RDA Preventive Dentistry and Patient Education — Questions and Answers
Question 1: Coronal polishing with a rubber cup and prophy paste is intended to remove:
- Subgingival calculus
- Supragingival calculus
- Extrinsic stains and soft deposits (plaque biofilm) (Correct answer)
- Intrinsic stains from tetracycline use
Correct answer: Extrinsic stains and soft deposits (plaque biofilm)
Coronal polishing removes extrinsic (surface) stains and soft deposits such as plaque biofilm from the clinical crowns of teeth. It does NOT remove calculus (tartar), which requires scaling instruments used by the hygienist or dentist. Intrinsic stains are within the tooth structure and cannot be removed by polishing.
Question 2: Which type of fluoride application requires the patient to refrain from eating or drinking for 30 minutes after application?
- Fluoride varnish
- Acidulated phosphate fluoride (APF) gel in trays (Correct answer)
- Fluoridated toothpaste
- Fluoride rinse (0.05% NaF daily rinse)
Correct answer: Acidulated phosphate fluoride (APF) gel in trays
APF gel applied in trays requires a post-treatment waiting period of 30 minutes to allow fluoride uptake into enamel before food or drink dilutes or removes it. Fluoride varnish, by contrast, can be applied and the patient may eat soft foods almost immediately because the varnish adheres to the tooth surface.
Question 3: A pit-and-fissure sealant is placed on posterior teeth primarily to:
- Strengthen enamel that has been weakened by acid erosion
- Seal the deep occlusal grooves that trap plaque and are prone to decay (Correct answer)
- Replace fluoride therapy in high-caries-risk patients
- Bond orthodontic brackets to enamel
Correct answer: Seal the deep occlusal grooves that trap plaque and are prone to decay
Sealants physically block the deep pits and fissures on occlusal surfaces of molars and premolars where toothbrush bristles cannot reach. This prevents bacteria and food from accumulating in these high-risk sites. Sealants complement, but do not replace, fluoride therapy.
Question 4: When instructing a patient on the Bass toothbrushing technique, the dental assistant should direct the patient to angle the brush bristles at approximately:
- 0 degrees (parallel to the occlusal plane)
- 30 degrees toward the gingival margin
- 45 degrees toward the gingival margin (Correct answer)
- 90 degrees perpendicular to the tooth surface
Correct answer: 45 degrees toward the gingival margin
The Bass technique places the bristles at a 45-degree angle to the gingival margin so they penetrate slightly into the gingival sulcus and disrupt subgingival plaque. This makes it effective for patients with gingivitis or periodontal disease. The bristles are then vibrated with short back-and-forth strokes.
Question 5: Which dietary carbohydrate is considered the most cariogenic (decay-causing) because oral bacteria ferment it most readily?
- Complex starches (e.g., bread, crackers)
- Sucrose (table sugar) (Correct answer)
- Sorbitol (sugar alcohol found in some gums)
- Fructose from whole fruits
Correct answer: Sucrose (table sugar)
Sucrose is the most cariogenic carbohydrate. Streptococcus mutans uses sucrose to produce both lactic acid (which demineralizes enamel) and the glucan matrix that helps biofilm adhere to teeth. Sugar alcohols like sorbitol are not fermented by cariogenic bacteria and are considered non-cariogenic.
Question 6: Before applying a resin-based pit-and-fissure sealant, the tooth surface is conditioned with phosphoric acid gel. The purpose of acid etching is to:
- Remove intrinsic stains from the fissures
- Kill bacteria remaining in the pit after cleaning
- Create a microscopically roughened surface that increases mechanical retention of the sealant (Correct answer)
- Remineralize early enamel lesions before sealing
Correct answer: Create a microscopically roughened surface that increases mechanical retention of the sealant
Phosphoric acid (typically 37%) creates microscopic porosities in enamel by selectively dissolving hydroxyapatite crystals. When the liquid sealant flows into these micro-porosities and cures, resin tags form, providing micromechanical retention. Without etching, bond strength would be insufficient.
RDA Preventive Dentistry and Patient Education
Coronal polishing with a rubber cup and prophy paste is intended to remove: