Fracture Resistance of Repaired 5Y-PSZ Zirconia Crowns after Endodontic Access

This study analyzed the fracture load before and after a chewing simulation of zirconia crowns that were trepanned and repaired using composite resin. Overall, 3 groups with 15 5Y-PSZ crowns in each group were tested. For group A, the fracture load of the unmodified crowns was evaluated. For group B, the crowns were trepanned and repaired using composite resin, also followed by a fracture test. For group C, crowns were prepared like in group B but received thermomechanical cycling before the final fracture tests. Furthermore, scanning electron microscopy (SEM) and X-ray microscopy (XRM) analysis were performed for group C. The mean fracture loads and standard deviation were 2260 N ± 410 N (group A), 1720 N ± 380 N (group B), and 1540 N ± 280 N (group C). Tukey-Kramer multiple comparisons showed a significant difference between groups A and B (p < 0.01) and groups A and C (p < 0.01). After ageing, surface fissures were detected via SEM, but no cracks that reached from the occlusal to the inner side of the crown were detected via XRM. Within the limitations of this study, it can be stated that trepanned and composite-repaired 5Y-PSZ crowns show lower fracture loads than 5Y-PSZ crowns without trepanation

Multilayered Adsorption of Commensal Microflora on Implant Surfaces: an Unconventional and Innovative Method to Prevent Bacterial Infections Associated with Biomaterials

Biomaterials may be colonized with infectious biofilms and this frequently leads to progressive loss of tissue. Bacteria encased within biofilms resist antibiotics and the host immune system. With life-threatening complications and the antibiotic resistance crisis, novel therapeutic approaches are essentially required to treat biofilm infections. Commensal microflora—particularly streptococci—modulate the immune system's ability to protect from pathogens. In imitation of this natural phenomenon, the present study describes a novel method of applying the commensal, Streptococcus oralis, as a coating on implants to prevent infectious biofilms. Implants are coated with a simple thermal process to circumvent sepsis persuaded by live microflora and for a stable multilayered coating. Titanium discs coated with S. oralis antagonize the biofilm-making capabilities of single, dual, or multispecies periodontal pathogens: Porphyromonas gingivalis, Treponema denticola, Veillonella dispar, and Actinomyces naeslundii—under both static and flow conditions. The bacterial adhesion force measured with atomic force microscopy (AFM) reduces on coated titanium suggesting that electrostatic interactions are mainly responsible for the decrease in maximum adhesion peak. Importantly, S. oralis coated implants are compatible with human gingival fibroblasts. S. oralis coating may provide a potent novel approach to prevent potentially fatal biofilm infections on biomaterials

Influence of 10-MDP Adhesive System on Shear Bond Strength of Zirconia-Composite Interfaces

Abstract Introduction: This in-vitro study investigated the initial 24h bond strength between different composites and zirconia after application of four different adhesive systems. Methods: A total of 120 specimens of zirconia (InCoris, Sirona, Germany, Bernsheim) were ground with a 165 µm grit rotating diamond disc. Thirty specimens were each additionally treated with Cimara Zircon &quot;CZ&quot; (VOCO GmbH, Germany, Cuxhaven), Futurabond U &quot;FBU&quot; (VOCO GmbH), Futurabond M+ &quot;FBM&quot; (VOCO GmbH) or Futurabond M+ in combination with the DCA activator &quot;FBMD&quot; (VOCO GmbH). One of three different types of compositesBifixSE (&quot;BS&quot;), BifixQM (&quot;BQ&quot;) or GrandioSO (&quot;G&quot;) (VOCO GmbH) -was bonded to ten specimens each in every group. Shear bond strength (SBS) was determined in a universal testing machine. Statistical analysis was performed with ANOVA and the Tukey test. Results: FBM and FBMD gave higher SBS than CZ and FBU in combination with all tested composites. In comparison to FBU, FBM gave statistically significant increases in SBS with BifixSE (19.4±5.7 MPa) (P&lt;0.013) and with GrandioSO (19.1±4.4 MPa) (P&lt;0.021). None of the other comparisons was statistically significant. Conclusion: The new 10-MDP-containing adhesive systems FBM and FBMD increases initial SBS between composites and zirconia in comparison to CZ and FBU

Effect of sandblasting on the surface roughness and residual stress of 3Y-TZP (zirconia)

A defined surface roughness is important for the adhesive bonding of veneering ceramic to zirconia frameworks. Thus, we investigated the effects that sandblasting has upon the surface roughness and residual stress of zirconia. So as to achieve well-defined blasting parameters and also generate highly reproducible results; a custom-made, automated sandblasting machine was constructed (based on a 3D-printer construction kit). Thirty-two samples (measuring 30 mm × 35 mm × 0.2 mm) were cut from densely sintered 3Y-TZP blanks and then ground with a 45 µm grinding disc. After undergoing regeneration firing, the samples were sandblasted with varying working parameters: blasting angle (45°, 60° and 90°); blasting pressure (2 bar, 4 bar and 6 bar); and working distance (0.5 cm, 1.0 cm and 1.5 cm). The sandblasting path was chosen so as to create samples with an even surface roughness. Changes in blasting pressure resulted in the greatest changes in the surface roughness, the highest surface roughness values were achieved with sandblastings perpendicular to the sample surface. Furthermore, a correlation was found between the mean surface roughness and the residual stress

Automated Remodelling of Connectors in Fixed Partial Dentures

In this study, an approach for automated parametric remodelling of the connector cross-sectional area in a CAD model of a given fixed partial denture (FPD) geometry was developed and then applied to a 4-unit FPD. The remodelling algorithm was implemented using Rhinoceros and the Grasshopper plugin. The generated CAD models were used to perform a finite element analysis with Ansys to analyse the stress distribution in an implant-supported 4-unit FPD for different connector designs. The results showed that the type of connector adjustment matters and that the resulting stress can be significantly different even for connectors with the same cross-sectional area. For tensile stresses, a reduction in the connector cross-sectional area from the gingival side showed the highest influence on each connector type. It can be concluded that the developed algorithm is suitable for automatic connector detection and adjustment

Influence of 10-MDP Adhesive System on Shear Bond Strength of Zirconia-Composite Interfaces

Introduction: This in-vitro study investigated the initial 24h bond strength between different composites and zirconia after application of four different adhesive systems. Methods: A total of 120 specimens of zirconia (InCoris, Sirona, Germany, Bernsheim) were ground with a 165 µm grit rotating diamond disc. Thirty specimens were each additionally treated with Cimara Zircon “CZ” (VOCO GmbH, Germany, Cuxhaven), Futurabond U “FBU” (VOCO GmbH), Futurabond M+ “FBM” (VOCO GmbH) or Futurabond M+ in combination with the DCA activator “FBMD” (VOCO GmbH). One of three different types of composites – BifixSE (“BS”), BifixQM (“BQ”) or GrandioSO (“G”) (VOCO GmbH) – was bonded to ten specimens each in every group. Shear bond strength (SBS) was determined in a universal testing machine. Statistical analysis was performed with ANOVA and the Tukey test. Results: FBM and FBMD gave higher SBS than CZ and FBU in combination with all tested composites. In comparison to FBU, FBM gave statistically significant increases in SBS with BifixSE (19.4±5.7 MPa) (

Abrasion Behavior of Different Charcoal Toothpastes on Human Dentin When Using Electric Toothbrushes

The aim of this study was to investigate abrasion on human dentin after brushing with activated charcoal toothpastes. A self-designed brushing machine was used to brush five groups (Group A: Water, Group B: Sensodyne Pro Schmelz, Group C: Splat Blackwood, Group D: Curaprox Black is White, and Group E: Prokudent Black Brilliant) with electrically powered toothbrushes for 4 h. The abrasive dentin wear was calculated using profilometry data. Furthermore, thermogravimetric analyses and scanning electron microscopy were used to analyze the composition of the toothpastes. Mean dentin loss by brushing were (71 ± 28) µm (Splat Blackwood), (44 ± 16) µm (Curaprox Black is White), (38 ± 13) µm (Prokudent Black Brilliant), (28 ± 14) µm (Sensodyne Pro Schmelz), and (28 ± 13) µm (Water). Groups A/B/D/E and group C each lie in one subset, which is statistically different from the other subset according to a post hoc Tukey test (p = 0.05). Within the limitations, it can be concluded that the content of activated charcoal in charcoal toothpastes had little influence on the observed abrasive behavior, although one of the charcoal toothpastes showed the highest abrasion on dentin

Internal and Marginal Fit of Modern Indirect Class II Composite Inlays

Introduction: This in vitro study investigates the marginal and internal fit of indirect class II composite restorations. Two different processes for chair-side restorations were compared. In group A, the restorations were fabricated using CAD/CAM technology (Cerec, Sirona, Germany, Bernsheim) and in group B they were made by hand (GrandioSO Inlay System, VOCO GmbH, Germany, Cuxhaven). Methods: For a metal tooth with a MOD cavity each 10 restorations were made for groups A and B. For each restoration, a replica of the cement-gap made from light body silicone was produced by placing the restoration into the cavity of the metal tooth. For this purpose, a special restoration-positioning machine was developed. Each replica was sectioned off in the longitudinal axis (L) and in the cross axis (C). The thickness of the replicas was measured in both directions, using picture analysis software under a light reflection microscope. To evaluate the fit of the restorations, a special fitting parameter was calculated. Statistical analysis was performed with the t test. Results: The fitting-parameter in group B (L: 97.6µm±73.0µm; C: 71.8µm±46.4µm) was significantly lower than that of group A (L: 155.1µm±102.3.0µm; C: 168.2µm±91.9µm) (