The aim of this systematic review was to assess the current scientific evidence of the antimicrobial potential of strontium (Sr) when used to functionalize titanium (Ti) for oral applications. Out of an initial list of 1081 potentially relevant publications identified in three electronic databases (MEDLINE via PubMed, Scopus, and Cochrane) up to 1 February 2021, nine publications based on in vitro studies met the inclusion criteria. The antimicrobial potential of Sr was investigated on different types of functionalized Ti substrates, employing different application methods. Nine studies reported on the early, i.e., 6–24 h, and two studies on the late, i.e., 7–28 days, antimicrobial effect of Sr, primarily against Staphylococcus aureus (S. aureus) and/or Escherichia coli (E. coli). Sr-modified samples demonstrated relevant early antimicrobial potential against S. aureus in three studies; only one of which presented statistical significance values, while the other two presented only the percentage of antimicrobial rate and biofilm inhibition. A relevant late biofilm inhibition potential against S. aureus of 40% and 10%—after 7 and 14 days, respectively—was reported in one study. Combining Sr with other metal ions, i.e., silver (Ag), zinc (Zn), and fluorine (F), demonstrated a significant antimicrobial effect and biofilm inhibition against both S. aureus and E. coli. Sr ion release within the first 24 h was generally low, i.e., below 50 µg/L and 0.6 ppm; however, sustained Sr ion release for up to 30 days, while maintaining up to 90% of its original content, was also demonstrated. Thus, in most studies included herein, Sr-functionalized Ti showed a limited immediate (i.e., 24 h) antimicrobial effect, likely due to a low Sr ion release; however, with an adequate Sr ion release, a relevant antimicrobial effect, as well as a biofilm inhibition potential against S. aureus—but not E. coli—was observed at both early and late timepoints. Future studies should assess the antimicrobial potential of Ti functionalized with Sr against multispecies biofilms associated with peri-implantitis.

Purpose: To evaluate the effect of different placing strategies performed in the connector area on fracture resistance and fracture behaviour of monolithic multi-layered translucent zirconia fixed dental prostheses (FDPs). Materials and Methods: Thirty 3-unit monolithic FDPs were produced and divided into three groups (n = 10) based on the different strategies for placing the connector area of FDPs in multi-layered zirconia blank with varying contents of yttria ranging from 4 to 5 mol%. The groups were as follows: FDPs with connectors placed in dentin layer with 4 mol% yttria content, FDPs with connectors placed in gradient layer, and FDPs with connectors placed in translucent layer with 5 mol% yttria content. A final group (n = 10) of conventional monolithic zirconia with a monolayer of yttria content (4 mol%) has been used as a control group. The specimens were artificially aged using thermocycling and pre-loading procedures and subsequently loaded to fracture using a universal testing machine. Fracture loads and fracture behaviour were analyzed using one-way ANOVA and Fisher’s exact tests and statistically evaluated (p ≤ 0.05). Results: There were no significant differences in fracture loads among the groups based on the placing strategies of the connector area of the FDPs in the multi-layered translucent zirconia blank (p > 0.05). There was no significant difference in fracture loads between monolithic multi-layered translucent zirconia and conventional monolithic translucent zirconia materials (p > 0.05). Fracture behaviour of FDPs with connector area placed in translucent layer differed significantly compared to FDPs with connector area placed in dentin layer and FDPs in control group (p = 0.004). Conclusion: The placing strategies of the connector used in the computer aided design and manufacturing procedures do not considerably affect fracture resistance of monolithic FDPs made of multi-layered translucent zirconia. Monolithic FDPs made of multi-layered translucent zirconia show comparable strength to FDPs made of conventional translucent zirconia, but with different fracture behaviour.

Objective: To evaluate fracture strength of veneered translucent zirconium dioxide crowns designed with different porcelain layer thicknesses. Materials and Methods: Sixty crowns, divided into six groups of 10, were used in this study. Groups were divided according to different thicknesses of porcelain veneer on translucent zirconium dioxide cores of equal thickness (0.5 mm). Porcelain thicknesses were 2.5, 2.0, 1.0, 0.8, 0.5 and 0.3 mm. Crowns were artificially aged before loaded to fracture. Determination of fracture mode was performed using light microscope. Results: Group 1.0 mm showed significantly (p ≤ .05) highest fracture loads (mean 1540 N) in comparison with groups 2.5, 2.0 and 0.3 mm (mean 851, 910 and 1202 N). There was no significant difference (p>.05) in fracture loads among groups 1.0, 0.8 and 0.5 mm (mean 1540, 1313 and 1286 N). There were significantly (p ≤ .05) more complete fractures in group 0.3 mm compared to all other groups which presented mainly cohesive fractures. Conclusions: Translucent zirconium dioxide crowns can be veneered with minimal thickness layer of 0.5 mm porcelain without showing significantly reduced fracture strength compared to traditionally veneered (1.0–2.0 mm) crowns. Fracture strength of micro-veneered crowns with a layer of porcelain (0.3 mm) is lower than that of traditionally veneered crowns but still within range of what may be considered clinically sufficient. Porcelain layers of 2.0 mm or thicker should be used where expected loads are low only.

Objective. To evaluate the flexural strength of two translucent multilayered zirconia materials produced with different multilayer technologies. Methodology. Eighty bar‐shaped zirconia specimens were prepared from two different multilayered zirconia materials (IPS e.max® ZirCAD Prime and KATANA™ Multilayered Zirconia HTML) and divided into eight groups (n = 10) based on the materials used and the individual layers of the disc for each material: Dentin Prime, Transition Prime, Translucent Prime, Multilayered Prime, Dentin HTML, Transition HTML, Translucent HTML, and Multilayered HTML. The bar‐shaped zirconia specimens were cut to include all the layers from translucent to dentin In Multilayered Prime and Multilayered HTML groups. All specimens were fully sintered after cutting from multilayered zirconia discs and subjected to three‐point flexural strength test using the universal testing machine. Results. The specimens made of HTML zirconia material showed significantly (P < 0.001) higher flexural strength than those made of IPS e.max® ZirCAD Prime material, with no significant difference (P > 0.05) compared to the specimens in the Dentin Prime group. The Dentin Prime specimens had the highest flexural strength (743 ± 116 MPa) compared to those in the Translucent Prime (514 ± 120 MPa), Transition Prime (575 ± 102 MPa), and Multilayered Prime (531 ± 132 MPa) groups. The flexural strength of the specimens from the individual layers of HTML zirconia material was not significantly different (P > 0.05) among the Dentin HTML (763 ± 56 MPa), Translucent HTML (791 ± 106 MPa), Transition HTML (816 ± 85 MPa), and Multilayered HTML (793 ± 102 MPa) groups. Conclusion. Multilayered zirconia materials produced with different yttria contents by layer have lower flexural strength than those produced with gradient shade technology and the same yttria content for each layer. Therefore, various factors such as the type of prostheses, nesting strategies of prostheses within the zirconia disc, and the desired aesthetical requirements should be considered when selecting the multilayered zirconia materials.