Shear Bond Strength and Mode of Failure of Polypropylene Fibers in Orthodontic Flash-Free Adhesive

Abstract

The purpose of this research is to evaluate the effects of magnetostrictive and piezoelectric scalers on the shear bond strength (SBS), failure mode of the polypropylene fiber adhesive brackets, and the load of both scaler tips. The adhesive precoated (APC) Flash-Free brackets were placed on the buccal surfaces of sixty maxillary first premolars, which were divided into three equal groups of 20 specimens each, following the control group (no scaling), the magnetostrictive group, and the piezoelectric group. All specimens were measured for SBS value by using a universal testing machine at a crosshead speed of 0.75 mm/minute. The mode of failure was examined under a×10 magnification light microscope digital camera and scores for the adhesive remnant index (ARI) were recorded and measured load between the magnetostrictive and piezoelectric groups. For statistical analysis, ANOVA and multiple comparison, as well as unpaired t-test and chi-square tests, at the 0.05 significance level were used. The results showed that the average SBS value of the control group was greater than that of the magnetostrictive group and the piezoelectric group. However, the SBS was not significantly influenced by ultrasonic instruments (p > 0.05). The ARI score and load showed no significant differences among the groups (p > 0.05). In conclusion, the SBS of the APC Flash-Free bracket wasn’t affected by using ultrasonic instrumentation around the base of the bracket.

Keywords: ARI score; dentistry; flash-free adhesive; orthodontics; shear bond strength; ultrasonic scaler.

Figure 4

ARI, adhesive remnant index; 0, all adhesive remains on the bracket base; 1, ≥50% of the adhesive remains on the bracket base; 2, <50% of the adhesive remains on the bracket base; and 3, no adhesive remains on the bracket base.

Figure 5

Distribution of adhesive remnant index (ARI) scores.

Figure 1

(a) The nonwoven polypropylene fibers used in the APC^TM Flash-Free adhesive consists of randomly oriented, entangled fibers (3M^TM APC^TM Flash-Free Adhesive, Technical Overview); (b) The image from the light microscope digital camera with ×10 magnification (EP50 Olympus, Tokyo, Japan).

Figure 2

(a) Cross-sectional SEM image of the teeth with metallic bracket (original magnification ×27, bar represents 500 μm); (b) A, enamel layer; B, adhesive layer; C, bracket base layer; black line, enamel–adhesive interface; white line, bracket base–adhesive interface.

Figure 3

Illustration of applied ultrasonic instrumentation.