title: Influence of hydrofluoric acid concentration on the flexural strength of a feldspathic ceramic.
abstract: This study evaluated the effects of etching with increasing hydrofluoric (HF) acid concentrations on the roughness and flexural strength of a feldspathic ceramic. One hundred and fifty ceramic specimens (14×4×1.2 mm(2)) were produced from ceramic blocks (VitaBlocks Mark II). All specimens were polished, chamfered and sonically cleaned in isopropyl alcohol. Specimens were randomly divided into 5 groups (n=30): SC (control) no ceramic surface etching; HF1, HF3, HF5 and HF10 ceramic surface etching for 60s with 1%, 3%, 5% and 10% HF acid concentrations, respectively. Profilometry was performed in all specimens to evaluate roughness prior to flexural strength testing. Data were analyzed using one-way ANOVA and Tukey׳s test (α=0.05). Weibull module (m) and characteristic stress (σc) were also determined. HF acid etching, regardless of the concentration used, led to significantly rougher surfaces than the control (p<0.05). However, the mean flexural strength values were not statistically different among the etched groups (106.47 to 102.02 MPa). Acid etching significantly reduced the mean flexural strength when compared with the control (143.3 MPa). Weibull modulus of the groups was similar, except for the HF5 group that was higher compared to HF3. Flexural strength was similarly affected by the different HF acid concentrations tested, but roughness increased higher the acid concentration. Ceramic etching led to a significant reduction in strength when compared to the untreated ceramic, regardless of its concentration.
authors.affiliation: Prosthodontics Unit, School of Dentistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul State, Brazil.
authors.forename: Andressa B
authors.initials: AB
authors.lastname: Venturini
authors.affiliation: Prosthodontics Unit, School of Dentistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul State, Brazil.
authors.forename: Catina
authors.initials: C
authors.lastname: Prochnow
authors.affiliation: Prosthodontics Unit, School of Dentistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul State, Brazil.
authors.forename: Liliana G
authors.initials: LG
authors.lastname: May
authors.affiliation: Department of Restorative Dentistry (Division of Dental Biomaterials), Indiana University School of Dentistry, Indianapolis, IN, USA.
authors.forename: Marco C
authors.initials: MC
authors.lastname: Bottino
authors.affiliation: Prosthodontics Unit, School of Dentistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul State, Brazil. Electronic address: lfvalandro@hotmail.com.
authors.forename: Luiz
authors.initials: L
authors.lastname: Felipe Valandro
mesh_terms: D002516:Ceramics; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006858:Hydrofluoric Acid / Q000008:administration & dosage*; D008422:Materials Testing; D018583:Pliability / Q000187:drug effects; D013314:Stress, Mechanical; D013499:Surface Properties / Q000187:drug effects
chemical_list: D003776:Dental Porcelain; D006858:Hydrofluoric Acid
keywords: Acid etching; Ceramic; Strength; Surface treatment