Effects of cleaning agents on bond strength to dentin.
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The cleaning of cavity walls aims to improve adhesive restorative procedures and longevity of restorations. This study has compared the effect of three cleaning agents--sodium bicarbonate jet (Profi II, Dabi Atlante, Sao Paulo, Brazil); pumice paste plus a biologic detergent (Tergestesim, Probem, Sao Paulo, Brazil); air water spray--on the bond strength between dentin and two different adhesive systems: Clearfil SE Bond (Kuraray, Kioto, Japan) and Scotchbond Multi-Purpose Plus (3M-ESPE, Sao Paulo, Brazil). Six groups (n: 10) of dental fragments obtained from young adult extracted teeth were prepared, and each one received one of the listed surface cleaning techniques. After the adhesive application, a cone-shaped test body was built with AP-X (Kuraray, Kioto, Japan) or Z100 (3M-ESPE, Sao Paulo, Brazil) composite resins, using a Teflon matrix. The specimens were tested for tensile bond strength after one-week storage in distilled water at 37 degrees C. Two pairs of fractured specimens of each group were randomly chosen and processed for scanning electron microscopy (SEM) analysis. ANOVA test of the bond strength values showed no statistical differences among the cleaning agents and neither between their interactions with the bonding systems. Upon SEM analysis, most surfaces showed mixed fractures of adhesive and cohesive failures in bonding resin to dentin. Based on statistical and SEM analysis, it was concluded that the cleaning agents studied did not interfere with the bond strength of the adhesive systems used to dentin. (+info)
An in vitro evaluation of pH variations in calcium hydroxide liners.
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The purpose of this present study was to determine the pH changes of five different commercially available calcium hydroxide liners and variations of pH at different time intervals. The following commercially available materials were investigated: Dycal (LD Caulk); Calcimol (Vocco Products); calcium hydroxide powder (Deepti Products); Calcimol LC (Vocco Products); Lime-Lite (Pulpdent Corporation). Five samples were prepared from each liner. The pH measurements were recorded at time intervals of 1 h, 24 h, 3 days and 7 days after mixing of the liner. The pH variations of each material at the given time intervals were recorded and the means were calculated. Comparison of the mean values at all time intervals with the statistical analysis showed significantly high differences (P < 0.001) between pH values induced by each material at all time intervals. Among the water-insoluble products, Dycal had the strongest alkaline effect after 7 days interval. The materials that chemically hardened produced higher pH values than materials that hardened by a visible light source after 7 days. (+info)
Influence of elasticity on gap formation in a lining technique with flowable composite.
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The purpose of this study was to investigate the effect of flowable composites as liners for direct composite restorations, with key focus on the elastic moduli of flowable and condensable composites. After treating the composite mold cavity surface with an adhesive system, one of the flowable composites was placed as a 1 mm-thick layer on the cavity floor and irradiated for 20 seconds. The rest of cavity was subsequently filled with a condensable composite and irradiated for 40 seconds. Gap formation at both interfaces--between the cavity floor and flowable composite, and between the flowable and condensable composites--was examined. No gaps were detected at the interface between the cavity floor and flowable composite. Gap percentage at the interface between the flowable and condensable composites was dependent on the difference in elastic modulus. It was concluded that flowable composite with high elastic modulus could inhibit gap formation between flowable and condensable composites. (+info)
Trends in the placement of posterior composites in dental schools.
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The aim of this paper is to review trends in the teaching of posterior composites in the United States, Canada, Ireland, and the United Kingdom over the last fifteen years. The authors compared the results of surveys of the teaching of posterior composites performed in 1989, 1997, and 2004-05. Historical and contemporary international trends were investigated. The amount of clinical and didactic teaching of posterior composites has increased over the past fifteen years. From a time over fifteen years ago, when very few dental students placed posterior composites in dental school, approximately one-third of posterior plastic restorations placed by U.S., Irish, and UK dental students are now composite, with the corresponding finding for Canadian dental schools being approximately 50 percent. Some variations were noted between dental schools in terms of the teaching of contraindications to placement as well as lining and basing techniques. There was some inappropriate teaching of techniques, in particular, in relation to the use of transparent matrix bands and light transmitting wedges. There was also evidence of limited student exposure to newer forms of technology, notably LED curing light units. There have been clear increases in the teaching of posterior composites in the United States, Canada, the United Kingdom, and Ireland in recent years; however, the proportion of posterior composite restorations placed by dental students relative to dental amalgams does not yet match the typical situation in contemporary clinical practice. Dental schools have a responsibility to ensure that their curricula are evidence-based to best prepare their students to meet the needs and expectations of their future patients. (+info)
Finite element stress analysis of indirect restorations prepared in cavity bases.
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The objective of this study was to analyze the distribution of tensile stresses in indirect restorations prepared in several composite cavity bases. Elastic moduli of 20 materials were measured by nanoindentation technique for finite element analysis. Axisymmetric models of posterior onlays were constructed using combinations of two onlay materials and three cavity base materials. Thickness of resin cement was 50 um. A vertical load of 95.5 N was applied on the cusp tip. Maximum stress of 18.1 MPa was found in the model consisting of a ceramic onlay and a flowable resin composite base. It was also found that tensile stress increased as the area of the base having a lower elastic modulus became wider. Base materials having higher elastic moduli were determined to be suitable as cavity base materials for posterior restorations. (+info)
Mechanical versus chemical retention for restoring complex restorations: what is the evidence?
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This article reports the findings from a study conducted to answer this research question: can adhesive resin liners provide retention that is the same as dentinal pins or pots and slots when restoring complex amalgam restorations? The study methodology consisted of two components: a review of the literature and a survey to assess methods and materials that general practitioners use in their clinical practice for restoring complex amalgam restorations. Even though a vast majority of the general practitioners surveyed reported using dentinal pins or pots and slots, the occurrence or frequency of use was under 50 percent. It was also reported from the survey that over half the respondents are using adhesive resin liners exclusively when restoring complex restorations. New and improved materials allow general practitioners to restore complex restorations without the risks associated with the placement of pins or pots and slots. A review of the available literature indicates that adhesive resin liners may be used as an alternative or adjunct to mechanical retention. Because of the improvements of bonding strength of adhesive resin liners, dentinal pins and pots and slots should not be the only methods considered when faculty assist students in the development of treatment plans for patients who need complex amalgam restorations. (+info)
The use of amorphous calcium phosphate composites as bioactive basing materials: their effect on the strength of the composite/adhesive/dentin bond.
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BACKGROUND: Amorphous calcium phosphate (ACP) composites release calcium and phosphate ions in aqueous environments, which may lead to deposition of apatitic mineral in tooth structure. The authors evaluate the strength of the composite/adhesive/dentin bond shear bond strength (SBS) for ACP basing-composites after various periods of water aging. METHODS: The authors made the experimental composites by using two resin matrices with various ACPs or a commercial strontium ion-leachable glass. They applied successive coats of a dentin adhesive and basing composite to an acid-etched dentin surface and photopolymerized them. They added a commercial resin-based composite and light cured it. They determined the specimens' SBS after they were aged in water for various periods at 37 degrees C. RESULTS: The SBS of the ACP composites was 18.3 +/- 3.5 megapascals, independent of filler type, resin composition and water-aging interval. After 24 hours of water aging, 92.6 percent of surfaces showed the adhesive failure. After two weeks of water aging, adhesive/cohesive failures were predominant in unmilled and milled ACP composites. CONCLUSIONS: The SBS of ACP composites appears to be unaffected by filler type or immersion time for up to six months. The type of adhesive failure occurring with prolonged aqueous exposure is affected by filler type. CLINICAL IMPLICATIONS: These materials may be effective remineralizing/antidemineralizing agents and may be clinically applicable as adhesives, protective liners and bases, orthodontic cements and pit-and-fissure sealants. (+info)
Bond strength of a resin cement to dentin using the resin coating technique.
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