Effect of provisional restorations on the final bond strengths of porcelain laminate veneers.
ABSTRACT The purpose of this in vitro study was to evaluate the effect of the different provisional restorations cementation techniques on the final bond strengths of porcelain laminate veneers (PLVs). Thirty-six extracted human central incisors were sectioned 2 mm below the cemento-enamel junction, and crown parts were embedded into self-cure acrylic resin. Standardized PLV preparations were carried out on labial surfaces of the teeth. Then the teeth were randomly divided into three groups of 12 each. In group 1, provisional restorations were cemented with eugenol-free cement. In group 2, prepared teeth surfaces were first coated with a desensitizing agent then provisional restorations were cemented with resin cement. In group 3, provisional restorations were not fabricated to serve as control. After specimens were stored in distilled water for 2 weeks, provisional restorations were removed and final IPS Empress 2 ceramic veneers were bonded with a dual-curing resin. Two microtensile samples from each tooth measuring 1.2 x 1.2 x 5 mm were prepared. These sections were subjected to microtensile testing and failure values were recorded. The data were analysed by one-way anova and Tukey HSD tests. The PLVs, placed on the tooth surface that had received a dentine desensitizer and provisional restorations luted with resin cement (group 2), showed the lowest bond strength in all test groups. But no statistically significant differences were found between the bond strength of PLVs in control group (no provisional restorations) and group 1 (provisional restorations cemented with eugenol-free cement before final cementations). Scanning electron microscopic (SEM) examination of this study also showed that the bonding to enamel surface was better in control group and group 1 than group 2.
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ABSTRACT: Past research has not controlled preparation surface area when examining the influence of dentin desensitizers on the retentive strength of cemented cast crowns, leading to inconsistent results. This research controlled crown preparation surface area and evaluated the effect of various dentin desensitizers and conventional cementing agents on the in vitro retentive strength of cast crowns. Freshly extracted human molars were prepared for a standardized crown preparation (26 degrees total convergence, 4 mm axial height) with a custom-made pantograph. Dentin desensitizers included none (control), a polymerizable material (All-Bond 2), and a nonpolymerizable desensitizer (Gluma Desensitizer). Cementing agents included zinc phosphate (Fleck's), glass ionomer (Ketac-Cem), resin-modified glass ionomer (Fuji II), and resin cement (Panavia 21). Twelve teeth were prepared for each test condition (144 teeth total). Individual castings were made from a base metal alloy (Rexillium III). Crowns were removed after storage at 26 degrees C for 48 hours at 100% relative humidity using a universal testing machine at a crosshead speed of 1.27 mm/min. The proportion of cement retained on the tooth and casting after debonding was quantified according to treatment. Statistical treatment included 1- and 2-way ANOVAs, followed by the Tukey-Kramer post hoc test at a preset alpha of 0.05.Results. Resin cement exhibited the highest retentive strength and all dentin treatments resulted in significantly different retentive values (All-Bond 2 (5.68 +/- 0.70 MPa) > control (4.67 +/- 0.48 MPa) > Gluma (4.12 +/- 0.37 MPa)). Retention of resin-modified glass ionomer was between the resin cement and glass ionomer groups: All-Bond 2 (3.46 +/- 0.26 MPa) > Gluma (2.81 +/- 0.15 MPa) = control (2.96 +/- 0.18 MPa). Conventional glass ionomer values were between those of Fuji Plus and zinc phosphate groups: All Bond 2 (2.23 +/- 0. 20 MPa) = control (2.36 +/- 0.20 MPa) > Gluma (1.98 +/- 0.23 MPa). Zinc phosphate had the lowest retention values: control (1.68 +/- 0. 08 MPa) > Gluma (0.81 +/- 0.11 MPa) > All-Bond 2 (0.67 +/- 0.14 MPa). The majority of cement was retained on the debonded tooth surface versus the casting, with the exception of zinc phosphate when used with dentin pretreatments. Controlled crown surface areas reduced the variation in strength values permitting high discrimination among retention values of desensitizer/cement combinations. In all but 1 combination, Gluma desensitizer significantly decreased crown retention. With resin cement and resin-modified glass ionomer, use of All-Bond 2 desensitizer significantly increased crown retention values.Journal of Prosthetic Dentistry 04/2000; 83(4):459-65. · 1.72 Impact Factor
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ABSTRACT: Minimal tooth preparation is required for porcelain laminate veneers, but an interim restoration is anticipated by patients to protect their teeth against thermal insult, chemical irritation, and to provide esthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and the fit and final bonding of the porcelain laminate veneer. This in vitro study inspected the tooth surface for remaining debris from cement after removal of a provisional restoration. Seventy-two extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with 3 bonding methods: temporary eugenol-free cement, spot etching combined with dual-curing luting cement, and polyurethane adhesive combined with dual-curing luting cement. After removal of provisional restorations 1 week later, the tooth surface was examined for residual luting material with an SEM. Traces of cement debris were found on provisionally prepared teeth for all 3 material methods. The use of polyurethane adhesive combined with the dual-curing cement revealed significantly less teeth with debris than the other methods. This difference was less distinct when the smear layer was removed.Journal of Prosthetic Dentistry 10/1999; 82(3):281-5. · 1.72 Impact Factor
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ABSTRACT: The cementation of artificial crowns is commonly accompanied by sensitivity, so the clinical application of desensitizing agents has become prevalent. This study investigated the effects of Imperva bonding agent and All-Bond desensitizing agent on the retention of artificial crowns. The cements selected for this study were: zinc phosphate, polycarboxylate, glass ionomer, and resin luting agents. Extracted, intact, human molars were mounted in autopolymerizing acrylic resin and prepared for complete cast copings. Thirty-two teeth were treated with All-Bond desensitizing agent, 32 teeth with Imperva bonding agent, and 32 remained untreated. Castings were cemented and tested on an Instron testing machine. The results demonstrated a significant reduction in retention when All-Bond desensitizing agent was used with polycarboxylate cement and some reduction with zinc phosphate cement. Imperva bonding agent demonstrated less retention with glass ionomer cement.Journal of Prosthetic Dentistry 03/1996; 75(2):129-34. · 1.72 Impact Factor