جستجوی مقالات مرتبط با کلیدواژه « سایلوران » در نشریات گروه « پزشکی »

The bleaching agents can lead to color and translucency changes in composite resins. Due to the increasing use of the nano composites and the silorane-based composites, this study aimed at examining the color and translucency changes of these restorations after bleaching agents.

In this experimental - laboratory study, 198 composite discs were divided into three groups of 66 specimens using three types of composite: the microhybrid composite Z250, the nanohybrid composite Z350 and the silorane-based composite P90. After acid etching, half of the specimens in each group were covered by a resin rebounding agent. Then, the color and translucency assessment was done by reflectance spectrophotometer, using CIE LAB system. Each group was divided into three subgroups of bleaching agents: the 40% hydrogen peroxide and 20% carbamide peroxide bleaching agents and the control group. After applying bleaching agents, the final color and translucency changes were assessed. Data were analyzed using Mann Whitney and Kruskal Wallis tests.

The effect of composite and bleaching agent type and bonding agent were significant (P<0.001). The color changes in the microhybrid composite were higher than nanohybrid and silorane-based composites (P<0.001) (∆E>3.3). Also, the color changes by 20% carbamide peroxide were higher than that of hydrogen peroxide and control groups (P<0.001). The results of translucency changes were generally consistent with color-change measurements (∆E>3.3).

According to the present study, the most color changes appeared in the microhybrid composite and by 20% carbamide peroxide bleaching agent. Rebound samples were generally less affected by bleaching agents. The least color and translucency changes were related to nanohybrid composites.

Methacrylate composite resins are widely used in restorative dentistry. The greatest disadvantage of these materials is polymerization shrinkage. The recent innovations include making silorane-based composites with the least amount of shrinkage. Herein, we sought to investigate micro-shear bond strength between the former and new composites using both bonding and composite systems.
Seventy-eight cylindrical methacrylate- and silorane-based composites with the height and diameter of 2 mm and 5 mm, respectively, were prepared and thermocycled for 1000 cycles for aging.Then, the blocks were divided into six subgroups: 1) Z250, after freshening and P90bonding, the new silorane layer was placed on them; 2) Z250, after freshening, acid etching, and P90bonding, the new silorane layer was attached; 3) Z250, after freshening, acid etching, and single bonding, the new Z250 layer was attached; 4) P90 composite, after freshening and P90bonding, the new silorane layer was attached; 5) P90, after freshening, acid etching, and P90bonding, the new silorane layer was attached; and 6) P90, after freshening, acid etching, and single bonding, the new Z250composite was attached. Then, all the bonded samples were tested for micro-shear bond strength by Instron machine at the speed of 1 mm/min; the samples were loaded until reaching the breaking point. To analyze the data, Kolmogorov–Smirnov test, one-way analysis of variance, and Tukey’s post hoc test were run in SPSS, version 17.
There was a significant difference in micro-shear bond strength between the groups (P=0.0001). The mean of micro-shear bond strength in the silorane-based composite group was significantly higher than that of the methacrylate-based composites (36.62±5.97 vs. 26.12±5.97; P=0.0001).
Acid etching does not significantly affect shear bond strength, but applying P90 bonding in silorane composites increases the shear bond strength. The greatest bond strength was observed in restoring the P90 silorane composite with a similar silorane composite and the least strength was found in restoring the Z250 methacrylate composite with a similar methacrylate composite. In general, the micro-shear bond strength of silorane-based composites was greater than that of the metacrylate-based composites.

This study aimed to evaluate the shear bond strength (SBS) of silorane-based and methacrylate-based composites repaired by silorane-based composites after different surface treatments.
In total, 32 composite cylinders were provided from each of the two composites types (e.g., P90: P and Z350: Z). Cylinders were allocated to four different groups as follows: no surface treatments (Z1 and P1), silane application (Z2, P2), erbium laser irradiation (Z3, P3) and sandblasting with alumina particles (Z4, P4). Afterwards, the bonding component of P90 adhesive system was applied to all the prepared composite surfaces, followed by the repairing of all the samples with P90 cylinders. Moreover, SBS of the repaired surface was evaluated using the universal testing machine (UTM). Data analysis was performed using the one-way analysis of variance (ANOVA) and Tukey HSD (honest significant difference) test (P≤0.05).
In this study, the highest SBS values in each group (P and Z) were observed in the groups of P4 (40.23 MPA) and Z4 (51.19 MPA). However, the groups of P3 (20 MPA) and Z3 (46.16 MPA) obtained lower ranks. Silane application led to lower bond strength, compared to the other mentioned groups, and this difference was statistically significant (P Silorane-based composites could be used to repair either methacrylate- or silorane-based composites by choosing proper surface treatments. In this study, while sandblasting and laser irradiation significantly improved bond strength of two composites, silane application indicated no such influence on bond strength.

One of the orthodontic treatment problems, which causes marginal gaps and microleakage between tooth and composite is microleakage of composite bonding of orthodontic brackets. The microleakage formation permitting the passage of bacteria and oral fluids, which may cause white spot lesions under the brackets surface area.This is a clinical problem during orthodontic treatment. Few studies have been conducted in this area. The aim of this study was comparison of microleakage of composite silorane base and methacrylate base composite in orthodontic brackets. Thirty human premolar were collected and divided into 2 groups. In group 1, 15 orthodontic brackets were bonded using silorane base composite, in group 2, 15 orthodontic brackets were bonded using methacrylate base composite. Then the teeth were kept in water and thermo cycled(500×, 5-55°C). Specimens were further sealed with nail varnish, stained with 5% basic fuchsin for 24 hours. Then, all teeth sectioned and dye penetration rate were examined by an esteriomicroscope, and scored 0 to 3 for marginal microleakage for the bracket- adhesive and adhesive-enamel interfaces. The data collected analyzed with SPSS16 software, and fisher exact and Mann Whitney tests. Microleakage values were lower in silorane composite than in the methacrylate group, and this difference was found to be statistically significant(P-value =0.03). Also, the rate of microleakage between adhesive-bracket than adhesive-enamel interface was meaningful(P-value=0.025). The results of the current relealed that silorane-bass silorane-base composite provided low microleakage for orthodontic brackets, for this reason, it could be used it for bonding brackets.

Orthodontic bracket failure during treatment is a common problem. With the introduction of low shrinkage composites the question is that whether: this sufficient has coefficient bond strength for bonding bracket during orthodontic treatment. The aim of this study was to compare the shear bond strength (SBS) of silorane-based and metacrylate-based composites to metal brackets.

30 human premolar teeth were collected and divided into 2 groups. In group 1, 15 orthodontic brackets were bonded using silorane-based composite, in group 2, 15 orthodontic brackets were bonded using metacrylate-based composite. The shear bond strength of each specimen was determined in an Instron machine. Amount of residual adhesive remaining on each tooth was evaluated using a stereomicroscope. Data were analyzed using T-test to compare the shear bond strength between groups and LSD method to compare the Adhesive Remnant Index (ARI) scores.

There was significant difference in the SBS between the test groups (P<0.001). The mean bond strength of bonding brackets to silorane-based composite was (42.42 ± 7.03) MPa, and the mean bond strength of bonding brackets metacrylate-based composite was (21.08±2.97) MPa. No significant difference in the ART was found between groups (P=0.66).

Silorane-based composite provided higher bond strength to orthodontic metal brackets.

Background and Microleakage occurs in posterior composite restorations due to polymerization shrinkage. In recent years low shrinkage silorane-based composites have been introduced to reduce microleakage. The aim of this study was to evaluate the effect of three different restoration techniques on gingival microleakage of a silorane-based composite in class II restorations. In this experimental study, class II cavities were prepared in mesial and distal surfaces in 40 sound human premolars. The gingival floor was located 1.0mm below the CEJ. Dimension of cavities were 3mm buccolingually and 1.5mm in axial depth of gingival floor. The specimens were randomly divided into 4 groups. Group1 (control) was restored incrementally with silorane based composite (Filtek P90). Group 2, 3 and 4 were restored using glass fiber, flowable composite and resin-modified glass ionomer (RMGI) liners, respectively. After finishing and polishing of the restorations and thermo-cycling, the specimens were immersed in 2% Basic Fuschin for one week. Microleakage was determined under a stereomicroscope (40X). Data was statistically analyzed by Kruskal-Wallis test (P<0.05). The statistical analysis revealed no significant difference in microleakage among study groups (P=0.243). The sealing ability of glass fiber inserts, flowable composite and resin modified glass ionomer liners is not better than that of the silorane-based composite alone in gingival margins of Class II restorations.

Polymerization shrinkage in composite resins is responsible for microleakage restoration. A recently introduced composite resin Filtek P90 is based on siloxanes and oxiranes which polymerize by cationic "ring opening" polymerization resulting in reduced polymerization shrinkage. The aim of this study was comparative evaluation of microleakage in class II cavities restored with a silorane resin composite (Filtek P90) or a methacrylate based composite (Z250) using two different techniques of total bonding and open sandwich. A class II cavity was prepared on the mesial and distal surfaces of twenty four caries-free premolars, with the gingival margin of the cavity being 1 mm under CEJ. Teeth were assigned to restorative material and operative techniques (total bonding, open Sandwich (resin composite, RMGI), to four groups of 12 cavities: I: silorane-based composite (Filtek P90); II: RMGI (Fuji II) & Filtek p90; III: methacrylate based composite (Z250); IV: RMGI & Z250. The restored teeth were examined for microleakage after thermocycling) 5-55°c) and immersion, in a basic fuchin 0.5% solution 24 hours) and sectioned with diamond disk, using stereomicroscope (20X). The degree of dye penetration was recorded and analyzed with SPSS16 and Fisher’s exact test. Differences between group I with other groups were significant (P 0.01). Group III showed most microleakage in the degree of dye penetration 2. No significant difference was observed in groups II, I and IV. Open sandwich technique (groups I, IV) and p90 composite (total bonding) in group I showed the least microleakage.