The Caiman Periodontium – A Review with a Guess

Human primary molars that are histologically attached to the alveolar bone are noted to be ankylosed. The teeth of many fish and reptiles are also attached to the alveolar bone and are also found to be ankylosed or fused to the alveolar process.
In the study reported by Thomas Diekwisch et al in 2002 we note that the authors have studied the periodontal histologic features of the Gecko (Hemidacylus turcicus), juvenile Caiman (Caiman crocodilus crocodilus), and the Swiss-Webster mouse (Mus musculus).
The Caiman was found to present with an intermediary form of periodontal ligament (PDL) between the mouse and the gecko…a form that was composed of a mineral free mouse ligament and the mineralized gecko PDL. The Caiman Hertwig’s epithelial root sheath (HERS) was perforated in similar fashion as compared with the mouse PDL. In addition, HERS covered the entire root surface of the Caiman and mouse model. In the gecko the HERS was found only on the coronal portion of the root surface. This blogger notes that the HERS is perforated in the mouse and very different from the continuous HERS of the gecko model…suggesting that the HERS plays a distinct role in the ankylosis to gomphosis continuum.

The casual observer might suggest that HERS plays an important role in the development of primary molar ankylosis.
The time frame of this pathology spans a period that approximates 2 years and 2 months in human oral development. Over this time period HERS may play a major role in the final outcome of the PDL attachment since the anatomic differences between the three models indicate that the HERS is histologically variant.
This blogger also suspects that primary molar ankylosis is controlled by stochastic epigentic mechanisms that are highly conserved and likely heritable.

Bibliography

Caiman periodontium as an intermediate between basal vertebrate ankylosis-type attachment and mammalian “true” periodontium
James E. McIntosh, Xochitl Anderton, Lavinia Flores-De-Jacoby, ,David S. Carlson, Charles F. Shuler and Thomas G.H. Diekwisch
Article first published online: 11 NOV 2002
DOI: 10.1002/jemt.10222