[Shear bond strength of MTA to composite resin in comparison with glass ionomer]

Nowadays, MTA has numerous clinical applications because of desirable properties. Many teeth which are treated by MTA need final composite restorations. In this situation, the bonding between composite and MTA has the main role in retention, durability and seal of the restoration. Evaluation of the bond strength between MTA and composite resin and its comparison with Resin Modified Glass Ionmoer [RMGI]. Sixty specimens were prepared for three experimental groups of white MTSA, gray MTA, and glass ionomer Fuji II LC. Ten specimens in each group were etched with 37% phosphoric acid for evaluation of the etching effect while ten speicments were not etched. All specimens were then bonded to the composite and shear bond strength test was performed, using Instron testing machine. In addition, the fractured surfaces of the samples were checked with stereomicroscope [x10]. Data were analyzed by ANOVA and Tukey HSD test. The highest shear bond strength value was seen in unetched glass ionomer subgroup and there were significant differences in shear bond strength of the composite to unetched glass ionomer in comparison with the other groups [p<0.001]. There were no significant differences in shear bond strength of the composite to etched and unetched white MTA, etched and unetched gray MTA, and etched glass ionomer [p > 0.05]. Shear bond strengthe between MTA and the composite is comparable with etched glass ionomer. The etching of the RMGI surface causes as significant decrease of bond strength to the composite but it has no effect on the bond strength of MTA to Composite

[ effect of topical fluoride on shear bond strength of resin modified light cured glass ionomer to the enamel of the primary upper canine: an in-vitro study]

One of the most important goals of topical fluoride application is to prevent dental caries in children. General opinion reveals that topical fluoride has a negative effect on composite bond and adhesive materials to tooth; otherwise, it could be considered in pediatric dentistry. The aim of this research was to evaluate and compare the effect of topical fluoride on shear bond strength of resin modified light cured glass ionomer to the etched and non-etched enamel of the primary tooth under different preparing conditions. In this in-vitro experimental study, 108 primary canine teeth free of caries and crack were prepared in three main groups respectively: 1] immediately after using APF,2] 24 hours after using APF, and 3] without using APF. Then, each main group was divided into three subgroups. The first subgroup received conditioner + GC Fuji LC2, the second received GC Fuji Lc2 + 3M phosphoric acid 35%, and the third one received composite 3 Mz [100] on the tooth surface. After thermocycling, the shear bond strength of the material on the teeth was measured by instron machine. Two- way ANOVA and Post hoc Bonferroni test was used for statistical analysis. There were no statistically significant differences between the mean shear bond strength of the groups in which APF was used and those which did not receive topical fluoride [p>0.05]. There was not a statistically significant difference, between the mean shear bond strength of GC Fuji LC2, using polyacrylic acid 20% and the same material using phosphoric acid 35%. However, there was a significant difference between the strength of shear bond of the two above materials and composite 3MZ[100]. According to the results of this study, it can be concluded that 1- Application of APF, has little effect on reducing the strength of shear bond in GC Fuji LC2 and 3MZ[100] composite. Moreover, 2- Using polyacrylic acid 20% and phosphoric acid 35% have similar effects on the strength of glass ionomer GC Fuji LC2 to the primary tooth enamel

[Effect of different types of surface treatment on shear bond strength of two luting resin cements to alumina base ceramic]

One of the most important problems in dentistry is to produce a suitable bond between tooth and all ceramic restoration, but there is little information on the use of resin cements and the importance of different surface treatments on their adhesion to high alumina containing ceramics. The aim of this study was to find the optimal choice of surface treatments and luting cement for bonding to In-Ceram, an aluminum oxide reinforced glass ceramic material. The bond strength of two different luting cement to the ceramic material was evaluated. The effect of surface treatment, etching, sandblasting, and silanizing was also investigated. Thirty In-ceram discs were fabricated and assigned to 3 groups. Group 1 specimens were treated with HF and Silane, Group 2 were sandblasted and then silane was applied, Group 3 were treated only with silane. Rely X cement was placed on all specimens and shear bond strength test was done. After the test, the discs were polished again and treated as previously mentioned in 3 groups. Then they received Panavia F cement and shear bond strength was evaluated using Instron testing machine. Using Tukey HSD test, it was shown the Panavia F provided higher bond strength values than Rely X cement. One way ANOVA determined that the use of sandblast provided higher bond strength values than other groups. Surface etching with 9.5% HF also increased bond strength in comparison with silanization alone. Based on the results of this study, the use of Panaiva F was better for In-Ceram restorations. Sandbalsting is preferred to etching for the increase of bond strength of resin cements to alumina ceramic

[Fracture resistance of root canal treated maxillary central incisors restored with FRC post in extensive composite restorations]

Using the post is one of the most important sequences in restoring endodontically treated teeth. It dates back more than 200 years as the most popular method of root canal treated teeth restoration; and still is an acceptable method of increasing retention and resistance in such teeth. When there is enough sound tooth structure, restoring the tooth with adhesive restoration is the best choice. New tooth-colored adhesive posts are compatible with conservative and esthetic technique. But the question still remained: how much of remaining tooth structure is enough to resist the forces, without using the post? The purpose of this comparative in vitro study was to determine compressive fracture resistance of crown in endodontically treated maxillary incisor teeth restored with or without adhesive tooth colored post and also in intact teeth. Thirty extracted maxillary central incisors were selected and allocated to three groups each of ten teeth. Group 1 teeth were kept intact as control. Group 2 were endodontically treated teeth with two approximal class III cavities in the middle one third of incisogingivally that were connected to access cavity, then restored with composite. Group 3 were endodontically treated and prepared teeth, similar to group 2 and received light post DT [RTDTM] and restored with composite. Then, the samples were loaded until fracture was happened in pull test machine. Mean values of forces required for fracture and mode of fracture were recorded. Mean fracture strength in group 1 was 68.67, in group 2, 41.44 and in group 3, 21.45 Kgf. Comparison of fracture resistance with one way ANOVA was statistically significant. Failure mode of group 3 was more repairable than group 2. Fracture strength in teeth resorted with post was less than the other groups. While considering more time and cost in using posts, this study does not recommend it in similar situations