309 research outputs found

    Luting of ceramic crowns with a self-adhesive cement: effect of contamination on marginal adaptation and fracture strength

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    Objectives: This study evaluated the percentages of continuous margins (%CM) and fracture strength (FS) of crowns made out from blocs of leucite-reinforced ceramic (IPS Empress CAD) and luted with a representative self-adhesive cement (RelyX Unicem) under four contaminating agents: saliva, water, blood, a haemostatic solution containing aluminium chloride (pH= 0.8) and a control group with no contamination. Study Design: %CM at both tooth-cement (TC) and cement-crown (CC) interfaces were determined before and after a fatigue test consisting of 600'000 chewing loads and 1'500 temperature cycles changing from 5º C to 50º C. Load to fracture was recorded on fatigued specimens. Kruskal-Wallis test was used to compare %CM and FS between the five groups with a level of confidence of 95%. Results: At the TC interface, no significant differences in marginal adaptation before loading could be detected between groups. After loading, a significant marginal degradation was observed in the group contaminated with aluminium chloride (52 ± 22 %CM) in respect to the other groups. No significant differences in %CM could be detected between the groups contaminated with saliva, water, blood and the control. At the CC interface, no significant differences in marginal adaptation were observed between the groups. The FS on loaded specimens was around 1637N, with no significant differences between groups as well. Conclusions: An adverse interaction of the highly acidic haemostatic agent with either dentin or the self-adhesive cement could explain the specimens' marginal degradation. The self-adhesive cement tested in this study was no sensitive to moisture contamination either with saliva, water or blood

    Morphology of the smear layer after the application of simplified self-etch adhesives on enamel and dentin surfaces created with different preparation methods

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    Mild self-etching adhesive systems modify and/or incorporate the smear layer into the resin-infiltrated demineralised dentin. Some factors such as type of bur and use of water spray might affect the thickness of the smear layer on substrates, enamel and dentin. Because of this, the present study evaluated the thickness of smear layers created by different finishing procedures, after the application of three simplified self-etching primers (Adper Prompt L-Pop and two experimental formulations) on enamel and dentin. After the application and removal of the primers' resinous component, the specimens were prepared for examination under a scanning electron microscope. Smear layers were thicker on enamel than on dentin, irrespective of the finishing methods used. Therefore, different thicknesses of smear layer on enamel/dentin might be an important factor to consider when evaluating the bonding efficacy of self-etching adhesives to both tooth substrate

    The competition between enamel and dentin adhesion within a cavity: An in vitro evaluation of class V restorations

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    To gain more insight into the consequences of curing contraction within the tooth cavity, we assessed the margin behavior of 12 contemporary restorative systems in class V restorations with margins located on enamel and dentin after mechanical loading and water storage. Mixed class V cavities were prepared on extracted human molars and restored using five etch and rinse and seven self-etch adhesive systems with their corresponding composites. Marginal adaptation was evaluated by using a computer-assisted quantitative marginal analysis in a scanning electron microscope (SEM) on epoxy replicas before, after thermal and mechanical stressing and after 1year of water storage. The interactions of "testing conditions”, "adhesive-composite combination” and "tooth substrate” with "marginal adaptation” were evaluated by two-way ANOVA. Fatigue, stress and storage conditions had significant effects on the marginal adaptation. Only two groups (Optibond FL and G Bond) presented equal percentages of marginal adaptation on enamel and dentin; in the other groups, the rate of degradation was product dependent. All materials tested showed a distinct behavior on enamel and dentin. In addition to mechanical resistance and long-term stability, differences within materials also exist in their ability to simultaneously bond to enamel and denti

    Marginal seal stability of one bottle adhesives in Class V vs. Class I cavities

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    The aim of this study was to test the influence of two different cavity configurations on marginal stability of recent one bottle "etch & rinse” and "self-etch” adhesives in Class V vs. Class I cavities, before and after thermo-mechanical loading under simulation of dentinal fluid. Forty human upper molars were selected and assigned to five experimental groups. Intrapulpal pressure was maintained during cavity preparation, restoration placement, finishing and stressing. Standardized Class I and V-Shaped Class V cavities were prepared on each tooth. Half of the margins of Class V cavities were located in enamel and half in dentin. All cavities were restored with different adhesives systems and a nano-hybrid composite. Materials were light-cured using a LED unit. Restored teeth were loaded in a computer-controlled chewing machine with 1.2 million mechanical occlusal cycles simultaneously with 3,000 thermal cycles (5-50-5°C). Impressions were made with polyvinylsiloxane of each restoration before and after loading. Gold-coated epoxy replicas were prepared for SEM examination at ×200 magnification. Significant differences between materials were found both before and after loading (Kruskal-Wallis, Bonferroni, p < 0.05). Significant differences were also found between Class I and V restorations (Wilcoxon Matched-Pairs Signed-Rank Test, p < 0.05). Even before thermo-mechanical loading, none of the groups had 100% continuous margin. Marginal seal stability of recent one bottle "etch & rinse” and "self-etch” adhesives are significantly different and susceptible to cavity configuratio

    Bulk filling of Class II cavities with a dual-cure composite: effect of curing mode and enamel etching on marginal adaptation

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    Objectives: This study attempted to find a simple adhesive restorative technique for class I and II cavities on posterior teeth. Study Design: The tested materials were a self-etching adhesive (Parabond, Coltène/Whaledent) and a dual-cure composite (Paracore, Coltène/Whaledent) used in bulk to restore the cavities. Class II MO cavities were performed and assigned to 4 groups depending on the orthophosphoric acid (H 3 PO 4 ) conditioning of enamel and polymerization method used (chemical or dual). Specimens were subjected to quantitative marginal analysis before and after thermo-mechanical loading. Results: Higher percentages of marginal adaptation at the total margin length, both before and after thermo-mechanical loading, were found in groups in which enamel was etched with phosphoric acid, without significant differences between the chemically and dual-cured modes. The restorations performance was similar on enamel and dentin, obtaining low results of adaptation on occlusal enamel in the groups without enamel etching, the lowest scores were on cervical dentin in the group with no ortophosphoric acid and self-cured. Conclusions: A dual-cure composite applied in bulk on acid etched enamel obtained acceptable marginal adaptation results, and may be an alternative technique for the restoration of class II cavities

    In vitro evaluation of marginal and internal adaptation after occlusal stressing of indirect class II composite restorations with different resinous bases and interface treatments. "Post-fatigue adaptation of indirect composite restorations”

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    The present study evaluated the influence of different composite bases and surface treatments on marginal and internal adaptation of class II indirect composite restorations, after simulated occlusal loading. Thirty-two class II inlay cavities were prepared on human third molars, with margins located in cementum. A 1-mm composite base extending up to the cervical margins was applied on all dentin surfaces in the experimental groups; impressions were made and composite inlays fabricated. The following experimental conditions were tested: no liner (control group), flowable composite treated with soft air abrasion (experiment 1), flowable composite sandblasted (experiment 2) and restorative composite sandblasted (experiment 3). All specimens were submitted to 1,000,000 cycles with a 100-N eccentric load. Tooth-restoration margins were analysed semi-quantitatively by scanning electron microscopy before and after loading; internal adaptation was also evaluated after test completion. The percentage of perfect adaptation in enamel was 79.5% to 92.7% before loading and 73.3% to 81.9% after loading. Perfect adaptation to dentin was reduced before loading (54.8% to 77.6%) and after loading (41.9% to 63%), but no difference was found among groups for pre- and post-loading conditions. No debonding occurred between the base and composite luting. A significant, negative influence of cyclic loading was observed. The results of the present study support the use of flowable or restorative composites as base/liner underneath large class II restorations. Soft air abrasion represents a potential alternative to airborne particle abrasion for treating cavities before cementation. The application of a composite base underneath indirect composite restorations represents a feasible non-invasive alternative to surgical crown lengthening to relocate cavity margins from an intra-crevicular to supra-gingival positio

    Influence of Storage Media on Color Stability of Different Resin Composites as Determined by \u394E and \u394E00

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    Objective: To evaluate the color stability of 3 different resin composites when exposed to storage in water, air or artificial saliva. Materials and Methods: Initial color of 81 specimens was assessed by a calibrated reflectance spectrophotometer over a black as well as a white background. Specifically, 9 disc shaped specimens made out of 3 resin composite materials were kept in distilled water, air and artificial saliva (Glandosane) at 37\ub0C. After a storage period of 4 weeks, spectrophotometric measurements were repeated and the color changes calculated by means of \u394E and \u394E00. Results: When analysed over a white background, median \u394E values varied from 0.6 (Filtek Supreme Dentin/water) to 7.1 (Filtek Supreme Enamel/Glandosane). When analysed over a black background median \u394E values varied from 0.4 (Filtek Supreme Dentin/water) to 5.0 (Filtek Supreme Enamel/Glandosane). When analysed over a white background, median \u394E00 values varied from 0.4 (Filtek Supreme Dentin/water) to 4.6 (Filtek Supreme Enamel/Glandosane). When analysed over a black background median \u394E00 values varied from 0.4 (Filtek Supreme Dentin/water) to 4.6 (Filtek Supreme Enamel/Glandosane). Statistical analysis performed by means of ANOVA and Fisher\u2019s LSD post hoc tests showed differences between groups. The correlation between \u394E and \u394E00 was 99.09% and 99.65% over black and white background, respectively. Conclusion: Within the limits of the present study, storage media significantly influenced color stability of resin composites

    In Vitro Assessment of Single-Retainer Tooth-Colored Adhesively Fixed Partial Dentures for Posterior Teeth

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    The purpose of this paper was to investigate, by means of marginal adaptation and fracture strength, three different types of single retainer posterior fixed partial dentures (FPDs) for the replacement of a missing premolar. Two-unit cantilever FPDs were fabricated from composite resin, feldspathic porcelain, and fiber-reinforced composite resin. After luting procedures and margin polishing, all specimens were subjected to a Scanning Electron Microscopic marginal evaluation both prior to and after thermomechanical loading with a custom made chewing simulator comprising both thermal and mechanical loads. The results indicated that the highest score of marginal adaptation, that is, the closest score to 100% of continuous margins, at the tooth-composite resin interface was attained by the feldspathic porcelain group (88.1% median), followed by the fiber-reinforced composite resin group (78.9% median). The worse results were observed in the composite resin group (58.05% median). Fracture strength was higher in feldspathic porcelain (196N median) when compared to resin composite (114.9 N median). All the fixed prostheses made of fiber-reinforced composite resin detached from the abutment teeth before fracturing, suggesting that the adhesive surface's retainer should be increased

    Light polymerization during cavity filling: influence of total energy density on shrinkage and marginal adaptation

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    The aim of the study was to evaluate the marginal adaptation and shrinkage stress development of a micro hybrid restorative composite as a function of energy density. Linear displacement and shrinkage forces were measured with custom-made devices for energies of 4,000, 8,000, 16,000 and 32,000mJ/cm2 at a constant power density of 800mW/cm2. Marginal adaptation of composite restorations cured with the same energy density was evaluated before and after mechanical loading with 300,000 cycles at 70N. The group "4,000mJ/cm2” showed the lowest shrinkage force [2.9(0.2)kg] and linear displacement [23.5(0.7)μm] but led to the worst marginal adaptation after loading [46.4(23.5)%CM] probably due to under-curing. When the maximum energy of 32,000mJ/cm2 was applied, a slight increase in shrinkage forces [3.6(0.2)kg and 29.2(0.8)μm], and a slight decrease in marginal adaptation after loading [75.4(11.5)%CM] were observed, but these changes were not significantly different in comparison to groups cured with energies of 8,000 and 16,000mJ/cm2. For the resin composite tested in this study, no differences in marginal adaptation could be detected above the energy threshold of 8,000mJ/cm2
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