Influence of additive manufacturing method and build angle on the accuracy of 3D-printed palatal plates

Clinical outcomes of novel CAD/CAM-designed functional space maintainers produced via additive and subtractive methods: A randomized controlled trial

OBJECTIVE

Since passive fixed space maintainers do not restore the lost tooth or provide chewing function, this study seeks to assess the effectiveness of an innovative approach for maintaining space following the premature extraction of first primary molars, utilizing functional space maintainers designed with CAD/CAM.

METHODS

This randomized controlled trial included 28 patients allocated into two groups (15 in 3D Printing group and 13 in Milling group). The inclusion criteria required extraction or loss of the first primary molar due to complications of caries, with a prolonged period until eruption of the successor. Space maintainers were fabricated using 3D printing metal (Co 69 %, Cr 25 %, W 9.5 %, Mo 3.5 %, Si 1 %, Scheftner, Germany) and milling composite (breCAM.HIPC, Bredent, Germany). This study evaluated the efficiency of space maintainers through clinical check-ups at one, three, and six months, maximum occlusal bite force, and masticatory performance assessments.

RESULTS

A positive clinical trend was noted over time, with the "type of space maintainer" factor (Milling vs. 3D Printing) influencing the degree of clinical assessment (p < 0.001). There were no significant differences in maximum occlusal bite force between sides for both types of space maintainers (p = 0.270 for 3D Printing and p = 0.765 for Milling). Significant improvements were observed in masticatory performance after the placement of both types of space maintainers.

CONCLUSION

A six-month follow-up showed that 3D-printed metal outperformed milled composite ones, with no significant differences in bite force or masticatory performance, indicating that CAD/CAM technology could set new standards in producing functional space maintainers.

CLINICAL SIGNIFICANCE

This study underscores the potential of the manufacturing technologies to set new standards in pediatric dentistry, particularly for maintaining space following premature tooth loss, while ensuring improved functional outcomes for young patients.

Effect of cleft palate type and manufacturing method on feeding plate adaptation: A volumetric micro-computed tomography analysis

PURPOSE

Feeding plates for cleft palate patients have been used by clinicians for many years to temporarily close the oro-nasal communication until definitive treatment with surgical techniques. The current in vitro study aimed to evaluate the adaptation of the feeding plates manufactured by two different techniques for three cleft types.

MATERIALS AND METHODS

Feeding plates were manufactured with conventional compression molding (CM) and 3-dimensional (3D) additive manufacturing on main models representing bilateral cleft, unilateral right, and unilateral left cleft types (n = 10). The 3D volumetric space between the feeding plate and the corresponding main model was measured by micro-CT to evaluate the adaptation. The adaptation of the plates was assessed based on three different measurement regions: anterior, left, and right. Repeated measure analysis of variance (ANOVA), three factorial ANOVA, and post hoc Bonferroni tests were used as statistical analysis (α = 0.05).

RESULTS

CM groups showed higher volumetric space measurements between the base and master model than 3D groups regardless of measurement region and cleft type, which refers to misfit (p ˂ 0.05). Cleft type differed in the adaptation of 3D groups yet not in CM groups (p ˂ 0.05). The volumetric space evaluation for the right measurement region resulted in higher values regardless of manufacturing method and cleft type (p ˂ 0.05).

CONCLUSION

Considering that 3D-printed feeding plates showed better adaptation compared to conventionally manufactured plates for all cleft types, 3D printing can be suggested as the manufacturing method of choice for feeding plates.

Three-Dimensional-Printed Osteochondral Scaffold with Biomimetic Surface Curvature for Osteochondral Regeneration

OBJECTIVES

Treatment of osteochondral defects is hindered by several challenges, including the failure of traditional scaffolds with a predefined cylindrical or cuboid shape to comprehensively match the natural osteochondral tissue. Herein, we employed reverse modeling and three-dimensional (3D) printing technologies to prepare subchondral bone and cartilage.

METHODS

The osteochondral scaffold was prepared by bonding the subchondral bone and cartilage layers, and the curvature distribution and biomechanical behavior were compared with those of the native tissue. Biocompatibility and osteochondral regeneration performance were further evaluated using cell adhesion and proliferation assays, as well as animal osteochondral defect repair tests.

RESULTS

We found that increasing the printing temperature or decreasing the layer height improved the dimensional accuracy of printed subchondral bones, whereas increasing the exposure time or decreasing the layer height enhanced the dimensional accuracy of the printed cartilage. Biomimetic scaffolds exhibited curvature distribution and biomechanical behavior more similar to native tissues than traditional cylindrical scaffolds. Incorporating gelatin methacryloyl into poly (ethylene glycol) diacrylate markedly improved the biocompatibility, and correspondingly prepared osteochondral scaffolds had better osteochondral regeneration ability than the traditional scaffolds.

CONCLUSIONS

Osteochondral scaffolds exhibiting biomimetic morphology and an internal structure could be prepared based on reverse modeling and 3D printing, facilitating personalized osteochondral injury treatment.

Surface characteristics, cytotoxicity, and microbial adhesion of 3D-printed hybrid resin-ceramic materials for definitive restoration

OBJECTIVE

This study investigated the surface properties, cytotoxicity, and microbial adhesion of 3D-printed specimens made from hybrid resin-ceramic materials intended for use in definitive crowns.

METHODS

Disc-shaped specimens were 3D-printed using six different hybrid resin-ceramic materials recommended for definitive restorations: Crowntec (CT), VarseoSmile Crown Plus (VS), Tera Harz TC-80DP Graphy (TH), C&B Permanent ODS (CB), Formlabs Permanent Crown (FP), and HeyGears (HG). Surface topography, surface roughness, and water contact angle values were measured for each material (n = 6). Cytotoxicity was assessed using direct contact and extract tests on human gingival fibroblasts (n = 4). Additionally, the adhesion of mixed oral bacteria to the surfaces of the specimens was evaluated by counting colony-forming units (CFUs) after a 2-hour incubation period (n = 6).

RESULTS

The TH group exhibited significantly lower surface roughness (Ra: 0.28 ± 0.13 μm) compared to the other materials (CT: 1.87 ± 0.34 μm; VS: 1.13 ± 0.09 μm; CB: 2.91 ± 0.27 μm; FP: 2.50 ± 0.08 μm; HG: 1.50 ± 0.55 μm). The VS group had the highest water contact angle (129.5 ± 1.1°), indicating greater hydrophobicity, in contrast to the other groups (CT: 72.6 ± 2.1°; TH: 75.0 ± 0.3°; CB: 69.1 ± 0.2°; FP: 93.0 ± 1.6°; HG: 77.7 ± 0.3°). Cytotoxicity testing showed no harmful effects, as relative cell viability exceeded 70 %, and lactate dehydrogenase (LDH) release remained below 30 % for all materials. The TH specimens also demonstrated the lowest bacterial adhesion.

CONCLUSIONS

The surface characteristics of the tested resin-ceramic materials varied significantly, with TH showing the smoothest surface and the least bacterial adhesion. All materials were found to be non-toxic. Therefore, TH material has the potential to provide definitive restorations with less microbial adhesion.

CLINICAL SIGNIFICANCE

The type of resin-ceramic material significantly affects the surface properties of 3D-printed specimens. These findings are crucial for selecting the appropriate resin-ceramic material for definitive restorations.

Zirconia crowns manufactured using digital light processing: Effects of build angle and layer thickness on the accuracy

OBJECTIVES

This study investigated the effects of build angle and layer thickness on the trueness and precision of zirconia crowns manufactured using digital light processing (DLP) technology.

MATERIALS AND METHODS

Single crowns were fabricated from zirconia using DLP technology. The crowns were manufactured with three different representative build angles (0°, 45°, and 90°) and two different layer thicknesses (30 μm and 50 μm). After printing, the specimens were non-contact-scanned, and their accuracy was assessed using a 3D analysis software. Root mean square (RMS) values were used to determine trueness and precision. Color maps were generated to detect deviations within the specimens. Statistical analyses were conducted using two-way ANOVA.

RESULTS

Build angle and layer thickness significantly affected trueness and precision (p < 0.05). At a 30-μm layer thickness, the crowns printed at angles of 0° (32.2 ± 3.2 μm) and 45° (33.9 ± 2.4 μm) demonstrated the best marginal trueness compared to those in other groups (p < 0.05). Notably, those printed at an angle of 90° exhibited the best intaglio surface trueness (37.4 ± 4.0 μm). At a 50-μm layer thickness, the crowns printed at an angle of 90° exhibited the lowest accuracy concerning marginal and intaglio surface aspects (27.7 ± 8.2 μm).

CONCLUSIONS

Both the build angle and layer thickness significantly affected the dimensional accuracy of DLP-printed zirconia crowns, with the 30-μm layer thickness offering superior trueness. Optimal results were achieved using build angles of 0° and 45° in conjunction with thinner layers, minimizing marginal defects.

CLINICAL SIGNIFICANCE

All zirconia crowns produced at different build angles and layer thicknesses satisfied clinical requirements. Specific combinations of these factors realized the fabrication of single crowns that possessed the highest accuracy.

3D-printed zirconia orthodontic brackets: Effect of printing method on dimensional accuracy

OBJECTIVES

This study investigated the effect of additive manufacturing (AM) methods on the slot height dimensions and accuracy of 3D-printed orthodontic brackets.

METHODS

A 3D model of a standard Mclaughlin Bennett Trevisi bracket was used as a reference to print the ceramic bracket in a 90° orientation using two representative AM methods: digital light processing (DLP) and material jetting (MJ). The dimensional accuracy and slot heights were determined using a scanning electron microscope and an optical scanner. Also, all specimens were analysed using the Geomagic Control X 3D inspection software. The root mean square (RMS) values were used for trueness and precision assessment. Statistical analyses were performed using an independent sample t-test.

RESULTS

Slot height dimensions, trueness RMS, and precision RMS were statistically affected by different AM methods (p < .01). There was a significant difference between the different printing methods, with DLP meeting the tolerance requirements (mean slot height = 0.557 ± 0.018 mm) and MJ being slightly below them (mean slot height = 0.544 ± 0.021 mm). However, MJ significantly outperformed DLP in terms of accuracy. Among the two printing methods, MJ was associated with higher trueness (RMS = 0.025 ± 0.004 mm) and precision (RMS = 0.038 ± 0.005 mm).

CONCLUSIONS

Both tested AM methods yielded clinically acceptable outcomes, with the RMS range set to ±100 μm and the slot height tolerance established at 0.549-0.569 mm. The MJ technology achieved the highest accuracy.

Potential for bracket bonding errors based on tray accuracy and fit: Evaluation of 6 photopolymer resins for indirect bonding trays

INTRODUCTION

We assessed the accuracy and fit of 3-dimensional (3D)-printed indirect bonding (IDB) trays fabricated using various photopolymer resin materials.

METHODS

A maxillary plaster model and 60 plaster replicas were created. IDB trays with arbitrary bracket configurations were 3D-printed using 3 hard resins (Amber [AB], TC85DAC [TC], Orthoflex [OF]) and 3 soft resins (IBT [IT], IDB2 [ID], and MED625FLX [MD]). A reference plaster model with a computer-aided design-designed IDB tray attached with nonfunctional, arbitrary bracket configurations on the buccal surface serving as reference points for measurement was superimposed on scanned plaster replicas holding 3D-printed trays to assess transfer accuracy and clinically acceptable error. Printing accuracy was assessed by comparing computer-aided design trays to printed trays, and tray fit was measured by the gap volume between the tray and plaster replica using a Fit-Checker (GC Corp, Tokyo, Japan).

RESULTS

Six tray groups showed significant linear transfer errors, particularly in the vertical direction (0.15 mm [95% confidence interval {CI}, 0.10-1.15]; P = 0.004). The OF group exhibited the largest vertical error (0.27 mm [95% CI, 0.19-0.35]), whereas the ID group had the smallest (0.10 mm [95% CI, 0.06-0.14]). Angular errors did not exhibit significant differences across the groups. Linear precision error was the highest in OF, followed by ID, TC, and MD, then AB and IT (P <0.001). Of all tray groups, 90.1% and 68.8% met the clinically acceptable linear (<0.25 mm) and angular errors (1°).

CONCLUSIONS

Linear errors, particularly vertical errors, are more material-dependent than angular errors. Gap volume alone was not a reliable predictor of IDB tray accuracy. Therefore, material-specific designs are needed to control the optimal fit and facilitate precise bracket placement.

Achieving automated and high-precision in situ analysis of the dimensional accuracy and dynamic deformation of 3D-printed surgical templates: an in vitro study

PURPOSE

To demonstrate the viability of a coordinate-measuring machine (CMM) for the geometric analysis of 3D printed surgical templates.

METHODS

The template was designed and modified by adding 18 cylindrical landmarks for CMM test and then classified into five groups according to the slicing software and resins (opaque and transparent): Streamflow-O, Streamflow-T, Shapeware-T, Rayware-T and Polydevs-T (N = 3). Three standing times (0 w, 1 w, and 2 w) were included to observe possible deformation. All the measurements were performed automatically by the CMM through a preset program. The Euclidian distance (dxyz) was regarded as the representation of global dimension accuracy, and displacements in the x-, y-, and z-axes were also calculated.

RESULTS

The average dxyz values of Streamflow-O, Streamflow-T, Shapeware-T, Rayware-T and Polydev-T are 32.6 μm, 31.3 μm, 56.4 μm, 96.4 μm, and 55.3 μm, respectively. Deviations were mainly induced by the upward bending of the free end region (positive direction of the z-axis). Different resins did not have a significant influence on the dimensional accuracy. Moreover, deformation appeared to be negligible after 2 weeks of storage, and the z-axis displacements were only approximately 30 μm at week 1 and 10 μm at week 2.

CONCLUSIONS

The deviations of the DLP-printed template are induced mainly by z-axis displacements and are determined by the processing accuracy. After 2 weeks, the dimensional stabilities of these templates are reliable, which is encouraging for clinicians. Moreover, the CMM is preliminarily demonstrated to be a feasible tool for achieving automated geometric analysis of surgical templates.

3D-printed and conventional provisional single crown fabrication on anterior implants: A randomized clinical trial

OBJECTIVES

The present study aims to compare provisional single crowns on anterior implants made using conventional PMMA and 3D-printed workflows. The study assessed the occurrence of failures, color variation, signs of early deterioration, operating time, and patients' satisfaction with the treatment through a randomized controlled trial.

METHODS

This study was conducted as a randomized controlled trial, following the SPIRIT and CONSORT guidelines. Patients were included in the study after meeting the eligibility criteria and were randomly assigned to one of two groups (conventional and 3D-printed). FDI criteria, visible plaque index (VPI), bleeding on probing (BOP), and color variation were considered as the primary outcomes. Operating time and patient satisfaction were also assessed as secondary outcomes. Fisher's exact test was performed to analyze the association between the primary and secondary outcomes and the study groups. Mann-Whitney test was used to compare the mean VAS satisfaction scores between the conventional PMMA and 3D-printed groups (STATA 14™, with an α = 0.05).

RESULTS

A total of 42 provisional single crowns (n = 21) were made for 33 patients. Only the fracture parameter (FDI) showed a statistically significant difference, with 3D-printed provisionals exhibiting higher rates of catastrophic failures compared to conventional ones (p = 0.05). Although the operating time for the 3D-printed group was shorter (p < 0.001), no statistical difference observed in patients' satisfaction regarding esthetics, phonetics, chewing, or comfort.

SIGNIFICANCE

3D-printed and conventional PMMA provisional single crowns showed comparable clinical performance, except for the observed fracture types. Although 3D-printed provisional restorations showed a shorter operating time, overall patients' satisfaction was not affected.

Flexural Strength Analysis of Different Complete Denture Resin-Based Materials Obtained by Conventional and Digital Manufacturing

PMMA (Polymethylmethacrylate) is the material of choice to fabricate denture bases. Recently, with the introduction of CAD-CAM and 3D printers in dentistry, new materials have been proposed for complete denture manufacturing.

AIM

This study compared the flexural strength of different resins fabricated using different technologies (conventional, CAD-CAM-milled, and 3D-printed) and polymerization techniques.

METHODS

A total of 11 different resins were tested: six PMMA conventional (Acrypol R, Acrypol LL, Acrypol HI, Acrypol Fast, Acryself and Acryslef P), two milled obtained from UDMA PMMA disks (Ivotion disk and Aadva disk, control groups), two 3D-printed PMMA resins (NextDent Denture 3D+, and SprintRayEU Denture Base), and one 3D-printed composite resin (GC Temp Print). Flexural strength was measured using a universal testing machine. One-way ANOVA and Bonferroni post hoc tests were performed; the p-value was set at 0.05 to consider statistically significant differences among the groups. Spearman test was used to evaluate the correlation between polymerization technique and the flexural strength of 3D-printed resins.

RESULTS

CAD-CAM-milled specimens showed the highest flexural strength (107.87 MPa for UDMA) followed by 3D-printed composite resins (102.96 MPa). Furthermore, 3D-printed resins polymerized for 40 min with the BB cure unit showed no statistically significant differences with conventional resin groups. Moreover, in all the 3D-printed specimens, a high correlation between polymerization technique and flexural strength was found.

CONCLUSIONS

In terms of flexural strength, the polymerization technique is a determinant for both acrylic and composite resins. Temp Print can be a potential alternative to fabricating removable dentures and showed promising results when used in combination with pink color resin powder.