Nadja Rohr

Loading capacity of zirconia implant supported hybrid ceramic crowns

OBJECTIVE Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type. METHODS Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p=0.05). RESULTS The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253±148N). Etching of the intaglio surface did not improve the fracture load. SIGNIFICANCE Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used.

Bacterial colonization of resin composite cements: influence of material composition and surface roughness

So-called secondary caries may develop in the cement gap between the tooth and the bonded restoration. Cement materials with a low susceptibility to biofilm formation are therefore desirable. In the present study, the adhesion of Strepococcus mutans onto three adhesive (Multilink Automix, RelyX Ultimate, and Panavia V5) and three self-adhesive (Multilink Speed Cem, RelyX Unicem 2 Automix, and Panavia SA plus) resin composite cements was evaluated. Previous studies have failed to evaluate concomitantly the effect of both the composition of the cements and their surface roughness on biofilm formation. The presence of S. mutans on cement surfaces with differing degrees of roughness was therefore recorded using fluorescence microscopy and crystal violet staining, and the composition of the cements was analyzed using energy-dispersive X-ray spectroscopy mapping. Biofilm formation on resin composite cements was found to be higher on rougher surfaces, implying that adequate polishing of the cement gap is essential. The use of copper-containing cements (Multilink Automix, Panavia V5, and Panavia SA plus) significantly reduced biofilm formation.

Tooth surface treatment strategies for adhesive cementation

PURPOSE The aim of this study was to evaluate the effect of tooth surface pre-treatment steps on shear bond strength, which is essential for understanding the adhesive cementation process. MATERIALS AND METHODS Shear bond strengths of different cements with various tooth surface treatments (none, etching, priming, or etching and priming) on enamel and dentin of human teeth were measured using the Swiss shear test design. Three adhesives (Permaflo DC, Panavia F 2.0, and Panavia V5) and one self-adhesive cement (Panavia SA plus) were included in this study. The interface of the cement and the tooth surface with the different pre-treatments was analyzed using SEM. pH values of the cements and primers were measured. RESULTS The highest bond strength values for all cements were achieved with etching and primer on enamel (25.6 ± 5.3 - 32.3 ± 10.4 MPa). On dentin, etching and priming produced the highest bond strength values for all cements (8.6 ± 2.9 - 11.7 ± 3.5 MPa) except for Panavia V5, which achieved significantly higher bond strengths when pre-treated with primer only (15.3 ± 4.1 MPa). Shear bond strength values were correlated with the micro-retentive surface topography of enamel and the tag length on dentin except for Panavia V5, which revealed the highest bond strength with primer application only without etching, resulting in short but sturdy tags. CONCLUSION The highest bond strength can be achieved for Panavia F 2.0, Permaflo DC, and Panavia SA plus when the tooth substrate is previously etched and the respective primer is applied. The new cement Panavia V5 displayed low technique-sensitivity and attained significantly higher adhesion of all tested cements to dentin when only primer was applied.

Correlations between fracture load of zirconia implant supported single crowns and mechanical properties of restorative material and cement

Zirconia implants that were restored with veneered zirconia displayed severe chipping rates of the restorations in clinical studies. Purpose of this study was to evaluate the fracture load of different zirconia implant supported monolithic crown materials (zirconia, alumina, lithium disilicate, feldspar ceramic and polymer-infiltrated ceramic) cemented with various cements (Harvard LuteCem SE, Harvard Implant Semi-permanent, Multilink Automix, VITA Adiva F-Cem). Flexural strength and fracture toughness of crown materials and compressive strength of the cements were measured. Fracture load values of crowns fabricated from lithium disilicate, feldspar ceramic and polymer-infiltrated ceramic were increased when cement with high compressive strength was used. Fracture loads for zirconia and alumina crowns were not influenced by the cement. Flexural strength and fracture toughness of the ceramics correlated linearly with the respective fracture load when using adhesive cement with high compressive strength. To achieve sufficient fracture load values, cementation with adhesive cement is essential for feldspar and polymer-infiltrated ceramic.

Influence of cement type and ceramic primer on retention of polymer-infiltrated ceramic crowns to a one-piece zirconia implant

Statement of problem. The best procedure for cementing a restoration to zirconia implants has not yet been established. Purpose. The purpose of this in vitro study was to measure the retention of polymer‐infiltrated ceramic crowns to zirconia 1‐piece implants using a wide range of cements. The effect of ceramic primer treatment on the retention force was also recorded. The retention results were correlated with the shear bond strength of the cement to zirconia and the indirect tensile strength of the cements to better understand the retention mechanism. Material and methods. The retention test was performed using 100 polymer‐infiltrated ceramic crowns (Vita Enamic) and zirconia implants (ceramic.implant CI) The crowns were cemented with either interim cement (Harvard Implant semipermanent, Temp Bond), glass‐ionomer cement (Ketac Cem), self‐adhesive cement (Perma Cem 2.0, RelyX Unicem Automix 2, Panavia SA), or adhesive cement (Multilink Implant, Multilink Automix, Vita Adiva F‐Cem, RelyX Ultimate, Panavia F 2.0, Panavia V5 or Panavia 21) (n=5). Additionally ceramic primer was applied on the intaglio crown surface and implant abutment before cementation for all adhesive cements (Multilink Implant, Multilink Automix: Monobond plus; RelyX Ultimate Scotchbond Universal; Vita Adiva F‐Cem: Vita Adiva Zr‐Prime; Panavia F2.0, Panavia V5: Clearfil Ceramic Primer) and 1 self‐adhesive cement containing 10‐methacryloyloxydecyl dihydrogen phosphate (MDP) (Panavia SA: Clearfil Ceramic Primer). Crown debond fracture patterns were recorded. Shear bond strength was determined for the respective cement groups to polished zirconia (n=6). The diametral tensile strength of the cements was measured (n=10). Statistical analysis was performed using 1‐way or 2‐way analysis of variance followed by the Fisher LSD test (&agr;=.05) within each test parameter. Results. Adhesive and self‐adhesive resin cements had shear bond strength values of 0.0 to 5.3 MPa and revealed similar retention forces. Cements containing MDP demonstrated shear bond strength values above 5.3 MPa and displayed increased retention. The highest retention values were recorded for Panavia F 2.0 (318 ±28 N) and Panavia 21 (605 ±82 N). All other adhesive and self‐adhesive resin cements attained retention values between 222 ±16 N (Multilink Automix) and 270 ±26 N (Panavia SA), which were significantly higher (P<.05) than glass‐ionomer (Ketac Cem: 196 ±34 N) or interim cement (Harvard Implant semipermanent: 43 ±6 N, Temp Bond: 127 ±13 N). Application of manufacturer‐specific ceramic primer increased crown retention significantly only for Panavia SA. Conclusions. Products containing MDP provided a high chemical bond to zirconia. Self‐adhesive and adhesive resin cements with low chemical bonding capabilities to zirconia provided retention force values within a small range (220 to 290 N).

Biofilm formation on restorative materials and resin composite cements

OBJECTIVES Monolithic zirconia, polymer-infiltrated ceramic and acrylate polymer cemented with resin composite cement have recently been identified as prosthetic treatment options for zirconia implants. The aim of the present study is to determine in vitro, to what extent bacteria adhere to these materials. METHODS Disks made of zirconia (Vita YZ [YZ]), polymer-infiltrated ceramic (Vita Enamic [VE]), acrylate polymer (Vita CAD-Temp [CT]), self-adhesive cement (RelyX Unicem 2 Automix [RUN]) and of two different adhesive cements (RelyX Ulimate [RUL] and Vita Adiva F-Cem [VAF]) were produced. The biofilm formation of three bacterial species (Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis) on each material was assessed over 72h using a flow chamber system. The biofilms were quantified by crystal violet staining (optical density 595nm) and visualized using SEM. The inorganic composition of the different materials was analyzed and the wettability of the specimens was measured. RESULTS For the restorative materials lowest biofilm formation was found on CT: OD 0.5±0.1, followed by VE: OD 0.8±0.1 and YZ: OD 1.4±0.3. The biofilm formation on resin composite cements was significantly lower on VAF: OD 0.6±0.1 than for RUL: OD 0.9±0.1 and RUN: OD 1.0±0.1. A high wettability of the specimens with saliva/serum mixture tended to result in a higher biofilm formation. Correlations were obtained between the organic/inorganic composition of the materials and the polar/dispersive part of the surface free energy. SIGNIFICANCE Three-species biofilm formation on restorative and cement materials strongly relies on the materials composition. If the restorative material CT and cement VAF also prevent excessive biofilm formation in a clinical situation should be further investigated.