Some biologic aspects of dental variations

Abstract

The casual reversion to a primitive hypothetical tooth formula 3.1.4.3., based on evidence from comparative anatomy and from the occurrence of supernumerary teeth, does not meet with common agreement. Stafne wonders: “If we assume that all supernumerary teeth which occur fall under the reversion hypothesis, an ancestral formula might be constructed which would include at least 52 teeth.” Osburn is doubtful: “No fossil connective links have been found to support this hypothesis of reversion”. The evidence at hand, however, tends to confirm the reductional behavior of the dental arch. This tendency is not new with our generation. The retromolar pits or rudimentary alveoli are taken to bear a relation to the fourth molar, now suppressed. The third molars are also becoming extinct, while the second molars are losing the distolingual cusp, and their roots are tending to fuse. “The second incisor in Bantu, unlike the corresponding tooth in the modern civilized white, is rarely degenerate either in form or in size” (Middleton-Shaw). “The lower second bicuspids, frequently absent in whites, are very seldom found to be missing in the Eskimos of Greenland” (Pedersen). We must search beyond the facts for a plausible explanation of them. Modern man has perhaps more teeth than biologically compatible with our species. If the theory of discontinuous variation, which designates loss of genes, holds good, more teeth would gradually be eliminated and the human race would in the course of time become edentulous, though the wheels of God grind slowly. Shall we comfort ourselves with the thought that in a less crowded mouth there will be less food impaction, hence less decay and less perifiental lesions?