Background: Although childhood cancer accounts for a small percentage of total cancer cases globally, it remains a critical public health issue. Studying the incidence of childhood and adolescent cancer in Ulaanbaatar, where nearly half of Mongolia's population resides, is essential for improving diagnosis and treatment quality. Objective: To investigate the patterns and trends of new childhood and adolescent cancer cases in Ulaanbaatar from 2015 to 2024. Material and Method: A descriptive cross-sectional study was conducted. Based on statistical data from the Center for Health Development, incidence rates per 100,000 population were calculated and analyzed using STATA 14.2 software. Results: A total of 516 new cases were recorded during the study period, with an average incidence rate of 9.0 per 100,000 population. The incidence increased by 35.2%, rising from 8.8 in 2015 to 11.9 in 2022. Regarding cancer types, hematological and lymphoid malignancies dominated (50%). The highest incidence was observed in the 0–4 age group (12.5). The male-to-female ratio was 1.4, showing a male predominance. By district, the highest overall incidence rates were observed in Bayangol (10.3 per 100,000), Songinokhairkhan (9.6), and Bayanzurkh (9.4), while the lowest rates were observed in Nalaikh (4.7) and Bagakhangai (0.0). Conclusion The incidence of childhood cancer in Ulaanbaatar has shown an increasing trend over the last decade. The patterns of cancer types, age, and sex distribution are consistent with international and Asian regional trends.

Background: Conventional methods for assessing exposure to environmental tobacco smoke rely mainly on questionnaires and biomarkers with short half-lives, such as urinary cotinine. In contrast, oral mucosal pigmentation may represent a visible, non-invasive biomarker of chronic exposure. However, its clinical and policy relevance, as well as its validity for screening purposes, remain insufficiently established. Aim: To summarize the evidence on the association between exposure to environmental tobacco smoke and oral mucosal pigmentation and to assess some confounding factors. Materials and Methods: We synthesized findings from observational studies that examined the association between environmental tobacco smoke exposure and oral mucosal pigmentation across all age groups. International electronic databases, including PubMed, Embase, Web of Science, and Scopus, were searched. Data were extracted on exposure–response relationships, measurement instruments, anatomical distribution of pigmentation, confounding by physiological pigmentation, and biochemical validation. The quality of included studies was assessed using the Mixed Methods Appraisal Tool (MMAT). A narrative synthesis was conducted, focusing on the biological plausibility of the biomarker, standardization of measurement, and its potential implications for screening and tobacco control policy. Results: Thirteen observational studies from seven countries, involving a total of 3,284 participants, met the inclusion criteria. Four studies reported a statistically significant association between duration of exposure and severity of pigmentation, while one cohort study showed that urinary cotinine levels increased with age among children. The Gingival Pigmentation Index and the Dummett Oral Pigmentation Index were the most commonly used assessment tools; however, methodological heterogeneity limited direct comparability across studies. The anterior gingiva was the most frequently affected anatomical site. Only a limited number of studies adequately controlled for physiological pigmentation, and skin color was identified as an important confounding factor. The pooled odds ratio was 2.35; however, the certainty of evidence was low due to the observational nature of the included studies. Conclusion Oral mucosal pigmentation may serve as a potential biomarker of long-term exposure to environmental tobacco smoke. Nevertheless, standardized assessment protocols, adequate control for physiological pigmentation, and validation against “gold-standard” biomarkers are required. If validated, this marker could be used for rapid identification of high-risk groups and incorporated into tobacco control policies.

Background: Passive smoking among children remains a serious public health concern, particularly because children’s ability to avoid household environmental tobacco smoke exposure is limited when parents smoke. In recent years, increasing scholarly attention has been given to oral mucosal pigmentation as a potential clinical sign of long-term passive smoking in children. However, no previous study has synthesized the available evidence on this topic. Aim: This systematic review and meta-analysis aimed to evaluate the association between passive smoking and oral pigmentation in children. Materials and Methods: A systematic search was conducted in international electronic databases, including PubMed, Scopus, Web of Science, and the Cochrane Library, in accordance with PRISMA guidelines. Observational studies assessing the association between passive smoking and oral pigmentation among children aged ≤18 years were included. Methodological quality was assessed using the Mixed Methods Appraisal Tool (MMAT). A random-effects meta-analysis was performed, and pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Between-study heterogeneity was assessed using the I² statistic, and the certainty of evidence was evaluated using the GRADE approach. Results: Seven studies involving a total of 1,582 participants met the inclusion criteria. The meta-analysis demonstrated that passive smoking was significantly associated with an increased risk of oral pigmentation in children, with a pooled OR of 2.58 (95% CI, 1.35-4.95; p=0.004). Compared with children without exposure to passive smoking, those exposed to environmental tobacco smoke had an absolute risk increase of 17% (95% CI, 6.3%-23.9%). Subgroup analysis by assessment method showed a consistent effect among studies using the Gingival Pigmentation Index (GPI) (OR, 2.12; 95% CI, 1.58-2.84), whereas studies using the Dummett Oral Pigmentation Index (DOPI) showed a wider confidence interval (OR, 3.26; 95% CI, 0.68-15.54). According to the MMAT assessment, the included studies demonstrated adequate participant selection in 100% of cases, appropriate outcome measurement in 76.9%, and adequate control of confounding factors in 46.2%. Owing to the observational nature of the included studies, moderate heterogeneity, and the potential risk of confounding by physiological pigmentation, the certainty of evidence was rated as low according to GRADE. Conclusion Children exposed to environmental tobacco smoke had a significantly higher likelihood of oral mucosal pigmentation than unexposed children. These findings suggest that screening for oral mucosal pigmentation during pediatric oral examinations may serve as a non-invasive marker of passive smoking exposure and may provide visible clinical evidence to support counseling parents on smoking cessation and smoke-free household environments.

Background: Mongolia ranks first in the world for liver cancer incidence and mortality, with more than 95% of cases associated with hepatitis B virus infection. Healthcare professionals are considered a priority group for vaccination. Aim: To investigate the level of hepatitis B virus immunization among dental specialist physicians. Materials and Methods: This retrospective, observational, analytical cross-sectional study was conducted with approval from the Research Ethics Committee of the Mongolian National University of Medical Sciences (MNUMS). We analyzed serum test data from 76 dentists officially registered in the Dentistry residency program during the 2025–2026 academic year, assessing hepatitis B virus infection status and immunization levels. Statistical analysis of quantitative data was performed using SPSS version 27. Results: Data from 76 dentists were analyzed. The mean age was 28.5±6.2 years; by age group, 70% (n=53) were aged 20–29 years, 22.3% (n=17) were 30–39 years, and 7.8% (n=6) were over 40 years (p<0.05). By sex, 13.2% (n=10) were male (p>0.05). Among the study participants, 97.4% were HBV-negative with a mean age of 28.2±5.3 years (Median: 27.0, IQR: 24.0–31.0), whereas 2.6% were infected; the mean age of infected physicians was 43.5±2.1 years (Median: 43.5, IQR: 42.0–45.0), indicating a high and statistically significant occurrence of HBV infection in the age group over 40 years (Fisher’s exact test, p=0.05). When classified by immunity level, 29.2% (n=19) had anti-HBs levels below 10 mIU/mL (insufficient), 24.6% (n=16) had anti-HBs levels of 10–99 mIU/mL (weak), and 46.2% (n=30) had anti-HBs levels above 100 mIU/mL (adequate immunity); however, no statistically significant association was observed between age groups and protective antibody levels (Fisher’s exact test, p=0.892). Conclusion Among participants, the prevalence of hepatitis B virus infection was 2.6%, vaccination coverage was 85.5%, and anti-HBs antibody titers were adequate in 46.2%.

Background: Although a considerable number of oral health studies have been conducted among children in Mongolia, most have focused on dental caries in school-aged children, and data on non-carious oral conditions in preschool children remain scarce. Aim: To determine the prevalence of oral mucosal, gingival and traumatic dental conditions among preschool children in Ulaanbaatar. Materials and Methods: In this cross-sectional pilot study, 686 children from six randomly selected kindergartens in Ulaanbaatar underwent oral examination in accordance with the World Health Organization (WHO) 2013 guidelines, using the WHO Oral Health Assessment Form for Children. The main outcomes were oral mucosal changes, including pigmentation, gingival bleeding, dental trauma and dental erosion. Analyses were restricted to the 598 children with complete records for these outcomes, and frequencies, percentages and Wilson 95% confidence intervals (CIs) were calculated using this common denominator (n=598). Results: Of the 598 children analysed, 86 (14.38%; 95% CI 11.80–17.42%) had at least one of the four main conditions. Dental erosion was observed in 74 children (12.37%; 95% CI 9.97–15.26%), confined to the enamel in 45 (7.53%) and extending into the dentine in 29 (4.85%). Oral mucosal changes were recorded in 10 children (1.67%; 95% CI 0.91–3.05%), gingival bleeding in 7 (1.17%; 95% CI 0.57–2.40%) and dental trauma in 1 (0.17%; 95% CI 0.03–0.94%), whereas oral mucosal pigmentation was observed in 64 children (10.70%; 95% CI 8.47–13.44%). Of the 86 children with findings, 85 (98.84%) attended two of the six participating kindergartens. Conclusion When dental caries was excluded, dental erosion was the most prevalent condition among preschool children, whereas oral mucosal changes, gingival bleeding and dental trauma were observed in a small proportion of children. The concentration of these findings in two of the six kindergartens may reflect local demographic and socioeconomic factors, as well as differences in examination and recording practices. Future studies should therefore standardise examination criteria in advance and include a larger number of kindergartens.

Background: The capital city of Mongolia, Ulaanbaatar is not only one of the coldest capitals in the world but has also become one of the most polluted cities in recent years due to the prolonged effects of severe cold. According to the World Health Organization (WHO), the most harmful air pollutant to human health is PM2.5. These fine particulate matters can penetrate the human body through the respiratory tract, causing various changes in the body and the oral cavity. Aim: Relationship between dental caries, gingivitis and periodontal status and PM2.5 air pollutant levels among 12 years old children in different areas of Ulaanbaatar. Materials and Methods: The study population consisted of 190 children aged 12 years old, who were selected from high and low level areas with air pollutant PM2.5 in Ulaanbaatar city, Mongolia. We obtained informed consent No.24-25/10-1 of the Ethical Committee, MNUMS. The oral examination of every child was done according to WHO recommendation (2013). We determined the prevalence of dental caries and mean DMFT score, and the prevalence of gingivitis, and CAL score. Statistical analysis was done by the SPSS 29 software. Results: The prevalence and mean DMF/t score of dental caries were 96% аnd 5.37±2.75 among children living in the high level area of the PM2.5 air pollutant; and 91% and 5.39±3.95 in the low level area, respectively (p<0.01). The prevalence of gingivitis was 23.2% among all children; 25.2% among children living in the high level area of the PM2.5 air pollutant and 20.5% in the low level area. The CAL score was 1.89±0.89 mm in the high polluted area and 1.94±0.77 mm in the low polluted area (p<0.001). Conclusion The prevalence of dental caries and gingivitis and the mean DMFT and CAL score among children living in air polluted areas were higher than low polluted areas.