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To evaluate the impact of reducing the radiographic field of view (FOV) on the trueness and precision of the alignment between cone beam computed tomography (CBCT) and intraoral scanning data for implant planning.Fifteen participants presenting with one of three clinical scenarios: single tooth loss (ST, n = 5), multiple missing teeth (MT, n = 5) and presence of radiographic artifacts (AR, n = 5) were included. CBCT volumes covering the full arch (FA) were reduced to the quadrant (Q) or the adjacent tooth/teeth (A). Two operators, an expert (exp) in virtual implant planning and an inexperienced clinician, performed multiple superimpositions, with FA-exp serving as a reference. The deviations were calculated at the implant apex and shoulder levels. Thereafter, linear mixed models were adapted to investigate the influence of FOV on discrepancies.Evaluation of trueness compared to FA-exp resulted in the largest mean (AR-A: 0.10 ± 0.33 mm) and single maximum discrepancy (AR-Q: 1.44 mm) in the presence of artifacts. Furthermore, for the ST group, the largest mean error (-0.06 ± 0.2 mm, shoulder) was calculated with the FA-FOV, while for MT, with the intermediate volume (-0.07 ± 0.24 mm, Q). In terms of precision, the mean SD intervals were ≤0.25 mm (A-exp). Precision was influenced by FOV volume (FA Q A) but not by operator expertise.For single posterior missing teeth, an extended FOV does not improve registration accuracy. However, in the presence of artifacts or multiple missing posterior teeth, caution is recommended when reducing FOV.

The accuracy of intraoral and model scanners has been widely investigated with heterogeneous results, but the impact of the applied diversity of measurement methods on the outcomes remains unknown. This study aimed to evaluate the influence of methodological factors on the measurement result when comparing full-arch scans.The evaluation referred to a 5M model to analyze whether accuracy measurements are affected by (1) the reference geometry, (2) mesh density of the standard tessellation language (STL) datasets, (3) operator, (4) inspection software, and (5) alignment procedure. STL datasets of full-arch reference models were measured with 29 different combinations of these factors. For each combination, 10 repeated measurements of the intermolar width were performed. Trueness was statistically analyzed with one-way ANOVA and T-tests, repeatability with Levene tests, and reproducibility with interclass correlation coefficients.Measurement method variations affected the intermolar width by up to 186 µm. The alignment algorithm had a significant effect on the measurement outcome (p = 0.001). Likewise, reference geometry influenced trueness and repeatability significantly (p = 0.001), whereas mesh density affected the repeatability only in some cases. The operator had no impact on the measurement result. The inspection software affected the repeatability but not the trueness.The factors reference geometry and alignment algorithm highly affected the measurement outcome, while the operator, inspection software, and mesh density showed no impact on the trueness of the outcome. Cylindrical reference geometries showed fewer differences than bar-shaped ones and best-fit alignments fewer variations than alignments based on boundary parameters.

Statement of problem Intraoral scanners (IOSs) are based on light-optical imaging methods. However, little is known about whether the ambient light in dental practices influences the accuracy and scanning time of the IOS. Purpose The purpose of this in vitro study was to investigate the influence of different illuminations on the accuracy of 4-unit and complete-arch scans of 6 IOSs. In addition, the required scanning time was evaluated. Material and methods A reference structure was attached to the first premolars (P) and second molars (M) in both quadrants (L/R) of a maxillary model. The resulting measured distances were M1-P1, M2-P2, P1-P2, and M1-M2. The investigation included 6 IOSs: TRIOS 3 (TRI), Cerec Omnicam (OC), iTero Element (ITE), CS 3600 (CS), Planmeca Emerald (EME), and GC Aadva (AAD). With each IOS, 17 scans at different illuminances (100, 500, 1000, and 5000 lux) were performed (N = 408). The precision and trueness for all distances were determined, and the scanning time was recorded. For statistical analyses, the Levene tests (precision) and 1-way analysis of variance with the post hoc Tukey honestly significant difference and Games-Howell tests (trueness) were calculated. Results Illuminance significantly influenced the trueness of 4-unit scans for OC, EME, and AAD. TRI, OC, ITE, and CS demonstrated comparable results. AAD (>96 ±22 μm; 1000 lux) and EME (>248 ±88 μm; 500 lux) revealed greater deviations. For complete-arch scans, illuminance did not influence TRI and AAD, but significant variations were detected for ITE, CS, EME, and AAD. The least deviations were achieved with TRI and OC. The scanning time was extended for all IOSs except ITE at more than 500 lux. The shortest scanning times with OC and EME were recorded at 100 lux; with TRI, CS, and AAD at 500 lux; and with ITE at both 100 and 5000 lux. At all illuminances, the fastest scans were obtained with TRI. Conclusions Ambient light was found to influence the accuracy and scanning time of IOSs. This influence varies depending on the device. For 4-unit scans, the effect was not clinically relevant, but for complete-arch scans, accuracy and scanning time can be improved with appropriate lighting.

ispartof: Clinical Oral Implants Research vol:30 issue:1 pages:47-47 status: published

Statement of problem Reliable studies comparing the accuracy of complete-arch casts from 3D printers are scarce. Purpose The purpose of this in vitro study was to investigate the accuracy of casts printed by using various extrusion- and photopolymerization-based printers. Material and methods A master file was sent to 5 printer manufacturers and distributors to print 37 identical casts. This file consisted of a standardized data set of a maxillary cast in standard tessellation language (STL) format comprising 5 reference points for the measurement of 3 distances that served as reference for all measurements: intermolar width (IMW), intercanine width (ICW), and dental arch length (AL). The digital measurement of the master file obtained by using a surveying software program (Convince Premium 2012) was used as the control. Two extrusion-based (M2 and Ultimaker 2+) and 3 photopolymerization-based printers (Form 2, Asiga MAX UV, and myrev140) were compared. The casts were measured by using a multisensory coordinate measuring machine (O-Inspect 422). The values were then compared with those of the master file. The Mann-Whitney U test and Levene tests were used to determine significant differences in the trueness and precision (accuracy) of the measured distances. Results The deviations from the master file at all 3 distances for the included printers ranged between 12 μm and 240 μm (trueness), with an interquartile range (IQR) between 17 μm and 388 μm (precision). Asiga MAX UV displayed the highest accuracy, considering all the distances, and Ultimaker 2+ demonstrated comparable accuracy for shorter distances (IMW and ICW). Although myrev140 operated with high precision, it displayed high deviations from the master file. Similarly, although Form 2 exhibited high IQR, it did not deviate significantly from the master file in the longest range (AL). M2 performed consistently. Conclusions Both extrusion-based and photopolymerization-based printers were accurate. In general, inexpensive printers were no less accurate than more expensive ones.