What Causes Gingivitis and Periodontitis? Gingivitis and Periodontitis are conditions that are caused by plaque and bacteria buildup on the teeth. This plaque if not removed can become hardened over time creating calculus. The bacteria in this layer produce toxins which causes irritation to the tissues surround the teeth including your gums, and bone. Over time these toxins cause inflammation and degradation of these tissues, creating large pockets between the gums and teeth allowing even more buildup of plaque and bacteria. The chronic inflammation of these supportive tissues leads to bone loss and can cause premature tooth loss as well.