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    Evaluation of fracture resistance of inlay-retained fixed partial dentures fabricated with different monolithic zirconia materials
    (Mosby-Elsevier, 2018) Gumus, Hilal Siriner; Polat, Nilufer Tulin; Yildirim, Guler
    Statement of problem. Data are lacking on the fracture resistance of monolithic zirconia inlay-retained fixed partial dentures as a conservative treatment for a single missing tooth. Purpose. The purpose of this in vitro study was to evaluate the fracture resistance of inlay-retained fixed partial dentures produced from 3 different monolithic zirconia materials and based on 2 preparation types and applications with and without thermocycling. Material and methods. A model with missing right and left mandibular first molars was used for different cavity preparations. A tube-shaped cavity and a box-shaped cavity were prepared. Seventy-two epoxy resin casts were prepared from an additional silicone impression. Twenty-four inlay-retained fixed partial dentures from each monolithic zirconia material (Prettau, Zirkonzahn; Katana, Noritake; and Copran, Whitepeaks) were fabricated for each preparation type and cemented to their epoxy model with dual-polymerizing adhesive resin cement; 50% of all specimens were thermocycled for 10 000 cycles. The specimens were subjected to a fracture resistance test using a universal testing machine with a crosshead speed of 0.5 mm/min. Fracture surfaces were examined with scanning electron microscopy (SEM), and a specimen from each group was examined for structural changes with differential thermal analysis (DTA). Results. No statistically significant differences in terms of fracture resistance were found among brands with both cavity designs and with and without thermal cycles (P>.05). However, SEM and DTA results showed some changes in monolithic zirconia structure after 1 year of aging. Conclusions. The brands and cavity preparation types for single posterior tooth loss generated similar fracture resistance.
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    Evaluation of marginal and internal adaptation of hybrid and nanoceramic systems with microcomputed tomography: An in vitro study
    (Mosby-Elsevier, 2017) Yildirim, Guler; Uzun, Ismail H.; Keles, Ali
    Statement of problem. The accuracy of recently introduced chairside computer-aided design and computer-aided manufacturing (CAD-CAM) blocks is not well established, and marginal integrity and internal adaptation are not known. Purpose. The purpose of this in vitro study was to evaluate the marginal and internal adaptation of hybrid and nanoceramics using microcomputed tomography (mu-CT). Material and methods. The marginal and internal adaptation of 3 polymer-infiltrated ceramic network (PICN) materials (Vita Enamic EVE]; Lava Ultimate [LU]; Vita Suprinity [VS]) were compared with lithium disilicate (IPS e.max.CAD, IPS). Ninety-six specimens (48 dies and 48 crowns) were prepared (n=12 each group) using a chairside CAD-CAM system. The restorations were scanned with mu-CT, with 160 measurements made for each crown, and used in 2-dimensional (2D) analysis. The marginal adaptation of marginal discrepancy (MD), absolute marginal discrepancy (AMD), internal adaptation of shoulder area (SA), axial space (AS), and occlusal space (OS) were compared using appropriate statistical analysis methods (alpha=.05). Cement volumes were compared using 3D analysis. Results. The IPS blocks showed higher MD (130 mu m), AMD (156 mu m), SA (111 mu m) (P<.05), AS (52 mu m), and OS (192 mu m) than the other blocks (P<.01). The adaptation values of VS were significantly lower than those of the IPS block (P<.05). The adaption values of the LU and VE blocks were significantly lower than those of others (P<.01) but were statistically similar to one another (P>.05). IPS had the largest cement space at 18 mm(3) (P<.01). Conclusions. The marginal and internal adaptation values were within a clinically acceptable range for all 3 hybrids and nanoceramics tested.