Accuracy of Dental Restorations Fabricated Using Milling vs 3D-Printed Molds: A Pilot Study.

PURPOSE: To compare the accuracy of 12 different dental restorations fabricated with milling or 3D-printed molds and robotically controlled casting. MATERIALS AND METHODS: Twelve dental restorations (11 inlays and onlays and 1 crown) were made per restoration type, one per each of the 12 different teeth models (total of 24 restorations). On each tooth preparation, two restorations were manufactured using different CAD/ CAM techniques: (1) milling and (2) robotically controlled casting and 3D-printed molds. In addition, twolayer restorations were manufactured with 3D-printed molds. The marginal and internal gaps were evaluated at 120 points per restoration based on micro-CT 3D imaging. Internal gaps were evaluated using a replica technique with silicone. RESULTS: Median values (interquartile ranges) for marginal gaps, middle internal gaps, and central internal gaps were significantly lower for 3D-printed mold restorations (44.3 [65.4] µm, 95.4 [96.2] µm, and 104.6 [78.1] µm) compared to milled restorations (58.4 [93] µm, 145.9 [85.8] µm, and 138.6 [65.7] µm). Internal gaps in the 3D-printed mold group were 6% to 51% smaller than in the milled group. CONCLUSIONS: The accuracy of restorations fabricated with 3D-printed molds may be preferable compared to milled restorations, except in the case of crown restoration. However, additional studies with a larger number of samples and different types of restorations are needed to confirm the results.

Repair bond strength of bulk-fill composites: influence of different primers and direction of debonding stress.

Background: The purpose of this in vitro study was to evaluate the effect of different adhesion primers on the repair bond strength of bulk-fill resin composite and short-term hydrolytic stability of the repair interface before and after accelerated aging. In addition, direction of debonding stress was examined. Materials and methods: Bulk-fill substrates were aged in water for 14 days at 37 °C. Smooth resin composite surfaces were prepared for the substrates with a superfine grinding paper (FEPA #500, #1200, #2000). Test specimens were produced by attaching bulk-fill composite to the substrate surfaces, using three different primer/bonding systems. Specimens were aged 24 h at 37 °C in water, or thermal cycled (5-55 °C/5,000 cycles). Subsequently, shear bond strength and micro-tensile bond strength were evaluated. In total there were 60 specimens for the shear bond strength and 60 specimens for the micro-tensile bond strength measurements (30 stored in water 24 h, 30 thermal cycled, n = 10 in each primer/bonding mode). Results: The mean shear bond strength was 9.1-13.1 MPa after 24 h water storage and 6.9-10.7 MPa after thermal cycling. The mean micro-tensile bond strength was 28.7-45.8 MPa after 24 h water storage and 22.7-37.9 MPa after thermal cycling. Conclusion: The Ceramic primer (silane containing) seems to perform better than the three-step etch and rinse adhesive or the Composite primer. Shear-type stress had an adverse effect on the repair bond strength of bulk-fill resin composites.

Challenges of the Direct Filling Technique, Adoption of CAD/CAM Techniques, and Attitudes Toward 3D Printing for Restorative Treatments Among Finnish Dentists.

PURPOSE: To evaluate the challenges of the direct filling technique, the use of dental chairside CAD/CAM milling, the use of 3D printing, and the attitudes toward 3D printing-based applications for restorative treatments among Finnish dentists. MATERIALS AND METHODS: An electronic questionnaire was sent to 3,777 Finnish dentists. Background information, challenges linked to the direct filling technique, use of dental chairside CAD/CAM milling, use of 3D printing, and attitudes toward 3D printing-based applications in restorative dentistry were asked in the questionnaire with multiple-choice questions. The number of replies was 760, and the response rate was 20.1%. RESULTS: Poor survival rates and moisture sensitivity were the main reported challenges associated with the direct filling technique. Use of chairside CAD/CAM milling was reported by 271 (35.7%) respondents. Use of 3D printing technique was reported by 54 (7.1%) respondents. Most respondents answered that they would consider using 3D printing for manufacturing tooth fillings in the future. CONCLUSION: If dental chairside CAD/CAM technology can provide a solution for manufacturing long-lasting indirect restorations with good esthetic properties and an effective cost-benefit ratio, the wider use of chairside CAD/CAM systems might be indicated, especially in the public sector. New 3D printing-based applications used for restorative treatments are attracting interest among Finnish dentists, but also indicate a need for further development of 3D printing techniques for cost-effective restorative treatment.

Digital Versus Conventional Impressions in Fixed Prosthodontics: A Review.

PURPOSE: To conduct a systematic review to evaluate the evidence of possible benefits and accuracy of digital impression techniques vs. conventional impression techniques. MATERIALS AND METHODS: Reports of digital impression techniques versus conventional impression techniques were systematically searched for in the following databases: Cochrane Central Register of Controlled Trials, PubMed, and Web of Science. A combination of controlled vocabulary, free-text words, and well-defined inclusion and exclusion criteria guided the search. RESULTS: Digital impression accuracy is at the same level as conventional impression methods in fabrication of crowns and short fixed dental prostheses (FDPs). For fabrication of implant-supported crowns and FDPs, digital impression accuracy is clinically acceptable. In full-arch impressions, conventional impression methods resulted in better accuracy compared to digital impressions. CONCLUSIONS: Digital impression techniques are a clinically acceptable alternative to conventional impression methods in fabrication of crowns and short FDPs. For fabrication of implant-supported crowns and FDPs, digital impression systems also result in clinically acceptable fit. Digital impression techniques are faster and can shorten the operation time. Based on this study, the conventional impression technique is still recommended for full-arch impressions.