Retentiveness of enamel-resin bonds using unfilled and filled resins

Comparison in shear bond strength of orthodontic brackets between five bonding systems related to different etching times: an in vitro study

New adhesives are continuously being marketed. The adhesive-bracket bond is still the weakest point in orthodontic bonding. A new device for the measurement of shear bond strength values (SBS) of orthodontic brackets is presented in this article. With this device, five commercial products were evaluated for their SBS: Lee Bond (LB), Concise (C), Super C (SC), Achieve-no-mix (ANM), and Panavia Ex (PE). After applying Begg brackets of laminated minimesh on lower human incisors, the specimens were thermocycled. The products investigated produced high bond strengths. The products tested showed shear bond strengths that were significantly lower than those stained with PE. The application of PE yielded the highest shear values. Nevertheless, some characteristics of this product might be clinically somewhat inconvenient. There was no significant difference in shear bond strength between 15 and 60 seconds enamel etching before bond application.

Evaluation of the sealant in orthodontic bonding

In the two-paste self-polymerizing orthodontic bonding systems, sealants are routinely used to protect enamel, to decrease marginal leakage, to enhance bond strength, and to increase interfacial permeability for the etched enamel, the bonding resin, and the bracket base. However, some studies have questioned the need for the sealant. Bond strengths with and without sealants in orthodontic bonding were compared in this study. The results indicated no statistical differences between the tensile bond strengths of the two evaluated groups. The distributions of debonding interface between groups were similar and also had no statistical difference. This study therefore indicated that use of the sealant in the two-paste orthodontic bonding system for enhanced strength is unnecessary. However, the use of a sealant may offer extra protection to the enamel during debonding procedures.

In vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin

The cumulative survival rate of 190 endodontically treated posterior teeth were assessed in a retrospective study; all teeth had an MO/DO or an MOD cavity restored with a composite resin without cuspal overlays after previous acid-etching of the enamel. In contrast to our previous study on endontically treated posterior teeth restored with amalgam, the survival rate of the MOD resin-restored teeth was equal to that of MO/DO teeth. Teeth restored with a light-activated resin had a much lower survival rate than teeth restored with a chemically-activated material, the cause presumably being that the light-activated resins were insufficiently irradiated. Nearly 25% of the teeth had been restored with a microfilled resin for anterior use and these teeth had a lower survival rate than had teeth restored with a macrofilled or hybrid resin. It was also found that a beveling technique did not decrease the fracture rate while the use of an intermediate layer of low-viscosity resin resulted in a significant improvement.

An investigation of shear bond strengths of various resin-bonded inner surface rest seat designs for removable partial dentures

Results and conclusions that can be drawn from this study are: All smooth, mesh, and seating preparation groups produced mean bond strengths significantly greater than that of the control group (p less than 0.01). The cast mesh rest seats exhibited significantly greater bond strengths at 24 hours (p = .0072). However, at 30 days, statistically significant differences between the three groups were not evident. Mean bond strengths for the electrolytically etched rest seat groups increased significantly at 30 days compared with the 24-hour means (p less than .05). These results suggest that an electrolytically etched resin-bonded rest seat can easily withstand the functional stresses exerted by a removable partial denture. The incorporation of seating preparation on an abutment tooth for an etched resin-bonded lingual rest seat seems to offer no advantage in terms of retentive strength.

Saliva contamination and resin bonding of etched metal retainers

This study was performed to determine how preapplication of unfilled resin and subsequent saliva contamination would affect the shear strength of the etched-metal resin-bonded retainer. There was no significant difference in the shear strength of the metal-resin bond among experimental groups when the metal retainer was bonded in the routine manner, when unfilled resin was applied and allowed to polymerize before bonding of filled resin, or when saliva contamination occurred before the addition of filled resin. Preapplication of unfilled resin to etched metal retainers may serve as a means of protecting the etched metal surface for routine try-in of "Maryland bridges" before final cementation.

Resin retention by immersion-etched alloy

An immersion technique for etching a nonnoble alloy was described. Shear strength measurements were made to compare the bonding of composite luting cement to immersion-etched alloy and to alloy etched by the electrolytic process. The study showed that statistically significant differences in the retention of cement could not be attributed to the method of etching.

Direct bonding of orthodontic brackets to esthetic restorative materials using a silane

Along with adult orthodontics comes a concern for direct-bonding techniques with esthetic anterior restorative materials. Two such materials available today are porcelain and a heat-cured composite resin. The ability to bond orthodontic brackets to these materials was tested with a normal direct-bonding technique. In addition, silane was used to theoretically enhance the bond to porcelain and the glass component of the composite. A normal acid-etch procedure to enamel served as a comparison. Bonding equivalent to the enamel acid-etch procedure was achieved with the heat-cured composite, whether silane was used or not. Silane enhanced the bond to porcelain, but the bond might not be adequate for clinical effectiveness.