Loading of gentamicin sulfate into poly [lactic-co-glycolic acid] biodegradable microspheres

Objective: In dental treatments, use of carriers for targeted antibiotic delivery would be optimal to efficiently decrease microbial count. In this study, gentamicin was loaded into polylactic co-glycolic acid [PLGA] microspheres and its release pattern was evaluated for 20 days

Methods: In this experimental study, PLGA microspheres loaded with gentamycin were produced by the W/O/W method. The correct morphology of loaded microspheres was ensured using scanning electron microscopy [SEM]. The rate of drug release from polymeric microspheres into the phosphate buffered saline [PBS] solution was measured during a 20-day period using spectroscopy. Data were analyzed using one-way ANOVA

Results: SEM micrographs showed that the produced microspheres had smooth and nonporous surfaces and 30-micron diameter. Assessment of the pattern of drug release from the PLGA microspheres loaded with gentamycin revealed a burst release on day six followed by a stable pattern of release until day 20

Conclusion: Considering the biocompatibility of PLGA and optimal pattern of drug release, PLGA microspheres loaded with gentamicin can be successfully used for infection control and reduction of microbial count in dental treatments

Diagnostic accuracy of digitized images using different resolution settings of digital camera in detection of proximal caries

Objective: When none of digital systems and scanners is accessible and it is essential to have digitized images of conventional radiographs, digital cameras can be used. The Aim of this study was to investigate whether digital images obtained by different resolutions of a digital camera are matched to the original radiographs in evaluation of caries

Methods: In this diagnostic accuracy in vitro study the conventional radiographs of168 proximal surfaces of 84 teeth were produced, Then they were digitized with digital camera in three different resolutions; high [2048x1536], medium [1600x1200] and low resolution [480x460]. Images were stored in Photoshop7.0 software, and were evaluated by5 observers to show the presence and depth of the caries. Cronbach's [alpha] calculated inter-observers agreement and in order to calculate the agreement with original conventional radiographs Kappa index was used

Results: In assessing the presence of caries, the agreement between low, medium and high resolutions with original radiographs were 0.286, 0.235 and 0 respectively. Also, assessing the depth of the caries agreement was reported0.21, 0.338 and 0.412 respectively. In most instances, there was a fair agreement between the different resolutions and original radiographs. The highest interobserver's agreement was reported in diagnosis of the presence of the caries with using high resolution [[alpha]=0.837] and the lowest inter-observer's agreement was reported in diagnosis of the depth of the caries with medium resolution [[alpha]=0.762].There was no significant difference reported in observations of different resolutions and original images

Conclusion: Using of high-resolution cameras did not show a significant difference with medium and low resolutions in caries evaluations. Therefore, considering the increase in the file size and difficulties in cameras selection, using of high-resolution digital cameras is not necessary in order to increase the diagnostic accuracy of digitized images

[ vitro evaluation of the long-term bond strength of two resin cements to enamel and dentin]

In this in vitro study, the long-term bond strength of a self-adhesive resin cement and conventional resin cements to human enamel and dentin was compared. 80 sections of intact human third molars were randomly assigned into eight groups according to the cement type [Rely X Unicem [RXU], Rely X ARC [RXA]], bond substrate [enamel, dentin] and the duration of water storage [24 h or 1 year]. Rods of cements [0.75×1 mm] were prepared on the top surface of specimens using Tygon tubes. The micro-shear bond strengths of specimens were measured by a micro-tensile tester. Data were analyzed using Wilcoxon signed ranks and Mann Whitney tests [alpha =0.05]. The bond strengths of RXA and RXU cements to enamel after 24h were 18.56 +/- 4.08 MPa and 14.99 +/- 4.17 MPa, and after 1 year were 19.41 +/- 6.24 MPa and 15.51 +/- 6.17 MPa, respectively. The bond strengths of RXA and RXU cements to dentin were 13.36 +/- 4.02 MPa and 14.16 +/- 4.69 MPa after 24h, and 14.63 +/- 5.96 MPa and 14.08 +/- 6.72 MPa after 1 year, respectively. Tooth substrate had significant effect only on the shear bond strength of RXA cement after 24h [P=0.01], while no other significant differences were found in this study [P>0.05]. According to the results of this study, one-step self-adhesive and multi-step conventional resin cements were similarly effective in bonding to enamel and dentin after 1 year water storage

Factors affecting the IQ of preterm born children of 4-6 years old

This research was carry out with aim of study of factors affecting the IQ of children 4-6 years old born preterm. This analytical-cross sectional study was carried out on 102 premature children with age 4-6 years old during years 2004 to 2006. The tools used in this study were Wechsler intelligence scale for children and questioner including demographical characteristic. In this study we used t-test and spearman correlation and also SPSS-18 was used to analyze data. In this study there was statistical relationship between normal child development and gestational age, birth weight, maternal education, multiple pregnancies, but there were not any statistical significant relationship between the history of preterm birth and child s gender, consanguinity parents, apgar, mother job. IQ in preterm babies who admitted in the NICU was lower than non-admitted preterm or term babies

Secondary caries in the posterior teeth of patients presenting to the department of operative dentistry, Shahid Beheshti dental school

Objective: Secondary caries is a common problem in dental treatments and its occurrence is attributed to several factors. The present study aimed at assessing the prevalence of secondary caries in posterior teeth of patients presenting to the Department of Operative Dentistry, Shahid Beheshti Dental School

Methods: This descriptive study was conducted on 350 patients with 1,339 posterior teeth restored with amalgam or composite resin. Restorations older than 3 years were evaluated. Data regarding presence or absence of secondary caries, age of restoration, location of receiving dental care, tooth brushing technique and use of dental floss and mouthwash were recorded in a questionnaire. Statistical analysis was done using chi-square test

Results: The prevalence of secondary caries was 26% among the understudy patients. Mesio Ocluso Distal restorations [19.2%] had the highest prevalence of secondary caries. Composite restorations had higher prevalence of secondary caries compared to amalgam restorations [p=0.01]. Teeth restored in private dental offices had a higher prevalence of secondary caries compared to those restored in university clinics [p=0.007]. Patients who used mouthwash had a significantly lower prevalence of caries recurrence [p=0.05]

Conclusion: The prevalence of secondary caries in patients presenting to the Department of Operative Dentistry of Shahid Beheshti Dental School was higher in the MOD restorations, composite restorations and teeth restored in private dental offices finally it was less in the patients using mouthwash

Effect of thermal and mechanical aging on flexural strength of zirkonzahn and mamut zirconia ceramics

Objective: Despite the high strength of zirconia restorations, aging in the oral environment and masticatory loading may result in transformation of tetragonal to monoclinic phase and decrease their strength. Statements in this regard are controversial. This study sought to compare the flexural strength [FS] of Zirkonzahn [ZirkonZahn, Cercon, Ceramill] and Mamut [Dubai Medical Equipment LLC, Dubai, UAE] zirconia ceramics and assess the effect of thermal and mechanical aging on their FS

Methods: In this in vitro experimental study, 40 bar-shaped specimens measuring 20×5×2 mm were cut from Zirkonzahn and Mamut zirconia blocks and polished. Specimens in the aging groups were subjected to thermocycling [12,000 cycles, 5-55[degree sign], dwell time of 20 seconds]. Next, they were subjected to mechanical stress in a chewing simulator [40,000 cycles, 200N force]. The three-point flexural strength [TPFS] was determined in megapascal [MPa] using a Universal Testing Machine at a crosshead speed of 0.5 mm/min. Data was analyzed using two-way ANOVA

Results: The mean and standard deviation [SD] of TPFS of Zirkonzahn and Mamut specimens in the no aging group was 809.57 [205.95] and 708.53 [158.72] MPa, respectively. These values were 810.53 [158.96] and 839.06 [217.49] MPa for the Zirkonzahn and Mamut specimens subjected to aging, respectively. Type of zirconia [Zirkonzahn or Mamut] and exposure to aging process [p=0.27] had no significant effect on TPFS of specimens

Conclusion: Within the limitations of this study, the results showed that the process of aging did not decrease the TPFS of Zirkonzahn and Mamut specimens. Thus, these ceramics may be successfully used in the clinical setting

Dental students' perceptions on restorative dentistry education in Shahid Beheshti dental school

Objective: Numerous studies have emphasized on the importance of developing an ideal educational system for high-quality dental education. The present study sought to assess the perception of dental students on operative dentistry education in Department of Restorative Dentistry, Shahid Beheshti Dental School, Tehran, Iran

Methods: In this descriptive cross-sectional study, 220 students were selected and given a questionnaire including demographic , grades in operative dentistry clinical and didactic courses, the efficacy of preclinical courses in preparing students for clinical practice, ways to improve competency and expertise of students for clinical setting, student's opinion on relating the assessment tests with the taught topics, required instructional resources for assessment of students' proficiency in restorative dentistry and satisfaction rate of students with clinical courses offered in the current curriculum. Data were analyzed using descriptive statistics [SPSS 18]

Results: The Clinical Operative Dentistry 3 and Preclinical Dental Anatomy received a mean satisfaction score of 3.31 and 2.74, respectively. Furthermore, 57.3% of students highly emphasized the necessity of studying textbooks of restorative dentistry. 50.5% of students believe that lectures by instructors along with active participation of students were the best method for didactic operative dentistry courses. In addition, 60.5% were in favor of using a combination of textbooks, lectures, and class notes for the assessment of students' learning

Conclusion: The present study revealed that Department of Restorative Dentistry in Shahid Beheshti Dental School is successful in its teaching and achieving students' satisfaction. However, some revisions need to be made in educational methods and contents and active participation of students in class discussions should be encouraged as well

microshear bond strength of composite-composite after salivary contamination

Contamination leads to decreased bond strength causing failure of restorative treatments. The present study evaluated micro-shear bond strength of composite-composite after saliva contamination and searched for the best method to maintain primary bond strength. In this in-vitro trial, specimens made by Z100 composite resin were divided into 7 groups each containing 15 samples and were prepared as follows: Group 1- Control [no contamination], Group 2: Saliva+air drying, Group 3- Saliva+rinsing+ air drying, Group 4- Saliva+ rinsing+ air drying+ etching, Group 5- Saliva+ rinsing+ air drying+ etching+ bonding, Group 6- Saliva+ alcohol, and Group 7- Saliva+ 0.5 mm removal of composite+ rinsing + air drying. Z100 composite was added through tiny tubes [0.7x1 mm] to the prepared surfaces and cured. The microshear bond strength was then determined. Data were analyzed using ANOVA and Tukey's multiple comparison tests. Mean and standard deviation of the microshear bond strength was 23.0 +/- 3.60 MPa in group 1, 11.71 +/- 2.49 MPa in group 2, 17.60 +/- 4.25 MPa in group 3, 21.84 +/- 6.34 MPa in group 4, 21.25 +/- 7.58 MPa in group 5, 21.65 +/- 5.53 MPa in group 6 and 17.34 +/- 5.95 MPa in group 7. Differences between groups 1 and 2 [P<0.0001], 2 and 4 [P<0.0001], 2 and 5 [P<0.001] and 2 and 6 [P<0.0001] were statistically significant. The results of this study showed that air drying of the surface after saliva contamination decreased microshear bond strength significantly. All cleansing methods increased bond strength of the specimens up to thatof the control group