These visits, along with daily brushing and flossing, play an important role in maintaining good oral health. Without dental insurance, the national average costs of common preventive services are as follows, according to the American Dental Association [1] : 1  Periodic examination by a general dentist – $44.10.2  Prophylaxis (cleaning) – $61.14 (child), $82.08 (adult). 3  Topical fluoride application – $31.70 (child), $32.59 (adult).owever, with dental insurance, preventive care may cost little or nothing on top of your monthly premium, which may cost as little as $15 per month. Many dental plans cover two preventive care visits per year at or near 100 percent.