A polyetheretherketone framework removable partial denture for a 6-year-old child with nonsyndromic oligodontia made using glass-ceramic hemispheres to enhance retention: A clinical report.

A 6-year-old child with nonsyndromic oligodontia in the mixed dentition received a removable dental prosthesis with a polyetheretherketone framework and artificial gingiva, restoring esthetics and function. Computer-aided design and computer-aided manufacturing hemispherical glass-ceramic attachments were added to the teeth under the guidance of acid-etching and bonding guides to obtain an undercut area. The bonding and cementation of the attachments and the prosthesis delivery were completed in a single visit. This method offers a suitable prosthodontic treatment option for treating children with oligodontia in the mixed dentition.

Application of digital impression and model in removable partial dentures for Kennedy classâ andâ ¡dentition defects.

OBJECTIVES: This study aimed to evaluate the application of digital impression and resin model technology in removable partial dentures (RPD) for Kennedy classⅠandⅡdentition defects. METHODS: Patients with Kennedy classⅠorⅡdental defect were selected and grouped in accordance with the following denture production processes: digital impression/resin model/cast cobalt-chromium alloy framework group (group A), digital impression/resin model/laser printed titanium framework group (group B), alginate impression/plaster model/cast cobalt-chromium alloy framework group (group C), and alginate impression/plaster model/laser printed titanium framework group (group D), with 40 cases in each group. The final RPD was examined in place in the mouth, and the evaluation indicators included the retention force of clamp ring, the tightness of connector and base, and the accuracy of occlusion. The evaluation scores of each index were used for analysis on the Kruskal-Wallis rank-sum test. RESULTS: No statistically significant difference in the score of each index was found among the four groups in RPD. CONCLUSIONS: The cast cobalt-chromium alloy and laser-printed titanium framework RPD using digital impression and resin model can meet the clinical restoration requirements of patients with Kennedy classⅠandⅡdentition defects.

Physical and biological implications of accelerated aging on stereolithographic additive-manufactured zirconia for dental implant abutment.

PURPOSE: This study aimed to comparatively investigate the effects of accelerated aging on the physical and biological features of zirconia manufactured by digital light processing (DLP) and conventional subtractive manufacturing (SM) with similar composition. METHODS: Both the DLP- and SM-fabricated zirconia samples (7 mm × 7.5 mm × 1.5 mm) were grouped according to aging (134 °C, 0.2 MPa, 100% humidity) times, including 0 h, 5 h, and 10 h. Phase assemblage and surface topography of zirconia manufactured by different technologies were evaluated before and after aging. The biological effects of zirconia on human gingival fibroblast (HGF) cell events, including cell viability, proliferation, morphology and adhesion, were also evaluated by live/dead viability assay, cck-8 assay, scanning electron microscopy and confocal laser scanning microscopy respectively. RESULTS: The DLP-fabricated zirconia showed a higher initial cubic phase content and rate of phase transformation than the SM-fabricated zirconia. Among the different aging time-based groups, the 5 h-aged group exhibited significantly lower sub-micron scale surface roughness compared with the other groups. Aging did not significantly alter cellular behavior in any zirconia type, except for minor changes in adhesive cell numbers recorded in an aging time/culturing time-dependent manner. In addition to small differences in cell alignment patterns and overall cell morphology, the two zirconia types presented comparable biological performance before and after aging. CONCLUSION: Although the microstructure and surface characteristics of DLP-fabricated zirconia can be affected by autoclave aging, this newly manufactured zirconia is likely to maintain desirable long-term biocompatibility as an implant abutment material.

Corrigendum to "Determination of Hardness and Fracture Toughness of Y-TZP Manufactured by Digital Light Processing through the Indentation Technique".

[This corrects the article DOI: 10.1155/2021/6612840.].

An investigation of the microstructure and mechanical properties of dental zirconia manufactured by digital light processing 3D printing.

OBJECTIVES: This study was performed to investigate the microstructure and mechanical properties of dental zirconia manufactured by digital light processing (DLP) 3D printing and the clinical application prospects of this material. METHODS: The experiment (DLP) group was zirconia manufactured by DLP 3D printing, and the control (MILL) group was milled zirconia. The density, grain size, and phase composition were measured to study the microstructure. Flexural strength was measured by using three-point bending tests, while Vickers hardness was determined through a Vickers hardness tester. Fracture toughness was tested using the single-edge V-notched beam method. RESULTS: Zirconia density of the DLP group was (6.019 8±0.021 3) g·cm-3, and the average grain size was (0.603 0±0.032 6) µm, but without statistical difference with the corresponding values of the MILL group (P>0.05). Tetragonal phase was found in the X-ray diffraction patterns of the DLP and MILL groups. The flexural strength of the DLP group was (1 012.7±125.5) MPa, and Vickers hardness was (1 238.5±10.8) HV1, which was slightly lower than that of the MILL group (P<0.05). The fracture toughness of the DLP group was (7.22±0.81) MPa·m1/2, which was not statistically different from that of the MILL group (P>0.05). CONCLUSIONS: Zirconia manufactured by DLP 3D printing had microstructure and mechanical properties similar to those of the milled zirconia. Only the flexural strength and the Vickers hardness of the experimental zirconia were slightly lower than those of the milled zirconia. Therefore, DLP-manufactured zirconia has a promising future for clinical use.

Determination of Hardness and Fracture Toughness of Y-TZP Manufactured by Digital Light Processing through the Indentation Technique.

OBJECTIVE: The purpose of the study was to determine the hardness and fracture toughness of dental yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) manufactured by digital light processing (DLP) technology to study its clinical prospects. METHODS: The experimental group was DLP-manufactured zirconia, and the control group was milled zirconia. The hardness was investigated under a range of test loads (0.49 N, 0.98 N, 1.96 N, 4.90 N, 9.81 N, 29.42 N, 49.03 N, 98.07 N, and 196.1 N). Meyer's law was applied to describe the indentation size effect (ISE). Meanwhile, the PSR model and MPSR model were utilized to generate true hardness values. The cracks were observed to be induced by indentation under loads above 49.03 N, while the cracks showed the radial-median type under the load of 196.1 N, under which the fracture toughness was calculated. RESULTS: The true hardness of DLP-manufactured zirconia was 1189 HV based on the PSR model and 1193 HV based on the MPSR model, a bit lower than that of milled zirconia. The fracture toughness was 3.43 ± 0.29 MPa√m, which showed no statistical difference with the milled zirconia. CONCLUSION: The dental zirconia manufactured by the DLP 3D printing technique is similar to that manufactured by the conventional milling process in hardness and fracture toughness, thus having a promising future of clinical use.

[Precise tooth preparation technique guided by 3D printing guide plate with quantitative hole].

The minimum amount of tooth preparation that can be fully controlled is crucial in achieving long-term, stable, and effective aesthetic restoration, which is also a major difficulty in aesthetic restoration. The tooth preparation can be imple-mented efficiently and accurately through digital technology based on the fixed-deep hole guiding technology. Prior the actual tooth preparation, the technology first designs the virtual contour, layering, and virtual occlusion of the prosthesis on the computer. Then, virtual tooth preparation is carried out by cutting back according to the virtual prosthesis. Next, the virtual drilling operation plan is designed according to the shape of the virtual tooth preparation and the contour of the abutment tooth. Finally, the tooth preparation guide plate is designed and printed in 3D. It realizes the whole process of quantitative and precise guidance of dental preparation, visualizes the restoration space, reduces the clinical operation time, and guarantees the quality of dental preparation. It also promotes the improvement of the teaching quality of digital practical exercises.