Background and Aim: The present study aimed at determination of the fatigue resistance and failure mode of cuspreplacing onlays in endodontically treated premolars using indirect COMPOSITE RESIN restorations. Materials and Method: In this experimental study, 84 human premolars were randomly divided into 7 groups of 12. These groups were prepared as follows: Intact teeth used in groupl as control, the second group covers the endodontically treated teeth, restored with indirect onlays using Z-250 COMPOSITE RESIN, the next two groups (i.e. 3,4) were similar to the second group, but subjected to 1 and 2 million fatigue load cycles, respectively. Groups 5, 6, 7 were similar to groups 2, 3, 4, respectively, however, in these groups Tetric Ceram used as the restorative material. All specimens were loaded using a Universal Testing Machine until fracture occurred and the mode of failure observed with naked eye. Kruskal-Wallis and Chi-Square tests were used to analyze the data (a=.05). Results: All specimens withstood the masticating simulation. The mean fracture strength for groups 1 to 7 were: 1276.92, 1269.05, 1217.80, 1188.13, 1228.97, 1127.86, 1105.58, respectively. No statistically significant differences were found between the groups in fracture strength and failure mode. There was no statistically significant difference between two types of RESIN COMPOSITE (P=0.203) and load cycles (P=0.298) after zero, 4 and 8 years aging. Conclusion: Within the limitation of this study, restored premolars with indirect COMPOSITE onlays show fatigue resistance equal to natural tooth up to 8 years after restoration. Furthermore, no statistically significant differences were found between 4 and 8 years of load cycles. Tetric Ceram Z-250 restoration agent showed no effect on the tooth fracture resistance with the most observed fractures to be occur under CEJ with no capability to be restored.

Discoloration of COMPOSITE RESINs is considered to be a major factor in esthetic restoration failures. The aim of this study was to evaluate color stability of IDM COMPOSITE (both light and self cure samples namely IL and IS), and to compare it with a self-cure COMPOSITE (Degufill named DS) and a light cure ormocer COMPOSITE (Definite, called DL in the Report). 60 disk shaped samples of each COMPOSITE were prepared, according to ISO-7491. The samples were divided into 3 groups and aged as follows: A- (Control) 7 days in dark 37 c chamber B- Foil covered and kept in 100% humidity, and 370 c in xenotest chamber for 24 hours, then transferred to a dark 370 c chamber for 6 more days.C- Kept in 370 c, 100% humidity under the emission of xenon lamp of xenotest chamber for 24 hours, and then transferred to 370 c dark chamber for 6 more days.The lightness and chromaticity values of samples were measured both before and after aging using a spectrophotometer (Data Flash). The total color changes as well as changes in lightness and chromaticity values were measured in the CIE L * a * b * scale, and analyzed. Color change was recorded to be significant in all samples after aging. The maximum change belonged to IL, which was significantly different from DL and DS. It seems, in order to have a durable esthetic restoration using IDM, more scientific and professional consideration is needed in the production process.

Introduction: The reaction of polymerization can be controlled by the light exposure pattern and the temperature. The purpose of this study was to evaluate the effect of different light exposure patterns and COMPOSITE temperatures on micro leakage of light cured COMPOSITE RESIN restorations. Materials and Methods: In this interventional study, class V cavities were prepared on 200 extracted human molars. Then the teeth were randomly divided into four main groups according to different light exposure patterns of High Intensity Program (HIP), Low Intensity program(LOP), Pulls Program(PUL) and Suggested Progressive Program(SUP) . and 5 subgroups according to different temperatures of COMPOSITE during curing (5°c, 20°c, 35°c, 50°c and 65°c). After thermo cycling and dye penetration, measurement of micro leakage was done using a stereomicroscope. The data were analyzed using SPSS software (ANOVA).Results: ANOV A showed that both in enamel and dentinal margins, a significant decrease in micro leakage has occurred in SUP group. Micro leakage in enamel and dentinal margins was significantly higher in HIP group than the other groups. No significant difference was observed in the rate of micro leakage among the 5 subgroups with different temperatures.Conclusion: SUP light curing pattern could be considered for improving COMPOSITE RESIN restorations as a superior light exposure pattern due to its ability in Polymerization control, reducing polymerization shrinkage stress and micro leakage. Prewar Ming of the COMPOSITEs is a practical and easy way to improve COMPOSITE properties for dental restorations.

Background and Aim: This study aimed to compare the dentin demineralization inhibitory potential of a bioactive COMPOSITE RESIN (ACTIVA-BioActive) with a conventional COMPOSITE RESIN.    Materials and Methods: In this in vitro experimental study, 45 class V cavities were prepared on the root surface of extracted human third molars. The teeth were then immersed in a demineralizing solution (lactic acid, pH=4.5) at 37˚C for 3 days to induce the formation of secondary caries. The cavities were restored with Single bond 2 + Z250 (group A), ACTIVA BioActive (group B), and Single bond 2 + ACTIVA BioActive (group C). The dentin microhardness was measured close to the restoration margin (marginally exposed dentin), and at approximately 4 mm distance from the margin in a varnish-covered dentin area (protected dentin). Three measurements were made at each site at 50, 100, and 150 µm depths from the external dentin surface. Data were analyzed with one-way ANOVA and Tukey test (alpha=0.05).     Results: The highest Vickers hardness number (VHN) was observed in ACTIVA+ bonding agent (49.46±4.15), followed by Z250 (44.57±3.87), and ACTIVA (43.44±3.76) group. The mineral index was significantly higher in ACTIVA+ bonding agent (76.87±3.80) compared to other groups while no significant difference was observed between ACTIVA (70.85±4.06) and Z250 (71.98±3.09) in this regard (P<0.001). Conclusion: The results showed that flowable ACTIVA BioActive COMPOSITE used with Single bond 2 resulted in a significantly smaller reduction in dentin microhardness and reduced secondary caries formation. ACTIVA BioActive with no adhesive had no advantage over Z250 COMPOSITE.

Background: Mineral trioxide aggregate (MTA) is a material that has recently gained popularity in the application of the vital pulp therapy. Along with the increasing use of MTA to this end, the permanent restoration material to be placed on MTA has become a significant issue. The aim of this in vitro study was to investigate the bond strength of the novel low-shrinkage silorane-based COMPOSITE RESIN (SBC) to MTA.Methods: Twenty acrylic blocks filled with MTA were prepared for this study. SBC was the test group and methacrylate-based COMPOSITE RESIN (MBC) was used as the control group. Shear bond strength test was performed to determine the bond strength. The surfaces of broken samples were evaluated under a stereomicroscope and grouped as adhesive, cohesive and mixed. Data were examined by statistical analysis.Results: Statistical analysis revealed that SBC exhibited higher shear bond strength than the control group. It was observed that most of the failures in the test group were of cohesive type within MTA.Conclusion: Based on the results, SBC showed higher shear bond strength than the control group; however, clinical follow-up is needed to evaluate the clinical success.

Background and purpose: Deep fissures of occlusal surface in recently erupted first permanent molars are prone to accumulation of bacterial plaque. Sealing these fissures by appropriate flowing materials, as pit and fissure sealants, is a conservative way to prevent caries. The purpose of this study was to compare retention of flowable COMPOSITE RESIN by RESIN modified glass ionomer sealant in six months period.Materials and methods: The occlusal surfaces of the first permanent mandibular molars of 50 children aged 6 to 12 attending pediatric department in dental school affiliated with Qazvin University of Medical Sciences were assessed via Williams probe, intra-oral mirror, and diagnodent. After confirming absence of caries, flowable COMPOSITE RESIN were placed on the left first permanent mandibular molars, and RESIN modified glass ionomer (RMGI) were placed on the opposite side. After 6 months, 46 patients referred for follow up, in whom the retention of sealants was assessed using sharp explorer and intra-oral mirror, and caries were assessed via diagnodent. Data was analyzed in SPSS20 applying Chi- square test.Results: The retention of flowable COMPOSITE (91.3%) was significantly more than that of the RESIN modified glass ionomer (56.5%) (P<0.05). There were no cases with total loss of material in flowable COMPOSITE. No caries were observed using the diagnodent.Conclusion: The flowable COMPOSITE RESIN could be used as a fissure sealant agent, due to its greater retention compared to RESIN modified glass ionomer.

Introduction: In patients requesting to bleach their teeth, bleaching treatment might affect microleakage of present restorations. Technique and concentrations of applied bleaching and bonding agents are some effective factors on microleakage of COMPOSITE restorations. The aim of this study was to evaluate the effect of bleaching method on microleakage of RESIN COMPOSITE restorations.Methods and Materials: 48 extracted carries free human premolars were selected and randomely divided into 4 groups. Class V cavities were prepared on buccal and lingual surfaces, with gingival margins located 1mm below CEJ. In group one Cleatfil, SE- bond and Single bond applied on buccal and lingual surfaces respectively, and cavities restored by Z 250 RESIN COMPOSITE. In group two, the cavities were restored as in group one and then were kept in distilled water for a period of one month. In group three, all the stages resembled group two and home bleaching regimen was used. In group four, all the stages resembled group two, but samples subjected to in office bleaching regimen. All the samples were thermocycled and examined for microleakage. Data analyzed using Wilcoxon, Kkruskal-wallis and Man-Whitney U tests (a = 0.05).Results: Single bond compared to SE- bond provided the best post bleaching results regarding microleakage. The amount of microleakage was higher in office bleach technique in both margins.Discussion: Single bond showed the best results regarding post bleaching microleakage. Bleaching had a negative effect on microleakage that was higher in office technique.

Introduction: Dentin hypersensitivity is a common condition of transient tooth pain associated with a variety of exogenous stimuli. The clinical cause of dentin hypersensitivity is exposed dentinal tubules as a result of gingival recession and subsequent loss of cementum on root surfaces. Two principal treatment strategies are used; Dentinal tubules can be covered by gingival grafts or dental restorations and desensitization of the nerve tissue can be done within the tubules using potassium nitrate. The Purpose of this study was to compare effect of two desensitizing agent nitrate potassium and sodium fluoride after periodontal surgery.Material and methods: In this clinical trial 12 patients that had peridontal surgery at minimum 3 quadrants, in each there was one sensitive tooth, were selected. The degree of sensitivity measured before using nitrate potassium and sodium fluoride the same as control group. Potassium and sodium fluoride gels used on the quadrants (upper or down. The degree of sensitivity measured after 7 and 14 days. Data analysis was done in SPSS software by Freedman and Willcoxon tests.Results: After 7 and 14 days in the all groups, decrease of sensitivity was statistically significant. But after 14 days, between three groups, there were no statistically significant differences.Conclusion: Even though using of nitrate potassium 3% and sodium fluoride 2% cause significant reduction of tooth sensitivity in a 2 weeks period but in compare to the control group did not show any superiority. Further study is needed to confirm this result.