Scanning electron microscope evaluation of the marginal gap and internal fit of additive versus subtractive fabrication techniques for posterior lithium disilicate crowns

Abstract

Statement of the problem:The wide use of digital dentistry in fixed prosthodontics using 3D printers and CAD/CAM in fabricating crowns and partial fixed dental prosthesis created a need for more information about their marginal gap and internal fit.Purpose: This study aimed to evaluate the effect of fabrication technique using CAD/CAM manufactured and heat pressed lithium dislicate crowns made from milled wax and 3D printed resin patterns on their marginal gap and internal fit. Material & Methods:A total of 50 prepared mandibular first molar resin models were used and divided into two main groups according to their fabrication phase: Patterns group and fully fabricated crowns group. Patterns group was subdivided into milled wax patterns (W) (n=10) and 3D printed resin patterns (P) (n=10). Fully fabricated crowns group was subdivided according to fabrication technique of lithium disilicate crowns into: Machinable ceramics (M), using IPS e-max CAD blocks (n=10), Pressable ceramics (Pw), using IPS e-max press ingots following wax milling (n=10) and Pressable ceramics (Pp), using IPS e-max press ingots following 3D resin printing (n=10). All patterns and ceramic crowns were cemented with Rely-X self-adhesive resin cement. Marginal and internal adaptations were measured using SEM at 300 × magnification. Kruskal-Wallis and Wilcoxon signed-rank tests were applied to compare between the groups. Data were presented as median and range values. The significance level was set at P ≤ 0.05.Results: P group showed a significant higher median total marginal gap of 111.4 μm (80.8-139.7) than W group of 51.3 μm (45.1-57.8) before heat pressing. While M group showed the significant highest median marginal gap of 138.4 μm (83.4-191.8) and no significant difference between heat pressed groups (Pw and Pp) (P ≤ .05). Regarding changes after heat pressing, Pw group showed no significant decrease, while Pp group showed a significant decrease in median total marginal gap. For internal fit, there was no significant difference between the pattern groups (2780)

Marginal Accuracy and Fracture Resistance of Posterior Crowns Fabricated from CAD/CAM PEEK Cores Veneered with HIPC or Nanohybrid Conventional Composite

“…10 It was then replicated to have 20 dental epoxy resin dies. 11 Each prepared die was scanned using 3D dental scanner (Identica hybrid; MEDIT corp., Seoul, Korea). Twenty cores were designed (exocad Dental CAD; exocad GmbH, Germany) and milled (K5; vhf camfacture AG, Germany) from PEEK blanks (breCAM.BioHPP Discs; Bredent, Senden, Germany, LOT: 400177), a thermoplastic resin which is partially crystalline and reinforced with ceramic particles.…”

3D Surface Deviation Wear Analysis of Veneered PEEK Crowns and Its Correlation with Optical Digital Profilometry

“…18 It was then duplicated to create 20 dental epoxy resin dies. 19 Each prepared die was scanned using a 3D dental scanner (Identica Hybrid T500; MEDIT corp., Seoul, Korea). Twenty crown cores were designed (exocad Dental CAD; exocad GmbH, Germany) and milled (K5; vhf camfacture AG, Germany) from PEEK blanks (breCAM.BioHPP Discs; bredent, Senden, Germany).…”

Comparative wear analysis of conventional versus CAD/CAM composite veneered PEEK crowns using 3D surface deviation

“…All-ceramic crown preparation of a typodont mandibular first molar tooth was performed, 17 followed by making molds from an additive silicone (President; Coltène whaledent, Altstätten, Switzerland) to produce 20 epoxy resin model duplications. 18,19 According to this design, PEEK discs (breCAM.BioHPP Discs, bredent, Senden, Germany) were used to mill 20 substructures (K5; vhf camfacture AG, Germany) from.…”

“…Following the manufacturer's directions, all crowns were bonded with their epoxy resin models utilizing self-adhesive resin cement (RelyXTM Unicem 2; 3M ESPE, Seefeld, Germany). 18,20,21 For 5 min all crowns were subjected to 250 g static load to ensure proper cement flow and crown adaptation.…”