Can oral presentations or public disclosure affect patent rights?

Yes. The following events may have the same effect as a publication in that they bar foreign rights and require any US patent to be filed within one year. Depending on the circumstances, the following may constitute public disclosure:

Any public disclosure such as an oral presentation or poster presentation, the invention was sold or offered for sale, the invention was used commercially, the invention was publicly displayed or used, or disclosed to colleagues in absence of a confidentiality agreement.