Flexural strength of the human dentin decreases after it is demineralized in vitro. This in vitro study demonstrates that resin-modified glass ionomer (RMGI) containing bioactive glass (BAG) can compensate for this loss of strength. RMGI without BAG does not restore the strength of such demineralized dentin. SUMMARYIntroduction: Recently, bioactive materials have been incorporated into glass ionomer cements to promote the precipitation of calcium phosphates in surrounding tooth structures. This in vitro study was undertaken to evaluate the effect of resin-modified glass ionomer (RMGI) containing bioactive glass (RMGI-BAG) on the flexural strength (FS) of demineralized dentin.

Introduction Recent advances in dental materials have led to the production of smart materials. Recently, addition of bioactive materials to glass-ionomer cements has resulted in new capabilities beyond the beneficial effects of fluoride release. This in vitro study compared the flexural strengths (FS) of a resin-modified glass-ionomer containing bioactive glass (RMGIBAG) with that of a commonly used resin-modified glass-ionomer (RMGI). Methods and materials A total of forty RMGI and RMGI-BAG bars (20 × 4 × 4 mm) were prepared in stainless steel molds. Each of the RMGI and RMGI-BAG bars was set for FS test. FS values of the specimens were measured using three-point bending test at a crosshead speed of 0.5 mm/min. The surface changes and the amounts of elements on the materials’ surfaces were also evaluated by SEM/EDS analyses. Data were analyzed using SPSS 11.5 and t-test (a = 0.05). Results The means ± SD in the study groups were 61.46 ± 22.52 and 39.90 ± 9.11 MPa respectively. There were significant differences between FS of the two study groups (p = 0.003). Conclusion While adding 20 wt% of BAG to the RMGI powder evaluated in this study decreases FS of the material significantly, the mean value of FS is in the acceptable range of the reported FS values for conventional GIs and RMGIs that are commercially available for clinical use. Clinical significance While flexural strength of RMGI decreases subsequent to addition of bioactive glass, it is still clinically acceptable considering the flexural strength values reported for clinically used GIs and RMGIs. Further studies are recommended. How to cite this article Mousavinasab SM, Khoroushi M, Keshani F, Hashemi S. Flexural Strength and Morphological Characteristics of Resin-modified Glass-ionomer Containing Bioactive Glass. J Contemp Dent Pract 2011;12(1):41-46.

Objectives: To compare the microleakage among experimental adhesives containing nanoclay fillers after the storages of 24 hours and 6 months. Materials and Methods: Class V cavities were prepared on extracted human molars with the occlusal margins located in enamel and the cervical margins in cementum. Phosphoric acid was applied to the enamel and dentin margins.Subsequently, the cavities were treated using four groups of experimental adhesive systems and restored with a resin composite. Adper Single Bond® was used as control group. After 24- hour and 6- month storages, the samples were subjected to thermocycling shocks and then immersed in silver nitrate as well as developer solution and finally evaluated for leakage. The data were analyzed using SPSS software. Results: Based on Kruskal –Wallis test, significant differences were found between groups regarding microleakage. The Mann- Whitney test showed that Leakage was significantly lower in Adper Single Bond® compared to the other groups in dentinal margins after 24 hours and 6 months and in enamel margins after 6 months. The Wilcoxon Signed Ranks test showed that the enamel leakage in experimental adhesives was significantly lower than dentinal leakage after 24 hours as well as enamel leakage in Adper Single Bond and adhesive with 0.5% PMAA-g-nanoclay was significantly lower than dentinal margins after storage period of 6 months. Conclusion: All the experimental adhesives were effective in reducing enamel leakage after 24 hours, but were not effective in reducing dentinal leakage after 24 hours as well as in enamel and dentinal leakage after a 6-month storage. No improvement was observed in the microleakage in dentin in both short (24 hrs) and long times (6 months).The high microleakage in the adhesives is probably attributed to the high concentration of HEMA in the recipe of the bonding agent.

Objectives:To compare curing performance of a second generation LED curing light with a high power tungsten quartz halogen (QTH).Methods:A hybrid composite resin (Filtek Z 250, 3M, USA) was used as test material and cured using a second generation LED light (Translux Power Blue™, Heraus Kulzer ,Germany) or a very high power QTH light unit (EMS, Switzerland). A two split aluminum mold was used to prepare ten samples with LED light source cured for forty seconds and ten samples prepared using high power QTH light unit, cured for four or six seconds recommended exposure time. Hardness, depth of cure (DOC) and thermal rise during exposure time by these light sources were measured. The data submitted to analysis of variance (ANOVA), Tukey’s and student’s t tests at 5% significance level.Results:Significant differences were found in hardness, DOC of samples cured by above mentioned light sources and also in thermal rises during exposure time. The curing performance of the tested QTH was not as well as the LED light. TPB light source produced the maximum hardness (81.25, 73.29, 65.49,55.83 and 24.53 for 0 mm, 1 mm, 2 mm, 3 mm and 4 mm intervals) and DOC (2.64 mm) values with forty seconds irradiation time and the high power (QTH) the least hardness (73.27, 61.51 and 31.59 for 0 mm, 1 mm and 2 mm, respectively) and DOC (2 mm) values with four seconds irradiation time. Thermal rises during 4 s and 6 s curing time using high power QTH and tested LED were 1.88°C, 3°C and 1.87°C, respectively.Conclusions:The used high power LED light produced greater hardness and depth of cure during forty seconds exposure time compared to high power QTH light with four or six seconds curing time. Thermal rise during 6 s curing time with QTH was greater compared to thermal changes occurred during 40 s curing time with tested LED light source. There was no difference seen in thermal changes caused by LED light with 40 s and QTH light with 4 s exposure time.

High C-factor values generated the largest gap formation. Silorane-based composite was more efficient for cavity sealing than methacrylate-based composites and resin modified glass ionomer.