Make your resume and resume differ from those of other candidates. As such, you should never start your resume with such general salutations as dear sir, or dear sir. Normally, when a company posts publicly a recruitment ad, it will surely address the name, address and contact number so as the resumes may be sent to correct address.
Almost people who tend to seek a job understand that resume is the decisive factor to whether you can make it to the interview round or not. Moreover, do not forget that resume and resume is two sides of the one which show your outstanding capability.