{'fraction_non_alphanumeric': 0.046875, 'fraction_numerical': 0.038125, 'mean_word_length': 4.7797833935018055, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Microdontia and hypodontia of premolars and permanent molars in childhood cancer survivors after chemotherapy.

BACKGROUND
Adverse long-term general and dental health effects of cancer and cancer therapy during childhood have been reported.


AIM
To examine the association between chemotherapy before the age of 8 years and (1): microdontia; (2): hypodontia of premolars and permanent molars.


MATERIAL AND METHODS
In The Danish Registry of Childhood Cancer (DBCR), we identified 203 children who met the following inclusion criteria: (1) age below 8 years at the start of treatment; (2) age between 12 to 18 years upon dental examination; (3) had received chemotherapy The exclusion criterion was radiotherapy to the head and neck. A total of 150 children fulfilled the inclusion criteria. As controls, a random sample of 193 age-matched unexposed children was included.


RESULTS
Microdontia was found in a total of 88 teeth in 29 (19.3%) of the 150 children who had been exposed to chemotherapy, while none of the controls had microdontia of premolars or permanent molars (difference: 19.3%; 95% CL: 13.5%; 26.4%). The earlier the exposure, the more frequent was microdontia. We found a total of 27 missing premolars and permanent molars in 14 (9.3%) of the exposed children and a total of 18 missing premolars and permanent molars in 8 (4.1%) of the controls (difference: 5.2%; 95% CL: -0.1%; 11.3%).


CONCLUSION
The present study confirms findings from previous studies that chemotherapy, especially in very young children, causes microdontia and hypodontia of premolars and permanent molars.