The forgotten contribution of J. E. Purkyně to dentistry

Objectives: the name of Jan Evangelista Purkyně (Purkinje in German), born in Bohemia in 1787 and died in Prague in 1869, is mainly associated with discoveries in histology and specialist fields of Medicine like embriology, histological techniques, ophthalmology, cardiology and neurophysiology. This short article presents a brief account of his life, commemorates his achievements in biology and medicine but also in in the politics and literature of his Country (he was elected to the Diet of Bohemia but also he composed poems and important translations from German, French and Italian languages into Czech) and examines in depth his contribution to Dentistry. Materials and Methods: Purkyně’s major contributions to Dentistry, which focused on embryology and dental histology, endodontics and periodontology, are traced to two dissertations in Latin which were discussed by his pupils (Meyer Fraenkel and Isaac Raschkow), at Breslau University in 1835: we present a brief summary of each, with the major innovative findings highlighted. Results: the two dissertations contain remarkable, though often overlooked, contributions to Dentistry. Among these we can indicate the individuation of: the dental cement (substantia ostoidea), the acquired dental pellicle, the nature of optical illusion of Hunter-Schreger lines, the “enamel pulp” from which the enamel would evolve, the sub-odontoblastic nervous plexus which is the cause of tooth sensitivity, the predentine, the organic nature of the process of enamel formation, the dentine and enamel formation in opposing directions, the presence of alveolus membrane (id est: the periodontium). Conclusions: after reviewing the main innovations these two dissertations made to Dentistry, Purkyně’s personal share in both is very clear. Both the two his pupils acknowledged their debt to Purkyně and also famous contemporary Purkinje scientists such as Alexander Nasmyth, Sir Richard Owen, Sir James Paget had no doubt he is had generated the ideas expressed in the two little treatises.

A new hybodont shark (Chondrichthyes, Elasmobranchii) from the Upper Triassic Tiki Formation of India with remarks on its dental histology and biostratigraphy

A new lonchidiid genus,Pristrisodus, from the Upper Triassic Tiki Formation of India is described based on multiple, well-preserved, isolated teeth. Comparative analysis resulted in synonymizingParvodus tikiensisandLissodus duffini,which are known from the same horizon and resulted in a new taxon,Pristrisodus tikiensisn. comb. These teeth are elongated with mesiodistal length greater than or equal to twice the labiolingual width and have a high principal cusp, lateral cusplets, a distinct ridge near the crown-root junction labially and higher up on the crown lingually, weak ornamentation, and linear depression along the crown-root junction. Five morphotypes based on overall shape, robustness and crown height are determined. The teeth show a gradual monognathic heterodonty. The anterolateral teeth (morphotypes I−II) have high, pyramidal principal cusp with two or three small but pointed cusplets, and triangular labial and lingual protuberance. The posterolateral teeth (morphotypes III−IV) have four incipient cusplets, relatively low principal cusp, bilobed/rounded, hanging labial and incipient lingual protuberances. Morphotype V comprises anterior teeth that are broad, triangular and robust, and have rounded/blunt principal cusp, one cusplet, and low, hanging labial peg. Multivariate analyses corroborate the qualitative assessment of the Indian hybodonts. Dental histology ofPristrisodusn. gen., shows that it is distinctly different from other lonchidiid genera. The assemblage of freshwater sharks, along with other vertebrate microfossils of the Tiki Formation, shows similarity with that of the lower Tecovas Formation of the Chinle Group, USA. The euryhaline nature resulted in the adaptation of the hybodonts to freshwater systems in India during the Carnian.