Shear-peel Bond Strength Research Articles

Bracket bond strength with transillumination of a light-activated orthodontic adhesive.

The literature describes transillumination as a means of curing orthodontic light-cured composite adhesive. The literature also recommends a 2 to 3 times increase in light exposure time when light curing using transillumination. The purpose of this study was to determine the transmittance of the curing light through human enamel and the effect of transillumination on the bond strength of orthodontic brackets. One hundred extracted human maxillary incisors were used in this study. Brackets with orthodontic composite adhesive were placed on the labial surface of the incisors and light cured from either the labial or the lingual (transillumination). The control sample was cured from the labial for a total of 40 seconds of light exposure. Experimental samples were cured from the lingual (transillumination) for 20, 30, 40, or 50 seconds. The shear-peel bond strengths were tested at 30 minutes and 24 hours after light application. The results of this study demonstrated no statistically significant difference between 40 seconds of labial curing and most of the lingually cured groups. The only experimental group that differed statistically from the control group was the 40-second lingual cure group tested at 30 minutes after light application. Actual bond strengths, however, were lower for all experimental samples. The samples tested at 24 hours that received 50 seconds of transillumination were nearly the same as the control values. This study demonstrated that transillumination of maxillary incisors is an acceptable method of curing orthodontic adhesive, particularly if the exposure time is increased from 40 to 50 seconds.

Shear peel bond strength of compomers veneered to amalgam

Statement of problem. The practice of veneering compomers to amalgam restorations has not been studied. Purpose. This in vitro study was designed to assess the shear peel bond strength and fracture pattern of 3 currently available compomers veneered to amalgam. Material and methods. Sixty cylindrical preparations were filled with amalgam. Half (30) had no surface treatment, whereas the other half were air abraded. In both groups, 10 specimens each were veneered with Dyract AP, Hytac, and F2000 according to the manufacturers' instructions. All samples were kept at 37°C in 100% relative humidity for 48 hours. SPBS was assessed with a universal testing machine and fracture patterns with a stereomicroscope. The results were analyzed with 2-way ANOVA and Tukey's multiple comparison test. Results. Dyract AP veneered to air-abraded amalgam had the highest SPBS (5.78 ± 1.30 MPa); F2000 veneered to non—air-abraded amalgam had the lowest (2.99 ± 1.4 MPa). Sandblasting significantly influenced SPBS in the case of Hytac (P<.02) and F2000 (P<.01). Within the non—air-abraded group, Dyract AP had significantly higher SPBS than Hytac (P<.03) and F2000 (P<.015). F2000 air-abraded specimens exhibited adhesive bond failure only, whereas all other groups showed both adhesive and combined bond failures. Conclusion. Of the 3 compomers tested for veneering to amalgam, Dyract AP showed the highest SPBS. Air-abrading the amalgam surface was found to improve the SPBS of Dyract AP, though not significantly. Low SPBS and poor adhesion indicated that F2000 is unsuitable for veneering amalgam. (J Prosthet Dent 2001;85:396-400.)

Shear peel bond strengths of esthetic orthodontic brackets

Anecdotal reports of bracket fracture and tooth damage associated with the use of certain esthetic orthodontic brackets have been reported in the literature. With the advent of new esthetic orthodontic brackets, the need has arisen to test the claims of the manufacturers. The objectives of this study were to determine: (1) shear peel bond strengths (SPBS) of various debonded orthodontic brackets, (2) SPBS of these rebonded esthetic brackets with and without use of silane, and (3) fracture sites of all groups examined. Seventy-five noncarious human premolar teeth were randomly divided into five groups (A through E). The teeth were cleaned, stored in 70% ethyl alcohol, and mounted for testing in the Instron machine. The following brackets were bonded to the teeth with Ortho-Concise bonding resin: (A) metal brackets, (B) Silkon brackets, (C) Transcend 2000 brackets, (D) debonded Transcend 2000 brackets, and (E) debonded silanized Transcend 2000 brackets. After wet storage at 37 degrees C for 7 days, the SPBS of brackets were recorded, and fracture sites observed. There were statistically significant differences between the SPBS of metal brackets when compared with the Transcend 2000 and the Silkon brackets. These groups exhibited clinically acceptable SPBS. Debonded silanized Transcend 2000 brackets showed clinically unacceptable SPBS. Fracture sites of metal and Transcend 2000 brackets were resin-bracket, whereas Silkon brackets fracture sites were predominantly resin-enamel.