We aimed to investigate the stress relaxation properties of five different thermoplastic aligner materials subjected to 14 days of constant deflection. Five different thermoplastic aligner materials were selected, whose elastic properties varied: F22 Evoflex, F22 Aligner, Durasoft, Erkoloc-Pro and Duran. The static properties of these materials—in particular, stiffness, stress–strain curve and yield stress—were measured with a three-point bending test. For all the tests that were performed, a minimum of three samples per material were tested. The yield load, yield strength, deformation and particularly the stiffness of each material were found to be similar in the single-layer samples, while the double-layer samples showed far lower stiffness values and were similar one to another. F22 Evoflex and Erkoloc-Pro maintained the highest percentages of stress, 39.2% and 36.9%, respectively, during the 15-day period. Duran and Durasoft obtained the lowest final stress values, 0.5 MPa and 0.4 MPa, respectively, and the lowest percentage of normalized stress, 4.6% and 3.9%, respectively, during the 15-day period. All the materials that we tested showed a rapidity of stress decay during the first few hours of application, before reaching a plateau phase. The F22 Evoflex material showed the greatest level of final stress, with relatively constant stress release during the entire 15-day period. Further research after in vivo aging is necessary in order to study the real aligners’ behavior during orthodontic treatment.

Background: The purpose of the present in vivo study was to compare the accuracy, in terms of trueness, between full-arch digital impressions of different intraoral scanning systems, using as a reference the ideality of the conventional impression technique. Methods: Polyvinyl siloxane (PVS) two-step technique impressions of 27 subjects were taken, and the stone casts were scanned using desktop scanners R500 3Shape. For each arch, in vivo scans were taken with intraoral scanners Carestream CS3600, CEREC Omnicam and Trios 3Shape. All the files were compared, superimposing them on the reference model to calculate the total 3D and 2D deviations. The efficiency of the digital and conventional workflows was evaluated by measuring the work time in minutes. Statistical analyses were performed using R software (R Core Team 2020) with a p-value < 0.05. Results: The three intraoral scanners differed from the PVS impression by differences of the order of 100–200 µm, and there was a trend of greater imprecision in the molar area in both dental arches. In comparison with PVS technique, CEREC tended to reduce the size of the impression, Trios presented the trend of greater precision, and Carestream showed minor differences the transversal distance. The areas of greatest discrepancy both in excess and in defect with respect to the PVS impression were the molar areas and incisal margins. Trios 3Shape recorded the shortest times and therefore with a more performing speed. Conclusion: The Trios 3Shape was found to be the most accurate single-tooth scanner, while the Carestream CS 3600 showed better inter-arch diameter performance compared to PVS impressions. The 3D and 2D analyses showed a trend of greater distortion of the impressions compared to the conventional one in the molar region.

Background: The aim of the study was to compare the accuracy and reproducibility of three different 3D facial scanning systems, relying, respectively, on stereophotogrammetry, structured light and a smartphone app and camera. Methods: Thirty subjects have been scanned with three different facial scanning systems, stereophotogrammetry, structured light and a smartphone app and camera. Linear measurements were compared with direct anthropometries measured on the patient's face, while the study of areas (forehead, tip of the nose, chin, right and left cheek) was evaluated by overlapping scans using the Geomagic Control X program. Statistical analyses were conducted using IBM SPSS v28 software. Results: The ANOVA test was used to compare linear distances and direct anthropometry measurements, revealing statically significant values for all distances investigated, especially for the Face Hunter scanner, except for the Prn–Pog′ distance (p = 0.092). The three facial scans were superimposed pairwise almost the 100 per cent of the overlapping areas fell within the tolerance limits for all three comparisons analysed. The chin was the most accurately reproduced, with no differences among scanners, while the forehead proved to be the least accurately reproduced by all scanners. Conclusions: All three acquisition systems proved to be effective in capturing 3D images of the face, with the exception of the Face Hunter scanner, that produced statistically significant differences in linear measurements for the distances Tr–Na′ and Zyg–Zyg with respect to direct anthropometric measurements.

Objectives: To compare the degree of accuracy of the Face Hunter facial scanner and the Dental Pro application for facial scanning, with respect to both manual measurements and each other. Materials and Methods: Twenty-five patients were measured manually and scanned using each device. Six reference markers were placed on each subject's face at the cephalometric points Tr, Na′, Prn, Pog′, and L–R Zyg. Digital measurement software was used to calculate the distances between the cephalometric reference points on each of the scans. Geomagic X Control was used to superimpose the scans, automatically determining the best-fit alignment and calculating the percentage of overlapping surfaces within the tolerance ranges. Results: Individual comparisons of the four distances measured anthropometrically and on the scans yielded an intraclass correlation coefficient index greater than .9. The t -test for matched samples yielded a P value below the significance threshold. Right and left cheeks reached around 60% of the surface, with a margin of error between 0.5 mm and −0.5 mm. The forehead was the only area in which most of the surface fell within the poorly reproducible range, presenting values out of tolerance of more than 20%. Conclusions: Three-dimensional scans of the facial surface provide an excellent analytical tool for clinical evaluation; it does not appear that one or the other of the measuring tools is systematically more accurate, and the cheeks are the area with the highest average percentage of surface in the highly reproducible range.

The aim was to compare the soft tissue changes in pretreatment and posttreatment facial scans of patients who had undergone various orthopedic treatments vs a control group of untreated growing patients. Facial scans were performed before (T0) and after (T1) orthopedic treatment in 15 patients prescribed rapid palatal expander (RPE), 15 cervical headgear (HG), and 15 facemasks (FM), as well as 6 months apart in 15 untreated growing patients. After best-fit scan alignment using Geometric Control X software (3D Systems Inc, Rock Hill, SC), a 3-dimensional (3D) analysis of soft tissue changes was performed, comparing 3D reference points (total 22) and 8 areas on T0 and T1 scans. Kruskal-Wallis nonparametric tests and pairwise comparison with Bonferroni's correction were applied to identify any statistically significant differences among groups (P <0.05). All analyses were conducted with SPSS software (version 28; IBM, Armonk, NY). At T1, reduced soft tissue projection was found at the nose and upper lip in the HG group, the lower lip in the HG and RPE groups, and the chin in the FM and RPE groups. The RPE group displayed a statistically significant increase in facial divergence, confirmed by gnathion position (RPE vs FM [P = 0.018] and RPE vs control [P = 0.046]), as well as an increase in the soft tissue projection of both cheeks (left cheek in range of 1-2 mm [P = 0.030] and range of 0 to -1 mm [P = 0.022]; right cheek in range of 1-2 mm [P = 0.003] and range -1 to -2 mm [P = 0.001]). There were no clinically significant differences among groups in mandibular right and left body areas. The 3D facial analysis revealed significant differences in soft tissues among orthopedic treatments, especially at the upper and lower lip and chin areas, as compared with untreated patients.

The widespread use of CAD/CAM transfer trays warrants evaluation of their accuracy as compared to PVS transfer trays. To quantify the accuracy of CAD/CAM and PVS transfer trays, investigating any differences between soft and hard trays CAD/CAM transfer trays. Eight different databases (Scopus, Web of Science, PubMed, Google Scholar, ProQuest, Embase, Cochrane Library, ClinicalTrials.gov) were searched, without restrictions, up to an end date of February 2023. Clinical trials (randomized and non-randomized) and in vitro studies reporting average imprecision values for bracket positioning obtained by digital superimpositions of digitally planned and real positions. Data eligibility, data extraction, and risk of bias (RoB-2 and ROBINS-I) were conducted independently. The data, where possible, were synthesized and quantitatively analysed (meta-analysis of mean differences with 95% confidence intervals). The Grade of Recommendation, Assessment, Development and Evaluation (GRADE) analysis of the quality of evidence was performed. The t-test for independent samples was used to compare the transfer accuracy of hard and soft CAD/CAM transfer trays. Thirteen studies were synthesized in this systematic review, and then eight studies were included in the quantitative meta-analysis. As regards linear measurements, there was a mean transfer error of 0.0752 mm (95%CI: 0.0428, 0.1076) for mesiodistal measures, 0.0943 mm (95%CI: 0.0402, 0.1484) for vertical, and 0.0815 mm (95%CI: 0.0469, 0.1160) for buccolingual. As for angular measurements, there was an average transfer error of 1.2279° (95% CI: 0.6011, 1.8548) for inclination, 0.9397° (95%CI: 0.4672, 1.4123) for angulation, and 0.8721° (95%CI: 0.4257, 1.3185) for rotation. CAD/CAM transfer trays were less accurate than polyvinylsiloxane (PVS) transfer trays, with those made of soft material being more accurate than the hard ones, except for vertical dimension. The GRADE quality of evidence ranged from very low to moderate. CAD/CAM transfer trays provide high bracket positioning accuracy, with soft transfer trays offering greater precision than rigid ones. Future randomized prospective trials are required to enhance the strength of the available evidence. Prospero (CRD42023401278 number)