Effects of oral habits' duration on dental characteristics in the primary dentition.

BACKGROUND: Studies dating to the 1870s have demonstrated that long-term nonnutritive sucking habits may lead to occlusal abnormalities, including open bite and posterior crossbite. However, little is known as to whether habits of shorter durations have lasting effects. METHODS: The authors collected longitudinal data on nonnutritive sucking among children through a series of questionnaires regularly completed by parents. Researchers examined the children at ages 4 to 5 years and obtained study models. The models were measured for dental arch parameters (including arch width, arch length and arch depth) and assessed for overjet, overbite and posterior crossbite. The authors compared the dental arch and occlusal conditions among groups of children with nonnutritive sucking habits of different durations. RESULTS: Children with nonnutritive sucking habits that continued to 48 months of age or beyond demonstrated many significant differences from children with habits of shorter durations: narrower maxillary arch widths, greater overjet and greater prevalence of open bite and posterior crossbite. In addition, compared with those who ceased their habit by 12 months of age, those with habits at 36 months of age had significantly greater mandibular canine arch widths, maxillary canine arch depths and overjet, while those with habits at 24 months and 36 months had significantly smaller palatal depths. Prevalence of anterior open bite, posterior crossbite and excessive overjet (> 4 millimeters) increased with duration of habits. CONCLUSIONS: While continuous nonnutritive sucking habits of 48 months or longer produced the greatest changes in dental arch and occlusal characteristics, children with shorter sucking durations also had detectable differences from those with minimal habit durations. CLINICAL IMPLICATIONS: It may be prudent to revisit suggestions that sucking habits continued to as late as 5 to 8 years of age are of little concern.