Journal of Islamic Dental Association of IRAN
Volume:24 Issue: 4, 2013

There are disadvantages in using MTA, such as the extended setting time and the difficulty in its manipulation. The aim of this in vitro study was to compare the primary setting time and surface porosity of two commercial brands of tooth colored MTA. In this experimental study two brands of MTA were evaluated; Group1: ProRoot MTA (Dentsply, USA), and group 2: Angelus MTA (Angelus, Brazil). Five samples of each material were prepared and evaluated for primary setting time with a Gilmore needle according to ISO 6876: 2001 with a cylindrical stainless steel mold (10mm×1mm) in an incubator with 37±1 degrees centigrade and relative humidity of over 95%. Specimens were prepared and observed under a scanning electron microscope (SEM) for surface porosity. Data were analyzed with T-test. Primary setting time of the materials were 38.72±0.61 and 22.46 ± 0.61 ProRoot and Angelus MTA, respectively. Statistical analysis revealed that the differences between setting times of the materials were significant (p<0.001). ProRoot MTA showed better surface characterization compared with Angelus MTA. The primary setting time of Angelus MTA was lower than that of ProRoot MTA but the surface characterization (topography and porosity) of ProRoot MTA was better than that of Angelus MTA after final setting time.

Longitudinal data are frequently obtained in medical studies. When the main aim of a study is marginal modeling of the mean and the correlation structure is considered as a nuisance parameter, the first- order generalized estimating equations (GEE1) is usually an appropriate option. However, when the modeling of correlation structure is considered the aim of a study, the second- order generalized estimating equations (GEE2) may be the first choice for analyzing the available data. The aim of the study was to evaluate application of first- and second-order generalized estimating equations to analyze longitudinal microleakage data. In this study, GEE1 and GEE2 methods were used to analyze data obtained from a study of microleakage in two root- end filling materials (CEM and MTA) in two different thicknesses and two diameters at three different times of measurement (one day, one week and one month after treatment). The obtained results from these statistical approaches were compared in continuous and binary (presence of absence) microleakage data. The results from the GEE1 and GEE2 methods showed that time of measurement, material type, diameter and thickness of filling material had significant effects on (continuous) microleakage rate. In addition, in binary microleakage data, these methods revealed that only time and material type were the significant factors. The correlations between measurements were not significant in continuous data, while they were significant in binary response microleakage data. Since the correlations between pairs of measurements were not significant in continuous microleakage data and the obtained estimates were similar in both GEE1 and GEE2 methods, so the simpler GEE1 method seems to be adequate for these data. In contrast, in binary microleakage data, significant correlations were found between measurements. Therefore, in this case the GEE2 methodology may be used to estimate the correlation structure more efficiently.

Although Wit’s appraisal is a valuable measurement for antero-posterior jaw relationship evaluation in orthodontic patients, occlusal plane detection is difficult in a lot of cases or is challenging due to its various inclinations. In this study a new method for assessment of sagittal skeletal relationship is introduced and the purpose of this investigation is evaluation of correlation between wit’s appraisal and this new method. Lateral cephalograms of 71 orthodontic patients (male and female) from all types of skeletal malocclusions (class I, II, III) were collected and analyzed. Two lines were traced from point A and point B while they were perpendicular to Frankfort Horizontal plane (FH) and also to functional occlusal plane (Wits) and the bothdistances were measured. Pearson Correlation analysis was performed for assessment the relationship between AO´-BO´ distance on FH (q) and wit’s appraisal. Correlation of these variables was evaluated with SNA, SNB, ANB and overjet, separately. The results showed a high correlation of variables using Frankfort Horizontal plane and wit’s appraisal (r= 0.82). Both methods revealed significant statistical relation with SNA, SNB, ANB and overjet (p< 0.05). The highest scores of correlation with ANB were obtained in using both methods. The use of measurement is as much valuable as the usual wit’s measurement and it can be a good alternative in patients when tracing the accurate occlusal plane is impossible or difficult.

Endodontic therapy is considered as one of the most stressful dental treatments. This study was designed with the aim of comparing stress levels during different stages of endodontic treatment among endodontic professionals under- and post-graduate students. In this ex-post facto investigation, three groups including professional endodontists (n=36), undergraduate (n=41) and postgraduate dental students (n=47) were involved by convenience sampling. A questionnaire including 48 items, with five-point scales (very few to very much), was prepared for this study based on interview. The questionnaire was filled out by participants in a self report method. Data were analyzed by multivariate analysis of variance and Scheffe’s post - hoc tests. The stress among undergraduate dental students in all fields were more than those of professionals and postgraduate dental students, except for the stress of local anesthetic injection with lidocaine. Stress levels of all three groups were significantly different in inferior alveolar block injections with lidocaine, with professionals having more stress than under- and post- graduate dental students. The most stressful aspect of endodontic treatment, among the three groups was canal obturation, followed by obturation of the molar canals, preparing molar access cavities in special conditions and taking the final radiographs. The suggested methods offered for occupational stress reduction, was experience and knowledge, adequate knowledge, concentration and self confidence, and trust to God, respectively. The stress among under graduate dental students in all fields was more than professionals and post graduate dental students, except for the stress of local anesthetic injections with lidocaine.

Along with improvements in aesthetics and longevity of restorations, finishing and polishing, can produce potentially injurious temperature rise within the pulp chamber. The purpose of the current study was to find whether different polishing methods and thickness of composites have any effect on temperature rise of composite restorative materials. Sixty composite resin specimens 9 mm in diameter were prepared and assigned to three experimental groups with three sample thicknesses (2, 3 and 4mm). Each group was divided into four subgroups randomly. Polishing in subgroups 1 and 2 (continuous and intermittent dry polishing) and subgroups 3 and 4 (continuous and intermittent wet polishing) was carried out with a slow speed contra-angle hand piece at a medium speed for 120 seconds in a roll on motion. Immediately after polishing, temperature was measured on the top and bottom surface of each sample using a laser thermometer. One and two way ANOVA, Duncan, and paired T-test was used to analyze the data. The mean temperature rise after polishing in different methods was significant; continuous dry polishing produced the maximum temperature rise. In addition, increasing the thickness of composite resin up to 4mm did not significantly affect thermal transfer from the top surface to the base during polishing. Copious use of water coolant during finishing and polishing procedures is considered a simple and effective method for pulpal protection. Increasing the thickness of composite resin does not have a significant role in compensating the heat generated during polishing procedure.

The prevalence of musculoskeletal symptoms in dentists is high although relatively few studies have been conducted in this profession. This study was undertaken to investigate the prevalence of musculoskeletal symptoms (MSDs) and to assess the risk of these symptoms among general dentists in Shiraz, Iran. In this descriptive cross-sectional study the Nordic standard questionnaire and questionnaire pertaining to questions about personal and job characteristics were administered to160 general dentists. Furthermore, the pictures of dentists were taken by camera during dental treatment and the most repetitive postures were selected and assessed by Rapid Upper Limb Assessment (RULA) method. The data were analyzed by SPSS version 16.0 software. A large number of dentists (139 subjects) reported MSDs symptoms in at least one region of their musculoskeletal systems during the past 12 months. The most prevalent MSDs symptoms were neck (105 subjects), shoulders (80 subjects), upper back (76 subjects), wrist/hand (63 subjects), and lower back (55 subjects), respectively. A significant difference was observed between men and women only in the wrist/hand (P>0.05). The results of posture analysis showed that all dentist's postures fell into corrective second and third action levels. The results of this study revealed that the prevalence of MSDs symptoms in dentists was high and MSDs risk levels were intermediate to high. Therefore, it is recommended that in an appropriate training program be contemplated to improve dentists’ awareness regarding MSDs symptoms.

Keratocystic odontogenic tumor (KCOT) is a locally aggressive lesion with a known potential for repeated recurrences. The distinct clinical features and explicit cystic histologic characteristics concurrent with the neoplastic nature of this lesion have led to several studies and comparisons with other odontogenic cysts and tumors. Fascin is an actin-bundling protein which has not been evaluated in odontogenic lesions. The aim of this study was to assess the expression of fascin in KCOT and dentigerous cyst (DC). In this cross-sectional investigation, the paraffin blocks of 18 KCOTs and 9 DCs were selected and subjected to immunohistochemistry using monoclonal antibody against fascin. Staining was scored by estimating the percentage of immunoreactive epithelial cells. Mann-Whitney-U test was applied for statistical analysis (P<0.05). Fascin expression was observed throughout the entire epithelial lining of the DCs, while in 50% of the KCOTs, immunostaining was negative in the basal layer and parakeratinized cells adjacent to the lumen. A statistically significant difference in the expression pattern of fascin was found between the studied KCOTs and DCs (P=0.01). Considering the variation in fascin expression patterns between the sample of KCOTs and DCs in the present investigation, it can be suggested that this protein might have a role in the biologic behavior and pathogenesis of KCOT and DC.

Development of new composite resins is one of the most important technological advances in the field of cosmetic dentistry. The aim of this study was to investigate the effectiveness of different light curing units and composite thicknesses on the shear bond strength composite to dentin. In this experimental in-vitro study, the test groups were composed of 80 dentinal samples, prepared on occlusal surfaces of 80 maxillary premolar teeth and routinely divided into 8 groups of 10. Two cylindrical molds (2×2 and 2×5 mm) were filled in bulk using P60 and Ceram X composites and light cured with LED and QTH light curing units. After curing and 3 months aging in 370c water, shear bond strength of all samples were obtained using a universal testing machine with 1mm/min crosshead speed. One- and three-way ANOVA were used for statistical analysis using SPSS software. The highest mean of shear bond strength (31.75 MPa) was in group (P60, QTH, 2) and the lowest (15.34 MPa) was recorded in (Ceram X, LED, 5). Type and thickness of composites had significant effects on the value of shear bond strength and no significant differences were obtained between two light curing units. The shear bond strengths of P60 and CeramX composites tested were much lower when cured in a 5-mm than in a 2-mm increment. The two types of light curing units tested did not show any significant differences in the amount of shear bond strengths.

Lack of appropriate seal is one of the major problems in composite restorations. Properties of the bonding system can play a crucial role in sealing ability of these restorations. The aim of this study was to evaluate the microleakage of composite restorations with varying irradiation time for curing dentin bonding agents with two different curing devices in class V cavities. In this experimental study, 60 intact extracted human molars and premolars were subjected to standard class V cavity preparations. Cavities were divided to six groups. Following etching, Excite bonding agent was applied and light cured using QTH and LED systems for 20, 30 and 40 seconds and cavities were filled with composite. The filled cavities were subjected to 3000 thermal cycles with 5-55 ° C temperatures. Teeth were immersed into 0.5% basic fushin dye and sectioned occlusogingivally from the restoration middle area and the microleakage was determined using stereomicroscope by a 5-scaled rankings. Data were analyzed by Mann-Whitney and Kruskal-Wallis tests with p<.0.05 as the level of significance. No leakage was found in enamel margins. The type of light curing device did not have any significant effect on dentin margins microleakage (p>0.05). Furthermore, no significant reduction in microleakage scores were observed in the restorations irradiated with different curing times (p>0.05). QTH and LED curing units in 20, 30, and 40 s curing time did not have any significant effect on microleakage of class V composite restoration margins.

Composite resins can play an important role in dentin support and enamel strength via bonding to tooth structure. The purpose of this study was to compare the effects of hybrid and microfilled composite restorations on the fracture resistance of extensively weakened teeth. In this case control study 40 intact maxillary premolars were mounted in transparent acrylic resin blocks. The samples were divided into 4 groups (n=10 each). Group PC comprised of intact teeth, without preparation and restoration. In other three groups MOD preparations with constant depths and converged walls toward occlusal surfaces were prepared. Group NC composed of teeth with preparations but without any restoration. Group HR included prepared and restored teeth using a hybrid composite and Group MR contained prepared and restored samples with a microfilled composite. Samples were thermocycled (500 cycles in 5-55° C), then were placed under compressive loads in a universal testing machine, and the curves were drawn with a software called Test Xpert. Mean fracture resistance in HR, MR, PC, and NC groups were 48.1010, 59.1773, 83.1420, and 21.9220, respectively. There was a statistically significant difference among the groups(P<0.05). The increasing effect of microfilled group on the fracture resistance of restored teeth is significantly more than that of hybrid group.