Morphological and chemical characterization of tooth enamel exposed to alkaline agents.

OBJECTIVES: In this study, morphological and chemical changes in teeth enamel exposed to alkaline agents, with or without surfactants, have been investigated. In addition, chemical effects of the organic surface layer, i.e. plaque and pellicle, were also investigated. METHODS: The present study was conducted using several techniques: Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). RESULTS: From XPS-measurements, it was found that exposure to alkaline solutions resulted in a massive removal of carbon from the tooth surface, and that the addition of surfactants increased the rate under present conditions. Based on the results from the FTIR-analysis, no substitution reactions between phosphate, carbonate and hydroxide ions in the enamel apatite could be detected. From a minor SEM-analysis, degradation and loss of substance of the enamel surface was found for the exposed samples. From XRD-analysis, no changes in crystallinity of the enamel apatite could be found between the samples. CONCLUSIONS: The findings in this study show that exposure to alkaline solutions results in a degradation of enamel surfaces very dissimilar from acidic erosion. No significant erosion or chemical substitution of the apatite crystals themselves could be discerned. However, significant loss of organic carbon at the enamel surface was found in all exposed samples. The degradation of the protective organic layer at the enamel surface may profoundly increase the risk for caries and dental erosion from acidic foods and beverages.

Enamel hypomineralization of permanent first molars: a morphological study and survey of possible aetiological factors.

OBJECTIVES: The aim of this study was to investigate the morphological appearance of severe hypomineralized enamel of permanent first molars by means of polarized light microscopy, and to estimate the possible time, severity and longevity of the insult. Furthermore, the aim was to survey some commonly implicated aetiological factors in order to gain knowledge about possible pathogenesis of the enamel disturbances which could be compared with future epidemiological studies. SAMPLE AND METHODS: Seventy-three teeth, which had been extracted due to severe hypomineralizations of the enamel, were collected and serially cut longitudinally in a bucco-lingual direction. The sections were examined in polarized light, dry and embedded in water. The children were also examined with respect to the demarcated opacities of other permanent teeth than those that were extracted. The parents were asked about their health during the mother's pregnancy, the time of gestation, birth weight and any complications. They were also asked about the child's health during the first 2 years of its life, the length of time of breast-feeding and also about fluoride supplements. RESULTS: The hypomineralized areas extended cervically from the cusps, comprising about half of the buccal and lingual sides. The cervical borders to normal enamel were well defined and mainly followed the lines of Hunter-Schreger. The hypomineralized zones were covered by thin well-mineralized enamel. The majority of the children had demarcated opacities of all their first molars and also of some permanent incisors. No obvious correlation to the anamnestic data could be found. CONCLUSIONS: The hypomineralized enamel in the investigated teeth demonstrated areas of porosity of varying degrees. The yellow/brown defects were more porous than the white-cream and extended through the whole enamel layer, while the white-cream opacities were situated in the inner parts of the enamel. There had probably been an interacting disturbance of short duration of systemic origin of the activity of the ameloblast during the first 2 years of the child's life, resulting in chronological dispersed hypomineralized demarcated opacities in the developing teeth.

A time-series analysis of caries status among adolescents in relation to socioeconomic variables in Göteborg, Sweden.

The aim of this study was to detect, using time-series analysis methods, whether measurable socioeconomic adjustments for the time period 1986-96, as presented by caries index values, could be related to a new trend in caries status development for specific age groups leaving the free state-organized dental care system. In the study, Göteborg was divided into four districts. The study showed a favorable development in dental health for the 15-19 age group. However, the caries incidence index DSa (decayed approximal surfaces) values showed no or only negligible signs of lower mean values. During the study period, the study showed an unfavorable trend concerning the socioeconomic variables related to health care. However, the incongruity for the different districts between the trend results of the caries index values and the contemporaneous socioeconomic variable development indicated few signs of relationship. In relation to general discussions of environmental questions, the idea of sustainable development was discussed when applied to the field of dental care. The results of this study indicate that dental health, in times of major economic adjustments and lack of resources for health care for the 15-19 age group in Göteborg--as interpreted by the caries indices used is an example of sustainable dental health development.

Aspects of teeth from archaelogic sites in Sweden and Denmark.

The purpose of this study was to examine ground sections of primary second molars and permanent first molars from the same jaws. Teeth from 11 individuals were collected from archaeologic sites in Sweden and Denmark. Longitudinal buccolingual sections were examined in a polarization light microscope and in a Philips scanning electron microscope (SEM). The seven teeth from Sweden appeared to have been subjected to environmental influences at their burial site, which had affected both the dentin and the enamel. The teeth from the Danish sites had a normal color, and no disintegration of the dentin was seen. The general morphologic appearance was normal in all primary and permanent teeth. The position of the neonatal line indicated a normal full-term gestational age. The observed accentuated incremental lines in both the primary and permanent enamel suggested periods of dietary changes, possibly related to periods of illness. SEM images of the surface area of the Swedish teeth showed an extremely porous enamel surface with severe changes in the prism structure as an effect of acid penetration. The Danish teeth did not show any marked changes in the enamel.

Differences in co-variation of inorganic elements in the bulk and surface of human deciduous enamel: an induction analysis study.

This paper demonstrates a method for determination of co-variation between some inorganic elements in the bulk and surface areas of human tooth enamel. The technique is based on a computerised induction analysis of data obtained by secondary ion mass spectrometry (SIMS). When comparing the present data with an earlier study from our laboratory, it became evident that with only a moderate increase in the amount of data for the induction analysis, the results increased very considerably in reliability and precision. The patterns of co-variation between different elements differed between the bulk- and surface enamel. Only Mg expressed a similar pattern. In the bulk enamel the elements Na and P expressed a high degree of co-variation. Similarly, Mg and C expressed a high degree of co-variation. Mg was an element often found to co-vary with bulk enamel elements. In the enamel surface, F and Cl co-varied. In addition, Cl was an element often found to co-vary with other enamel surface elements.

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.