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Browsing Dentistry School Theses and Dissertations by Subject "Acid Etching, Dental"
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Item Enamel conditioning effect on penetration and microleakage of glass ionemer-based sealants(2009) Ahmed, Senan Raad; Cabezas, Carlos Gonzales; Chu, Tien-Min Gabriel; Fontana, Margherita Ruth, 1966-; Matis, Bruce; Cochran, MichaelWhile most sealants available are resin-based, glass ionomer-based cements can be used as sealants, with the advantage of being more tolerant to moisture during placement and of releasing fluoride. The objective of this study was to evaluate the influence of different fissure conditioning techniques on penetration and microleakage of glass ionomer (GI) and resin-modified glass ionomer cements (RMGI) used as sealants. Clinically sound extracted human molars were distributed into nine experimental groups (n = 15 each). Group 1 (control) was sealed with resin-based sealant (Delton) following clinically accepted techniques. Groups 2 through 6 were sealed with RMGI (Vitremer) after having the fissure conditioned with either polyacrylic acid (RMGI-control), 35-percent H3PO4, low viscosity 35-percent H3PO4 with a surfactant, self-etch conditioner, or 35-percent H3PO4 followed by self-etch conditioner. Groups 7 through 9 were sealed with GI sealant (Fuji Triage) after having the fissures conditioned with either polyacrylic acid (GI-control), 35- percent H3PO4 or low viscosity 35-percent H3PO4 with a surfactant. After aging through thermocycling (2500 cycles), specimens were incubated in methylene blue for four hours and sectioned at multiple locations. Digital images were obtained using a digital stereomicroscope, and microleakage was determined by scoring the dye penetration along the enamel-sealant interface. The penetration of the material was determined by calculating the percentage of the total length of the fissure penetrated by the material. Results: The use of self etch-conditioner significantly increased RMGI penetration, while surface conditioning with 35-percent phosphoric acid with surfactant significantly decreased microleakage of GI. The resin-based sealant placed after 35-percent phosphoric acid surface conditioning showed the best penetration and the least level of microleakage. In conclusion, results from this study suggest that the placement of glass ionomer-based sealants can be enhanced by modifying current conditioning methods.Item A laboratory comparison of the adhesion of unfilled and composite resins to acid etched enamel(1973) Aubuchon, Robert W. (Robert Wayne), 1946-; Starkey, Paul E.; Swartz, Marjorie L.; Koerber, Leonard G.; Barton, Paul; Roche, James R., 1924-The purpose of this laboratory study was to determine if the bond strengths of composite resins and unfilled resins was affected similarly when applied to enamel surfaces which had been previously etched with 50 per cent phosphoric acid. The test specimens were subjected to 24 hours, 30 days, and 6 months storage in water and then subjected to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strengths of the composite resins (Adaptic and HL-72) and the unfilled resin (Sevriton). The following results were obtained: (1) Pretreating the enamel surface with 50 per cent phosphoric acid for 60 seconds significantly increased the bond strength of composite resins; (2) when placed on acid etched enamel, there was no significant difference in initial bond strengths obtained for the Adaptic and unfilled Sevriton resins; (3) with prolonged water storage, the Adaptic composite resins developed significant loss of bond strength when compared to the unfilled Sevriton resins and the composite HL-72 resins; (4) when Adaptic resins and the HL-72 resin specimens were compared, there was no significant difference in initial bond strengths but the HL-72 specimens were less affected by storage time. Ca45 was used to assess the marginal seal of Adaptic, HL-72, and Sevriton in acid etched and non-etched Class V restorations. One-half of the specimens were thermal cycled 2500 times and stored in water for one week. Control specimens were tested at the end of one week without the thermal cycle. On the basis of these results, it was concluded that acid etching enhances the marginal seal of both composite and unfilled resins. Both composite and unfilled resins experienced increased marginal leakage when the acid etch preparations were thermal cycled, but there were no observable difference in the marginal seal of unfilled resins and composite resins when placed in acid etched restorations.Item A laboratory study of the adhesion of a restorative acrylic resin and a polycarboxylate cement on bovine enamel etched with fifty per cent phosphoric acid(1970) Lee, Brian Dalvin, 1942-; Gilmore, H. William (Homer William); Mercer, Victor H., 1928-; Garner, La Forrest Dean, 1933-The purpose of this laboratory study was to determine whether etching of flat bovine enamel surfaces with a 50 per cent aqueous solution of phosphoric acid for 60 seconds increases the bonding of a conventional restorative acrylic resin and a new polycarboxylate cement. The test specimens were subjected to 24 hours, 30 days and six months storage in water and then subjected• to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strength of both materials. The results of the Newman-Keul's test showed that pretreating the enamel surface with 50 per cent phosphoric acid significantly increased the bonding of the restorative resin, and that the cavity sealer supplied by the manufacturer further improved the resin attachment to enamel surfaces previously etched with phosphoric acid. The bonding of the resin to acid-etched enamel surfaces pretreated with or without the cavity sealer was unaffected by prolonged storage in water, temperature stress cycling, and intermittent tensile stress cycling. However, a significant reduction in the adhesion of the acrylic resin to polished-enamel surfaces pretreated with or without the cavity sealer was observed when the test specimens were subjected to the same testing conditions. The data obtained for the polycarboxylate cement test specimens showed that etching of the enamel surface with phosphoric acid also provided slightly higher adhesive values than the control specimens. Results obtained revealed that prolonged storage in water, and temperature and mechanical stress cycling did not affect the adhesion of the polycarboxylate cement to acid-etched enamel surfaces. However, thermal and mechanical stress cycling after prolonged storage in water appeared to decrease the adhesion of the cement to polished enamel surfaces. When Ca45 was used to assess the marginal seal of resin restorations placed into acid-etched Class V cavity preparations in extracted human teeth, the autoradiographs showed that etching of the cavity preparations with 50 per cent phosphoric acid improved the marginal seal of the restorative resin after one-week storage in water. When both the acid-etched and control restorations were thermal stress cycled 2500 times at a 40°C temperature differential, a slight improvement in the marginal seal of the acid-etched restorations was observed.Item Retention of resin restorations by means of enamel etching and by pins(1971) Ayers, Alvin James, Jr., 1941-; Gilmore, H. William (Homer William); Norman, Richard Daviess, 1927-; Garner, La Forrest Dean, 1933-An investigation was conducted into the effect of acid etching of the enamel and the use of pins on the retention of direct filling resins when used for restoration of fractured incisor teeth. The retention secured by these techniques as related to the cavity design also was studied. Four different cavity preparations were used. The retention of the resin in all four was compared when there was no pretreatment of the enamel, when the enamel was etched by 50 per cent phosphoric acid, and when pins were used for retention. Retention was assessed on the basis of resistance of the restoration to displacement by a lingual force. No significant difference was observed in retention as related to cavity design in the control specimens. In all four cavity preparations, acid etching of the enamel and the use of two retentive pins increased the resistance of the restorations to displacement. (However; when only one "L" shaped retentive pin was employed in Conjunction with a flat incisal preparation the force required to accomplish displacement was no greater than for controls.) The acid etch technique when employed with a cavity preparation that extended 1.7 mm. or more onto the lingual surface of the enamel generally offered a higher resistance to lingual force than double pin retained restorations. There was no significant difference between the resistance offered by a circumferential preparation when the resin was retained by either acid etching or by two pins. In the acid etch technique the enamel surface area and its distribution are important factors in retention.Item The Influence of Etching Times and Fluoride Acid Gels on the Bonding of Orthodontic Brackets(1988) Hoagburg, Steven Joseph; Garner, LaForrest D.; Shanks, James C., Jr.; Moore, B. Keith; Nelson, Charles L.; Hennon, David K.This study evaluated the influence of etching times and the addition of fluoride to a phosphoric acid gel on the tensile bond strength of orthodontic brackets bonded to human enamel using a 40% phosphoric acid gel containing no fluoride, 0.44% sodium fluoride and 0.8% stannous fluoride. The percent cohesive failure after debonding was also studied. In addition, the enamel surface was evaluated for reaction products and etching morphology by scanning electron microscopy. Such a reduction in etching times and the addition of fluorides into the etchants should result in less damage to the tooth and a decrease in enamel decalcification. For the tensile bond strength part of the study, 189 noncarious and nonrestored human premolar teeth were divided into three groups corresponding to the three different etching gels. Each group was subdivided into three other groups which consisted of the three etching times, 15, 30 and 60 seconds. There were a total of 21 samples in each of the nine groups. After etching with the appropriate gels and etching times, brackets were bonded to the buccal surfaces of the teeth with Concise orthodontic resin. The samples were thermocycled and stored in 37°C until testing. Seven days after bonding, the samples were tested in tension in an Instron testing machine. After debonding, the percent cohesive failure was evaluated under the microscope at 40X. All groups were compared using the two way analysis of variance. There was no significant difference in tensile bond strength between the three etchants. However, etching with the NaF etchant for 15 seconds produced significantly different results from the other NaF groups. However, there was no significant difference related to etching times for the other two etchants. The highest tensile bond strength (71.7 ± 2 3.0 kg/cm2 ) was recorded with the H3PO4 gel when etched for 60 seconds and the lowest tensile bond strength (48.9 ± 13.6 kg/cm2) was recorded with the NaF etchant when etched for 15 seconds. There was no significant difference in the percent cohesive failure between the three etchants. There was a significant difference in the NaF group when the etching times were changed. Etching with the NaF group for 15 seconds showed a significant difference when compared with the other NaF groups. However, the other two etchants showed no significant difference between the different etching times. Cohesive failure for all groups occurred mainly at the mesh-resin interface. The highest percent cohesive failure (95.7 ± 14.8%) occurred in the SnF2 group when etched for 30 seconds. The lowest percent cohesive failure (70.9 ± 40.6%) occurred in the NaF group when etched for 15 seconds. In the second part of this study nine human maxillary premolar teeth were etched with the three different gels at the three time intervals and were evaluated under the SEM at magnifications of 1500X and 5000X for reaction products and etching morphology. Fluorides incorporated into the etching gels should reduce enamel decalcification, and decreasing the etching times also reduces enamel loss. Results of the present study suggest that incorporating of these fluorides in the etchants, along with decreasing the etching times, warrants clinical evaluation.