A Study on Retention of Wisdom Teeth in Nagasakians

A total of 1, 173 Nagasakians, males and females and from 6 to 30 in age, were given panoramic roentgenography and investigated for retention, eruption, impaction, and absence of wisdom teeth. The results were as follows : 1. For the subjects as a whole, the retention rates of wisdom teeth were 73.8% in the maxilla and 80.3% in the mandible for the males, and 77.5% in the maxilla and 83.1% in the mandible for the females. The mandible showed higher retention rates than the maxilla for both males and females. 2. The retention rates for the subjects 15 years old and older were 77.4% in the maxilla and 86.5% in the mandible for the males, and 74.7% in the maxilla and 83.6% in the mandible for the females. The mandible showed significantly higher rates than the maxilla. Bilateral and sex differences were not recognized. 3. By the number of wisdom teeth retained in both jaws, the type with 4 teeth present was found most frequently with 63.9% for the males and 62.0% for the females. The type with 4 teeth absent was found in 4.7% of the males and 7.7% of the females. 4. The eruption rates for the subjects 15 years old and older were 39.3% in the maxilla and 41.5% in the mandible for the males, and 27.7% in the maxilla and 35.6% in the mandible for the females. The eruption rates sharply increase after the age of twenty. The mandible showed higher rates than the maxilla and the males showed higher rates than the females. 5. Non-eruption of 4 wisdom teeth was found in 44.5% and eruption of 4 teeth in 25.1% of the males. The respective rates for the females were 54.0% and 18.5%. Other types were few. 6. The impaction rates of wisdom teeth for age group of 15 years old and older decreased with age, showing a sharp decrease after 23-24 years of age. 7. Impaction of 4 teeth was the highest with 24.5% for the males and 28.6% for the females, followed by bilateral impaction the mandible with 7.7% for the males and 6.4% for the females. 8. The impaction rate to the number of the wisdom teeth present was 49.3% in the maxilla and 52.1% in the mandible for the males, and 62.9% in the maxilla and 57.4% in the mandible for the females. The females showed higher rates than the males. 9. The impaction rates at unerupted sites were 62.8% in the maxilla and 76.9% in the mandible for the males, and 65.0% in the maxilla and 74.5% in the mandible for the females. Although no differences by sex were recognized, the mandible showed higher rates than the maxilla for both males and females. 10. The absence rates of wisdom teeth were 37.2% in the maxilla and 24.1% in the mandible for the males, and 35.0% in the maxilla and 25.5% in the mandible for the females. The maxilla showed higher rates than the mandible.