Cuspal deflection of teeth restored with bulk fill flowable composite resins, with and without fiber-reinforcement and evaluated by Micro-computed Tomography.

Polymerisation shrinkage of composite resins is a clinical challenge which has been well documented in the literature. Many studies investigating polymerisation shrinkage stress measure cuspal deflection, which is a manifestation of this stress. The introduction of flowable bulk-fill composite (BFRBC) materials has streamlined the restorative process, though the shrinkage and cuspal deflection from these BFRBCs has not been compared with regards to its use with polyethylene fibers (Ribbond fibers). The authors describe a method to measure the cuspal deflection of flowable BFRBCs placed in cavities of standardised dimensions at distinct steps of the restorative process, with and without fiber-reinforcement and using x-ray micro-computed tomography. Co-ordinate points are established on the buccal and lingual aspects of scanned specimens using the Volume Graphics VG Studio max 3.2.5 (Hiedelberg, Germany 2018) software. The system allows for these landmarks to be established across each scan (of the same tooth), ensuring standardization of each specimen. Further anatomical points are used to enable analysis. Comparison of angles generated across these points determines the extent of cuspal deflection.•A method of measuring the cuspal deflection of composite resins is proposed.•Experimental procedures are provided.•Data analysis methods are outlined.

Determination of orthodontic bracket and tooth adaptation using an X-ray micro-computer tomography scanner.

The determination of the orthodontic brackets' adaptation to the curvatures of teeth is a difficult topic to study. The complexity arise due to the different designs of their fitting surfaces, margins and curvatures of orthodontic brackets. Teeth on the other hand have variation in their curvatures and the question remains how well an orthodontic brackets truly adapt to the teeth. Previous methods from the literature determined the curvature of teeth through the superimposition of circular templates onto dental plaster models as well as the use of acrylic arcs of various diameters. Here the authors describe a method to compare the curvatures obtained from an industrial X-ray micro-computer tomography scanner and processing software of orthodontic brackets and plaster casts of teeth. Three orthodontic brackets could be assessed by establishing co-ordinate points of proposed standardized landmarks on the orthodontic brackets. These standardized landmarks from each orthodontic bracket can be applied onto the various plaster teeth that was scanned. The adaptation of the three brackets to the various teeth can be compared by looking at their radii and angles that were determined in this method.•The analysis of orthodontic brackets and teeth curvatures have been streamlined on a virtual platform.•Analysis of X-ray micro-computer tomography of tooth curvatures provide a guide to the range of curvatures that orthodontic brackets need to fit.•X-ray micro-computer tomography of orthodontic brackets can enhance the design of the brackets to fit a large array of tooth curvatures.