Four-year Caries Incidence in Iowa Fluoride Study Teenagers

Objectives: Caries prevention strategies depend on knowledge of tooth and surface types most heavily affected by caries, but there are few studies of caries incidence in teenagers.  The purpose of this report is to characterize which teeth and surfaces have the highest caries incidence from age 13 to 17 among Iowa Fluoride Study teenagers.

Methods: Iowa Fluoride Study participants were recruited at birth from 8 Iowa hospitals and followed longitudinally with dental exams at ages 5, 9, 13 and 17.  All subjects with both age 13 and age 17 dental exams (currently N=239) were evaluated by 3 calibrated dentists for caries using standardized criteria (Sound, D₀, D₁, D₂, F) at the tooth surface level in primarily visual exams without radiographs.  Increases in D₂ and F were tabulated for each tooth’s surface type and overall.  Intraclass correlations were used to evaluate within-subject caries associations by tooth type.

Results: Most new caries was fillings, with D₂ increments found on only 0.1% of incisors, 0.2% of canines, 0.2% of premolars and 1.9% of molars, with most (1.4%) on the molar occlusal surfaces.  New fillings were found on 0.5% of incisors, 0.4% of canines, 1.3% of premolars and 14.5% of molars, with most (13.7%) on the molar occlusal surfaces.  Maxillary/mandibular incisor/canine/premolar incidence was similar, with 1.4% D₂F incidence per maxillary tooth and 0.6% D₂F incidence per mandibular tooth. Maxillary/mandibular molar incidence was also similar, with 15.1% D₂F incidence per maxillary molar and 17.2% D₂F incidence per mandibular molar. Within-subject intraclass correlations of D₂F incidence for incisors, canines and premolars was low (ICC=0.16, 0.11, and 0.10, respectively), but higher for molars (ICC=0.28).

Conclusions: Most new caries activity within the Iowa Fluoride Study cohort is occurring on the occlusal surfaces of the molars, and it is mostly fillings, rather than new D₂.