Fifty-seven porcelain samples were randomly subjected to a variety of topical fluorides for time intervals of 4 to 64 minutes. Half of each porcelain surface was masked to prevent contact with the fluoride. Measurements of roughness were made for the fluoride-treated and the untreated porcelain surfaces to evaluate the effect of the different fluoride preparations over time. The resulting surfaces were also examined using an SEM. Conclusions from this study include the following. Statistically significant differences in roughness were found among surfaces exposed to 1.23% acidulated phosphate fluoride gel, 8% stannous fluoride, and the control surfaces. There were no significant differences in roughness between the test and control surfaces with 0.05%, 0.2%, and 2% sodium fluoride solutions or 0.4% stannous fluoride gel. The dentist should be aware of the potentially deleterious effects of prescribing or administering a topical fluoride for patients with porcelain/metal restorations.
"HF acid gel is often indicated to be applied between 20 s and 1 min whereas APF gel for a longer period (2–5 min), where the latter is also used for topical fluoride application. Some studies demonstrated that the bond strength of resin composites to silanized ceramics after being etched with APF was comparable to that of HF acid etching   . However, the results were derived from shear tests. "
[Show abstract][Hide abstract] ABSTRACT: This study evaluated the durability of bond strength between resin cement and a feldspathic ceramic submitted to different etching regimens with and without silane coupling agent application.
Thirty-two blocks (6.4 mm x 6.4 mm x 4.8 mm) were fabricated using a microparticulate feldspathic ceramic (Vita VM7), ultrasonically cleaned with water for 5 min and randomly divided into four groups, according to the type of etching agent and silanization method: method 1, etching with 10% hydrofluoric (HF) acid gel for 1 min + silanization; method 2, HF only; method 3, etching with 1.23% acidulated phosphate fluoride (APF) for 5 min + silanization; method 4, APF only. Conditioned blocks were positioned in their individual silicone molds and resin cement (Panavia F) was applied on the treated surfaces. Specimens were stored in distilled water (37 degrees C) for 24h prior to sectioning. After sectioning the ceramic-cement blocks in x- and y-axis with a bonded area of approximately 0.6mm(2), the microsticks of each block were randomly divided into two storage conditions: Dry, immediate testing; TC, thermal cycling (12,000 times)+water storage for 150 d, yielding to eight experimental groups. Microtensile bond strength tests were performed in universal testing machine (cross-head speed: 1mm/min) and failure types were noted. Data obtained (MPa) were analyzed with three-way ANOVA and Tukey's test (alpha=0.05).
Significant influence of the use of silane (p<0.0001), storage conditions (p=0.0013) and surface treatment were observed (p=0.0014). The highest bond strengths were achieved in both dry and thermocycled conditions when the ceramics were etched with HF acid gel and silanized (17.4 +/- 5.8 and 17.4 +/- 4.8 MPa, respectively). Silanization after HF acid gel and APF treatment increased the results dramatically (14.5+/-4.2-17.4+/-4.8 MPa) compared to non-silanized groups (2.6 +/- 0.8-8.9 +/- 3.1 MPa) where the failure type was exclusively (100%) adhesive between the cement and the ceramic.
Silanization of the feldspathic ceramic surface after APF or HF acid etching increased the microtensile bond strength results significantly, with the latter providing higher results. Long-term thermocycling and water storage did not decrease the results in silanized groups.
"The use of acidulated fluoride is known to attack the surface of porcelain chemically (Gau and Krause, 1973; Copps et al., 1984; Rawson et a/., 1984; Sposetti et a/., 1986; Wunderlich and Yaman, 1986). Such chemical degradation can: (1) increase the abrasiveness of the ceramic against opposing teeth and other restorative materials, (2) change the appearance of the ceramic, (3) increase the retention of plaque, and (4) increase the susceptibility of the ceramic to future chemical attack. "
[Show abstract][Hide abstract] ABSTRACT: The degradation of dental ceramics generally occurs because of mechanical forces or chemical attack. The possible physiological side-effects of ceramics are their tendency to abrade opposing dental structures, the emission of radiation from radioactive components, the roughening of their surfaces by chemical attack with a corresponding increase in plaque retention, and the release of potentially unsafe concentrations of elements as a result of abrasion and dissolution. The chemical durability of dental ceramics is excellent. With the exception of the excessive exposure to acidulated fluoride, ammonium bifluoride, or hydrofluoric acid, there is little risk of surface degradation of virtually all current dental ceramics. Extensive exposure to acidulated fluoride is a possible problem for individuals with head and/or neck cancer who have received large doses of radiation. Such fluoride treatment is necessary to minimize tooth demineralization when saliva flow rates have been reduced because of radiation exposure to salivary glands. Porcelain surface stains are also lost occasionally when abraded by prophylaxis pastes and/or acidulated fluoride. In each case, the solutes are usually not ingested. Further research that uses standardized testing procedures is needed on the chemical durability of dental ceramics. Accelerated durability tests are desirable to minimize the time required for such measurements. The influence of chemical durability on surface roughness and the subsequent effect of roughness on wear of the ceramic restorations as well as of opposing structures should also be explored on a standardized basis.
Advances in Dental Research 10/1992; 6:82-9. DOI:10.1177/08959374920060012201
[Show abstract][Hide abstract] ABSTRACT: The surface roughness of prosthodontic materials is an important factor that influences the amount of microbial plaque accumulation, thereby increasing the risk of caries and periodontal inflammation of abutment or adjacent teeth. Few studies exist that have investigated the influence of disinfectant materials on the surface roughness of prosthodontic materials. The purpose of this study is to evaluate the roughness changes in metal-ceramic and IPS Empress 2 ceramic structures, finished by either manual-polishing or glazing, followed by immersion in 2% glutaraldehyde solution for either 30 minutes (disinfection procedure) and 10 hours (sterilization procedure). The study consisted of 26 metalceramic specimens and 26 Empress 2 specimens measuring 10 x 10 x 2 mm. One-half of each group of specimens was polished by using rotatory instruments and the other half was glazed in a glazing oven (subgroups). Afterwards, the specimens were submitted to sterilization and disinfection in 2% glutaraldehyde for either 30 minutes or 10 hours, respectively. 3 specimens from each group were sterilized in autoclave, and for control group, the initial measurement of each specimen before the disinfection and sterilization procedures was obtained. The surface roughness was determined by a Hommel Tester T-1000, using the mean arithmetic Ra as roughness parameter. The results were statistically analyzed using a 4-way analysis of variance (ANOVA) method for individual comparisons among the means and the Tukey test at a significance level of p<.05. The results showed that there were no statistically significant differences of roughness in both groups, after immersion in chemical solution and sterilization in autoclave (p<.05). The mean of ceramic materials ranged from .631mm to 1.687mm in surface roughness. There was a statistically significant difference only among final polishing of ceramics (F=19.00; p<.001) and in the interaction between polishing and material used (F=18.83; p<.001). No significant changes in surface roughness of tested ceramic materials occurred after completion of the disinfection and sterilization procedures used in this study. Clinical implications: Infection control procedures are indispensable steps before cementation of prostheses. Based on the results of this study, prosthodontic materials can be disinfected or sterilized without causing significant changes in surface roughness.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.