var bt_home_over=new Image(); 
bt_home_over.src="images/bt_home_over.png";
var bt_family_over=new Image(); 
bt_family_over.src="images/bt_family_over.png";
var bt_cosmetic_over=new Image(); 
bt_cosmetic_over.src="images/bt_cosmetic_over.png";
var bt_orthodontics_over=new Image(); 
bt_orthodontics_over.src="images/bt_orthodontics_over.png";
var bt_doctors_over=new Image(); 
bt_doctors_over.src="images/bt_doctors_over.png";
var bt_faq_over=new Image(); 
bt_faq_over.src="images/bt_faq_over.png";
var bt_patient_over=new Image(); 
bt_patient_over.src="images/bt_patient_over.png";
var bt_contact_over=new Image(); 
bt_contact_over.src="images/bt_contactus_over.png";
var bt_facebook_over=new Image(); 
bt_facebook_over.src="images/bt_facebook_over.png";