Intraoral scanners (IOS) have reached a point where their impact in the dental office cannot be denied. The distance between the tip of the IOS and the preparation may have implications on the accuracy of the digital model. The objective of this study was to evaluate the differences in accuracy between digital impressions in the scenario of different scanning distances. Twenty consecutive scans were performed at five predetermined distances: 5 mm, 10 mm, 15 mm, 20 mm and 23 mm by a single operator. The scanning distance of 10 mm displayed the best accuracy with an overall trueness value of 23.05 μm and precision value of 4.2 μm. The drawn conclusion was that increased scanning distances can decrease the accuracy of a digital impression.
In the present study are depicted valuable observations for practitioners, obtained from an in vitro study which aims to evaluate the compressive strength of occlusal veneers fabricated from 3 type of restorative materials, before and after 1 month of acidic artificial saliva exposure (pH = 2.939). In this context, 90 extracted human molars were prepared to receive computer-aided design/computer-aided manufacturing (CAD/CAM) occlusal veneers. The restorative materials considered in this study were: Cerasmart; Straumann Nice and Tetric CAD. The occlusal veneers were designed, milled and cemented with an adhesive dual-cure resin cement. From all the extracted human molars, only sixty specimens were immersed in acidic artificial saliva, for 1 month, at 37 °C ± 1 °C and part of this specimens were also thermo-cycled, between 5 and 55 °C ± 2 °C, before compressive strength test. The results showed a lower compressive strength for both the samples exposed to acidic artificial saliva as well as for the samples exposed to acidic artificial saliva and thermo-cycled. Scanning electron microscopy (SEM) showed that after compressive strength, all the specimens non-exposed to acidic artificial saliva, present extensive cracks formation at the surface of the restorations, and after exposure to acidic artificial saliva for 1 month, the surface damage was characterized by longitudinal and profound fractures of the restoration, as well as the fracture of the tooth structure. Between CAD/CAM materials tested, nanoceramic resin shows more favorable fracture patterns, both before and after acidic artificial saliva exposure.
The aim of this study was to evaluate the influence of different settings of ambient light intensity inside the dental office on the accuracy (trueness and precision) of an intraoral scanner (IOS). A full crown preparation was conducted on a resin molar which was scanned using a high resolution extraoral scanner to obtain a reference model. Six light settings were chosen based on the most clinically relevant light conditions inside the workspace, and the preparation was scanned using an intraoral scanner (PlanScan, Planmeca). The obtained data was analyzed using a professional 3D quality control software (Geomagic Control X). There was no statistically relevant difference between the groups when regarding trueness, although a slight influence of the light intensity could be observed on the trueness values. Regarding precision, the best results were obtained in the 3800 lux group, with the other groups presenting close values, excepting the extreme values (400 lux and 11 000 lux) groups that proved to be the most deficient.
Background: The aim of this study was to assess the accuracy of printed interim fixed partial dentures (i-DPSs) fabricated on 3D-printed models using different printing angles. Materials and Methods: Six printing angles were chosen, namely 90°, 75°, 60°, 45°, 30° and 15°, to fabricate sixty i-DPSs, ten for each. The measurements were performed at 100 points cervical and 100 points axial occlusal. Statistical analyses were carried out using Med Calc software and the Kolmogorov–Smirnov and Kruskal–Wallis tests. Results: The marginal fit ranged between 39.302 µm and 74.470 µm, with the best values for the 60° (39.302 µm) and 30° (43.287 µm) printing angles. The mean values for the internal fit were between 72.876 µm and 114.26 µm, with the best values for the 30° (72.876 µm) and 60° (78.049 µm) printing angles. The Kruskal–Wallis test returned a p value of p < 0.0001.
Is the accuracy of the older generation of IOSs an impediment for obtaining a quality intraoral digital impression? The aim of this study was to evaluate the differences in accuracy between four intraoral scanners (two of the latest IOSs and two older IOSs) in the scenario of a short span fixed partial denture, and to determine if these differences have a major impact on the quality of the final digital impression. Four intraoral scanners: Cerec PrimeScan, Medit i700, Cerec Omnicam and Planmeca PlanScan and one laboratory scanner were used in this study. The scanned data were processed with the help of Geomagic Control X, a metrology software. For the statistical data analysis, the level of significance was set as 0.05 (α = 0.05). The Medit i700 group displayed the best level of trueness with the median value of 23.25 µm, PrimeScan group with a median of 25.55 µm, Omnicam group with a median of 32.3 µm and the PlanScan group which displayed the lowest level of trueness with a median value of 75.8 µm. From the precision data analysis, it was concluded that the PrimeScan group showed the best results, followed by Medit i700, Omnicam and the PlanScan group which showed the lowest precision. Even if there are some significant differences in accuracy between old and new IOSs, in the in vitro scenario of short span dental prostheses, the accuracy values were within the clinically acceptable range and may present important clinical implications.
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