مجله تحقیق در علوم دندانپزشکی
سال هشتم شماره 2 (پیاپی 28، تابستان 1390)

Antimicrobial effects of nano silver particles have received enormous attention in medical and dental applications. Despite of wide spread use of nanosilver there is not enough studies about its side effects on human. Some studies have exhibited cytotoxicity of nano-silver particles. This research was designed to investigate the cytotoxic effect of nano silver particles on L929 fibroblasts cells, by MTT assay. In this experimental study, nano silver particles with 5,10,20,30,40 and 50 ppm concentration were exposed to 10.000 L929 fibroblast cells then cell vitality was assessed after 2,24,48 and 72 hours by MTT method. The light absorption was evaluated by Elisa Reader and recorded. Data was subjected to ANOVA test for statistical analysis. In all concentration groups, vitality of cells were the least after 24 hours, but the vitality of cells increased after 48 hours. The increase after 48H was statistically significant (p<0.05). Also concentrations more than 20 ppm in 2,24 and 48 H were significantly cytotoxic for fibroblasts. Nano silver particles at concentrations less than 20 ppm after 72 hours did not have toxic effects.

Quality and quantity of cells attachment to retrograde filling materials, determines its biocompatibility, the aim of this study was comparison of quantity of fibroblasts cell attachment to three retrogradefilling materials: Geriostore, MTA and CEM

In this invitro study, eight discs from each retrofilling materials were prepared and placed in fibroblasts culture, then specimens were fixed in Osmium and different concentration of alchohol, after three time periods of 24,48 hours and one week, fibroblast cells counting was done by scanning electron microscope (SEM) and data were analyzed by one way Anova and Tukey Tests.

The result showed that fibroblasts cell attachment to CEM were (1.4 ± 0.24),(8.6 ± 0.4),(8.2 ± 0.2) to MTA were (0.4 ± 0.24), (2.8 ± 0.96),(6.8 ± 0.37) and to Geriostore were (0.6 ± 0.2),(0.4 ± 0.2),(0.2 ± 0.2) in 24, 48 hours and one week respectively. There was significant differences between three materials in every periods of time. (p<0.05)

the most fibroblasts cell attachment related to CEM in 72 hours and the least one was Geriostore in one week period. Cell attachment increased with increasing the time in CEM and MTA but decreased in Geriostore.

Detection of Horizontal root fracture is completely related to radiography and application of new methods is indispensable. The aim of this study was to compare the diagnostic accuracy of reverse contrast option of digital radiography with original images for detection of horizontal root fracture. In this diagnostic study, digital radiographs were taken from 40 maxillary anterior teeth mounted in a dry alveolar socket with vertical angles of 0° and 15 ⁰. Root fractures were created in the horizontal plane on each root and after relocating root fragments radiographs were repeated in a same position. Images were processed with reverse contrast option and assessed by observers. Data were analyzed with proportion test and Cochran’s Q test. There was no significant difference in sensitivity, specificity, PPV(Positive Predictive value) and NPV (Negative Predictive Value) between 0° and 15°radiographs in original and reverse contrast images. In either image groups, when fractures were certainly diagnosed by observers, 0°radiographs obtained higher sensitivities (P=0.014); Also when fractures were likely diagnosed, sensitivity and NPV were significantly higher for 0°radiographs (P=0.035), (P=0.023)respectively. The diagnostic accuracy of reverse contrast option of digital images are equal to original images, although 0° radiographs are more appropriate.

Equipments and surfaces in dental clinics and centers are always in risk of contamination. When there is no possibility of sterilizing them, fast acting disinfecting agents are used. In this study, antibacterial effect of a new disinfecting solution, named Nanex,against streptococcus mutans and pseudomonas aeroginosa was compared with pure Nano silver solution and Deconex 53 plus. In this experimental study, in order to determine the effective antibacterial concentration, serial dilution technique, evaluation of (MIC) and (MBC) were used. Finally bacterial growth was assessed. The # 4 solution (containing 100 ppm Nano silver and 2% Deconex) showed the least MIC and MBC for streptococcus mutans. The # 7 solution (containing 133 ppm Nano silver and 1% Deconex) showed the least MIC and MBC for psuedomonas aerogenosa. Thus, antibacterial effect of Nanex solution was more potent and effective than pure solution of nano silver and deconex.

Hurmonal changes during pregnancy can change many organs of the body such as oral cavity and saliva. The purpose of this study was to compare of calcium, phosphor and total protein and antioxidant levels of prepregnancy and each trimester of pregnancy. 30 women referring for consultation with gynecologist were selected for this semi-experimental study. Their whole unstimulated saliva was collected at that session and at every trimester. The salivary composition mentioned above was measured by spectrophotometry. Data was analysed by repeated measure test and and paired t-test. There was significant difference in phosphor, protein, total antioxidant level of saliva in prepregnancy and during pregnancy (p<0/01),(p= 0/01) respectively. There was no significant difference in salivary calcium rate of prepregnancy and during pregnancy. (p=0/08). During pregnancy the rate of salivary phosphor and total antioxidant was increased. Protein level was decreased but calcium level was not changed.

Dimensional stability of die is very important factor in fixed prosthodontic treatments and different impression techniques is one of the most factors in this specify, the aim of this study was comparison of three impression. Techniques: one step and two step with out spacer and two step with spacer on die dimensional variation. This experimental study, was carried out using laboratory stainless steel master models that contained three complete crown abutment preparations with 22 mm distance, 7 mm diameter 7.5 mm height and 3 ° convergence. To prepare master casts three impression techniques was done by using president silicone impression material. Twelve impression were taken for each technique and Elite Rock tip IV casting material was used to prepare stone models. Profile projector and micrometer were used to measure different dimensions of laboratory model. Anova test were used for data analysis. The study was carried out on 36 impressions in three groups. The measurement location for crowns distances and height of the main model to the impression methods (p<0.4) and in HC distance is similar. The results in main model was 7.4+0.06, in one step 7.37+0.04, in two steps 7.31+0.03 and in 2 steps with space was 7.33+0.05 micrometers (p<0.6). It seems the impressions methods do not affect on the dimensional changes of die and their dimensional changes are not significant. The study on other related factors on dimentional changes of die is recommended.

Pit and fissure sealant, as a part of community oral health program, is performed with the purpose of caries prevention (reduction) in the permanent teeth. The purpose of this study was to evaluate the effect of the pit and fissure sealant performed in the community oral health program in caries prevention of the first permanent molars. This research was performed in the form of a historical cohort study. The fissure sealant program has been started in the Community Center of Zahedan dental school since 2005. The dental status of children who attended in the sealant program (case group: n=134) was compared with the children from the same area who were not exposed to the program (control group: n=134) 3 years after the implementation of the program. The findings of dental caries in the case and control groups were analyzed by χ2 and t-test. The mean age of children at the time of sealant placement was 6.7 years and average of 38 months had passed after its placement. Dental caries in the case and control group was 14% and 21.6% respectively (p<0.001). The risk of caries incidence in control group in comparison of the case group was 1.5 (RR). The pit and fissure sealant program was successful in caries prevention of occlusal surfaces, although it showed less effectiveness compared to other studies.

Mental foramen is one of normal anatomic landmarks of mandible witch is positioned bilaterally. Radiologic position of this landmark was studied in most of populations but so far, there is no precise study in Iranian population. The aim of this study was radiographic evaluation of location and shape of mental foramen in a selective Iranian population. This descriptive-analytic study was conducted on 190 panoramic radiographs of patients referring to radiology department of Tabriz dental school for diagnostic purposes, Obtained radiographs were evaluated by two trained radiology specialist in the following manner: Location of mental foramen in relationship with long axis of mandibular teeth on both sides, location of mental foramen in relationship with posterior border of ramus and midline, the vertical position of mental foramen in relationship with lower border of mandible and alveolar crest, assessment of bilateral symmetry and determination of shape of foramen on both sides. The most common location of mental foramen was between first and second premolar of mandible on both sides. The most common shape of foramen on both sides was round and foramens on both sides in 83.68% were symmetric. Significant differences were between our study and other studies in regard to position and shape of mental foramen and the most important justification for these differences is the issue of race differences.