CAD-CAM milled complete dentures with custom disks and prefabricated artificial teeth: A dental technique.

A digital complete denture was manufactured from a disk customized for each patient. The custom disk was made of resin and contained prefabricated artificial teeth. Both the denture base and the artificial teeth in the custom disk were milled in this technique, resulting in dentures with a high bond strength between the artificial teeth and denture base, excellent esthetics because of the prefabricated artificial teeth, and accurate occlusion because of the custom occlusal surface.

Evaluation of trueness and precision of stereolithography-fabricated photopolymer-resin dentures under different postpolymerization conditions: An in vitro study.

STATEMENT OF PROBLEM: Stereolithography (SLA) additive manufacturing (AM) technologies have become popular for the fabrication of complete dentures; however, the trueness and precision of the dentures under different postpolymerization conditions remain unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of different postpolymerization times and temperatures on the trueness and precision of SLA dentures. MATERIAL AND METHODS: Specimens simulating maxillary complete dentures were fabricated by SLA 3D printing. They were polymerized for 15 minutes or 30 minutes at different temperatures (40 °C, 60 °C, and 80 °C). The intaglio surface trueness of the specimens was evaluated by superimposing the postpolymerization standard tessellation language (STL) file on the original STL file for each specimen via a best-fit method (n=10). The precision was measured across specimens by superimposing the postpolymerization STL file from each specimen group and using the combination formula (n=45). Subsequently, root-mean-square estimates (RMSEs) and color map data were obtained, and a normality test was conducted on the obtained data. The results indicated that the distributions were not normal; therefore, nonparametric Kruskal-Wallis and Mann-Whitney tests were used to analyze the data (α=.05). RESULTS: For trueness, the lowest RMSE corresponded to the postpolymerization time of 30 minutes and a temperature of 40 °C. This result was significantly different from specimens those of the 15-minute and 60 °C, 15-minute and 80 °C, and 30-minute and 80 °C specimens (P<.001). For precision, the median of the lowest RMSE corresponded to the 30-minute and 40 °C specimens. This median value was significantly different from those of other specimens (P<.001). The findings indicate that the postpolymerization condition of 30 minutes and 40 °C affords the highest trueness and precision and the most favorable intaglio surface adaptation of the denture. CONCLUSIONS: The postpolymerization conditions influenced the RMSE values of the trueness and precision of a clear photopolymer resin. The RMSE and color map data associated with the 30-minute and 40 °C condition corresponded to the greatest trueness and precision of all the SLA denture specimens considered.

Trueness and precision of artificial teeth in CAD-CAM milled complete dentures with custom disks.

STATEMENT OF PROBLEM: Insufficient information is available regarding the trueness and precision of artificial teeth in computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete dentures fabricated from custom disks, including prefabricated teeth. PURPOSE: The purpose of this in vitro study was to determine the trueness and precision of the position of the artificial teeth arranged in CAD-CAM milled complete dentures manufactured by using a custom disk method and to compare the trueness and precision of different tooth types and the occlusal surface and entire surface of the teeth. MATERIAL AND METHODS: The milling data were designed by using a CAD software program. Four types of artificial teeth (maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar) were arranged concentrically in the disk with 3 corresponding teeth per disk. Five custom disks were milled based on the milling data. The sample size for maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar was 15. The standard tessellation language data were obtained by scanning the milled disks with cone beam computed tomography. The obtained data were superimposed by using a CAD software program to assess the trueness and precision of the tooth positions. For the occlusal surface, the data were superimposed after trimming to assess the trueness and precision of the tooth position with respect to the entire tooth surface. After data superimposition, the deviation was analyzed by using a 3-dimensional analysis software program to obtain the mean absolute error values and color maps. The data were analyzed by using 2-way ANOVA and the Games-Howell post hoc test (α=.05). RESULTS: Significant differences were found in the mean absolute error values of the position trueness of the entire surface between the different teeth, except for maxillary-left first premolar and maxillary-left first molar (P<.05). Moreover, significant differences in the mean absolute error values of the precision for the entire surface were observed between mandibular-left central incisor and maxillary-left first premolar, as well as between mandibular-left central incisor and maxillary-left first molar (P<.05). The mean absolute error values of the position trueness of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar (P<.05). Finally, the mean absolute error values of the position precision of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor and maxillary-left first premolar (P<.05). CONCLUSIONS: The trueness and precision of the posterior teeth were higher than that of anterior teeth. The trueness of the movement of the artificial teeth during the manufacturing of dentures by using the custom disk method was found to be within a clinically acceptable range.

Mechanical properties of a polymethyl methacrylate block for CAD/CAM dentures.

This study compared the mechanical properties and molecular distribution of a polymethyl methacrylate (PMMA) block (Dry) with specimens that were fabricated by a conventional method and cured in a wet environment (Control). Two specimen types were fabricated with heat-curing denture base resin. Dry specimens were polymerized at high pressure and in a dry system, while Control specimens were polymerized with a heat-curing method, in accordance with the manufacturer's recommended procedures. Specimens from each group were evaluated for three-point bending, water sorption and solubility, and color change, and by gel permeation chromatography (GPC). Mean values for the flexural strengths and moduli of the Dry specimens were significantly higher than those of the Control specimens (P > 0.05). Water sorption and discoloration values of the Dry group were significantly lower than those of the Control group. Mean weight-average molecular weights of the Dry group were higher than those of the Control group. As compared with the conventional method, the present method of fabricating PMMA blocks under high pressure yields superior mechanical properties for the denture base.

Effect of printing direction on stress distortion of three-dimensional printed dentures using stereolithography technology.

Fabrication of complete dentures using a 3D printer is quicker and more economic than conventional methods. However, the photopolymer resins used in 3D printers has a lower flexural strength than heat-cured resin. Furthermore, photopolymer resins exhibit anisotropic properties depending on the printing direction, but no studies have evaluated their mechanical properties. The impact of stress distribution caused by changing the printing direction of the 3D printed denture has not been clarified. This study aimed to investigate the effect of different printing directions (0°, 45°, and 90°) of stereolithography (SLA) 3D printed dentures on stress distribution. Artificial mucosa was fabricated to fit a maxillary edentulous model, which was scanned to generate a standard tessellation language (STL) file. Subsequently, the upper denture was designed using computer-aided design (CAD) software, output as an STL file (master data), and set in three different printing directions (0°, 45°, and 90°). It was printed by the SLA 3D printer using photopolymer resin (n=6, in each printing direction). The stress distributions of the dentures were monitored using four rosette strain gauges, which were cemented to the midline of each denture as follows: above the labial frenum (A), at the incisive papilla (B), at the endpoint of the denture (D), and at the mid-point of B and D (C). A load was applied to the posterior region at a loading rate of 20 N/s from 0 N to 200 N using a universal testing machine. Changes in the applied load and strain at each point were recorded. The maximum principal strain (MPS) and the direction of the MPS (θ) were calculated. Each mean MPS was compared using Kruskal-Wallis and Steel-Dwass multiple comparison tests (p < 0.05). The stress distribution showed that the MPS for 45° printing was the lowest at each measurement point except for A under 200 N loading. The MPS at C for 0° was significantly different from that at C for 45° and 90°. The MPS at D in all the printing directions showed significant differences. The MPS at B for 45° was significantly different from that at B for 90°. The MPS at A in all printing directions showed no significant difference. Within the limitations of this study, differences in printing direction affected the stress distribution of SLA 3D printed dentures. The results showed that the stress distribution of the denture printed at 45° by the 3D printer system was the smallest compared with dentures printed at 0° and 90°. These results suggest that a printing direction of 45° is preferable when fabricating dentures using a 3D printer in clinical setting.

Effect of Printing Direction on the Accuracy of 3D-Printed Dentures Using Stereolithography Technology.

This study evaluated the effects of the differences in the printing directions of stereolithography (SLA) three-dimensional (3D)-printed dentures on accuracy (trueness and precision). The maxillary denture was designed using computer-aided design (CAD) software with an STL file (master data) as the output. Three different printing directions (0°, 45°, and 90°) were used. Photopolymer resin was 3D-printed (n = 6/group). After scanning all dentures, the scanning data were saved/output as STL files (experimental data). For trueness, the experimental data were superimposed on the master data sets. For precision, the experimental data were selected from six dentures with three different printing directions and superimposed. The root mean square error (RMSE) and color map data were obtained using a deviation analysis. The averages of the RMSE values of trueness and precision at 0°, 45°, and 90° were statistically compared. The RMSE of trueness and precision were lowest at 45°, followed by 90°; the highest occurred at 0°. The RMSE of trueness and precision were significantly different among all printing directions (p < 0.05). The highest trueness and precision and the most favorable surface adaptation occurred when the printing direction was 45°; therefore, this may be the most effective direction for manufacturing SLA 3D-printed dentures.

Digital impression and jaw relation record for the fabrication of CAD/CAM custom tray.

PURPOSE: This article describes the protocol of a digital impression technique to make an impression and recording of the jaw relationship of edentulous patients for the fabrication of CAD/CAM custom tray using computer-aided design and manufacturing (CAD/CAM) technology. METHODS: Scan the maxillary and mandibular edentulous jaws using an intraoral scanner. Scan the silicone jig with the maxillary and mandibular jaws while keeping the jig between the jaws. Import the standard tessellation language data of the maxillary and mandibular jaws and jig to make a jaw relation record and fabricate custom trays (CAD/CAM trays) using a rapid prototyping system. Make a definitive impression of the maxillary and mandibular jaws using the CAD/CAM trays. CONCLUSIONS: Digitalization of the complete denture fabrication process can simplify the complicated treatment and laboratory process of conventional methods In addition, the proposed method enables quality control regardless of the operator's experience and technique.

Evaluating the influence of ambient light on scanning trueness, precision, and time of intra oral scanner.

PURPOSE: This study evaluated the influence of illuminance and color temperature of ambient light on the trueness, precision, and scanning time of a digital impression. METHODS: Master data were acquired with a high-accuracy coordinate-measuring machine. The illuminance of ambient light was set at 0lux, 500lux, and 2500lux with a light-emitting diode (LED). Using a conversion filter, the color temperature was set at 3900 Kelvin (K) (yellow), 4100K (orange), 7500K (white), and 19,000K (blue). There were thus a total of 12 possible lighting conditions. The reference model was scanned five times under each condition by an intraoral scanner. Trueness was calculated as the mean difference between the master data and experimental data. Precision was calculated as the mean difference between the repeated scans in each test group. Statistical analysis was performed with two-way analysis of variance (ANOVA) and post hoc Tukey's multiple comparison test. The significance level was 0.05. RESULTS: For trueness, the mean deviation was significantly lower at 500lux than at 0lux and 2500lux. At 500lux, the mean deviation was significantly lower at 3900K than at other temperatures. Regardless of the color temperature, the scanning time was significantly longer at 2500lux than at other illuminance levels. CONCLUSIONS: The 3900K and 500lux condition is the most appropriate lighting condition for taking a digital impression. This condition is typical of clinical settings. High illuminance ambient light increased the scanning time.

In vitro evaluation of basal shapes and offset values of artificial teeth for CAD/CAM complete dentures.

STATEMENT OF PROBLEM: Artificial teeth are bonded onto the recesses of a milled denture base in a complete denture prepared using computer-aided design/computer-aided manufacturing (CAD/CAM). Little is known, however, about the effects of basal shapes and offset values on the accuracy of positions of the bonded artificial teeth.