Restorative & Materials · patient case with 6 questions
Wear, erosion and a burning mouth
demo: 31-year-old female
chief: Sensitive front teeth that look increasingly thin, and occasional pain that comes and goes.
history: She drinks four cans of soda daily and has a history she is reluctant to discuss regarding eating patterns. She is otherwise well.
meds: None.
findings: Marked erosion of the lingual surfaces of the maxillary teeth with intact buccal surfaces. Smooth, shiny, saucer-shaped cervical lesions on the buccal aspects of several premolars. Parotid regions appear full bilaterally.
Question 1
Erosion confined to the lingual surfaces of the maxillary teeth is most suggestive of:
Show answer and explanation
Correct answer: D. Intrinsic acid exposure from regurgitation
- A. Attrition from parafunction produces flat, matched wear facets on occluding surfaces, not smooth loss of the palatal enamel.
- B. Dietary acid tends to affect labial and occlusal surfaces first, following the path the drink takes through the mouth.
- C. Abrasion from brushing affects buccal and cervical surfaces, precisely where the brush reaches, not the palatal surfaces.
- D. Correct. This pattern, called perimylolysis, follows repeated exposure to gastric acid, whether from self-induced vomiting or from gastro-oesophageal reflux. The tongue directs the refluxate against the palatal surfaces of the upper teeth while shielding the lower ones, which is why the distribution is so distinctive. Approach the conversation with care and coordinate with medical and psychological support.
Question 2
A smooth, shiny, wedge-shaped cervical lesion on the buccal surface with sharp internal angles is best described as:
Show answer and explanation
Correct answer: C. Abfraction
- A. Attrition is tooth-to-tooth wear on occlusal and incisal surfaces.
- B. Erosion is a smooth, shallow, cupped or concave loss without sharp angles, and it does not respect a cervical distribution.
- C. Correct as this question is keyed. Abfraction is attributed to occlusal loading flexing the tooth and producing microfractures in cervical enamel and dentin. Its described appearance is a sharply angled wedge-shaped defect, often on a single tooth with heavy occlusal contact.
- D. Abrasion from brushing is a broader, rounder, saucer-shaped lesion typically affecting several adjacent teeth, most often canines and premolars on the side opposite the dominant hand.
Note: The mechanism of abfraction remains debated, and many lesions are multifactorial, combining occlusal stress, acid and abrasion. The recall offered abfraction and abrasion as the two choices, so the distinguishing feature to fix is the lesion shape: sharp wedge for abfraction, broad saucer for abrasion.
Question 3
What is the typical pH of a carbonated soft drink?
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Correct answer: A. Approximately 2.5
- A. Correct. Most colas sit around pH 2.4 to 2.6 because of phosphoric and carbonic acid, and many other soft and sports drinks fall between 2.5 and 3.5. Enamel demineralises below about 5.5, so these drinks sit far below the critical pH. It is the frequency and duration of exposure that determines damage, not the volume.
- B. 6.5 is near neutral and would not be erosive.
- C. 4.5 is closer to some fruit juices, which are still erosive but less so than cola.
- D. A pH of 8 is alkaline; no common soft drink is alkaline.
Question 4
How long should a patient wait before brushing after consuming acidic food or drink?
Show answer and explanation
Correct answer: A. 30 to 60 minutes
- A. Correct as this question is keyed. Acid softens the enamel surface temporarily, and brushing during that window abrades away the softened layer. Waiting roughly 30 to 60 minutes lets salivary buffering restore the pH and allows some remineralisation. Rinsing with water or milk immediately after is helpful and carries no such risk.
- B. Ten minutes is still well within the softened window.
- C. Brushing immediately compounds the damage by mechanically removing softened enamel.
- D. Five minutes is far too short for the surface to reharden.
Note: Recommendations vary between 30 and 60 minutes across sources, and the recall listed 60 among its options. The examinable principle is the delay itself and the reason for it.
Question 5
What is the most relevant property of a topical fluoride agent for sustained caries prevention?
Show answer and explanation
Correct answer: A. Substantivity, the ability to be retained and released over time
- A. Correct. Substantivity means the agent binds to oral surfaces and continues releasing fluoride long after application. Calcium fluoride-like deposits act as a reservoir, releasing fluoride when pH drops. This is why fluoride varnish outperforms a rinse that is cleared in minutes, and it is the same property that makes chlorhexidine effective.
- B. Fluoride does inhibit bacterial enolase at high concentration, but its principal action is on the mineral phase rather than antibacterial.
- C. Bioavailability at the moment of application matters for uptake, but a high concentration cleared quickly gives little sustained protection.
- D. Viscosity affects handling and retention time somewhat, but it is not the underlying property being tested.
Question 6
For a patient with oral mucositis using chlorhexidine, which change is appropriate?
Show answer and explanation
Correct answer: A. Substitute a bland or povidone-iodine rinse for alcohol-containing chlorhexidine
- A. Correct. Alcohol-containing chlorhexidine stings intensely on ulcerated mucosa and worsens dryness, so compliance collapses. Alcohol-free formulations, bland saline or sodium bicarbonate rinses, or povidone-iodine are better tolerated. Comfort and continued gentle hygiene matter more than antiseptic potency here.
- B. A higher concentration increases irritation and staining without benefit in mucositis.
- C. Stopping hygiene invites secondary infection. Gentle mechanical cleaning with a soft brush continues throughout.
- D. Hydrogen peroxide is irritating to ulcerated mucosa and disrupts healing granulation tissue.