Bonding Performance for Repairs Using Bulk Fill and Conventional Methacrylate Composites

This study compared the bond strength of a composite repair made with a bulk fill composite and a conventional one using different surface treatments. Specimens were prepared as truncated cones (bases: 4 mm × 2 mm, height: 4 mm) using a bulk fill (OBFa: Filtek One) or a conventional resin (FTKa: Filtek Z250) (n = 66). They were artificially aged (10,000 cycles, 5°C–55°C, 30 sec) and subdivided according to surface treatments: NT—no treatment (control), Abr—abrasion with a diamond tip, and sand—sandblasting with aluminum oxide (50 μm). Treatments were performed over the smaller diameter surface, followed by adhesive (Scothbond Universal) application. A new specimen with similar dimensions was constructed over it using either the OBF or the FTK, totaling 12 groups (n = 11). Bond strength was assessed by tensile test. The data were submitted to two-way ANOVA separately for OBFa and FTKa, followed by Tukey’s test ( p < 0.05 ). For the aged OBFa groups, there was significant differences for composite type and surface treatment, with higher values of bond strength when repaired with the same material (OBFa/OBF > OBFa/FTK), and sandblasting and bur abrasion presented higher values compared to the control group (NT). For the aged FTKa groups, there were no differences for the composite or surface treatment. Therefore, the bulk fill resin composite tested present better repair performance when the same composite was used, while the conventional resin composite was less influenced by the material and the surface treatment performed.

Analytical Model and Numerical Analysis of Composite Wrap System Applied to Steel Pipeline

Composite overwraps are a cost-effective repair technology, appropriate for corrosion defects, dents, and gouges for both onshore and offshore steel pipelines. The main benefit of polymer-based sleeves is safe installation without taking the pipeline out of service. This paper presents a new calculation procedure proposed in the form of an algorithm for the sizing of composite repairs of corroded pipelines when the sleeve is applied at zero internal pressure. The main objective of the presented methodology is determination of the effective thickness of the composite repair without its overestimation or underestimation. The authors used a non-linear finite element method with constitutive models allowing analysis of the steel, putty, and composite structures. The validation of the results of numerical computations compared to the experimental ones showed an appropriate agreement. The numerical calculations were applied to compare the analytical results in relation to those obtained by the standards ASME PCC-2 or ISO/TS 24817. The comparison showed that the proposed solution confirmed its effectiveness in reducing the thickness of the sleeve significantly, thus, showing that the current industrial standards provide a considerably excessive composite wrap around the steel pipe corroded area, which leads to an unnecessary increase in the repair costs.

Trends in Resin Composite Restoration Repair Teaching in Dental Colleges in Pakistan

Background The paradigm shift from replacement to repair of defective resin composite restorations to implement minimal intervention approaches has been popular. Therefore, the teaching of composite repair strategies is included in contemporary dental curricula across the globe. Methods A validated 18-item questionnaire pertaining to existing educational practices related to the teaching of defective composite restorations repair was acquired form dental colleges in Pakistan. Results The response rate was 63% and the majority of dental colleges (67%) reported that they have included the teaching of composite restorations repair in the curricula, where four colleges (33%) implemented only didactic teaching and eight colleges (66%) reported a combination of didactic teaching and clinical training. The composite repair indications taught included tooth substance conservation 100% (12), reduced cost to patient 84.3% (10) and dentist 100% (12), reduced iatrogenic pulpal damage 100% (12), and reduced chair side treatment time 91.3% (11), restoration-related defects (66% preferred repair), anterior tooth fracture from incisal/proximal margin (80% teach repair), and in case of posterior tooth cusp fracture (20% teach repair). Our results revealed that the choice of mechanical and adhesive substrate surface conditioning depended on case selection. Conclusion The teaching of defective composite restorations repair was less widespread and certain variations in teaching were identified. Nearly all dental colleges reported to incorporate current evidence of minimum invasive strategies of composite repair in curricula in future.