One of the problems is that the bibliographic information is not identical: 1) "self performed" vs. "self-performed", and I do not know whether "Dentist" vs. "dentist" may be also a problem. 2) The abstracts are not identical. 3) Co-authors indicated only in one of these. 4) Journal indicated only in one of these. See also the exceptions for merging indicated in https://help.researchgate.net/hc/en-us/articles/14293081125777-Reviewing-editing-and-featuring-your-research, and among these: "you have added both of the research items yourself".