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A comparative study of periodontal ligament development in teeth with and without predecessors in marmosets.

T H E A C C O U N T S O F P E R I O D O N T A L ligament formation in teeth without primary predecessors 1,2,3,7 differ in several respects from the report on ligament histogenesis in secondary succedaneous teeth. In teeth without predecessors alveolodental fibers extending from bone to cementum are formed before the tooth erupts into the oral cavity. In secondary succedaneous teeth, on the other hand, only dentogingival and alveolar crest fiber groups are discernible upon emergence of the tooth. The remaining principal fibers are formed subsequent to eruption in apical progression. Hinrichson, 5 Trott, 6 and Bernick and Levy 3 found no intermediate plexus in the periodontal ligaments of developing deciduous teeth, while Grant and Bernick 4 noted an intermediate plexus during ligament histogenesis in secondary succedaneous teeth. Miura and coworkers 8 described an intermediate plexus but failed to show the intermediate zone as reported by Sicher, and by Grant and Bernick. These researchers interpret a central zone in the periodontal ligament as "splicing" of fiber bundles in accord with later concepts of Sicher 1 1 and Orban. 1 2 In contrast, Zwarych and Quigley 1 3 interpreted similar photomicrographs as evidence of fiber continuity and questioned the existence of an intermediate plexus. To help resolve the seeming discrepancies, the developmental sequence of periodontal ligament formation in teeth with and without predecessors has been studied.