Even in digital workflows, models are required for fitting during the fabrication of dental prostheses. This study examined the influence of different parameters on the dimensional accuracy of ...three-dimensionally printed models. A stereolithographic data record was generated from a master model (SOLL). With digital light processing (DLP) and stereolithography (SLA) printing systems, 126 models were produced in several printing runs—SolFlex350 (S) (DLP, n = 24), CaraPrint 4.0 (C) (DLP, n = 48) and Form2 (F) (SLA, n = 54)—and their accuracy was compared with plaster and milled polyurethane models. In addition to the positioning on the build platform, a distinction was made between parallel and across arrangement of the models to the printer’s front, solid and hollow models, and printing with and without support structures. For accuracy assessment, five measurement sections were defined on the model (A–E) and measured using a calibrated digital calliper and digital scans in combination with the GOM Inspect Professional software 2021. The mean deviation between the measurement methods for all distances was 79 µm. The mean deviation of the models from the digital SOLL model were 207.1 µm for the S series, 25.1 µm for the C series and 141.8 µm for the F series. While positioning did not have an influence, there were clinically relevant differences mainly regarding the choice of printer, but also individually in alignment, model structure and support structures.
Background and aim: Good dentofacial growth is a major goal in the treatment of unilateral cleft lip and palate (UCLP). The aim was to evaluate dental arch relationships at age 5 years after four ...different protocols of primary surgery for UCLP.
Design: Three parallel randomised clinical trials were undertaken as an international multi-centre study by 10 cleft teams in five countries: Denmark, Finland, Sweden, Norway, and the UK.
Methods: Three different surgical procedures for primary palatal repair (Arms B, C, D) were tested against a common procedure (Arm A) in the total cohort of 448 children born with non-syndromic UCLP. Study models of 418 patients (273 boys) at the mean age of 5.1 years (range = 4.8-7.0) were available. Dental arch relationships were assessed using the 5-year index by a blinded panel of 16 orthodontists. Kappa statistics were calculated to assess reliability. The trials were tested statistically with t- and Chi-square tests.
Results: Good-to-very good levels of intra- and interrater reliability were obtained (0.71-0.94 and 0.70-0.87). Comparisons within each trial showed no statistically significant differences in the mean 5-year index scores or their distributions between the common method and the local team protocol. The mean index scores varied from 2.52 (Trial 2, Arm C) to 2.94 (Trial 3, Arm D).
Conclusion: The results of the three trials do not provide statistical evidence that one technique is better than the others. Further analysis of the possible influence of individual surgical skill and learning curve are being pursued in this dataset.
Trial registration: ISRCTN29932826.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Minimal evidence exists on the efficacy of different digital manufacturing techniques in the fabrication of precise dental working models and provisional prosthesis.
The objective was to evaluate the ...effect of two digital fabrication techniques (CAD/CAM milling and 3D printing) on the accuracy of PMMA working models and marginal fit of PMMA provisional prosthesis.
Two abutment teeth of modified typodont were prepared. A reference stone model was fabricated, and an optical impression was performed to obtain a CAD reference model. Four CAM milled working models and four printed working models were fabricated. CAD software was used to design the provisional prostheses. Group A tested four milled provisional prosthesis, and group B tested four 3D printed prosthesis. The 3D accuracy of working models was assessed by superimposition of the control reference working model on the CAD test working model. A stereo-optical microscope was used to assess vertical marginal fit of the provisional dental prosthesis. Student's
and Mann-Whitney U tests were utilized to compare the two groups.
Results showed no statistically significant difference between the two tested groups.
The two digital working model fabrication techniques recorded comparable accuracy. Similarly, 3D printed provisional prosthesis showed comparable marginal fit to the CAD/CAM milled ones.
Based on the hypothesis that the fabrication of dental models using fused deposition modeling and poly-lactic acid (PLA), followed by recycling and reusing, would reduce industrial waste, we aimed to ...compare the accuracies of virgin and recycled PLA models. The PLA models were recycled using a crusher and a filament-manufacturing machine. Virgin PLA was labeled R, and the first, second, and third recycles were labeled R1, R2, and R3, respectively. To determine the accuracies of the virgin and reused PLA models, identical provisional crowns were fitted, and marginal fits were obtained using micro-computed tomography. A marginal fit of 120 µm was deemed acceptable based on previous literature. The mesial, distal, buccal, and palatal centers were set at M, D, B, and P, respectively. The mean value of each measurement point was considered as the result. When comparing the accuracies of R and R1, R2, and R3, significant differences were noted between R and R3 at B, R and R2, R3 at P, and R and R3 at D (
< 0.05). No significant difference was observed at M. This study demonstrates that PLA can be recycled only once owing to accuracy limitations.
(1) Background: Various 3D printers are available for dental practice; however, a comprehensive accuracy evaluation method to effectively guide practitioners is lacking. This in vitro study aimed to ...propose an optimized method to evaluate the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a special structurized dental model, and provide the preliminary evaluation results of six 3D printers. (2) Methods: A structurized dental model comprising several geometrical configurations was designed based on dental crown and arch measurement data reported in previous studies. Ninety-six feature sizes can be directly measured on this original model with minimized manual measurement errors. Six types of photo-curing 3D printers, including Objet30 Pro using the Polyjet technique, Projet 3510 HD Plus using the Multijet technique, Perfactory DDP and DLP 800d using the DLP technique, Form2 and Form3 using the SLA technique, and each printer's respective 3D-printable dental model materials, were used to fabricate one set of physical models each. Regarding the feature sizes of the simulated dental crowns and dental arches, linear measurements were recorded. The scanned digital models were compared with the design data, and 3D form errors (including overall 3D deviation; flatness, parallelism, and perpendicularity errors) were measured. (3) Results: The lowest overall 3D deviation, flatness, parallelism, and perpendicularity errors were noted for the models printed using the Objet30 Pro (overall value: 45 μm), Form3 (0.061 ± 0.019 mm), Objet30 Pro (0.138 ± 0.068°), and Projet 3510 HD Plus (0.095 ± 0.070°), respectively. In color difference maps, different deformation patterns were observed in the printed models. The feature size proved most accurate for the Objet30 Pro fabricated models (occlusal plane error: 0.02 ± 0.36%, occlusogingival direction error: -0.06 ± 0.09%). (4) Conclusions: The authors investigated a novel evaluation approach for the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a structurized dental model. This method can objectively and comprehensively evaluate the spatial trueness of 3D-printed dental models and has a good repeatability and generalizability.
3D tooth segmentation is a challenging fundamental problem in computer-aided design (CAD) systems for orthodontic treatment planning. Existing methods of tooth segmentation cannot meet the ...requirements for both efficiency and accuracy. This paper presents a coarse-to-fine 3D tooth segmentation algorithm, called C2F-3DToothSeg, to improve tooth segmentation. The algorithm consists of two steps: extraction of the coarse gum line and optimization of this line. A concavity-sensitive harmonic field is searched in a local region of entire dental meshes to produce a series of isolines. The best isoline is selected as the coarse gum line, which is then optimized by a heuristic feature line extraction scheme to yield an accurate gum line. Extensive visual and numerical experiments demonstrate that our C2F-3DToothSeg has better overall performance in accuracy and efficiency compared to other existing methods directly applicable in orthodontic CAD systems. A point on the tooth surface is loosely found to locate the center zone of each individual tooth via a simple intuitive single click of the operation. The experiments also show that our method is robust to different complex dental models; for example, it copes with bulge bubbles, decay and cavity issues, and dental accessories.
Display omitted
•Coarse-to-fine 3D tooth segmentation.•Combining the concavity-aware harmonic field and heuristic feature line extraction.•The concavity-aware harmonic field could get a closed coarse gum line to ensure our segmentation algorithm robust.•The heuristic feature line extraction algorithm can optimize the closed coarse gum line for precise segmentation.•The algorithm is robust to handle very complex and abnormal cases.
To review the research progress of digital occlusion setup in orthognathic surgery.
The literature related to digital occlusion setup in orthognathic surgery in recent years was consulted, and the ...imaging basis, methods, clinical applications as well as existing problems were reviewed.
Digital occlusion setup in orthognathic surgery includes manual, semi-automatics, and fully automatic methods. The manual method mainly relies on visual cues for operation, which is difficult to ensure the best occlusion set up, though relatively flexible. The semi-automatic method utilizes the computer software for partial occlusion set up and adjustment, but the occlusion result is still largely depended by manual operation. The fully automatic method completely depends on the operation of computer software, and targeted algorithms for different occlusion reconstruction situations are needed.
The preliminary research results have confirmed the accuracy and reliability of digital occlusion setup in orthognathic surgery, but th
On the basis of studying the calibration method of the camera and the rotating platform, we designed an automatic camera calibration scheme based on four azimuth circles, which can realize the ...automatic sorting of the mark points. In order to improve the efficiency of identifying the center of the calibration plate, this paper uses RANSAC to improve the RED ellipse center detection algorithm. Experimental verification shows that the improved RED algorithm has increased 29.34% in anti-noise interference ability and 30.10% in center detection accuracy, which effectively guarantees the measurement stability and accuracy of the measurement system. Then, with the aid of the designed calibration board, we fit the rotation center of the turntable using the principle of three points in a circle, which provides a basis for the subsequent point cloud splicing. Experiments show that the back-projection error of the calibration method in this paper is less than 1 pixel, and the calibration accuracy is better than Zhang’s algorithm.
Objective:
To evaluate the gingival condition due to adult orthodontic treatment using the clinical crown height (CCH) as an index.
Design:
Retrospective study.
Setting:
Department of Orthodontics at ...a university.
Participants:
A total of 21 adult female patients with healthy periodontal tissue were treated by means of the multi-bracket appliance with extraction of four first premolars.
Methods:
Three-dimensional (3D) digital dental models were reconstructed to assess the vertical movement of the free gingival margin caused by adult orthodontic treatment. Pre- and post-treatment CCH were measured, and changes in CCH due to treatment were examined.
Results:
The change in CCH by orthodontic treatment was able to be assessed objectively using 3D digital models of the dental casts. In the upper dentition, a significant reduction in CCH was found on the labial and lingual sides of the central incisor, with a mean of –0.28 mm and –0.34 mm, respectively (P < 0.001). In contrast, a significant increase in CCH was found on the labial side of the lateral incisor with a mean of 0.75 mm (P < 0.001). In the lower dentition, CCH on the lingual side of the canine, the second premolar and the first molar increased significantly (P < 0.001), with a mean of 0.41 mm, 0.45 mm and 0.50 mm, respectively. For the buccal side, the second premolar showed a significant increase in CCH with a mean of 0.61 mm (P < 0.001).
Conclusion:
By using the CCH as an index, it was possible to assess the gingival condition after active orthodontic treatment.
Key Clinical Message
This research investigates the trueness and precision of 3D printing technology in dental applications, specifically focusing on dimensional variations observed in models printed ...at different angles. The methodology involved importing a dental model into slicing software, adjusting its orientation, and implementing support structures for stability. Subsequently, the model underwent 3D printing five times for each orientation using appropriate equipment and underwent post‐processing steps, including cleaning, washing, and UV‐light post‐curing. The printed models were then scanned using a specialized desktop scanner for further analysis. Accuracy assessment was carried out using dedicated software, employing an algorithm for precise alignment by comparing the scanned files. Color deviation maps were utilized to visually represent variations, aiming to evaluate how positioning during printing influences the trueness and precision of 3D‐printed dental models. Trueness and precision analyses involved the Shapiro–Wilk test for normality and a one‐way ANOVA to compare means of three independent groups, with statistical analyses conducted using IBM SPSS Statistics software. The color maps derived from 3D comparisons revealed positive and negative deviations, represented by distinct colors. Comparative results indicated that models positioned at 0° exhibited the least dimensional deviation, whereas those at 90° showed the highest. Regarding precision, models printed at 0° demonstrated the highest reproducibility, while those at 15° exhibited the lowest. Based on the desired level of precision, it is recommended that printed models be produced at an inclination angle of 0°.
PDF
