The best wetting is obtained when preparations are completed with finishing burs, allowing high p... more The best wetting is obtained when preparations are completed with finishing burs, allowing high precision castings. However, the smooth surface generated may reduce the frictional retention of traditional, nonadhesive luting agents. Although it is known that different dental rotary instrument types produce distinct surface roughness of the axial walls which may contribute to the clinical performance of a cast restoration, the ideal roughness that produces optimum wetting at the adhesive interface is unclear. Purpose. The purpose of this study was to characterize the surface roughness and its influence on wettability of teeth prepared for complete veneer crowns with different dental rotary instruments. Material and methods. Sixty standardized tooth preparations for complete crowns were completed using a modified milling machine on extracted human teeth with diamond, tungsten carbide finishing, and cross-cut carbide rotary instruments of similar shape (n=20). Morphological changes obtained were investigated with a surface texture analyzer. Two additional specimens from each group were treated and prepared for scanning electron microscopy. The contact angle of a drop of distilled water on each of the prepared surfaces was used as the measure of wettability with a goniometer microscope. The data were analyzed with 1-way ANOVA and Tukey's Honestly Significant Difference (HSD) test (α=.05). Results. Surface preparation resulted in significant differences for surface topography and wettability (P<.001). The carbide burs had significantly higher mean roughness readings (SD) for all parameters: Ra (8.6 (1.9) µm), Rq (10.9 (2.2) µm), and Ry (41.1 (2.1) µm), except for the mean Rz (12.1 (3.1) µm) value, which was recorded for diamonds. The other roughness parameters for the diamond rotary instruments were intermediate. Teeth completed with carbide finishing burs produced a smoother surface Ra (1.2 (0.5) µm), Rq (1.6 (0.6) µm), Ry (6.4 (2.6) µm), and Rz (1.9 (0.6) µm). The highest mean contact angle (SD), 81.5 (9.1) degrees, was associated with diamond rotary instruments, and the lowest (75.3 (5.9) degrees) was recorded for finishing burs. The contact angle for teeth prepared with tungsten carbide burs was intermediate: 76.1 (5.9) degrees. The selection of dental rotary instruments for tooth preparation significantly affects surface roughness and wettability of dentin, which may influence the retention of cast restorations. (
On considkre la cubique J" =x3-Ax-B, A, BE Z, et on suppose que A = 16(4A'-27B') # 0. On exprime ... more On considkre la cubique J" =x3-Ax-B, A, BE Z, et on suppose que A = 16(4A'-27B') # 0. On exprime dans ce travail des conditions ntcessaires et suffkantes pour que mM (resp. T+mM) soit A-entier, lorsque M est un point A-entier, T un point de 2-torsion sur Q de la courbe, et m un entier rationnel. Ces conditions portent sur les polynhmes 4, et I), qui permettent d'exprimer l'abscisse de mM. Nous donnons des exemples d'application qui montrent que ces conditions peuvent &tre utiliskes dans la pratique. Si la courbe est de rang 1 sur Q avec Cventuellement des points de 2-torsion rationnels, on peut espkrer trouver tous les points A-entiers de la courbe.
To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite o... more To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite on the fracture resistance of weakened marginal ridges in molar teeth. 50 sound extracted human mandibular molars were used. Specimens were divided into five groups (n = 10). Group 1: served as a control for comparison; Group 2: Class I cavity preparation with resin composite (Prodigy); Group 3: Class I cavity preparation with polyethylene ribbon fiber (Ribbond) and resin composite. Group 4: Class II cavity preparation with resin composite restoration; Group 5: Class II cavity preparation with polyethylene woven fiber and resin composite. Specimens were stored in 100% humidity at 37 degrees C for 7 days. Compressive loading of the teeth was performed with a universal testing machine at a cross-head speed of 0.5 mm/minute until failure. The data were analyzed with 1-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch Multiple Range Test (alpha = 0.05). Reinforcement with polyethylene fiber...
The best wetting is obtained when preparations are completed with finishing burs, allowing high p... more The best wetting is obtained when preparations are completed with finishing burs, allowing high precision castings. However, the smooth surface generated may reduce the frictional retention of traditional, nonadhesive luting agents. Although it is known that different dental rotary instrument types produce distinct surface roughness of the axial walls which may contribute to the clinical performance of a cast restoration, the ideal roughness that produces optimum wetting at the adhesive interface is unclear. Purpose. The purpose of this study was to characterize the surface roughness and its influence on wettability of teeth prepared for complete veneer crowns with different dental rotary instruments. Material and methods. Sixty standardized tooth preparations for complete crowns were completed using a modified milling machine on extracted human teeth with diamond, tungsten carbide finishing, and cross-cut carbide rotary instruments of similar shape (n=20). Morphological changes obtained were investigated with a surface texture analyzer. Two additional specimens from each group were treated and prepared for scanning electron microscopy. The contact angle of a drop of distilled water on each of the prepared surfaces was used as the measure of wettability with a goniometer microscope. The data were analyzed with 1-way ANOVA and Tukey's Honestly Significant Difference (HSD) test (α=.05). Results. Surface preparation resulted in significant differences for surface topography and wettability (P<.001). The carbide burs had significantly higher mean roughness readings (SD) for all parameters: Ra (8.6 (1.9) µm), Rq (10.9 (2.2) µm), and Ry (41.1 (2.1) µm), except for the mean Rz (12.1 (3.1) µm) value, which was recorded for diamonds. The other roughness parameters for the diamond rotary instruments were intermediate. Teeth completed with carbide finishing burs produced a smoother surface Ra (1.2 (0.5) µm), Rq (1.6 (0.6) µm), Ry (6.4 (2.6) µm), and Rz (1.9 (0.6) µm). The highest mean contact angle (SD), 81.5 (9.1) degrees, was associated with diamond rotary instruments, and the lowest (75.3 (5.9) degrees) was recorded for finishing burs. The contact angle for teeth prepared with tungsten carbide burs was intermediate: 76.1 (5.9) degrees. The selection of dental rotary instruments for tooth preparation significantly affects surface roughness and wettability of dentin, which may influence the retention of cast restorations. (
On considkre la cubique J" =x3-Ax-B, A, BE Z, et on suppose que A = 16(4A'-27B') # 0. On exprime ... more On considkre la cubique J" =x3-Ax-B, A, BE Z, et on suppose que A = 16(4A'-27B') # 0. On exprime dans ce travail des conditions ntcessaires et suffkantes pour que mM (resp. T+mM) soit A-entier, lorsque M est un point A-entier, T un point de 2-torsion sur Q de la courbe, et m un entier rationnel. Ces conditions portent sur les polynhmes 4, et I), qui permettent d'exprimer l'abscisse de mM. Nous donnons des exemples d'application qui montrent que ces conditions peuvent &tre utiliskes dans la pratique. Si la courbe est de rang 1 sur Q avec Cventuellement des points de 2-torsion rationnels, on peut espkrer trouver tous les points A-entiers de la courbe.
To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite o... more To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite on the fracture resistance of weakened marginal ridges in molar teeth. 50 sound extracted human mandibular molars were used. Specimens were divided into five groups (n = 10). Group 1: served as a control for comparison; Group 2: Class I cavity preparation with resin composite (Prodigy); Group 3: Class I cavity preparation with polyethylene ribbon fiber (Ribbond) and resin composite. Group 4: Class II cavity preparation with resin composite restoration; Group 5: Class II cavity preparation with polyethylene woven fiber and resin composite. Specimens were stored in 100% humidity at 37 degrees C for 7 days. Compressive loading of the teeth was performed with a universal testing machine at a cross-head speed of 0.5 mm/minute until failure. The data were analyzed with 1-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch Multiple Range Test (alpha = 0.05). Reinforcement with polyethylene fiber...
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