Accuracy of 3-unit fixed dental prostheses fabricated on 3D-printed casts.

STATEMENT OF PROBLEM: Three-dimensional (3D)-printed casts are used successfully as diagnostic casts in orthodontics. However, whether 3D-printed casts are sufficiently accurate to be used as definitive casts for fixed dental prostheses (FDPs) is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the fit of 3-unit FDPs fabricated on 3D-printed casts made by digital light processing and to investigate the clinical applicability of 3D printing. MATERIAL AND METHODS: A master model was fabricated from epoxy resin. Stone casts were made from dual viscosity impressions (conventional stone cast [CS] group, n=10). The 3D-printed casts were fabricated using a 3D printer after obtaining digital virtual casts by digital scans (3D-printed cast [3DP] group, n=10). All FDPs were fabricated with a 5-axis milling machine. The master model and intaglio surface of the milled FDPs was superimposed using 3D analysis software to measure the accuracy. Two-way ANOVA was performed to identify a significant difference between the groups (3DP and CS) and sides (pontic side, nonpontic side) and their interactive effects (α=.05). The Tukey honestly significant difference test was used for post hoc analysis. RESULTS: Two-way ANOVA showed significant differences between the 2 groups (3DP and CS) in the marginal and internal root mean square (RMS) values (P<.001). However, no significant difference was found in the marginal RMS values (P=.762) between the pontic and nonpontic sides. The 3DP showed significantly higher RMS values than the CS (P<.001). CONCLUSIONS: The fit of FDPs produced from 3D-printed casts was inferior to that of conventional stone casts; however, all FDPs showed clinically acceptable accuracy. These results suggest that 3D-printed casts have clinical applicability but that further improvement of the 3D printer is necessary for their application in prosthodontics.

A comparison of different thicknesses of mouthguards according to the groove shape of sheets.

BACKGROUND/AIMS: Previous studies have compared the thickness of the device with and without grooves. The result was a difference in thickness of the device along the groove. The aim of this study was to assess the differences in thickness of mouthguards that result from different groove shapes of ethylene vinyl acetate sheets used to make these appliances. MATERIALS AND METHOD: Mouthguards were made using a 3-dimensional printer, and produced by softening 4 mm transparent circular sheets. Four different shapes of sheets were evaluated: normal sheets, sheets with anterior V-shaped grooves, sheets with anterior A-shaped grooves, and sheets with posterior A-shaped grooves. The groove was 3 mm deep and 5 mm wide. The thickness of the appliance was assessed with respect to the anterior incisal edge, labial surface, palatal surface, posterior cusp, buccal surface, and palatal surface. The Kruskal-Wallis test was used to analyze differences in thickness among the different groove shapes. RESULTS: No significant difference was detected between the thickness of mouthguards made using sheets with grooves and that of mouthguards made using sheets without grooves (P > .05). CONCLUSION: The presence of grooves on the sheets did not influence mouthguard thickness.

Pressure Differences from Clear Aligner Movements Assessed by Pressure Sensors.

OBJECTIVES: In this study, a clear aligner was moved at intervals of 0.25 mm and pressure variations were assessed using a sensor. METHODS: The model used for producing the clear aligner was created using a 3-dimensional printer. A clear, circular thermoplastic of 0.75 mm thickness was used for making the clear aligner using the vacuum forming method. A pressure sensor was used to assess the pressure in the device, and the variation in the sheet pressure was statistically analyzed tooth movement using the clear aligner, moving at an interval of 0.25 mm, is recommended. RESULTS: The results of pressure sensor assessment showed that the pressure of the devices with 0.25 mm and 1.00 mm movements was identical to that of the device with 0 mm movement. In other words, the pressure sensor could not distinguish the pressure of devices that moved 0.25 mm and 1.00 mm. CONCLUSIONS: This experiment demonstrated that a movement of more than 0.50 mm is needed to apply the appropriate pressures needed for orthodontics in a clear polymer sheet.

Comparing the accuracy (trueness and precision) of models of fixed dental prostheses fabricated by digital and conventional workflows.

PURPOSE: This study aimed to evaluate and compare the accuracy. METHODS: A reference model was prepared with three prepared teeth for three types of restorations: single crown, 3-unit bridge, and inlay. Stone models were fabricated from conventional impressions. Digital impressions of the reference model were created using an intraoral scanner (digital models). Physical models were fabricated using a three-dimensional (3D) printer. Reference, stone, and 3D printed models were subsequently scanned using an industrial optical scanner; files were exported in a stereolithography file format. All datasets were superimposed using 3D analysis software to evaluate the accuracy of the complete arch and trueness of the preparations. One-way and two-way analyses of variance (ANOVA) were performed to compare the accuracy among the three model groups and evaluate the trueness among the three types of preparation. RESULTS: For the complete arch, significant intergroup differences in precision were observed for the three groups (p<.001). However, no significant difference in trueness was found between the stone and digital models (p>.05). 3D printed models had the poorest accuracy. A two-way ANOVA revealed significant differences in trueness among the model groups (p<.001) and types of preparation (p<.001). CONCLUSIONS: Digital models had smaller root mean square values of trueness of the complete arch and preparations than stone models. However, the accuracy of the complete arch and trueness of the preparations of 3D printed models were inferior to those of the other groups.

Panax ginseng enhances cognitive performance in Alzheimer disease.

Recent experimental evidences suggest protective and trophic effects of ginseng in the memory function of Alzheimer disease (AD). Thus, we investigated the clinical efficacy of Panax ginseng in the cognitive performance of AD patients in an open-label study. Consecutive AD patients were randomly assigned to the ginseng (n=58) or the control group (n=39), and the ginseng group was treated with Panax ginseng powder (4.5 g/d) for 12 weeks. Cognitive performances were monitored using the mini-mental state examination (MMSE) and Alzheimer disease assessment scale (ADAS) during 12 weeks of the ginseng treatment and at 12 weeks after the ginseng discontinuation. MMSE and ADAS scales showed no baseline difference between the groups. After ginseng treatment, the cognitive subscale of ADAS and the MMSE score began to show improvements and continued up to 12 weeks (P=0.029 and P=0.009 vs. baseline, respectively). After discontinuing ginseng, the improved ADAS and MMSE scores declined to the levels of the control group. These results suggest that Panax ginseng is clinically effective in the cognitive performance of AD patients.

Evaluation of the marginal and internal fit of a single crown fabricated based on a three-dimensional printed model.

PURPOSE: To evaluate the fit of a crown produced based on a 3D printed model and to investigate its clinical applicability. MATERIALS AND METHODS: A master die was fabricated with epoxy. Stone dies were fabricated from conventional impressions (Conventional stone die group: CS, n=10). Digital virtual dies were fabricated by making digital impressions (Digital Virtual die group: VD, n=10). 3D data obtained from the digital impression was used to fabricate 3D printed models (DLP die group: DD, n=10, PolyJet die group: PD, n=10). A total of 40 crowns were fabricated with a milling machine, based on CS, VD, DD and PD. The inner surface of all crowns was superimposed with the master die files by the "Best-fit alignment" method using the analysis software. One-way and 2-way ANOVA were performed to identify significant differences among the groups and areas and their interactive effects (α=.05). Tukey's HSD was used for post-hoc analysis. RESULTS: One-way ANOVA results revealed a significantly higher RMS value in the 3D printed models (DD and PD) than in the CS and DV. The RMS values of PD were the largest among the four groups. Statistically significant differences among groups (P<.001) and between areas (P<.001) were further revealed by 2-way ANOVA. CONCLUSION: Although the fit of crowns fabricated based on the 3D printed models (DD and PD) was inferior to that of crowns prepared with CS and DV, the values of all four groups were within the clinically acceptable range (<120 µm).

Evaluation of shear bond strength of veneering ceramics and zirconia fabricated by the digital veneering method.

PURPOSE: The purpose of this study was to evaluate the shear bond strength (SBS) of veneering ceramic and zirconia fabricated by the digital veneering method. METHODS: A total of 50 specimens were fabricated, i.e., 10 specimens each for the metal-ceramic (control) group and the four zirconia groups. The zirconia groups comprised specimens fabricated by the digital veneering method, the heat pressing method, and hand layering method for two groups, respectively. Furthermore, the shear bond strength was measured with a universal testing machine (Model 3345, Instron, Canton, MA, USA) and statistically analyzed using one-way ANOVA set at a significance level of P<0.05. The corresponding mode of failure was determined from Scanning Electron Microscope (FESEM JSM 6701F, Jeol Ltd., Japan) observations. RESULTS: One-way analysis of variance (ANOVA) revealed that the metal-ceramic group had the highest SBS (43.62MPa), followed by the digital veneering method (28.29MPa), the heat pressing method (18.89MPa), and the layering method (18.65, 17.21MPa). The samples fabricated by digital veneering had a significantly higher SBS than the other zirconia samples (P<0.05). All of the samples exhibited mixed failure. CONCLUSIONS: Veneering ceramic with a zirconia core that was fabricated via the digital veneering method is believed to be effective in clinical use since, its shear bond strength is significantly higher than that resulting from the conventional method.

Transcriptional and translational expression of calbindin-D9k in the duodenum, kidney and uterus of a female canine model.

Calbindin-D9k (CaBP-9k) is a cytosolic calcium-binding protein expressed in tissues in the intestine, uterus, placenta, kidney, pituitary gland and bone. Its exact function is unknown, but it is considered to regulate intracytoplasmic concentration and transport of free ions (Ca(2+)). CaBP-9k protein is involved in intestinal calcium absorption in the intestine and in the regulation of myometrial activity by intracellular calcium in the uterus. Renal CaBP-9k protein is expressed at the site of calcium re-absorption in the kidney and expressed in distal convoluted tubules, where it is thought to facilitate calcium re-absorption. Expression of the CaBP-9k gene has been explored in most mammalians except in a canine model. Presently, we elucidated the expression of CaBP-9k mRNA and protein in the duodenum, kidney and uterus in a canine model involving two adult (2.5-year-old) female beagles. To collect tissues, the dogs were euthanized and then the abdominal cavity was exposed by midline incision. The proximal duodenum, cortex of kidney and uterine horn were collected. Expression of CaBP-9k mRNA was confirmed by reverse transcriptionpolymerase chain reaction (RT-PCR) and real-time PCR. CaBP-9k protein expression and localization were ascertained by Western blot analysis and immunohistochemistry, respectively. CaBP-9k mRNA was detected in the duodenum, but not in the kidney and uterus. Its protein was expressed only in the enterocytes of the duodenum. Taken together, the results indicate that CaBP-9k mRNA and protein are highly expressed in the enterocytes of the duodenum of a canine model, consistent with findings in other mammalian species.