Can an entry-level 3D printer create high-quality anatomical models? Accuracy assessment of mandibular models printed by a desktop 3D printer and a professional device

This study was performed to determine whether an in-house printed mandible model is sufficiently accurate for daily clinical practice. Ten example mandible models were produced with a desktop 3D printer (fused filament fabrication, FFF) and compared with 10 equivalent mandible models fabricated using a professional-grade 3D printer (selective laser sintering, SLS). To determine the precision of the printed models, each model was scanned with an optical scanner. Subsequently, every model was compared to its original standard tessellation language (STL) file and to its corresponding analogue. Mean ± standard deviation and median (interquartile range) differences were calculated. Overall these were −0.019 ± 0.219 mm and −0.007 (−0.129 to 0.107) mm for all 10 pairs. Furthermore, correlation of all printed models to their original STL files showed a high level of accuracy. Comparison of the SLS models with their STL files revealed a mean difference of −0.036 ± 0.114 mm and median difference of −0.028 (−0.093 to 0.030) mm. Comparison of the FFF models with their STL files yielded a mean difference of −0.055 ± 0.227 mm and median difference of −0.022 (−0.153 to 0.065) mm. The study findings confirm that in-house 3D printed mandible models are economically favourable as well as suitable substitutes for professional-grade models, in particular considering the geometric aspects.     

Comparing the accuracy (trueness and precision) of models of fixed dental prostheses fabricated by digital and conventional workflows

Purpose

This study aimed to evaluate and compare the accuracy.

Trueness and precision of digital impressions obtained using an intraoral scanner with different head size in the partially edentulous mandible

Purpose

It remains unclear whether digital impressions obtained using an intraoral scanner are sufficiently accurate for use in fabrication of removable partial dentures. We therefore compared the trueness and precision between conventional and digital impressions in the partially edentulous mandible.

Comparison of the accuracy of maxillary position between conventional model surgery and virtual surgical planning

The aim of this study was to determine whether virtual surgical planning (VSP) is an accurate method for positioning the maxilla when compared to conventional articulator model surgery (CMS), through the superimposition of computed tomography (CT) images. This retrospective study included the records of 30 adult patients submitted to bimaxillary orthognathic surgery. Two groups were created according to the treatment planning performed: CMS and VSP. The treatment planning protocol was the same for all patients. Pre- and postoperative CT images were superimposed and the linear distances between upper jaw reference points were measured. Measurements were then compared to the treatment planning, and the difference in accuracy between CMS and VSP was determined using the t-test for independent samples. The success criterion adopted was a mean linear difference of <2 mm. The mean linear difference between planned and obtained movements for CMS was 1.27 ± 1.05 mm, and for VSP was 1.20 ± 1.08 mm. With CMS, 80% of overlapping reference points had a difference of <2 mm, while for VSP this value was 83.6%. There was no statistically significant difference between the two techniques regarding accuracy (P > 0.05).     

Accuracy of implant position when placed using static computer-assisted implant surgical guides manufactured with two different optical scanning techniques: a randomized clinical trial

Data from cone beam computed tomography (CBCT) and optical scans (intraoral or model scanner) are required for computer-assisted implant surgery (CAIS). This study compared the accuracy of implant position when placed with CAIS guides produced by intraoral and extraoral (model) scanning. Forty-seven patients received 60 single implants by means of CAIS. Each implant was randomly assigned to either the intraoral group (n = 30) (Trios Scanner, 3Shape) or extraoral group (n = 30), in which stereolithographic surgical guides were manufactured after conventional impression and extraoral scanning of the stone model (D900L Lab Scanner, 3Shape). CBCT and surface scan data were imported into coDiagnostiX software for virtual implant position planning and surgical guide design. Postoperative CBCT scans were obtained. Software was used to compare the deviation between the planned and final positions. Average deviation for the intraoral vs. model scan groups was 2.42° ± 1.47° vs. 3.23° ± 2.09° for implant angle, 0.87 ± 0.49 mm vs. 1.01 ± 0.56 mm for implant platform, and 1.10 ± 0.53 mm vs. 1.38 ± 0.68 mm for implant apex; there was no statistically significant difference between the groups (P > 0.05). CAIS conducted with stereolithographic guides manufactured by means of intraoral or extraoral scans appears to result in equal accuracy of implant positioning.     

Three-dimensional evaluation of marginal and internal fit of 3D-printed interim restorations fabricated on different finish line designs

PurposeTo evaluate the influence of fabrication method and finish line design on marginal and internal fit of full-coverage interim restorations.MethodsFour typodont models of maxillary central-incisor were prepared for full-coverage restorations. Four groups were defined; knife-edge (KE), chamfer (C), rounded-shoulder (RS), rounded-shoulder with bevel (RSB). All preparations were digitally scanned. A total of 80 restorations were fabricated; 20 per group (SLA/3D-printed n = 10, milled n = 10). All restorations were positioned on the master die and scanned using micro-computed tomography. The mean gaps were measured digitally (ImageJ). The results were compared using MANOVA (α = .05).ResultsInternal and marginal gaps were significantly influenced by fabrication method (P = .000) and finish-line design (P = .000). 3D-Printed restorations showed statistically significant lower mean gap compared to milled restorations at all points (P = .000). The mean internal gap for 3D-printed restorations were 66, 149, 130, 95 μm and for milled restorations were 89, 177, 185, 154 μm for KE, C, RS, RSB respectively. The mean absolute marginal discrepancy in 3D-printed restorations were (30, 41, 30, 28 μm) and in milled restorations were (56, 54, 52, 38 μm) for KE, C, RS, RSB respectively.ConclusionsThe fabrication methods showed more of an influence on the fit compared to the effect of the finish-line design in both milled and printed restorations. SLA-printed interim restorations exhibit lower marginal and internal gap than milled restorations. Nonetheless, for both techniques, all values were within the reported values for CAD/CAM restorations.Significance3D-printing can offer an alternative fabrication method comparable to those of milled restorations.     

Accuracy assessment of prototypes produced using multi-slice and cone-beam computed tomography

The objective of this study was to assess and quantify the dimensional error of prototypes produced using multi-slice and cone-beam computed tomography (MSCT and CBCT). Titanium screws were inserted into a dry skull at different points of the midface. The skull was scanned using MSCT (LightSpeed16^®) with pixel size 0.3 mm and CBCT (i-CAT Cone-Beam 3D?) with voxel sizes 0.25 and 0.4 mm. Prototypes were printed (fabricated) using a ZPrinter 310^® device. Both the dry skull (gold standard) and the prototypes were measured using a Mitutoyo 3D coordinate measuring system with three perpendicular axes (X, Y, and Z). The prototype produced from MSCT data presented a mean dimensional error of 0.62%; the two models produced with CBCT images yielded errors of 0.74% with voxel size 0.25 mm and 0.82% with voxel size 0.40 mm. No significant differences in dimensional errors were observed across the prototypes (p = 0.767; Friedman's non-parametric test). Prototypes produced from CBCT data using voxel sizes of 0.25 and 0.4 mm, and also the one produced from MSCT data using pixel size 0.3 mm, showed acceptable dimensional errors and can therefore be used in the fabrication of prototypes in dentistry.     

The effect of hydrofluoric acid concentration on the fatigue failure load of adhesively cemented feldspathic ceramic discs

Objective

This study investigated the influence of hydrofluoric acid (HF) etching at different concentrations on the fatigue failure load of adhesively cemented feldspathic ceramic discs (Vita Mark II). Besides, their effect on the micromorphology of ceramic surface was investigated.

The virtual human face: Superimposing the simultaneously captured 3D photorealistic skin surface of the face on the untextured skin image of the CBCT scan

The aim of this study was to evaluate the impact of simultaneous capture of the three-dimensional (3D) surface of the face and cone beam computed tomography (CBCT) scan of the skull on the accuracy of their registration and superimposition. 3D facial images were acquired in 14 patients using the Di3d (Dimensional Imaging, UK) imaging system and i-CAT CBCT scanner. One stereophotogrammetry image was captured at the same time as the CBCT and another 1 h later. The two stereophotographs were individually superimposed over the CBCT using VRmesh. Seven patches were isolated on the final merged surfaces. For the whole face and each individual patch: maximum and minimum range of deviation between surfaces; absolute average distance between surfaces; and standard deviation for the 90th percentile of the distance errors were calculated. The superimposition errors of the whole face for both captures revealed statistically significant differences (P = 0.00081). The absolute average distances in both separate and simultaneous captures were 0.47 and 0.27 mm, respectively. The level of superimposition accuracy in patches from separate captures was 0.3–0.9 mm, while that of simultaneous captures was 0.4 mm. Simultaneous capture of Di3d and CBCT images significantly improved the accuracy of superimposition of these image modalities.     

Influence of additional reinforcement of fixed long-term temporary restorations on fracture load

Purpose

In implant dentistry, temporary restorations (TR) might often be required for up to one year. The aim of this in vitro study was to evaluate the long-time performance of four-unit TRs in the posterior region based on different materials and reinforcement methods.

Comparing the precision of reproducibility of computer-aided occlusal design to conventional methods

Purpose

Reconstruction of patients’ dental occlusion should be performed to fulfill esthetic and functional demands. These applied restorations should be in harmony with the existing occlusion and should not have any negative effects on intraoral dynamics. The aim of this clinical study is to compare the accuracy of the occlusal design shaped by conventional Wax Up methods and computer-aided design (CAD) regarding their similarity to the natural tooth morphology.

In vitro evaluation of the early erosive lesion in polished and natural human enamel

Objective

This study evaluated the capability of profilometry, microhardness, Optical Coherence Tomography (OCT) and Tandem Scanning Confocal Microscopy (TSM) in characterising the early erosive lesion in polished and natural human enamel in vitro.

Ultimate force and stiffness of 2-piece zirconium dioxide implants with screw-retained monolithic lithium-disilicate reconstructions

Purpose

The aims were to analyze stiffness, ultimate force, and failure modes of a 2-piece zirconium dioxide (ZrO₂) implant system.

Evaluation of two-dimensional lateral cephalogram and three-dimensional cone beam computed tomography superimpositions: a comparative study

Superimposition of radiographic imaging is used to evaluate patient growth and the effects of surgical and/or orthodontic treatment. The purpose of this study was to compare the outcomes of superimposition between two-dimensional (2D) and three-dimensional (3D) superimpositions. 2D lateral cephalograms were generated from the initial and final cone beam computed tomography scans (CBCT) of 18 patients and superimposed. Both 3D CBCT and 2D CBCT generated lateral cephalograms were oriented to the Frankfort horizontal plane and superimposed according to the American Board of Orthodontics recommendations. Changes in landmark position were quantified from the resulting superimposition outcomes via linear measurements made with Dolphin software. Differences between the two methods were analyzed using paired t-tests. Measurements were repeated twice for 10 randomly selected scans to assess reliability by intra-class correlation coefficient (ICC) analysis. Intra-examiner reliability was high for all measurements (ICC > 0.84). Agreement between 2D and 3D superimposition outcomes, as measured by P-values, was low for ANS (P = 0.026), B-point (P < 0.001), ST Upper lip (P = 0.019), U1 tip (P = 0.010), and U1 apex (P = 0.026). 2D measurements were significantly higher than 3D measurements for ANS, B-point, ST Upper lip, U1 tip, and U1 apex. Findings indicated that both methods of superimposition (2D and 3D) are highly reliable. Statistical differences between 2D and 3D superimposition outcomes were below the threshold of clinical significance.     

Validation of the Vectra H1 portable three-dimensional photogrammetry system for facial imaging

Three-dimensional (3D) surface imaging using stereophotogrammetry has become increasingly popular in clinical settings, offering advantages for surgical planning and outcome evaluation. The handheld Vectra H1 is a low-cost, highly portable system that offers several advantages over larger stationary cameras, but independent technical validation is currently lacking. In this study, 3D facial images of 26 adult participants were captured with the Vectra H1 system and the previously validated 3dMDface system. Using error magnitude statistics, 136 linear distances were compared between cameras. In addition, 3D facial surfaces from each system were registered, heat maps generated, and global root mean square (RMS) error calculated. The 136 distances were highly comparable across the two cameras, with an average technical error of measurement (TEM) value of 0.84 mm (range 0.19–1.54 mm). The average RMS value of the 26 surface-to-surface comparisons was 0.43 mm (range 0.33–0.59 mm). In each case, the vast majority of the facial surface differences were within a ±1 mm threshold. Areas exceeding ±1 mm were generally limited to facial regions containing hair or subject to facial microexpressions. These results indicate that 3D facial surface images acquired with the Vectra H1 system are sufficiently accurate for most clinical applications.     

Digital replacement of the distorted dentition acquired by cone beam computed tomography (CBCT): a pilot study

During cone beam computed tomography (CBCT) scanning, intra-oral metallic objects may produce streak artefacts, which impair the occlusal surface of the teeth. This study aimed to determine the accuracy of replacement of the CBCT dentition with a more accurate dentition and to determine the clinical feasibility of the method. Impressions of the teeth of six cadaveric skulls with unrestored dentitions were taken and acrylic base plates constructed incorporating radiopaque registration markers. Each appliance was fitted to the skull and a CBCT performed. Impressions were taken of the dentition with the devices in situ and dental models were produced. These were CBCT-scanned and the images of the skulls and models imported into computer-aided design/computer-aided manufacturing (CAD/CAM) software and aligned on the registration markers. The occlusal surfaces of each dentition were then replaced with the occlusal image of the corresponding model. The absolute mean distance between the registration markers in the skulls and the dental models was 0.09 ± 0.02 mm, and for the dentition was 0.24 ± 0.09 mm. When the method was applied to patients, the distance between markers was 0.12 ± 0.04 mm for the maxilla and 0.16 ± 0.02 mm for the mandible. It is possible to replace the inaccurate dentition on a CBCT scan using this method and to create a composite skull which is clinically acceptable.     

Three-dimensional soft tissue prediction in orthognathic surgery: a clinical comparison of Dolphin,ProPlan CMF,and probabilistic finite element modelling

Three-dimensional surgical planning is used widely in orthognathic surgery. Although numerous computer programs exist, the accuracy of soft tissue prediction remains uncertain. The purpose of this study was to compare the prediction accuracy of Dolphin, ProPlan CMF, and a probabilistic finite element method (PFEM). Seven patients (mean age 18 years; five female) who had undergone Le Fort I osteotomy with preoperative and 1-year postoperative cone beam computed tomography (CBCT) were included. The three programs were used for soft tissue prediction using planned and postoperative maxillary position, and these were compared to postoperative CBCT. Accurate predictions were obtained with each program, indicated by root mean square distances: RMS_Dolphin = 1.8 ± 0.8 mm, RMS_ProPlan = 1.2 ± 0.4 mm, and RMS_PFEM = 1.3 ± 0.4 mm. Dolphin utilizes a landmark-based algorithm allowing for patient-specific bone-to-soft tissue ratios, which works well for cephalometric radiographs but has limited three-dimensional accuracy, whilst ProPlan and PFEM provide better three-dimensional predictions with continuous displacements. Patient or population-specific material properties can be defined in PFEM, while no soft tissue parameters are adjustable in ProPlan. Important clinical considerations are the topological differences between predictions due to the three algorithms, the non-negligible influence of the mismatch between planned and postoperative maxillary position, and the learning curve associated with sophisticated programs like PFEM.     

In-vitro wear of natural tooth surface opposed with zirconia reinforced lithium silicate glass ceramic after accelerated ageing

Objective

To evaluate the effect of different pH media on zirconia-reinforced lithium silicate glass ceramic and how they interact with opposing dentition after being aged in different pH cycling and high temperature conditions.