On longitudinal caries index data. A comparison study between cohort and cross-sectional attempts.

The aim of the present study was to compare registered data of caries prevalence and incidence from cross-sectional studies of specified age groups with the corresponding caries data from cohorts of individuals receiving dental health service from the same dental clinic during the years studied. The study covered two 15-19-year groups, who had been offered complete dental care from three years of age in the City of Göteborg for the time periods 1986/7-1990/1. When compared, the longitudinal cohort attempts often gave statistically significant different values to those of the cross-sectional year classes, which should be considered when presenting caries index mean values in dental health reviews. It is not indifferent to choose between longitudinal cohort and cross-sectional year class attempts when searching for dental health treatment effects. Due to the advantages of using longitudinal cohort study methods, and with regard to the differences of the study design used, as pointed out in the study, the use of longitudinal cohort patient material, extracted from cross-sectional epidemiological data bases, could favour analysis of the effects of different preventive dental care programs.

Caries extreme groups among adolescents, leaving organised dental care in Göteborg, Sweden.

The aim was--in a longitudinal respect--to study whether 15-year-old children, in caries-free groups, and groups with high frequency of carious lesions, had a stable caries development from 15 to 19 years of age, when they left the organised Public Dental Care. Caries index values were analysed for the period 1986/7-1990/1 for patients born 1971-72 and residing in Göteborg. The groups of caries-free children seemed to be stable in their dental health in about 60-70% according to the prevalence indices used; and about 80% according to the incidence index DS-a. The caries prevalence index mean values of the 15-year-old patient groups with high frequencies of lesions showed between 1.5 to 3.5 percentile units higher mean values when the individuals were 19 years of age. However, the corresponding caries incidence index values were as low as half the size, indicating a possible treatment effect of the caries prevention programme used. Related to the DFS-a index, the 20% groups with the highest caries index values were registered for about 80% of all approximal lesions, of special interest for dental care costs.

Mineralization defects in deciduous teeth of low birthweight infants.

A group of 91 children with birthweights below 2000 g and 48 healthy full-term children, reference group, were examined for mineralization disturbances of the enamel of deciduous teeth. Perinatal data were collected retrospectively from obstetric and neonatal records. Within the low birthweight group, children with enamel hypoplasia had on the 5% level a significantly lower intake of breast milk during the first week of life than children without disturbances. The only perinatal complication associated with development of mineralization defects was IRDS. Infants with IRDS, however, had a significantly lower intake of breast milk during the first week of life than low birthweight without IRDS. A low frequency of enamel defects was found in the growth-retarded sub-group of the low birthweight infants. These infants had a significantly higher intake of breast milk during the first week compared to the AGA-group. A seasonal variation was found, with the highest prevalence of mineralization disturbances in infants born during winter months. It is concluded that the occurrence of mineralization defects of the deciduous teeth in LBW infants seems to be dependent upon the amount of breast milk given during the early neonatal period and also possibly in which season of the year they are born.

Traumatic injuries to enamel formation in rat incisors.

Twenty-three fullgrown white male rats were fitted with an inclined plane on the mandibular incisors with consequent raising of the bite by 2.5 mm. After an observation period of between 1 and 30 d the animals were killed. In all cases traumatic injuries to the enamel organs were seen. The defects were mainly of four different types. Type 1 occurred in the early maturation zone of the enamel as a local defect with dedifferentiated ameloblasts. Vascular injury was moderate and deformation of the dentin was seen. After 30 d there was still a local defect of the enamel organ. Type 2 occurred apically to the maturation zone and caused a two-layered ameloblastoma resembling a sandwich. Hemorrhages were commmon in the surrounding connective tissue, with accompanying appearance of phospholipids in the tissue. After 30 d some restitution of the enamel formation was seen. Type 3 was necrosis was seen in the surrounding tissue. After 30 d a new ameloblastoma had developed in some areas. These three types appeared separately or combined. Type 4 occurred as a folding of newly formed apical dentin in areas without differentiated ameloblastoma and was seen in all of the experimental animals.

Inorganic pyrophosphatase in isolated enamel organ and odontoblasts from the rat incisor.

The inorganic pyrophosphatase (PPiase) activity was determined by a colorimetric method in the odontoblasts and the parts of the enamel organ related to enamel matrix formation and enamel maturation. The effects on PPi hydrolysis by EDTA, R 8231, urea and heat treatment were found to be almost identical to those reported for nonspecific alkaline phosphatase (APase) in the same tissues. The Mg2+ activation curve for PPiase was also similar. Like those of APase, these characteristics of PPiase activity were identical in the three locations studied. It is suggested that the close similarity in the properties of PPiase and APase is due to activity of the same enzyme, a concept which is in agreement with recent biochemical and histochemical studies of calcification.