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Evaluation of four adhesives of the Class II resin-based composite restorations is conducted by testing the microtensile strength of teeth remodeled with the adhesives.

Dentists should insulate impressions from hot and cold weather when packaging them and make sure the packaging does not touch the impression. Impressions are made of teeth in order to create bridges and dentures and they are usually shipped to the manufacturers of these devices through the mail. However, temperatures inside some mail vans can reach 140 degrees F. Researchers found that such temperatures would deform impressions made from polyether and polyvinylsiloxane. It is best to follow the manufacturer's instructions and pour the impression in stone before shipment.

The article focuses on a study on the corrosion caused by the disinfectants on a nickel-chromium alloy commonly used in partial denture restorations. The study uses the light and scanning electron microscopic observation to determine the effect of high-level disinfectant Alcide, two medium-level disinfectants Biocide and Clorox, and deionized water on nickel-chromium alloy specimens. The before-disinfection photographs were compared with those after disinfection at specific time periods. The results show no visible change in the control specimens after immersion in deionized water for all time periods. Outline of the grain structure was observed with Alcide and Biocide after a three-minute immersion. Clorox and water solution were found to be least effective on the alloy.

The article analyzes the effect of an air-polishing device on tensile bond strength of a dental sealant. As reported, the tensile bond strength of sealants prepared with various techniques was measured. It was seen that air polishing and acid etching produced the highest bond strength of all the groups tested. A significant higher mean bond strength was found after air polishing and acid etching than after no cleansing prior to acid etching. Rubber cup polishing produced lower bond strengths than air polishing and acid etching, but this was not statistically significant. Scanning electron microscopic observation of the fracture sites revealed cohesive failures for all treatment groups.

The article presents a research study that focuses on assessing the effect of rinsing times and washing techniques on bond strength of dental composite resin materials to gel-etched enamel. It describes the method and materials used in the study, in which shear bond strength was measured after cleansing the gel-etched surface with a water-only or water/air spray. The study revealed weaker bond strength of composite resin and enamel that was cleansed at 60 seconds with water/air spray technique and stressed that a prolonged rinse with water/air spray may also damage the etched enamel.

The article discusses a clinical technique which was successful in eliminating postoperative sensitivity after placement of posterior composite dental resin restorations. The technique involved protection of the dentin before acid etching and appropriate placement of the composite resin material. For the technique, freshly extracted premolars were placed in formalin and refrigerated for scanning electron microscopy. It was observed that dentin adhesive materials were not effective in sealing the dentin tubules if the acid contacted the adhesive, also, that postoperative sensitivity can be eliminated by employing this technique which protects the dentin, bevels the enamel, and places the resin material in thin increments along the cavity walls until restoration is completely built up.

The article presents a study for examining the ability of several commercially available dentin adhesives for protection of dentin from acid etching. The study used a scanning electron microscope for investigating the materials that were placed on the prepared dentin of freshly extracted teeth. It was found that these products were not effective by themselves in the maintenance of protection for the dentinal tubules against acid attack especially the chlorophosphate ester type materials. The dentin adhesive from Johnson & Johnson was removed by acid and it opened the dentinal tubules. The combination system from Den-Mat Corp. was attacked by the acid inspite of producing a thick film. The usage of a technique and material that seals the dentin has been suggested.

The article offers information on a dental research conducted in order to determine the effect of the packing technique on polymerization shrinkage in composite resin restoration. Seven premolar teeth, freshly extracted, were stored in 10% formalin and refrigerated. A scanning electron microscope was used in order to observe the composite resin placed in extracted teeth. The resin was placed in teeth using the bulk-pack technique. The research has revealed that polymerization shrinkage was present in all teeth that were placed using the bulk-pack technique.

The purpose of this study was to test the adherence strength of oxides to some silver-free high-palladium alloys, and to compare the results to values obtained from Au-Pd and Ni-Cr metals. The results showed that the adherence strengths of the oxides were greater than the reported cohesive strength of opaque porcelain. This would indicate that the oxides formed on the alloys examined in this study are sufficiently adherent to their substrates to produce adequate porcelain bonds. [ABSTRACT FROM AUTHOR]

This paper presents shear bond strength data and scanning electron photo micrographs of six dentinal adhesives: All-Bond 2, etched and unetched; Syntac; Prisma Universal Bond 3; Scotchbond Multi-Purpose; Tenure Solution; and Adhesive By Choice. The methods used in tooth treatment and scanning electron microscopic observation were identical to those used in previous studies. This permitted comparisons among a total of 13 dentinal adhesives (seven from previous studies), all treated under the same experimental conditions and all currently available to the practitioner. Scanning electron micrographs showed the types of failures that occurred when the composite resin was fractured from the dentin. Most of the fractures were adhesive, with the exception of Scotchbond Multi-Purpose, which had many cohesive failures in the dentin or the composite resin. There was no significant difference among any of the shear bond strength values with the exception of Scotchbond Multi-Purpose, which was significantly stronger than the other five adhesives studied. [ABSTRACT FROM AUTHOR]

Much attention has been directed toward producing dentinctl adhesives that withstand the forces involved during polymerization shrinkage of composite resins. Studies have shown that an effective dentin-adhesive bond depends on the wetting and penetration characteristics of the dentinal adhesive system and the reactivity of the treated dentinal surface. The structure of the collagen in the demineralized dentinal layer also seems to influence the behavior of the bond. Adhesive systems that do not completely denature the fibrous collagen and leave interwoven banded collagen in the demineralized layer produce superior bond strengths (greater than 20 MPa). Other research efforts seek to develop a nonshrinking high-performance polymer for use as a matrix material for dental composite resins. Spiroorthocarbonates that expand during polymerization have been developed. In combination with a three-component epoxy comonomer, matrix resins have been produced that expand during polymerization and whose mechanical properties, water sorption, solubility, and degree of polymerization are acceptable for dental use. Further developments of nonshrinking composite resins and improved dentinal adhesives will greatly increase the longevity of 21st-century composite resin restorations and should significantly ease clinical placement. [ABSTRACT FROM AUTHOR]

This final paper in a series of three uses transmission and scanning electron microscopy to compare the category III dentinal adhesive systems--those with shear bond strength values near or exceeding 17 MPa. Contemporary commercial dentinal adhesive systems such as Superbond and Scotchbond Multi-Purpose, chosen for their varied chemical pretreatments, are contrasted; a contemporary commercial system (Prisma Universal Bond 3) with characteristics of category I and II dentinal adhesives is also included for comparison. The shear bond strength values attained with most category III systems are high enough to cause cohesive failure of the dentin during bond strength testing. This result is attributed to a combination of factors that include effective wetting and penetration of the prepared dentinal surface as well as a tendency to leave collagen fibers at the adhesive-dentin interface in an apparently structurally intact state. [ABSTRACT FROM AUTHOR]

The first paper in this series presented a categorization of dentinal adhesive systems that was organized roughly according to chronology, chemistry, and shear bond strength values. Category I dentinal adhesives demonstrate the lowest shear bond strength values, approximately 5 to 7 MPa. Category II dentinal adhesives, including experimental ferric and aluminum oxalate pretreatments and two commercial products, demonstrate shear bond strength values between 8 and 14 MPa. This second category of dentinal adhesives is the subject of this paper. An attempt is made to draw a parallel between the penetrative ability of the adhesive (the wettability of the dentinal substrate) and the efficacy of the adhesive bond as determined by shear bond strength values. Category III dentinal adhesives will be discussed in another paper. [ABSTRACT FROM AUTHOR]

Three categories of dentinal adhesive are proposed: category I includes adhesives with shear bond strength values between 5 and 7 MPa; category II includes dentinal adhesives with shear bond strengths between 8 and 14 MPa; and category III includes adhesives with shear bond strength values up to 20 MPa. In part I of this article, photomicrographs of the dentinal smear layer and three category I first-generation dentin-adhesive interfaces are presented. The photomicrographs show that the wetting and penetration of the first-generation dentinal adhesives were not adequate to produce high shear bond strengths. When the category I adhesives were tested for shear bond strength, failures occurred at the interface or in the resin adhesive. Future articles will explain wetting and adhesive performance of category II and III adhesives. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to determine the shear bond strengths of three new dentinal adhesives and to compare them to the strengths of four adhesives studied previously. With Superbond as the adhesive, fractures occurred cohesively in the composite resin or in the bonding material. Mirage Bond fractures occurred at the interface of the adhesive and the intermediate bonding material. XR-bonding system specimens fractured at the interface of the primer and the smear layer or at the interface of the primer and the bonding material. The bond strength of Superbond was significantly greater than that of XR-bond and Mirage Bond, and XR-bond had significantly greater strength than did Mirage Bond. When strength values for these adhesives were compared to those from a previous study, it was found that there was no statistically significant difference between Scotchbond 2 and Superbond, none between Tenure and XR-bond, and none between Mirage Bond, Gluma, and Dentin Adhesit. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to evaluate the effects of time of storage and thermocycling on the shear bond strength of three dentinal adhesives. The shear bond strength of Mirage Bond was significantly greater than that of Scotchbond 2, which was significantly greater than that of Scotschbond Dual Cure (P ≤ .05). Thermocycling significantly lowered the shear bond strength of Scotchbond Dual Cure and Scotchbond 2, but not that of Mirage Bond (P ≤ .05). Time of storage did not affect the shear bond strength of the other adhesives, but Mirage Bond had a significantly greater shear bond strength after 1 month of storage (P ≤ .05). Scanning electron microscopic observations showed that the fracture patterns were all at the smear layer-adhesive interface for scotchbond Dual Cure, the majority of the fractures were at the primer-adhesive interface for Scotchbond 2, and most of the fractures were cohesive in the bonding agent for Mirage Bond. [ABSTRACT FROM AUTHOR]

The purpose of this study was to test the difference between the strength of the marginal ridge of extracted teeth with a Class I composite resin restoration and the strength of the marginal ridge of teeth with a Class II amalgam restoration with retention grooves. A statistically significant difference in fracture strengths was found among groups. No statistically significant difference was found among restored preparations, beveling technique, and restorative material. Statistically significant differences in fracture strength were found between the whole tooth group and treatment groups; between the whole tooth group and Class II amalgam restoration group; and between the unrestored tooth preparation group and all other tooth groups. [ABSTRACT FROM AUTHOR]

Two groups of maxillary premolars with Class I cavities were prepared with one marginal ridge thickness to a width of 1.0 mm. One group was restored with amalgam and the other group with composite resin. Two groups of Class II cavities also were prepared and restored with amalgam and composite resin. The teeth in the four treatment groups were subjected to a centric load at the marginal ridge until fracture occurred. A two-factor analysis of variance revealed a statistically significant difference between the class of preparation (Class I preparations were weaker than were Class II preparations) but differences in strength between restorative materials (composite resin versus amalgam) and the interaction effect (class of preparation x restorative materials) were not found to be statistically significant (α = .05). A Newman-Keuls sequential range test found no statistically significant differences in strength between groups (α = .05). Fracture patterns were observed under scanning electron microscope. Fractures extended into the enamel and into the material in the Class 1 composite resin, Class I amalgam, and Class II composite resin restorations. Fractures extended only into the material in Class II amalgam restorations. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to compare the shear bond strengths of four dentinal adhesives. The shear bond strength was determined by testing specimens in the Instron universal testing machine at a crosshead speed of 0.5 mm/min. Scanning electron microscopic observations between × 10 and × 5000 magnifications demonstrated that the majority of the fracture patterns were either, in dentin or composite resin with Scotchbond 2 and near the adhesive interface with Tenure, Dentin Adhesit, and Gluma. A Tukey range statistic at P ≤ .05 indicated no statistically significant difference between the bond strengths of Gluma and Dentin Adhesit; the bond strength of Tenure was significantly greater than that of Gluma or Dentin Adhesit, but less than that of Scotchbond 2; and the shear strength of Scotchbond 2 was significantly greater than that of Gluma, Dentin Adhesit, or Tenure. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the enamel-sealant interface following the use of standard sealant placement techniques and an air-polishing system. Twenty-five caries-free premolars were extracted and stored in distilled water for 2 days. Five teeth were randomly assigned to each of five treatment groups. The occlusal surface was (1) air polished for 20 seconds, (2) cleaned with pumice for 20 seconds, or (3) not cleaned. Following treatment, 35% orthophosphoric acid was applied for 60 seconds. In two control groups, the acid-etching procedure was eliminated, and one group (4) was air polished for 20 seconds, while the other group (5) was not cleaned. Tinted self-curing sealant was applied to the entire occlusal surface of each tooth. Following the treatment, scanning electron photomicrographs were taken at X 1000 magnification. To evaluate the enamel-resin interface, the number of resin tags were counted by one precalibrated rater. A statistically significant difference was found among the treatment groups and the control groups. Air polishing combined with acid etching resulted in an improved surface for resin wetting as determined by the number of resin tags formed; however, the differences among the treatment groups were not large enough to be statistically significant. [ABSTRACT FROM AUTHOR]

The article focuses on an in vitro study that measures the retentive strength of etched porcelain bridges bonded to the abutment teeth with composite resin. The study aims at determining the force necessary to fracture etched porcelain bridges and to compare the strength of five different types of abutment tooth attachments. 70 porcelain bridges, extending from maxillary central incisor to maxillary lateral incisor, were constructed. The specimens were separated into seven groups of 10 specimens each. Multiple comparisons were analyzed using the Newman-Keuls technique. An analysis of variance indicated significant differences among the means. Results showed that the porcelain/metal substructure bridge with box preparations in the abutment teeth provided the greatest strength.

This study used photoelastic stress analysis to compare the location and magnitude of periradicular stresses created by load application directed through two anatomically different natural teeth and three different implant designs. Also studied was the contribution made by the periodontal ligament in the transfer of these stresses. Within the limits of this study, results suggest that the abutment structures with the greatest amount of periodontal support tend to distribute stresses in the most favorable manner. Also, the conical shape of the tooth root, with its large cervical area, has a distinctly positive effect on stress distribution. [ABSTRACT FROM AUTHOR]