Ramtin Sadid‐Zadeh

Purpose This in vitro study aimed to compare flexural strength, surface roughness, and biofilm formation of ceramic‐reinforced polyetheretherketone (PEEK) with conventionally heat‐compressed and milled polymethylmethacrylate (PMMA) denture base materials. Materials and Methods Thirty strips (6.4 mm × 10 mm × 3 mm) and 30 discs (10 mm × 1 mm) were fabricated from a heat‐compressed PMMA, milled PMMA, and ceramic‐reinforced PEEK, 10 each. One surface of each sample was polished to mimic the laboratory procedure for denture base materials. Strips were then subjected to a three‐point bend test using a universal testing machine at a crosshead speed of 5.0 mm/min. An optical profilometer was used to assess the Ra value (mm) of the discs on polished and unpolished sides. Biofilm formation behavior was analyzed by measuring the colony‐forming unit (CFU)/mL of Candida albicans on the unpolished surface of the discs. One‐way ANOVA followed by Tukey multiple comparison tests were used to compare the flexural strength, Ra value, and biofilm formation of the studied materials ( a = 0.05). Results Ceramic‐reinforced PEEK showed significantly higher flexural strength (178.2 ± 3.2 MPa) than milled PMMA (89.6 ± 0.8 MPa; p < 0.001) and heat‐compressed PMMA (67.3 ± 5.3 MPa; p < 0.001). Ceramic‐reinforced PEEK exhibited a significantly higher Ra value than the other groups on unpolished sides; however, the polishing process significantly reduced the Ra values of all studied groups ( p < 0.05). There was no significant difference in C. albicans adhesion among the groups ( p < 0.05). Conclusion The flexural strength of tested materials was within acceptable limits for clinical use as a denture base material. Ceramic‐reinforced PEEK had the highest surface roughness; however, its similarity in biofilm formation to other groups indicates its clinical acceptability as denture base material.

Purpose To assess the shade match ability of four varieties of all‐ceramic crowns to a neighboring bilayered lithium disilicate crown. Material and methods A dentiform was used to fabricate a bilayered lithium disilicate crown on the maxillary right central incisor, following the anatomy and shade of a selected natural tooth. Two crowns (one full‐contour, one cutback) were then designed on a prepared maxillary left central incisor, following the contour of the neighboring crown. The designed crowns were used to manufacture monolithic lithium disilicate, bilayered lithium disilicate, bilayered zirconia, and monolithic zirconia crowns, 10 each. An intraoral scanner and a spectrophotometer were used to assess the frequency of matched shades and to calculate the color difference (Δ E ) between the two central incisors at the incisal, middle, and cervical thirds. Kruskal–Wallis and two‐way ANOVA were used to compare the frequency of matched shades and Δ E values, respectively ( α = 0.05). Results There was no significant ( p > 0.05) difference in frequencies of matched shades for each group at the three sites; except bilayered lithium disilicate crowns. Bilayered lithium disilicate crowns had significantly ( p < 0.05) higher match frequency than monolithic zirconia at the middle third. The Δ E value was not significantly ( p > 0.05) different among the groups at the cervical third. However, monolithic zirconia had significantly ( p < 0.05) higher Δ E values than bilayered lithium disilicate and zirconia at the incisal and middle thirds. Conclusions Bilayered lithium disilicate and zirconia appeared to most closely match the shade of an existing bilayered lithium disilicate crown.