A resume should start with short but clear and open sentences. Your goal is to show that how much you understand about the job, why you love that job and how much experience you have gained when doing similar jobs. Then, why do not you put those in your resume and it in a professional way?
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.