Study On Periodic Growth Of Deciduous Enamel

Objectives The aim of this study was to compare daily enamel secretion rates,initial enamel extension rates and average enamel extension rates in anterior teeth group and molar teeth group of deciduous teeth.The relationship between initial enamel extension rates and enamel-dentinal junction(EDJ)lengths,and the relationship between Retzius line periodicity and enamel thickness were observed,in order to analyze the role of periodic growth in enamel development provides an important basis for further research on biological rhythm,ontogeny and taxonomy.Methods 1 Microstructure of deciduous enamel: 1)Preparation of samples: Forty pieces of deciduous teeth samples were prepared,divided them into anterior teeth group and molar teeth group.All sections were observed by using a high power microscope,images were captured with a microscope digital camera and analyzed in a software.2)Daily enamel secretion rates of the deciduous teeth: The crown enamel of deciduous teeth in each group was divided into cuspal enamel area and lateral enamel area,each area from EDJ to outer enamel surface(OES)was divided into three regions of equal thickness(inner,middle and outer region).Daily enamel secretion rates of each part in cuspal enamel and lateral enamel were measured respectively,The results of two groups were compared by a independent-samples T test.The results of inner,middle and outer regions of each group were compared by a one-way factor analysis.3)Initial enamel extension rates and average enamel extension rates of the deciduous teeth: The initial enamel extension rates and average enamel extension rates in anterior teeth group and molar teeth group were compared by a independent-samples T test.The relationship between initial enamel extension rates and EDJ lengths was analyzed by a correlation analysis.4)The relationship between Retzius line periodicity and enamel thickness: The relationship between Retzius line periodicity and enamel thickness was analyzed by a correlation analysis.2 Ultrastructure of deciduous enamel: Sixteen complete deciduous teeth were selected,and electron microscope samples were prepared.The ultrastructure of transverse and longitudinal sections were observed under field emission scanning electron microscope.Results 1 Microstructure of deciduous enamel: 1)Daily enamel secretion rates of the deciduous teeth: The data of anterior teeth group were higher than those of molar teeth group(P<0.05).The data in outer regions were higher than those in middle regions,and the data in inner regions were the lowest(P<0.05).2)Initial enamel extension rates and average enamel extension rates of the deciduous teeth: The data of anterior teeth group were higher than those of molar teeth group(P<0.05).The initial enamel extension rates were positively correlated with EDJ lengths(P<0.05).3)The relationship between Retzius line periodicity and enamel thickness: The Retzius line periodicity in two groups were positively correlated with enamel thickness(P<0.05).2 Ultrastructure of deciduous enamel: The distance of cross striations decreased gradually from cuspal enamel to cervical enamel.Most of enamel prisms' type was Type 3B,and the diameter of enamel prism at the OES was larger than that at the EDJ.Conclusions 1 The periodic growth rates of deciduous anterior teeth are higher than those of deciduous molars.2 The periodic growth rates of deciduous enamel decrease gradually from cuspal enamel to cervical enamel,and increase gradually from EDJ to OES.3 The periodic growth of deciduous enamel are positively correlated with crown height and enamel thickness.4 Most of the transections of enamel prisms' type is Type 3B,and the diameter of enamel prism increases from the inside to the outside.The research results show that the characteristics of the periodic growth of deciduous enamel and provide a basis for clarifying the influence of biological rhythm on the development of deciduous teeth,and have reference significance for ontogeny and animal taxonomy.Figure 20;Table 5;Reference 130...