Fish keratocytes can generate rearward directed traction forces within front portions of the lamellipodium, suggesting that a retrograde flow of actin may also occur here but this was not detected by previous photoactivation experiments. To investigate the relationship between retrograde flow and traction force generation, we have transfected keratocytes with GFP-actin and used fluorescent speckle microscopy, to observe speckle flow. We detected a retrograde flow of actin within the leading lamellipodium that is inversely proportional to both protrusion rate and cell speed. To observe the effect of reducing contractility, we treated transfected cells with ML7, a potent inhibitor of myosin II. Surprisingly, ML7 treatment led to an increase in retrograde flow rate, together with a decrease in protrusion and cell speed, but only in rapidly moving cells. In slower moving cells, retrograde flow decreased, whereas protrusion rate and cell speed increased. These results suggest that there are two mechanisms for producing retrograde flow. One involves slippage between the cytoskeleton and adhesions, that decreases traction force production. The other involves slippage between adhesions and the substratum, which increases traction force production. We conclude that a biphasic relationship exists between retrograde actin flow and adhesiveness in moving keratocytes.

Purpose To determine if surface treatment and cement selection for traditional 3 mol% yttria partially stabilized zirconia (3Y‐PSZ), “translucent” 5 mol% yttria‐stabilized zirconia (5Y‐Z), or lithium disilicate crowns affected their fracture load. Materials and Methods Crowns with 0.8 mm uniform thickness (96, n = 8/group) were milled of 3Y‐PSZ (Lava Plus), 5Y‐Z (Lava Esthetic), or lithium disilicate (e.max CAD) and sintered/crystallized. Half the crowns were either particle‐abraded with 30 µm alumina (zirconias) or etched with 5% hydrofluoric acid (lithium disilicate), and the other half received no surface treatment. Half the crowns from each group were luted with resin‐modified glass ionomer (RMGI, RelyX Luting Plus) and half were luted with a resin cement (RelyX Unicem 2) to resin composite dies. Crowns were load cycled (100,000 cycles, 100 N force, 24°C water) and then loaded with a steel indenter until failure. A three‐way ANOVA examined the effects of material, cement, and surface treatment on fracture load. Post‐hoc comparisons were performed with the Tukey‐Krammer method. Results Fracture load was signficiantly different for materials and cements (p < 0.0001) but not surface treatments (p = 0.77). All lithium disilicate crowns luted with RMGI failed in fatigue loading cycling; 3Y‐PSZ and 5Y‐Z crowns luted with resin showed a higher fracture load compared with RMGI (p < 0.001). With resin cement, there was no signficant difference in fracture load between 5Y‐Z and lithium disiliciate (p = 1) whereas 3Y‐PSZ had a higher fracture load (p < 0.0001). Conclusions Cement type affected fracture load of crowns but surface treatment did not. The 0.8 mm uniform thick crowns tested benefited from using resin cement regardless of type of ceramic material. Crowns fabricated from 5Y‐Z may be particle‐abraded if luted with resin cement.

In this study, dentin bond fatigue resistance and interfacial science characteristics of universal adhesives through etch-and-rinse and self-etch modes were investigated. Resin composite was bonded to human dentin with four universal adhesives, namely, Adhese Universal, All-Bond Universal, G-Premio Bond, and Scotchbond Universal Adhesive. The initial bond strengths, bond fatigue strengths, and interfacial science characteristics of the universal adhesives with dentin through etch-and-rinse and self-etch modes were determined. Bond fatigue resistance (initial bond strength and bond fatigue strength) of universal adhesives in etch-and-rinse mode showed no significant difference in contrast to that in self-etch mode and was material-dependent regardless of the etching mode. Although phosphoric acid conditioning of dentin did not have a strong impact on the bond fatigue resistance, surface free energy and parameters of dentin were significantly decreased by etching and by application of universal adhesives regardless of etching mode. Changes in γ S and γ S h for when universal adhesive was applied to etched and ground dentin were significantly different depending on the adhesive. The results suggest that bonding performance of universal adhesives was effective in both etching modes; however, bonding mechanisms may be different for each. Keywords; light-curing of dental adhesives, dental debonding, dental etching, dental restoration failure, dental stress analysis Materials and Methods Study materials Four universal adhesives were used in this study: (i) Adhese Universal (AU, Ivoclar Vivadent, Schaan, Liechtenstein), (ii) All-Bond Universal (AB, Bisco, Schaumburg, IL, USA), (iii) G-Premio Bond (GB, GC, Tokyo, Japan), and (iv) Scotchbond Universal Adhesive (SU, 3M Oral Care). Ultra-Etch (Ultradent, South Jordan, UT, USA) was used as a 35% phosphoric acid pre-etching agent and Z100 Restorative (3M Oral Care) as the resin composite employed to make specimens. Table 1 lists the tested materials and their lot numbers and components. Specimen preparation This study used de-identified extracted human molar teeth. To comply with research ethics, the protocol was reviewed and approved by the Ethics Committee for Human Studies of NU (#2015-06) and Biomedical Institutional Review Board at CU (#760765-1). Preparation of the teeth was done in the manner described in the study by Nagura et al. [18], except that a flat dentin surface, rather than enamel surface, was prepared. Specimens with and without etching were prepared for each adhesive, giving a total of eight experimental groups for each of the procedures performed (Table 2). Initial bond strength testing Initial bond strength testing was carried out as described by Nagura et al. [18]. Bond fatigue strength testing Bond fatigue strength testing was carried out as described by Nagura et al. [18].

SUMMARY Bonding to enamel has been shown to provide reliable results, and thus conservative tooth preparations are key to the success of ceramic bonded restorations. The wax-up is the first diagnostic tool available to evaluate discrepancies between current and ideal tooth proportions. The clinician's diagnostic mock-up provides the patient with a visual perception of the size and shape of the proposed restorations. The use of reduction guides assists the restorative dentist in evaluating the specific amount of tooth structure to be removed during preparation. Furthermore, total isolation with a rubber dam prior to bonding the final restorations is crucial for the success of adhesive protocols. The aim of this report is to demonstrate a conservative approach to tooth preparation with a complete isolation technique prior to bonding eight ceramic restorations.

Novel translucent monolithic zirconia has improved optical properties, and it may fulfill patient's esthetic demands and overcome the chipping risk of bilayer metal‐ceramic restorations. New zirconia's microstructures allow us to mimic natural teeth.

This in vitro study aimed to evaluate the final shade of translucent zirconia laminate veneers with varying thicknesses over teeth with different shades. Seventy-five chairside computer-aided design/computer-aided manufacturing (CAD/CAM) shade A1 third-generation zirconia dental veneers, with thicknesses of 0.50 mm, 0.75 mm, and 1.00 mm, were placed on resin composite teeth with shades ranging from A1 to A4. The laminate veneers were divided into groups based on thickness and background shade. All restorations were evaluated with a color imaging spectrophotometer, to map the veneer surface from A1 to D4. Regardless of the thickness or background shade, all dental veneers showed color alteration from the original shade. Veneers with 0.5 mm thickness tended to display the B1 shade, while veneers with 0.75 mm and 1.0 mm thickness primarily exhibited the B2 shade. The thickness of the laminate veneer and background shade significantly modified the original shade of the zirconia veneer. One-way analysis of variance was performed and a Kruskal–Wallis test was used to determine the significance between the three veneer thicknesses groups. The results indicated that the thinner restorations showed higher values with the color imaging spectrophotometer, suggesting that thinner veneers may result in more consistent color matching. This study underscores the importance of carefully considering thickness and background shade when selecting zirconia laminate veneers, to ensure optimal color matching and overall aesthetic outcomes.

PURPOSE The aim of this study was to investigate shade changes in fully- and pre-crystalized CAD-CAM lithium disilicate crowns after the required and additional firing processes. MATERIALS AND METHODS One hundred and five crowns of shade A1 with high translucency were milled out of CAD-CAM lithium disilicate blocks and categorized as follows (n = 15): (1) restorations fabricated from Straumann n!ce with no additional sintering process; (2) restorations fabricated from Straumann n!ce with one additional sintering process; (3) restorations fabricated from Straumann n!ce with two additional sintering processes; (4) restorations fabricated from Amber Mill with one sintering process; (5) restorations fabricated from Amber Mill with two sintering processes; (6) restorations fabricated from IPS e.max CAD with one sintering process; (7) restorations fabricated from IPS e.max CAD with two sintering processes. All restorations were evaluated with a color imaging spectrophotometer. RESULTS All restorations presented some color alteration from the original shade both after a single and after two firing processes. CONCLUSION The required and additional sintering processes for restorations fabricated with chairside CAD-CAM lithium disilicate blocks cause an alteration of the original shade selected. Shade A1 high translucency restorations tend to change to a more yellowish B1 shade after a sintering process.

Milling complete dentures is becoming a popular option for clinicians because subtractive technology can make the fabrication of high-quality dentures faster and easier. Additive technology is one of the newest techniques for making complete dentures, and its primary advantage is that a printer is more financially accessible than a milling machine. Printing and milling technologies as methods for denture fabrication have similar steps and time frames for their processes. The production of immediate complete dentures also follows similar procedures for both systems. The aim of this article is to compare subtractive and additive technologies for the manufacture of immediate complete dentures and to present two case reports.