Aim: To investigate risk factor/s involved in the development of hypomineralised second primary molars and to relate the location of the affected tooth in the dental arches with the timing of the illness/condition incidence.
Study design: A cluster sample of 1,000, Iraqi 7-9 year-old children were invited to have their second primary molars examined for demarcated hypomineralised lesions.
Methods: Mothers of 823 children completed a questionnaire-based interview regarding pregnancy and childhood systemic health history. In the clinical examination, the buccal, occlusal and lingual/palatal surfaces of the second primary molar were evaluated for demarcated hypomineralisation lesions by visual examination.
Results: A response rate of 82.3% was obtained. Of the children examined, 53 (6.6%) had hypomineralisation defects in at least one second primary molar and were considered as the hypomineralised second primary molar-affected group. Of the total affected teeth (n=83), maxillary molars were the teeth most frequently affected by hypomineralisation throughout all developmental stages (69.9%). Demarcated opacities were the most prevalent lesion type (71.0%). Ninety-four percent of subjects diagnosed with demarcated defects reported various medical conditions possibly associated with hypomineralisation compared with 44% for their non-affected counterparts. Peri-natal medical conditions (45.3%) were the most frequently reported followed by pre-natal and post-natal conditions (24.5%, 9.4%; respectively).
Statistics: Ill health during pregnancy, delivery complications, neonatal complications, acute childhood illness, birth weight and duration of breast feeding were significant potential risk factors (p<0.05). The greater the number of health events reported, the higher was the chance of developing the defect. Children who experienced neonatal complications and whose mothers reported pregnancy and birth problems were approximately six times more likely to have the defect than those whose mothers had delivery complications only (80% vs 14.6%) (p<0.001). Also of those children whose mothers did not report delivery complications, but were breastfed for less than six months, of low birth weight and had history of upper respiratory tract infection, the chance of hypomineralised defects was over four times more likely to happen than in those who did not suffer any of these problems (25.8% vs 6.7%) (p<0.01). No statistically significant association was revealed between the time of the illness/condition occurrence and the location of the tooth in the dental arches.
Conclusions: Children with hypomineralised second primary molars had experienced more medical conditions than their unaffected peers particularly during the peri-natal period. No single factor was identified as a potential cause, leaving the aetiology of the defect unclear.