Accuracy evaluation of 3D printed interim prosthesis fabrication using a CBCT scanning based digital model

An in vitro comparison of the marginal fit of provisional crowns using the virtual tooth preparation workflow against the traditional technique

Aim

This study investigates the effectiveness of an innovative virtual tooth preparation workflow for the fabrication of dental crowns using cone-beam computed tomography (CBCT) and intraoral scanners (IOSs) with conventional workflow using extraoral/laboratory scanners.

Settings and Design

This in vitro experimental study was conducted in the laboratory of a university in Chennai, India. The dental laboratory and research facilities at the institution were utilized for the fabrication of the temporary crowns and the data acquisition process.

Materials and Methods

Institutional approval was obtained from the university. It was basically a comparison between the virtual prep technique using CBCT and IOS and the conventional digital technique using extra oral scanners (EOS) for temporary crown fabrication. The sample size was estimated using an effect size of 1.5004, assuming a normal distribution, a significance level of 0.05, and a power of 0.95 in G power software. Based on this calculation, an extracted second lower molar was used to fabricate 10 samples in each group. The samples were divided into three groups: the CBCT (Group 1), the IOS (Group 2), and laboratory scanner (Group 3 as control) groups. The vertical marginal gap of all the surfaces of the crown was evaluated using a scanning electron microscope.

Statistical Analysis Used

Data were analyzed using one-way ANOVA using the SPSS software version 26.0, IBM, Armonk, NY, USA.

Results

Acceptable marginal discrepancy values were obtained in all three groups. There was no significant difference in the marginal discrepancy recorded (P = 0.113).

Conclusion

Virtual tooth preparation using CBCT and IOSs can be used as an alternative to the conventional workflow for provisional crown and bridge fabrication.

Flexural strength, surface roughness, micro-CT analysis, and microbiological adhesion of a 3D-printed temporary crown material

OBJECTIVE

To evaluate the thermocycling effect of 3D-printed resins on flexural strength, surface roughness, microbiological adhesion, and porosity.

MATERIALS AND METHODS

150 bars (8 × 2 × 2 mm) and 100 blocks (8 × 8 × 2 mm) were made and divided into 5 groups, according to two factors: "material" (AR: acrylic resin, CR: composite resin, BIS: bis-acryl resin, CAD: CAD/CAM resin, and PRINT: 3D-printed resin) and "aging" (non-aged and aged - TC). Half of them were subjected to thermocycling (10,000 cycles). The bars were subjected to mini-flexural strength (σ) test (1 mm/min). All the blocks were subjected to roughness analysis (Ra/Rq/Rz). The non-aged blocks were subjected to porosity analysis (micro-CT; n = 5) and fungal adherence (n = 10). Data were statistically analyzed (one-way ANOVA, two-way ANOVA; Tukey's test, α = 0.05).

RESULTS

For σ, "material" and "aging" factors were statistically significant (p < 0.0001). The BIS (118.23 ± 16.26A) presented a higher σ and the PRINT group (49.87 ± 7.55E) had the lowest mean σ. All groups showed a decrease in σ after TC, except for PRINT. The CRTC showed the lowest Weibull modulus. The AR showed higher roughness than BIS. Porosity revealed that the AR (1.369%) and BIS (6.339%) presented the highest porosity, and the CAD (0.002%) had the lowest porosity. Cell adhesion was significantly different between the CR (6.81) and CAD (6.37).

CONCLUSION

Thermocycling reduced the flexural strength of most provisional materials, except for 3D-printed resin. However, it did not influence the surface roughness. The CR showed higher microbiological adherence than CAD group. The BIS group reached the highest porosity while the CAD group had the lowest values.

CLINICAL RELEVANCE

3D-printed resins are promising materials for clinical applications because they have good mechanical properties and low fungal adhesion.

Digital versus Conventional Workflow in Oral Rehabilitations: Current Status

In recent years, computer-aided design and computer-aided manufacturing (CAD-CAM) technology has developed along with its applications in dentistry, including several new techniques that are used in oral rehabilitation applications [...]

Three-Dimensional (3D) Stereolithographic Tooth Replicas Accuracy Evaluation: In Vitro Pilot Study for Dental Auto-Transplant Surgical Procedures

After immediate tooth extraction or after alveolar socket healing, tooth transplants are increasingly used for functional restoration of edentulous maxillary areas. Recent studies have shown the periodontal ligament (PDL) viability and the tooth housing time in the adapted neo-alveolus as key factors for transplantation success. During surgical time, 3D stereolithographic replicas are used for fitting test procedures. In this paper, the accuracy of 3D dental replicas, compared with the corresponding natural teeth, is assessed in surgical transplantation. Lamb skulls were selected and submitted to Cone Beam Computer Tomography (CBCT). Scanning information, converted into Standard Digital Imaging and Communications in Medicine (DICOM) and Standard Triangulation Language (STL), was sent to the Volux X-ray Centre for 3D replica printing. After the tooth extractions, all lambs’ incisors were measured with a digital caliber and compared with the 3D replicas. Volume and dimensional error values were evaluated. All replicas showed macroscopically smaller volume (45.54%). Root replicas showed higher variations compared with the crown areas, with several unreplicated apical root areas. The cement–enamel junction tooth area was replicated quite faithfully, and the base area relative error showed 9.8% mean value. Even further studies with a larger number of replicas are needed. Data obtained confirmed high volumes of macroscopic discrepancies with several unreproduced apical root sites. The achieved accuracy (90.2%) confirmed that the 3D replicas cannot be used to reduce the surgical time during transplantation predictable procedures.

Main Applications and Recent Research Progresses of Additive Manufacturing in Dentistry

In recent ten years, with the fast development of digital and engineering manufacturing technology, additive manufacturing has already been more and more widely used in the field of dentistry, from the first personalized surgical guides to the latest personalized restoration crowns and root implants. In particular, the bioprinting of teeth and tissue is of great potential to realize organ regeneration and finally improve the life quality. In this review paper, we firstly presented the workflow of additive manufacturing technology. Then, we summarized the main applications and recent research progresses of additive manufacturing in dentistry. Lastly, we sketched out some challenges and future directions of additive manufacturing technology in dentistry.

Techniques to improve the accuracy of complete-arch implant intraoral digital scans: A systematic review

STATEMENT OF PROBLEM

The best method of optimizing the accuracy of complete-arch intraoral digital scans is still unclear. For instance, the location of the scan bodies can be significantly distorted with respect to their actual positions, which would lead to a nonpassive fit of the definitive prosthesis.

PURPOSE

The purpose of this systematic review was to analyze available techniques for improving the accuracy of digital scans in implant-supported complete-arch fixed prostheses.

MATERIAL AND METHODS

Three databases (Medline, Embase, and Google Scholar) were searched, and the results obtained were supplemented by a hand search. Specific descriptors identified techniques whose objective were to increase the accuracy of digital scans in implant-supported complete-arch fixed prostheses. Titles and abstracts were screened by 2 independent reviewers, and unclear results were discussed with a third independent reviewer. A qualitative analysis based on procedural parameters was used. The interexaminer agreements of both were assessed by the Cohen kappa statistic, and the Risk of Bias Tool was used to assess the risk of bias across the studies.

RESULTS

A total of 17 techniques matching the inclusion criteria were evaluated. Higher accuracy but also differences regarding the need for supplementary devices, number of intraoral scans, and time consumption of clinical and software program steps were observed compared with the conventional digital scanning protocol. The use of a splinting device was common to most of the studies. The outcome variables for the evaluation of the effectiveness of these protocols were heterogeneous.

CONCLUSIONS

The use of additional techniques during intraoral scanning can improve accuracy in implant-supported complete-arch fixed prostheses. However, higher complexity for those procedures should be expected.

Effect of Printing Layer Thickness on the Trueness and Margin Quality of 3D-Printed Interim Dental Crowns

The information in the literature on the effect of printing layer thickness on interim 3D-printed crowns is limited. In the present study, the effect of layer thickness on the trueness and margin quality of 3D-printed composite resin crowns was investigated and compared with milled crowns. The crowns were printed in 3 different layer thicknesses (20, 50, and 100 μm) by using a hybrid resin based on acrylic esters with inorganic microfillers or milled from polymethylmethacrylate (PMMA) discs and digitized with an intraoral scanner (test scans). The compare tool of the 3D analysis software was used to superimpose the test scans and the computer-aided design file by using the manual alignment tool and to virtually separate the surfaces. Deviations at different surfaces on crowns were calculated by using root mean square (RMS). Margin quality of crowns was examined under a stereomicroscope and graded. The data were evaluated with one-way ANOVA and Tukey HSD tests. The layer thickness affected the trueness and margin quality of 3D-printed interim crowns. Milled crowns had higher trueness on intaglio and intaglio occlusal surfaces than 100 μm-layer thickness crowns. Milled crowns had the highest margin quality, while 20 μm and 100 μm layer thickness printed crowns had the lowest. The quality varied depending on the location of the margin.