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Objective: This study is to evaluate fracture resistance, failure mode, and gap formation at the restorative interface of unrestored or restored non-carious cervical lesions (NCCLs) submitted to a short-term erosive environment., Materials and Methods: Artificial NCCLs were produced in vitro in bovine incisors, and were randomly divided into four restorative resins groups (n = 22): nanohybrid-NR; bulk-fill-BR; flow with a nanohybrid layer-FNR; bulk-fill with a nanohybrid layer-BNR; and a group unrestored-UR (n = 16). Half of the specimens were submitted to an erosive challenge (per 5 min, 3 × a day for 7 days, before and after restoration), and the other half, was immersed in artificial saliva. After, all teeth undergone thermal (5 ºC, 37 ºC, and 55 ºC, 3600 cycles) and mechanical (50 N, 2 Hz, 300,000 cycles) aging. Eighty teeth were subjected to compressive loading, and resistance and failures were analyzed, while 24 teeth were evaluated for gaps by microcomputed tomography. Statistical tests were performed (p < 0.05)., Results: The restorative approaches affected fracture resistance (η 2 p  = 0.14, p = 0.023), and gap formation (η 2  = 0.18, p = 0.012) and so did the immersion medium (fracture η 2 p  = 0.09, p = 0.008; gap η 2  = 0.09, p = 0.017). BNR showed the highest resistance, while UR the lowest. FNR showed the highest gaps in both immersion media. Neither the resin groups nor the immersion media were associated with failure mode., Conclusions: The erosive immersion medium based in acid beverages has been shown to affect NCCLs with or without restoration, but when Bulk-Fill resin is covered by nanohybrid resin, the performance is good., Clinical Relevance: Erosion negatively affects restorations, but unrestored NCCL shows worse biomechanical performance in stress-bearing situations., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The objective of this paper is to critically review the literature regarding the mechanics, geometry, load application and other testing parameters of "micro" shear and tensile adhesion tests, and to outline their advantages and limitations. The testing of multiple specimens from a single tooth conserves teeth and allows research designs not possible using conventional 'macro' methods. Specimen fabrication, gripping and load application methods, in addition to material properties of the various components comprising the resin-tooth adhesive bond, will influence the stress distribution and consequently, the nominal bond strength and failure mode. These issues must be understood; as should the limitations inherent to strength-based testing of a complicated adhesive bond joining dissimilar substrates, for proper test selection, conduct and interpretation. Finite element analysis and comprehensive reporting of test conduct and results will further our efforts towards a standardization of test procedures. For the foreseeable future, both "micro" and "macro" bond strength tests will, as well as various morphological and spectroscopic investigative techniques, continue to be important tools for improving resin-tooth adhesion to increase the service life of dental resin-based composite restorations., (Copyright 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)