<meta name="twitter:image:src" content="assets//assets/twitterfbimage-recommendedcamerapage.jpg" />
You’ll need to specify a fully qualified URL to your image. It looks like you probably want to use http://www.dentalphotographymadeeasy.com/assets/twitterfbimage-recommendedcamerapage.jpg as the value. Also, you should change the name of that tag to twitter:image. I think you’ll be all set after that.