TEETH: Dental caries (decay) is a bacterial infection within the teeth. Teeth are in a constant change of acidic environment. Acidity causes tooth demineralization, your body through saliva re mineralizes teeth. Once this balances is overwhelmed, cavities result. Older and younger patients are susceptible to caries. In younger patients, due to increase sugar consumption, which bacteria process into acids. In older patients decrease in saliva can result in cavities. Fluoride aids in demineralization. Today modern dentistry offers many different treatment options. All forms of fillings, 'restorations' in the mouth have life span, therefore even though you may not be getting new decay, older fillings may need to be replaced.