Effect of the difference water amounts and hydrolysis times of silane coupling agent on the shear bond strength between lithium disilicate glass ceramic and composite resin.

This study was to evaluate the effect of different water amounts and hydrolysis times of silane coupling agent on shear bond strength between lithium disilicate glass ceramic (LDS) and composite resin. Fourteen groups (n=7) of different water amounts (90, 50 and 10%v/v) and hydrolysis times (5, 19, 75 and 300 s) of experimental silane coupling agent that were prepared for silanization, non-silanization and commercial silane coupling agent (CSC) groups. Two-way analysis of variance (ANOVA) revealed no interaction between water amounts and hydrolysis times of ESC on shear bond strength between LDS and composite resin. One-way ANOVA exhibited the highest shear bond strength and the highest mean percentage in mixed failure mode in the 50%v/v group. Molecular analysis of 13C and 29Si indicated that nuclear magnetic resonance spectra of M2 and M3 hydrolysis species were found in 50%v/v group. The presenting of M2 and M3 which was predominant factor contributing to the highest shear bond strength.

Effects of build orientation and bar addition on accuracy of complete denture base fabricated with digital light projection: An in vitro study.

PURPOSE: We evaluated the effects of build orientation and bar addition between lingual flanges on the accuracy of mandibular denture bases fabricated using a digital light processing (DLP) device. METHODS: Mandibular denture bases with and without a bar at the lingual flanges were virtually designed and assigned to eight build orientations. Six dentures per condition were fabricated using a DLP device with a methacrylate-based photopolymerizable monomer (Dima Print denture base) (n=96). The fabricated denture surfaces were digitized, and intaglio surfaces were obtained. These digitized surfaces were compared via superimposition using graphical software (Artec studio12 profession) to their original designed files, and root mean square estimates were obtained. The trueness of the entire and intaglio data was statistically analyzed non-parametrically. RESULTS: The range of trueness of the entire and intaglio denture bases was 0.15-0.31 mm and 0.11-0.38 mm, respectively. The trueness at 135° and 270° for the entire denture base and that at 270° for the intaglio data without the bar were significantly lower than those for the other build orientations. The trueness at 270° was <0.15 mm irrespective of the conditions. The trueness with the bar of all build orientations, except that of 0° for intaglio data, was significantly smaller than or equal to the trueness without the bar of the corresponding build orientations. CONCLUSIONS: Build orientation and bar addition influenced the accuracy of the complete dentures fabricated using DLP. A build orientation of 270° is recommended for fabricating a mandibular complete denture, irrespective of the bar addition.

Effects of build orientation on adaptation of casting patterns for three-unit partial fixed dental prostheses fabricated by using digital light projection.

STATEMENT OF PROBLEM: The lost-wax technique is commonly used for fabricating partial fixed dental prostheses. The casting patterns can be fabricated by using vat photopolymerization (a type of additive manufacturing), but the adaptation of these casting patterns has not been elucidated. PURPOSE: The purpose of this in vitro study was to evaluate the effect of build orientation on the adaptation of casting patterns fabricated by digital light projection (DLP). MATERIAL AND METHODS: A 3-unit partial fixed dental prosthesis with mandibular left second premolar and second molar abutment teeth was scanned and virtually designed with a computer-aided design software program. The cement space was designed to be 30 µm. Specimens were fabricated with 3 build orientations: 0 degrees (with the occlusal surface parallel to the platform), 30 degrees, and 45 degrees (by rotating the file along the long axis). The casting patterns were fabricated by using DLP (Cara Print 4.0) with a photopolymerizable monomer (dima Print Cast Q). Photopolymerization, cleaning, and postpolymerization processes were performed according to the manufacturer's instructions. The adaptation of the specimens was examined by using a silicone replica method. The vertical marginal discrepancy and axial wall, occlusal, and marginal gaps were measured by using a digital measuring microscope. The effect of build orientation at each cross-sectional area was statistically analyzed by using the Kruskal-Wallis test followed by the pairwise Wilcoxon rank sum test with Bonferroni correction (α=.05). RESULTS: Excess polymerized resin was observed along the intaglio buccal wall at build orientations of 30 degrees and 45 degrees. Vertical marginal discrepancies in the buccolingual section ranged from -50 to 248 µm, while those in the mesiodistal section ranged from -25 to 182 µm. The gaps in the buccolingual section ranged from 0 to 236 µm, while those in the mesiodistal section ranged from 0 to 177 µm. According to the observation of vertical marginal discrepancies and gaps, the 30-degree specimens inclined during insertion, and the 45-degree specimens were not completely seated. However, the marginal gaps of the 0- and 30-degree specimens were within the clinically acceptable limit of 120 µm. CONCLUSIONS: The limited data indicated that the build orientation influenced the adaptation of casting patterns for 3-unit partial fixed dental prostheses fabricated by using DLP. A build orientation of 0 degrees is recommended for fabricating casting patterns for 3-unit partial fixed dental prostheses because no excess polymerization of the intaglio buccal wall was observed.

Effects of build conditions and angle acuteness on edge reproducibility of casting patterns fabricated using digital light projection.

The aim of the present study was to evaluate the effects of build conditions and angle acuteness on edge reproducibility of the casting patterns fabricated using a digital light process. The prism-shaped patterns with various vertex angles were fabricated in three build orientations. The height from the base to the vertex angle point of the fabricated pattern was measured and the incomplete height was calculated as the discrepancy between the original and measured heights. Two-way ANOVA revealed that the vertex angle and build orientation and their interaction were significant (p<0.05). The incomplete height significantly decreased with an increase of the vertex angle. When the vertex angle was 20° and the build-up direction was parallel to the edge of vertex angle and perpendicular to the triangular base, the incomplete height was the smallest. Therefore, build orientation and angle acuteness influenced the edge reproducibility of the casting patterns fabricated using a digital light process.