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Browsing by Subject "Acid etching"
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Item The effect of acid etching on remineralization of incipient caries lesions : a micro-ct study(2009) Yeslam, Hanin E.; Ando, Masatoshi; Gonzalez-Cabezas, Carlos, 1966-; Chu, Tien-Min Gabriel; Lund, Melvin; Cochran, MichaelEtching of enamel caries lesions has been demonstrated to enhance remineralization. However, this effect reaches a plateau after a period of time. This study aimed at investigating the effectiveness of additional acid etching on remineralization. Forty 1 mm × 2 mm human enamel blocks with chemically induced artificial incipient lesions were used. Ten specimens were randomly selected at the end of demineralization for transverse microradiography (TMR) analysis. The remaining specimens were then divided into three groups (n = 10). Group A was remineralized by a pH cycling system with 1100 ppm sodium fluoride for 20 days. In group B, the specimens were etched with 35-percent phosphoric acid for 30 s and then remineralized. Group C was remineralized by same procedure as group B plus and given an additional acid etch after 10 days of remineralization. Mineral density was measured by x-ray microtomography (µ-CT). The volumetric mineral content [VM (µm3×105)] was determined between 91 and 0-wt%. The µ-CT % mineral recovery (%) was calculated using the formula 100×(remineralize VM - demineralization VM) / (sound VM - demineralization VM). One-hundred-μm sections of demineralized and remineralized specimens were used to assess the mineral loss (IML: vol%×µm) and lesion depth (µm) using TMR. The three groups showed no significant difference in mineral change or mineral content for µ-CT or TMR lesion depth. The TMR IML showed a significant difference between the demineralized specimens and the three remineralized groups. The correlation between TMR IML and TMR lesion depth was 0.66 (p < 0.0001). The µ-CT percent mineral recovery from demineralization was correlated with neither TMR IML nor TMR lesion depth. When evaluated with µ-CT, the twice-acid-etched group presented lower mineral gain values than the group etched only once with acid. Also, the twice-etched group presented lower mineral gain and greater TMR IML compared with the non-acid etch group. TMR images revealed reduction of surface layer in the acid-etched groups, especially in the twice-etched group, in which significant reduction or loss of surface layer occurred. Based on these results, we conclude that additional acid etching with 35-percent phosphoric acid does not enhance remineralization compared with a single application of acid etching. We believe that the viable existence of the surface layer is essential for remineralization of the lesion. Further investigations into the accuracy of µ-CT to detect minute mineral changes in incipient caries lesions are probably needed.Item Influence of ceramic (feldspathic) surface treatments on the micro-shear bond strength of composite resin(E.H Angle Education and Research Foundation, 2010-07-01) Yadav, Sumit; Upadhyay, Madhur; Borges, Gilberto Antonio; Roberts, W. Eugene; Orthodontics and Oral Facial Genetics, School of DentistryObjective: To test the null hypothesis that surface treatment has no influence on the micro-shear bond strength between orthodontic composite resin cement and ceramics (feldspathic porcelain). Materials and Methods: Circular specimens of feldspathic porcelain were fabricated and randomly divided into six groups: (1) no treatment; (2) treatment with a mixture of acidic primer and silane agent for 20 seconds; (3) etching with 9.5% hydrofluoric acid; (4) etching with 9.5% hydrofluoric acid and coating with a mixture of acidic primer and silane agent for 20 seconds; (5) airborne-particle abrasion with 50-μm aluminum oxide; and (6) airborne-particle abrasion and coating with a mixture of acidic primer and silane agent for 20 seconds. The porcelain disks were then bonded to resin cylinders with composite resin cement. A micro-shear bond test was carried out to measure the bond strength. Moreover, each ceramic surface was observed morphologically by scanning electron microscopy. One-way analysis of covariance was used to compare the groups for differences in micro-shear bond strength. Results: The mean micro-shear bond strength varied as a function of surface treatment. It ranged from 3.7 to 20.8 MPa. The highest values for micro-shear bond strength were found when the surface was acid-etched with hydrofluoric acid and coated with silane. On the other hand, the control group (no treatment) had significantly lower micro-shear bond strength than all the other groups. Conclusion: The null hypothesis that the surface treatment has no influence on the micro-shear bond strength of orthodontic composite resin was rejected. The bond strength between ceramics and orthodontic resin cement is affected by the ceramic surface treatment. The bond failure was of the adhesive type, except with the hydrofluoric acid + silane group, where it was a cohesive bond failure.