Accuracy of 3D-Printed Occlusal Devices of Different Volumes Using a Digital Light Processing Printer

Assessing the Impact of IOS Scanning Accuracy on Additively Manufactured Occlusal Splints

Introduction: Digital workflow and intraoral scanners (IOSs) are used to clinically obtain data for a wide range of applications in restorative dentistry. The study aimed to compare two different IOSs with inexperienced users in the digital workflow of oral split manufacturing. Material and Methods: Anonymous stone models of upper and lower dentate patients were used. Both models were scanned with a desktop 3D scanner 3Shape D2000 to obtain the reference models (STLR). Ten inexperienced operators scanned each model three times with each IOS system (3Shape TRIOS 3 and Carestream CS 3800). Finally, 20 intraoral scanners were randomly chosen from the obtained dataset (10 per IOS system) to design and manufacture 20 nightguards. All the nightguards were scanned. Trueness and precision were calculated and compared between the two IOS systems. Results: All the mean errors both for trueness and precision were below 40 µm, more than acceptable for the design and manufacturing of intraoral devices such as nightguards. All the mean errors (except one) for trueness between the inner part of the nightguards and the upper control model were below 100 µm, less than a printed layer height. For inexperienced operators, both IOSs are suitable for a digital workflow of manufacturing occlusal splints.

Effect of build orientation on the trueness of occlusal splints fabricated by three-dimensional printing

PURPOSE

Scientific evidence pertaining to the evaluation of trueness of occlusal splints fabricated using different three-dimensional (3D) printers and build orientations compared to subtractive technologies is lacking.

METHODS

Overall, one hundred and ten occlusal splints were manufactured using two different 3D printers and a dental mill. Five groups of ten were fabricated using the 3D printers at different build orientations (0, 30, 45, 60, and 90 degrees). In addition, a comparison group of ten occlusal splints was subtractively manufactured using a five-axis dental mill. All occlusal splints were scanned and exported as a standard tessellation language file. Analysis was conducted with metrology software with root mean square estimate average positive deviation and average negative deviation used as the measured outcome.

RESULTS

The 0 degree printing orientation was the most accurate for printer one with the root mean square value of 0.05 ± 0.01 mm, and 60 degree printing orientation was most accurate for printer two with the RMS value of 0.11 ± 0.01 mm. Subtractively manufactured occlusal splint had significantly higher trueness with the lowest RMS value of 0.03 ± 0.05 mm.

CONCLUSION

Build orientations influence the trueness of additively manufactured occlusal splints while occlusal splints produced by subtractive manufacturing were statistically significantly more accurate.

Study of Forming Performance and Characterization of DLP 3D Printed Parts

In order to explore the effect of printing parameter configurations on the forming performance of Digital Light Processing (DLP) 3D printed samples, printing experiments were carried out on the enhanced adhesion and efficient demolding of DLP 3D printing devices. The molding accuracy and mechanical properties of the printed samples with different thickness configurations were tested. The test results show that when the layer thickness increases from 0.02 mm to 0.22 mm, the dimensional accuracy in the X and Y directions increases first and then decreases, while the dimensional accuracy in the Z direction decreases, and the dimensional accuracy is the highest when the layer thickness is 0.1 mm. The mechanical properties of the samples decline with an increasing layer thickness of the samples. The mechanical properties of the 0.08 mm layer thickness are the best, and the tensile, bending, and impact properties are 22.86 Mpa, 48.4 Mpa, and 35.467 KJ/m², respectively. Under the condition of ensuring molding accuracy, the optimal layer thickness of the printing device is determined to be 0.1 mm. The analysis of the section morphology of samples with different thicknesses illustrates that the fracture of the sample is a river-like brittle fracture, and there are no defects such as pores in the section of samples.

Steering Potential for Printing Highly Aligned Discontinuous Fibre Composite Filament

DcAFF (discontinuous aligned fibre filament) is a novel material for fused filament fabrication (FFF) 3D printing made of highly aligned discontinuous fibres produced using high performance discontinuous fibre (HiPerDiF) technology. It reinforces a thermoplastic matrix to provide high mechanical performance and formability. Accurate printing of DcAFF poses a challenge, especially for complex geometries, because: (i) there is a discrepancy between the path where the filament experiences the adhering pressure from the filleted nozzle and the nozzle path; and (ii) the rasters display poor adhesion to the build platform immediately after deposition, which causes the filament to be dragged when the printing direction changes. This paper explains the implication of these phenomena on steering capabilities and examines the techniques for improving DcAFF printing accuracy. In the first approach, the machine parameters were adjusted to improve the quality of the sharp turning angle without changing the desired path, but this showed insignificant effects in terms of precision improvements. In the second approach, a printing path modification with a compensation algorithm was introduced. The nature of the inaccuracy of the printing at the turning point was studied with a first-order lag relationship. Then the equation to describe the deposition raster inaccuracy was determined. A proportional-integral (PI) controller was added to the equation to calculate the nozzle movement in order to bring the raster back to the desired path. The applied compensation path is shown to give an accuracy improvement in curvilinear printing paths. This is particularly beneficial when printing larger circular diameter curvilinear printed parts. The developed printing approach can be applied with other fibre reinforced filaments to achieve complex geometries.

Enhanced Adhesion—Efficient Demolding Integration DLP 3D Printing Device

A novel forming method of enhanced adhesion-efficient demolding integration is proposed to solve the problems of weak adhesion between the initial forming layer and the printing platform as well as the excessive stripping force at the bottom of the liquid tank when the printing platform rises. Therefore, a digital light processing (DLP) 3D printing forming device equipped with a porous replaceable printing platform and a swing mechanism for the liquid tank is manufactured and verified by experiments. The experimental results show that the porous printing platform can enhance the adhesion between the initial forming layer and the printing platform and improve the demolding efficiency of the forming device. In addition, the pull-out design of the printing platform plate reduces the maintenance cost of the forming device. Therefore, the device has a good application prospect.