2.8- OBSERVATIONS REGARDING SAMPLE CALCULATION Was assumed that the minimum number of bonded restorations to be held in each of the six arms (G1 to G6) is 35 (210 restorations). The researchers did not have detailed information that allows the estimation of the sample size based on power analysis (the effect of the expected difference to the end of the time considered for the study). Thus, using rules of thumb usually considered in research situations where there is no prior information concerning the performance evaluation of these class IIa medical devices available on the market. In this case, considering that it intends to make a prospective longitudinal study, in which the result "failure" can be data processing target through Kaplan Meier curves and Cox regression to determine factors associated with failure rate and reduced clinical performance criteria of the restorations (evaluation of clinical performance over time, of the medical devices under study), and to detect effects depends the number of events (failure, for example, or other event that is to be considered in the defined evaluation criteria) and not the number of patients/participants, the thumb rules stipulate a minimum of 10 cases by group. Moreover, when considering an "simple" analysis comparison using a McNemar test (repeated measures) in six groups would be necessary in total, including at least 80 cases (to restore teeth) in the sample. When considering at least 35 restorations by group, researchers are greatly increasing the minimum number stipulated in any of the aforementioned techniques. In addition, clinical studies previously performed on this issue (between 2004 and 2012) relative to the post-market clinical evaluation performance of class IIa medical devices, in the context of restorative dentistry field, has enabled to measure a minimum of 30 restorations as viable for determining events in a short/medium-term as the clinical performance evaluation of a similar nature of medical devices.