This study evaluated the effects of print orientation and thermal aging on the flexural strength (FS) and flexural modulus (FM) of novel permanent three-dimensional (3D)-printed polymethyl methacrylate (PMMA) resins reinforced with nano-zirconia and nano-silica. Bar-shaped specimens (25 × 2 × 2 mm) were fabricated using a digital light processing (DLP) 3D printer (Asiga Max UV, Asiga Inc., Australia) in two orientations (0° and 90°). Specimens underwent three-point bending tests at 24 h and after artificial thermal aging (10,000 and 30,000 cycles) to simulate one and three years of intraoral conditions. Scanning electron microscopy (SEM) was used to analyze fracture patterns. Print orientation did not significantly affect FS or FM (p > 0.05). However, artificial aging significantly reduced FS and FM after 10,000 cycles (p < 0.001), with further deterioration after 30,000 cycles. The micro hybrid resin composite exhibited higher FS than the 3D-printed materials throughout aging. SEM analysis revealed distinct fracture patterns, with 3D-printed resins displaying radial fractures and the micro hybrid composite exhibiting horizontal fractures. These findings indicate that aging plays a more critical role in the long-term mechanical performance of 3D-printed restorative resins than print orientation. This study provides original data on the effects of print orientation and prolonged thermal aging on the mechanical behavior of permanent three-dimensional (3D)-printed dental resins. Furthermore, the comparative evaluation of aging protocols simulating one and three years of intraoral service represents a novel contribution to the existing literature. Further studies are required to optimize the mechanical durability of 3D-printed dental restorations.

This study aimed to assess the impact of various fabrication techniques and polishing procedures on the surface roughness (Ra) of resin-based materials used in the fabrication of complete dentures. A total of 90 specimens were produced from three different resin materials: heat-polymerized polymethyl methacrylate (PMMA) resin, CAD-CAM milled PMMA resin, and 3D-printed resin (n = 30). Each specimen measured 10 mm in diameter and 2 mm in height. The surface roughness (Ra) values of the specimens were initially determined using a contact profilometer following fabrication. Subsequently, each group of specimens was polished with 600-, 800-, and 1000-grit silicon carbide abrasive papers under running water. A second measurement of the surface roughness (Ra) values was then performed. The data were analyzed statistically using the Kruskal-Wallis test, Mann-Whitney U test, Wilcoxon signed-rank test, and paired samples t-test (p = 0.05). A statistically significant difference was identified between the groups in terms of surface roughness (Ra) prior to the polishing process (p < 0.001). However, no statistically significant difference was observed between the milled and heat-polymerized PMMA base materials following the polishing process. The 3D-printed specimens showed the most notable improvement in surface roughness due to the polishing process. Nevertheless, their surface roughness remained statistically significantly higher compared to the other samples, both before and after polishing (p < 0.001). The fabrication method of complete denture base materials was observed to influence surface roughness. The surface roughness values of the base materials fabricated using the 3D printing method were higher compared to those fabricated with milled and heat-polymerized PMMA resin, both before and after polishing.

This study aimed to evaluate the effect of cavity depth on the accuracy of intraoral scanners (IOS) in intra-coronal restorations, focusing on trueness and precision as defined by International Organization for Standardization (ISO) 5725 standards. Three intra-coronal cavity designs with depths of 2.5 mm (n = 10), 5 mm (n = 10), and 7.5 mm (n = 10) were fabricated using 3-Dimentional (3D) printed tooth models. Scans (n = 30) were performed using the Trios 3 intraoral scanner, and accuracy was assessed by comparing scanned models to reference models. Trueness was measured as the root mean square (RMS) deviation, and precision was calculated from the interquartile range of average absolute distances. Statistical analyses were conducted using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction. The accuracy of the IOS was significantly lower at a cavity depth of 7.5 mm compared to 5 mm and 2.5 mm (p < 0.05). RMS values were highest for the 7.5 mm depth, while the lowest precision was observed at this depth. Cavity depth significantly affects the accuracy of IOS in intra-coronal restorations, with deeper cavities resulting in reduced accuracy. This highlights the importance of considering cavity depth when planning IOS workflows. This study shows that scanning accuracy decreases when the distance between the cavity floor and the cusp tip exceeds 5 mm. Elevating the cavity floor with direct methods may help improve scanning accuracy and enhance restoration outcomes.

Objectives: Although spectrophotometers are commonly used in shade analysis in dentistry; digital cameras, photographic lighting systems, computer programs and photographs have also become the part of this field. The aim of this study was to compare the success of spectrophotometer and calibrated digital photography on shade selection. Materials and Methods: 3D-Master toothguide (VITA) with 29 tabs was used for the analyses. L, a, b values were determined by a spectrophotometer (Minolta CM-2300D, Konica) and these values were matched with digital photographic measurements. Photographs were transferred to an image analyzing software (Adobe Photoshop CC). Results: There were significant differences between L* values of the spectrophotometric analyses and digital measurements in 3 different regions of the tab (p<0.05). For the evaluation of ΔE values, Post hoc Bonferroni analysis which was performed between the 3 regions of shade tabs revealed significant difference between the middle (21.92 ± 2.31), incisal (13.67 ± 1.69) and cervical (19.57 ± 2.47) region of the tabs (p<0.05). Conclusion: Spectrophotometer was found to be a more accurate shade determination technique compared to calibrated digital photography.

Objective: This in vitro study aimed to assess the accuracy of an intraoral scanner in inlay preparations with different geometry. Methods: The upper second premolar tooth-shaped models were designed and prepared using a 3D printer (Phrozen Mega 8K, Phrozen, Taiwan). Three distinct inlay preparation configurations were utilized, including buccal and palatal wall divergence at 6°, 8°, and 10°. The reference 3D images were acquired through scanning of each model with varying inlay preparation using an extraoral scanner (E1, 3Shape, Denmark). Thirty 3D images (samples) were obtained from each of the three models (n = 10) using an intraoral scanner (Trios 3, 3Shape, Denmark). The samples and reference images were saved in Standard Tessellation Language (STL) and imported into software (Geomagic Control X 2022, 3D Systems Inc., USA). Discrepancies between the reference image and the samples were recorded as root mean square (RMS) and standard deviation (SD). Kruskal Wallis and Mann Whitney U tests, and interquartile range (IQR) were used for statistical analysis with THE significance level p