ABSTRACT
Objectives: This study aimed to evaluate and compare the effect of plasma treatment versus conventional treatment on the micro shear bond strength (µSBS), surface roughness, and wettability of three different CAD/CAM materials. Materials and methods: Sixty cylindrical specimens (5 mm diameter × 3 mm height) were prepared from three different CAD/CAM materials: Group A: Zirconia, Group B: Lithium disilicate, and Group C: Resin nano-ceramic. Each group was subdivided into two subgroups according to surface treatment used: Subgroup I: Conventional treatment, zirconia was sandblasted with Al2O3, while lithium disilicate and resin nano-ceramic were etched with hydrofluoric acid. Subgroup II: Plasma treatment, the surface of each material was treated with a plasma device (PiezoBrush® PZ3 Handheld Device, Relyon Plasma, Regensburg, Germany). G-Multi PRIMER was applied, then self-adhesive cement (G-CEM ONE) was applied using a split mold (1 mm diameter × 3 mm height), and µSBS was tested in a universal testing machine. The surface roughness was measured using a profilometer. Nine additional specimens of each material for wettability test using an optical tensiometer. Statistical analysis: The data were analyzed using ANOVA and Bonferroni test at a level of significance of 0.05. Results: The highest mean of µSBS was recorded by AII (27.3 MPa), while the lowest was recorded by AI (17.9 MPa). One-way ANOVA test revealed a significant difference among groups. Bonferroni test showed each two subgroups significant difference except subgroups AI, CI and BII, CII, where there was a non-significant difference. For all CAD/CAM materials, conventional treatment increased the surface roughness compared to plasma treatment, while the contact angle decreased after plasma treatment. Conclusion: Plasma treatment increased the µSBS of resin cement to zirconia significantly while not significantly affecting the µSBS of resin nano-ceramic. Conventional treatment of lithium disilicate provided significantly higher µSBS than plasma treatment.
ABSTRACT
Objectives: This in vitro study aimed to evaluate and compare the fracture resistance and mode of failure of endodontically treated maxillary premolar teeth restored with different direct composite restorative techniques. Materials and Methods: Forty freshly extracted maxillary premolar teeth with comparable sizes were used in this in vitro study. Each tooth received mesio-occluso-distal cavity preparation (3 mm width and 6 mm depth) followed by endodontic treatment. Canals were instrumented with RACE EVO rotary files (FKG, Dentaire, Switzerland) up to MAF 25/.06. Canals were obturated using a single cone technique, then the teeth were divided arbitrarily into five groups (n = 8): Group A: direct composite resin only using a centripetal technique, Group B: direct composite resin with glass fiber post, Group C: direct composite resin with short fiber-reinforced composite (everX Flow), Group D: direct composite resin with leno wave ultra high molecular weight polyethylene (LWUHMWPE) fibers placed on cavity floor, and Group E: direct composite resin with LWUHMWPE fibers placed circumferentially around the cavity walls (wallpapering technique). The teeth were then stored in distilled water at 37°C for 24 hr. The fracture resistance of each sample was measured using a universal testing machine in Newton (N). The data were analyzed using one-way analysis of variance (ANOVA) and the Bonferroni test with a significance level of 0.05. Results: Group E recorded the maximum mean of fracture load (2,139.375 N), while Group A recorded the minimum mean of fracture load (689.6250 N). The one-way ANOVA test revealed a significant difference between the groups. The Bonferroni test showed a significant difference between each two groups, with the exception of those between Groups B and C and between Groups D and E, where there were no statistically significant differences (p > 0.05). Conclusion: Restoration of endodontically treated teeth using the wallpapering technique recorded the highest mean of fracture resistance with a repairable mode of fracture.
ABSTRACT
OBJECTIVE: This study aimed to evaluate the accuracy in terms of trueness and precision of eight intraoral scanners (IOS) and the effect of different finishing line designs on the IOS's accuracy. MATERIALS AND METHODS: Three printed models of the maxillary arch with maxillary right first molar virtually prepared with chamfer, shoulder, and vertical preparation designs were used as master models in this study. Each model was scanned 30 times with each IOS: Medit i700, Planscan Emerald S, CEREC Primescan, TRIOS 3, CS3600, MEDIT i500, Heron 3Disc, and Cerec Omnicam. The trueness was measured by superimposition of the scanned dataset made with IOS and the scanned dataset made with a lab scanner (In Lab Medit T710) that was used as a reference and the deviation was measured and expressed as a color-coded map by the metrology program (Medit compare, version 2.3.5.892), while precision was measured by the superimposition of the scans of each IOS on each other.The data were analyzed statistically using repeated measure analysis of variance (ANOVA) test, one-way ANOVA test, and Bonferroni test at significance level of 0.05. RESULTS: The tested IOS showed significant differences in trueness and precision. Medit i700 and CEREC Primescan recorded the highest precision with no significant difference between them, while Medit i700 recorded the highest trueness as compared to other IOS. Each IOS showed significant differences in trueness and precision with the three finishing line designs except CEREC Primescan and Heron 3 disc that showed no significant difference in trueness with the three finishing line designs and CS3600 that showed no significant difference in precision with the three finishing line designs. CONCLUSION: A significant difference in accuracy was found among the tested IOS and the type of finishing line design had a significant effect on IOS's accuracy.
ABSTRACT
OBJECTIVE: The aim of this study was to evaluate the influence of different marginal designs (deep chamfer, vertical, and modified vertical with reverse shoulder) on the fracture strength and failure modes of monolithic zirconia crowns. MATERIALS AND METHODS: Thirty sound human maxillary first premolar teeth with comparable size were used in this study. The teeth were divided randomly into three groups according to the preparation design (n = 10): (1) group A: teeth prepared with a deep chamfer finish line; (2) group B: teeth prepared with vertical preparation; and (3) group C: teeth prepared with modified vertical preparation, where a reverse shoulder of 1 mm was placed on the buccal surface at the junction of middle and occlusal thirds. All samples were scanned by using an intraoral scanner (CEREC Omnicam, Sirona, Germany), and then the crowns were designed by using Sirona InLab 20.0 software and milled with a 5-axis machine. Each crown was then cemented on its respective tooth with self-adhesive resin cement by using a custom-made cementation device. A single load to failure test was used to assess the fracture load of each crown by using a computerized universal testing machine that automatically recorded the fracture load of each sample in Newton (N). STATISTICAL ANALYSIS: The data were analyzed statistically by using one-way analysis of variance test and Bonferroni test at a level of significance of 0.05. RESULTS: The highest mean of fracture load was recorded by chamfer (2,969.8 N), which followed by modified vertical (2,899.3 N) and the lowest mean of fracture load was recorded by vertical (2,717.9 N). One-way ANOVA test revealed a significant difference among the three groups. Bonferroni test showed a significant difference between group A and group B, while a nonsignificant difference was revealed between group C with group A and group B. CONCLUSION: Within the limitations of this in vitro study, the mean values of fracture strength of monolithic zirconia crowns of all groups were higher than the maximum occlusal forces in the premolar region. The modification of the vertical preparation with a reverse shoulder placed at the buccal surface improved the fracture strength up to the point that it was statistically nonsignificant with the chamfer group.
