Intensity output and effectiveness of light curing units in dental offices

Background: The aims of the study were measuring the light intensity of light curing units used in Qazvin?s dental offices, determining the relationship between the clinical age of these units and their light intensity, and identifying the reasons for repairing them. Material and Methods: In this cross-sectional study, the output intensity of 95 light curing devices was evaluated using a radiometer. The average output intensity was divided up into four categories (less than 200, 200-299, 300- 500, and more than 500 mW/cm 2 ). In addition, a questionnaire was designed to obtain information mainly about the type, clinical age, and frequency of maintenance of the units and the reasons for fixing them. Data were analyzed using Kolmogorov-Smirnov, chi-squared, and t-tests ( p < 0.05) on SPSS 24. Results: A total of 95 light curing units were examined, with 61 (64.2%) of them being of the LED type and 34 (35.8%) of the QTH type. While average light intensity in LED units was significantly higher than in QTH devices, the two device types were not significantly different regarding desirable light intensity (i.e., ? 300 mw/cm 2 ). A negative correlation was observed between clinical age and light intensity. In addition, bulb replacement in QTH devices was over three times as much as in LED units. Also, repairing QTHs was more than twice as much frequent as fixing LEDs. The most common reason for repair was the breakage of the tip of the device. Conclusions: The light intensity of LED units is significantly higher than that of QTH devices, and the frequency of repairing in QTHs was significantly more than in LEDs. Furthermore, light intensity decreases with aging, and dentists should regularly monitor the conditions of light unit

Microleakage comparison of resin modified glass ionomer and OrthoMTA used as a coronal barrier in nonvital teeth bleaching

Background and Aim: Common causes of dental discoloration include trauma, drugs, genetic defects, decay, and age. In order to correct discoloration of pulpless teeth, internal bleaching is recommended. The aim of this study was to compare microleakage of resin modified glass ionomer and OrthoMTA used as an intraorifice barrier in non-vital bleaching. Methods: In this experimental study, 36 extracted mandibular premolars were selected and randomly divided into two experimental (n = 16) and two control groups (n = 2). 2mm of OrthoMTA and RMGI cements were placed as intraorifice barriers in the experimental groups. Subsequently, we placed a mixture of sodium perborate and 30% hydrogen peroxide as internal bleaching material into the canal and replaced it every three days. Leakage was measured using pH diffusion method by a digital PH meter. Data were statistically analyzed by using T- independent test and repeated measures and variance analysis (P<0.05). Results: The pH value of the negative control group was as same as the PH of normal saline while the PH value of positive control group was significantly higher than those of other groups. PH values of Ortho MTA and RMGI at the baseline and on the first, sixth and ninth day did not show significant differences with one another, while microleakage of OrthoMTA group was significantly lower on the third day. Conclusions: In general, OrthoMTA had less leakage than RMGI but both materials can be used as suitable barriers for internal tooth bleaching Keywords: Tooth bleaching, OrthoMTA, Glass ionomer, leakag

A Comparative Investigation of the Microleakage of Biodentine and Mineral Trioxide Aggregate as Coronal Barrier in Nonvital Bleaching

Background: Internal bleaching is recommended to correct the discoloration of pulpless teeth. This study aimed to compare the microleakage of biodentine and mineral trioxide aggregate (MTA) used as an intracanal barrier in non-vital bleaching. Methods: An experimental study was performed in which 36 extracted mandibular premolars were randomly divided into two experimental groups (n= 16) and two control groups (n= 2). In experimental groups, 2mm of OrthoMTA and biodentine cement were placed as intracanal barriers. The control groups were prepared similar to experimental groups, except that in positive control group the orifice barrier material was not used and in negative control group the whole root surface was covered with nail polish and orifice barrier material was not used. Subsequently a mixture containing sodium perborate and 30% hydrogen peroxide was placed into the pulp chambers and replaced every three days. Microleakage was measured using a pH diffusion method by digital pH meter. pH was checked before placement and at days 1, 3, 6, and 9 after placement. Data analysis was done in SPSS V24 Results: The pH value in negative control group was similar to that in normal saline group, while the pH value in positive control group was found to be significantly higher than other groups (P< 0.05). Nosignificant differences were seen in pH values between the experimental groups at baseline and days 1 and 6, but pH values of biodentine were significantly higher than orthoMTA at days 3 and 9 (P< 0.05). Conclusions: MTA can be used as an efficient orifice barrier during internal bleaching, specifically in cases where there is probability for cervical root resorption. Keywords: tooth bleaching, mineral trioxide aggregate, dental leakag

The Effect of Casein Phosphopeptide-Amorphous Calcium Phosphate Containing Bonding Agents on Dentin Shear Bond Strength and Remineralization Potential: An in Vitro Study

Objective: To assess the effect of Casein Phosphopeptide-Amorphous Calcium Phosphate (ACP) containing bonding agents on dentin shear bond strength and remineralization potential. Material and Methods: This in vitro study evaluated 45 extracted human premolars. The teeth were decoronated, and the tooth crown was split into buccal and lingual halves. The specimens were then flat-grounded by a 180-grit abrasive. The specimens were then randomized into three groups (n=15). Adper Scotchbond Multi-Purpose (SBMP) primer and adhesive were used for bonding in the control group. ACP in 10wt% and 20wt% concentrations was added to SBMP adhesive and used in groups 2 and 3, respectively. After the application of primer and adhesive and light-curing them for 10 s, a transparent silicon cylinder was placed on a dentin surface and cured for 10 s; then, the cylinder was filled with composite resin and was cured for the 40s from each side. The specimens underwent 3000 thermal cycles, and a universal testing machine measured the SBS. To assess the remineralization quality, a total of 6 dentin samples (2 specimens for group) were prepared and underwent X-ray diffraction, attenuated total reflection Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray analysis. One-way analysis of variance was used to analyze the data. The level of p0.05) — the addition of ACP to SBMP adhesive enhanced dentin remineralization. Increasing the ACP concentration from 10% to 20% increased the formation of hydroxyapatite. Conclusion:Adding amorphous calcium phosphate confers remineralizing property to SBMP adhesive without compromising its shear bond strength to dentin