Abstract
This study investigate the influence of thumb-sucking on the anterior and posterior of the primary dentition. The subjects were 930 patients aged from 3to 5 of the Aichi-Gakuin University Pediatric Dental clinic. They were distributed into two groups. The first group was the thumb-sucking group of 259 children, and the second group was the non-oral habit group of 671 children. The data on overjet, overbite and types of the terminal plane, were collected from the clinical records.
The summaries of results were as follows;
1. The frequencies of maxillary protrusion of the non-oral habit group were as follow; 9.5% in 3 year old children,9.8% in 4 year old children and 10.0%in 5 year old children. Those of the thumb-sucking group were as follows; 23.7% in 3 year old children,16.3% in 4 year old children and 24.2% in 5 year old children. Comparing both groups, the rates of the thumb-sucking group were higher than those of the non-oral habit group at all ages, especially there was significant difference in the 3 year old children.
2. The frequency of open bite of the non-oral habit group was approximate 2-3%in all age groups. Those of the thumb-sucking group were as follow; 12.6%in 3 year old children,7.7% in 4 year old children and 15.1 % in 5 year old children. Comparing both groups, those of the thumb-sucking group showed higher rates than the non-oral habit group at all ages, especially there were significant difference in the 3 and 5 year old children.
3. As for the frequency of the types of terminal plane in 3 and 4 year old children, there were no differences between the non-oral habit and the thumb-sucking groups.
4. As for the frequency of the type of terminal plane in 5 year old children, the mesial step type of the thumb-sucking group showed a lower rate and the distal step type of the thumb-sucking group showed a higher rate than that of the non-oral habit group. There were significant differences in these rates.
