Influence of bioactive glass-coating of zirconia implant surfaces on human osteoblast behavior in vitro.

OBJECTIVE: The recently developed bioactive glass PC-XG3, which is suitable to coat zirconia implant surfaces with high adhesion strength may reduce the time of osseointegration and the marginal bone loss following implantation. The glass composition has been previously evaluated for cytotoxicity on fibroblast cells, and will now be used to evaluate the cell behavior of osteoblast cells. METHODS: Three different surface morphologies were created with PC-XG3 on zirconia discs. A clinically tested zirconia implant surface as well as polished and machined zirconia served as a reference. Cell viability after 24 h, cell spreading after 30 min and 24 h and the respective morphology of human osteoblasts using scanning electron microscopy were evaluated. Additionally, the corrosive process of PC-XG3 in cell culture medium up to 7 d was measured. RESULTS: Initial cell behavior of human osteoblasts was not accelerated by the PC-XG3 surface when compared to zirconia. Additionally, it was found that a decreased surface roughness promoted initial cell spreading. Storage in cell culture medium resulted in the accumulation of C and N on the bioglass surface while Mg, Si, K and Ca were decreased and crack formation was observed. SIGNIFICANCE: Since initial spreading quality to a biomaterial is a crucial factor that will determine the subsequent cell function, proliferation, differentiation, and viability it can be assumed that a coating of zirconia implants with this bioactive glass will unlikely reduce osseointegration time.

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.

Adhesive bonding to polymer infiltrated ceramic.

Aim of this study was to investigate the mechanism of adhesive bonding to the polymer-infiltrated ceramic VITA Enamic [VE]. Shear bond strength was measured with three resin composite cements: RelyX Unicem 2 Automix, Clearfil SA and Variolink II on polished surfaces of VE and its components silicate ceramic [SC] and polymer [PM] (n=12). Further, the effect of etching VE with 5% HF for 15-240 s and the application of silane coupling agents was analyzed in a screening test (n=6). Shear bond strength measurements were performed after 24 h of water storage at 37°C. Significant bonding to polished substrates could only be achieved on VE and SC when silane coupling agents were used. Etching of VE with 5% HF increased shear bond strength. Following silanization of etched VE, a further increase in shear bond strength could be established. Etching for more than 30 s did not improve shear bond strength.

A systematic approach to standardize artificial aging of resin composite cements.

OBJECTIVE: The aim of the investigation was to contribute to the ongoing discussion at the international standardization committee on how to artificially age dental resin composite cements. METHODS: Indirect tensile strength (n=30) of a dual-cured resin composite cement (Panavia F2.0) was measured to evaluate the effect of water storage at 37°C or thermal cycling (5°C/55°C/1min) for up to 64 days. The influence of water temperature (5-65°C) after 16 days and the effect of 1 day water storage at 37°C prior to aging were assessed. Storage in air at 37°C served as control. RESULTS: Thermal cycling affected the indirect tensile strength most, followed by water storage at 55°C, whereas water storage at 37°C had only little influence. Major deterioration occurred before day 4 (≈6000 cycles). A 1-day pre-treatment by water storage at 37°C prior to thermal cycling attenuated the effect of aging. SIGNIFICANCE: For the material investigated, thermal cycling for 4 days is the most efficient aging procedure. A 1-day water storage at 37°C prior to thermal cycling is recommended to allow complete polymerization. A 4-day water storage at 55°C may be considered as a viable alternative to thermal cycling.

Analysis of the effects of air polishing powders containing sodium bicarbonate and glycine on human teeth.

OBJECTIVES: The aim of this study was an analysis of the root surface roughness caused by air polishing powders containing sodium bicarbonate or glycine. METHODS: The roots of human molars were sectioned into dentin discs and irradiated with three different powders: (A) sodium bicarbonate (dv50 = 62 µm), (B) glycine (dv50 = 49 µm) and (C) glycine (dv50 = 21 µm). Standardized conditions in terms of instrumentation time (5 and 10 s), pressure (1.8 bar), distance (2 and 5 mm) and angulation (45° and 90°) were applied. Surface roughness (DIN EN ISO 4287:1998) of the probes was analysed by means of the surface profile values "Pa" and "Pt" and the surface roughness value "Rz". The effect of treatment (treated vs. untreated) was studied on each disc. Geometric mean ratios (GMRs) from mixed effects models and confidence intervals (95% CI) were calculated. RESULTS: For Pa, the comparison revealed significant differences between powders A and B (GMR 3.57, 95 % CI 2.87-4.43, p < 0.001) and powders A and C (GMR 2.72, 95% CI 2.20-3.37, p < 0.001) for the overall effects. With respect to Pt, significant differences occurred between powders A and B (GMR 2.49, 95% CI 2.11-2.94, p < 0.001) and powders A and C (GMR 2.39, 95% CI 2.03-2.82, p < 0.001). Between powders B and C, there were no significant differences for Pa, Rz and Pt. CONCLUSION: Air polishing powders containing glycine caused significantly less alterations on human root surfaces compared to powders containing sodium bicarbonate. CLINICAL SIGNIFICANCE: Powders containing glycine caused a significantly lower increase in root surface roughness compared to those containing sodium bicarbonate. Powders containing sodium bicarbonate may not be indicated for root surface treatment.

[Determination of the corrosion resistance of dental alloys with a new measurement method]. / Bestimmung der Korrosionsbeständigkeit von Dentallegierungen mit einer neuartigen Messmethode.

A corrosion sensor newly developed by the Swiss Society for Corrosion, modified for a potential application in the oral cavity, was tested in vitro. By measuring the impedance with a special sensor in the size of a bur handpiece, it allows a quick determination of the corrosion resistance. For the evaluation of the method, measurements were done on six conventional dental alloys (two precious alloys, one Pd-based alloy and three non-precious alloys) which had been tested in crevice corrosion by the authors in an earlier stage. Qualitatively the results are quite in concordance with the ones got with the usual tests. On the base of the present results the use directly in the oral cavity of this corrosion test method appears to be very promising.

[First clinical experiences with ceramic ball attachments for overdentures]. / Erste klinische Erfahrungen mit Retentionselementen aus Keramik.

In this prospective clinical study on 40 patients with similar clinical conditions (edentulous jaw with 2 interforaminal implants) commercially available ceramic ball attachments (ruby) were compared to commercial titanium ball attachments. The primary aim of the study was to measure the wear of the ball attachments after being 1 year in function. However, in the course of the study already after 7 to 12 months multiple failures with ceramic ball attachments occurred. Twelve (28%) of 43 ceramic ball attachments had to be replaced, mostly because of fractures (8) of the ceramic ball. It seems that ceramic ball attachments of the investigated design are not able to withstand normal intraoral stresses. The short-term susceptibility to fractures didn't allow to examine the ceramic-inherent features such as compressive strength and wear resistance. Furthermore, a secure connection between a titan base and a ceramic ball seems to be challenging. Based on these results, in implant-retained removable prosthesis the use of metal-based retainers is still recommended, although during maintenance a higher wear has to be expected. This wear can be compensated by either activating or changing the matrix or the patrix.

[Metal intolerance. A frequent condition, but difficult to diagnose]. / Metall-Unverträglichkeit. Eine häufige Erkrankung, aber schwierig zu diagnostizieren.

Many of the methods and devices used for incompatibility testing of metals and alloys today are of questionable scientific value. Neither epicutaneous testing nor other diagnostic adjuncts from the realm of alternative medicine, nor patient-history data contained in so-called dental alloy passports, are generally able to yield any useful information. Analysis is particularly difficulty in situations where metallic components are cemented in place in the oral cavity. For many years now, the so-called splinter test has proven its value as a means of non-destructively identifying the type of alloy used. It can also be used for detecting persistent corrosion-prone adhesive oxides and soldering joints as causative agents of metal-related noxious processes. This article presents a number of case reports to demonstrate the reliability and the precision of the splinter test. Over a period of 10 years, more than 1600 splinter analyses have been performed at the University of Basle Center of Dentistry. According to a pertinent survey, these analyses were able to contribute to full treatment success in 63% of the cases, to partial success in 27% of the cases, and to no success in only 10% of the cases.