Three-dimensional (3D) printing in dental practice: Applications, areas of interest, and level of evidence.

OBJECTIVES: The aim of this review to overview three-dimensional (3D) printing technologies available for different dental disciplines, considering the applicability of such technologies and materials development. MATERIALS AND METHODS: Source Arksey and O'Malley's five stages framework using PubMed, EMBASE, and Scopus (Elsevier) databases managed this review. Papers focusing on 3D printing in dentistry and written in English were screened. Scientific productivity by the number of publications, areas of interest, and the focus of the investigations in each dental discipline were extracted. RESULTS: Nine hundred thirty-four studies using 3D printing in dentistry were assessed. Limited clinical trials were observed, especially in Restorative, endodontics, and pediatric dentistry. Laboratory or animal studies are not reliable for clinical success, suggesting that clinical trials are a good approach to validate the new methods' outcomes and ensure that the benefits outweigh the risk. The most common application for 3D printing technologies is to facilitate conventional dental procedures. CONCLUSIONS: The constantly improving quality of 3D printing applications has contributed to increasing the popularity of these technologies in dentistry; however, long-term clinical studies are necessary to assist in defining standards and endorsing the safe application of 3D printing in dental practice. CLINICAL RELEVANCE: The recent progress in 3D materials has improved dental practice capabilities over the last decade. Understanding the current status of 3D printing in dentistry is essential to facilitate translating its applications from laboratory to the clinical setting.

The trueness of scans using one intraoral scanner in different partially edentulous conditions.

PURPOSE: To investigate the trueness of intraoral scanning in 8 commonly seen partially edentulous conditions. MATERIALS AND METHODS: A maxillary dentoform was modified into the 8 commonly seen partially edentulous conditions. Each modification was scanned with a laboratory desktop scanner. Each modification was then scanned 10 times (n = 10) with an intraoral scanner. All scans were exported as STL files and then imported into a surface matching software using the best-fit alignment method. The dimensional differences between the study STL files from the intraoral scanner were compared to the corresponding reference STL files. The measurements were calculated as the root mean square (RMS) and defined as the trueness of the intraoral scans. In addition to the RMS values, qualitative assessments were completed on the color maps. The color maps produced by the surface matching software were used to visualize the areas of deviation between scans from the intraoral scanner and their corresponding reference files. One-way analysis of variance (ANOVA), followed by pair-wise comparisons using Fisher's Protected Least Significant Difference were utilized to compare the differences between the groups in RMS values (α = 0.05). RESULTS: Partially edentulous condition significantly affected the trueness of the intraoral scans. Group 8 (Class IV) had significantly lower RMS (0.1878 ± 0.0455 mm) than all other groups (p < 0.001). Group 2 (Class II) and Group 7 (Class III modification I) are not significantly different from each other (Group 2: 0.5758 ± 0.0300 mm; Group 7: 0.5602 ± 0.0231 mm, p = 0.571), while they both had significantly higher RMS than all other groups (p < 0.001). The remaining groups showed the RMS values were within the range of 0.3001 ± 0.0891 mm (Group 6 - Class III with Long Edentulous Span) and 0.4541 ± 0.1039 mm (Group 1 - Class I). CONCLUSION: Different partially edentulous conditions affected the trueness of the scans generated from the selected intraoral scanner. Class IV edentulous condition had the highest intraoral scan trueness. It is unknown if RMS values are clinically significant, and the validity of using intraoral scans directly for PRDP fabrication will need further studies.

Effect of cementation, cement type and vent holes on fit of zirconia copings.

OBJECTIVES: To investigate the effect of cementation, cement type and vent-holes on the marginal and internal fit of Zirconia (Zr) Copings. MATERIALS AND METHODS: Extracted premolars (N = 100) were mounted in resin and prepared for Zr crowns. Samples were randomly divided into 5 groups (n = 20); A: No Cementation; B: Cementation with Glass-Ionomer (GI); C: GI + Vent-Holes; D: Cementation with Resin Cement (RC); E: RC + Vent-Holes. The copings were fabricated using semi sintered Zr Blocks with a standardized cement space of 20 µm. Groups C & E were designed to have 0.5 mm of Vent-Holes on the Buccal and Lingual Cusp Tips. The copings were tried, cemented, thermocycled, re-embedded in resin and cross sectioned into two halves. The copings were examined with 3D-Digital Microscope (HIROX, KH-7700, Tokyo, Japan) at 50-200X. The gaps were recorded at 9 predetermined points. RESULTS: The non-cemented groups showed statistically better fit compared to the cemented groups P < 0.05 except vs Group E (RC plus vent holes). No significance was found between the cemented groups P > 0.05. Copings with vent-holes showed statistically better fit than copings without holes P < 0.05. CONCLUSION: Marginal and Internal gap values designed in the software programs differed than the actual values measured for the non-cemented copings. Cementation process also influenced the fit of the Zr copings, the resin cement being the more accurate. The addition of vent-holes on the occlusal surface improved the fit.