Methods: this longitudinal study was conducted on plaster casts of 20 Vietnamese children, 10 boys and 10 girls, taken biannually from age 6.5 to 13.5 years. The subjects had less than 4mm of dental crowding or spacing. The casts were photographed in series with a same set-up system. The photos were then analysed with Procluso – Procuste and their superimposition in chronological order was done with APS. ttest was used.
Results: The general morphology of dental arches was ovoid throughout the study period. Both arches changed with age (p<0.01), essentially in the mandible, where the dental arch shortened, rounded off and became more divergent. The intercanine distances showed a tendency to increase from 6.5 to 12 years-old (26.27±1.39mm to 27.44±1.65mm in the mandible, 33.13±2.5mm to 35.5±2.26mm in the maxilla) before slightly decreasing from 12 years-old. Similar tendency was observed with intermolar distances (47.27±3.43mm to 49.33±2.81mm in mandible, 52.93±1.98mm to 55.89±2.49mm in the maxilla). At 13.5 years-old, the intercanine distance in the mandible returned approximately to its value at 9-10 years-old (27.22±1.59mm). The arch depth was stable from 6 to 9 years-old in the mandible (84.82±4.94mm) and then slightly decreased, while it increased steadily in the maxilla until 12 years-old (93.47±4.75mm to 97.22±5.6mm). The transverse dimensions and arch depth were greater in boys; however, there was no statistically significant difference (p>0.05).
Conclusions: Throughout the mixed dentition, the dental arches of Vietnamese children presented an ovoid form, with morphological and dimensional modifications at different stages. It could be hypothesized that the intercanine distance in the mandible reached its final dimension at about 9-10 years-old.