تحليل الخصائص المورفومترية للأحواض النهرية (السفح الجنوبي لجبل بيرات) بين وادي زنتا ونهر الزاب الكبير

Abstract

Background and Objectives: This in vitro study was performed to assess the shear bond strength (SBS) of three different fixed lingual retainers using two types of different adhesive systems and fracture modes (Adhesive Remnant Index -ARI) of different retainer’s wire-adhesive combination. Materials and methods: one hundred eighty (180) extracted sound human upper premolar teeth were divided into two groups (90 for each group). Then each group subdivided to three subgroups (30 for each subgroup) bonded with three different fixed lingual retainers (Straight-8 strand braided flat soft wire 0.028 x 0.008 inches db UK, 3M Unitek coaxial multi strand 0.0195-inch wire USA and Ultra-Flex Lingual Retainer 0.9 mm x 0.4 mm IOS USA), which were bonded to the lingual surface of the teeth using two types of different adhesive systems (3M™ Transbond™ LR Adhesive USA and HeyTec Flow SE Composite, Heydent Germany). To assess the shear bond strength, the samples were debonded using a Universal testing machine (Instron). For each specimen, the site of failure was examined using a Stereomicroscope. One-way analysis of variance was used for the statistical analysis. Results: There was a high statistically significant difference between the two study groups (p < 0.001). Straight-8 strand braided flat soft wire combined with 3M Transbond LR Adhesive had the strongest shear bond strength (14.0 ± 4.0 MPa) whereas the minimal SBS was noted in Ultra-Flex Lingual Retainer 0.9 mm x 0.4 mm bonded with HeyTec Flow SE Composite (4.5 ± 2.7 MPa). The site of failure in group one was predominantly at the wire composite interface (cohesive failure), while in group two was in enamel/composite interface (adhesive failure). Conclusion: The simplified bonding procedures (self-etching composite) resulted in unfavorable reduction in shear bond strength. There is still support for the traditional multi-step adhesive technique