Background: The development of caries is dependent on the interaction of four primary factors. These are a host (tooth surface), a substrate (food), the presence of oral bacteria, and time. Caries will not develop if any of these four primary factors are not present. Although the primary molars are naturally replaced by the age of 10–12 years, caries, pulpitis, periapical periodontitis, primary molar defects, even loss of primary molars can have adverse effects on the permanent teeth. The bite force is created by the dynamic action of the muscles during the physiologic act of mastication. Determination of individual bite force level has been widely used in dentistry, mainly to understand the mechanics of mastication for evaluation of the therapeutic effects of prosthetic devices and to provide reference values for studies on the biomechanics of prosthetic devices. Methods: The 4-5 year olds who were treated at the National University of Medical Sciences, School of Dentistry, Dental Hospital were admitted to this study. The magnitude of the bite force in Newtons (N) was measured (Occlusal Force Meter GM10) bilaterally corresponding with the 1st and 2nd primary molars using a specifically designed single tooth bite force gauge. Results: Fifty three children were included in the study. The prevalence of dental caries was found to be 66.04% respective. No significant differences were found between the male and the female in bite force and p values of the study. Analysis of variance evaluated difference among the three groups. The means of maximum bite force were 258.83, 216.43 and 189.15 N for the groups. Significant differences between first molar and second molar’s occlusal surface area were detected. The analysis of correlation showed that the caries and bite force presented weak inverse (r=-0.36) correlation. Conclusion The bite force of 4-5 years old children was independent of gender, body weight, body height and side of mastication. The bite force on teeth with caries were 189.15 N. The caries was in weak inverse correlation with the bite force quantity. The amount of bite force measured was dependent on tooth occlusal surface area.

Introduction : Intravascular ultrasound (IVUS) is an advanced technology used to guide percutaneous coronary intervention (PCI) in patients with stable coronary artery disease (CAD). Goal: This study aims to describe the first successful implementation of IVUS in patients with stable CAD in Mongolia. Materials and Methods : Patients with CAD who underwent either CAG or IVUS-guided PCI were prospectively selected. All patients provided informed consent, which was approved by the Ethical Committee of the Ministry of Health of Mongolia (March 17, 2023, №23/014). For patients who underwent CAG-guided PCI, stent deployment was performed under conventional CAG guidance, while stent implantation was performed under IVUS guidance in patients who underwent IVUS-guided PCI. Stent restenosis at 1-year follow-up was selected as the primary endpoint. The differences between the CAG-guided PCI and IVUS-guided PCI groups were compared using independent sample t-tests and chi-square tests. The association between treatment strategy (CAG-guided PCI vs. IVUS-guided PCI) and all cause restenosis (the study endpoint) was analyzed. Results: A total of 51 patients with stable coronary artery disease (CAD) who underwent coronary angiography CAG guided PCI and intravascular ultrasound (IVUS)-guided PCI were included in the present study. The mean age was 63±9.44 years, with 88.2% male (n=45). In the IVUS-guided PCI group, the minimal lumen area (mm²) was 4.46±1.1, and after stenting, the minimal stent area was 8.59±0.5, showing a statistically significant difference (p<0.001). The stent restenosis rate at 1-year follow-up in the CAG-guided PCI group and the IVUS-guided PCI group were 16% and 3.84%, respectively. The restenosis rate in the IVUS-guided PCI group was lower than in the CAG-guided PCI group. Conclusion Complete expansion of the stent on the coronary artery wall is effective in improving long term outcomes of PCI, and IVUS guided coronary artery intervention has better long-term results compared to angiography-guided PCI group (96.1% vs 84%).