My gums do not bleed upon flossing, brushing, using a sulcabrush but i have horizontal bone loss. i do not understand why this is. probable causes?

Need exam: There are a couple of things that may be giving on. First even though you do not have bleeding you may still have gum disease with calculus build up under yor gums. Habits like smoking will increase bone loss. Clenching or grinding can also be a factor. You should see your dentist for a complete periodontal exam and treatment.

History: Although it sounds as if your oral hygeine habits are quite good presently, the fact remains that at some point of your past, periodontal bone loss occured. Localized juvenile periodontitis may begin in adolescence. Once it starts, it is difficult to manage. Even the greatest of care won't undue the damage in later years. But take heart, it sounds as if you are doing everything correctly- now.

Multiple factors: The horizontal bone loss could be due to past smoking, past orthodontic work, crowded teeth, grinding teeth (also called bruxism or parafunctional habits).