[ 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

[SEM evaluation and comparison of marginal integrity of glass-ionomer and composite restorations with immediate or delayed polishing]

Marginal seal in class V cavities and determining the best restorative material to decrease microleakage is of great importance in operative dentistry. The aim of this study was to evaluate the effect of polishing time on the microleakage of three types of tooth-colored restorative materials in class V cavity preparations and to assess the marginal integrity of these materials using scanning electron microscope [SEM]. In this in vitro study, class V cavity preparations were made on the buccal and lingual surfaces of 30 bovine incisors [60 cavities]. The specimens were divided into three groups each containing 10 teeth [20 cavities]: group 1, Filtek Z 350 [nanocomposite]; group 2, Fjui IX/G Coat Plus [CGIC]; and group 3, Fuji II LC [RMGI]. In each group, half of the specimens [n=20] were finished/polished immediately and the rest of them were finished/polished after 24 hours. All the specimens were thermocycled for 2000 cycles [5-50 [degree sign] C]. epoxy resin replicas of 12 specimens [2 restorations in each subgroup] were evaluated using SEM and the interfacial gaps were measured. Finally, the teeth were immersed in 0.5% basic fuchsin dye for 24 hours at room temperature, sectioned and observed under stereomicroscope. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests and the comparison between incisal and cervical microleakage was made with Wilcoxon test. Incisal and cervical microleakage were not affected by polishing time in none of the three restorative materials [P>0.05]. Cervical microleakage only in Fuji IX with immediate polishing was significantly higher than incisal microleakage [P<0.05]. Incisal and cervical microleakage with immediate or delayed polishing were not significantly different in Fuji IX, Fuji II LC, and Z350 [P>0.05]. Immediate polishing is recommended in tooth-colored class V restorations

[Evaluation of disinifecting of 5% sodium hypochlorite solution diluted to 2:100 along with the use of disposable covers on HBV contaminated dental office surfaces and equipments]

The efficiency of disinfecting materials and procedures in removal of contamination from dental surfaces and equipments is essential. In authors' previous study, daily use of 2:100 dilution of 5% sodium hypochlorite in water and disposable covers were recommended since HBV contamination was found on semi-critical parts of the operative dentistry department. The aim of this study was to evaluate the HBV contamination following application of the recommended procedures. The study was conducted in two parts. In the first cross-sectional part, samples were collected from 17 sites of dental surfaces. In the second interventional part samples were collected from 10 sites of 9 dental and 3 sites of 2 light cure units, before and after disinfection with 5% sodium hypochlorite solution diluted to 2:100. Sterile cotton swabs moistened with sterile BSAS [Bovcine Serum Albumin in Sodium Chloride] solution were used for sampling. Samples were tested by PCR technique in Pasteur Institute, Iran. None of the samples collected in the first part of the study showed contamination. In the second part of the study, from 96 samples taken from various parts of dental and light cure units, before and after disinfecting, there was only on HBV contaminated site before disinfection which showed not contamination after disinfection. Based on the results of this study, disinfecting procedure with 5% sodium hypochlorite solution diluted to 2:100 along with using disposable covers is effective in preventing HB contamination

Effect of filler type on 3-body abrasion of dental composite

The relatively poor wear resistance of dental composite in stress bearing posterior situations has restricted wider clinical application of this restorative material. The aim of this study was to evaluate the three body abrasive wear of a dental composite based on a new filler [leucite: KAl Si2O6] and to compare it with the wear resistance of a composite based on commonly used Aluminium - Barium Silicate filler. This research was an interventional study done in Iran polymer institute. Five specimens were considered in each group. All ceramic IPS Empress [R] [Ivoclar- Vivadent] ingots based on leucite crystals were ball milled, passed through an 800 sieve and used as filler. Experimental composites were prepared by mixing the silane- treated fillers with monomers [BisGMA and TEGDMA]. Camphorquinone and amine were used as photoinitiator system. Degree of conversion of the light-cured and post-cured composites was measured using FTIR spectroscopy. The prepared pastes were inserted into plexy-glass mold and light cured [700 mw/cm[2], 40 s]. Then for maximum degree of conversion specimens were post- cured [120°C, 5 hours]. Three body abrasion wear testing was performed using a wear machine with 50 rpm rotational movement. In this machine, pumice [150 meshes] was used as the third body. Weight loss of specimens in each group was measured by balance after each 50 hours. After wear testing SEM examination was made specimens in each group. The data were analyzed and compared using ANOVA and Tukey HSD tests [P<0.05]. Tetric Ceram was tested as commercial composite. There were significantly differences between three body abrasive wear of composites. The ranking from lowest to highest was as follows: leucite composite [19%] < Tetric Ceram [22%] < glass composite [28%]. leucite composite showed the highest wear resistance value, propably due to the crystalliniy and hardness of filler. Introduction of this new filler as an alternative to glass filler, significantly increases the wear resistance of the resin composites. Further investigations on mechanical properties of new composites would be beneficial in the development of new dental materials

[ comparative study on the durability and effectiveness of Nd: YAG laser and dentin binding agents in dentin hypersensitivity]

Background and aim: dentin hypersensitivity is a chronic complaint among adult patients. The goal of' this study was to compare the durability of the application of two techniques, Nd: YAG laser and dentin bonding agents, in the elimination of hypersensitivity

Materials and Methods: twenty - eight patients with 116 hypersensitive teeth, who referred to the Operative Dentistry Department, Faculty of Dentistry, Tehran University of Medical Sciences, were enrolled in this clinical trial. The left lower and upper teeth received Nd: YAG laser treatment [0.3 w, 0.4 w, 0.5 w, 0.6 w, 0.7 w, 0.8 w, 0.9 and 1 w, each for 30 seconds]. Then, dentin hypersensitivity was investigated applying forced air and in positive cases, laser treatment was repeated. The hypersensitive teeth, on the right side, were firstly etched with % 37 phosphoric acid for 5 seconds, washed with water and air-dried. Then a single layer of excite adhesive was applied and after 30-second air-drying, the teeth were light cured for 20 seconds. In case of hypersensitivity, this technique was reapplied. In 3 and 6 months follow-ups, hypersensitivity was investigated and the data were analyzed using Mann-Whitney test

Results: in 6-month follow-up, the success rate of dentin bondings was %62.7 where as that of laser was %42.1 showing a statistically significant difference [p<0.05]

Conclusion: although both techniques lead to the reduction or total elimination of dentin sensitivity, dentin bonding agents exert a more durable effect