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Background: Two intra‐coronal preparation designs with varying extensions of cuspal coverage can perform differently regarding their fracture resistance against introral forces. Methods: Two materials (IPS e‐max CAD [EX], VITA ENAMIC [EN]), and two different preparation designs (EX‐D1), (EX‐D2), (EN‐D1), and (EN‐D2) were investigated to compare their fracture resistance. A total of 40 (n = 40) caries free human mandibular molars were used. All the prepared samples were scanned using CEREC Omnicam scanner and the preparations were checked by the software for any sharpness and undercuts before restoration designing and fabrication. All restorations were milled using Cerec MCXL 4.4 milling machine. Duo‐Link resin cement was used for cementation. After thermocycling and chewing simulation, all samples were loaded in the Universal testing machine in order to evaluate fracture resistance of all samples. Results: Fracture resistance testing revealed that e‐max CAD (2134 N) showed statistically significantly higher mean fracture resistance values than Vita Enamic (1728 N). On the other hand, there was no statistically significant difference between mean fracture resistances between the two tested designs. Conclusions: Within the confines of this investigation, it can be said that although preparation design had no appreciable impact on fracture resistance, the CAD/CAM ceramic material utilized did. Clinical Significance: When restoring compound cavitties indirectly; a conservative defect oriented approach should be used. Glass Ceramic are prefered as restorative material. [ABSTRACT FROM AUTHOR]

Purpose: This article reviews a press-on metal (POM) ceramic versus a conventional veneering system regarding marginal gaps, fracture resistance, microhardness, and surface roughness. This was done to provide clinical recommendations for its use. Materials and Methods: Forty crowns were constructed and divided into two main groups according to the metal coping design. Group 1: Twenty metal copings with metal margin extending to the axiogingival line angle. Group 2: Twenty metal copings with metal margin 1 mm occlusal to the axiogingival line angle. The specimens of each group were further subdivided into two subgroups (A and B) according to the veneering porcelain used. The vertical marginal gaps of the crowns were measured after veneering placement. For fracture resistance testing, the crowns were subjected to compressive load to failure. Representative samples of the two main groups were selected to measure surface roughness and microhardness. Results: No statistically significant difference was evident regarding the vertical marginal gap distance in relation to the margin design of both tested groups ( p= 0.249, p= 0.815); however, the POM veneer group with metal porcelain margin showed statistically lower marginal gaps than the conventional ceramic veneer group ( p= 0.043). Fracture resistance values did not show statistically significant difference regarding the margin design ( p= 0.858, p= 0.659) or type of the ceramic veneer material ( p= 0.592, p= 0.165). Both groups showed no significant difference in their mean roughness values ( p= 0.235). Conventional ceramics showed statistically significantly higher mean microhardness values than POM did ( p= 0.008). Conclusion: This study showed superior marginal adaptation, decreased microhardness, and similar load to failure and roughness values of the POM ceramic system. Moreover, considerable ease and speed of fabrication of this system were evident. The high variation in range values of some tested groups is among the limitations of this study, along with the lack of clinical trials to test the system in vivo. [ABSTRACT FROM AUTHOR]

This study was undertaken to assess the influence of three-veneering materials on the marginal fit, fracture resistance, and failure pattern of In-Ceram alumina crowns. Forty In-Ceram cores were constructed and divided into four groups of ten each. Ten alumina cores were left unveneered, forming the first group for core testing, while the other 30 copings were divided into three groups depending on the veneering material used. The vertical marginal gaps of the alumina copings were measured before and after veneer placement at 16 sites using an optical microscope. The specimens were then loaded to fracture at a crosshead speed of 1 mm/min. Fractured specimens were examined, and the fracture patterns of the crowns were recorded. Selected specimens were examined using scanning electron microscope. Data were presented as means and standard deviation values. One-way ANOVA was used to compare between mean gap areas and fracture resistance of the three materials. Duncan's post hoc test was used for pairwise comparison between the means when ANOVA test was significant. Vitadur-N-veneered crowns showed statistically the highest mean vertical gaps, while no significant difference was evident between the marginal fits of Vitadur-α- and VM7-veneered crowns. Regarding the strength, a statistically significant decrease in fracture resistance of the cores was evident after veneering with Vitadur-N; however, no significant change in mean fracture resistance value of Vitadur-α- and VM7-veneered crowns was evident compared to the alumina cores. VM7-veneered crowns showed the highest fracture resistance values. Vitadur-N-veneered crowns showed the highest mean vertical gaps and the lowest mean fracture resistance values of the tested groups, while VM7-veneered crowns combined the highest fracture resistance values and clinically acceptable margins. The best interface quality and finest ceramic texture were evident in case of VM7 material. [ABSTRACT FROM AUTHOR]

Purpose: This study was designed to evaluate three veneering materials for an all-ceramic alumina system in terms of bond strength, microhardness, and core/veneer interface quality. Materials and Methods: Fifteen In-Ceram cores were constructed for this study, forming three groups of five specimens each divided by the veneering ceramic disc fired on the occlusal surface of the alumina core: Vitadur N, Vitadur Alpha, or VM7. The specimens underwent shear bond and microhardness testing. Gross examination of debonded discs by SEM and EDAX analysis was conducted. Data for shear bond strength (SBS) and microhardness were presented as means and standard deviation (SD) values. One-way ANOVA and Duncan's post hoc test were used for pairwise comparison between the means when ANOVA test was significant. Results: VM7 showed the highest shear bond value and lowest microhardness values of the three tested veneering materials. No statistically significant difference was evident between the SBSs of Vitadur N and Vitadur Alpha to the alumina cores. Vitadur Alpha showed statistically the highest mean VHN, followed by Vitadur N, while VM7 showed statistically the lowest mean values of VHN. Conclusions: In-Ceram core/Vitadur N disc debondings appeared to be interfacial by complete delaminations, leaving a shiny visible and quite distinct area, whereas there appeared to be perfect adhesion between the core and VM7 veneering material. VM7 appeared to possess ultra-fine texture with intimate contact to the core, forming what seemed like a transition zone where the ceramic and core appeared to blend for a distance. VM7's finer particle size has improved the core/veneer bond strength and decreased micohardness values. This new veneering material will probably enhance the performance and esthetics of the In-Ceram system. [ABSTRACT FROM AUTHOR]

Purpose: This study was designed to compare an alternative indirect treatment to repair fractured or chipped veneering metal ceramic using recently developed ultra-low-fusing ceramics. Materials and Methods: One conventional feldspathic ceramic, Vita Omega, and three ultra-low-fusing ceramics (ULFC), Finesse, Duceram LFC, and Vision-low, were used. Forty ceramic specimens were prepared and divided into two groups. Group I (n = 20) was designed for bond strength testing. It comprised four subgroups (A, B, C, D): one Ceramic-resin (A) and three Ceramic-ULFC disc specimens of different diameters (B, C, D). Group II was composed of repaired ceramic discs using direct and indirect repair methods for biaxial testing. It was comprised of five subgroups: the fractured discs from subgroup A; Omega discs (n = 20) formed the repaired specimens of the four remaining subgroups: B, C, D, E. Data were presented as means and standard deviation (SD) values. One-way analysis of variance (ANOVA) was used for comparison between means. Tukey's post hoc test was used for pairwise comparison between the means when ANOVA test was significant. The significance level was set at p≤ 0.05. Results: Within group I, Omega-Ducera LFC showed the statistically highest mean bond strength (25.8 MPa) values, followed by Omega-Finesse (15.8 MPa). No statistically significant difference was apparent between Omega-Vision (9.3 MPa) and the control Omega-Composite group (7.5 MPa). Regarding group II, the Control Omega subgroup showed statistically the highest mean biaxial strength values (168.8 MPa). No statistically significant difference was evident between the values of Omega-Finesse (78.7 MPa), Omega-Vision (78.4 MPa), and Omega-Composite (82.5 MPa). Omega-Ducera LFC subgroup, showed statistically the lowest mean values (53 MPa). Conclusions: Omega-Ducera LFC yielded the statistically highest mean bond strength values, and the lowest biaxial strength values. All values were within the reported bond strength values for resin repair. All the tested groups showed significantly lower values compared to the initial biaxial strength mean values of the Omega ceramic; however, two of the tested ULFC (Vision, Finesse), recorded means that were statistically equal to the resin-ceramic direct subgroup. Duceram LFC showed the lowest values, probably due to its totally glass composition, which showed low strength values of the repaired specimens. The recorded bond and biaxial values suggest that indirect repair of fractured LFC using some ULFC ceramics may offer an alternative solution to the traditional direct resin repair method; however, the choice of the used ceramic should be one containing some leucite crystals. Further studies are needed to investigate the long-term performance of the proposed repair treatment. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare the effect of three curing modes of a high-powered curing-light source on the shear bond strength and marginal gap of light- and dual-cured adhesive resin cements to dentin. Materials and Methods: Twelve freshly extracted intact human mandibular molars were selected for this study and stored in the saline solution. Three of the axial surfaces of the teeth were prepared to obtain flat dentinal surfaces. Thirty-six ceramic disks (4-mm diameter, 2- mm thick) were constructed from a pressable glass-ceramic (Vision). The discs were etched with hydrofluoric acid and primed, and then divided into two equal groups, groups I and II (n = 18 each). Two adhesive systems were used following manufacturer's instructions. The discs of group I were bonded to the conditioned dentin surface using adhesive resin (Rely X Veneer), and group II discs were bonded to dentin using Rely X ARC. For each group, the resin was cured using three modes (fast, ramp, pulse). Interfacial gap at the dentin/resin interface was measured at eight predetermined sites for each specimen using a stereomicroscope, and shear bond strength of the bonded specimens was carried out using a universal testing machine. Results: Ramp-cured specimens recorded significantly higher mean shear bond strengths for both dual- and light-polymerized resins than those with fast and pulse modes. Moreover, fewer interfacial gaps were found at the resin/dentin interface in association with ramp cure modes of both resins. Most failures were adhesive failures at the dentin–resin luting agent (RLA) interface in specimens polymerized using high-powered LED fast or pulse modes, while a cohesive failure pattern within the resin was associated with the ramp-curing mode. Conclusion: Within the limitations of this study, the shear bond strength of an RLA to dentin was found to be enhanced with light- or dual-polymerized adhesive resin using an LED light in ramp mode, whereas shear bond strength was significantly lower when polymerized using LED in fast or pulse modes. [ABSTRACT FROM AUTHOR]

Purpose: This study assessed the efficiency of reinforcing provisional restorations by adding a fine gauze metallic mesh or polyethylene fibers between the abutments spanning the pontic length. Materials and Methods: Forty-five resin fixed partial dentures (FPDs) were constructed using three provisional resins. The three resin groups were further divided into three subgroups depending on their reinforcement. Specimens were loaded compressively, and the load required to fracture the specimens was recorded in Newtons. Data were presented as means and standard deviation values. A regression model with two-way ANOVA was used in testing significance. Duncan's post hoc test was used for pairwise comparison ( p≤ 0.05). Results: Duralay resin and Duralay fiber-reinforced restorations showed the highest fracture-resistance values, followed by Protemp and Snap, which showed statistically similar values. The three mesh-reinforced resin restoration materials showed no statistically significant difference between their fracture resistance values. Reinforcement did not alter the fracture resistance of Duralay and Protemp resin subgroups, but significantly increased that of Snap, equalizing it with the other resins. The three resin materials had similar moduli. Significant alterations occurred after fiber reinforcement. Results showed that fiber-reinforced Duralay resin showed the highest modulus values, while no statistical difference was found between the moduli of fiber-reinforced Protemp and Snap. Regarding the mesh-reinforced groups, Duralay had the highest modulus followed by Protemp and Snap. Reinforcements altered the modulus values of Duralay resin only. Mesh-reinforced Duralay resin showed the highest mean modulus, but no statistically significant difference was apparent between fiber-reinforced and control groups. As for Protemp and Snap resin subgroups, their moduli remained unchanged by reinforcements. Conclusion: Initially, Duralay resin had higher fracture resistance values than Protemp II and Snap. Fiber and mesh reinforcements increased the fracture resistance of Snap. No statistically significant difference was evident among the fracture resistances of the three mesh-reinforced resin FPD restorations. The three resins had similar moduli. Fiber and mesh reinforcement increased the modulus of Duralay resin but did not change that of Protemp and Snap. Fiber and metal mesh reinforcements may alter the fracture strength and modulus of some, but not all, provisional resins. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated the effect of artificial saliva storage on the hardness, crack length, and fracture toughness of a glazed, polished, and bleached hydrothermal low-fusing glass-ceramic (Duceram LFC). Materials and Methods: Forty ceramic discs were constructed. The discs were assigned to four groups (n = 10) according to their surface finish: Gp1—Autoglaze, Gp2—Autoglaze/ground/diamond-polished, Gp3—Overglaze, Gp4—Overglaze/ground/diamond-polished. Each group was further divided into two subgroups forming eight total subgroups (n = 5). Subgroup A was unbleached; Subgroup B was bleached. Testing was performed before and after 21 days of artificial saliva storage. Data were presented as means and standard deviation (SD). ANOVA was used, along with Duncan's post hoc test for pairwise comparison between the means when ANOVA test was found significant ( p≤ 0.05). Results: Surface treatments such as glazing, polishing, and bleaching, saliva storage, and the interaction between these variables had a statistically significant effect on mean values of microhardness, crack length, and fracture toughness of the specimens. There was a statistically significant increase in microhardness and fracture toughness mean values, while crack length values decreased after saliva storage. Polished specimens recorded the smallest crack lengths and fracture toughness, and highest hardness values before and after saliva storage. No difference in fracture toughness values was evident between glazed and polished specimens. Mean crack lengths decreased after saliva storage in all the tested specimens. Hardness values increased after saliva storage. The autoglazed group showed significantly higher fracture toughness, lower crack length, and microhardness than the overglazed group. Conclusions: Surface finishing procedures and artificial saliva storage had a statistically significant effect on mean values of microhardness, crack length, and fracture toughness. This in vitro study suggests that fracture toughness of ceramics may be affected by different surface treatments such as glazing, polishing, bleaching, or a combination; however, in this study Duceram LFC proved its self-healing property after 3-week storage in artificial saliva. [ABSTRACT FROM AUTHOR]

Purpose: This study examined the effect of a manufacturer's proposed bleaching protocol on surface properties of a low-fusing ceramic. Materials and Methods: Forty ultra low-fusing ceramic samples (Ducera LFC) were constructed for this study. Half the discs were autoglazed, and the other half were overglazed. The two main groups (autoglaze, overglaze) were further divided into subgroups of four. Group I: autoglazed (control group I), bleached autoglaze, diamond polished, diamond polished and bleached. The same division was applied to Group II: overglazed (control group II), bleached overglazed, diamond polished, diamond polished and bleached. The total number of subgroups was eight. Control groups I and II (n = 10) were both immersed in distilled water, which was changed daily for 1 week. The other six subgroups (n = 30) were subjected to the following protocol: 2-hour bleaching using carbamide peroxide 35%, followed by six 8-hour bleaching applications using 15% carbamide peroxide gel. Every two bleaching procedures were interrupted by a 10-hour fluoride gel application. At the end of each bleaching step, the treated specimens were washed under running water in readiness for the next application. Results: Bleaching did not significantly affect the surface roughness of the autoglazed group; however, it significantly increased the roughness of the overglazed ceramic, especially after polishing. Regarding whiteness, the overglazed group had significantly increased values compared to the autoglazed group. It appeared that bleaching whitened the overglazed specimens significantly, whereas polishing alone showed less whiteness. There appeared to be a strong inverse relation between the roughness and the whiteness of the autoglazed specimens as affected by the bleaching. On the other hand, a weak inverse relation was found between the roughness and whiteness of the overglazed specimens, as affected by the bleaching. Conclusions: In-office bleaching with 35% carbamide peroxide, followed by home bleaching with 15% carbamide peroxide and a fluoride gel may affect the roughness and whiteness of overglazed and polished/overglazed Duceram LFC restorations. No significant change in roughness or whiteness was detected by this bleaching system on autoglazed Ducera LFC. Ceramic restorations should be protected before any bleaching for fear of altering their roughness and whiteness. Patients should be advised that their existing porcelain restorations may not match their natural teeth after bleaching. [ABSTRACT FROM AUTHOR]