Микропропустливоста и јачината на врската кај композитните материјали со примена на различни техники на апликација

Abstract

Bulk-fill composites were created from the need to make the restorative procedure simpler and shorten the clinical working time required for posterior composite fillings. Increased translucency allows polymerization of these composites to a depth of of 4-5 mm. Indications for the use of Bulk fill composite materials are: direct restorations in the posterior region (cavities I and II class), restorations of V-th class cavities ( cervical caries, root erosions), restorations of deciduous teeth, Extended fissure sealing in molars and premolars. They can also be used for indirect restoration including inlays, onlays and veneers, splinting, repair of defects in porcelain restorations, enamel, and temporaries. Low shrinkage bulk fill materials are used as base/liner under direct restorations, and can also be used in minimal invasive tunnel preparation. However, the question arises whether the adhesion and microleakage of bulk-fill materials with altered composition are comparable to conventional composites. Therefore, the aim of our study was to evaluate the microleakage and shear bond strength between the composite material and the hard dental tissue in different composite restorative materials, using different adhesive systems and different application techniques, to determine whether the type of composite material, the composition affects the microleakage and shear bond strength of composite material with hard dental tissues. In our research we used 100 extracted molars and standardized plastic molds were used to perform the experiments for shear bond strength test and 30 extracted molars for microleakage assessment. The teeth were without caries, fractures and restoration. Immediately after extraction, they were stored in distilled water at room temperature until the start of the study. We have prepared the research samples and their dentine surface according to the recommendations of ISO standards for adhesion tests. The following composites were used in the study: Filtek Z250 (3M ESPE) –hybrid composite, Gradia posterior (GC Corp. Tokyo. Japan) - microhybrid composite and bulk fill composites - TetricEvoCeram Bulk Fill (Ivoclar Vivadent AG. Liechtenstein), Tetric EvoFlow Bulk Fill (Ivoclar. Vivadent. AG. Liechtenstein) и SureFil® SDR® Flow (Dentsply. Konstanz. Germany). The adhesives systems how we used in our study are: Adper Singl bond Plus Adhesive (3M ESPE) и G bond (GC Corp. Tokyo. Japan). The "self-etch" and "total-etch" adhesive application protocols were used as per manufacturers’ instructions. The prepared research samples for the shear strength test were randomly selected 10 groups with 10 teeth. Group I (FiltekTM Z250 + Adper Singl bond Plus adhesive), Group II (FiltekTM Z250+ G bond), Group III (Gradia + Adper Singl bond Plus adhesive), Group IV (Gradia +G bond), Group V (Tetric evoflow bulk fill + Adper Singl bond Plus adhesiv Group e), VI (Tetric evoflow bulk fill + G bond), Group VII (SDR - Adper Singl bond Plus adhesive), VIII Group (SDR –G bond), Group IX (Tetric evoceram bulk fill + Adper Singl bond Plus adhesive) и Group X (Tetric evoceram bulk fill + G bond). We measured the shear strength test with a universal testing machine INSTRON 4301 where we performed a SBS test with a curved edge (NOCHED EDGE) at a speed of 1 mm per minute. On the occlusal surface of 30 extracted molars to analyze the micro-permeability, we made preparation class I cavities with a depth of 5 mm. Then we randomly selected the teeth into 10 groups with 3 samples and restored them in the order of groups as for the shear strength test. We used a scanning electron microscope from the TESCAN, VEGA3LMU model, plus an additional 10 mm2 SDD detector x-act, a co-method of passive color penetration of a 50% solution of silver nitrate to analyze the microleakage . Statistical analysis is made in statistical programs: STATISTICA version 10; IBM SPSS 20.0. The collected data are processed using the following statistical methods: (average and standard deviation), Mann-Whitney U test, Analysis of Variance -ANOVA, Post hoc Tukey HSD test, Shapiro-Wilk. For CI (confidence interval ± 95% CI), the statistical significance for a level of error less than 0,05(p) is defined. Based on the realization of the set goals and our zero hypothesis that the micro permeability and shear strength of Bulk fill composite materials is the same as hybrid conventional composite materials, we have come to our own knowledge about bulk fill restorative materials. From the acquired knowledge we took the following conclusions: Bulk fill composite materials, estimated in our study, satisfy the requirements of this type of materials in terms of their marginal adaptation to the wall of cavity. The color penetration test showed that there was no high permeability (66.7%) of the tested restorations. The best micro - permeability score was obtained with the SDR independent of the adhesive system. The analysis of the results of the average values of the shear strength test showed that in the second group the average value of the strength was the highest 5.6 ± 1.8 Mpa, in the third group the mean value of the strength was the smallest 3.2 ± 1.1 Mpa. This difference is due to the statistically significant difference between FiltekTM Z250 + G bond versus SDR - Adper Singl bond Plus adhesive; FiltekTM Z250 + G bond vs. Gradia direct posterior + Adper Singl bond Plus adhesive and FiltekTM Z250 + G bond versus Tetric evoceram bulk fill + Adper Singl bond Plus adhesive other differences are statistically non-significant. The type of restorative material, and its composition, affects the strength of the connection. Materials that contain a higher percentage of filler in their composition may exhibit a better bond strength. The type of restorative technique does not affect micro-permeability while the type of adhesive system affects the micro-permeability between the composite and the walls of the cavity, in fact with total-etching adhesive systems, we obtain a better marginal adaptation of the composite material compared to self-etching adhesive systems. The difference between the average bond strength values in the composite materials depending on the Application Technique - layered technique (in all groups, 4.4 ± 1.7) versus Application Technique - Bulk technique (in all groups, 4.0 ± 1.5), is statistically not significant. These results indicate that the application technique of the composite material does not affect the strength of the bond, in fact bulk fill composites have a bond strength as well as conventional hybrid composites, regardless of the type of adhesive system. Bulk fill composite materials can provide reliable alternatives to conventional hybrid composites. This can be of potential benefit to dentists because bulk fill composites are simpler to handle than conventional composites and can be applied more effectively in clinical practice. We completed research samples at the European University - Faculty of Dentistry, we completed testing of the shear strength at the Jože Stefan Institute, Department of Stomatology, Ljubljana, in the accredited Laboratory, while the assessment of the micropermeability of the faculty for biological and technical sciences, Goce Delcev University - Stip.