Journal of Dental Medicine

Background and Aims: Poly methyl methacrylate (PMMA) is still the most commonly used material in prosthetic dentistry. However, there are problems with the mechanical properties of this type of material including low flexural strength. Addition of nanoparticles into the polymer is one way to improve the mechanical properties of acrylic resin. In the present study, the effect of silicon dioxide (SiO₂) nanoparticles addition into the heat-cured acrylic resin in different concentrations was investigated. Because of the controversy had been observed in previous articles, the aim of this study was to investigate the mechanical properties of PMMA/SiO₂ nanoparticle obtained from different percentages of SiO₂.
Materials and Methods: In this in-vitro study, acrylic resin specimens containing 0, 1, 3 and 5% silicon dioxide (SiO₂) were prepared. The specimens were placed inside the gypsum molds and placed under pressure for three times. The mold cured in boiling water for 30 min. A trimmer was used to remove the additives. Sandpapers with 180, 320 and 600 grains of silicon-carbide were used for final finishing and polishing. Finally, the flexural strengths were measured using a universal testing machine. Data were finally analyzed by ANOVA and Tukey tests at a significant level of 5% using SPSS software.
Results: The mean flexural strengths and standard deviations of control group, 1% filler, 3% filler, and 5% filler, were 57.24±8.30, 69.98±7.26, 60.16±9.18, and 61.59±9.28 MPa, respectively. After comparing significant values between each group with the control group, a significant difference was observed between the control and 1% filler group (P=0.021). However, no significant difference was observed between 3 and 5% fillers with the control group or each other. The significant differences (P-value) between 3% filler and control group were 0.892 and between 5% filler and control group was 0.975.
Conclusion: The results of the present study showed that the use of low percentage of silicone dioxide (SiO₂) nanofiller could improve the flexural strength of poly methyl methacrylate acrylic resin.

Background and Aims: Numerous researches have been conducted in the field of dental public health in the country so far, and therefore the purpose of this study was to investigate the distribution of studies conducted in this field in terms of quantity and coverage of different subjects.
Materials and Methods: This study was conducted in 4 phases in Iran in 2023. The initial phase or the comparative study was to extract the doamins and sub-domains related to the dental public health studies, types of the research dissemination models, and the list of researchers in this field. The second phase included holding virtual Delphi meetings with researchers to finalize the information collecting checklists including the domains and sub-domains. In a virtual group of about 140 researchers, the domains and their proposed sub-domains were discussed and revisions continued until consensus was reached. In the third phase, the necessary data were collected and entered into the forms. The main source for data collection was google scholar profile. The final phase included the design of the system in the Access program for archiving and classifying information with the ability to search and report. Finally, the frequency and relative frequency of research titles were categorized according to the topic and the university conducting the research and the reports presented in the form of graphs and tables.
Results: Based on the first and second phases of the study, the selected model had 6 domains and 11 sub-domains. Epidemiology with the largest share (35%) was first rank, and the health system (30%) and health promotion (19%) ranked second and third, respectively. Ethics (1%) was at the lowest rank. Universities of Tehran (33%), Isfahan (25%) and Shahid Beheshti (22%) had the most publications in the field of community oral health. In the domian of epidemiology, oral health surveys with 204 articles (74%) and oral health risk factors with 69 articles (26%) were the highest number of published articles.
Conclusion: Some sub-domains of the community oral health filed are not well covered that might interrupt their application to improve the oral health situation in the country.