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]