Retrogressive Changes of Dental Lamina Rests in Human Fetal Maxilla

Abstract

In order to elucidate the retrogressive changes of dental lamina rest (DLR) in human fetuses, 232 human maxillas were examined histologically. In 227 maxillas prepared for light microscopy, the dental laminas were composed of three portions: the dental lamina ridge, the primary dental lamina, and the secondary dental lamina. All of the dental laminas were separated into numerous small islets, i.e., dental lamina rests (DLRs). DLRs of the dental lamina ridge especially showed heavy keratinization in their center. Almost all of the DLRs from the primary and secondary dental laminas became atrophic and degenerative. While abundant capillary proliferation was observed in the vicinity of the DLRs, occasionally small numbers of inflammatory cells infiltrated around the atrophic DLRs. In five cases prepared for electron-microscopy, the degenerating DLRs showed tonofilaments which were reduced in number and considerably aberrant. The basal laminas of the degenerating epithelial cells were gradually destroyed with the increase of gestational age, and a few inflammatory cells containing a large quantity of Iysozome adhered to the DLR to destroy the entire basal lamina directly. In this study we confirmed that the DLRs were resorbed by the processes of both self-degeneration and the cytotoxic reaction of inflammatory cells.