ABSTRACT
OBJECTIVES: Optimum viewing conditions facilitate identification of radiographic details and decrease the need for retakes, patients' costs and radiation dose. This study sought to evaluate the effects of different viewing conditions on radiographic interpretation. MATERIALS AND METHODS: This diagnostic study was performed by evaluating radiograph of a 7mm-thick aluminum block, in which 10 holes with 2mm diameters were randomly drilled with depths ranging from 0.05 mm to 0.50mm. The radiograph was viewed by four oral radiologists independently under four viewing conditions, including a white light viewing light box in a lit room, yellow light viewing light box in a lit room, white light viewing light box in a dark room and yellow light viewing light box in a dark room. Number of circular shadows observed on the film was recorded. The data were analyzed by two-way ANOVA. RESULTS: The mean number of detected circular shadows was 6.75, 7.5, 7.25 and 7.75 in white light viewing light box in a lit room, white light viewing light box in a dark room, yellow light viewing light box in a lit room and yellow light viewing light box in a dark room, respectively. Although the surrounding illumination had statistically significant effect on the radiographic details (P≤0.03), the light color of the viewing light box had no significant effect on visibility of the radiographic details. CONCLUSION: White and yellow light of the viewing light box had no significant effect on visibility of the radiographic details but more information was obtained in a dark room.
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OBJECTIVE: Bond failure of brackets during orthodontic treatment is a common problem; which results in treatment interference, increased treatment time and prolonged clinical time for rebonding of failed brackets. The purpose of this study was to evaluate the effects of Coca-Cola and a non-alcoholic beer on the shear bond strength and adhesive remnant index (ARI) of orthodontic metal brackets in vitro. MATERIALS AND METHODS: Eighty intact human premolars were divided into two experimental groups of Coca-Cola and non-alcoholic beer (Istak), and a control group of artificial saliva. Over a period of thirty days, the test groups were immersed in the respective soft drinks for 5 minutes, twice a day. For the remainder of the time, they were kept in artificial saliva at 37°C. The control group was stored in artificial saliva during the experiment. All samples were subjected to shearing forces using Universal Testing Machine. ARI was determined with a stereomicroscope at ×12 magnification. The data of shear bond strength were statistically analyzed by one-way ANOVA and Tukey's Post-Hoc test and the data of ARI scores were analyzed by Kruskal-Wallis test. RESULTS: No significant difference was observed in ARIs of the three groups (P≤ 0.552). The shear bond strength of Coke group was significantly lower than that of the two other groups (P≤ 0.035); but there was no significant difference between the shear bond strength of Istak and the control group (P≤ 0.999). CONCLUSION: Coca-Cola decreased the shear bond strength of orthodontic brackets.
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OBJECTIVE: Successful endodontic therapy depends on adequate mechanical and chemical debridement of the canal which requires knowledge of the canal morphology. Conventional radiography has been used to evaluate the canal type; however, direct digital radiography has recently been practiced for this purpose due to the shortcomings of conventional radiography. The aim of the present study was to compare the accuracy of digital and conventional radiography taken at 0° and 30° angles in the diagnosis of the canal type of extracted maxillary premolars. MATERIALS AND METHODS: This diagnostic study was performed on 90 extracted maxillary premolars. Conventional and digital radiographies were taken of all teeth at 0° and 30° horizontal angles. The images were assessed by an oral and maxillofacial radiologist. The clearing technique was used as the gold standard. The canal type was determined using Weine classification. The agreement between each one of the 4 radiographic modalities and gold standard was determined by kappa statistics. RESULTS: The kappa values for the agreement of parallel conventional, 30° conventional, parallel digital and 30° digital modalities with the clearing technique were 0.059, 0.215, 0.043 and 0.391, respectively. Parallel modalities were unable to determine the tooth canal type. Radiographic images taken at 30° significantly determined the canal type, although only a poor level of agreement was noted between the two modalities and the clearing technique. CONCLUSION: All modalities had limited value to determine the root canal type in maxillary premolars. However, direct digital imaging taken at 30° angle showed the highest accuracy for canal type assessment.
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OBJECTIVE: This study compared the push-out bond strength of EndoSequence Root Repair Material (ERRM) and Bioaggregate (BA), new bioceramic materials, to that of mineral trioxide aggregate (MTA) after incubation in phosphate-buffered saline (PBS), a synthetic tissue fluid, for either 1 week or 2 months. MATERIALS AND METHODS: One-hundred and twenty root sections were filled with ProRoot MTA, BA, or ERRM. Each tested material was then randomly divided into two subgroups (n = 20): root sections were immersed in PBS for 1 week or 2 months. The bond strengths were measured using a universal testing machine. After that, the failure modes were examined with stereomicroscopy and scanning electron microscopy (SEM). The push-out data and failure mode categories were analyzed by two-way ANOVA and chi-square tests, respectively. RESULTS: The bond strength of ERRM was significantly higher than that of BA and MTA at both incubation periods. No significant difference was found between the bond strength of MTA and BA at either 1 week or 2 months. Increasing the incubation time to 2 months resulted in a significant increase in bond strength of all the materials. The failure mode was mainly mixed for MTA and BA, but cohesive for ERRM at both incubation periods. CONCLUSION: ERRM had significantly higher bond strength to root canal walls compared to MTA and BA. Increasing the incubation time significantly improved the bond strength and bioactive reaction products of all materials.
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BACKGROUND: The use of photoactivated disinfection has had a significant medical and technological effect in bacterial inactivation, as an alternative to conventional antimicrobial methods. The main goal of this study was to investigate the effect of photoactivated disinfection on Streptococcus mutans, when Radachlorin(®) was used as a photosensitizer. METHODS: Streptococcus mutans samples of two different initial concentrations were treated with Radachlorin(®) gel (0.1%), irradiated by the light of a He-Ne laser (633nm), with energy density of 6J/cm(2), and cell viability was evaluated after culturing. RESULTS: It was observed that the combination of Radachlorin(®) and laser was more effective than Radachlorin(®) or laser alone (p<0.05), in reduction of S. mutans and Radachlorin(®) was cytotoxic, in the dark, only for the lower concentration of bacteria. Lower concentration of S. mutans resulted in higher amount of killing, in the case of using Radachlorin(®) with or without laser. CONCLUSIONS: The photoactivation of Radachlorin(®) using a He-Ne laser could inactivate S. mutans to a significant level. In addition Radachlorin(®) might be cytotoxic in the dark, for the lower concentration of bacteria.
