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BACKGROUND/OBJECTIVES: The use of different models for the fabrication of custom-fit mouthguards (MTGs) can affect their final thickness, adaptation, and shock-absorption properties. This study aimed to evaluate the adaptation, thickness, and shock absorption of ethylene-vinyl acetate (EVA) thermoplastic MTGs produced using conventional plaster or three-dimensional (3D) printed models. MATERIALS AND METHODS: A typical model with simulated soft gum tissue was used as the reference model to produce MTGs with the following two different protocols: plast-MTG using a conventional impression and plaster model (n = 10) and 3DPr-MTG using a digital scanning and 3D printed model (n = 10). A custom-fit MTG was fabricated using EVA sheets (Bioart) plasticized over different models. The MTG thickness (mm), internal adaptation (mm) to the typodontic model, and voids in the area (mm2) between the two EVA layers were measured using cone-beam computed tomography images and Mimics software (Materialize). The shock absorption of the MTG was measured using a strain-gauge test with a pendulum impact at 30° with a steel ball over the typodont model with and without MTGs. Data were analyzed using one-way analysis of variance with repeated measurements, followed by Tukey's post hoc tests. RESULTS: The 3DPr-MTG showed better adaptation than that of the Plast-MTG at the incisal/occlusal and lingual tooth surfaces (p < 0.001). The 3DPr-MTG showed a thickness similar to that of the Plast-MTG, irrespective of the measured location. MTGs produced using both model types significantly reduced the strain values during horizontal impact (3DPr-MTG 86.2% and Plast-MTG 87.0%) compared with the control group without MTG (p < 0.001). CONCLUSION: The MTGs showed the required standards regarding thickness, adaptation, and biomechanical performance, suggesting that the number and volume of voids had no significant impact on their functionality. Three-dimensional printed models are a viable alternative for MTG production, providing better adaptation than the Plast-MTG at the incisal/occlusal and lingual tooth surfaces and similar performance as the MTG produced with the conventional protocol.

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PURPOSE: This technical procedure describes the accuracy of "cut-out-rescan" and "data exchange by over scanning" on cast areas using computer-aided design and computer-aided manufacturing software and two intraoral scanners (IOSs). METHODS: A customized cast was used as a reference standard and scanned using an ATOS Triple Scan digitizer. Two IOS setups were used in three scanning groups, namely, the control, cut-out-rescan, and data exchange by over scanning groups. Sixty digital files (n = 10 per group) were obtained and converted into the standard tessellation language format. A metrology program was used to evaluate the difference in accuracy between the control group and the other groups using Welch's unequal variances t-test. CONCLUSION: For trueness and precision of complete arch scans, the present technique provides statistical evidence that using data exchange by over scanning and a Primescan IOS results in higher accuracy scans compared to using cut-out-rescan and a Primescan IOS. The cut-out-rescan procedure provides scans with higher accuracy when using an Omnicam IOS. This technique is simple and saves time in workflows using a Primescan IOS.

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OBJECTIVE: To assess whether digital workflow gives better results than the conventional one in the single implant crowns, when analyzing the impression time, patient preference, time efficiency, and adjustment time. MATERIAL AND METHODS: MEDLINE, Embase, and Cochrane were searched and supplemented via hand search up to June 19, 2019. Only clinical trials assessing conventional versus digital workflows for single implant crowns were included. Impression time was evaluated using random effects meta-analysis, while patient preference, adjustment time, and time efficiency were reported descriptively. RESULTS: Among 1,334 publications identified, ten studies were included. The random effects models revealed statistically significant reduction in time in the digital impression group when compared to the conventional group by the mean meta-analysis (MD: 8.22 [95% CI: 5.48, 10.96]). Analysis from immediate digital impression versus conventional (MD: 3.84 [95% CI: 3.30, 4.39]) and regular digital impression versus conventional (MD:10.67 [95% CI: 5.70, 15.65]) showed statistically significant reduction in time on using the digital impression. Impression time in the digital process ranged between 6 min 39 s and 20 min, whereas for conventional, it was between 11.7 and 28.47 min. Patients showed greater preference for digital impression. Adjustment time in the digital process ranged between 1.96 and 14 min, whereas for conventional, it was between 3.02 and 12 min. Time efficiency in the digital process ranged between 36.8 and 185.4 min, whereas for conventional, it was between 55.6 and 332 min. CONCLUSION: The digital workflow has demonstrated better clinical efficiency considering impression time, patient preference, and time efficiency. According to the adjustment time, different results were presented.

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AIM: The study evaluated the marginal vertical misfit of feldspathic ceramic crowns fabricated by the computer-aided design (CAD)/computer-aided manufacturing (CAM) technology and compared the two methods of scanning techniques: direct digital impression and indirect digital impression. MATERIALS AND METHODS: The titanium specimens were divided into two groups: scanning with the direct digital impression (DDI) at the milled prosthetic abutment level and indirect digital impression (IDI) at the cast model and after milled feldspathic ceramics blocks. Vertical marginal misfit was analyzed. The t-test was used for the analysis of the comparison factor between the groups and the one-way analysis of variance (ANOVA) test, and post hoc Tukey test was used to compare the variance of crown analysis regions within the group. A significance level of 5% was considered for the analyses. RESULTS: There was no significant difference in vertical marginal misfit between the groups of DDI and IDI (p = 0.345). In relation to each region measured within the studied groups, it was observed the similarity between the six regions analyzed in the DDI group (p >0.05) and IDI group, a significant difference between two areas. CONCLUSION: The vertical marginal adaptation was similar between digital scanning methods. Based on the data evaluated, vertical marginal adaptation indices were within acceptable clinical standards. CLINICAL SIGNIFICANCE: The direct digital scanning in unit bodies was reliable, pointing that the coating of titanium dioxide in the titanium abutment did not negatively influence the vertical marginal adaptation of the feldspathic ceramic crowns.

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ABSTRACT Objective: The aim of the study was to verify and compare the accuracy of full-arch digital impressions obtained using two intraoral scanners and three scanning methodologies. Methods: A resin model created with dental 3-D printing was scanned by a reference scanner (Zfx Evolution - Zimmer Biomet, Palm Beach Gardens, FL) in order to obtain a 3D reference; the same resin model was then scanned with two different intraoral scanners (Zfx IntraScan and Carestream 3600 - CS 3600®, Carestream, Rochester, NY, USA) using: Technique A (from tooth #27 up to tooth #17); Technique B (from tooth #11 up to tooth #17 and then from tooth #21 up to tooth #27) and Technique C (from tooth #22 up to tooth #17, and then from tooth #12 up to tooth #27 - the MeshLab software v. 1.3.3 was then used to match the two scans). The scans obtained were superimposed over the reference scan by means of a software, and the volumetric discrepancies were calculated. Results: The mean results for the Zfx Intrascan scanner were: Technique A = 302.47 ± 37.42 µm; Technique B = 180.45 ± 29.86 µm; Technique C = 147.34 ± 28.23 µm. The mean results for the Carestream 3600 scanner were: Technique A = 303.59 ± 40.20 µm; Technique B = 181.53 ± 29.61 µm; Technique C = 142.28 ± 35.33 µm. Technique C, used by both scanners, produced less volumetric discrepancies compared to the other techniques. Conclusions: The scanning technique had a statistically significant effect on the quality of the scan (p< 0.0001), whereas the scanner did not present any significant influence (p= 0.91).

RESUMO Objetivo: o objetivo do presente estudo foi verificar e comparar a precisão de modelos digitais de uma arcada dentária completa obtidos utilizando-se dois tipos de scanners e três metodologias de digitalização. Métodos: um modelo de resina feito com impressão 3D foi digitalizado em um scanner de referência (Zfx Evolution - Zimmer Biomet, Palm Beach Gardens, FL) para se obter uma referência em 3D; o mesmo modelo de resina foi, então, digitalizado com dois scanners intrabucais diferentes (Zfx IntraScan e Carestream 3600 - CS 3600®, Carestream, Rochester, NY, EUA) utilizando: Técnica A (do dente #27 ao dente #17); Técnica B (do dente #11 ao dente #17 e, em seguida, do dente #21 ao dente #27); e Técnica C (do dente #22 ao dente #17 e, em seguida, do dente #12 ao dente #27 - osoftware MeshLab v. 1.3.3 foi, então, usado para mesclar as duas leituras). Em seguida, as imagens digitalizadas foram sobrepostas à imagem de referência, utilizando-se um software, e as discrepâncias volumétricas foram calculadas. Resultados: a média dos resultados para o scanner Zfx Intrascan foram: Técnica A = 302,47 ± 37,42 µm; Técnica B = 180,45 ± 29,86 µm; Técnica C = 147,34 ± 28,23 µm. A média dos resultados para o scanner Carestream 3600 foram: Técnica A= 303,59 ± 40,20 µm; Técnica B = 181,53 ± 29,61 µm; Técnica C = 142,28 ± 35,33 µm. A Técnica C, utilizada em ambos os scanners, produziu as menores discrepâncias volumétricas, quando comparada às outras técnicas. Conclusões: a técnica de digitalização teve um efeito estatisticamente significativo sobre a qualidade do modelo digital (p< 0,0001), enquanto o tipo de scanner usado não apresentou qualquer influência significativa (p= 0,91).

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OBJECTIVE: This in vitro study aimed to evaluate marginal and internal fit of single crowns produced from high-frequency ultrasound based digital impressions of teeth prepared with finish lines covered by porcine gingiva, in comparison with those obtained by optical scanners with uncovered finish lines. METHODS: Ten human teeth were prepared and forty zirconia crowns were fabricated from STL-datasets obtained from four dental scanners (n=10): extraoral CS2 (Straumann), intraoral Lava COS (3M), intraoral Trios (3Shape) and extraoral ultrasound scanner. The accuracy of the crowns was compared evaluating marginal and internal fit by means of the replica technique with measurements in four areas; P1: occlusal surface; P2: transition between occlusal and axial surfaces; P3: middle of axial wall; and P4: marginal gap. Restoration margins were classified according to their mismatch as regular, underextended or overextended. Kruskal-Wallis one-way ANOVA and Mann-Whitney U test were used to evaluate the differences between groups at p<0.05. RESULTS: The median value of marginal gap (P4) for Ultrasound (113.87µm) differed statistically from that of CS2 (39.74µm), Lava COS (41.98µm) and Trios (42.07µm). There were no statistical differences between ultrasound and Lava COS for internal misfit (P1-P3), however there were statistical differences when compared with the other two scanners (Trios and CS2) at P1 and P2. SIGNIFICANCE: The ultrasound scanner was able to make digital impressions of prepared teeth through porcine gingiva (P4), however with less accuracy of fit than that of conventional optical scanners without coverage of the finish lines. Where no gingiva was available (P1-P3), the ultrasound accuracy of fit was similar to that of at least one optical scanner (Lava COS).

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