peer-reviewed journals and only those written in the English language were considered. The search for relevant literature began by employing subject headings such as 'halitosis, oral malodor, volatile sulfur compounds, artificial intelligence, and olfaction' in databases such as PubMed/Medline, Scopus, Google Scholar, Web of Science, and EMBASE. Additionally, a thorough hand search of references was conducted to ensure the comprehensiveness of the review. After amalgamating the search outcomes, a comprehensive analysis revealed the existence of precisely 134 full-text articles that bore relevance to the study. Abstracts and editorial letters were excluded from this study, and almost 50% of the full-text articles were deemed immaterial to dental practice. Out of the remaining articles, precisely 54 full-text articles were employed in this review. As primary healthcare providers, dentists are responsible for diagnosing and treating oral issues that may contribute to the development of halitosis. To effectively manage this condition, dentists must educate their patients about the underlying causes of halitosis, as well as proper oral hygiene practices such as tongue cleaning, flossing, and selecting appropriate mouthwash and toothpaste. This narrative review summarises all possible AI olfaction in halitosis.

Detection of PPB-Level H2S Concentrations in Exhaled Breath Using Au Nanosheet Sensors with Small Variability, High Selectivity, and Long-Term Stability

The continuous monitoring of hydrogen sulfide (H2S) in exhaled breath enables the detection of health issues such as halitosis and gastrointestinal problems. However, H2S sensors with high selectivity and parts per billion-level detection capability, which are essential for breath analysis, and facile fabrication processes for their integration with other devices are lacking. In this study, we demonstrated Au nanosheet H2S sensors with high selectivity, ppb-level detection capability, and high uniformity by optimizing their fabrication processes: (1) insertion of titanium nitride (TiN) as an adhesion layer to prevent Au agglomeration on the oxide substrate and (2) N2 annealing to improve nanosheet crystallinity. The fabricated Au nanosheets successfully detected H2S at concentrations as low as 5.6 ppb, and the estimated limit of detection was 0.5 ppb, which is superior to that of the human nose (8-13 ppb). In addition, the sensors detected H2S in the exhaled breath of simulated patients at concentrations as low as 175 ppb while showing high selectivity against interfering molecules, such as H2, alcohols, and humidity. Since Au nanosheets with uniform sensor characteristics enable easy device integration, the proposed sensor will be useful for facile health checkups based on breath analysis upon its integration into mobile devices.

Characteristics of extra-oral halitosis induced by functional constipation: a prospective cohort study

Characteristics of extra-oral halitosis induced by functional constipation (FC) have never been revealed. To address this, this prospective cohort was conducted with 100 FC patients, who were divided into a halitosis group and a negative group. Organoleptic score (OLS) ⩾ 2 in nose breath was diagnosed as extra-oral halitosis. Concentration of overall volatile sulfur compounds (VSCs) measured by Halimeter, concentration of hydrogen sulfide (HS), methanethiol (MT), dimethyl sulfide (DMS) and their total amount measured by OralChroma in nose breath was recorded asC-VSC,C-HS,C-MT,C-DMS andC-sum respectively. We found that 82% (82/100) of the FC patients had extra-oral halitosis. However, only 12.5% (3/82) and 1.22% (1/82) of halitosis group were correctly diagnosed with the current diagnostic threshold ofC-VSC ⩾ 110 parts per billion (ppb) and ⩾150 ppb.C-VSC,C-DMS andC-sum were significantly higher in the halitosis group compared to the negative group (allP< 0.001), with ratios of about 2.2 times, 3.1 times and 2.1 times respectively.C-HS andC-MT were low and not significantly different between the groups. Positive correlations were observed among OLS,C-VSC,C-DMS andC-sum. The area under curve of receiver operating characteristics ofC-VSC, C-DMS andC-sum for predicting FC-induced halitosis was 0.909, 0.9073 and 0.962 respectively, with the threshold values of ⩾36 ppb, ⩾52 ppb and ⩾75 ppb respectively. Therefore, we conclude that: (1) DMS is the primary contributor to FC-induced extra-oral halitosis. (2) OLS, Halimeter and OralChroma are consistent in detecting FC-induced extra-oral halitosis. (3) The diagnostic threshold for Halimeter should be adjusted toC-VSC ⩾ 36 ppb and the diagnostic threshold for OralChroma should be set asC-DMS ⩾ 52 ppb for diagnosing FC-induced extra-oral halitosis.

A structural color hydrogel for diagnosis of halitosis and screening of periodontitis

Oral pathogens can produce volatile sulfur compounds (VSCs), which is the main reason for halitosis and indicates the risk of periodontitis. High-sensitivity detection of exhaled VSCs is urgently desired for promoting the point-of-care testing (POCT) of halitosis and screening of periodontitis. However, current detection methods often require bulky and costly instruments, as well as professional training, making them impractical for widespread detection. Here, a structural color hydrogel for naked-eye detection of exhaled VSCs is presented. VSCs can reduce disulfide bonds within the network, leading to expansion of the hydrogel and thus change of the structural color. A linear detection range of 0-1 ppm with a detection limit of 61 ppb can be achieved, covering the typical VSC concentration in the breath of patients with periodontitis. Furthermore, visual and in situ monitoring of Porphyromonas gingivalis responsible for periodontitis can be realized. By integrating the hydrogels into a sensor array, the oral health conditions of patients with halitosis can be evaluated and distinguished, offering risk assessment of periodontitis. Combined with a smartphone capable of color analysis, POCT of VSCs can be achieved, providing an approach for the monitoring of halitosis and screening of periodontitis.

Gastric Helicobacter pylori infection does not contribute to extraoral halitosis and its eradication cannot achieve substantial reduction of halitosis

Background

Some researchers have suggested that Helicobacter pylori (H. pylori) infection is attributed to extraoral halitosis. However, this viewpoint is increasingly challenged by clinical practice. This study was conducted with the aim of investigating changes of extraoral halitosis before and after H. pylori eradication.

Materials and Methods

Data of patients who had H. pylori infection and extraoral halitosis were retrospectively collected. H. pylori infection was diagnosed by positive 13C urea breath test (UBT). Extraoral halitosis was diagnosed by organoleptic score (OLS) ≥2 in nose breath. A 14‐day bismuth‐based quadruple therapy was administered for H. pylori eradication. Extraoral halitosis was examined before eradication (T1), on the first day after eradication (T2), 1 month after eradication (T3), and 3 months after eradication (T4). Eradication effect was checked by UBT at T3.

Results

A total of 100 patients were included. Eradication was successful in 74 out of 100 (74%) patients (success group) and failed in 26 out of 100 (26%) patients (failure group). 32 out of 74 (43.24%) patients in success group and 10 out of 26 (38.46%) patients in failure group had reduced halitosis at T2, 9 out of 74 (12.16%) patients in success group and 2 out 26 (7.69%) patients in failure group had relapsed halitosis at T3, and 23 out of 74 (31.08%) patients in success group and 8 out of 26 (30.77%) patients in failure group had relapsed halitosis at T4, without significant difference between groups at any time (p = 0.918, p = 0.808, and p = 0.808 respectively).

Conclusions

Helicobacter pylori infection does not contribute to extraoral halitosis. H. pylori eradication can achieve sustained but slight reduction of extraoral halitosis, probably due to its antibiotic effects on the gut microbiota rather than H. pylori.

Causes and Management of Halitosis: A Narrative Review

Halitosis is defined as the presence of an unpleasant odor in exhaled air, regardless of its cause. In most patients with halitosis, the condition causes embarrassment and interferes with social interactions and daily life. Furthermore, bad breath can be a sign of an underlying disease. Understanding the factors and causes that lead to halitosis and its manifestations could facilitate proper management of this condition. To properly diagnose and treat patients, healthcare professionals, including primary care physicians and dental professionals, must be familiar with the etiology and appropriate management of the disease. Consequently, this review aims to provide practitioners with up-to-date information on the etiological factors of halitosis to facilitate the establishment of preventive measures and provide accurate diagnosis and management.

Is bad breath associated with dyspepsia? An association and an equivalence study

Halitosis affects all populations worldwide. The presence of chronic halitosis may be related to a health problem. Patients with bad breath usually seek a gastroenterologist and, in some cases, invasive and expensive exams, such as digestive endoscopy, are performed to investigate the etiology of halitosis. This study aimed to investigate whether the prevalence of bad breath in patients diagnosed with dyspepsia (any pain or discomfort in the upper abdomen) is higher than or equivalent to that in non-dyspeptic patients. This is a cross-sectional study that included 312 patients from university hospitals in the city of Rio de Janeiro (141 dyspeptic patients and 171 non-dyspeptic ones). The presence of halitosis was defined based on different cutoff points. Association analyses were performed using a log-binomial model and 95% confidence intervals were calculated for the coefficients, adjusting for sex and age. The equivalence test (Westlake) was used to test the hypothesis of equivalence between the proportions of patients with bad breath in the two groups (dyspeptic vs. non-dyspeptic), considering an equivalence band of ± 15%. The prevalence of bad breath ranged from 30% to 64% according to the definition of bad breath. Dyspepsia was not associated with bad breath in any of the three definitions of bad breath (two specific ones and a sensitive one). The proportion of patients with marked bad breath was equivalent in patients with and without dyspepsia.

Wearable chemical sensors based on 2D materials for healthcare applications

Chemical sensors worn on the body could make possible the continuous, noninvasive, and accurate monitoring of vital human signals, which is necessary for remote health monitoring and telemedicine. Attractive for creating high-performance, wearable chemical sensors are atomically thin materials with intriguing physical features, abundant chemistry, and high surface-to-volume ratios. These advantages allow for appropriate material-analyte interactions, resulting in a high level of sensitivity even at trace analyte concentrations. Previous review articles covered the material and device elements of 2D material-based wearable devices extensively. In contrast, little research has addressed the existing state, future outlook, and promise of 2D materials for wearable chemical sensors. We provide an overview of recent advances in 2D-material-based wearable chemical sensors to overcome this deficiency. The structure design, manufacturing techniques, and mechanisms of 2D material-based wearable chemical sensors will be evaluated, as well as their applicability in human health monitoring. Importantly, we present a thorough review of the current state of the art and the technological gaps that would enable the future design and nanomanufacturing of 2D materials and wearable chemical sensors. Finally, we explore the challenges and opportunities associated with designing and implementing 2D wearable chemical sensors.

Improvement of halitosis by probiotic bacterium Weissella cibaria CMU: A randomized controlled trial

Several in vitro and in vivo studies have evaluated the effect of probiotics on oral health; however, human clinical studies are still limited. Therefore, this study aimed to examine the effects of Weissella cibaria Chonnam Medical University (CMU)-containing tablets on halitosis. This randomized, double-blinded, placebo-controlled study included 100 adults with halitosis (age, 20-70 years). The participants were randomly assigned to the test group (n = 50) and control group (n = 50). One tablet [1 × 10⁸ colony forming units (CFU)/tablet] was to be taken each day over 8 weeks. The concentrations of volatile sulfur compounds (VSCs), bad breath improvement scores, and oral colonization of W. cibaria were measured. Psychosocial indicators including depression, self-esteem, oral health-related quality of life, and subjective oral health status were evaluated. Most variables were assessed at baseline, 4, and 8 weeks, and W. cibaria number and safety variables were assessed at baseline and 8 weeks. Intergroup comparisons were carried out using Student's t-test, Chi-square test, or Fisher's exact test on per-protocol analysis. Intragroup differences before and after intake were analyzed using the linear mixed-effect model (LMM). Per-protocol analysis was carried out in the test group (n = 45) and control group (n = 46). Total VSC was significantly lower in the probiotics group than in the placebo group at baseline (week 0, p = 0.046) and at 8 weeks (p = 0.017). The sum of hydrogen sulfide and methyl mercaptan did not differ significantly between the groups at baseline; however, it was significantly lower in the probiotics group than in the placebo group at week 8 (p = 0.012). Bad breath improvement (BBI) scores were significantly reduced at week 8 (p = 0.006) in the probiotics group. Statistically significant intergroup differences were observed for changes in the level of W. cibaria at week 8 (p < 0.001). Psychological indicators significantly improved from baseline to week 8 in the probiotics group. No safety issues were observed in either group. The levels of W. cibaria was higher in patients with halitosis using W. cibaria CMU-containing tablets. The subjective degree of bad breath and psychological indicators were improved in patients with halitosis using W. cibaria CMU-containing tablets.

[Halitosis. Multidisciplinary approach]

Halitosis is a common complaint among patients. Up to 50% of people worldwide claim to have persistent or intermittent bad breath. Often, bad breath not only disrupts the social life of patients, but is also a symptom of systemic diseases. An important step in the treatment of halitosis is the localization of the source and possible cause of the unpleasant smell. Most often, the problem of halitosis is solved by dentists, because intraoral halitosis accounts for up to 90% of all cases, but doctors of many specialties should deal with the differential diagnosis of its causes. This article considers the main causes of halitosis in patients with diseases of various organ systems.

The tongue biofilm metatranscriptome identifies metabolic pathways associated with the presence or absence of halitosis

Intra-oral halitosis usually results from the production of volatile sulfur compounds, such as methyl mercaptan and hydrogen sulfide, by the tongue microbiota. There are currently no reports on the microbial gene-expression profiles of the tongue microbiota in halitosis. In this study, we performed RNAseq of tongue coating samples from individuals with and without halitosis. The activity of Streptococcus (including S. parasanguinis), Veillonella (including V. dispar) and Rothia (including R. mucilaginosa) was associated with halitosis-free individuals while Prevotella (including P. shahi), Fusobacterium (including F. nucleatum) and Leptotrichia were associated with halitosis. Interestingly, the metatranscriptome of patients that only had halitosis levels of methyl mercaptan was similar to that of halitosis-free individuals. Finally, gene expression profiles showed a significant over-expression of genes involved in L-cysteine and L-homocysteine synthesis, as well as nitrate reduction genes, in halitosis-free individuals and an over-expression of genes responsible for cysteine degradation into hydrogen sulfide in halitosis patients.

Volatile composition of the morning breath

We have measured the composition of volatile organic compounds (VOCs) in the morning breath of 30 healthy individuals before and after tooth brushing. The concentrations of VOCs in the breath samples were measured with proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and further identification was performed with a combination of solid phase microextraction (SPME) and offline gas chromatography-mass spectrometry (GC-MS). We hypothesize that compounds, whose concentrations significantly decreased in the breath after tooth brushing are largely of microbial origin. In this study, we found 35 such VOCs. Out of these, 33 have been previously connected to different oral niches, such as salivary and subgingival bacteria. We also compared the concentrations of the 35 VOCs found in increased amounts in the morning breath to their respective odor thresholds to evaluate their ability to cause odor. Compounds that could contribute to the breath odor include many volatile sulfur compounds, such as methanethiol, hydrogen sulfide, dimethyl sulfide, and 2-methyl-1-propanethiol, but also other VOCs, such as acetic acid, butyric acid, valeric acid, acetaldehyde, octanal, phenol, indole, ammonia, isoprene, and methyl methacrylate.

Volatolomics in healthcare and its advanced detection technology

Various diseases increasingly challenge the health status and life quality of human beings. Volatolome emitted from patients has been considered as a potential family of markers, volatolomics, for diagnosis/screening. There are two fundamental issues of volatolomics in healthcare. On one hand, the solid relationship between the volatolome and specific diseases needs to be clarified and verified. On the other hand, effective methods should be explored for the precise detection of volatolome. Several comprehensive review articles had been published in this field. However, a timely and systematical summary and elaboration is still desired. In this review article, the research methodology of volatolomics in healthcare is critically considered and given out, at first. Then, the sets of volatolome according to specific diseases through different body sources and the analytical instruments for their identifications are systematically summarized. Thirdly, the advanced electronic nose and photonic nose technologies for volatile organic compounds (VOCs) detection are well introduced. The existed obstacles and future perspectives are deeply thought and discussed. This article could give a good guidance to researchers in this interdisciplinary field, not only understanding the cutting-edge detection technologies for doctors (medicinal background), but also making reference to clarify the choice of aimed VOCs during the sensor research for chemists, materials scientists, electronics engineers, etc.

Moisture-resistant, stretchable NOx gas sensors based on laser-induced graphene for environmental monitoring and breath analysis

The accurate, continuous analysis of healthcare-relevant gases such as nitrogen oxides (NO_x) in a humid environment remains elusive for low-cost, stretchable gas sensing devices. This study presents the design and demonstration of a moisture-resistant, stretchable NO_x gas sensor based on laser-induced graphene (LIG). Sandwiched between a soft elastomeric substrate and a moisture-resistant semipermeable encapsulant, the LIG sensing and electrode layer is first optimized by tuning laser processing parameters such as power, image density, and defocus distance. The gas sensor, using a needlelike LIG prepared with optimal laser processing parameters, exhibits a large response of 4.18‰ ppm^-1 to NO and 6.66‰ ppm^-1 to NO₂, an ultralow detection limit of 8.3 ppb to NO and 4.0 ppb to NO₂, fast response/recovery, and excellent selectivity. The design of a stretchable serpentine structure in the LIG electrode and strain isolation from the stiff island allows the gas sensor to be stretched by 30%. Combined with a moisture-resistant property against a relative humidity of 90%, the reported gas sensor has further been demonstrated to monitor the personal local environment during different times of the day and analyze human breath samples to classify patients with respiratory diseases from healthy volunteers. Moisture-resistant, stretchable NO_x gas sensors can expand the capability of wearable devices to detect biomarkers from humans and exposed environments for early disease diagnostics.

A Literature Review and Framework Proposal for Halitosis Assessment in Cigarette Smokers and Alternative Nicotine-Delivery Products Users

Halitosis is a health condition which counts cigarette smoking (CS) among its major risk factors. Cigarette smoke can cause an imbalance in the oral bacterial community, leading to several oral diseases and conditions, including intraoral halitosis. Although the best approach to decrease smoking-related health risks is quitting smoking, this is not feasible for many smokers. Switching to potentially reduced-risk products, like electronic vapor products (EVP) or heated tobacco products (HTP), may help improve the conditions associated with CS. To date, there have been few systematic studies on the effects of CS on halitosis and none have assessed the effects of EVP and HTP use. Self-assessment studies have shown large limitations owing to the lack of reliability in the participants' judgment. This has compelled the scientific community to develop a strategy for meaningful assessment of these new products in comparison with cigarettes. Here, we compiled a review of the existing literature on CS and halitosis and propose a 3-layer approach that combines the use of the most advanced breath analysis techniques and multi-omics analysis to define the interactions between oral bacterial species and their role in halitosis both in vitro and in vivo. Such an approach will allow us to compare the effects of different nicotine-delivery products on oral bacteria and quantify their impact on halitosis. Defining the impact of alternative nicotine-delivery products on intraoral halitosis and its associated bacteria will help the scientific community advance a step further toward understanding the safety of these products and their potentiall risks for consumers.

Salivary β-galactosidase, halitosis parameters in periodontal health and disease, and their changes after periodontal treatment

BACKGROUND

In this study, we aimed to evaluate the salivary β-galactosidase and Halimeter values (HMV), organoleptic scores (OLS) and Winkel tongue coating index (WTCI) in periodontal health and periodontitis (P), and also their changes after phase I periodontal therapy and tongue cleaning.

METHODS

The participants were separated as follows: 25 P with halitosis (Group 1), 25 P without halitosis (Group 2) and 25 healthy controls (Group 3). Periodontal recordings, HMV, OLS and WTCI scores were recorded, and whole saliva β-galactosidase levels were measured colorimetrically in the samples at baseline and 1 month after the therapy.

RESULTS

The baseline values of HMV, OLS, WTCI and salivary β-galactosidase levels were significantly higher in Group 1 than in Group 2 (P < 0.05). There was a statistically significant decrease in periodontal recordings, HMV, OLS, WTCI and salivary β-galactosidase levels in all P patients by the therapy (P < 0.05). However, major reductions in halitosis measurements and saliva enzyme levels were observed in Group 1 after the treatment.

CONCLUSION

Our results showed that salivary β-galactosidase was associated with halitosis parameters and phase I periodontal therapy played an important role to reduce this enzyme level and halitosis parameters in P.

Targeted Chemometrics Investigations of Source-, Age- and Gender-Dependencies of Oral Cavity Malodorous Volatile Sulphur Compounds

Halitosis is a highly distressing, socially unaesthetic condition, with a very high incidence amongst the adult population. It predominantly arises from excessive oral cavity volatile sulphur compound (VSC) concentrations, which have either oral or extra-oral etiologies (90–95% and 5–10% of cases, respectively). However, reports concerning age- and gender-related influences on the patterns and concentrations of these malodorous agents remain sparse; therefore, this study’s first objective was to explore the significance and impact of these potential predictor variables on the oral cavity levels of these malodorants. Moreover, because non-oral etiologies for halitosis may represent avatars of serious extra-oral diseases, the second objective was to distinguish between etiology- (source-) dependent patterns of oral cavity VSCs. Oral cavity VSC determinations were performed on 116 healthy human participants using a non-stationary gas chromatographic facility, and following a 4 h period of abstention from all non-respiratory oral activities. Participants were grouped according to ages or age bands, and gender. Statistical analyses of VSC level data acquired featured both univariate/correlation and multivariate (MV) approaches. Factorial analysis-of-variance and MV analyses revealed that the levels of all VSCs monitored were independent of both age and gender. Principal component analysis (PCA) and a range of further MV analysis techniques, together with an agglomerative hierarchal clustering strategy, demonstrated that VSC predictor variables were partitioned into two components, the first arising from orally-sourced H2S and CH3SH, the second from extra-orally-sourced (CH3)2S alone (about 55% and 30% of total variance respectively). In conclusion, oral cavity VSC concentrations appear not to be significantly influenced by age and gender. Furthermore, (CH3)2S may serve as a valuable biomarker for selected extra-oral conditions.

Highly Sensitive and Selective NiO/WO3 Composite Nanoparticles in Detecting H2S Biomarker of Halitosis

Indirectly monitoring halitosis via the detection of hydrogen sulfide (H₂S) biomarkers using gas sensors is a newly emerging technique. However, such H₂S sensors are required with critically high selectivity and sensitivity, as well as a ppb-level detection limit, which remains technologically challenging. To address such issues, here, we have developed highly sensitive and selective H₂S sensors with NiO/WO₃ nanoparticles (NPs), which have been synthesized by firstly hydrolyzing WO₃ NPs and subsequently decorating with NiO NPs in a hydrothermal process. Theoretically, the NiO/WO₃ NPs assist in forming a thicker electron depletion layer, adsorbing more oxygen species O₂^- to oxidize H₂S and finally release more electrons. Beneficially, 2.1 wt % NiO/WO₃ NPs show high sensitivity to H₂S (R_a/R_g = 15031 ± 1370 @ 10 ppm, 100 °C), which is 42.6-fold higher than that of the pristine WO₃ NPs (R_a/R_g = 353 ± 5.6 @ 10 ppm, 100 °C). Further, the H₂S sensor shows ppb-level detection limit (R_a/R_g = 4.95 ± 2.9 @ 0.05 ppm, 100 °C) and high selectivity. Practically, NiO/WO₃ NP sensor prototype has been employed to detect the simulated exhaled halitosis compared with that of gas chromatography, revealing a close concentration of H₂S. Our investigation offers an experimental base in future intelligent medical applications.

Association of periodontitis with oral malodor in Korean adults

This study aimed to evaluate the association of periodontitis with the organoleptic score (OLS)-defined oral malodor after validating OLS with odoriferous sulfur compounds in mouth air among Korean adults. A total of 330 adults aged 47–86 years were recruited from the Yangpyeong health cohort, South Korea, in 2015. Oral malodor was assessed using a 6-point OLS by a trained dentist and validated with the concentrations of hydrogen sulfide (HS) and methyl mercaptan (MM) using a gas chromatographer. Periodontitis was measured by assessing the radiographic alveolar bone loss on digital orthopantomography. Statistical analyses including descriptive statistics, partial correlation, ANOVA, and multivariable logistic regression with putative confounders were applied. OLS was significantly correlated with the concentrations of HS and MM (partial r = 0.401 and 0.392, respectively; both p<0.001) after controlling for confounders. Individuals with periodontitis had 1.8 times the risk of OLS-defined oral malodor in multivariable models (adjusted odds ratio = 1.77 in the model with the number of teeth and 1.82 in the model with denture wearing; p = 0.047 and 0.035, respectively). Periodontitis was associated with OLS-defined oral malodor among Korean adults independent of known confounders. Periodontal conditions should be considered for clinical practice and research of oral malodor.

Role of the oral microbiome, metabolic pathways, and novel diagnostic tools in intra-oral halitosis: a comprehensive update

Halitosis or oral malodor is one of the most common reasons for the patients' visit to the dental clinic, ranking behind only dental caries and periodontitis. In the present times, where social and professional communications are becoming unavoidable, halitosis has become a concern of growing importance. Oral malodor mostly develops due to the putrefaction of substrates by the indigenous bacterial populations. Although culture-based studies have provided adequate information on halitosis, the high throughput omics technologies have amplified the resolution at which oral microbial community can be examined and has led to the detection of a broader range of taxa associated with intra-oral halitosis (IOH). These microorganisms are regulated by the interactions of their ecological processes. Thus to develop effective treatment strategies, it is important to understand the microbial basis of halitosis. In the current review, we provide an update on IOH in context to the role of the oral microbiome, metabolic pathways involved, and novel diagnostic tools, including breathomics. Understanding oral microbiota associated with halitosis from a broader ecological perspective can provide novel insights into one's oral and systemic health. Such information can pave the way for the emergence of diagnostic tools that can revolutionize the early detection of halitosis and various associated medical conditions.

Knowledge and Management of Halitosis in France and Lebanon: A Questionnaire-Based Study

Halitosis is a growing issue and its management is highly challenging. The aim of this study was to evaluate the knowledge and treatment strategies used by French (FD) and Lebanese (LD) dentists. A self-administered structured questionnaire was sent to FD and LD comprising questions about professional characteristics, management, and treatment of halitosis, patients’ referral, and halitosis-related knowledge. A multivariate analysis was conducted to determine differences between FD and LD and to identify parameters that could influence dentists’ management of halitosis. The questionnaire was filled out by 156 FD and 257 LD. Among them, 78.8% of FD and 68.9% of LD were confronted with halitosis management, while only a few routinely asked their patients about halitosis (16% FD, 13.2% LD). Regarding anamnesis, oral hygiene habits were more investigated by FD than LD (p < 0.05). The overall treatment satisfaction was low with 39.7% of FD and 28.4% of LD considering their treatment effective. Regarding halitosis-related knowledge, extra-oral causes were overestimated in both populations. FD (83.4%) and LD (65.8%) considered their education regarding halitosis as insufficient. This study highlights the need of professional education in both countries, targeting proper diagnosis and treatment strategies of halitosis.

Volatile sulphur compounds in people with chronic kidney disease and the impact on quality of life

The objectives are to identify volatile sulphur compounds (VSCs) in individuals with Chronic Kidney Disease (CKD) and to relate quality of life and oral health. A case-control study with 32 individuals with CKD in haemodialysis in the study group (SG) and 32 healthy individuals in the control group (CG) was performed. The VSCs were identified by gas chromatograph before (BC) and after cysteine (AC) mouthwash and an organoleptic test. For oral health assessment, oral health index was used. For quality of life, the Oral Health Impact Profile (OHIP-14) and Medical Outcomes Study 36-Item Short Form Health Survery (SF-36) were used. The hydrogen sulphide AC, methyl mercaptan AC, tongue coating, dry mouth, plaque index, and DMFT were significantly higher in the SG. VSCs did not negatively affected the impact of oral health on the quality of life in the SG but did in the CG. As for the impact of general health on quality of life, methyl mercaptan BC and AC worsened overall health in vitality and mental health, respectively. Individuals with CKD have more halitosis than healthy individuals, and it is more related to methyl mercaptan. The halitosis worsened the general quality of life of individuals with CKD. The diagnosis and identification of the origin of halitosis is important to prevent one more factor that it worsened the global quality of life of patients with CKD.

Colorimetric Dye-Loaded Nanofiber Yarn: Eye-Readable and Weavable Gas Sensing Platform

The colorimetric gas sensor offers an opportunity for the simple and rapid detection of toxic gaseous substances based on visually discernible changes in the color of the sensing material. In particular, the accurate detection of trace amounts of certain biomarkers in a patient's breath provides substantial clues regarding specific diseases, for example, hydrogen sulfide (H₂S) for halitosis and ammonia (NH₃) for kidney disorder. However, conventional colorimetric sensors often lack the sensitivity, selectivity, detection limit, and mass-productivity, impeding their commercialization. Herein, we report an inexpensive route for the meter-scale synthesis of a colorimetric sensor based on a composite nanofiber yarn that is chemically functionalized with an ionic liquid as an effective H₂S adsorbent and lead acetate as a colorimetric dye. As an eye-readable and weavable sensing platform, the single-strand yarn exhibits enhanced sensitivity supported by its high surface area and well-developed porosity to detect the breath biomarker (1 ppm of H₂S). Alternatively, the yarn loaded with lead iodide dyes could reversibly detect NH₃ gas molecules in the ppm-level, demonstrating the facile extensibility. Finally, we demonstrated that the freestanding yarns could be sewn into patterned textiles for the fabrication of a wearable toxic gas alarm system with a visual output.

Halitosis, reduced salivary flow and the quality of life in pre-kidney transplantation patients

Background

Halitosis is a condition that affects 50% of adults and one third of patients with chronic kidney disease. The aim of this study was to evaluate oral manifestations and volatile sulfur compounds (VSCs) associated with halitosis and quality of life in pre-kidney transplantation candidates.

Material and Methods

The organoleptic test (OT) and halimetry (HA) (before and after cysteine mouthwash) were performed in patients with the Oralchroma® device, stimulated (SE) and non-stimulated sialometry (SN), Tongue Coating Index (TCI). The OHIP-14 questionnaire was administered to assess the impact of oral health on quality of life.

Results

Fourteen individuals with a mean age of 49.64 ± 13.35 years were evaluated. In the organoleptic test, 57.14% of the individuals presented halitosis. Oralchroma results showed that dimethyl sulfide was above the threshold in 85.71% of the individuals, while hydrogen sulfide and methyl mercaptan were above threshold in 28.57%; after the use of cysteine, hydrogen sulfide was present in 100% of the cases, dimethyl sulfide in 57.14% and methyl mercaptan in 50%. In the non-stimulated sialometry, 57.14% of the individuals presented hyposalivation and 21.42% in the stimulated. Regarding the tongue coating index, 100% of the individuals presented tongue coating, with a mean of 7.64. The assessment of impact of oral health on quality of life showed a negative impact in all dimensions.

Conclusions

Tongue coating, in association with hydrogen sulfide, was the main cause of halitosis in the study subjects, and hyposalivation may contribute to higher tongue-coating indices. These oral changes negatively affect the quality of life for pre-kidney transplantation patients.

Key words:Halitosis, chronic kidney disease, quality of life, kidney transplantation.

Validation of the Brazilian version of the Halitosis Associated Life-Quality Test (HALT)

The present study aimed to validate (cross-culturally adapt and test psychometric properties) the Brazilian version of the Halitosis Associated Life-Quality Test (HALT). A process of translation and cross-cultural adaptation was conducted by a group of dental researchers. The first draft of the Brazilian Portuguese version was pre-tested on a sample of 33 individuals leading up to the final version of the questionnaire. The Brazilian version of the HALT (B-HALT) was applied to 100 individuals with halitosis (organoleptic score ≥ 2) and 100 individuals without halitosis (organoleptic score < 2). Exploratory factor analysis (EFA) was performed to evaluate the dimensionality of B-HALT. Cronbach's alpha (α) and interclass correlation coefficient (ICC) were used to measure its reliability. For convergent validity, Spearman's correlation was conducted between the B-HALT and the organoleptic scores. The discriminant validity was evaluated through the Mann-Whitney and Kruskal-Wallis tests. EFA confirmed the unidimensionality of B-HALT, which has also demonstrated excellent internal consistency (α = 0.96) and test-retest reliability (ICC = 0.93). There was a positive correlation between B-HALT and organoleptic scores (r = 0.33; p < 0.001). B-HALT was able to discriminate between the groups with and without halitosis measured by the organoleptic method (p < 0.001) and self-reported halitosis (p < 0.001). B-HALT has demonstrated to be a reliable and valid tool to evaluate the oral health-related quality of life associated to halitosis in Brazilian adults.

The Role of Oral Microbiota in Intra-Oral Halitosis

Halitosis is a common ailment concerning 15% to 60% of the human population. Halitosis can be divided into extra-oral halitosis (EOH) and intra-oral halitosis (IOH). The IOH is formed by volatile compounds, which are produced mainly by anaerobic bacteria. To these odorous substances belong volatile sulfur compounds (VSCs), aromatic compounds, amines, short-chain fatty or organic acids, alcohols, aliphatic compounds, aldehydes, and ketones. The most important VSCs are hydrogen sulfide, dimethyl sulfide, dimethyl disulfide, and methyl mercaptan. VSCs can be toxic for human cells even at low concentrations. The oral bacteria most related to halitosis are Actinomyces spp., Bacteroides spp., Dialister spp., Eubacterium spp., Fusobacterium spp., Leptotrichia spp., Peptostreptococcus spp., Porphyromonas spp., Prevotella spp., Selenomonas spp., Solobacterium spp., Tannerella forsythia, and Veillonella spp. Most bacteria that cause halitosis are responsible for periodontitis, but they can also affect the development of oral and digestive tract cancers. Malodorous agents responsible for carcinogenesis are hydrogen sulfide and acetaldehyde.

The Underestimated Problem of Intra-Oral Halitosis in Dental Practice: An Expert Consensus Review

Approximately 90% of halitosis cases originate within the oral cavity (intra-oral halitosis). With a focus on intra-oral halitosis, this narrative review article provides a current summary of the epidemiology, diagnosis and management of halitosis and discusses practical considerations for healthcare professionals (HCPs), including dentists, dental hygienists, general practitioners, community pharmacists, nurses and medical specialists. MEDLINE and PubMed were searched up to 31 December 2019. Additional information was sourced from reference lists of relevant published literature. Full-text articles which reported on the epidemiology, diagnosis and management of halitosis were considered for inclusion. Halitosis affects substantial numbers of individuals globally and is an underestimated problem in dental practice. Current estimates of the prevalence of halitosis, in addition to diagnostic methods and management considerations for halitosis, are discussed. Although not a life-threatening condition, halitosis has a significant impact on patients’ quality of life and can result in psychological consequences including social, professional and affective limitations. Using a simple step-wise approach for diagnosis and treatment, dentists and dental hygienists are ideally placed to respond to an initial consultation for halitosis.

Etiology and characteristics of halitosis in patients of a halitosis center in Northern Italy

BACKGROUND

As there are few studies in Europe describing characteristics of breath malodor for large groups of patients, this retrospective study was designed to analyse the etiology of halitosis among patients attending a breath malodor center in Northern Italy.

METHODS

Clinical records of 547 consecutive patients were reviewed and data on self-perceived halitosis, organoleptic scores, volatile sulphur compound (VSC) levels, and oral health condition were extracted and analysed.

RESULTS

The prevalence of intra-oral halitosis was 90.7%. In 21 patients no objective signs of breath malodor could be found. Periodontitis and gingivitis were the main cause of bad breath in 33.9% of subjects and in combination with tongue coating in 55.2%. Only eight subjects have tongue coating as the only cause of halitosis. Ear, nose and throat (ENT)/extra-oral causes were found in 5.2% of the patients. VSC concentrations were lower in the psychogenic halitosis group, whereas no statistically significant differences were detected when comparing intra-oral and extra-oral halitosis except for (CH3)2S.

CONCLUSIONS

Psychogenic halitosis is a rare condition among subjects complaining of suffering from bad breath. The most prevalent cause of halitosis is intra-oral, in particular a combination of tongue coating and periodontal disease. Tongue coating is rarely the primary cause of oral malodor.

Oral health and halitosis among type 1 diabetic and healthy children

AIM

To evaluate the oral health status, oral health related habits and halitosis of children with and without type 1 diabetes.

MATERIALS AND METHODS

In this study the oral health status of children with and without type 1 diabetes were evaluated by using different indices (dmft/DMFT, International Caries Detection and Assessment System(ICDAS) II, pufa, gingival and periodontal indices). Halitosis was determined by organoleptic assessment and sulfur monitoring.

RESULTS

One hundred children with the age range between 6-13 years, 50 type 1 diabetics (24 boys,26 girls) with mean age (±sd) of 10.3 ± 2.1 years and 50 healthy (30 boys, 20 girls) with mean age (±sd) of 9.9 ± 1.5 years, participated in the study. The median values of dmft and dmfs was lower in children with type 1 diabetes, while for DMFT and DMFS indices were similar with the healthy group. Cavitated caries lesions were observed in 60.0% of children with diabetes and in 58.0% of healthy children. According to the ICDAS II index, 42.0% of children with diabetes and 56.0% of healthy children had severe decay. The mean plaque index was statistically significantly less in diabetic children (p = 0.04). In 12.0% of children with type 1 diabetes and in 18.0% of healthy children, volatile sulfur compounds (VSC) were determined to be ≥150 ppb and the most diagnosed score was 1 in both groups. In diabetic children with the cut off value of 7.5% HbA1c, there was no statistically significant difference in oral health indices results and VSC scores.

CONCLUSION

Findings of the present study are insufficient to support a significant effect of diabetes on increasing the risk of oral and periodontal diseases. Nonetheless, it is important to emphasize the importance of oral and dental health, regular oral care and dental visits both to the patients with type 1 diabetes and their parents.

Impact of oral cleansing strategies on exhaled volatile organic compound levels

RATIONALE

The analysis of volatile organic compounds (VOCs) within exhaled breath potentially offers a non-invasive method for the detection and surveillance of human disease. Oral contamination of exhaled breath may influence the detection of systemic VOCs relevant to human disease. This study aims to assess the impact of oral cleansing strategies on exhaled VOC levels in order to standardise practice for breath sampling.

METHODS

Ten healthy volunteers consumed a nutrient challenge followed by four oral cleansing methods: (a) water, (b) saltwater, (c) toothbrushing, and (d) alcohol-free mouthwash. Direct breath sampling was performed using selected ion flow tube mass spectrometry after each intervention.

RESULTS

Proposed reactions suggest that volatile fatty acid and alcohol levels (butanoic, pentanoic acid, ethanol) declined with oral cleansing interventions, predominantly after an initial oral rinse with water. Concentrations of aldehydes and phenols (acetaldehyde, menthone, p-cresol) declined with oral water rinse; however, they increased after toothbrushing and mouthwash use, secondary to flavoured ingredients within these products. No significant reductions were observed with sulphur compounds.

CONCLUSIONS

Findings suggest that oral rinsing with water prior to breath sampling may reduce oral contamination of VOC levels, and further interventions for oral decontamination with flavoured products may compromise results. This intervention may serve as a simple and inexpensive method of standardisation within breath research.

Simulations of Benzene and Hydrogen-Sulfide Gas Detector Based on Single-Walled Carbon Nanotube over Intrinsic 4H-SiC Substrate

Carbon nanotubes (CNTs)-based sensors have gained significant importance due to their tremendous electrical and physical attributes. CNT-based gas sensors have high sensitivity, stability, and fast response time compared to that of solid-state sensors. On exposure to a large variety of organic and inorganic compounds, the conductivity of CNT changes. This change in electrical conductivity is being used as a detection signal to detect different target molecules. Hydrogen-sulfide and benzene are hazardous gases that can cause serious health issues in humans. Therefore, it is mandatory to detect their presence in industrial and household environments. In this article, we simulated CNT-based benzene and hydrogen-sulfide sensor with a nanoscale semiconductor device simulator-Quantumwise Atomistix Toolkit (ATK). The change in the device density of states, electric current, and photocurrent in the presence of target molecules have been calculated. The change in photocurrent in the presence of target molecules has been proposed as a novel detection mechanism to improve the sensor selectivity and accuracy. This change in photocurrent as well as electric current in the presence of target molecules can be used simultaneously as detection signals. Our intension in the future is to physically fabricate this simulated device and use photocurrent as well as electric current as detection mechanisms.

Microbiota and Malodor-Etiology and Management

Accumulating evidence indicates that microbiota plays a critical role in physiological processes in humans. However, it might also contribute to body malodor by producing numerous odorous molecules such as ammonia, volatile sulfur compounds or trimethylamine. Although malodor is commonly overlooked by physicians, it constitutes a major problem for many otherwise healthy people. Thus, this review aims to investigate most common causes of malodor and describe potential therapeutic options. We searched PUBMED and Google Scholar databases to identify the clinical and pre-clinical studies on bad body smell, malodor, halitosis and microbiota. Unpleasant smell might originate from the mouth, skin, urine or reproductive fluids and is usually caused by odorants that are produced by resident bacterial flora. The accumulation of odorous compounds might result from diet, specific composition of microbiota, as well as compromised function of the liver, intestines and kidneys. Evidence-based guidelines for management of body malodor are lacking and no universal treatment exists. However, the alleviation of the symptoms may be achieved by controlling the diet and physical elimination of bacteria and/or accumulated odorants.

Carbon nanotubes-CuO/SnO2 based gas sensor for detecting H2S in low concentration

Porous CuO/SnO₂ nanofibers were prepared by co-dissolution and electrospinning, followed by annealing, and compounded with different amounts of carbon nanotubes (CNTs, 0-5 wt%). The performance of the composite based sensor was tested in different concentrations of H₂S range from 0.1 to 0.5 ppm. The results showed that the gas sensor based CuO/SnO₂ doped by CNTs (CNTs-CuO/SnO₂) has a low optimum operating temperature, 40 °C, good behavior in detecting low concentration H₂S, short response and recovery time (8.3 and 11.5 s, respectively). And at the same time, compared with other gases, 3 wt% CNTs-CuO/SnO₂ composite nanomaterial had excellent selectivity to H₂S at low concentrations. The prepared gas sensor had great advantages in detecting low concentration H₂S.

Combining culture and culture-independent methods reveals new microbial composition of halitosis patients' tongue biofilm

Background

Oral malodor is a very discomforting condition deriving from the presence of volatile sulfur compounds in the expired air. In halitosis of intraoral etiology, the volatile sulfur compounds are metabolic products of the oral microorganisms within the biofilm coating the tongue dorsum as well as other tissues in the oral cavity. The aim of this study was to characterize and compare the microbial composition of tongue biofilm in volunteers suffering from halitosis and healthy volunteers by means of both the culture method and culture‐independent cloning technique.

Results

A high bacterial variety (more than 80 different species) was detected using the combination of both methods. A distinct bacterial composition was revealed in the halitosis‐associated biofilms compared with the health‐associated biofilms. Actinomyces graevenitzii was shown to be significantly associated with the halitosis condition. The culture method identified 47 species, included Veillonella rogosae, never isolated from the tongue biofilm of halitosis patients so far. In the healthy condition, the culture‐dependent method showed that the most frequent species were Streptococcus parasanguinis among the aerobes and Veillonella spp. among the anaerobes. The culture‐independent cloning method detected more than 50 species. Streptococci, in particular S. mitis/oralis, S. pseudopneumoniae, and S. infantis as well as Prevotella spp., were found most frequently in halitosis patients. Streptococcus salivarius and Rothia mucilaginosa were found more frequently in the healthy condition.

Conclusions

The combination of the culture‐dependent and culture‐independent cloning techniques allowed for a widespread analysis of the tongue biofilm in halitosis patients. The results can support further pharmacological research for new antimicrobial agents and halitosis therapy strategies.

Exhaled volatile substances in children suffering from type 1 diabetes mellitus: results from a cross-sectional study

Monitoring metabolic adaptation to type 1 diabetes mellitus in children is challenging. Analysis of volatile organic compounds (VOCs) in exhaled breath is non-invasive and appears as a promising tool. However, data on breath VOC profiles in pediatric patients are limited. We conducted a cross-sectional study and applied quantitative analysis of exhaled VOCs in children suffering from type 1 diabetes mellitus (T1DM) (n = 53) and healthy controls (n = 60). Both groups were matched for sex and age. For breath gas analysis, a very sensitive direct mass spectrometric technique (PTR-TOF) was applied. The duration of disease, the mode of insulin application (continuous subcutaneous insulin infusion vs. multiple daily insulin injection) and long-term metabolic control were considered as classifiers in patients. The concentration of exhaled VOCs differed between T1DM patients and healthy children. In particular, T1DM patients exhaled significantly higher amounts of ethanol, isopropanol, dimethylsulfid, isoprene and pentanal compared to healthy controls (171, 1223, 19.6, 112 and 13.5 ppbV vs. 82.4, 784, 11.3, 49.6, and 5.30 ppbV). The most remarkable differences in concentrations were found in patients with poor metabolic control, i.e. those with a mean HbA1c above 8%. In conclusion, non-invasive breath testing may support the discovery of basic metabolic mechanisms and adaptation early in the progress of T1DM.

Non-Invasive Assessment of Metabolic Adaptation in Paediatric Patients Suffering from Type 1 Diabetes Mellitus

An analysis of exhaled volatile organic compounds (VOC) may deliver systemic information quicker than available invasive techniques. Metabolic aberrations in pediatric type 1 diabetes (T1DM) are of high clinical importance and could be addressed via breathomics. Real-time breath analysis was combined with continuous glucose monitoring (CGM) and blood tests in children suffering from T1DM and age-matched healthy controls in a highly standardized setting. CGM and breath-resolved VOC analysis were performed every 5 minutes for 9 hours and blood was sampled at pre-defined time points. Per participant (n = 44) food intake and physical activity were identical and a total of 22 blood samples and 93 minutes of breath samples were investigated. The inter-individual variability of glucose, insulin, glucagon, leptin, and soluble leptin receptor relative to food intake differed distinctly between patients and controls. In T1DM patients, the exhaled amounts of acetone, 2-propanol, and pentanal correlated to glucose concentrations. Of note, the strength of these correlations strongly depended on the interval between food intake and breath sampling. Our data suggests that metabolic adaptation through postprandial hyperglycemia and related oxidative stress is immediately reflected in exhaled breath VOC concentrations. Clinical translations of our findings may enable point-of-care applicability of online breath analysis towards personalized medicine.

Induction and inhibition of oral malodor

Volatile sulfur compounds (VSCs) such as hydrogen sulfide (H₂ S) and methyl mercaptan (CH₃ SH) are the main components of oral malodor, and are produced as the end products of the proteolytic processes of oral microorganisms. The main pathway of proteolysis is the metabolism of sulfur-containing amino acids by gram-negative anaerobic bacteria. Gram-positive bacteria may promote VSC production by gram-negative anaerobes by cleaving sugar chains from glycoproteins and thus providing proteins. A large variety of bacteria within the oral microbiota are thought to be involved in the complex phenomenon of halitosis. Oral microbiota associated with a lack of oral malodor, oral microbiota associated with severe and H₂ S-dominant oral malodor, and oral microbiota associated with severe and CH₃ SH-dominant oral malodor have been distinguished through molecular approaches using the 16S rRNA gene. Pathological halitosis may primarily be addressed through treatment of causative diseases. In all cases, plaque control is the basis of oral malodor control, and dentifrices, mouthwashes, and functional foods play a supplementary role in addition to brushing. Recently, the use of natural ingredients in products tends to be favored due to the increase in antibiotic-resistant strains and the side effects of some chemical ingredients. In addition, probiotics and vaccines are expected to offer new strategies for improving the oral conditions through mechanisms other than antibacterial agents.

Bioinspired Cocatalysts Decorated WO3 Nanotube Toward Unparalleled Hydrogen Sulfide Chemiresistor

Herein, we incorporated dual biotemplates, i.e., cellulose nanocrystals (CNC) and apoferritin, into electrospinning solution to achieve three distinct benefits, i.e., (i) facile synthesis of a WO₃ nanotube by utilizing the self-agglomerating nature of CNC in the core of as-spun nanofibers, (ii) effective sensitization by partial phase transition from WO₃ to Na₂W₄O₁₃ induced by interaction between sodium-doped CNC and WO₃ during calcination, and (iii) uniform functionalization with monodispersive apoferritin-derived Pt catalytic nanoparticles (2.22 ± 0.42 nm). Interestingly, the sensitization effect of Na₂W₄O₁₃ on WO₃ resulted in highly selective H₂S sensing characteristics against seven different interfering molecules. Furthermore, synergistic effects with a bioinspired Pt catalyst induced a remarkably enhanced H₂S response ( R_air/ R_gas = 203.5), unparalleled selectivity ( R_air/ R_gas < 1.3 for the interfering molecules), and rapid response (<10 s)/recovery (<30 s) time at 1 ppm of H₂S under 95% relative humidity level. This work paves the way for a new class of cosensitization routes to overcome critical shortcomings of SMO-based chemical sensors, thus providing a potential platform for diagnosis of halitosis.

Facile Synthesis of Pt-Functionalized Meso/Macroporous SnO2 Hollow Spheres through in Situ Templating with SiO2 for H2S Sensors

Although single-nozzle electrospraying seems a versatile technique in the synthesis of spherical semiconducting metal oxide structures, the synthesized structures find limited use in gas-sensing applications because of their thick and dense morphology, which minimizes the accessibility of their inner surfaces. Herein, unprecedented spherical SiO₂@SnO₂ core-shell structures are synthesized upon calcination of single-nozzle as-electrosprayed spheres (SPs) containing tin (Sn) and silicon (Si) precursors. Subsequent etching of SiO₂ in NaOH (pH 12) affords meso/macroporous SnO₂ hollow spheres (HSPs) with short diffusion length (31.4 ± 3.1 nm), small crystallites (15.5 nm), and large Brunauer-Emmett-Teller surface area (124.8 m² g^-1). Apart from surface meso/macropores, diffusion of gases into porous SnO₂ sensing layers is realized through inner interconnection of voids of the SnO₂ HSPs into a three-dimensional network. Functionalization of the postetched SnO₂ HSPs with platinum (Pt) nanoparticles at 0.08 wt % yields gas-sensing materials with outstanding response ( R_a/ R_g = 1.6, 10.8, and 105.1-0.1, 1, and 5 ppm of H₂S, respectively) and selectivity toward H₂S against interfering gas molecules at 250 °C. The SiO₂ phase in the postcalcined SiO₂@SnO₂ SPs acts as a sacrificial template for pore creation and crystal growth inhibition, whereas the small amount of SiO₂ residues in HSPs enhances the selectivity.

Assessment of Volatile Sulfur Compounds in Adult and Pediatric Chronic Tonsillitis Patients Receiving Tonsillectomy

OBJECTIVES

To study the volatile sulfur compound (VSC) concentration profile in chronic tonsillitis patients before and after tonsillectomy, and to evaluate the difference between adult and pediatric (children and adolescents) patients.

METHODS

Thirty adult patients (older than 20 years old) and 30 pediatric patients (younger than 20 years old) who were assigned to get tonsillectomy due to chronic tonsillitis were enrolled in this prospective nonrandomized clinical study. The concentrations of the three main VSCs related to halitosis (hydrogen sulfide, methyl mercaptan, and dimethyl sulfide) were assessed in each patient using a portable chromatograph (Oral Chroma^TM) at 1 day before operation, postoperative 1 day, 1 week, and 2 weeks.

RESULTS

Average concentration of hydrogen sulfide, methyl mercaptan, and dimethyl sulfide preoperatively were 99.5 ppb, 24.6 ppb, and 9.45 ppb in adult patients, and 97.4 ppb, 26 ppb, and 10.5 ppb in pediatric patients, respectively. The concentrations of the three VSCs in both groups were highest in first day after surgery, and decreased signigicantly after 2 weeks compared to preoperative values (P<0.001). There was no significant difference of the concentration of the three VSCs between adult and pediatric patients in any time point.

CONCLUSION

The concentrations of hydrogen sulfide, methyl mercaptan, and dimethyl sulfide decreased significantly after tonsillectomy in chronic tonsillitis patients. The concentrations of the three VSCs were not significantly different between pediatric and adult patients before and after tonsillectomy.