Dental caries and oral-health prevention — branching viva

Stage 1 — The brown upper front teeth

Examiner: A three-year-old's upper front teeth have gone brown over the last year. She falls asleep each night with a bottle of sweetened milk. What is this, and why those teeth? [6]

Candidate: This is early childhood caries. The American Academy of Pediatric Dentistry defines it as any decayed, missing or filled primary tooth surface in a child 71 months or younger, and the pattern here is its classic form — smooth-surface caries of the maxillary anterior primary teeth. The upper front teeth are bathed in the cariogenic substrate of the bedtime bottle while the child sleeps and salivary flow is low; the lower anterior teeth are spared because they sit under the tongue and are bathed in protective saliva. [6] [7]

Examiner: Walk me through the mechanism. [7]

Candidate: Caries is a biofilm-mediated, sugar-driven, dynamically demineralising disease. The milk sugar feeds an acidogenic plaque dominated by Streptococcus mutans, which ferments it to acid within minutes and drops the plaque pH below the critical value of about 5.5 for enamel. Below that threshold the saliva is no longer supersaturated with respect to enamel, so calcium and phosphate leave the tooth — demineralisation. As the pH recovers, mineral returns — remineralisation. Repeated nocturnal acid attacks tip the balance toward a white spot, then a cavity. [7] [8]

Stage 2 — The prevention ladder and the age-specific fluoride

Examiner: What is your prevention plan, and be precise about the fluoride toothpaste for her age. [2]

Candidate: Stop the nocturnal bottle and switch to water, reduce the frequency of free sugars, brush twice daily with a fluoride toothpaste, and establish a dental home with recall set by caries risk. For her age — three years — the toothpaste is a pea-sized amount of a fluoride toothpaste of at least 1000 parts per million, twice daily. The 2019 Cochrane review found 1000 ppm and above significantly more effective than the 250 to 440 ppm low-fluoride children's pastes, which is why we adjust the amount (a rice-grain smear under three, a pea-sized amount three to six) rather than drop the concentration. The child should spit, not rinse, and brushing is supervised until around seven to eight years. [2] [1]

Examiner: And fluoride varnish? [1]

Candidate: For a child at elevated caries risk like this one, five percent sodium fluoride varnish (22600 ppm fluoride) is applied two to four times a year to the primary teeth; the USPSTF recommends fluoride varnish from tooth eruption through age five, and the 2013 Cochrane review confirmed varnish reduces the caries increment in both dentitions. For her cavitated lesions, silver diamine fluoride 38 percent is a reasonable non-operative option that arrests around two-thirds of active primary-tooth lesions, at the cost of a permanent black stain that must be consented. [1] [4]

Examiner: How would you distinguish her caries from a developmental enamel defect such as molar-incisor hypomineralisation or amelogenesis imperfecta? [10]

Candidate: The key is whether the enamel was formed wrongly or is being dissolved. Caries is plaque-tracked and progressive, favouring pits, fissures and the maxillary anterior teeth. Molar-incisor hypomineralisation gives chalky demarcated opacities of the first permanent molars (erupting around six) and often the incisors, in a child whose other teeth are normal. Amelogenesis imperfecta is pan-dental and usually familial, with thin, discoloured or soft enamel across most or all the teeth, and some forms associate with renal disease. [10] [11]

Stage 3 — The swollen face from a necrotic tooth

Examiner: Now a four-year-old arrives with a two-day history of left facial swelling, fever, and increasing difficulty opening his mouth; he has had toothache from a lower left primary molar. What is your concern, and what do you do in the first hour? [8]

Candidate: My concern is a spreading odontogenic infection — a periapical abscess from the necrotic molar tracking into the submandibular space — that can threaten the airway. In the first hour I assess and secure the airway, sit him upright, establish intravenous access, give analgesia, and start intravenous antibiotics with anaerobic cover such as amoxicillin with clavulanate or clindamycin in penicillin allergy, and I refer urgently to dental or maxillofacial surgery for imaging, drainage and source control. This is not a tooth that will settle with oral antibiotics. [8] [9]

Examiner: How far would you investigate before the surgeon arrives? [9]

Candidate: A full blood count and C-reactive protein to gauge severity and systemic involvement; if a deep-space infection or airway compromise is suspected, computed tomography of the neck and face is the modality of choice to define the collection and the airway. The definitive treatment is drainage and extraction or root treatment of the source tooth — antibiotics alone do not cure a collection. [9]