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.
Do not miss these important details and do not forget to start your resume professionally with clear address of the company and even, the name of the responsible person. The employer will understand that you have researched carefully about them and correct your resume before sending to them, and, you have gained a good score then!