[Comparison of temperature rise in silorane-based and methacrylate-based composites cured by LED and Argon laser]

Temperature rise occurs during photoactivation of dental composites due to the exothermic polymerization reaction and different curing units. The aim of this study was evaluation of temperature rise in two kinds of composites with different curing units. In this experimental study, five samples of each composite resin [Filtek Z250, Filtek P90] were placed in two-millimeter deep Teflon molds which were 4mm in diameter. Curing was done from top surface with LED, high power LED and argon laser and temperature was recorded by a thermometer placed under the samples. After reaching room temperature, samples were cured and the temperature was recorded again. The time of maximum temperature was also recorded. The data were analyzed by two-way ANOVA and Tukey HSD. Composites and curing units had statistically significant influence on the temperature rise [p<0.001] Silorane-based composites showed significantly higher temperature rise than methacrylate-based ones. A significantly lower rise in temperature occurred when illumination was performed by argon laser. There was no significant difference in temperature rise between the two types of LEDs. The type of composite had no effect on the time of maximum temperature and in all samples the maximum temperature was recorded at the beginning of irradiation. Silorane-based composites showed higher temperature rise than methacrylatebased ones. Argon laser revealed less heat than LEDs. The maximum temperature rise was recorded at the beginning of irradiation

[Effects of different surface treatments on bond strengths of a non-metallic post in root's canal]

The establishment of reliable bonds at root-post-core interfaces is critical for the clinical success of post retained restorations. Severe stress concentration at post-cement interface increases the probability of post depending from the root. The aim of this study was to investigate the effects of different surface treatments on bond strengths of a non-metallic post in the root. Fifty extracted human canines or premolars that had just one root canal were endodontically treated. D.T Light Posts [RTD/France] received surface treatments in five categories: 1] Application of silane. 2] Sandblast with Alumina particles. 3] Sandblast with Alumina particles+ application of silane. 4] Etching with hydrofluoric acid+ application of silane. The posts were cemented in roots using panavia F 2.0 resin cement. A push-out test was performed on three different sections of each root to measure bond strengths. Data were analyzed with ANOVA and Post hoc tests at P<0.05. Failure modes were observed under a stereomicroscope [10]. Surface treatments used in this study [silane application, sandblast, sandblast+ silane, HF etching+ silane] did not increase the push-out bond strengths of fiber post used in this study. [P>0.05]. The most failures in different groups of surface treatments occurred at the cement material-post interface. The use of silane, sandblast method and etching with HF did not increase the push-out bond strength of fiber post used in this study

[In vitro evaluation of Fuji IX glass ionomer to microleakage after exposure to hydrogen peroxide 35% in class V restoration]

Fuji IX packable glass ionomer has anti-carious properties by adhesion to tooth structure. It seems to provide adequate seal between tooth structure and restoration due to the development of ionic crosslinks. Furthermore, bleaching may affect the marginal seal of restorations, subsequently increasing the leakage of oral fluids and bacteria into the restored structure. The aim was to evaluate the effect of packable glass ionomer [Fuji IX] on the microleakage of Class V restoration exposed with and without H2O2 35%. Forty sound human molars and premolars were selected and class V standard cavities were prepared on each tooth. The specimens were assigned in two case and control groups while cases were exposed to H2O2 35% for the subsequent 5 days [30 minutes each day thrice] and the controls were stored in serum physiology. The specimens were thermocycled, stained with fushin and sectioned longitudinally. The microleakage scores were determined and subjected to Mann-Whitney U and Friedman tests in both groups. The mean and median of leakage scores in four regions of control specimens were 1.588 and 1.625 while the ratios were 1.913 and 2.25 for the teeth exposed to H2O2. The teeth exposed to H2O2 35% leaked higher than control specimens in the mesial region [p<0.04], while no significant differences were observed between two groups in the other areas. The use of Fuji IX glass ionomer cements in the restoration of class V cavities is an acceptable treatment modality for the restoration of bleached teeth

[ effects of different surface treatments of a fiber post on its bond strength with a composite core in endodontically treated teeth]

In order to improve the bond strength between fiber post and composite core, many surface treatment procedures have been performed on posts. The aim of this study was to investigate the effects of different surface treatments of a quartz fiber post [DT Light Post] on its bond strength with a composite core [Clearfil Photocore] after water storage and thermocycling. In this interventional, in-vitro study, fifty human canine teeth were endodontically treated and post spaces were prepared. A total of fifty fiber posts were divided into five groups according to the surface treatment preformed as control [no treatment], silanenized, sandblasted, sandblasted and silanized, etched with hydrofluoric acid and silanized. After cementation of posts with Panavia F2 in the canals, composite cores were built on them. Consequently, the core parts were cut and stored in deionized water at room temperature for three months. Then thermocycling in 3000 cycles was performed between 5°C and 55°C. Then two 1 mm-diameter slices were obtained from each core. Finally, bond strength was measured by the push out test. Data were analyzed with one-way ANOVA. Data of all five groups followed normal distribution, but there were no significant differences between them. The sandblasted and silanized group had the highest bond strength [11.3 +/- 4.6] and the control group had the lowest bond strength [9.6 +/- 3.7]. In this study, sandblasting, etching with hydrofluoric acid and silanization did not increase the bond strength between fiber post and composite core

[Evaluation of monomer elution from two dentin bonding agents cured with halogen and LED lights]

Polymerization of resin-based dental materials is not complete; and the release of unreacted monomers has undesirable effects on biocompatibility and integrity of material. The aim of this study was to evaluate the type and effect of dentin bonding agents, type of light curing unit, the distance between the tip of curing unit and surface of bonding agents on monomer leaching. This experimental study used 40 sound extracted teeth, with prepared cavities about 3x3x2 and 3x3x4 mm on the smooth surfaces. A self-etch bonding [Clearfil SE Bond Curary, Japan] and one etch and rinse [Scotch Bond multipurpose, USA] were applied on cavities according to the manufacturer's instruction. The bonding agents were cured with halogen [Optilux 501, Colten] and LED [Ultalume 2, Vivadent] lights. The samples were saved in pure methanol with 37°C for 24h. Liquids were studied with gas chromatography [GC] for detection of different monomers. Data were analyzed using 3-Way ANOVA and Independent T-tests. The type of bonding agent had significant effect on monomer release. Scotch Bond released more monomer than Clearfil SE Bond [P=0.001]. The effect of light curing unit on monomer leaching was not significant, but the samples of Scotch Bond with more distance released more monomer. Only HEMA monomer was detected from dentin bonding agents in this study. Scotch Bond released more HEMA than Clearfil SE Bond. Halogen and LED lights had no significant effect on monomer leaching. More distance between the tips of light causes less degree of polymerization

[Color stability of dental composite materials after exposure to staining solutions: a spectrophotometer analysis]

The success rate of composite restorative materials depends very much on their color stability in the oral cavity. The purpose of this study was to investigate the color changes of four different brands of dental composite resin materials by using four staining solutions. A total of 128 disk-shaped specimens of 15-2 mm were prepared out of 4 composite resin materials. Two nanocomposites: Filtek supreme, Tetric Evoceram and two micro hybrid composites: Filtek Z250 and Tetric ceram, were prepared. The specimens were then divided into 4 groups of 8 specimens each and they were immersed in 4 staining solutions [Coffee, Tea, Cola, and Artificial Saliva] for 3 hours daily over a 24 day testing period. The color of specimens was measured with a spectrophotometer using CIELab color space relative to illuminant D65 at baseline and after staining. The color differences [delta E] were calculated. The delta E=3.3 was used as an acceptable value in subjective visual evaluations. Data was analyzed using ANOVA and Post-hoc test at significance level of 0.05. All tested materials showed unacceptable color change in coffee and tea groups [delta E>3.3]. The greatest color change was observed in Filtek supreme in coffee. The specimens in cola and artificial saliva didn't cause a notable color change clinically. Coffee and tea can significantly influence the discoloration of dental resin composite materials under investigation. The nanocomposite Filtek supreme color change was significantly more than other composites when exposed to coffee. Therefore, color stability of composite restorative materials depends very much on dietary habits

Postoperative thermal sensitivity reduction after amalgam fillings; A clinical evaluation and presentation of a new method

Prepared cavities are usually treated with liners prior to amalgam placement. Light cured glass ionomer [RMGI] have been widely used for this purpose. The aim of this study was to compare the effect of RMGI on decreasing postoperative sensitivity with a new method of applying self etch bonding and glass ionomer simultaneously. In a blind randomized clinical trial study, A total of 36 patients with 2 deep caries in their posterior teeth [cavities with less than 2 mm distance from pulp in radiography] were included. Diagnostic tests [cold-heat, percussion, electric pulp test] were performed for each tooth prior to final restoration. After cavity preparation, one tooth was treated by light cured glass ionomer, the next one with SE bond and glass ionomer randomly, followed by amalgam restoration. Diagnostic tests were performed three days, thirty days and three months after amalgam restoration. The statistical analysis was performed using SPSS software version 11.5 as well as Friedman and Wilcoxon signed-rank tests. In second follow up, the sensitivity to cold was significantly less than the conventional method [P < 0.05] in our suggested compound method. However, there was no significant difference between the two groups when using the other vitality tests. Using SE bond and light cured glass ionomer simultaneously was an effective new method of decreasing the postoperative sensitivity in short term, [1 month] although, there was no difference between the two groups in the long term